JP2004200408A - Light receiving element, light receiving device with built-in circuit, and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light receiving element capable appropriately performing servo control for an optical disc device that uses short wavelength light. <P>SOLUTION: A p-type diffusion layer 201 and a p-type semiconductor layer 202 are provided on a silicon substrate 200. First and second n-type semiconductor parts 203a and 203b are provided on the surface of the p-type semiconductor layer 202, while a p-type surface diffusion part 206 is provided between the first and second n-type semiconductors 203a and 203b. Since the p-type surface diffusion part 206 has a depth d of 4μm and a width w of 2μm, a relatively wide crosstalk width is provided even against the incident light of short wavelength to allow detection of deviation in incident light across a relatively wide range. So, the optical disc device using short wavelength light is appropriately servo-controlled. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light receiving element, a light receiving device with a built-in circuit, and an optical disk device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an optical pickup unit provided in an optical disk device focuses and irradiates the emitted light of a semiconductor laser onto an optical disk with a lens, and receives reflected light whose light intensity is modulated by a data portion formed on the optical disk. The device is receiving light. An output signal from the light receiving element that has received the reflected light is processed by a signal processing circuit to detect a data signal indicating data written on the optical disk and also detect a focus signal and a servo signal. The optical disk device controls the focus of the lens based on the focus signal, and controls the irradiation position of the laser beam on the disk based on the servo signal.
[0003]
2. Description of the Related Art Conventionally, as a light receiving element used in the above-described optical disk device, there is a light receiving element as shown in FIG. This light receiving element is provided with an N-type diffusion layer 606 and an N-type semiconductor layer 601 on a P-type semiconductor substrate 600 in order, and the first and the second layers formed of P-type impurities are formed on the surface of the N-type semiconductor layer 601. It includes second P-type surface diffusion portions 602a and 602b. An impurity formed of an N-type impurity at a surface portion of the N-type semiconductor layer 601 and between the first and second P-type surface diffusion portions 602a and 602b and having an impurity concentration higher than the impurity concentration of the N-type semiconductor layer 601. An N-type surface diffusion portion 604 having a concentration is formed. The N-type semiconductor layer 601 is located on both left and right sides of the first and second P-type surface diffusion portions 602a and 602b in FIG. 6, and the N-type diffusion layer 606 extends from the surface of the N-type semiconductor layer 601. Is formed. The N-type diffusion portion 603 has an impurity concentration higher than the impurity concentration of the N-type semiconductor layer 601. An antireflection film 605 is provided on the surface of the N-type semiconductor layer 601. The N-type surface diffusion portion 604 prevents a leakage current between the first and second P-type surface diffusion portions 602a and 602b due to the surface inversion of the N-type semiconductor layer 601.
[0004]
The optical carriers generated by the first and second P-type surface diffusion units 602a and 602b are separately extracted from two output terminals (not shown) connected to the first and second P-type surface diffusion units 602a and 602b, respectively. . On the basis of the amounts of the optical carriers separately extracted from the first and second P-type surface diffusion portions 602a and 602b, ie, the output values detected from the two output terminals, a laser beam is actually applied to the optical disk. The irradiation position is calculated. The servo control of the optical disk device is performed based on the calculated irradiation position of the laser beam.
[0005]
The servo control of the optical disk device is performed as follows. That is, when the irradiation position of the laser beam on the optical disc deviates from the normal position, the position where the reflected light of the optical disc is incident on the light receiving element shifts. By shifting the position where the reflected light enters the light receiving element, the ratio of the output values from the first and second P-type surface diffusion portions 602a and 602b changes. From the amount of change in the output ratio, the shift of the irradiation position of the laser light on the optical disk is calculated, and the optical pickup unit and the like are driven so as to reduce the calculated shift. In order to perform such servo control, when the reflected light of the laser light applied to the normal position of the optical disc is incident on the light receiving element, the center of the incident light is the first and second P-type surface diffusion portions 602a. , 602b so as to be located at the center in the width direction of the N-type surface diffusion portion 604. Thus, when the laser beam is irradiated to the normal position of the optical disc, the ratio of the output current obtained from each of the first and second P-type surface diffusion portions 602a and 602b is 1: 1. Then, servo control is performed so as to maintain the output current ratio at 1: 1.
[0006]
FIG. 7 is a diagram showing crosstalk characteristics when light having a wavelength of 650 nm is incident on the light receiving element of FIG. The crosstalk characteristic is indicated by a curve representing the relationship between the position of the center of the incident light on the surface of the light receiving element and the output current from the first and second P-type surface diffusion portions 602a and 602b of the light receiving element. . In FIG. 7, the horizontal axis indicates the distance from the first P-type surface diffusion portion 602a to the second P-type surface diffusion portion 602b on the surface of the light receiving element. The horizontal axis of 0 μm corresponds to the center of the first P-type surface diffusion portion 602a in the width direction in FIG. Further, 9.5 μm on the horizontal axis corresponds to the center in the width direction of the N-type surface diffusion portion 604. Further, 19 μm on the horizontal axis corresponds to the center of the second P-type surface diffusion portion 602b in the width direction in FIG. The vertical axis represents the output current from the first and second P-type surface diffusion portions 602a and 602b, and the maximum output current value is 1. As can be seen from FIG. 7, when the reflected light enters such that the center of the reflected light is located at the center of the first P-type surface diffusion portion 602a, an output current is obtained only from the first P-type surface diffusion portion 602a. Then, as the incident position of the reflected light approaches the N-type surface diffusion portion 604, the output current from the second P-type surface diffusion portion 602b increases. When the center of the reflected light coincides with the center of the N-type surface diffusion unit 604, the output current from the first P-type surface diffusion unit 602a and the output current from the second P-type surface diffusion unit 602b are 1: 1. become. Further, as the incident position of the reflected light shifts toward the second P-type surface diffusion portion 602b, the output current from the first P-type surface diffusion portion 602a decreases, and the output current from the second P-type surface diffusion portion 602b decreases. Increase.
[0007]
Here, in the crosstalk characteristic shown in FIG. 7, the vicinity of the N-type surface diffusion portion 604 where the curve of the output current of the first P-type surface diffusion portion 602a and the curve of the output current of the second P-type surface diffusion portion 602b intersect. , In which the ratio of the output current values is 5% or more and 95% or less, is referred to as a crosstalk area. In this crosstalk region, a width that appears on a straight line connecting the center of the first P-type surface diffusion portion 602a and the center of the second P-type surface diffusion portion 602b is referred to as a crosstalk width. In the crosstalk region, the value of the output current of the first P-type surface diffusion portion 602a and the value of the output current of the second P-type surface diffusion portion 602b are both 5% or more and 95% or less. For example, a region where any of the current values is equal to or more than 10% and equal to or less than 90% may be a crosstalk region in accordance with the circuit configuration of the signal processing circuit. As can be seen from FIG. 7, the smaller the crosstalk width is, the steeper the amount of change in the output current with respect to the shift of the incident light from the center of the N-type surface diffusion portion 604. Therefore, if the crosstalk width is small, the width of the shift of the incident light that can be detected by the output values of the first and second P-type surface diffusion portions 602a and 602b is narrowed, and servo control becomes difficult. As a result of another experiment, it has been found that a crosstalk width of 4 μm or more is necessary for performing servo control appropriately. As shown in FIG. 7, when light having a wavelength of 650 nm is incident on the light receiving element having the structure of FIG. 6, a crosstalk width of 4 μm or more is obtained, so that appropriate servo control can be performed.
[0008]
[Patent Document 1]
JP 2001-148503 A (FIG. 3)
[0009]
[Problems to be solved by the invention]
However, there is a problem that the above-mentioned conventional light receiving element is not suitable for an optical disk device using short-wavelength light. FIG. 8 is a diagram showing crosstalk characteristics when short-wavelength light having a wavelength of 405 nm is incident on the conventional light receiving element of FIG. As shown in FIG. 8, since the cross-talk width of the conventional light receiving element when short-wavelength light is incident is about 2.5 μm, the width of the detectable shift of the incident light as described above is small. However, the servo control of the optical disk device cannot be performed properly.
[0010]
Therefore, an object of the present invention is to provide a light receiving element capable of appropriately executing servo control of an optical disk device using short-wavelength light.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a light-receiving element of the present invention includes a first semiconductor layer of a first conductivity type,
A plurality of first semiconductor portions of the second conductivity type formed on a surface portion of the first semiconductor layer;
A first conductive type second semiconductor portion formed between the plurality of first semiconductor portions and having an impurity concentration higher than the impurity concentration of the first semiconductor layer and having a width of 2 μm or more;
It is characterized by having.
[0012]
According to the above configuration, the center of the incident light with respect to the light incident on the light receiving element is, for example, one second semiconductor portion and, for example, two first semiconductor portions adjacent to the second semiconductor portion. If the center of the second semiconductor portion is shifted toward one of the two first semiconductor portions, the output value obtained from each of the two first semiconductor portions is the magnitude of the shift of the incident light. Make a ratio corresponding to Here, since the second semiconductor portion has a width of 2 μm or more, the range in which an input value can be obtained from the two first semiconductor portions in a state where a ratio corresponding to the shift of the incident light is obtained is the conventional light receiving portion. Larger than the element. That is, the so-called crosstalk width of the two first semiconductor portions is larger than in the related art. Therefore, for example, even for short-wavelength incident light, a shift of the incident light is detected over a relatively wide range. As a result, the light receiving element of the present invention can appropriately detect the deviation of the reflected light of the optical disk and appropriately execute the servo control in, for example, an optical disk device using short wavelength light.
[0013]
Here, not only the two first semiconductor portions adjacent to the one second semiconductor portion but also the two or more first semiconductor portions adjacent to the one second semiconductor portion are not limited to the second second semiconductor portions. Outputs are respectively obtained from the two or more first semiconductor portions in a ratio corresponding to the deviation from the semiconductor portion. Also in this case, since the second semiconductor portion has a width of 2 μm or more, the crosstalk width of the two or more first semiconductor portions can be increased as compared with the related art.
[0014]
In addition, the ratio corresponding to the shift of the incident light from the second semiconductor unit is not limited to the one second semiconductor unit, but may be two or more first semiconductor units adjacent to the plurality of second semiconductor units. An output is obtained from each of the two or more first semiconductor units. Also in this case, since the second semiconductor portion has a width of 2 μm or more, the crosstalk width of the plurality of second semiconductor portions with respect to the two or more first semiconductor portions adjacent to the second semiconductor portion, respectively. Can be expanded.
[0015]
In one embodiment, the width of the second semiconductor portion is 8 μm or less.
[0016]
According to the above embodiment, since the width of the second semiconductor portion is 8 μm or less, a light-receiving element having good sensitivity can be formed. Here, if the width of the second semiconductor portion is larger than 8 μm, the sensitivity to incident light is sharply reduced, so that, for example, servo control of the optical disk becomes inaccurate.
[0017]
In a light receiving device with a built-in circuit according to the present invention, the light receiving element of the present invention and a signal processing circuit for processing a signal output from the light receiving element are formed on the same substrate.
[0018]
According to the above configuration, the signal processing circuit and the light receiving element are monolithically formed to be small, and a circuit built-in type capable of detecting a shift of incident light from the center of the second semiconductor portion over a relatively wide range. A light receiving device is obtained.
[0019]
The optical disk device of the present invention includes the light receiving element of the present invention or the light receiving device with a built-in circuit of the present invention.
[0020]
According to the above configuration, since the light receiving element of the present invention or the light receiving device with a built-in circuit of the present invention is provided, the deviation of the irradiation position of light onto the optical disc from the normal position can be detected over a relatively wide range, An optical disk device having excellent servo performance can be formed. Also, for example, in an optical disk device using short-wavelength light, appropriate servo performance can be obtained.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
[0022]
(1st Embodiment)
FIG. 1 is a diagram showing a change in the crosstalk width when the width w of the N-type surface diffusion portion 604 is changed for a light receiving element having the same components as the light receiving element in FIG. Note that, with respect to the crosstalk width shown in FIG. 1, a region where the ratio of the output current value of the first and second P-type surface diffusion portions 602a and 602b in FIG. 6 is 5% or more and 95% or less is defined as a crosstalk region. . The incident light of the light receiving element is incident light of a wavelength of 450 nm having a penetration length smaller than the formation depth d of the N-type surface diffusion portion 604. In FIG. 1, the horizontal axis is the width w (μm) of the N-type surface diffusion portion 604, and the vertical axis is the crosstalk width (μm). The light receiving element of the present invention is a light receiving element in which the width w of the N-type surface diffusion layer 604 is 2 μm or more. In the light receiving element of FIG. 6, the N-type semiconductor layer 601 is a first semiconductor layer of the first conductivity type, and the first and second P-type surface diffusion portions 602a and 602b formed of P-type impurities are the second conductivity type. Are a plurality of first semiconductor units. Further, the N-type surface diffusion portion 604 formed of N-type impurities and having a width of 2 μm or more is the second semiconductor portion of the first conductivity type of the present invention.
[0023]
As can be seen from FIG. 1, as the width w of the N-type surface diffusion portion 604 increases, the crosstalk width increases. Specifically, by forming the width w of the N-type surface diffusion portion to be 2 μm or more, a crosstalk width of 4 μm or more can be obtained. Also, according to another experiment, when light of another wavelength whose penetration length is smaller than the formation depth d of the N-type surface diffusion portion 604 is incident, the width w of the N-type surface diffusion portion 604 is set to 2 μm or more. It was found that a crosstalk width of 4 μm or more was obtained by forming. In addition, a crosstalk width of 4 μm or more was obtained even when light of another wavelength having a penetration depth larger than the formation depth d of the N-type surface diffusion portion 604 was incident.
[0024]
From these facts, by forming the width of the N-type surface diffusion portion 604 to be 2 μm or more, regardless of the size of the penetration length of the incident light and the formation depth of the N-type surface diffusion portion 604, the cross-section of 4 μm or more is required. The talk width can be obtained. Therefore, an optical disc device capable of executing appropriate servo control can be formed by the light receiving element of the present invention. In particular, even for short-wavelength light, in which the crosstalk width was insufficient for performing the servo control of the optical disk, a sufficient crosstalk width can be obtained by setting the formation width of the N-type surface diffusion portion 604 to 2 μm or more. Can be formed. As a result, appropriate servo control can be performed in an optical disk device using short-wavelength light.
[0025]
In the crosstalk region, the output current value of the first P-type surface diffusion portion 602a and the output current value of the second P-type surface diffusion portion 602b in FIG. However, the present invention is not limited to this ratio of the output current value. For example, a region having another ratio such that each output current value is 10% or more and 90% or less may be used as the crosstalk region.
[0026]
The inventor of the present invention has found that the crosstalk width greatly changes depending on whether the penetration length determined by the wavelength of the incident light of the light receiving element is smaller or larger than the formation depth d of the N-type surface diffusion portion 604. I found it. That is, in the conventional light receiving element of FIG. 6, the formation depth d of the N-type surface diffusion portion 604 is 2.5 μm, which is smaller than the penetration length of light having a wavelength of 650 nm of 3.3 μm. In this case, the incident light generates photocarriers in the portion of the N-type semiconductor layer 601 and below the N-type surface diffusion portion 604. At the depth where the photocarriers are formed, the N-type semiconductor layer 601 has a constant concentration profile over the width direction in the cross section in FIG. 6, and there is no change in potential. Therefore, the optical carriers generated below the N-type surface diffusion portion 604 move in the N-type semiconductor layer 601 in the width direction by diffusion. Therefore, even when the incident light is shifted from the center of the N-type surface diffusion portion 604 toward the first P-type surface diffusion portion 602a, the opposite side of the N-type surface diffusion portion 604 from the first P-type surface diffusion portion 602a. A relatively large number of carriers reach the second P-type surface diffusion portion 602b. As a result, a relatively large output current is obtained from the second P-type surface diffusion portion 602b, and the crosstalk width becomes relatively large.
[0027]
On the other hand, when light having a wavelength of 405 nm is incident on the conventional light receiving element, the penetration depth of the light is 0.1 μm, which is smaller than the formation depth d of the N-type surface diffusion portion 604. In this case, in order for the photocarriers generated on the first P-type surface diffusion portion 602a side to reach the second P-type surface diffusion portion 602b side, they must cross the potential barrier of the N-type surface diffusion portion 604. Therefore, almost no carriers reach the second P-type surface diffusion portion 602b, so that the crosstalk width is reduced.
[0028]
From these facts, if the formation depth of the N-type surface diffusion portion 604 is made smaller than the light penetration length, a sufficient crosstalk width can be obtained. However, for example, when light having a wavelength of 405 nm is incident, the penetration length of the incident light is 0.1 μm. Therefore, forming an N-type surface diffusion portion whose formation depth is shallower than 0.1 μm is a process technology. Above, very difficult. Therefore, the present inventor conducted a study for the purpose of obtaining a sufficiently wide crosstalk width even when the formation depth d of the N-type surface diffusion portion 604 is deeper than the wavelength of the incident light. Has also been found to vary depending on the width w of the N-type surface diffusion portion 604. Then, the relationship between the crosstalk width when light having a penetration length smaller than the formation depth d of the N-type surface diffusion portion 604 and the width w of the N-type surface diffusion portion 604 is clarified, and the present invention is formed. It was reached.
[0029]
(2nd Embodiment)
FIG. 2 is a sectional view showing a light receiving element according to a second embodiment of the present invention. The light receiving element of this embodiment has a concentration of 1 × 10 ¹⁸ cm ^-3 P-type diffusion layer 201 having a thickness of about 1 μm and a concentration of 1 × 10 ¹³ ~ 1 × 10 ¹⁶ cm ^-3 And a P-type semiconductor layer 202 as a first conductive type first semiconductor layer having a thickness of about 10 to 20 μm. On the P-type semiconductor layer 202, a concentration of 1 × 10 ¹⁷ ~ 1 × 10 ¹⁹ cm ^-3 First and second N-type semiconductor portions 203a and 203b as a plurality of first semiconductor portions of the second conductivity type having a thickness of about 2 μm are formed. Between the first and second N-type semiconductor portions 203a and 203b, a P-type surface diffusion portion 206 as a second semiconductor portion of the first conductivity type is formed. The P-type surface diffusion portion 206 has a depth d of 4 μm and a width w of 2 μm. The impurity forming the P-type surface diffusion portion 206 may be a trivalent element, such as boron or indium. The impurity concentration of the P-type surface diffusion portion 206 is set to 1 × 10 ¹⁹ cm ^-3 The concentration is as follows. In the vicinity of the left and right ends in FIG. 2 of the P-type semiconductor layer 202 and the first and second N-type semiconductor portions 203a and 203b, P-type diffusion for contacting the P-type diffusion layer 201 from the light receiving element surface is provided. The portion 204 is formed so as to reach the surface of the P-type diffusion layer 201 from the surfaces of the first and second N-type semiconductor portions 203a and 203b. The impurity forming the P-type diffusion layer 201 and the P-type diffusion portion 204 may be any element having a valence of III, such as boron or indium.
[0030]
An anti-reflection film 205 formed using a normal silicon process is provided on at least a light incident area between the surfaces of the first and second N-type semiconductor portions 203a and 203b and the surface of the P-type surface diffusion portion 206. ing.
[0031]
In the light receiving element having the above-described configuration, either light having a wavelength longer than 4 μm, which is the formation depth d of the P-type surface diffusion portion 206, or light having a shorter wavelength than 4 μm, is used. Even when the light enters, the P-type surface diffusion portion 206 has a width w of 2 μm, so that a crosstalk width of 4 μm or more can be obtained.
[0032]
In the above embodiment, the same effect can be obtained even if the N-type and P-type components of the light receiving element are reversed. Further, even without the antireflection film 205, an appropriate crosstalk width of 4 μm or more can be obtained.
[0033]
(Third embodiment)
FIG. 3 shows the sensitivity of the light receiving element having the same configuration as that of FIG. 6 by changing the width w of the N-type surface diffusion portion 604 as the second semiconductor portion of the first conductivity type from 1 μm to 12 μm. FIG. 9 is a diagram showing the results of an experiment performed when an experiment for measuring a change in was performed. In FIG. 3, the horizontal axis represents the width w (μm) of the N-type surface diffusion portion 604, and the vertical axis represents the sensitivity (A / W) of the light receiving element. In this experiment, light having a wavelength of 405 nm was incident on the light receiving element. FIG. 3 shows that the impurity concentration on the surface of the N-type surface diffusion portion 604 is 1 × 10 ^Fifteen cm ^-3 It is an experimental result when. In addition to the experimental conditions for obtaining the experimental results of FIG. 3, the impurity concentration on the surface of the N-type surface diffusion portion 604 was set to 1 × 10 ^Fifteen ~ 3 × 10 ¹⁹ cm ^-3 The same experiment was performed while changing the range. As a result, the same experimental results as in FIG. 3 were obtained at any impurity concentration. That is, when the width w of the N-type surface diffusion portion 604 exceeds 8 μm, it becomes clear that the sensitivity of the light receiving element rapidly deteriorates. Similar results were obtained when the experiment was performed by changing the incident light to light having a wavelength other than 405 nm.
[0034]
For these reasons, by forming the width w of the N-type surface diffusion portion 604 to be 2 μm or more and 8 μm or less, a light receiving element having a sufficient crosstalk width and good sensitivity characteristics can be obtained.
[0035]
In the above embodiment, the portion other than the N-type surface diffusion portion 604 may have another structure. For example, an N-type semiconductor substrate may be used instead of the P-type semiconductor substrate 600. Further, it may have a structure like the light receiving element shown in FIG. Also, the N-type and P-type components of the light receiving element may be reversed.
[0036]
(Fourth embodiment)
FIG. 4 is a cross-sectional view showing a light receiving device with a built-in circuit according to a fourth embodiment of the present invention. The light receiving device with a built-in circuit includes a light receiving section D as a light receiving element having the same components as the light receiving element of the present invention, and a transistor section as a signal processing circuit for processing a signal output from the light receiving section D. T are formed on the same substrate. In the light receiving device with a built-in circuit of FIG. 4, for example, a multilayer wiring, an interlayer film, and the like formed after the processing step of the metal wiring are omitted.
[0037]
As shown in FIG. 4, the boron concentration is 1 × 10 ^Fifteen cm ^-3 In order to reduce the parasitic resistance generated on the anode of the light receiving portion on the P-type semiconductor substrate 400, the thickness is 1-2 μm and the boron concentration is 1 × 10 ¹⁸ ~ 1 × 10 ¹⁹ cm ^-3 About the first P-type semiconductor layer 401. On the first P-type semiconductor layer 401, a thickness of 15 to 16 μm and a boron concentration of 1 × 10 ¹³ ~ 1 × 10 ¹⁴ cm ^-3 A second P-type semiconductor layer 402 is formed. Then, on this second P-type semiconductor layer 402, a film thickness of 1-2 μm and a boron concentration of 1 × 10 ¹³ ~ 1 × 10 ¹⁴ cm ^-3 A third P-type semiconductor layer 411 is formed. An N-type semiconductor layer serving as a collector 413 of an NPN transistor is formed between the second P-type semiconductor layer 402 and the third P-type semiconductor layer 411 and on the transistor section T side. Further, a LOCOS region 403 for performing element isolation is formed on the third P-type semiconductor layer 411. An insulating film 419 is formed on the surface of the transistor portion T.
[0038]
The surface portion of the third P-type semiconductor layer 411 on the light receiving portion D side has, for example, a phosphorus concentration of 1 × 10 ¹⁹ ~ 1 × 10 ²⁰ cm ^-3 Thus, two N-type surface diffusion portions 405a and 405b as a plurality of first semiconductor portions having a junction depth of about 0.3 to 0.8 μm are formed. Here, the third P-type semiconductor layer 411 functions as a first semiconductor layer. Between the two N-type surface diffusion portions 405a and 405b, the boron concentration is 1 × 10 ¹⁸ cm ^-3 And a P-type surface diffusion portion 407 having a width of 2 μm and a formation depth of 4 μm is formed.
[0039]
The surface of the third P-type semiconductor layer 411, the N-type surface diffusion portions 405a and 405b, and the P-type surface diffusion portion 407 of the light receiving portion D, at least in a region irradiated with light, has an anti-reflection film for incident light. 404 are formed.
[0040]
Further, in order to connect the first P-type semiconductor layer 401 formed on the P-type semiconductor substrate 400 to the metal wiring formed above the fourth P-type semiconductor layer 411, the boron concentration is 1 × 10 ¹⁹ ~ 1 × 10 ²⁰ cm ^-3 About P-type semiconductor portions 408 and 409 are formed.
[0041]
Further, the region where the transistor T is formed in the third P-type semiconductor layer 411 has, for example, a phosphorus concentration of 2 × 10 ^Fifteen ~ 2 × 10 ¹⁶ cm ^-3 The N-type well structure 412 is formed. A part of the N-type well structure 412 has, for example, a phosphorus concentration of 1 × 10 ¹⁹ ~ 1 × 10 ²⁰ cm ^-3 The N-type diffusion part of the degree is formed. A part of the N-type well structure 412 has a base 415 of a transistor T, for example, having a boron concentration of 1 × 10 4. ¹⁷ ~ 2 × 10 ¹⁷ cm ^-3 An approximately P-type diffusion layer is formed, and an N-type diffusion layer serving as the emitter 416 is formed in a part of the P-type diffusion layer by solid layer diffusion from, for example, arsenic-implanted polysilicon.
[0042]
Further, a cathode electrode (not shown) and an anode electrode 417 of the light receiving section D, and a collector electrode 418, a base electrode 406, and an emitter electrode 410 of the transistor section T are formed.
[0043]
In the light receiving device with a built-in circuit having the above-described configuration, good crosstalk characteristics were obtained for incident light having any wavelength. Also, good crosstalk characteristics were obtained even when the width of the P-type surface diffusion portion 407 was formed to be 2 μm or more.
[0044]
In this embodiment, an NPN transistor is used for the signal processing circuit. However, a PNP transistor may be used, or a signal processing circuit may be formed using both NPN and PNP transistors. Further, the structure of the transistor is not limited to the structure of this embodiment, and another structure may be used. Further, the light receiving section D as the light receiving element is not limited to the structure of the present embodiment, and for example, another light receiving element such as the light receiving element of the first embodiment can be used.
[0045]
(Fifth embodiment)
FIG. 5 is a schematic diagram illustrating an optical pickup unit included in an optical disc device according to a fifth embodiment of the present invention.
[0046]
As shown in FIG. 5, the optical pickup unit of the optical disc device according to the present embodiment includes a semiconductor laser 500 that emits short-wavelength light. There is provided a diffraction grating 501 that divides the short wavelength light emitted from the semiconductor laser 500 into three beams of two tracking sub-beams and a signal reading main beam. The three beams separated by the diffraction grating pass through the hologram element 502 as zero-order light, are converted into parallel light by the collimator lens 503, and are then focused on the optical disk 505 by the objective lens 504. ing. The condensed light is reflected by the light intensity modulated by pits that are formed on the optical disc 505 and represent data. This reflected light is diffracted by the hologram element 502 after passing through the objective lens 504 and the collimating lens 503. The primary light component of the diffracted light is incident on a light receiving element 506 of the present invention having light receiving portions D1 to D5 divided into five. Then, a data signal and a tracking signal are obtained by adding and subtracting output values from the light receiving units D1 to D5.
[0047]
The optical disc device having the optical pickup unit has the light receiving element 506 of the present invention, and the light receiving element 506 has a width of 2 μm at a portion between the five divided light receiving units D1 to D5. A semiconductor unit is provided. Therefore, each of the light receiving portions D1 to D5 of the light receiving element 506 has an appropriate crosstalk width. This makes it possible to appropriately detect the shift of the incident position on the light receiving element 506 for the short wavelength light emitted from the semiconductor laser 500 and reflected on the optical disk. As a result, the optical pickup unit of the optical disk device can obtain good servo performance. Also, good servo characteristics can be obtained when light of any wavelength is used, not limited to short-wavelength light. Further, the optical pickup section has good servo performance, so that good frequency characteristics can be obtained.
[0048]
In the above embodiment, the light receiving element is not limited to the light receiving element having the five-divided light receiving section, but may be any light emitting element having a PN junction irradiated with a plurality of lights.
[0049]
Further, the light receiving element 506 may be a light receiving device with a built-in circuit according to the present invention. Further, the optical unit of the optical disk device of the present embodiment is configured by the diffraction grating 501, the hologram element 502, the collimating lens 503, and the objective lens 504, but an optical system of another configuration may be used.
[0050]
【The invention's effect】
As is apparent from the above, according to the light receiving element of the present invention, the first semiconductor layer of the first conductivity type and the plurality of first semiconductor portions of the second conductivity type formed on the surface portion of the first semiconductor layer And a second semiconductor portion of a first conductivity type formed between the plurality of first semiconductor portions and having an impurity concentration higher than that of the first semiconductor layer and having a width of 2 μm or more. Therefore, the so-called crosstalk width of the plurality of first semiconductor portions can be increased as compared with the related art, so that even for incident light having a short wavelength, for example, a shift of the incident light can be detected over a relatively wide range. As a result, for example, in an optical disk device using short-wavelength light, a deviation of reflected light from the optical disk can be appropriately detected, and servo control can be appropriately performed.
[0051]
Further, according to the light receiving element of another embodiment, since the width of the second semiconductor portion is 8 μm or less, a light receiving element having good sensitivity can be formed. As a result, for example, in an optical disk device, the deviation of the reflected light from the optical disk can be appropriately detected, and the servo control can be appropriately performed.
[0052]
According to the light receiving device with a built-in circuit of the present invention, the light receiving element of the present invention and the signal processing circuit for processing a signal output from the light receiving element are formed on the same substrate. A light receiving device with a built-in circuit capable of detecting a shift of incident light from the center of the second semiconductor portion over a relatively wide range can be obtained.
[0053]
Further, according to the optical disk device of the present invention, since the optical disk device of the present invention or the light receiving device with a built-in circuit of the present invention is provided, an optical disk device having good servo performance can be formed. Even when used, appropriate servo performance can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing a change in a crosstalk width of a light receiving element when a width of an N-type surface diffusion portion is changed in the light receiving element of the first embodiment.
FIG. 2 is a sectional view showing a light receiving element according to a second embodiment of the present invention.
FIG. 3 is a diagram showing an experimental result of measuring a change in sensitivity of a light receiving element by changing a width of an N-type surface diffusion portion from 1 μm to 12 μm.
FIG. 4 is a cross-sectional view illustrating a light receiving device with a built-in circuit according to a fourth embodiment of the present invention.
FIG. 5 is a schematic diagram illustrating an optical pickup unit included in an optical disc device according to a fifth embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a conventional light receiving element.
FIG. 7 is a diagram illustrating crosstalk characteristics of a conventional light receiving element.
FIG. 8 is a diagram showing crosstalk characteristics when short-wavelength light is incident on a conventional light receiving element.
[Explanation of symbols]
200 silicon substrate
201 P-type diffusion layer
202 P-type semiconductor layer
203a 1st N-type semiconductor unit
203b 2nd N type semiconductor part
204 P-type diffusion unit
205 Anti-reflective coating
206 P type surface diffusion part

Claims (4)

A first semiconductor layer of a first conductivity type;
A plurality of first semiconductor portions of the second conductivity type formed on a surface portion of the first semiconductor layer;
A first conductivity type second semiconductor portion formed between the plurality of first semiconductor portions and having an impurity concentration higher than the impurity concentration of the first semiconductor layer and having a width of 2 μm or more. Characteristic light receiving element. The light-receiving element according to claim 1,
A light receiving element, wherein the width of the second semiconductor portion is 8 μm or less. 3. A light receiving device with a built-in circuit, wherein the light receiving element according to claim 1 and a signal processing circuit for processing a signal output from the light receiving element are formed on the same substrate. An optical disk device comprising the light receiving element according to claim 1 or 2, or the light receiving device with a built-in circuit according to claim 3.

Images