JP2005162600A - Cover glass plate for semiconductor package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cover glass plate for a semiconductor package containing no As<SB>2</SB>O<SB>3</SB>as a clarifier and containing fewer bubbles while restricting contents of Sb<SB>2</SB>O<SB>3</SB>and Sb<SB>2</SB>O<SB>5</SB>. <P>SOLUTION: The glass contains, by mass %, 58-72% SiO<SB>2</SB>, 0.5-15% Al<SB>2</SB>O<SB>3</SB>, 8-18% B<SB>2</SB>O<SB>3</SB>, 7.5-20% alkali metal oxide, 0-20% alkaline earth metal oxide, 0-10% ZnO, 0-0.2% (Sb<SB>2</SB>O<SB>3</SB>+Sb<SB>2</SB>O<SB>5</SB>), 0.01-3% (F<SB>2</SB>+Cl<SB>2</SB>+C+SO<SB>3</SB>+SnO<SB>2</SB>) and does not substantially contain As<SB>2</SB>O<SB>3</SB>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cover glass for a semiconductor package that is attached to the front surface of a semiconductor package that mainly contains a solid-state image sensor, protects the solid-state image sensor, and is used as a light-transmitting window.

  A cover glass having a flat light-transmitting surface is disposed on the front surface of the solid-state imaging device to protect the semiconductor device. This cover glass was sealed in a package formed of a ceramic material such as alumina, a metal material, or a resin material using adhesives made of various organic resins or low-melting glass, and stored inside the package. It protects the solid-state image sensor and functions as a transparent window for visible light and the like.

  The most widely used optical semiconductor as a solid-state imaging device is a CCD (Charge Coupled Device). CCDs are mainly mounted on video cameras in order to capture high-definition images, but in recent years, the use range of images has been rapidly expanded as the use of image data processing has accelerated. In particular, they are mounted on digital still cameras and mobile phones, and are increasingly used to convert high-definition images into electronic information data. With the demand for space saving, package materials tend to be thinner, and alumina ceramic packages having higher strength and reliability than resin packages are being used.

Since CCDs need to convert images to electronic information accurately, the cover glass used for them has strict standards for dirt, scratches, foreign matter adhesion, etc. on its surface, and high-quality cleanliness. It is requested. In addition to the cleanliness of the surface, there are no bubbles, striae, crystals, or the like in the glass, and it is also required to prevent contamination of foreign substances such as platinum. Furthermore, in order to seal well with various packages, it is also required to have a linear thermal expansion coefficient approximate to that of the package material. Further, this type of glass is required to have excellent weather resistance so that the surface quality does not deteriorate over a long period of time, and to have a low density so that the weight can be reduced. In addition, if the glass contains radioactive isotopes U (uranium) or Th (thorium), α-rays are likely to be emitted from the glass, and if the emission amount is large, noise (soft error, etc.) of the solid-state imaging device. Therefore, it is required to contain as little U and Th as possible. Therefore, when manufacturing glass, a high-purity raw material is used, or the inner wall of a melting tank for melting the raw material is formed from a refractory with a low radioisotope (for example, alumina electrocast refractory, quartz refractory, platinum), etc. Measures are taken. For example, Patent Documents 1 to 3 propose a cover glass for a solid-state imaging device package in which radioactive isotopes are reduced and the amount of α-ray emission is reduced.
Japanese Patent No. 2660891 Japanese Patent Application Laid-Open No. 6-121539 JP 7-215733 A

  As described above, the cover glass for a solid-state imaging device package is required to have few internal defects such as bubbles. This is because if a large amount of bubbles are present in the glass, this becomes an optical defect, and noise is easily generated in the solid-state imaging device. In order to obtain a homogeneous glass without bubbles, the gas generated during the vitrification reaction is expelled from the glass melt by the clarification gas, and the bubbles are generated by the clarification gas that has generated the remaining fine bubbles again during the clarification. It is necessary to lift the diameter and remove it.

The fining agent for glass of this kind conventionally, wide but temperature range As ₂ O ₃ which can generate fining gas (1300-1700 approximately ° C.) has been widely used, As ₂ O ₃ is in the raw materials Since it is easy to contain radioactive isotopes, there is a problem that the amount of alpha rays emitted from the glass increases.

Under these circumstances, Sb ₂ O ₃ and Sb ₂ O ₅ are being used as clarifying agents in place of As ₂ O ₃ , but Sb ₂ O ₃ and Sb ₂ O ₅ are environmentally hazardous substances, so It is desirable not to contain.

The present invention has been made in view of the above circumstances, does not contain As ₂ O ₃ as a fining agent, and limits the content of Sb ₂ O ₃ or Sb ₂ O ₅ , and for semiconductor packages with less bubbles. It is a technical problem to provide a cover glass.

Semiconductor package cover glass of the present invention made to solve the above technical problem, in _{mass%, SiO 2 58~72%, Al} 2 O 3 0.5~15%, B 2 O 3 8~18 %, Alkali metal oxide 7.5 to 20%, alkaline earth metal oxide 0 to 20%, ZnO 0 to 10%, Sb ₂ O ₃ + Sb ₂ O ₅ 0 to 0.2%, F ₂ + Cl ₂ + C + SO ₃ + SnO ₂ 0.01 to 3% is contained, and As ₂ O ₃ is not substantially contained.

Since the cover glass for a semiconductor package of the present invention does not substantially contain As ₂ O ₃ , it can prevent the mixing of radioactive isotopes due to this, and F ₂ , Cl ₂ , C, SO ₃ , Since SnO ₂ is contained in a total amount of 0.01 to 3%, good clarity can be obtained and bubbles can be reduced.

The cover glass for a semiconductor package of the present invention is, by mass%, SiO ₂ 58 to 72%, Al ₂ O ₃ 0.5 to 15%, B ₂ O ₃ 8 to 18%, alkali metal oxide 7.5 to 20 %, Alkaline earth metal oxide 0-20%, ZnO 0-10% basic composition, Sb ₂ O ₃ + Sb ₂ O ₅ 0-0.2% as fining agent, F ₂ + Cl ₂ + C + SO ₃ + SnO _{Since 2} + CeO ₂ is contained in an amount of 0.01 to 3%, bubbles that cause optical defects can be eliminated without containing As ₂ O ₃ .

The glass having the above composition can easily reduce U and Th mixed from the glass raw material. For example, the U content in the glass can be controlled to 5 ppb or less, and the Th content can be controlled to 10 ppb or less. As a result, the amount of α rays emitted from the glass can be reduced to 0.005 c / cm ² · hr or less, and noise of the solid-state imaging device due to α rays can be reduced. Further, by making the U content 4ppb or less and the Th content 8ppb or less, it is possible to reduce the amount of alpha rays emitted from the glass to 0.003c / cm ² · hr or less. Therefore, even when mounted on a small solid-state imaging device with high pixels (for example, 1 million pixels or more), it is possible to reduce noise caused by α rays. In addition, since U emits alpha rays more easily than Th, the allowable amount of U is smaller than the allowable amount of Th.

Moreover, the cover glass for semiconductor packages of this invention can adjust the average thermal expansion coefficient in a temperature range of 30-380 degreeC to 30-85 * 10 < ^-7 > / degreeC. Therefore, even if it is sealed with an alumina package (about 70 × 10 ⁻⁷ / ° C.) or various resin packages using an adhesive made of organic resin or low-melting glass, there is no internal distortion and it will last for a long time. It is possible to maintain a good sealing state. A preferable thermal expansion coefficient of the cover glass is 35 to 80 × 10 ⁻⁷ / ° C., and a more preferable thermal expansion coefficient is 50 to 75 × 10 ⁻⁷ / ° C.

Moreover, the cover glass for semiconductor packages of the present invention can be adjusted to a glass density of 2.45 g / cm ³ or less and an alkali elution amount of 1.0 mg or less. It is suitable for. That is, devices such as a video camera, a digital still camera, a mobile phone, and a PDA (Personal Digital Assistant) are sometimes used outdoors, and thus are required to be lightweight, suitable for carrying and having high weather resistance. Therefore, the cover glass for a solid-state imaging device package used for these applications has stable weather resistance in addition to the characteristics of being lightweight, and the surface quality does not deteriorate even when used outdoors in harsh environments. It must have both the characteristics. For this reason, it is desirable that the cover glass used for this purpose be lighter by reducing the density of the glass or improve the weather resistance by reducing the alkali elution amount.

  Moreover, it is preferable that the cover glass for semiconductor packages of this invention is 0.05-0.7 mm in thickness. As the wall thickness increases, the transmittance decreases and becomes an obstacle to weight reduction. Further, as the thickness is reduced, the practical strength is insufficient, or the deflection of the large plate glass is increased, which makes handling difficult. A more preferable thickness is 0.1 to 0.5 mm, and a more preferable thickness is 0.1 to 0.4 mm.

  The reason why the content of each component constituting the cover glass for a semiconductor package of the present invention is limited as described above will be described below.

SiO ₂ is the main component that forms the skeleton of glass, and is effective in improving the weather resistance of glass. However, if it is too much, the high-temperature viscosity of the glass will increase, and the meltability and clarity will deteriorate. Tend to. Therefore SiO ₂ is 58-72%, preferably 60% to 70%, more preferably from 62 to 68.5%.

Al ₂ O ₃ is a component that improves the weather resistance of the glass, but if it is too much, the high-temperature viscosity of the glass will increase, and the meltability and clarity will tend to deteriorate. Thus Al ₂ O ₃ is 0.5 to 15%, preferably from 1.1 to 12%, more preferably, 3.5 to 12%, most preferably from 5.5 to 11%.

B ₂ O ₃ is a component that acts as a flux, lowers the viscosity of the glass, and improves meltability and clarity. However, if the amount of B ₂ O ₃ increases too much, the weather resistance of the glass decreases, and volatilization at the time of melting increases, and striae easily occur. Therefore, B ₂ O ₃ is 8 to 18%, preferably 9 to 18%, more preferably 11 to 18%, and most preferably 12 to 17%.

Alkali metal oxides (Na ₂ O, K ₂ O, Li ₂ O) are components that lower the viscosity of the glass, improve the meltability and clarity, and adjust the thermal expansion coefficient. However, when these components are contained in a large amount, the coefficient of thermal expansion tends to increase, and the weather resistance of the glass significantly decreases. Therefore, the alkali metal oxide is 7.5 to 20%, preferably 8 to 20%, more preferably 9 to 15%. However, since Li ₂ O tends to contain a radioisotope in the raw material, 0 to 6%, preferably 0 to 5.5%, more preferably 0 to 5%, still more preferably 0 to 4.5%, most preferably Should be regulated to 0-1.0%.

  Alkaline earth metal oxides (MgO, CaO, SrO, BaO) are components that improve the weather resistance of the glass, lower the viscosity of the glass, and improve the meltability. There is a tendency for density to increase as it becomes more transparent. Therefore, the alkaline earth metal oxide is 0 to 20%, preferably 0.5 to 18%, and more preferably 1.0 to 18%.

  In particular, CaO is relatively easy to obtain a high-purity raw material and is excellent in the effect of improving the weather resistance. Therefore, CaO is preferably contained in an amount of 0.5 to 10%, more preferably 1 to 8%. However, since BaO and SrO tend to increase the density and easily contain a radioisotope in the raw material, it is preferable to regulate each to 3% or less, and further to 1.4% or less.

ZnO is excellent in the effect of improving weather resistance, improves the meltability of the glass, and is effective in suppressing volatilization of B ₂ O ₃ and alkali metal oxides from the molten glass. Then, the glass tends to be devitrified and the density is increased. Therefore, the glass should be suppressed to 10% or less, preferably 9% or less, more preferably 6% or less. Particularly in the present invention, when Al ₂ O ₃ is 3% or less, the weather resistance tends to be remarkably lowered. When B ₂ O ₃ is 14% or more, volatilization increases and striae easily occur. Therefore, when Al ₂ O ₃ is 3% or less or B ₂ O ₃ is 14% or more, ZnO is preferably contained at 2% or more, and more preferably 4.5% or more.

Sb ₂ O ₃ and Sb ₂ O ₅ act as refining agents, but it is better to be as small as possible from the environmental viewpoint. Therefore, the total amount of Sb ₂ O ₃ and Sb ₂ O ₅ is 0 to 0.2%, preferably 0 to 0.1%, and most preferably not substantially contained. In the present invention, substantially not containing means that the amount is mixed as an impurity.

F ₂ , Cl ₂ , C, SO ₃ , SnO ₂ , and CeO ₂ are all components that act as fining agents. These fining agents are inferior to the fining action as compared to As ₂ O ₃ and Sb ₂ O ₃ , but the cover glass of the present invention having the above composition has low viscosity and is easy to fining, so F ₂ , Cl ₂ , C , SO ₃ , SnO ₂ , and CeO ₂ can be sufficiently defoamed by containing 0.01 to 3% of one or more of them. However, since the clarification effect increases as these clarifiers increase, the total amount is preferably 0.02 to 3%, more preferably 0.05 to 3%, and most preferably 0.2 to 3%. .

The glass of the present invention, the temperature corresponding to 10 ^2.5 poise is hot viscosity of about 1300 to 1600 ° C., in particular Cl ₂ and SO _3, since the fining gas prone in such a temperature range, these In a total amount of 0.02 to 2%, more preferably 0.05 to 2%. However, since CeO ₂ colors the glass, its content should be regulated to 1% or less, more preferably 0.7% or less.

In the present invention, in addition to the above components, 5% or less of components such as P ₂ O ₅ , Y ₂ O ₃ , Nb ₂ O ₃ , La ₂ O _{3 and the} like are included within a range not impairing the properties of the glass. Can do.

However, when As ₂ O ₃ is used as described above, radiation isotopes are likely to be mixed in and should not be substantially contained. PbO and CdO are highly toxic components and should be avoided.

Fe ₂ O ₃ can also be used as a fining agent, but in order to color the glass, its content should be regulated to 500 ppm or less, preferably 300 ppm or less, more preferably 200 ppm or less.

TiO ₂ has the effect of improving the weather resistance of the glass and lowering the high-temperature viscosity. However, since TiO ₂ promotes coloring by Fe ₂ O ₃ , it is not preferable to contain it in a large amount. However, if Fe ₂ O ₃ is 200 ppm or less, it can be contained up to 5%.

ZrO ₂ is a component that improves weather resistance, but it should be regulated to 0 to 2%, preferably 0 to 0.5%, and more preferably 500 ppm or less because it easily contains a radioisotope in the raw material.

The cover glass for a semiconductor package of the present invention employs a high-purity raw material and a molten environment prepared so that impurities are difficult to be mixed while having the above-described composition, so that U, Th, Fe ₂ O ₃ , It is possible to precisely control the content of PbO, TiO ₂ , MnO ₂ , ZrO _2, etc., especially about Fe ₂ O ₃ , PbO, TiO ₂ , MnO ₂ that affects the transmittance in the vicinity of ultraviolet rays, Each can be managed on the order of 1 to 100 ppm, and U and Th that cause a soft error of the CCD element due to α-rays can be managed on the order of 0.1 to 10 ppb.

  Next, a method for producing the semiconductor package cover glass of the present invention will be described.

  First, a glass raw material formulation is prepared so as to obtain a glass having a desired composition. As the glass raw material, a high-purity raw material with few impurities such as U and Th is used. Specifically, high-purity raw materials having U and Th contents of 5 ppb or less are used. Next, the prepared glass raw material is charged into a melting tank and melted. A platinum vessel may be used for the melting tank, but it is easy to mix platinum in the glass, so at least the inner wall (side surface, bottom surface, etc.) of the melting tank should be made of refractory with less U and Th. Is preferred. Specifically, alumina refractories (for example, alumina electrocast bricks) and quartz-based refractories (for example, silica blocks) are less likely to erode, and the contents of U and Th can each be 1 ppm or less. This is preferable because there is little elution of Th into the glass. Next, homogenization (defoaming and striae removal) of the molten glass is performed in a clarification tank. What is necessary is just to produce this clarification tank from a refractory material or platinum. Zirconia refractories contain a lot of radioisotopes and should be avoided.

  Thereafter, the homogenized molten glass is put into a mold and cast or molded, or continuously drawn on a stretched sheet and molded into a predetermined shape. Next, the obtained glass molded body (glass ingot) is slowly cooled, cut out to a certain thickness, and then subjected to polishing on the surface to form a large plate glass having a predetermined thickness. A cover glass is produced by chopping the glass.

  In addition to the above method, the molten glass is formed into a plate shape by a downdraw method or a float method, and after obtaining a plate glass having a desired thickness, it is shredded to a predetermined size and chamfered as necessary. A cover glass may be produced. As the down draw method, an overflow down draw method or a slot down draw method can be used. Particularly, when glass sheet is formed by the overflow down draw method, the surface quality is improved, so that the polishing process is unnecessary and the production cost can be reduced. .

  Hereinafter, the package cover glass of the present invention will be described based on examples.

  Table 1 shows Examples (Sample Nos. 1 to 7) and Comparative Examples (Sample No. 8) of the present invention.

  Each sample in the table was prepared as follows.

  First, a high-purity glass raw material prepared so as to obtain 500 g of the glass having the composition shown in the table is put into a crucible made of platinum rhodium or a quartz-based refractory, and is subjected to conditions at 1570 ° C. for 2 hours in an electric melting furnace having a stirring function. The molten glass was poured out onto a carbon plate. Furthermore, this plate glass was gradually cooled to obtain a glass sample.

As is clear from the table, the example glass (sample Nos. 1 to ⁷ ) has a thermal expansion coefficient of 54.1 to 68.3 × 10 ⁻⁷ / ° C. and a density of 2.45 or less, 10 ^2.5 dPa · s. The temperature corresponding to the viscosity of 1,500 ° C. or less, the alkali elution amount is 0.07 mg or less, and the α-ray emission amount is 0.0030 c / cm ² · hr or less, which is suitable as a cover glass for a solid-state imaging device package. It was. Moreover, the number of bubbles of the example glass was equivalent to the number of bubbles of the comparative glass (sample No. 8) containing 0.5% of Sb ₂ O ₃ , and was excellent in clarity.

  The contents of U and Th in Table 1 were measured by ICP-MASS. The coefficient of thermal expansion was determined by measuring the average coefficient of thermal expansion at 30 to 380 ° C. using a dilatometer. The density was determined by the well-known Archimedes method.

The strain point and annealing point were measured according to the method of ASTM C336-71, and the softening point was measured according to the method of ASTM C338-93. The 10 ⁴ Pa · s temperature, the 10 ³ Pa · s temperature, and the 10 ^2.5 Pa · s temperature were determined by a well-known platinum ball pulling method. The 10 ^2.5 Pa · s temperature is obtained by measuring a temperature corresponding to a high temperature viscosity of 10 ^2.5 poise, and the lower this value, the better the meltability.

  Furthermore, the alkali elution amount was measured based on JIS R3502. The amount of α-ray emission was measured using an ultra-low level α-ray measuring device (LACS-4000M manufactured by Sumitomo Chemical Co., Ltd.). The number of bubbles was determined by counting the number of bubbles of 100 μm or more in the glass and converting it to the number of bubbles per 100 g.

The cover glass for a package of the present invention is suitable as a cover glass for a solid-state imaging device package, and besides this, it can be used as a cover glass for various semiconductor packages including a package containing a laser diode. In addition, since this cover glass can be adjusted to have an average coefficient of thermal expansion of 30 to 85 × 10 ⁻⁷ / ° C. in the temperature range of 30 to 380 ° C., besides the alumina package, resin, tungsten metal, Kovar alloy Sealed with various kinds of packages made of molybdenum metal, 36Ni-Fe alloy, 42Ni-Fe alloy, 45Ni-Fe alloy, 46Ni-Fe alloy, 52Ni-Fe alloy using organic resin or low melting point glass Is possible.

Claims (7)

By _{mass%, SiO 2 58~72%, Al} 2 O 3 0.5~15%, B 2 O 3 8~18%, alkali metal oxides from 7.5 to 20%, an alkaline earth metal oxide 0 20%, ZnO 0-10%, Sb ₂ O ₃ + Sb ₂ O ₅ 0-0.2%, F ₂ + Cl ₂ + C + SO ₃ + SnO ₂ + CeO ₂ 0.01 to 3%, substantially As ₂ O _A cover glass for a semiconductor package, characterized by not containing ₃ ; 2. The cover glass for a semiconductor package according to claim 1, wherein an average coefficient of thermal expansion in a temperature range of 30 to 380 ° C. is 30 to 85 × 10 ⁻⁷ / ° C. 3. 3. The cover glass for a semiconductor package according to claim 1, wherein the amount of alpha rays emitted from the glass is 0.005 c / cm ² · hr or less.   The cover glass for a semiconductor package according to any one of claims 1 to 3, wherein the glass has a U content of 5 ppb or less and a Th content of 10 ppb or less. The cover glass for semiconductor packages according to any one of claims 1 to 4, wherein the density is 2.45 g / cm ³ or less.   6. The cover glass for a semiconductor package according to claim 1, wherein the alkali elution amount is 1.0 mg or less.   The cover glass for a semiconductor package according to claim 1, wherein the cover glass is used for a package that houses a solid-state imaging device.