JPS6084869A - Manufacture of solid-state image pickup device - Google Patents

Abstract

PURPOSE:To enable to obtain a short channel stopper length by a method wherein a masking film is selectively formed, and selective diffusion is performed; thereafter a masking film is formed again from above, which is then thermally oxidized. CONSTITUTION:After an oxide film 2 is formed on the surface of a P type Si substrate 1, an Si nitride film 3 is formed by the method of LPCVD. The film 3 is partly removed by the plasma etching succeeding a photolithography, and a P<+> region 4 is formed by boron ion implantation to the removed part. Next, an Si nitride film 3 is partly removed after the process of forming this film again, and an oxide film 5 is formed at the removed part. Then, a polycrystalline Si film 6 is formed by the method of LPCVD, and this film is partly removed by the plasma etching succeeding a photolithography. For the purpose of forming a mask against phosphorus ion implantation, a mask made of a resist film 8 is formed by the use of photolithography, and a region 7 is formed by phosphorus ion implantation. Finally, the resist film is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a solid-state imaging device.

(Conventional structure and its problems) In recent years, with the development of semiconductor integrated circuit technology, MOS (
Development of solid-state imaging devices using metal oxide semiconductor (metal oxide semiconductor) structures is progressing and has already reached the stage of practical use.

1(a) to 1(f) show a conventional method for manufacturing a solid-state imaging device, and FIG. 1(a) shows a single crystal semiconductor substrate 1.
In the process of forming an oxide film 2 and a masking wave f3 on the surface of the substrate 0, a part of the masking film 3 is removed and an opening is formed, as shown in FIG. FIG. 1C shows a step of selectively thermally oxidizing the portion where the masking film 3 has been removed to form a so-called LOGO8 oxide film 5. Figure (d) is masking Kawanami jli3
1st step of removing the polycrystalline silicon film 6 to form a polycrystalline silicon film 6
Figure (e) shows a step of removing a part of the polycrystalline silicon film 6;
FIG. 1(f) shows the process of forming a region 7 having a conductivity type opposite to that of the substrate 1 in a region other than the LOC and O8 oxide films 5 in the removed portion of the polycrystalline silicon film 6. ing.

Figure 2 shows the photoelectric conversion part of a one-dimensional solid-state imaging device manufactured by a conventional manufacturing method.
) is a plan view of the photoelectric conversion section at the time of photomask design.

Reference numeral 7 denotes a photocharge storage section having a conductivity type opposite to that of the substrate 1;
is a channel stopper region partitioning each pixel, which is made of the same conductive material as the substrate 1 and has a higher concentration than the substrate 1. It has been found that in order to improve the resolution characteristics of a solid-state imaging device, it is necessary to reduce the length of the channel stopper 4 in the pixel arrangement direction. However, in the conventional selective oxidation method described above, the so-called LOCO8 method, as shown in FIG. There is a phenomenon called , and the actual channel stopper area 4 is wider than the channel stopper area 4 in FIG. 2(a), that is, the channel stopper area at the time of mask design. Figure 2 (CC) shows a plan view of a one-dimensional solid-state imaging device manufactured using the conventional LOCO8 method.Comparing with the plan view of Figure 2 (a) at the time of mask design, the pixel arrangement of the channel stopper 4 is The length in the direction tends to be wider in FIG. 2(C) by about the thickness of the LOCO8 oxide film. In recent years, the pixel pitch has become smaller, and the channel stopper length at the time of design has become close to the limit value in semiconductor device manufacturing.
The expansion 9 equivalent to the thickness of the O8 film is a major obstacle to improving resolution characteristics.

(Object of the Invention) In view of the above-mentioned drawbacks of the conventional example, the present invention provides a method for manufacturing a solid-state imaging device that can obtain a short channel stopper length.

(Structure of the Invention) In order to achieve this object, the method of the present invention selectively forms a masking film that exhibits a masking effect against impurity introduction and thermal oxidation, performs selective diffusion, and then repeats the process again. A masking film is formed on top, followed by thermal oxidation. As a result, a short channel stopper length can be obtained.

(Explanation of Examples) Examples will be described below with reference to the drawings.

FIG. 3 shows a method for manufacturing a solid-state imaging device according to an embodiment of the present invention. First, on the surface of a P-type 7 silicon substrate 1,
A 50oi oxide film 2 is formed by thermal oxidation, and then 1
A silicon nitride film 3 of 20 OA is formed by the LPCVD method (Fig. 3 (ω)). Next, a part of the silicon nitride film 3 is removed by photolithography followed by plasma etching. Boron ions are implanted into the removed portion of the film 3 to form a P region 4, and then the photoresist is removed (see Fig. 3(b)).
)).

Next, a process of forming 1,200 solicon nitride films 3 again in the same manner as above (FIG. 3(C)),
Thereafter, a portion of the silicon nitride film 3 is removed by plasma etching following photolithography (FIG. 3(d)).

Further, an oxide film 5 having a thickness of 500A is selectively formed on the removed portion of the silicon nitride film 3 by thermal oxidation (FIG. 3(e)). Next, the silicon nitride film 3 is removed by plasma etching, and then thermal oxidation is performed so that the total thickness of the oxide film 2 becomes 100X, and then a polycrystalline silicon film 6 with a thickness of 4000X is formed by LP. CV
Formed by method D (3rd @ (f)). Next, a part of the polycrystalline silicon film 6 is removed by photolithography followed by plasma etching (FIG. 3@). Further, in order to form a mask for phosphorus ion implantation, a resist film 8 is formed using photolithography, and then phosphorus ions are implanted to form a region 7 (FIG. 3(h)).

Finally, the resist film 8 is removed (FIG. 3(i)).

As described above, in the method for manufacturing a solid-state imaging device of the present invention, after performing impurity diffusion to form a channel stopper, a silicon nitride film is again formed on the entire surface of the silicon nitride M3, and the impurity is Cover the diffusion area. Further, the silicon nitride film is removed only from the necessary portions, but thermal oxidation is performed while leaving the photoelectric conversion portions as they are.

Therefore, the length of the channel stopper in this portion is increased by 9 times.

(Effects of the Invention) As described above, according to the manufacturing method of the present invention, it is possible to maintain the length of the channel stopper fairly faithfully to the design dimension, and to obtain a short channel stopper length, making it possible to achieve practical The effects are huge.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a series of manufacturing steps of a conventional solid-state imaging device, FIG. 2 is a diagram showing a photoelectric conversion part of a solid-state imaging device manufactured by a conventional manufacturing method, and FIG. It is a figure showing a series of manufacturing steps of one example. 1... Semiconductor substrate, 2...
...Oxide film, 3...Silicon nitride film, 4......A region that has the same conductivity type as the substrate and has a higher impurity concentration than the substrate, 5... ...LO
CO8 oxide film, 6... Polycrystalline silicon film, 7... Region having a conductivity type opposite to that of the substrate. Patent applicant Matsushita Electronics Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 3

Claims (1)

[Claims] An oxide film is formed on the surface of the semiconductor substrate, and on top of that,
forming a masking film that exhibits a masking effect against impurity introduction and thermal oxidation, opening a part of the masking film and introducing a first impurity into that part;
a step of forming a region having the same conductivity type as the semiconductor substrate and having a high impurity concentration, and forming a film of the same type as the masking film again to cover the opening, and at the same time covering the opening at a required location. a step of selectively removing the masking film again; a step of thermally oxidizing only the selectively removed portion; and a step of forming a polycrystalline film after removing all of the masking film and forming a part of the masking film. and a step of forming a photoresist pattern and introducing a second impurity into the opening thereof to form a region of a conductivity type opposite to that of the semiconductor substrate. Method of manufacturing the device.