JPH02272768A - Solid state image sensor - Google Patents

Abstract

PURPOSE:To suppress hillock and to eliminate an irregularity in sensitivities of pixels by forming a light shielding Al-Si film and a wiring Al-Si film of a plurality of layers. CONSTITUTION:A light shielding film 8' and a wiring film 10' are respectively formed of two layers of Al-Si films 8a, 8b and Al-Si films 10a, 10b in such a manner that the Si content ratios of the upper layers 8a, 10a are 0-0.5% and the Si content ratios of the lower layers 8b, 10b are 0.8-1.6%. Thus, since the layers 8a, 10a are reduced in the Si content ratio, the Al-Si film is deposited on an insulating film 7, a N-type diffused layer 11, hillock can be suppressed in a heat treating step. Since the layers 8b, 10b are slightly increased or decreased in the Si content ratio as compared with prior art, it does not pass through the layer 11 to obtain a satisfactory contact.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a solid-state imaging device in which variations in sensitivity of each pixel are reduced.

(Prior Art) In recent years, the imaging performance of solid-state imaging devices has been rapidly improving, and there is a growing demand for higher performance.

FIG. 2(a) shows a schematic cross-sectional side view of a unit cell of a conventional solid-state image sensor. This is the light receiving area (N)1 of the photodetector,
Enhancement region (P”) of the transmission gate portion 2. Including the buried channel (N”) 3 and the transmission gate 4.
A set of vertical transfer register sections that carry charges in the vertical direction is formed with an insulating isolation region (P+) consisting of a channel stopper 5 interposed therebetween. A P-well 6 selectively formed on the N-type semiconductor substrate 12 and a light-shielding film 8 that determines the area of the light-receiving region 1 are formed on the transmission gate 4 via an insulating film 7.

Further, FIG. 2(b) shows a schematic cross-sectional side view of the peripheral MOS transistor shown in FIG. 2(a). 9 is a gate electrode, 10
11 is a wiring film, 11 is an N-type diffusion layer, and the other parts are the same as in FIG.

The light shielding film 8 in FIG. 2(a) and the wiring film 10 in FIG. 2(b) are formed at the same time during manufacturing, and the light shielding film 8 and the wiring film 10 are
However, in the case of FIG. 2(b), if pure Ad is used, AQ will penetrate into the thin N-type diffusion layer 11, so conventionally, Ad containing Si (1.0%) in AI+ has been used. −
3i (1.0%) was used to prevent Al from penetrating into the N-type diffusion layer.

(Problems to be Solved by the Invention) However, on the other hand, since Si is contained in the Al, hillocks 8h occur in the light shielding film 8 and the wiring film 10 during manufacturing.

10h (llill・ock) has become more likely to occur. This is done by using the A+2-Si film as the insulating film 7 and the N-type diffusion layer 11.
It is thought that this occurs due to recrystallization during the process of vapor deposition and heat treatment.

Hillock 8h in Figure 2(a) is light receiving area 1 as shown in the figure.
Because it protrudes from the outside and partially blocks light, it affects the variation in sensitivity of each pixel on the imaging screen. Also, Figure 2(b)
As shown in FIG. 1, the hillock toh causes the wiring film 10 to have thinner areas and thicker areas, resulting in a change in resistance value (increase) and variation.

It is an object of the present invention to suppress the occurrence of hillocks in the light shielding film and wiring film, to eliminate variations in the sensitivity of each pixel, and to ensure good wiring contact.

(Means for Solving the Problems) In order to achieve the above object, the present invention has a two-layer structure for the light-shielding film and the wiring film, and the film material is an Al1-3i film, and the Si content of the upper and lower layers is It is characterized by changing the

(Function) In the present invention, the upper Alt-Si film has a Si content of 0 to 0.5%.
.

Lower layer (7) Al-8L film (7) S i is 0.8 to 1.
By containing each in the range of 6%, the upper layer contains less Si than before to suppress the occurrence of hillocks, and the lower layer contains slightly more or less Si than before to improve contact.

(Example) FIG. 1 shows a schematic sectional view of an example of the present invention, (a)
is a unit cell, and (b) is a MoS transistor in the peripheral area. In both figures (a) and (b), the light shielding film 8' and the wiring film 10' are a two-layer AI-SL film 8a,
8b.

and 10a, 10b, the Si content of the upper layer 8a, 10a is O~0.5%, and the lower layer (7) 8b, 10
b(7) They are manufactured with Si content ranging from 0.8% to 1.6%.

With this configuration, the upper layers 8a and 10a have a Si content of 1.0% to at most 1/1% compared to the conventional one.
As a result, the occurrence of hillocks 8h and 10h occurred during the process of depositing the A+2-8L film on the insulating film 7 (figure a) and the N-type diffusion layer 11 (figure b) and heat-treating it. suppress,
In the case of (a), the variation in sensitivity of each pixel in the light-receiving area 1 is reduced. In addition, the lower layers 8b and 10b are made of Si compared to the conventional one.
Since the content rate is only slightly decreased or increased by 0.2 to 0.6% from 1.0%, in the case of figure (b), the thin N-type diffusion layer 11
Good contact can be obtained without penetrating the surface.

Note that the standard Si content is 0.
5% and 1.0% for the lower layer sb and tab was optimal for suppressing material mixture and hillocks, eliminating variations in pixel sensitivity, and establishing good wiring contacts.

(Effects of the Invention) As explained above, in the present invention, the light shielding film of the +4 cell and the wiring film of the peripheral MOS transistor, which are formed simultaneously during manufacturing, are changed from the conventional one-layer structure to a two-layer structure, and the Af! −
The Si content of the 3j film was made lower in the upper layer and higher in the lower layer to suppress the occurrence of hillocks in the upper layer and to improve contact in the lower layer.

As a result, variations in the sensitivity of each pixel in the jll-cell are eliminated, resulting in improved quality.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of an embodiment of the present invention, and FIG. 2 is a schematic sectional side view of a conventional solid-state image sensor. 1... Light receiving area, 2... Enhancement, 3...
...Embedded channel, 4...Transmission gate, 5...
Channel stopper, 6...P well, 7...
・Insulating layer, 8, 8'... Light shielding film, 8a, 10a
- Upper layer, 8b, 10b...lower layer. 9...Gate electrode, 10.10'...Wiring film,
11...N-type diffusion layer, 12...N-type semiconductor substrate. Patent developer Matsushita Electronics Co., Ltd.

Claims (1)

[Claims] In a solid-state imaging device having a plurality of unit cells each consisting of a photoelectric conversion element section, a transmission gate section, and a vertical transfer register section, an Al-Si film for light shielding and an Al-Si film for wiring are formed as two-layered films. A solid-state imaging device featuring: