JPH1050970A - Solid-state image sensor, glass plate and production of solid-state image sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image sensor excellent in shape accuracy and reliability. SOLUTION: The solid-state image sensor is made of glass and components are mounted on a base plate 1 having upper surface where warping is suppressed. A frame member 2 having an elongated central hole is bonded onto the base plate 1. A chip 3 mounting a charge transfer element is set in the hole. Leads 4a, 4b corresponding, in number, to the electrode terminals of the chip 3 are arranged on the frame member 2. Each lead 4a, 4b is connected with the electrode terminals of the chip 3 through a bonding wire 5a, 5b. A frame member 6 is bonded onto the frame member 2 while sandwiching the lead 4a, 4b. An elongated hole for ensuring the region of the chip 3 and the region of the bonding wires 5a, 5b connecting the chip 3 with the lead 4 is made in the center of the frame member 6. A cover glass 7 is bonded onto the frame member 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device for converting an optical image into an electric signal, a glass plate used for the solid-state imaging device, and a method for manufacturing the solid-state imaging device. The present invention relates to a glass plate for mounting a charge transfer element, and a method for manufacturing a solid-state imaging device using the charge transfer element.

[0002]

2. Description of the Related Art A solid-state imaging device using a charge transfer element is
It is also used for area sensors, such as image scanners and facsimile line sensors. Charge transfer devices include a CCD (Charge Coupled Device) and a BBD (Bu
cket Brigade Dvice). These charge transfer elements are stored in a sealed chip package for the purpose of supplying power to the chip, distributing signals, radiating heat, and protecting the circuit. As this type of chip package, a ceramic package, a plastic package, or a glass ceramic package is generally used.

The ceramic package is a chip package mainly made of a sintered body of alumina, in which a chip is bonded inside and a cover glass or the like is bonded thereon.

A plastic package uses plastic as a package material. For example,
"Microelectronics Packaging Handbook" (Nikkei BP, 1991) describes a plastic molded IC package.

A glass ceramic package is formed by molding and firing glass powder like a ceramic. The material may be glass powder or mixed with ceramic particles to obtain the desired properties. Furthermore, if a glass powder that easily crystallizes is used, it can be crystallized during firing. As an example of a solid-state imaging device using a glass ceramic package, there is a solid-state imaging device disclosed in Japanese Patent Application Laid-Open No. 1-173639. This solid-state imaging device improves reliability by considering the thermal expansion coefficient of the glass ceramic package.

[0006]

However, each of the chip packages used in the conventional solid-state imaging device has the following problems.

The ceramic package is manufactured through a process of molding and firing a powder material such as alumina. However, since shrinkage occurs due to sintering of particles during firing, it is difficult to manufacture a chip package with high accuracy. In particular, the base plate to which the chip is bonded tends to be warped. The warpage of the base plate leads to the warpage of the chip. In the case of a chip package for a solid-state imaging device, if the chip warps, the focus is deviated and the image is deteriorated. Alumina is mainly used for ceramic packages,
Since the alumina crystal is a hard material, it takes a long time to process, and the cost is high.

Japanese Patent Application Laid-Open No. 55-159678 discloses a solid-state imaging device in which optical glass is adhered to a CCD chip in order to solve the problem of warpage of a base plate in a ceramic package. According to this solid-state imaging device, by using the surface of the optical glass having high flatness adhered on the chip as a reference of the optical system, it is possible to correct the deviation of the optical system caused by the warpage of the chip. However, in this solid-state imaging device, an accurate optical system cannot be obtained over the entire range of the CCD chip because the warped CCD chip does not become flat.

A plastic package is easy to mold and can be manufactured at low cost because the material cost is generally low, but has the drawback of poor reliability and heat dissipation. In particular, plastic has extremely low thermal conductivity as compared with alumina ceramic material, and it is difficult to release heat generated in the chip. If it is difficult to release heat, the rise in temperature of the chip during operation cannot be suppressed, which may cause malfunction. Also,
Plastic has a high hygroscopicity, and water penetrates into the chip package, which tends to adversely affect the operation of the chip. Therefore, the plastic package is difficult to use as a chip package for a high-performance electronic circuit.

[0010] The glass ceramic package is inferior in shape accuracy because the glass particles shrink during firing similarly to the ceramic package. In addition, bubbles and grain boundaries tend to remain when the glass particles are sintered, so that a smooth surface cannot be obtained, and the airtightness tends to be impaired, so that the production yield is poor. Further, the production cost of the glass ceramic package is high because a step of pulverizing the glass and a step of mixing the additional particles are required.

The present invention has been made in view of the above points, and has as its object to provide a solid-state imaging device having excellent shape accuracy and reliability. Another object of the present invention is to
An object of the present invention is to provide a glass plate used for a solid-state imaging device having excellent shape accuracy and reliability.

It is another object of the present invention to provide a method of manufacturing a solid-state imaging device having excellent shape accuracy and reliability.

[0013]

According to the present invention, in order to solve the above-mentioned problems, in a solid-state imaging device having a charge transfer element mounted thereon, a chip package in which a mounting area on which the charge transfer element is mounted is made of glass, Is provided.

According to this solid-state imaging device, since the portion on which the charge transfer element is mounted is made of glass, a mounting area with less warpage can be formed, and the charge transfer element can be accurately arranged in a desired optical system. .

[0015] In addition, a mounting area for mounting the charge transfer element is provided, and the maximum value of the distance between the line segment obtained by connecting two points in the mounting area and the mounting area is the length of the line segment. A glass plate is provided that has a value of 1/4000 or less.

If this glass plate is used in a solid-state imaging device, the charge transfer element can be mounted on a mounting area with very little warpage. Further, in the method for manufacturing a solid-state imaging device equipped with a charge transfer element, the charge transfer element is bonded to a base plate made of glass, and a frame having leads is bonded so as to surround the charge transfer element, A method for manufacturing a solid-state imaging device is provided, wherein the lead is connected to an electrode of the charge transfer element, and a cover glass is adhered on the frame portion.

According to this method of manufacturing a solid-state imaging device, a solid-state imaging device using glass having high shape accuracy as a base plate can be manufactured.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing an embodiment of the solid-state imaging device of the present invention. This is a solid-state imaging device using a CCD. Each component of the solid-state imaging device is mounted on a base plate 1 made of glass. The upper surface of the base plate 1 is flat with little warpage. The upper surface and the lower surface of the base plate 1 are substantially parallel. Although the cover glass is omitted in this figure, the upper part of the package is actually sealed with the cover glass (the state sealed with the cover glass is shown in FIG. 1).

On the upper surface of the base plate 1, a frame member 2 having a rectangular hole in the center is bonded. A chip 3 on which a charge transfer element is mounted is arranged in the hole. This chip 3 is also adhered to the base plate 1. The leads 4 are arranged on the frame member 2 by the number of electrode terminals of the chip 3. Each lead 4 has a bonding wire 5 connected to an electrode terminal of the chip 3.
Connected by The portion of the lead 4 protruding from the frame member 2 is bent toward the base plate 1.

A frame member 6 is adhered on the frame member 2 so as to sandwich the lead 4 therebetween. A rectangular hole is formed in the center of the frame member 6 so as to secure a region for the chip 3 and a region for the bonding wire 5 connecting the chip 3 and the lead 4.

FIG. 1 is a sectional view of a solid-state imaging device according to the present invention. On the base plate 1, a frame member 2 and a chip 3 are mounted. The leads 4 a and 4 b, the frame member 6, and the cover glass 7 are bonded on the frame member 2 in this order. The leads 4a, 4b on both sides of the chip 3 are connected to the electrode terminals of the chip 3 by bonding wires 5a, 5b.

A method for manufacturing the above-described solid-state imaging device will be described below. First, the material of each component of the solid-state imaging device will be described. The material of the base plate 1 is a glass substrate which has excellent chemical durability and can be molded or processed into a plate shape. As the glass substrate, silicate glass, borosilicate glass, aluminosilicate glass, or the like is preferable.

The material of the base plate 1 is as follows.
It is conceivable to use soda lime glass, non-alkali glass, photosensitive glass, or various crystallized glasses. As soda lime glass, “SiO ₂
But 65 to 75%, CaO is 5~15%, Na ₂ O is 7
18%, 18% or more of SiO ₂ + CaO + Na ₂ O ”as a basic component.

As the alkali-free glass, “S
iO ₂ is 40~65%, Al ₂ O ₃ is 5 to 25%, B ₂
O ₃ is 1 to 25%, BaO is 0.1 to 35%, SiO ₂
+ Al ₂ O ₃ + B ₂ O ₃ + BaO is 85% or more ”as a basic component.

As the photosensitive glass, "SiO 2"
₂ is 55~85%, Al ₂ O ₃ is 2 to 20%, Li ₂ O
Is 5 to 15%, and SiO ₂ + Al ₂ O ₃ + Li ₂ O is 85
% Or more as a basic component, and “Au is 0.001 to 0.0
5%, Ag 0.001 to 0.5%, Cu ₂ O 0.0
01 to 1% "as a photosensitive component,
There are those containing as a photosensitizer agent "CeO ₂ is from 0.001 to 0.2%."

As the crystallized glass, a general crystallized glass obtained by melting and shaping the glass and then heat-treating the glass can be used. For example, in weight% "SiO ₂ 7
0~85%, Al ₂ O ₃ is 1~8%, Li ₂ O is 7-1
5%, 85% or more of SiO ₂ + Al ₂ O ₃ + Li ₂ O ”
Is used as a basic component, and “K ₂ O + Na ₂ O is 0.1 to
_5%, P ₂ O 5 is _{0.5~5%, As 2 O 3 +} Sb 2 O
There is a lithium-disilicate-based crystallized glass obtained by crystallizing a glass having a component of “ ₃ to 0.1% to 2%”. This is because of the thermal conductivity of commercially available soda-lime glass.
Since it is nearly twice, it is advantageous in terms of heat dissipation.

Other crystallized glasses include β-quartz solid solution, β-spodumene, cordierite, Si
A crystallized glass substrate on which O ₂ , garnite, spinel, or the like is deposited can be used.

It is desirable to use a glass substrate of the same material as the material used for the base plate 1 for the frame members 2 and 6, but it is not always necessary that all the glass members be the same. That is, glasses having different characteristics can be used in combination as needed. However, when glasses having different properties are used in combination, it is necessary to combine glasses having similar thermal expansion coefficients. When glass with extremely different coefficients of thermal expansion are combined, during the heat treatment of the bonding process and the subsequent sealing process,
Stress distortion due to the difference in thermal expansion coefficient is likely to occur,
As a result, it causes adhesion failure and cracks. Specifically, the difference in expansion coefficient is 10 × 10 ⁻⁷ / ° C.
It is preferred to combine less than glass. Particularly preferably, a combination of glasses having a difference in expansion coefficient of less than 5 × 10 ⁻⁷ / ° C. is used.

The expansion coefficient difference between the base plate 1 and the frame members 2, 6 and the leads 4 is also 10 × 10 ^-7 /
The glass is desirably less than ° C, particularly preferably a glass having a difference in expansion coefficient of less than 5 × 10 ⁻⁷ / ° C.

After the glass substrate made of the above material is prepared, the glass substrate is processed into a predetermined shape. Processing is
Perform the following procedure. First, the molten glass is molded and gradually cooled. Then, the glass is polished. At this time, if the base material of the glass is a block shape, the glass in the block shape is sliced and then polished. In the case of a commercially available glass substrate having a predetermined thickness, such as soda lime glass or non-alkali glass, the glass substrate can be cut out and used as it is. If the plate can be cut and used as it is, the number of steps can be reduced, and each plate can be produced at low cost. In addition, a resist film can be formed and extracted by sandblasting or etching.

In particular, when the glass substrate is a photosensitive glass, a glass plate used for the base plate 1 and the frame members 2 and 6 is prepared as follows. First, the photosensitive glass is exposed while masking a portion to be left as a glass part on the photosensitive glass to form a latent image corresponding to the exposed portion. Next, the exposed portion composed of the latent image is heat-treated and crystallized. The crystallized exposed portion is removed by, for example, an etching process using a hydrofluoric acid-based etchant to obtain a non-exposed photosensitive glass part. The obtained photosensitive glass component may be re-exposed and crystallized for use.

In the above-mentioned processing, the finish polishing of the glass plate for the base plate needs to be performed with high precision. Specifically, the glass plate used for the base plate 1 is finished with an accuracy of a surface roughness (Ra) of 10 nm or less and a parallelism of 50 μm or less. Preferably, the surface roughness (Ra) is 5 nm or less, and the parallelism is 10 μm.
Finish with the following accuracy.

As described above, the base plate 1 and the frame members 2 and 6 are manufactured. Then, the manufactured base plate 1, the frame members 2, 6 and the leads are overlapped and bonded. As the adhesive, an organic adhesive or low-melting glass is used. As the organic adhesive, for example, a one-component or two-component epoxy adhesive of a thermosetting type or an ultraviolet setting type may be used. As the low melting point glass, for example, there is a general low melting point glass such as lead boric acid. However,
In the case of low-melting glass, it is necessary to consider the thermal expansion compatibility with non-adhesive glass in order to prevent the occurrence of cracks in the bonded portion. In the case of an organic adhesive, since the bonding temperature is low and the difference in the thermal expansion characteristics of the glass substrate can be absorbed, the range of selection of the glass material is widened, and the manufacturing cost can be reduced. Note that a screen printing method, a dispenser method, or the like can be used for applying the adhesive.

Thus, a chip package for mounting the charge transfer element is manufactured. A CCD chip is mounted on this chip package, and electrode terminals of the chip and leads are connected by wire bonding. Then, by sealing with a cover glass, the solid-state imaging device shown in FIG. 1 can be manufactured.

In the solid-state imaging device manufactured as described above, since the base plate is made of glass,
Very little warpage. Therefore, the CCD chip mounted on the base plate does not need to be warped. as a result,
Focus can be focused accurately, and a clear image can be obtained.

Here, the warpage is measured as follows. First, a line segment obtained by connecting any two points in the area on the base plate where the CCD chip is to be mounted is set. Since the CCD chip is generally rectangular, this line segment is a line connecting both ends of the CCD chip in parallel with the long side. Then, the maximum value of the distance between the line segment and the surface of the mounting area is measured. This maximum value is 1/40 of the length of the line segment
If it is 00 or less, even if a CCD chip is mounted,
The defocus does not cause the CCD chip to warp.

In addition, the glass base plate can easily obtain a high flatness on the surface and a high parallelism between the upper surface and the lower surface. Therefore, if the solid-state imaging device is accurately arranged in the optical system, the mounted charge transfer element is also accurately arranged in the optical system (the light receiving surface is perpendicular to the optical axis). Further, since glass does not have high hygroscopicity like plastic, chips are not adversely affected by moisture. Further, glass has heat dissipation sufficient for practical use as a chip package for a solid-state imaging device.

Since high precision processing of glass is easy, the base plate can be kept inexpensive even if the shape precision is improved in the processing of glass as described above. By the way, in the above description, the case where a glass substrate is used for the two frame members 2 and 6 adhered on the base plate 1 has been described. However, these frame members 2 and 6 may be made of plastic. When a plastic is used, it is preferable to use a material having low hygroscopicity and high heat resistance, such as polyphenylene ether, polyphenylene sulfide (PPS), or an epoxy resin. In particular, a material obtained by adding a glass filler to the above resin is more preferable for adjusting the thermal expansion coefficient, the heat resistance temperature, and the water absorption. In addition, if it is formed in a frame shape by an injection molding method or the like, manufacturing costs can be reduced. Further, when the resin and the lead are integrally molded together, the number of steps is reduced, and the cost can be further reduced.

If the frame member is made of plastic, the frame member can be obtained at very low cost. Therefore, a more inexpensive chip package can be manufactured while maintaining high reliability and high shape accuracy by the glass base plate.

[0040]

Next, embodiments of the present invention will be described. Table 1 shows the composition of the base plate of the chip package described as an example and various measurement data.

[0041]

[Table 1]

This table shows four examples and three comparative examples for comparing the properties of the examples.
The composition of each substance is shown by weight% (wt%). As comparative data, the coefficient of thermal expansion (× 10 ⁻⁷ / °)
C), thermal conductivity (cal / cm · sec · ° C), surface roughness (n
m) and warpage (μm) were measured and the results are shown. In addition, the warpage shown in the table is such that the surface on which the chip is placed on the base plate is
This is the difference between the maximum value and the minimum value when scanning has been performed m times. That is, the distance between a certain line segment and the surface on which the chip is mounted is measured, and the difference between the maximum value and the minimum value is determined. this is,
A fixed line segment is set on the surface on which the chip is placed, and is equal to the maximum value of the distance between the line segment and the surface. In this example, 40 mm
Is considered, the difference between the maximum value and the minimum value is 10
If it is less than μm, the degree of warpage will be sufficiently low.

The first embodiment is an example of a photosensitive glass. This means that a photomask patterned with a chrome film on a portion to be left as a glass part is brought into close contact with the photosensitive glass, and the photosensitive glass is exposed for about 20 seconds using a 1 kW ultraviolet irradiation lamp while masking, corresponding to the exposed portion. A latent image was formed. Next, the obtained latent image forming photosensitive glass was placed in a heat treatment furnace and subjected to a heat treatment at a temperature of 550 ° C. to 650 ° C. to crystallize the latent image portion in the photosensitive glass. The surface roughness is 10 nm or less, and the parallelism is 5
After polishing on both sides to a thickness of 0 μm or less, the crystallized exposed portion was removed by etching using a hydrofluoric acid-based etchant to obtain a non-exposed photosensitive glass part.

A thermosetting epoxy adhesive was applied to these parts using a screen printer. The component to which the adhesive was applied was superimposed on a lead made of 42 alloy, and cured at 150 ° C. for 1 hour while applying a load. Thus, the base plate of the first embodiment was obtained.

The second embodiment is an example of non-alkali glass. A resist film was formed on glass that had been polished on both sides so that the surface roughness was 10 nm or less and the parallelism was 50 μm or less, and was extracted by sandblasting. A thermosetting epoxy adhesive was applied to these parts using a screen printer. The component to which the adhesive was applied was superimposed on a lead made of 42 alloy, and cured at 150 ° C. for 1 hour while applying a load. The warpage of the cured base plate was measured.

The third embodiment is an example of soda lime glass. The glass substrate was cut into a bet plate shape and polished on both sides so that the surface roughness was 10 nm or less and the parallelism was 50 μm or less. In addition, other plates were made using polyphenylene sulfide. At this time, 4
It was integrally molded in a shape sandwiching two alloy leads. A thermosetting epoxy adhesive was applied to a glass base plate using a screen printing machine. The parts to which the adhesive was applied were overlapped and cured at 150 ° C. for 1 hour while applying a load.

The fourth embodiment is an example of crystallized glass. This means that a glass having the composition shown in
Heat treatment is performed at 0 ° C. to precipitate lithium zinc silicate crystals. A crystallized glass polished on both sides so as to have a surface roughness of 10 nm or less and a parallelism of 50 μm or less was processed by sandblasting. A low-melting glass paste was applied to these parts using a screen printer. Table 2 below shows the composition of the low-melting glass paste.

[0048]

[Table 2]

Parts coated with low melting glass paste and 4
Two alloy leads are overlapped and 500
Heat treatment was performed at 1 ° C. for 1 hour. The first comparative example is a ceramic package using an alumina sintered body. The second comparative example is a glass ceramic package in which glass powder and SiO ₂ are mixed, molded and sintered. The third comparative example is a plastic package.

The thermal expansion coefficients of the four examples and the three comparative examples are compared, and the first example, the third example,
And the fourth embodiment have similar values. Therefore, these glass substrates can be used in combination. Comparing the thermal conductivity, it can be seen that all the examples of the present invention have good thermal conductivity. The surface roughness is 10 μm or less in all the examples of the present invention, and the surface roughness is very high. The warp of the base plate of the present invention is 3 μm in the first embodiment, 3 μm in the second embodiment, 3 μm in the third embodiment, and 4 μm in the fourth embodiment. On the other hand, the warp of the first comparative example is 17 μm, the warp of the second comparative example is 20 μm, and the warp of the third comparative example is 32 μm.
Therefore, the base plate obtained in the embodiment of the present invention is:
It can be seen that the warpage is extremely small as compared with the conventional one.

The thermal expansion coefficient of a general lead is 4
It is about × 10 ⁻⁶ (cal / cm · sec · ° C). Therefore,
In the second embodiment of the present invention, the difference in the coefficient of thermal expansion between the lead and the base plate is 10 × 10 ⁻⁷ (cal / cm · sec · °).
C). Thereby, the reliability is further improved.

Here, the chips were bonded to the base plates of the above four examples, and the chips and leads were connected by bonding wires. Then, the optical cover glass to which the adhesive was applied was superimposed on the frame member, and cured at 150 ° C. for 1 hour while applying a load. A high-temperature and high-humidity test (60 ° C., 90
% Rh) and a high temperature test (150 ° C.). As a result, all the solid-state imaging devices cleared 1000 hours.
The heat cycle test (-40 / 125 ° C) was 30
Cleared 0 cycles. As a result of this test, it was shown that high reliability can be ensured by using the chip package shown in the embodiment of the present invention in a solid-state imaging device.

[0053]

As described above, in the solid-state imaging device according to the present invention, since the region where the charge transfer element is to be mounted is made of glass, it is easy to suppress the warpage of the region. As a result, when the solid-state imaging device is arranged in the optical system, the charge transfer element does not warp, and the charge transfer element can be set at an accurate position.

Further, in the glass plate of the present invention, since the warpage of the portion to be the charge transfer element is extremely reduced,
By using this glass plate as a mounting portion of the charge transfer element of the solid-state imaging device, it is possible to suppress the charge transfer element from warping.

In the method of manufacturing a solid-state imaging device according to the present invention, a solid-state imaging device can be manufactured using a base plate made of glass. A very flat solid-state imaging device can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a solid-state imaging device according to the present invention.

FIG. 2 is a diagram illustrating an embodiment of a solid-state imaging device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base plate 2 Frame member 3 Chip 4, 4a, 4b Lead 5, 5a, 5b Bonding wire 6 Frame member 7 Cover glass

Claims (8)

[Claims] 1. A solid-state imaging device equipped with a charge transfer element, wherein a mounting region on which the charge transfer element is mounted has a chip package made of glass. 2. The chip package according to claim 1, wherein a maximum value of a distance between a line segment obtained by connecting two points in the mounting region and a surface of the mounting region is 1/1 of a length of the line segment.
The solid-state imaging device according to claim 1, wherein the value is 4000 or less. 3. The chip package is made of glass, and is provided so as to surround the charge transfer element on the base plate provided with the mounting region, and has a difference in thermal expansion coefficient between the base plate and the base plate of 10. The solid-state imaging device according to claim 1, further comprising: a frame member having a temperature of less than × 10 ^-7 / ° C. 4. The chip package, wherein a lead for connecting to an electrode terminal of the charge transfer element is sandwiched between frame members made of glass, and a difference in thermal expansion coefficient between the lead and the frame member is provided. Is 10 × 10 ^-7 /
The solid-state imaging device according to claim 1, wherein the temperature is lower than ° C. 5. A solid-state imaging device equipped with a charge transfer element, wherein a maximum value of a distance between a line segment obtained by connecting two points in a mounting area on which the charge transfer element is to be mounted and a surface of the mounting area is provided. A chip package having a value of 1/4000 or less of the length of the line segment. 6. A mounting area for mounting a charge transfer element, wherein a maximum value of a distance between a line segment obtained by connecting two points in the mounting area and the mounting area is a length of the line segment. A glass plate having a value of 1/4000 or less. 7. A method of manufacturing a solid-state imaging device having a charge transfer element, wherein the charge transfer element is adhered on a base plate made of glass, and a frame portion having leads is formed.
A method for manufacturing a solid-state imaging device, comprising: bonding the charge transfer element so as to surround the charge transfer element; connecting the lead to an electrode of the charge transfer element; and bonding a cover glass on the frame portion. 8. The manufacturing of the solid-state imaging device according to claim 7, wherein when bonding the frame portion, a plastic resin integrally molded in a shape sandwiching a lead is used as the frame portion. Method.