JPH0738135A - Semiconductor photoelectric conversion element - Google Patents

Abstract

PURPOSE:To provide a semiconductor photoelectric conversion element which is improved in spectral characteristics and response characteristics to incident light. CONSTITUTION:All intrinsic semiconductor layer (I layer) 2 is formed on an N-type semiconductor layer 1, a P-type semiconductor layer 10 is provided onto the I-type layer 2, an antireflection film 9 of transparent conductive high refractive index film such as an ITO film or a TiN film is formed on a light, receiving surface, and a P-type semiconductor layer 10 as a diffusion layer is formed to be shallow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor photoelectric conversion device capable of ultra-high speed response, and more particularly to a semiconductor photoelectric conversion device having improved spectral characteristics and response characteristics of short wavelength in the ultraviolet region. Is.

[0002]

2. Description of the Related Art A pin junction type photodiode is usually used as a semiconductor photoelectric conversion element capable of an ultra-high speed response. This photoelectric conversion element is one in which a high-purity i-layer without impurities is provided between pn junctions, and a depletion layer without carriers due to the i-layer is formed thick to reduce the capacitance, thereby providing a high-speed response. Is possible. Figure 7
(A) is sectional drawing which shows an example of the pin junction type photodiode. In the figure, a P type diffusion layer 3 is formed on an i layer 2 of a semiconductor substrate in which an intrinsic semiconductor layer (i layer) 2 is laminated on an N type semiconductor layer 1. An insulating film 4 such as a silicon oxide film (SiO ₂ ) is formed around the surface of the semiconductor substrate on the light receiving side which is irradiated with the light hν, and the silicon nitride film (Si ₃ N ₄ ) is reflected to enhance the light receiving sensitivity. The prevention film 8 is applied. The antireflection film 8 is provided with an opening 5, the front surface electrode 6 serving as an anode is in ohmic contact with the P-type semiconductor layer 3 exposed in the opening 5, and the rear surface of the N-type semiconductor layer 1 is A back surface electrode 7 serving as a cathode is formed.

The distribution (diffusion profile) of the impurity concentration with respect to the diffusion depth X _j of the P-type semiconductor layer 3 is shown in FIG.
As shown in (1), the Gaussian distribution is obtained, and the impurity concentration on the surface of the semiconductor substrate is diffused to a high concentration of 1 × 10 ¹⁹ atoms / cm ³ or more. Therefore, the depletion layer spreads over the i-layer 2, but has a characteristic that it hardly spreads over the P-type semiconductor layer 3 that is highly doped with impurities.

[0004]

In the above-mentioned semiconductor photoelectric conversion element, the insulating film which is the antireflection film 8 made of the silicon nitride film (Si ₃ N ₄ ) is formed on the light receiving surface so as to easily absorb light. As a result, there is a drawback that the resistance component in series with respect to the load is large, and as a result, the response characteristics to incident light deteriorate. Incidentally, FIG. 7C shows an equivalent circuit of the semiconductor photoelectric conversion device, where Vp is a photovoltaic power, Cj is a junction capacitance, Rp is a parallel resistance (loss resistance) of a pn junction, and Rs is a series of diodes. Each show resistance,
When irradiated with light, the current Ie is changed according to the light energy.
There occurs, the output current I _P with flowing diode current I _D and the parallel resistance current I _RP is flowing in the load resistor.

Explaining with reference to FIG. 7C, when the sheet resistance of the P-type semiconductor layer 3 increases, the series resistance Rs is increased.
, And the response characteristics to light deteriorate. In addition, if the antireflection film 8 covering the surface of the P-type semiconductor layer 3 is insulative, the series resistance Rs similarly becomes large and the response characteristics deteriorate. When the reverse bias voltage is applied to the semiconductor photoelectric conversion element, the spread of the depletion layer depends on the applied voltage and the impurity concentration of the semiconductor layer forming the junction. , Depends on the impurity concentration. Therefore, the depletion layer extends to the i layer 2, but does not spread much to the P-type semiconductor layer 3 having a high impurity concentration on which light is incident.

That is, light is incident on the depletion layer to generate electron-hole pairs, electrons are accelerated to the anode electrode, and holes are accelerated to the cathode electrode to generate current Ie. Therefore, it is effective for the depletion layer to spread near the surface of the P-type semiconductor layer 3 to improve the response characteristics to light, but as shown in FIG. Impurities are injected, and the depletion layer is hard to spread, which is a factor of deteriorating the response characteristics to light having a short wavelength in the ultraviolet region. Of course, it is a factor that deteriorates the spectral characteristics of the semiconductor photoelectric conversion element.

The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a semiconductor photoelectric conversion element which improves spectral characteristics and light response characteristics.

[0008]

To achieve the above object, the semiconductor photoelectric conversion device of the present invention is characterized in that the antireflection film formed on the light receiving surface of the semiconductor photoelectric conversion device is made of a transparent conductive film. It is what The semiconductor photoelectric conversion element includes a semiconductor layer of a first conductivity type, an intrinsic semiconductor layer stacked on the semiconductor layer of the first conductivity type, and a semiconductor of a second conductivity type formed in the intrinsic semiconductor layer. And an antireflection film formed of a transparent conductive film formed on the light receiving surface of the second conductive type semiconductor layer.

In the semiconductor photoelectric conversion element, a semiconductor layer of the first conductivity type, an intrinsic semiconductor layer laminated on the semiconductor layer of the first conductivity type, and a second conductivity formed in the intrinsic semiconductor layer. Type semiconductor layer and an antireflection film made of a transparent conductive film formed on the light receiving surface of the second conductivity type semiconductor layer, and the first conductivity type semiconductor layer has a shallow diffusion depth, It is characterized by forming a superficial junction.

[0010]

In the semiconductor photoelectric conversion device of the present invention, the antireflection film formed on the light receiving surface of the semiconductor photoelectric conversion device of the present invention is a transparent conductive film, and the impurity concentration of the second conductivity type semiconductor layer on the light receiving side is adjusted. By lowering and reducing the resistance component in series with the load resistance, the light-receiving sensitivity to short-wave light (ultraviolet rays) is increased, thereby improving the spectral characteristics and the response characteristics. Further, in the semiconductor photoelectric conversion element of the present invention, the antireflection film formed on the light receiving surface of the semiconductor photoelectric conversion element is a transparent conductive film, and the second conductivity type semiconductor layer on the light receiving side is a shallow diffusion layer, The super staircase junction enhances the light receiving sensitivity to short-wave light (ultraviolet rays) to improve the spectral characteristics and the response characteristics to light.

[0011]

EXAMPLE An example of the semiconductor photoelectric conversion device of the present invention will be described below with reference to FIG. Figure 1 is a pin
It is sectional drawing which shows one Example of a junction type photodiode. In FIG. 1, an intrinsic semiconductor layer (i layer) 2 is laminated on an N-type semiconductor layer 1 to form a semiconductor substrate.
A P-type semiconductor layer 10 is diffused and formed on the layer 2 to form a pin junction. An insulating film 4 such as a silicon oxide film doped with tin oxide is formed around the surface of the semiconductor substrate on the light receiving side on which the light hν is incident, and an indium oxide film (ITO film) is formed on the light receiving surface to enhance the light receiving sensitivity. Film) or an antireflection film 9 such as a titanium nitride film (TiN film) is deposited to form an anode electrode. The antireflection film 9 is in ohmic contact with the P-type semiconductor layer 10, and the back surface electrode 7 serving as a cathode is formed on the back surface of the N-type semiconductor layer 1.

The antireflection film 9 such as an ITO film or a TiN film is
It is a transparent conductive film, which can reduce the series resistance Rc shown in FIG. 7C, has a high refractive index, and has favorable light absorption. Further, as shown in the diffusion profile of FIG. 1B, the P-type semiconductor layer 10 has an impurity concentration of 1 × 10 ¹⁶ to 1 × 10 ¹⁸ atoms /
Set in the range of cm ³ . Optimally 1 × 10 ¹⁷ atoms / cm ³
And the diffusion depth Xj is 0.5 to
Set to 2 μm.

By configuring as in the above embodiment, the antireflection film 9 is a transparent conductive film having a high refractive index, and the impurity concentration of the P-type semiconductor layer 10 is lowered. When a reverse bias voltage is applied, the depletion layer extends deeply into the P-type semiconductor layer 10 and also extends to the i-layer 2, so depletion that facilitates absorption of ultraviolet rays of short wavelength (450 to 300 nm) on the surface is facilitated. The radiation sensitivity (light receiving sensitivity) can be improved by reaching the layer. However, since the impurity concentration of the P-type semiconductor layer 10 is lowered, the sheet resistance is slightly increased as compared with the conventional one, but the antireflection film 9 that covers most of the light-receiving surface of the P-type semiconductor layer 10 is transparent and conductive. By using a high refractive index film,
Since the increase in sheet resistance of the P-type semiconductor layer 10 can be compensated for, the spectral characteristics and response characteristics can be improved.

Next, another embodiment of the semiconductor photoelectric conversion device of the present invention will be described with reference to FIG. In this embodiment, the cross-sectional view has a structure similar to that of FIG.
As shown in FIG. 2, the diffusion profile of the p-type semiconductor layer 10 is such that the diffusion depth Xj is set to 0.2 to 0.25 μm and the impurity concentration is in the range of 1 × 10 ^{20 to} 7 × 10 ¹⁸ atoms / cm ³ . Set to. Of course, the antireflection film 10 is made of ITO film or Ti.
A transparent conductive high refractive index film such as an N film is used. Therefore,
The P-type semiconductor layer 10 diffuses high impurities to have a low specific resistance, but a transparent conductive high refractive index film is used as the antireflection film 10, and the diffusion layer thereof is extremely shallow. Also, the radiation sensitivity (light receiving sensitivity) can be increased even for light having a short wavelength such as ultraviolet rays.

In the above embodiment, the transparent conductive film is used as the antireflection film 9 formed on the light receiving surface, as shown in FIG.
As shown in FIG. 5, a surface electrode 12 may be formed on the antireflection film 9 to make an ohmic contact. Alternatively, as shown in FIG. 5B, an opening 11 is formed in the antireflection film 9. Surface electrode 1
2 may form an ohmic contact. These surface electrodes 12
The wire is welded to. As described above, the electrode structure can have various forms.

The method of manufacturing the semiconductor photoelectric conversion device of the present invention will be briefly described with reference to FIG. Figure 6
As shown in (a), the N-type semiconductor layer 1 is formed in the intrinsic semiconductor layer 2 (phosphorus impurity concentration is 1 × 10 ¹⁰ to 1 × 10 ¹² atoms / cm ³ ) by using thermal diffusion or the like. Thereafter, as shown in FIG. 6B, the insulating film 4 is formed by thermal oxidation, the insulating film on the light receiving surface is removed, and the insulating film 4 is formed around the insulating film. After that, as shown in FIG. 6C, a P-type dopant is ion-implanted into the surface of the intrinsic semiconductor layer 2 using the resist film, the oxide film, or the like as a mask, and an annealing treatment is performed.
As shown in (d), the diffusion depth Xj is 0.5 to 2.0 μm.
A P-type semiconductor layer 10 composed of m shallow diffusion layers is formed. Subsequently, as shown in FIG. 6E, surface electrode (pad electrode) 1 is formed by evaporating and patterning aluminum.
Form 2. Subsequently, as shown in FIG. 6F, a back surface electrode 7 is formed on the back surface of the N-type semiconductor layer 1, and the back surface electrode 7 is formed as shown in FIG.
The semiconductor photoelectric conversion element of is formed.

Of course, the P-type semiconductor layer 10 can be formed into a shallow diffusion layer by various known methods. Moreover, FIG.
As a method of forming a super staircase junction as in the embodiment of
As an example thereof, a P-type dopant is ion-implanted into the intrinsic semiconductor layer 2 at a high concentration through a thermal oxide film formed on the surface of the intrinsic semiconductor layer 2 and an annealing treatment is performed, so that the surface has a high concentration. A P-type dopant is implanted to form a hyperstep junction. After that, the thermal oxide film is removed and the antireflection film 9 is formed to form a semiconductor photoelectric conversion element. Of course,
It is obvious that the method of forming the super staircase junction is not limited to the above-mentioned method and can be formed by various known methods.

Next, the spectral characteristics and light response characteristics of the embodiments of FIGS. 1 and 2 will be described in comparison with the conventional example. 3 shows the wavelength (nm) of incident light on the horizontal axis, the vertical axis shows the spectral characteristics showing the radiation sensitivity (A / W), and FIG. 4 shows the frequency (Hz) on the horizontal axis. The vertical axis represents the response characteristic indicating the relative output (dB). In these figures, (a) shows the characteristic of the conventional example, (b) shows the characteristic of the embodiment of FIG. 2) shows the characteristics of the embodiment of FIG. It is shown that the spectral characteristics and the light response characteristics of the embodiment are superior to the conventional semiconductor photoelectric conversion element. In particular, as in the embodiment shown in FIG. 2, by using a hyper-step junction composed of a shallow diffusion layer and a transparent conductive high-reflectance film as its antireflection film, the radiation sensitivity (light receiving sensitivity) of short wavelength in the ultraviolet region is obtained. ) Is increased, the spectral characteristics are improved, and the response characteristics to light are improved.

[0019]

As described above, according to the present invention, the antireflection film is a transparent conductive high reflectance film, the impurity concentration of the P-type semiconductor layer on the light receiving side is suppressed to be low, and the depletion layer is irradiated with ultraviolet rays. The short-wavelength light in the region can easily reach, or the step depth junction is formed by making the junction depth of the P-type semiconductor layer shallow so that the short-wavelength light in the ultraviolet region can be received. Is improved, so that the spectral characteristics and the response characteristics are improved.

[Brief description of drawings]

FIG. 1A is a sectional view showing an embodiment of a semiconductor photoelectric conversion element of the present invention, and FIG. 1B is a view showing a diffusion profile of a semiconductor layer on the light receiving side thereof.

FIG. 2 is a diagram showing a diffusion profile for explaining another embodiment of the semiconductor photoelectric conversion device of the present invention.

FIG. 3 is a diagram showing radiation sensitivity with respect to a wavelength of incident light.

FIG. 4 is a diagram showing response characteristics to light irradiation.

5A and 5B are cross-sectional views showing a structure of a surface electrode.

6A to 6F are cross-sectional views showing a method for manufacturing a semiconductor photoelectric conversion element of the present invention.

7A is a cross-sectional view showing an example of a conventional semiconductor photoelectric conversion device, FIG. 7B is a diagram showing a diffusion profile of a semiconductor layer on the light receiving side thereof, and FIG. It is an equivalent circuit diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 N-type semiconductor layer 2 Intrinsic semiconductor layer (i layer) 4 Insulating film 7 Backside electrode 9 Antireflection film 10 P-type semiconductor layer 11 Opening 12 Surface electrode

[Procedure amendment]

[Submission date] November 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 3

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

In the above-mentioned semiconductor photoelectric conversion element, the insulating film which is the antireflection film 8 made of the silicon nitride film (Si ₃ N ₄ ) is formed on the light receiving surface so as to easily absorb light. As a result, there is a drawback resistance components of the series is greater ing to the load, thereby there is a drawback that response to incident light is deteriorated. Incidentally, FIG. 7C shows an equivalent circuit of the semiconductor photoelectric conversion device, where Vp is a photovoltaic power, Cj is a junction capacitance, Rp is a parallel resistance (loss resistance) of a pn junction, and Rs is a series of diodes. Resistances are shown respectively, and when light is irradiated, a current Ie is generated according to the light energy, and a diode current I _D and a parallel resistance current I _RP are generated.
And the output current I _P flows through the load resistance.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

Namely, the hole in electron-hole pairs the light is incident on the depletion layer is generated in the anode electrode, electrons are accelerated into the cathode current Ie is generated. Therefore, it is effective for the depletion layer to spread near the surface of the P-type semiconductor layer 3 to improve the response characteristics to light, but as shown in FIG. Impurities are injected, and the depletion layer is hard to spread, which is a factor of deteriorating the response characteristics to light having a short wavelength in the ultraviolet region. Of course, it is a factor that deteriorates the spectral characteristics of the semiconductor photoelectric conversion element.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

In the semiconductor photoelectric conversion element, a semiconductor layer of the first conductivity type, an intrinsic semiconductor layer laminated on the semiconductor layer of the first conductivity type, and a second conductivity formed in the intrinsic semiconductor layer. Type semiconductor layer and an antireflection film made of a transparent conductive film formed on the light receiving surface of the second conductive type semiconductor layer, and the second conductive type semiconductor layer has a shallow diffusion depth. it is characterized in that the formation of the ultra stairs bonding.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

[0011]

EXAMPLE An example of the semiconductor photoelectric conversion device of the present invention will be described below with reference to FIG. Figure 1 is a pin
It is sectional drawing which shows one Example of a junction type photodiode. In FIG. 1, an intrinsic semiconductor layer (i layer) 2 is laminated on an N-type semiconductor layer 1 to form a semiconductor substrate.
A P-type semiconductor layer 10 is diffused and formed on the layer 2 to form a pin junction. An insulating film 4 such as a silicon oxide film doped with phosphorus is formed around the surface of the semiconductor substrate on the light receiving side on which the light hν enters, and an oxide indium film (ITO film) is formed on the light receiving surface to enhance the light receiving sensitivity. ) Or a titanium nitride film (TiN film) or the like is applied to form an anode electrode. The antireflection film 9 is in ohmic contact with the P-type semiconductor layer 10, and the back surface electrode 7 serving as a cathode is formed on the back surface of the N-type semiconductor layer 1.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

By configuring as in the above embodiment, the antireflection film 9 is a transparent conductive film having a high refractive index, and the impurity concentration of the P-type semiconductor layer 10 is lowered. , when a reverse bias voltage is applied, a depletion layer with extends deeper into the semiconductor layer 10 of P-type, since even extending the i-layer 2, ultraviolet is absorbed by the surface easily short wavelength (450~300nm) is easily depleted The radiation sensitivity (light receiving sensitivity) can be improved by reaching the layer. However, since the impurity concentration of the P-type semiconductor layer 10 is lowered, the sheet resistance is slightly increased as compared with the conventional one, but the antireflection film 9 that covers most of the light-receiving surface of the P-type semiconductor layer 10 is transparent and conductive. By using a high refractive index film,
Since the increase in sheet resistance of the P-type semiconductor layer 10 can be compensated for, the spectral characteristics and response characteristics can be improved.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Next, the spectral characteristics and light response characteristics of the embodiments of FIGS. 1 and 2 will be described in comparison with the conventional example. 3 shows the wavelength (nm) of incident light on the horizontal axis, the vertical axis shows the spectral characteristics showing the radiation sensitivity (A / W), and FIG. 4 shows the frequency (Hz) on the horizontal axis. The vertical axis represents the response characteristic indicating the relative output (dB). In these figures, (a) shows the characteristic of the conventional example, (b) shows the characteristic of the embodiment of FIG. 2) shows the characteristics of the embodiment of FIG. It is shown that the spectral characteristics and the light response characteristics of the embodiment are superior to the conventional semiconductor photoelectric conversion element. In particular, as in the embodiment shown in FIG. 2, by forming a hyper-step junction composed of a shallow diffusion layer and using a transparent conductive high refractive index film as its antireflection film, the radiation sensitivity (light receiving sensitivity) of the short wavelength in the ultraviolet region ) Is increased, the spectral characteristics are improved, and the response characteristics to light are improved.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

[0019]

As described above, according to the present invention, the antireflection film is a transparent conductive high refractive index film, the impurity concentration of the P-type semiconductor layer on the light receiving side is suppressed to a low level, and the depletion layer is exposed to ultraviolet rays. The short-wavelength light in the region can easily reach, or the step depth junction is formed by making the junction depth of the P-type semiconductor layer shallow so that the short-wavelength light in the ultraviolet region can be received. Is improved, so that the spectral characteristics and the response characteristics are improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Tamura 1500 Onjuku, Susono, Shizuoka Prefecture Yazaki Corporation

Claims (3)

[Claims] 1. A semiconductor photoelectric conversion element, wherein the antireflection film formed on the light receiving surface of the semiconductor photoelectric conversion element is made of a transparent conductive film. 2. In a semiconductor photoelectric conversion device, a semiconductor layer of a first conductivity type, an intrinsic semiconductor layer laminated on the semiconductor layer of the first conductivity type, and a first semiconductor layer formed on the intrinsic semiconductor layer. A semiconductor photoelectric conversion device comprising: a two-conductivity-type semiconductor layer; and an antireflection film formed of a transparent conductive film formed on the light-receiving surface of the second-conductivity-type semiconductor layer. 3. In a semiconductor photoelectric conversion element, a semiconductor layer of a first conductivity type, an intrinsic semiconductor layer formed on the semiconductor layer of the first conductivity type, and a first semiconductor layer formed on the intrinsic semiconductor layer. The semiconductor layer of the second conductivity type and the antireflection film formed of the transparent conductive film formed on the light receiving surface of the semiconductor layer of the second conductivity type, and the semiconductor layer of the first conductivity type having a shallow diffusion depth. The semiconductor photoelectric conversion device is characterized by having a super-junction.