TWI400208B - Cover glass for semiconductor package - Google Patents

Description

Glass cover for semiconductor packaging

The present invention relates to a glass cover for a semiconductor package and a method of manufacturing the same, wherein the glass cover is mounted on a front surface of a semiconductor package for housing a solid-state imaging element or a laser diode for protecting a solid-state imaging element or a laser diode The body is also used as a light transmission window.

In front of the solid-state imaging element, in order to protect the semiconductor element, a glass cover having a flat transparent surface is provided, and the glass cover is formed of a ceramic material such as alumina or a metal material or a resin material. In this case, the sealing material formed by using various organic resins or low-melting-point glass is sealed, and then functions as a light-transmitting window while protecting the solid-state imaging element housed inside the package.

Regarding solid-state imaging devices, the semiconductors that are commonly used today are CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor). The CCD is used to capture high-definition images, mainly on a camera. In recent years, image data. The utilization of processing accelerates and rushes to expand its range of applications. In particular, it is loaded on a digital camera or a mobile phone, and is mostly used to convert high-definition images into electronic information. Moreover, CMOS is called a complementary metal oxide semiconductor, and it can be miniaturized compared with a CCD, and power consumption is reduced to about one-fifth, and a microprocessor process can be utilized without increasing the cost of equipment investment. Moreover, it is advantageous in that it can be manufactured inexpensively, and therefore it is often mounted on an image input device such as a mobile phone or a small personal computer.

CCD or CMOS, because the image needs to be correctly converted into electronic information, the glass cover used thereon has strict standards for the stains or scratches on the surface, and requires a high level of cleanliness. In addition to the cleanliness of the surface, it is also required that bubbles, textures, and crystals are not present inside the glass, and foreign matter such as platinum is prevented from entering. Furthermore, in order to be well sealed with various packages, it is required to have a thermal expansion coefficient similar to that of the packaging material. Moreover, such a glass is also required to have excellent weather resistance which is not lowered over a long period of time, and which is low in density and light in weight.

Furthermore, in the case of CCD use, if a glass element contains a radioactive element such as uranium (U) or strontium (Th), it is easy to emit α-rays from the glass, and since this radiation is large, soft error will be caused. Therefore, it is required to try not to contain uranium or plutonium. Therefore, the countermeasure is to use a high-purity raw material in the production of the CCD glass cover, and to form an inner wall of the melting furnace for melting the raw material with a refractory or a platinum having a small radioisotope. For example, Patent Literatures 1 to 3 listed below propose a glass cover for solid-state imaging element packaging which reduces radioactive isotope and reduces the amount of α-ray emission.

Patent Document 1: Japanese Patent No. 2660891

Patent Document 2: Japanese Laid-Open Patent Publication No. Hei 6-211539

Patent Document 3: Japanese Laid-Open Patent Publication No. Hei 7-211539

As described above, the amount of use of the glass cover for solid-state photographic element packaging is rapidly increasing due to the expansion of use and the development of image data. However, since the conventional glass cover for solid-state photographic element packaging is produced by the following method, the surface grade is not good, and it is not suitable for mass production. In other words, when manufacturing a glass cover for solid-state image sensor packaging, first, the glass raw material is melted in a melting furnace, and defoaming and graining are performed to homogenize, and then the glass melt is poured into a mold to be cast, or The glass melt is continuously drawn out on the extension plate to form a certain shape. Next, by extruding the obtained glass formed body (glass ingot), the chips are cut to a certain thickness to obtain a diced shape, and the surface thereof is subjected to a grinding process to obtain a large-sized plate glass having a certain thickness. The glass is finely cut to a certain size. As a result, although the polishing process is applied to both surfaces of the light-transmissive surface of the cover glass for solid-state imaging device packaging, numerous fine irregularities (small flaws) are formed on the surface by polishing. On the other hand, in recent years, solid-state imaging devices have been required to have high image quality and miniaturization, and the amount of light received per element has been reduced with high image quality and miniaturization, and the light-transmissive surface of the glass cover is formed. The fine concavities and convexities cause the incident light to be easily scattered, so that the amount of light received by a part of the components is insufficient, and this result may have a concern that the components may malfunction.

In addition, if foreign matter or air bubbles are mixed in the glass cover for solid-state imaging device packaging, and dust is attached to the surface, a good display image cannot be obtained. Since this is a fatal defect of the glass cover, image inspection is always performed before the glass cover is shipped. . However, as described above, numerous fine concavities and convexities are formed on the light transmissive surface of the glass cover. At the time of image inspection, the concave and convex illumination light of the translucent surface of the glass cover causes the illumination light to be refracted, and the visible portion and the dark portion are visible. Some will mix and it will not be able to detect the presence of foreign matter or dust.

Further, the light-transmissive surface of the glass cover can be made to have a small unevenness by a very precise and long-time polishing process. However, such precision polishing is not suitable for mass production, and must be greatly increased in order to cope with the increase in demand. device. Further, the precision machining is carried out by a rotary grinding machine equipped with artificial leather while supplying a slurry of free abrasive grains such as cerium oxide dispersed in water. However, the glass powder generated by the grinding enters the artificial leather. A portion of the artificial leather forms a raised portion. Because of the raised portion of the artificial leather formed by the glass frit, the surface of the glass cover is cut during grinding, which becomes a cause of forming a partial groove. Then, since such a groove has a relatively wide and shallow shape, it is ignored in the image inspection step by electronic inspection, and when such a glass cover is loaded on the solid-state imaging device, black lines are generated in the display image. . Further, the cerium oxide used as the free abrasive grains contains a dopant Th, and if the cerium oxide adhered to the glass is not completely removed after the polishing, it may become a source of α rays.

The above-mentioned precision grinding which impairs productivity, or the adverse effect on the solid-state imaging element produced, is limited to grinding, and is a problem that is unavoidable to some extent.

In view of the above problems, an object of the present invention is to provide a glass cover for a semiconductor package which is smoothed without polishing, so that various problems associated with polishing can be eliminated.

In order to solve the above-described problems, the glass cover for a semiconductor package of the present invention is characterized in that it has a light-transmissive surface having no polished surface and has a surface roughness (Ra) of 1.0 nm or less. Here, "Ra" is an arithmetic mean roughness defined in JIS B0601-1994.

Further, the glass cover for a semiconductor package of the present invention is characterized in that it is formed by a down draw method or a float method, and the surface roughness (Ra) of the light transmitting surface is 1.0 nm or less.

Further, the glass cover for semiconductor package of the present invention is characterized in that it contains 52 to 70% of SiO ₂ , 5 to 20% of Al ₂ O _{3 ,} 5 to 20% of B ₂ O _{3 , and} 5 to 20% of alkaline earth metal oxides in mass%. The basic composition of 30% and ZnO 0 to 5% does not substantially contain an alkali metal oxide. The average thermal expansion coefficient in the temperature range of 30 to 380 ° C is 30 to 85 × 10 ^-7 / ° C, and the glass viscosity of the liquid phase temperature. It is 10 ^5.2 dPa‧s or more.

Further, the glass cover for semiconductor package of the present invention is characterized in that it contains 58 to 75% of SiO ₂ , 0.5 to 15% of Al ₂ O ₃ , 5 to 20% of B ₂ O ₃ , and 1 to 20 of alkali metal oxide in mass%. %, alkaline earth metal oxide 0-20%, ZnO 0-10% basic composition, the average thermal expansion coefficient in the temperature range of 30 ~ 380 ° ° C is 30 ~ 85 × 10 ^-7 / ° C, liquid phase temperature glass viscosity It is 10 ^5.2 dPa‧s or more.

Further, in the method for producing a glass cover for a semiconductor package of the present invention, a glass raw material is introduced into a melting tank in which at least an inner wall of the refractory is formed, and after melting, it is formed into a plate shape by a down-draw method or a float method.

Since the glass cover for a semiconductor package of the present invention has a light-transmissive surface having no polishing surface and a surface roughness (Ra) of 1.0 nm or less, it is possible to suppress malfunction of components caused by incident light scattering, and to detect whether or not the image inspection is correct. Foreign matter or dust, and prevent poor display like black stripes. Further, since the step of precision machining can be omitted, it can be produced inexpensively and in a large amount, and since no free abrasive grains are used without polishing, it is possible to prevent α-ray emission due to cerium oxide.

Further, according to the method for producing a glass cover for a semiconductor package according to the present invention, it is possible to easily produce a glass cover for a semiconductor package having less platinum particles, no polished surface on a light transmitting surface, and a surface roughness (Ra) of 1.0 nm or less.

The glass cover for semiconductor package of the present invention is characterized in that it has a light-transmissive surface having no polished surface and has a surface roughness (Ra) of 1.0 nm or less. Such a glass cover having a high surface quality can be formed by a down-draw method or a float method. As the down-draw method, it is suitable to use the overflow down-draw method or the slit down-draw method. However, especially in the case of using the overflow down-draw method, since the surface of the glass is a free surface, it does not come into contact with other members by controlling the melting thereof. Under the conditions and molding conditions, it is preferable to obtain a plate glass having a desired thickness (0.01 to 0.7 mm in the case of a glass cover for a semiconductor package) and having excellent surface smoothness. In other words, if the overflow down-draw method is used, since the surface (transparent surface) does not need to be polished, a smooth surface can be obtained, and minute scratches due to polishing are not formed, and the surface roughness (Ra) can be made 1.0. A glass cover of nm or less, 0.5 nm or less, or even 0.3 nm or less. The smaller the surface roughness (Ra) of the light-transmissive surface of the glass cover, the lower the incidence of component malfunction due to the scattered light of the transparent surface of the glass cover, and the improvement of image inspection for detecting foreign matter and the like. Precision. Further, the surface roughness (Ra) is a grade for indicating the smoothness of the surface, and measurement can be performed using an experimental method based on JIS B0601.

Further, as the float method, a method of forming the molten glass into a molten metal tin bath in a reducing gas atmosphere to form a plate, or a method of supplying molten glass on a support, in the support and the glass In the meantime, a thin film of a vapor film vaporized by a vapor film forming agent is slid to each other to form a plate shape (refer to Japanese Laid-Open Patent Publication No. Hei 9-295819, Japanese Laid-Open Patent Publication No. 2001-192219). Further, since the glass cover formed by the float method is inferior in surface quality as compared with the glass cover formed by the lower method, it is preferable to apply surface processing as needed. However, even in this case, since the polishing time is short, the decrease in productivity can be reduced as much as possible, and the adverse effect on the solid-state imaging element due to polishing can be reduced as much as possible.

Further, in the glass cover for a semiconductor package of the present invention, when the glass viscosity (liquidus viscosity) at a liquidus temperature is 10 ^5.2 dPa ‧ or more, the transparent material is less likely to be lost in the glass, and can be formed by a down-draw method. That is, when a glass substrate of SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ -RO (or R ₂ O) type is formed by the following drawing, the glass viscosity of the molded portion is approximately equal to 10 ^5.0 dPa‧S. Therefore, if the liquid viscosity of the glass is in the vicinity of 10 ^5.0 dPa‧S or below, the lost glass is likely to be lost in the formed glass. If a transparent material is lost in the glass, it may not be used for the glass cover because it may impair the light transmittance. In the case where the glass cover is formed by the down-draw method, it is preferable to make the liquid phase viscosity of the glass as high as possible, and the liquid crystal viscosity of the glass cover for semiconductor encapsulation needs to be 10 ^5.2 dPa ‧ s or more. The liquid viscosity is preferably 10 ^5.4 dPa ‧ or more, more preferably 10 ^5.8 dPa ‧ s or more.

Further, the glass cover for semiconductor package of the present invention has an average thermal expansion coefficient of 30 to 85 × 10 ^-7 / ° C in a temperature range of 30 to 380 ° C, even if an organic resin or a low melting point glass is used. The material is packaged in an alumina package (approximately 70 × 10 ^-7 / ° C) or a variety of resin packages that do not strain internally and remain in a good package for extended periods of time. The coefficient of thermal expansion of the glass cover is preferably from 35 to 80 × 10 ^-7 / ° C, more preferably from 50 to 75 × 10 ^-7 / ° C.

Further, in the glass cover for semiconductor package of the present invention, by reducing the amount of α-ray emission to 0.01 c/cm ² ‧ hr, it is possible to achieve a soft error in the solid-state imaging device caused by the reduction of the α-ray. In order to limit the amount of α-ray emission to 0.01 c/cm ² ‧ hr or less, it is preferable to prevent the impurities from the raw material or the melting furnace from being mixed, and it is preferable to suppress the amount of U in the glass to 10 ppb or less and the amount of Th to be 20 ppb or less. The α-ray of the glass cover is preferably 0.005 c/cm ² ‧ hr or less, more preferably 0.003 c/cm ² , because the solid imaging element is highly patterned and miniaturized to cause soft erroneous recording due to α-rays. Below ‧hr Further, the U amount is 5 ppb or less, the Th amount is 10 ppb or less, preferably the U amount is 4 ppb or less, and the Th amount is 8 ppb or less. In addition, compared with Th, U easily emits α rays, so the allowable amount of U is smaller than the allowable amount of Th.

Further, the glass cover for a semiconductor package of the present invention has a glass having a density of 2.55 g/cm ³ or less (preferably 2.45 g/cm ³ or less) and an alkali elution amount of 1.0 mg or less (preferably 0.1 mg or less, more preferably). When it is preferably 0.01 mg or less, it is particularly suitable for use in a portable electronic device that is used outdoors. That is, since the cameras such as digital cameras, digital cameras, mobile phones, and personal digital assistants (PDAs) have outdoor use conditions, they are required to be lightweight and suitable for carrying, and have high weather resistance. Therefore, the cover glass for solid-state photographic elements used for such applications must have stable weather resistance in addition to lightweight properties, and the characteristics of surface quality are not lowered even when used outdoors in a harsh environment. . Therefore, in particular, the glass cover used for such use is preferably lightweight by reducing the density, and the amount of alkali elution is lowered to improve the weather resistance.

Further, the glass cover for a semiconductor package of the present invention preferably has a thickness of 0.05 to 0.7 mm. When the thickness is large, the transmittance is lowered, and the weight and thickness of the machine are difficult to be obtained, which is not preferable. Further, if the thickness is too thin, the practical strength is insufficient and the deflection of the large sheet glass becomes large, which causes difficulty in operation. A preferred thickness is from 0.1 to 0.5 mm, and a more preferred thickness is from 0.1 to 0.4 mm.

Further, the glass cover for a semiconductor package of the present invention has a Young's modulus of 65 GPa or more, and more preferably 67 GPa or more. The Young's ratio indicates the degree of easy deformation under the condition that a certain external force is applied to the cover glass. If the Young's rate is large, it will not be easily deformed. The higher the Young's rate of the glass cover, the direct pressure applied to the glass cover can be prevented, and as a result, the damage of the element can be prevented.

Further, the glass cover for semiconductor package of the present invention has a Young's ratio (Young's ratio/density) of 27 GPa/g‧cm ^-3 , and is particularly suitable for carrying because it can satisfy the characteristics of being lightweight and not easily deformed. A glass cover for a solid-state imaging element used in an electronic device. From this point of view, the Young's ratio of the glass cover for the solid-state imaging element is preferably as large as possible, and is preferably 28 GPa/g‧cm ^-3 or more.

Further, in the glass cover for a semiconductor package of the present invention, when the Vickers hardness is 500 or more, it is preferable that the surface is less likely to be scratched on the surface. The reason for this is that if a slight flaw is caused to the surface during the assembly step or the conveyance step of the electronic device, the image inspection step after being mounted on the solid-state imaging element may cause a defect. Therefore, the Vickers hardness is preferably 520 or more.

In the present invention, in consideration of weather resistance, it is preferable to contain 52 to 70% of SiO ₂ , 5 to 20% of Al ₂ O _{3 ,} 5 to 20% of B ₂ O _{3 , and} 4 to 20% of alkaline earth metal oxides in mass%. The basic composition of 30% and ZnO 0 to 5% does not substantially contain an alkali metal oxide. The glass cover having such a composition has an advantage that the alkali elution amount is less than 0.01 mg, and the weather resistance is excellent, and the appearance quality is not lowered even if used for a long period of time. Further, "substantially not contained" in the present invention means that the content of the component is less than 2000 ppm. Further, the amount of alkali elution can be measured by using an experimental method based on JIS R3502.

The reason for limiting the components constituting the glass cover described above is as follows.

SiO ₂ is a main component of the skeleton constituting the glass and has an effect of improving the weather resistance of the glass. However, when the amount is too high, the high-temperature viscosity of the glass increases, and the meltability is deteriorated, and the liquid viscosity tends to be high. Accordingly, the content of SiO ₂ is from 52 to 70%, preferably from 53 to 67%, more preferably from 55 to 65%.

Al ₂ O ₃ is a component which improves the weather resistance and the liquidus viscosity of the glass. When the amount is too high, the high-temperature viscosity of the glass increases, and the meltability deteriorates, and the liquid viscosity tends to be high. Accordingly, the content of Al ₂ O ₃ is 5 to 20%, preferably 8 to 19%, more preferably 10 to 18%.

B ₂ O ₃ is a component that acts as a melting agent, reduces the viscosity of the glass, and improves the meltability. Further, it is a component for increasing the viscosity of the liquid phase. However, when B ₂ O _{3 is} too large, the weather resistance of the glass tends to decrease. Accordingly, the content of B ₂ O ₃ is 5 to 20%, preferably 6 to 15%, more preferably 7 to 13%.

Alkaline earth metal oxides (MgO, CaO, SrO, BaO), while improving the weather resistance of the glass, reduce the viscosity of the glass, and improve the meltability. However, if the glass is too much, the glass tends to lose transparency. The tendency for density to rise. Accordingly, the content of the alkaline earth metal oxide is 4 to 30%, preferably 5 to 20%, more preferably 6 to 16%.

In particular, CaO is a highly pure raw material that is relatively easy to handle, and is a component that remarkably improves the meltability and weather resistance of the glass. When the content of CaO is less than 1.5%, the above effect is small, and if it exceeds 15%, the weather resistance is lowered. In order to achieve a more stable grade, the content of CaO is preferably from 2 to 12%, more preferably from 3 to 10%.

Further, since BaO and SrO significantly increase the density of the glass, when the glass density is low, the respective contents are limited to 12% and 10% or less, and further preferably, the total amount of the two contents is limited to 6.5. ~13%. Further, since BaO and SrO are likely to contain a radioactive isotope in the raw material, when it is desired to reduce the α-ray, the total content of the two is limited to 8.5% or less, preferably 3% or less, and more preferably 1.4 or less.

ZnO improves the meltability of the glass and has an effect of suppressing volatilization of B ₂ O ₃ or an alkaline earth metal oxide from the molten glass. However, when the content is too large, the glass tends to lose transparency and the density is increased, which is not preferable. Therefore, the upper limit of the content is 5% or less, preferably 3% or less, more preferably 1% or less.

However, when an alkali metal oxide (Na ₂ O, K ₂ O, or Li ₂ O) is contained, the amount of elution of alkali eluted from the glass is increased, and the weather resistance is lowered, so that the content is preferably suppressed to less than 0.2%. In order to achieve more stable weatherability, the content of the alkali metal oxide is preferably less than 0.1%, more preferably less than 0.05%.

Further, when the amount of the alkali metal oxide in the glass is small, there is an advantage that the deterioration of the adhesive for sealing the package is suppressed. That is, the glass cover for encapsulating the solid-state imaging element is usually made of an organic resin (for example, an epoxy resin) for adhesion, and if the glass cover contains an alkali component, the alkali component is gradually eluted into the adhesive. Since an organic resin such as an epoxy resin has a property of lowering the adhesive strength due to an alkali component, it is easy to gradually reduce the adhesion strength between the glass cover and the package. As a result, a gap is formed between the two, and the cover of the glass is peeled off, so that the desired effect of protecting the solid-state imaging element cannot be achieved.

Further, in the present invention, in particular, in consideration of the production surface, SiO _{2 is} contained in an amount of 58 to 75%, Al ₂ O _{3 is} 0.5 to 15%, B ₂ O _{3 is} 5 to 20%, and alkali metal oxide is 1 to 20% by mass. %, alkaline earth metal oxide 0 to 20%, ZnO 0 to 10% basic composition, glass cover having such a composition, the meltability is improved, and the liquidus viscosity is easily adjusted.

The reason for limiting the components constituting the above glass cover is as follows.

SiO ₂ is a main component of the skeleton constituting the glass and has an effect of improving the weather resistance of the glass. However, when the amount is too high, the high-temperature viscosity of the glass increases, and the meltability is deteriorated, and the liquid viscosity tends to be high. Accordingly, the content of SiO ₂ is 58 to 75%, preferably 58 to 72%, more preferably 60 to 70%, most preferably 60 to 68.5%.

Al ₂ O ₃ is a component which is necessary for increasing the viscosity of the liquid phase. When the amount is too large, the high-temperature viscosity of the glass increases, and the meltability tends to be deteriorated. Accordingly, the content of Al ₂ O ₃ is from 0.5 to 15%, preferably from 1.1 to 12%, more preferably from 3.5 to 12%, most preferably from 6 to 11%.

B ₂ O ₃ is a component that acts as a melting agent, reduces the viscosity of the glass, and improves the meltability. Further, it is a component for increasing the viscosity of the liquid phase. However, when B ₂ O _{3 is} too large, the weather resistance of the glass tends to decrease. Accordingly, the content of B ₂ O ₃ is 5 to 20%, preferably 9 to 18%, more preferably 11 to 18%, most preferably 12 to 18%.

Alkali metal oxides (Na ₂ O, K ₂ O, Li ₂ O) are components that effectively adjust the coefficient of thermal expansion and liquid viscosity while reducing the viscosity of the glass and improving the meltability. However, if the amount is large, the glass will be significantly Weather resistance deteriorates. Accordingly, the content of the alkali metal oxide is from 1 to 20%, preferably from 5 to 18%, more preferably from 7 to 13%.

In particular, Na ₂ O has a large effect on the adjustment of the coefficient of thermal expansion, and K ₂ O has a large effect on the viscosity of the liquid phase. Therefore, when Na ₂ O or K ₂ O is used in combination, the coefficient of thermal expansion can be adjusted while maintaining the viscosity of the high liquid phase. Accordingly, the content of Na ₂ O is preferably from 0.1 to 11%, and the content of K ₂ O is preferably from 0.1 to 8%, and the content of the two is preferably from 7.6 to 18% when used in combination.

In the present invention, if the ratio of (Na ₂ O+K ₂ O)/Na ₂ O is limited to 1.1 to 10, a high liquidus viscosity is easily obtained. The ratio of this (Na ₂ O+K ₂ O)/Na ₂ O is preferably from 1.1 to 5, more preferably from 1.2 to 3.

Further, in the present invention, as the SiO ₂ decreases, the degree of increase in Al ₂ O ₃ and K ₂ O tends to increase the viscosity of the liquid phase, and the ratio of SiO ₂ /(Na ₂ O+K ₂ O) is limited to When 3 to 12, preferably 4 to 10, the weather resistance and the meltability of the glass can be maintained, and a high liquidus viscosity can be obtained.

However, since Li ₂ O easily contains a radiation isotope in the raw material, the content thereof is 0 to 5%, preferably 0 to 3%, more preferably 0 to 1%, most preferably 0 to 0.5%.

Alkaline earth metal oxides (MgO, CaO, SrO, BaO), while improving the weather resistance of the glass, reduce the viscosity of the glass, and improve the meltability. However, if the glass is too much, the glass tends to lose transparency. The tendency for density to rise. Accordingly, the content of the alkaline earth metal oxide is from 0 to 20%, preferably from 0.5 to 18%, more preferably from 1.0 to 18%.

In particular, CaO is a highly pure raw material that is relatively easy to handle, and is a component that remarkably improves the meltability and weather resistance of the glass. The content thereof is preferably from 0.5 to 10%, more preferably from 1 to 8%. However, the total amount of such contents must be limited to 13% or less, preferably 10% or less, more preferably 7% or less. Further, since BaO and SrO are likely to contain radioactive ectopic elements in the raw material, when it is desired to reduce the α ray to 0.01 c/cm ² ‧ hr or less, the total content of both is limited to 3% or less, preferably 1.4%. the following.

ZnO has an excellent effect of improving weather resistance, improves the meltability of glass, and has an effect of suppressing volatilization of B ₂ O ₃ or an alkali metal oxide from molten glass. In particular, when the content of Al ₂ O ₃ is 3% or less, the weather resistance is remarkably lowered, and the content of ZnO is 2% or more, preferably 4.5% or more. However, if the content of ZnO is too large, the glass tends to lose transparency and the density increases. Therefore, the content of ZnO is limited to 10% or less, preferably 9% or less, and more preferably 6 or less.

Furthermore, in the present invention, in addition to the above components, components such as P ₂ O ₅ , Y ₂ O ₃ , Nb ₂ O ₃ , and La ₂ O ₃ may be contained in a range of not less than 5% of the glass characteristics. Various clarifying agents are 3% or less. For example, one or two or more kinds of metal powders such as SB ₂ O ₃ , Sb ₂ O ₅ , F ₂ , Cl ₂ , C, SO ₃ , SnO ₂ or Al or Si can be used.

Since As ₂ O ₃ can generate a clear gas in a wide temperature range (to the extent of 1300 to 1700 ° C), such a clarifier has been widely used in the past, but it is easy to contain a radiation isotope in a raw material. The toxicity is still very strong, and it causes environmental pollution during the glass manufacturing step and the disposal of the waste glass. Therefore, it must be substantially free of As ₂ O ₃ . Moreover, since PbO and CdO are also highly toxic, they must be avoided. Further, SB ₂ O ₃ and Sb ₂ O _{5 are} also components having an excellent clarifying effect as in the case of As ₂ O ₃ . However, since they are also highly toxic, they are preferably not contained as much as possible.

Therefore, in the case of the SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ -RO-based glass of the present invention, the ratio of the clarifier component is preferably 0.05 to 2.0 in terms of the total amount of SB ₂ O ₃ and Sb ₂ O ₅ . The total amount of %, F ₂ , Cl ₂ , C, SO ₃ , and SnO ₂ is 0.1 to 3.0% (particularly, Cl ₂ is 0.005 to 1.0%, and SnO ₂ is 0.01 to 1.0%). Further, in the case of SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ -RO-based glass, the ratio of SB ₂ O ₃ and Sb ₂ O ₅ is preferably 0.2% in order to improve the meltability. ₂ , the total amount of Cl ₂ , C, SO ₃ , and SnO ₂ is 0.1 to 3.0%.

Further, Fe ₂ O ₃ may be used as a clarifying agent. However, in order to color the glass, the content thereof is limited to 500 ppm or less, preferably 300 ppm or less, more preferably 200 ppm or less. CeO2 can also be used as a clarifying agent. However, in order to color the glass, the content thereof is 2% or less, preferably 1% or less, more preferably 0.7% or less. TiO2 has the effect of improving the weather resistance of the glass and lowering the high-temperature viscosity, but it is not preferable because it promotes the coloring by Fe ₂ O ₃ . However, when Fe ₂ O ₃ is 200 ppm or less, it can be contained to 5%. ZrO2 is a component which improves weather resistance. However, since it is easy to contain a radioactive isotope, its content is 0 to 2%, preferably 0 to 0.5%, more preferably 500 ppm or less.

The glass cover for semiconductor package of the present invention can precisely control U, Th, Fe ₂ O ₃ , PbO, TiO ₂ , MnO by having the above-described basic composition and using a molten environment in which high-purity raw materials and impurities are hard to be mixed. ₂ , the content of ZrO _2, etc. In particular, Fe ₂ O ₃ , PbO, TiO ₂ , and MnO ₂ which affect the transmittance in the vicinity of ultraviolet rays can be individually managed at a level of 1 to 100 ppm, resulting in a soft misreport of the CCD element due to α rays. Th, individually managed at a level of 1 to 10 ppb. Furthermore, CCD is prone to soft mis-recording due to alpha ray. Today, it is desirable that the amount of alpha ray emitted from the glass cover is less than 0.005 c/cm ² ‧ hr. In the case of CMOS, soft erroneous recording due to alpha ray is less likely to occur, and alpha ray from the glass cover The amount of release is less than 0.5 c/cm ² ‧ hr can also be used. Therefore, in the case of producing a glass cover for CMOS, it is not always necessary to use a high-purity raw material, and it is not necessary to reduce the mixing of U and Th during melting.

Next, a method of manufacturing a glass cover for a semiconductor package in which the amount of α-ray emission is small will be described by way of an example.

First, a glass raw material blend capable of forming a glass having a desired composition is prepared. As the glass raw material, a high-purity raw material having less impurities such as U and Th is used. More specifically, a high-purity raw material having a content of U and Th of 5 ppb or less is used. Next, the blended glass raw materials are put into a melting tank to be melted. A platinum container (including a platinum crucible container) can be used for the melting tank. However, since it is easy to mix the platinum particles in the glass, it is preferable that at least the inner wall (the zenith, the side surface, and the bottom surface) of the melting tank is made of a refractory having a small U and Th content. Specifically, alumina refractories (for example, alumina electroformed bricks) or quartz refractories (for example, 矽block) are not easily corroded, and U and Th contents are each 1 ppm or less, and U and Th are glass-oriented. The amount of dissolution is low and is preferred. Next, homogenization of the molten glass (defoaming and removal of the grain) is performed in the clarification tank. This clarification tank can be made of refractory or platinum. In addition, the general zirconia refractory, on the reverse side with very good corrosion resistance, must be avoided in use due to its large amount of radiation isotope. However, if the impurities in the zirconia refractory are lowered, U and Th will be When the content is reduced to 1 ppm or less, it is used as an inner wall of the melting tank, and a glass cover for semiconductor package having a small amount of α-ray emission can be produced.

Thereafter, the homogenized glass is formed into a plate shape by a pulling method to obtain a plate glass having a desired thickness. The pulldown method can use the overflow pulldown method or the slit pulldown method. The sheet glass obtained in this way is subjected to fine cutting processing in a certain size, and is subjected to leveling processing as needed to fabricate a glass cover.

The glass cover for packaging of the present invention will be described below based on examples.

Fig. 1 shows a glass cover 10 for an embodiment of a semiconductor package. The glass cover 10 for a semiconductor package is a plate-shaped glass including a first light-transmissive surface 10a and a second light-transmissive surface 10b that face the thickness direction of the sheet, and constitutes the side surface 10c of the edge. The size of the glass cover 10 is 14 × 16 × 0.5 mm, and the first light-transmissive surface 10a and the second light-transmissive surface 10b are non-abrasive surfaces, and any of the surface roughness (Ra) is 0.5 nm or less. Moreover, although the side surface 10c is omitted in the drawings, it has a flat shape.

Next, the results of the above-described method for producing a glass cover for a semiconductor package and its performance evaluation test will be described.

The initial production step of the sheet glass is a step of producing a large sheet glass having a side of 500 mm or more. As described above, it is preferable to use an overflow down-draw method to form a sheet glass excellent in surface quality. In the overflow down-draw method, as shown in Fig. 2, the gutter 11 formed of the refractory material causes the molten glass 12 to flow, and the molten glass 12 overflowing from both sides of the gutter 11 is fused at the bottom of the gutter 11 to form a plate shape. And the method of moving down. According to this method, since the free surface of the molten glass forms the front surface of the plate glass, the large plate glass 13 excellent in smoothness can be obtained. Further, by controlling the melting conditions and the molding conditions, it is possible to easily form a large plate glass having a thickness of 0.05 to 0.7 mm and a surface roughness (Ra) of 1.0 nm or less. According to this, it is possible to produce a glass cover for a semiconductor package which does not need to be polished on the surface of the large plate glass 13 and is subjected to fine cutting only by a predetermined size.

The fine cutting method of the large plate glass can be mechanical cutting or laser cutting. Laser cutting first uses a hot-processed laser cutting device. On one side of a large piece of plate glass, the laser beam moves at a speed of 180 ± 5 mm/sec or 220 ± 5 mm/sec, and the laser output is 120 ± 5W, or 160±5W, cut to about 20% thickness in the direction of the plate thickness, and processed into a checkerboard eye shape. Next, as shown in the concept of FIG. 3, the machined surface 13a of the bulk plate glass 13 is moved from the opposite side in the moving direction M by the metal wire head 14 while being processed by the large plate glass 13. The surface of the surface 13a is pressed by a mold (not shown), and stress is applied to the processed surface 13a of the large-sized plate 13 to perform cutting. When the cutting is performed in this manner, a sheet-shaped glass having a short book shape which is divided along a predetermined line formed in a checkerboard shape is obtained. The sheet glass of the cut strip glass is pressed and pressed by the vacuum clamp (not shown) to the next step. Then, the short strip-shaped plate glass is again subjected to a cutting process to obtain a glass cover having a certain size.

Table 1 shows examples (sample Nos. 1 to 5) of the glass cover for packaging of the present invention comprising SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ -RO-based glass.

The glass samples of Table 1 were produced as follows. First, the high-purity glass raw material prepared as shown in Table 1 was placed in a platinum crucible, and melted in an electric melting furnace having a stirring function at 1600 ° C for 20 hours. Next, the molten glass was discharged on a carbon plate and quenched to prepare a glass sample, and various characteristics were investigated.

As shown in Table 1, the amount of alkali elution is very small regardless of the glass, and the density, the Young's ratio, the Young's ratio, the Vickers hardness, and the thermal expansion coefficient can satisfy the conditions required for the glass cover for semiconductor packaging. Further, since the liquidus temperature is 1130 ° C or lower and the liquidus viscosity is 10 ^5.2 dPa ‧ s or more, the loss of transparency is excellent.

Further, Tables 2 and 3 show examples (sample Nos. 6 to 17) of the glass cover for packaging of the present invention formed of SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ -R ₂ O-based glass.

Each of the glass samples in Tables 2 and 3 was produced as follows.

First, the high-purity glass raw material prepared as shown in the table is put into a crucible made of one of platinum rhodium, alumina, and quartz, and is subjected to an electric melting furnace having a stirring function at 1550 ° C for 6 hours. The molten glass was melted, and the molten glass was allowed to flow out on a carbon plate, and the plate glass was quenched to obtain a glass sample.

As clearly indicated in the table, each glass sample satisfies the requirements of the thermal expansion coefficient, density, and α-ray emission amount to satisfy the glass cover for semiconductors, and the viscosity is excellent because the viscosity of 10 ^2.5 dPa·s is 1500 ° C or less. The viscosity is 10 ^5.8 dPa‧s or more and the loss of transparency is excellent.

Further, the amount of alkali elution in the table is measured based on JIS R3502. The density is measured by the well-known Archimedes method. Young's rate is calculated by the non-destructive elastic measuring device (KI-11) made by Zhongfang (stock), and the Young's rate and density measured by the resonance method are calculated. The Vickers hardness is measured based on JIS Z2244-1992. The coefficient of thermal expansion is measured by using a dilatometer to measure the average coefficient of thermal expansion in the temperature range of 30 to 380 °C. The liquidus temperature was pulverized to a particle size of 300 to 500 μm, placed in a platinum boat, and kept in a temperature-matched furnace for 8 hours, and observed under a microscope. The measurement revealed that the interior of the glass sample lost transparency (crystallization). The highest temperature of the foreign matter, which is the liquidus temperature. Moreover, the viscosity of the glass at the liquidus temperature is taken as the liquid phase viscosity. The glass samples of No. 11 and 12 did not lose transparency, and in particular, they had excellent resistance to loss of transparency. The contents of U and Th were measured by ICP-MASS. Further, the strain point and the cold point were measured in accordance with the method of ASTM C336-71, and the softening point was measured in accordance with the method of C338-93. 10 ⁴ dPa‧S, 10 ³ dPa‧S and 10 ^2.5 dPa‧S, obtained by the well-known platinum ball rising method. 10 ^2.5 dPa‧S temperature is measured at a temperature of 10 ^2.5 poise, and the lower the value, the better the meltability. The amount of α-ray emission was measured using an ultra-low-grade α-ray measuring device (LACS-400M manufactured by Sumitomo Chemical Co., Ltd.).

Further, the glass samples of Nos. 1, 6, 11, 14, and 15 of Tables 1 to 3 were melted in an experimental melting tank (alumina refractory), and a plate having a thickness of 0.5 mm was formed by an overflow down-draw method. The glass cover with a vertical dimension of 14 mm and a horizontal dimension of 16 mm was produced by laser cutting without grinding.

Further, for comparison, the raw material of the glass constituting the sample No. 1 was dissolved in the above-mentioned experimental melting tank, cast in a size of 800 × 300 × 300 mm, and cut into a sheet thickness by a wire saw. 1.5mm plate shape. Thereafter, both sides of the plate glass were subjected to precision grinding processing by a rotary grinder to form a large plate glass (thickness: 0.5 mm), and finely cut by laser cutting to prepare a vertical size of 14 mm and a horizontal size of 16 Mm glass cover.

The surface roughness (Ra) of the light-transmissive surface (the first light-transmissive surface and the second light-transmitting surface) in the surface of each of the glass covers produced in this manner was probe-type surface roughness measuring machine Talystep (Tayler-Hobson) The measurement was carried out, and the results are shown in Table 4.

As clearly shown in Table 4, the glass cover of the example has a surface roughness (Ra) of the first light-transmissive surface or the second light-transmissive surface of 0.23 nm or less, and has an extremely smooth surface, and the comparative example The glass cover has a surface roughness (Ra) of 0.56 or more even when precision polishing is applied. Further, the light-transmissive surface of each of the glass covers was observed by an atomic force microscope (AFM), and the glass cover of the comparative example was formed with minute scratches on the entire surface thereof, and the glass cover of the example was found to have no such flaw.

Industrial availability

The glass cover for packaging of the present invention is suitable for a glass cover for solid-state imaging device packaging, and is also applicable to a glass cover for packaging various semiconductor packages such as a laser diode. Moreover, the average thermal expansion coefficient of the glass cover in the temperature range of 30 to 380 ° C is 30 to 85 × 10 ^-7 / ° C, except for the alumina package, for the resin, tungsten metal, cobalt alloy, molybdenum alloy, 36Ni- Various packages made of Fe alloy, 42 Ni-Fe alloy, 45Ni-Fe alloy, 46Ni-Fe alloy, and 52Ni-Fe alloy can be packaged with organic resin or low melting point glass.

10. . . Glass cover for semiconductor packaging

10a. . . First light transmission surface

10b. . . Second light transmission surface

10c. . . side

11. . . Trench

12. . . Molten glass

13. . . Large plate glass

13a. . . Machined surface

14. . . Linear head

M. . . Direction of action

FIG. 1 is a perspective view showing a glass cover for a semiconductor package of an embodiment.

2 is an explanatory view showing a method of forming a sheet glass using an overflow down-draw method.

Figure 3 illustrates a method of finely cutting a large sheet of glass using laser cutting.

10. . . Glass cover for semiconductor packaging

10a. . . First light transmission surface

10b. . . Second light transmission surface

10c. . . side

Claims (11)

A glass cover for a semiconductor package, characterized by having a light-transmissive surface having no polished surface, having a surface roughness (Ra) of 1.0 nm or less, and having SiO ₂ 52 to 70% by mass%, and Al ₂ O ₃ 5 to 20 The basic composition of %, B ₂ O ₃ 5 to 20%, alkaline earth metal oxide 4 to 30%, and ZnO 0 to 5% does not substantially contain an alkali metal oxide. The glass cover for a semiconductor package according to the first aspect of the invention is characterized in that it is formed by a down-draw method or a float method. A glass cover for a semiconductor package according to claim 2, wherein the pull-down method is an overflow down-draw method. The glass cover for semiconductor package according to claim 1, wherein the glass viscosity at a liquidus temperature is 10 ^5.2 dPa ‧ s or more. The glass cover for semiconductor package according to claim 1, wherein the average thermal expansion coefficient in the temperature range of 30 to 380 ° C is 30 to 85 × 10 ^-7 / ° C. The glass cover for semiconductor package according to the first aspect of the invention is characterized in that the amount of α-ray emission is 0.01 c/cm ² ‧ hr or less. The glass cover for semiconductor encapsulation according to claim 1, wherein the alkali elution amount is 1.0 mg or less. The glass cover for semiconductor package according to the first aspect of the invention is characterized in that the thickness is 0.05 to 0.7 mm. The glass cover for semiconductor package according to the first aspect of the invention is characterized in that the density is 2.55 g/cm ³ or less. A glass cover for a semiconductor package according to the first aspect of the invention is characterized in that a package containing a solid-state imaging element is used. A glass cover for a semiconductor package according to the first aspect of the invention is characterized in that a package in which a laser diode is housed is used.