JP2008107215A - Image sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image sensor capable of preventing charging on a window side substrate without generating an eddy current, and preventing deformation or breakage caused by charging. <P>SOLUTION: In this image sensor including an element side substrate, a detection part formed on the element side substrate, and the window side substrate fixed to the element side substrate so as to cover the detection part, the element side substrate and the window side substrate are connected together electrically through a resistance layer formed on the element side substrate and connected to the element side substrate. In the image sensor including the element side substrate, the detection part formed on the element side substrate, and the window side substrate fixed to the element side substrate so as to cover the detection part, the element side substrate and the window side substrate are connected together electrically through the resistance layer formed on the window side substrate and connected to the window side substrate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image sensor and a manufacturing method thereof, and more particularly to a thermal infrared image sensor including a vacuum micropackage and a manufacturing method thereof.

  In a thermal (non-cooled) infrared image sensor, the infrared detection unit has a heat insulating structure that is thermally isolated from the substrate in order to increase the infrared detection sensitivity. Moreover, in order to improve heat insulation, the infrared detection part is sealed in the vacuum package.

For example, the infrared image sensor described in Patent Document 1 has a heat insulating structure in which an infrared detection unit is held by a support leg on a recess provided in a wafer. On the wafer, a window-side substrate is connected by a solder layer so as to cover the infrared detection unit. A vacuum package is formed by the wafer, the solder layer, and the window side substrate, and the infrared detection unit is disposed in the vacuum package in a vacuum state.
A pad is formed on the element side substrate. In order to connect to bonding wires or the like, the pads are arranged outside the vacuum package. The wiring layer that connects the readout circuit and the like of the infrared image sensor and the pad is formed under the metallization layer provided on the element side substrate in the vacuum package, and between the wiring layer and between the wiring layer and the metallization layer. An insulating film is provided between them.
In such an infrared image sensor, the window side substrate is made of Si or Ge instead of metal so that infrared rays can be transmitted, and an antireflection film made of an insulating film is provided on the surface of the window side substrate.
Japanese National Publication No. 9-506712

  However, as a result of intensive studies by the inventors, in the conventional infrared image sensor, since the antireflection film is generally made of an insulating film such as diamond-like carbon, charging occurs due to static electricity on the antireflection film. It has been found that there is a problem that an electric field is generated between the window side substrate and the infrared detection unit due to charging, and the infrared detection unit held on the support leg is deformed and destroyed.

  In order to prevent charging, the window side substrate and the element side substrate can be electrically connected. However, an overcurrent due to charging flows into a readout circuit or the like formed on the element side substrate, causing malfunction or circuit failure. I also found that there was a problem of destruction.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image sensor that prevents charging on a window-side substrate without generating an overcurrent, and prevents deformation and destruction due to charging.

  The present invention is an image sensor including an element side substrate, a detection unit formed on the element side substrate, and a window side substrate fixed on the element side substrate so as to cover the detection unit. An image sensor is characterized in that the window side substrate is electrically connected through a resistance layer formed on the element side substrate and connected to the element side substrate.

Further, the present invention is a method of manufacturing an image sensor for fixing a window side substrate to an element side substrate in a state of being connected via a resistance layer,
a) forming a detection portion on the element side substrate; forming a resistance layer connected to the element side substrate; forming a wiring layer connected to the resistance layer; and connecting to the wiring layer Forming a device-side metallized layer, and a device-side step including:
b) a window side step including a step of forming a wiring layer connected to the window side substrate, and a step of forming a window side metallization layer connected to the wiring layer;
and c) a step of connecting the element-side metallization layer and the window-side metallization layer with a solder layer.

  As described above, in the image sensor according to the present invention, the element-side substrate and the window-side substrate can be set to the same potential, and deformation or destruction of the detection unit or the like due to the electric field formed between the two substrates can be prevented.

  Further, in the image sensor according to the present invention, it is possible to prevent an overcurrent due to the electric charge accumulated in the window side substrate from flowing into the element side substrate, and to prevent the detection unit from being destroyed.

  Furthermore, in the manufacture of the image sensor according to the present invention, such an image sensor can be manufactured.

Embodiment 1 FIG.
FIG. 1 is a top view of a wafer having an infrared image sensor (vacuum micropackage) according to a first embodiment of the present invention, and shows a state in which a plurality of infrared image sensors 100 are formed on a wafer 101. FIG. 2 is a cross-sectional view of FIG. 1 viewed in the II-II direction. In FIG. 1, the window side substrate 3 is omitted for easy understanding.

  As shown in FIGS. 1 and 2, a plurality of infrared image sensors 100 are formed in a matrix on the wafer 101. The wafer 101 is made of, for example, silicon. In each of the infrared image sensors 100, the window side substrate 3 on which the antireflection films 9a and 9b are formed on both surfaces is joined to the wafer 101 by the solder 2. The antireflection films 9a and 9b are provided to increase infrared transmission efficiency, and are made of, for example, diamond like carbon (DLC) that is an insulator. The window side substrate 3 is also made of, for example, silicon. The space surrounded by the window side substrate 3, the solder layer 2, and the wafer 101 is maintained in a vacuum.

  3 is a top view of a single infrared image sensor (vacuum micropackage) 100 cut out from the wafer 101, and FIG. 4 is a cross-sectional view of FIG. 3 viewed in the IV-IV direction. In FIG. 3, the window side substrate 3 is not shown for easy understanding.

  As shown in FIGS. 3 and 4, the infrared sensor (vacuum micropackage) 100 according to the first embodiment of the present invention includes an element-side substrate 1 made of, for example, silicon. The element side substrate 1 is produced by dicing the wafer 101 of FIG.

  The element side substrate 1 has an infrared detection region 20. In the infrared detection region 20, a plurality of infrared detection units 22 are arranged in a matrix. Each infrared detection unit 22 has a detection film such as a bolometer film, for example, and detects the temperature change of the infrared detection unit 22 by converting it into a current. Each infrared detecting unit 22 is held by a support leg (not shown) on the recess 21 provided in the element side substrate 1. Thereby, the infrared detection part 22 and the element side board | substrate 1 are thermally insulated.

  An insulating layer 12 made of, for example, silicon oxide is provided on the element side substrate 1. In the insulating layer 12, a thin film resistance layer 11 and a wiring layer 10 connected to the thin film resistance layer 11 are provided. The thin film resistance layer 11 is made of, for example, titanium nitride (TiN), and can be set to an arbitrary resistance value by changing the width and length of the thin film resistance layer and the sheet resistance value. Here, the resistance value is set to 500 kΩ to 2 MΩ. The wiring layer 10 is made of, for example, aluminum, titanium, tungsten, or the like. The wiring layer 10 is provided with an external pad 5 and connected to, for example, a bonding wire.

  Further, a metallized layer 6 made of, for example, Au / Ni / Cr is provided on the insulating layer 12 so as to surround the infrared detection region 20. The metallized layer 6 is connected to the wiring layer 10 through the through hole 8. In addition, the metallization layer 6 as used in this Embodiment is corresponded to the element side metallization layer of this invention.

On the element side substrate 1, the window side substrate 3 is placed. The window-side substrate 3 is made of silicon or germanium having a high infrared transmittance, is n-type, and has a resistivity of 5 Ω · cm to 50 Ω · cm.
Antireflection films 9 a and 9 b are provided on both surfaces of the window side substrate 3. The antireflection films 9a and 9b are made of, for example, diamond like carbon (DLC). The antireflection film 9a and the antireflection film 9b may be made of the same material or different materials. A metallized layer 7 made of, for example, Au / Ni / Cr is provided around the antireflection film 9b. The metallized layer 7 is connected to the window side substrate 3 through the through hole 13. In addition, the metallization layer 7 as used in this Embodiment is corresponded to the window side metallization layer of this invention.

  The element side substrate 1 and the window side substrate 3 are joined by connecting the metallized layer 6 and the metallized layer 7 with a solder layer 2 such as AnSn, for example. The solder layer 2 is formed on the surface of the metallized layer 6 and / or on the surface of the metallized layer 7 by a plating method or a preform method. By bonding the element side substrate 1 and the window side substrate 3, the infrared detection region 20 can be sealed in a vacuum state (vacuum micropackage).

  Thus, in the infrared image sensor 100 according to the present embodiment, the window side substrate 3 is connected to the element side substrate 1 via the metallized layer 7, the solder 2 layer, the metallized layer 6, the wiring layer 10, and the thin film resistor layer 11. Electrically connected.

  Here, the “element” refers to a region where a detection unit, a circuit, a wiring, a pad, and the like are formed, and the “detection unit” refers to a region where a heat insulating structure for detecting infrared rays is formed. Say.

  Next, a method for manufacturing the infrared image sensor 100 according to the first embodiment will be described with reference to FIG. In this manufacturing method, one infrared image sensor 100 will be described.

  First, the preparation process of the element side substrate 1 provided with the infrared detection part etc. is performed. This process includes the following processes 1 to 6.

  Step 1: As shown in FIG. 5A, an insulating layer 12 made of, for example, silicon oxide is formed on an element-side substrate 1 made of, for example, silicon. Subsequently, a readout circuit and an infrared detection unit (not shown) are formed on the element side substrate 1.

  Process 2: As shown in FIG.5 (b), the through-hole 23 is formed in the insulating layer 12 using a photolithographic process or an etching process.

  Step 3: As shown in FIG. 5C, a titanium nitride layer is formed by using, for example, a sputtering method, and this is patterned to form a thin film resistance layer 11. By changing the width and length of the thin film resistance layer 11, the resistance value of the thin film resistance layer 11 is set to a desired value.

  Step 4: As shown in FIG. 5D, an aluminum layer is formed by using, for example, a vapor deposition method, and this is patterned to form the wiring layer 10.

  Process 5: As shown in FIG.5 (e), the insulating layer 12 is formed using the thermal CVD method so that the thin film resistive layer 11 and the wiring layer 10 may be covered, for example.

  Step 5: As shown in FIG. 5F, through holes 8 are formed in the insulating layer 12 so as to reach the wiring layer 10 by using a photolithography process or an etching process.

Step 6: As shown in FIG. 5G, after an Au / Ni / Cr layer is formed on the insulating layer 12 by, for example, vapor deposition so as to fill the through hole 8, a photolithography process or an etching process is used. Then, the metallized layer 6 is formed.
Subsequently, a concave portion is formed by wet etching below the infrared detecting portion formed on the element side substrate 1. For example, KOH or TMAH is used as the etching solution. Thereby, the heat insulation structure by which the infrared detection part was hold | maintained on the recessed part with the support leg is formed in an infrared detection area | region (not shown, refer FIG. 4).
Through the above steps, the element-side substrate 1 provided with the infrared detection unit and the like can be obtained.

  Next, a preparation process of the window side substrate 3 provided with an antireflection film or the like is performed. This process includes the following processes 1 to 3.

  Step 1: As shown in FIG. 6A, a window-side substrate 3 made of silicon or germanium is prepared, and antireflection films 9a and 9b made of, for example, diamond-like carbon (DLC) are formed on both surfaces by sputtering or the like. Are sequentially formed.

  Step 2: As shown in FIG. 6B, an opening 16 is formed in the antireflection film 9b so as to reach the window-side substrate 3.

Step 3: As shown in FIG. 6C, after an Au / Ni / Cr layer is formed on the antireflection film 9b by, for example, vapor deposition so as to fill the through hole 16, a photolithography step and an etching step are performed. Using this, the metallized layer 7 is formed.
Through the above steps, the window-side substrate 3 provided with the antireflection films 9a and 9b on both sides can be obtained.

Finally, the window-side substrate 3 is fixed on the element-side substrate 1 produced in the above process.
Specifically, the solder layer 2 which is a conductive bonding material is disposed on the metallized layer 7 of the window side substrate 3. The solder layer 2 may be formed by a plating method, or a preformed solder layer 2 may be placed thereon.

  On the metallized layer 6 of the element side substrate 1, the metallized layer 7 of the window side substrate 3 provided with the solder layer 2 is placed. In this state, the window side substrate 3 is fixed on the element side substrate 1 by heating and melting the solder layer 2 in a vacuum atmosphere and then cooling.

  The infrared image sensor 100 according to the present embodiment is completed through the above steps.

  In addition, although the infrared image sensor 100 was demonstrated in this Embodiment 1, the vacuum micropackage used with the infrared image sensor 100 can be used also for the other sensor which has a heat insulation structure. For example, when the window side substrate 3 does not need to transmit infrared rays as in the case of an acceleration sensor, a material other than Si or Ge can be used as the material of the window side substrate 3. Further, when the antireflection films 9 a and 9 b are unnecessary, the metallized layer 7 can be directly formed on the window side substrate 3. The micropackage can be filled with an inert gas such as nitrogen.

  As described above, in the infrared image sensor 100 according to the first exemplary embodiment, the window-side substrate 3 includes the element through the metallized layer 7, the two solder layers, the metallized layer 6, the wiring layer 10, and the thin film resistor layer 11. It is electrically connected to the side substrate 1. Thus, even if the window-side substrate 3 is charged by connecting the window-side substrate 3 and the element-side substrate 1 with the thin-film resistance layer 11 having a predetermined resistance value interposed therebetween, the window-side substrate 3 is excessively charged to the element-side substrate 1. The current does not flow, and the circuit formed on the element side substrate 1 can be prevented from being broken.

  Further, since no potential difference is generated between the element side substrate 1 and the window side substrate 3, no electric field is formed between the element side substrate 1 and the window side substrate 3. For this reason, for example, the infrared detection unit 22 held on the support leg is not deformed by the electrostatic force due to the electric field, and the contact between the element side substrate 1 and the infrared detection unit 22 or the damage of the infrared detection unit 22 is prevented. Etc. can be prevented.

  Further, the metallized layer 6 on the element substrate side 1 and the metallized layer 7 on the window side substrate 3 are connected by the solder layer 2 to form a vacuum micropackage, whereby the inside of the vacuum micropackage in which the infrared detection region 20 is formed is formed. It can be kept in a vacuum state.

  Furthermore, by using the method according to the present embodiment, the infrared image sensor 100 having the above structure can be manufactured. In particular, such a manufacturing method can be applied to the production of a vacuum micropackage structure having a detection unit other than the infrared detection unit.

Embodiment 2. FIG.
FIG. 7 is a top view of the infrared image sensor (vacuum micropackage) according to the second embodiment, the whole being represented by 200, and FIG. 8 is a cross section when FIG. 7 is viewed in the VIII-VIII direction. FIG. In FIG. 7, the window side substrate 3 is not shown for easy understanding.
7 and 8, the same reference numerals as those in FIGS. 3 and 4 denote the same or corresponding parts. In the infrared image sensor 200, the thin film resistance layer 15 provided on the element side substrate 1 in the above-described infrared image sensor 100 is provided on the window side substrate 3 instead.

  The resistivity of the window side substrate 1 is preferably 5 Ω · cm or more and 50 Ω · cm or less. Thereby, the element side board | substrate 1 and the window side board | substrate 3 can be made into the same electric potential, without the fall of the transmittance | permeability of infrared rays. Other structures are the same as those of the infrared image sensor 100.

  That is, in the infrared image sensor 200, first, a reading circuit, an infrared detection unit (not shown), and wiring layers 4 and 10 are formed on the element side substrate 1. An insulating layer 12 is formed thereon. An opening is provided in the insulating layer 12, and a metallized layer 6 connected to the wiring layer 10 is provided.

  On the other hand, antireflection films 9 a and 9 b are provided on both sides of the window-side substrate 3, and a thin film resistance layer 15 is provided on the antireflection film 9 b so as to fill the opening 16. The resistance value of the thin film resistance layer 15 can be determined by the width and length of the thin film resistance layer 15 and the sheet resistance value. Here, the resistance value is set to 500 kΩ to 2 MΩ. Further, a metallized layer 7 is provided on the thin film resistor layer 15.

  By connecting the metallized layer 6 and the metallized layer 7 with the solder layer 2, an infrared image sensor 200 in which the window-side substrate 3 is fixed on the element-side substrate 1 is obtained. In this case, the vacuum micropackage of the infrared image sensor 200 can be kept in a vacuum state.

Next, a method for manufacturing the infrared image sensor 200 according to the second embodiment will be briefly described.
For the element-side substrate 1, the wiring layer 10 is directly formed on the element-side substrate 1, and then the insulating layer 12 is formed. Subsequently, after forming the opening 8 in the insulating layer 12, the metallized layer 6 is formed. The manufacturing process of the wiring layer 10 and the like is the same as the manufacturing process of the infrared image sensor 100 described above.

  On the other hand, as shown in FIG. 9A, after the antireflection films 9a and 9b are formed on both surfaces of the window side substrate 3, the window side substrate 3 is formed on the antireflection film 9b as shown in FIG. 9B. Opening 16 is formed.

  Further, as shown in FIG. 9C, a thin-film resistance layer 15 made of, for example, titanium nitride is formed on the antireflection film 9b so as to fill the opening 16. Subsequently, a metallized layer 7 made of, for example, Au / Ni / Cr is formed so as to be connected to the thin film resistance layer 15.

Finally, the metallized layer 6 and the metallized layer 7 are connected to each other by the solder layer 2, and the supplementary rotator image sensor 200 in which the window side substrate 3 is fixed on the element side substrate 1 is completed.
The steps other than those shown here are almost the same as the manufacturing method of the infrared image sensor 100 described above.

  As described above, also in the infrared image sensor 200 according to the second embodiment, the window side substrate 3 and the element side substrate 1 are electrically connected via the thin film resistor layer 15 and the like, as in the infrared image sensor 100 described above. Connected to the same potential. As a result, even if the window-side substrate 3 is charged, no overcurrent flows from the window-side substrate 3 to the element-side substrate 1, and the circuit formed on the element-side substrate 1 can be prevented from being destroyed.

  In addition, since no potential difference is generated between the element side substrate 1 and the window side substrate 3, it is possible to prevent the infrared detection unit 22 from being deformed or broken due to electrostatic force.

  Further, the metallized layer 6 on the element substrate side 1 and the metallized layer 7 on the window side substrate 3 are connected by the solder layer 2 to form a vacuum micropackage, whereby the inside of the vacuum micropackage in which the infrared detection region 20 is formed is formed. It can be kept in a vacuum state.

1 is a top view of a wafer including an infrared image sensor according to a first embodiment of the present invention. It is sectional drawing of the wafer containing the infrared image sensor concerning Embodiment 1 of this invention. It is a top view of the infrared image sensor concerning Embodiment 1 of this invention. It is sectional drawing of the infrared image sensor concerning Embodiment 1 of this invention. It is sectional drawing of the manufacturing process of the infrared image sensor concerning Embodiment 1 of this invention. It is sectional drawing of the manufacturing process of the infrared image sensor concerning Embodiment 1 of this invention. It is a top view of the infrared image sensor concerning Embodiment 2 of this invention. It is sectional drawing of the infrared image sensor concerning Embodiment 2 of this invention. It is sectional drawing of the manufacturing process of the infrared image sensor concerning Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Element side board | substrate, 2 Solder layer, 3 Window side board | substrate, 4, 10 Wiring layer, 5 External pad, 6, 7 Metallization layer, 8, 13 Opening part, 9a, 9b Antireflection film, 11 Thin film resistance layer, 12 Insulation layer , 15 Conductive thin film, 20 Infrared detection region, 21 Recess, 22 Infrared detection unit, 100 Infrared image sensor.

Claims (9)

An element side substrate;
A detector formed on the element-side substrate;
An image sensor including a window side substrate fixed on the element side substrate so as to cover the detection unit,
An image sensor, wherein the element side substrate and the window side substrate are electrically connected via a resistance layer formed on the element side substrate and connected to the element side substrate. On the element side substrate, having a wiring layer connected to the resistance layer, and an element side metallization layer connected to the wiring layer,
On the window side substrate, a wiring layer connected to the window side substrate, and a window side metallization layer connected to the wiring layer,
The image sensor according to claim 1, wherein the element-side metallization layer and the window-side metallization layer are connected by a solder layer. An element side substrate;
A detector formed on the element-side substrate;
An image sensor including a window side substrate fixed on the element side substrate so as to cover the detection unit,
An image sensor, wherein the element side substrate and the window side substrate are electrically connected through a resistance layer formed on the window side substrate and connected to the window side substrate. On the element side substrate, a wiring layer connected to the element side substrate, and an element side metallization layer connected to the wiring layer,
On the window side substrate, having a wiring layer connected to the resistance layer, and a window side metallization layer connected to the wiring layer,
The image sensor according to claim 3, wherein the element-side metallization layer and the window-side metallization layer are connected by a solder layer.   The image sensor according to claim 1, wherein the window-side substrate is made of n-type Si or n-type Ge and has a resistivity of 5 Ω · cm to 50 Ω · cm.   The image sensor according to claim 1, wherein the resistance layer has a resistance value of 500 kΩ or more and 2 MΩ or less.   The image sensor according to claim 1, wherein the detection unit is sealed between the element side substrate and the window side substrate connected by the solder layer. An image sensor manufacturing method for fixing a window side substrate to a device side substrate in a state of being connected via a resistance layer,
a) forming a detection unit on the element side substrate; forming the resistance layer connected to the element side substrate; forming a wiring layer connected to the resistance layer; Forming a device-side metallization layer connected to the wiring layer;
b) a window side step including a step of forming a wiring layer connected to the window side substrate, and a step of forming a window side metallization layer connected to the wiring layer;
and c) a step of connecting the element-side metallization layer and the window-side metallization layer by a solder layer. An image sensor manufacturing method for fixing a window side substrate to a device side substrate in a state of being connected via a resistance layer,
a) forming a detection portion on the element side substrate; forming a wiring layer connected to the element side substrate; and forming an element side metallization layer connected to the wiring layer. Including element side processes;
b) forming the resistance layer connected to the window-side substrate; forming a wiring layer connected to the resistance layer; and forming a window-side metallization layer connected to the wiring layer. Window side process,
and c) a step of connecting the element-side metallization layer and the window-side metallization layer by a solder layer.

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