JPH0212954A - Semiconductor device - Google Patents

Abstract

PURPOSE:To maintain a semiconductor element at predetermined low temperature and to obtain a semiconductor device in which stable and satisfactory element characteristics are always obtained by providing a first semiconductor substrate having a silicon oxide film on its surface including the inner face of a groove and a second semiconductor substrate formed with the element, and feeding refrigerant in the groove. CONSTITUTION:A liquid circulating groove 2 communicating with an upper face is formed on a CCD type image sensor, a less dopant irregularity is formed, for example, by a MCZ method on a first Si substrate 1 formed with a thin silicon dioxide film 3 on its surface, a P-type second Si substrate 4 formed as thin as possible employs an Si substrate of a double structure thermally adhering with the film 3 as a medium, CFC-113 controlled, for example, at a constant temperature of 0 deg.C or lower is fed as a refrigerant into the groove 2 formed on the upper face of the first substrate 1 thereby to maintain the element temperature at constant temperature near 0 deg.C.

Description

[Detailed Description of the Invention] [Summary] Regarding semiconductor devices, especially semiconductor devices equipped with a cooling means in the substrate, the device temperature is maintained at a constant low temperature and is always stable and unaffected by changes in environmental temperature. A first semiconductor substrate having a groove on its upper surface and a silicon oxide film on its surface including the inner surface of the groove; The second semiconductor substrate is bonded to a surface having a groove via the silicon oxide film and has a semiconductor element formed thereon, and has a structure in which a coolant is allowed to flow within the groove.

[Industrial application field]

The present invention relates to a semiconductor device, and more particularly to a semiconductor device including a cooling means within a substrate.

In the era of VLSI, single crystal silicon manufactured by the pulling method is still used as a material for semiconductor devices such as DRAMs and image sensors.

On the other hand, G-R (generation-recomb
inati.

n) Lifetime of minority carriers generated from the center,
One example is the diffusion current generated from the bulk.

This current generated from the G-R center and the diffusion current are
This causes deterioration of device characteristics, such as a reduction in the refresh time in the image sensor and a decrease in the S/N ratio in the image sensor.

Therefore, a means for reducing the current generated from the center of the G-R and the current diffused from the substrate is desired.

[Conventional technology]

FIG. 5 is a diagram schematically showing a cross section of the light receiving part of a conventional image sensor. As shown in this figure, in the conventional image sensor, 200 to 30
For example, a p-type silicon (Si) substrate 5 with a thickness of about 0 μm.
A plurality of n-type diffusion regions 54 defined and separated by a field oxide film 52 and a p-type channel stopper 53 are formed directly on the layer 1, and the n-type diffusion regions 54 and the p-type Si
A photodiode (P,
D) was used as a pixel.

[Problem to be solved by the invention]

In such an image sensor, a G-R layer is formed in a depletion layer 55 formed at the junction of photodiodes (P, D) that are pixels.
If the center 56 exists, the G-1? The carriers generated at the center 56 do not disappear due to recombination, but instead pass through the junction and move within the depletion layer, resulting in a junction leakage current. In addition, in the low-concentration substrate used for the image sensor, some of the diffusion current caused by carriers formed by generation centers caused by various defects in the bulk passes through the junction without being annihilated by recombination. These junction leak currents become the dark signal (dark output signal) of the photodiode, and the ratio of the output signal voltage during light reception and the output signal voltage during dark, which corresponds to the devil of the photodiode, is S. /N ratio is reduced.

As mentioned above, the current generated from the center of the G-R and the diffusion current are detected as junction leakage current, and it has been confirmed that the junction current can be reduced by heat-treating the Si substrate in advance. However, the effect is reduced to about 1/2 at most.

On the other hand, since the junction leakage current has a property of increasing exponentially as the temperature rises, suppressing the rise in element temperature has a particularly large effect in preventing deterioration of element characteristics.

Therefore, the present invention maintains the element temperature at a constant low temperature,
It is an object of the present invention to provide a structure of a semiconductor device that can always provide stable and good device characteristics without being affected by changes in environmental temperature.

[Means to solve the problem]

The above problem is to provide a first semiconductor substrate having a groove on its upper surface and a silicon oxide film on the surface including the inner surface of the groove, and a silicon oxide film on the surface of the first semiconductor substrate having the groove. The problem is solved by a semiconductor device according to the present invention, which has a second semiconductor substrate bonded via a semiconductor substrate and on which a semiconductor element is formed, and in which a coolant is allowed to flow.

[For production]

That is, in the semiconductor device of the present invention, the Si substrate is placed on a first St substrate having a liquid circulation groove on the upper surface, with a Si oxide film interposed therebetween, and a high quality element is formed as thin as possible. It has a double structure in which two Si substrates are bonded together.

In the present invention, the second Si substrate on which the element is formed is formed as thin as possible to reduce the diffusion current generated in the second Si substrate, and the second Si substrate is made of an oxidized Si film. The first thick Si substrate is insulated from the lower thick first Si substrate, and the diffusion current generated in the first thick Si substrate does not flow into the element region.

In addition, the second Si substrate on which the element is formed is maintained at a constant low temperature by circulating a coolant having a constant low temperature in the liquid circulation groove, so that the current generated at the center of G-R and the diffusion The current decreases and remains stable.

As a result, a semiconductor device is provided in which the junction leakage current of the element is always kept at a small value without being affected by changes in environmental temperature, and has stable and good element characteristics.

〔Example〕 The present invention will be specifically explained below with reference to illustrated embodiments.

FIG. 1 is a plan view (a) of an embodiment of the present invention and a sectional view taken along the line A-A), FIGS. 2 (a) to (el are plan views of the manufacturing process according to the present invention), (a) to (e) are A- in Figure 2.
FIG. 4, which is a cross-sectional view of the manufacturing process taken in the direction of arrow A, is a diagram showing the effects of the present invention.

Identical objects are indicated by the same reference numerals throughout the figures.

For example, as shown in FIG. 1, the CCD type imaging device according to the present invention uses the pulling method, that is, the CZ method, in which a communicating liquid circulation groove 2 is formed on the upper surface and a thin silicon dioxide (SiOz) film 3 is formed on the surface. MC is pulled onto the first Si substrate (regardless of conductivity type) by applying a parallel magnetic field, for example.
A p-type second Si substrate 4, formed by the Z method with little dopant unevenness and as thin as possible without affecting device characteristics, is heat-bonded using the SiO□ film 3 as a medium. Using a double structure Si substrate,
A field oxide film 5 is formed on the surface of the second Si substrate 4 to separate the photodiode and CCD regions which are normally aligned, and a p-type channel stopper 6 is formed below the field oxide film 5. A photodiode PD, , PD consisting of an n-type diffusion region 7 and a p-type Si substrate 4 is located in a region defined by 5.

, PD are formed, and n-type diffusion regions 8A, 8B, etc., and first layer transfer electrodes G0, Gl! , G13. Vertical charge-coupled device V consisting of six 2Nth transfer electrodes 1, Go, hs, etc.
A liquid circulation groove 2 is formed on the upper surface of the first Si substrate 1 and has a structure in which CCD+, VCCDz, etc. are formed.
For example, Freon 113 (CCLzFCCtF,) whose temperature is controlled at a constant temperature of 0° C. or lower flows as a refrigerant within the device, so that the element temperature is maintained at a constant temperature near 0° C.

Note that TG2 and TG are transfer gates, and a p-type diffusion region having a higher concentration than that of the substrate 4 is formed on the substrate surface of this portion.

The present invention is characterized by having a substrate structure as shown in the above embodiments. Therefore, the substrate structure according to the present invention will be explained in more detail below by the manufacturing method with reference to the drawings.

In order to form the double-structured Si substrate used in the imaging device of the above embodiment, it is formed by, for example, the usual CZ method, and the entire warpage is 25 μm or less. Warp in mouthfeel is 6
A resist H9 with a thickness of about 0.5 to 1 μm is coated on a first Si substrate 1 with a diameter of 4 inches and a thickness of about 500 μm, which has an arbitrary plane orientation and dopant, and a resist H9 with a thickness of about 0.5 to 1 μm is applied to the substrate 1 by a normal photo process. A meandering open pattern 10 is formed on the photoresist layer 9 as shown in the figure, and then, using the resist layer 9 as a mask, a mixed solution of fluoronitric acid (IF: HNO
+=1:2) for about 100 degrees and wet etching is applied to one surface of the first substrate, for example, for liquid circulation in a meandering pattern? 112
form.

this? R2 is formed to have a depth (D) of about 100 pm and a width (w) of about 500 pm, for example.

Although the groove 2 may be formed by active ion etching, there are disadvantages in that the resist mask becomes significantly thicker and it takes a longer time.

Refer to FIGS. 2(b) and 3(b). Next, the resist layer 9 is removed, and the substrate 1 is cleaned with a mixture of aqueous ammonia (NH4011) and hydrogen peroxide (HiOz). Thermal oxidation is performed at 900° C. for about 30 minutes in dry oxygen to form a thin SiOg film 3 with a thickness of about 200 mm on the surface of the substrate 1.

Refer to FIGS. 2(0) and 3(C) Next, on the Si substrate 1 on which the Si0g film 3 was formed,
For example, a second layer having a p-type with a thickness of about 500 pm is formed on a clean surface manufactured by the MCZ method, polished on both sides, and washed with a mixed solution of, for example, sulfuric acid (HgSO4) and H,0□.
A Si substrate 4 of 1 is placed thereon and heat treated in nitrogen at 1100° C. for about 30 minutes. Through this heat treatment, the first and second Si substrates 1
and 4 are hermetically joined via the SiO2 film 3.

Refer to FIG. 2(d) and FIG. 3(d) Next, the second Si substrate 4 side is single-sided polished to the thinnest possible thickness (1), for example, 50 μm, without adversely affecting the characteristics of the device formed on the substrate. Grind until it reaches the desired level. The polishing method is, for example, a mechanochemical polishing method.
Colloidal silica is used as the abrasive, and the pressure during polishing is 2
50Kg/cm".

Refer to FIG. 2(0) and FIG. 3(i). Next, the first Si is etched from the back side by wet etching using a resist as a mask or by ion milling.
Liquid circulation holes 1 reaching both ends of the liquid circulation groove 2 in the substrate 1
1 and 12, thereby forming 2 used in the present invention.
A Si substrate having a layered structure and equipped with a coolant circulation means is completed.

Thereafter, a semiconductor element such as a CCD type image pickup element as shown in FIG. 1 is formed on the second Si substrate 4 according to a normal semiconductor element forming method, thereby completing a semiconductor device according to the present invention.

FIG. 4 is a diagram illustrating the effect of the present invention, in which the dark output voltage of the CCD type image pickup device according to the example was measured while changing the substrate temperature by circulating a coolant.

As shown in this figure, Freon-113 (
If a refrigerant such as CCI□FCCIF, ) is allowed to flow through the liquid circulation groove 2 and the substrate temperature is cooled to, for example, 0°C, the implied output voltage will be reduced to about 174 compared to the normal usage condition when the substrate temperature is 30°C. The SN ratio of the image sensor can be greatly improved.

Furthermore, in the present invention, since the substrate on which the device is formed, that is, the device active region, is formed very thinly by polishing, the diffusion current generated in the active region is significantly reduced, and in this respect, junction leakage is also reduced and the device The signal-to-noise ratio is improved.

Furthermore, since the residual strain in the area where the substrate is attached has an impurity gettering effect, it is also effective in improving device characteristics.

Note that the present invention is applicable not only to the imaging device shown in the above embodiments but also to various semiconductor ICs such as semiconductor memory devices.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to significantly reduce junction leakage of semiconductor elements, thereby improving the performance of semiconductor devices, such as improving the S/N ratio of solid-state imaging devices and extending the memory retention time of semiconductor memory devices. and is effective in improving reliability.

[Brief explanation of the drawing]

FIG. 1 is a plan view (a) and a sectional view taken along the line A-A (b) of an embodiment of the present invention, and FIGS. 2 (a) to (e) are plan views of the manufacturing process according to the present invention.
3(a) to (8) are sectional views of the manufacturing process according to the present invention,
FIG. 4 is a diagram showing the effects of the present invention, and FIG. 5 is a schematic side sectional view of the conventional structure. In the figure, 1 is a first Si substrate, 2 is a liquid circulation groove, 3 is an SiO2 film, 4 is a second (p-type) Si substrate, 5 is a field oxide film, 6 is a p1 type channel stopper, and 7 is a p1 type channel stopper. n-type diffusion region, 8A, 8B are n-type diffusion regions, 9 is a resist layer, 1O is an opening pattern, 11.12 is a liquid flow hole, PD+, PD2, PD are photodiodes, 'II
, Gl□, G13 are the first layer transfer electrodes, Gz+ s
Gtz, Gz3 are second layer transfer electrodes, VCCD+,
VCCDg indicates a vertical charge coupled device. (d) Plan view (b A-A arrow tread mouth Invention related to the invention, 1. Floor plan activation (-+/) 2) Meme

Claims (1)

[Claims] a first semiconductor substrate having a groove on the upper surface and a silicon oxide film on the surface including the inner surface of the groove; and bonding onto the surface of the first semiconductor substrate having the groove via the silicon oxide film. and a second semiconductor substrate on which a semiconductor element is formed, and a refrigerant is allowed to flow in the groove.