JPH07297443A - Photoreceptor element - Google Patents

Abstract

PURPOSE:To provide a photoreceptor element having a plurality of photodiodes on one chip and can operate at a high speed without giving any adverse influence to its light sensitivity profile. CONSTITUTION:A plurality of photodiodes D1,..., D5 are arranged in the X- direction with dividing areas X1,..., X3 elongated in the Y-direction (perpendicular to the plane of the figure) in belt-like states in a light receiving area D in between on the surface of a P-type semiconductor substrate 1. An N-type semiconductor layer 4 is formed on the surface of the substrate 1 so that the photodiodes D1,..., D5 can generate their outputs through the P-N junction formed by the semiconductor layer 4 and substrate 1. First P-type separating diffusion layers 3 and 5 are formed in the dividing areas X1,..., X3. First light shielding layers 9 which cover the separating diffusion layers 3 and 5 are provided in the dividing areas X1 and X3 other than the area X2 which receives a condensed beam at the operating time and N<+>-type buried diffusion layers are partially provided immediately below the light shielding layers 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light receiving element, and more particularly to a split type photodiode used for forming an optical pickup. The present invention can be applied to a circuit built-in light receiving element in which a circuit for processing a photoelectric conversion signal is built in the same chip.

[0002]

2. Description of the Related Art In recent years, as optical disc devices have become smaller and have higher performance, the reduction in size and weight of optical pickups has become an important issue. As an optical pickup that realizes this, FIG.
As shown in, a structure is proposed in which a tracking beam generation function, an optical branching function, and an error signal generation function are integrated in one hologram element 202, and a laser diode LD and a five-division photodiode PD are arranged in one package. ing. The five-division photodiode PD has a rectangular chip shape as a whole, and individually produces outputs.
Two photo detectors (hereinafter referred to as "photodiodes") D
1, D2, D3, D4, D5. The photodiodes D1 and D5 are provided along the opposing long sides of the chip, respectively, and the photodiode D4 occupies half of the region sandwiched by the photodiodes D1 and D5 in the longitudinal direction. The photodiodes D2 and D3 are provided by dividing the remaining area in the longitudinal direction. The five-division photodiode PD is arranged beside the laser diode LD with the long side of the chip facing the laser diode LD.

In this optical pickup, the laser light emitted from the laser diode LD passes through the diffraction grating 201 for tracking beam generation, and thereby three laser beams, that is, two tracking sub-beams and an information signal reading main beam are provided. Divided into light beams. Then, the hologram element 202 is transmitted as zero-order light, and the collimator lens 203
After being converted into parallel light by
It is focused on the recording surface of the disk 205. Disc 205
The reflected light that has been modulated by the pits in the recording surface passes through the objective lens 204 and the collimator lens 203, is diffracted by the hologram element 202, and is guided to the five-division photodiode PD as first-order diffracted light.
The hologram element 202 is composed of two regions having different diffraction periods. Of the reflected light of the main beam, the light incident on one region of the hologram element 202 is condensed on the dividing line of the photodiodes D2 and D3, while the light incident on the other region of the hologram element 202 is the photodiode. It is focused on D4. Further, the reflected light of the sub-beam is collected on the photodiodes D1 and D5, respectively. Here, the output of each photodiode is S
Assuming 1, S2, S3, S4, S5, the focus error signal FES is given by FES = S2-S3. The tracking error is detected by the so-called 3-beam method. Since the tracking sub-beams are focused on the photodiodes D1 and D5, respectively, the tracking error signal TES is given by TES = S1-S5. The reproduction signal RF is given by RF = S2 + S3 + S4.

When manufacturing an optical pickup, since the laser diode LD and the five-division photodiode PD are incorporated into one package, the diffraction grating 201 and the hologram element 202 are bonded to the upper surface of the package. Positioning variations with the photodiode PD occur. In addition, the diffraction angle of the diffracted light that has passed through the hologram element 202 changes due to the variation in the oscillation wavelength of the laser diode LD among individuals and the change in the oscillation wavelength of the laser diode LD due to the temperature change.
It changes in the direction connecting the laser diode LD and the photodiode PD (hereinafter referred to as “Y direction”). Therefore, as shown in detail in FIG. 11, the pattern of each photodiode needs to be long in the Y direction.

On the other hand, in the direction perpendicular to the Y direction (hereinafter referred to as the "X direction"), the oscillation wavelength of the laser diode LD varies among individuals, and the oscillation wavelength change of the laser diode LD due to temperature fluctuation may be different. The incident position on the photodiode PD does not change. Further, the positional variation between the laser diode LD and the photodiode PD can be adjusted by rotating the hologram element 202 adhered to the upper surface of the package. Therefore, it is not necessary to lengthen the pattern of each photodiode in the X direction. Rather, in the X direction, 3 arranged in this X direction
If the beams are distant from each other, adjustment becomes difficult when the optical pickup is incorporated into the optical disk device. Therefore, the width of each photodiode D1, D2, D3, D4, D5 and the area separating the adjacent photodiodes (hereinafter referred to as "division area"). The width of X1, X2, X3, X1 ', X3' must be narrowed.

For this reason, the pattern of each photodiode is set to be long in the Y direction and short in the X direction, and as a result, the overall shape of the photodiode PD is also a rectangle long in the Y direction. In addition, each divided area X1, X
Since the widths of 2, X3, X1 ', and X3' must be narrowed, the electrodes of each photodiode are provided outside the light receiving region (region defined by the envelope of the pattern of all photodiodes) D. There is. That is, the anode electrodes E _A and E _A ′ are connected to the photodiodes D1, D2 and D, respectively.
3, D4 and D5 are common and are provided along the outer long sides of the photodiodes D1 and D5, respectively. In addition, each photodiode D1, D2, D3, D
4, cathode electrodes E _C1 , E _C2 , E _C3 , E corresponding to D5
_C4 and E _C5 are provided along the outer short side of each photodiode.

The five-division photodiode PD is manufactured by the procedure shown in FIG.
(Corresponding to the AA ′ line cross section of 1). First, as shown in FIG. 12B, the P-type buried diffusion layers 103, 103, 103 are formed on the surface of the P-type silicon substrate 101 at the portions to be the divided regions X1, X2, X3. At the same time, the P-type buried diffusion layers 103 ′, 1 are formed at the positions which should be the boundaries of the light receiving region D.
To form 03 '. Next, as shown in FIG. 12 (a), an N-type epitaxial layer 104 is formed on the entire surface of the substrate 101, and subsequently, N-type epitaxial layers 104 and 103 'are formed at locations corresponding to the P-type buried diffusion layers 103 and 103'. P-type isolation diffusion layers 105 and 105 'reaching the P-type buried diffusion layers 103 and 103' from the surface of the epitaxial layer 104 are formed. This P-type buried diffusion layer 1
03, 103 'and P-type isolation diffusion layers 105, 105'
The portions of the N-type epitaxial layer 104 belonging to the photodiodes D1, D2, D3, D5 are electrically isolated. Next, the P-type isolation diffusion layer 105 'at the right end
A shallow P-type diffusion layer 106 is formed in a region extending from the surface to the surface of the P-type isolation diffusion layer 105 'at the left end. At the same time, the silicon oxide film 107 is formed on the surface of the P-type diffusion layer 106.
Is formed. Next, of the oxide film 107, the P-type isolation diffusion layer 105 ′ on the right end to the P-type isolation diffusion layer 1 on the left end is formed.
The part up to 05 'is removed and a silicon nitride film 108 is provided instead. The film thickness of the silicon nitride film 108 is set according to the wavelength of the laser diode so that the film 108 acts as an antireflection film. After that, as shown in FIG. 11, the photodiodes D1, D2, D3, D
Anode electrodes E _A and E _A ′ common to the electrodes 4 and D5 and cathode electrodes E _C1 , E _C2 , E _C3 , E _C4 and E _C5 corresponding to the photodiodes D1, D2, D3, D4 and D5, respectively. Form. In this way, five photodiodes D
1, D2, D3, D4, D5 are formed (this structure is the structure proposed in Japanese Patent Laid-Open No. 4-180269).

The divided areas X1 'and X3' have the same structure as the divided areas X1 and X3.

In this structure, the divided regions X1, X2, X
Since the surface portions of the PN junctions formed on both sides of 3, X1 'and X3' are covered with the P-type diffusion layer 106, the nitride film 108 is directly provided thereon, but the junction leak increases. There is no such thing. Further, since the silicon nitride film 8 is provided in the divided region X2 that actually receives the focused beam during operation, and the antireflection structure is formed as in the pattern of the photodiodes D2 and D3, the sensitivity can be enhanced.

[0010]

However, in the above-mentioned conventional five-division photodiode PD, the division region X2 is used.
Not only that, the divided regions X1, X3, X1 ', X3' also have an antireflection structure, so that there is a problem that the signal-to-noise ratio (S / N ratio) is lowered when stray light or the like is incident.

Further, as shown in FIG. 12, cathode electrodes E _C1 , E _C2 , E _C3 , E _C4 , and E _C5 are provided along the outer short sides of the photodiodes D1, D2, D3, D4, D5. Therefore, as shown in FIG. 13 (corresponding to the BB ′ line cross section in FIG. 11), the N-type epitaxial layer 104 is formed.
There is a problem that the internal resistance R increases along the longitudinal direction of the. As is known, an increase in internal resistance R
This increases the R time constant (the product of the junction capacitance of the photodiode and the internal resistance), which hinders the speedup of each photodiode.

When the pattern size of the photodiode D2 was set to 40 μm × 400 μm and the magnitude of the internal resistance R was roughly calculated, the following results were obtained. For example, the specific resistance of the N-type epitaxial layer 104 is set to 1
Ωcm, its thickness is 3 μm, and the specific resistance of the substrate 101 is 1
When the resistance is 0 Ωcm, the series resistance on the cathode side of the photodiode D2 is 33 kΩ. On the other hand, regarding the series resistance on the anode side, considering that the anode electrode is formed along the outer long side of the entire split photodiode, 20 μm in the depth direction of the substrate 101 contributes to the internal resistance. I shall. Then, the photodiode D2
The distance from the anode electrode E _A to 100 μm. At this time, the series resistance on the anode side of the photodiode D2 becomes 1 kΩ or less. From this result, it can be seen that the increase in the internal resistance is mainly due to the increase in the series resistance R on the cathode side.

In order to reduce the internal resistance of each photodiode, if the N-type buried diffusion layer is simply formed between the substrate 101 of each photodiode and the N-type epitaxial layer 104, the sensitivity of each photodiode is increased. The problem arises that the profile changes. That is, since the depth of the PN junction changes at the place where the N-type buried diffusion layer is provided, the conversion efficiency changes depending on the place where the laser light is incident.

Therefore, an object of the present invention is to provide a light receiving element having a plurality of photodiodes in the same chip,
An object of the present invention is to provide a light receiving element that can maintain a high S / N ratio even when stray light enters. At the same time, another object of the present invention is to provide a light-receiving element capable of realizing high-speed operation by reducing the internal resistance of each photodiode without adversely affecting the sensitivity profile.

[0015]

In order to achieve the above-mentioned object, a light-receiving element according to claim 1 is provided on a semiconductor substrate having a first conductivity type in one direction along the substrate surface and in this one direction. A plurality of photodiodes extending in the one direction are formed side by side in the other direction in the light receiving region with a divided region extending in the one direction in a strip shape therebetween. A semiconductor layer having a second conductivity type is formed on the semiconductor substrate, each photodiode includes a part of the semiconductor layer, and the semiconductor layer and the semiconductor substrate are An output is generated through a PN junction formed by the semiconductor device, the divided region having the first conductivity type, reaching the surface of the semiconductor substrate from the surface of the semiconductor layer, Photo die In a light receiving element in which a first separation diffusion layer that electrically separates portions belonging to each other from each other is formed, in the division regions other than the division region that receives a focused beam during operation, the first division diffusion layer is formed. The first light-shielding layer that covers the separation diffusion layer is provided.

Further, in the light receiving element according to claim 2, the width of the first light shielding layer in the other direction is set to be wider than the width of the first isolation diffusion layer in the other direction, and the second direction. A first buried diffusion layer having a conductivity type set to have a higher impurity concentration than that of the semiconductor layer and extending in the one direction between the semiconductor substrate and the semiconductor layer directly below the first light shielding layer. It is characterized by

According to a third aspect of the present invention, in a light receiving element, a photodiode formed at both ends of the light receiving area in the other direction and a portion outside the light receiving area are electrically isolated from each other. A second isolation diffusion layer of the first conductivity type is formed, and a second light-shielding layer that covers the second isolation diffusion layer and extends over the photodiodes at both ends in the other direction by a predetermined width is provided. The photodiodes at both ends in the other direction have the second conductivity type and are set to have a higher impurity concentration than the semiconductor layer, and the photodiode is formed between the semiconductor substrate and the semiconductor layer directly below the second light shielding layer. A second buried diffusion layer extending in the above-mentioned one direction is formed.

Further, a light receiving element according to a fourth aspect is the light receiving element according to any one of the first to third aspects, wherein each of the photo detectors is provided in a region of the semiconductor substrate outside the light receiving region. A feature is that a signal processing circuit that processes a signal output from the diode is formed.

[0019]

In the light-receiving element according to the first aspect, the first light-shielding layer that covers the first separation / diffusion layer is provided in the divided regions other than the divided region that receives the focused beam during operation. Even if stray light or the like enters the light receiving region, the stray light is blocked by the first light shielding layer. It does not enter the first separation diffusion layer provided in the divided region that does not receive the focused beam. Therefore, the signal-to-noise ratio (S / N ratio) is kept high as compared with the conventional light receiving element.

In the light receiving element of the second aspect, the first buried diffusion layer having the same conductivity type as that of the semiconductor layer on the substrate and having a higher impurity concentration than that of the semiconductor layer is formed. The first buried diffusion layer has a lower resistance than the semiconductor layer, depending on the setting of the impurity concentration. Since the first buried diffusion layer extends in one direction between the semiconductor substrate and the semiconductor layer, the internal resistance of each photodiode in the one direction is reduced. Therefore, high-speed operation becomes possible as compared with the conventional case. Further, since the first buried diffusion layer is provided directly below the first light shielding layer, light does not enter the region of the first buried diffusion layer. Therefore, as compared with the case where the first buried diffusion layer is not provided,
The sensitivity profile of each photodiode does not change and is not adversely affected.

According to a third aspect of the present invention, a second isolation diffusion layer is formed on both ends of the light receiving region in the other direction, and the second isolation diffusion layer is covered and the photodiodes on both ends of the other direction are formed. The second that extends above each by a predetermined width
Immediately below the light-shielding layer, a second buried diffusion layer having a lower resistance than the semiconductor layer is formed according to the setting of the impurity concentration. The second buried diffusion layer reduces the internal resistance of the photodiodes at both ends in the other direction in the one direction. As a result, in the photodiodes on both ends in the other direction, there is a room to omit the first buried diffusion layer on the divided region side from the viewpoint of internal resistance. By omitting the first buried diffusion layer, the width of the divided region in the other direction is reduced. Therefore, when the optical pickup is configured by using this light receiving element and the optical pickup is incorporated into the optical pickup, the adjustment becomes easy, and the degree of freedom in designing the optical pickup increases. Further, since the second embedded diffusion layer is provided directly below the second light shielding layer, light does not enter the region of the second embedded diffusion layer. Therefore, as compared with the case where the second buried diffusion layer is not provided, the sensitivity profile of the photodiodes at both ends in the other direction does not change and is not adversely affected.

In the light receiving element of the fourth aspect, since the signal processing circuit for processing the signal output from each of the photodiodes is formed in the region other than the light receiving region of the semiconductor substrate, the signal processing circuit is separately provided. In comparison with the case where the optical pickup is provided, the optical pickup and the like are manufactured in a small size, light weight, and at low cost.

[0023]

EXAMPLES The light receiving element of the present invention will be described in detail below with reference to examples.

The five-division photodiode according to the embodiment of the present invention described here is similar to that shown in FIG. 11, and five photodiodes D1 which individually generate an output in a rectangular light receiving region D as a whole. , D2, D3, D4, D
It has 5 patterns. Photodiode D1, D
5 are provided along the opposite long sides of the light receiving region D, and the photodiode D4 is the photodiode D1,
It occupies half of the region sandwiched by D5 in the longitudinal direction (Y direction). The photodiodes D2 and D3 are provided by dividing the remaining area in the longitudinal direction. Between the photodiodes D1 and D2, D2 and D3, D3 and D5, divided regions X1, X2, and X3 extending in the Y direction in a strip shape are formed, respectively. In addition, the photodiodes D1 and D4,
Between D4 and D5, divided regions X1 'and X3' extending in the Y-direction in strips are formed. The electrodes of each photodiode are provided outside the light receiving area (area defined by the envelope of the pattern of all photodiodes) D. That is, the anode electrodes E _A and E _A ′
Are photodiodes D1, D2, D3, D4, D5
Common to the photodiodes D1 and
It is provided along the outer long side of D5. The cathode electrodes E _C1 , E _C2 , E _C3 , E _C4 , and E _C5 corresponding to the photodiodes D1, D2, D3, D4, and D5 are provided along the outer short sides of the photodiodes, respectively. .

FIG. 1 shows a cross section in the direction (X direction) perpendicular to the long side of the light receiving region D of the five-division photodiode of the above-described embodiment. As shown in FIG. 1, an N-type epitaxial layer 4 as a semiconductor layer is formed on a P-type silicon substrate 1 as a semiconductor substrate. Each photodiode D
1, D2, D3, D4, and D5 each include a part of the N-type epitaxial layer 4, and an output is generated through a PN junction formed by the N-type epitaxial layer 4 and the substrate 1.

In each of the divided regions X1, X2 and X3, as a first isolation diffusion layer, it reaches the surface of the substrate 1 from the surface of the N type epitaxial layer 4 to reach the surface of the N type epitaxial layer 4.
Of the photodiodes D1, D2, D3, D4, D
A P-type isolation diffusion layer 5 and a P-type buried isolation diffusion layer 3 for electrically isolating the portions belonging to 5 from each other are formed. At both ends of the light receiving region D, as second isolation diffusion layers, portions reaching from the surface of the N-type epitaxial layer 4 to the surface of the substrate 1 and belonging to the photodiodes D1 and D5 at both ends of the N-type epitaxial layer 4. A P-type isolation diffusion layer 5'and a P-type embedded isolation diffusion layer 3'for electrically isolating the light-receiving region D from the outside are formed.

Division area X that does not receive a focused beam during operation
On the P-type isolation diffusion layers 5 and 5 of X1, X3, the first
Metal films 9 and 9 serving as light shielding layers are provided, and metal films 9 ′ and 9 ′ serving as second light shielding layers are provided on the P-type isolation diffusion layers 5 ′ and 5 ′ at both ends of the light receiving region D, respectively. Is provided. The widths of the metal films 9 and 9 are set to be wider than the widths of the P-type isolation diffusion layers 5 and 5, and the photodiodes D2 and D, respectively.
It extends to the 3 side by a predetermined width. The widths of the metal films 9'and 9'are set wider than the widths of the P-type isolation diffusion layers 5'and 5 '.
Each extends to the side of the photodiodes D1 and D5 by a predetermined width. Division area X2 that receives the focused beam during operation
A light-shielding layer is not provided on the upper surface because it is necessary to increase sensitivity.

In the photodiodes D2 and D3, as the first buried diffusion layers, the metal films 9 and the substrate 1 immediately below the metal films 9 are respectively formed.
N type buried diffusion layers 2 and 2 extending in the Y direction (direction perpendicular to this cross section) between the N type epitaxial layer 4 and the N type epitaxial layer 4 are formed. In the photodiodes D1 and D5, as the second buried diffusion layer, the substrate 1 directly below the metal films 9'and 9 ', respectively.
N-type buried diffusion layers 2 ', 2'extending in the Y direction between the n-type epitaxial layer 4 and the N-type epitaxial layer 4 are formed.

The divided areas X1 'and X3' have the same structure as the divided areas X1 and X3, respectively.

This five-division photodiode is manufactured as follows.

First, as shown in FIG. 2 (a), N type buried diffusion layers 2 and 2'are formed in a region to be the light receiving region D on the surface of the P type silicon substrate 1. Then, the divided areas X1,
The P-type embedded separation / diffusion layer 3 is formed in each of the regions X2 and X3, and the P-type embedded separation / diffusion layer 3'is formed at both ends of the light receiving region D.

Next, as shown in FIG. 2B, an N type epitaxial layer 4 is grown on the entire upper surface of the P type silicon substrate 1. Subsequently, P-type isolation diffusion layers 5 and 5 ′ reaching the P-type embedded isolation diffusion layers 3 and 3 ′ from the surface of the N-type epitaxial layer 4 are provided at the locations corresponding to the respective P-type embedded diffusion layers 3 and 3 ′. Form.

Next, a shallow P-type diffusion layer 6 is formed in a region extending from the surface of the P-type isolation diffusion layer 5'at the right end to the surface of the P-type isolation diffusion layer 5'at the left end. At the same time, a silicon oxide film 7 is formed on the surface of the P type diffusion layer 6.

Next, as shown in FIG. 1, the oxide film 7 is formed.
Of the above, the part from the rightmost P-type isolation diffusion layer 5'to the leftmost P-type isolation diffusion layer 5'is removed and the silicon nitride film 8 is provided instead. The film thickness of the silicon nitride film 8 is set according to the wavelength of the laser diode so that the film 8 acts as an antireflection film.

Next, as shown in FIG. 11, the anode electrodes E _A and E _A ′ common to the photodiodes D1, D2, D3, D4 and D5 and the photodiodes D respectively.
Cathode electrodes E corresponding to 1, D2, D3, D4 and D5
_C1 , E _C2 , E _C3 , E _C4 , and E _C5 are formed. At this time, simultaneously, metal films 9 and 9 '(FIG. 1) are formed on both sides of the divided areas X1 and X3 and the light receiving area D. In this way, the five photodiodes D1, D2, D3, D4, D5 are formed (manufacturing completed).

In this five-division photodiode, a metal film 9 for covering the separation diffusion layer 5 is provided in the divided regions X1, X3, X1 ', X3' other than the divided region X2 that receives the focused beam during operation. It is provided. Further, at both ends of the light receiving region D, a metal film 9'covering the separation diffusion layer 5'is provided. Therefore, even if stray light or the like enters the light receiving region D, the stray light is blocked by the metal films 9 and 9'and does not enter the separation diffusion layers 5 and 5 '. Therefore, the signal-to-noise ratio (S / N ratio) can be kept high as compared with the conventional light receiving element.

Further, each split type photodiode D1, D
The N-type buried diffusion layers 2 or 2'formed in 2, D3, D4 and D5 have lower resistance than the N-type epitaxial layer 4 depending on the setting of the impurity concentration. Since the N type buried diffusion layers 2 and 2'extend in the Y direction between the substrate 1 and the N type epitaxial layer 4, the internal resistance of each photodiode in the Y direction is reduced. Therefore, it is possible to perform a high speed operation as compared with the related art. Actually, when the frequency characteristic of the photodiode D2 was measured,
The results shown in FIGS. 8 and 9 were obtained. 8 shows frequency characteristics of the structure of the present invention shown in FIG. 1, and FIG. 9 shows FIG.
The frequency characteristics of the conventional structure shown in (a) are shown. As is clear from this result, according to the present invention, the frequency characteristic can be improved about 20 times as compared with the conventional one.

Further, since the N type buried diffusion layers 2 and 2'are provided directly under the metal films 9 and 9 ', respectively, light is incident on the regions of the N type buried diffusion layers 2 and 2'. There is no such thing.
Therefore, the sensitivity profile of each photodiode does not change as compared with the case where the N type buried diffusion layers 2 and 2'are not provided, and there is no adverse effect.

Further, the photodiodes D at both ends in the X direction
1 and D5, since the N-type buried diffusion layer 2'is provided directly below the metal film 9 ', the metal film 9 is extended to the photodiodes D1 and D5 side by a predetermined width as shown in FIG. The width of each of the divided regions X1 and X3 can be reduced as compared with the case where the N type buried diffusion layer 2'is provided immediately below. That is, in the example of FIG. 3, the width Δ ′ of the divided region is the width of the P-type buried isolation diffusion layer 3, the width of the two buried diffusion layers 2 and 2 ′, and the width of the two gaps between the diffusion layers. Specified by and.
On the other hand, in the example of FIG. 1, the widths Δ of the divided regions X1 and X3 are the width of the P-type embedded separation diffusion layer 3, the width of one embedded diffusion layer 2, and one gap between the diffusion layers. And the width of. Therefore, the width of the divided regions X1 and X3 can be reduced. Therefore, it is possible to configure an optical pickup by using this light receiving element, facilitate adjustment when incorporating the optical pickup into the optical disc device, and increase the degree of freedom in designing the optical pickup.

Further, the present invention can be applied to a circuit built-in light receiving element in which a split type photodiode and a signal processing circuit for processing a signal output from the split type photodiode are integrated on the same semiconductor substrate. it can.

FIG. 4 shows a cross section of a main part of such a light receiving element with a built-in circuit. In FIG. 4, D indicates a light receiving region in which the same 5-division photodiode as shown in FIG. 1 is formed, and B indicates a signal processing circuit region in which an NPN transistor is formed. The NPN transistor includes an emitter diffusion layer 20, a base diffusion layer 16, an N-type buried diffusion layer 12 serving as a collector, an N-type epitaxial layer 4 and an N-type collector extraction diffusion layer 14. 1
Reference numerals 9, 19 ', 19 "denote an emitter electrode, a base electrode and a collector electrode, respectively.

This circuit built-in light receiving element is manufactured as follows.

First, as shown in FIG. 5 (a), on the surface of the P-type silicon substrate 1, N-type buried diffusion layers 2 and 2 ', and a signal processing circuit region B are formed in a region to be the light receiving region D. The N type buried diffusion layer 12 is formed in the power region. Subsequently, the P-type embedded separation diffusion layer 3 is formed in each of the regions to be the divided regions X1, X2, and X3 in the light-receiving region D, and the P-type embedded separation diffusion layers 3 ′ are formed at both ends of the light-receiving region D. . At the same time, the P-type buried isolation diffusion layers 13 are formed at both ends of the signal processing circuit area B.

Next, as shown in FIG. 5B, an N type epitaxial layer 4 is grown on the entire surface of the P type silicon substrate 1. Then, the P-type isolation diffusion layers 5 reaching the P-type embedded isolation diffusion layers 3, 3 ′, 13 from the surface of the N-type epitaxial layer 4 to the locations corresponding to the P-type embedded diffusion layers 3, 3 ′, 13 respectively. , 5 ', 15 are formed.

Next, as shown in FIG. 4, a shallow P-type diffusion layer is formed in a region from the surface of the P-type isolation diffusion layer 5'at the right end of the light receiving region D to the surface of the P-type isolation diffusion layer 5'at the left end. 6 is formed. At the same time, the base diffusion layer 16 of the NPN transistor is formed in the signal processing circuit area B.

Next, in the signal processing circuit region B, the emitter diffusion layer 20 of the NPN transistor is formed. The silicon oxide film 7 is formed on the surface of the N-type epitaxial layer 4 by the steps.

Next, in the oxide film 7, the light receiving region D
Of the silicon nitride film 8 instead of the portion from the P-type isolation diffusion layer 5'at the right end to the P-type isolation diffusion layer 5'at the left end and the portion above the contact region of the signal processing circuit region B. To provide. The film thickness of the silicon nitride film 8 is set according to the wavelength of the laser diode so that the film 8 acts as an antireflection film.

Next, after removing the portion of the silicon nitride film 8 on the contact region, the anode and cathode electrodes of each photodiode in the light receiving region D and the metal films 9 and 9'in the divided region are formed. At the same time, the emitter electrode 19 of the NPN transistor in the signal processing circuit area B,
A base electrode 19 'and a collector electrode 19 "are formed.

In this way, a normal bipolar IC
A light receiving element with a built-in circuit can be manufactured without increasing the number of steps for the (integrated circuit).

In this light receiving element with a built-in circuit, it is possible to realize a smaller size, higher performance, and lower cost as compared with the case where the light receiving element and the signal processing circuit are formed separately. Therefore, an optical pickup or the like can be manufactured in a small size, a light weight, and a low cost. Further, since the wire connection for connecting the light receiving element and the signal processing circuit is performed by the wiring inside the IC, the resistance to external noise can be improved.

FIG. 6 shows a pattern of a multi-division photodiode according to another embodiment of the present invention. This split type photodiode has photodiodes D11, ..., D18 in a light receiving region D '. The pattern of this split type photodiode is adapted to form an optical pickup of a type different from the optical pickup shown in FIG.

FIG. 7 corresponds to a cross section taken along the line CC ′ in FIG. 6, and the same components as those in FIG. 1 are designated by the same reference numerals.

Divided area X that does not receive a focused beam during operation
A metal film 9 as a first light-shielding layer is provided on each of the P-type isolation diffusion layers 5 of 12, and on the P-type isolation diffusion layers 5'and 5'at both ends of the light receiving region D ', respectively. Metal films 9'and 9'as second light shielding layers are provided. The width of the metal film 9 is set wider than the width of the P-type isolation diffusion layer 5,
It extends to the side of the photodiodes D16 and D17 by a predetermined width. The widths of the metal films 9'and 9'are set wider than the widths of the P-type isolation diffusion layers 5'and 5 ', and extend to the photodiodes D15 and D18 side by a predetermined width, respectively.
The light-shielding layer is not provided on the divided region X11 that receives the focused beam during operation, because it is necessary to enhance the sensitivity.

In the photodiodes D16 and D17, as the first buried diffusion layer, N extending in the X direction (direction perpendicular to this cross section) between the substrate 1 immediately below the metal film 9 and the N type epitaxial layer 4 is provided. A buried buried diffusion layer 2 is formed. In the photodiodes D15 and D18, as the second buried diffusion layer, the N-type buried diffusion layer 2 extending in the X direction between the substrate 1 and the N-type epitaxial layer 4 immediately below the metal films 9'and 9 ', respectively. ', 2'is formed.

In this split type photodiode, even if stray light or the like is incident on the light receiving region D ', the stray light is blocked by the metal films 9 and 9', similarly to the five split type photodiode shown in FIG. It does not enter the separation diffusion layers 5 and 5 '. Therefore, the signal-to-noise ratio (S / N ratio) can be kept high as compared with the conventional light receiving element.

Further, each divided photodiode D15,
N-type buried diffusion layer 2 formed in D16, D17 and D18
Alternatively, 2'denotes a resistance lower than that of the N-type epitaxial layer 4 depending on the setting of the impurity concentration. Since the N type buried diffusion layers 2 and 2'extend in the X direction between the substrate 1 and the N type epitaxial layer 4, the internal resistance of each photodiode in the X direction is reduced. Therefore, it is possible to perform a high speed operation as compared with the related art.

Further, since the N type buried diffusion layers 2 and 2'are provided directly under the metal films 9 and 9 ', light is incident on the regions of the N type buried diffusion layers 2 and 2'. There is no such thing.
Therefore, the sensitivity profile of each photodiode does not change as compared with the case where the N type buried diffusion layers 2 and 2'are not provided, and there is no adverse effect.

Further, the photodiodes D1 at both ends in the Y direction
5 and D18, the N-type buried diffusion layer 2'is formed immediately below the metal film 9 '.
Since the metal film 9 in the divided region X12 is extended toward the photodiodes D15 and D18 by a predetermined width and the N-type buried diffusion layer 2'is provided immediately below the divided region X12, the divided region X12 is provided. The width of can be reduced. Therefore, it is possible to configure an optical pickup by using this light receiving element and easily adjust the optical pickup when the optical pickup is assembled,
Also, the degree of freedom in designing the optical pickup can be increased.

Although the semiconductor substrate is a P type in this embodiment, it is not limited to this, as a matter of course. The semiconductor substrate may be N-type, and the conductivity types of the other diffusion layers may be reversed accordingly.

[0060]

As is apparent from the above, in the light-receiving element according to the first aspect, in the divided regions other than the divided region that receives the focused beam during operation, the first divided diffusion layer is covered. Since the light shielding layer is provided, even if stray light or the like is incident on the light receiving area, the stray light is shielded by the first light shielding layer and the first separation / diffusion provided in the divided area that does not receive the focused beam. It does not enter the layer. Therefore, the signal-to-noise ratio (S / N ratio) can be kept high as compared with the conventional light receiving element.

In the light receiving element of the second aspect, the first buried diffusion layer having the same conductivity type as that of the semiconductor layer on the substrate and having a higher impurity concentration than that of the semiconductor layer is formed. The first buried diffusion layer has a lower resistance than the semiconductor layer, depending on the setting of the impurity concentration. Since the first buried diffusion layer extends in one direction between the semiconductor substrate and the semiconductor layer, the internal resistance of each photodiode in the one direction is reduced. Therefore, it is possible to perform a high speed operation as compared with the related art. Further, since the first buried diffusion layer is provided directly below the first light shielding layer, light does not enter the region of the first buried diffusion layer. Therefore, as compared with the case where the first buried diffusion layer is not provided, the sensitivity profile of each photodiode does not change and is not adversely affected.

In the light-receiving element of the third aspect, the second isolation diffusion layer is formed at both ends of the light-receiving region in the other direction, and the second isolation diffusion layer is covered and the photodiodes at both ends in the other direction are formed. The second that extends above each by a predetermined width
A second buried diffusion layer having a lower resistance than that of the semiconductor layer is formed immediately below the light-shielding layer according to the setting of the impurity concentration. The internal resistance of the photodiode in one direction can be reduced. As a result, in the photodiodes on both ends in the other direction, there is a margin to omit the first buried diffusion layer on the side of the divided region from the viewpoint of internal resistance, and by omitting the first buried diffusion layer, The width of the divided area in the other direction can be reduced. Therefore, it is possible to configure an optical pickup by using this light receiving element, facilitate adjustment when incorporating the optical pickup into the optical disc device, and increase the degree of freedom in designing the optical disc device. Further, since the second embedded diffusion layer is provided directly below the second light shielding layer, light does not enter the region of the second embedded diffusion layer. Therefore, as compared with the case where the second buried diffusion layer is not provided, the sensitivity profile of the photodiodes at both ends in the other direction does not change and is not adversely affected.

In the light receiving element of the fourth aspect, since the signal processing circuit for processing the signal output from each of the photodiodes is formed in the region other than the light receiving region of the semiconductor substrate, the signal processing circuit is separately provided. The optical pickup and the like can be manufactured in a small size, light weight, and at a low cost, as compared with the case of providing.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section of a main part of a five-division photodiode according to an embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the five-division photodiode.

FIG. 3 is a diagram showing a modification of the five-division photodiode.

FIG. 4 is a diagram showing a cross section of a main part of a light receiving element with a built-in circuit according to another embodiment of the present invention.

FIG. 5 is a diagram showing a manufacturing process of the light-receiving element with a built-in circuit.

FIG. 6 is a diagram showing a pattern of a multi-division photodiode according to another embodiment of the present invention.

FIG. 7 is a diagram showing a cross section of a main part of the multi-division photodiode.

FIG. 8 is a diagram showing frequency characteristics of the five-division photodiode.

FIG. 9 is a diagram showing frequency characteristics of a conventional five-division photodiode.

FIG. 10 is a diagram showing a schematic configuration of a general optical disc device.

FIG. 11 is a diagram showing a pattern of a general 5-division photodiode.

FIG. 12 is a diagram showing a manufacturing process of a conventional five-division photodiode.

FIG. 13 is a view showing a cross section along the longitudinal direction of a conventional five-division photodiode.

[Explanation of symbols]

2, 2 ', 12 N type buried diffusion layer 3, 3', 13 P type buried separation diffusion layer 5, 5 ', 15 P type separation diffusion layer 9, 9' Metal film B Signal circuit area D, D ' Regions D1, ..., D5, D11, ..., D18 Photodiodes X1, X1′X2, X3, X3 ′, X11, X12 Divided regions

Claims (4)

[Claims] 1. A semiconductor substrate having a first conductivity type has a light receiving region extending in one direction along the substrate surface and in another direction perpendicular to the one direction, and the one direction is provided in the light receiving region. Is a light-receiving element in which a plurality of photodiodes extending in a line are formed side by side in the other direction with a divided region extending in a band shape in the one direction interposed therebetween, and a semiconductor having a second conductivity type on the semiconductor substrate. A layer is formed, each of the photodiodes includes a part of the semiconductor layer, and an output is generated through a PN junction formed by the semiconductor layer and the semiconductor substrate. A first isolation diffusion layer having a conductivity type of 1 and reaching the surface of the semiconductor substrate from the surface of the semiconductor layer to electrically isolate the portions of the semiconductor layer belonging to the photodiodes from each other is formed. In the light-receiving element are, in the divided areas other than the divided area to be focused beam during operation of the divided regions, the second covering the first isolation diffusion layer 1
2. A light receiving element, characterized in that the light shielding layer is provided. 2. The light receiving element according to claim 1, wherein the width of the first light shielding layer in the other direction is set to be wider than the width of the first isolation diffusion layer in the other direction, A first buried diffusion layer having a conductivity type set to have a higher impurity concentration than that of the semiconductor layer and extending in the one direction between the semiconductor substrate and the semiconductor layer directly below the first light shielding layer. A light-receiving element characterized in that. 3. The light-receiving element according to claim 2, wherein a photodiode formed at both ends of the light-receiving area in the other direction and a portion outside the light-receiving area are electrically separated from each other. A second separation diffusion layer of the first conductivity type is formed, and a second light shielding layer is provided to cover the second separation diffusion layer and extend over the photodiodes at both ends in the other direction by a predetermined width. The photodiodes on both ends in the other direction have the second conductivity type and are set to have a higher impurity concentration than the semiconductor layer, and the photodiode is formed between the semiconductor substrate and the semiconductor layer directly below the second light shielding layer. A light-receiving element, characterized in that a second buried diffusion layer extending in the above-mentioned one direction is formed. 4. The light receiving element according to claim 1, wherein a signal processing for processing a signal output from each photodiode is provided in a region of the semiconductor substrate outside the light receiving region. A light-receiving element having a circuit formed therein.