JPH01143256A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To prevent any spike noise from being produced and an S/N from being deteriorated by reducing the occurrence of any crystal defect and any disturbance on an oxide film and a semiconductor substrate by flattening the surface of the semiconductor substrate at a photoelectric converter part and a charge transfer part. CONSTITUTION:A p-type silicon semiconductor substrate 1 of silicon is oxidized to form an insulating film 7' and further a polycrystalline silicon film 6 is formed thereon, on which film 16 a silicon nitride film 10 is formed by a chemical vapor phase growing method. The film 10 is etched into a predetermined pattern. Then, a resist film 12 is patterned to form an N-type region 5 of a photodiode. After removal of the resist film 12, a resist film 13 is patterned, and the film 16 is selectively etched with use of the film 10 as a mask to form an N-type region 6 of a charge transfer part. In succession, when the film 16, which is left at the photodiode part, is completely oxidized into a silicon oxide film, semiconductor substrate surface fractions corresponding to the photodiode part and the charge transfer part are selectively oxidized. Further, the film 14 is left to form a channel stop region 8. Films 7'', 7''', 7' are removed by etching and oxidized on their surfaces to form an insulating film 7. An interface between the insulating film 7 and the substrate 1 is flattened at the photodiode part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device, and particularly to a two-arrow solid-state imaging device using CC1).

[Conventional technology]

In general, a solid-state imaging device using a CCU (charge transfer unit) has a photoelectric conversion section consisting of a plurality of photodiodes formed on the surface of a semiconductor substrate by a P-N junction, a charge transfer section that transfers signal charges, and a photodiode and charge transfer section. It consists of an adjacent transfer gate region for transferring signal charges, an adjacent photodiode, and a channel stop region for electrically separating the photodiode and the charge transfer section.

FIG. 4 is a cross-sectional view of a chip showing the main parts of a conventional example, in which the photodiode 2 is constituted by an N-type region 5 formed on the surface of a P-type semiconductor substrate 10.

The charge transfer section 3 is configured as a buried child type CCD by a polycrystalline silicon electrode 4 formed on the insulating film 7 on the surface of the semiconductor substrate 1 and an N-type region 6 formed under this electrode. The transfer region 9 is a P-type region, and a signal is read out from the photodiode 2 to the charge transfer section 3 by applying a read pulse to the multi-packed silicon electrode 5. Each photodiode is [,
It is separated from the adjacent photodiode and charge transfer section by a channel stop region 8, which is a high-strength P-type region.

In the conventional example shown in FIG. 4, the interface between the substrate and the insulating film of the photodiode 2 and the charge transfer section 3 is recessed. This prevents the impurities from the highly doped P-type region (8) from diffusing laterally into the N-type region 6 of the charge transfer section in the heat treatment in the subsequent step, thereby preventing the area of the N-type region 6 from decreasing.

The structure shown in FIG. 4 can be formed in a self-aligned manner by selective oxidation using a silicon nitride film.

That is, as shown in FIG.
Deposit 0.

Next, as shown in FIG. 5fb), the silicon nitride film 10 is etched into a predetermined pattern.

Next, as shown in FIG. 5(C), the resist film 12 is patterned by photolithography. Thereafter, the N-type region 5 of the photodiode is formed by ion implantation.

After removing the resist film 12, the resist film 13 is similarly patterned by photolithography to form the N-type region 6 of the charge transfer section 3, as shown in FIG. 5(d).

Next, after removing the resist film, as shown in FIG. 5(e), a thick insulating film 7'' is formed by selectively oxidizing the photodiode and the charge transfer portion.

Next, as shown in FIG. 5 (fl), a resist film 15 is provided in the transfer gate region, and a heavily doped P-type region is formed as a channel stop region 8 by ion implantation.

Finally, the insulating films 7' and 7'' are removed by etching, the surface is oxidized to form the insulating film 7, and the polycrystalline silicon electrode 4 is patterned and formed to form a solid-state imaging device as shown in FIG. be able to.

[Problem that the invention seeks to solve]

In the conventional solid-state imaging device described above, the surface of the semiconductor substrate in the photodiode portion is selectively oxidized and recessed. For this reason, crystal defects due to surface stress and disorder of the oxide film and semiconductor substrate do not occur in the photodiode part.
Occurrence of fixed spike noise in solid-state imaging devices and S
/N has the disadvantage of causing deterioration.

[Means for solving problems]

The solid-state imaging device of the present invention includes a photoelectric conversion section and a charge transfer section selectively provided on the entire surface of a first conductivity type semiconductor substrate, and a charge transfer section provided adjacent to the charge transfer section. In the solid-state imaging device having a high concentration 14m type channel stop region, the surface of the semiconductor substrate is flat and concave at the photoelectric conversion section and the charge transfer section, respectively.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of a chip showing the main parts of an embodiment of the present invention.

FIG. 2 (al to FIG. 2 ff) are chip cross-sectional views showing the order of steps for explaining the manufacturing method of this embodiment.

A hemi-type region 5 of a photodiode and an N-type region 6 of a charge transfer region are selectively formed on the main surface of a P-type semiconductor substrate made of silicon, and a channel stop region 8 and a transfer gate region 9 are formed as in the conventional example. It is formed in the same manner as shown in FIG.

The difference of this embodiment from the conventional example is that the interface between the insulating film 7 and the semiconductor substrate 1 in the photodiode portion is not concave but flat.

This solid-state imaging device can be created by self-alignment as follows.

First, as shown in FIG. 2(a), P made of silicon
The type semiconductor substrate 1 is oxidized to form an insulating film 7', and a polycrystalline silicon film 16 is formed to a thickness of about 20 nm, and then a silicon nitride film 10 is formed on this polycrystalline silicon film 16 by chemical vapor deposition. form.

Next, as shown in FIG. 2+bl, the silicon nitride film 10 is etched into a predetermined pattern.

Furthermore, the resist film 12 is patterned by the 'cX etching method as shown in FIG. 2 fc). Thereafter, the N-type region 5 of the photodiode is formed by ion implantation.

After removing the resist film 12, the resist film 13 is patterned by photolithography as shown in FIG. 2(d). Next, the polysilicon film 16 is selectively etched using the patterned silicon nitride film 10 as a mask. Furthermore, the N type region 6 of the stain transfer portion is formed by ion implantation.

Next, after removing the resist film 13, the polycrystalline silicon film 16 left in the photodiode part is oxidized until it becomes a silicon oxide film, and as shown in FIG. Oxidized.

Next, as shown in FIG. 2, a resist film 14 is left in the transfer gate region, and a heavily doped P-type head region is formed as a channel stop region 8 by ion implantation. Finally, selective oxide films 7", 7"' and oxidized &7' are removed by etching and the surface is oxidized to form insulating film 7 into shape 5, L, and polycrystalline silicon electrode 4 is patterned and formed, as shown in FIG. The solid-state imaging device of the present invention can be created as follows.

In this embodiment, the surface of the semiconductor substrate is concave in the charge transfer section, which prevents narrowing of the N-type region as in the conventional example, but since the photodiode section is flat, crystal defects occur due to surface stress. There is no fixed spike noise or 8/N deterioration in low illuminance.

FIG. 3 is a cross-sectional view of a chip showing the main parts of a second embodiment of the present invention.

In this embodiment, instead of selectively oxidizing the charge transfer portion to make the interface between the substrate 1 and the insulating film 7 concave as in the first embodiment, deep grooves are formed by etching the substrate 1. The interface between the substrate 1 and the insulating film 7 in the charge transfer section is made concave. In this embodiment, not only is it possible to prevent impurity diffusion from the highly-concentrated P-type head region (8) to prevent narrowing of the N-type region 6 of the charge transfer section, but also the amount of transferred charge is increased by increasing the depth of the groove. can be increased.

〔Effect of the invention〕

As explained above, in the present invention, since the interface between the semiconductor substrate and the insulating film in the charge transfer section is in a concave state, the impurity region in the charge transfer section is narrowed due to impurity diffusion from the channel stop region, and the amount of transferred charge is reduced. It will not decrease. Furthermore, since the interface between the substrate and the insulating film of the photodiode section is flat, image quality deterioration such as generation of fixed spike noise in a solid-state imaging device and deterioration of S/N at low illuminance does not occur.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a chip showing the main parts of the first embodiment of the present invention, and FIG. Figure 3 is a cross-sectional view of the chip showing the main parts of the second embodiment of the present invention, Figure 4 is a cross-sectional view of the chip showing the main parts of the conventional example, and Figures 5+a) to 5 Figure 3) is a cross-sectional view of a chip shown in order of steps for explaining a conventional manufacturing method. ■...P-type semiconductor substrate, 2...Photodiode, 3...Charge transfer section, 4...Polycrystalline silicon electrode, 5... Photodiode N
Type region, 6...N type region of charge transfer section, 7.7
', 7", 7"...Insulating film, 8...Channel stop region, 9...Transfer gate region.

Claims (1)

[Claims] A photoelectric conversion section and a charge transfer section including a second conductivity type region selectively provided on one main surface of a semiconductor substrate of a first conductivity type, and a highly concentrated first charge transfer section provided adjacent to the charge transfer section. A solid-state imaging device having a conductive type channel stop region, wherein the surface of the semiconductor substrate is flat and concave at the photoelectric conversion section and the charge transfer section, respectively.