JPH06302801A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To provide a solid-state image sensing device wherein a thermal resistance is lowered more than that in conventional cases, mechanical strength is enhanced and an image can be replayed at good image quality. CONSTITUTION:A solid-state image sensing device is constituted of a p<+> type semiconductor substrate composed of high-impurity-density p<+> type Si, of a semiconductor layer 24 formed on the p type semiconductor substrate 11, of an electrode layer 25 formed on the semiconductor layer 24 and of a reinforcement substrate 10 composed of Al as a conductor on the rear surface of the p<+> type semiconductor substrate 11. The layer thickness of the reinforcement substrate 10 is a prescribed value of 300 to 1000mum. The layer thickness of the p<+> type semiconductor substrate 11 is a prescribed value within a range of 5 to 80mum and the substrate is formed to be nearly smooth by a mechanical etching operation. As a result, since Joule's heat generated from an electrode in a photoelectric conversion means is dissipated to the side of the reinforcement substrate, a thermal resistance is lowered, and the mechanical strength of the device is enhanced. Consequently, it is possible to prevent a thermal noise from being generated and to prevent the device from being degraded thermally, and an image can be replaced at good image quality.

Description

Detailed Description of the Invention

[0001]

This invention relates to a CCD on a semiconductor substrate.
The present invention relates to a solid-state imaging device having an image sensor.

[0002]

2. Description of the Related Art FIG. 3 is a plan view showing the structure of an FFT (full frame transfer) type CCD solid-state image pickup device. The FFT CCD is a MOS capacitor type integrated circuit, and includes a photoelectric conversion unit 30 having a function of converting an optical signal into a charge signal, and an output unit 40 having a function of sequentially outputting the signal charges.

The photoelectric conversion section 30 includes an array of photosensitive pixels 32 for converting an optical signal into a charge signal and storing the charge signal, and a shift gate (not shown) disposed in each of the photosensitive pixels 32 to control the transfer of the signal charge. , Each of these photosensitive pixels 32
5 columns of vertical shift registers 31 for transferring the signal charges of (1) to the horizontal shift register 41 are formed.

The output section 40 includes a horizontal shift register 41 that horizontally transfers the signal charges transferred from the vertical shift register 31, and a charge-voltage conversion amplifier 43 that converts the signal charges transferred from the horizontal shift register 41 into an output voltage. ,
It has an output terminal 44 that outputs a voltage that has been subjected to charge-voltage conversion.

FIG. 4 (a) is a sectional view taken along the line AA in the case where the plan view shown in FIG. 3 is taken as a conventional example, and FIG. 4 (b) is likewise taken along the line BB. FIG. The conventional solid-state imaging device includes a p ^{+ type} semiconductor substrate 11 having a high impurity density, a semiconductor layer 24 formed on the p ^{+ type} semiconductor substrate 11, and an electrode layer 25 formed on the semiconductor layer 24. I have it.

The semiconductor layer 24 includes a p-type semiconductor layer 12 and a p ⁺ layer formed around the upper region of the p-type semiconductor layer 12.
In the upper region of the p-type semiconductor layer 13 and the p-type semiconductor layer 12, p ⁺
N-type semiconductor layer 14 formed inside the n-type semiconductor layer 13
And n ⁻ formed in the upper region of the n-type semiconductor layer 14.
Shaped semiconductor layer 15.

The electrode layer 25 includes an insulating layer 16, first transfer electrodes 17 and second transfer electrodes 18 formed in the insulating layer 16, and a first control electrode 19 which is in contact with the first transfer electrode 17. A second control electrode 20 in contact with the second transfer electrode 18, an insulating layer 21 formed on the insulating layer 16, an insulating layer 22 formed on the insulating layer 21, and an insulating layer 22 and a light shielding layer 23 formed on the layer 22.

The p ^{+ type} semiconductor substrate 11 is formed in a concave shape opened downward, and the layer thickness at its outer edge is 500.
The thickness of the inner concave portion located below the photosensitive pixel 32 is a predetermined value in the range of 5 to 80 μm.
The p-type semiconductor layer 12 has a layer thickness of about 10 μm, and the n-type semiconductor layer 14 has a layer thickness of about 1 μm.

When light passes through the first transfer electrode 17, the second transfer electrode 18, etc. and enters the n-type semiconductor layer 14 during the opening period of the electronic shutter, which is an external mechanism (not shown), the p-type semiconductor layers 12 and n are exposed. In the depletion layer of the photosensitive pixel 32 of the pn junction photodiode formed by the semiconductor layer 14 and its vicinity, the heat parallel state is broken by the energy of light to generate electron-hole pairs, and the first transfer electrode 17 and the second transfer electrode 17 are formed. Electric charges are accumulated in the potential well below the transfer electrode 18. By applying the clock pulse voltage for one cycle to the first control electrode 19 and the second control electrode 20 during the closing period of the electronic shutter (not shown), the signal charges for one row of each vertical shift register 31 are transferred to the horizontal shift register 41. The line shift is performed in parallel.

Similarly, when a clock pulse voltage is applied to the horizontal shift register 41 to change the potential well, one row of the vertical shift register 31 is output from the output terminal 44 via the charge-voltage conversion amplifier 43. Signal charges of are output in series. Hereinafter, by repeating the line shift operation and the output by the horizontal shift register 41, the signal charges in all the rows of the vertical shift register 31 are output.

Further, by setting the thickness of the p-type semiconductor layer 12 on the p ^{+ -type} semiconductor substrate 11 to be thin, excess electrons generated in the neutral region of the p-type semiconductor layer 12 are diffused to the adjacent photosensitive pixels 32. Is suppressed. Furthermore, by reducing the thickness of the p ⁺ -type semiconductor substrate 11, the diffusion of the signal charge based on the electron-hole pairs that did not disappear recombined in the p ⁺ -type semiconductor substrate 11 is suppressed, the image quality It is possible to prevent smear that causes deterioration.

Further, the p ^{+ type} semiconductor substrate 11 is formed into a concave shape by chemical etching so that the layer thickness of the outer edge portion is thick and the layer thickness inside the n type semiconductor layer 12 receiving light is thin. As a result, p ^{+ type} semiconductor substrate 1
Corresponding to the layer thickness inside 1, it is possible to cut the sensitivity on the predetermined long wavelength side with respect to the light incident from the photoelectric conversion section 30 side. As a prior art document of this type, there is Japanese Patent Publication No. 4-44469.

[0013]

By the way, in order to increase the number of photosensitive pixels in order to improve the resolution in the above-mentioned conventional solid-state image pickup device, an electrode for transferring the signal charge accumulated in each photosensitive pixel is provided. Need to increase. However, since these electrodes have a specific resistance value, the power consumption increases due to the increase in the number of electrodes, and the amount of Joule heat generated increases. Therefore, in a device formed of a semiconductor substrate having a thin layer thickness, there are problems that thermal noise is generated in an output signal and the device is thermally destroyed.

Further, the conventional solid-state image pickup device is cooled by CC.
When used as D, a vacuum is drawn during cooling in order to prevent dew condensation on the surface of this CCD. However,
Since the layer thickness of the semiconductor substrate is thin, there is a problem that mechanical breakdown occurs due to lack of mechanical strength.

Furthermore, when a semiconductor substrate in the above-mentioned conventional solid-state image pickup device is formed into a concave shape by chemical etching as in the conventional case, since a chemical reaction by a chemical is used, fluctuations in liquid temperature in the etching liquid, generation of bubbles, and It is necessary to pay attention to changes in liquid composition. However, for example, it takes 1 to 2 days to etch the layer thickness of about 400 μm, and an error of about ± 3 μm occurs.
Therefore, the conventional solid-state imaging device such as CCD has an analog L
Since it is SI, the non-uniformity of the layer thickness due to such an error causes the generation of fixed pattern noise.
There is a problem that the image quality is significantly deteriorated in the infrared region of 0 nm or more.

Therefore, the present invention has been made in view of the above problems, and has a solid-state image pickup device capable of reproducing an image with a high image quality, in which the thermal resistance is lowered and the mechanical strength is further improved as compared with the prior art. The purpose is to provide.

[0017]

In the present invention, in order to achieve the above object, a photoelectric conversion means and a charge transfer means are provided on the upper surface side of a semiconductor substrate, and light incident on the semiconductor substrate from the upper surface side is detected. In the solid-state imaging device, the semiconductor substrate is thinned from the lower surface side so as to have a predetermined layer thickness in the range of 5 to 80 μm, and a reinforcing substrate made of a conductor is attached to the lower surface of the semiconductor substrate. It is characterized by being

In the present invention, in order to achieve the above object, a solid-state image pickup device having a photoelectric conversion means and a charge transfer means on the upper surface side of a semiconductor substrate and detecting light incident on the semiconductor substrate from the upper surface side. In, the semiconductor substrate is
A reinforcing substrate made of an insulator having a relatively high thermal conductivity is attached to the lower surface of the semiconductor substrate, which is thinned from the lower surface side so as to have a predetermined layer thickness in the range of 5 to 80 μm. It is characterized by

[0019]

According to the present invention, since the reinforcing substrate made of a conductor or an insulator having a relatively high thermal conductivity is attached to the lower surface of the semiconductor substrate, the Joule heat generated in the electrodes of the photoelectric conversion means is prevented. Because heat is dissipated to the reinforcing substrate side,
It is possible to prevent generation of thermal noise and thermal deterioration of the device.

Further, since the reinforcing substrate is attached to the lower surface of the semiconductor substrate having a thin layer thickness, the mechanical strength of the device is improved, so that mechanical breakage or the like can be prevented.

Further, by forming the layer thickness of the semiconductor substrate to be substantially smooth by a predetermined value in the range of 5 to 80 μm by mechanical etching, the occurrence of fixed pattern noise and the like is reduced, so that the quality of the reproduced image is improved. You can

[0022]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3 of the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is an FF according to an embodiment of the present invention.
It is a perspective view showing the structure in the solid-state imaging device of T type CCD. First, the solid-state imaging device of the first embodiment is higher as the p ⁺ -type semiconductor substrate 11 made of p ⁺ -type Si impurity density semiconductor layer formed on the p ⁺ -type semiconductor substrate 11 24
An electrode layer 25 formed on the semiconductor layer 24, p
^On the lower surface of the ^{+ type} semiconductor substrate 11, a reinforcing substrate 10 made of a conductive Al is provided.

The semiconductor layer 24 and the electrode layer 25 in this embodiment are basically the same as the structure shown in FIG. Therefore, this FFT CCD has a photoelectric conversion unit 30 having a function of converting an optical signal into a charge signal, as in the conventional example described above.
The output unit 40 has a function of sequentially outputting the signal charges.

FIG. 2A is a sectional view taken along the line AA in the case where the plan view shown in FIG. 3 is taken as the embodiment shown in FIG. 1, and FIG. 2B is the same BB. It is sectional drawing along a line. The semiconductor layer 24 includes the p-type semiconductor layer 12 and the p-type semiconductor layer 12.
Ap ^{+ type} semiconductor layer 13 formed around the upper region of the p type semiconductor layer 12, an n type semiconductor layer 14 formed inside the p ^{+ type} semiconductor layer 13 in the upper region of the p type semiconductor layer 12, and The n ⁻ -type semiconductor layer 15 is formed in the upper region of the n-type semiconductor layer 14.

The electrode layer 25 is an insulating layer 1 made of SiO _2.
6, a transparent first transfer electrode 17 and a second transfer electrode 18 made of polycrystalline Si formed in the insulating layer 16,
A first control electrode 19 made of Al in contact with the first transfer electrode 17, and a second control electrode 19 made of Al in contact with the second transfer electrode 18.
The control electrode 20 and PSG (Ph formed on the insulating layer 16
insulating layer 21 made of ospho-Silicate Glass) and an insulating layer 22 made of SiO ₂ formed on the insulating layer 21.
And a light shielding layer 23 made of Al formed on the insulating layer 22.

The layer thickness of the p ^{+ type} semiconductor substrate 11 is in the range of 5 to 8
The predetermined value is 0 μm, and the entire surface is almost smooth. The layer thickness of the reinforcing substrate 10 is 300 to 1000 μm.
The p-type semiconductor layer 12 has a layer thickness of about 10 μm, and the n-type semiconductor layer 14 has a layer thickness of about 1 μm.

According to the above construction, the operating principle of this embodiment is almost the same as that of the conventional example. However, since the reinforcing substrate 10 is formed of a conductor, it has a high thermal conductivity. Therefore, most of the Joule heat generated in the first transfer electrode 17, the second transfer electrode 18, etc. is transferred to the reinforcing substrate 10 and radiated to the outside. Therefore, even when this embodiment is used as a cooling CCD, the cooling effect is greater than in the conventional case. At this time, vacuuming is performed so that dew condensation does not occur on the surface of the element, but mechanical breakdown does not occur due to the increase in mechanical strength of the reinforcing substrate, and the operation of the device is not hindered.

Further, the p ⁺ type semiconductor substrate 11 is manufactured by being installed in a revolving type jig and mechanically etched. Therefore, a substantially smooth p ^{+ type} semiconductor substrate 11 having a layer thickness nonuniformity of about ± 1 μm can be obtained in a short time, and the cause of fixed pattern noise can be eliminated.

Next, the solid-state image pickup device of the second embodiment is provided with the reinforcing substrate 10 made of alumina, which is an insulator having a relatively high thermal conductivity, and the other parts are the same as those of the first embodiment. Is. Since the operation principle is almost the same as that of the first embodiment, most of the Joule heat is radiated to the outside through the reinforcing substrate 10, and the mechanical strength of the device is improved. Further, since the p ^{+ type} semiconductor substrate 11 is manufactured by mechanical etching, the generation of fixed pattern noise is reduced.

The present invention is not limited to the above embodiment, but various modifications can be made.

For example, in the first embodiment, the conductor Al has been described as the reinforcing substrate, but any conductor having a high thermal conductivity may be used.

In the second embodiment described above, alumina which is an insulator has been described as the reinforcing substrate, but any insulator having a relatively high thermal conductivity may be used.

As the semiconductor substrate of the above embodiment, Si is used.
However, the semiconductor may be made of another semiconductor.

As the semiconductor layer of the above embodiment, p ^{+ type} is n ^{+ type} , p type is n type, n type is p type, and n ^{− type} is p type.
^- same effect as the above embodiment be substituted respectively can be expected to form.

Further, SiO _{2 is used} as the insulating layer in the above embodiment.
However, other insulators may be used.

Further, in the above embodiment, the FFT type CCD
However, when applied to an FT-type CCD or the like, the same operational effects as those of the above embodiment can be expected.

[0038]

As described above, according to the present invention, since a reinforcing substrate made of a conductor or an insulator having a relatively high thermal conductivity is attached to the lower surface of a thin semiconductor substrate, photoelectric conversion is achieved. Joule heat generated in the electrodes of the means is radiated to the reinforcing substrate side, and the mechanical strength of the device is improved. Therefore, generation of thermal noise, thermal deterioration of the device, mechanical destruction, etc. can be prevented, so that there is a remarkable effect that the quality reliability and thermal characteristics can be improved more than ever before.

Further, by forming the layer thickness of the semiconductor substrate to be substantially smooth by a predetermined value in the range of 5 to 80 μm by mechanical etching, the occurrence of fixed pattern noise etc. is reduced.
Therefore, there is a remarkable effect that an image can be reproduced with better image quality than ever before.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of an FFT CCD solid-state imaging device according to an embodiment of the present invention.

2A is a sectional view taken along line AA in the case where the plan view shown in FIG. 3 is used as the embodiment shown in FIG.
(B) is a sectional view taken along the similar line BB.

FIG. 3 is a plan view showing a configuration of an FFT CCD solid-state imaging device.

4A is a sectional view taken along line AA in the case where the plan view shown in FIG. 3 is taken as a conventional example, and FIG. 4B is a similar sectional view taken along line BB. Is.

[Explanation of symbols]

10 ... Reinforcing substrate, 11 ... P ^{+ type} semiconductor substrate, 12 ... P type semiconductor layer, 13 ... P ^{+ type} semiconductor layer, 14 ... N type semiconductor layer, 15 ... N ^{− type} semiconductor layer, 16 ... Insulating layer, 17 ... First
Transfer electrode, 18 ... second transfer electrode, 19 ... first control electrode,
20 ... 2nd control electrode, 21 ... Insulating layer, 22 ... Insulating layer, 2
3 ... Light shielding layer, 24 ... Semiconductor layer, 25 ... Electrode layer, 30 ...
Photoelectric conversion unit, 31 ... Vertical shift register, 32 ... Photosensitive pixel, 40 ... Output unit, 41 ... Horizontal shift register, 43 ...
Charge-voltage conversion amplifier, 44 ... Output terminal.

Claims (2)

[Claims] 1. A solid-state imaging device, comprising photoelectric conversion means and charge transfer means on an upper surface side of a semiconductor substrate, and detecting light incident on the semiconductor substrate from the upper surface side, wherein the semiconductor substrate has a range of 5 to 80 μm. 2. A solid-state imaging device characterized in that a thin plate is formed from the lower surface side so as to have a predetermined thickness, and a reinforcing substrate made of a conductor is attached to the lower surface of the semiconductor substrate. 2. A solid-state imaging device, comprising photoelectric conversion means and charge transfer means on the upper surface side of a semiconductor substrate and detecting light incident on the semiconductor substrate from the upper surface side, wherein the semiconductor substrate has a range of 5 to 80 μm. And a reinforcing substrate made of an insulator having a relatively high thermal conductivity is attached to the lower surface of the semiconductor substrate. Solid-state imaging device.