JP2011080772A - Infrared sensor and method for manufacturing the same - Google Patents

Abstract

The present invention provides an infrared sensor with higher accuracy and smaller size than conventional ones.
An infrared sensor includes a quantum photoelectric conversion element having a photoelectric conversion unit having a function of detecting light in an infrared region, and a lead frame (not shown) electrically connected to the quantum photoelectric conversion element. 2) a connection terminal 3, a resin mold 2 for sealing the quantum photoelectric conversion element 1 and the connection terminal 3, and an optical adjustment unit 5 electrically connected to the connection terminal 3 through a metal ball 4. . The optical adjustment unit 5 has a function of guiding light in the infrared region to the quantum photoelectric conversion element 1. The connection terminal 3 is provided with pads 3a to 3d between the metal balls 4 (3c and 3d are not shown). The optical adjustment unit 5 includes a heating element 7 and a temperature measuring element 8, and these elements are electrically connected to the connection terminals 3 a to 3 d through the pads 6 a to d. The quantum photoelectric conversion element 1 is connected to an external circuit via connection terminals 3e to 3f. By causing a current to flow instantaneously through the heating element 7, condensation on the substrate of the optical adjustment unit 5 and its surroundings can be prevented.
[Selection] Figure 1

Description

  The present invention relates to an infrared sensor and a manufacturing method thereof, and more particularly to an infrared sensor including a quantum photoelectric conversion element and a manufacturing method thereof.

  It is difficult to achieve high sensitivity in an infrared sensor that detects light having a long wavelength, for example, a wavelength of 3 μm or more. The reasons include atmospheric background radiation and the occurrence of a phenomenon in which moisture due to condensation on the sensor window absorbs light. Therefore, in many applications, particularly infrared analysis devices that require high-precision measurement, background correction and dew condensation prevention mechanisms are required.

  Also, since the window part of the device itself generates heat and generates radiation, even if the light to be measured does not enter the light receiving element of the device, parasitic radiation from the window part is detected, causing measurement errors. ing.

  An example of a technique for preventing dew condensation on a window in an optical sensor is described in Patent Document 1. In this technique, a plurality of resistors are installed around the optical sensor, and current flows through these resistors, so that the resistors generate heat, and condensation of the optical sensor can be prevented.

JP 2003-099880 A

  However, in the above-described prior art, the size of the entire optical sensor is increased by providing a large number of elements around the optical sensor such as an infrared sensor. In addition, since the system becomes complicated, it is difficult to reduce the size of the optical sensor.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a highly accurate and small-sized infrared sensor as compared with the prior art. Another object of the present invention is to provide a method for manufacturing an infrared sensor that is more accurate and smaller than the conventional one.

  In order to achieve such an object, according to a first aspect of the present invention, there is provided a quantum photoelectric conversion element including a photoelectric conversion unit having a function of detecting light in an infrared region, and an electrical connection to the quantum photoelectric conversion element. A first connection terminal connected to the first connection terminal, a second connection terminal electrically insulated from the first connection terminal, the quantum photoelectric conversion element, the first connection terminal, and the second connection terminal. A resin mold that seals the connection terminal of the optical connection unit, and an optical adjustment unit that is electrically connected to the second connection terminal, wherein the optical adjustment unit transmits light in the infrared region to the quantum photoelectric conversion element. The infrared sensor is characterized in that at least one of a heating element and a temperature measuring element is formed on the optical adjustment unit.

  Further, according to a second aspect of the present invention, in the first aspect, at least one of the heating element and the temperature measuring element is electrically connected to the second connection terminal via a metal ball. It is characterized by.

  According to a third aspect of the present invention, in the first or second aspect, the heating element and the temperature measuring element are both formed on the optical adjustment unit, and the heating element and the temperature measuring element are: Wiring is performed using the same metal material.

  According to a fourth aspect of the present invention, in the first aspect, the light adjusting unit has an optical filter function of selectively transmitting a desired wavelength band.

  According to a fifth aspect of the present invention, in the first aspect, the quantum photoelectric conversion element is formed of a compound semiconductor containing In or Sb.

  According to a sixth aspect of the present invention, there is provided a quantum photoelectric conversion element including a photoelectric conversion unit having a function of detecting light in an infrared region, and a first connection electrically connected to the quantum photoelectric conversion element. Sealing a terminal and a second connection terminal electrically insulated from the first connection terminal with a resin mold, forming a metal ball on the second connection terminal, Flip-chip joining the second connection terminal and an optical adjustment unit that guides light in the infrared region to the quantum photoelectric conversion element so as to be electrically connected via the metal ball. In the infrared sensor manufacturing method, at least one of a heating element and a temperature measuring element is formed on the optical adjustment unit.

  According to a seventh aspect of the present invention, in the sixth aspect, the infrared sensor is an infrared sensor according to any one of the second to fifth aspects.

  According to the infrared sensor of the present invention, high accuracy is realized by providing a heating element or a temperature measuring element on the optical adjustment unit, and the connection terminal formed from the optical adjustment unit and the lead frame is connected via a metal ball. Miniaturization can be realized by electrically connecting and fixing.

  In addition, according to the method for manufacturing an infrared sensor of the present invention, high accuracy is achieved by using an optical adjustment unit including a heating element or a temperature measurement element, and the optical adjustment unit and the quantum photoelectric conversion element are interposed via a metal ball. Thus, miniaturization can be realized by flip-chip bonding so as to be electrically connected.

(A) is sectional drawing of the infrared sensor by embodiment of this invention, (b) is a top view which shows the detailed structure of the optical adjustment part with which the infrared sensor by embodiment of this invention is provided. It is a figure for demonstrating the structure of a general quantum type infrared sensor, Comprising: It is sectional drawing which showed the light-receiving part used for a quantum type infrared sensor. (A)-(d) is a figure for demonstrating the preparation process of the quantum type infrared sensor of an Example. It is sectional drawing along the IV-IV line of FIG.3 (c).

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

  Fig.1 (a) is sectional drawing of the infrared sensor by embodiment of this invention. The infrared sensor 10 includes a quantum photoelectric conversion element 1 including a photoelectric conversion unit having a function of detecting light in the infrared region, and a lead frame (not shown) electrically connected to the quantum photoelectric conversion element 1. A connection terminal 3, a resin mold 2 that seals the quantum photoelectric conversion element 1 and the connection terminal 3, and an optical adjustment unit 5 that is electrically connected to the connection terminal 3 through a metal ball 4 are provided.

  Pads 3a to 3d (3c and 3d are not shown) are formed on the connection terminal 3 of the lead frame so as to be electrically connected to the optical adjustment unit 5. Specifically, a part of the lead frame 3 is exposed, and the exposed parts become pads 3a to 3d. The metal balls 4 are shown between the pads 3a to 3d and the pads 6a to 6d of the optical adjustment unit 5, but specific materials such as In bumps or solder balls have good electrical conductivity and mechanical strength. High material may be used. Here, the role of the metal ball 4 is to mechanically fix and electrically connect the optical adjusting unit 5. In some cases, a fixing method may be used in which the metal balls 4 are formed with a solder paste, and then the optical adjustment unit 5 is placed and heat treatment is performed so that the solder paste is hardened.

The optical adjustment unit 5 has a function of guiding light in the infrared region to the quantum photoelectric conversion element 1. An example of the function of the optical adjustment unit 5 is an optical filter that selects only a part of the wavelength range of the detected light. In this case, the material of the optical member of the filter is a material that transmits predetermined infrared rays such as silicon (Si, glass (SiO ₂ ), sapphire (Al ₂ O ₃ ), Ge, ZnS, ZnSe, CaF ₂ , BaF _2, etc. In addition, as a thin film material deposited on this, silicon (Si), glass (SiO ₂ ), sapphire (Al ₂ O ₃ ), Ge, ZnS, TiO ₂ , MgF ₂ , SiO ₂ , ZrO _{2 are used.} Ta ₂ O ₅ etc. In addition, a dielectric multilayer filter in which dielectric materials having different refractive indexes are laminated in layers on an optical member is formed on both surfaces with a predetermined thickness configuration different on the front and back surfaces. Alternatively, the antireflection film may be formed on only one surface, or an antireflection film may be formed on the front surface, both surfaces of the back surface, or the outermost layer of one surface for the purpose of preventing unnecessary reflection. .

  FIG.1 (b) is a top view which shows the detailed structure of the optical adjustment part with which the infrared sensor by embodiment of this invention is provided. This figure is the figure which looked at the optical adjustment part 5 from the side facing the quantum photoelectric conversion element 1. FIG. The optical adjustment unit 5 includes a heating element 7 and a temperature measurement element 8 on a substrate, and these elements are electrically connected to the connection terminal 3 via pads 6a to 6d. Pads 6a to 6d correspond to pads 3a to 3d, respectively. As shown in FIG. 1A, the light to be detected passes through the optical adjustment unit 5 and enters the quantum photoelectric conversion element 1. In FIG. 1B, the heating element 7 and the temperature measuring element 8 are shown as being formed by separate wirings, but the heating function and the temperature measuring function may be performed by the same wiring. For example, when one wiring is formed on the substrate of the optical adjustment unit 5 and the temperature is measured, the resistance of this wiring is measured, and then the value is converted into the temperature. In the case of heat generation for this purpose, the wiring may be provided with two functions of flowing current so that the wiring generates heat.

  The heating element 7 and the temperature measuring element 8 (or only one element having both functions) are formed using the photolithographic technique and the metal forming technique after the optical filter structure as described above is formed on the substrate of the optical adjustment unit 5. Formed. As a specific forming method, a photoresist is applied, and then patterning is performed using a photomask on which a pattern of the heating element 7 and the temperature measuring element 8 is drawn, and the metal wiring is formed by vapor deposition or sputtering. The pattern of the heating element 7 and the temperature measuring element 8 is formed by performing lift-off of the metal portion that is formed and finally unnecessary. The structure of the metal wiring may be a short film material, or two or more layers of metal material may be used to improve the adhesion of the optical adjustment unit 5 to the substrate. Ti can be used as a material for improving adhesion. It is preferable to form a layer of Pt, Au, etc. after forming Ti. The heating element 7 and the temperature measuring element 8 may be formed of the same material. In this case, it can be formed by a single photolithography process and metal wiring formation process, which may be desirable.

  When the light in the infrared region reaches the quantum photoelectric conversion element 1, the quantum photoelectric conversion element 1 generates an electrical signal corresponding to the intensity of the light. The heating element 7 and the temperature measuring element 8 are designed so as not to interfere with light. This electrical signal is output to the outside through a wire and a terminal (not shown). The terminal for the output signal can be formed on the same lead frame as the connection terminal 3.

  The infrared sensor 10 of the present embodiment can prevent condensation on the substrate of the optical adjustment unit 5 and its surroundings by causing an electric current to flow instantaneously through the heating element 7, thereby reducing the incident efficiency of light by moisture. In addition, stable operation is possible even in an unstable humidity environment. Thereby, the high sensitivity of the quantum photoelectric conversion element 1 can be maintained.

  Further, by using a same heating element 7 to flow a constant current, it is possible to emit constant radiation due to heat generation. Using this radiation, the sensitivity of the quantum photoelectric conversion element 1 can be calibrated.

  Further, by measuring the resistance value of the heating element 7 or the temperature measuring element 8, the temperature around the window can be accurately measured. Using the temperature information of the optical adjustment unit 5 and its surroundings, the temperature correction of the infrared sensor 10 itself can be performed. This temperature correction can be realized by an external signal processing circuit.

  In addition, by using the metal balls 4, the pads 3 a to d on the connection terminal 3, and the pads 6 a to d on the optical adjustment unit 5, the heating element 7 included in the optical adjustment unit 5 is fixed simultaneously with the fixing of the optical adjustment unit 5. Alternatively, the temperature measuring element 8 can be connected to an external circuit via the connection terminal 3 formed from a lead frame, and the number of components can be reduced and the size can be reduced. The optical adjustment unit 5 and the quantum photoelectric conversion element 1 are electrically connected to an external circuit through the same connection terminal 3, but at the stage of device creation, the connection terminals 3a to 3d (optical adjustment unit) are formed by a dicing process or the like. The upper heating element and temperature measuring element connection) and the connection terminals 3e to 3f (for connecting the quantum photoelectric conversion element 1) are electrically insulated, and the heating element and temperature measuring element circuit and the quantum photoelectric conversion element 1 are connected. The circuit can be electrically isolated. As a specific example of the above dicing process, there is a dicing method used for DFN (Dual Flat No-Lead Package).

  In the above description, the case where both the heating element 7 and the temperature measuring element 8 are formed on the optical adjustment unit 5 has been considered. However, even when only one of them is formed, the above-described high At least one of the effects related to accuracy can be achieved, and the infrared sensor 10 can be highly accurate.

  Further, the optical adjustment unit 5 may have a filter function. For example, when detecting radiation from the human body, a wavelength around 10 μm (for example, 5 to 30 μm) emitted by the human body can be selected to make it easy to distinguish from other heat generating objects.

  Next, a method for manufacturing an infrared sensor according to an embodiment of the present invention will be described. First, a quantum photoelectric conversion element 1 including a photoelectric conversion unit having a function of detecting light in the infrared region, and a connection terminal 3 of a lead frame (not shown) electrically connected to the quantum photoelectric conversion element 1 Is sealed with a resin mold 2 (step 1). Next, the metal ball 4 is formed on the pads 3a to 3d on the connection terminal 3 (step 2). Finally, the pads 6a to 6d of the optical adjustment unit 5 are fixed to the pads 3a to 3d via the metal balls 4 by using a flip chip method (step 3). The optical adjustment unit 5 including the heating element 7 and the temperature measurement element 8 in the region of the window 9 is electrically connected to the connection terminal 3 through the metal ball 4. By utilizing this manufacturing method, a small and high-performance infrared sensor can be realized.

Embodiment FIG. 2 is a view for explaining the configuration of a general quantum infrared sensor, and is a cross-sectional view showing a light receiving portion used in the quantum infrared sensor. The photoelectric conversion unit is constituted by a plurality of photoelectric conversion elements 21 provided on, for example, a semi-insulating GaAs substrate 12. In FIG. 2, each of the plurality of photoelectric conversion elements 21 is an InSb-based quantum pin photodiode, and is connected to each other in series. The wiring connecting the photodiodes is a wiring 13 made of a single layer of metal or the like. Each photoelectric conversion element 21 includes an n-type compound semiconductor layer (n layer) such as InSb containing indium (In) and antimony (Sb), a non-doped compound semiconductor layer layer (π layer), and a band gap on the substrate 12. In this structure, a compound semiconductor layer such as AlInSb whose n is larger than the n layer and the π layer and a p-type compound semiconductor layer (p layer) doped with a high concentration of P-type impurities are sequentially stacked. . Infrared rays I indicated by arrows in the figure enter the photoelectric conversion element 21 from the back surface of the substrate 12. Due to the incidence of the infrared rays I, a photovoltaic force corresponding to the amount of radiation of the infrared rays I is generated in the photoelectric conversion element 21. The generated photovoltaic power is output to the outside of the photoelectric conversion unit through the connection wiring.

  The light receiving portion shown in FIG. 2 is molded into a mold resin, and a part of the light receiving portion is exposed so that light enters as shown in FIG. Pads 3a to 3f are formed on the same surface as the light incident surface (becomes connection terminals for the lead frame). Metal balls 4 are formed on the pads a to f, and then the optical adjustment unit 5 is fixed as shown in FIG. The final shape is shown in FIG. The pads 3a to 3d are used for fixing the optical adjustment unit 5, and the pads 3e and 3f are used for electrical connection of the quantum photoelectric conversion element 1.

  FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. Here, the quantum photoelectric conversion element 1 is electrically connected to the pads 3e and 3f via the wire 11 in the package. The pads 3e and 3f are provided for connecting an electronic signal generated in the quantum photoelectric conversion element 1 to an external circuit.

  If such a structure is realized, an infrared sensor with an optical filter, a dew condensation prevention mechanism, a temperature measurement mechanism, and a sensitivity correction mechanism having a very small size, for example, a thickness of 3 mm or less and a depth × width of, for example, 5 mm × 5 mm or less can be realized. Further, when the material of the quantum photoelectric conversion element 1 shown in FIG. 2 (π layer is InSb) is used, the wavelength can be detected from 1 μm to 7 μm, but only the wavelength of, for example, 4 to 4.2 μm is detected depending on the application. If desired, the optical adjusting unit 5 that transmits only this wavelength may be used. In addition, by accurately measuring the temperature of the optical adjustment unit 5, it is possible to correct parasitic radiation by the optical adjustment unit 5. This temperature measurement can be performed by the temperature measuring element 7. For example, if the material of the temperature measuring element 8 is Pt, it can be used as a Pt thermistor. Further, the sensitivity of the sensor can be calibrated by using the same wiring (heating element 7). For example, a current is passed through the heating element 7 to generate a certain amount of radiation by the heat generation, and the quantum photoelectric conversion element 1 detects the light. Since the calibration of the sensitivity of the quantum photoelectric conversion element 1 can be instantaneously performed using the radiation from the heating element 7, it is possible to measure the detected light with higher accuracy than in the past.

  In addition, when measuring infrared light in an unstable humidity environment, condensation on the window may affect the measurement accuracy. In this case, the heat generating element 7 of the present invention is used to generate heat at the window portion and its vicinity, thereby preventing condensation due to heating.

  Therefore, when the infrared sensor of the present invention is used, high-precision measurement of a long-wavelength infrared sensor can be realized with an ultra-small infrared sensor even in an environment where humidity is unstable.

DESCRIPTION OF SYMBOLS 1 Quantum type photoelectric conversion element 2 Mold resin 3 Lead frame connection terminal 3a-d Pad on connection terminal 3 4 Metal ball 5 Optical adjustment part 6a-d Pad on optical adjustment part 5 7 Heating element 8 Temperature measurement element 10 Infrared Sensor 11 Wire 12 Board 13 Wiring

Claims (7)

A quantum photoelectric conversion element including a photoelectric conversion unit having a function of detecting light in the infrared region;
A first connection terminal electrically connected to the quantum photoelectric conversion element;
A second connection terminal electrically insulated from the first connection terminal;
A resin mold for sealing the quantum photoelectric conversion element, the first connection terminal, and the second connection terminal;
An optical adjustment unit electrically connected to the second connection terminal,
The optical adjustment unit guides light in the infrared region to the quantum photoelectric conversion element,
An infrared sensor, wherein at least one of a heating element and a temperature measuring element is formed on the optical adjustment unit.   2. The infrared sensor according to claim 1, wherein at least one of the heating element and the temperature measuring element is electrically connected to the second connection terminal via a metal ball. The heating element and the temperature measuring element are both formed on the optical adjustment unit,
The infrared sensor according to claim 1, wherein the heating element and the temperature measuring element are wired using the same metal material.   The infrared sensor according to claim 1, wherein the light adjusting unit has an optical filter function of selectively transmitting a desired wavelength band.   The infrared sensor according to claim 1, wherein the quantum photoelectric conversion element is formed of a compound semiconductor containing In or Sb. A quantum photoelectric conversion element including a photoelectric conversion unit having a function of detecting light in the infrared region;
A first connection terminal electrically connected to the quantum photoelectric conversion element;
A second connection terminal electrically insulated from the first connection terminal;
Sealing with a resin mold,
Forming a metal ball on the second connection terminal;
Flip-chip joining the second connection terminal and an optical adjustment unit that guides light in the infrared region to the quantum photoelectric conversion element so as to be electrically connected via the metal ball. ,
An infrared sensor manufacturing method, wherein at least one of a heat generating element and a temperature measuring element is formed on the optical adjustment unit.   The said infrared sensor is the infrared sensor in any one of Claims 2-5, The manufacturing method of Claim 6 characterized by the above-mentioned.

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