JPH0969617A - Detection of crosstalk, light receiving element and wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and easily detect crosstalk at a low cost. SOLUTION: A plurality of picture elements 22 (22a, 22b and 22c) made of photodiode are formed on the surface of a silicon board, and isolation diffusion 23 is formed between respective elements 23. Further, a silicon oxide film 24 is formed on the surface of the elements 22 and isolation diffusion 23. A pattern 25 for measuring crosstalk which is made of aluminum film is formed on the film 25 in a manner that the entrance of light into a picture element other than the specified picture element 22b may be limited. The incident light 26 is allowed to enter only the element 22b, and photoelectric currents generating in the element 22b and elements 22a and 22c adjacent thereto in this state are detected, then both currents are compared with each other to detect crosstalk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosstalk detecting method, a light receiving element, and a wafer, and more particularly, by accurately and easily preventing crosstalk generated in the light receiving element by limiting the incidence of light on a pixel other than a specific pixel. The present invention relates to a crosstalk detecting method, a light receiving element, and a wafer capable of being detected.

[0002]

2. Description of the Related Art A semiconductor image sensor receives light,
It is a type of light receiving element that detects an image in response to the received light, and examples thereof include a line sensor and a light receiving section in which light receiving portions (pixels) formed of photodiodes and the like are one-dimensionally arranged. There is an area sensor or the like formed by arranging two-dimensionally.

FIG. 4 is a sectional view showing an example of the configuration of a semiconductor image sensor. In this semiconductor image sensor, a plurality of pixels 22 composed of photodiodes by N-type diffusion are formed on the surface of a P-type silicon substrate 21. A P-type separation diffusion 23 is formed between each pixel 22, and each pixel 22 is separated. further,
A silicon oxide film 24 is formed on the surface of the pixel 22 and the separation diffusion 23.

Although omitted in FIG. 4 for the sake of simplicity, a wiring layer made of aluminum is formed on the separation diffusion 23, and light from a position (separation diffusion 23) other than the pixel 22 is formed. Also has the role of limiting the incidence of. Further, at a position where the wiring layer is not formed on the separation diffusion 23, in order to limit the incidence of light from that position,
A light-shielding film (not shown) made of an aluminum film is formed on the surface of the silicon oxide film 24. In other words, the light is
The light is incident on the surface of the pixel 22.

In this semiconductor image sensor, when light is incident on the silicon substrate 21 via each pixel 22, charges corresponding to the incident light are generated in the silicon substrate 21. Then, when the charges generated in the silicon substrate 21 reach the corresponding pixels 22, a photocurrent flows in the pixels 22. An image is read by detecting this photocurrent as an output signal of each pixel 22.

By the way, as shown in FIG. 4, an electric charge 37 is generated in the silicon substrate 21 by the incident light 26b incident from the surface of a predetermined pixel 22b of the pixels 22, for example. Is the silicon substrate 21
Spread isotropically inside. Therefore, this electric charge 37 should be detected only in the pixel 22b, but
The pixels 22a and 22c adjacent to the pixel 22b reach the pixels 22a and 22c, and undesired photocurrents (output signals) are generated in the pixels 22a and 22c (that is, the pixels 22a and 22c).
Crosstalk occurs in a and 22c). The occurrence of this crosstalk is one of the factors that deteriorate the spatial signal resolution of the image sensor.

The above-mentioned crosstalk is used as one criterion for representing the performance of the semiconductor image sensor (that is, the smaller the crosstalk, the better the resolution of the semiconductor image sensor). Therefore, in order to measure the performance of the semiconductor image sensor, various methods of detecting crosstalk generated in the semiconductor image sensor have been conventionally proposed, and examples thereof will be shown below.

Usually, in order to measure the crosstalk, light is made incident on only one pixel of a plurality of pixels (light receiving portion formed of a photodiode or the like) formed on the substrate,
Photocurrent generated in the pixel adjacent to that pixel (output signal)
Has been adopted.

FIG. 5 is a sectional view for explaining an example of a method for detecting crosstalk generated in a semiconductor image sensor. In the method shown in FIG. 5, a condenser lens 40 arranged on a movable fine movement stage (not shown) is arranged at a desired position, light from a predetermined light source is condensed, and the condensed light is collected. Is irradiated only to a predetermined pixel 22r formed on the silicon substrate 21. In this state, the photocurrent (output signal) generated in the predetermined pixel 22r and the pixels 22q and 22s adjacent to the pixel 22r is detected, and the two are compared to obtain the crosstalk.

FIG. 6 is a sectional view for explaining another example of the method for detecting the crosstalk generated in the semiconductor image sensor. In this method, a slit 50 (a slit in which a hole having a size corresponding to the size of one pixel is formed) formed on a fine movement stage (not shown) is arranged at a desired position and a predetermined light source is used. Light emitted from the pixel 22
Only r is irradiated. In this state,
Pixel 2 adjacent to the predetermined pixel 22r and pixel 22r
The photocurrent (output signal) generated in 2q and 22s is detected,
Crosstalk can be obtained by comparing the two.

[0011]

However, the above-described crosstalk detection method shown in FIGS. 5 and 6 has the following problems.

That is, in the crosstalk detecting method shown in FIGS. 5 and 6, the condenser lens 40 and the slit 50 are mounted on a fine movement stage (not shown) and arranged at a desired position to specify the light. Since only the pixel (pixel 22r in FIGS. 5 and 6) is irradiated, there is a problem that the fine movement stage for moving the condenser lens 40 and the slit 50 increases the cost. .

Further, in recent years, pixels of semiconductor image sensors have been downsized (for example, 10 pixels).
5 × 500 pixels (photodiodes) are formed in the × 10 μm image sensor), FIG.
Or the slit 5 shown in FIG.
There is also a problem that it is difficult to cause light to enter only one predetermined pixel by using 0.

The present invention has been made in view of such a situation, and an object thereof is to detect crosstalk accurately and easily at low cost.

[0015]

According to a first aspect of the present invention, there is provided a crosstalk detecting method, wherein a light-shielding pattern for limiting light incidence is formed on a light-receiving surface of a light-receiving portion other than the predetermined light-receiving portion, and the predetermined light-receiving portion is received. It is characterized in that the output signal of the light receiving unit and the output signal of the light receiving unit other than the predetermined light receiving unit in which the light shielding pattern is formed on the light receiving surface are measured and the two are compared.

According to a second aspect of the present invention, there is provided a light-receiving element having a light-shielding pattern formed on the light-receiving surface of the light-receiving section, which restricts light from entering the light-receiving sections other than a predetermined light-receiving section among the plurality of light-receiving sections. It is characterized by being provided.

According to a sixth aspect of the present invention, in a crosstalk detecting method, a plurality of light receiving elements and at least one light receiving element for measuring crosstalk for measuring crosstalk generated in the light receiving elements are provided on one wafer. The crosstalk generated in the light receiving element is measured by using the above-described light receiving element for crosstalk measurement.

According to a seventh aspect of the present invention, there is provided a crosstalk detecting method comprising: a wafer on which a plurality of light receiving elements are formed; and a wafer on which a crosstalk measuring light receiving element for measuring crosstalk generated in the light receiving elements is formed. Are manufactured in the same lot, and the crosstalk generated in the light receiving elements of the same lot is measured using the light receiving element for crosstalk measurement.

A wafer according to an eighth aspect is characterized in that at least one of the plurality of light receiving elements is a crosstalk measuring light receiving element for measuring crosstalk.

In the crosstalk detecting method according to the first aspect, a light-shielding pattern for limiting the incidence of light is formed on the light-receiving surface of a light-receiving portion other than the predetermined light-receiving portion, and an output signal of the predetermined light-receiving portion is provided. , The output signals of the light-receiving portions other than the predetermined light-receiving portion, in which the light-shielding pattern is formed on the light-receiving surface, are measured and compared with each other.

In the light receiving element according to claim 2, a light shielding pattern formed on the light receiving surface of the light receiving portion for limiting the incidence of light on the light receiving portion other than the predetermined light receiving portion among the plurality of light receiving portions. Equipped with.

In the crosstalk detecting method according to the sixth aspect of the present invention, a plurality of light receiving elements and at least one light receiving element for measuring crosstalk for measuring crosstalk generated in the light receiving elements are provided in one sheet. The crosstalk generated on the light receiving element is measured by using the light receiving element for crosstalk measurement formed on the wafer.

In the crosstalk detecting method according to claim 7, a wafer having a plurality of light receiving elements formed therein and a wafer having a crosstalk measuring light receiving element for measuring crosstalk occurring in the light receiving elements formed therein are formed. Are manufactured in the same lot, and the crosstalk generated in the light receiving element is measured using the light receiving element for crosstalk measurement.

In the wafer according to the eighth aspect, at least one of the plurality of light receiving elements is a crosstalk measuring light receiving element for measuring crosstalk.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. Parts corresponding to those in the conventional case are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

FIG. 1 is a plan view showing the manufacturing process of a photodetector for crosstalk measurement to which the present invention is applied. Usually, a plurality of semiconductor image sensors are formed on a single wafer, and are manufactured by cutting and separating each. The crosstalk measuring light receiving element of the present embodiment is configured by using at least one of a plurality of semiconductor image sensors formed on one wafer.

That is, in FIG. 1, a plurality of semiconductor image sensors 11 (a plurality of pixels (light receiving portions including photodiodes or the like) are formed therein).
Is formed on the wafer 10 made of silicon,
One of them (the shaded portion in the drawing) is used as the crosstalk measuring light-receiving element 11A of this embodiment. The dotted line in FIG. 1 represents a dicing line, and the individual semiconductor image sensors 11 are manufactured by cutting and separating the wafer 10 along the dicing line.

FIG. 2 is a plan view (that is, an enlarged view of the crosstalk measuring light receiving element 11A shown in FIG. 1) showing the structure of the crosstalk measuring light receiving element 11A of this embodiment, and FIG. Crosstalk measurement light receiving element 1 shown in FIG.
FIG. 1B is a sectional view taken along line AA ′ of 1A. As is clear from FIG. 3, the configuration of the crosstalk measurement light receiving element 11A of the present embodiment is basically the same as the configuration of the semiconductor image sensor shown in FIG. 4, and the pixels 22 (pixels other than the predetermined pixel 22b 22a, 22c, etc.), a crosstalk measurement pattern 25 made of an aluminum film is formed on the silicon oxide film 24 to limit the incidence of light.

The crosstalk measurement pattern 25 is
The light-shielding film (not shown) formed on the silicon oxide film 24 in the position where the wiring layer is not formed or the wiring layer formed in the normal semiconductor image sensor described in the conventional example is used. Formed.

For example, the wiring layer (not shown) formed on the separation diffusion 23 in FIG. 3 is a metal layer such as aluminum, and normally, at a position where the wiring layer is not required (on the pixel 22 or the like), It is removed by the etching process. The crosstalk measurement pattern 25 is formed by leaving the wiring layer that is originally removed without removing it.

In this case, the crosstalk measurement pattern 25 is used as a pattern for processing the wiring layer and the light shielding film.
However, the manufacturing process is not changed.

When the light receiving element for crosstalk measurement prepared as described above is arranged in front of a predetermined light source, the light emitted from the predetermined light source is restricted by the crosstalk measurement pattern 25. It is incident on a predetermined pixel 22b which is not illuminated. In this state, the predetermined pixel 2
Crosstalk is detected by detecting the photocurrent (output signal) generated in 2b and the photocurrent generated in the pixels 22a and 22c adjacent to the pixel 22b and comparing the two.

This crosstalk measuring light receiving element 11A
Are manufactured under the same conditions as those of the semiconductor image sensor 11 formed on the same wafer 10, so it can be considered that both have the same performance (spatial resolution). Therefore, it is estimated that the semiconductor image sensor 11 formed on the same wafer 10 has the same crosstalk as the crosstalk detected by the crosstalk measuring light receiving element 11A. In other words, the crosstalk of the semiconductor image sensor 11 is measured using the crosstalk measurement light-receiving element 11A, and the performance (good spatial resolution) is determined. As described in the conventional example, the spatial resolution of the semiconductor image sensor formed on the wafer 10 is considered to be better as the crosstalk detected by the crosstalk measurement light-receiving element 11A is smaller.

In this embodiment, a crosstalk measuring pattern 25 for limiting the incidence of light on pixels other than the predetermined pixel 22b is provided on the surface of the semiconductor image sensor (see FIG. 3).
, On the surface of the silicon oxide film 24). Therefore, crosstalk can be detected accurately and easily as compared with the case of using a condenser lens, a slit, etc. as in the conventional example. Further, since it is not necessary to configure a fine movement stage for moving the condenser lens, the slit, etc., it is possible to measure the crosstalk at low cost.

In the present embodiment, the aluminum film is used to form the crosstalk measurement pattern 25, but the present invention is not limited to this, and the crosstalk measurement pattern 25 may be formed by another member that limits the incidence of light. May be formed.

In this embodiment, one of the plurality of semiconductor image sensors 11 formed on one wafer 10 is used as the crosstalk measuring light receiving element 11A. Not limited to this, for example, all of the semiconductor image sensors on one wafer out of about 20 wafers (wafers of the same lot) manufactured at the same time are formed as light receiving elements for crosstalk measurement, and on other wafers. All may be formed as a normal semiconductor image sensor. In this embodiment, even if variations occur at each position on the wafer, this variation can be detected. In this case, it is considered that the performances of the semiconductor image sensors (of the same lot) manufactured at the same time are the same.

[0037]

According to the crosstalk detecting method, the light receiving element and the wafer of the present invention, the incidence of light to the pixels other than the predetermined pixels is limited, so that the crosstalk can be produced at low cost, accurately and easily. Can be detected.

[Brief description of drawings]

FIG. 1 is a plan view illustrating a manufacturing process of a photodetector for crosstalk measurement to which the present invention is applied.

FIG. 2 is a plan view showing a configuration of an embodiment of a crosstalk measurement light receiving element to which the present invention is applied.

FIG. 3 is a cross-sectional view taken along the line A-A ′ in FIG.

FIG. 4 is a cross-sectional view showing a configuration example of a semiconductor image sensor.

FIG. 5 is a cross-sectional view showing an example of a conventional crosstalk detection method.

FIG. 6 is a sectional view showing another example of a conventional crosstalk detecting method.

[Explanation of symbols]

 10 Wafer 11 Semiconductor Image Sensor 11A Crosstalk Measurement Light-Receiving Element 21 Silicon Substrate 22, 22a to 22c, 22q to 22s Pixel 23 Separation Diffusion 24 Silicon Oxide Film 25 Crosstalk Measurement Pattern 26, 26b Incident Light 37 Charge 40 Condensing Lens 50 slits

Claims (8)

[Claims] 1. A crosstalk detection method for detecting crosstalk generated in a light receiving element comprising a plurality of light receiving portions for receiving light and a substrate on which the light receiving portions are formed. A limiting light-shielding pattern is formed on the light-receiving surface of the light-receiving portion other than the predetermined light-receiving portion, and the output signal of the predetermined light-receiving portion and the light-shielding pattern other than the predetermined light-receiving portion are on the light-receiving surface. A crosstalk detecting method comprising: measuring an output signal of the formed light receiving unit and comparing the two. 2. A light receiving element comprising a plurality of light receiving sections for receiving light, and a substrate having the light receiving sections formed on a surface thereof, wherein the plurality of light receiving sections other than the predetermined light receiving section are provided. A light-receiving element comprising a light-shielding pattern formed on the light-receiving surface of the light-receiving unit, which limits the incidence of light on the light-receiving unit. 3. The light receiving element according to claim 2, wherein the light shielding pattern is made of an aluminum film. 4. The light shielding pattern is formed by extending a wiring layer formed between the plurality of light receiving portions on the surface of the substrate. Light receiving element. 5. The light-receiving element according to claim 4, wherein the light-shielding pattern is separated from the wiring layer. 6. A plurality of light receiving elements and at least one,
A crosstalk measuring light receiving element for measuring crosstalk generated in the light receiving element is formed on one wafer, and the crosstalk generated in the light receiving element is formed by using the crosstalk measuring light receiving element. A method for detecting crosstalk, which comprises measuring 7. A wafer on which a plurality of light receiving elements are formed,
A wafer on which a crosstalk measuring light receiving element for measuring crosstalk generated in the light receiving element is formed,
A crosstalk detecting method, which is manufactured in the same lot, and measures the crosstalk generated in the light receiving elements of the same lot by using the light receiving element for crosstalk measurement. 8. A wafer having a plurality of light receiving elements formed thereon, wherein at least one of the plurality of light receiving elements is used as a crosstalk measuring light receiving element for measuring crosstalk.