JP2805848B2 - Solid-state imaging device - Google Patents
Solid-state imaging deviceInfo
- Publication number
- JP2805848B2 JP2805848B2 JP1153706A JP15370689A JP2805848B2 JP 2805848 B2 JP2805848 B2 JP 2805848B2 JP 1153706 A JP1153706 A JP 1153706A JP 15370689 A JP15370689 A JP 15370689A JP 2805848 B2 JP2805848 B2 JP 2805848B2
- Authority
- JP
- Japan
- Prior art keywords
- region
- charge transfer
- type
- imaging device
- film
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
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- Solid State Image Pick-Up Elements (AREA)
Description
【発明の詳細な説明】 ［産業上の利用分野］ 本発明は、強い光が入射した時に問題となるスミアを
抑圧せしめた固体撮像素子に関する。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device in which smear, which becomes a problem when strong light is incident, is suppressed.
［従来の技術］ 従来の固体撮像素子の断面図を第３図に示す。同図に
おいて、１はシリコンからなるＮ型半導体基板、２は、
Ｎ型半導体基板１の表面領域内に形成されたＰ型ウェル
領域、３は、Ｐ型ウェル領域２内に形成されたＮ型フォ
トダイオード領域、４は、Ｐ型ウェル領域２内に形成さ
れ、Ｎ型フォトダイオード領域から転送されてきた光電
変換キャリアを転送する電荷転送素子（垂直CCD）の埋
込みチャネルとして動作するＮ型電荷転送領域、９は、
Ｎ型フォトダイオード領域３からＮ型電荷転送領域４へ
の光電変換キャリアの転送路となる電荷読み出し領域、
５は、Ｎ型フォトダイオード領域間およびＮ型フォトダ
イオード領域３とＮ型電荷転送領域４との間を分離する
P+型チャネルストッパ領域、６は、多結晶シリコンによ
り形成された電荷転送素子のゲート電極、８は、半導体
基板表面およびゲート電極６を覆う絶縁膜、７はＮ型フ
ォトダイオード領域３の上方以外の部分を覆う遮光膜で
ある。[Prior Art] FIG. 3 is a cross-sectional view of a conventional solid-state imaging device. In the figure, 1 is an N-type semiconductor substrate made of silicon, and 2 is
A P-type well region 3 formed in the surface region of the N-type semiconductor substrate 1, an N-type photodiode region formed in the P-type well region 2, and a P-type well region 4 formed in the P-type well region 2; An N-type charge transfer region 9 operating as a buried channel of a charge transfer device (vertical CCD) for transferring photoelectric conversion carriers transferred from the N-type photodiode region,
A charge readout region serving as a transfer path for photoelectric conversion carriers from the N-type photodiode region 3 to the N-type charge transfer region 4;
Reference numeral 5 separates between the N-type photodiode regions and between the N-type photodiode region 3 and the N-type charge transfer region 4.
P + type channel stopper region, 6 is a gate electrode of a charge transfer element formed of polycrystalline silicon, 8 is an insulating film covering the surface of the semiconductor substrate and the gate electrode 6, 7 is other than above the N type photodiode region 3. This is a light-shielding film that covers the portion.
この固体撮像素子においては、Ｐ型ウェル領域２は、
Ｎ型フォトダイオード領域３の下で一部浅くなってお
り、この部分を通して、Ｎ型フォトダイオード領域から
オーバーフローする光電変換キャリアはＮ型半導体基板
１へ引き抜かれる。In this solid-state imaging device, the P-type well region 2
The part is shallow below the N-type photodiode region 3, through which photoelectric conversion carriers overflowing from the N-type photodiode region are drawn into the N-type semiconductor substrate 1.
［発明が解決しようとする課題］ 上述した固体撮像素子では、Ｐ型ウェル領域で発生す
る光電変換キャリアの大部分はＮ型フォトダイオード領
域３に流入して蓄積されるが一部は横方向拡散によりＮ
型電荷転送領域４に吸収される。また、第３図に示すよ
うに、斜め入射した光が半導体基板１と遮光膜７との間
で多重反射してＮ型電荷転送領域４に到達し、そこでキ
ャリアを発生させる。これらＮ型電荷転送領域４に吸収
されたキャリアは、スミア成分と呼ばれるものであり、
これがＮ型フォトダイオード領域３に蓄積されるキャリ
アの0.1％位になると、テレビ画面において白い縦縞が
発生する。上述したスミアとなる２つのキャリア成分の
内、前者は、縦型オーバーフロードレイン構造を採用す
ることにより実用上問題とならない程度に低減せしめる
ことができるが、後者に対しては有効な手段が講じられ
ていないので、現在では前者と後者の比は約1:10となっ
ている。[Problems to be Solved by the Invention] In the solid-state imaging device described above, most of the photoelectric conversion carriers generated in the P-type well region flow into the N-type photodiode region 3 and are accumulated, but part of the photoelectric conversion carriers are diffused in the lateral direction. By N
It is absorbed by the type charge transfer region 4. Further, as shown in FIG. 3, the obliquely incident light is multiply reflected between the semiconductor substrate 1 and the light-shielding film 7 to reach the N-type charge transfer region 4, where carriers are generated. The carriers absorbed in the N-type charge transfer region 4 are called smear components.
When this is about 0.1% of the carriers accumulated in the N-type photodiode region 3, white vertical stripes occur on the television screen. Of the two carrier components that cause smear, the former can be reduced to a level that does not pose a practical problem by adopting a vertical overflow drain structure, but effective measures are taken for the latter. The ratio of the former to the latter is now about 1:10.
よって、本発明の目的とするところは斜め入射光が反
射して電荷転送領域に入射するのを防止することであ
り、もって、スミア成分を減少させることである。Accordingly, it is an object of the present invention to prevent obliquely incident light from being reflected and incident on the charge transfer region, thereby reducing smear components.
［課題を解決するための手段］ 本発明の固体撮像素子は、半導体基板の表面に複数の
フォトダイオード領域と、フォトダイオードの電荷を転
送する電荷結合素子とが形成されたものであり、電荷結
合素子のゲート電極は電荷転送領域上において多結晶シ
リコン膜と導電性遮光膜との二層膜により構成されそれ
以外の部分において多結晶シリコン膜のみにより構成さ
れる。[Means for Solving the Problems] A solid-state imaging device according to the present invention includes a plurality of photodiode regions and a charge-coupled device that transfers charges of the photodiode formed on a surface of a semiconductor substrate. The gate electrode of the device is composed of a two-layer film of a polycrystalline silicon film and a conductive light-shielding film on the charge transfer region, and is composed of only the polycrystalline silicon film in other portions.
［実施例］ 次に、本発明の実施例について図面を参照して説明す
る。Example Next, an example of the present invention will be described with reference to the drawings.
第１図は、本発明の参考例示す断面図であって、同図
において、第３図の従来例の部分と共通する部分には同
一の参照番号が付されているので重複する説明は省略す
る。この参考例ではゲート電極６が多結晶シリコン膜6a
とタングステンやモリブデン等の高融点金属膜6bとの二
層構造となっている。FIG. 1 is a cross-sectional view showing a reference example of the present invention. In FIG. 1, the same reference numerals are given to portions common to those of the conventional example in FIG. I do. In this reference example, the gate electrode 6 is a polycrystalline silicon film 6a.
And a high-melting metal film 6b such as tungsten or molybdenum.
このような構造において、斜め入射光は、Ｎ型フォト
ダイオード領域３の表面で反射した後は、遮光膜７で再
び反射するが、次には高融点金属膜6bの表面で反射する
為Ｎ型電荷転送領域４には到達しない。In such a structure, the obliquely incident light is reflected on the surface of the N-type photodiode region 3 and then again on the light-shielding film 7, but then reflected on the surface of the refractory metal film 6b. It does not reach the charge transfer region 4.
また、参考例の固体撮像素子は、ゲート電極のシート
抵抗が低くなされているので、高速転送時に問題となる
クロックパルス波形のだれをなくすことができ、転送効
率を向上させることができるという副次的効果も有す
る。Further, in the solid-state imaging device of the reference example, since the sheet resistance of the gate electrode is reduced, it is possible to eliminate the droop of the clock pulse waveform which is a problem at the time of high-speed transfer and improve the transfer efficiency. It also has a positive effect.
第２図は、本発明の一実施例を示す断面図である。こ
の実施例の先の参考例と相違する点は、ゲート電極６
が、多結晶シリコン膜6cとＮ型電荷転送領域４上のみに
存在する高融点金属膜6dとによって構成されている点で
ある。この構成によれば、Ｎ型電荷転送領域以外で発生
した光電変換キャリアの内、幾分かをＮ型フォトダイオ
ード領域３に収集できるので、先の参考例よりもフォト
ダイオードの感度を増加させることができる。また、Ｎ
型フォトダイオード領域３で反射した後高融点金属膜の
下面で反射してＮ型電荷転送領域内に入射する光を減少
させることができる。FIG. 2 is a sectional view showing an embodiment of the present invention. The difference between this embodiment and the previous embodiment is that the gate electrode 6
Is that the polycrystalline silicon film 6c and the refractory metal film 6d existing only on the N-type charge transfer region 4. According to this configuration, since some of the photoelectric conversion carriers generated in regions other than the N-type charge transfer region can be collected in the N-type photodiode region 3, the sensitivity of the photodiode can be increased as compared with the reference example. Can be. Also, N
After the light is reflected by the photodiode region 3, the light reflected by the lower surface of the refractory metal film and incident on the N-type charge transfer region can be reduced.
なお、以上の実施例では、ゲート電極６を高融点金属
膜を下層とし多結晶シリコン膜を上層として形成してい
たが、この順序を逆にして高融点金属膜を上層としても
よい。また、高融点金属膜に替えて高融点金属のシリサ
イド膜を採用してもよい。In the above embodiment, the gate electrode 6 is formed with the refractory metal film as the lower layer and the polycrystalline silicon film as the upper layer. However, the order may be reversed and the refractory metal film may be formed as the upper layer. Further, a high melting point metal silicide film may be employed instead of the high melting point metal film.
［発明の効果］ 以上説明したように、本発明は、ゲート電極の電荷転
送領域上の部分を高融点金属（またはそのシリサイド）
膜の遮光膜と多結晶シリコン膜との二層構造により構成
しそれ以外の部分を多結晶シリコン膜のみにより構成し
たものであるので、本発明によれば、フォトダイオード
領域に入射する光を妨害することなく電荷転送領域への
光の入射を防止することができ、感度の低下を招くこと
なくスミアを著しく低減させることができる。[Effects of the Invention] As described above, according to the present invention, a portion of a gate electrode on a charge transfer region is formed of a high melting point metal (or a silicide thereof).
According to the present invention, since the light shielding film and the polycrystalline silicon film have a two-layer structure and the other portions are composed only of the polycrystalline silicon film, light incident on the photodiode region is obstructed. It is possible to prevent light from entering the charge transfer region without performing the process, and to significantly reduce smear without lowering the sensitivity.
第１図は、本発明の参考例を示す断面図、第２図は、本
発明の一実施例を示す断面図、第３図は、従来例を示す
断面図である。 １……Ｎ型半導体基板、２……Ｐ型ウェル領域、３……
Ｎ型フォトダイオード領域、４……Ｎ型電荷転送領域、
５……P+チャネルストッパ領域、６……ゲート電極、6
a、6c……多結晶シリコン膜、6b、6d……高融点金属
膜、７……遮光膜、８……絶縁膜、９……電荷読み出し
領域。FIG. 1 is a sectional view showing a reference example of the present invention, FIG. 2 is a sectional view showing an embodiment of the present invention, and FIG. 3 is a sectional view showing a conventional example. 1 ... N-type semiconductor substrate, 2 ... P-type well region, 3 ...
N-type photodiode region, 4... N-type charge transfer region,
5 ... P + channel stopper region, 6 ... Gate electrode, 6
a, 6c: polycrystalline silicon film, 6b, 6d: high melting point metal film, 7: light shielding film, 8: insulating film, 9: charge readout region.
Claims (1)
複数の第２導電型のフォトダイオード領域と、前記第１
導電型半導体領域の表面に形成され前記複数のフォトダ
イオード領域から信号電荷の転送を受けこの信号電荷の
転送路となる第２導電型の電荷転送領域と、前記電荷転
送領域上にゲート絶縁膜を介して形成された複数のゲー
ト電極とを具備する固体撮像素子において、前記ゲート
電極は前記電荷転送領域上において多結晶シリコン膜と
導電性遮光膜との二層膜により構成されそれ以外の部分
において多結晶シリコン膜のみにより構成されているこ
とを特徴とする固体撮像素子。A second conductive type photodiode region formed on a surface of the first conductive type semiconductor region;
A second conductive type charge transfer region formed on the surface of the conductive type semiconductor region and receiving signal charges from the plurality of photodiode regions and serving as a transfer path for the signal charges; and a gate insulating film on the charge transfer region. In a solid-state imaging device having a plurality of gate electrodes formed through the gate electrode, the gate electrode is formed of a two-layer film of a polycrystalline silicon film and a conductive light-shielding film on the charge transfer region, and in other portions A solid-state imaging device comprising only a polycrystalline silicon film.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1153706A JP2805848B2 (en) | 1989-06-16 | 1989-06-16 | Solid-state imaging device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1153706A JP2805848B2 (en) | 1989-06-16 | 1989-06-16 | Solid-state imaging device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0319367A JPH0319367A (en) | 1991-01-28 |
| JP2805848B2 true JP2805848B2 (en) | 1998-09-30 |
Family
ID=15568325
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1153706A Expired - Lifetime JP2805848B2 (en) | 1989-06-16 | 1989-06-16 | Solid-state imaging device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2805848B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10242450A (en) * | 1997-03-03 | 1998-09-11 | Nec Corp | Charge-transferring device and its manufacture |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63120463A (en) * | 1986-11-10 | 1988-05-24 | Matsushita Electric Ind Co Ltd | Solid-state image sensing device |
| JPH02264440A (en) * | 1989-04-04 | 1990-10-29 | Mitsubishi Electric Corp | Manufacture of charge-transfer device |
-
1989
- 1989-06-16 JP JP1153706A patent/JP2805848B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0319367A (en) | 1991-01-28 |
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