JP2009277862A - Light receiving element, optical pickup apparatus, optical disk apparatus, and light receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light receiving element capable of improving frequency characteristics with maintaining an adding output independent of shape of a photodiode. <P>SOLUTION: A PN junction type photodiode is configured by a semiconductor substrate 10 and a semiconductor layer 11. A reflection preventing film 12 is formed on an upper surface of the semiconductor layer 11, and an interlayer film 13 having an opening 13A corresponding to a light reception surface 1A is formed on the reflection preventing film. The reflection preventing film 12 has a lamination structure in which a first insulating film 12A and a second insulating film 12B are laminated. A groove 12C that elongates along an end edge 13B of the opening 13A is provided to the first insulating film 12A. A semiconductor layer 11 is exposed at a bottom surface of the groove 12C, and a cathode electrode 14 configured by including silicide is provided in the groove 12C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light receiving element (Photo Detector IC: PDIC) which can be suitably applied to, for example, a purpose of detecting reflected light from an optical disk or monitoring the power of light emitted from a light emitting element, and light having the same. The present invention relates to a pickup device, an optical disc device, and a light receiving device.

  Photodiodes can be classified mainly into signal photodiodes (RF PDs) and front monitor photodiodes (FRONT PDs) depending on the application. The RF PD reads a signal reflected from the optical disk, and the FRONT PD monitors the laser power of the semiconductor laser in order to keep the optical output level of the semiconductor laser constant. Usually, PD divided into a plurality of regions is used for RF PD, and large area PD is used for FRONT PD.

  In a general photodiode, for example, as shown in FIGS. 15 and 16, an n-type impurity layer 311 is formed on the upper surface of a p-type silicon substrate 310, and the p-type silicon substrate 310 and the n-type impurity layer 311 are formed. Thus, a PN junction type diode structure is formed. This photodiode serves as an anode common between a p-type silicon substrate and an n-type cathode, and converts light incident on the photodiode into an electrical signal (photocurrent) by photoelectric conversion. 15 shows a top view of the photodiode, and FIG. 16 shows a cross-sectional configuration view in the direction of arrows AA in FIG.

An antireflection film 312 having a laminated structure of an SiO ₂ layer 312A and an Si ₃ N ₄ layer 312B is formed on the surface of the photodiode in order to reduce the light reflectance. The antireflection film 312 is exposed in the opening 313A of the interlayer film 313 made of SiO ₂ formed on the antireflection film 312, and the portion of the antireflection film 312 exposed in the opening 313A. Is the light receiving surface S of the photodiode.

When forming the light receiving surface 312A of the photodiode, it is necessary to selectively etch the interlayer film 313 formed on the antireflection film 312 to form the opening 313A in the interlayer film 313. In etching the interlayer film 313, it is common to use the Si ₃ N ₄ layer 312B as a stopper by utilizing the difference in etching rate between SiO ₂ and Si ₃ N ₄ . At this time, wet etching is used for etching the interlayer film 313 in order to eliminate damage to the Si ₃ N ₄ layer 312B, but the cathode electrode 314 of the photodiode is formed by an etchant used for etching the interlayer film 313. It is formed of a metal that is easily etched. Therefore, the cathode electrode 314 is formed sufficiently away from the opening end 313B in consideration of the positional deviation of the opening 313A so that even the cathode electrode 314 provided in the interlayer film 313 is not etched. It is important to keep (see Patent Document 1).

JP 2003-163344 A

  However, when the cathode electrode 314 is formed at a position far from the opening end 313B, the distance from the light incident position to the cathode electrode 314 is increased, and the resistance of the cathode is increased. For this reason, in particular, in the FRONT PD having a large area of the light receiving surface S and a large capacity, there is a problem that the CR product becomes large and the frequency characteristics are deteriorated. Further, in the RF PD, for example, as shown in FIG. 17, when a plurality of photodiodes (PD) are arranged in a complicated manner, the cathode electrode wiring (not shown) of the central photodiode is connected to the opening portion. In consideration of misalignment, when it is routed sufficiently away from the edge of another photodiode (the opening end of the interlayer film), the interval D2 between adjacent photodiodes increases with the cathode electrode in between. As a result, the area other than the photodiode becomes wider, and the light incident on the photodiode is reduced, so that the effective component of the reflected light is lost, the calculation accuracy is lowered, and the added output of all PDs is reduced. there were. Therefore, it is conceivable that the cathode electrode of the central photodiode is constituted by a diffusion layer formed on the surface of the semiconductor substrate so that the distance D2 is not so wide. However, in such a case, the area other than the photodiode is narrowed, and the light incident on the photodiode is increased, but instead the resistance is increased and the frequency characteristics are degraded.

  The present invention has been made in view of such problems, and an object thereof is to provide a light receiving element capable of improving the frequency characteristics while maintaining the added output without depending on the photodiode shape, and the same. An object of the present invention is to provide an optical pickup device, an optical disc device, and a light receiving device.

  In the light receiving element of the present invention, a first conductive semiconductor layer includes a second conductive semiconductor layer, an antireflection film having a light receiving surface, and an interlayer film having an opening in the light receiving surface on the first conductive semiconductor layer. It is prepared in order from the side. The light receiving element further includes an electrode electrically connected to the second conductivity type semiconductor layer, and the electrode includes silicide.

  An optical pickup device of the present invention includes a light emitting element that outputs light toward a disk area on which an optical disk is placed, an optical system provided between the disk area and the light emitting element, and light emitted from the light emitting element. And a light receiving element for receiving the light reflected by the optical disk. The light receiving element includes a first conductive type semiconductor layer, a second conductive type semiconductor layer, an antireflection film having a light receiving surface on which reflected light from an optical disk is incident, and an interlayer film having an opening on the light receiving surface. It has in order from the conductive semiconductor layer side. The light receiving element further includes an electrode electrically connected to the second conductivity type semiconductor layer, and the electrode includes silicide.

  The optical disc apparatus of the present invention includes an optical pickup device and an information processing unit that transmits input information to the optical pickup device or receives information written on the optical disc from the optical pickup device. The optical pickup device is provided between a light emitting element that outputs light according to information transmitted from an information processing unit toward a disk area on which an optical disk is placed, and the disk area and the light emitting element. An optical system and a light receiving element that receives light reflected from the optical disk out of light emitted from the light emitting element. The light receiving element includes a first conductive type semiconductor layer, a second conductive type semiconductor layer, an antireflection film having a light receiving surface on which reflected light from an optical disk is incident, and an interlayer film having an opening on the light receiving surface. It has in order from the conductive semiconductor layer side. The light receiving element further includes an electrode electrically connected to the second conductivity type semiconductor layer, and the electrode includes silicide.

  The light-receiving device of the present invention includes a light-emitting element, an optical system that reflects part of light emitted from the light-emitting element, and a light-receiving element that receives light reflected by the optical system among light emitted from the light-emitting element. And an information processing unit that receives information input from the light receiving element and transmits information corresponding to the received information to the light emitting element. The light receiving element includes a second conductive type semiconductor layer, an antireflection film having a light receiving surface on which reflected light from the optical system is incident, and an interlayer film having an opening on the light receiving surface on the first conductive type semiconductor layer. 1 conductive type semiconductor layer from the side. The light receiving element further includes an electrode electrically connected to the second conductivity type semiconductor layer, and the electrode includes silicide.

  In the light receiving element, the optical pickup device, the optical disk device, and the light receiving device of the present invention, the electrode electrically connected to the second conductivity type semiconductor layer includes silicide. For this reason, the electrode can be formed between the second conductive type semiconductor layer and the antireflection film, for example, at the periphery of the light receiving surface. It is not necessary to form it sufficiently away from the surface. As a result, the electrode can be disposed near the open end. In addition, when electrodes are routed between adjacent photodiodes, it is not necessary to consider the positional deviation of the openings formed in the interlayer film, so the interval between adjacent photodiodes should be reduced. Can do. Further, since the sheet resistance of silicide is sufficiently smaller than that of the diffusion layer formed on the semiconductor substrate, the resistance of the electrode can be reduced when the electrode is routed.

  According to the light receiving element, the optical pickup device, the optical disk device, and the light receiving device of the present invention, the electrode that is electrically connected to the second conductive type semiconductor layer is configured to include silicide. Near the open end. Thereby, since the distance from a light incident position to an electrode can be shortened, a frequency characteristic can be improved. In addition, when an electrode is routed between adjacent photodiodes, the resistance of the electrode can be reduced, and in this case, the frequency characteristics can be improved. In addition, when electrodes are routed between adjacent photodiodes, the interval between adjacent photodiodes can be reduced. As a result, the area other than the photodiode is narrowed, and reduction of the added output can be prevented. As described above, according to the present invention, the frequency characteristics can be improved while maintaining the added output without depending on the photodiode shape.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First embodiment]
FIG. 1 shows a top surface configuration of the light receiving element 1 according to the first embodiment of the present invention, and FIG. 2 shows a cross-sectional configuration of the light receiving element 1 in FIG. The light receiving element 1 includes a semiconductor layer 11 of a second conductivity type (for example, n-type) different from the first conductivity type on an upper surface of a semiconductor substrate 10 (first conductivity type semiconductor layer) of a first conductivity type (for example, p-type). Is a PN junction type photodiode that is suitable for use in monitoring the power of light emitted from a light emitting element.

  The semiconductor substrate 10 is a silicon substrate doped with an impurity of the first conductivity type. The semiconductor layer 11 is formed, for example, by doping the upper surface of the semiconductor substrate 10 with a second conductivity type impurity.

An antireflection film 12 is formed on the upper surface of the semiconductor layer 11. Further, an interlayer film 13 having an opening 13A in a predetermined region is formed on the antireflection film, and the upper surface of the antireflection film 12 is exposed on the bottom surface of the opening 13A. The interlayer film 13 is made of, for example, silicon oxide (for example, SiO ₂ ). A portion of the upper surface of the antireflection film 12 exposed at the bottom surface of the opening 13 </ b> A is a light receiving surface 1 </ b> A of the light receiving element 1.

The antireflection film 12 reduces the reflectance of light incident on the semiconductor layer 11 from the outside with respect to light in a wavelength band that the light receiving element 1 wants to detect. For example, as shown in FIG. 1, the antireflection film 12 has a laminated structure in which a first insulating film 12A and a second insulating film 12B are laminated in order from the semiconductor layer 11 side. The first insulating film 12A is made of, for example, silicon oxide (for example, SiO ₂ ), and the second insulating film 12B is made of an insulating material different from that of the first insulating film 12A. Here, the outermost surface (second insulating film 12B) of the antireflection film 12 is preferably made of an insulating material having resistance to an etchant used for selective etching of the interlayer film 13 in the manufacturing process. For example, when HF (hydrogen fluoride) is used as the etchant, the second insulating film 12B is preferably made of, for example, silicon nitride (eg, Si ₃ N ₄ ). The thicknesses of the first insulating film 12A and the second insulating film 12B are defined by the relationship with the wavelength band of light desired to be detected by the light receiving element 1.

  The antireflection film 12 preferably functions as an etching stop layer when the interlayer film 13 is selectively etched in the manufacturing process to form the opening 13A in the interlayer film 13. Specifically, the second insulating film 12B is preferably made of a material having resistance to an etchant that can etch the interlayer film 13.

  In the antireflection film 12, the first insulating film 12A has a groove extending in one in-plane direction of the first insulating film 12A (specifically, along the bottom edge 13B of the opening 13A). 12C is provided, and the semiconductor layer 11 is exposed on the bottom surface of the groove 12C. A diffusion layer 11A containing a second conductivity type impurity having a concentration higher than the concentration of the second conductivity type impurity contained in the semiconductor layer 11 is formed in a portion of the semiconductor layer 11 exposed at the bottom surface of the groove 12C. Has been. A cathode electrode 14 is provided in the groove 12C. The cathode electrode 14 extends in one in-plane direction of the first insulating film 12A (specifically, along the edge 13B on the bottom surface side of the opening 13A), and on the periphery of the light receiving surface 1A. Is formed. The cathode electrode 14 is in ohmic contact with a portion of the upper surface of the semiconductor layer 11 exposed at the bottom surface of the groove 12 </ b> C, and is electrically connected to the semiconductor layer 11.

  As shown in FIG. 2, the cathode electrode 14 is preferably formed between the semiconductor layer 11 and the second insulating film 12B and covered with the second insulating film 12B. Moreover, it is preferable that the cathode electrode 14 includes a conductive material having resistance to an etchant used for selective etching of the interlayer film 13 in the manufacturing process. For example, when the cathode electrode 14 is formed between the semiconductor layer 11 and the second insulating film 12B, the cathode electrode 14 is preferably configured to include, for example, silicide. Silicide is a material that can be formed between the semiconductor layer 11 and the second insulating film 12B. Silicide is a material capable of extremely reducing the resistance per unit area (for example, several Ω / □), and is relatively higher than the resistance value of a metal material such as a diffusion layer 11A (described later). Unlike a member having a resistance value, it is a material that can be used as a substitute material for a metal material.

  A cathode connection terminal 15 reaching the upper surface of the interlayer film 13 is electrically connected to one end of the cathode electrode 14. The cathode connection terminal 15 is provided at the periphery of the light receiving surface 1A and adjacent to the opening 13A. The cathode connection terminal 15 is made of a conductive material such as metal.

  A semiconductor layer 16 of the first conductivity type is provided around the semiconductor layer 11 in the semiconductor substrate 10. The semiconductor layer 16 contains a first conductivity type impurity whose concentration is higher than the concentration of the first conductivity type impurity contained in the semiconductor substrate 10. For example, the first conductivity type impurity is formed on the upper surface of the semiconductor substrate 10. It is formed by doping. An anode electrode (not shown) is provided on the upper surface of the semiconductor layer 16, and this anode electrode extends in one in-plane direction (for example, along the cathode electrode 14) of the upper surface of the semiconductor layer 16. is doing. Further, an anode connection terminal (not shown) reaching the upper surface of the interlayer film 13 is electrically connected to the upper surface of the anode electrode. The anode connection terminal is made of a conductive material such as metal.

  The light receiving element 1 having such a configuration can be formed as follows, for example.

  3A to 3E, FIGS. 4A and 4B, and FIGS. 5A and 5B show examples of the cross-sectional configuration of the element in the process of forming the light receiving element 1. FIG. . First, after forming the semiconductor layers 11 and 16 on the surface of the semiconductor substrate 10, the first insulating film 12D is formed on the semiconductor layers 11 and 16 (FIG. 3A). Next, after forming a photoresist R1 having an opening H1 in a predetermined region on the first insulating film 12D, the first insulating film 12D is selectively etched using the photoresist R1 as a mask to form the groove 12C. A first insulating film 12A is formed (FIG. 3B). Next, using the photoresist R1 as a mask, an impurity having the same conductivity type as that of the semiconductor layer 11 is doped into a portion of the semiconductor layer 11 corresponding to the bottom surface of the opening H1, thereby forming a diffusion layer 11A (see FIG. FIG. 3 (C)). Thereafter, the photoresist R1 is removed.

  Next, after forming the cathode electrode 14 in the opening H1 (FIG. 4A), the second insulating film 12B is formed on the surface including the cathode electrode 14, and the first insulating film 12A and the second insulating film 12B are formed. An antireflection film 12 is formed (FIG. 4B). At this time, the cathode electrode 14 is covered with the second insulating film 12B.

  Next, after an interlayer film 13D is formed on the entire surface including the antireflection film 12, a photoresist R2 having an opening H2 in a predetermined region is formed on the interlayer film 13D (FIG. 5A). Next, the interlayer film 13D is selectively etched by wet etching using the photoresist R2 as a mask. Thereby, the interlayer film 13 having the opening 13A is formed, the antireflection film 12 is exposed on the bottom surface of the opening 13A, and the light receiving surface 1A is formed (FIG. 5B). Thereafter, the photoresist R2 is removed.

  Next, a hole (not shown) reaching the cathode electrode 14 and a hole (not shown) reaching the semiconductor layer 16 are formed in a portion corresponding to one end of the cathode electrode 14 in the interlayer film 13. Note that these holes may be formed simultaneously with the opening 13A. Thereafter, a cathode connection terminal 15 and an anode connection terminal (not shown) are formed in these holes. In this way, the light receiving element 1 of the present embodiment is manufactured.

  Meanwhile, other elements such as a driving element for driving the light receiving element 1 are usually formed on the semiconductor substrate 10, and each element on the semiconductor substrate 10 is partially used in order to reduce the number of manufacturing steps. These processes are shared. For example, when the cathode electrode 14 of the light receiving element 1 is formed of silicide, it is possible to share the process of using silicide in other elements on the semiconductor substrate 10. Therefore, an example of a series of steps when forming the cathode electrode 14 of the light receiving element 1 and the electrode of the MOS transistor included in the driving element with silicide will be described below.

  6 (A), 6 (B), 7 (A), 7 (B) and 8 (A) to 8 (C) are examples of the cross-sectional configuration of the element in the step of forming the cathode electrode 14 and the electrode of the MOS transistor. It is a representation.

First, after forming the SiO ₂ layer 22 that protects the PD region in the PD region of the surface of the semiconductor substrate 10 made of Si, the polysilicon layer 20 and the sidewall layers 21D are formed in the MOS region of the surface of the semiconductor substrate 10. (FIG. 6A). Next, after a photoresist layer 23 is formed on the entire surface, an opening 23A is formed in the PD region, and the SiO ₂ layer 22 is selectively removed through the opening 23A, for example, by wet etching (FIG. 6B). ).

Next, after removing the photoresist layer 23, a first insulating film 12D is formed over the entire surface (FIG. 7A). Subsequently, after forming a photoresist 24 having openings H1 and H2 corresponding to the openings of the SiO ₂ layer 22 and the MOS region, the first insulating film 12D and the sidewalls are formed through the openings H1 and H2 by, for example, wet etching. The layer 21D is selectively removed (FIG. 7B). Thereby, the first insulating film 12 </ b> A on the bottom surface side of the antireflection film 12 is formed, and the sidewall layer 21 is formed on the side surface of the polysilicon layer 20.

Next, after removing the photoresist 24, a cobalt layer 25 is formed on the entire surface (FIG. 8A). Subsequently, heat treatment is performed to diffuse cobalt in the cobalt layer 25 into the polysilicon layer 20 and the semiconductor substrate 10 to form silicide layers 26, 27, and 28 made of cobalt silicide (for example, CoSi ₂ ) (FIG. 8). (B)). Thereafter, unreacted cobalt is removed. Thereafter, the second insulating film 12B is formed on the entire surface, and the antireflection film 12 is formed (FIG. 8C). Thus, the gate electrode 29 is formed by the polysilicon layer 20 and the silicide layer 26, and the source electrode and the drain electrode are formed by the silicide layers 27 and 28.

  In the light receiving element 1 having such a configuration, for example, when a reverse bias voltage is applied between the cathode connection terminal 15 and the anode connection terminal while the anode connection terminal is set to the ground potential, A depletion layer is formed at and near the interface between the 16 non-formed regions (first conductivity type impurity layer) and the semiconductor layer 11 (second conductivity type impurity layer). At this time, when light from the outside enters the light receiving surface 1A, light in a predetermined wavelength band passes through the antireflection film 12 and enters the depletion layer, and then is absorbed by the depletion layer and output of the absorbed light. It is converted into an electric signal (photocurrent) corresponding to the level. This current signal is output to an arithmetic circuit (not shown) via a wire (not shown) electrically connected to the cathode connection terminal 15 and the anode connection terminal, and then converted into a voltage signal in the arithmetic circuit. When the light receiving element 1 is used as a front PD, it is used as an optical output monitor signal.

  By the way, in the present embodiment, when the cathode electrode 14 is configured to include a conductive material having resistance to an etchant used for selective etching of the interlayer film 13, or the second insulating film 12 B is formed of the interlayer film 13. And the cathode electrode 14 is covered with the second insulating film 12B (between the second insulating film 12B and the semiconductor layer 11). If provided, the cathode electrode 14 does not need to be formed sufficiently away from the edge 13B of the opening 13A in consideration of the positional deviation of the opening 13A. As a result, the cathode electrode 14 can be disposed near the edge 13B, so the distance D1 between the cathode electrode 14 and the edge 13B of the interlayer film 13, that is, the distance from the light incident position to the cathode electrode 14 is shortened. can do. As a result, frequency characteristics can be improved. In particular, when a low resistance material such as silicide is used for the cathode electrode 14, the frequency characteristics can be greatly improved. In the present embodiment, since the cathode electrode 14 is formed around the light receiving surface 1A, the area of the photodiode region is not reduced. Therefore, there is no possibility that the addition output of the light receiving element 1 is lowered.

  In the present embodiment, the edge 13B of the cathode electrode 14 and the interlayer film 13 is compared to the case of the conventional light receiving element in which the cathode electrode is formed sufficiently away from the opening end in consideration of the positional deviation of the opening. When the distance D1 is reduced, there is no restriction that the area of the light receiving surface 1A must be smaller than the area of the light receiving surface of the conventional light receiving element. That is, in the present embodiment, as with the distance D1 between the cathode electrode 14 and the edge 13B of the interlayer film 13, the area of the light receiving surface 1A can be freely changed, and the degree of freedom in layout is extremely high.

  Further, in the present embodiment, when silicide is used as the cathode electrode 14, it is possible to share the process of using silicide in other elements on the semiconductor substrate 10 when forming the cathode electrode 14. . As a result, the number of processes does not increase due to the use of silicide as the cathode electrode 14, and there is no possibility that the manufacturing cost will increase.

[Modification]
In the above embodiment, the cathode electrode 14 is formed on the periphery of the light receiving surface 1A. For example, as shown in FIGS. 9 and 10, the cathode electrode 14 is located in the region facing the light receiving surface 1A from the periphery of the light receiving surface 1A. It may be formed to extend up to. 9 shows a top view of a modification of the light receiving element 1, and FIG. 10 shows a cross-sectional configuration view in the direction of arrows AA in FIG. 9 and 10 exemplify a case where the cathode electrode 14 is branched in a region facing the light receiving surface 1A and the intervals between adjacent branches are substantially equal. Yes.

  In this case, since the distance from the light incident position to the cathode electrode 14 can be further shortened, the frequency characteristics can be further improved. In this case, since the cathode electrode 14 is also formed in the region facing the light receiving surface 1A, the incident light is slightly lost due to the influence of the cathode electrode 14. However, in the conventional light receiving element in which the cathode electrode is made of metal, the cathode electrode cannot be formed in a region facing the light receiving surface, and light reception is required when the distance from the light incident position to the cathode electrode is shortened. It was necessary to divide the surface into multiple pieces. Therefore, it can be said that the present modification has a preferable configuration for an application in which the frequency characteristics are particularly important while minimizing the decrease in the addition output.

[Second Embodiment]
FIG. 11 shows the top surface configuration of the light receiving element 2 according to the second embodiment of the present invention, and FIG. 12 shows the cross-sectional configuration of the light receiving element 2 in FIG. The light receiving element 2 includes a second conductive type (for example, n-type) semiconductor layer different from the first conductive type on an upper surface of a first conductive type (for example, p-type) semiconductor substrate 10 (first conductive type semiconductor layer). Reference numeral 11 denotes a PN junction type photodiode in which a plurality are formed. The light receiving element 2 includes photodiodes corresponding to the individual semiconductor layers 11 so that an electric signal (photocurrent) can be obtained from each photodiode. Therefore, the light receiving element 2 can be suitably applied to an application for detecting reflected light from the optical disk.

  The plurality of semiconductor layers 11 are arranged on the semiconductor substrate 10 with the one semiconductor layer 11 as the center and the remaining semiconductor layer 11 surrounding the central semiconductor layer 11. The plurality of semiconductor layers 11 are arranged via a predetermined gap, for example, as shown in FIG. 11, arranged via the first conductivity type semiconductor layer 17. The central semiconductor layer 11 has a rectangular shape, for example, and the peripheral semiconductor layer 11 (hereinafter simply referred to as “the peripheral semiconductor layer 11”) is cut away at a portion facing the central semiconductor layer 11. L-shaped.

  In addition, the central semiconductor layer 11 has a region (extracting region) for leading out the cathode electrode 14 </ b> A electrically connected to the central semiconductor layer 11 in one gap between the surrounding semiconductor layers 11. Yes. The width D2 of the gap in which the extraction region is formed is wider by at least the width of the extraction region than the width D3 of the other gap in which the extraction region is not formed.

  On the surface of the extraction region, a cathode electrode 14A electrically connected to the extraction region is formed. The cathode electrode 14A extends in the extending direction of the extraction region, and extends from the periphery of the light receiving surface 1A to a region facing the light receiving surface 1A. Therefore, the portion of the cathode electrode 14 provided in the region facing the light receiving surface 1 </ b> A acts as a reflection mirror for incident light, and may be a factor that prevents the incident light from entering the semiconductor layer 11. Accordingly, it is preferable that the width of the portion of the cathode electrode 14 provided in the region facing the light receiving surface 1A is as narrow as possible.

  When it is desired to reduce the light incident on the extraction region as much as possible, it is preferable to make the width of the extraction region as narrow as possible, and as close as possible to the width of the cathode electrode 14A. This is because in the photodiode corresponding to the central semiconductor layer 11, it is difficult to distinguish light incident on the extraction region from light incident on the central region of the central semiconductor layer 11.

  A cathode electrode 14B that is electrically connected to the surrounding semiconductor layer 11 is formed on the surface of the surrounding semiconductor layer 11 opposite to the side on which the central semiconductor layer 11 is formed. The cathode electrode 14B is formed on the periphery of the light receiving surface 1A, and extends along the periphery of the light receiving surface 1A (the edge 13B of the opening 13A). Accordingly, the cathode electrode 14B does not prevent incident light from entering the semiconductor layer 11.

  The cathode electrodes 14A and 14B are preferably covered with the second insulating film 12B as shown in FIG. Moreover, it is preferable that the cathode electrodes 14A and 14B include a conductive material having resistance to an etchant used for selective etching of the interlayer film 13 in the manufacturing process. For example, when HF (hydrogen fluoride) is used as the etchant, it is preferable that the cathode electrodes 14A and 14B include, for example, silicide.

  A cathode connection terminal 15 reaching the upper surface of the interlayer film 13 is electrically connected to one end of the cathode electrodes 14A and 14B. Further, a semiconductor layer 16 is provided in a region surrounding all the semiconductor layers 11 in the semiconductor substrate 10. An anode electrode (not shown) is provided on the upper surface of the semiconductor layer 16, and an anode connection terminal (not shown) reaching the upper surface of the interlayer film 13 is electrically connected to the upper surface of the anode electrode. Has been.

  The antireflection film 12 is formed over the upper surfaces of all the semiconductor layers 11, and has one light receiving surface 1 </ b> A for all the photodiodes formed corresponding to the respective semiconductor layers 11. . In other words, in the present embodiment, the interlayer film 13 has only one opening 13A corresponding to one light receiving surface 1A. Therefore, the amount of incident light incident on the light receiving surface 1A is larger than when the openings are separately formed in the interlayer film for each photodiode.

  In the light receiving element 2 having such a configuration, for example, when a reverse bias voltage is applied between the cathode connection terminal 15 and the anode connection terminal while the anode connection terminal is set to the ground potential, Depletion layers are formed on the open surfaces of the non-formation regions 16 and 17 (first conductivity type impurity layers) and the semiconductor layers 11 (second conductivity type impurity layers) and in the vicinity thereof. At this time, when light from the outside enters the light receiving surface 1A, light in a predetermined wavelength band passes through the antireflection film 12 and enters the depletion layer of the photodiode corresponding to the light incident region of the light receiving surface 1A. After that, it is absorbed by the depletion layer and converted into an electric signal (photocurrent) corresponding to the output level of the absorbed light. This current signal is output to an arithmetic circuit (not shown) via a wire (not shown) electrically connected to the cathode connection terminal 15 and the anode connection terminal of each photodiode, and then the voltage is output in the arithmetic circuit. When the light receiving element 1 is used as an RF PD, it is used as a pit signal, a tracking signal, and a focus signal.

  By the way, in the present embodiment, when the cathode electrodes 14A and 14B are configured to include a conductive material having resistance to an etchant used for selective etching of the interlayer film 13, or the second insulating film 12B is an interlayer. It has resistance to an etchant used for selective etching of the film 13, and the cathode electrodes 14A and 14B are covered with such a second insulating film 12B (the second insulating film 12B and the semiconductor layer 11). The cathode electrodes 14A and 14B need not be formed sufficiently apart from the edge 13B of the opening 13A in consideration of the positional deviation of the opening 13A. As a result, the cathode electrode 14A can be formed in a region facing the light receiving surface 1A, and the cathode electrode 14B can be disposed near the end edge 13B, so that from the light incident position to the cathode electrodes 14A and 14B. The distance can be shortened. As a result, frequency characteristics can be improved. In particular, when a low resistance material such as silicide is used for the cathode electrode 14, the frequency characteristics can be greatly improved. In the present embodiment, since the cathode electrode 14B is formed around the light receiving surface 1A, the area of the photodiode region is not reduced. Further, since it is not necessary to cover the cathode electrode 14A with the interlayer film 13, the lead region (cathode electrode 14A) is formed as compared with the case where the cathode electrode 14A is constituted by the diffusion layer 11A (see FIG. 4A). The width D2 of the gap can be reduced. As a result, the area other than the photodiode is narrowed, and the reduction of the added output can be prevented. For these reasons, the added output of the light receiving element 1 can be improved as compared with the case where the cathode electrode 14A is constituted by the diffusion layer 11A (see FIG. 4A).

  In the present embodiment, as in the above embodiment, the distance D1 between the cathode electrode 14 and the edge 13B of the interlayer film 13 and the area of the light receiving surface 1A can be freely changed, and the degree of freedom in layout is increased. Extremely expensive.

[First application example]
The light receiving element 1 according to the first embodiment and its modification and the light receiving element 2 according to the second embodiment are an information reproducing apparatus and a recording medium for reproducing information recorded on a recording medium (optical disk). The present invention can be applied in various ways to devices such as an information recording device for recording information, an information recording / reproducing device having both functions, or a communication device, and an example thereof will be described below.

  FIG. 13 illustrates an example of a schematic configuration of the information recording / reproducing apparatus 100 according to this application example, and includes an optical device 110 and an information processing unit 120.

  The information processing unit 120 receives the information recorded on the recording medium 101 from the optical device 100 and outputs the input information to the optical device 110 as well as the output from the light receiving element 1. Based on this, it has an APC circuit (Auto Power Control Unit) that controls the semiconductor light emitting device LD so that the output of the semiconductor light emitting device LD is stabilized. On the other hand, the optical device 110 is used as an optical pickup device for high-density recording / reproduction using, for example, a DVD or the like, and includes a semiconductor light-emitting device LD that outputs light toward a region on which the recording medium 101 is mounted, and a recording An optical system provided between the region where the medium 101 is placed and the semiconductor light emitting device LD is provided. A large number of pits (projections) having a size of, for example, several μm are formed on the surface of the recording medium 101. The optical system is disposed in the optical path from the semiconductor light emitting device LD to the recording medium 101. For example, the grating (GRT) 111, the polarization beam splitter (PBS) 112, the collimating lens (CL) 113, and a quarter wavelength. A plate (λ / 4 plate) 114 and an objective lens (OL) 115 are provided. The optical system also includes, for example, a light receiving element 1 that monitors the output of the semiconductor light emitting device LD on an optical path through which light transmitted from the PBS 112 without being reflected by the PBS 112 passes out of the light output from the semiconductor light emitting device LD. have. Further, this optical system includes a cylindrical lens (CyL) 116 and a recording medium 101 out of light emitted from the semiconductor light emitting device LD on an optical path through which light transmitted through the PBS 112 among reflected light from the recording medium 101 passes. And a light receiving element 2 for receiving the light reflected by the light source.

  In this information recording / reproducing apparatus 100, the light from the light source (semiconductor light emitting device LD) passes through the GRT 111, is reflected by the PBS 112, and focuses on the recording medium 101 through the CL 113, the λ / 4 plate 114, and the OL 115, for example. Reflected by the pits on the surface of the recording medium 101. The light reflected by the recording medium 101 enters the light receiving element 2 through the OL 115, the λ / 4 plate 114, the CL 113, the PBS 112, and the CyL 116, and the information processing unit 120 reads the pit signal, tracking signal, and focus signal. . A part of the light from the semiconductor light emitting device LD passes through the GRT 111 and the PBS 112 and enters the light receiving element 1, and feedback control based on the output from the light receiving element 1 is performed on the light source by the information processing unit 120.

  Since the information recording / reproducing apparatus 100 of the present embodiment uses the light receiving element 2 of the above-described embodiment for reading information recorded on the recording medium 101, both the frequency characteristics and the added output in reading are high. Further, since the light receiving element 1 according to the first embodiment or its modification is used for APC control, both the frequency characteristics and the added output in the feedback control are high.

[Second application example]
The light receiving element 1 according to the first embodiment and its modification and the light receiving element 2 according to the second embodiment can be applied to a light receiving device having an APC function, and an example thereof will be described below. To do.

  FIG. 14 illustrates an example of a cross-sectional configuration of the light receiving device 200 according to this application example, and includes an optical device 210 and an information processing unit 220.

  The optical device 210 includes a semiconductor light emitting device LD as a light source, a mirror 211 that reflects a part of light emitted from the semiconductor light emitting device LD, a light receiving element 1 that receives light reflected by the mirror 211, and semiconductor light emission. It has a support substrate 212 that supports the device LD and the light receiving element 1, and a transparent substrate 213 that supports the mirror 211 and transmits light emitted from the semiconductor light emitting device LD. The information processing unit 220 includes an APC circuit that controls the semiconductor light emitting device LD so that the output of the semiconductor light emitting device LD is stabilized based on the output from the light receiving element 1.

  In the light receiving device 200, part of the light from the semiconductor light emitting device LD passes through the transparent substrate 213 and is emitted to the outside. In addition, light incident on the mirror 211 among the light from the semiconductor light emitting device LD is reflected by the mirror 211 and then received by the light receiving element 1, and feedback control based on the output from the light receiving element 1 is performed by the information processing unit 220. For the device LD.

  In the light receiving device 200 of the present embodiment, since the light receiving element 1 according to the first embodiment or its modification is used for APC control, both the frequency characteristics and the added output in the feedback control are high.

  The present invention has been described with the embodiment, the modification, and the application example. However, the present invention is not limited to the above-described embodiment and the like, and various modifications can be made.

  For example, although the PN junction type is used as the photodiode included in the light receiving elements 1 and 2 in the above-described embodiment and the like, a PIN junction type may be used.

  In the above-described embodiment and the like, the photodiode is configured by the semiconductor substrate 10 and the semiconductor layer 11. However, the photodiode is configured by the semiconductor layer containing the same conductivity type impurity as the semiconductor substrate 10 and the semiconductor layer 11. Also good.

It is a top view of the light receiving element according to the first embodiment of the present invention. It is sectional drawing of the AA arrow direction of the light receiving element of FIG. It is sectional drawing for demonstrating an example of the manufacturing process of the light receiving element of FIG. It is sectional drawing for demonstrating the process following FIG. It is sectional drawing for demonstrating the process following FIG. It is sectional drawing for demonstrating the other example of the manufacturing process of the light receiving element of FIG. It is sectional drawing for demonstrating the process following FIG. It is sectional drawing for demonstrating the process following FIG. It is an upper surface of the light receiving element which concerns on one modification. It is sectional drawing of the AA arrow direction of the light receiving element of FIG. It is an upper surface of the light receiving element which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the AA arrow direction of the light receiving element of FIG. It is a schematic block diagram of the information reproduction | regeneration recording device which concerns on one application example. It is a schematic block diagram of the light-receiving device which concerns on the other application example. It is a top view of the conventional light receiving element. It is sectional drawing of the AA arrow direction of the light receiving element of FIG. It is a top view showing the example of in-plane arrangement of a photodiode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 ... Light receiving element 10 ... Semiconductor substrate 11, 11A, 16, 17 ... Semiconductor layer, 12 ... Antireflection film, 12A ... 1st insulating film, 12B ... 2nd insulating film, 12C ... Groove part, 13 ... Interlayer film, 13A ... opening, 13B ... edge, 14 ... cathode electrode, 15 ... cathode connection terminal, 20 ... polysilicon layer, 21,21D ... sidewall layer, 22 ... SiO ₂ layer, 23, 24 ... photoresist layer , 23A, 24A ... opening, 25 ... cobalt layer, 26, 27, 28 ... silicide layer, 29 ... gate electrode, 100 ... information reproduction recording device, 101 ... recording medium, 110 ... optical device, 111 ... GRT, 112 ... PBS 113 ... CL, 114 ... λ / 4 plate, 115 ... OL, 116 ... CyL, 120 ... information processing unit, 200 ... light receiving device, 210 ... light device, 211 ... mirror, 212 ... support substrate, 13 ... transparent substrate, 220 ... information processing unit.

Claims (11)

A first conductivity type semiconductor substrate or a first conductivity type semiconductor layer;
One or a plurality of second conductive semiconductor layers formed on the first conductive semiconductor substrate or the first conductive semiconductor layer;
An antireflection film formed on the second conductive semiconductor layer and having a light receiving surface corresponding to the second conductive semiconductor layer;
An interlayer film formed on the antireflection film and having an opening on the light receiving surface;
An electrode electrically connected to the second conductivity type semiconductor layer,
The electrode is a light receiving element containing silicide.   The light receiving element according to claim 1, wherein the electrode is formed on a periphery of the light receiving surface.   The light receiving element according to claim 1, wherein the electrode extends from a peripheral edge of the light receiving surface to a region facing the light receiving surface. A plurality of the second conductivity type semiconductor layers;
At least one of the plurality of second conductivity type semiconductor layers (first semiconductor layer) is surrounded by a layer other than the first semiconductor layer (second semiconductor layer) of the plurality of second conductivity type semiconductor layers. Surrounded by
The light receiving element according to claim 1, wherein an electrode electrically connected to the first semiconductor layer is formed to extend to a peripheral edge of a light receiving surface provided corresponding to the second semiconductor layer. The interlayer film includes silicon oxide,
The light receiving element according to claim 1, wherein the antireflection film includes silicon nitride on an uppermost surface.   The light receiving element according to claim 5, wherein the antireflection film has a stacked structure in which a silicon oxide layer and a silicon nitride layer are sequentially stacked from the second conductivity type semiconductor layer side.   The light receiving element according to claim 5, wherein the electrode is formed between the second conductive type semiconductor layer and the antireflection film at a periphery of the light receiving surface. The antireflection film has a groove on the periphery of the light receiving surface of the silicon oxide layer,
The light receiving element according to claim 6, wherein the electrode is formed in the groove. A light emitting element that outputs light toward a disk area on which the optical disk is mounted;
An optical system provided between the disk area and the light emitting element;
A light receiving element that receives light reflected from the optical disc out of the light emitted from the light emitting element, and
The light receiving element is
A first conductivity type semiconductor substrate or a first conductivity type semiconductor layer;
One or a plurality of second conductive semiconductor layers formed on the first conductive semiconductor substrate or the first conductive semiconductor layer;
An antireflection film formed on the second conductive type semiconductor layer and having a light receiving surface on which reflected light from the optical disc is incident, corresponding to the second conductive type semiconductor layer;
An interlayer film formed on the antireflection film and having an opening on the light receiving surface;
An electrode electrically connected to the second conductivity type semiconductor layer,
The electrode is an optical pickup device including silicide. An optical pickup device;
An information processing unit that transmits input information to the optical pickup device or receives information written on an optical disc from the optical pickup device, and
The optical pickup device is:
A light emitting element that outputs light according to information transmitted from the information processing unit toward a disk area on which the optical disk is mounted;
An optical system provided between the disk area and the light emitting element;
A light receiving element that receives light reflected from the optical disc among light emitted from the light emitting element;
The light receiving element is
A first conductivity type semiconductor substrate or a first conductivity type semiconductor layer;
One or a plurality of second conductive semiconductor layers formed on the first conductive semiconductor substrate or the first conductive semiconductor layer;
An antireflection film formed on the second conductive type semiconductor layer and having a light receiving surface on which reflected light from the optical disc is incident, corresponding to the second conductive type semiconductor layer;
An interlayer film formed on the antireflection film and having an opening on the light receiving surface;
An electrode electrically connected to the second conductivity type semiconductor layer,
The optical disk apparatus, wherein the electrode includes silicide. A light emitting element;
An optical system that reflects a portion of the light emitted from the light emitting element;
A light receiving element that receives light reflected by the optical system out of light emitted from the light emitting element;
An information processing unit that receives information input from the light receiving element and transmits information corresponding to the received information to the light emitting element, and
The light receiving element is
A first conductivity type semiconductor substrate or a first conductivity type semiconductor layer;
One or a plurality of second conductive semiconductor layers formed on the first conductive semiconductor substrate or the first conductive semiconductor layer;
An antireflection film formed on the second conductive semiconductor layer and having a light receiving surface on which reflected light from the optical system is incident, corresponding to the second conductive semiconductor layer;
An interlayer film formed on the antireflection film and having an opening on the light receiving surface;
An electrode electrically connected to the second conductivity type semiconductor layer,
The electrode is a light receiving device containing silicide.

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