JPS60217662A - Solid-state image pickup board - Google Patents

Abstract

PURPOSE:To improve the dimensional accuracy of finishing, and to enhance reliability and durability by constituting a polycrystalline silicon film under aluminum or an aluminum alloy layer for an electrode wiring in a solid-state image pickup board. CONSTITUTION:Light-receiving sections 12, signal transfer sections 13, insulating films 14 consisting of SiO2 or PSG or the like and signal transfer gates 15 are constituted to a silicon substrate 11. A polycrystalline silicon film 16 is formed on the whole surface through a decompression CVD method, and an aluminum film 17 is shaped on the whole surface of the polycrystalline silicon film 16. A predetermined resist is applied on the surface of the aluminum film 17, and a resist film 18 according to a prescribed pattern is formed through exposure etching. The aluminum film 17 is shaped according to a predetermined pattern for electrode wirings through plasma etching while using the resist film 18 as a mask. Plasma etching is completed, and the polycrystalline silicon film 16 on the surfaces of the light-receiving sections 12 is removed by treating the film 16 by a mixed solution of substances such as approximately 1% hydrofluoric acid and nitric acid, thus obtaining a solid-state image pickup board in which there is the polycrystalline silicon film 16 under the aluminum film 17 for electrode wirings.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a solid-state imaging plate.

[Prior art and its problems]

In recent years, solid-state imaging plates are increasingly required to have high resolution.

This requirement for high resolution can be achieved by miniaturizing solid-state image sensor elements and increasing pixel density.

However, in order to miniaturize a solid-state imaging plate element to, for example, about 2 μITI, etching of 5in2, AZ, etc. constituting the element cannot be achieved by wet etching using a solution, and plasma etching must be used.

In other words, by adopting the plasma etching method as the etching method for 5in2 and kt, it is possible to
It becomes possible to perform fine processing to a certain extent, and it becomes possible to obtain a high-resolution solid-state imaging plate.

However, when attempting to obtain a solid-state imaging plate using plasma etching techniques, problems arise that do not occur when wet etching techniques are used. For example, the miniaturization of solid-state image sensor elements naturally means that the area of the light-receiving part also becomes smaller, so in order to increase sensitivity, it is necessary to allow as much light as possible to enter the light-receiving part. No. However, when plasma etching technology is used, residual material that is difficult to remove remains on the surface of the light receiving section after plasma etching, and as a result, the amount of light incident on the light receiving section is reduced accordingly, resulting in a decrease in sensitivity.

That is, as shown in FIGS. 3 and 4, the conventional solid-state image pickup plate includes a silicon substrate 1, a light receiving part (source) 2, a signal transfer part (drain, in) 3, an insulating film 4 such as Sin, and a signal After the transfer gate 5 and the like are constructed, an aluminum or aluminum alloy (hereinafter simply referred to as aluminum) film 6 for electrode wiring is formed on the entire surface, and a prescribed resist film is formed on this aluminum film 6 to form a prescribed pattern. By performing plasma etching using the formed resist film 7 as a mask, a solid-state imaging plate as shown in FIG. 3 is obtained in which the aluminum film 6 forms turns for predetermined electrode wiring.

However, since this solid-state imaging plate uses plasma etching (reactive ion etching) technology to form the aluminum film into a predetermined pattern for electrode wiring, the polymer film and aluminum produced during etching are Components such as Si and Cu (even if it is not an aluminum alloy, aluminum materials contain trace amounts of unavoidable impurities, and these unavoidable impurity components) remain on the surface of the light receiving part 2! i, 8, and these residues 8
Since the light scatters or absorbs the incident light, the sensitivity of the solid-state image pickup plate is reduced.

Hey, what's left of the above? If h,8 is of a polymeric film formed during etching, it is almost impossible to remove such residues.

[Means for solving problems]

A polycrystalline silicon film is formed under the aluminum or aluminum alloy layer for electrode wiring of the solid-state imaging plate.

〔Example〕

FIG. 1 is an explanatory diagram of one embodiment of a solid-state imaging plate according to the present invention,
FIG. 2 is an explanatory diagram in the middle of the solid-state imaging plate manufacturing process of FIG. 1.

In the figure, 11 is a silicon substrate, for example, and this silicon substrate 11 includes a light receiving part 12, a signal transfer part 13, an insulating film 14 such as PSG, and a signal transfer part 13, as in the case of a conventional solid-state image pickup plate. A gate 15 is configured.

After these structures are completed, a polycrystalline silicon film 16 is formed to a thickness of about 500 A over the entire surface by low pressure CVD, and an aluminum film 17 is formed to a thickness of about 1 μm over the entire surface of the polycrystalline silicon film 16.

Thereafter, a predetermined resist is applied onto the surface of this aluminum film 17, and exposed and etched to form a resist film 18 having a predetermined pattern.

Then, using this resist film 18 as a mask, for example, C.
Plasma etching is performed using a chlorine compound etchant such as Ct4 or a mixed gas of CCt and Bct3 to form the aluminum film 17 into a predetermined pattern for electrode wiring.

After that, after the plasma etching of the aluminum film 17 is completed, the polycrystalline silicon film 1 on the surface of the light receiving part 12 is removed.
6 is removed by treating with a mixed solution of about 1% hydrofluoric acid and nitric acid, for example, to form a solid state with a polycrystalline silicon film 16 under the aluminum film 17 for electrode wiring as shown in FIG. Obtain an imaging plate.

In the solid-state imaging plate having the above configuration, the aluminum film 17
Since there is a polycrystalline silicon film 16 underneath, electromicrobial crepe on the aluminum film is prevented, and even if an undercut occurs during plasma etching of the aluminum film 17, the polycrystalline silicon film 16 under the resist film 18 can be etched. Therefore, undercuts are minimized, and the etching accuracy of the aluminum film for electrode wiring is improved. In other words, the accuracy of the electrode wiring is significantly improved, and the reliability and durability are improved accordingly.

Since polycrystalline silicon is conductive, there is no problem in using it as part of the electrode wiring.

Furthermore, during plasma etching of the aluminum film, when the etching of the aluminum film 17 is completed, etching of the polycrystalline silicon film 16 begins, so the emission spectrum due to the etching of the polycrystalline silicon is observed, and when this emission spectrum is observed, It is only necessary to finish the plasma etching, that is, the plasma etching can be easily controlled, thereby improving the precision of the plasma etching and the precision of the electrode wiring.

Further, even if a residue similar to that in the conventional method is generated on the polycrystalline silicon film 16 due to the plasma etching of the aluminum film, it can be easily removed by removing the polycrystalline silicon film 16. First, after the plasma etching of the aluminum film 17 is completed, the polycrystalline silicon film 16 on the exposed surface of the light receiving part 12 can be easily removed by immersing it in a mixed solution of about 1% hydrofluoric acid and nitric acid. As a result, there is no residue on the surface of the light receiving part 12, and the polycrystalline silicon film 1 is removed.
6 is thinner than the aluminum film 17,
A polycrystalline silicon film 16 on the light receiving part 12 surface is formed in a short time.
The aluminum film 17 for electrode wiring can be removed with almost no effect on the aluminum film 17 for electrode wiring.
dimensional accuracy hardly decreases.

As a result, there is no unnecessary material on the surface of the light-receiving section 12, and since it does not reduce the incident light, the sensitivity of the image pickup plate is improved. This is preferable because even if the S + 02 insulating film 14 is damaged by this, the damaged layer can be removed.

〔effect〕

The processing dimensional accuracy of the aluminum or aluminum alloy layer for electrode wiring is improved, and it becomes highly reliable and durable.

Furthermore, there is no etching residue on the light-receiving surface that would block incident light, resulting in a solid-state imaging plate with improved sensitivity.

Furthermore, it is possible to miniaturize the elements, that is, it is possible to employ means for increasing the pixel density, resulting in a high-resolution solid-state imaging plate.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of one embodiment of a solid-state imaging plate according to the present invention, and FIGS. 3 and 4 are explanatory diagrams of a conventional solid-state imaging plate. 16... Polycrystalline silicon film (polycrystalline silicon layer), 1
7... Aluminum film (aluminum or aluminum alloy layer for electrode wiring).・(“1 ;-2 fil fishing 2n 3rd figure 4th figure

Claims (1)

[Claims] A solid-state imaging plate comprising a polycrystalline silicon layer under an aluminum or aluminum alloy layer for electrode wiring of the solid-state imaging plate.