JPS60262459A - Manufacture of solid-state image pickup device - Google Patents

Abstract

PURPOSE:To inhibit a blooming phenomenon by forming an optical shielding body to an insulating film between an optical shielding body and an electrode terminal even in the longitudinal direction. CONSTITUTION:An n type photodiode region 2 and a CCD region 12 are formed to the surface of a p type substrate 1. A gate electrode 4 is shaped, and an insulating film 5 is formed onto the electrode 4. A shielding body 11 for beam- shielding a charge transfer region is shaped onto the film 5. An insulating film 6 is formed onto the shielding body 11, and a contact hole 16 for a metallic electrode is shaped to the films 5, 6 on the region 2. The metallic electrode 7 is formed onto the whole surface. The electrode 7 and the film 6 on the shielding body 11 are etched approximately vertically through a resist 17 as a mask to form stepped sections 13. A metallic film 15 is shaped onto the whole surface, and the film 15 is etched while the film 15 is left only on the side surfaces of the stepped section 13 sections of the film 6. Amorphous Si 8 to which an n type impurity is doped, photoconductive films 9-1, 18 and a transparent electrode 10 are formed onto the substrate 1 having such structure. According to such constitution, propagation in the lateral direction of carriers generated in Si 8 can be inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a solid-state imaging device, and particularly to a stacked solid-state imaging device in which a photoconductive film is formed on a semiconductor substrate having a charge transfer function or a switching function. It is related to the field of manufacturing equipment.

Conventional configuration and its problems Conventionally, MOS switches are arranged in a matrix or circuit elements having a charge transfer function such as BBD and COD, and
-X to read signal by Y shift register
In the combination of the Y matrix type and the photoconductive film, it is necessary to generate optical signal charges in an area corresponding to the lower electrode film of the photoconductive film and to block the excess 3/, ... - light.

Referring to FIG. 1, a detailed explanation will be given of a device having a power structure in which the signal charge storage section is a photodiode and the charge transfer section is a COD transfer element. As shown in FIG. The light transmitted without being absorbed by the film 9 passes through the gap l between the metal electrodes 7 and reaches the semiconductor substrate, where electron and hole pairs are generated.The holes move to the substrate, but the electrons This flowed into the diode region 2 for optical information storage and the CAN charge transfer section 12. As a result, C
Since the OD charge transfer section is electrically connected in the vertical direction, electrons generated in the semiconductor substrate and entering the CCD section spread in the vertical direction, which is a blooming phenomenon in which signals appear in areas where signals are originally large. was causing

In order to eliminate this phenomenon, as shown in FIG. 2, a method is proposed in which a light shield 11 is provided between the second insulating film 6 and the first insulating film 60 and at a position covering the gap between the metal electrodes. 10393
It is shown in No. 4. However, in this method, the light shield 1
There are drawbacks and problems between both the metal electrode 1 and the metal electrode 7, which will be explained below.

The first issue is the misalignment between the metal electrode 7 and the light shield 11. Alignment is originally designed with some margin, but increasing the safety factor tends to reduce the original element characteristics of the solid-state imaging device. First of all, it is possible to consider increasing the area of the metal electrode, but the etching technique for separating the metal electrode is further limited by the density of the lateral dark current of the photoconductive film formed on the top of the metal electrode. . The width of the light shield is also subject to limitations due to etching limitations and alignment limitations with the photodiode section. Next, as the second insulating film 6 becomes thicker and thicker, it becomes easier for light to leak from the lateral direction.Especially after the gate electrode 4 is formed as shown in the same figure, the substrate level difference becomes large, and leakage due to diffused reflection of one light increases. Notable. On the other hand, if the second insulating film 6 is thin, the metal electrode 7 and the light shield 11 are likely to short-circuit. Next, a high voltage 61,- is applied to the gate electrode 4.

When a clock pulse is applied, nozzles are likely to occur and are induced in the metal electrode 7 due to stray capacitance between the gate electrode 4 and the metal electrode 7, causing many problems such as deterioration of image characteristics.

Here, 3 in FIGS. 1 and 2 is a gate insulating film, and 8 is a hole blocking layer.

Purpose of the Invention The present invention provides a solid-state imaging device having the above configuration,
By forming a light shield in the vertical direction on the insulating film between the light shield and the electrode terminal to more safely perform light shielding, blooming phenomenon can be suppressed. It is an object of the present invention to provide a method for manufacturing a solid-state imaging device that reduces inter-element dark current and has fewer noise components.

Structure of the Invention The present invention provides a semiconductor circuit board having a transfer region for continuously transmitting signal charges accumulated in a charge storage region, a plurality of insulating films formed on the semiconductor circuit board, and a plurality of insulating films formed on the insulating film for each unit pixel. When manufacturing a solid-state imaging device having an electrode formed on a photoconductive film and a light-transmitting electrode further formed through a photoconductive film, a light shielding material is almost completely removed between the plurality of insulating films and between the electrode terminal and the surface of the insulating film. The structure formed on the entire surface provides more complete light shielding and suppresses the blooming phenomenon.The light shielding on the electrode terminal and the surface of the insulating film is achieved by etching a portion of the insulating film in the vertical direction and etching the etched side surface of the insulating film. This etched side surface is formed with an extremely steep shape, so when forming a photoconductive film on an insulating film and a metal electrode, the uniformity of the growth of the photoconductive film is affected by the steep steps. As a result, the lateral propagation of carriers in the photoconductive film is suppressed, and together with the light shielding effect, it is possible to improve the resolution of the photoconductive film.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows a cross-sectional structure of a solid-state imaging device according to an embodiment of the present invention. For ease of explanation, the same component numbers as in the conventional example are used, and FIGS. Same as the figure. 1 is a p-type silicon substrate, 2 is a diode region, 3 is a gate insulating film, 4 is a gate electrode, 6 is a first insulating film, 6 is a second insulating film, 77, '<-; is a metal electrode, 8: hole blocking layer, 9 and 18 are photoconductive films;
10] a transparent electrode, 11 a light shield, and 12 a COD charge transfer section. Furthermore, a second insulating film 6 between the metal electrodes 7
is etched almost vertically to form a step 13, and the 13 steps are etched to a depth of approximately 10% to 10% of the thickness of the second insulating film 6, and a metal electrode 7 is formed on the side surface 14 of the step 13. A metal film 15 made of the same material or capable of ohmic contact and light shielding is formed.

To further explain with reference to FIG.
and is absorbed by the photoconductive film 9 to generate electron and hole pairs,
Holes are trapped in the hole blocking layer, and electrons are absorbed as optical information in the unit picture element region of the metal electrode 7 and accumulated in the n diode region 2.

Here, the light that is not absorbed by the photoconductive film and reaches the 7 parts of the metal electrode in the unit picture element area is connected to the metal film 16 provided on the side surface 14 of the 13 steps of the second insulating film 60 and the first and second insulating film 60. The light is blocked by the light shielding member 11 provided between the insulating films, and carriers generated by light leaking into the semiconductor substrate can be eliminated.

A hole blocking layer 8 is formed on the step 13 of the second insulating film 6 of the octopus.
The photoconductive film 9 and the photoconductive film 9 are sequentially formed by a sputter deposition method or a CVD method, but at this time, unlike the growth deposition on the step portion 13 or the flat portion, the uniformity is impaired.

Therefore, the lateral propagation of carriers generated in the photoconductive film is suppressed, and signal leakage between picture elements in the hole blocking layer and photoconductive film layer is increased, making it possible to separate the picture elements. Then,
Improving resolution will help.

FIG. 4 explains the manufacturing process of this example.

Figure 4a shows p-type (100) 10Ω-n on the surface of the solder substrate 1.
A type impurity is formed at a desired position to form a diode region. At this time, one n-type layer is used as a photodiode 2, and the other is used as a COD region 12 for charge transfer. A gate insulating film 3 of about 0.1 .mu.m and a polycrystalline silicon film 4 of about 0.6 .mu.m are formed as a gate electrode, and a signal charge transfer electrode is transferred intermittently. The gate oxide film 3 on the photodiode 2 is patterned by a photoetching process.

In FIG. 4, an insulating film 6 is formed on the gate electrode 4.
The insulating film 5 is silicon glass containing phosphorus (hereinafter referred to as PSG).
A film (referred to as a film) of approximately 1 μm is formed and flowed at high temperature to reduce irregularities on the substrate surface and flatten it. Next, the light shield 11
Then, a metal thin film such as MO or Ti p Tl + Or is formed to a thickness of about 02 μm over the entire surface. Next, a photo-etching process is performed to leave the light shield 11 only in desired portions.

Further, as an insulating film 6, a silicon oxide film or a PSG film is grown by vapor phase to a thickness of about 0.6 μm on the light shielding member 11 at reduced pressure or at normal pressure at a low temperature. Next, through a photo-etching process, the insulating films 6, 6 on the photodiode 2 are selectively etched to form a contact hole 16 for a metal electrode.

The lower electrode of the photoconductive film is formed on the insulating film 6 shown in FIG.
The metal electrode 7, which also serves as a light shield, is provided on the entire surface.

is deposited to a thickness of about 0.2 μm. M in the explanation.

However, as described above, the material of the metal electrode is configured to serve both as an electrode terminal on one side of the photoconductive film and as a light shield, so it must have the effects of both. As for the material, when amorphous silicon is used for the photoconductive film, a material that exhibits Schottky characteristics is effective, so for example, MO9Or, Ti, kl, etc. having a small work function are effective.

Subsequently, a metal electrode film 7 using Mo is formed by a photo process.
Make a pattern on top. At this time, the light shielding body 11 sandwiched between the insulating films 5 and 6 does not need to be careful about overlapping, and it is sufficient that the pattern underneath cannot be seen between the metal electrode 7 and the light shielding body 11 after etching. .

Etching when using MO uses a mixed gas of CF4 gas and oxygen gas, and patterning can be done by plasma etching.When carrying out wet etching, a 1:1 ratio of hydrogen peroxide and water is used. This can be done with a mixed solution.

Next, the exposed portion of the insulating film 6 is etched almost vertically leaving the resist 17 serving as a mask as it is to form a step 13 so as to leave about 10% to 10% of the deposited film thickness. The insulating film 6 was etched by reactive ion etching using 05F8 gas at 0.1 Torr.
r.

This is possible under conditions of about 200 W, and to make the etched surface perpendicular, it is possible to set the degree of vacuum to a higher degree of vacuum.

FIG. 4d shows that after a step 13 is formed on the insulating film 6, the resist 17 serving as a mask is removed and cleaned, and then the same material as that used to form the metal electrode is formed over the entire surface with almost the same thickness. Next, the film formed over the entire surface is etched by, for example, reactive ion etching. At this time, etching is performed under conditions that are very directional, and the film is etched on flat areas and smooth step areas of the substrate, but in areas with steep steps 13, the apparent thickness of the formed film is It becomes thicker in the vertical direction, and even if the flat parts and smooth stepped parts are removed by etching, they remain.

In FIG. d, a film is formed on the metal electrode, and the surface is etched by the thickness of the film, leaving the metal film 16 only on the side surface 14 of the step 13.

The conditions for reactive ion etching are OF2C1, gas, and s o m Torr when the metal film 15 is Mo.

Under the condition of 200W, only the stepped side surface can be left.

In Figure 8, after cleaning the structure shown in Figure d,
In a plasma or RF:J varnish batter, amorphous silicon 8 with an n-type impurity and a tope is formed. The thickness of the film is about 300 A, and this layer becomes the hole blocking layer 18. Further, in vacuum, hydrogenated amorphous silicon film with 1.0 to 1
．． A photoconductive film layer 9-1 is formed with a thickness of about 6 μm. The substrate temperature at this time was 250'C, and then B
Mix 2H6 gas and C4 gas with SiH4 gas in an appropriate ratio, and hydrogenate amorphous 5iC9-2 at 600 to 1o0.
0 person formation.

This 5i-G film also becomes a photoconductive film. ITOlo is formed on this layer as a transparent electrode.

The present invention is constructed through the steps described below, but in particular, when forming a photoconductive film, the presence of steep steps in the separation region of each picture element on the 81 substrate side causes problems in the photoconductive film. When growing up,
The uniformity at the step portion is disrupted, and the lateral propagation of carriers generated in the amorphous silicon layer is suppressed. This, fl
, is due to the fact that the film formation at steeply stepped areas cannot be deposited with a uniform thickness unlike at flat areas, and in abnormal cases, cavities may be formed at the bottom of the steps. Sometimes it happens. In the drawings showing the embodiments, Al wiring as driving wiring for gate electrodes and the like is electrode-attached by a well-known method before forming the metal electrode 7.

Effects of the Invention As described in Section 2, the present invention provides a lower layer light shielding body with an insulating film interposed between the metal electrodes separated for each unit picture element, and furthermore, the lower layer light shielding body is provided between the metal electrode and the lower layer light shielding body. By providing a step in the insulating film and providing a light shield on the side surface of the step, oblique incidence can also be blocked.

Furthermore, by forming the photoconductive film on the stepped surface, the uniformity of the photoconductive film is impaired and the lateral propagation of internally generated carriers is prevented, thereby making the separation of each pixel more reliable. High-resolution imaging for 14 months - 7 Figure 1 is a cross-sectional view of a conventional solid-state imaging device with a photoconductive film.
FIG. 2 is a sectional view of a conventional solid-state imaging device with a light shield and a photoconductive film, FIG. 3 is a sectional view of a solid-state imaging device fabricated by the method of an embodiment of the present invention, and FIG. 4a -ei FIG. 5 is a sectional view of the manufacturing process of a solid-state imaging device according to an embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1...P-type silicon substrate, 2...Diode region, 9-1.18...Photoconductive film, 10
...Transparent electrode, 11... Light shielding body, 1
2...Group/charge transfer section, 13...Step, 16.
...Metal film.

Name of agent: Patent attorney Toshio Nakao and 1 other person
Ward Sozuka 303-

Claims (2)

[Claims] (1) When manufacturing a solid-state imaging device in which a transparent electrode film and a photoconductive film are laminated on an upper layer, a lower electrode film is connected to a signal charge storage region, and has a transfer region for transferring the signal charge,
forming a shield for shielding the signal charge transfer region from light through an insulating layer; forming an insulating film on the shield and providing apertures in a large number of signal charge storage regions; Next, a step of forming a conductive and light-shielding electrode film connected to each of the five openings, and then vertically etching the surface exposed part of the insulating film on the shield, so that the entire surface is covered with the above-mentioned film. A process of forming a film that can have the same effect as the electrode film, removing the film by etching vertically from the surface, leaving the film only on the side surfaces of the stepped portion of the insulating film, and then etching the film uniformly over the substrate with the structure described above. 2. A method of manufacturing a solid-state imaging device, comprising the steps of: forming a photoconductive film on the first part, and forming a transparent electrode film on the second part. (2) The film forming materials after forming the step on the lower electrode film and the insulating film are the same, Mo, Ta, W, Cr, kl.
2. The method of manufacturing a solid-state imaging device according to claim 1, wherein the electrode film made of 4-4 or its silicide also serves as a light shield.