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KR930006278B1 - Photo shield structure of ccd imager - Google Patents

Photo shield structure of ccd imager Download PDF

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Publication number
KR930006278B1
KR930006278B1 KR1019900008529A KR900008529A KR930006278B1 KR 930006278 B1 KR930006278 B1 KR 930006278B1 KR 1019900008529 A KR1019900008529 A KR 1019900008529A KR 900008529 A KR900008529 A KR 900008529A KR 930006278 B1 KR930006278 B1 KR 930006278B1
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photodiode
film
layer
light shielding
shielding film
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KR1019900008529A
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Korean (ko)
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KR920001740A (en
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김시호
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금성일렉트론 주식회사
문정환
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components 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
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/148—Charge coupled imagers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components 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
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Electromagnetism (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Solid State Image Pick-Up Elements (AREA)

Abstract

The shielding film structure of the CCD image sensor is mfd. by (a) forming a P-well (2) on the n-type substrate (1), P+ buried layer (3) on the boundary surface of the P-well (2) and the substrate (1), and a channel stop (4), a n-layer (5a) of the photodiode and a charge transmission region (7) on the surface of the P-well (2), (b) depositing a gate oxide film and a polysilicon, and then selectively lifting off the polysilicon to form a polygate (8), P+ layer (5b), a photodiode (5) and an oxide film (10), (c) lifting off the film (10) using a PR (9), and then lifting off the PR, (d) depositing a silicide (TaSi2 or TiSi2), and then selectively lifting off the silicide to form a shielding film (11), and (e) forming a protecting film (12) on the film (11) and the photodiode (5).

Description

CCD 영상센서의 차광막 구조Light shielding film structure of CCD image sensor

제1도는 본 발명의 제조공정을 나타낸 단면도.1 is a cross-sectional view showing a manufacturing process of the present invention.

제2도는 종래 CCD 영상센서의 단면도.2 is a cross-sectional view of a conventional CCD image sensor.

제3도는 종래 다른 실시예의 CCD 영상센서의 단면도.3 is a cross-sectional view of another conventional CCD image sensor.

* 도면의 주요부분에 대한 부호의 설명* Explanation of symbols for main parts of the drawings

1 : 기판 2 : P-웰1 substrate 2 P-well

3 : P+매몰층 4 : 채널스톱부3: P + buried layer 4: Channel stop part

5 : 포토다이오드 6 : 채널영역5: photodiode 6: channel area

7 : 전하전송영역 8 : 폴리게이트7 charge transfer region 8 poly gate

9 : P/R 10 : 산화막9: P / R 10: oxide film

11 : 차광막 11: 보호막11: shading film 11: protective film

본 발명은 CCD 영상센서에 관한 것으로 특히 스미어(Smear현상 및 화상결함을 감소시킬 수 있는 CCD 영상센서(Image Sensor의 차광막(Photoshield) 구조에 관한것이다.BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CCD image sensor, and more particularly, to a structure of a light shielding film (photoshield) of a CCD image sensor capable of reducing smear and image defects.

일반적으로 CCD 영상센서에 나타나는 스미어 현상은 입사된 빛의 누설과 포토다이오드 밖에서 발생된 전자의 확산에 의하여 발생되는데, 주로 입사빛의 누설이 주요 원인이 되고 있다.In general, smear phenomenon appearing in CCD image sensor is caused by leakage of incident light and diffusion of electrons generated outside photodiode, mainly due to leakage of incident light.

또한, 화상결함은 포토다이오드 표면부분에서는 전하가 불안정하므로 발생한다. 종래에는 제2도와 같이 종래의 CCD 영상센서의 구조는 제2도와 같이 포토다이오드(5)영역과 전하전송영역(7)이 형성된 기판의 전하전송영역(7)상부에 전하전송전극인 폴리게이트(14)가 형성되고, 전면에 절연막(SiO2)(15)이 두껍게 형성되며 전하전송영역(7) 상부의 절연막(15)위에 차광막(13)이 형성되고 전면이 보호막(12)으로 보호되어 있는 구조이다.Image defects also occur because charges are unstable at the photodiode surface. Conventionally, as shown in FIG. 2, the conventional CCD image sensor has a polygate as a charge transfer electrode on the charge transfer region 7 of the substrate on which the photodiode 5 region and the charge transfer region 7 are formed. 14, a thick insulating film (SiO 2 ) 15 is formed on the front surface, and a light shielding film 13 is formed on the insulating film 15 on the charge transfer region 7 and the front surface is protected by the protective film 12. Structure.

즉, Al등의 금속막을 이용하여 포토다이오드 영역(5)을 제외한 전부분의 빛을 차광막(13)이 차단하고 있으나, 이는 다음과 같은 이유에 의하여 빛의 누설경로가 발생한다.That is, although the light shielding film 13 blocks light of all parts except the photodiode region 5 by using a metal film such as Al, this causes a light leakage path for the following reasons.

먼저, (a)와 같이 경사지게 입사된 빛은 포토다이오드(5)의 외측에서 Si에 흡수되어 스미어전하(Smear Change)를 발생한다.First, the incident light obliquely as shown in (a) is absorbed by Si outside the photodiode 5 to generate smear charges.

그리고 (b)와 같이 수직입사된 빛은 보호층(12)의 오목렌즈효과에 의하여 회절되므로 빛의 누설이 발생한다.And as the vertically incident light as shown in (b) is diffracted by the concave lens effect of the protective layer 12, light leakage occurs.

또한 (c)와 같이 포토다이오드(5)의 표면층에서 반사된 차단막(13)과 폴리게이트(14)사이를 계속 투과하여 광의 도파관 효과에 의하여 빛의 누설이 발생한다. 즉, 종래에는 차단막(13)과 포토다이오드(5)사이에 두꺼운 SiO2층(15)이 존재하여 빛의 누설을 완전히 차단하지 못하므로 스미어를 완전히 제거시키지 못하였다. 한편, 제3도는 제2도와 같은 종래의 구조에서 발생되는 스미어 현상을 방지하기 위한 것으로 포토다이오드(5)영역과 전하전송영역(7)이 형성된 기판의 전하전송영역(7)상에 전하전송전극인 폴리게이트(14)가 형성되고, 폴리게이트(14)상측 및 측면에 제1절연막(15)이 두껍게 형성되며, 전면에 제2절연막(16)이 얇게 형성되고, 전하전송영역(7)상측의 제2절연막(16)위에 차광막(13)이 제1절연막(15)측벽에까지 형성된다.In addition, as shown in (c), light is continuously leaked between the blocking film 13 and the polygate 14 reflected from the surface layer of the photodiode 5 to cause light leakage due to the waveguide effect of the light. That is, in the related art, a thick SiO 2 layer 15 exists between the blocking film 13 and the photodiode 5 and thus does not completely block the leakage of light, thereby preventing the smear from being completely removed. On the other hand, Figure 3 is to prevent the smear phenomenon occurring in the conventional structure as shown in Figure 2, the charge transfer electrode on the charge transfer region 7 of the substrate on which the photodiode 5 region and the charge transfer region 7 is formed Phosphorus poly gate 14 is formed, the first insulating film 15 is thickly formed on the upper side and the side of the poly gate 14, the second insulating film 16 is thinly formed on the front surface, and the upper portion of the charge transfer region 7 is formed. The light shielding film 13 is formed on the side wall of the first insulating film 15 on the second insulating film 16.

따라서, 제1절연막(15)이 두껍게 형성되기 때문에 차광막(13)과 전하전송전극인 폴리게이트(14)간의 부유용량을 감소시키고 포토다이오드(5) 측벽에까지 차광막(13)이 형성되므로 스미어 현상을 방지하여 광차폐효과가 향상되었다.Therefore, since the first insulating layer 15 is formed thick, the stray capacitance between the light shielding layer 13 and the polygate 14 serving as the charge transfer electrode is reduced, and the light shielding layer 13 is formed up to the sidewalls of the photodiode 5, thereby forming a smear phenomenon. Prevents the light shielding effect.

그러나, 제2도 및 제3도와 같은 종래의 CCD영상센서 차광막 구조에서 제2도에서는 스미어 현상 및 화상결함의 문제가 발생하며, 제3도에서는 스미어 현상은 방지할 수 있으나 포토다이오드(5) 표면부위가 차광막(13)과 제2절연막(16)에 의해 격리되어 있으므로 바이어스를 인가할 수 없어 포토다이오드 표면부위의 전하불안정 상태로 인한 화상결함은 해결되지 못한 문제점이 있다.However, in the conventional light shielding film structure of the CCD image sensor shown in FIGS. 2 and 3, smearing and image defects occur in FIG. 2, and smearing is prevented in FIG. 3, but the surface of the photodiode 5 is prevented. Since the part is separated by the light shielding film 13 and the second insulating film 16, the bias cannot be applied, and thus an image defect due to an unstable state of charge on the surface of the photodiode is not solved.

본 발명은 이와 같은 종래의 결점을 해결하기 위하여 안출한 것으로 화상결함을 방지하기 위하여 포토다이오드 표면에 접지전위를 갖는 P+층을 형성하고, 차광막층을 P+층과 직접 연결하여 차광막층이 빛을 차광함은 물론 접지전극으로 사용할 수 있도록 TiSi2, TaSi2등의 실리사이드를 사용하여 스미어 현상 및 화상결함을 방지하는데 그 목적이 있다.The present invention has been made in order to solve such a conventional defect, to form a P + layer having a ground potential on the surface of the photodiode in order to prevent image defects, the light shielding film layer is light by connecting the light shielding film layer directly with the P + layer The purpose of this is to prevent smear phenomenon and image defects by using silicides such as TiSi 2 and TaSi 2 so as to be used as a shielding electrode as well as a ground electrode.

이하에서 이와 같은 ccd영상센서의 차광막 제조공정을 첨부된 도면 제1도에 의하여 더욱 상세히 설명하면 다음과 같다.Hereinafter, the light shielding film manufacturing process of the ccd image sensor will be described in more detail with reference to FIG. 1.

먼저 (a)와 같이 n형기판(1)위에 P-웰(2)을 형성한뒤 (b)와 같이 전하전송영역이 형성될 P-웰(2)과 기판(1)계면에 P+매몰층(3)을 형성하고, P-웰(2) 표면부위에 채널스톱부(4) 그리고 포토다이오드의 n층(5a)과 채널영역(6) 및 전하전송영역(7)를 형성한다.First, a P-well 2 is formed on an n-type substrate 1 as shown in (a), and then P + buried in the interface between the P-well 2 and the substrate 1 where a charge transfer region is to be formed as shown in (b). The layer 3 is formed, and the channel stop portion 4 and the n layer 5a of the photodiode, the channel region 6 and the charge transfer region 7 are formed on the surface of the P-well 2.

이때 상기 전하전송영역(7) 아래에 P+매몰층(3)이 위치되게 한다. 다음에 (c)와 같이 게이트 산화막과 폴리실리콘을 증착하고, 폴리실리콘을 선택적으로 제거하여 전하를 전송하기 위한 전극인 폴리게이트(8)를 형성하고 포토다이오드의 n층(5a)표면에 표면부위에서 전하의 불안정으로 인하여 발생하는 화상결함을 방지하기 위한 P+층(5b)을 형성하여 포토다이오드(5)를 형성한 다음, 전면에 산화막(10)을 두껍게 형성한다.At this time, the P + buried layer 3 is positioned below the charge transfer region 7. Next, as shown in (c), a gate oxide film and polysilicon are deposited, and polysilicon is selectively removed to form a polygate 8, which is an electrode for transferring electric charges, and the surface portion is formed on the surface of the n-layer 5a of the photodiode. To form a photodiode 5 by forming a P + layer (5b) to prevent the image defects caused by the instability of the charge, then the oxide film 10 is formed thick on the entire surface.

그리고 (d)와 같이 P/R(Photo Resist)(9)를 사용하여 포토다이오드(5)위의 산화막(10)을 제거한 후 P/R(9)을 제거한다.As shown in (d), the oxide film 10 on the photodiode 5 is removed using P / R (Photo Resist) 9 and then the P / R 9 is removed.

이후 (e)와 같이 TaSi2또는 TiSi2등 실리사이드를 증착하고 포토에치공정으로 포토다이오드(5)위의 상기 실리사이드를 선택적으로 제거하여 차광막(11)을 형성한다.Thereafter, silicides such as TaSi 2 or TiSi 2 are deposited as shown in (e), and the light blocking layer 11 is formed by selectively removing the silicide on the photodiode 5 by a photoetch process.

이때의 차광막(11)은 전하전송영역(7)쪽의 산화막(10) 측벽에도 형성됨을 물론 포토다이오드, (5)양측의 P+층(5b)에 연결되도록 형성된다. 또한, 마지막 공정으로 (F)와 같이 차광막(11)과 포토다이오드(5)에 걸쳐 보호막(12)을 형성한다.In this case, the light blocking film 11 is formed on the sidewalls of the oxide film 10 toward the charge transfer region 7 as well as to be connected to the photodiode and the P + layer 5b on both sides (5). In the final step, the protective film 12 is formed over the light shielding film 11 and the photodiode 5 as shown in (F).

이와 같은 제조공정을 갖는 본 발명의 CCD영상센서 차광막구조에 있어서는 차광막(11)이 포토다이오드(5)의 P+층(5b)에 직접 접촉되어 있으므로 경사지게 입사되는 빛의 누설을 완전히 차단시킬 수 있어 스미어를 제거할 수 있으며, 이러한 차광막(11)으로 TaSi2, TiSi2등의 실리사이드를 사용하므로 금속의 정크션스파크를 방지할 수 있다.In the CCD image sensor light shielding film structure of the present invention having such a manufacturing process, since the light shielding film 11 is in direct contact with the P + layer 5b of the photodiode 5, it is possible to completely block the leakage of light incident at an oblique angle. Smear can be removed, and since silicides such as TaSi 2 and TiSi 2 are used as the light shielding film 11, it is possible to prevent junk sparking of metals.

또한, 별도의 바이어스 전극이 필요없이 차광막(11)을 전극으로 사용하여 포토다이오드(5) 상측부의 P+층(5b)에 바이어스 전압을 인가할 수 있으므로 포토다이오드 표면부분에서 발생되는 전하불안정으로 인한 화상결함을 방지할 수 있는 등의 효과가 있다.In addition, a bias voltage can be applied to the P + layer 5b on the upper side of the photodiode 5 by using the light shielding film 11 as an electrode without the need for a separate bias electrode, resulting in charge instability generated at the surface portion of the photodiode. It is effective in preventing image defects.

Claims (2)

표면부위에 채널스톱영역(4), 포토다이오드(5), 채널영역(6), 전하전송영역(7)이 형성된 기판(1)과, 상기 기판의 채널영역(6)과 전하전송영역(7)상에 게이트 산화막을 사이로 하여 형성되는 포토다이오드(5)영역을 제외한 부위에 두껍게 형성되는 산화막(10)과, 상기 포토다이오드 표면부위에 형성되는 P+층(5b)과, 상기 P+층(5b)양측에 연결되도록 산화막(10)위에 형성되는 차광막(11)을 포함하여 이루어짐을 특징으로 하는 CCD 영상센서의 차광막 구조.A substrate 1 having a channel stop region 4, a photodiode 5, a channel region 6, and a charge transfer region 7 formed on a surface thereof, and a channel region 6 and a charge transfer region 7 of the substrate. A thick oxide film 10 formed at a portion other than the photodiode 5 region formed on the photodiode 5 with the gate oxide film interposed therebetween, a P + layer 5b formed on the surface of the photodiode, and a P + layer ( 5b) A light shielding film structure of a CCD image sensor comprising a light shielding film (11) formed on the oxide film (10) so as to be connected to both sides. 제1항에 있어서, 차광막(11)으로 TaSi2, TiSi2의 실리사이드를 사용함을 특징으로 하는 CCD 영상센서의 차광막 구조.The light shielding film structure of a CCD image sensor according to claim 1, wherein silicides of TaSi 2 and TiSi 2 are used as the light shielding film (11).
KR1019900008529A 1990-06-11 1990-06-11 Photo shield structure of ccd imager KR930006278B1 (en)

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KR930006278B1 true KR930006278B1 (en) 1993-07-09

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