JPH05175538A - Photosensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To get spectral sensitivity property over all wavelength band areas by providing it with SOI structure. CONSTITUTION:A single crystal of Si film 2, a single crystal of Si1-xGex film 3, and a single crystal of Si film 5 are stacked in this order on the surface of a substrate 1 consisting of a single crystal insulator such as sapphire, spinel, etc., and the surfaces and the side peripheries of the Si film 2, the Si1-xGex film 3, and the Si film 5 are covered with an SiO2 film 6, and impurities are implanted into the Si film 2, the Si1-xGex film 3, and the Si film 5 from the hole bored in the SiO2 film 6. And, a light semiconductor element 4 is constituted of the PIN junction being made up by disposing each region 4a, 4b, and 4c of p type, i type, and n type alternately, in the direction parallel with the surface of the substrate 1, within the Si film 2, the Si1-xGex film 3, and the Si film 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sensor having an SOI (Silicon On Insulator) structure in which a photo-sensing semiconductor element is formed in a single crystal semiconductor thin film deposited on an insulating substrate or an insulating film, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Insulator substrates such as sapphire and spinel,
Alternatively, a so-called SOI structure, in which a photo-sensing semiconductor element or the like is formed on the surface of a SiO ₂ film formed on a semiconductor substrate, has the advantages of easy element isolation, low parasitic capacitance, and easy high-speed operation. It is known as an effective means of eliminating device latch-up, and it can be used for CM
Various attempts have been made to realize an optical IC that is a combination of an OS device and an optical sensor device.

Conventionally, as an optical sensor having an SOI structure, SiO _{2 is used.}
For single crystal Si film grown by laser recrystallization method on the film
Technology for manufacturing PN diodes (Symposium on VLSI Techno
Digest 34-35 (1985)), or a technique for producing a photosensor in a Si film by using a Si / SiGe superlattice quantum well structure (IEEE IEDM90 637-1990). However, the former is not practical as a color sensor because the single crystal Si film has a large band gap and poor sensitivity to long-wavelength light. For example, a thin single crystal Si film having a thickness of about 7,000 Å is difficult to detect red light. The latter is intended for detection of light in the long wavelength band (infrared region), and is specifically as shown in FIG.

FIG. 1 is a cross-sectional structural view showing a conventional optical sensor, in which a Si film 2 is formed on the surface of a substrate 1 made of sapphire.
410 nm is deposited, and the SiO ₂ film 6 is deposited in such a manner as to cover the surface and the side peripheral surface of the Si film 2, and a region 4a having a P type conductivity type is formed in the Si film 2 through the holes formed in the SiO ₂ film 6. An impurity for forming and an impurity for forming the N-type region 4c are ion-implanted respectively to form a P-type region 4a, a Si film 2 and an original I-type region 4
b, N type regions 4c are alternately formed in a direction parallel to the surface of the substrate 1. As a result, the light-sensitive semiconductor element 4 is formed by the PIN junctions arranged in the direction parallel to the surface of the substrate 1.
Then, through the through hole formed in the SiO ₂ film 6, the P
An electrode 7 communicating with the mold region 4a and the N-type region 4c is formed.

[0005]

By the way, in a full-color sensor, it is usually premised that a predetermined spectral sensitivity characteristic is obtained in all wavelength bands, but in the conventional optical sensor as described above, the light-receiving sensitivity in a long wavelength band is obtained. The characteristics were insufficient. To improve the sensitivity, increase the thickness of the Si film 2,
In addition, it is effective to increase the Ge composition, but if the film thickness increases, the processing process for element isolation becomes difficult,
Further, when the Ge composition is increased, defects in the film are likely to occur due to the difference in the characteristics of Si and Ge, and there is another problem that the process conditions must be changed significantly. The present invention has been made in view of the above circumstances, and an object thereof is to have an SOI structure and high sensitivity in a long wavelength light region,
An optical sensor that can be manufactured by a simple process and a manufacturing method thereof.

[0006]

A photosensor according to the present invention is a photosensor in which a single crystal semiconductor film is provided on a surface of an insulator, and a photosensing semiconductor element is formed in the semiconductor film. and Si film on the surface of, Si _1-x Ge _x and film laminated, characterized in that the formation of the light sensitive semiconductor element to the Si _1-x Ge _x film. The method for producing an optical sensor according to the present invention is a method for producing an optical sensor comprising a single crystal semiconductor thin film having a photosensitive semiconductor element formed on the surface of an insulator, wherein a Si film, Si _1- forming a _x Ge _x film in this order, said Si _1-x Ge _x film to form a PIN junction arranged in a direction parallel to the substrate and a step of forming the light sensitive semiconductor element Characterize.

[0007]

In the photosensor according to the present invention, since the photosensing semiconductor element is formed in the Si _1-x Ge _x film formed on the surface of the insulator, the bandgap is small and the Si _1-x Ge _x film is small. lattice strain occurring in Si _1-x Ge _x film is further narrowing the bandgap by lattice mismatch at the hetero interface between the Si film is a membrane and its underlying layer, thereby the enhanced sensitivity for long wavelength light. Further, in the method for manufacturing an optical sensor of the present invention, a Si film and a Si _1-x Ge _x film are formed in this order on the surface of an insulator, and
Since PIN junctions are formed in the Si _1-x Ge _x film in a direction parallel to the surface of the insulator to form a light-sensitive semiconductor element, the Si film functions as a buffer layer and suppresses the diffusion of impurities from the insulator. Also, the light absorption function of the Si film can improve the sensitivity.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing a case where the present invention is applied to a visible light sensor. FIG. 2 is a cross-sectional structural view of an optical sensor according to the present invention, in which 1 denotes a substrate made of a single crystal insulator such as sapphire. On the surface of the substrate 1 Si film 2 of the single crystal, Si _1-x Ge _x film 3 single crystal, a single crystal Si film 5 is deposited in this order, the Si film 5, Si _1-x Ge
_{In the} film extending over the _x film 3 and the Si film 2, the regions 4a, 4b, 4c having conductivity of P type, I type, N type are alternately contacted in this order in a direction parallel to the plane of the substrate 1. A photosensitive semiconductor element 4 is provided which is arranged and arranged to be positioned.

[0009] Then the Si film 2, Si _1-x Ge _x film 3, Si film SiO ₂ film 6 on the substrate 1 so as to cover the entire surface of 5 is formed, the P-type regions in the SiO ₂ film 6 Electrodes 7 made of Al are provided so as to be in contact with the P-type regions 4a and N-type regions 4c through through holes formed at positions corresponding to the 4a and N-type regions 4c, respectively. Thus, in such an optical sensor, when the light passing through the substrate 1 is input to the light-sensitive semiconductor element 4, it is photoelectrically converted and the light intensity is transmitted through each electrode 7,
An electric signal corresponding to the wavelength will be output.

Next, a method of manufacturing the optical sensor according to the present invention as described above will be described with reference to FIGS. Figure 3-
FIG. 5 is an explanatory view showing the main manufacturing steps of the optical sensor according to the present invention. First, as shown in Fig. 3 (a), 750
A Si molecular beam of 1 × 13 ¹³ atom was formed on the main surface (1/10 2) of the substrate 1 made of a single crystal insulator such as sapphire heated to about ℃.
Irradiate at an intensity of s / cm ² s for 30 minutes to clean the surface.

Next, as shown in FIG. 3 (b), the temperature of the substrate 1 is
After raising the temperature to 800 ° C and growing a Si single crystal to a thickness of 200 nm on the main surface of the substrate 1 by the molecular beam epitaxy method to form the Si film 2 which functions as a buffer layer, the substrate is formed as shown in Fig. 3 (c). The temperature of 1 is set to 550 ° C and the Si molecular beam is emitted by the E-type electron gun.
Also, Ge molecular beams are generated and irradiated in the Knudsen cell to form a single crystal Si _0.8 Ge _0.2 film 3 on the surface of the Si film 2.
It is grown to 200 nm, and subsequently, as shown in Fig. 3 (d), the Si
_A single crystal Si film 5 is grown to a thickness of 10 nm on the surface of the _0.8 Ge _0.2 film 3 as described above. The Si film 2 as the buffer layer is Si _1-x Ge _x
As a base layer of the film 3, a good crystalline base is provided.

[0012] FIGS. 4 (a) to Si film 2 as shown, Si _1-x Ge _x film 3, the surface of the Si film 5, to form a SiO ₂ film 6 in a manner to cover the side peripheral surface, further the SiO ₂ film As shown in FIG. 4 (b), a photoresist 8 is coated on the surface of the substrate 6 and patterned to form SiO ₂
The surface of the membrane 6 is partially exposed, and the exposed portion
After forming the hole 6a by etching the SiO ₂ film 6 to the vicinity of the lower surface of the Si film 5 which is a base layer, an impurity, for example, B ⁺ a Si film 5, Si _1-x Ge _x film 3 and the Si film Ions are implanted to a depth reaching the lower surface of 2 to form a region 4a having a P-type conductivity type therein.

As shown in FIG. 5 (a), the hole 6a is filled with a photoresist and back-filled, and then at a position separated by a predetermined distance in the same manner as shown in FIG. 4 (b). the hole 6b formed, an impurity, for example, P ⁺ a-Si film 5, Si _1-x Ge _x film 3 and the Si film implanted to a depth reaching the lower surface of 2, wherein the conductivity type of the N-type region Form 4c.

[0014] Similarly Si film 5 by returning embedding holes 6b in photoresist, Si _1-x Ge _x film 3, Si film 2 for ion implantation by forming conductive type a P-type over into film, originally Si
Film 2, Si film 5, Si _1-x Ge _x film 3, Si film 5 each configured I type in people, each region of N-type formed by ion implantation 4
The a, 4b, and 4c are alternately arranged in a direction parallel to the surface of the substrate 1 to form the photosensitive semiconductor element 4 in which PIN junctions are repeatedly arranged. After that, a through hole is provided in the SiO ₂ film 6 at a position corresponding to the P-type region 4a and the N-type region 4c, and the electrode 7 made of Al is formed therein, whereby the optical sensor shown in FIG. Will be produced.

In the above embodiment, the Si _1-x Ge _x film 3 is used.
Shows the case where the Ge composition x is 0.2 and the film thickness is 200 nm. The Ge composition x is within 0.2 ± 0.1 (0.1 ≤ x ≤ 0.3), and the film thickness is within 250 nm. Good.

FIG. 6 shows the Si _1-x Ge _x film thicknesses of 200 nm and 800 nm.
6 is a graph showing the relationship between the absorbance and the Ge composition x in each case, in which the horizontal axis represents the Ge composition x and the vertical axis represents the absorbance (relative intensity). The reason was plotted by ○ mark in the graph if the thickness of the Si _1-x Ge _x film is 200 nm,
Also, the plots with ● marks show the respective results when the film thickness is 800 nm.

As is clear from the line plotted with the ● marks in FIG. 6, the absorbance usually increases as the Ge composition x increases and the band gap decreases, and as the film thickness increases, Si _{1- x} Ge _{x When} the film thickness is 200 nm, when Ge composition x = 0.2, the film thickness is 800 nm.
It is understood that the same absorbance as that at the Ge composition x = 0.5 is obtained. This is probably because the lattice strain caused the band gap of the Si _0.8 Ge _0.2 film to become narrower than in the unstrained state. Although not specifically shown in FIG. 6, it was confirmed that the same effect was obtained when the thickness of the Si _1-x Ge _x film was 260 nm or less.

Table 1 shows the results of measuring the lattice constants of the Si film 2 and the Si _0.8 Ge _0.2 film 3 formed on the surface of the Si film 2 by changing the thickness by the double crystal X-ray diffraction method. Si _0.8 Ge
The respective lattice constants (Å) in the case where the _0.2 film is formed in three thicknesses of 200 nm, 260 nm and 300 nm are shown.

[0019]

As is clear from Table 1, when the thickness of the Si _0.8 Ge _0.2 film 3 is 200 nm, the lattice constant is 5.484 Å, which is compared with the lattice constant 5.68 Å of unstrained bulk Si _0.8 Ge _0.2. It can be seen that the crystal lattice is large and is distorted in the growth direction. The lattice constant of the Si _0.8 Ge _0.2 film 3 of 260 nm is the strain-free bulk Si of 300 nm.
_0.8 distortion of the crystal lattice have the same 5.468 Å and the lattice constant of Ge _0.2 is not measured, which is Si _0.8 Ge _0.2 layer 3
It is considered that when the film thickness is less than 260 nm, misfit dislocations do not occur in the growth layer and the lattice mismatch at the SiGe / Si interface is relaxed by the misfit dislocations.

FIG. 7 is a graph showing comparative test results between the optical sensor according to the present invention shown in FIG. 2 and the conventional optical sensor shown in FIG. 1, in which the horizontal axis represents wavelength (nm) and the vertical axis represents optical wavelength. The current (mA) and the ratio I _A / I _B between the photocurrent I _A of the photosensor according to the present invention and the photocurrent I _B of the conventional photosensor are shown. The solid line in the graph shows the result of the optical sensor according to the present invention, and the alternate long and short dash line shows the result of the conventional optical sensor. The broken line indicates the ratio I _A / I _B of the photocurrent I _A of the photosensor according to the present invention and the photocurrent I _B of the conventional photosensor.

As is apparent from this graph, wavelengths of 400 to 10
It can be seen that the photocurrent of the photosensor according to the present invention is significantly improved as compared with the conventional photosensor over the entire visible light region of 00 nm. In particular, as is clear from the photocurrent ratio I _A / I _B, it can be seen that the detection capability of the optical sensor according to the present invention is significantly improved as the wavelength becomes longer. In the above-described embodiment, the substrate has a structure in which the Si film 2 or the like is sequentially grown on a single crystal insulator such as sapphire or spinel. However, for example, an insulating film is deposited on the surface of a conventionally known semiconductor substrate. The Si film 2 and the like may be sequentially grown on this insulating film.

[0023]

In the optical sensor and a manufacturing method thereof according to the above as the present invention exhibits, sequences form a PIN junction oriented parallel to the substrate surface during Si _1-x Ge _x film formed on the Si film Therefore, due to the crystal lattice distortion of the Si _1-x Ge _x film caused by the lattice mismatch at the Si _1-x Ge _x / Si hetero interface, the band gap can be further narrowed and high sensitivity to long wavelength light can be obtained. Therefore, the present invention has excellent effects such that it can be used as a color sensor or the like and can be manufactured without changing process conditions.

[Brief description of drawings]

FIG. 1 is a sectional structural view of a conventional optical sensor.

FIG. 2 is a sectional structural view of an optical sensor according to the present invention.

FIG. 3 is an explanatory diagram showing a manufacturing process of the optical sensor according to the invention.

FIG. 4 is an explanatory view showing a manufacturing process of the optical sensor according to the invention.

FIG. 5 is an explanatory diagram showing a manufacturing process of the optical sensor according to the invention.

FIG. 6 is a graph showing the relationship between the composition x of a Si _1-x Ge _x film and the absorbance.

FIG. 7 is a graph showing a comparison test result of the optical sensor according to the present invention and the conventional optical sensor.

[Explanation of symbols]

Single crystal insulator substrate 2 made of Si film 3 Si _1-x Ge _x layer 4 light sensitive semiconductor elements 4a P-type region 4b I-type region 4c N-type region 5 Si film 6 SiO ₂ film 7 electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Kawai 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A single crystal semiconductor film is provided on a surface of an insulator,
The optical sensor obtained by forming a light sensitive semiconductor element in the semiconductor film, wherein the insulator Si film on the surface of, Si _1-x Ge _x and film laminated to said Si _1-x Ge _x film An optical sensor comprising the light-sensitive semiconductor element. 2. A method for manufacturing an optical sensor, comprising a single crystal semiconductor thin film having a photosensitive semiconductor element formed on the surface of an insulator, comprising: forming a Si film or a Si _1-x Ge _x film on the surface of the insulator. A photosensor characterized by including the steps of forming in order and forming the photo-sensing semiconductor device by forming PIN junctions arranged in a direction parallel to the substrate on the Si _1-x Ge _x film. Manufacturing method.