JPS622463B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a high-sensitivity, high-density solid-state imaging device having a photoconductive film.

As shown in the top view in FIG. 1a and the X,X' cross-sectional view in FIG. A picture element section 2 (specific structure will be described later) consisting of a charge transfer element etc. that transfers an optical signal is provided, and around this picture element section 2 there is a shift register or a CCD that drives the picture element section. A driving unit 3 such as the above is provided.

Further, a conductor wiring 5 is provided which is connected to the terminal of the drive part 3 through the opening in the insulating film and extends to the external wiring pad part 4.

Furthermore, on the picture element part 2, a photoconductive film (for example, ZnSe-Zn _1-x Cd _x Te, amorphous silicon, etc.) 6, a transparent electrode 7, and an adhesive 8 are provided.
Color filters 9 are provided respectively.
Further, 10 is an insulating film.

Next, regarding a BBD type element which is an example of a solid-state image sensor, a part of the picture element part 12 (Figs. 1 and 2 a
This will be explained using the enlarged view of A) in the middle (FIGS. 3a and 3b), and its operation will be explained using FIGS. 3 and 4.

In FIGS. 3a and 3b, the n ⁺ diffusion region 22 forms a photodiode with the p-type substrate 23. In FIGS. The n ⁺ region 24 is a diffusion region constituting the BBD, and is the first
By applying a voltage to the gate region 25, n ⁺
This is a region to which charge charges are transferred from region 22. 26 and 27 are insulators, respectively. The electrode 28 is made of Mo, is electrically connected to the n ⁺ region 22, and also serves as an electrode of the photoconductive film 29.
The second gate electrode 30 constitutes a BBD gate. 31 is a transparent electrode.

Next, the optical information reading operation of the solid-state image sensor will be explained with reference to FIGS. 4a and 4b. FIG. 4a shows the driving pulse pattern, and FIG. 4b shows the potential change in the n ⁺ region 22.

When a read pulse φ ₁ of V _CH is applied to the first gate electrode 25 at time t ₁ , the potential in the region 22 becomes (V _CH −V
_T ) is charged. Here, V _T is n ⁺ area 2
2, 24 and the first gate electrode 25.

Now, when there is incident light A, electron-hole pairs are generated in the photoconductive film 29, and each electron-hole pair is generated at the electrode 2.
8. It reaches the transparent electrode 31 and the potential of the n ⁺ region 22 decreases. Moreover, this potential drop is proportional to the amount of incident light and is accumulated for one field period, so V
Decreases to _S.

Furthermore, when a read pulse φ ₁ of V _CH is applied to the first gate electrode 25 at time t ₂ , the surface potential of the substrate underneath increases, and as a result, electrons move from the n ⁺ region 22 to the n ⁺ region 24 . occurs.
Subsequently, the potential of n ⁺ region 22 rises again to (V _CH -V _T ). Therefore, the total amount of charge transferred to the n ⁺ region 24 corresponds to the incident light.

The optical information read into the n ⁺ region 24 in this way is transferred to the BBD by applying a transfer pulse _φ2 shown in FIG. 4a to the first gate electrode 30.
In the form of charge transfer, optical information is transferred up and down the page.

That is, the signal photoelectrically converted by the photodiode can be sent to the output stage as a two-phase clock signal.

Now, conventionally, in the manufacturing process of the solid-state image sensor described above, after forming the conductor wiring 5 and the photoconductive film connection electrode, a method of forming the photoconductive film 6 and the transparent electrode 7 only on the upper surface of the picture element part is as follows. A method has been used in which a metallic cover mask is used to perform vapor deposition only on predetermined areas (hereinafter referred to as mask vapor deposition method).

In general, photoconductive films are susceptible to deterioration in sensitivity due to solvents and moisture, and are conventionally used in the manufacture of semiconductor devices. Resist (e.g. product name,
KTFR, AZ1350J, etc.) If you use the photolithography method, you can remove the resist using a removal solution such as J-100.
or ignited nitrous acid, etc., and the characteristics deteriorate significantly.

Therefore, in the past, manufacturing was possible only by the mask evaporation method, but with this mask evaporation method, when aligning the metal mask on the substrate,
Many defects occurred due to scratches on the substrate, adhesion of dust, etc., and when the completed solid-state image sensor was operated, many line scratches and dots appeared.

Furthermore, photoconductive films and transparent electrodes formed by vapor deposition generally have very low strength, making it difficult to remove dust that adheres when cutting completed wafers by cleaning or the like. The remaining dust was also a major cause of defects that occurred when the color filters were glued together (normally, the gap between the color filter and the transparent electrode must be bonded to a thickness of about 5 to 6 microns, so the dust was compressed by the filter). (This may cause defects in the device.)

In view of the above-mentioned drawbacks, the present invention is capable of depositing a photoconductive film and a transparent electrode on the entire surface without using a metal mask, thereby preventing scratches caused during alignment and adhering dust, and, moreover, depositing a photoconductive film and a transparent electrode on a predetermined area. The etching mask for leaving the photoconductive film and transparent electrode consists of two layers: a cured resin film pattern made of photocurable resin and a second resin film pattern, and after further etching, only the second resin film pattern is removed. However, the first photocuring resin film pattern remains and is used as a protective film when cutting a wafer or adhering a filter, with the aim of greatly improving the defect-free manufacturing yield of solid-state imaging devices. .

Hereinafter, embodiments of the present invention will be described in detail using FIG. 2.

First, a normal MOS
After the picture element section 12 consisting of a photodiode for sensing an optical image and a transfer BBD element and the driving section 13 consisting of a MOS transistor and a CCD element are formed using a process, a conductive wiring 15 and a photodiode are formed via an insulating film 14. An electrode 16 is formed to connect the photoconductive film and the photoconductive film.

Next, a photoconductive film (e.g. ZnSeZn _1-x Cd _x Te) 1
7 and transparent electrodes (e.g. doped with Sn)
In ₂ O ₃ ) 18 is sequentially deposited over the entire surface (FIG. 2a).

After that, photocurable resin 31 with good transparency (for example, product name Summers UV-74, Norland NOA-6)
1 to a thickness of 1 to 2 μm using a spinner) was coated on the entire surface (Fig. 2b), and light was irradiated using a photomask B having a predetermined pattern (2nd
After development, the first resin film pattern 19 remains only on the upper surface of the picture element portion 12 (FIG. 2d).

Furthermore, a resin that decomposes with light (for example, Shipley, AZ1350J) is applied and exposed and developed using a predetermined pattern mask to form a second resin film pattern 19' (Fig. 2e). Then, using the second resin film pattern as an etching mask, unnecessary portions of the photoconductive film 17 and transparent electrode 18 are removed by etching. Note that if the photoconductive film 17 is ZnSe-Zn _1-x Cd _x Te, it is
Etching can be done in 3 minutes. Amorphous silicon can be easily etched with hydrofluoric acid or hydrofluoric nitric acid. Alternatively, plasma etching or sputter etching may be used. On the other hand, in the case of transparent electrode ITO, it can be easily removed with 10% oxalic acid at 80°C to 90°C (Figure 2 f).

Thereafter, the entire surface is irradiated with light and only the second resin film pattern 19' is removed using a developer. Here, the second
When a photodegradable resin, that is, a positive resist is used for the first resin film pattern 19', it is easily decomposed by light irradiation, so a developer can be used to selectively remove the first cured resin film pattern 19 without damaging it. Moreover, only the second resin film pattern 19' can be easily removed.

Next, the wafer 11 is cut into a predetermined size and cleaned using the cured resin film pattern 19 as a protective film without removing it. That is, at this time, the transparent electrode 18 and photoconductive film 17 left by etching are removed from the first cured resin film pattern 19.
Since there is no contact with water or cleaning solvents, no damage will occur.

Finally, the color filter 21 is bonded onto the first cured resin film pattern 19 using the adhesive 20, and wire bonding 15' is performed for the external leads, pad portions, and transparent electrodes to complete the solid-state image sensor. (Figure 2g).

As a second embodiment, the second cured film pattern may be formed by using a photocurable resin instead of a photodegradable resin, such as a negative resist, as the second resin.
The same effect can be obtained if the first cured film pattern remains and can be selectively removed. When an epoxy-based photocurable resin is used for the first cured resin film and KTFR from Kodak Co., Ltd. is used for the second cured resin film,
Only KTFR can be easily removed with xylene or toluene. In addition, in this case, after coating the first and second resin films in layers, the first resin film can be coated using one mask.
It is also possible to simultaneously expose the first and second resin films, develop the second film, and then develop the first film.

As a third embodiment, if UV-curable adhesives are used for both the first cured resin film pattern and the adhesive, the two layers of resin between the transparent electrode 18 and the color filter 21 will have the same refractive index. This is convenient because the optical properties are improved and the adhesiveness between the resins is also good. Furthermore, the time required for adhesion can be significantly reduced.

As described above, according to the method of the present invention, the mask vapor deposition method is not used for vapor deposition of the photoconductive film and the transparent electrode, so the probability of scratches on the device and non-adherence of dust is much higher than in the conventional method. It becomes less. Moreover, since the photocurable resin left after etching is not removed and is used as a protective mask when cutting the wafer, moisture does not penetrate and dirt can be easily washed away with water after cutting. Moreover, since this photocurable resin remains even when the filter is bonded, defects that occur during bonding can be greatly reduced.

Therefore, a high-sensitivity, high-density solid-state imaging device can be manufactured with a high yield.

Furthermore, if a UV-curable adhesive is used for both the first cured resin film pattern and the adhesive, no interface will be formed in the adhesive resin layer, resulting in better optical properties, significantly shortening the curing time, and improving manufacturing efficiency. climb.

[Brief explanation of the drawing]

FIG. 1a is a plan view of a solid-state image sensor with a photoconductive film;
Figure 1b is a sectional view taken along line X-X', Figure 2a, b,
c, d, e, f, g are process cross-sectional views for explaining one embodiment of the method for manufacturing a solid-state image sensor of the present invention,
FIGS. 3a and 3b are diagrams for explaining the pixel portion of a solid-state image sensor obtained by the same manufacturing method, where FIG. 3a is a plan view, FIG. 3b is a sectional view taken along line X-X', and FIG. Figure 4 a, b
1 is a diagram showing clock pulses and diode potentials used in the same solid-state image sensor. 11... Base substrate (silicon wafer), 12...
... picture element section, 13 ... drive section, 17 ... photoconductive film,
18...Transparent electrode, 19...First resin pattern, 19'...Second resin pattern, 20...Adhesive, 21...Color filter.

Claims (1)

[Scope of Claims] 1. A step of sequentially forming a photoconductive film and a transparent electrode on the entire surface of a substrate on which a picture element part and a drive circuit part are formed, and applying a photocurable resin on the photoconductive film. , forming a first cured resin film pattern of the photocurable resin on the surface of the picture element portion by exposure and development using a predetermined pattern mask; and on the first cured resin film pattern, forming a second resin film pattern on the first cured resin film pattern by applying a second resin and performing an exposure phenomenon using a predetermined pattern mask; The mask includes a step of etching the transparent electrode and the photoconductive film, and a step of selectively removing only the second resin film pattern with a developer after exposing the entire surface of the second resin film pattern. . A method for manufacturing a solid-state image sensor, characterized in that the first cured resin film pattern is left as a protective film. 2. The method for manufacturing a solid-state imaging device according to claim 1, wherein the second resin is a photodegradable resin. 3. The solid according to claim 1, wherein the second resin is a photocurable resin, and after etching the photoconductive film, the second resin film pattern is removed using an organic solvent. A method for manufacturing an image sensor. 4. A step of sequentially forming a photoconductive film and a transparent electrode on the entire surface of the substrate on which the picture element part and the drive circuit part are formed, and applying a photocurable resin on the photoconductive film and applying a predetermined pattern mask. a step of forming a first cured resin film pattern of the photocurable resin on the surface of the picture element portion by exposing and developing the photocurable resin, and applying a second resin on the first cured resin film pattern. a step of forming a second resin film pattern on the first cured resin film pattern by exposure and development using a predetermined pattern mask; and a step of forming the transparent electrode using the second resin film pattern as a mask. and a step of etching the photoconductive film, and a step of selectively removing only the second resin film pattern with a developer after exposing the entire surface of the second resin film pattern, Solid-state imaging characterized in that the resin film pattern is left as a protective film, and a color filter is adhered on the first cured resin film pattern using a resin of the same type as the first cured resin film pattern. Method of manufacturing elements. 5. A step of sequentially forming a photoconductive film and a transparent electrode on the entire surface of the substrate on which the picture element part and the drive circuit part are formed, and applying a photocurable resin on the photoconductive film and applying a predetermined pattern mask. a step of forming a first cured resin film pattern of the photocurable resin on the surface of the picture element portion by exposing and developing the photocurable resin using a photocurable resin, and applying a second resin on the first cured resin film pattern. a step of forming a second resin film pattern on the first cured resin film pattern by exposure and development using a predetermined pattern mask; and a step of forming the transparent electrode using the second resin film pattern as a mask. and a step of etching the photoconductive film, and a step of selectively removing only the second resin film pattern with a developer after exposing the entire surface of the second resin film pattern, The resin film pattern is left as a protective film, the second resin is a photodegradable resin, the second resin film pattern is removed using an organic solvent, and the first photocurable resin film is removed. A method for manufacturing a solid-state image sensor, which comprises bonding a color filter onto a pattern using an adhesive.