JPH04218963A - Optical detector - Google Patents

Abstract

PURPOSE:To ensure a higher S/N ratio and achieve high integration by reducing a crosstalk signal in the title optical detector. CONSTITUTION:Phototransistors 301, 302 are formed on a semiconductor circuit board 32, physically isolated on the same board. Emitters 331, 332, and 34 are formed in grooves 35 serving to physically isolate the phototransistors 301, 302.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to photodetectors. Specifically, the present invention relates to a hybrid photodetector (image sensor) consisting of a phototransistor array and a signal processing substrate formed on different semiconductor substrates.

0002

2. Description of the Related Art In recent years, as photodetectors have been required to have higher image quality and a larger number of pixels, there has been a demand for higher integration, improved signal-to-noise ratio, reduced inter-pixel crosstalk, and prevention of blooming. To meet these demands, photodetectors using phototransistor arrays that can amplify optical signals have been provided.
In this, a phototransistor and a signal processing section are formed on the same substrate.

FIG. 6 shows a configuration diagram of an example of a conventional photodetector in which a phototransistor and a signal processing section are formed on the same substrate. In the figure, phototransistors 21 and 22 are formed on an n-Si substrate 1, and a signal processing section (not shown) for transferring signal charges generated by the phototransistors is also formed. As is well known in the art, when light is irradiated onto the pn junction collector/base region, carriers are generated and current flows between the collector and emitter, thereby operating as a photo-electrical signal conversion element.

0004

[Problems to be Solved by the Invention] In conventional photodetectors, the phototransistor and the signal processing section are formed on the same substrate. The proportion occupied in the chip decreases, making it difficult to achieve high integration and increase the number of pixels.
As shown in FIG. 2, since the area of the collector region cannot be made very large, there is a problem that the efficiency of using the optical signal decreases and the S/N ratio deteriorates.

Furthermore, as shown in FIG. 6, in the conventional example, a pn junction in the n-Si substrate 1 is used to separate the phototransistors 21 and 22. The long wavelength portion of the photosensitive wavelength range is absorbed in the deep part of the base region of the substrate 1, and carriers are generated, which are transferred to the phototransistor 21 of the substrate 1.
, 22 and enters the adjacent phototransistor 22 as a crosstalk signal, resulting in so-called blurring. Similarly, when there is a large amount of light, crosstalk signals enter not only adjacent phototransistors but also many transistors, resulting in so-called blooming.

As described above, the conventional method that uses a pn junction in an n-Si substrate to separate phototransistors has the problem of deterioration of image quality due to blurring and blooming. This problem also occurred in devices in which the signal processing section and the signal processing section were formed on different types of substrates.

The present invention can reduce crosstalk signals,
Moreover, it is an object of the present invention to provide a photodetector that can obtain a high signal-to-noise ratio and achieve high integration.

[0008]

[Means for Solving the Problems] FIG. 1 shows a diagram illustrating the principle of the present invention. In the figure, 301, 302 are phototransistors, collectors 311, 312 are connected to the semiconductor circuit board 32, and emitters 331, 332,
34 are connected in common. In a photodetector having such a configuration, the present invention provides that each phototransistor 301
, 302 are physically separated structures on the semiconductor circuit board 32.

Furthermore, the emitters 331, 332, and 34 are formed in grooves 35 that physically separate the phototransistors 301, 302.

0010

[Operation] In the present invention, the phototransistors 301, 3
02 is provided in a separate part from the semiconductor circuit board 32 on which the signal processing section is formed, so if the board area is the same as the conventional example, the proportion occupied by the phototransistor part within the chip can be increased, resulting in high integration and a large number of pixels. can. Furthermore, emitters 331 and 332 are formed in the adjacent phototransistor isolation trench 35.
, 34, when viewed from the perspective of one phototransistor, the emitter can be formed around the entire area of the phototransistor, and the collectors 311, 312
Since the collector region can be provided on the back side, the area of the collector region can be made sufficiently larger than in the conventional example, and the efficiency of using optical signals can be increased, and the S/N ratio can be improved. Furthermore, since the phototransistors 301 and 302 are physically separated by the common emitter 34, the optical signal generated in each phototransistor does not flow into the adjacent phototransistor as crosstalk, which prevents blurring and blooming as in the conventional example. This does not occur and the image quality can be improved.

[0011]

Embodiment FIG. 2 shows a block diagram of a first embodiment of the present invention. In the figure, a CdTe substrate 5 is used as an epitaxial substrate, and phototransistors 61 and 62 are formed by epitaxial growth, ion implantation, or the like. The phototransistors 61 and 62 have p-HgCdTe base regions 71 and 72 formed by epitaxial growth, collector regions 81 and 82 and emitter regions 91 and 92 formed by ion implantation.
, ZnS regions 101 and 102. In this case, the phototransistors 61 and 62 are separated by plasma anisotropic etching using CF4 gas as a main component on the p-HgCdTe epitaxial crystal.
When forming the separation groove 11 reaching the Te substrate 5, HgCd
Since the damage caused to the Te epitaxial crystal becomes n+ type (emitter regions 91, 92), this is used as an isolation region.

Reference numeral 12 denotes a p-Si signal processing substrate, on which n+ regions 131, 132 and a SiO2 layer 14 are formed, and a signal processing section (not shown) is formed therein. 151
, 152 are metal bumps, each n+ region 131
and collector region 81 , and connects n+ region 132 and collector region 82 . Reference numeral 16 denotes a common emitter (metal electrode) that connects the emitter regions 91 , 92 of the separation groove 11 and a predetermined circuit portion (not shown) of the signal processing board 12 to physically separate the phototransistors 61 , 62 . There is.

As shown in FIG. 2, in the present invention, the phototransistors 61 and 62 and the signal processing section are disposed on different substrates (Cd
Since the phototransistor portion is formed on the Te substrate 5 and the signal processing substrate 12), if the phototransistor portion is to be highly integrated and have a large number of pixels, if the substrate area is the same as the conventional example, the proportion of the phototransistor portion within the chip will be reduced. Can be increased, highly integrated,
A large number of pixels can be achieved. Moreover, as shown in FIG. 3, the emitter region 91 (92) is connected to the phototransistor 61
(62) is formed around the entire region, and the collector electrodes (metal bumps 151, 152) are provided on the back side, so the area of the collector region 81 (82) is smaller than that of the conventional example shown in FIG. It can be made sufficiently large, thereby increasing the utilization efficiency of optical signals and improving the S/N ratio.

The present invention also provides a phototransistor 61
, 62 are physically separated by a common emitter (metal electrode) 16, so that the optical signal generated in each phototransistor does not flow into the adjacent phototransistor as crosstalk, and the conventional example shown in FIG. Image quality can be improved without causing blurring or blooming.

Furthermore, since the emitter regions 91 and 92 can be formed at the same time as the separation groove 11, the process can be simplified.

FIG. 4 shows a configuration diagram of a second embodiment of the present invention. In the figure, the same components as those in FIG. 2 are designated by the same numbers and their explanations will be omitted. This is C in the second embodiment.
The dTe substrate 5 (FIG. 2) is removed by polishing or chemical etching. As shown in FIG. 2, when there is a CdTe substrate 5 and a p-Si substrate 12, distortion occurs due to the difference in thermal expansion coefficient between the different types of substrates, and the metal bumps 151, 15
There is a risk that 2 may peel off, but if there is only one substrate as in the second embodiment, there is no such risk.

FIG. 5 shows a configuration diagram of a third embodiment of the present invention. In the figure, the same components as those in FIG. 2 are given the same numbers and their explanations will be omitted. In FIG. 5, 201 and 202 are phototransistors, and the base region 2 of p-HgCdTe is
11, 212, collector area 221, 221'
, 222 , 222 ′, emitter regions 231 , 23
2, ZnS regions 241 and 242. A common emitter (metal electrode) 25 physically separates the phototransistors 201 and 202. 26 is an adhesive part, which connects the phototransistors 201, 202 and p-
The Si substrate 12 is bonded.

When manufacturing the phototransistors 201 and 202, a CdTe substrate (epitaxial substrate) is used, and a p-HgCdTe base region is formed thereon by epitaxial growth, in substantially the same manner as in the first embodiment shown in FIG. Then, the CdTe substrate is removed and collector regions 221, 222 are formed by ion implantation, emitter regions 231, 232, and common emitter 2 are formed.
form 5. Thereafter, the phototransistors 201 and 202 and the p-Si substrate 12 are bonded together using an adhesive. Since the third embodiment is not provided with metal bumps, the height can be made lower than that of the first and second embodiments.

Note that the epitaxial crystal constituting the collector region is of the II-VI group (
HgCdTe), III-V group (GaAlAs,
GaAs) or IV-VI group (PbSnTe) may be used.

[0020]

[Effects of the Invention] According to the present invention, since the phototransistor is provided separately from the semiconductor circuit board, the phototransistor portion can be highly integrated and have a large number of pixels compared to the conventional example in which the phototransistor is provided on the same substrate. Since the emitter is formed in the groove for separating adjacent phototransistors, the emitter can be formed around the entire area of the phototransistor, and the area of the collector can be made sufficiently larger than in the conventional example. Since the signal usage efficiency can be increased, the S/N ratio can be improved. Furthermore, since the phototransistors are physically separated by a common emitter, the optical signals generated in each phototransistor will not flow into adjacent phototransistors as crosstalk, and blurring or blooming will not occur, improving image quality.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a configuration diagram of a first embodiment of the present invention.

FIG. 3 is a plan view of a phototransistor portion in the present invention.

FIG. 4 is a configuration diagram of a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional example.

FIG. 7 is a plan view of a phototransistor portion in a conventional example.

[Explanation of symbols]

5 CdTe substrate 61 , 62 , 201 , 202 , 301 , 30
2 Phototransistors 71 , 72 , 211 , 212 Base region 8
1 , 82 , 221 , 222 , 311 , 312
Collector areas 91 , 92 , 231 , 231 ′, 232 , 2
32', 331, 332 Emitters 11, 35 Separation groove 12 Signal processing board 151, 152, 361, 362 Metal bumps 16, 34 Common emitter 26 Adhesive part 32 Semiconductor circuit board

Claims (3)

[Claims] Claim 1: Using phototransistors (301, 302) as photodetecting elements, each photoresistor (3
01 , 302 ) collector ( 311 , 312 )
is connected to a semiconductor circuit board (32) provided with a signal processing section, and the emitters (331, 332, 34) of each phototransistor (301, 302) are commonly connected. The transistors (301, 302) are connected to the semiconductor circuit board (32).
) A photodetector characterized in that it has a physically separated configuration. Claim 2: The emitter (331, 332,
34) represents each of the phototransistors (301, 30
2) A photodetector according to claim 1, characterized in that the photodetector is formed in a groove (35) that physically separates the photodetector. 3. The phototransistor (301,
302) and the semiconductor circuit board (32) are connected to each other by metal bumps (361, 362) or adhesive.