JPS631058A - Photosensor - Google Patents

Abstract

PURPOSE:To obtain a large-sized image sensor having high preformance by forming a photodetection element and a signal processing circuit to a polycrystalline semiconductor layer. CONSTITUTION:Polycrystalline semiconductor layers 12, 15 are shaped onto an insulator substrate 11, and a photodetection element 23 and a signal processing circuit 27 are formed to each semiconductor layer 12, 15. Accordingly, electrical characteristics such as the speed of response are improved, and monolithic integration is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical sensor having a photodetecting element and a signal processing circuit for processing a signal output from the photodetecting element.

[Summary of the invention]

The present invention provides a high-performance and large-sized optical sensor by forming a polycrystalline semiconductor layer on an insulating substrate, and forming a photodetecting element and a signal processing circuit on this polycrystalline semiconductor layer. This image sensor can be provided at low cost.

[Conventional technology]

2. Description of the Related Art In recent years, large-sized image sensors have been required in various optical devices such as facsimiles and copying machines in order to simplify optical systems for condensing light, etc., and thereby reduce the size and cost of the optical devices.

However, since it is not easy to manufacture large-diameter semiconductor wafers, it is not easy to create a large-sized image sensor within a semiconductor substrate.

For this reason, attempts have been made to form a thin film semiconductor on an insulating substrate whose diameter can be easily increased, and to create a large image sensor using this thin film semiconductor. Examples of such thin film semiconductors include a-3i: tl and Cd.

A chalcogen semiconductor such as Se is used.

[Problem that the invention seeks to solve]

However, when any of the above thin film semiconductors is used, the response speed of the photodetecting element is slow, making it difficult to obtain desired performance.

Furthermore, if a signal processing circuit for processing the signal output from the photodetecting element is also formed on the thin film semiconductor and monolithically integrated, the processing speed of this signal processing circuit is still slow. For this reason, it is necessary to incorporate separate components for the signal processing circuit into an insulating substrate for hybrid integration, but in this case the implementation cost is high.

[Means for solving problems]

In the optical sensor according to the present invention, a polycrystalline semiconductor layer 12.15 is formed on an insulating substrate 11, and a photodetection element 23 and a signal processing circuit 27 are formed on this polycrystalline semiconductor layer 12.15. .

[Effect]

In the optical sensor according to the present invention, since both the photodetecting element 23 and the signal processing circuit 27 are formed in the polycrystalline semiconductor layer 12.15, electrical characteristics such as response speed are good (and monolithic integration is possible). It is possible.

Further, since the polycrystalline semiconductor layer 12.15 on which the photodetector element 23 and the signal processing circuit 27 are formed is formed on the insulator substrate 11, it is easy to increase the size.

〔Example〕

Hereinafter, an embodiment of the present invention applied to a thin film image sensor using a PIN-PD as a photodetecting element will be described with reference to FIGS. 1 and 2.

Although FIG. 1 shows this embodiment, its manufacturing process will first be explained based on FIG. 2. In order to manufacture this example, first, SiO
A polycrystalline Si layer 12 with a thickness of about 800 layers is grown on □iO□1.

Then, by implanting Si'° ions into the polycrystalline St layer 12, the polycrystalline Si layer 12 is once made amorphous.
Thereafter, heat treatment is performed at a temperature of about 600°C. Then, due to this heat treatment, the polycrystalline 5iJli, which had become amorphous,
12 becomes polycrystalline again, but the polycrystalline Si layer 1 at this point
No. 2 has good crystallinity and therefore good electrical characteristics.

Next, as shown in FIG. 2B, polycrystalline Si is formed by CVD.
A 5i02 layer 13 is grown on the layer 12, and this SiO2 layer 13 is grown on the layer 12.
□An opening 14 is formed in a region of the layered work 3 where a PIN-PD is to be formed.

Next, a polycrystalline St layer 15 is epitaxially grown selectively only in the opening 14 as shown in FIG. 2C at a high temperature using a mixed gas of SiH4 or 5illzC1z and IIcI.

Since the polycrystalline Si layer 15 is formed by epitaxial growth, there is no interface between the polycrystalline 5tJli 515 and the polycrystalline Si layer 12. The total thickness of the polycrystalline Si layers 15 and 12 is selected based on the wavelength of the light to be detected, but approximately 2.0 μm is required.

Next, as shown in FIG. 2D, the entire SiO□ layer 13 is formed,
Furthermore, by selectively etching the polycrystalline Si layer 12, element isolation regions 16 are formed in regions other than the region where the PIN-PD is to be formed and the region where the CMO 5 for signal processing is to be formed. Note that this elemental portion 11iI region 16 may be formed in the step of forming the polycrystalline Si layer 12 shown in FIG. 2A.

Next, as shown in FIG. 2E, a gate electrode 1 made of the above CMO3 gate insulating films 17a and 17b and polycrystalline Si is formed.
8a and 18b are formed.

Next, as shown in FIG. 2F, regions other than the region between the polycrystalline Si layer 15 and the gate electrode 118b are covered with a mask 21. Then, as shown in FIG. In this state, ions of a pentavalent element are implanted.

Next, after removing the mask 21, as shown in FIG. 2G, the region where ions were implanted in the step of FIG. 2F and the polycrystalline S
The vicinity of the i-layer 15 is covered with a mask 22. In this state, ions of a trivalent element are implanted. Note that either the process in FIG. 2F or the process in 20UA may occur first.

In this way, as shown in Figure 2H, Pl! 1-PD2
3 P shadow area 24, I shadow area 25, N shadow area 26 and C
Source/drain regions 28a, 28b and channel regions 29a, 29b of MO 327 are formed.

Furthermore, as is clear from this Fig. 2H, PIN-PD2
Both the boundary surface 23a between the P shadow region 24 and the I shadow region 25 and the boundary surface 23b between the N shadow region 26 and the I shadow region 25 in No. 3 are formed in the polycrystalline Si layer 12. The areas of the boundary surfaces 23a and 23b are very small.

Next, as shown in FIG. 2H, the mask 22 is removed,
As shown in Figure 1, it is made of 5in2, PSG, etc. and has a thickness of 5.
The thickness of the interlayer insulating film 31 is about 50,000.
By forming approximately 00 A1 electrodes 32, the thin film image sensor of this embodiment is formed.

In PIN-PD23 in this thin film image sensor, I
In the shadow region 25, the polycrystalline Si layer 15 and this polycrystalline Si
It consists of a polycrystalline Si layer 12 directly below the layer 15 and has a thickness of 2.0 μm.
The incident light is absorbed by the portion having a thickness of about 100 mL, and is made only of polycrystalline 5ilW12.

Incident light is not absorbed in a portion having a thickness of only about O.

〔Effect of the invention〕

The optical sensor according to the present invention has good electrical characteristics such as response speed, can be monolithically integrated, and can be easily enlarged. Therefore, it is possible to provide a high-performance, large-sized image sensor at low cost. Can be done.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention, and FIG. 2 is a side sectional view sequentially showing the manufacturing process of the embodiment. In addition, in the symbols used in the drawings, 11-...-----5402 substrate 12
, 15----- polycrystalline Si layer 23--
−・−−−−−−−−P I N -P D27・・
---m-・-・-----CM OS.

Claims (1)

[Claims] An optical sensor having a photodetecting element and a signal processing circuit for processing a signal output from the photodetecting element, comprising: a polycrystalline semiconductor layer formed on an insulating substrate; An optical sensor in which the photodetecting element and the signal processing circuit are formed in a polycrystalline semiconductor layer.