US20120241751A1 - Nitride semiconductor device and method for manufacturing same - Google Patents
Nitride semiconductor device and method for manufacturing same Download PDFInfo
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- US20120241751A1 US20120241751A1 US13/238,666 US201113238666A US2012241751A1 US 20120241751 A1 US20120241751 A1 US 20120241751A1 US 201113238666 A US201113238666 A US 201113238666A US 2012241751 A1 US2012241751 A1 US 2012241751A1
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- 239000004065 semiconductor Substances 0.000 title claims abstract description 273
- 150000004767 nitrides Chemical class 0.000 title claims abstract description 105
- 238000000034 method Methods 0.000 title claims description 24
- 238000004519 manufacturing process Methods 0.000 title claims description 18
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 39
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 38
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 18
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 13
- 239000001301 oxygen Substances 0.000 claims description 13
- 229910052760 oxygen Inorganic materials 0.000 claims description 13
- 239000000758 substrate Substances 0.000 claims description 11
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 4
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 3
- 229910004205 SiNX Inorganic materials 0.000 description 25
- 229910002601 GaN Inorganic materials 0.000 description 24
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 24
- 239000000463 material Substances 0.000 description 15
- 238000010438 heat treatment Methods 0.000 description 8
- 238000005530 etching Methods 0.000 description 6
- 238000001039 wet etching Methods 0.000 description 6
- 230000015556 catabolic process Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 230000005684 electric field Effects 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 238000002955 isolation Methods 0.000 description 4
- 230000005533 two-dimensional electron gas Effects 0.000 description 4
- 230000005669 field effect Effects 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000001312 dry etching Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 2
- 229910017107 AlOx Inorganic materials 0.000 description 1
- -1 SiON and HfSiON Chemical compound 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- RNQKDQAVIXDKAG-UHFFFAOYSA-N aluminum gallium Chemical compound [Al].[Ga] RNQKDQAVIXDKAG-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 229910021478 group 5 element Inorganic materials 0.000 description 1
- CJNBYAVZURUTKZ-UHFFFAOYSA-N hafnium(IV) oxide Inorganic materials O=[Hf]=O CJNBYAVZURUTKZ-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/778—Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface
- H01L29/7786—Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface with direct single heterostructure, i.e. with wide bandgap layer formed on top of active layer, e.g. direct single heterostructure MIS-like HEMT
- H01L29/7787—Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface with direct single heterostructure, i.e. with wide bandgap layer formed on top of active layer, e.g. direct single heterostructure MIS-like HEMT with wide bandgap charge-carrier supplying layer, e.g. direct single heterostructure MODFET
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- H01L29/66409—Unipolar field-effect transistors
- H01L29/66446—Unipolar field-effect transistors with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET]
- H01L29/66462—Unipolar field-effect transistors with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET] with a heterojunction interface channel or gate, e.g. HFET, HIGFET, SISFET, HJFET, HEMT
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- H01L29/778—Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface
- H01L29/7786—Field effect transistors with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface with direct single heterostructure, i.e. with wide bandgap layer formed on top of active layer, e.g. direct single heterostructure MIS-like HEMT
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- H01L29/41725—Source or drain electrodes for field effect devices
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Definitions
- Embodiments described herein relate generally to a nitride semiconductor device and a method for manufacturing the same.
- SiC silicon carbide
- nitride semiconductors devices using new materials taking the place of silicon, such as silicon carbide (SiC) and nitride semiconductors, are developed these days.
- GaN gallium nitride
- AlGaN aluminum gallium nitride
- FIG. 1 is a schematic cross-sectional view illustrating the configuration of a nitride semiconductor device according to a first embodiment
- FIG. 2 is a schematic plan view of the nitride semiconductor device according to the first embodiment
- FIG. 3 is a schematic cross-sectional view illustrating the configuration of another nitride semiconductor device according to the first embodiment
- FIG. 4 is a schematic cross-sectional view illustrating the configuration of still another nitride semiconductor device according to the first embodiment
- FIG. 5 is a schematic cross-sectional view illustrating the configuration of still another nitride semiconductor device according to the first embodiment
- FIG. 6 is a schematic cross-sectional view illustrating the configuration of a nitride semiconductor device according to a second embodiment
- FIG. 7 is a schematic cross-sectional view illustrating the configuration of a nitride semiconductor device according to a third embodiment
- FIG. 8A to FIG. 9C are schematic cross-sectional views describing an example of a manufacturing method sequentially
- FIG. 10A to FIG. 11C are schematic cross-sectional views describing an example of a manufacturing method sequentially.
- FIGS. 12A to 12C are schematic cross-sectional views describing an example of a manufacturing method sequentially.
- a nitride semiconductor device includes a first semiconductor layer, a second semiconductor layer, a first electrode, a second electrode, a third electrode, a first insulating film and a second insulating film.
- the first semiconductor layer includes a nitride semiconductor.
- the second semiconductor layer is provided on the first semiconductor layer, includes a nitride semiconductor having a band gap wider than a band gap of the first semiconductor layer, and includes a hole.
- the first electrode is provided in the hole.
- the second electrode is provided on the second semiconductor layer and electrically connected to the second semiconductor layer.
- the third electrode is provided on the second semiconductor layer so that the first electrode is disposed between the third electrode and the second electrode.
- the third electrode is electrically connected to the second semiconductor layer.
- the first insulating film includes oxygen, is provided between the first electrode and an inner wall of the hole and between the first electrode and the second electrode, and is provided spaced from the third electrode.
- the second insulating film includes nitrogen and is provided in contact with the second semiconductor layer between the first electrode and the third electrode.
- a method for manufacturing a nitride semiconductor device.
- the method can include forming a first semiconductor layer including a nitride semiconductor on a support substrate, and forming a second semiconductor layer having a band gap wider than a band gap of the first semiconductor layer and including a nitride semiconductor on the first semiconductor layer.
- the method can include forming a second insulating film including nitrogen on the second semiconductor layer.
- the method can include forming a hole by removing parts of the second insulating film and the second semiconductor layer.
- the method can include forming a first insulating film including oxygen so as to cover an inner wall of the hole and the second insulating film.
- the method can include removing at least a part of the first insulating film on one side as viewed from the hole.
- the method can include forming a second electrode electrically connected to the second semiconductor layer on another side as viewed from the hole, and forming a third electrode electrically connected to the second semiconductor layer on the one side as viewed from the hole spaced from the first insulating film.
- the method can include forming a first electrode in the hole via the first insulating film.
- FIG. 1 is a schematic cross-sectional view illustrating the configuration of a nitride semiconductor device according to a first embodiment.
- FIG. 2 is a schematic plan view of the nitride semiconductor device according to the first embodiment.
- FIG. 1 is a schematic cross-sectional view taken in the direction of arrows A-A′ shown in FIG. 2 .
- a nitride semiconductor device 110 includes a first semiconductor layer 3 , a second semiconductor layer 4 , a first electrode 10 , a second electrode 7 , a third electrode 8 , a first insulating film 6 , and a second insulating film 5 .
- the first semiconductor layer 3 is formed via a buffer layer 2 formed on a support substrate 1 .
- the direction from the first semiconductor layer 3 toward the second semiconductor layer 4 is referred to as upward (the upper side), the opposite direction is referred to as downward (the lower side).
- the first semiconductor layer 3 includes a nitride semiconductor.
- the second semiconductor layer 4 is provided on the first semiconductor layer 3 .
- the second semiconductor layer 4 includes a nitride semiconductor having a band gap wider than the band gap of the first semiconductor layer 3 .
- the second semiconductor layer 4 includes a hole 4 a.
- the hole 4 a illustrated in FIG. 1 reaches the first semiconductor layer 3 .
- nitride semiconductor includes all semiconductors expressed by the chemical formula of B ⁇ In ⁇ Al ⁇ Ga 1- ⁇ - ⁇ - ⁇ N (0 ⁇ 1, 0 ⁇ 1, 0 ⁇ 1,0 ⁇ + ⁇ + ⁇ 1) in which composition ratios ⁇ , ⁇ , and ⁇ are changed in the respective ranges. Furthermore, in the chemical formula mentioned above, those further including a group V element other than N (nitrogen), those further including various elements added in order to control various properties such as the conduction type, and those further including various elements unintendedly included are also included in the “nitride semiconductor.”
- GaN and AlGaN which are group III-V nitride semiconductors, are used as examples of the nitride semiconductor.
- the nitride semiconductor device 110 is a normally OFF field effect transistor.
- an undoped Al X Ga 1-X N (0 ⁇ X ⁇ 1) is used for the first semiconductor layer 3 .
- “undoped” refers to a state where intended impurity doping is not performed.
- the first semiconductor layer 3 is GaN.
- the first semiconductor layer 3 functions as a channel layer.
- An undoped Al Y Ga 1-Y N (0 ⁇ Y ⁇ 1, X ⁇ Y) is used for the second semiconductor layer 4 .
- the second semiconductor layer 4 is AlGaN with an Al content of 25 percent (%).
- the band gap of the second semiconductor layer 4 that is undoped AlGaN is wider than the band gap of the first semiconductor layer 3 that is undoped
- the first electrode 10 is provided in the hole 4 a.
- the first insulating film 6 is provided between the first electrode 10 and the inner wall of the hole 4 a.
- the first electrode 10 has a portion embedded in the hole 4 a via the first insulating film 6 .
- a recess structure 9 is formed by embedding the first electrode 10 in the hole 4 a via the first insulating film 6 .
- the first electrode 10 is a gate electrode.
- the gate electrode is a MIS (metal insulator semiconductor) gate electrode.
- the second electrode 7 is provided on the second semiconductor layer 4 and electrically connected to the second semiconductor layer 4 .
- the second electrode 7 is joined to the second semiconductor layer 4 by ohmic junction.
- the second electrode 7 is a source electrode.
- the third electrode 8 is provided on the second semiconductor layer 4 so that the first electrode 10 is disposed between the third electrode 8 and the second electrode 7 .
- the third electrode 8 is electrically connected to the second semiconductor layer 4 .
- the third electrode 8 is joined to the second semiconductor layer 4 by ohmic junction.
- the third electrode 8 is a drain electrode.
- the first insulating film 6 is a film including oxygen.
- the first insulating film 6 is provided between the first electrode 10 and the inner wall of the hole 4 a and between the first electrode 10 and the second electrode 7 .
- the first insulating film 6 is provided spaced from the third electrode 8 . That is, a region where the first insulating film 6 is not provided is present between an end 6 a of the first insulating film 6 on the third electrode 8 side and the third electrode 8 .
- the second insulating film 5 is a film including nitrogen.
- the second insulating film 5 is provided in contact with the second semiconductor layer 4 between the first electrode 10 and the third electrode 8 .
- Silicon nitride SiN x
- SiN x Silicon nitride
- the first electrode 10 , the second electrode 7 , and the third electrode 8 each are provided in a plurality and extend in one direction.
- the second electrode 7 and the third electrode 8 are alternately arranged and connected to the respective pads P 2 and P 3 on the sides opposite to each other.
- the second electrode 7 and the third electrode 8 extend from the respective pads P 2 and P 3 in a comb teeth configuration and are alternately arranged.
- the first electrode 10 is placed between the second electrode 7 and the third electrode 8 adjacent to each other.
- the plurality of first electrodes 10 are electrically connected to a pad P 1 on one side.
- first electrode 10 is placed in a position near to the second electrode 7 between the second electrode 7 and the third electrode 8 .
- the space between the first electrode 10 and the third electrode 8 is wider than the space between the first electrode 10 and the second electrode 7 .
- a configuration is formed in which a plurality of elements (field effect transistors) are connected in parallel corresponding to such a layout of electrodes.
- a region around an element region S in which the plurality of elements are formed forms an element isolation region IS.
- a voltage is applied to the first electrode (gate electrode) 10 to control the current flowing between the third electrode 8 and the second electrode 7 in a state where the second electrode (source electrode) 7 is grounded and a plus voltage is applied to the third electrode (drain electrode) 8 .
- the interface between the first semiconductor layer (undoped GaN) 3 , which is a channel through which a current flows, and the second semiconductor layer (undoped AlGaN) 4 is divided by the recess structure 9 provided between the third electrode 8 and the second electrode 7 .
- the second electrode 7 By applying a voltage positive with respect to the second electrode 7 to the first electrode 10 , electrons can be generated at the interface between the first semiconductor layer 3 and the second insulating film 5 .
- a drain current can be passed from the third electrode 8 to the second electrode 7 . That is, the nitride semiconductor device 110 according to the embodiment achieves normally OFF operation.
- the interface between the first insulating film 6 that is, for example, SiO 2 and the first semiconductor layer 3 that is, for example, GaN is used as the interface that forms a channel below the first electrode 10 .
- SiO 2 as the first insulating film 6 that forms a gate insulating film, an element having low ON resistance and high reliability can be provided as compared to the case of using SiN x as the gate insulating film.
- SiO 2 has a large band gap and is suitable as an insulating film of electrons to GaN. Furthermore, SiO 2 is a stable amorphous material and easily provides a film with a small number of trapping centers. Thereby, the reliability in regard to the gate insulating film of the transistor can be improved, and operational stability in the ON state of the transistor can be obtained.
- the second insulating film 5 that is SiN x is provided on the surface of the second semiconductor layer 4 that is AlGaN in a state of contact with the second semiconductor layer 4 .
- the second insulating film 5 functions as a protection film of the second semiconductor layer 4 .
- the oxygen of the SiO 2 may diffuse into the film of SiN x .
- heat treatment for example, is needed. During the heating, the oxygen of the SiO 2 may diffuse into the film of SiN x .
- the film thickness may be thickened.
- the film thickness of the SiN x is thickened, due to the stress caused by the difference in the coefficient of thermal expansion with the film of SiO 2 stacked with the film of SiN x , the surface of the nitride semiconductor is degraded and a decrease in reliability may be caused.
- the first insulating film 6 that is SiN x is provided spaced from the third electrode 8 . That is, SiO 2 is not superposed on SiN x in a region R 1 that is the space between the first insulating film 6 and the third electrode 8 .
- SiO 2 that may cause oxidation of the surface of the second semiconductor layer (nitride semiconductor) 4 is not provided in the region R 1 , the oxidation of the surface of the second semiconductor layer 4 resulting from the oxygen of SiO 2 can be suppressed.
- the trapping of electrons at the surface of the nitride semiconductor that may cause current collapse mainly occurs in a region at some distance from the recess structure 9 , in particular on the drain side (the third electrode 8 side) of the end of the first electrode 10 that is the gate electrode.
- a configuration is employed in which the first insulating film (SiO 2 ) 6 is not provided on the second insulating film (SiN x ) 5 between the first electrode 10 and the third electrode 8 , and the end of the first insulating film 6 exists as close as possible to the end of the first electrode 10 .
- the ON resistance increase due to current collapse can be suppressed to a minimum.
- the nitride semiconductor device 110 can achieve the following: (1) by using SiO 2 as the first insulating film 6 that forms the gate insulating film, the ON resistance is reduced and the reliability is improved; (2) by protecting the second semiconductor layer 4 with the second insulating film 5 that is SiN x , the breakdown voltage is increased; and (3) by not superposing SiO 2 on SiN x in the region R 1 , the ON resistance increase due to current collapse is suppressed to a minimum.
- FIG. 3 is a schematic cross-sectional view illustrating the configuration of another nitride semiconductor device according to the first embodiment.
- a nitride semiconductor device 111 differs from the nitride semiconductor device 110 shown in FIG. 1 in the respect of an end 61 a of a first insulating film 61 on the third electrode 8 side.
- the end 61 a on the third electrode 8 side is not provided on the second insulating film 5 .
- the first insulating film 61 is formed along the inner wall of the hole 4 a, and on the third electrode 8 side, the first insulating film 61 is provided so as to stand up along the inner wall and not to cover the second insulating film 5 .
- the space between the first insulating film 61 and the third electrode 8 is configured to be larger than that of the nitride semiconductor device 110 . That is, in a region R 2 that is the space between the first insulating film 61 and the third electrode 8 , the first insulating film 61 is not provided on the second insulating film 5 . The region R 2 is larger than the region R 1 . Therefore, in the nitride semiconductor device 111 , the oxidation of the surface of the second semiconductor layer (nitride semiconductor) 4 resulting from the oxygen of the SiO 2 that is the first insulating film 61 can be more effectively suppressed than in the nitride semiconductor device 110 .
- FIG. 4 is a schematic cross-sectional view illustrating the configuration of still another nitride semiconductor device according to the first embodiment.
- a nitride semiconductor device 112 differs from the nitride semiconductor device 110 shown in FIG. 1 in the shape of the end of the first electrode 10 .
- an end 10 a of the first electrode 10 of the nitride semiconductor device 112 is provided so as to extend to the third electrode 8 side and cover the end 6 a of the first insulating film 6 .
- the shield effect of the electric field can be exhibited for the end 6 a of the first insulating film 6 .
- the electric field applied between the first electrode 10 that is the gate electrode and the third electrode 8 that is the drain electrode is concentrated at the end 10 a of the first electrode 10 on the third electrode 8 side.
- the end 6 a of the first insulating film 6 on the third electrode 8 side is configured to exist on the second insulating film 5 .
- the oxygen of the SiO 2 may affect the second semiconductor layer 4 that is a nitride semiconductor, and if a high electric field is applied to here, current collapse may be caused.
- the end 10 a of the first electrode 10 is formed so as to cover the outside of the end 6 a of the first insulating film 6 like the nitride semiconductor device 112 .
- the surface of the second semiconductor layer 4 that has experienced the effect of oxidation due to the first insulating film 6 that is SiO 2 is shielded by the first electrode 10 , and protected from a high electric field.
- the factor in current collapse can be suppressed.
- FIG. 5 is a schematic cross-sectional view illustrating the configuration of still another nitride semiconductor device according to the first embodiment.
- a nitride semiconductor device 113 differs from the nitride semiconductor device 110 shown in FIG. 1 in that a fourth electrode 11 is added.
- the fourth electrode 11 is provided so as to cover the end 6 a of the first insulating film 6 . Although the fourth electrode 11 is spaced from the first electrode 10 that is the gate electrode, both are electrically connected.
- the fourth electrode 11 By providing the fourth electrode 11 thus configured, the surface of the second semiconductor layer 4 that has experienced the effect of oxidation due to the first insulating film 6 that is SiO 2 is shielded by the fourth electrode 11 , and protected from a high electric field. Thereby, the factor in current collapse can be suppressed.
- FIG. 6 is a schematic cross-sectional view illustrating the configuration of a nitride semiconductor device according to a second embodiment.
- a nitride semiconductor device 120 includes the first semiconductor layer 3 , the second semiconductor layer 4 , the first electrode 10 , the second electrode 7 , the third electrode 8 , the first insulating film 6 , and the second insulating film 5 .
- the first insulating film 6 is provided in contact with the second semiconductor layer 4 between the first electrode 10 and the second electrode 7 .
- An insulating film provided between the first electrode 10 that is the gate electrode and the second electrode 7 that is the source electrode influences the operating characteristics of the nitride semiconductor device 120 . For example, the hysteresis of the drain current to the gate voltage is influenced.
- the influence of the hysteresis mentioned above can be suppressed as compared to the case of SiN x .
- a nitride semiconductor device 130 according to the third embodiment differs from the nitride semiconductor device 110 shown in FIG. 1 in the respect of the insulating film between the first electrode 10 and the second electrode 7 .
- the first insulating film 6 provided between the first electrode 10 and the second electrode 7 is provided in contact with the second semiconductor layer 4 .
- the effects of (1) to (3) mentioned above can be obtained similarly to the nitride semiconductor device 110 by using SiO 2 as the first insulating film 6 that forms the gate insulating film, protecting the second semiconductor layer 4 with the second insulating film 5 that is SiN x , and not superposing SiO 2 on SiN x in the region R 1 .
- the nitride semiconductor device 130 since the first insulating film 6 provided between the first electrode 10 and the second electrode 7 is provided in contact with the second semiconductor layer 4 , similar effects to the nitride semiconductor device 120 can be obtained. That is, the influence of the hysteresis of the operating characteristics (the drain current to the gate voltage) of the nitride semiconductor device 130 can be suppressed.
- a fourth embodiment is a method for manufacturing the nitride semiconductor devices 110 , 111 , 112 , and 113 according to the first embodiment.
- a method for manufacturing the nitride semiconductor device 112 is described as an example.
- FIG. 8A to FIG. 9C are schematic cross-sectional views describing an example of the method for manufacturing the nitride semiconductor device 112 sequentially.
- the buffer layer 2 is formed on the support substrate 1 , and the first semiconductor layer 3 and the second semiconductor layer 4 are formed thereon.
- the first semiconductor layer 3 is, for example, GaN.
- the second semiconductor layer 4 is, for example, AlGaN.
- the first semiconductor layer 3 and the second semiconductor layer 4 are sequentially stacked using, for example, an MOCVD (metal organic chemical vapor deposition) method.
- the second insulating film 5 has a thickness of, for example, approximately 10 nanometers (nm) to 20 nm.
- openings are formed in the positions in the second insulating film 5 where the second electrode 7 and the third electrode 8 will be formed.
- the opening is formed by, for example, performing wet etching on the second insulating film 5 .
- parts of the second insulating film 5 , the second semiconductor layer 4 , and the first semiconductor layer 3 are etched to form the hole 4 a.
- the second insulating film 5 made of SiN x is removed by, for example, wet etching, and the second semiconductor layer 4 that is AlGaN and the first semiconductor layer 3 that is GaN are removed by, for example, dry etching.
- SiO 2 that is the first insulating film 6 is formed over the entire surface of the support substrate 1 .
- the SiO 2 that is the first insulating film 6 is formed by, for example, CVR (chemical vapor reaction).
- the first insulating film 6 is formed on the inner wall of the hole 4 a and on the second insulating film 5 .
- the etching of the first insulating film 6 is performed.
- the first insulating film 6 is removed in the position where the second electrode 7 will be formed and in the region from the position where the third electrode 8 will be formed to the position of the hole 4 a.
- the first insulating film 6 that is SiO 2 is removed by, for example, wet etching.
- PDA post-deposition annealing
- heat treatment for example, heat treatment of 900° C. and about 10 minutes is performed. This stabilizes the interface between the SiO 2 that is the first insulating film 6 and the nitride semiconductor (GaN or AlGaN).
- the second electrode 7 and the third electrode 8 are formed in the respective positions where the second semiconductor layer 4 is exposed.
- the third electrode 8 is formed on one side as viewed from the hole 4 a
- the second electrode 7 is formed on the other side as viewed from the hole 4 a.
- the second electrode 7 and the third electrode 8 are joined to the second semiconductor layer 4 by ohmic junction by, for example, heat treatment of 650° C. and approximately 15 seconds.
- the second electrode 7 functions as the source electrode
- the third electrode 8 functions as the drain electrode.
- an element isolation region (not shown) is formed around the element region.
- the first electrode 10 is formed in the hole 4 a.
- the first electrode 10 is formed in the hole 4 a via the first insulating film 6 .
- the recess structure 9 is formed.
- the first electrode 10 functions as the gate electrode.
- the nitride semiconductor device 112 is completed in which the first insulating film 6 that is SiN x is provided spaced from the third electrode 8 on the third electrode 8 side of the recess structure 9 .
- the nitride semiconductor devices 110 , 111 , and 113 can be manufactured by similar processes other than that the shape to be etched of the first electrode 10 shown in FIG. 9C is altered.
- a fifth embodiment is a method for manufacturing the nitride semiconductor device 120 according to the second embodiment.
- FIG. 10A to FIG. 11C are schematic cross-sectional views describing an example of the method for manufacturing the nitride semiconductor device 120 sequentially.
- the buffer layer 2 is formed on the support substrate 1 , and the first semiconductor layer 3 and the second semiconductor layer 4 are formed thereon.
- the first semiconductor layer 3 is, for example, GaN.
- the second semiconductor layer 4 is, for example, AlGaN.
- SiN x that is the second insulating film 5 is formed on the second semiconductor layer 4 .
- the second insulating film 5 has a thickness of, for example, approximately 10 nm to 20 nm.
- openings are formed in the position where the third electrode 8 will be formed and in the region from the position where the hole 4 a will be formed to the position where the second electrode 7 will be formed.
- the opening is formed by, for example, performing wet etching on the second insulating film 5 .
- part of the exposed portion of the second semiconductor layer 4 and part of the first semiconductor layer 3 are etched to form the hole 4 a.
- the second semiconductor layer 4 that is AlGaN and the first semiconductor layer 3 that is GaN are removed by, for example, dry etching.
- SiO 2 that is the first insulating film 6 is formed over the entire surface of the support substrate 1 .
- the SiO 2 that is the first insulating film 6 is formed by, for example, CVR.
- the first insulating film 6 is formed on the inner wall of the hole 4 a, on the second insulating film 5 on one side of the hole 4 a, and on the second semiconductor layer 4 on the other side of the hole 4 a.
- the etching of the first insulating film 6 is performed.
- the first insulating film 6 is removed in the position where the second electrode 7 will be formed and the position where the third electrode 8 will be formed.
- the first insulating film 6 that is SiO 2 is removed by, for example, wet etching.
- PDA treatment is performed.
- heat treatment for example, heat treatment of 900° C. and approximately 10 minutes is performed. This stabilizes the interface between the SiO 2 that is the first insulating film 6 and the nitride semiconductor (GaN or AlGaN).
- the second electrode 7 and the third electrode 8 are formed in the respective positions where the second semiconductor layer 4 is exposed.
- the third electrode 8 is formed on one side as viewed from the hole 4 a
- the second electrode 7 is formed on the other side as viewed from the hole 4 a.
- the second electrode 7 and the third electrode 8 are joined to the second semiconductor layer 4 by ohmic junction by, for example, heat treatment of 650° C. and approximately 15 seconds.
- the second electrode 7 functions as the source electrode
- the third electrode 8 functions as the drain electrode.
- an element isolation region (not shown) is formed around the element region.
- the first electrode 10 is formed in the hole 4 a.
- the first electrode 10 is formed in the hole 4 a via the first insulating film 6 .
- the first electrode 10 functions as the gate electrode. This completes the nitride semiconductor device 120 in which the second semiconductor layer 4 is in contact with the first insulating film 6 that is SiO 2 between the first electrode 10 and the second electrode 7 .
- a sixth embodiment is a method for manufacturing the nitride semiconductor device 130 according to the third embodiment.
- FIGS. 12A to 12C are schematic cross-sectional views describing an example of the method for manufacturing the nitride semiconductor device 130 sequentially.
- the etching of the first insulating film 6 is performed.
- the first insulating film 6 is removed in the position where the second electrode 7 will be formed and in the region from the position where the third electrode 8 will be formed to the position of the hole 4 a.
- the first insulating film 6 that is SiO 2 is removed by, for example, wet etching.
- PDA treatment is performed.
- heat treatment for example, heat treatment of 900° C. and approximately 10 minutes is performed. This stabilizes the interface between the SiO 2 that is the first insulating film 6 and the nitride semiconductor (GaN or AlGaN).
- the second electrode 7 and the third electrode 8 are formed in the respective positions where the second semiconductor layer 4 is exposed.
- the third electrode 8 is formed on one side as viewed from the hole 4 a
- the second electrode 7 is formed on the other side as viewed from the hole 4 a.
- the second electrode 7 and the third electrode 8 are joined to the second semiconductor layer 4 by ohmic junction by, for example, heat treatment of 650° C. and approximately 15 seconds.
- the second electrode 7 functions as the source electrode
- the third electrode 8 functions as the drain electrode.
- an element isolation region (not shown) is formed around the element region.
- the first electrode 10 is formed in the hole 4 a.
- the first electrode 10 is formed in the hole 4 a via the first insulating film 6 .
- the first electrode 10 functions as the gate electrode. This completes the nitride semiconductor device 130 .
- a material that allows a nitride semiconductor to grow epitaxially is sufficient to be used for the support substrate 1 .
- GaN, SiC, sapphire, and Si are given as the support substrate 1 .
- the conduction type of the semiconductor layer may be one of an n type, a p type, and a semi-insulating type.
- any material that can function as a base body during the growth of the first semiconductor layer 3 is sufficient to be used for the material thereof.
- an AlN layer that has grown at low temperature and a superlattice structure in which AlGaN and GaN are alternately stacked may be used.
- undoped GaN is used as the material of the first semiconductor layer 3 .
- the main purpose of the first semiconductor layer 3 is to generate two-dimensional electron gas at the interface of the first semiconductor layer 3 on the second semiconductor layer 4 side and cause the generated two-dimensional electron gas to function as the channel. Therefore, the material of the first semiconductor layer 3 is not limited to undoped materials but a material doped to an n type or p type may be used.
- a nitride semiconductor such as AlGaN, InAlN, and InAlGaN may be used for the first semiconductor layer 3 .
- the first semiconductor layer 3 does not need to be a layer made of a single material but may be a stacked structure such as GaN and AlGaN, and GaN and p-type
- undoped AlGaN is used as the material of the second semiconductor layer 4 .
- the main function of the second semiconductor layer 4 is to generate two-dimensional electron gas at the interface of the first semiconductor layer 3 on the second semiconductor layer 4 side. Therefore, the material of the second semiconductor layer 4 is not limited to undoped materials but a material doped to an n type or p type may be used.
- a nitride semiconductor such as InAlN and InAlGaN may be used for the second semiconductor layer 4 . It is sufficient to satisfy the condition of having a band gap wider than that of the first semiconductor layer 3 .
- the second semiconductor layer 4 does not need to be a layer made of a single material but may be a stacked structure such as AlGaN, GaN and AlGaN, and AlGaN and AlN.
- the second semiconductor layer 4 may be used as the bottom.
- either of the recess structures 9 may be used to the extent that the function of a normally OFF element is obtained.
- SiO 2 is used as an example of the first insulating film 6 in all the embodiments described above, AlO x , MgO, and HfO 2 are possible and also an oxide film including nitrogen such as SiON and HfSiON, which are common in Si devices, is possible.
- SiN x is used as an example of the second insulating film 5 , also a high resistance nitride semiconductor such as AlN and BN is possible.
- the nitride semiconductor device and the method for manufacturing the same according to the embodiment can achieve low ON resistance, high breakdown voltage, and high reliability.
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Abstract
According to one embodiment, a nitride semiconductor device includes a first semiconductor layer, a second semiconductor layer, a first electrode, a second electrode, a third electrode, a first insulating film and a second insulating film. The first semiconductor layer includes a nitride semiconductor. The second semiconductor layer is provided on the first layer, includes a nitride semiconductor, and includes a hole. The first electrode is provided in the hole. The second electrode is provided on the second layer. The third electrode is provided on the second layer so that the first electrode is disposed between the third and second electrodes. The first insulating film is provided between the first electrode and an inner wall of the hole and between the first and second electrodes, and is provided spaced from the third electrode. The second insulating film is provided in contact with the second layer between the first and third electrodes.
Description
- This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2011-064254, filed on Mar. 23, 2011; the entire contents of which are incorporated herein by reference.
- Embodiments described herein relate generally to a nitride semiconductor device and a method for manufacturing the same.
- Devices using new materials taking the place of silicon, such as silicon carbide (SiC) and nitride semiconductors, are developed these days.
- As an example, it is known that if a hetero-junction in which gallium nitride (GaN), which is a nitride semiconductor, and an aluminum gallium nitride (AlGaN) are stacked is formed, two-dimensional electron gas (2DEG) is generated at the interface of the hetero-junction. A hetero-structure field effect transistor (HFET) unitizing the 2DEG as a channel has the properties of high breakdown voltage and low ON resistance.
- Here, as a structure to achieve normally OFF operation in the GaN-based HFET, there is a structure in which a recess structure is formed and a gate electrode is formed via an insulating film. There is a need for further improvement to obtain low ON resistance, high breakdown voltage, and high reliability in such a nitride semiconductor device.
-
FIG. 1 is a schematic cross-sectional view illustrating the configuration of a nitride semiconductor device according to a first embodiment, -
FIG. 2 is a schematic plan view of the nitride semiconductor device according to the first embodiment, -
FIG. 3 is a schematic cross-sectional view illustrating the configuration of another nitride semiconductor device according to the first embodiment, -
FIG. 4 is a schematic cross-sectional view illustrating the configuration of still another nitride semiconductor device according to the first embodiment, -
FIG. 5 is a schematic cross-sectional view illustrating the configuration of still another nitride semiconductor device according to the first embodiment, -
FIG. 6 is a schematic cross-sectional view illustrating the configuration of a nitride semiconductor device according to a second embodiment, -
FIG. 7 is a schematic cross-sectional view illustrating the configuration of a nitride semiconductor device according to a third embodiment, -
FIG. 8A toFIG. 9C are schematic cross-sectional views describing an example of a manufacturing method sequentially, -
FIG. 10A toFIG. 11C are schematic cross-sectional views describing an example of a manufacturing method sequentially, and -
FIGS. 12A to 12C are schematic cross-sectional views describing an example of a manufacturing method sequentially. - In general, according to one embodiment, a nitride semiconductor device includes a first semiconductor layer, a second semiconductor layer, a first electrode, a second electrode, a third electrode, a first insulating film and a second insulating film. The first semiconductor layer includes a nitride semiconductor. The second semiconductor layer is provided on the first semiconductor layer, includes a nitride semiconductor having a band gap wider than a band gap of the first semiconductor layer, and includes a hole. The first electrode is provided in the hole. The second electrode is provided on the second semiconductor layer and electrically connected to the second semiconductor layer. The third electrode is provided on the second semiconductor layer so that the first electrode is disposed between the third electrode and the second electrode. The third electrode is electrically connected to the second semiconductor layer. The first insulating film includes oxygen, is provided between the first electrode and an inner wall of the hole and between the first electrode and the second electrode, and is provided spaced from the third electrode. The second insulating film includes nitrogen and is provided in contact with the second semiconductor layer between the first electrode and the third electrode.
- In general, according to one embodiment, a method is disclosed for manufacturing a nitride semiconductor device. The method can include forming a first semiconductor layer including a nitride semiconductor on a support substrate, and forming a second semiconductor layer having a band gap wider than a band gap of the first semiconductor layer and including a nitride semiconductor on the first semiconductor layer. The method can include forming a second insulating film including nitrogen on the second semiconductor layer. The method can include forming a hole by removing parts of the second insulating film and the second semiconductor layer. The method can include forming a first insulating film including oxygen so as to cover an inner wall of the hole and the second insulating film. The method can include removing at least a part of the first insulating film on one side as viewed from the hole. The method can include forming a second electrode electrically connected to the second semiconductor layer on another side as viewed from the hole, and forming a third electrode electrically connected to the second semiconductor layer on the one side as viewed from the hole spaced from the first insulating film. In addition, the method can include forming a first electrode in the hole via the first insulating film.
- Various embodiments will be described hereinafter with reference to the accompanying drawings.
- The drawings are schematic or conceptual; and the relationships between the thickness and width of portions, the proportional coefficients of sizes among portions, etc., are not necessarily the same as the actual values thereof. Further, the dimensions and proportional coefficients may be illustrated differently among drawings, even for identical portions.
- In the specification of the application and the drawings, components similar to those described in regard to a drawing thereinabove are marked with the same reference numerals, and a detailed description is omitted as appropriate.
-
FIG. 1 is a schematic cross-sectional view illustrating the configuration of a nitride semiconductor device according to a first embodiment. -
FIG. 2 is a schematic plan view of the nitride semiconductor device according to the first embodiment. -
FIG. 1 is a schematic cross-sectional view taken in the direction of arrows A-A′ shown inFIG. 2 . - As shown in
FIG. 1 , anitride semiconductor device 110 according to the first embodiment includes afirst semiconductor layer 3, asecond semiconductor layer 4, afirst electrode 10, asecond electrode 7, athird electrode 8, a firstinsulating film 6, and a secondinsulating film 5. - In the
nitride semiconductor device 110, thefirst semiconductor layer 3 is formed via abuffer layer 2 formed on asupport substrate 1. Here, for convenience of description, the direction from thefirst semiconductor layer 3 toward thesecond semiconductor layer 4 is referred to as upward (the upper side), the opposite direction is referred to as downward (the lower side). - The
first semiconductor layer 3 includes a nitride semiconductor. Thesecond semiconductor layer 4 is provided on thefirst semiconductor layer 3. Thesecond semiconductor layer 4 includes a nitride semiconductor having a band gap wider than the band gap of thefirst semiconductor layer 3. Thesecond semiconductor layer 4 includes ahole 4 a. Thehole 4 a illustrated inFIG. 1 reaches thefirst semiconductor layer 3. - Here, in the specification, “nitride semiconductor” includes all semiconductors expressed by the chemical formula of BαInβAlγGa1-α-β-γN (0≦α≦1, 0≦β≦1, 0≦γ≦1,0≦α+β+γ≦1) in which composition ratios α, β, and γ are changed in the respective ranges. Furthermore, in the chemical formula mentioned above, those further including a group V element other than N (nitrogen), those further including various elements added in order to control various properties such as the conduction type, and those further including various elements unintendedly included are also included in the “nitride semiconductor.”
- In the embodiment, GaN and AlGaN, which are group III-V nitride semiconductors, are used as examples of the nitride semiconductor.
- The
nitride semiconductor device 110 is a normally OFF field effect transistor. - An undoped AlXGa1-XN (0≦X≦1) is used for the
first semiconductor layer 3. Here, “undoped” refers to a state where intended impurity doping is not performed. As an example, in the embodiment, thefirst semiconductor layer 3 is GaN. Thefirst semiconductor layer 3 functions as a channel layer. - An undoped AlYGa1-YN (0≦Y≦1, X≦Y) is used for the
second semiconductor layer 4. As an example, in the embodiment, thesecond semiconductor layer 4 is AlGaN with an Al content of 25 percent (%). The band gap of thesecond semiconductor layer 4 that is undoped AlGaN is wider than the band gap of thefirst semiconductor layer 3 that is undoped - GaN
- The
first electrode 10 is provided in thehole 4 a. The firstinsulating film 6 is provided between thefirst electrode 10 and the inner wall of thehole 4 a. In other words, thefirst electrode 10 has a portion embedded in thehole 4 a via the first insulatingfilm 6. Arecess structure 9 is formed by embedding thefirst electrode 10 in thehole 4 a via the first insulatingfilm 6. In the embodiment, thefirst electrode 10 is a gate electrode. In this example, the gate electrode is a MIS (metal insulator semiconductor) gate electrode. - The
second electrode 7 is provided on thesecond semiconductor layer 4 and electrically connected to thesecond semiconductor layer 4. In other words, thesecond electrode 7 is joined to thesecond semiconductor layer 4 by ohmic junction. In the embodiment, thesecond electrode 7 is a source electrode. - The
third electrode 8 is provided on thesecond semiconductor layer 4 so that thefirst electrode 10 is disposed between thethird electrode 8 and thesecond electrode 7. Thethird electrode 8 is electrically connected to thesecond semiconductor layer 4. In other words, thethird electrode 8 is joined to thesecond semiconductor layer 4 by ohmic junction. In the embodiment, thethird electrode 8 is a drain electrode. - The first
insulating film 6 is a film including oxygen. The firstinsulating film 6 is provided between thefirst electrode 10 and the inner wall of thehole 4 a and between thefirst electrode 10 and thesecond electrode 7. The firstinsulating film 6 is provided spaced from thethird electrode 8. That is, a region where the first insulatingfilm 6 is not provided is present between anend 6 a of the first insulatingfilm 6 on thethird electrode 8 side and thethird electrode 8. - Silicon oxide (SiO2), for example, is used for the first insulating
film 6. - The second
insulating film 5 is a film including nitrogen. The secondinsulating film 5 is provided in contact with thesecond semiconductor layer 4 between thefirst electrode 10 and thethird electrode 8. - Silicon nitride (SiNx), for example, is used for the second
insulating film 5. - As shown in
FIG. 2 , thefirst electrode 10, thesecond electrode 7, and thethird electrode 8 each are provided in a plurality and extend in one direction. Thesecond electrode 7 and thethird electrode 8 are alternately arranged and connected to the respective pads P2 and P3 on the sides opposite to each other. In other words, thesecond electrode 7 and thethird electrode 8 extend from the respective pads P2 and P3 in a comb teeth configuration and are alternately arranged. Thefirst electrode 10 is placed between thesecond electrode 7 and thethird electrode 8 adjacent to each other. The plurality offirst electrodes 10 are electrically connected to a pad P1 on one side. - In the example shown in
FIG. 2 , foursecond electrodes 7 aligned parallel and threethird electrodes 8 aligned parallel are disposed in mutual spaces. Thefirst electrode 10 is placed in a position near to thesecond electrode 7 between thesecond electrode 7 and thethird electrode 8. In other words, the space between thefirst electrode 10 and thethird electrode 8 is wider than the space between thefirst electrode 10 and thesecond electrode 7. - A configuration is formed in which a plurality of elements (field effect transistors) are connected in parallel corresponding to such a layout of electrodes. A region around an element region S in which the plurality of elements are formed forms an element isolation region IS.
- In the
nitride semiconductor device 110 thus configured, for example, a voltage is applied to the first electrode (gate electrode) 10 to control the current flowing between thethird electrode 8 and thesecond electrode 7 in a state where the second electrode (source electrode) 7 is grounded and a plus voltage is applied to the third electrode (drain electrode) 8. - As shown in
FIG. 1 , the interface between the first semiconductor layer (undoped GaN) 3, which is a channel through which a current flows, and the second semiconductor layer (undoped AlGaN) 4 is divided by therecess structure 9 provided between thethird electrode 8 and thesecond electrode 7. Thus, by applying a voltage positive with respect to thesecond electrode 7 to thefirst electrode 10, electrons can be generated at the interface between thefirst semiconductor layer 3 and the secondinsulating film 5. Thereby, a drain current can be passed from thethird electrode 8 to thesecond electrode 7. That is, thenitride semiconductor device 110 according to the embodiment achieves normally OFF operation. - In the
nitride semiconductor device 110 according to the embodiment, the interface between the first insulatingfilm 6 that is, for example, SiO2 and thefirst semiconductor layer 3 that is, for example, GaN is used as the interface that forms a channel below thefirst electrode 10. By using SiO2 as the first insulatingfilm 6 that forms a gate insulating film, an element having low ON resistance and high reliability can be provided as compared to the case of using SiNx as the gate insulating film. - That is, SiO2 has a large band gap and is suitable as an insulating film of electrons to GaN. Furthermore, SiO2 is a stable amorphous material and easily provides a film with a small number of trapping centers. Thereby, the reliability in regard to the gate insulating film of the transistor can be improved, and operational stability in the ON state of the transistor can be obtained.
- Furthermore, between the
first electrode 10 and thethird electrode 8, the secondinsulating film 5 that is SiNx is provided on the surface of thesecond semiconductor layer 4 that is AlGaN in a state of contact with thesecond semiconductor layer 4. Thereby, the secondinsulating film 5 functions as a protection film of thesecond semiconductor layer 4. By protecting thesecond semiconductor layer 4 with the secondinsulating film 5 that is SiNx, the breakdown voltage of thenitride semiconductor device 110 is increased. - Here, in the case where a stacked structure of SiNx and SiO2 is formed as an insulating film provided on the
second semiconductor layer 4 that is a nitride semiconductor, the oxygen of the SiO2 may diffuse into the film of SiNx. - For example, to stabilize the interface between the SiO2 that is the gate insulating film and the nitride semiconductor (GaN or AlGaN) that is the
second semiconductor layer 4, heat treatment of 600° C. or more, for example, is needed. During the heating, the oxygen of the SiO2 may diffuse into the film of SiNx. - If the oxygen diffuses into the film of SiNx, the surface of the nitride semiconductor in contact with the film of SiNx may be oxidized. In view of this, to sufficiently protect the nitride semiconductor with the insulating film of SiNx, the film thickness may be thickened. However, if the film thickness of the SiNx is thickened, due to the stress caused by the difference in the coefficient of thermal expansion with the film of SiO2 stacked with the film of SiNx, the surface of the nitride semiconductor is degraded and a decrease in reliability may be caused.
- In the embodiment, on the
third electrode 8 side of therecess structure 9, the first insulatingfilm 6 that is SiNx is provided spaced from thethird electrode 8. That is, SiO2 is not superposed on SiNx in a region R1 that is the space between the first insulatingfilm 6 and thethird electrode 8. In other words, since SiO2 that may cause oxidation of the surface of the second semiconductor layer (nitride semiconductor) 4 is not provided in the region R1, the oxidation of the surface of thesecond semiconductor layer 4 resulting from the oxygen of SiO2 can be suppressed. - Here, the trapping of electrons at the surface of the nitride semiconductor that may cause current collapse mainly occurs in a region at some distance from the
recess structure 9, in particular on the drain side (thethird electrode 8 side) of the end of thefirst electrode 10 that is the gate electrode. In view of this, a configuration is employed in which the first insulating film (SiO2) 6 is not provided on the second insulating film (SiNx) 5 between thefirst electrode 10 and thethird electrode 8, and the end of the first insulatingfilm 6 exists as close as possible to the end of thefirst electrode 10. Thereby, the ON resistance increase due to current collapse can be suppressed to a minimum. - Thus, the
nitride semiconductor device 110 according to the embodiment can achieve the following: (1) by using SiO2 as the first insulatingfilm 6 that forms the gate insulating film, the ON resistance is reduced and the reliability is improved; (2) by protecting thesecond semiconductor layer 4 with the secondinsulating film 5 that is SiNx, the breakdown voltage is increased; and (3) by not superposing SiO2 on SiNx in the region R1, the ON resistance increase due to current collapse is suppressed to a minimum. -
FIG. 3 is a schematic cross-sectional view illustrating the configuration of another nitride semiconductor device according to the first embodiment. - As shown in
FIG. 3 , anitride semiconductor device 111 differs from thenitride semiconductor device 110 shown inFIG. 1 in the respect of anend 61 a of a first insulatingfilm 61 on thethird electrode 8 side. - In the first insulating
film 61 of thenitride semiconductor device 111, theend 61 a on thethird electrode 8 side is not provided on the secondinsulating film 5. The first insulatingfilm 61 is formed along the inner wall of thehole 4 a, and on thethird electrode 8 side, the first insulatingfilm 61 is provided so as to stand up along the inner wall and not to cover the secondinsulating film 5. - In the
nitride semiconductor device 111 thus configured, the space between the first insulatingfilm 61 and thethird electrode 8 is configured to be larger than that of thenitride semiconductor device 110. That is, in a region R2 that is the space between the first insulatingfilm 61 and thethird electrode 8, the first insulatingfilm 61 is not provided on the secondinsulating film 5. The region R2 is larger than the region R1. Therefore, in thenitride semiconductor device 111, the oxidation of the surface of the second semiconductor layer (nitride semiconductor) 4 resulting from the oxygen of the SiO2 that is the first insulatingfilm 61 can be more effectively suppressed than in thenitride semiconductor device 110. -
FIG. 4 is a schematic cross-sectional view illustrating the configuration of still another nitride semiconductor device according to the first embodiment. - As shown in
FIG. 4 , anitride semiconductor device 112 differs from thenitride semiconductor device 110 shown inFIG. 1 in the shape of the end of thefirst electrode 10. - More specifically, an
end 10 a of thefirst electrode 10 of thenitride semiconductor device 112 is provided so as to extend to thethird electrode 8 side and cover theend 6 a of the first insulatingfilm 6. - By such a structure of the
first electrode 10, the shield effect of the electric field can be exhibited for theend 6 a of the first insulatingfilm 6. - That is, the electric field applied between the
first electrode 10 that is the gate electrode and thethird electrode 8 that is the drain electrode is concentrated at theend 10 a of thefirst electrode 10 on thethird electrode 8 side. On the other hand, theend 6 a of the first insulatingfilm 6 on thethird electrode 8 side is configured to exist on the secondinsulating film 5. At theend 6 a of the first insulatingfilm 6, the oxygen of the SiO2 may affect thesecond semiconductor layer 4 that is a nitride semiconductor, and if a high electric field is applied to here, current collapse may be caused. - In view of this, the
end 10 a of thefirst electrode 10 is formed so as to cover the outside of theend 6 a of the first insulatingfilm 6 like thenitride semiconductor device 112. Thereby, the surface of thesecond semiconductor layer 4 that has experienced the effect of oxidation due to the first insulatingfilm 6 that is SiO2 is shielded by thefirst electrode 10, and protected from a high electric field. Thus, the factor in current collapse can be suppressed. -
FIG. 5 is a schematic cross-sectional view illustrating the configuration of still another nitride semiconductor device according to the first embodiment. - As shown in
FIG. 5 , anitride semiconductor device 113 differs from thenitride semiconductor device 110 shown inFIG. 1 in that afourth electrode 11 is added. - More specifically, the
fourth electrode 11 is provided so as to cover theend 6 a of the first insulatingfilm 6. Although thefourth electrode 11 is spaced from thefirst electrode 10 that is the gate electrode, both are electrically connected. - By providing the
fourth electrode 11 thus configured, the surface of thesecond semiconductor layer 4 that has experienced the effect of oxidation due to the first insulatingfilm 6 that is SiO2 is shielded by thefourth electrode 11, and protected from a high electric field. Thereby, the factor in current collapse can be suppressed. -
FIG. 6 is a schematic cross-sectional view illustrating the configuration of a nitride semiconductor device according to a second embodiment. - As shown in
FIG. 6 , anitride semiconductor device 120 according to the second embodiment includes thefirst semiconductor layer 3, thesecond semiconductor layer 4, thefirst electrode 10, thesecond electrode 7, thethird electrode 8, the first insulatingfilm 6, and the secondinsulating film 5. - In the
nitride semiconductor device 120 according to the second embodiment, the first insulatingfilm 6 is provided in contact with thesecond semiconductor layer 4 between thefirst electrode 10 and thesecond electrode 7. - An insulating film provided between the
first electrode 10 that is the gate electrode and thesecond electrode 7 that is the source electrode influences the operating characteristics of thenitride semiconductor device 120. For example, the hysteresis of the drain current to the gate voltage is influenced. - By using the first insulating
film 6 that is SiO2 as the insulating film in contact with thesecond semiconductor layer 4 between thefirst electrode 10 and thesecond electrode 7 like the embodiment, the influence of the hysteresis mentioned above can be suppressed as compared to the case of SiNx. - As shown in
FIG. 7 , anitride semiconductor device 130 according to the third embodiment differs from thenitride semiconductor device 110 shown inFIG. 1 in the respect of the insulating film between thefirst electrode 10 and thesecond electrode 7. - More specifically, in the
nitride semiconductor device 130, the first insulatingfilm 6 provided between thefirst electrode 10 and thesecond electrode 7 is provided in contact with thesecond semiconductor layer 4. - In the
nitride semiconductor device 130 thus configured, the effects of (1) to (3) mentioned above can be obtained similarly to thenitride semiconductor device 110 by using SiO2 as the first insulatingfilm 6 that forms the gate insulating film, protecting thesecond semiconductor layer 4 with the secondinsulating film 5 that is SiNx, and not superposing SiO2 on SiNx in the region R1. - Furthermore, in the
nitride semiconductor device 130, since the first insulatingfilm 6 provided between thefirst electrode 10 and thesecond electrode 7 is provided in contact with thesecond semiconductor layer 4, similar effects to thenitride semiconductor device 120 can be obtained. That is, the influence of the hysteresis of the operating characteristics (the drain current to the gate voltage) of thenitride semiconductor device 130 can be suppressed. - A fourth embodiment is a method for manufacturing the
nitride semiconductor devices nitride semiconductor device 112 is described as an example. -
FIG. 8A toFIG. 9C are schematic cross-sectional views describing an example of the method for manufacturing thenitride semiconductor device 112 sequentially. - First, as shown in
FIG. 8A , thebuffer layer 2 is formed on thesupport substrate 1, and thefirst semiconductor layer 3 and thesecond semiconductor layer 4 are formed thereon. Thefirst semiconductor layer 3 is, for example, GaN. Thesecond semiconductor layer 4 is, for example, AlGaN. Thefirst semiconductor layer 3 and thesecond semiconductor layer 4 are sequentially stacked using, for example, an MOCVD (metal organic chemical vapor deposition) method. - SiNx that is the second
insulating film 5 is formed on thesecond semiconductor layer 4. The secondinsulating film 5 has a thickness of, for example, approximately 10 nanometers (nm) to 20 nm. - Next, as shown in
FIG. 8B , openings are formed in the positions in the secondinsulating film 5 where thesecond electrode 7 and thethird electrode 8 will be formed. The opening is formed by, for example, performing wet etching on the secondinsulating film 5. - Next, as shown in
FIG. 8C , parts of the secondinsulating film 5, thesecond semiconductor layer 4, and thefirst semiconductor layer 3 are etched to form thehole 4 a. The secondinsulating film 5 made of SiNx is removed by, for example, wet etching, and thesecond semiconductor layer 4 that is AlGaN and thefirst semiconductor layer 3 that is GaN are removed by, for example, dry etching. - Next, as shown in
FIG. 8D , SiO2 that is the first insulatingfilm 6 is formed over the entire surface of thesupport substrate 1. The SiO2 that is the first insulatingfilm 6 is formed by, for example, CVR (chemical vapor reaction). The firstinsulating film 6 is formed on the inner wall of thehole 4 a and on the secondinsulating film 5. - Next, as shown in
FIG. 9A , the etching of the first insulatingfilm 6 is performed. In the etching, the first insulatingfilm 6 is removed in the position where thesecond electrode 7 will be formed and in the region from the position where thethird electrode 8 will be formed to the position of thehole 4 a. The firstinsulating film 6 that is SiO2 is removed by, for example, wet etching. After the first insulatingfilm 6 is etched, PDA (post-deposition annealing) treatment is performed. As the PDA treatment, for example, heat treatment of 900° C. and about 10 minutes is performed. This stabilizes the interface between the SiO2 that is the first insulatingfilm 6 and the nitride semiconductor (GaN or AlGaN). - Next, as shown in
FIG. 9B , thesecond electrode 7 and thethird electrode 8 are formed in the respective positions where thesecond semiconductor layer 4 is exposed. Thethird electrode 8 is formed on one side as viewed from thehole 4 a, and thesecond electrode 7 is formed on the other side as viewed from thehole 4 a. Thesecond electrode 7 and thethird electrode 8 are joined to thesecond semiconductor layer 4 by ohmic junction by, for example, heat treatment of 650° C. and approximately 15 seconds. Thesecond electrode 7 functions as the source electrode, and thethird electrode 8 functions as the drain electrode. - After the
second electrode 7 and thethird electrode 8 are formed, an element isolation region (not shown) is formed around the element region. - Then, as shown in
FIG. 9C , thefirst electrode 10 is formed in thehole 4 a. Thefirst electrode 10 is formed in thehole 4 a via the first insulatingfilm 6. Thereby, therecess structure 9 is formed. Thefirst electrode 10 functions as the gate electrode. Thereby, thenitride semiconductor device 112 is completed in which the first insulatingfilm 6 that is SiNx is provided spaced from thethird electrode 8 on thethird electrode 8 side of therecess structure 9. Thenitride semiconductor devices first electrode 10 shown inFIG. 9C is altered. - A fifth embodiment is a method for manufacturing the
nitride semiconductor device 120 according to the second embodiment. -
FIG. 10A toFIG. 11C are schematic cross-sectional views describing an example of the method for manufacturing thenitride semiconductor device 120 sequentially. - First, as shown in
FIG. 10A , thebuffer layer 2 is formed on thesupport substrate 1, and thefirst semiconductor layer 3 and thesecond semiconductor layer 4 are formed thereon. Thefirst semiconductor layer 3 is, for example, GaN. Thesecond semiconductor layer 4 is, for example, AlGaN. SiNx that is the secondinsulating film 5 is formed on thesecond semiconductor layer 4. The secondinsulating film 5 has a thickness of, for example, approximately 10 nm to 20 nm. - Next, as shown in
FIG. 10B , in the secondinsulating film 5, openings are formed in the position where thethird electrode 8 will be formed and in the region from the position where thehole 4 a will be formed to the position where thesecond electrode 7 will be formed. The opening is formed by, for example, performing wet etching on the secondinsulating film 5. - Next, as shown in
FIG. 10C , part of the exposed portion of thesecond semiconductor layer 4 and part of thefirst semiconductor layer 3 are etched to form thehole 4 a. Thesecond semiconductor layer 4 that is AlGaN and thefirst semiconductor layer 3 that is GaN are removed by, for example, dry etching. - Next, as shown in
FIG. 10D , SiO2 that is the first insulatingfilm 6 is formed over the entire surface of thesupport substrate 1. The SiO2 that is the first insulatingfilm 6 is formed by, for example, CVR. The firstinsulating film 6 is formed on the inner wall of thehole 4 a, on the secondinsulating film 5 on one side of thehole 4 a, and on thesecond semiconductor layer 4 on the other side of thehole 4 a. - Next, as shown in
FIG. 11A , the etching of the first insulatingfilm 6 is performed. In the etching, the first insulatingfilm 6 is removed in the position where thesecond electrode 7 will be formed and the position where thethird electrode 8 will be formed. The firstinsulating film 6 that is SiO2 is removed by, for example, wet etching. After the first insulatingfilm 6 is etched, PDA treatment is performed. As the PDA treatment, for example, heat treatment of 900° C. and approximately 10 minutes is performed. This stabilizes the interface between the SiO2 that is the first insulatingfilm 6 and the nitride semiconductor (GaN or AlGaN). - Next, as shown in
FIG. 11B , thesecond electrode 7 and thethird electrode 8 are formed in the respective positions where thesecond semiconductor layer 4 is exposed. Thethird electrode 8 is formed on one side as viewed from thehole 4 a, and thesecond electrode 7 is formed on the other side as viewed from thehole 4 a. Thesecond electrode 7 and thethird electrode 8 are joined to thesecond semiconductor layer 4 by ohmic junction by, for example, heat treatment of 650° C. and approximately 15 seconds. Thesecond electrode 7 functions as the source electrode, and thethird electrode 8 functions as the drain electrode. - After the
second electrode 7 and thethird electrode 8 are formed, an element isolation region (not shown) is formed around the element region. - Then, as shown in
FIG. 11C , thefirst electrode 10 is formed in thehole 4 a. Thefirst electrode 10 is formed in thehole 4 a via the first insulatingfilm 6. Thefirst electrode 10 functions as the gate electrode. This completes thenitride semiconductor device 120 in which thesecond semiconductor layer 4 is in contact with the first insulatingfilm 6 that is SiO2 between thefirst electrode 10 and thesecond electrode 7. - A sixth embodiment is a method for manufacturing the
nitride semiconductor device 130 according to the third embodiment. -
FIGS. 12A to 12C are schematic cross-sectional views describing an example of the method for manufacturing thenitride semiconductor device 130 sequentially. - In the manufacturing method according to the sixth embodiment, the processes illustrated in
FIGS. 10A to 10D of the manufacturing method according to the fifth embodiment are similarly performed, and therefore a description is given from the subsequent process. - Next, as shown in
FIG. 12A , the etching of the first insulatingfilm 6 is performed. In the etching, the first insulatingfilm 6 is removed in the position where thesecond electrode 7 will be formed and in the region from the position where thethird electrode 8 will be formed to the position of thehole 4 a. The firstinsulating film 6 that is SiO2 is removed by, for example, wet etching. After the first insulatingfilm 6 is etched, PDA treatment is performed. As the PDA treatment, for example, heat treatment of 900° C. and approximately 10 minutes is performed. This stabilizes the interface between the SiO2 that is the first insulatingfilm 6 and the nitride semiconductor (GaN or AlGaN). - Next, as shown in
FIG. 12B , thesecond electrode 7 and thethird electrode 8 are formed in the respective positions where thesecond semiconductor layer 4 is exposed. Thethird electrode 8 is formed on one side as viewed from thehole 4 a, and thesecond electrode 7 is formed on the other side as viewed from thehole 4 a. Thesecond electrode 7 and thethird electrode 8 are joined to thesecond semiconductor layer 4 by ohmic junction by, for example, heat treatment of 650° C. and approximately 15 seconds. Thesecond electrode 7 functions as the source electrode, and thethird electrode 8 functions as the drain electrode. - After the
second electrode 7 and thethird electrode 8 are formed, an element isolation region (not shown) is formed around the element region. - Then, as shown in
FIG. 12C , thefirst electrode 10 is formed in thehole 4 a. Thefirst electrode 10 is formed in thehole 4 a via the first insulatingfilm 6. Thefirst electrode 10 functions as the gate electrode. This completes thenitride semiconductor device 130. - In all the embodiments described above, a material that allows a nitride semiconductor to grow epitaxially is sufficient to be used for the
support substrate 1. GaN, SiC, sapphire, and Si, for example, are given as thesupport substrate 1. The conduction type of the semiconductor layer may be one of an n type, a p type, and a semi-insulating type. In regard to thebuffer layer 2 between thesupport substrate 1 and thefirst semiconductor layer 3, any material that can function as a base body during the growth of thefirst semiconductor layer 3 is sufficient to be used for the material thereof. For example, an AlN layer that has grown at low temperature and a superlattice structure in which AlGaN and GaN are alternately stacked may be used. - In all the embodiments described above, undoped GaN is used as the material of the
first semiconductor layer 3. However, the main purpose of thefirst semiconductor layer 3 is to generate two-dimensional electron gas at the interface of thefirst semiconductor layer 3 on thesecond semiconductor layer 4 side and cause the generated two-dimensional electron gas to function as the channel. Therefore, the material of thefirst semiconductor layer 3 is not limited to undoped materials but a material doped to an n type or p type may be used. In addition to GaN, also a nitride semiconductor such as AlGaN, InAlN, and InAlGaN may be used for thefirst semiconductor layer 3. Furthermore, thefirst semiconductor layer 3 does not need to be a layer made of a single material but may be a stacked structure such as GaN and AlGaN, and GaN and p-type - GaN.
- In all the embodiments described above, undoped AlGaN is used as the material of the
second semiconductor layer 4. However, the main function of thesecond semiconductor layer 4 is to generate two-dimensional electron gas at the interface of thefirst semiconductor layer 3 on thesecond semiconductor layer 4 side. Therefore, the material of thesecond semiconductor layer 4 is not limited to undoped materials but a material doped to an n type or p type may be used. In addition to AlGaN, also a nitride semiconductor such as InAlN and InAlGaN may be used for thesecond semiconductor layer 4. It is sufficient to satisfy the condition of having a band gap wider than that of thefirst semiconductor layer 3. Furthermore, thesecond semiconductor layer 4 does not need to be a layer made of a single material but may be a stacked structure such as AlGaN, GaN and AlGaN, and AlGaN and AlN. - Furthermore, although a structure that penetrates through the
second semiconductor layer 4 and uses thefirst semiconductor layer 3 as the bottom is illustrated as therecess structure 9 in the embodiments described above, thesecond semiconductor layer 4 may be used as the bottom. In any embodiment, either of therecess structures 9 may be used to the extent that the function of a normally OFF element is obtained. - Furthermore, although SiO2 is used as an example of the first insulating
film 6 in all the embodiments described above, AlOx, MgO, and HfO2 are possible and also an oxide film including nitrogen such as SiON and HfSiON, which are common in Si devices, is possible. Moreover, although SiNx is used as an example of the secondinsulating film 5, also a high resistance nitride semiconductor such as AlN and BN is possible. - As described above, the nitride semiconductor device and the method for manufacturing the same according to the embodiment can achieve low ON resistance, high breakdown voltage, and high reliability.
- Hereinabove, embodiments and variations thereof are described. However, the invention is not limited to these examples. For example, one skilled in the art may appropriately make additions, removals, and design changes of components to the embodiments or the variations described above, and may appropriately combine features of the embodiments; such variations also are included in the scope of the invention to the extent that the spirit of the invention is included.
- While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.
Claims (17)
1. A nitride semiconductor device comprising:
a first semiconductor layer including a nitride semiconductor;
a second semiconductor layer provided on a part of the first semiconductor layer, including a nitride semiconductor having a band gap wider than a band gap of the first semiconductor layer, and including a hole;
a first electrode provided in the hole;
a second electrode provided on the second semiconductor layer and electrically connected to the second semiconductor layer;
a third electrode provided on the second semiconductor layer so that the first electrode is disposed between the third electrode and the second electrode, the third electrode being electrically connected to the second semiconductor layer;
a first insulating film including oxygen, provided between the first electrode and an inner wall of the hole and between the first electrode and the second electrode, and provided spaced from the third electrode; and
a second insulating film including nitrogen and provided in contact with the second semiconductor layer between the first electrode and the third electrode.
2. The device according to claim 1 , wherein the first insulating film is in contact with the second semiconductor layer.
3. The device according to claim 1 , wherein the first electrode is provided so as to cover an end of the first insulating film on a side of the third electrode.
4. The device according to claim 1 , further comprising a fourth electrode electrically connected to the first electrode and covering an end of the first insulating film on a side of the third electrode.
5. The device according to claim 1 , wherein the first insulating film includes silicon oxide.
6. The device according to claim 1 , wherein the second insulating film includes silicon nitride.
7. The device according to claim 1 , wherein
the first semiconductor layer includes AlXGa1-XN (0≦X≦1) and
the second semiconductor layer includes AlYGa1-YN (0≦Y≦1, X≦Y).
8. The device according to claim 1 , wherein the first semiconductor layer includes a channel in a normally OFF transistor.
9. The device according to claim 1 , wherein
the first electrode is a gate electrode of a transistor,
the second electrode is a source electrode of the transistor, and
the third electrode is a drain electrode of the transistor.
10. A nitride semiconductor device comprising:
a first semiconductor layer including a nitride semiconductor;
a second semiconductor layer provided on a part of the first semiconductor layer, including a nitride semiconductor having a band gap wider than a band gap of the first semiconductor layer, and including a hole;
a first electrode provided in the hole;
a second electrode provided on the second semiconductor layer and electrically connected to the second semiconductor layer;
a third electrode provided on the second semiconductor layer so that the first electrode is disposed between the third electrode and the second electrode, the third electrode being electrically connected to the second semiconductor layer;
a first insulating film including oxygen and provided in contact with the second semiconductor layer between the first electrode and an inner wall of the hole and between the first electrode and the second electrode; and
a second insulating film including nitrogen and provided in contact with the second semiconductor layer between the first electrode and the third electrode.
11. The device according to claim 10 , wherein the first insulating film includes silicon oxide.
12. The device according to claim 10 , wherein the second insulating film includes silicon nitride.
13. The device according to claim 10 , wherein the first semiconductor layer includes AlXGa1-XN (0≦X≦1) and
the second semiconductor layer includes AlYGa1-YN (0≦Y≦1, X≦Y).
14. The device according to claim 10 , wherein the first semiconductor layer includes a channel in a normally OFF transistor.
15. The device according to claim 10 , wherein
the first electrode is a gate electrode of a transistor,
the second electrode is a source electrode of the transistor, and
the third electrode is a drain electrode of the transistor.
16. A method for manufacturing a nitride semiconductor device comprising:
forming a first semiconductor layer including a nitride semiconductor on a support substrate and forming a second semiconductor layer having a band gap wider than a band gap of the first semiconductor layer and including a nitride semiconductor on the first semiconductor layer;
forming a second insulating film including nitrogen on the second semiconductor layer;
forming a hole by removing parts of the second insulating film and the second semiconductor layer;
forming a first insulating film including oxygen so as to cover an inner wall of the hole and the second insulating film;
removing at least a part of the first insulating film on one side as viewed from the hole;
forming a second electrode electrically connected to the second semiconductor layer on another side as viewed from the hole and forming a third electrode electrically connected to the second semiconductor layer on the one side as viewed from the hole spaced from the first insulating film; and
forming a first electrode in the hole via the first insulating film.
17. A method for manufacturing a nitride semiconductor device comprising:
forming a first semiconductor layer including a nitride semiconductor on a support substrate and forming a second semiconductor layer having a band gap wider than a band gap of the first semiconductor layer and including a nitride semiconductor on the first semiconductor layer;
forming a second insulating film including nitrogen on the second semiconductor layer;
forming a hole by removing a part of the second insulating film and removing a part of a portion of the second semiconductor layer where the second insulating film is removed;
forming a first insulating film including oxygen so as to cover an inner wall of the hole, the second insulating film provided on one side as viewed from the hole, and the second semiconductor layer provided on another side as viewed from the hole;
forming a third electrode electrically connected to the second semiconductor layer on the one side as viewed from the hole and forming a second electrode electrically connected to the second semiconductor layer on the another side as viewed from the hole; and
forming a first electrode in the hole via the first insulating film.
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CN110911490A (en) * | 2018-09-18 | 2020-03-24 | 株式会社东芝 | Semiconductor device with a plurality of semiconductor chips |
US11626513B2 (en) * | 2018-12-13 | 2023-04-11 | Intel Corporation | Antenna gate field plate on 2DEG planar FET |
WO2021123382A1 (en) * | 2019-12-20 | 2021-06-24 | Thales | Hemt transistor |
Also Published As
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JP2012204351A (en) | 2012-10-22 |
CN102694019A (en) | 2012-09-26 |
JP5597581B2 (en) | 2014-10-01 |
CN102694019B (en) | 2015-04-22 |
US9412857B2 (en) | 2016-08-09 |
US20150123141A1 (en) | 2015-05-07 |
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