JP2674563B2 - Solid-state imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a charge coupled device (CC).
The present invention relates to a solid-state image pickup device using D) or the like, and more particularly to a solid-state image pickup device that improves image quality by suppressing a temperature rise of a solid-state image pickup element.

[0002]

2. Description of the Related Art In recent years, in the solid-state image pickup device, the number of pixels has been increased to meet the needs of high resolution due to the development of process technology. Due to the increase in the number of pixels, the operating frequency rises, and accordingly, the amount of heat generated in the element portion increases and the temperature of the chip surface on which the solid-state imaging device is formed on the silicon substrate rises.

As a result, the influence of the heat generation has become non-negligible, and, in particular, the dark current of a specific pixel increases remarkably as the temperature rises, and the specific pixel portion becomes white in the dark state. The defects that become visible and whose contrast increases depending on the temperature increase become remarkable. This defect significantly deteriorates the image quality because the dark current increases about twice at 10 degrees.

Further, the increase in dark current also causes the dynamic range to be narrowed. The actual self-heating of the solid-state imaging device itself is about 0.3 to 0.5 W, which causes a temperature rise of about 20 degrees with respect to the ambient temperature, resulting in a decrease in S / N of image information. , The dynamic range was deteriorated.

As a solution to this problem, there is a method of cooling the chip using an electronic cooling element or the like. Reducing the temperature of the chip can reduce dark current and thermal noise.
FIG. 3 (a) is a plan view of a conventional solid-state imaging device provided with this type of cooling means, and FIG. 3 (b) is C- of FIG. 3 (a).
It is sectional drawing of the D line. In the conventional technique, as shown in FIG. 3, the metal plate 1 is provided on the cooling side electrode 3a of the electronic cooling element 3.
The solid-state image pickup device 1 is mounted with the light receiving region 14 facing upward via 3 and the electrode 3b on the heat radiation side of the electronic cooling device is mounted on the heat radiation plate 1.
5 was in contact. With this configuration, the heat generated by the solid-state imaging element itself is absorbed by the electronic cooling element 3, while the heat generated by the electronic cooling element is released to the heat dissipation plate 15 to prevent the temperature of the chip from rising. A solid-state imaging device equipped with this type of cooling means is known, for example, from Japanese Patent Laid-Open No. 4-123462.

[0006]

However, in the above-mentioned conventional solid-state image pickup device, since the cooling is performed from the back surface of the chip, the entire chip must be cooled in order to suppress the temperature rise of the heat source on the chip surface. I won't. That is,
The cooling heat applied from the back surface of the silicon substrate having a thickness of 400 to 700 μm reaches the front surface of the chip while cooling the entire silicon substrate with the efficiency of heat conduction of silicon, and heat generation of the solid-state electronic device formed on the front surface. This is to cool the part.

As a result, the overall heat capacity that must be cooled increases, and the electronic cooling element for suppressing the temperature rise of the heat generating portion of the element becomes large in size and its power consumption also increases. Further, since the thermal conductivity of silicon is lower than that of metal, it takes a long time to cool the entire chip to reach saturation.

The present invention is to solve the above problems, and provides a solid-state imaging device capable of suppressing the temperature rise of the solid-state imaging device with low power consumption in a short time and obtaining good image quality. To aim.

[0009]

To achieve the above object, according to the present invention, the metal light-shielding film formed on the surface of the solid-state image pickup device is directly cooled by the electronic cooling device. And a solid-state image pickup device. That is, more specifically, a solid-state imaging device characterized in that the metal light-shielding film formed on the surface of the solid-state imaging device is connected to an electrode of the electronic cooling element or a metal substrate provided with the electronic cooling element, Will be provided.

[0010]

According to the present invention, since the metal light-shielding film having a large thermal conductivity is cooled by the above-mentioned structure, and the wiring such as the transfer electrode and the semiconductor active layer are present in the vicinity of the metal light-shielding film. Therefore, the heating element can be cooled effectively and in a short time. As a result, it is possible to suppress the temperature rise of the solid-state imaging device with low power consumption, and it is possible to realize a solid-state imaging device having a wide dynamic range and good image quality with a small-scale cooling means.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. 1A is a plan view showing a first embodiment of the present invention, and FIG. 1B is a sectional view taken along the line AB. As shown in FIG. 1A, the solid-state imaging device 1
A metal light-shielding film 4 having a light receiving opening 6 is formed on the surface of, and contact portions 5 are formed at two end portions of the metal light-shielding film 4. The contact portion 5 is connected to the cooling-side electrode of the electronic cooling element (not shown) via the metal wire 2.

As shown in FIG. 1B, an n-type semiconductor region 9a serving as a photoelectric conversion region is formed below the light-receiving opening 6 formed in the metal light-shielding film 4, and this n-type semiconductor region 9a is formed. Adjacent to the semiconductor region 9a, an n-type semiconductor region 9b for transferring the signal charges generated in this photoelectric conversion region is formed. These two types of n-type semiconductor regions 9a and 9b
Is surrounded by a p ⁺ type semiconductor region 10 for element isolation except a region (charge reading region) for coupling the two. Further, the n-type semiconductor region 9a, which is a photoelectric conversion region, is covered with the p ⁺ -type semiconductor region 10 in order to make this region a buried type.

Each of these semiconductor regions is formed in the surface region of the p-type semiconductor region 11 formed on the n-type silicon substrate 12. A silicon oxide film 8 is formed on the semiconductor substrate.
A first transfer electrode 7a and a second transfer electrode 7b are formed surrounded by. The signal charges generated in the n-type semiconductor region 9a by these transfer electrodes are read out to the n-type semiconductor region 9b which is a charge transfer region, and then transferred in the direction perpendicular to the paper surface.

In the solid-state image pickup device constructed as described above, when the electronic cooling element is cooled, the metal wire 2 is cooled by heat conduction of the metal. By cooling the metal wire 2, the metal light-shielding film 4 is gradually cooled from the contact portion 5, and the cooling heat is propagated to the whole metal light-shielding film 4 by free electrons in the metal, and is saturated and cooled to a uniform temperature.

Then, the cooling heat from the metal light-shielding film 4 cooled to a uniform temperature is transmitted through the silicon oxide film 8 to the first,
It is transmitted to the second transfer electrode and the diffusion layer, and cools the transfer electrode and the semiconductor regions such as the photoelectric conversion region and the charge transfer region. Thus, as shown in FIG. 1B, the distance from the back surface of the semiconductor substrate to the front surface of the substrate is 400 to 700.
Although the thickness is about μm, the metal light-shielding film 4 to the transfer electrode 7
The distance to a and 7b is about 1 μm, and the distance to the diffusion layer on the substrate surface is about 2 μm. Therefore, in the present embodiment, the thermal resistance is small, the cooling effect is high, and the temperature rise can be suppressed by the remarkably low power consumption as compared with the conventional example. Further, the cooling means can be downsized.

FIG. 2 is a perspective view showing a second embodiment of the present invention. As shown in the figure, in this embodiment, the metal light-shielding film on the solid-state image sensor 1 and the electronic cooling element 3 are used.
Three metal wires each between the cooling side electrode and
Connected by By increasing the number of metal wires connecting the electronic cooling element and the metal light-shielding film in this manner, the thermal resistance between the electronic cooling element and the metal light-shielding film becomes lower than that in the first embodiment, and the efficiency is improved. It becomes possible to perform effective cooling.

FIG. 3 is a perspective view showing a third embodiment of the present invention. As shown in the figure, in this embodiment, the cooling-side electrodes of the electronic cooling element 3 are directly connected to both sides of the metal light-shielding film on the solid-state imaging device 1. With this configuration, the thermal resistance between the electronic cooling element and the metal light-shielding film is further reduced, and more efficient cooling can be performed.

In the above embodiments, the metal wire is connected to the cooling side electrode of the electronic cooling element or the electrode is directly connected to the metal light-shielding film, but instead of this, insulation is provided on the metal substrate. It is also possible to form a plurality of electrodes on the cooling side via a film and to provide a cooling element on the electrodes, and to connect the back surface of this metal substrate to the metal light-shielding film via a wire or the like. Further, the solid-state imaging device may be mounted on another electronic cooling device by combining the above-described embodiment and the conventional example.

[0019]

As described above, in the solid-state image pickup device of the present invention, the metal light-shielding film provided on the surface of the solid-state image pickup element is directly cooled by the electronic cooling element.
The distance to the heating element can be made much closer than in the conventional method, and efficient cooling can be achieved in a short time. Therefore, according to the present invention, it is possible to suppress the temperature rise of the solid-state image pickup element by a small-scale cooling means with low power consumption, and it is possible to realize a solid-state image pickup apparatus with good image pickup quality. .

[Brief description of the drawings]

FIG. 1 is a plan view showing a first embodiment of the present invention and its A.
-B sectional drawing of line.

FIG. 2 is a perspective view showing a second embodiment of the present invention.

FIG. 3 is a perspective view showing a third embodiment of the present invention.

FIG. 4 is a plan view of a conventional example and a sectional view taken along line C-D thereof.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Solid-state image sensor 2 Metal wire 3 Electronic cooling element 4 Metal light-shielding film 5 Contact part 6 Light-receiving opening 7a First transfer electrode 7b Second transfer electrode 8 Silicon oxide film 9a n-type semiconductor region (photoelectric conversion region) 9b n Type semiconductor region (charge transfer region) 10 p ⁺ type semiconductor region 11 p type semiconductor region 12 n type silicon substrate 13 metal plate 14 light receiving region 15 heat sink

Claims (4)

(57) [Claims] 1. A solid-state image pickup device, wherein a metal light-shielding film formed on a surface of the solid-state image pickup element is directly cooled by an electronic cooling element. 2. The solid-state imaging device according to claim 1, wherein the metal light-shielding film is connected to an electrode of the electronic cooling element or a metal substrate provided with the electronic cooling element. 3. The solid-state imaging device according to claim 1, wherein the metal light-shielding film is connected to an electrode of the electronic cooling element or a metal substrate provided with the electronic cooling element via a metal wire. . 4. The solid-state imaging device according to claim 1, wherein the solid-state imaging device is mounted on another electronic cooling device.