CN113328007A - Novel silicon carbide ultrathin n-type ohmic contact layer n-i-p type extreme deep ultraviolet detector and preparation method thereof - Google Patents
Novel silicon carbide ultrathin n-type ohmic contact layer n-i-p type extreme deep ultraviolet detector and preparation method thereof Download PDFInfo
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- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by at least one potential-jump barrier or surface barrier, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
- H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier
- H01L31/105—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier the potential barrier being of the PIN type
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- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
- H01L31/0264—Inorganic materials
- H01L31/028—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic System
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- H—ELECTRICITY
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- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System
- H01L31/1812—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System including only AIVBIV alloys, e.g. SiGe
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Abstract
The invention discloses a novel silicon carbide ultrathin n-type ohmic contact layer n-i-p type extreme deep ultraviolet detector and a preparation method thereof, wherein the detector comprises a substrate, a p-type SiC highly-doped epitaxial layer, a p-type SiC low-doped epitaxial layer, an n-type SiC ultrathin highly-doped epitaxial layer and an n-type ohmic contact electrode which are sequentially connected from bottom to top, the p-type SiC highly-doped epitaxial layer is provided with the p-type ohmic contact electrode, the n-type ohmic contact electrode and the p-type ohmic contact electrode are both provided with metal conductive electrodes, and the thickness of the n-type SiC ultrathin highly-doped epitaxial layer is not more than 30 nm. The invention effectively avoids the strong absorption of EUV photons in a surface highly-doped p-type layer when the conventional ultraviolet detector with the conventional p-i-n structure is applied to EUV band detection, and effectively improves the quantum efficiency of the EUV band detector; meanwhile, the risk of the Schottky junction EUV detector in the aspects of irradiation stability and temperature stability when the Schottky junction EUV detector is applied to high-energy photon irradiation and high-temperature environment is effectively avoided.
Description
Technical Field
The invention relates to a novel silicon carbide (SiC) ultrathin n-type ohmic contact layer n-i-p type extreme deep ultraviolet (EUV) detector and a preparation method thereof, belonging to the technical field of photoelectric detection of semiconductor devices.
Background
In recent years, with the rapid development of integrated circuit manufacturing technology, the integrated circuit industry has formally entered the 7nm process line width era. The key to realizing large-scale and high-efficiency production of the 7nm process is 'the fifth generation EUV lithography machine adopting 13.5nm EUV light as an exposure light source', however, the technology is monopolized by ASML company in the Netherlands and blocked by the technology of Western countries, so that the localization and autonomy of the EUV lithography technology must be realized. An indispensable key component in the EUV lithography machine is an EUV detector, the EUV detector has numerous application scenarios in EUV lithography, such as light source power calibration (if EUV lithography is to be realized, the power of 250W at a central focus is required, and the EUV light intensity after multiple reflection losses is also required to be calibrated by the EUV detector), light source spectrum calibration (i.e. the light-emitting wavelength of the EUV light source is determined to be 13.5nm, which is directly related to the process line width of a product), light source stability monitoring (which requires the EUV detector to have long-range stability, which directly affects the product yield), and light spot position detection (since the EUV photon transmission depth is extremely shallow, the mask plate of the EUV lithography is required to be a reflective mirror surface, and the appearance and position of a reflective light spot both affect the integrated circuit processing precision). In summary, the performance of the EUV detector directly concerns the yield and productivity of the EUV lithography machine, and the development of a high-performance EUV detector is important for the research of the EUV lithography technology. In addition, the EUV detection technology, as a new emerging photoelectric detection technology in recent years, has a very wide application prospect in many scientific researches and industrial production fields such as plasma physics, satellite space environment monitoring and the like.
EUV detectors are mainly used for detecting short-wavelength, high-energy ultraviolet light in the wavelength range between 5-150 nm. Compared with the conventional visible light band and the conventional ultraviolet band, the EUV band has special properties. Firstly, the transmission depth of EUV photons in medium materials such as SiC and the like is extremely shallow, so that electron hole pairs generated by incident EUV photons are easily compounded by defect states at the surface/interface of a device, so that the external quantum efficiency of the device is extremely low, and a detection signal is weak; secondly, high-energy photon irradiation induces an external photoelectric effect and a thermal effect, which may cause degradation of the EUV detector performance. Therefore, combining EUV optical characteristics and problems faced by EUV lithography, EUV detectors need to meet the following performance requirements: the silicon (Si) -based detector has the advantages of surface junction, strong radiation resistance, excellent noise characteristic and good temperature stability, and the requirements are obviously difficult to achieve.
Compared with a Si-based EUV detector, the 4H-SiC device has the advantages of low leakage current, strong radiation resistance, good temperature stability, high visible light blindness and high thermal conductivity, and does not need to be additionally provided with a complex and expensive filter and cooling equipment, so that the 4H-SiC EUV detector has obvious advantages compared with the existing Si-based EUV detector. The SiC-based detector for EUV band detection at the present stage is mainly of a Schottky structure, and because EUV photons have the characteristic of high photon energy, positive vacancy is easily generated on the surface of a Schottky device due to EUV photon irradiation, so that the Schottky barrier height is reduced due to the image force effect, and the leakage current of the device is increased. Therefore, how to effectively improve the device stability of the EUV detector is one of the key scientific problems faced by the preparation of 4H-SiC-based EUV detectors.
Disclosure of Invention
The invention provides a novel SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector and a preparation method thereof, and aims to solve the problems that the detector is low in detection efficiency and poor in irradiation stability and temperature stability in an EUV band device.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
the utility model provides a novel ultra-thin n type ohmic contact layer n-i-p type extreme deep ultraviolet detector of carborundum, includes substrate, the high epitaxial layer that dopes of p type SiC, the ultra-thin epitaxial layer that dopes of n type SiC and n type ohmic contact electrode that from the bottom up meets in proper order, is equipped with p type ohmic contact electrode on the high epitaxial layer that dopes of p type SiC, all is equipped with metal conductive electrode on n type ohmic contact electrode and the p type ohmic contact electrode, and the ultra-thin epitaxial layer that dopes of n type SiC is less than 30nm in thickness.
The novel SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector is different from a p-i-n structure adopted by a conventional ultraviolet band detector and a Schottky structure adopted by a traditional EUV detector, the detector adopts an n-i-p structure with an ultrathin n-type ohmic contact layer, the loss of EUV photons in a thick p-type SiC highly-doped epitaxial layer on the surface of the device is effectively avoided, the incident EUV photons can effectively enter an active absorption region on the surface of the device, and the detection efficiency of the device in EUV bands, particularly in vacuum ultraviolet bands, is improved; in addition, the detector adopts a pn junction structure, the influence of high-energy photon irradiation and temperature change on a built-in electric field and leakage current of the device is small, compared with a Schottky structure, the leakage current is low, the temperature stability is good, the influence of temperature change and high-energy photon irradiation on the detection performance of the device is small, the application potential of long-time stable work in high-temperature and strong-radiation environments is achieved, and the irradiation stability and the temperature stability of the device can be effectively improved.
The p-type ohmic contact electrode is connected with a negative voltage in the test; the p-type SiC low-doped epitaxial layer is a structural layer for receiving incident photons, and the lower doping concentration enables the device to obtain a wider depletion region under low bias voltage even zero bias voltage; the n-type ohmic contact electrode is used for forming ohmic contact; the metal conductive electrode can effectively improve the current transmission and charge collection capability of the device, and is used for packaging a routing and grounding electrode in testing; and the passivation layer is used for device isolation.
In order to further improve the performance of the device, the substrate is made of SiC; the p-type SiC highly-doped epitaxial layer is made of SiC; the p-type SiC low-doped epitaxial layer is made of SiC; the n-type SiC ultrathin high-doping epitaxial layer is made of SiC.
In order to further improve the device performance, it is preferable that the doping concentration of the SiC substrate be 1 × 1018cm-3～1×1020cm-3More preferably 1X 1019cm-3(ii) a The doping concentration of the p-type SiC highly-doped epitaxial layer is more than 1 multiplied by 1018cm-3More preferably 1X 1018cm-3～1×1019cm-3More preferably 3X 1018cm-3(ii) a The doping concentration of the p-type SiC low-doped epitaxial layer is lower than 1 multiplied by 1016cm-3Further, furtherPreferably 1X 1014cm-3～1×1016cm-3More preferably 3X 1015cm-3(ii) a The doping concentration of the n-type SiC ultrathin highly-doped epitaxial layer is higher than 1 multiplied by 1017cm-3More preferably 1X 1018cm-3～2×1019cm-3More preferably 3X 1018cm-3。
The thickness of the n-type SiC ultrathin highly-doped epitaxial layer is less than 30nm, and more preferably 15 nm; the thickness of the p-type SiC low-doped epitaxial layer is more than 0.3 μm, more preferably more than 0.5 μm, and still more preferably 0.7 μm; the thickness of the p-type SiC highly-doped epitaxial layer is more than 1 mu m.
In order to ensure the comprehensive performance of the device, the metal conductive electrode is provided with a passivation layer along the periphery, and the material of the passivation layer is SiO2、Si3N4、Al2O3One or a mixture of two or more of AlN and other materials in any proportion; the p-type ohmic contact electrode is made of one or a mixture of more than two of materials such as nickel, titanium, aluminum, gold and the like in any proportion, and is preferably a nickel layer with the thickness of 100-300 nm; the n-type ohmic contact electrode is made of one of metal materials with low work functions such as titanium and aluminum, and the thickness of the n-type ohmic contact electrode is 3-10 nm; the total thickness of the metal conductive electrode is at least 1 mu m, preferably, the metal conductive electrode is composed of a titanium layer and a gold layer, the thickness of the titanium layer is 450-550 nm, and the thickness of the gold layer is 450-550 nm; the metal conductive electrode comprises a Pad area used for lead bonding and a line area used for conducting, wherein the side length of the Pad area is 90-110 mu m, and the width of the line area is 25-35 mu m, so that the packaging of the device is facilitated, and the conductivity and the area of an active area of the device can be better considered.
In order to further improve the quantum efficiency, the n-type ohmic contact electrode is of an incomplete filling structure, and the filling factor is 10-90%; preferably, the fill factor is 50%. Ohmic contact is formed between the incompletely filled n-type ohmic contact electrode and the n-type SiC ultrathin highly-doped epitaxial layer, an electron-hole pair excited by incident EUV photons is separated under the combined action of a pn junction built-in electric field and a drift electric field to form photoresponse current, so that the EUV photons are detected, and the influence of a large amount of loss and photoelectric effect of the incident photons on the metal electrode can be effectively avoided by the incompletely filled design of the n-type ohmic contact electrode. More preferably, the n-type ohmic contact electrode is in the form of a grid, a mesh, or a ring. When the n-type ohmic contact electrode is in a grid shape, the width of the strip electrode in the grid-shaped electrode is less than 5 micrometers, and the interval between two adjacent strip electrodes is less than 5 micrometers.
The principle of the scheme is as follows: incident EUV photons penetrate an n-type SiC ultrathin highly-doped epitaxial layer on the surface of the device and enter an active region of the device and are excited to generate electron-hole pairs, the photo-generated electron-hole pairs are separated under the combined action of a pn junction built-in electric field and a drift electric field, and electrons and holes are respectively collected by a cathode and an anode of the device to form photocurrent; for the grid-shaped and other semi-transparent n-type ohmic contact electrodes, under the action of reverse bias voltage or zero bias voltage, the n-type SiC ultrathin highly-doped epitaxial layer below the grid-shaped and other electrodes is used as a conducting layer to realize the transverse expansion of an electric field, so that the collection of carriers in an electrodeless region is realized; the design of the incomplete filling electrode structure can effectively reduce the reflection and absorption of incident photons on the surface of the metal electrode, and greatly improve the detection efficiency of the device.
In order to reduce the leakage of the device and improve the stability of the device, an oxide film is deposited in the electrode-free region, for example, when the n-type ohmic contact electrode is in a bar shape, the adjacent two bar-shaped electrodes are separated by the ultrathin oxide film. Preferably, the material of the oxide film is SiO2And the thickness is less than 5 nm.
The preparation method of the novel SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector comprises the following steps of sequentially connecting:
1) sequentially epitaxially growing a p-type SiC highly-doped epitaxial layer, a p-type SiC low-doped epitaxial layer and an n-type SiC ultrathin highly-doped epitaxial layer on the upper surface of the substrate; preferably, a p-type SiC highly-doped epitaxial layer, a p-type SiC lowly-doped epitaxial layer and an n-type SiC ultrathin highly-doped epitaxial layer are epitaxially grown on the upper surface of the substrate in a high-temperature Chemical Vapor Deposition (CVD) mode;
2) photoetching and etching the epitaxial wafer to form a p-type ohmic contact electrode window structure on the p-type SiC highly-doped epitaxial layer, and then performing sacrificial oxidation and corroding the oxide layer to reduce etching damage(ii) a Preferably, the surface of the epitaxial wafer is etched by adopting an inductively coupled plasma etching (ICP) method and then is placed in oxygen (O)2) Preparing a sacrificial oxide layer in an atmosphere;
3) depositing a passivation layer on the epitaxial wafer to further realize device isolation and reduce device leakage current; preferably, a passivation layer is deposited on the epitaxial wafer by adopting a Plasma Enhanced Chemical Vapor Deposition (PECVD) method or a Low Pressure Chemical Vapor Deposition (LPCVD) method;
4) spin-coating photoresist on the passivation layer, defining a p-type ohmic contact electrode window positioned on the p-type SiC high-doping epitaxial layer and an optical window positioned on the n-type SiC ultrathin high-doping epitaxial layer through exposure and development, corroding the passivation layer in a window area, and then carrying out dry oxygen oxidation to form a compact ultrathin oxide film in the window area; preferably, the in-situ oxidation adopts dry oxygen oxidation or wet oxygen oxidation; further preferably dry oxygen oxidation; the growth rate is strictly controlled, and a compact oxide film is formed. By forming the ultrathin oxide film, the surface state/interface state density of the device can be effectively reduced, the surface of the exposed SiC epitaxial layer is protected, and the transmission efficiency of incident EUV photons can be ensured;
5) spin-coating photoresist on the surface of the epitaxial wafer, removing an oxide film at the window position of a p-type ohmic contact electrode on the p-type SiC highly-doped epitaxial layer by wet etching according to a photoetching pattern obtained by exposure and development, depositing the p-type ohmic contact electrode at the window position by adopting a PVD (physical vapor deposition) mode, and then annealing at high temperature to form ohmic contact;
6) spin-coating photoresist on the surface of the epitaxial wafer, removing the ultrathin oxide film in an optical window area on the n-type SiC ultrathin high-doping epitaxial layer by wet etching according to a photoetching pattern obtained by exposure and development, depositing an n-type ohmic contact electrode in the optical window area, and then carrying out low-temperature annealing to form ohmic contact; preferably, an n-type ohmic contact electrode is deposited in the optical window area by adopting a PVD mode; the preferred low-temperature annealing process avoids the surface roughening of the ohmic electrode, reduces the diffusion of metal in the n-type SiC ultrathin high-doping epitaxial layer while reducing the contact resistivity of the ohmic contact surface;
7) and depositing metal conductive electrodes at the edge position of the n-type ohmic contact electrode and on the p-type ohmic contact electrode, and then performing secondary low-temperature annealing to eliminate damage in the device preparation process, thereby completing the preparation of the novel SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector. Preferably, the metal conductive electrode is deposited by PVD.
In order to prepare the incompletely filled electrode, step 6) is to etch off the ultrathin oxide film in the optical window area at intervals according to the photoetching pattern obtained by exposure and development, so that the ultrathin oxide film is reserved in part of the area on the optical window area, the rest area is the exposed SiC material, the n-type ohmic contact electrode is deposited in the part where the ultrathin oxide film is etched off in the optical window area, and after stripping, low-temperature annealing is carried out, so that the incompletely filled n-type ohmic contact electrode is formed.
The prior art is referred to in the art for techniques not mentioned in the present invention.
The novel SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector effectively avoids strong absorption of EUV photons in a surface highly-doped p-type layer when a conventional UV detector with a conventional p-i-n structure is applied to EUV band detection, and effectively improves the quantum efficiency of the EUV band detector; meanwhile, the risks of irradiation stability and temperature stability of the traditional Schottky junction EUV detector when the traditional Schottky junction EUV detector is applied to high-energy photon irradiation and high-temperature environments are effectively avoided.
Drawings
FIG. 1 is a flow chart of a method for preparing a novel silicon carbide ultrathin n-type ohmic contact layer n-i-p type extreme deep ultraviolet detector;
FIG. 2(a) is a schematic side view of a novel silicon carbide ultrathin n-type ohmic contact layer n-i-p type extreme deep ultraviolet detector in an embodiment of the present invention;
FIG. 2(b) is a schematic diagram of a partial top view structure of a novel silicon carbide ultrathin n-type ohmic contact n-i-p type extreme deep ultraviolet detector in an embodiment of the present invention;
FIG. 3 is a current-voltage characteristic curve of a novel silicon carbide ultrathin n-type ohmic contact layer n-i-p type extreme deep ultraviolet detector in example 1 of the present invention;
FIG. 4 is a quantum efficiency curve of a novel silicon carbide ultrathin n-type ohmic contact layer n-i-p type extreme deep ultraviolet detector (curve) ' of the invention) and a conventional p-i-n structure ultraviolet detector (curve) ' of the invention ' in the wavelength range of 50-100nm under a bias voltage of 0V in embodiment 1;
FIG. 5 is a quantum efficiency curve of a novel silicon carbide ultrathin n-type ohmic contact n-i-p type extreme deep ultraviolet detector in example 1 of the present invention under bias voltages of 0V and-10V in a wavelength range of 5-140 nm;
FIG. 6 is a dark current curve of a novel silicon carbide ultrathin n-type ohmic contact n-i-p type extreme deep ultraviolet detector (b) and a Schottky junction EUV detector (a) with the same size under a reverse bias voltage of 0-20V after irradiation for different durations in example 1 of the present invention;
FIG. 7 is a dark current curve of a novel silicon carbide ultrathin n-type ohmic contact n-i-p type extreme deep ultraviolet detector (b) and a Schottky junction EUV detector (a) with the same size under reverse bias voltage of 0-20V at different working temperatures in example 1 of the present invention;
in the figure, 1 is an n-type SiC substrate; 2 is a p-type SiC highly-doped epitaxial layer; 3 is a p-type SiC low-doped epitaxial layer; 4 is an n-type SiC ultrathin high-doping epitaxial layer; 5 is SiO2A passivation layer; 6 is an n-type ohmic contact electrode; 7 is a p-type ohmic contact electrode; 8 is a metal conductive electrode; 9 is an ultrathin oxide film.
Detailed Description
In order to better understand the present invention, the following examples are further provided to illustrate the present invention, but the present invention is not limited to the following examples.
Example 1
As shown in FIG. 2(a), the SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector comprises an n-type SiC substrate 1, a p-type SiC highly-doped epitaxial layer 2, a p-type SiC lowly-doped epitaxial layer 3, an n-type SiC ultrathin highly-doped epitaxial layer 4 and an n-type ohmic contact electrode 6 which are sequentially connected from bottom to top, wherein the p-type SiC highly-doped epitaxial layer 2 is provided with a p-type ohmic contact electrode 7, and the n-type ohmic contact electrode 6 and the p-type ohmic contact electrode 7 are both provided with SiO along the periphery2And metal conductive electrodes 8 are arranged on the passivation layer 5, the n-type ohmic contact electrode 6 and the p-type ohmic contact electrode 7. As shown in FIG. 2(b), the n-type ohmic contact electrode 6 is formed in a stripe shapeThe two adjacent strip electrodes are separated by an ultrathin oxide film 9, the width of each strip electrode is 4 mu m, and the width of each ultrathin oxide film is 4 mu m.
As shown in fig. 1, the device preparation process is as follows:
102, spin-coating photoresist on the n-type SiC ultrathin highly-doped epitaxial layer 4, defining a window through exposure and development, etching the surface of the epitaxial wafer by adopting an inductive coupling plasma etching technology, and under the protection action of a photoresist mask, etching the n-type SiC ultrathin highly-doped epitaxial layer 4 and the p-type SiC lowly-doped epitaxial layer 3 at the position of the window to expose the p-type SiC highly-doped epitaxial layer 2 to form a p-type ohmic contact electrode window and realize device isolation; then placing the SiC epitaxial wafer in O2Preparing sacrificial oxide layer in atmosphere, and oxidizing in-situ formed SiO2The layer is etched clean with Buffered Oxide Etchant (BOE) to reduce device surface damage.
103, depositing SiO with the thickness of 500nm on the n-type SiC ultrathin high-doping epitaxial layer and the p-type ohmic contact electrode window by adopting a PECVD method2And the passivation layer 5 is used for reducing a leakage path on the surface of the device and reducing the leakage current of the device.
106, spin-coating a photoresist on the surface of the epitaxial wafer, and removing the oxide film at the position of the optical window on the n-type SiC ultrathin highly-doped epitaxial layer 4 grown in the step 104 by wet etching according to a photoetching pattern obtained by exposure and development; and then, a semi-transparent Ti metal film with the thickness of 5nm is deposited at the position of the optical window by a PVD method, and the epitaxial wafer after metal deposition is placed into an annealing furnace for low-temperature annealing, so that an n-type ohmic contact electrode 6 is formed on the n-type SiC ultrathin high-doping epitaxial layer 4.
And 107, spin-coating photoresist on the front surface of the epitaxial wafer, forming a photoetching pattern of a metal conductive electrode on the edge position of the n-type ohmic contact electrode and the p-type ohmic contact electrode after photoetching and developing, sequentially depositing metal Ti/Au with the thickness of about 500/500nm through PVD (physical vapor deposition), stripping to form the metal conductive electrode 8, wherein the width of the metal conductive electrode is 30 microns, the side length of Pad of the metal conductive electrode is 100 microns, and performing secondary low-temperature annealing, so that damage in the device preparation process is reduced, the device stability is further improved, and the device leakage current is reduced.
And 108, splitting the wafer, dividing the epitaxial wafer into single devices, packaging the finished devices on the TO tube seat in a routing mode, carrying out further electro-optical test, connecting the p-type ohmic contact electrode 7 with a negative voltage in the test, and connecting the metal conductive electrode with a grounding electrode.
Compared with the conventional ultraviolet detector with the conventional p-i-n structure, the obtained SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector can effectively reduce the loss of incident EUV photons on a thick p-type layer on the surface of a device, and greatly improves the detection performance of the device; meanwhile, the risks of irradiation stability and temperature stability of the traditional Schottky junction EUV detector when the traditional Schottky junction EUV detector is applied to high-energy photon irradiation and high-temperature environments are effectively avoided. Incident EUV photons penetrate an n-type SiC ultrathin highly-doped epitaxial layer on the surface of the device and then enter an active region (p-type SiC lowly-doped epitaxial layer) of the device, electron-hole pairs excited by the EUV photons are separated under the combined action of an electric field and a drift electric field built in an n-i-p junction, and photo-generated electrons and holes are respectively collected by a cathode and an anode of the device to form photocurrent, so that the calibration of the incident light intensity is realized.
As can be seen from FIG. 3, the prepared SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector has excellent noise characteristics, and the leakage current of the prepared device is in the pA level under the room temperature condition and the-20V reverse bias voltage.
FIG. 4 is a quantum efficiency curve of the SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector and the conventional p-i-n structure ultraviolet detector manufactured in the above way under the bias voltage of 0V and in the wavelength range of 50-100 nm. As can be seen from FIG. 4, in the above wavelength band with the photon transmission depth of about 10-33nm, the quantum efficiency of the prepared SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector is far higher than that of a traditional p-i-n structure ultraviolet detector, which proves that the loss of incident EUV photons in a non-active absorption region on the surface layer of a device can be effectively reduced by applying the ultrathin n-type ohmic contact layer n-i-p type structure.
FIG. 5 is a quantum efficiency curve of the SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector prepared in the above way in the wavelength range of 5-140nm under bias voltages of 0V and-10V. As can be seen from fig. 5, the quantum efficiency manufactured as described above does not fluctuate substantially with the change of the bias voltage, which indicates that the device can effectively avoid the influence of ripples or stray signals in the circuit, and has superior detection performance and stability.
FIG. 6 shows that the SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector and the Schottky junction EUV detector are irradiated for different durationsDark current curve at reverse bias voltage of 0-20V. As can be seen from FIG. 6, the dark current of the Schottky junction EUV detector was changed from 10 to 10 after 12 hours of 13.5nm wavelength EUV light irradiation-12The magnitude is increased to 10-9The magnitude (see curve (a)) is small, and the leakage current of the SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector provided by the invention hardly rises (see curve (b)), which shows that the SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector provided by the invention has excellent irradiation stability.
FIG. 7 is a dark current curve of the SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector and a Schottky junction EUV detector with the same size under reverse bias voltage of 0-20V at different working temperatures. As can be seen from FIG. 7, the dark current of the Schottky junction EUV detector is controlled to be 5 × 10 within the range of 298K-423K-13Up to 5X 10-10Magnitude (see curve (a)), leakage current rises 1000 times; the leakage current value of the SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector is 1 multiplied by 10-12Up to 3X 10-11(see curve (b)), the leakage current only rises by a factor of 30. Meanwhile, the leakage current of the prepared SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector under 423K is only 6% of the leakage current of the Schottky junction EUV detector with the same size; the n-i-p type EUV detector with the SiC ultrathin n-type ohmic contact layer has excellent temperature stability.
Claims (8)
1. A novel silicon carbide ultrathin n-type ohmic contact layer n-i-p type extreme deep ultraviolet detector is characterized in that: the high-doping epitaxial layer is formed by sequentially connecting a substrate, a p-type SiC high-doping epitaxial layer, a p-type SiC low-doping epitaxial layer, an n-type SiC ultrathin high-doping epitaxial layer and an n-type ohmic contact electrode from bottom to top, wherein the p-type SiC high-doping epitaxial layer is provided with the p-type ohmic contact electrode, the n-type ohmic contact electrode and the p-type ohmic contact electrode are both provided with metal conductive electrodes, and the thickness of the n-type SiC ultrathin high-doping epitaxial layer is not more than 30 nm.
2. The novel silicon carbide ultra-thin n-type ohmic contact layer n-i-p type extreme deep ultraviolet detector as claimed in claim 1, wherein: of ultra-thin highly doped epitaxial layer of n-type SiCThe doping concentration is higher than 1 x 1017cm-3。
3. A novel silicon carbide ultra-thin n-type ohmic contact layer n-i-p type extreme ultraviolet detector as claimed in claim 1 or 2, wherein: the doping concentration of the p-type SiC low-doped epitaxial layer is lower than 1 multiplied by 1016cm-3The thickness of the p-type SiC low-doped epitaxial layer is more than 0.3 mu m.
4. A novel silicon carbide ultra-thin n-type ohmic contact layer n-i-p type extreme ultraviolet detector as claimed in claim 1 or 2, wherein: the doping concentration of the p-type SiC highly-doped epitaxial layer is more than 1 multiplied by 1018cm-3And the thickness of the p-type SiC highly-doped epitaxial layer is more than 1 mu m.
5. A novel silicon carbide ultra-thin n-type ohmic contact layer n-i-p type extreme ultraviolet detector as claimed in claim 1 or 2, wherein: the n-type ohmic contact electrode is an incomplete filling structure.
6. A novel SiC ultra-thin n-type ohmic contact layer n-i-p type EUV detector as claimed in claim 1 or 2, characterized in that: the substrate is made of SiC and has a doping concentration of 1 × 1018cm-3～1×1020cm-3(ii) a The metal conductive electrode is provided with a passivation layer along the periphery, and the passivation layer is made of SiO2、Si3N4、Al2O3Or AlN; the p-type ohmic contact electrode is made of at least one of nickel, titanium, aluminum or gold; the material of the n-type ohmic contact electrode is one of titanium or aluminum.
7. A novel SiC ultrathin n-type ohmic contact n-i-p type EUV detector as claimed in claim 6, characterized in that: the p-type ohmic contact electrode is a nickel layer; the metal conductive electrode comprises a titanium layer and a gold layer which are sequentially connected from bottom to top.
8. The method for preparing a novel SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector as claimed in any of claims 1 to 7, wherein: comprises the following steps that:
1) sequentially epitaxially growing a p-type SiC highly-doped epitaxial layer, a p-type SiC low-doped epitaxial layer and an n-type SiC ultrathin highly-doped epitaxial layer on the upper surface of the substrate;
2) etching a p-type ohmic contact electrode window, then carrying out sacrificial oxidation and corroding an oxide layer;
3) depositing a passivation layer on the n-type SiC ultrathin high-doping epitaxial layer and the p-type ohmic contact electrode window;
4) wet etching the passivation layer, defining a p-type ohmic contact electrode window and an optical window positioned on the n-type SiC ultrathin high-doping epitaxial layer, and then carrying out in-situ oxidation to form a compact oxidation film in a window area;
5) removing the oxide film in the window area of the p-type ohmic contact electrode by wet etching, depositing the p-type ohmic contact electrode, and then carrying out high-temperature annealing to form the p-type ohmic contact electrode;
6) removing the ultrathin oxide film in the optical window area by wet etching, depositing an n-type ohmic contact electrode, and then annealing at low temperature to form the n-type ohmic contact electrode;
7) and depositing metal conductive electrodes at the edge position of the n-type ohmic contact electrode and on the p-type ohmic contact electrode, then performing secondary low-temperature annealing, and repairing the damage of the device to obtain the novel SiC ultrathin n-type ohmic contact layer n-i-p type EUV detector.
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