JPH06163967A - Ultraviolet radiation detecting device and its manufacture - Google Patents

Abstract

PURPOSE:To obtain an ultraviolet radiation detecting device wherein sensitivity to ultraviolet radiation is excellent, formation together with a signal processing circuit in an Si semiconductor chip is possible, and miniaturization and cost reduction are enabled. CONSTITUTION:A porous Si region 8 is formed by anodizing a specified region of the epitaxial layer 4. By controlling the processing condition in the case of anodizing, the porous Si region 8 outputs light (visible light) of photoluminescence, when ultraviolet radiation is absorbed. N-type impurities diffusion layers 3, 6 are formed under the region 8 and in the side part of the region 8. A P-N photodiode is constituted of the N-type impurities diffusion regions 3, 6 and P-type regions (a substrate 1 and the epitaxial layer 4).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet ray detecting device and a method of manufacturing the same which can form an ultraviolet ray detecting element and a circuit for processing a signal output from the ultraviolet ray detecting element on the same semiconductor chip.

[0002]

2. Description of the Related Art The ultraviolet region has a wide target wavelength (energy) region, and when it is optically applied, there are few that have sufficiently satisfactory properties for filters, window materials, light sources and the like. For this reason, the technique for quantitatively evaluating ultraviolet rays is particularly delayed as compared with the case of visible light.

Conventionally, as the ultraviolet ray detecting element, there are a photoconductive element using a compound semiconductor and a photoelectric type detecting element having a tube-shaped photoelectric surface. For the photoconductive element for detecting ultraviolet rays, Z
Compound semiconductors such as nS, Cd ₄ SiS ₆ and Cd ₄ GeS ₆ have been used. ZnS has an energy band gap of 3.7 eV and a wavelength sensitivity peak of about 340.
nm. In addition, Cd ₄ SiS ₆ and Cd ₄
The wavelength sensitivity peaks of GeS ₆ are at about 430 nm and about 470 nm, respectively.

On the other hand, in the photoelectric type ultraviolet detecting element, CsI, KBr, LiF, CsTe and MgF mainly containing an alkali halide compound are mainly formed on the tube-shaped photocathode.
_Second grade is used, and high quantum efficiency is obtained. Further, as the window material, MgF ₂ , silica glass (Fused Si)
kica) and UV glass are used. In FIG.
An example of the spectral sensitivity characteristics of various ultraviolet photocathodes and the transmission characteristics of window materials will be shown. However, in FIG. 12, the solid line indicates the quantum efficiency, the broken line indicates the transmittance of each window material when the thickness is 1 mm,
[O] is opaque (Opeque type), [T] is semi-transparent (Se
mi-Transmitting type) is shown.

[0005]

However, the conventional ultraviolet ray detecting device has the following problems. That is, in recent years, in various detection devices other than the ultraviolet detection device, a detection element and a signal for performing processing such as amplification of a signal output from the detection element or conversion of an analog signal into a digital signal that can be easily processed. The processing circuit tends to be formed on the same semiconductor chip. In this way, the technology for forming the sensing element and the signal processing circuit on the same semiconductor chip is
This is extremely important in order to reduce the volume of the entire detection device, promote miniaturization of the device, and obtain high sensitivity and high reliability. On the other hand, since it is extremely difficult to integrate the signal processing circuit with the compound semiconductor in the conventional ultraviolet ray detecting device, all of them are formed as a single element. Therefore, a circuit for performing signal processing is required separately from the ultraviolet ray detecting element, which hinders downsizing of the device. Further, in the case of an ultraviolet ray detection device using a compound semiconductor, the compound semiconductor is extremely smaller than Si when viewed as a resource, so that there is a drawback that the product cost is inevitably high.

The present invention has been made in view of the above problems, has a good sensitivity to ultraviolet rays, can be formed on a Si semiconductor chip together with a signal processing circuit, and can reduce the size and cost of the device. It is an object of the present invention to provide an ultraviolet ray detection device and a manufacturing method thereof.

[0007]

An ultraviolet detector according to the present invention comprises a porous Si region which is formed by selectively anodizing the surface of a Si semiconductor substrate and which emits light by photoluminescence when receiving ultraviolet light. And a photoelectric conversion element formed on the semiconductor substrate so as to surround the porous Si region.

The method of manufacturing an ultraviolet detector according to the present invention comprises a step of forming a photoelectric conversion element by surrounding a predetermined region on the surface of a Si semiconductor substrate, and anodizing the predetermined region to form a porous Si region. And a step of performing.

[0009]

The porous Si exhibits photoluminescence, which absorbs ultraviolet rays and emits visible light. In the ultraviolet detector according to the present invention, a photoelectric conversion element such as a photodiode is arranged around the porous Si region formed by the anodization treatment, and when the porous Si region absorbs ultraviolet rays and emits visible light. The visible light is detected by the photoelectric conversion element and converted into an electric signal. Therefore, the ultraviolet ray detecting device according to the present invention can detect the ultraviolet ray with good sensitivity and can easily reduce the size of the device.

Further, in the method of the present invention, a photoelectric conversion element is formed by surrounding a predetermined region on the surface of the Si semiconductor substrate,
After that, the predetermined region is subjected to anodization treatment to form a porous Si region exhibiting photoluminescence. After various experimental studies, the inventors of the present application have found that when anodizing the Si substrate, the anodized layer exhibits photoluminescence characteristics by appropriately controlling the treatment conditions.
FIG. 13 is a graph showing the treatment conditions when the anodized layer shows the photoluminescence characteristics, with the horizontal axis representing the current density during the anodizing treatment and the vertical axis representing the HF concentration. For example, a Si substrate having a crystal orientation of (100) is subjected to conditions within the range shown in FIG. 13 (HF concentration is 20 to 50% by volume, current density is 1 to 10 mA / cm ² , processing temperature is 10 ± 0.5 ° C.).
When the anodization process is carried out at, it has two absorption bands in the ultraviolet region with a wavelength of 230 to 300 nm and a wavelength of 590 to 600.
It is possible to obtain an anodized layer that emits visible light (red) of nm. In addition, the condition (HF) within the range shown in FIG.
Concentration is several to 30% by volume, current density is 1 to 700 mA / c
When the Si substrate is subjected to anodization treatment at m ² and a treatment temperature of 10 ± 0.5 ° C., it has one absorption band in the ultraviolet region of wavelength 230 to 300 nm and visible light of wavelength 600 to 630 nm (red to orange). It is possible to obtain an anodized layer that emits color). Further, when the Si substrate is anodized under the conditions shown in FIG. 13, the anodized layer does not show photoluminescence.

FIGS. 14 (a) and 14 (b) are graphs showing an example of the ultraviolet absorption characteristics of the anodized layer formed under the conditions shown in FIG. Also. Figure 1
FIGS. 5A and 5B are graphs showing an example of the relationship between the wavelength and the intensity of the light emitted from the anodized layer formed under the conditions shown in FIG.

The full width at half maximum (FWHM) of the light output from the porous Si formed by the anodizing treatment is
The thickness is about 65 to 85 nm (in the case of porous Si formed under the conditions shown in FIG. 13) and about 90 to 130 nm (when formed under the conditions shown in FIG. 13).
In particular, the porous Si formed under the conditions shown in FIG. 13 has a feature that the width is narrower than the half-value width of the light output from the porous Si formed by the conventional method.
The porous Si formed under the conditions within the range shown in FIG. 13 has a higher sensitivity to ultraviolet rays than the porous Si formed under the conditions within the range shown in FIG. 13, but depending on the application, either Anodization treatment may be performed.

In the method of the present invention, the ultraviolet ray detecting element is formed in a process substantially the same as the ordinary IC (integrated circuit) manufacturing process except for the anodizing treatment, so that the ultraviolet ray detecting element and the signal processing circuit are the same. It can be formed on a semiconductor chip.

[0014]

Embodiments of the present invention will now be described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an ultraviolet ray detecting device according to an embodiment of the present invention.

A p-type epitaxial layer 4 is formed on the p-type Si substrate 1, and a porous Si region 8 formed by anodizing the epitaxial layer 4 is formed in a predetermined region of the epitaxial layer 4. Is provided.
Further, n is provided below and to the side of the porous Si region 8, respectively.
Type impurity diffusion regions 3 and 6 are formed, and porous Si
Region 8 is surrounded by these n-type impurity diffusion regions 3 and 6.

A Si ₃ N ₄ film 7 is formed on the epitaxial layer 4.
Are formed, and the porous Si region 8 is formed by this Si ₃ N ₄
It is exposed from the opening 7a provided in the film 7. Also,
A contact hole 7b is selectively formed in the Si ₃ N ₄ film 7, and the Al electrode 9 is formed by extending the contact hole 7b onto the embedded Si ₃ N ₄ film 7.

The n-type impurity diffusion regions 3 and 6 and the p-type impurity regions (epitaxial layer 4 and substrate 1) contacting the n-type impurity diffusion regions 3 and 6 are PN photodiodes having photosensitivity due to a pn junction. Constitute. That is, Al
The electrode 9 is an electrode of this PN photodiode. When the porous Si region 8 receives ultraviolet rays, it outputs visible light by photoluminescence. The visible light output from the porous Si region 8 is received by the above-mentioned PN photodiode and converted into an electric signal.

Although the sensitivity of the porous Si region 8 to ultraviolet rays varies depending on the processing conditions during the anodizing treatment, good sensitivity can be obtained by appropriately controlling the processing conditions. Further, in this embodiment, since the porous Si region 8 is formed surrounded by the photodiodes, the visible light output from the porous Si region 8 can be detected with high efficiency. Therefore, the ultraviolet ray detection device according to this embodiment can detect ultraviolet rays with good sensitivity.

2 to 10 are sectional views showing a method of manufacturing the ultraviolet ray detecting device according to this embodiment in the order of steps.

First, as a material, as shown in FIG. 2, a p-type Si substrate 1 having a crystal orientation (100) and an electric resistivity of 2 to 6 Ω · cm is prepared.

Next, as shown in FIG. 3, after the SiO ₂ film 2 is formed on the surface of the substrate 1, the SiO ₂ film 2 is selectively removed to form the opening 2a. Then, an n-type impurity is introduced into the surface of the substrate 1 through the opening 2a and diffused to form an n-type impurity diffusion region 3 having a diffusion depth of about 3 μm.

Next, as shown in FIG. 4, Si on the substrate 1
The O ₂ film 2 is removed, and a p-type epitaxial layer 4 is formed on the substrate 1 to a thickness of about 10 μm, as shown in FIG.

Next, as shown in FIG. 6, a SiO ₂ film 5 is formed on the epitaxial layer 4, and the n-type impurity diffusion region 3 is formed.
The portion of the SiO ₂ film 5 corresponding to the edge portion is removed selectively to form the opening 5a. Thereafter, as shown in FIG. 7, an n-type impurity is introduced into the epitaxial layer 4 through the opening 5a to form an n-type impurity diffusion region 6 which is in communication with the n-type impurity diffusion region 3.

Next, as shown in FIG. 8, after removing the SiO ₂ film 5, a Si ₃ N ₄ film 7 is formed to a thickness of about 150 nm on the entire surface of the epitaxial layer 4, and the n-type impurity diffusion region 6 is formed. The Si ₃ N ₄ film 7 in a region corresponding to the portion surrounded by is selectively removed to form an opening 7a.

Next, as shown in FIG. 9, an HF liquid having a concentration of 50% by volume was used as a processing liquid, the liquid temperature was 10 ± 0.5 ° C., the current density was 1 mA / cm ² , and the charge amount was 1200 C (coulomb). The epitaxial layer 4 is subjected to anodization treatment under the condition (1) to form the porous Si region 8. Note that NH ₄ OH or the like may be used as the alkaline electrolyte during the anodization treatment.

Then, as shown in FIG. 10, Si ₃ N ₄
A contact hole 7b is selectively formed in the film 7, and an Al electrode is formed so as to fill the contact hole. As a result, the ultraviolet detector according to this embodiment shown in FIG. 1 is completed.

The emission intensity of the porous Si region 8 can be controlled in the depth direction by controlling the pore size and oxidation state. The deep portion of the porous Si region 8 (that is,
By controlling the pore diameter and the oxidation state of the porous Si region 8 so that the emission intensity in the portion close to the photodiode) becomes high, the sensitivity when detecting the light output from the porous Si region 8 with the photodiode can be improved. . Further, by performing anodization under the conditions shown in FIG. 13, the porous Si region has two peak sensitivities in the ultraviolet region, and good sensitivity to ultraviolet rays can be obtained.

According to the method of the present embodiment, the ultraviolet detector is manufactured through the steps substantially similar to the normal IC manufacturing steps such as the introduction of impurities into the Si substrate and the formation of the epitaxial layer. That is, according to the method of this embodiment, the ultraviolet ray detecting element and the circuit for processing the signal output from this ultraviolet ray detecting element can be formed on the same semiconductor chip.

For visible light detection, FIG.
A pn diode for detecting light by the pn junction shown in FIG. 11A, a PIN diode for detecting light by the pi (intrinsic semiconductor) -n junction shown in FIG. 11B, FIG.
An avalanche diode and a reach-through avalanche diode that detect light by using the electron avalanche phenomenon (avalanche phenomenon) shown in (c) and (d) are used. In the above-described embodiments, the case where the light output from the porous Si region is converted into an electric signal by the PN photodiode is described, but as the photoelectric conversion element of the ultraviolet ray detection device according to the present invention, a PIN diode,
Of course, it may be an avalanche diode, a reach through avalanche diode, or the like.

[0031]

As described above, the ultraviolet ray detecting device according to the present invention includes the porous Si region which emits light by photoluminescence when absorbing the ultraviolet ray, and the photoelectric conversion element formed surrounding the porous Si region. Therefore, ultraviolet rays can be detected with high sensitivity. Further, the ultraviolet ray detecting device according to the present invention can be formed on the same semiconductor chip together with the signal processing circuit, so that it is possible to reduce the size of the entire device and reduce the product cost.

On the other hand, in the method of the present invention, a photoelectric conversion element such as a photodiode is formed so as to surround a predetermined region on the surface of the Si substrate, and the predetermined region is subjected to anodization to obtain the porous S.
Since the i region is formed, it is possible to form an element that detects ultraviolet rays and a signal processing circuit on the same semiconductor chip.
Further, by controlling the processing conditions during the anodizing treatment, it is possible to control the sensitivity characteristic of the porous Si region to ultraviolet light.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an ultraviolet ray detection device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing one step of the same manufacturing method.

FIG. 3 is a cross-sectional view showing one step of the same manufacturing method.

FIG. 4 is a cross-sectional view showing one step of the same manufacturing method.

FIG. 5 is a cross-sectional view showing one step of the same manufacturing method.

FIG. 6 is a cross-sectional view showing one step of the same manufacturing method.

FIG. 7 is a cross-sectional view showing one step of the same manufacturing method.

FIG. 8 is a cross-sectional view showing one step of the same manufacturing method.

FIG. 9 is a cross-sectional view showing one step of the same manufacturing method.

FIG. 10 is a cross-sectional view showing one step of the same manufacturing method.

11A to 11D are cross-sectional views each showing a photoelectric conversion element.

FIG. 12 is a graph showing an example of spectral sensitivity characteristics of various ultraviolet photocathodes and transmission characteristics of window materials.

FIG. 13 is a graph showing treatment conditions during anodization treatment capable of obtaining an anodized layer exhibiting photoluminescence.

14A and 14B are graphs showing an example of ultraviolet absorption characteristics of an anodized layer formed under the conditions shown in FIG.

15 (a) and 15 (b) are graphs each showing an example of the relationship between the wavelength and the intensity of light emitted from the anodized layer formed under the conditions shown in FIG. .

[Explanation of symbols]

1; Si substrate 2, 5; SiO ₂ film 3, 6; n-type impurity diffusion region 7; Si ₃ N ₄ film 8; porous Si region 9; Al electrode

Claims (3)

[Claims] 1. A porous Si region which is formed by selectively anodizing the surface of a Si semiconductor substrate and emits light by photoluminescence when receiving ultraviolet light, and the porous Si region.
An ultraviolet detector comprising a photoelectric conversion element formed on the semiconductor substrate so as to surround a region. 2. A step of forming a photoelectric conversion element surrounding a predetermined region on the surface of a Si semiconductor substrate, and a step of anodizing the predetermined region to form a porous Si region. Ultraviolet detector manufacturing method. 3. The concentration of the anodizing treatment is 20 to 5
The treatment temperature is 10 ± 0.
The method for manufacturing an ultraviolet detector according to claim 2, wherein the method is carried out under conditions of 5 ° C. and a current density of 1 to 10 mA.