JP2010177605A - Method of manufacturing infrared imaging element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an infrared imaging element that resolves troubles such that imaging sensitivities vary depending on a light-receiving spot and can obtain stable images. <P>SOLUTION: Thickness distribution of an imaging device chip 40 that is obtained by laminating an optical absorption layer 10 and a silicon layer 20 on a substrate 30 is measured. When a spot exceeding a desired thickness is found, the surface of the silicon layer 20 at the portion is polished and the thickness is reduced. Thereafter, a lens unit 51 having a number of lenses 50 is laminated on the surface of the silicon layer 20 and an imaging element 1 is obtained. The distance from the surface of the lens 50 to the optical absorption layer 10 becomes constant and a stable image can be obtained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an infrared imaging device.

  Along with recent advances in silicon LSI technology, an infrared solid-state imaging device that combines a photoelectric conversion circuit in which a large number of infrared detectors are arranged in a one-dimensional or two-dimensional array on a semiconductor substrate and a charge transfer circuit for reading signal charges Has been developed. Among them, an infrared solid-state imaging device for 3 to 5 μm band using a PtSi / p-Si Schottky barrier diode as an infrared detector and a CCD (Charge Coupled Device) as a charge transfer circuit is an infrared lens, It has already been put into practical use as an infrared camera in combination with a drive circuit, a cooler, and the like (see Patent Document 1, etc.).

  In general, as shown in FIGS. 1 and 2, an infrared imaging element includes a light absorbing layer 10 that absorbs infrared light and a silicon layer 20 that transmits light containing infrared light on the surface side of a substrate 30 that outputs an electrical signal. The imaging device chip 40 is configured by stacking in this order, and a lens unit 51 in which a large number of lenses 50 are arranged in a matrix is bonded to the silicon layer 20 of the imaging device chip 40.

  In this imaging device 1, light of the imaging target is incident from the lens unit 51 side, the light is collected by each lens 50, and light including infrared light passes through the silicon layer 20, and infrared light is transmitted through the light absorption layer 10. The light and darkness of the image that is absorbed and imaged for each lens 50 is photoelectrically converted into an amount of electric charge, which is sequentially read out and converted into an electrical signal as image information.

JP-A-5-206432

  By the way, in the conventional imaging device shown in FIGS. 1 and 2, since there are fine irregularities on the surface of the silicon layer 20 (the surface on the lens 50 side), the imaging sensitivity depends on the light receiving location, that is, the lens 50. In some cases, the sensitivity changes and imaging becomes unstable.

  Therefore, an object of the present invention is to provide a method for manufacturing an infrared imaging device that can solve the problem that the imaging sensitivity varies depending on the light receiving location and can obtain stable imaging.

  The present invention relates to an imaging device including a lens that collects light, a silicon layer that transmits at least infrared rays of the light collected by the lens, and a light absorption layer that absorbs infrared rays that have passed through the silicon layer. An imaging device manufacturing process for obtaining an imaging device in which a light absorption layer is laminated on a silicon layer, a thickness distribution measuring process for measuring a thickness distribution of the imaging device, and a measurement result of the thickness distribution The silicon layer polishing process for selectively polishing from the silicon layer side where the thickness in the imaging device exceeds the desired thickness based on the above, and a state in which the silicon layer is sandwiched between the lens and the light absorption layer And a lens laminating step of laminating the lens on the imaging device.

  In the present invention, the thickness distribution of the imaging device obtained first is measured, and if a location exceeding the desired thickness is recognized, the surface of the silicon layer at that location is polished to reduce the thickness. Thereafter, a lens is laminated on the surface of the silicon layer to obtain an imaging device. By polishing the surface of the silicon layer to reduce the thickness of the imaging device within a desired range, the distance from the lens surface to the light absorbing layer can be made constant, and thus the lens light The degree of light collection with respect to the absorption layer can be made constant. Therefore, the imaging sensitivity based on the electrical signal output according to the light is stabilized, and as a result, stable imaging can be obtained.

  According to the present invention, the distance from the surface of the lens to the light absorption layer can be made constant, thereby eliminating the problem that the imaging sensitivity differs depending on the light receiving location, and an infrared imaging device that can obtain stable imaging. There is an effect that it can be provided.

It is a perspective view which shows the structure of an infrared imaging element typically. FIG. It is a perspective view which shows the process of the manufacturing method of the infrared imaging element which concerns on one Embodiment of this invention in order of (a)-(c).

Hereinafter, with reference to FIG. 3, the manufacturing method of the infrared image pick-up element which concerns on one Embodiment of this invention is demonstrated.
[1] Imaging Device Chip Manufacturing Process As shown in FIG. 3A, the light absorption layer 10 and the silicon layer 20 having the same size and shape as the substrate 30 are formed on the surface side of the substrate 30 made of a rectangular semiconductor or the like. Are stacked in this order to obtain the imaging device chip 40. A predetermined adhesive is used for the bonding. The light absorbing layer 10 is made of an infrared absorbing material such as single crystal silicon, and the silicon layer 20 is made of a silicon material that transmits light including infrared light.

[2] Thickness distribution measurement step The thickness distribution of the imaging device chip 40 is measured by a predetermined thickness measuring device to check whether the imaging device chip 40 is within a desired thickness range.

[3] Silicon Layer Polishing Step If the location exceeding the desired thickness is found as a result of measuring the thickness distribution, the surface on the silicon layer 20 side of the location is polished to reduce the thickness within the desired range. .

[4] Lens Laminating Step A lens unit 51 in which a large number of lenses 50 are arranged in a matrix is bonded to the surface of the silicon layer 20 using an adhesive, and a silicon layer is interposed between the lens unit 51 and the light absorption layer 10. An image sensor 1 with 20 sandwiched between them is obtained.

  The above is the manufacturing method of one embodiment, and according to the obtained image pickup device 1, the light incident from the lens unit 51 side is collected by each lens 50, and the light containing infrared light passes through the silicon layer 20, Infrared rays are absorbed by the light absorption layer 10. Then, the light and darkness of the image formed for each lens 50 is photoelectrically converted into an amount of electric charge, which is sequentially read out and converted into an electrical signal as image information.

  In the above manufacturing method, before the lens unit 51 is laminated on the surface of the silicon layer 20, the thickness distribution of the imaging device chip 40 is measured to polish the silicon layer 20 at a location exceeding the desired thickness. The point is to perform a process of reducing the thickness of the imaging device chip within a desired range.

  Thereby, the distance from the surface of the lens 50 laminated | stacked on the silicon layer 20 to the light absorption layer 10 can be closely approached, and the condensing degree with respect to the light absorption layer 10 of the lens 50 can be made constant. Therefore, the imaging sensitivity based on the electrical signal output according to the light is stabilized, and as a result, stable imaging can be obtained.

  The imaging device chip 40 is obtained by dividing a wafer-like imaging device that is an aggregate of a large number of imaging device chips 40. In the above embodiment, the imaging device chip 40 is a single piece after dividing the wafer. Although the silicon layer 20 of the imaging device chip 40 is polished, the silicon layer 20 may be polished at the stage of the wafer before division.

DESCRIPTION OF SYMBOLS 1 ... Infrared image sensor 10 ... Light absorption layer 20 ... Silicon layer 30 ... Substrate 40 ... Imaging device chip 50 ... Lens 51 ... Lens unit

Claims (1)

A method of manufacturing an imaging device, comprising: a lens that collects light; a silicon layer that transmits at least infrared light of the light collected by the lens; and a light absorption layer that absorbs infrared light transmitted through the silicon layer. And
An imaging device manufacturing process for obtaining an imaging device in which the light absorption layer is laminated on the silicon layer;
A thickness distribution measuring step for measuring the thickness distribution of the imaging device;
A silicon layer polishing step of selectively polishing from the silicon layer side a portion where the thickness of the imaging device exceeds a desired thickness based on the measurement result of the thickness distribution;
A lens laminating step of laminating the lens on the imaging device in a state where the silicon layer is sandwiched between the lens and the light absorption layer;
A method for manufacturing an infrared imaging device, comprising:

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