JP2007329235A - Solid-state image sensing element and method for manufacturing the same - Google Patents

Solid-state image sensing element and method for manufacturing the same Download PDF

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JP2007329235A
JP2007329235A JP2006158341A JP2006158341A JP2007329235A JP 2007329235 A JP2007329235 A JP 2007329235A JP 2006158341 A JP2006158341 A JP 2006158341A JP 2006158341 A JP2006158341 A JP 2006158341A JP 2007329235 A JP2007329235 A JP 2007329235A
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charge transfer
transfer electrode
silicon nitride
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nitride film
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Kazuaki Igaki
和明 井垣
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Fujifilm Corp
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<P>PROBLEM TO BE SOLVED: To provide a solid-state image sensing element that can improve while defect and read characteristic, and also to provide a method for manufacturing the solid-state image sensing element. <P>SOLUTION: The solid-state image sensing element includes a semiconductor substrate 11, a photoelectric converter formed on the semiconductor substrate 11, a charge transfer 31 for transferring charges generated by the photoelectric converter, a first charge transfer electrode 17, and a second charge transfer electrode 21. In the method for manufacturing this solid-state image sensing element; a silicon oxide film 13, a silicon nitride film 14, and a silicon oxide film 15 are sequentially laminated on the semiconductor substrate 11 to form a gate insulating film 12. A part 16 where the silicon nitride film 14 is not provided is formed on the charge transfer 31, a first charge transfer electrode 17 is patterned, and an upper silicon nitride layer 18 is also formed on the part 16 extruded from the first charge transfer electrode 17. Thereafter, a second charge transfer electrode 21 is patterned. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、固体撮像素子及び固体撮像素子の製造方法に関する。   The present invention relates to a solid-state imaging device and a method for manufacturing the solid-state imaging device.

一般に、固体撮像素子は、シリコンなどの半導体基板に形成されたフォトダイオードなどの光電変換部と、前記光電変換部で生じた電荷を転送するための電荷転送電極とを備えた構成である。   In general, a solid-state imaging device includes a photoelectric conversion unit such as a photodiode formed on a semiconductor substrate such as silicon and a charge transfer electrode for transferring charges generated in the photoelectric conversion unit.

また、従来の固体撮像素子には、半導体基板と電荷転送電極との間に、第１酸化シリコン膜と、窒化シリコン膜と、第２酸化シリコン膜とを順に堆積してなるゲート絶縁膜を設けた構成のものがある。このような固体撮像素子では、電荷転送ゲートの電荷読み出し経路でホットキャリアが発生し、ゲート絶縁膜の窒化シリコン膜に、電荷がトラップされることに起因して読み出し電圧の経時劣化を引き起こしてしまうという問題があった。そこで、図４に示すように、半導体基板１上のゲート絶縁膜２を構成する、酸化シリコン膜３と、窒化シリコン膜４と、酸化シリコン膜５のうち、電荷がトラップされる箇所の窒化シリコン膜４を選択的にエッチングで除去した除去部６を形成することで読み出し電圧の経時劣化を抑制することを図っている（例えば、下記特許文献１から３参照）。図４において、７は第１電荷転送電極を示し、９は第２電荷転送電極を示し、８は層間絶縁膜を示している。ｔは電荷転送領域を示している。また、図５に示す固体撮像素子のように、半導体基板１上のゲート絶縁膜２を局所的に除去する構成のものがある。   Further, the conventional solid-state imaging device is provided with a gate insulating film formed by sequentially depositing a first silicon oxide film, a silicon nitride film, and a second silicon oxide film between the semiconductor substrate and the charge transfer electrode. There are things with different configurations. In such a solid-state imaging device, hot carriers are generated in the charge read path of the charge transfer gate, and the charge is trapped in the silicon nitride film of the gate insulating film, which causes deterioration of the read voltage over time. There was a problem. Therefore, as shown in FIG. 4, among the silicon oxide film 3, the silicon nitride film 4, and the silicon oxide film 5 constituting the gate insulating film 2 on the semiconductor substrate 1, the silicon nitride at the portion where charges are trapped. The removal portion 6 in which the film 4 is selectively removed by etching is formed to suppress deterioration with time of the read voltage (for example, see Patent Documents 1 to 3 below). In FIG. 4, 7 indicates a first charge transfer electrode, 9 indicates a second charge transfer electrode, and 8 indicates an interlayer insulating film. t indicates a charge transfer region. Further, there is a configuration in which the gate insulating film 2 on the semiconductor substrate 1 is locally removed as in the solid-state imaging device shown in FIG.

特許文献３は、特許文献２をさらに改良し、白キズの発生を防止することと、読み出し特性をより一層改善できる構造の固体撮像素子及びその製造方法に関するものである。   Patent Document 3 relates to a solid-state imaging device having a structure that can further improve Patent Document 2 to prevent the occurrence of white flaws and further improve readout characteristics, and a method for manufacturing the same.

特開２００６−３２５４７号公報JP 2006-32547 A 特開２００６−４１０２２号公報JP 2006-41022 A 特開２００１−４４４０７号公報JP 2001-44407 A

図４に示す固体撮像素子のように、ゲート絶縁膜２のうち窒化シリコン膜４を部分的に除去する構成では、第１電荷転送電極７と第２電荷転送電極９との間に層間絶縁膜８を形成するため、酸化工程を行う際に、半導体基板１と第１電荷転送電極７との境界部において、層間絶縁膜８が第１電荷転送電極７の底部側に入り込んだ状態で酸化されてしまう。このように、層間絶縁膜８が第１電荷転送電極７の底部側にオーバーハング状に入り込んだ部位を、断面視において、鳥の嘴状に見えることから、ゲートバーズビークともいう。この影響で、次の（i）から（iii）のような不具合が発生する。   In the configuration in which the silicon nitride film 4 is partially removed from the gate insulating film 2 as in the solid-state imaging device shown in FIG. 4, an interlayer insulating film is provided between the first charge transfer electrode 7 and the second charge transfer electrode 9. When the oxidation process is performed, the interlayer insulating film 8 is oxidized at the boundary between the semiconductor substrate 1 and the first charge transfer electrode 7 so as to enter the bottom side of the first charge transfer electrode 7. End up. As described above, the portion where the interlayer insulating film 8 enters the overhang shape on the bottom side of the first charge transfer electrode 7 is also referred to as a gate bird's beak because it looks like a bird cage in a cross-sectional view. Due to this influence, the following problems (i) to (iii) occur.

（i）電荷転送電極に印加した際の電界が、該電荷転送電極のエッジ部で本来加えるべき電界を加えることができず、電荷の読み出しを妨げる一つの要因となる。また、層間絶縁膜の厚さのばらつきに応じてゲートバーズビークの形状も変動して電荷の読み出し特性が不安定になる要因となる。
（ii）第１電荷転送電極と第２電荷転送電極との間に層間絶縁膜を形成する際の層間酸化時に生じるゲートバーズビークで応力が発生し、結晶欠陥が生じて白キズが増加する要因となる。
（iii）層間酸化時に、半導体基板の表面も酸化されて表面のボロン層が偏析により濃度が低下し、白キズの要因となる。 (I) The electric field applied to the charge transfer electrode cannot apply an electric field that should be originally applied at the edge portion of the charge transfer electrode, which is one factor that hinders reading of charges. In addition, the shape of the gate bird's beak varies according to the variation in the thickness of the interlayer insulating film, which causes the charge reading characteristics to become unstable.
(Ii) Factors in which stress is generated in the gate bird's beak generated during interlayer oxidation when an interlayer insulating film is formed between the first charge transfer electrode and the second charge transfer electrode, resulting in crystal defects and white defects increasing It becomes.
(Iii) During the interlayer oxidation, the surface of the semiconductor substrate is also oxidized, and the concentration of the boron layer on the surface is lowered due to segregation, which causes white scratches.

または、第１電荷転送電極と第２電荷転送電極との間の層間絶縁膜を熱酸化膜ではなく、ＣＶＤ法で形成する構造の場合には、層間酸化膜を全面エッチングしてサイドウォールを形成し、該サイドウォールを層間酸化膜として用いることもできる。このような構成において、図４に示す窒化シリコン膜を部分的に除去した構成と組み合わせた場合に、図５に示すように、第１電荷転送電極７のパターニングの合わせずれマージンを確保するため、第１電荷転送電極７から電荷転送部ｔ上にはみ出した部位をエッチング除去する。この除去の際に、半導体基板１の表面が露出し、露出した部位にエッチングダメージが発生して白キズが増加してしまう点で改善の余地があった。   Alternatively, in the case where the interlayer insulating film between the first charge transfer electrode and the second charge transfer electrode is formed not by a thermal oxide film but by a CVD method, the interlayer oxide film is entirely etched to form a sidewall. The sidewall can also be used as an interlayer oxide film. In such a configuration, when combined with the configuration in which the silicon nitride film shown in FIG. 4 is partially removed, as shown in FIG. 5, in order to secure a misalignment margin for patterning of the first charge transfer electrode 7, The portion protruding from the first charge transfer electrode 7 onto the charge transfer portion t is removed by etching. At the time of this removal, there is room for improvement in that the surface of the semiconductor substrate 1 is exposed, etching damage occurs in the exposed portion, and white scratches increase.

なお、特許文献１では、局所的に除去した箇所でシリコン基板が酸化されてしまい、応力発生や不純物の解析を引き起こすことや、電荷転送電極の底部でエッチング残りが発生してしまう点で改善の余地があった。   In addition, in patent document 1, a silicon substrate is oxidized in the location removed locally and causes analysis of stress generation and an impurity, and an etching residue generate | occur | produces in the bottom part of a charge transfer electrode. There was room.

本発明は、上記事情に鑑みてなされたもので、その目的は、白キズや読み出し特性を改善することができる固体撮像素子及び固体撮像素子の製造方法を提供することにある。   The present invention has been made in view of the above circumstances, and an object thereof is to provide a solid-state imaging device capable of improving white scratches and readout characteristics and a method for manufacturing the solid-state imaging device.

本発明の上記目的は、半導体基板と、前記半導体基板に形成された光電変換部と、前記光電変換部で生じた電荷を転送する電荷転送部と、第１電荷転送電極と、第２電荷転送電極とを備えた固体撮像素子の製造方法であって、前記半導体基板上に、酸化シリコン膜と、窒化シリコン膜と、酸化シリコン膜とを順に積層させてなるゲート絶縁膜が形成され、前記電荷転送部上に前記窒化シリコン膜を設けない除去部を形成し、前記第１電荷転送電極をパターン形成し、前記第１電荷転送電極からはみ出す前記除去部上に上層窒化シリコン膜を形成した後で、前記第２電荷転送電極をパターン形成することを特徴とする固体撮像素子の製造方法によって達成される。   The object of the present invention is to provide a semiconductor substrate, a photoelectric conversion unit formed on the semiconductor substrate, a charge transfer unit for transferring charges generated in the photoelectric conversion unit, a first charge transfer electrode, and a second charge transfer. A method of manufacturing a solid-state imaging device including an electrode, wherein a gate insulating film formed by sequentially stacking a silicon oxide film, a silicon nitride film, and a silicon oxide film is formed on the semiconductor substrate, and the charge After forming a removal portion without providing the silicon nitride film on the transfer portion, patterning the first charge transfer electrode, and forming an upper silicon nitride film on the removal portion protruding from the first charge transfer electrode This is achieved by a method of manufacturing a solid-state imaging device, wherein the second charge transfer electrode is patterned.

また、本発明の上記目的は、半導体基板と、前記半導体基板に形成された光電変換部と、前記光電変換部で生じた電荷を転送する電荷転送部と、第１電荷転送電極と、第２電荷転送電極とを備えた固体撮像素子であって、前記半導体基板上に、酸化シリコン膜と、窒化シリコン膜と、酸化シリコン膜とを順に積層させてなるゲート絶縁膜が形成され、前記電荷転送部上に前記窒化シリコン膜を設けない除去部が形成され、前記第１電荷転送電極からはみ出す前記除去部上に上層窒化シリコン膜が形成されていることを特徴とする固体撮像素子によって達成される。   In addition, the object of the present invention is to provide a semiconductor substrate, a photoelectric conversion unit formed on the semiconductor substrate, a charge transfer unit that transfers charges generated in the photoelectric conversion unit, a first charge transfer electrode, and a second charge transfer electrode. A solid-state imaging device including a charge transfer electrode, wherein a gate insulating film formed by sequentially stacking a silicon oxide film, a silicon nitride film, and a silicon oxide film is formed on the semiconductor substrate, and the charge transfer This is achieved by a solid-state imaging device, wherein a removal portion not provided with the silicon nitride film is formed on the portion, and an upper silicon nitride film is formed on the removal portion protruding from the first charge transfer electrode. .

本発明は、ゲート絶縁膜の窒化シリコン膜のない除去部に上層窒化シリコン膜を形成している。すると、第１電荷転送電極と第２電荷転送電極との間の層間絶縁膜を層間酸化で形成する際に、上層窒化シリコン膜が形成されている領域では層間絶縁膜が形成されることを防止できる。このため、層間酸化によって、第１電荷転送電極とゲート絶縁膜との間にゲートバーズビークが形成されることを防止することができる。また、窒化シリコン膜の除去部が、上層窒化シリコン膜によって覆われているため、半導体基板の表面が層間酸化の際に、ダメージをうけてしまうことを防止することができる。   In the present invention, the upper silicon nitride film is formed in the removed portion of the gate insulating film without the silicon nitride film. Then, when the interlayer insulating film between the first charge transfer electrode and the second charge transfer electrode is formed by interlayer oxidation, the interlayer insulating film is prevented from being formed in the region where the upper silicon nitride film is formed. it can. For this reason, it is possible to prevent the gate bird's beak from being formed between the first charge transfer electrode and the gate insulating film due to the interlayer oxidation. Further, since the removed portion of the silicon nitride film is covered with the upper silicon nitride film, it is possible to prevent the surface of the semiconductor substrate from being damaged during the interlayer oxidation.

本発明によれば、白キズや読み出し特性を改善することができる固体撮像素子及び固体撮像素子の製造方法を提供できる。   ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the solid-state image sensor and solid-state image sensor which can improve a white crack and read-out characteristic can be provided.

以下、本発明の実施形態を図面に基づいて詳しく説明する。
図１（ａ）から（ｃ）は、第１実施形態の固体撮像素子の製造方法の手順を説明するための図である。
本実施形態の固体撮像素子は、シリコンなどの半導体基板１１を備えており、半導体基板１１には、図示しないフォトダイオードなどの光電変換部と、不純物イオンドーピングによって、電荷転送チャネルやストッパ領域が形成されている。また、半導体基板１１には、光電変換部で生じた電荷を転送する電荷転送部３１が形成されている。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIGS. 1A to 1C are diagrams for explaining the procedure of the method for manufacturing the solid-state imaging device according to the first embodiment.
The solid-state imaging device of this embodiment includes a semiconductor substrate 11 such as silicon, and a charge transfer channel and a stopper region are formed in the semiconductor substrate 11 by a photoelectric conversion unit such as a photodiode (not shown) and impurity ion doping. Has been. The semiconductor substrate 11 is formed with a charge transfer unit 31 that transfers charges generated in the photoelectric conversion unit.

半導体基板１１の上には、酸化シリコン膜１３と、窒化シリコン膜１４と、酸化シリコン膜１５と、が順に、ＣＶＤ法などによって積層されている。酸化シリコン（ＳｉＯ２）膜１３と、窒化シリコン（Ｓｉ３Ｎ４）膜１４と、酸化シリコン（ＳｉＯ２）膜１５とにより、ゲート絶縁膜１２が構成されており、いわゆる、ＯＮＯ膜構造を有している。本実施形態では、酸化シリコン膜１３の膜厚を３５ｎｍとし、窒化シリコン膜１４の膜厚を５０ｎｍとし、酸化シリコン膜１５の膜厚を５ｎｍとした。 A silicon oxide film 13, a silicon nitride film 14, and a silicon oxide film 15 are sequentially stacked on the semiconductor substrate 11 by a CVD method or the like. A silicon oxide (SiO 2 ) film 13, a silicon nitride (Si 3 N 4 ) film 14, and a silicon oxide (SiO 2 ) film 15 constitute a gate insulating film 12, which has a so-called ONO film structure. is doing. In this embodiment, the silicon oxide film 13 has a thickness of 35 nm, the silicon nitride film 14 has a thickness of 50 nm, and the silicon oxide film 15 has a thickness of 5 nm.

ゲート絶縁膜１２において、電荷転送部３１上の領域には、窒化シリコン膜１４を設けない、該窒化シリコン膜１４の除去部１６が形成されている。つまり、除去部１６の領域においては、ゲート絶縁膜１２が酸化シリコン膜１３，１５とを堆積させた構成となる。除去部１６は、窒化シリコン膜１４を酸化シリコン膜１３上にＣＶＤ法で形成した後、除去部１６を形成する箇所だけレジストをマスクに用いてエッチングし、該窒化シリコン膜１４を除去することで形成される。除去部１６を設けることで、電荷転送時に電荷転送部によって転送される電荷が窒化シリコン膜１４にトラップされてしまうことを回避することができる。   In the gate insulating film 12, in the region on the charge transfer portion 31, the removal portion 16 of the silicon nitride film 14 that does not include the silicon nitride film 14 is formed. That is, in the region of the removal portion 16, the gate insulating film 12 is configured to deposit the silicon oxide films 13 and 15. The removal portion 16 forms the silicon nitride film 14 on the silicon oxide film 13 by the CVD method, and then etches only the portion where the removal portion 16 is formed using a resist as a mask to remove the silicon nitride film 14. It is formed. By providing the removal unit 16, it is possible to avoid the charge transferred by the charge transfer unit from being trapped in the silicon nitride film 14 during the charge transfer.

ゲート絶縁膜１２を形成した後、ポリシリコンなどからなる電極材料層を積層し、レジストマスクでパターン形成することで第１電荷転送電極１７を形成する。このとき、第１電荷転送電極とゲート絶縁膜１２との境界部が、電荷転送部３１上の領域に含まれるとともに、除去部１６を形成した領域が、第１電荷転送電極１７とゲート絶縁膜１２との境界部からはみ出すように構成する。   After the gate insulating film 12 is formed, an electrode material layer made of polysilicon or the like is stacked, and a first charge transfer electrode 17 is formed by patterning with a resist mask. At this time, the boundary portion between the first charge transfer electrode and the gate insulating film 12 is included in the region on the charge transfer portion 31 and the region where the removal portion 16 is formed is the first charge transfer electrode 17 and the gate insulating film. 12 so that it protrudes from the boundary with 12.

図１（ａ）に示すように、本実施形態では、第１電荷転送電極１７をパターン形成した後、できるだけ薄い膜厚（１０〜２０ｎｍ）で上層窒化シリコン（Ｓｉ３Ｎ４）膜１８を形成する。このとき、窒化シリコン膜１８は、第１電荷転送電極１７とゲート絶縁膜１２との境界部からはみ出ている除去部１６を全て覆うように形成される。窒化シリコン膜１８を形成する手順は、まず、ゲート絶縁膜１２上の第１電荷転送電極１７を含めた全面にＣＶＤ法などによって形成し、その後、第１電荷転送電極１７とゲート絶縁膜１２との境界部からはみ出ている除去部１６を覆うように、パターニングする。 As shown in FIG. 1A, in the present embodiment, after patterning the first charge transfer electrode 17, an upper silicon nitride (Si 3 N 4 ) film 18 is formed with the smallest possible film thickness (10 to 20 nm). To do. At this time, the silicon nitride film 18 is formed so as to cover all of the removal portion 16 protruding from the boundary between the first charge transfer electrode 17 and the gate insulating film 12. The silicon nitride film 18 is formed by first forming the silicon nitride film 18 on the entire surface including the first charge transfer electrode 17 on the gate insulating film 12 by CVD or the like, and then forming the first charge transfer electrode 17, the gate insulating film 12, Patterning is performed so as to cover the removal portion 16 protruding from the boundary portion.

ここで、薄い膜厚の上層窒化シリコン膜１８を用いるのは、層間絶縁膜を形成する際の層間酸化時に第１電荷転送電極１７表面の酸化や除去部の酸化を抑制するためであり、第２電荷転送電極のエッチング時の選択比を考慮した最小限の厚さであればよい。また、上層窒化シリコン膜１８は、更に上層に形成する図示しない遮光膜との位置関係にもよるが、薄ければ薄いほどスミアの増加を抑制することができる。   Here, the thin upper silicon nitride film 18 is used to suppress oxidation of the surface of the first charge transfer electrode 17 and oxidation of the removed portion during interlayer oxidation when forming the interlayer insulating film. A minimum thickness may be used in consideration of the selection ratio during etching of the two charge transfer electrodes. Further, although the upper silicon nitride film 18 further depends on the positional relationship with a light shielding film (not shown) formed in an upper layer, it is possible to suppress an increase in smear as the thickness is thinner.

図１（ｂ）に示すように、上層窒化シリコン膜１８を形成した後で、層間酸化を行い、第１電荷転送電極１７の上面及び側面に層間絶縁膜１９を形成する。本実施形態では、熱酸化によって層間絶縁膜１９を形成する。このとき、第１電荷転送電極１７の表面の、上層窒化シリコン膜１８に覆われた箇所では、酸化が妨げられるため、層間絶縁膜が形成されない。そして、層間絶縁膜１９を形成した後、図１（ｃ）に示すように、第２電荷転送電極２１をパターン形成する。なお、第２電荷転送電極は、第１電荷転送電極と同様に、レジストをマスクとして用いてエッチング除去することでパターニングすることができる。   As shown in FIG. 1B, after forming the upper silicon nitride film 18, interlayer oxidation is performed to form an interlayer insulating film 19 on the upper surface and side surfaces of the first charge transfer electrode 17. In this embodiment, the interlayer insulating film 19 is formed by thermal oxidation. At this time, since the oxidation is hindered at the portion of the surface of the first charge transfer electrode 17 covered with the upper silicon nitride film 18, the interlayer insulating film is not formed. Then, after the interlayer insulating film 19 is formed, the second charge transfer electrode 21 is patterned as shown in FIG. Note that the second charge transfer electrode can be patterned by etching away using a resist as a mask, like the first charge transfer electrode.

本実施形態の製造方法では、ゲート絶縁膜１２の窒化シリコン膜１４のない除去部１６に上層窒化シリコン膜１８を形成している。すると、第１電荷転送電極１７と第２電荷転送電極２１との間の層間絶縁膜１９を層間酸化で形成する際に、上層窒化シリコン膜１８が形成されている領域では層間絶縁膜１９が形成されることを防止できる。このため、層間酸化によって、第１電荷転送電極１７とゲート絶縁膜１２との間にゲートバーズビークが形成されることを防止することができる。また、窒化シリコン膜１４の除去部１６が、上層窒化シリコン膜１８によって覆われているため、半導体基板１１の表面が層間酸化の際に、ダメージをうけてしまうことを防止することができる。   In the manufacturing method of the present embodiment, the upper silicon nitride film 18 is formed on the removed portion 16 of the gate insulating film 12 where the silicon nitride film 14 is not present. Then, when the interlayer insulating film 19 between the first charge transfer electrode 17 and the second charge transfer electrode 21 is formed by interlayer oxidation, the interlayer insulating film 19 is formed in the region where the upper silicon nitride film 18 is formed. Can be prevented. Therefore, it is possible to prevent the gate bird's beak from being formed between the first charge transfer electrode 17 and the gate insulating film 12 due to the interlayer oxidation. Further, since the removed portion 16 of the silicon nitride film 14 is covered with the upper silicon nitride film 18, it is possible to prevent the surface of the semiconductor substrate 11 from being damaged during the interlayer oxidation.

図２及び図３に、本発明にかかる第２実施形態を示す。なお、以下に説明する実施形態において、すでに説明した部材などと同等な構成・作用を有する部材等については、図中に同一の符号又は相当する符号を付すことにより、説明を簡略化或いは省略する。   2 and 3 show a second embodiment according to the present invention. In the embodiments described below, members having the same configuration / action as those already described are denoted by the same or corresponding reference numerals in the drawings, and the description is simplified or omitted. .

図２（ａ）に示すように、最初に、上記第１実施形態と同様に、半導体基板１１上にゲート絶縁膜１２を形成し、ゲート絶縁膜１２上に第１電荷転送電極１７を構成する材料層と、第１電荷転送電極１７の上層に窒化シリコン膜１７ａとを形成する。本実施形態のゲート絶縁膜１２は、第１実施形態と同様に、電荷転送部３１上の領域に、窒化シリコン膜１４を設けない、該窒化シリコン膜１４の除去部１６が形成されている。窒化シリコン膜１７ａ上には、第１電荷転送電極１７をパターンエッチングするためのレジスト層Ｒが形成されている。   As shown in FIG. 2A, first, similarly to the first embodiment, the gate insulating film 12 is formed on the semiconductor substrate 11 and the first charge transfer electrode 17 is formed on the gate insulating film 12. A silicon nitride film 17 a is formed on the material layer and on the first charge transfer electrode 17. As in the first embodiment, the gate insulating film 12 of the present embodiment is provided with a removal portion 16 of the silicon nitride film 14 that is not provided with the silicon nitride film 14 in a region on the charge transfer portion 31. A resist layer R for pattern etching the first charge transfer electrode 17 is formed on the silicon nitride film 17a.

図２（ｂ）に示すように、エッチングによって、第１電荷転送電極１７及び窒化シリコン膜１７ａをパターニングする。次に、図２（ｃ）に示すように、第１電荷転送電極１７からはみ出ている除去部１６を完全に覆うように、窒化シリコン膜１８を形成する。   As shown in FIG. 2B, the first charge transfer electrode 17 and the silicon nitride film 17a are patterned by etching. Next, as illustrated in FIG. 2C, a silicon nitride film 18 is formed so as to completely cover the removed portion 16 protruding from the first charge transfer electrode 17.

窒化シリコン膜１８を形成した後、図３（ａ）に示すように、ＣＶＤ法によって層間絶縁膜２２を全面に形成する。そして、図３（ｂ）に示すように、層間絶縁膜２２を全面ドライエッチングにより除去することで、層間絶縁膜２２を第１電荷転送電極１７の両側（図３における左右の両側）にサイドウォール状に残す。そして、図３（ｃ）に示すように、第１電荷転送電極１７及び窒化シリコン膜および層間絶縁膜２２を覆うように、全面に酸化シリコン膜２３を形成し、その後、第２電荷転送電極２１を上記実施形態と同様にパターン形成する。   After the silicon nitride film 18 is formed, an interlayer insulating film 22 is formed on the entire surface by CVD as shown in FIG. Then, as shown in FIG. 3B, the interlayer insulating film 22 is removed on the entire surface by dry etching, so that the interlayer insulating film 22 is sidewalls on both sides (left and right sides in FIG. 3) of the first charge transfer electrode 17. Leave in shape. Then, as shown in FIG. 3C, a silicon oxide film 23 is formed on the entire surface so as to cover the first charge transfer electrode 17, the silicon nitride film and the interlayer insulating film 22, and then the second charge transfer electrode 21. The pattern is formed in the same manner as in the above embodiment.

本実施形態の製造方法によれば、電荷転送電極１７と第２電荷転送電極２１との間の層間絶縁膜２２をＣＶＤ法で形成する場合には、上層窒化シリコン膜１８によってゲートバーズビークが形成されることを防止できる。また、窒化シリコン膜１４の除去部１６が、上層窒化シリコン膜１８によって覆われているため、半導体基板１１の表面が、層間絶縁膜２２のエッチングの際に、エッチングダメージをうけてしまうことを防止することができる。   According to the manufacturing method of the present embodiment, when the interlayer insulating film 22 between the charge transfer electrode 17 and the second charge transfer electrode 21 is formed by the CVD method, the gate bird's beak is formed by the upper silicon nitride film 18. Can be prevented. Further, since the removed portion 16 of the silicon nitride film 14 is covered with the upper silicon nitride film 18, the surface of the semiconductor substrate 11 is prevented from being damaged by etching when the interlayer insulating film 22 is etched. can do.

第１実施形態の固体撮像素子の製造方法の手順を説明する図である。It is a figure explaining the procedure of the manufacturing method of the solid-state image sensor of 1st Embodiment. 第２実施形態の固体撮像素子の製造方法の手順を説明する図である。It is a figure explaining the procedure of the manufacturing method of the solid-state image sensor of 2nd Embodiment. 第２実施形態の固体撮像素子の製造方法の手順を説明する図である。It is a figure explaining the procedure of the manufacturing method of the solid-state image sensor of 2nd Embodiment. 従来の固体撮像素子の製造方法を説明する図である。It is a figure explaining the manufacturing method of the conventional solid-state image sensor. 従来の固体撮像素子の製造方法を説明する図である。It is a figure explaining the manufacturing method of the conventional solid-state image sensor.

符号の説明Explanation of symbols

１１ 半導体基板
１２ ゲート絶縁膜
１３，１５ 酸化シリコン膜
１４ 窒化シリコン膜
１６ （窒化シリコン膜の）除去部
１７ 第１電荷転送電極
１８ 上層窒化シリコン膜
１９，２２ 層間絶縁膜
２１ 第２電荷転送電極
３１ 電荷転送部
DESCRIPTION OF SYMBOLS 11 Semiconductor substrate 12 Gate insulating films 13 and 15 Silicon oxide film 14 Silicon nitride film 16 (silicon nitride film) removal part 17 First charge transfer electrode 18 Upper silicon nitride films 19 and 22 Interlayer insulating film 21 Second charge transfer electrode 31 Charge transfer unit

Claims (2)

半導体基板と、前記半導体基板に形成された光電変換部と、前記光電変換部で生じた電荷を転送する電荷転送部と、第１電荷転送電極と、第２電荷転送電極とを備えた固体撮像素子の製造方法であって、
前記半導体基板上に、酸化シリコン膜と、窒化シリコン膜と、酸化シリコン膜とを順に積層させてなるゲート絶縁膜が形成され、前記電荷転送部上に前記窒化シリコン膜を設けない除去部を形成し、前記第１電荷転送電極をパターン形成し、前記第１電荷転送電極からはみ出す前記除去部上に上層窒化シリコン膜を形成した後で、前記第２電荷転送電極をパターン形成することを特徴とする固体撮像素子の製造方法。 Solid-state imaging device comprising: a semiconductor substrate; a photoelectric conversion unit formed on the semiconductor substrate; a charge transfer unit that transfers charges generated in the photoelectric conversion unit; a first charge transfer electrode; and a second charge transfer electrode A method for manufacturing an element, comprising:
A gate insulating film formed by sequentially stacking a silicon oxide film, a silicon nitride film, and a silicon oxide film is formed on the semiconductor substrate, and a removal portion not provided with the silicon nitride film is formed on the charge transfer portion. And patterning the first charge transfer electrode, forming an upper silicon nitride film on the removal portion protruding from the first charge transfer electrode, and patterning the second charge transfer electrode. Manufacturing method of a solid-state imaging device. 半導体基板と、前記半導体基板に形成された光電変換部と、前記光電変換部で生じた電荷を転送する電荷転送部と、第１電荷転送電極と、第２電荷転送電極とを備えた固体撮像素子であって、
前記半導体基板上に、酸化シリコン膜と、窒化シリコン膜と、酸化シリコン膜とを順に積層させてなるゲート絶縁膜が形成され、前記電荷転送部上に前記窒化シリコン膜を設けない除去部が形成され、前記第１電荷転送電極からはみ出す前記除去部上に上層窒化シリコン膜が形成されていることを特徴とする固体撮像素子。 Solid-state imaging device comprising: a semiconductor substrate; a photoelectric conversion unit formed on the semiconductor substrate; a charge transfer unit that transfers charges generated in the photoelectric conversion unit; a first charge transfer electrode; and a second charge transfer electrode An element,
A gate insulating film formed by sequentially stacking a silicon oxide film, a silicon nitride film, and a silicon oxide film is formed on the semiconductor substrate, and a removal portion not provided with the silicon nitride film is formed on the charge transfer portion. A solid-state imaging device, wherein an upper silicon nitride film is formed on the removal portion that protrudes from the first charge transfer electrode.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013509005A (en) * 2009-10-27 2013-03-07 ヴァリアン セミコンダクター イクイップメント アソシエイツ インコーポレイテッド Method for enhancing surface trapping by reducing surface recombination in solar cells

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013509005A (en) * 2009-10-27 2013-03-07 ヴァリアン セミコンダクター イクイップメント アソシエイツ インコーポレイテッド Method for enhancing surface trapping by reducing surface recombination in solar cells

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