JP5404315B2 - Solid-state image sensor manufacturing method and solid-state image sensor - Google Patents

Description

  The present invention relates to a method for manufacturing a solid-state imaging device.

In recent years, solid-state imaging devices that capture subject images have been widely used in cameras, mobile phones, and the like. Some solid-state imaging devices are configured such that the surface of a silicon substrate on which pixels for photoelectric conversion are formed is covered with an interlayer insulating film such as SiO ₂ . In such a solid-state imaging device, a part of the light from the subject reaching the pixel is reflected in the interlayer insulating film. There is a problem that an interference waveform is generated in the photoelectric output due to interference between the reflected light in the interlayer insulating film and the light directly incident on the element. Therefore, for example, Patent Document 1 discloses a technique for forming a height difference on the light incident surface of the solid-state imaging device to suppress light interference.

  However, in the prior art, a base layer pattern is formed on the interlayer insulating film, the base layer pattern is etched, and further, the base layer pattern is covered with the upper layer film by a CVD method, so that the light incident surface of the solid-state imaging device is covered. A difference in height is formed. Further, the pad electrode disposed on the interlayer insulating film is also covered with the base layer pattern and the upper layer film. Therefore, in addition to the above steps, a step of etching the underlying layer pattern and the upper layer film is necessary to expose the pad electrode.

  Therefore, in the prior art, there is a problem that in the manufacturing process of the solid-state imaging device, the number of processes increases in order to suppress the interference of light, and the manufacturing cost is difficult to suppress.

JP-A-6-125068

  An object of the present invention is to provide a method for manufacturing a solid-state imaging device capable of forming a stepped shape that suppresses light interference while suppressing the number of steps on a light incident surface.

  According to one aspect of the present invention, an interlayer insulating film is formed on a surface of a silicon substrate on which a photoelectric conversion element is formed, a pad electrode is formed on the surface of the interlayer insulating film, and the protective film covers the interlayer insulating film and the pad electrode And patterning a resist on the surface of the protective film so as to have a first opening formed at a position facing the photoelectric conversion element and a second opening formed at a position facing the pad electrode, There is provided a method for manufacturing a solid-state imaging device, wherein isotropic etching is performed on the protective film through the second opening.

  According to the present invention, there is an effect that a step shape that suppresses interference of light while suppressing the number of manufacturing steps of the solid-state imaging device can be formed on the light incident surface.

1 is a diagram showing a cross-sectional configuration of a solid-state imaging element according to a first embodiment of the present invention. The schematic diagram for demonstrating suppression of the interference of the light by a 1st dent part. The figure for demonstrating the manufacturing process of a solid-state image sensor. The figure for demonstrating the manufacturing process of a solid-state image sensor. The figure for demonstrating the manufacturing process of a solid-state image sensor. The figure for demonstrating the manufacturing process of a solid-state image sensor. The figure for demonstrating the manufacturing process of a solid-state image sensor. The flowchart explaining the manufacturing process of a solid-state image sensor. 1 is a block diagram showing a schematic configuration of a CCD image sensor as an example of a solid-state image sensor.

  Hereinafter, a solid-state imaging device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by this embodiment.

(First embodiment)
FIG. 1 is a diagram showing a cross-sectional configuration of the solid-state imaging device according to the first embodiment of the present invention. The solid-state imaging device 1 includes a silicon substrate 2, a photoelectric conversion element 3, an interlayer insulating film 4, a wiring (first layer wiring) 6, a pad electrode (second layer wiring) 8, and a protective film 10.

On the surface of the silicon substrate 2, a photoelectric conversion element 3 that converts light from a subject into signal charges is formed. The surface of the silicon substrate 2 on which the photoelectric conversion element 3 is formed is covered with a silicon oxide (SiO ₂ ) film as the interlayer insulating film 4. A wiring 6 is disposed in the layer of the interlayer insulating film 4. A pad electrode 8 is disposed on the surface of the interlayer insulating film 4. For the wiring 6 and the pad electrode 8, for example, aluminum is used.

The surfaces of the interlayer insulating film 4 and the pad electrode 8 are covered with the protective film 10. For example, a silicon oxide film or a silicon nitride film (Si ₃ N ₄ ) is used for the protective film 10. In the protective film 10, a first dent 12 and a second dent 14 are formed. The first dent 12 is formed to suppress light interference. The first dent 12 is formed at a position facing the photoelectric conversion element 3 formed on the silicon substrate 2. As a result, the first recess 12 is formed in a region through which light incident on the photoelectric conversion element 3 is transmitted. The first recess 12 is formed so as to penetrate the protective film 10 and cut out a part of the interlayer insulating film 4. The first recess 12 is formed in a shape having a curvature in at least one direction.

  The second recess 14 is formed so as to penetrate the protective film 10. The second recessed portion 14 is formed at a position facing the pad electrode 8. The second recess 14 is formed so as to penetrate the protective film 10, and the pad electrode 8 is exposed from the second recess 14.

  FIG. 2 is a schematic diagram for explaining suppression of light interference by the first recess 12. A part of the light from the subject that has reached the photoelectric conversion element 3 is reflected by the photoelectric conversion element 3 as indicated by an arrow 16. The light reflected by the photoelectric conversion element 3 is reflected again by the surface of the first recess 12. The light reflected from the surface of the first recess 12 travels in the direction indicated by the arrow 18 due to the curvature of the first recess 12. Therefore, the light reflected by the first recess 12 is less likely to enter the photoelectric conversion element 3 again, and interference with light from the subject can be suppressed.

  Next, the manufacturing process of the solid-state imaging device 1 will be described. 3-7 is a figure for demonstrating the manufacturing process of the solid-state image sensor 1. FIG. FIG. 8 is a flowchart for explaining a manufacturing process of the solid-state imaging device 1.

  First, as shown in FIG. 3, the photoelectric conversion element 3 as an impurity layer is formed on the surface of the silicon substrate 2 (step S1). Next, as shown in FIG. 4, the surface of the silicon substrate 2 is covered with the interlayer insulating film 4, the wiring 6 is disposed inside the interlayer insulating film 4, and the pad electrode 8 is disposed on the surface of the interlayer insulating film 4. (Step S2). Next, as shown in FIG. 5, the surfaces of the interlayer insulating film 4 and the pad electrode 8 are covered with a protective film 10 (step S3). Next, as shown in FIG. 6, a resist 20 is applied to the surface of the protective film 10 (step S4). Here, the resist 20 is patterned so as to have the first opening 20a and the second opening 20b. The 1st opening 20a is formed in the position which opposes the photoelectric conversion element 3, and is provided in order to form the 1st dent part 12 in the solid-state image sensor 1 at the next process. The second opening 20b is formed at a position facing the pad electrode 8, and is provided for forming the second recess 14 in the solid-state imaging device 1 in the next step.

  Next, isotropic etching is performed through the first opening 20a and the second opening 20b formed in the resist 20 to etch the protective film 10 (step S5). Here, the interlayer insulating film 4 is also etched by penetrating the protective film 10 by isotropic etching through the first opening 20a. As a result, the first recess 12 is formed across the protective film 10 and the interlayer insulating film 4.

  Since the protective film 10 is formed with a substantially uniform thickness, if the protective film 10 is penetrated by isotropic etching through the first opening 20a as described above and the interlayer insulating film 4 is also etched, the second film is formed. The protective film 10 is reliably penetrated even on the opening 20b side, and the pad electrode 8 can be more reliably exposed. Thereby, the exposure failure of the pad electrode 8 can be suppressed and the yield can be improved. In addition, when the pad electrode 8 is exposed, signal charges can be taken out via the pad electrode 8. Next, by peeling off the resist 20 (step S6), the solid-state imaging device 1 including the first dent portion 12 and the second dent portion 14 as shown in FIG. 1 can be obtained.

  As described above, after the surfaces of the interlayer insulating film 4 and the pad electrode 8 are covered with the protective film 10, the step of exposing the pad electrode 8 by performing isotropic etching and the light of the solid-state imaging device 1 are performed. The step of forming the step shape (the first dent 12) on the incident surface can be performed in one step. Thereby, it can be set as the manufacturing method of the solid-state image sensor 1 provided with the level | step difference shape which suppresses interference of light, suppressing the number of manufacturing processes.

  FIG. 9 is a block diagram illustrating a schematic configuration of a CCD image sensor 21 as an example of a solid-state imaging device. The CCD image sensor 21 includes a CCD (Charge Coupled Device) as a charge transfer unit and the like, and also includes a plurality of photoelectric conversion elements 3. The photoelectric conversion element 3 converts light into signal charges. The CCD 22 reads the converted signal charge from the photoelectric conversion element 3 and transfers it to the amplifier 24. The amplifying unit 24 converts the transferred signal charge into a signal voltage and sends the signal voltage to the output circuit 26. The output circuit 26 outputs the received signal voltage to a predetermined output destination. Although not shown in FIG. 9, the CCD image sensor 21 also includes a silicon substrate, an interlayer insulating film, wiring, pad electrodes, and a protective film. Also in the manufacture of such a CCD image sensor 21, by using the manufacturing process described in the first embodiment, it is possible to obtain a highly reproducible image while suppressing light interference. Further, the manufacturing cost can be reduced by reducing the number of manufacturing steps of the CCD image sensor 21.

DESCRIPTION OF SYMBOLS 1 Solid-state image sensor, 2 Silicon substrate, 3 Photoelectric conversion element, 4 Interlayer insulating film, 6 wiring (1st layer wiring), 8 pad electrode (2nd layer wiring), 10 protective film, 12 1st dent part, 14 1st 2 recessed portions 16, 18 arrows, 20 resist, 20a first opening, 20b second opening, 21 CCD image sensor, 22 CCD, 24 amplifying unit, 26 output circuit.

Claims (2)

An interlayer insulating film is formed on the surface of the silicon substrate on which the photoelectric conversion element is formed,
Wiring is disposed around a region facing the photoelectric conversion element in the interlayer insulating film,
Forming a pad electrode on the surface of the interlayer insulating film;
Forming a protective film covering the interlayer insulating film and the pad electrode;
Patterning a resist on the surface of the protective film so as to have a first opening formed at a position facing the photoelectric conversion element and a second opening formed at a position facing the pad electrode;
There row isotropic etching with respect to the protective film and the interlayer insulating film through said first opening and said second opening, a first recess formed at a position avoiding the wiring area opposite to,
A method of manufacturing a solid-state imaging device , wherein isotropic etching is performed on the protective film through the second opening to form a second recess exposing the electrode pad . A silicon substrate having a photoelectric conversion element formed on the surface;
An interlayer insulating film covering the surface of the silicon substrate;
A pad electrode formed on the surface of the interlayer insulating film;
A protective film covering the interlayer insulating film and the pad electrode;
Among the layers of the interlayer insulating film, wiring disposed around a region facing the photoelectric conversion element,
The photoelectric conversion element is formed from the protective film to the interlayer insulating film at a position facing the photoelectric conversion element in the interlayer insulating film and the protective film and avoiding a region facing the wiring. A first dent having a curvature towards
A solid-state imaging device, comprising: a second recess formed in the protective film at a position facing the pad electrode and exposing the pad electrode.

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