JP2002231923A - Solid-state image pickup element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain appropriate curvature in a layer inner lens in the upper layer in a layer structure including a region where an electrode film is in a single layered and a double-layered region. SOLUTION: Two layers of electrode films 114 and 116 are formed on a semiconductor substrate 110 where a photosensor and a transfer register are formed, and an auxiliary film 122 for adjusting height is formed at a region where the electrode film 116 is arranged on a single layer. The auxiliary film 122 cancels out the deviation of the step between a part where the two layers of electrode films 114 and 116 are overlapped and a part be arranged on a single layer. Then, a light-shielding film 118 is formed on the upper layer, and the intralayer lens 120 is formed on the upper layer. When the intralayer lens 120 is to be formed by the reflow method such as BPSG, uniform flow behavior such as BPSG can be obtained over the entire region for formation with uniform and appropriate curvature.

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 pickup device having a structure in which a plurality of electrode films are formed on a semiconductor substrate on which a photosensor, a transfer register and the like are formed, and an inner lens is formed thereon. .

[0002]

2. Description of the Related Art Heretofore, in this type of solid-state imaging device, a large number of photosensors constituting imaging pixels and a transfer register for transferring signal charges accumulated in each photosensor are formed on a semiconductor substrate. Thereafter, an electrode film such as a polysilicon film is formed on the upper surface, and a light-shielding film and an inner lens are formed thereon. Each photosensor is arranged in a matrix, a plurality of vertical transfer registers are formed along each column of each photosensor, and a horizontal transfer register is formed so as to be orthogonal to each vertical transfer register.
Then, two layers of electrode films for driving these transfer registers are formed in a grid on the semiconductor substrate, respectively.
They are arranged in a partially overlapping state. In addition, a light-shielding film is formed in a region other than the light receiving region of each photosensor on an upper layer of each electrode film, and an intralayer lens is formed on the light-shielding film. This inner layer lens is generally formed by providing a film of BPSG or the like and then performing a reflow process.

FIGS. 6A and 6B are cross-sectional views showing the layer structure of each electrode film, light-shielding film, and inner lens in such a conventional solid-state image sensor. FIG. It is sectional drawing which cut | disconnected the pixel in the horizontal direction, and FIG.6 (B) is sectional drawing which cut | disconnected each pixel in the vertical direction. On the semiconductor substrate 10 on which the above-described photosensor and transfer register are formed, two layers of electrode films 14 and 16 are selectively formed with an insulating film 12 interposed therebetween. Membrane 1
8 are selectively formed. Then, this light shielding film 18
The inner lens 20 is formed in a layer above the semiconductor substrate 10. In the example shown in FIG. 6, only the upper electrode film 16 is formed as a single layer in the cross section shown in FIG. 6A, and the lower electrode film 14 is formed in the cross section shown in FIG. The upper electrode film 16 is formed in an overlapping state.
Therefore, the light-shielding film 18 and the inner-layer lens 20 shown in FIG. 6B are formed in a state in which the light-shielding film 18 and the inner-layer lens 20 shown in FIG.

[0004]

However, in the conventional layer structure of the solid-state imaging device, the electrode films 14 and 16 have a cross section shown in FIG. 6A and a cross section shown in FIG.
6A is different from that of FIG. 6A, and the position of the top of the inner lens 20 formed on the upper layer is different.
The cross section shown in FIG. 6 and the cross section shown in FIG.
Will have different curvatures. That is, the in-layer lens 20
Is determined in accordance with the amount of the film material flowing from the high region to the low region in the reflow treatment.
In the horizontal direction shown in FIG. 6A, since the step between the top of the single-layer electrode film and the region sandwiched by the top is small, the curvature of the inner lens 20 is small (the radius of curvature is large), and FIG.
In the vertical direction shown in (B), the step between the top of the two-layer electrode film and the region sandwiched by the two is large, so that the curvature of the inner lens 20 is large (the radius of curvature is small). Even if film materials having different fluidities are used, it is difficult to obtain an appropriate curvature unless a difference in height between a single-layer region and a two-layer region of the electrode film is eliminated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a solid-state imaging device capable of obtaining an appropriate curvature of an inner lens formed on an electrode film even in a layer structure including a single-layer region and a two-layer region. And a method for manufacturing the same.

[0006]

According to the present invention, in order to achieve the above object, a plurality of electrode films are formed on a semiconductor substrate on which a plurality of photosensors and transfer registers are formed, and a light-shielding film and a layer are formed thereon. In a solid-state imaging device having an inner lens, an auxiliary film for height adjustment is provided in a region where the electrode film is arranged as a single layer among the plurality of electrode films. Further, the present invention forms a plurality of electrode films on a semiconductor substrate on which a plurality of photosensors and transfer registers are formed,
In a method for manufacturing a solid-state imaging device, wherein a light-shielding film is selectively formed on the upper layer and an inner lens is formed on the light-shielding film, the height of the plurality of electrode films is increased in a region where the electrode film is arranged in a single layer. It is characterized in that an auxiliary film for adjustment is formed, and an inner lens is formed thereon.

In the solid-state image pickup device according to the present invention, an auxiliary film for adjusting the height is provided in a region where the electrode film is arranged as a single layer among a plurality of electrode films formed on the semiconductor substrate. The thickness of the auxiliary film cancels out the variation in the level difference between the portion where the multiple layers of electrode films overlap and the portion where the single layer is arranged. Therefore, the unevenness of the step due to the electrode film is eliminated, and the inner lens provided in the upper layer can be formed with a uniform curvature in the entire region. A large curvature can be obtained. In addition, the height adjustment function based on the thickness of the auxiliary film as described above makes it possible to intentionally adjust the curvature of the inner lens. For example, in a solid-state imaging device having a rectangular light receiving area, By changing the curvature of the in-layer lens according to the difference between the vertical and horizontal directions, it is possible to improve the light-collecting characteristics for each photosensor and improve the sensitivity.

In the method of manufacturing a solid-state imaging device according to the present invention, similarly, an auxiliary film for adjusting height is formed in a region where the electrode film is arranged as a single layer among a plurality of electrode films on a semiconductor substrate. This makes it possible to offset the variation in the level difference between the portion where the multiple layers of electrode films overlap and the portion where the single layer is arranged by the thickness of the auxiliary film. Therefore, the unevenness of the steps due to the electrode film can be eliminated, and the inner lens of the upper layer can be formed with a uniform curvature in the entire region. Therefore, by appropriately selecting the film material of the inner layer, the appropriate curvature of the inner lens can be obtained. Can be obtained. In addition, the height adjustment function based on the thickness of the auxiliary film as described above makes it possible to intentionally adjust the curvature of the inner lens. For example, in a solid-state imaging device having a rectangular light receiving area, By changing the curvature of the inner lens in accordance with the difference between the vertical and horizontal distances, it is possible to improve the light-collecting characteristics for each photosensor and improve the sensitivity.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a solid-state imaging device and a method of manufacturing the same according to the present invention will be described. Figure 1
FIGS. 1A and 1B are cross-sectional views showing a layer structure of each electrode film, a light-shielding film, and an inner lens in a solid-state imaging device according to an embodiment of the present invention, and FIG. FIG. 1B is a cross-sectional view of each pixel cut in a vertical direction. FIG. 2 is a plan view showing the planar shape of each film in the solid-state imaging device shown in FIG. Note that FIG. 1A shows a cross section taken along the line XX ′ of FIG. 2, and FIG. 1B shows a cross section taken along the line YY ′ of FIG.

This solid-state image pickup device comprises an insulating film 1 on a semiconductor substrate 110 on which a photosensor and a transfer register are formed.
12, two electrode films 114 and 116 are selectively formed. Then, as shown in FIG. 1A, the region where the upper electrode film 116 is disposed as a single layer is
An auxiliary film 122 for height adjustment is formed on the upper layer 16 via an insulating film 112. The auxiliary film 122 is made of, for example, a refractory metal film such as tungsten or a silicon nitride film, and has a single-layered electrode film 116.
Has a thickness substantially equal to the difference between the thickness of the electrode film 114 and the total thickness of the two electrode films 114 and 116 (that is, as shown in FIG.
The film thickness is slightly larger than 4). Such an auxiliary film 1
22 offsets the difference in level (h1 and h2 in FIG. 1) between the portion where the two electrode films 114 and 116 overlap and the portion where the single layer is arranged. The light-shielding film 118 is selectively formed on the upper layer on which the auxiliary film 122 is formed, with the insulating film 112 partially interposed therebetween. The light shielding film 118 is formed in a state where an opening 120A corresponding to a light receiving area of the photo sensor is opened.

Further, the light shielding film 118 and the semiconductor substrate 1
An inner lens 120 is formed on the upper layer 10. The inner lens 120 is formed of a film material such as BPSG or PSG. For example, after a BPSG film having a uniform thickness is formed by a CVD method, FIG.
It is formed in a lens shape as shown in FIG. When the unevenness of the inner lens 120 is obtained by the reflow method, the two-layer electrode film 1 is formed by the auxiliary film 122 described above.
Since the variation in the level difference between the portion where the portions 14 and 116 overlap and the portion where the single layer is arranged is eliminated, uniform fluidity such as BPSG can be obtained over the entire region.
As a result, an even and appropriate curvature of the inner lens 120 can be obtained, and the inner lens 120 with the optimized curvature is formed.

Next, a method for manufacturing the auxiliary film 122 in such a solid-state imaging device will be described. FIG. 3 (A)
FIG. 3B is a cross-sectional view illustrating the method of manufacturing the auxiliary film 122 in this example. FIG. 3A corresponds to the cross section of FIG. 1A, and FIG. ). As shown in the figure, first, after forming the above-described electrode films 114 and 116 and the insulating film 112 on the semiconductor substrate 110, the entire surface film 122A such as the above-described refractory metal or silicon nitride film is formed thereon by CVD or the like. Form. Next, a photoresist film is patterned on the entire surface film 122A, and the photoresist film 124 is left only in a region where the electrode film 116 is arranged as a single layer, and the entire region film 122A in other regions is dry-etched or the like. By removing, the above-described auxiliary film 122 is formed. Thereafter, the photoresist film 124 is removed, and the light-shielding film 118 and the inner lens 120 described above are formed.

FIGS. 4 (A) and 4 (B) show each electrode film, light shielding film,
FIG. 4 is a cross-sectional view showing a layer structure of an inner lens and FIG.
4A is a cross-sectional view of each pixel cut in a horizontal direction, and FIG. 4B is a cross-sectional view of each pixel cut in a vertical direction.
In addition, the same code | symbol is attached | subjected about the structure similar to the example shown in FIGS. 1-3. In the example shown in FIGS.
The auxiliary film 122 is formed between the single-layered electrode film (insulating film 112) 116 and the light shielding film 118. In the example shown in FIG. 4, the auxiliary film 122 is formed on the light shielding film 118. It is. The method of forming the auxiliary film 122 is the same as in the above-described example, and the other configuration is the same as in the above-described example.

FIG. 5 is a plan view showing a planar shape of each film in a solid-state image sensor according to a third embodiment of the present invention. In the example shown in FIG.
Although the example of the pixel pattern having A has been described, FIG.
As shown in (1), in a solid-state imaging device having a pixel pattern having a rectangular opening 120B, it may be effective to change the curvature of the inner lens 120 between the vertical direction and the horizontal direction. In this case, the auxiliary film 122 described above
When the height of the region where the electrode film 116 is arranged in a single layer and the height of the region where the two layers of electrode films 114 and 116 overlap are made to coincide with each other, the interval between the vertical direction and the horizontal direction is different. In some cases, the difference in the curvature of the lens 120 may be rather large, and the light-collecting characteristics to the photosensor may be deteriorated.

Therefore, such a rectangular opening 120
In the solid-state imaging device having the pixel pattern having B, the step of the underlying layer forming the inner lens 120 is intentionally adjusted by the height adjustment function based on the thickness of the auxiliary film, and the vertical direction of each electrode film is adjusted. By changing the curvature of the inner lens according to the difference between the horizontal distance and the horizontal direction, the light collecting characteristics for each photosensor are improved, and the sensitivity is improved. In this way, using the height adjustment function based on the thickness of the auxiliary film, the step of the underlayer forming the inner lens 120 is intentionally adjusted,
Optimizing the curvature of the inner lens 120 is also included in the scope of the present invention.

[0016]

As described above, in the solid-state imaging device according to the present invention, a plurality of electrode films are formed on a semiconductor substrate on which a plurality of photosensors and transfer registers are formed, and a light-shielding film and an inner layer are formed thereon. In a solid-state imaging device having a lens formed thereon, an auxiliary film for height adjustment is provided in a region where the electrode film is arranged as a single layer among the plurality of electrode films. Therefore, the thickness of the auxiliary film offsets the variation in the level difference between the portion where the multiple layers of electrode films overlap and the portion arranged in a single layer, and the variation in the level difference due to the electrode film is eliminated. Is formed with a uniform curvature in the entire region, so that an appropriate curvature of the inner lens can be obtained by appropriately selecting a film material and the like of the inner lens. In addition, the height adjustment function based on the thickness of the auxiliary film
It is also possible to intentionally adjust the curvature of the inner lens.For example, in a solid-state imaging device having a rectangular light-receiving area, the curvature of the inner lens is adjusted according to the difference between the vertical and horizontal intervals of each electrode film. By changing, it is possible to improve the light-collecting characteristics for each photosensor and improve the sensitivity and the like.

Further, according to a method of manufacturing a solid-state imaging device according to the present invention, a plurality of electrode films are formed on a semiconductor substrate on which a plurality of photosensors and transfer registers are formed, and a light-shielding film is selectively formed thereon. A method for manufacturing a solid-state imaging device in which an inner lens is formed on the upper layer, wherein an auxiliary film for height adjustment is formed in a region where the electrode film is arranged in a single layer among the plurality of electrode films, and In this case, an inner lens is formed. Therefore, the variation in the level difference between the portion where the multiple layers of electrode films overlap and the portion arranged in a single layer can be offset by the thickness of the auxiliary film, and the variation in the level difference due to the electrode film can be eliminated. Since the lens can be formed with a uniform curvature in all regions, a proper curvature of the inner lens can be obtained by appropriately selecting a film material and the like of the inner lens. In addition, the height adjustment function by the thickness of the auxiliary film makes it possible to intentionally adjust the curvature of the inner lens.For example, in a solid-state imaging device having a rectangular light-receiving area, the vertical direction of each electrode film can be adjusted. By changing the curvature of the inner lens according to the horizontal interval difference, it is possible to improve the light-collecting characteristics for each photosensor and improve the sensitivity and the like.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a layer structure of each electrode film, a light shielding film, and an inner lens of a solid-state imaging device according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a planar shape of each film in the solid-state imaging device shown in FIG.

FIG. 3 is a sectional view illustrating a method for manufacturing the solid-state imaging device illustrated in FIG.

FIG. 4 is a cross-sectional view illustrating a layer structure of each electrode film, a light shielding film, and an inner lens of a solid-state imaging device according to a second embodiment of the present invention.

FIG. 5 is a plan view showing a planar shape of each film in a solid-state imaging device according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a layer structure of each electrode film, light-shielding film, and inner lens in a conventional solid-state imaging device.

[Explanation of symbols]

100: semiconductor substrate, 112: insulating film, 114, 1
16 ... electrode film, 118 ... light shielding film, 120 ... in-layer lens, 122 ... insulating film.

Claims (14)

[Claims] 1. A solid-state imaging device in which a plurality of electrode films are formed on a semiconductor substrate on which a plurality of photosensors and transfer registers are formed, and a light-shielding film and an inner lens are formed thereon. A solid-state imaging device, wherein an auxiliary film for height adjustment is provided in a region of the electrode film where the electrode film is arranged in a single layer. 2. The solid-state imaging device according to claim 1, wherein the auxiliary film is formed between an insulating film formed on the electrode film and the light-shielding film formed on the insulating film. element. 3. The solid-state imaging device according to claim 1, wherein the auxiliary film is formed on the light-shielding film. 4. The method according to claim 1, wherein the auxiliary film has a thickness substantially equal to a difference between a thickness of the electrode film arranged as the single layer and a total thickness of the plurality of electrode films. The solid-state imaging device according to claim 1. 5. The solid-state imaging device according to claim 1, wherein said auxiliary film is formed of a refractory metal film. 6. The solid-state imaging device according to claim 1, wherein said auxiliary film is formed of a silicon nitride film. 7. A plurality of electrode films are formed on a semiconductor substrate on which a plurality of photosensors and transfer registers are formed, a light-shielding film is selectively formed thereon, and an intra-layer lens is formed thereon. In the method for manufacturing a solid-state imaging device, an auxiliary film for height adjustment is formed in a region where the electrode film is arranged as a single layer among the plurality of electrode films, and an intralayer lens is formed thereon. A method for manufacturing a solid-state imaging device. 8. The solid-state imaging device according to claim 7, wherein the auxiliary film is formed between an insulating film formed on the electrode film and the light-shielding film formed on the insulating film. Device manufacturing method. 9. The method according to claim 7, wherein the auxiliary film is formed above the light shielding film. 10. The auxiliary film is formed to have a thickness substantially equal to a difference between a thickness of the electrode film arranged in the single layer and a total thickness of the plurality of electrode films. The method for manufacturing a solid-state imaging device according to claim 7. 11. The method according to claim 7, wherein the auxiliary film is formed of a refractory metal film. 12. The method according to claim 7, wherein the auxiliary film is formed of a silicon nitride film. 13. The method for manufacturing a solid-state imaging device according to claim 7, wherein the inner lens is formed by forming a predetermined film material and then performing a reflow process. 14. The method according to claim 13, wherein the predetermined film material is BPSG or PSG.