JPH06283701A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To provide a solid-state image sensing device whose reliability is high as a device. CONSTITUTION:The air inside a recessed part 50 is discharged from a ventilation passage 60 which has been formed in the side face of a semiconductor substrate 20. As a result, when a device 10 is used is a cooled COD and when a vacuum suction operation is performed in order to prevent the surface of an element from being dewed, the air inside the recessed part 50 is discharged from the ventilation passage 60, and also the inside of the recessed part 50 becomes vacuum in the same manner as the outside. Consequently, the device 10 is not destroyed due to a stress.

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 such as a CCD image sensor.

[0002]

2. Description of the Related Art Conventionally, as a technique in such a field,
Japanese Patent Publication No. 4-44469 is known. This document discloses a technique of cutting long-wavelength sensitivity by providing a recess on the back surface of a solid-state imaging device to reduce the thickness of the semiconductor substrate of the light-receiving portion.

[0003]

By the way, a conventional solid-state image pickup device having a recess on the back surface of a semiconductor substrate is usually fixedly used on a base substrate. When this is used as a cooling type CCD, for example, a vacuum is drawn during cooling in order to prevent dew condensation on the element surface. By this evacuation, a pressure difference is generated between the inside and the outside of the recess on the back surface of the semiconductor substrate, and stress is induced. Then, this stress causes plastic deformation, which causes the device to be destroyed. In particular, in the conventional example, since the back surface of the semiconductor substrate is thinly shaved, the mechanical strength of the device is lowered, and the device is easily broken by stress, which is a problem.

In addition, when a vacuum is applied to the outside, the air in the recess may exert an abnormal pressure on the device and destroy the device.

The present invention aims to solve such a problem.

[0006]

In order to solve the above problems, in the solid-state image pickup device of the present invention, an air passage from the recess is formed on the side surface of the semiconductor substrate.

[0007]

According to the solid-state imaging device of the present invention, since the back surface of the semiconductor substrate is fixed to the base substrate and the opening of the recess is sealed by the base substrate, the air in the recess is removed from the semiconductor substrate. The air is discharged only from the ventilation passages formed on the side surface.

The solid-state image pickup device of the present invention can be applied to, for example, a cooling type CC.
When used as D (it is necessary to evacuate the element surface to prevent dew condensation), the air in the recess is discharged from the ventilation passage by this evacuation, and the interior of the recess is evacuated like the outside. Become. Therefore, the air pressures inside and outside the recess are kept substantially equal, and stress due to the pressure difference is not induced.

In the conventional example having no ventilation passage, a vacuum is applied to the outside, so that an abnormal pressure is applied to the inside of the device by the air in the recess. The solid-state imaging device of the present invention can prevent such a problem.

As described above, since the solid-state image pickup device of the present invention hardly induces an abnormal pressure, the device is not destroyed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1A and 1B are perspective views showing the appearance of a solid-state image pickup device according to this embodiment. The solid-state imaging device 10 of the present embodiment includes a p ⁺ type S that is a high-concentration semiconductor substrate.
an i substrate 20, a p-type semiconductor layer 21 formed on the Si substrate 20, and an n-type semiconductor layer 22 (not shown in FIG. 1) formed by ion implantation in the p-type semiconductor layer 21. , An insulating film 30 such as SiO ₂ and a CCD operating region 40 are provided. In the CCD operation area 40, a light receiving portion 41 and a light receiving area 43 including an isolation portion 45 are provided. Further, on the back surface of the Si substrate 20, a recess 50 is formed in a portion corresponding to the light receiving region 43, and a groove-shaped ventilation passage 60 is formed from the side surface of the Si substrate 20 to the recess 50.

The air passage 60 functions so that the air in the recess 50 is discharged when a vacuum is drawn to prevent dew condensation on the element surface during cooling. Normally, the solid-state imaging device 10 is fixed on the base substrate 70, so that the opening portion of the recess 50 is sealed by the substrate 70. Therefore, such an air passage 60 is necessary for adjusting the air pressure inside the recess 50 and outside. In addition, ventilation path 6
The gas discharged from 0 is not limited to air but may be a predetermined gas.

Next, the features of this embodiment will be described. The solid-state imaging device 10 of the present embodiment is effective when the entire device is evacuated for use as, for example, a cooling CCD.
That is, when vacuuming is performed, the air inside the recess 50 is discharged from the ventilation passage 60, and the inside of the recess 50 is also evacuated like the outside. Therefore, the pressure inside the recess 50 and the pressure outside are kept substantially equal, and stress due to the pressure difference is not induced. As described above, in the solid-state imaging device 10 of the present embodiment, the stress due to the pressure difference is hard to be induced, so that the solid-state imaging device 10 is not destroyed by the plastic deformation due to the stress.

Further, in the conventional example in which the ventilation passage 60 is not provided, a vacuum is applied to the outside, so that an abnormal pressure is applied to the inside of the apparatus by the air inside the recess 50. In this embodiment,
Such a problem can also be prevented.

Next, the structure of the solid-state image pickup device 10 of this embodiment will be described with reference to the sectional view of FIG. The solid-state imaging device 10 of the present embodiment epitaxially grows a p ⁺ type Si substrate 20 which is a high concentration semiconductor substrate having a thickness of about 500 μm and a low concentration impurity having a thickness of about 10 μm on the upper surface of the Si substrate 20. The p-type semiconductor layer 21 thus formed and the n-type semiconductor layer region 22 having a depth of about 1 μm are formed in the p-type semiconductor layer 21. FIG. 2 shows an example of a cross-sectional structure of the vertical transfer electrode portion of the CCD operating region 40. A transfer electrode 42 made of a transparent material such as polysilicon is formed on a gate oxide film of about 0.1 μm, and a light receiving portion 41 is formed. Covers. An n ⁻ region 23 for creating a potential barrier is formed in the n-type semiconductor layer 22.
Are formed.

A recess 50 and a ventilation passage 60 are formed on the back surface of the Si substrate 20 by using an etching technique. The recess 50 is formed on the back surface of the Si substrate 20 for the following reason. When light is emitted from the upper portion of the solid-state imaging device 10, the light receiving unit 41 receives the emitted light. Among the electron-hole pairs generated in each semiconductor region by this light reception, the electron-hole pairs generated in the high-concentration p ⁺ -type Si substrate 20 are because the Si substrate 20 is p ⁺ having a high impurity concentration. All the generated electron-hole pairs should recombine and disappear. However, in reality, the electron-hole pairs are not completely extinguished, and some contribute to the signal charge. Further, since the high-concentration p ⁺ -type Si substrate 20 corresponds to a neutral region, the signal charges generated in the high-concentration p ⁺ -type Si substrate 20 are diffused and spread. The spread of the signal charges affects the adjacent pixels, resulting in deterioration of image quality. Therefore, in order to eliminate the signal charge itself occurs at a high concentration p ⁺ -type Si substrate 20 to form a high-concentration p ⁺ -type Si substrate 20 in the recess.

The ventilation passage 60 may be a triangular groove as shown in FIG. 3 in addition to the rectangular groove as shown in FIG.

In the above embodiments, the p ⁺ type Si substrate 20, the p type semiconductor layer 21 and the n type semiconductor layer 22 are used, but the n type Si substrate 20 and the p type semiconductor layer are used. Two
2, or p-type Si substrate 20 and n-type semiconductor layer 22
May be a combination of. Further, a semiconductor substrate other than the Si substrate 20 may be used, and an insulating film other than the SiO ₂ film may be used.

[0020]

According to the solid-state imaging device of the present invention, the air in the recess is discharged from the ventilation passage formed on the side surface of the semiconductor substrate. For this reason (when cooling is performed in order to prevent dew condensation on the surface of the element when vacuuming), the air in the recess is exhausted from the ventilation passage, and the inside of the recess becomes vacuum as well as the outside.

As described above, according to the present invention, the reliability of the device can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an appearance of a solid-state imaging device according to an embodiment.

FIG. 2 is a cross-sectional view showing the structure of the solid-state imaging device according to the present embodiment.

FIG. 3 is a perspective view showing the shape of an air passage.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Solid-state imaging device, 20 ... Si substrate, 21 ... Semiconductor layer, 22 ... Area of opposite conductivity type to 21 ... 23 ... Area for forming potential barrier, 30 ... Insulating film, 40 ... CCD operating area, 4
DESCRIPTION OF SYMBOLS 1 ... Light receiving part, 42 ... Transfer electrode, 43 ... Light receiving area, 45 ...
Isolation, 50 ... Recess, 60 ... Ventilation path, 70 ...
substrate.

Claims (1)

[Claims] 1. A solid-state imaging device comprising: a semiconductor substrate having a recess on the back surface thereof; and a light-receiving portion provided on the top surface of the semiconductor substrate, wherein the back surface of the semiconductor substrate is fixed on a base substrate. A solid-state image pickup device, wherein a ventilation path from the recess is formed on a side surface of a semiconductor substrate.