JPH1084102A - Split photodiode and light-receiving element with built-in circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance photosensitivity in the split parts of a split photodiode as the light reflectivity on the light-receiving surface of the split photodiode is even by a method wherein a silicon nitride film is formed on a silicon oxide film formed on the entire surface of a semiconductor region of first conductivity type and an antireflection film is constituted of the silicon oxide film and the silicon nitride film. SOLUTION: A silicon oxide film 111 of an even film thickness is formed on the entire surface of a substrate 1 and a silicon nitride film 112 of an even film thickness is formed on the surface of the film 111. An antireflection film 110 on the light-receiving surface of a split photodiode is constituted of the films 111 and 112. The films 111 and 112 are set in such a film thickness as to constitute an antireflection film of low reflection to the wave length of light, which is used in a photopickup. Thereby, the light reflectivity on the light- receiving surface of the split photodiode is improved and the photosensitivity in the split parts of the split photodiode can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a divided photodiode and a light-receiving element with a built-in circuit, and more particularly to a structure for improving light sensitivity in a divided portion of a divided photodiode in which a light receiving region is divided into a plurality of photodetectors. .

[0002]

2. Description of the Related Art Such a divided photodiode has been conventionally used, for example, as a signal detecting element of an optical pickup.

In recent years, as optical disk devices have become smaller and more sophisticated, it has become important to reduce the size and weight of optical pickups.
In order to realize this, a function for generating a tracking beam, a function for performing optical branching, and a function for generating an error signal are integrated into one hologram element, and a laser diode, a photodiode, and the like are integrated into one hologram element. An optical module having a structure in which the hologram element is housed in a package (not shown) and the hologram element is arranged on the upper surface of the package has been proposed.

FIG. 5 shows a schematic configuration of the pickup optical system. Briefly explaining signal detection and burying in this optical system, light emitted from a laser diode LD is:
The tracking beam generating diffraction grating 30 disposed on the back side of the hologram element 31 divides the light beam into three light beams of two tracking sub-beams and an information signal reading main beam.

The light transmitted through the hologram element 31 on the upper surface of the package as 0-order light is converted into a parallel light by a collimator lens 32, and then converted into an objective lens 33.
Is focused on the disk 34. This disk 3
The reflected light modulated by the pits on 4 passes through the objective lens 33 and the collimating lens 32, is then diffracted by the hologram element 31, and has five divided light detecting portions D1 to D5 as l-order diffracted light. The light is guided onto the five-division photodiode PD.

The hologram element 31 is composed of two regions having different diffraction periods. Of the reflected light of the main beam, the light incident on one of the regions is detected by the photodetector D.
The reflected light of the main beam incident on the other area on the division line B dividing the light beams D2 and D3 is the light detection unit D4.
The light is focused on the top. The reflected light of the sub beam is condensed on the photodetectors Dl and D5 by the hologram element 31, respectively. In addition, the above optical system responds to a change in the distance between the hologram element 31 and the disc 34,
The position of the reflected light of the main beam on the photodiode PD changes in the direction in which the photodetectors D2 and D3 are arranged. When the main beam is focused on the disk,
The reflected light is incident on the division B between the photodetectors D2 and D3.

Accordingly, the five-division photodiode PD
Outputs corresponding to the respective light detection units D1 to D5 are represented by S1 to S5.
Then, the focus error signal FES is given by FES = S2-S3. On the other hand, a tracking error is detected by a so-called three-beam method. Since the two tracking sub-beams are respectively condensed on the photodetectors D1 and D5, the tracking error signal TES is given by TES = S1-S5. When the error signal TES is 0, it means that the main beam is located on the track to be irradiated. Further, the reproduction signal RF is given by RF = S2 + S3 + S4 as the sum of the outputs of the photodetectors D2 to D4 that receive the reflected light of the main beam.

As described above, in the divided photodiode, the laser beam is applied to the divided portion B, so that the light sensitivity and responsiveness in the divided portion B are important.

FIG. 3 is a diagram showing the structure of a divided photodiode incorporated in the configuration of the optical system.
2 shows a cross-sectional structure taken along the line II-III.

In FIG. 1, reference numeral 201 denotes the divided photodiode PD having an N-type silicon substrate 1 and a P-type diffusion layer 2 selectively formed in a surface region of the substrate 1. And each of the P-type diffusion layers 2 to detect signal light and output a photoelectrically converted signal.
2, D3, and D5. In FIG. 3,
Although not shown, the photodetector D4 shown in FIG. 5 is also formed on the surface of the substrate 1. Further, a silicon oxide film 11 is formed on the entire surface of the substrate 1, and the film thickness of a portion corresponding to the divided portion B of the divided photodiode is set so as to have low reflection with respect to the wavelength of light to be used. Is set.

Next, a brief description will be given of a method of manufacturing the split photodiode 201. First, a silicon oxide film 11 is formed on the entire surface of the N-type silicon substrate 1 by processing the substrate in an oxidizing atmosphere. Subsequently, the window of the oxide film 11 is opened by selectively removing the oxide film on the region where the photodetection section is to be formed by using a well-known photolithography technique and an oxide film etching technique. Next, P-type impurities are solid-phase diffused into the surface of the substrate through the opening of the oxide film 11 by using, for example, a deposition technique, thereby forming a P-type diffusion layer 2. By the heat treatment at this time, a silicon oxide film is formed on the surface of the P-type diffusion layer 2.

FIG. 4 is a view for explaining a sectional structure of a divided photodiode having a sectional structure different from that of the divided photodiode 201 shown in FIG. 3, and a sectional view corresponding to a line III-III in FIG. Shows the structure.

In the drawing, reference numeral 202 denotes the above-mentioned split photodiode. The split photodiode 202 is formed on the P-type diffusion layer 2 on the surface of the substrate 1 instead of the silicon oxide film 11 in the split photodiode 201 shown in FIG. A silicon oxide film 11a having an opening 11b in a corresponding portion is provided.
The silicon nitride film 12 is formed by a CVD method or the like on the surface of the substrate exposed in b. Other configurations are the same as those shown in FIG.

[0014]

In the divided photodiode used in the above-described optical pickup and the like, the light sensitivity and the responsiveness of the divided portion B are important. FIG. 6 shows the reflectance of light of a wavelength of 650 nm in the resin mold state of the divided photodiode 201 shown in FIG.
FIG. As shown in FIG. 6, in the range of the film thickness of the silicon oxide film, the light reflectance is 15 to 19%, and the silicon oxide film thickness of the divided portion of the divided photodiode is changed. Even if the reflectivity of the light is controlled so as to be low with respect to the light used, the reflectivity of the light can be reduced only to at most 15%. Will be high. Therefore, there is a problem that the light sensitivity of the divided photodiode cannot be sufficiently increased.

The divided photodiode 2 shown in FIG.
In 02, the oxide film on the P-type diffusion layer 2 portion of the silicon substrate 1 is removed to form an oxide film opening 11b. In this state, a silicon nitride film having a higher refractive index than the silicon oxide film is formed on the entire surface. Therefore, the light reflectance on the P-type diffusion layer 2 can be made low (about 3%).

However, since the silicon oxide film 11a is formed on the surface of the split portion B of the split photodiode on which light is incident, the silicon oxide film 11a is formed on the P-type diffusion layer 2 where only the silicon nitride film is formed. The light reflectance differs on the divided portion where the silicon nitride film is formed via the film.

FIG. 7 shows the reflectance of light on the substrate surface in a structure in which a silicon nitride film is laminated on a silicon substrate with a silicon oxide film interposed therebetween, in a range of a predetermined thickness (0 to 700 nm) of the silicon oxide film. ). This FIG.
From this, it can be seen that the reflectance of the light greatly differs depending on the thickness of the oxide film.

The divided photodiode 2 shown in FIG.
In the structure of No. 02, the oxide film thickness at the divided portion B is determined by the heat treatment for forming the silicon oxide film over the entire surface of the N-type silicon substrate 1 and the formation of the P-type diffusion layer 2 by solid-phase diffusion of P-type impurities. The thickness variation of the oxide film in the divided portion depends on the variation in the heat treatment when forming the silicon oxide film and the variation in the heat treatment when forming the P-type diffusion layer 2. receive. For this reason, it is difficult to control the oxide film thickness of the divided portion with high accuracy.

Therefore, in some cases, there is a problem in that a divided photodiode having low photosensitivity is produced due to a variation in the oxide film thickness.

In order to accurately control the thickness of the oxide film in the divided portion, a method of etching the silicon oxide film by wet etching to form a desired silicon oxide film before forming the silicon nitride film is known. As conceivable, performing such an etching process requires a step of measuring the thickness of the silicon oxide film before etching, which leads to an increase in cost. Also, in this case, the thickness of the silicon oxide film in the forming process varies.
In addition, the thickness of the oxide film in the divided portion cannot be controlled with sufficient accuracy because the thickness of the film is varied in the etching process.

Accordingly, the light reflectance at the divisional portion to which light is irradiated in an actual use state varies in the manufacturing process of the divided photodiodes, so that it is not possible to obtain a divided photodiode having a sufficiently low reflection. .

If a silicon nitride film is directly formed on the surface of the N-type silicon substrate 1 by a method such as CVD in order to reduce the light reflectivity at the divided portion of the divided photodiode, the reflection on the divided portion is reduced. In this case, the PN junction formed by the N-type silicon substrate 1 and the P-type diffusion layer 2 is not covered with the thermal oxide film, and the PN junction directly contacts the silicon nitride film. Therefore, there is a problem that junction leakage increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is intended to reduce the light sensitivity at the divided portion irradiated with the light beam without increasing the junction leak and at the light receiving surface. It is an object of the present invention to obtain a divided photodiode capable of improving the light reflectance while preventing the light reflectance from becoming non-uniform, and a light receiving element with a built-in circuit equipped with the same.

[0024]

According to a first aspect of the present invention, there is provided a divided photodiode, comprising: a first conductivity type semiconductor region; and a plurality of selectively formed surface regions of the first conductivity type semiconductor region. A second conductivity type semiconductor layer, wherein the first conductivity type semiconductor region and each of the second conductivity type semiconductor layers constitute a plurality of photodetectors for detecting signal light and outputting a photoelectric conversion signal thereof. Is what it is.

This divided photodiode has a uniform thickness silicon oxide film formed on the entire surface of the first conductivity type semiconductor region, and a uniform thickness silicon nitride film formed on the silicon oxide film. And the silicon oxide film and the silicon nitride film constitute an antireflection film. Thereby, the above object is achieved.

According to a second aspect of the present invention, there is provided a divided photodiode, comprising: a first conductivity type semiconductor region; a second conductivity type semiconductor layer formed on the first conductivity type semiconductor region;
A first conductivity type semiconductor layer formed so as to reach the surface of the first conductivity type semiconductor region from the surface of the conductivity type semiconductor layer and dividing the second conductivity type semiconductor layer into a plurality of second conductivity type semiconductor regions. The first conductivity type semiconductor region and each of the second conductivity type semiconductor regions constitute a plurality of photodetectors for detecting signal light and outputting the photoelectric conversion signal.

This divided photodiode has a uniform thickness silicon oxide film formed on the entire surface of the second conductivity type semiconductor layer, and a uniform thickness silicon nitride film formed on the silicon oxide film. And the silicon oxide film and the silicon nitride film constitute an antireflection film. Thereby, the above object is achieved.

According to a third aspect of the present invention, there is provided a photodetector with a built-in circuit, wherein the circuit element constituting the signal processing circuit for processing the photoelectric conversion signal is the same as the semiconductor chip together with the divided photodiode according to the first or second aspect. It is mounted on top.

According to a fourth aspect of the present invention, in the photodetector with a built-in circuit according to the third aspect, the silicon oxide film formed on the surface of the divided photodiode is replaced by an oxidation process using an oxidizing atmosphere containing water vapor. This is an oxide film formed by an oxidation treatment.

According to a fifth aspect of the present invention, in the photodetector with a built-in circuit according to the third or fourth aspect, the silicon oxide film has a thickness of 50 nm or less.

Hereinafter, the operation of the present invention will be described.

In the present invention (claims 1 and 2), a silicon oxide film having a uniform thickness formed on the entire surface of the first conductivity type semiconductor region serving as a light receiving surface in the divided photodiode, and the silicon oxide film Having a silicon nitride film having a uniform thickness formed thereon and forming an anti-reflection film on the surface of the divided photodiode by the silicon oxide film and the silicon nitride film.
Without increasing junction leakage at each photodetector comprising the first conductivity type semiconductor region and the second conductivity type semiconductor layer selectively formed on the surface thereof, and at the center of the photodiode in the divided photodiode The light reflectance at the divided portion can be reduced while avoiding non-uniform light reflectance at the divided portion. Thereby, the light sensitivity at the divisional portion of the divided photodiode can be improved without increasing the junction leak and making the light reflectance nonuniform on the surface of the divided photodiode.

In the present invention (claim 3), the circuit elements constituting the signal processing circuit for processing the photoelectric conversion signal from the photodetector are mounted on the same semiconductor chip together with the divided photodiode. It is possible to obtain a light-receiving element with a built-in circuit equipped with a divided photodiode having improved light sensitivity without increasing junction leakage or causing non-uniform light reflectance on the surface of the divided photodiode.

According to the present invention (claim 4), the silicon oxide film formed on the surface of the divided photodiode is
Since the oxide film was formed by an oxidation process other than the wet oxidation process using an oxidizing atmosphere containing water vapor, NPN was used.
The breakdown voltage characteristics of the transistor can be favorably maintained.

In the present invention (claim 5), since the thickness of the silicon oxide film is set to 50 nm or less, the oxidation process for a long time is avoided, and the breakdown voltage characteristic of the NPN transistor is prevented from being deteriorated by the oxidation process. it can.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIG. 1 is a view for explaining a split photodiode according to Embodiment 1 of the present invention, and shows a cross-sectional structure thereof. In this figure, structures formed after the metal wiring processing step, for example, a multilayer structure, a protective film, and the like are omitted.

In the figure, reference numeral 101 denotes a divided photodiode according to the first embodiment, which is an N-type silicon substrate (first conductive type semiconductor region) 1 and a P-type diffusion layer selectively formed in a surface region of the substrate 1. 2 (second conductive type semiconductor layer), and the substrate 1 and each of the P-type diffusion layers 2 detect signal light and output a photoelectric conversion signal thereof.
2, D3, and D5. Although not shown in FIG. 1, a portion corresponding to the photodetector D4 shown in FIG. 5 is also formed on the surface of the substrate 1.

A silicon oxide film 111 having a uniform thickness is formed on the entire surface of the substrate 1, and a silicon nitride film 112 having a uniform thickness is formed on the surface of the silicon oxide film 111.
Are formed, and the silicon oxide film 111 and the silicon nitride film 112 thereon form an antireflection film 110 on the light receiving surface of the divided photodiode.

Next, a method of manufacturing the split photodiode 101 will be briefly described. First, as in the conventional method of manufacturing the divided photodiode 201, the N-type silicon substrate 1 is treated in an oxidizing atmosphere to form a silicon oxide film on the entire surface. Next, the well-known photo
The window of the oxide film is opened using the lithography technology and the oxide film etching technology. That is, the oxide film on the region where the photodetectors D1 to D5 are to be formed on the substrate surface is selectively removed to form an oxide film opening.

Next, for example, using a deposition technique,
P-type impurities are solid-phase-diffused on the substrate surface through the oxide film openings to selectively form a P-type diffusion layer 2. At the time of the heat treatment at this time, a silicon oxide film is formed on the surface of the P-type diffusion layer 2 simultaneously with the formation of the P-type diffusion layer 2.

Then, the silicon oxide film on the photodiode region P including the divided portion B is once removed, and then heat treatment is performed again in an oxidizing atmosphere, so that the photodiode region P including the divided portion B is removed. A silicon oxide film 111 is formed. As a result, the oxide film thickness of the divided portion B of the divided photodiode 101 is only affected by the variation in the heat treatment, and therefore, a silicon oxide film having a small variation in film thickness can be formed.

Further, a silicon nitride film 112 is formed on the silicon oxide film 111 by a method such as CVD.
At this time, the silicon oxide film 111 and the silicon nitride film 11
2, the film thickness is set so as to form an antireflection film having low reflection with respect to the wavelength of light used in the optical pickup.

For example, as shown in FIG. 7, when the wavelength of light used in the optical pickup is 650 nm and the thickness of the silicon nitride film 112 is 50 nm, the thickness of the silicon oxide film 111 is set to, for example, 30 nm. You.

As described above, by setting the thickness of the silicon oxide film 111 and the thickness of the silicon nitride film 112 constituting the antireflection film 110, the divided photodiode 10
The light reflectivity can be reduced to about 4% over the entire light receiving surface of No. 1. That is, in the divided photodiode 101 of the first embodiment, the light reflectance is 15 to 19% in comparison with the conventional divided photodiode 201 using only the silicon oxide film as the antireflection film. The rate has been improved by 10% or more, which means that the photosensitivity at the divided portion of the divided photodiode has been improved by 10% or more.

(Embodiment 2) FIG. 2 shows Embodiment 2 of the present invention.
FIG. 1 is a diagram for explaining a light-receiving element with a built-in circuit according to FIG. In this figure, as in the divided photodiode of the first embodiment shown in FIG. 1, the structure formed after the metal wiring processing step, for example, a multilayer structure, a protective film, and the like are omitted.

In the drawing, reference numeral 102 denotes a light receiving element with a built-in circuit according to the second embodiment. The light receiving element 102 is different from the light receiving element according to the first embodiment in which the configuration of the anti-reflection film in the divided photodiode 101 of the first embodiment is applied. Has a structure in which divided photodiodes having different structures are mounted on the same semiconductor chip as a circuit element for processing a photodetection signal.

In this light receiving element 102, the divided photodiode is a photodiode region P of the P-type silicon substrate 3.
1, a P-type silicon substrate (first conductivity type semiconductor region) 3, an N-type epitaxial layer (second conductivity type semiconductor layer) 6 formed on the P-type silicon substrate 3,
A P-type diffusion layer (first conductive type semiconductor) formed so as to reach the surface of the P-type silicon substrate 3 from the surface of the N-type epitaxial layer 6 and dividing the N-type epitaxial layer 6 into a plurality of N-type epitaxial regions 6a. Layers) 5 and 7). In this divided photodiode, the P-type silicon substrate 3 and each of the N-type epitaxial regions 6a detect a signal light and output a photoelectric conversion signal to the photodetector D.
1, D2, D3, and D5. Although not shown in FIG. 1, a portion corresponding to the light detection unit D <b> 4 shown in FIG. 5 is also formed on the surface of the substrate 3.

In a circuit element region S of the P-type silicon substrate 3 which is electrically separated from the photodiode region P1, a signal for processing a photoelectric conversion signal photoelectrically converted by the divided photodiode is provided. An NPN transistor is formed as a circuit element constituting the processing circuit. In the circuit element region S, the P-type silicon substrate 3 and N
An N-type buried layer 4 is formed at the boundary between the N-type epitaxial layer 6 and the N-type buried layer 4.
A P-type diffusion layer 8 serving as a base diffusion region of the NPN transistor is formed in a portion facing the mold buried layer 4.
On the surface of the P-type diffusion layer 8, an N-type diffusion layer 9 serving as an emitter diffusion region of the NPN transistor is formed.
Here, the N-type epitaxial region 6b between the P-type diffusion layer 8 and the N-type buried layer 4 is a collector region of the NPN transistor. Further, an N-type diffusion layer 10 is formed on the surface of the N-type epitaxial region 6b so as to be adjacent to the P-type diffusion layer 8 so as to face the N-type buried layer 4. Reference numeral 10 denotes a diffusion region for taking out a collector electrode.

A silicon oxide film 111 having a uniform thickness is formed on the entire surface of the N-type epitaxial layer 6, and a silicon nitride film 112 having a uniform thickness is formed on the surface of the silicon oxide film 111. Is formed, and the silicon oxide film 111 and the silicon nitride film 112 form an antireflection film 11 on the light receiving surface of the split photodiode.
0 is configured.

Next, a method of manufacturing the light receiving element 102 with a built-in circuit will be described. First, the P-type silicon semiconductor substrate 3
An N-type buried diffusion layer 4 is formed in a circuit element region S on which an NPN transistor is to be formed on the surface of the semiconductor device, and then a P region is formed in a region serving as a dividing portion of a divided photodiode and a region serving as a separating portion of each circuit element. A mold buried diffusion layer 5 is formed.

Subsequently, an N-type epitaxial layer 6 is formed on the entire surface of the P-type silicon substrate 3 including the N-type buried diffusion layer 4 and the P-type buried diffusion layer 5. Thereafter, a P-type diffusion layer 7 is formed so as to reach the P-type buried diffusion layer 5 from the surface of the N-type epitaxial layer 6. As a result, a region that becomes the division portion B of the division photodiode and a region that electrically separates circuit elements are formed, and a plurality of divided photodetectors in the division photodiode are formed. The circuit element is electrically separated from the circuit element. By the heat treatment at this time, a silicon oxide film is formed on the surfaces of the N-type epitaxial layer 6 and the P-type diffusion layer 7 simultaneously with the formation of the P-type diffusion layer 7.

Next, a P-type diffusion layer 8 serving as a base diffusion region of the NPN transistor is formed in a part of the circuit element region S where the NPN transistor is formed, and an emitter diffusion region is formed in a part of the base diffusion region. An N-type diffusion layer 9 to be formed and an N-type diffusion layer 10 to be a diffusion region for taking out a collector electrode of an NPN transistor are formed adjacent to the base diffusion region.

After that, as in the first embodiment, the silicon oxide film on the photodiode region P1 including the divided portion is removed, and heat treatment is performed again in an oxidizing atmosphere, so that the photodiode region P1 including the divided portion is removed. A silicon oxide film 111 is formed. Further, the silicon oxide film 111
A silicon nitride film 112 is formed thereon by a method such as CVD. At this time, the thicknesses of the silicon oxide film 111 and the silicon nitride film 112 are set so as to form the antireflection film 110 having low reflection with respect to the wavelength of light used in the optical pickup.

Here, in the step of removing the silicon oxide film on the photodiode region P1 including the divided portion B and performing the heat treatment again using an oxidizing atmosphere,
A silicon oxide film was formed by an oxidation treatment other than a wet oxidation treatment (steam oxidation treatment) using an oxidizing atmosphere containing water vapor.

FIG. 8 shows the wet oxidation treatment and the HC treatment, respectively.
1 shows the results of measuring the change in the oxide film thickness before and after the oxidation treatment in each part of the NPN transistor as the circuit element for each oxidizing atmosphere used in the oxidation treatment and the dry oxidation treatment. In this measurement test, as a sample, an NPN transistor is formed in an N-type epitaxial layer on a P-type silicon substrate as in the case of the light receiving element according to the second embodiment, and an emitter diffusion region, a base diffusion region, and an element of the NPN transistor are formed. An oxide film having a predetermined thickness (before oxidation) as shown in FIG. 8 is used in advance on a field region for isolation.

As shown in FIG. 8, only the sample subjected to the wet oxidation treatment is abnormally oxidized on the emitter diffusion region.
Further, it can be seen that oxidation is progressing also on the base diffusion region.

FIG. 9 shows the results of the above wet oxidation treatment and H
The graph shows the breakdown voltage characteristics of the NPN transistor in the sample subjected to the Cl oxidation treatment and the dry oxidation treatment.

As can be seen from FIG. 9, the sample subjected to the oxidation treatment other than the wet oxidation treatment has a good breakdown voltage characteristic of the NPN transistor, but the sample subjected to the wet oxidation treatment has a large breakdown voltage characteristic of the NPN transistor. Is declining.

FIG. 10 shows the reason for such deterioration of the breakdown voltage characteristics.
This will be briefly described with reference to FIG. FIG. 10 shows a detailed sectional structure near the emitter diffusion region 9 and the base diffusion region 8 of the NPN transistor.

When the wet oxidation treatment is performed, the oxidation rate on the surface of the junction between the emitter diffusion region 9 and the base diffusion region 8 (hereinafter referred to as the emitter-base junction) is large, and therefore, the -Excessive stress due to wet oxidation is applied to the locos edge portion A of the base joint. In FIG. 10, reference numeral 20 denotes a LOCOS oxide film (SiO.sub.2).
₂ film). As a result, crystal defects occur at the emitter-base junction, and the breakdown voltage characteristics of the NPN transistor are degraded.

Accordingly, the above-mentioned photodiode portion P is formed by an oxidation process other than the wet oxidation process (steam oxidation process).
By performing the re-oxidation in step 1, it is possible to avoid a decrease in yield due to a breakdown voltage failure of the NPN transistor mounted on the same chip as the divided photodiode.

Even in the case of using an oxidation process other than the wet oxidation process (steam oxidation process), if the oxidation process is performed for a long time, the oxidation on the emitter diffusion region 9 and the base diffusion region 8 proceeds. , The breakdown voltage characteristics of the NPN transistor decrease.

Therefore, in consideration of this and the relationship between the oxide film thickness and the light reflectance shown in FIG. 7, it is desirable to set the film thickness of the silicon oxide film to 50 nm or less.

[0064]

As described above, according to the present invention, the anti-reflection film of the divided photodiode is formed by a silicon oxide film formed on the entire surface of the photodiode forming region including the divided portion.
Since a laminated structure composed of the silicon nitride film and the silicon nitride film formed on the surface of the silicon oxide film is used, the light sensitivity at the divided portion irradiated with the light beam can be increased by increasing the junction leakage and the light at the surface of the divided photodiode. There is an effect that the reflectance can be improved without causing non-uniformity of the reflectance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a sectional structure of a divided photodiode according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a sectional structure of a divided photodiode according to a second embodiment of the present invention.

FIG. 3 is a diagram showing a cross-sectional structure of a conventional split photodiode.

FIG. 4 is a diagram showing another cross-sectional structure of a conventional split photodiode.

FIG. 5 is a diagram showing a configuration of an optical pickup using a conventional split photodiode.

FIG. 6 is a diagram showing the relationship between light reflectance and oxide film thickness when only SiO ₂ (oxide film) is formed as an antireflection film on the light receiving surface of a divided photodiode.

FIG. 7 is a diagram showing the relationship between light reflectance and oxide film thickness when SiN and SiO ₂ are formed as an anti-reflection film on the light receiving surface of a divided photodiode.

FIG. 8 is a diagram showing a change in an oxide film thickness of each part of an NPN transistor due to an oxidation process using an oxidizing atmosphere for various oxidation processes.

FIG. 9 is a diagram showing the effect of the oxidation treatment using an oxidizing atmosphere on the breakdown voltage characteristics of the NPN transistor for various oxidation treatments.

FIG. 10 is a diagram showing a detailed cross-sectional structure in the vicinity of an emitter diffusion region and a base diffusion region of an NPN transistor.

[Explanation of symbols]

 Reference Signs List 1 N-type silicon substrate 2 P-type diffusion layer 3 P-type silicon substrate 4 N-type buried layer 5 P-type buried layer 6 N-type epitaxial layer 6 a, 6 b N-type epitaxial region 7 P-type diffusion layer 8 P-type base diffusion layer 9 N -Type emitter diffusion layer 10 N-type diffusion layer for taking out collector electrode 101 Divided photodiode 102 Light receiving element with built-in circuit 110 Anti-reflection film 111 Silicon oxide film 112 Silicon nitride film B Division D1-D5 Photodetector P, P1 Photodiode area S Circuit element area

Claims (5)

[Claims] A first conductive type semiconductor region; and a plurality of second conductive regions selectively formed on a surface portion of the first conductive type semiconductor region.
A first conductive type semiconductor region and each of the second conductive type semiconductor layers, a plurality of photodetectors configured to detect signal light and output a photoelectric conversion signal thereof are configured. A photodiode having a uniform thickness silicon oxide film formed on the entire surface of the first conductivity type semiconductor region; and a uniform thickness silicon nitride film formed on the silicon oxide film. A divided photodiode in which an anti-reflection film is formed by the silicon oxide film and the silicon nitride film. 2. A first conductivity type semiconductor region, a second conductivity type semiconductor layer formed on the first conductivity type semiconductor region, and a first conductivity type semiconductor region from a surface of the second conductivity type semiconductor layer. A first conductivity type semiconductor layer formed to reach the surface of the first conductivity type and dividing the second conductivity type semiconductor layer into a plurality of second conductivity type semiconductor regions. A divided photodiode in which a plurality of photodetectors for detecting signal light and outputting the photoelectric conversion signal by the type semiconductor region are formed, and the uniform photodiode formed on the entire surface of the second conductive type semiconductor layer A silicon oxide film having a uniform thickness and a silicon nitride film having a uniform thickness formed on the silicon oxide film, wherein the silicon oxide film and the silicon nitride film constitute an antireflection film. Photodiode. 3. A light receiving element with a built-in circuit, wherein a circuit element constituting a signal processing circuit for processing the photoelectric conversion signal is mounted on the same semiconductor chip together with the divided photodiode according to claim 1. 4. The photodetector with a built-in circuit according to claim 3, wherein the silicon oxide film formed on the surface of the divided photodiode is formed by an oxidation process other than an oxidation process using an oxidizing atmosphere containing water vapor. A light receiving element with a built-in circuit. 5. The light-receiving element with built-in circuit according to claim 3, wherein the silicon oxide film is formed to have a thickness of 50 nm or less.