JPH04212459A - Solid image pick-up element - Google Patents

Abstract

PURPOSE:To provide the title solid image pick-up element casting almost no reflection on the surface of an electrode wiring thereby developing no defective smear. CONSTITUTION:An electrode material 6 comprising Al or Al-Si is formed on the whole surface of a silicon substrate 1 and then a titanium metal is sputtered in nitride gas atmosphere so as to form a reflection preventive film 21 comprizing titanium nitride on the electrode wiring material 6. Through these procedures, the incoming beams on the surface of the electrode wiring are almost prevented from being reflected at all by the reflection preventive film so that almost no reflecting beams may come into the photodetector thereby enabling the defective smear to be avoided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image sensing device.

0002

2. Description of the Related Art FIG. 6 is a sectional view of a conventional CCD (charge coupled device) solid-state imaging device. In FIG. 6, 1 is a silicon substrate, 2 is a light receiving section, 3 is a charge transfer region, 4 is an oxide film, 5 is a polysilicon electrode for charge transfer, 6 is an electrode wiring that also serves as a light-shielding metal, and 7 is an SiO2 film or SiN It is a transparent protective film for the membrane.

FIG. 7 is a cross-sectional view showing the manufacturing process of this solid-state image sensor. Here, FIG. 7(a) shows a state in which the electrode wiring material 6 is formed on the entire surface of the silicon substrate 1. As shown in FIG. From this state, a positive resist 8 is applied as shown in FIG. 7B, and then the light receiving section 2 and a part of the field section 9 are selectively exposed using a glass mask as shown by the arrow. FIG. 7C shows a state in which the phenomenon of resist 8 is performed after that. Figure 7
(d) shows a state in which the electrode wiring material 6 has been etched using the unexposed portion of the resist 8 as an etching mask. Next, after removing the resist 8, a protective film 7 is formed as shown in FIG. 7(e). Then, as shown in FIG. 7(f),
A hole is made in the bonding pad portion 10 in order to perform wire bonding. This step can be performed by forming a positive resist on the protective film 7, and performing exposure, development, etching, and resist removal as in steps (b), (c), and (d).

0004

[Problems to be Solved by the Invention] By the way, the conventional solid-state image sensing device described above uses Al or Al as the material for the electrode wiring 6.
-Si (1%) is used and is formed by sputtering under conditions of an output of 10 kW or more and a vacuum of 10 mm Torr or less, but since these are metals with high reflectance,
Most of the light incident on the electrode wiring 6 through the transparent protective film 7 is reflected. In addition, the electrode wiring 6 is a collection of microcrystals, and its surface is not flat, and the underlying surface before the electrode wiring is formed has unevenness formed by the previous manufacturing process of the electrode 5, etc. The shape of the upper surface of the electrode wiring 6 also inherits the unevenness. Therefore, the reflected light on the surface of the electrode wiring becomes diffusely reflected, and a part of it enters the light receiving section 2. The light incident on the light receiving section 2 due to this diffused reflection is a light beam other than the signal light beam, and therefore causes smear failure. Further, the same can be said of a color solid-state image sensor in which cyan, magenta, yellow, and green color filters are formed above the light receiving section 2.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a solid-state image sensing device that has less diffused reflection on the surface of electrode wiring and does not cause smear defects.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the first invention provides a method for forming a plurality of light receiving sections and a charge transfer region adjacent to each of the light receiving sections on a substrate. forming a charge transfer electrode on and forming an insulating layer to cover the charge transfer electrode and the light receiving section; forming an electrode wiring on the insulating layer on each of the charge transfer electrodes;
Furthermore, in a solid-state image sensor with a protective film formed thereon,
The present invention is characterized in that an antireflection film having a reflectance smaller than that of the electrode wiring is formed on the upper surface of the electrode wiring.

In a second aspect of the invention, a charge transfer electrode is formed on the charge transfer region on a substrate on which a plurality of light receiving portions and a charge transfer region adjacent to each of the light receiving portions are formed, and a charge transfer electrode is formed on the charge transfer region. In a solid-state imaging device, an insulating layer is formed to cover the charge transfer electrode and the light receiving part, electrode wiring is formed on the insulating layer on each of the charge transfer electrodes, and a protective film is further formed thereon, The present invention is characterized in that an antireflection film having a reflectance smaller than that of the electrode wiring is formed on the upper and side surfaces of the electrode wiring.

Further, in a third aspect of the present invention, a charge transfer electrode is formed on each of the charge transfer regions on the substrate on which a plurality of light receiving sections and a charge transfer region adjacent to each of the light receiving sections are formed, and a charge transfer electrode is formed on each of the charge transfer regions. In a solid-state imaging device, an insulating layer is formed to cover the transfer electrode and the light receiving section, electrode wiring is formed on the insulating layer on each of the charge transfer electrodes, and a protective film is further formed on the insulating layer. , the electrode wiring is made of an Al--Si film formed under conditions such that the surface has a low reflectance.

[0009] Furthermore, both the first invention and the second invention,
The anti-reflection film may be a titanium nitride film or a metal oxide film, or an Al-
A Si film (hereinafter referred to as "low reflection Al-Si film") can be used. Furthermore, the metal oxide can be titanium oxide or titanium nitride oxide.

[0010] Furthermore, as the electrode wiring of the third invention,
It is possible to use low-reflection Al--Si electrode wiring formed by lowering the output and increasing the degree of vacuum under sputtering conditions than in the past.

[0011]

[Operation] In the first invention, since an anti-reflection film having a reflectance smaller than that of the electrode wiring is formed on the upper surface of the electrode wiring, light that is incident on the upper surface of the electrode wiring through the protective film is formed on the upper surface of the electrode wiring. Since almost no light is reflected by the anti-reflection film, almost no reflected light enters the light receiving section, making it possible to prevent smear defects from occurring.

Furthermore, in the second aspect of the invention, an antireflection film having a reflectance smaller than that of the electrode wiring is formed on the top and side surfaces of the electrode wiring. Since almost no light incident on the top surface and side surfaces is reflected by the antireflection film, the amount of reflected light incident on the light receiving portion is even smaller than in the first invention, and the occurrence of smear defects can be further prevented.

Furthermore, in the third invention, since almost no light that has passed through the protective film and entered the upper surface of the electrode wiring is reflected by the electrode wiring, almost no reflected light enters the light receiving section, resulting in smear defects. can be prevented from occurring.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to illustrated embodiments.

Embodiment of the First Invention FIG. 1 is a sectional view showing the manufacturing process of a CCD image sensor according to an embodiment of the first invention.

Similar to FIG. 7A, FIG. 1A shows a state in which an electrode wiring material 6 of Al or Al-Si (1%) is formed over the entire surface of a silicon substrate 1. As shown in FIG. From this state, titanium metal is then sputtered in a nitrogen gas atmosphere to form an antireflection film 21 of titanium nitride on the electrode wiring material 6 as shown in FIG. 1(b). Next, in FIG. 1C, similarly to FIG. 7B, after applying a positive resist 8, the light receiving section 2 and a part of the field section 9 are selectively exposed using a glass mask as shown by the arrow. FIG. 1(d) shows the state after the resist 8 phenomenon is performed. Figure 1(e)
2 shows a state in which the antireflection film 21 and the electrode wiring material 6 are etched using the unexposed portion of the resist 8 as an etching mask, and then the resist 8 is removed. Next, after forming a protective film 7 thereon, as shown in FIG. 1(f), a hole is formed in the bonding pad portion 1 for wire bonding. This step can be performed by forming a positive resist on the protective film 7, and performing exposure, development, etching, and resist removal.

[0017] The CCD image sensor manufactured in this way is as follows:
Since the reflectance of the titanium nitride film 21 formed on the upper surface of the electrode wiring 6 is very low, almost no light incident on the electrode wiring through the protective film 7 is reflected by the titanium nitride film 21. The amount of light incident on 2 is greatly reduced compared to the conventional example, and smear defects are greatly improved. It has been confirmed that when this CCD image sensor is used in a video camera, there is almost no problem under normal usage conditions such as indoors.

However, since the reflectance of titanium nitride is not sufficiently small, smear defects may occur when the video camera is used outdoors on a sunny day or in the presence of strong lights.

Therefore, in order to prevent smear defects even in such a case, the above-mentioned anti-reflection film 2 must be
1 may be a material having a lower reflectance than titanium nitride, such as titanium oxide (TixOy) or titanium nitride oxide (TixNyOz).

The anti-reflective film of titanium oxide is formed by sputtering titanium in a mixed gas of argon gas and oxygen gas, and the anti-reflective film of titanium nitride oxide is formed by sputtering titanium in a mixed gas of argon gas and oxygen gas. It is formed by sputtering in a mixed gas of and nitrogen gas. Since both of these materials are black, their reflectance is lower than that of titanium nitride, and smear defects are improved.

[0021] In addition, FIGS. 4(a) and 4(b) show, respectively,
An example is shown in which a low-reflection Al--Si film is used as an antireflection film. As shown in Fig. 4(a), when Al (100%) is used as the electrode wiring material, Al-Si is sputtered under conditions of an output of 10 kW or less and a vacuum of 10 mm Torr or more after the electrode wiring is formed. Then, an antireflection film 33 made of a low-reflection Al--Si film is formed on the electrode wiring 6.

Furthermore, as shown in FIG. 4(b), when Al--Si is used as the electrode wiring material, first Al (100%)
The film 34 is formed as a light-shielding film by sputtering, and then sputtering is performed under conditions of an output of 10 kW or less and a vacuum of 10 mm Torr or more to form an antireflection film made of a low-reflection Al-Si film on the Al (100%) film 34. Form. For example, when sputtering Al-Si under conditions of an output of 7 kW and a degree of vacuum of 20 mm Torr, the reflectance is about 50% of that in the conventional case.

In addition to the method described above, there is a method shown in FIG. 2 as a method for forming the antireflection film of titanium oxide or titanium nitride oxide.

FIG. 2(a) shows a state in which the electrode wiring material 6 is formed on the entire surface of the silicon substrate 1, similar to FIG. 1(a). From this state, a film 31 of titanium or titanium nitride is then formed on the electrode wiring material 6 by sputtering, as shown in FIG. 2(b). FIG. 2C shows a state in which a positive resist 8 is coated on the film 31, and then the light-receiving part 2 and a part of the field part 9 are selectively exposed using a glass mask to effect the phenomenon of the resist 8. Figure 2 (d
) uses the unexposed part of the resist 8 as an etching mask,
A state in which the resist 8 is removed after etching the antireflection film 31 and the electrode wiring material 6 is shown. Next, heat treatment is performed in an oxygen atmosphere to oxidize the titanium or titanium nitride film 31 to form an antireflection film 32 of titanium oxide or titanium nitride oxide as shown in FIG. 2(e). obtain. The heating temperature at this time is A
In the case of l-based materials, the temperature is preferably 500°C or less. Next, Figure 2
As shown in FIG. 1F, a protective film 7 is formed in the same manner as in FIG. 1F, and holes for bonding pad portions 10 are formed. The oxidation of titanium or titanium nitride by heat treatment may be performed after the step shown in FIG. 2(b).

Embodiment of the Second Invention FIG. 3 is a sectional view showing the manufacturing process of a CCD image sensor according to an embodiment of the second invention.

The image sensor of this example has an anti-reflection film formed only on the top surface of the electrode wire, whereas the image sensor shown in FIG. 1 has an anti-reflection film formed only on the top surface of the electrode wire. The other structure is the same as that of FIG. Identical components are given the same reference numerals and their explanations will be omitted.

FIG. 3(a) shows a state in which the patterning of the electrode wiring 6 has been completed. Next, as shown in FIG. 3(b), titanium metal is sputtered in a nitrogen gas atmosphere to form a titanium nitride film 21 on the entire surface of the substrate 1, and then a positive resist 8 is applied thereon. selective exposure is performed so that the upper and side surfaces of the electrode wiring 6 are covered with the titanium nitride film 21. Next, after developing the positive resist 8, the titanium nitride film 21 is etched using the remaining positive resist 8 as an etching mask, resulting in the state shown in FIG. 3(c). After removing the remaining positive resist 8 to obtain the state shown in FIG. 3(d), as shown in FIG. 3(e), a protective film 7 is formed in the same manner as in FIG. 1(f), and the bonding pad area is 10
Drill the hole.

Since the anti-reflection film of titanium nitride was formed on both the top and side surfaces of the electrode wiring 6 in this way, the anti-reflection film was formed only on the top surface of the electrode wiring in the embodiment of the first invention. Compared to this, diffused reflection is reduced, and smear defects can be further reduced. In addition, also in this example,
As in the embodiment of the first invention, instead of forming an anti-reflective film of titanium nitride, an anti-reflective film of titanium oxide, titanium nitride oxide, or a low-reflection Al-Si film is formed. Smear defects can be further reduced. Note that when a low-reflection Al-Si film is used as an antireflection film, the reflectance is higher than that of an antireflection film using titanium oxide or titanium nitride oxide, but the yield is high.

Embodiment of the Third Invention FIG. 5 shows a structural sectional view of a CCD image sensor according to an embodiment of the third invention.

In forming the electrode wiring, sputtering is performed under conditions of an output of 10 kW or less and a vacuum of 10 mm Torr or more, and etching is performed to form a low-reflection Al--Si electrode wiring 35 as shown in FIG. Next, a protective film 7 is formed thereon, and then a bonding pad portion 10 for wire bonding is formed.

In this way, the low reflection Al--Si electrode wiring 35
, the irregular reflection is reduced compared to the conventional Al--Si electrode wiring 6, and smear defects can be reduced.

[0032]

Effects of the Invention As is clear from the above, the solid-state imaging device of the first invention has an anti-reflection film formed on the upper surface of the electrode wiring with a reflectance smaller than that of the electrode wiring, so that it is protected. Since almost no light entering the upper surface of the electrode wiring through the film is reflected by the anti-reflection film, almost no reflected light enters the light receiving section, making it possible to prevent smear defects from occurring.

Further, in the solid-state imaging device of the second invention, since an anti-reflection film having a reflectance smaller than that of the electrode wiring is formed on the top and side surfaces of the electrode wiring, the above-mentioned Since almost no light incident on the top and side surfaces of the electrode wiring is reflected by the anti-reflection film, the amount of reflected light incident on the light receiving section is even smaller than in the first invention, making it possible to further prevent the occurrence of smear defects. can.

Furthermore, in the solid-state imaging device of the third invention, since the electrode wiring is formed using a low-reflection Al-Si film, almost no light that enters the electrode wiring through the protective film is reflected. Therefore, the amount of reflected light incident on the light receiving section is smaller than that of conventional electrode wiring not provided with an antireflection film, and smear defects can be more effectively prevented.

Further, in both the solid-state imaging device of the first invention and the solid-state imaging device of the second invention, the antireflection film is made of a metal oxide such as titanium oxide or titanium nitride oxide, or a low-reflection Al- By using a Si film as an antireflection film, smear defects can be more effectively prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the manufacturing process of an embodiment of the first invention.

FIG. 2 is a sectional view showing the manufacturing process of another embodiment of the first invention.

FIG. 3 is a sectional view showing the manufacturing process of an embodiment of the second invention.

FIG. 4 (a) and (b) are low-reflection Al
FIG. 2 is a structural cross-sectional view of an embodiment of the first invention in which a -Si film is used as an antireflection film.

FIG. 5 is a structural sectional view of an embodiment of the third invention.

FIG. 6 is a structural sectional view of a conventional example.

FIG. 7 is a cross-sectional view showing a conventional manufacturing process.

[Explanation of symbols]

1 Silicon substrate 2 Light receiving section 3 Charge transfer region 4 Oxide film 5 Charge transfer electrode 6 Electrode wiring 7 Protective film 8 Positive resist 9 Field section 10 Electrode pad section 21 Antireflection film such as titanium nitride 31 Metal film such as titanium 32 Titanium Antireflection film 33 of metal oxide such as oxide
Low reflection Al-Si anti-reflection film 34 Al (100%) film 35 Low reflection Al-Si electrode wiring

Claims (3)

[Claims] 1. A charge transfer electrode is formed on each of the charge transfer regions on a substrate on which a plurality of light receiving portions and a charge transfer region adjacent to each of the light receiving portions are formed, and the charge transfer electrode and the light receiving portion are formed on the substrate. forming an insulating layer so as to cover the charge transfer electrodes, and forming electrode wiring on the insulating layer on each of the charge transfer electrodes;
Furthermore, in a solid-state image sensor with a protective film formed thereon,
A solid-state image sensing device characterized in that an antireflection film having a reflectance smaller than that of the electrode wiring is formed on the upper surface of the electrode wiring. 2. A charge transfer electrode is formed on each of the charge transfer regions on a substrate on which a plurality of light receiving portions and a charge transfer region adjacent to each of the light receiving portions are formed, and the charge transfer electrode and the light receiving portion are formed on the substrate. forming an insulating layer so as to cover the charge transfer electrodes, and forming electrode wiring on the insulating layer on each of the charge transfer electrodes;
Furthermore, in a solid-state image sensor with a protective film formed thereon,
A solid-state imaging device characterized in that an antireflection film having a reflectance smaller than that of the electrode wiring is formed on the upper and side surfaces of the electrode wiring. 3. A charge transfer electrode is formed on each of the charge transfer regions on a substrate on which a plurality of light receiving portions and a charge transfer region adjacent to each of the light receiving portions are formed, and the charge transfer electrode and the light receiving portion are connected to each other. forming an insulating layer so as to cover the charge transfer electrodes, and forming electrode wiring on the insulating layer on each of the charge transfer electrodes;
Furthermore, in a solid-state image sensor with a protective film formed thereon,
A solid-state imaging device characterized in that the electrode wiring is made of an Al-Si film formed under conditions such that the surface has a low reflectance.