JP2010205858A - Photodetector, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photodetector solving problems associated with pixel-based connection due to an In bump while attaining size reduction and generating no high stress around a connection part of a photodiode with a readout circuit. <P>SOLUTION: The photodetector is characterized in that a pixel electrode 11 is provided per pixel in a light receiving element array type sensor chip 50, a readout electrode 71 constituted of a metal protrusion is provided in the readout circuit 70, an anisotropic conductive film 60 for conductive-connecting the pixel electrode of the light receiving element array type sensor chip with the readout electrode of the readout circuit per pixel is provided, and the anisotropic conductive film 60 fills space between the light receiving element array type sensor chip and the signal readout circuit to adhere the light receiving element array type sensor chip to the readout circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light detection device including a light receiving element array type sensor in which a plurality of photodiodes are formed in a stacked body of compound semiconductors, and a readout circuit for reading an electric signal from the light receiving element array type sensor, and It relates to the manufacturing method.

In the detection device in which the photodiodes are arranged, the readout electrodes of the signal readout silicon IC (ROIC: Read Out IC) and the electrodes of the arranged photodiodes face each other, and conduction is made for each photodiode forming the pixel. Be taken. The photodiode is formed of a compound semiconductor in the near infrared region or the infrared region longer than the visible region. For this reason, a near-infrared or infrared light detection device is sometimes called a hybrid device because it combines a compound semiconductor and a silicon IC that forms a readout circuit. The crystal of the above compound semiconductor is weak in mechanical force, and particularly in the case of an infrared detector, since a photodiode that requires low-temperature cooling is often used, in the peripheral part including the conduction part for each pixel, Thermal stress is repeatedly generated. Due to this repeated thermal stress, the connection peripheral portion of the compound semiconductor is easily broken, and proposals have been made on materials and structures for providing durability to overcome this (Patent Documents 1 and 2).
In addition, when the above-described hybrid configuration including an infrared detection device is formed, soft indium (In) having a low melting point is often used for the bump. Due to this characteristic, indium bumps are likely to be irregular and irregular in shape when they are provided on a photodiode electrode or ROIC readout electrode. For example, it often does not align in a columnar shape, but a burr protrudes along the edge of the top, or collapses to one side and is bent into a truncated cone shape in many cases. One detection apparatus is provided with tens of thousands to hundreds of thousands of bumps, and bumps having a large shape deviation are always generated therein. A bump having a large shape deviation does not realize one-to-one conduction at the time of pressure bonding, fusion, or the like, and protrudes beyond a pixel region to contact an adjacent bump, or does not even realize one-to-one conduction. Such defective pixels are unsightly in the case of imaging, and cause deterioration in resolution in the case of substance detection and inspection, thus reducing the commercial value.

  Many proposals have been made to solve the above problems. In order to uniformly control the shape of the In bump in the hybrid configuration, (1) it is easy to align the shape of the In bump by heating and melting at the time of lift-off using an In vapor deposition film that has been alloyed to lower the melting point. A method has been proposed (Patent Document 3). In addition, (2) a proposal has been made to provide a compound semiconductor substrate and a silicon substrate with a fitting structure with concave and convex portions in order to prevent lateral displacement during bonding of bumps having a hybrid structure (Patent Document 4). In addition, (3) a method of inserting an interval adjusting member for making the interval in the vertical direction (thickness direction) appropriate for the purpose of preventing defective bonding of bumps when bonding bumps was proposed (patent). Reference 5). Further, (4) a method of using an insulating resin grid-like member, inserting the above bumps into holes in the grid, surrounding the bumps by non-holes, and isolating from the adjacent bumps has been proposed (Patent Document 6). .

Japanese Patent Laid-Open No. 5-145089 JP 7-218335 A JP-A-5-136147 JP-A-7-38076 JP 2002-299650 A JP-A-7-153905

The improved methods (1) to (4) have the following problems.
(1) (i) Applications are limited. Since the melting point of 157 ° C. In is a method of further lowering the melting point, the reduced melting point bump does not exist due to the heat generated in the IC, the atmospheric temperature in summer, and the like. For this reason, the use is limited to an infrared sensor or the like that is cooled and used like MCT (HgCdTe). In addition, die bonding materials for mounting on a package after hybrid configuration, and bonding materials for sealing by bonding a lid to the package are used from the viewpoint of preventing remelting of the bumps that may cause a short circuit between pixels. Furthermore, it is necessary to select a material having a lower melting point, and the options are extremely small. (Ii) In the case of In vapor deposition, since there is a variation in the amount of vapor deposition, it is difficult to align the heights of In bumps. For example, even if an In bump is formed on both the photodiode and the ROIC to absorb the variation, the top of the In bump is not flat, and it may slip during bonding and cause a short circuit between pixels.
(2) High cost. In order to form the concave / convex fitting structure, it is necessary to form a mask pattern on both the compound semiconductor substrate and the silicon substrate and perform dry etching or the like. The man-hour for this increases.
(3) Bonding yield is low. When bonding is performed using In bumps having height variations and shape variations, uneven bonding occurs in the initial stage of bonding.
(4) Bonding yield is low. Although a short circuit due to a lateral shift can be prevented by the non-hole portion of the lattice, a short circuit due to an overflow due to a height variation or a disconnection of an insufficient height portion cannot be suppressed.
The above problems can be solved by increasing the pixel interval, but as a result, it becomes impossible to increase the definition of the photodetection device, and if the number of pixels is increased, the detection device becomes large.

  The present invention solves problems such as generation of defective pixels due to connection by In bumps while reducing the size, and has high locality around the connection portion between the light receiving element array type sensor chip and the signal readout circuit so as to reduce durability. An object of the present invention is to provide a photodetector and a method for manufacturing the same that do not generate stress.

  The light detection device of the present invention includes a light receiving element array type sensor chip in which a plurality of pixels are formed in a stack of compound semiconductors for converting light into an electric signal, and an electric signal from the light receiving element array type sensor chip. And a separate signal readout circuit for reading out each pixel. In this photodetection device, a pixel electrode is provided for each pixel in the light receiving element array type sensor chip, and the signal readout circuit reads out the metal protrusion for each pixel facing the light receiving element array type sensor chip. An electrode is provided, and an anisotropic conductive film that conductively connects the pixel electrode of the light receiving element array type sensor chip and the readout electrode of the signal readout circuit for each pixel is provided. This anisotropic conductive film fills the space between the light receiving element array type sensor chip and the signal readout circuit, and bonds the light receiving element array type sensor chip and the readout circuit.

According to the above configuration, since an anisotropic conductive film that does not cause a short circuit with an adjacent pixel is used without using an In bump or the like, the pixel (element) pitch of the light receiving element array is narrowed to promote downsizing. Can do. Further, local high stress is not generated on the sensor chip. A very significant advantage is in the following points. The surface layer (selective diffusion mask pattern side) of the compound semiconductor sensor chip requires delicate handling, and causes an increase in dark current and a reduction in life due to moisture and the like. The anisotropic conductive film fills a gap formed between the sensor chip and the readout circuit and does not expose to the atmosphere. This eliminates the need for highly airtight packaging that is sealed with a vacuum or an inert gas, thereby reducing costs and preventing yield loss due to packaging defects. By forming a resin seal using an anisotropic conductive film, packaging can be realized very simply. Further, by bonding, it is possible to prevent a high local stress that reduces durability from being generated around the connection portion between the photodiode and the readout circuit. The ground electrode is naturally provided in the sensor chip and the readout circuit, and is conductively connected. The light receiving element array may be a one-dimensional array or a two-dimensional array.
Here, the light receiving element array type sensor chip is abbreviated as a sensor chip or a light receiving element array, and one or a plurality of light receiving elements may be called a photodiode. The signal readout circuit may be abbreviated as a readout circuit or ROIC in some cases.

The compound semiconductor laminate is formed of (1) a compound semiconductor substrate, a light-receiving layer positioned directly on the substrate or via a buffer layer, and a cap layer positioned on the light-receiving layer: (2 ) A selective diffusion mask pattern / insulating separation film having an opening for each pixel is positioned on the cap layer, and the selective diffusion mask pattern / insulating separation film having an opening for each pixel is selectively diffused so as to reach the light receiving layer through the cap layer from the opening of the selective diffusion mask pattern. Pixels formed by impurity regions of one polarity: (3) Pixel electrodes located on the cap layer for each impurity region of the first polarity: (4) Connected to a compound semiconductor substrate or buffer layer in common with the pixels The reverse polarity ground electrode: (5) The pixel electrode and the ground electrode which are located on the same side of the stacked body and have the same height can be formed.
Thereby, in the sensor chip, the heights of the arrayed first polarity pixel electrodes (eg, p-side electrode) and second polarity ground electrodes (eg, n-side electrode) can be made uniform. Since the anisotropic conductive film is relatively thin, by aligning the height of all the electrodes of the sensor chip, reliable conductive connection with each electrode of the signal readout circuit, and resin sealing that does not leave a gap, It can be easily realized.

  The sensor chip is formed on an InP substrate and has any one of an InGaAs, InGaAsN, InGaAs / GaAsSb multiple quantum well structure, and InGaAsN / GaAsSb multiple quantum well structure as a light receiving layer, and an absorption edge wavelength at room temperature of 1.6 μm. This can be done. According to this light receiving element array type sensor chip, it is not necessary to use it after cooling to −100 ° C. or lower like indium antimony (InSb) or MCT (HgCdTe). For this reason, an anisotropic conductive film can be used very suitably for conductively connecting the readout electrode for each pixel. Since the anisotropic conductive film is mainly composed of resin, there is a high risk of destruction due to repeated cooling. However, the above light receiving element array type sensor chip has a small noise current even if it is not cooled. Eliminates significant cooling. As a result, it is possible to obtain a long-life photodetection device with excellent durability.

  The method for manufacturing a photodetection device according to the present invention includes a sensor chip in which a plurality of pixels are formed in a stack of compound semiconductors for converting light into an electric signal, and reading out an electric signal from the sensor chip for each pixel. And a separate signal readout circuit. In this manufacturing method, the light-receiving layer of the sensor chip is formed of an InP-based compound semiconductor having an absorption edge wavelength of 1.6 μm or more at room temperature, and the sensor chip and a metal provided at a position corresponding to the pixel electrode of the sensor chip An anisotropic conductive film for conductively connecting the pixel electrode and the readout electrode for each pixel is sandwiched between the readout circuit having the readout electrode of the protrusion, and heated while being pressed, and the sensor chip and the readout circuit And a step of filling the gap with an anisotropic conductive film and bonding and curing the film.

  By the above method, the pixel (element) pitch of the light receiving element array can be narrowed to promote downsizing. That is, while reducing the size, problems such as defective pixel generation due to connection by In bumps are solved, and locally high stress that reduces durability is not generated around the connection portion between the photodiode and the readout circuit. Further, the anisotropic conductive film fills a gap formed between the sensor chip and the readout circuit and is not exposed to the atmosphere. This eliminates the need for highly airtight packaging that is sealed with a vacuum or an inert gas, thereby reducing costs and preventing yield loss due to packaging defects. By forming a resin seal using an anisotropic conductive film, packaging can be realized very simply. Note that the conductive connection between the ground electrodes is naturally performed on the electric circuit in parallel with the conductive connection between the pixel electrode and the readout electrode.

  The main component of the resin of the anisotropic conductive film is an epoxy resin, and the degree of cure of the epoxy resin in the process of heating by applying pressure and bonding and curing is determined by the near-infrared absorption spectrum using the photodetector. can do. The epoxy resin is softened, nearly melted, or melted by the above heating, and fills between the light receiving element array type sensor chip and the readout circuit. At this time, although the conductive particles in the anisotropic conductive film realize conduction in the thickness direction, the degree of cure of the epoxy resin needs to be a certain level or more in order to stably maintain this conductive connection state for a long period of time. The degree of cure of the epoxy resin can be determined nondestructively by measuring the absorption spectrum of the epoxy resin in the wavelength range of 2.1 μm to 2.3 μm. For this reason, the curing degree of the epoxy resin in the resin sealing can be determined by a photodetecting device having a light receiving layer of an InP-based compound semiconductor having an absorption edge wavelength of 1.6 μm or more at room temperature.

  The present invention solves problems such as generation of defective pixels due to connection by In bumps while reducing the size, and does not cause locally high stress that lowers durability in the vicinity of the connection portion between the sensor chip and the readout circuit. A photodetection device can be obtained.

It is sectional drawing which shows the photon detection apparatus in Embodiment 1 of this invention. It is the top view which looked at the sensor chip of the detection apparatus of FIG. 1 from the multiplexer side. FIG. 3 is an enlarged view of a pixel in FIG. 2. It is sectional drawing which shows the anisotropic conductive film 60 of the part of the adjacent pixel electrode 11 in FIG. It is a figure which shows the manufacturing method of the sensor chip of this Embodiment, (a) is the state which formed the laminated body of the compound semiconductor, (b) is the state which formed the selective diffusion mask pattern by mesa etching, (c) FIG. 3 is a view showing a state where a p-type region is formed by selective diffusion of Zn. FIG. 5C shows a manufacturing method subsequent to FIG. 5C, in which FIG. 5A shows a state where a SiON protective film is formed and a p-side electrode is formed in a p-type region, and FIG. 5B shows an n-side electrode formed and attached to glass. State (c) is a view showing a state in which an AR film is formed after the back surface polishing. It is sectional drawing which shows the photon detection apparatus in Embodiment 2 of this invention. A method for manufacturing a sensor chip is shown, (a) is a state in which a compound semiconductor layer is epitaxially grown on an InP substrate, (b) is a state in which an n-type buffer layer at the peripheral portion of the sensor chip 50 is exposed, and (c) is a state in which It is a figure which shows the state which removed the InP cap layer of the part adjacent to the exposed n-type buffer layer. FIG. 8C shows a manufacturing method subsequent to FIG. 8C, in which FIG. 8A shows a state in which a selective diffusion mask layer is formed, FIG. 8B shows a state in which zinc is selectively diffused using a patterned selective diffusion mask pattern, and FIG. FIG. 6D is a diagram showing a state where a SiON protective film is formed on a selective diffusion mask pattern, and FIG. 8D is a diagram showing a state where an n-side electrode and a p-side electrode are formed.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a photodetection device 100 according to Embodiment 1 of the present invention. A light receiving element array type sensor chip (hereinafter referred to as a sensor chip) 50 is formed in a laminate of InP substrate 1 / n type buffer layer 2 / light receiving layer (light absorption layer) 3 / cap layer 4. In each light receiving element, p-type impurity zinc (Zn) is selectively diffused and introduced to form a p-type region 6, and a pn junction 15 is formed at the front. A p-side electrode 11 is in ohmic contact with the p-type region 6, and is connected to a readout electrode 71 of a readout circuit (multiplexer) 70 via an anisotropic conductive film 60. The read electrode 71 is formed by a metal protrusion. A CMOS (Complementary Metal Oxide Semiconductor) is used for the multiplexer of the readout circuit 70. The p-type region 6 is a portion corresponding to the pixel. The n-side electrode 12 that applies a common ground potential to the p-side electrode 11 that is the pixel electrode is continuously connected to the second-polar common electrode 12a that is in ohmic contact with the n-side buffer layer 2, and the common electrode 12a. The wiring electrode portion 12b is located on the SiON protective film 37 also serving as an AR (Anti-Reflection) film and also facing the ground electrode 72 of the CMOS 70. The wiring electrode portion 12 b faces the CMOS ground electrode 72 on the selective diffusion mask layer 36 and the AR film 37. As will be described later, the n-side electrode 12 may be provided in a frame shape so as to surround all of the plurality of pixels and border the sensor chip 50, but may be provided as intermittent point-like protrusions. Similarly to the readout electrode 71, the ground electrode 72 of the CMOS 70 is also formed by a metal protrusion (frame shape or intermittent dot protrusion). Similarly to the n-side electrode 12 of the sensor chip 50, the ground electrode 72 is provided in common to each readout electrode 71 of the CMOS 70. The light is incident on the bottom surface of the InP substrate 1, and an antireflection film 35 is preferably provided on the bottom surface. Further, the selective diffusion mask pattern 36 used for selective diffusion of the p-type region 6 is left as it is, and also serves as an insulating separation film between pixels together with a protective film 37 that also serves as an AR film.
In the present embodiment, the n-type buffer layer 2 is disposed on the InP substrate 1, and the buffer layer 2 is doped with an n-type impurity concentration so that the common electrode 12a is in ohmic contact. In this case, a semi-insulating substrate can be used as the InP substrate. An n-type InP substrate can also be used. When the n-type InP substrate 1 is used and the n-type impurity concentration is so high that the common electrode 12a is in ohmic contact, the n-type buffer layer 2 is omitted and the n-side common electrode 12a is formed on the n-type InP substrate 1. can do.

The first point in the photodetector 100 of the present embodiment is that the anisotropic conductive film 60 is used for conductive connection between the sensor chip 50 and the CMOS 70. The anisotropic conductive film 60 is mainly composed of a resin (including a curing agent that accelerates curing by heating) that is an insulating adhesive, and conductive particles dispersed in the resin within a predetermined volume ratio range. To do. Electrically, it has conductivity in the thickness (longitudinal) direction and is an insulator in the plane (lateral) direction. Therefore, the pixel electrode 11 and the n-side electrode 12 of the sensor chip 50 can be individually connected to the readout electrode 71 and the ground electrode 72 of the CMOS 70.
The second point in the photodetector 100 of the present embodiment is that the height of the p-side electrode (pixel electrode) 11 and the height of the n-side electrode (ground electrode) 12 are aligned. Another point is that the electrodes 71 and 72 of the readout circuit are formed of metal protrusions having the same height. In order to make the heights of the electrodes 11 and 12 of the sensor chip uniform, (1) the thickness of the selective diffusion mask pattern 36, (2) the thickness of the SiON protective film 37 that also serves as the AR film, and (3) the wiring electrode 12b The sum of the thicknesses is made the same as (4) the thickness of the p-side electrode 11. The wiring electrode portion 12 b of the n-side electrode 12 is on the selective diffusion mask layer 36 / SiON protective film 37 on the cap layer 4 in a portion facing the electrode 72 of the CMOS 70. The p-side electrode 11 is on the cap layer 4. As described above, if the total thickness of the (selection diffusion mask layer 36 / SiON protective film 37 / wiring electrode portion 12b) and the thickness of the p-side electrode 11 are the same, the height relative to the CMOS 70 can be made the same. it can. The common electrode 12a of the n-side electrode 12 is preferably made of AuGeNi so as to be in ohmic contact with the n-type InP buffer layer or the InGaAs buffer layer 2, and the p-side electrode 11 is ohmically contacted with the InP cap layer 4. It is good to form with AuZn.

The following effects (E1) to (E3) can be obtained from the first and second points.
(E1) By sandwiching the anisotropic conductive film 60 between the sensor chip 50 having the electrodes 11 and 12 having the same height and the readout circuit 70 having the electrodes 71 and 72 of the metal protrusion having the same height, A reliable conductive connection can be easily realized while preventing a short circuit with an adjacent pixel. That is, the 1: 1 conductive connection between the pixel electrode 11 and the readout electrode 71 is realized in the thickness direction (vertical direction). Then, reliable insulation in the horizontal direction (horizontal direction) can be obtained, and a short circuit with an adjacent pixel electrode can be prevented. This action is derived from the electrical characteristics of the anisotropic conductive film 60.
(E2) Further, the electrodes having the same height as described above also have a beneficial effect on reliable resin sealing by the anisotropic conductive film 60. The surface layer (on the selective diffusion mask pattern 36 side) of the sensor chip 50 of InP-based compound semiconductor requires delicate handling, and causes an increase in dark current and a reduction in life due to moisture and the like. The anisotropic conductive film 60 fills a gap formed between the sensor chip 50 and the CMOS 70 and does not expose to the atmosphere. For this reason, packaging with high airtightness sealed with vacuum or inert gas becomes unnecessary, and cost reduction and yield reduction due to packaging failure can be prevented. By forming the resin seal using the anisotropic conductive film 60, packaging can be realized very simply.
(E3) The anisotropic conductive film further realizes not only resin sealing of the sensor chip 50 but also adhesion between the sensor chip 50 and the CMOS 70. Since the bonding is performed by the resin, no large stress is locally generated, and no large local stress is observed in the conductive connection by the conventional indium bump. By this adhesion, the conductive connection of (E1) can be maintained. In addition, it effectively works to reduce the size of the photodetection device 100.

FIG. 2 is a view of the sensor chip 50 as viewed from the CMOS 70 or the anisotropic conductive film 60 side. For example, the number of pixels P is 320 × 256, the pitch is 25 μm, and the overall size is 10 mm □. In common with the sensor chip 50, the common electrode 12a of the second polarity of the n-side electrode 12 and the wiring electrode portion 12b are provided so as to surround the pixel array.
FIG. 3 is a diagram illustrating the pixel P. A broken-line circle indicates the p-type region 6 in which the p-side electrode 11 is located. The periphery of the p-side electrode is covered with a selective diffusion mask pattern 36 made of SiN and a SiON protective film 37 that also serves as an AR film.

  FIG. 4 is a conceptual diagram showing the anisotropic conductive film 60 in the portion of the adjacent pixel electrode 11 in FIG. Examples of the anisotropic conductive film 60 include those having a thermosetting resin (curing agent) 62 and conductive particles 61 as main components. For example, a epoxy resin can be suitably used as the thermosetting resin 62. The anisotropic conductive film 60 is sandwiched between the sensor chip 50 and the CMOS 70 and heated while receiving pressure, so that the anisotropic conductive film 60 is in a softened state, a state close to melting, or a molten state. And fill the gap. Then, the sensor chip 50 and the CMOS 70 are bonded by being cured by the action of the curing agent. The volume ratio, shape, and the like of the conductive particles 61 are set such that adjacent pixel electrodes 11 are not short-circuited as shown in FIG. A thermosetting epoxy resin or the like is preferably used for the resin 62 of the anisotropic conductive film 60, but a silicone resin or a polyimide resin having excellent heat resistance may also be used. In the case of using an epoxy resin, a resin called a bisphenol-based resin produced by reacting bisphenol A or bisphenol F with epichlorohydrin can be used. A novolac resin may be used. As the conductive particles 61 of the anisotropic conductive film 60, metal particles having various shapes (granular, needle-like, etc.), metal-plated resin core particles, and the like can be used. The metal particles are preferably granular or acicular nickel particles, and the metal plating resin core particles are preferably gold plating particles having acrylic or polystyrene as a core.

The third point of the photodetecting device 100 of the present embodiment is that the sensor chip 50 can receive light having a wavelength of 1.6 μm or more at room temperature without requiring a large cooling mechanism. Since there is no large-scale cooling mechanism, it is possible to obtain a highly durable photodetection device that does not repeatedly generate thermal stress. For this purpose, the sensor chip 50 has the following structure.
(1) Structure of Sensor Chip Referring to FIGS. 1 and 2, the light receiving element P of each pixel has a III-V group semiconductor stacked structure (epitaxial wafer) having the following configuration on an InP substrate 1.
(InP substrate 1 / n-type InP buffer layer 2 / single-layer light-receiving layer, or light-receiving layer 3 / InP cap layer 4 having a multiple quantum well structure of InGaAs (N) and GaAsSb)
When forming a light receiving layer having a multiple quantum well structure, an InGaAs diffusion concentration distribution adjusting layer (not shown) may be inserted between the light receiving layer 3 and the InP cap layer 4. Here, the case where a single layer is used for the light receiving layer 3 without using the multiple quantum well structure and the diffusion concentration distribution adjusting layer will be described. Examples of the single light-receiving layer having sensitivity at a wavelength of 1.6 μm or more include InGaAs, GaInNAs, and the like. The p-type region 6 located so as to reach from the InP cap layer 4 to the light-receiving layer 3 is formed by selectively diffusing Zn of the p-type impurity from the opening of the selective diffusion mask pattern 36 of the SiN film. Introducing diffusion within the periphery of each pixel in a plane-limited manner is realized by diffusing using the selective diffusion mask pattern 36 of the SiN film. On the selective diffusion mask pattern 36, a SiON protective film 37 that also serves as an AR film is usually laminated.
The SiON protective film 37 is opened, and the p-side electrode 11 made of AuZn is provided in the p-type region 6, and the AuGeNi second-polar common electrode 12 a is provided in ohmic contact with the n-type InP buffer layer 2. ing. In this case, the n-type InP buffer layer 2 is doped with an n-type impurity to ensure a predetermined level of conductivity. An SiON AR film 35 may be provided on the back surface of the InP substrate 1 to promote the incidence of light from the back surface side of the InP substrate.

In the light receiving layer 3, a pn junction 15 is formed at a position corresponding to the boundary front of the p-type region 6. By applying a reverse bias voltage between the p-side electrode 11 and the n-side electrode 12, n A depletion layer is formed more widely on the side with the lower impurity concentration (n-type impurity background). The background in the light receiving layer 3 is about 5 × 10 ¹⁵ / cm ³ or less in terms of n-type impurity concentration (carrier concentration). The position 15 of the pn junction is determined by the intersection of the background (n-type carrier concentration) of the light receiving layer 3 and the concentration profile of the p-type impurity Zn.

(2) Sensor Chip Manufacturing Method FIGS. 5A to 5C and FIGS. 6A to 6C show an outline of a sensor chip manufacturing method. This is a continuous manufacturing process from the stage of FIG. 5A to the stage of FIG. In FIG. 5A, it is preferable to use a semi-insulating Fe-doped InP substrate for the InP substrate 1. On the semi-insulating Fe-doped InP substrate 1, a Si-doped InP buffer layer 2 (thickness 2 μm, n-type, carrier concentration 1e17 cm ⁻³ ) and a non-doped light-receiving layer 3 (thickness) are formed by OMVPE (Organo-Metallic Vapor Phase Epitaxy) method. 2 μm to ³ μm, n-type, carrier concentration 1e15 cm ⁻³ ) and a non-doped InP cap layer 4 (thickness 0.2 μm, n-type, carrier concentration 2e15 cm ⁻³ ) are epitaxially grown. The thickness, carrier concentration, etc. are examples. Next, the peripheral portion Ka of the sensor chip 50 is mesa-etched to expose the Si-doped InP buffer layer 2 where the n-side electrode 12 is conductively connected. Thereafter, a selective diffusion mask pattern 36 is formed (see FIG. 5B). Although only one opening 36h corresponding to the pixel P is displayed, it goes without saying that a plurality of light receiving element array type sensor chips are arranged. Next, as shown in FIG. 5C, Zn is diffused and introduced to form the p-type region 6 and the pn junction 15 described above. The p-type region 6 is a region corresponding to the pixel P, and as shown in FIG. 1, the adjacent p-type region 6 is separated by a non-doped InP cap layer. By forming the p-type region 6 for each pixel by selective diffusion of Zn, crosstalk and dark current can be reduced even if the pixels are densely arranged at a fine pitch.
Next, it is covered with a SiON protective film 37. Thereafter, the pixel-corresponding portion of the SiON protective film 37 is opened to form the p-side electrode 11 as shown in FIG. Next, the SiN selective diffusion mask layer 36 / SiON protective film 37 is opened at the location where the n-side electrode of the peripheral edge Ka is formed. Next, a second polarity common electrode 12a and a wiring electrode portion 12b continuous to the common electrode are formed so as to be conductively connected to the InP buffer layer 2. Here, the p-side electrode 11 and the n-side electrode 12 (common electrode 12a and wiring electrode portion 12b) have the same height. Then, the p-side electrode 11 and the n-side electrode 12 having the same height are attached to the flat glass 81 (see FIG. 6B). With respect to the sensor chip 50 attached to the glass 81, the back surface of the InP substrate 1 is polished to smooth the back surface serving as the light incident surface. After the backside polishing, the glass is peeled off, and an SiON AR film 35 is laminated on the backside.

(Embodiment 2)
FIG. 7 is a cross-sectional view showing photodetection device 100 according to Embodiment 2 of the present invention. The sensor chip 50 is formed in a laminate of InP substrate 1 / n-type buffer layer 2 / light receiving layer (light absorption layer) 3 / cap layer 4. In the sensor chip 50, (1) the wiring electrode portion 12b of the n-side electrode 12 is placed on the light receiving layer 3 / the selective diffusion mask layer 36 / the SiON protective film 37, and the cap layer 4 is removed. (2) The thickness of the cap layer 4 and the total thickness of the selective diffusion mask layer 36 and the SiON protective film 37 are the same, and the structure is special with respect to the first embodiment. Become. Other parts are the same as those of the first embodiment. The first to third points of the light detection device in the first embodiment also apply to this embodiment. However, the structure for realizing the second point is a special structure in the structure of the first embodiment. That is, the structure in which the height of the p-side electrode (pixel electrode) 11 and the height of the n-side electrode (ground electrode) 12 are aligned is a special case of the first embodiment.

In the present embodiment, the thickness of the cap layer 4 and the total thickness of the selective diffusion mask layer 36 and the SiON protective film 37 are made the same in order to make the heights of the electrodes 11 and 12 of the sensor chip uniform. The wiring electrode portion 12b of the n-side electrode 12 is on the light receiving layer 3 / selective diffusion mask layer 36 / SiON protective film 37 in a portion facing the electrode 72 of the CMOS 70, and the cap layer 4 is a portion thereof. Only excluded. The p-side electrode 11 is on the light receiving layer 3 / cap layer 4. As described above, if the total thickness of the selective diffusion mask layer 36 and the SiON protective film 37 and the thickness of the cap layer 4 are made the same, the wiring electrode portion 12b and the p-side electrode 11 are made of the same metal material at the same opportunity. Thus, the same height can be obtained by stacking with the same thickness. The common electrode 12a of the n-side electrode 12 is preferably formed of AuGeNi so as to be in ohmic contact with the n-type buffer layer 2, and the p-side electrode 11 is formed of AuZn so as to be in ohmic contact with the InP cap layer 4. Is good. Therefore, the wiring electrode portion 12 b of the n-side electrode 12 can be formed of the same AuZn as the p-side electrode 11. The metal AuGeNi and the metal AuZn can easily realize ohmic contact with the counterpart semiconductor, respectively. In this manufacturing method, the p-side electrode 11 is not formed first, but the n-side electrode common electrode 12a is formed first. Thereafter, after performing a predetermined opening process, the p-side electrode 11 and the wiring electrode portion 12b are preferably formed simultaneously.
Thereby, all the heights of the electrodes of the sensor chip 50 can be made uniform while saving the manufacturing process. As a result, the anisotropic conductive film 60 is sandwiched between the sensor chip 50 having the electrodes 11 and 12 having the same height and the signal readout circuit 70 having the electrodes 71 and 72 having the metal protrusions having the same height. A reliable conductive connection can be easily realized. Naturally, the effects (E1) to (E3) in the first embodiment can be obtained.

Next, a method for manufacturing the sensor chip 50 will be described with reference to FIGS. This is a continuous manufacturing process from the stage of FIG. 8A to the stage of FIG. On the semi-insulating Fe-doped InP substrate 1, by OMVPE method, as shown in FIG. 8A, a Si-doped InP buffer layer 2 (thickness 2 μm, n-type, carrier concentration 1e17 cm ⁻³ ), and a non-doped light-receiving layer 3 (Thickness 3 μm, n-type, carrier concentration 1e15 cm ⁻³ ) and non-doped InP cap layer 4 (thickness 0.2 μm, n-type, carrier concentration 2 e15 cm ⁻³ ) are epitaxially grown. The thickness, carrier concentration, etc. are examples. Next, as shown in FIG. 8B, using the resist film 41 as a mask, the peripheral portion Ka of the sensor chip 50 is mesa-etched to form the Si-doped InP buffer layer 2 at the location where the n-side electrode 12 is conductively connected. Expose. Next, as shown in FIG. 8C, the InP cap layer 4 is etched with dilute hydrochloric acid only in the portion Kb where the wiring electrode portion 12b of the n-side electrode 12 is placed. The light-receiving layer 3 is not etched with hydrochloric acid because the above-described InGaAs, GaInNAs, etc. contain As, and only the portion Kb of the InP cap layer 4 can be removed by the above-described dilute hydrochloric acid etching.
Thereafter, as shown in FIG. 9A, a SiN film 36 of a selective diffusion mask that also serves as an insulating separation film was formed to a thickness of 0.2 μm by plasma CVD. The thickness of the SiN film 36 is adjusted to be the same as the thickness of the InP cap layer 4 as described above. Next, after patterning the SiN film 36 to form a selective diffusion mask pattern having an opening, as shown in FIG. 9B, selective diffusion is performed while separating zinc (Zn) from the opening for each pixel and adjacent pixels. To do. By this selective diffusion, a pn junction is formed for each pixel in the InGaAs light receiving layer 3. The pixel size is, for example, a circle having a diameter of 15 μm and a two-dimensional array of 256 rows × 320 columns (81,920 pixels) at a pitch of 20 μm. Next, as shown in FIG. 9C, a SiON protective film 37 is formed so as to cover the selective diffusion mask pattern 36 and the InP cap layer 4. Thereafter, as shown in FIG. 9D, the SiON protective film 37 and the selective diffusion mask 36 are removed from the portion where the electrode is to be formed to form an opening, and the p-side electrode 11 and the n-side electrode are formed there. To do. At this time, first, the n-side common electrode 12a is formed of AuGeNi so as to be in ohmic contact with the n-type InP buffer layer 2. Next, the wiring electrode portion 12b is formed of AuZn from the common electrode 12a to the selective diffusion mask 36 of the portion Kb. On the same occasion, as described above, the p-side electrode 11 is formed of AuZn in parallel. The p-side electrode 11 can be in ohmic contact with the Zn diffusion introducing portion (p-type region) 6 of the InP cap layer 4 by AuZn. For this reason, the wiring electrode part 12b and the p-side electrode 11 of the n-side electrode 12 can be formed with the same material and the same thickness on the same occasion. As described above, since the total thickness of the SiN film 36 and the SiON protective film 37 of the selective diffusion mask and the thickness of the InP cap layer 4 are both set to 0.2 μm, the wiring electrode portions 12b and p having the same thickness are formed. With the side electrode 11, all the heights of the electrodes of the sensor chip 50 can be made uniform.

  Although the embodiments and examples of the present invention have been described above, the embodiments and examples of the present invention disclosed above are merely examples, and the scope of the present invention is the implementation of these inventions. It is not limited to the form. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  According to the photodetector of the present invention, since the anisotropic conductive film is used for the conductive connection between the pixel electrode and the readout electrode, the problem associated with the connection by the In bump is solved while reducing the size, and the photodiode and the readout circuit are There is no local stress high enough to degrade the durability around the connection. Further, since the anisotropic conductive film is bonded while filling the gap between the sensor chip and the signal readout circuit, packaging with high airtightness is not necessary. That is, packaging can be realized very simply by resin sealing with an anisotropic conductive film.

  1 InP substrate, 2 n-type buffer layer, 3 light receiving layer (InGaAs, multiple quantum well structure), 4 cap layer, 6 p-type region, 11 p-side electrode, 12 n-side electrode, 12a n-side common electrode, 12b wiring electrode Part, 15 pn junction, 35 AR film, 36 selective diffusion mask layer (mask pattern), 36h opening of mask pattern, 37 SiON protective film, 41 resist film, 50 sensor chip (light receiving element array), 60 anisotropic conduction Film, 61 conductive particles, 62 resin part, 70 readout circuit (CMOS), 71 readout electrode, 72 ground electrode, 81 glass plate, 100 detector, Ka sensor chip peripheral edge, Kb wiring electrode part of Embodiment 2 Part of the cap layer to be placed, P pixel.

Claims (5)

A light receiving element array type sensor chip in which a plurality of pixels are formed in a stack of compound semiconductors for converting light into an electric signal, and a separate body for reading out the electric signal from the light receiving element array type sensor chip for each pixel A signal reading circuit, and a photodetection device comprising:
The light receiving element array type sensor chip is provided with a pixel electrode for each pixel, and the signal readout circuit has a metal projection readout electrode for each pixel facing the light receiving element array type sensor chip. Provided,
An anisotropic conductive film that conductively connects the pixel electrode of the light receiving element array type sensor chip and the readout electrode of the signal readout circuit for each pixel,
The anisotropic conductive film fills a space between the light receiving element array type sensor chip and the signal readout circuit, and bonds the light receiving element array type sensor chip and the readout circuit, Photodetector.   The compound semiconductor laminate is formed of a compound semiconductor substrate, a light receiving layer positioned directly on the substrate or via a buffer layer, and a cap layer positioned on the light receiving layer, the cap layer A selective diffusion mask pattern / insulating separation film having an opening for each pixel is located above, and the selective diffusion mask is interposed between the pixels so that the pixels are separated for each pixel and reach the light receiving layer. The compound semiconductor is formed by an impurity region of a first polarity selectively diffused from an opening of a pattern, and the pixel electrode is located on the cap layer for each impurity region of the first polarity. A ground electrode of reverse polarity connected to the substrate or the buffer layer is provided, and the pixel electrode and the ground electrode are located on the same side of the stacked body, and the pixel electrode Wherein the height of the pre-ground electrode is aligned, the light detecting device according to claim 1.   The light receiving element array type sensor chip is formed on an InP substrate, and has one of an InGaAs, InGaAsN, InGaAs / GaAsSb multiple quantum well structure, and InGaAsN / GaAsSb multiple quantum well structure as a light receiving layer, and absorbs at room temperature. The photodetection device according to claim 1, wherein an end wavelength is 1.6 μm or more. A light receiving element array type sensor chip in which a plurality of pixels are formed in a stack of compound semiconductors for converting light into an electric signal, and a separate body for reading out the electric signal from the light receiving element array type sensor chip for each pixel A signal reading circuit, and a method of manufacturing a photodetection device comprising:
Forming a light receiving layer of the light receiving element array type sensor chip with an InP-based compound semiconductor having an absorption edge wavelength of 1.6 μm or more at room temperature;
Between the light receiving element array type sensor chip in which a pixel electrode is provided for each pixel and the readout circuit having a metal projection readout electrode provided at a position corresponding to the pixel electrode of the light receiving element array type sensor chip In addition, an anisotropic conductive film for conductively connecting the pixel electrode and the readout electrode for each pixel is sandwiched and heated while being pressurized, and the gap between the light receiving element array type sensor chip and the readout circuit is And a step of filling with an anisotropic conductive film, bonding and curing, and a method of manufacturing a photodetection device. The main component of the resin of the anisotropic conductive film is an epoxy resin, and the degree of cure of the epoxy resin in the step of heating while applying pressure and bonding and curing is determined by a near-infrared absorption spectrum using the photodetector. The method according to claim 4, wherein the determination is performed by:

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