JP2002348142A - Cover glass for semiconductor package and solid-state imaging element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass for semiconductor package in which intermixing of platinum granules can be supressed, and provide a glass usable for semiconductor package of a solid-state imaging element, etc. SOLUTION: A cover glass for semiconductor package, which contains platinum, substantially does not contain a platinum foreign matter having a particle diameter of >=2 μm, or even when it contains, the content is <=10 pieces/100 mL. The solid-state imaging element is equipped with the cover glass for semiconductor package.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass for a semiconductor package such as a CCD (solid-state image sensor) used for a video camera or the like. More specifically, the present invention has a low content of U (uranium), which has a particularly large amount of α-ray emission among radioactive isotopes, and can effectively reduce soft errors in a solid-state imaging device and the like, and The present invention relates to a glass having various excellent characteristics for use in a package and a method for producing the glass.

[0002]

2. Description of the Related Art Since semiconductors such as CCDs cause soft errors due to α rays emitted from glass for packaging, the amount of radioisotopes emitting α rays contained in glass for packaging has been reduced. I have. As radioisotopes, uranium (U), thorium (T
h) and radium (Ra).

[0003] Among radioisotopes, uranium (U) emits a large amount of α-rays, and is about 5 to 10 times as large as thorium (Th). Therefore, there is a report that it is particularly important to reduce the content of uranium (U) in reducing the amount of α-ray emission in a peripheral material of a semiconductor. In recent years, with the increase in the density of solid-state imaging devices, noise and soft errors due to α rays have become a major obstacle to improving image quality. for that reason,
It has become increasingly important to reduce the amount of emitted α-rays, and the amount of emitted α-rays has been targeted to be 0.01 c / cm ² · h or less [Insbeck 1985 Spring No. 3 (No. 3) 83-8]
8]. However, the demand for reducing the amount of α-ray emission has become more severe, and recently, the target is 0.004 c / cm ² · h or less. However, in order to achieve this goal, it was practically impossible with a glass having a content of U having a large α-ray emission exceeding 10 ppb.

Heretofore, it has been considered that most of radioactive isotopes contained in glass are derived from glass raw materials. However, the present inventor, as a raw material of the glass, a trial production of a glass using an ultra-high purity thing having a very small content of radioisotopes, the amount of radioisotopes contained in the obtained glass is still high Level. In addition, ultra-high-purity glass raw materials have a practical problem in terms of cost. Thus, it has been found that in order to reduce the radioisotope contained in the glass, it is necessary to suppress the contamination from the glass manufacturing process in addition to carefully selecting the raw material of the glass. Therefore, one of the objects of the present invention is to provide a method for producing glass which can suppress the incorporation of radioisotopes, particularly U (uranium) having a large amount of α-ray radiation.

[0005] Incidentally, reduction of the content of radioisotopes
In addition to the above, (1) Internal chipping
Optically homogenous material with no defects or surface defects,
(2) a highly reliable material with little deterioration over time;
And (3) sealed with an alumina ceramic package
Is required to be a material that does not crack or strain
You. Regarding (1), internal defects such as bubbles, foreign matter, and striae
And surface defects such as polishing flaws and chips. In addition to this
In recent years, with the increase in density of solid-state
Foreign matter, especially due to platinum used as a glass melting vessel
Large foreign matter made of platinum (hereinafter referred to as platinum butter)
Is becoming an obstacle. Regarding (2), long-term
During use, fogging occurred on the glass surface due to moisture
And the transmittance decreases due to the solarization phenomenon.
In some cases. Therefore, the cover glass for the package
Therefore, high weather resistance and solarization resistance are required.
Regarding (3), for example, in the case of a CCD,
The CCD chip with the three-color mosaic filter is made of aluminum
Set in a ceramic package and cover it
ー The structure is made by bonding glass with epoxy resin etc.
You. Therefore, cover glass and alumina ceramic package
It is necessary to match the coefficient of thermal expansion of the cage. A
The thermal expansion coefficient of lumina ceramics is usually 60-75 × 10
^-7K^-1And the thermal expansion coefficient of the glass is the same.
Equal or slightly smaller 45-75 × 10 ^-7K^-1Is in the range
It is desirable.

[0006]

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a method for producing glass for a semiconductor package capable of suppressing the incorporation of radioactive isotopes, particularly U, into glass and the incorporation of platinum particles into glass. Is to provide.

Further, a second object of the present invention is to provide a solid material which has a low content of U among platinum buttes and radioisotopes, and which has high weather resistance, solarization resistance and good sealing properties with an alumina ceramic package. It is an object of the present invention to provide a glass useful for a semiconductor package such as an imaging device.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for producing glass for packaging, characterized in that at least the raw material batch is vitrified in a refractory container.

[0009] The present invention further relates to a borosilicate glass having a U content of 5 ppb or less and a Th content of 20 ppb or less.

In general, optical glass represented by a lens used in various optical systems is required to have extremely high homogeneity. However, in a refractory tank, the melting temperature of the glass is high, so that the glass is easily corroded, and striae and bubbles are generated in the glass. Therefore, platinum or a platinum alloy excellent in heat resistance and corrosion resistance is frequently used in a glass melting tank. In the case of manufacturing a glass for a package, since a relatively high-temperature melting is required, a platinum container having high heat resistance and being hardly corroded by the molten glass is used. However,
As a result of investigation by the present inventors, a large amount of platinum dust was generated when the raw material batch was melted and vitrified in a platinum container and further purified in the platinum container. Furthermore, as a result of the investigation, surprisingly, when vitrified in a platinum container, U
And the amount of Th also increased. On the other hand, it has been found that when at least the melt vitrification of the raw material batch is performed in a refractory vessel, the generation of platinum dust can be suppressed, and the increase in the amounts of U and Th can be significantly suppressed, and the present invention has been completed. .

In the present invention, refractories include, for example, alumina (Al ₂ O ₃ ), quartz (SiO ₂ ), clay (Al ₂ O ₃₎
+ SiO ₂ ), zirconia (ZrO ₂ ), etc. as a main component. These ceramics are more easily corroded by molten glass than platinum, and have not been used for melt vitrification of a raw material batch in the production of optical glass requiring high homogeneity.
According to the study of the present inventors, the mixing amount of the ceramic container into the molten glass is about 0.03 to 0.3%, whereas the mixing amount of the platinum container into the molten glass is 0%. .0
It is about 003 to 0.003%. Nevertheless, the amount of U and Th mixed into the molten glass when the ceramic container was used was much smaller than that when the platinum container was used. Therefore, it is estimated that the amounts of U and Th contained in a ceramic container such as alumina, clay, zirconia, and quartz are orders of magnitude smaller than that of a platinum container. When melt vitrification is performed using a ceramic container as in the present invention, the container itself is slightly corroded, but the amount of radioisotope mixed into the glass is significantly smaller than that of platinum. Further, since these ceramics and the like are usually composed of common elements with the components of the glass, there is no problem with the physical properties of the glass when mixed. In the present invention, the refractory preferably has a U content of 2%.
Ceramics of 0 ppm or less, more preferably 10 ppm or less, and still more preferably 5 ppm or less can be mentioned. When the content of U exceeds 20 ppm, the amount of α-ray emission desirable as glass for a package is 0.004 c /
It is difficult to obtain glass having a size of cm · h or less. Further, the refractory is preferably a ceramic mainly composed of an oxide of aluminum, silicon or zirconium.

In the production method of the present invention, at least the raw material batch is vitrified in a refractory vessel. In the production of glass, generally, a raw material batch is heated and melted to be vitrified, defoamed and homogenized, and further homogenized to remove striae in the glass. As raw material batches, in addition to oxides such as silicic acid (SiO ₂ ), ZnO and Sb ₂ O ₃ , carbonates and nitrates of alkali metals and alkaline earth metals (eg, Li ₂ CO ₃ , LiNO ₃ , Na ₂ CO ₃ , K ₂ CO ₃ ,
BaCO ₃ ), aluminum hydroxide (Al (OH) ₃ ),
Boric acid (H ₃ BO ₃ ), NaCl or the like is used. For example, an alkali metal carbonate causes a decarboxylation reaction when heated, and an alkali metal oxide (for example, L
i ₂ O, Na ₂ O, K ₂ O, etc.) melts oxides such as silicic acid (SiO ₂ ) to vitrify. However, alkali metal oxides and the like generated during the melt vitrification reaction have high activity,
Intensely erodes the container wall. Therefore, in the present invention, the melt vitrification of the raw material batch is performed in a refractory container that has a low content of radioisotope and can become a glass component, and even if the wall surface of the container is eroded, the radioisotope Suppresses mixing of element and platinum.

In the production method of the present invention, at least the raw material batch is melted and vitrified in a refractory container, and further, defoaming, homogenization and homogenization for removing striae are also performed in the refractory container. Can also be done. Alternatively, the defoaming / homogenization and the homogenization for removing striae can be performed in a container made of platinum. Compared with the melt vitrification, in the defoaming / homogenization and the homogenization for the removal of striae, the erosion of the container is less likely to occur, and even in the case of a platinum container, the mixing of the radioisotope and platinum is less. In particular, the homogenization for removing stria is preferably performed in a platinum container. By performing homogenization in a platinum container, bubbles and striae, which are internal defects in glass, can be more easily removed.

In the production method of the present invention, any form of compounds such as oxides, carbonates, nitrates, hydroxides and sulfates can be used as glass raw materials. In the production method of the present invention, the mixing of radioisotope and platinum from the container during the glass production process can be suppressed, but from the viewpoint of reducing the content of radioisotope in the obtained glass, as a raw material batch, It is preferable to use a high-purity raw material batch. In particular, the high-purity raw material batch has a U content of 3 ppb or less and a Th content of 15 ppb.
It is preferable that it is not more than pb from the viewpoint of manufacturing a glass for a package having a small content of U and Th.
By blending such raw materials to produce a raw material batch and melt vitrification, finally a glass having a U content of 5 ppb or less and a Th content of 20 ppb or less can be obtained.

Next, the glass of the present invention will be described. The glass for packaging of the present invention is a borosilicate glass having a U content of 5 ppb or less and a Th content of 20 ppb or less. When the content of U and Th is not more than the above values, it is possible to obtain a glass which is desirable as a glass for a package, has an α-ray emission of 0.004 c / cm ² · h or less, and has a very low soft error rate. .

The borosilicate glass of the present invention, preferably _{SiO 2 50~78% B 2 O 3} 5~25% by weight percent _{Al 2 O 3 0~ 8% Li} 2 O 0~ 5% Na 2 O 0 -18% K ₂ O 0-20% (however, Li ₂ O + Na ₂ O + K ₂ O 5-20%), the content of the above components is at least 80% or more, and the thermal expansion coefficient is 45-75 × Suitably, it is 10 ⁻⁷ K ⁻¹ .

The operation of each component and the reason for setting the numerical values within a certain range will be described below. SiO ₂ and B ₂ O ₃ are components that form the skeleton of borosilicate glass. When the content of SiO ₂ is less than 50% and the content of B ₂ O ₃ exceeds 25%, the weather resistance tends to decrease. Further, SiO ₂ exceeds 78% and B ₂ O ₃ is 5%.
%, The meltability tends to deteriorate. Therefore, Si
O ₂ is in the range of 50-78%, and B ₂ O ₃ is 5 to 2
Suitably, it is in the range of 5%. Al ₂ O ₃ is a component that improves the weather resistance of glass. However, if it exceeds 8%, striae are liable to be generated in the glass, and the production tends to be difficult. Therefore, the content of Al ₂ O ₃ is suitably set to 8% or less.

Li ₂ O, Na ₂ O and K ₂ O are components that act as fluxes and improve devitrification resistance. For that purpose, the total content of one or more of these components is suitably at least 5%. However, if the total content of one or more of these components exceeds 20%, the weather resistance tends to be poor and the coefficient of thermal expansion tends to be too large. Further, among these components, Li ₂
When O is added in a large amount, the devitrification resistance tends to deteriorate, and the effect of invading the refractory container is also strong. Therefore, the content of Li ₂ O is preferably set to 5% or less. If Na ₂ O and K ₂ O exceed 18% and 20%, respectively, the weather resistance tends to deteriorate, and the coefficient of thermal expansion tends to be too large. Therefore, the contents of Na ₂ O and K ₂ O are preferably set to 18% or less and 20% or less, respectively.

In addition to the above components, alkaline earth metal oxides (MgO, MgO, etc.) may be used within a range of 20% or less for the purpose of improving weather resistance, melting property, devitrification resistance, etc., and adjusting the thermal expansion coefficient. Ca
O, SrO, BaO, etc.), ZnO, halogens such as chlorine and the like can be added. Furthermore, As ₂ O ₃ and Sb
_A defoaming agent such as ₂ O ₃ can be appropriately added as needed. Further, other trivalent or higher polyvalent metal oxides can be added to such an extent that desired properties are not impaired.

In the glass of the present invention, particularly when high weather resistance is required, Pb is used as a solarization inhibitor.
It is effective to add O, TiO ₂ , Nb ₂ O _{5 and the} like. However, the content of U is 3 ppb or less, and Th
Raw material having a content of 15 ppb or less is easily available, and
Most preferably, PbO having a sharp ultraviolet absorption is added. However, it is not necessary to add PbO excessively, and on the contrary, disadvantages such as excessive absorption of ultraviolet light occur. Therefore, it is appropriate to set the amount to 3% or less. That is, by containing 0.01 to 3% by weight of PbO, a glass having high reliability for long-term exposure can be obtained.

[0021]

The present invention will be further described with reference to the following examples.
First, the contents of platinum and U and Th contained in the glass obtained by the production method of the present invention were compared with those of the glass obtained by the conventional production method. Example 1 No. 1 in Table 1. Raw material batches (U content 2 ppb, Th content 14
ppb) (raw material batch (1)). 300 kg of this raw material batch is transferred to a 200 liter SiO ₂
After melting and vitrifying at 1300 ° C. using a crucible, granular cullet was obtained. Using 35 kg of this cullet, melting and purification (defoaming and homogenization) were performed in a 1460 ° C. electric furnace in a 16-liter platinum crucible. A glass block was obtained by casting into an iron metal frame and performing predetermined annealing (this is referred to as glass A). Next, non-defective parts were selected from the glass block, and the end face was polished to inspect for internal defects.
First, the number of platinum particles was observed with a 20 × stereo microscope, and counting was performed using a 100 × optical microscope by distinguishing platinum particles having a particle diameter of 2 μm or more from bubbles and the like. Table 2 shows the glass production conditions, and Table 3 shows the analysis test results.
Shown in

Comparative Example 1 35 kg of the same raw material batch as used in Example 1 was directly charged into a 16-liter platinum crucible and melt-vitrified at 1460 ° C., and subsequently melted and refined (defoamed) with a platinum crucible. And homogenization), followed by casting and annealing to obtain a glass block (this is referred to as comparative glass A). Further, defects inside the glass of this glass block were inspected in the same procedure as in Example 1. Table 2 shows the glass production conditions, and Table 3 shows the analysis test results.

Example 2 Using 1800 kg of the same raw material batch as used in Example 1, using a clay (clay) crucible having a capacity of about 800 liters, the glass was melted and vitrified at 1450 ° C. by gas heating.
Subsequently, it was melted and refined (defoaming and homogenizing) at 1450 ° C. to obtain a glass block. (This is glass B).
Further, defects inside the glass of this glass block were inspected in the same procedure as in Example 1. Table 2 shows glass production conditions
The results of the analysis test are shown in Table 3.

The amounts of U and Th contained in the raw material batches of Examples 1 and 2 and Comparative Example 1 and the three types of glasses were determined by IC.
P (Inductively Coupled Pla)
quantified by sma) -MASS analysis. Table 3 shows the results. As shown in Table 3, the glass contamination in the melting and refining process was the least in the glass B of Example 2 in which all of the production steps were performed in a container made of a refractory. Further, from the results of Example 1, it was clarified that when using a container made of platinum, the initial melting and vitrification step can be remarkably reduced by using a container made of a refractory. In these examples, the intermittent melting method was used, but the same tendency was shown in the continuous melting method.

Example 3 No. 3 in Table 1 A raw material batch was prepared using a highly purified ultra-high purity raw material so as to have one composition (this is referred to as a raw material batch (2)). The amount of U in the raw material batch is 1
The ppb and Th amount was 5 ppb. This raw material batch 1
Using 800 kg, using a clay crucible having a capacity of about 800 liters and melting and refining at 1460 ° C. using a clay crucible in the same manner as in Example 2, followed by melting and refining (defoaming and homogenizing) at 1460 ° C. A glass block was obtained (this is called glass C). Defects inside the glass of this glass block were inspected in the same procedure as in Example 1. further,
ICP-MASS analysis was also performed. Table 2 shows glass production conditions
The results of the analysis test are shown in Table 3.

Comparative Example 2 The same ultra-high-purity raw material batch (2) as that used in Example 3 was directly charged into a platinum crucible and melted and vitrified at 1460 ° C., and then melted and refined (defoaming and defoaming) with a platinum crucible. Homogenization), further casting, and annealing were performed to obtain a glass block (this is referred to as comparative glass B). Defects inside the glass of this glass block were inspected in the same procedure as in Example 1. Furthermore, ICP-MASS analysis was also performed. Table 2 shows the glass production conditions, and Table 3 shows the analysis test results.

Example 4 Next, in Table 1 PbO having a U content of 0.02 ppb or less and a Th content of 0.02 ppb or less was added to the composition in an amount of 1%, and melted and vitrified in a SiO ₂ crucible in the same manner as in Example 1 to obtain a cullet. Was melt-refined in a 16-liter platinum crucible to obtain a glass block. (This is glass D). Glass D has approximately the same U and Th contents as glass A in Table 2, and 10 pieces of platinum butter.
/ 100 ml or less. A sample was cut out from the glass D and the glass A, and polished face-to-face to a thickness of 10 mm, and Shimadzu MP
The transmittance was measured at -2000. Next, after irradiating with ultraviolet rays based on the Japan Optical Glass Industrial Association measurement standard JOGIS-04, the transmittance was measured, and the change in transmittance before and after the irradiation was compared. As a result, the transmittance was slightly reduced in glass A, but no change was observed in glass D. That is, it was confirmed that the addition of PbO was effective for improving the solarization resistance.

Test Example A cover glass made of the glasses A, B and C obtained in the examples and the comparison glasses A and B was sealed in an alumina ceramic package having a built-in CCD chip having 580,000 effective pixels. The presence or absence of a soft error when used in an image sensor was investigated. Table 3 shows the results. It has been found that the use of a cover glass according to the invention can significantly reduce soft errors.

Example 5 In Table 1, No. 2, 3 and No. Also for glasses having compositions of 5 to 8, the raw material batch (U
Content of 3 ppb or less and Th content of 15 ppb or less), and the glass of the present invention was produced in the same manner as in Example 1. As a result of measuring the contents of U and Th for this glass, each of the glasses was almost the same as the glass A of Example 1, the U content was 5 ppb or less, and the Th content was 20 ppb or less. Further, in all the glasses, the number of platinum particles was 10/100 ml or less.

Table 1 shows the glass composition of the present invention in terms of percent by weight. In the table, the coefficient of thermal expansion is a value measured by a TMA analyzer, and the weather resistance shows the surface state when the polished sample was exposed to an atmosphere at 65 ° C. and a relative temperature of 90% for 500 hours. Each of them has a coefficient of thermal expansion suitable for sealing with alumina ceramic and excellent weather resistance.

[0031]

[Table 1] {NO 1 2 3 4 5 6 7 8} ─────────────────────────────── SiO ₂ 69.4 65.4 69.4 59.0 67.8 67.3 61.4 74.5 B ₂ O ₃ 17.6 17.6 15.0 20.0 15.8 15.8 17.8 6.3 Al ₂ O ₃ 3.6 3.6 3.0 2.5 3.1 1.6 6.6 Li ₂ O 0.7 0.7 Na ₂ O 0.7 0.7 10.0 4.3 10.7 6.2 K ₂ O 8.0 8.0 1.6 15.4 8.1 7.2 1.3 BaO 1.3 5.1 ZnO 4.0 4.0 2.6 0.2 3.1 10.0 NaCl 2.0 Sb ₂ O ₃ 1.0 1.0 0.4 0.2 0.2 0.2 0.4 ────────────────────────────────── Coefficient of thermal expansion 48 50 67 72 65 64 47 55 (× 10 ^-7 K ^-1 ) Weather resistance Change pear Change pear Change pear Change pear Change pear Change pear Change pear Change pear ───────────────── ─────────────────

[0032]

[Table 2] 原料 Raw materials used Melting conditions Vitrification process Clarification process ── ───────────────────────────────── Raw material batch (1) No. 4 in Table 1 ──── ──── Glass A Same as above SiO ₂ crucible Platinum crucible 1300 ° C 1460 ° C Comparative glass A Same as above Platinum crucible 1460 ° C 1460 ° C Glass B Same as above Clay crucible 1450 ° C 1450 ° C ───────── ────────────────────────── Raw material batch (2) No. 1 in Table 1 ──── ──── Glass C Same as above Clay crucible Clay Crucible made 1460 ° C 1460 ° C Comparative glass B Same as above Platinum crucible Platinum crucible 1460 ° C 1460 ° C ───────────── ─────────────────────

[0033]

[Table 3] Ｕ U content Th content Number of platinum bumps Soft error (ppb) (ppb) (q / 100ml) 原料 Raw material batch (1 ) 2 14 ─── ─── Glass A 417 <10 less Comparative glass A 721> 10 ^{2 more} Glass B 3 15 None very little ────────────────── ───────────────── Raw material batch (2) 15 ─── ─── Glass C 2 8 None Very little Comparative glass B 7 10> 10 ² More ──── ───────────────────────────────

[0034]

According to the present invention, it is possible to provide a glass for a semiconductor package such as a solid-state image pickup device having a very low content of platinum particles and extremely low contents of U and Th and a remarkably low soft error rate. it can. Further, by limiting the composition to a specific composition range, it is possible to provide a glass having excellent weather resistance and having a coefficient of thermal expansion with good compatibility with the alumina ceramic package. The glass of the present invention has a remarkably low U and Th content, and can significantly reduce the occurrence of soft errors caused by α rays from the glass. or,
Excellent optical and thermal characteristics and weather resistance enable the production of highly reliable solid-state imaging devices without image distortion, contributing to higher resolution and higher density of solid-state imaging devices. can do. Further, according to the production method of the present invention, it is possible to significantly suppress the mixing of radioisotopes and platinum particles in the glass in the production process, and to obtain glass suitable for glass for packaging. In particular, by using a high-purity raw material as a glass raw material, it is possible to produce a glass having a lower content of radioactive isotopes such as U than glass obtained so far.

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Claims (3)

[Claims] (1) The composition contains platinum, but contains substantially no platinum foreign matter having a particle size of 2 μm or more, or has a particle size of 2
A cover glass for a semiconductor package, which is a glass having a content of platinum foreign matter having a size of not less than 10 μm and not more than 10/100 ml. 2. The cover glass for a semiconductor package according to claim 1, wherein said glass is borosilicate glass. 3. A solid-state imaging device comprising the semiconductor package cover glass according to claim 1.