JP3206804B2 - Window glass for solid-state imaging device package - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass used for a package window of a solid-state image pickup device used for a video camera or the like, and more particularly to a window glass for a solid-state image pickup device package in which noise generation of the solid-state image pickup device is reduced. .

[0002]

2. Description of the Related Art A solid-state image sensor is an LSI which is a light receiving element.
The chip is housed in an alumina ceramic package, a color separation mosaic filter is superimposed on the light receiving surface thereof, wire-bonded, and a cover glass is further sealed thereon using epoxy resin or glass frit. The cover glass used here not only protects the LSI chip by hermetically sealing with an alumina ceramic package but also efficiently introduces light to the light receiving surface. Transmission characteristics are required. Also, the glass used in such applications must not crack or strain when sealed with the alumina ceramic package. That is,
It is necessary to match the coefficient of thermal expansion of glass and alumina ceramic packages. Therefore, conventionally, borosilicate glass has been used as this kind of glass.

On the other hand, not only ordinary ICs, but also various super LSI chip semiconductor devices such as large capacity memory devices,
It is known that a low-melting glass for airtight sealing or a filler thereof used for an assembly emits α-ray particles and causes a soft error. This is because fillers (eg, Zircon Zr.) Are mainly used for adjusting the coefficient of linear expansion of low-melting glass and improving strength.
Etc. SiO ₄₎ is caused, as a result of the sealing material is difficult to separate the radioactive element is used, increased α-ray radiation rate significantly, it is not appropriate to use as a sealing material for highly integrated IC It is known.

[0004]

A solid-state image sensor as an image sensor applied to a television camera or the like has a tendency to increase the number of pixels as demands for higher resolution. At the same time, as the size of the camera-integrated VTR has become smaller and lighter, the size of the optical system has been reduced from 1/2 inch system to 1/3 inch system. Therefore, since the pixel area is reduced as a whole and the number of pixels further increases, the signal level per pixel relatively decreases, and the minute noise, which has not been a problem in the past, has become a major hindrance to improving the image quality. . In order to achieve higher resolution of the solid-state imaging device, it is necessary to increase sensitivity per pixel and reduce noise as much as possible.

The present inventors have found that when a window glass of a solid-state image sensor such as a CCD contains a large amount of α-ray-emitting elements and emits α-ray particles, the solid-state image sensor causes a temporary malfunction and causes noise. I found that. α-particles include naturally occurring uranium (U), thorium (Th), and radium (R).
a) Charged particles emitted when a radioisotope such as a) decays by α. In order to eliminate noise caused by α-ray particles, radioactive isotopes contained as impurities in glass may be removed. For this purpose, it is necessary to use a raw material that has been purified to the highest possible purity and to prevent the contamination of impurities in the melting step to produce glass. There are various physical and chemical methods for refining raw materials, but there are technical and economical limitations, and in particular, there are raw materials from which radioisotopes can be easily separated and raw materials that are difficult, so radioactive It was difficult to easily obtain isotope-free glasses.

The present invention has been made in view of these circumstances, and has substantially no noise in a solid-state image pickup device due to glass, especially an α-ray emitting element in the glass, and is substantially similar to alumina ceramic. An object of the present invention is to provide a window glass for a solid-state imaging device package having a thermal expansion coefficient.

[0007]

In order to achieve the above object, the present invention is to reduce α-ray emission from glass by selectively combining glass composition components which can be used as raw materials. That is, the present invention relates to a method for preparing SiO 2 by weight percentage.
₂ 50-75%, Al ₂ O ₃ 0.2-5.0%, B
₂ O ₃ 5-20%, Li ₂ O 0-1%, Na ₂ O
_{0.5~9.5%, K 2 O 0.2~6%} , Li 2 O +
Na ₂ O + K ₂ O 5-12%, MgO 0-3%, Ca
O 0-5%, BaO 0-6%, ZnO 0-5%,
MgO + CaO + BaO + ZnO 0 to 12%, As ₂
O ₃ 0-1%, Sb ₂ O ₃ 0-1%, Cl ⁻ 0-0.
2%, F ^- 0 to 0.5%, As ₂ O ₃ + Sb ₂ O ₃ + C
l ^- + F - have a basic composition of 0.02 to 1.5%, the thermal expansion coefficient of a glass of 48~75 × 10 ^-7 K ^-1,
The total content of radioisotopes in glass is 100 pp
b or less, and the amount of α-ray emission from the glass is 0.05 c /
A window glass for a solid-state imaging device package, wherein the window glass is not more than cm ² · h.

Further, Fe ₂ O ₃ and TiO in the above glass
It is characterized in that the content of ₂ , PbO and ZrO ₂ is 100 ppm or less, respectively.

Next, the action of the components constituting the glass of the present invention and the reason for limiting the content thereof as described above will be described.

If the content of SiO ₂ is less than 50%, the coefficient of thermal expansion becomes large, which hinders hermetic sealing with the alumina ceramic package. If it exceeds 75%, the melting property of the glass deteriorates. If B ₂ O ₃ is less than 5%, the meltability becomes poor,
If it exceeds 20%, the chemical durability deteriorates and weathering occurs on the surface during long-term use, resulting in unclear images. Al ₂ O
_{If the} content of ₃ is less than 0.2%, phase separation of the glass occurs and molding becomes difficult, and if it exceeds 5%, striae occur and a homogeneous glass cannot be obtained. Li ₂ O + Na ₂ O + K ₂ O acts as a flux and improves the meltability of the glass, but also has the effect of adjusting the thermal expansion coefficient of the glass.
Below, the viscosity increases, the melting property deteriorates, and the coefficient of thermal expansion becomes too low. On the other hand, if it exceeds 12%, the weathering resistance becomes poor and the coefficient of thermal expansion becomes too high, which is not suitable. ZnO has the effect of suppressing the volatilization of B ₂ O ₃ and alkali components during melting, but when it exceeds 5%, the devitrification increases. BaO, MgO, and CaO have an effect of improving chemical durability when used in an amount of 5 to 6% or less. ZnO
Has the same effect, but when the total amount exceeds 12%, the devitrification increases. In addition, as a fining agent for the glass,
As ₂ O ₃ , Sb ₂ O ₃ , F ⁻ , and Cl ⁻ are each used at less than 1%. In this case, re-foaming occurs, which is not desirable.

The above-mentioned glass can be refined in raw materials to form an effective composition, and the contained α-radioactive elements (U, Th, Ra, etc.) can be suppressed within 100 ppb. In addition, the concentration of α radioactive element is 100p
Above pb, the amount of alpha ray emission is 0.05 c / cm ² · h
It increases above and causes noise of the solid-state imaging device. Therefore, it is preferable to suppress the α-ray emission rate from the window glass for a solid-state imaging device package to 0.05 c / cm ² · h or less.

[0012] Further, it is difficult to purify and separate the α-radioactive element.
For e ₂ O ₃ , TiO ₂ , PbO, ZrO _2, etc.
It is necessary to prevent contamination from raw materials and the melting process. Even if these are mixed in the glass, 100p each
pm or less. If each of these components exceeds 100 ppm, the concentration of the α-radioactive element exceeds 100 ppb, and the amount of α-ray emission increases sharply.

The average thermal expansion coefficient (0 to 300 ° C.) is 48 to
The reason for limiting to 75 × 10 ⁻⁷ K ⁻¹ is that the package material is mainly made of alumina (Al ₂ O ₃ ) ceramic. This is for maintaining the same or lower than that for improving the sealing strength and preventing deformation such as warpage.

[0014]

Embodiments of the present invention will be described below. Using the raw materials purified to various high purity so as to be in the range of the above glass composition, after mixing and mixing so that the final glass composition becomes 1000 g, using a platinum crucible in an electric furnace at 1480 ° C. for 5 hours. Melted. After that, it is taken out of the furnace and the block formed on the iron plate is
The resulting glass was transferred to an electric furnace at a temperature of 0 ° C. and gradually cooled to room temperature. The obtained glass was optically polished to a predetermined size to obtain a glass plate for a solid-state imaging device package window.

The measurement of the amount of α emitted from these glass plates is performed by an ultra-low level α-ray measuring device using a 2π gas flow type proportional counter, and at the same time, the chemical analysis of transition elements and α-ray emitting elements is performed by ICP-IC. The measurement was performed by MASS, and the average coefficient of thermal expansion was measured by a TMA analyzer. Then, these glasses were actually sealed in an alumina package containing a CCD chip having an effective pixel number of 380,000 pixels, and the presence or absence of noise when used in a solid-state imaging device was examined.

As a result, the glass of the present invention has a good sealing property with an alumina package, and has a content of an α-radioactive element,
Both the α-ray emission amounts were low, indicating excellent characteristics in which no noise was observed in the solid-state imaging device.

[0017]

EXAMPLES Examples of the present invention are shown in Table 1. Sample N in Table 1
Nos. 1 to 6 show Examples of the present invention, and No. 7 is a conventional example in which a glass containing an α-ray emitting element was prepared. Further, the compositions in the table are shown by weight ratio.

In order to obtain the compositions shown in Table 1,
A window glass for a solid-state imaging device package was manufactured according to the method described in the embodiment of the present invention. The analysis results of each sample by ICP-MASS, the measurement results of the amount of emitted α-rays, the average thermal expansion coefficient, and the results of a mounting test on a CCD solid-state imaging device are shown in the table.

[0019]

[Table 1]

From the results shown in Table 1, it is found that Fe ₂ O ₃ ,
TiO ₂ , PbO, ZrO ₂ content is 100 ppm each
In the samples of Nos. 1 to 6 in which the total content of the α-radioactive elements of U, Th, and Ra is 100 ppb or less, the α-ray emission amount is 0.05 c / cm ² · h or less. No noise is observed in the solid-state imaging device. On the other hand, in the conventional example in which the above-mentioned content is out of the range of the present invention, the amount of emitted α-rays is increased to 0.05 c / cm ² · h or more, and noise occurs in the solid-state imaging device.

[0021]

As described above, the glass of the present invention emits a small amount of α-rays, and when used as a window glass for a package of a solid-state imaging device, significantly reduces the generation of noise due to α-rays from the glass. be able to. Further, since it has excellent optical and thermal characteristics, no distortion occurs when sealing with an alumina ceramic package, and no distortion occurs in imaging on a solid-state imaging device. Therefore, the glass of the present invention is extremely suitable as a window glass for a package of a solid-state imaging device, and can contribute to higher resolution of the solid-state imaging device.

Continuation of the front page (56) References JP-A-1-320236 (JP, A) JP-A-1-17639 (JP, A) JP-A-59-169955 (JP, A) JP-A-1-104747 (JP, A) , U) Tokiko Hei 2-10099 (JP, B2) "Inspec" Spring 1985, No. 3, pp. 83-88 (58) Fields investigated (Int. Cl. ⁷ , DB name) C03C 3/091 C03C 4/00 H04N 5/335

Claims (3)

(57) [Claims] 1. The composition according to claim 1, wherein the weight percentage of SiO _{2 is} 50-75%,
Al ₂ O ₃ 0.2-5.0%, B ₂ O ₃ 5-20
_{%, Li 2 O 0~1%,} Na 2 O 0.5~9.5
_{%, K 2 O 0.2~6%,} Li 2 O + Na 2 O + K 2
O 5-12%, MgO 0-3%, CaO 0-5
%, BaO 0-6%, ZnO 0-5%, MgO + C
aO + BaO + ZnO 0 to 12%, As ₂ O ₃ 0
1%, Sb ₂ O ₃ 0 to 1%, Cl ⁻ 0 to 0.2%, F
^{_{- 0~0.5%, As 2 O 3}} + Sb 2 O 3 + Cl - + F
^- has a basic composition of 0.02 to 1.5%, the thermal expansion coefficient of a glass of 48~75 × 10 ^-7 K ^-1, the total content of radioactive isotopes in the glass below 100ppb Α-ray emission from glass is 0.05 c / cm ² ·
h or less, a window glass for a solid-state image sensor package. 2. The method according to claim 2, wherein Fe ₂ O ₃ , TiO ₂ , Pb
_{2. The} window glass for a solid-state imaging device package according to claim 1, wherein the contents of O and ZrO ₂ are each 100 ppm or less. 3. Substantially Fe ₂ O ₃ , TiO ₂ , Pb
Thermal expansion coefficient not containing O and ZrO ₂ 48 to 75 × 10 ^-7
K- ¹ borosilicate glass, wherein the total content of radioisotopes in the glass is 100 ppb or less, and the amount of α-ray emission from the glass is 0.05 c / cm ² · h or less. Window glass for a solid-state image sensor package.