JPS59172763A - Manufacture of solid-state image pickup device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing an imaging device such as an interline transfer type 00D solid-state imaging device. In particular, it relates to improvements in the method of forming a light shield film around a photosensitive area.

[Technical background of the invention and its problems]

FIG. 1 shows the structure of a conventional solid-state imaging device (for example, a COD solid-state imaging device using an interline transfer method). FIG. 1(a) is a plan view of one pixel, and FIG. 1(b) is a sectional view thereof.

Next, the manufacturing method will be explained step by step.

[1] For example, selective diffusion, etching, opening, etc. are performed on the surface of the p-type silicon substrate 1 by a known method, and a photosensitive part (
An n+ type region 2, an n++ buried region 8 adjacent to this photosensitive section 2, a drain section 4 for discarding signal charges generated excessively in the photosensitive section 2, and a gate section 5 for this drain section 4. , channel stopper region (p+ type region 6
form each.

[Illusion] Next, a first layer insulating film 7 is formed on the substrate 1, and then a first layer transfer electrode 8 made of rainbow polycrystalline silicon or the like and a first layer transfer electrode 9 of an adjacent pixel are formed by photolithography. Form. Next, a second layer insulating film 10 is formed on the first layer insulating film 7 including these transfer electrodes 8 and 9, and a second layer transfer electrode 11 is formed thereon. The second layer transfer electrode 11 and the first layer transfer electrode form a readout section for reading out signal charges accumulated in the photosensitive section 2 in pairs.

[3] Next, the eighth layer insulating film 12 is formed on the second layer transfer electrode 11. When forming the third layer insulating film 12, a recess 13 is formed above the photosensitive section 2. In other words, the first and second N transfer electrodes 9 and 11 are not provided, making the structure thinner.

[4] Next, a light shield film 144' such as A7 is formed on the third layer insulating film 12! Provided for. This light shield film tA
serves as an electrode for blocking incident light and controlling the gate section 5 corresponding to the drain section 4. The light shield film 14 has an opening 15 in a portion corresponding to the photosensitive portion 2 . This opening 15 functions as a light entrance window.

[5] Finally, a protective film 16 such as a PSG film is provided on the entire surface to complete the manufacturing. However, after the protective film 16 is provided, the surface of the protective film 16 is not uniform because a concave portion 17 is formed in relation to the opening 15. This causes problems as described below.

[Problems with background technology]

As mentioned above, the concave portion 17 is formed in the protective film 16 using the conventional manufacturing method. The difference in level is μm
J・ru in degree. Due to the presence of this concave portion 17, Example: 2
．． If this is not the case in the later process and dust inevitably enters the recessed part 17 (c), it should be very carefully Therefore, the original shield film 14 controls the gate portion 5 due to the insulating film 7.1.
Since the film thickness is above the total film thickness J of 0.12, variations in the Threnhold 11°C pressure (Vth) IC occur between each image formation, resulting in a difference in the amount of saturation of the photosensitive area. This often leads to poor quality of the edges of the surface when the image is taken. As a result, the thickness of the insulating film under the electrode '6 which controls the gate portion 5 is uniform, and the improvement in characteristics can be seen.

For this reason, the surface of the imaging device, and thus the surface of the protective film 16, should be made uniformly flat without forming concave portions 17 as much as possible.

[Purpose of the invention]

The present invention solves the above-mentioned problems, and provides a solid-state device in which the surface of the first-dimensional device is made uniform with no unevenness, and the thickness of the insulating film on the gate portion with respect to the drain portion is made uniform. Our goal is to provide a method for manufacturing a photographing device.

[Summary of the invention]

In order to achieve the above object, the manufacturing method according to the present invention includes:
On the semiconductor substrate, signal charges 'ff-
It controls the photosensitive part that accumulates through the pn junction, the readout part that reads out the accumulated signal charges, the drain part that discards excessively generated signal charges, and the gate part that transfers the signal charges to this drain part. In the method for manufacturing a solid-state imaging device that includes a light shielding film that sets an incident light window at a position corresponding to the photosensitive part, the light shielding film is formed immediately after forming the readout part,
Next, a protective film is formed on the upper surface of the light shield film.

[Embodiments of the invention]

The present invention will be described below based on illustrated embodiments.

A second embodiment of the method for manufacturing a solid-state imaging device according to the present invention will be described in a second embodiment.
As shown in the figure. In FIG. 2, the same or overlapping parts as in FIG.

In the manufacturing process of the present invention, among the steps shown above, [1] and [phantom step] are the same, so the explanation will be given starting from step [8].

C8J After the second layer transfer electrode 11 is completely formed, the third layer insulating film 12 is formed on the entire surface. Immediately thereafter, a MoSi film that allows light to pass through is deposited on the entire surface to form a light shield region 1 that also serves as a control electrode for the gate section 7.
4 B i is formed. Next, an insulating film 18 is deposited on the light shield film 14B, and the surface of this insulating film 18 is made flat using, for example, the BPSG method. As a result of this process, the hollow recess 13 shown in FIG. 1 becomes very shallow.

[4] Finally, a protective film 16 such as a PSG film is formed on the insulating film 18. Note that the wiring can be the same as the conventional one [Al, etc.].

〔Effect of the invention〕

As described above, if the present invention is applied, unlike the conventional manufacturing method, the light shielding film is formed immediately after the formation of the second layer transfer electrode, so that the surface flatness can be greatly improved. An improvement in flatness means that recesses are likely to be present, and even if they are, they are very shallow.

Therefore, even if dirt or dust adheres to the surface of the denocent chair in a later process, it can be easily removed.

There is almost no fluctuation in the threshold voltage vth at the gate section relative to the drain section where the excess charge is discarded.

Thus, according to the present invention, it is possible to prevent defects such as surface unevenness due to unevenness of vth and defects caused by black spots due to adhesion of dust, and to achieve a significant improvement in yield.

[Brief explanation of drawings]

, FIG. 1 (at is the CO of the conventional interline transfer method.
D is a partial plan view of the solid-state imaging device, (1:I) is a longitudinal sectional view thereof, and FIG. 2 is a longitudinal sectional view of the solid-state imaging device formed according to the present invention. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Photosensitive part, 4... Drain part, 5... Gate part, 8... First layer transfer electrode, 9
... First layer transfer electrode of adjacent pixel, IO... Second layer transfer electrode, 14B... Light shield film, 16... Protective film, 18... Absolute@ layer. Applicant's agent Seiji Inomata 1 Figures (0) and (b) also 2 Figures

Claims (1)

[Claims] 1. A signal charge (7) generated by light on a semiconductor substrate (
It controls the photosensitive part that accumulates in the RPN junction, the readout part that reads out the accumulated signal charge, the drain part that discards the excessively generated signal charge, and the gate part that transfers the signal charge to this drain part. Also, according to the method for manufacturing a solid-state imaging device including a light shielding film having an incident light window at a position corresponding to the photosensitive part, the light shielding film is formed immediately after the formation of the readout part,
A method of manufacturing a solid-state imaging device, comprising: then forming a protective film on the top surface of the light shield film with an insulating film interposed therebetween. 2. A method for manufacturing a solid-state imaging device, which is based on the method set forth in claim 1, and is characterized in that the readout section is comprised of first and second transfer electrodes laminated with an insulating film interposed therebetween. 3. A method for manufacturing a solid-state imaging device as claimed in claim 2, characterized in that the optical shield film is formed immediately after the second transfer electrode is formed. 4゜In the method according to claim 1, 2 or 3, the light shielding film is made of MoS that does not allow light to pass through.
A solid-state imaging device characterized by i□ is a manufacturing method of the device.