JPH0366162A - Solid-state image sensing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device, and particularly to a technique that is effective when applied to a solid-state imaging device that requires high image quality.

[Conventional technology]

A solid-state imaging device that converts an optical image into an electrical signal has a large number of photoelectric conversion elements (also called light receiving elements or pixels) such as independent photodiodes arranged regularly on a semiconductor substrate. A device that electrically reads out the amount of light that has arrived, and is used in VTR cameras and the like.

A solid-state imaging device is mainly composed of primary components. That is, it has a light receiving section in which a large number of photoelectric conversion elements are arranged in one or two dimensions, and a scanning circuit that is arranged around the light receiving section and outputs information photoelectrically converted by these photoelectric conversion elements. It integrates a semiconductor chip (solid-state imaging chip), outer leads (outer leads, external terminals), and inner leads (also called inner leads, internal terminals, or bonding posts), and electrically connects the outside and the semiconductor chip. A lead frame for storage, a lower ceramic body (package) for holding the semiconductor chip and the lead frame (i.e. a lower ceramic substrate on which the lead frame and semiconductor chip are placed, and a storage space for the semiconductor chip). an upper ceramic frame having an opening), a light beam made of a material such as glass with high light transmittance, which is adhered to the upper surface of the upper ceramic frame so as to cover the opening of the upper ceramic frame, and is used to introduce light into the light receiving section. This is the optical window (optical glass cap, window glass) that is the introduction part.

The light receiving section of the semiconductor chip occupies most of the surface of the semiconductor chip, and a scanning circuit is arranged at the periphery of the semiconductor chip.

The lead frame is sandwiched between two upper and lower ceramic bodies, and is fixed to both ceramic bodies with low melting point glass (frit glass).

The semiconductor chip is mounted either directly on the lead frame or provided within an opening provided in the center of the lead frame on a lower ceramic substrate on which the lead frame rests. That is, when establishing electrical continuity from both the front and back sides of a semiconductor chip, the semiconductor chip is placed directly on the lead frame. On the other hand, when electrical continuity is established only from the surface of the semiconductor chip, it is provided not on the lead frame but on the lower ceramic substrate at the opening of the lead frame. The multiple bonding pads, which are electrodes formed on the periphery of the top surface of the semiconductor chip, and the multiple inner leads of the lead frame are made of multiple thin wires made of aluminum (AQ), gold (Au), etc. (i.e., bonding wire). The plurality of outer leads provided on the lead frame protrude from between the upper and lower ceramic bodies, and are each bent at a substantially right angle to the larger surface of the ceramic body.

In addition, in color solid-state imaging devices, color filters (spectral filters) made of organic resins such as gelatin and acrylic resin, which separate light into three primary colors, are installed at predetermined locations on glass plates (thin sheets for holding the filters). It is provided on the light receiving section of the semiconductor chip via a transparent glass plate (transparent glass plate).

Regarding solid-state imaging devices, for example, the Japan Industrial Development Organization (Japan Industrial Development Organization)
Co., Ltd.) Video information 25-31 issued on May 1, 1986
It is written on the page.

[Problem to be solved by the invention]

In solid-state imaging devices, the bonding wires, bonding pads, inner leads of lead frames, scanning circuit parts of semiconductor chips, etc. located near the light-receiving part of the semiconductor chip are made of metals such as aluminum and gold, so reflections do not occur. rate is high. Therefore, when light is incident through the optical window, this incident light is reflected by these components. When this reflected light enters the light receiving section of the semiconductor chip, this light becomes an optical false signal such as flare, causing halation or the like on the screen, resulting in a problem of deterioration of image quality.

In addition to the above-mentioned components, when the pedestal portion of the semiconductor chip or the like is made of a material with high reflectance, the incident light from the window may be reflected by these portions, causing a similar problem.

In a CCD (charge force pulled device) solid-state imaging device using a bonded color filter, areas other than the area where the color filter is installed on the glass plate for holding the color filter are dyed black. There are some devices that try to prevent optical false signals by installing a black filter, but this black filter is only installed on the light receiving surface of the semiconductor chip, so it is difficult to prevent optical false signals caused by components such as bonding wires. I can't.

An object of the present invention is to provide a solid-state imaging device that can prevent the occurrence of the light value a and improve image quality.

[Means to solve the problem]

In order to achieve the above object, the solid-state imaging device of the present invention includes a semiconductor chip having a light receiving section in which a large number of photoelectric conversion elements are arranged and a scanning circuit that outputs photoelectric conversion information of the photoelectric conversion elements. , a lead frame having an outer lead and an inner lead electrically connected to an electrode of the semiconductor chip, a package for holding the semiconductor chip and the lead frame, and a light introduction part for introducing light into the light receiving part. and a portion other than the light introducing portion and the light receiving portion is coated with a material having low reflectance.

Further, in the solid-state imaging device of the present invention, at least a bonding wire that electrically connects the electrode of the semiconductor chip and the inner lead is made of a material with low reflectance, in a portion other than the light introducing section and the light receiving section. By coating, it is possible to obtain the effect of reducing the light value signal.

In addition, in the light introduction part, it is sufficient that the part into which light is substantially introduced is not coated with this low reflectance substance.

Further, in the solid-state imaging device of the present invention, by selecting a material with good moisture resistance as the low reflectance substance, the moisture resistance function of the package can be improved.

[Effect]

In the solid-state imaging device of the present invention, the light-receiving portion of the semiconductor chip and the portion other than the light introducing portion for taking in light into the light-receiving portion are coated with a low-reflectance material.
Incident light from a light introducing section such as an optical window is reflected by each component such as a bonding wire, and the reflected light enters the light receiving section and can prevent optical false signals such as flare, thereby improving image quality. can be done.

〔Example〕

7- FIGS. 1(a) to 1(e) are diagrams showing the structure of a solid-state imaging device according to an embodiment of the present invention. Hereinafter, the entire structure will be referred to as a solid-state imaging device DVC, and the portion (that is, the container) of the solid-state imaging device DvC excluding the semiconductor chip CHI (solid-state imaging chip) will be referred to as a package PKG.

In the figure, (a) is a top view of the solid-state imaging device DVC when viewed from the light-receiving surface side of the chip CHI. Based on the top view (a), (b) is a side view when viewed from above, (c) is a sectional view taken along the c-a cutting line, (d
) is a side view when viewed from the right side, (e) is e −e
FIG. 3 is a cross-sectional view taken along a cutting line.

GLS is a translucent sealing plate made of borosilicate glass (B2
It is made of a glass material such as 0a・S i O2).

Hereinafter, GLS will be referred to as window glass.

The semiconductor chip CHI is made using monolithic semiconductor integrated circuit technology, and a plurality of photoelectric conversion elements such as photodiodes are arranged on the surface (light-receiving surface) on the window glass GLS side, and the back surface is made of silver paste material such as 8- The lower ceramic substrate LOW is bonded with adhesive to the lower ceramic substrate LOW.The lower ceramic substrate LOW has a mounting part MNT which is a concave part for mounting the semiconductor chip CHI in the center.
The height relationship between the semiconductor chip CHI and the inner lead IL is adjusted by this recess.

The upper ceramic frame UPP has a light-receiving window WDW hollowed out in the center so that external light hits the semiconductor chip CHI.

The lead LD is a lead for electrically connecting between the semiconductor chip CHI and an external application circuit such as a printed wiring board, and a low melting point glass FLT such as frit glass is connected between the upper and lower ceramic bodies UPP and LOW. is fixed. The lead LD has an inner lead part IL for connection with the semiconductor chip CHI and an outer lead part OL for connection with an external circuit, and both lead parts are formed continuously (integrated). frame).

The inner leads IL have the same tip shape and are located in the middle of the 16 inner leads IL 1, and the inner leads IL have a round hole in the center and have a thick tip shape and are located in the four corners. There are 4 inner leads IL2, 20 in total. This special shape of the inner lead IL2 is useful for lead position pattern recognition during automatic wire bonding.

Wire WIR connects inner lead IL and semiconductor chip CH
For electrically connecting with the bonding pad of I,
This is a metal bonding wire made of AI, Au, etc.

Due to the recess of the mounting part MNT, the semiconductor chip CHI
Since the upper surface of the inner lead IL is lower than the upper surface of the inner lead IL, the wire WIR hangs down and the semiconductor chip CH
It is possible to prevent defects such as contact with the edge of I and short circuit.

Metal plates REFI and REF2 are metal plates for making reference holes HLl and HL2. semiconductor chip CHI
When the is automatically die-bonded to the mount part MNT, its positioning is performed based on the reference holes HLl, HL2 and/or the inner lead IL2, so the relative position of the reference holes HLI, HL2 and the semiconductor chip CHI is determined with accuracy. Well set up. Therefore, the solid-state imaging device DVS is
When mounting on applied products such as TR cameras, use the reference hole HL1.
．． If HL2 is used as a positioning reference, the center of the lens of the applied product and the center of the photodiode array of the semiconductor chip CHI can be aligned with high precision.

The recess IDX is a recess provided in the upper and lower ceramic bodies UPP and LOW, and is an index indicating the circuit arrangement reference position of the 20 outer leads ILL. This index IDX is used as a means to prevent incorrect connection when inserting the solid-state imaging device DVS (that is, the outer lead ILL) into the printed circuit board by placing a pin or the like that fits into the recess of the index IDX on the printed circuit board side. is also helpful.

Next, a method for assembling the solid-state imaging device DVS will be briefly described.

First, a lead frame in which the lead LD and the reference hole horse metal plates REFI, 11-REF2, etc. are connected is formed from a single metal plate by press bottom molding or etching. As a metal material, for example, 42 is compatible with ceramics.
An alloy (alloy with weight ratio of Ni: 42% and Fe: 58%) is chosen.

Next, a lead frame made by vertically bending the outer lead OL is attached to the lower ceramic substrate LO, which is coated with frit glass FLT in a frame shape on the high part around the mount part MNT.
W, sandwiched with the upper ceramic frame UPP, and fused with frit glass FLT.

Next, the semiconductor chip CHI is automatically die-bonded to the mount part MNT, and the inner lead IL and the semiconductor chip C
Automatic wire bonding is performed between the HI and HI using wire WIR.

Next, the window glass GLS is attached to the upper ceramic frame Upp using an organic adhesive or the like.

Finally, cut off the unnecessary part of the lead frame LD and
Outer lead OL and reference Okawa metal plate REFI, RE
Separate each of F2. The convex portions BRD of the reference metal plates REFI and REF2 shown in the top view of (a) 12- are the remains after removing unnecessary bridge portions.

In the solid-state imaging device of this embodiment, the light receiving part of the semiconductor chip CHH to which the light is irradiated, and the window glass GL to introduce the light.
The surface of all parts except S, that is, the bonding wire WIR, the bonding pad, the inner lead IL, the scanning circuit around the semiconductor chip CHI, the upper ceramic frame UPP, the lower ceramic substrate LOW, etc. It is painted with a reflective material, for example black paint (indicated by diagonal lines; the dotted diagonal line indicates the upper surface of the upper ceramic frame UPP with black paint below the window glass GLS without black paint).

Therefore, even if light is incident from the window glass GLS, this incident light will not be reflected by the above-mentioned components, and it is possible to prevent light value signals such as flare that conventionally occur, thereby improving image quality. .

FIGS. 2 to 4 are diagrams showing a step of coating a portion of the semiconductor chip CHI excluding the light receiving portion and the window glass GLS with a low reflectance material in the solid-state imaging device of the present invention.

In each case, (a) is a top view of the solid-state imaging device DVC, and (b) is a cross-sectional view taken along the bb cutting line.

FIGS. 2(a) and (b) show that the semiconductor chip CHI and the lead frame are attached and housed in the upper and lower ceramic bodies UPP and LOW, and the bonding pads of the semiconductor chip CHH and the inner leads IL are connected with the bonding wires WI.
It shows a state in which the window glass GLS is connected at R and the window glass GLS is not adhered to the upper surface of the upper ceramic frame UPP.

First, the light-receiving part of the semiconductor chip CHI is coated with a removable material that serves as a mask (indicated by crossed diagonal lines) (Fig. 2(a)
), (b)). As the removable substance, for example, a substance that is in a liquid or semi-liquid state before application and hardens into a solid or semi-solid state after application is used.

This substance is dissolved in a solvent and applied. After some time, the solvent evaporates and the substance becomes hard, making it easy to peel off in a later step.

Next, the entire surface of the solid-state imaging device is painted with black paint (as shown by diagonal lines in FIG. 3(a)). There are various methods of painting, and I will not specify them, but here we will use a method in which the paint is dissolved in a solvent, filled in a container, and the solid-state imaging device is dipped upside down in the container so that the outer lead OL is not submerged. According to this method, all parts other than the parts covered by the mask, including the bonding wire WIR, can be covered with a low reflectance material. Alternatively, the coating may be applied by spraying from multiple directions. After painting, a baking process is performed (referred to as a dry loop process).

Next, the removable material, which is a mask covering the light-receiving part, is removed mechanically or by dissolving it using an appropriate chemical. Through this process, a solid-state imaging device is obtained in which all parts other than the light receiving part are covered with black paint (Figure 4(a)).
, (b)).

Finally, the window glass GLS is adhered onto the upper surface of the upper ceramic frame UPP to complete the solid-state imaging device (see Fig. 1 (
a), (c)).

As in the above embodiment, it is desirable to cover all parts other than the light receiving part and the window glass GLS with a low reflectance material, but at least the bonding wire WIR should be covered with a low reflectance material. Therefore, the effect of reducing the optical color signal can be obtained.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various changes can be made without departing from the spirit of the invention.

For example, in a window glass GLS, it is sufficient that the part that substantially introduces light is not coated with a material with low reflectance.
For example, even if the portion of the window glass GLS overlapping the upper ceramic frame UPP is coated with a low reflectance material, the effects of the present invention will not be affected. In addition, bonding wire WI
When painting black paint on R, bonding wire WI
Before bonding R, paint is applied, and bonding wire WIR is bonded to semiconductor chip C using ultrasonic bonding.
It may be connected to the bonding pad of HI and the inner lead IL. During this connection, the coating was peeled off only at the end of the bonding wire WIR to be bonded due to the ultrasonic waves, and the black coating remained on the other wire portions.

〔Effect of the invention〕

As explained above, in the solid-state imaging device of the present invention, the light-receiving portion of the semiconductor chip and the portions other than the light-introducing portion that substantially takes in light into the light-receiving portion are coated with a low-reflectance material. It is possible to prevent light color signals generated when the incident light from the introduction part is reflected by components such as bonding wires, and to improve image quality.

[Brief explanation of drawings]

FIG. 1(a) is a top view of a solid-state imaging device according to an embodiment of the present invention, FIG. 1(b) is a side view of FIG. 1(a), and FIG. 1(d) is a side view of FIG. 1(a), and FIG.
) is a cross-sectional view taken along the line ee in FIG. FIG. 3 is a diagram illustrating an example of a process of coating with a reflective material. UPP...Upper ceramic frame LOW...Lower ceramic board CI-I I...Semiconductor chip FIT...Low melting point glass OL...Outer lead IL...Inner lead GLS...Window glass (light Introduction) WIR...bonding wire

Claims (1)

[Scope of Claims] 1. A semiconductor chip having a light receiving section in which a large number of photoelectric conversion elements are arranged and a scanning circuit that outputs photoelectric conversion information of the photoelectric conversion elements, an outer lead and an electrode of the semiconductor chip, and an electrical connection between the outer lead and the electrode of the semiconductor chip. a lead frame having an inner lead connected to the semiconductor chip, a package for holding the semiconductor chip and the lead frame, and a light introduction section for introducing light into the light receiving section, and a substantial portion of the light introduction section. 1. A solid-state imaging device, wherein a portion other than a portion into which light is introduced and the light receiving portion is coated with a material having low reflectance. 2. A semiconductor chip having a light receiving section in which a large number of photoelectric conversion elements are arranged and a scanning circuit that outputs photoelectric conversion information of the photoelectric conversion elements, a lead frame having an outer lead and an inner lead, and an electrode of the semiconductor chip; It has a bonding wire that electrically connects the inner lead, a package that holds the semiconductor chip and the lead frame, and a light introduction section that takes in light to the light receiving section. A solid-state imaging device characterized in that at least a bonding wire of a portion other than a portion into which light is introduced and the light receiving portion is coated with a material having a low reflectance. 3. The solid-state imaging device according to claim 1 or 2, wherein a material with good moisture resistance is selected as the low reflectance substance.