JP4628667B2 - Cover glass for solid-state image sensor - Google Patents

Description

  The present invention relates to a cover glass for a solid-state image sensor made of flat glass, which is attached to the front surface of a package that houses a solid-state image sensor, protects the solid-state image sensor, and is used as a light transmission window.

  A cover glass having a planar light-transmitting surface is disposed on the front surface of the solid-state imaging device for protecting the device. This cover glass is sealed with various adhesives to a package made of a ceramic material such as alumina, a metal material, or a plastic material, and protects a solid-state image pickup device housed in the package, and also visible light rays and the like. It functions as a translucent window.

  As a solid-state imaging device housed in a package, currently used optical semiconductors include a charge coupled device (CCD), a complementary metal oxide semiconductor (CMOS), and the like. Of these, CMOS is also called a complementary metal oxide semiconductor, but it can be downsized compared to a CCD, consumes only about one-fifth of the power, and can utilize the manufacturing process of a microprocessor. In addition, there is an advantage that the capital investment is not expensive and can be manufactured at low cost, and it is increasingly mounted on an image input device such as a mobile phone or a small personal computer.

On the other hand, in CCDs and CMOSs, because of the need to accurately convert images into electronic information, the cover glass used has strict standards regarding dirt and scratches on the surface, adhesion of foreign matters, etc., and high-quality cleanliness. A degree has been required. Furthermore, in addition to the cleanliness of the surface, it is generated due to U (uranium) and Th (thorium), which are radioactive components that are contained in trace amounts, to prevent crystal defects inside the glass and contamination of foreign substances such as platinum. In order to prevent soft errors caused by α rays, high-purity raw materials have been adopted, and various countermeasures against advanced problems have been taken. For example, in Patent Documents 1 and 2, measures are taken to improve problems with cost, weather resistance, and trace components. Further, the cover glass for a solid-state image sensor needs to take measures since the scratches and chipping on the surface in addition to the homogeneity similar to the optical glass cause the accurate transmission of image information. As for edge chipping that affects the strength of the cover glass for a solid-state image sensor, the prevention measures have been studied conventionally. For example, according to the method disclosed in Patent Document 3, the inspection accuracy of edge chipping is studied. Can be increased. Moreover, according to the method disclosed in Patent Document 4, it is possible to efficiently perform chamfering for preventing chipping of the edge portion.
JP-A-7-206467 Japanese Patent Application Laid-Open No. 6-121539 JP 2001-241921 A JP-A-6-106469

In recent years, in the field of solid-state image sensors, CMOS has been recognized as a particularly widespread application. CMOS has been increasingly used for applications such as mobile phones and PDAs (Personal Digital Assistants) because of the low cost of the elements. On the other hand, since these devices are generally used in an environment where impact force or external stress is easily applied, the CMOS equipped in these devices is protected, and the solid-state image sensor cover glass that becomes a light-transmitting window is protected. However, higher strength than ever, particularly high impact strength and weather resistance have been required. Therefore, the cover glass for a solid-state imaging device used for these applications must have characteristics such as high strength and stable weather resistance in addition to the characteristics of being inexpensive and lightweight. However, as described above, some measures have been taken with regard to cost and weather resistance, but the light weight and strength characteristics have not sufficiently achieved the level required for the above applications. This is the actual situation.

  An object of the present invention is to provide a cover glass for a solid-state imaging device that has high quality with respect to defects on the surface and inside, is inexpensive, has excellent weather resistance, and is lighter and has higher strength.

In order to solve the above-mentioned problems, the present invention comprises a flat glass made of inorganic oxide glass, and a first light-transmitting surface and a second light-transmitting surface facing each other in the thickness direction of the flat glass, and the flat glass In the cover glass for a solid-state imaging device having a side surface constituting the periphery, the side surface is divided into a plurality of side surface portions adjacent in the circumferential direction via the ridge line portion, and each side surface portion is adjacent to the first light-transmitting surface, respectively. A first side surface portion and a second side surface portion adjacent to the first side surface portion and the second light transmitting surface, the surface roughness of the first side surface portion is greater than the surface roughness of the second side surface portion, About the side surface portion, the distance Z in the thickness direction from the boundary line between the first side surface portion and the second side surface portion to the first light transmitting surface is obtained, and when the average value is Za, distance Z is less than the relationship -0.2 ≦ (Z-Za) /Za≦0.2 , On the ridge line portion between the side surface portions, the line end of the boundary line between the first side surface portion and the second side surface portion in one side surface portion, and the boundary between the first side surface portion and the second side surface portion in the other side surface portion The distance between the wire ends is 3% or less of the thickness of the flat glass, the Ra value of the surface roughness of the first side surface portion is 0.1 to 10 nm, and the Rmax value is 0.1 to 30 nm. The Ra value of the surface roughness of the second side surface portion is 0.01 to 5 nm, and the Rmax value is 0.01 to 20 nm . Here, the ratio {(Z−Za) / Za} may be the same value or different values between the side surface portions.

In the above configuration, the first side surface portion and the second side surface portion in each side surface portion are divided by the boundary line formed due to the difference in surface properties, mainly the surface roughness, and this boundary line is, for example, 50 times It can be clearly recognized by performing microscopic observation at a magnification of about. Usually, a 1st side part adjoins a 1st translucent surface over the perimeter of flat glass, and a 2nd side part adjoins a 1st side part and a 2nd translucent surface over the perimeter of flat glass.

The distance Z in the thickness direction from the boundary line between the first side surface portion and the second side surface portion to the first light-transmitting surface is usually substantially constant in each side surface portion. Therefore, when the distance Z is different between two side portions adjacent to each other in the circumferential direction, the boundary line in the two side portions is discontinuous on both ridge lines. For this reason, the ridge line portion has three types of properties: a boundary between two first side surface portions, a boundary between two second side surface portions, and a boundary between the first side surface portion and the second side surface portion. Become. As a result of numerous tests and investigations, the inventors of the present invention have found that the edge of the boundary line that is discontinuous on the ridge line part causes microcracks and microchipping. It has been found that when the ratio {(Z-Za) / Za} is outside the range of -0.2 to 0.2, the ratio is remarkably increased.

This type of microcracking and microchipping is particularly problematic because there is a higher probability that such defects will occur in subsequent processes than in the step of forming flat glass, and therefore damage is large and countermeasures are difficult. Because it becomes. In other words, if a defect occurs at the molding stage, it can be dealt with by screening, that is, by rejecting the defective product and selecting only the non-defective product. This is because the higher the rate, the more time and money it has taken so far, and more losses.

The inventors of the present invention have that the boundary line is discontinuous in the ridge line portion between the side surface portions, and the ridge line portion itself has a complicated shape in which defects such as microcracks and microchipping are likely to occur. Not only that, the boundary between the first side surface portion and the second side surface portion having different surface roughness is formed on the ridge line portion, which causes the occurrence of defects such as micro cracks and micro chipping. I found out. That is, in the ridge line portion, the first side surface portions having the same surface roughness and the first side surface having different surface roughnesses are not observed in the surface roughness of the boundary between the first side surface portions and the second side surface portions. The surface roughness of the boundary between the side surface portion and the second side surface portion is in a rougher state than the rougher surface roughness. Therefore, the length of the boundary between the first side surface portion and the second side surface portion on the ridge line portion is preferably as small as possible. From this viewpoint, the ratio {(Z-Za) / Za} is preferably in the range of -0.2 to 0.2. When the above ratio is smaller than −0.2 or larger than 0.2, a microcrack or the like is formed at a corner portion of the plate glass, that is, a ridge line portion of the side surface at the time of processing the flat glass or in the conveyance or assembly process. The probability of occurrence of defects is increased. By setting the ratio {(Z-Za) / Za} within the range of -0.2 to 0.2, it is possible to satisfy the high strength characteristics required for practical use as a cover glass for a solid-state imaging device. .

Further, when more stable conditions are adopted and higher quality is required for the cover glass, the ratio {(Z-Za) / Za} is preferably set within the range of -0.05 to 0.05. . As a result, the occurrence rate of microcracks in the process after processing can be reduced, and the occurrence rate of microcracks during processing can also be improved.

In the above configuration, the ratio of the area of the first side surface portion to the area of the side surface {area of the first side surface portion / (area of the first side surface portion + area of the second side surface portion)} is 0.1 to 0.3. Preferably there is.

In the cover glass for a solid-state imaging device of the present invention, it is necessary for the reason of the manufacturing process that the side surface is composed of the first side surface portion and the second side surface portion having different surface properties. That is, the first side surface portion is usually formed by crack line processing, and the second side surface portion is usually formed by cleavage processing. If the area ratio is smaller than 0.1, defects such as chipping may occur frequently when performing a cleaving process for forming the second side surface portion. On the other hand, since the first side surface portion has a tendency that the surface roughness (Ra value, Rmax value) is larger than that of the second side surface portion, the area is preferably relatively small, and the area ratio is at most 0. 3 is preferred. That is, when the area ratio exceeds 0.3, there arises a problem that chipping is likely to occur during conveyance. When aiming for higher quality, the upper limit of the area ratio is preferably 0.27, and 0.25 if more stable quality is required.

The area ratio represents the ratio of the total area of the first side surface portion (the total area of the first side surface portions in all the side surface portions) to the total area of the side surfaces (the total area of all the divided side surface portions). For example, when the flat glass is substantially square, the side surface is divided into four side surface portions in the circumferential direction. In this case, the area ratio is four side surface portions with respect to the total area of the four side surface portions. It is a ratio of the sum total of the area of the 1st side part in. When the area ratio is calculated for each side part, the area ratio may be a different value for each side part, and the area ratio is out of the above range for some side parts. Also good. Preferably, the area ratio is within the above range for all side surface portions. In addition, the area ratio may be the same value for two opposing side surface portions of the four as necessary.

In the cover glass for a solid-state imaging device of the present invention, the Ra value of the surface roughness of the first side surface portion is 0.1 to 10 nm, the Rmax value is 0.1 to 30 nm, and the surface roughness Ra of the second side surface portion. the value 0.01~5nm, Rmax value Ru 0.01~20nm der. It is preferable that the angle formed by the first side surface portion with respect to the first light transmitting surface is within a range of 90 ° ± 5 °, and the angle formed by the second side surface portion with respect to the first side surface portion is 8 ° or less. .

The reason why the angle formed by the first side surface portion with respect to the first light transmitting surface is in the range of 90 ° ± 5 ° is as follows. That is, if the angle is less than 85 ° or greater than 95 °, it is not preferable because it is difficult to position the cover glass with respect to the solid-state imaging device in the assembly process. Further, when the side surface is divided into a plurality of portions in the circumferential direction depending on the shape of the flat glass, and a ridge line portion is formed between the adjacent side surfaces, the ridge line portion of the first side surface portion, that is, the corner of the first light transmitting surface There is a high risk that defects such as microcracks and microchipping will occur in the vicinity of the portion, and in particular in the processes such as transport and assembly, the rate of occurrence of defects due to microcracks and microchipping at the above-described locations increases. For this reason, problems in actual use such as a problem in product strength after assembling the solid-state imaging device occur.

The reason why the angle formed by the second side surface portion with respect to the first side surface portion is 8 ° or less is as follows. That is, when the angle exceeds 8 °, in other words, the angle formed by the second side surface portion with respect to the first light-transmitting surface is less than 77 ° or greater than 103 °, the cover glass It becomes difficult to adjust the clearance with the plastic tray etc. that is stored when transporting the cover, and the edge of the side surface of the cover glass or the ridge line of the second side surface due to external stress such as vibration or impact applied during transportation This is not preferable because defects such as microcracks and microchipping tend to occur near the corners of the second light-transmitting surface. Further, the same problem as described above also occurs with respect to the mechanical strength characteristics after being mounted on the solid-state imaging device.

Any processing method may be adopted for the first side surface portion and the second side surface portion of the side surface as long as the above conditions are satisfied. In this way, the side surface of the flat glass is composed of two surfaces, the first side surface portion and the second side surface portion, each having different surface properties, so that the micro glass generated on the side surface of the flat glass at the time of manufacturing the cover glass for a solid-state imaging device. It is possible to suppress the generation of glass dust due to cracks and microchipping. Therefore, strength reduction of flat glass due to redeposition of glass dust generated as a result of micro cracks, micro chipping, etc. to the translucent surface, or ridges on the side surfaces, that is, micro cracks generated at the corners of flat glass. It becomes possible to solve such problems.

And it is confirmed by the process sampling inspection in a manufacturing process, a forced acceleration test, etc. that it has the said structure, Preferably if it is a flat glass which has a composition and a characteristic mentioned later, the process in a manufacturing process, washing | cleaning, conveyance, inspection As a result, it becomes difficult to cause defects in the side surface, particularly the edge portion of the side surface, that is, the corner portion of the flat glass during a series of processes such as, and can withstand an impact test after being assembled as a cover glass that protects the solid-state imaging device. It will be a thing.

The light-transmitting surface having the maximum area in the cover glass for a solid-state image sensor has a role of transmitting visible light in order to accurately transmit image information, and thus the surface needs to have high flatness. As for the side surface, as described above, if there are defects such as fine microcracks on the surface, the strength of the flat glass is remarkably lowered, which is not preferable. Furthermore, the surface of the flat glass needs to be kept clean enough. If there is a foreign object or dirt, it becomes an obstacle to the transmission of visible light, etc., or it leads to a decrease in mechanical strength. In some cases, caution is required.

Further, the cover glass for a solid-state imaging device of the present invention has a surface roughness Ra value of 0.1 to 5.0 nm and an Rmax value on the side surface of the flat glass in order to achieve more stable quality. 1.0 to 15 nm, Ra value of the second side surface portion is 0.1 to 3.0 nm, Rmax value is 0.5 to 12 nm, and the angle formed by the first side surface portion with respect to the light transmitting surface is 90 ° ± 3 The angle formed by the second side surface portion with respect to the first side surface portion is preferably 5 ° or less.

In addition, the process management frequency of the machining process is increased, the positioning accuracy at the time of cleaving is improved, and the quality improvement such as the homogeneity of the plate glass to be processed is accumulated, so that a stable manufacturing state is always achieved. By making a device that can be realized, the surface roughness of the first side surface portion and the second side surface portion can be higher. Thereby, generation | occurrence | production of glass dust can be suppressed much more effectively. And the surface roughness in such a case is Ra value 0.3-1.2 nm and Rmax value 2.0-12.0 nm about a 1st side part, and Ra value 0. It is preferable that it is 3-1.0 nm and Rmax value is 1.5-10.0 nm.

Further, the cover glass for a solid-state imaging device of the present invention having the above-described configuration has, for example, various dimensions of 2 to 50 mm in length, 2 to 50 mm in width, and 0.1 to 1 mm in thickness, and the translucent surface is a mirror surface. Presents a condition. Further, no foreign matter, bubbles or the like are observed inside the glass, and the color tone due to the transmitted light in the thickness direction is colorless.

In the cover glass for a solid-state imaging device of the present invention, on the ridge line portion between adjacent side surface portions, the line end of the boundary line between the first side surface portion and the second side surface portion in one side surface portion, and the other side surface portion The line end of the boundary line between the first side surface portion and the second side surface portion is substantially on the same point. More preferably, the ridgeline portion should be free from microcracks.

Here, “substantially on the same point” means that, on the ridge line portion, the line end of the boundary line between the first side surface portion and the second side surface portion in one side surface portion, and the first in the other side surface portion . In addition to the configuration in which the line end of the boundary line between the side surface part and the second side surface part is completely on the same point, both line ends are at a distance of 3% or less, preferably 1% or less of the plate glass thickness. Separate configurations are also included.

  If the distance between the ends of the two lines exceeds 3% of the thickness of the flat glass, the length of the boundary between the first side surface portion and the second side surface portion having different surface roughness will be excessive in the ridge line portion. As a result of the difference in the surface roughness of the surface being reflected in the ridge line portion, a failure such as the surface roughness on the ridge line portion becoming significantly rough occurs. Therefore, in addition to the generation of microcracks during processing, there may be a problem in the transport and assembly processes. Further, when the required quality is more strict and it is necessary to ensure a more stable quality, the distance between the ends of both the wires should be 1% or less of the thickness of the flat glass.

  For example, when processing the side surface of a flat glass with a laser cutting device, in order to obtain the shape of the ridge line portion as described above, the first side surface portion in the vertical and horizontal directions of each flat glass having a substantially rectangular outline When processing the above, the relative movement speed of the laser beam is precisely controlled, and the speed fluctuation is controlled within ± 5% of the set value, and the output fluctuation of the laser beam is also within ± 5% of the set value. It is preferable to manage.

Further, “there is no microcrack in the ridge portion” means that the length from the origin to the crack tip is 10 times or more the surface roughness of the surface where the crack exists, that is, the Ra value of the surface roughness of the ridge portion. This means that there is no crack having a size of. Although it is certain that the larger the size of the crack, the more serious the defect is. However, even if the size is small, depending on the direction in which the crack enters, microchipping easily occurs, and the generated fine glass piece is flat glass. May cause problems such as adhering to the light-transmitting surface of the light, and there is a possibility that the optical characteristics may be hindered. Therefore, even small cracks cannot be neglected, but on the other hand, in light of the quality required as a cover glass for solid-state image sensors, even the smallest cracks that can be ignored are managed. Doing so leads to an increase in manufacturing cost, management cost, and product cost, which is not realistic. Taking these circumstances into consideration, it is advantageous to restrict the microcracks in the ridge line portion to the above-mentioned level in order to ensure the quality required for the cover glass for a solid-state imaging device and to suppress the cost increase.

  Flat glass with ridgeline microcracks regulated to the above level satisfies sufficiently high quality as a cover glass for solid-state image sensors, and has high performance in inspection, transportation, assembly, etc. with respect to strength characteristics after the processing process. Can be maintained.

  The cover glass for a solid-state imaging device of the present invention preferably has a linear internal transmittance of visible light having a wavelength of 500 nm and a wavelength of 600 nm of 95% or more, respectively.

  Here, the "linear internal transmittance" means that the linear transmitted light is incident on the flat glass from the side of one light-transmitting surface, is transmitted through the flat glass, and is emitted from the other light-transmitting surface. It is the spectral transmittance excluding the reflection loss, and means the ratio of the emitted light quantity to the incident light quantity. Measuring this transmittance is important in determining whether or not the performance as a cover glass for a solid-state imaging device for recording an image is satisfied. If this linear internal transmittance is lower than 95%, it is difficult to use as a cover glass for a solid-state imaging device.

Moreover, the composition of the cover glass for a solid-state image sensor of the present invention is SiO ₂ 50 to 70%, Al ₂ O ₃ 0.5 to 20%, B ₂ O ₃ 5 to 20%, RO 0.1 in mass%. ~30% (RO = MgO + CaO + ZnO + SrO + BaO), ZnO 0~9%, characterized by containing the _{MO 1~20% (MO = Li 2} O + Na 2 O + K 2 O).

SiO ₂ is a main component that is a skeleton constituting the cover glass for a solid-state image sensor of the present invention. When the content of this component is less than 50%, it is used as a solid-state image sensor, particularly for mobile phones and the like. Use in applications that have not been emphasized so far, such as information terminals, is not preferable because of problems in terms of weather resistance. In order to achieve more stable weather resistance, the SiO ₂ content is preferably 53% or more. On the other hand, if the SiO ₂ content exceeds 70%, it becomes difficult to melt the glass raw material, and it becomes necessary to prepare an expensive melting equipment to overcome this problem. It is not realistic because it leads to cost increase.

Al ₂ O ₃ is a component that contributes to the improvement of the weather resistance of the glass. When the amount of this component added is less than 0.5%, a remarkable effect cannot be obtained. Then, in order to obtain a more reliable effect, Al ₂ O ₃ is often better to 1.5% or more, more preferably better to 2.0% or more. On the other hand, when the amount of Al ₂ O ₃ added exceeds 20%, the initial solubility of Al ₂ O ₃ is deteriorated when the glass raw material is melted, which often becomes an obstacle to producing a homogeneous product. . As a result, in actual use as a cover glass for a solid-state image sensor, troubles are likely to occur in optical characteristics and mechanical performance. In order to realize more stable solubility, the upper limit of the amount of Al ₂ O ₃ added is preferably 16%.

B ₂ O ₃ acts as a glass flux and is added to improve the initial melting of the glass. However, if the amount added is too large, there is a tendency that a problem occurs in the weather resistance of the glass. Therefore, B ₂ O ₃ should be 5 to 20%, preferably 6 to 15%, more preferably 7 to 13%.

  RO (RO = MgO + CaO + ZnO + SrO + BaO) is a component that improves the weather resistance of glass by adding oxides of Mg, Ca, Zn, Sr, and Ba, which are alkaline earth metal elements, into glass. It is a component that has the effect of improving the solubility of glass and greatly contributing to homogenization by lowering the viscosity of. If the addition amount of RO is less than 0.1%, the above effect cannot be obtained sufficiently. Conversely, if the addition amount of RO exceeds 30%, crystals tend to precipitate during dissolution, and the tendency to devitrification increases. As a result, the glass transmittance may be adversely affected, or the glass homogeneity may be reduced, thereby reducing the strength of the plate glass.

  Furthermore, it is preferable that the addition amount of CaO is 0.1 to 25% by mass with respect to each component of the alkaline earth oxide. This is because CaO has a function of improving the weather resistance of the glass, but if the addition amount is less than 0.1%, the addition effect is small. In order to realize a more stable addition effect, addition of 0.4% or more is preferable. On the other hand, if CaO is added in an excessive amount, the weather resistance is lowered. Therefore, the upper limit of the added amount is preferably 25%. When the addition amount exceeds 25%, a tendency to deteriorate the water resistance is recognized. In order to realize more stable quality, the upper limit of the addition amount is preferably 23%.

ZnO is a component that suppresses volatilization of B ₂ O ₃ and alkali metal components from the molten glass. Even if this component is not added, it can be melted if there is a suitable melting facility. However, depending on the melting equipment, the effect may not be recognized unless the addition amount is 0.03% or more by mass%, and in order to realize a more clear effect, addition of 0.07% or more is required. is necessary. On the other hand, if ZnO is added too much, the weather resistance will be adversely affected. If the added amount exceeds 9%, the adverse effect on the weather resistance will increase. In order to realize more stable weather resistance, the upper limit of the addition amount is preferably 5%, and more preferably 3.7%.

In addition, alkali metal oxide (MO is a component that can be expressed as an oxide component described above, and MO is limited to 1 to 20% (MO = Li ₂ O + Na ₂ O + K ₂ O)) helps the solubility of glass, It is easy to obtain a material that can be melted even when a small melting equipment is used and it is difficult to melt at a high temperature. The mass% of the amount is required to be 1% or more, and more preferably 2% or more. On the other hand, if the amount added is too large, the expansion coefficient becomes high, which impedes chemical durability. For this reason, the addition amount needs to be 20% or less in mass% as a total amount, and preferably 18% or less.

Moreover, the composition of the cover glass for a solid-state image sensor of the present invention is SiO ₂ 50 to 70%, Al ₂ O ₃ 0.5 to 20%, B ₂ O ₃ 5 to 20%, RO 0.1 in mass%. It is characterized by containing -30% (RO = MgO + CaO + ZnO + SrO + BaO), 0-9% ZnO and substantially not containing an alkali metal oxide.

In other words, the alkali metal element brings about the above-mentioned effects to the glass, but considering the performance after the production, if a melting facility for making a more preferable limitation can be prepared, an alkali metal element can be used. It is preferable that the metal oxide is not substantially contained. Therefore, in addition to the above, the composition of the cover glass for a solid-state imaging device of the present invention is expressed in terms of mass%, SiO ₂ 50 to 70%, Al ₂ O ₃ 0.5 to 20%, B ₂ O ₃ 5 to 20%. , RO 0.1-30% (RO = MgO + CaO + ZnO + SrO + BaO), ZnO 0-9%, substantially no alkali metal oxide.

Further, the cover glass for a solid-state image sensor of the present invention has the above composition and adopts a high-purity raw material and its maintained melting environment, thereby allowing U (uranium), Th (thorium), Fe (iron). ), Pb (lead), Ti (titanium), Ba (barium), Cl (chlorine), Sn (tin), As (arsenic), Sb (antimony), S (sulfur), Zn (zinc), P (phosphorus) ), Mn (manganese), Zr (zirconium) content can be precisely adjusted, and particularly the Fe (iron), Pb (lead), Ti (titanium) affecting the transmittance near the ultraviolet region ), Cl (chlorine), Mn (manganese) can be managed in the order of 100 ppm to 10 ppb, and U (uranium) and Th (thorium), which cause soft errors due to α rays, 10ppb ~ It is possible to realize the order management of .1ppb.

The cover glass for a solid-state imaging device of the present invention has an alkali elution amount of 0.1 mg or less, a density of 2.8 g / cm ³ or less, and a specific Young's modulus (Young's modulus / density) of 27 GPa / d according to JIS-R3502. It is preferable that the g · cm ⁻³ or more and the Vickers hardness be 500 kg / mm ² or more.

  Here, “the alkali elution amount is 0.1 mg or less according to the standard of JIS R3502” represents the quality of the weather resistance of the cover glass for a solid-state imaging device of the present invention, and the test based on the Japanese Industrial Standard (JIS R3502: 1995). By applying the method, when the amount of alkali elution from the product of the cover glass for a solid-state imaging device of the present invention is measured, the measured value is 0.1 mg or less. As a quality for realizing more stable weather resistance, the alkali elution amount is preferably 0.08 mg or less.

In addition, when the density is 2.8 g / cm ³ or less, it is important to use the mobile phone while carrying it, such as a mobile phone, and the weight of the cover glass for the solid-state imaging device is required to be as light as possible. This is suitable for portable electronic device applications.

In the case of portable electronic devices, the strength of the cover glass is important, but the Young's modulus indicates how easily the cover glass can be deformed with a certain external force applied. The cover glass becomes harder to be deformed as it becomes larger. By setting the specific Young's modulus (= Young's modulus / density) to 27 GPa / g · cm ⁻³ or more, it will satisfy the characteristics of being lightweight and difficult to deform, and for solid-state imaging devices used in portable electronic devices Suitable as cover glass.

Further, when the Vickers hardness is 500 kg / mm ² or more, the surface of the cover glass is hardly damaged. The reason why this characteristic is important is that it is mounted on an electronic device used for portable purposes, and even if it is used in a protected state, the assembly process and transport process of the electronic device before it is mounted This is because it is necessary for the glass material to be difficult to be damaged. Because, if there are micro cracks on the surface of the cover glass in the assembly process or transport process of the electronic device, there is a problem in the image in the image inspection after mounting on the solid-state imaging device in the inspection process of the electronic device, etc. This is because it becomes a defective product and is not sold in the market. However, microcracks that are often overlooked because they are not directly related to the inspection image, such as the side of the cover glass, may be overlooked in quality inspections such as image inspection, and may be shipped as is. Is done. In such a case, the solid-state imaging device having a defect in the cover glass is mounted on a portable electronic device or the like, and the electronic device receives a large bending stress in a state where it is put in a jeans pocket with a strong impact force such as dropping. As a result, the cover glass is subjected to strong stress, and cracks due to microcracks may occur. Accordingly, the Vickers hardness of the cover glass surface is preferably 500 kg / mm ² or more.

  In addition to the above-described characteristics, the cover glass for a solid-state image sensor of the present invention preferably satisfies the following characteristics. That is, regarding acid resistance, it is preferable that the powder mass reduction rate after immersion treatment in 0.01N nitric acid for 60 minutes in an acid resistance evaluation test according to JOGIS06-1999 is less than 020%. Moreover, there is nothing that disturbs the homogeneity such as striae and knots in the flat glass, and it is preferable to have a high degree of homogeneity.

  In addition, the flat glass according to the present invention can be used as a thin glass for filters by adding a predetermined amount of a transition metal element at a predetermined concentration or by precipitating a noble metal element or the like in a colloidal state. In addition, it can be used for electronic devices used in window glass of laser diodes and optical functional parts. Furthermore, it is also possible to adjust the optical characteristics by applying a deposited film or the like to the surface of the flat glass by various methods such as CVD.

As described above, the cover glass for a solid-state imaging device of the present invention satisfies the relationship of −0.2 ≦ (Z−Za) /Za≦0.2, and thus the flat glass caused by the ridge line portion between the side surfaces. The probability that the strength deterioration occurs can be reduced, and the production of a cover glass for a solid-state imaging device having a stable quality is enabled .

  In the cover glass for a solid-state image pickup device according to the present invention, the first side surface portion is a substantially vertical surface that forms 90 ° ± 5 ° with respect to the light-transmitting surface. When assembling the cover glass, it is possible to easily align the cover glass with the solid-state imaging device.

Moreover, since the ratio of the total area of the 1st side part with respect to the total area of a side surface is 0.1-0.3, the cover glass for solid-state image sensors of this invention WHEREIN: Ra value of surface roughness of a side surface, Rmax value It is possible to reduce the occurrence rate of microcracks on the side surfaces that depend on the surface properties such as the surface roughness.

In the cover glass for a solid-state imaging device of the present invention, the Ra value of the surface roughness of the first side surface portion is 0.1 to 10 nm, the Rmax value is 0.1 to 30 nm, and the surface roughness Ra of the second side surface portion. value 0.01～5Nm, since Rmax value is 0.01～20Nm, glass caused by microcracks and its micro-cracks generated in the flat glass sides of the assembly process in manufacturing processes and electronic equipment flat glass Dust can be remarkably reduced, improving impact strength characteristics after mounting on a solid-state image sensor and improving the cleanliness of the plate glass.

Moreover, the cover glass for a solid-state imaging device of the present invention has a line end of the boundary line between the first side surface portion and the second side surface portion in one side surface portion on the ridge line portion between adjacent side surface portions , and the other side. Since the line end of the boundary line between the first side surface portion and the second side surface portion in the side surface portion is substantially on the same point and there is no micro crack in the ridge line portion, the ridge line portion even after being assembled as a solid-state imaging device The flat glass does not cause a significant decrease in strength over time, and maintains a stable quality.

  The cover glass for a solid-state image sensor of the present invention has a linear internal transmittance of 95% or more for visible light having a wavelength of 500 nm and a wavelength of 600 nm, respectively, so that it has a high function when mounted on a solid-state image sensor. It becomes possible to exhibit without impairing the performance.

In the cover glass for a solid-state imaging device of the present invention, the flat glass is 50% to 70% SiO ₂ , 0.5% to 20% Al ₂ O ₃ , 5% to 20% B ₂ O ₃ RO 0. 1-30% (RO = MgO + CaO + ZnO + SrO + BaO), ZnO 0-9%, MO 1-20% (MO = Li ₂ O + Na ₂ O + K ₂ O) Satisfies various optical, chemical and mechanical properties.

In the cover glass for a solid-state imaging device of the present invention, the flat glass is SiO ₂ 50 to 70%, Al ₂ O ₃ 0.5 to 20%, B ₂ O ₃ 5 to 20 in terms of mass%. % RO 0.1 to 30% (RO = MgO + CaO + ZnO + SrO + BaO), ZnO 0 to 9%, and substantially containing an alkali metal oxide, therefore, translucency required for a material as a cover glass of a solid-state imaging device It satisfies various higher properties such as optical properties such as safety, chemical and mechanical properties such as weather resistance.

The cover glass for a solid-state imaging device of the present invention has an alkali elution amount of 0.1 mg or less, a density of 2.8 g / cm ³ or less, and a specific Young's modulus (= Young's modulus / density) of 27 GPa according to the standard of JIS-R3502. / G · cm ⁻³ or more, and Vickers hardness of 500 kg / mm ² or more, it exhibits high performance required as a cover glass of a solid-state image sensor with respect to the weather resistance and temporal strength characteristics of the flat glass surface.

  (1) As described above, the cover glass for a solid-state imaging device according to the present invention includes microcracks generated on the side surface of the flat glass in the flat glass manufacturing process and electronic device assembly process, and glass dust generated by the microcracks. It is a significant reduction, and it improves impact strength characteristics after mounting on a solid-state image sensor and improves the cleanliness of flat glass. This makes it possible to effectively use the solid-state imaging device.

  (2) Further, the cover glass for a solid-state image sensor of the present invention can easily align the cover glass with the solid-state image sensor when the cover glass is sealed to assemble the solid-state image sensor. Therefore, the assembly of the solid-state image sensor can be performed quickly and efficiently, and this greatly contributes to stable production of a solid-state image sensor having high performance.

  (3) Further, the cover glass for a solid-state imaging device of the present invention can suppress the Ra value of the surface roughness of the side surface of the flat glass and the Rmax value of the maximum surface roughness, and the surface properties such as the surface roughness. In addition, it is possible to reduce the incidence of microcracks on the side of the flat glass that occurs as a secondary effect depending on the It is possible to alert the user to the usage.

  (4) Moreover, the cover glass for solid-state image sensors of this invention can reduce the probability that the strength deterioration of the flat glass resulting from the ridgeline part of the side surface of flat glass will generate | occur | produce, and was stable Since it is possible to produce a high-quality solid-state image sensor cover glass, it is possible to simplify the inspection in the process of using the solid-state image sensor cover glass, and it is inexpensive and highly reliable. It is possible to mass-produce a solid-state imaging device having

  (5) The cover glass for a solid-state image sensor of the present invention does not cause a significant decrease in strength over time of the flat glass due to the ridge line portion on the side surface even after being assembled as a solid-state image sensor, and has a stable quality. Since it can be realized, it has a function suitable as a cover glass mounted on a solid-state imaging device used in a field requiring high strength such as portable use.

  (6) Furthermore, since the cover glass for a solid-state imaging device of the present invention can be exhibited without impairing the performance of a semiconductor device having a high function when mounted on the solid-state imaging device, Until then, due to the weakness of the package side, such as cover glass that protects semiconductors, the use of higher performance semiconductors that have been refrained from using them will increase the range of use of semiconductor elements in more diverse fields. It can be expanded.

  (7) Since the cover glass for a solid-state image sensor of the present invention satisfies various optical, chemical and mechanical properties required for the material for the cover glass of the solid-state image sensor, It can be widely used not only for applications but also for solid-state imaging devices mounted as electronic parts of various electronic devices.

  (8) Moreover, the cover glass for solid-state image sensors of this invention becomes the quality which exhibits the high performance required as a cover glass of a solid-state image sensor about the weather resistance of a flat glass surface, and a temporal strength characteristic. Therefore, the present invention can greatly contribute to further development of the entire optical communication industry related to information transmission in which a solid-state imaging device is used.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a cover glass 10 for a solid-state image sensor according to this embodiment. The cover glass 10 for a solid-state imaging device is made of a flat glass made of inorganic oxide glass. The first light transmitting surface 11a and the second light transmitting surface 11b facing each other in the thickness direction of the flat glass, and the flat glass And a side surface 12 constituting a peripheral edge. The flat glass has a substantially quadrangular shape, and the side surface 12 is divided into four parts in the circumferential direction corresponding to each side of the flat glass (hereinafter, each part of the side surface thus divided (each side surface) is divided. Each referred to as "side portion 12"). Each side surface portion 12 includes a first side surface portion 12a that is substantially perpendicular to the first light-transmitting surface 11a and a second side surface portion 12b that is inclined with respect to the first side surface portion 12a. The surface roughness of the first side surface portion 12a is larger than the surface roughness of the second side surface portion 12b. The first side surface portion 12a is provided over the entire circumference of the flat glass, and the first side surface portion 12a of each side surface portion 12 is in direct contact with the first light transmitting surface 11a. Similarly, the second side surface portion 12b is also provided over the entire circumference of the flat glass, and the second side surface portion 12b of each side surface portion 12 is in direct contact with the second light transmitting surface 11b.

  As described above, it is difficult to manufacture a flat glass having a side surface constituted by only one surface because the side surface 12 is composed of the two surfaces of the first side surface portion 12a and the second side surface portion 12b. That's why. That is, if it is going to shape | mold the flat glass which comprised the side surface only with the 1st side part, the linearity of a side surface will be impaired and it will become a curved side surface shape. Moreover, if it is going to shape | mold the flat glass which comprised the side surface only with the 2nd side part, the surface accuracy of a side surface will deteriorate further. Of course, it is possible to correct the surface accuracy by mirror-polishing the side surface after molding, but since the manufacturing cost of the flat glass becomes extremely high, it is not possible to supply an inexpensive cover glass desired by the market. Accordingly, mirror polishing of the side surface of the flat glass is not realistic even if physically possible.

  The first side surface portion 12a and the second side surface portion 12b are separated by a boundary line 14, and a ridge line portion 13 exists between two adjacent side surface portions 12. On the ridge line portion 13, the line end (line end point) of the boundary line 14 of one side surface portion 12 and the line end (line end point) of the boundary line 14 of the other side surface portion 12 are substantially on the same point 13 a. Is located.

  As shown in FIG.1 (b), the 1st side part 12a makes | forms the angle (alpha) with respect to the 1st translucent surface 11a, and this angle (alpha) is 90 degrees +/- 5 degrees. Further, the second side surface portion 12b forms an angle β with respect to the first side surface portion 12a, and the angle β is 8 ° or less. As long as the angle β is 8 ° or less, the angle β may be an angle toward the inside of the flat glass or an angle toward the outside as illustrated.

  FIG. 2 shows an enlarged view of one side portion 12. The side surface portion 12 is composed of a first side surface portion 12a and a second side surface portion 12b, and a boundary line 14 therebetween is substantially parallel to the first light transmitting surface 11a. Accordingly, in the side surface portion 12, the distance Z in the thickness direction from the boundary line 14 to the first light transmitting surface 11a is substantially constant. The boundary line 14 is also substantially parallel to the second light transmitting surface 12b. In the flat glass of this embodiment, there are three other side surface portions 12 similar to the side surface portion 12 shown in FIG. The aforementioned area ratio, that is, {area of the first side surface portion 12a / (area of the first side surface portion 12a + area of the second side surface portion 12b)} is 0.1 to 0.3 for each side surface portion 12, respectively. is there. Further, the ratio {(Z−Za) / Za} described above is −0.2 to 0.2 for each side surface portion 12. This ratio {(Z-Za) / Za} is preferably as small as possible, but in particular, if it is -0.05 to 0.05, the quality becomes more stable. These ratios may be the same value or different values for the four side surface portions 12.

  The ridge line portion 13 is a connecting line between the apex 15a and the apex portion 15b of the corner of the flat glass, and the point 13a (substantially the same point) is located on the ridge line portion 13.

  FIG. 3 shows an enlarged corner of the flat glass. In this embodiment, as a result of the distance Z shown in FIG. 2 being different from each other for the two side surface portions 12 adjacent to each other, the boundary line 14 a and the boundary line 14 b in the two side surface portions 12 are discontinuous on the ridge line portion 13. It has become. That is, on the ridge line portion 13, the line end (line end point) 13a1 of the boundary line 14a of one side surface portion 12 and the line end (line end point) 13a2 of the boundary line 14b of the other side surface portion 12 are made of flat glass. It is slightly separated by a distance of 3% or less, preferably 1% or less of the plate thickness T. For this reason, the ridge line part 13 is a boundary between the first side part 12a1 and the first side part 12a2 adjacent to each other, a boundary between the second side part 12b1 and the second side part 12b2, and the first side part 12a2 and the second side part. It consists of three types of boundaries, that is, the boundary with the part 12b1.

  In the ridgeline portion 13, the boundary between the first side surface portion 12a1 and the first side surface portion 12a2, that is, the distance from the vertex 15a of the corner of the flat glass to the line end point 13a1, reflects the distance Z shown in FIG. It becomes. Therefore, in the ridge line portion 13, the boundary between the first side surface portion 12a2 and the second side surface portion 12b1, that is, the distance between the line end point 13a1 and the line end point 13a2, is the ratio {(Z−Za) / Za}. The smaller, the smaller. From this viewpoint, the ratio {(Z-Za) / Za} is set to -0.2 to 0.2, preferably -0.05 to 0.05.

  Further, the distance between the line end point 13a1 and the line end point 13a2 is 3% or less, preferably 1% or less, of the plate thickness T of the flat glass, and can be regarded as substantially the same point 13a in visual observation.

  Since the boundary between the first side surface portion 12a2 and the second side surface portion 12b1 in the ridge line portion 13, that is, the region between the line end point 13a1 and the line end point 13a2, is a boundary between surfaces having different surface roughnesses. As a result of reflecting the surface state, the surface state becomes rougher than the rougher surface (first side surface portion 12a2). For this reason, there is a tendency that microcracks tend to occur starting from the region of the ridge line portion 13. By controlling the length of the region of the ridge line portion 13, that is, the distance between the line end point 13a1 and the line end point 13a2, to 3% or less, preferably 1% or less of the plate thickness T of the flat glass, the above-mentioned micro Generation of cracks can be prevented.

  Further, by appropriately adjusting the processing conditions, the surface roughness of the first side surface portion 12a and the second side surface portion 12b is made as close as possible, and further, by taking measures such as improving the sampling inspection frequency of the processed surface. The variation with respect to the average value (Za) of the distance between the vertex 15a and the line end point 13a1 at the corner of the flat glass and the distance between the vertex 15a and the line end point 13a2 is ± 10% or less, preferably ± 8% or less. More preferably, it should be ± 5% or less.

  Next, a method for producing the above-described cover glass for a solid-state imaging device and a result of an evaluation test for the performance will be described.

First, the first step of the flat glass manufacturing process is a process for producing a large plate glass of about 300 mm in a thin plate. There are two types of this process, one is a method by stretch molding and the other is precision grinding and polishing. This is a method based only on processing. In the case of stretch molding, for example, a base plate glass having a width of 850 mm, a thickness of 5 mm, and a length of 3 m is prepared using a plate glass previously melted in a melting furnace. Then, the base plate glass 20 is subjected to a polishing process by automatically supplying a slurry in which free abrasive grains such as cerium oxide are dispersed in water or the like by a rotary polishing machine (not shown) provided with artificial leather. Polishing is performed to a mirror surface with a roughness Ra value of 1.1 nm, followed by washing and drying to obtain, for example, a thick plate glass 20 having a thickness of 4.5 ± 0.5 mm. And this thick glass 20 is set to the stretch molding apparatus 30 shown in FIG. 4, and it heats with the heating furnace 30a hold | maintained at the temperature from which a glass viscosity will be 105 dPa * s, By the taking-out heat-resistant roller 30b attached to the lower part By carrying out at 10 times the carrying-in speed | velocity, it shape | molds in the sheet glass 40, and scribe-molds both sides of this sheet glass 40, and shape | molds the plate-shaped large plate glass of 300 mm of one side.

  In addition, in the case of precision grinding and polishing, glass that has been melted and homogenized in a melting furnace is cast into a size of, for example, 800 × 300 × 300 mm, and a wire saw that uses loose abrasive grains is used from there. To obtain a thin glass plate having a thickness of 1.5 mm. And thin plate-shaped large plate glass is obtained by performing grinding | polishing processing to this thin plate glass using the rotary polishing processing machine as mentioned above. The dimensions of the large plate glass that can be produced by the two methods described above can be formed in the range of vertical: 50 to 600 mm, horizontal: 50 to 600 mm, and plate thickness: 0.1 to 50 mm. It can be changed accordingly.

Next, there are two types of methods for chopping the thin plate-like large glass, one is to employ laser scribe using a so-called laser cutting device, and the other is heating with heating ceramic powder. A processing method using a protruding roller is adopted. First, for laser scribing, a laser beam moving speed of 180 ± 5 mm / sec or 220 ± 5 mm / sec on one surface of the thin glass up to a thickness of 20% in the thickness direction using a thermal processing laser cutting device. First, a grid-like first process is performed under the conditions of sec, laser output 120 ± 5 W or 160 ± 5 W. Next, as conceptually shown in FIG. 5, the metallic line-shaped head 16 is moved from the opposite side to the working direction M with respect to the first processed surface 15 of the thin glass 17, and at the same time, By pressing the translucent surface on the one processed surface 15 side with a jig (not shown), stress is applied to the first processed surface 15 of the thin glass plate 17 to perform splitting. By carrying out the cleaving of the second processing in this way, a strip-shaped plate glass divided along the planned line formed by the first processing is obtained. The strip-shaped plate glass that has been cut and split in this manner is transported to the next process using vacuum tweezers (not shown). Then, the final cover glass for a solid-state image sensor is obtained by again splitting the strip-shaped plate glass.

  In addition, the processing method that uses the heated projection roller with ceramic powder is currently in the development stage, but by pressing and moving the sharp roller plate with ceramic powder attached to the tip surface against the surface of the plate glass, it is moved. By heating the plate glass surface and using a pre-cooling plate with a Peltier element immediately after that, the tension in the direction perpendicular to both the glass surface generated at the crack tip of the plate glass surface and the laser moving direction acts on the plate glass surface. By continuing to do so, cutting can be performed without using the cooling water necessary for laser cutting, and processing almost equivalent to laser scribe can be performed.

Even if any of the above processing methods is adopted, a flat glass having a side thickness of 0.1 mm to 1 mm as shown in FIG. 6 can be obtained. FIG. 6 is a photograph of a portion near the corner of the side surface of the actually obtained cover glass for a solid-state imaging device. The side surface is formed by the first side surface portion V formed by the first processing and the second processing thereafter. It can be seen that the second side surface portion W is constituted by two surfaces. The first side surface portion V formed by the first processing has a surface property exhibiting an appearance recognized on the surface subjected to the heat processing, and the surface V is recognized as a mirror surface. The surface roughness Ra value is 0.3 to 2.0 nm, and the Rmax value is 2.0 to 20.0 nm. The feature of the surface V is that the fracture surface has a high speed of progress, and is a surface state recognized on a mechanical cutting surface such as a mechanical scribe using a dicing saw or the like, that is, a rib having a large unevenness with a narrow interval ( Rib) There is a characteristic fracture surface mark that occurs when the fracture surface of the mark or the like proceeds at high speed, and at the same time, the Ra value of the surface roughness is greater than 50 nm and the irregularity that results in an Rmax value exceeding 100 nm. The surface state is clearly different from the severe fracture surface. On the other hand, the second side surface portion W formed by the second processing has a feature that several curved rib marks with a gap between the corner portions may be recognized and a wide range of mirror surfaces are recognized. In this case, the Ra value of the surface roughness in this case is 0.3 to 10 nm, and the Rmax value is 2.0 to 20.0 nm.

  It should be noted that the surface roughness of both surfaces is preferably as small as possible and is managed so as not to have foreign matter or dirt. Further, the surface roughness of the first side surface portion V has a Ra value of 0.3 to 1 by managing the processing accuracy more frequently and executing a series of steps such as increasing the frequency of regular maintenance. .2 nm, Rmax value 3.0 to 9.0 nm, and the surface roughness of the second side surface W can be controlled to Ra value 0.3 to 1.0 nm and Rmax value 2.5 to 8.0 nm. .

  (Performance Evaluation 1) Next, a performance evaluation test was performed on the cover glass for a solid-state imaging device of the present invention formed by the manufacturing method as described above. The results are specifically shown below.

First, a glass raw material prepared and mixed in advance so as to have the composition shown in Table 1 is held in an electric melting furnace having a stirring function using a platinum rhodium crucible having a volume of 1000 cc and melted at 1550 ° C. for 20 hours. Thereafter, the molten glass was poured into a carbon mold and gradually cooled to form an appropriate shape so that each characteristic can be measured. And the characteristic of each obtained glass sample was measured with the following method. That is, the alkali elution amount was measured according to JIS R3502. What is written as ND in the table indicates that it is difficult to detect. The density was measured by a well-known Archimedes method. Further, the specific Young's modulus was calculated from Young's modulus and density measured by a bending resonance method using a non-destructive elastic modulus measuring device (KI-11) manufactured by Kanebo Co., Ltd. And about Vickers hardness, it measured according to JISZ2244-1992. In addition, for the linear internal transmittance, the surface is subjected to the same polishing process as in the plate glass manufacturing process described above, and the glass thickness is the same as that of the cover glass product for a solid-state imaging device. The transmittance was measured using a Hitachi spectrophotometer (UV-3100).

  From the measurement results shown in Table 1, it was found that all the samples satisfy the conditions of the present invention with respect to the alkali elution amount, density, specific Young's modulus, Vickers hardness, and linear internal transmittance. However, the performance of the cover glass for a solid-state imaging device of the present invention can be realized by satisfying these compositions and various characteristics and having the surface quality of the side surface having the high quality as described above.

Next, a cover glass for a solid-state image sensor (samples A to E) was prepared, and the surface properties of the side surfaces were confirmed. Samples A to D (Examples) were prepared by producing a base glass plate that satisfies the above-mentioned characteristics, and further processing to make a thin glass plate, and forming the first side surface portion of the side surface by laser scribing (first processing). In addition, the second side surface portion is formed by cleaving (second processing), that is, pressing. On the other hand, Sample E (Comparative Example) is formed by forming the first side surface portion of the side surface by mechanical scribing and the second side surface portion by splitting. Then, for each of the first side surface portion and the second side surface portion of each sample, the surface roughness is measured (by Digital Instruments), an atomic force microscope (NanoScope III Tapping Mode AFM), and a stylus type surface roughness. Measurement was performed using a thickness measuring machine Talystep (Tayler-Hobson). The results are shown in Table 2.

Regarding the measurement of the surface roughness, in the measurement using an atomic force microscope, measurement was performed 10 times for a measurement length of 40 μm, and the average value was obtained (the value is shown in the circle 1 column in Table 2). In the measurement using the stylus type surface roughness measuring instrument Taly Step, the measurement length was 0.25 mm, the measurement speed was 0.0025 mm / sec, the filter was 0.33 Hz, and the magnification was 200,000 times (the value was It is shown in the circle 2 column in Table 2.) Both are measured by scanning the probe in a direction parallel to the side surface of the sample. From the measurement results shown in Table 2, the samples A to D (Examples) are all good in that the Ra value and Rmax value of the surface roughness of the first side surface portion and the second side surface portion satisfy the conditions of the present invention. It was confirmed to have a good surface texture. On the other hand, Sample E (Comparative Example) is in a state in which the Ra value of the surface roughness of the first side surface portion exceeds 72.5 nm and 50 nm and is very rough, and the surface properties of Samples A to D (Examples) are high. The difference could be clearly discerned by microscopic observation.

  Moreover, when the angle of the 1st side part with respect to the translucent surface was measured about sample AD (Example), it was 88-93 degrees, and the inclination angle of the 2nd side part with respect to the 1st side part was measured. 2 to 7 °. Accordingly, each of the samples A to D has a side surface shape that is necessary and sufficient as the cover glass for a solid-state imaging device of the present invention.

  Furthermore, a cover glass for a solid-state image sensor (samples F and G) was prepared, and the surface state of the light-transmitting surface was evaluated using a stylus type surface roughness measuring instrument Talystep (manufactured by Taylor-Hobson). Sample F and Sample G each employ the two types of large glass processing methods described above, Sample F is manufactured by precision grinding and polishing, and Sample G is manufactured by stretch molding. As measurement conditions, a measurement length of 1 mm was measured at a measurement speed of 0.025 mm / sec, a filter of 0.33 Hz, and a magnification of 1,000,000. The results shown in Table 3 were obtained.

  From the measurement results shown in Table 3, it can be seen that both Sample F and Sample G have sufficient smoothness as the light-transmitting surface of the cover glass for the solid-state imaging device.

  As described above, the cover glass for a solid-state imaging device of the present invention has a smooth surface property that can sufficiently perform the function as a cover glass for a solid-state imaging device, in addition to the surface quality of the side surface. .

(Performance Evaluation 2) In order to evaluate the strength characteristics of the cover glass for a solid-state image sensor of the present invention, the following impact strength characteristics evaluation test was conducted. In other words, in order to conduct an impact test in the state where it is actually mounted on a mobile phone, a solid-state image sensor in a commercially available camera equipped with a solid-state image sensor is taken out, and a cover glass for the solid-state image sensor to be tested is screwed instead. It was sealed with an adhesive on an alumina substrate having the same weight as that of the solid-state imaging device having a stop hole, and this was screwed to a mobile phone and attached to make a mobile phone device to be tested for an impact test. Next, attach a cylindrical guide made of PVC to the mobile phone device under test so that the corner closest to the position where the solid-state image sensor of the mobile phone device is attached is always the impact point. The cellular phone device under test was dropped on a oak tree plate having a thickness of 3 cm from a height of 1 m while being held in a state where it passed through a column of a metal cylinder having a length of 1.2 m held vertically.

  In the test, 30 samples of alumina substrate sealing bodies using the cover glass for a solid-state imaging device of the present invention (dimensions: 7 × 7 × 0.3 mm) as an example were processed by the same number of mechanical scribes as a comparative example. Thirty specimens of the same size optical glass BK7 were used. The test method is to perform a drop test from 1 m 200 times for each test object, take out the alumina substrate sealing body after the test, visually observe, observe with a stereo microscope of 20 times, and further cracks are recognized. The specimens were observed with a scanning electron microscope for 50 times microscopic observation and the presence or absence of microcracks.

As a result, no abnormality was observed in the 30 specimens mounted with the cover glass for the solid-state image pickup device of the present invention, which was an example, and a new microscopic observation was also made by observation using a scanning electron microscope. The occurrence of cracks could not be confirmed. On the other hand, in the case of using flat glass whose side surface was formed by mechanical scribing in the comparative example, a very thin plastic deformation zone was formed between the first side surface portion and the light transmitting surface of the side surface in a prior investigation. The surface roughness Ra value was about 105 to 320 nm, but as a result of the test, cracks due to such microcracks were observed in two specimens. Therefore, as a result of wavefront analysis using the scanning electron microscope for these two specimens, the stress is shocked by using the microcrack existing on the first side surface of the flat glass as the origin for both of the two specimens. It was found that there were fracture surfaces with fracture surface characteristics that were observed when added. In addition, when the remaining test specimens in which no cracks were observed were also observed under a 50-fold microscope, microchipping due to microcracks was present on the first side surface of the side surface of the flat glass. Confirmed to do.

  Through the above test, the cover glass for a solid-state imaging device of the present invention can sufficiently withstand even an impact test that causes a problem in strength with the conventional flat glass. It was found to have high performance.

  (Performance Evaluation 3) In order to evaluate the strength characteristics of the cover glass for a solid-state imaging device of the present invention, the following comparative test of strength characteristics over time was performed. This test was evaluated by harshly reproducing the strength characteristics during long-term use by utilizing the transport process in the actual use stage by combining the weather resistance test and the strength test.

  First, a total of 4000 flat glasses formed with the dimensions of the cover glass to be mounted on the solid-state imaging device were prepared for the examples (samples H to O) and 3000 in total for the comparative examples (samples P to T). . Table 4 summarizes the outer shape and surface properties of the flat glass used and the results at the end of the test.

In the table, the ratio {(Z−Za) / Za} of the two items from the top is the first translucent surface from the boundary line between the first side surface portion and the second side surface portion in each of the four side surfaces as described above. In the thickness direction from the boundary line between the first side surface portion and the second side surface portion to the first translucent surface, on each side surface, with respect to the arithmetic average value Za obtained by dividing the sum of the distances in the thickness direction up to 4 This is the ratio of variation in the distance Z. And this table | surface has shown the average of the measured value about the flat glass corner | angular part of 20 samples of each conditions, ie, a total of 80 places. The third item (distance between line ends) from the top is the line end (line end point) of the boundary line of one side surface and the other side surface on the ridge line part between two adjacent side surfaces. Is the distance between the line end (line end point) of the boundary line (for example, the distance between the line end point 13a1 and the line end point 13a2 in the example shown in FIG. 3).

  About 500 samples each for samples H to O of the example, 500 samples each for samples P to S of the comparative example, and 1000 samples for sample T were prepared under the same conditions. For the samples H to O of the examples, laser scribing is employed for crack line processing on the flat glass side surface, and processing is performed under conditions of a laser beam moving speed of 120 ± 5 mm / sec, or 150 ± 5 mm / sec, and a laser output of 120 ± 5 W. Then, the cleaving is formed by splitting, the surface roughness of the first side surface portion and the second side surface portion, the ratio {(Z-Za) / Za}, the distance ratio between the line ends (distance between the line ends / flat glass The values shown in Table 4 were realized as the plate thickness), the angle of the first side surface portion with respect to the translucent surface, and the angle of the second side surface portion with respect to the first side surface portion.

  On the other hand, for the sample of the comparative example, for the sample P, the sample Q, the sample R, and the sample S, a laser scrub is adopted for crack line processing. By intentionally changing the moving speed in the range of 25 to 40% and further changing the output in the range of 90 to 220 W, the ratio {(Z−Za) / Za} exceeds 20%, and the distance between the line ends The distance ratio (distance between line ends / plate thickness of flat glass) was set to exceed 3%. Further, in Sample R and Sample S, the angle of the second side surface portion with respect to the first side surface portion in Sample R by intentionally changing the irradiation angle of the laser beam and intentionally changing the stress application direction during the splitting process. In the sample S, the angle of the first processed surface with respect to the translucent surface was over 95 °. In Sample T, the first side surface portion was molded by mechanical scribing, and the second side surface portion was molded by splitting.

  And the surface roughness of each sample was measured by the above-mentioned stylus type surface roughness measuring instrument Taly Step (manufactured by Taylor-Hobson). As measurement conditions, a measurement length of 1 mm was measured at a measurement speed of 0.025 mm / sec, a filter of 0.33 Hz, and a magnification of 1,000,000 times. Further, the distance between line ends on the ridge line part, and the angles of the first side face part and the second side face part were measured using a projection measuring machine, a laser microscope, a micrometer, and the like.

  As a result, in all the examples, the surface roughness of the first side surface portion is within the range of 0.1 to 5.0 nm in terms of Ra value and 1.0 to 15 nm in terms of Rmax value. It was found that the surface roughness was in the range of 0.1 to 3.0 nm in terms of Ra value and 1.0 to 12 nm in terms of Rmax value. On the other hand, for the comparative example, the sample P, the sample Q, the sample R, and the sample S have a surface roughness in the same range as the example, but the sample T has an Ra value of 10 nm on the first side surface portion. The Rmax value was greater than 30 nm.

  Furthermore, regarding the ratio {(Z−Za) / Za}, all of the examples had a value of 20% or less. On the other hand, in the samples P and Q of the comparative example, the ratio {(Z−Za) / Za} exceeds 20%, and the total distance between the line ends on the ridge line portion is about 200 μm for one sample. As a result of microscopic observation, the surface roughness of the ridge line portion was rougher than that of the first side surface. On the other hand, in the example, the sum of the distances between the line ends on the ridge line portion was 200 μm or less, and when the ridge line portion was observed with a microscope, it was confirmed that it was not a rough surface state as in the comparative example. . In the sample H, the sample I, the sample J, the sample K, the sample L, and the sample M of the example, the ratio {(Z-Za) / Za} is 5% or less, and the line on the ridge line portion for one sample The sum of the end-to-end distances was shorter than about 40 μm. Moreover, although the line end distance ratio (distance between line ends / plate thickness of flat glass) was recognized from 1.0% to 14.5% in the examples, the ridge portion was observed by microscopic observation. Samples whose surface roughness tends to be the same as or smaller than that of the first side surface are sample H, sample I, sample J, sample K, sample L, and sample whose ratio is 3.0% or less. M. Further, this tendency was more remarkable in the sample K, the sample L, and the sample M in which the ratio is 1.0% or less. On the other hand, in the sample T of the comparative example, although the ratio {(Z−Za) / Za} is small, since the surface roughness of the first side surface portion is rough, the ridge line portion has a degree corresponding thereto and is in a rough state. there were.

  The samples of the examples and comparative examples having the above-mentioned external qualities are all stored in a plastic tray for shipment and kept at a temperature of 80 ° C. and a humidity of 80% as they are. The car was packed in cardboard as it was, and then used as a truck, and a running vibration test was conducted between Otsu City, Shiga Prefecture and Fujisawa City, Kanagawa Prefecture, that is, 10 round trips of about 450 km or more, totaling 9000 km or more. . In this way, after holding the flat glass in a high-temperature and high-humidity environment for a long period of time, a severe vibration test in a transported state was carried out in combination with the packaging form. About the test body which the test was complete | finished, both the Example and the comparative example implemented the stereoscopic microscope observation, 50 times microscope observation, and also the scanning microscope observation.

  As a result, for the samples H to M of the examples, neither microcracking nor microchipping was observed in both the stereoscopic microscope observation and the 50-fold microscope observation. In addition, for sample N and sample O, microchipping and microcracks were observed, but when the cause was investigated, adhesion of metal foreign matter was observed on the plastic tray. It was found that they are not related to flat glass. In Sample K and Sample O, the adhesion of foreign matter was observed on the surface of the flat glass. However, as a result of analysis, it was found that it was caused not by glass foreign matter but by contamination of the plastic tray. Therefore, about the Example, the abnormality resulting from flat glass was not recognized.

  On the other hand, in the comparative examples, the occurrence of microcracks and microchipping was observed for all of the samples P to T. In particular, for the sample P, when the occurrence location of the microcrack was specified, 90% of the 3.5% microcrack was the boundary between the first side surface portion and the second side surface portion on the ridge line portion in the flat glass corner portion. The location of the line (the area between the line ends) was the origin of the crack. Further, 70% of chipping of the sample P was chipping originating from the region between the line ends on the ridge line portion. Further, in the sample S, the incidence of microcracks tends to be high on the side surfaces other than the corners, and when investigated, 40% occur near the boundary between the first side surface and the second side surface other than the corners. It was.

  Moreover, about the sample T of the comparative example, the microcrack which was not recognized before the test was confirmed about the side surface of 23 samples among 1000 samples, and the incidence was 2.3%. And about six of them, it originated in the glass powder which generate | occur | produced by the chipping of the 1st side part. Moreover, about 13 samples, the adhering foreign material by the component eluted from the glass was recognized by the side surface, and the generation | occurrence | production rate was 1.3%. Furthermore, about 2 samples, the damage | wound of the glass plate surface which generate | occur | produced in the middle of conveyance with the glass powder pinched | interposed between the plastic tray and flat glass was confirmed.

  From the above evaluation results, the cover glass for a solid-state imaging device of the present invention has excellent weather resistance, and appropriate processing is applied to the side surface of the flat glass, and there is no problem in strength even in a process such as conveyance. It has been found that it has excellent performance and can maintain stable quality.

1 is a perspective view (FIG. A) and a partial cross-sectional view (FIG. B) of a cover glass for a solid-state image sensor according to the present invention. It is a side part enlarged view of the cover glass for solid-state image sensors of this invention. It is a corner | angular part enlarged view of the cover glass for solid-state image sensors of this invention. It is explanatory drawing of the method of manufacturing thin glass from the base material of thick glass. It is explanatory drawing of the processing method at the time of performing a 2nd process after a 1st process of a sheet glass. It is the microscope picture which expanded about a part of side part of the cover glass for solid-state image sensing devices concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cover glass 11a for solid-state image sensors 1st light transmission surface 11b 2nd light transmission surface 12 Side surface 12a (12a1, 12a2) 1st side surface part 12b (12b1, 12b2) 2nd side surface part 13 Ridge line part 13a (13a1, 13a2) Line end (line end point) of the boundary line on the edge
14 (14a, 14b) Boundary line α Angle formed between the light transmitting surface and the first side surface portion β Angle formed between the first side surface portion and the second side surface portion

Claims (5)

A solid-state imaging device comprising a flat glass made of an inorganic oxide glass and having first and second light-transmitting surfaces opposed to each other in the thickness direction of the flat glass, and a side surface constituting the periphery of the flat glass Cover glass for
The side surface is divided into a plurality of side surface portions adjacent in the circumferential direction via a ridge line portion,
Each of the side portions includes a first side surface portion adjacent to the first light transmitting surface, and a second side surface portion adjacent to the first side surface portion and the second light transmitting surface, and the first side surface portion. The surface roughness of the part is larger than the surface roughness of the second side part,
For each of the side surface portions, the distance Z in the thickness direction from the boundary line between the first side surface portion and the second side surface portion to the first light transmitting surface is determined, and the average value is Za. wherein said distance Z in each side portion, meets the relationship of -0.2 ≦ (Z-Za) /Za≦0.2 ,
On a ridge line portion between the side surface portions, a line end of a boundary line between the first side surface portion and the second side surface portion in one of the side surface portions, and the first side surface portion and the first in the other side surface portion. The distance between the line end of the boundary line with the two side surfaces is 3% or less of the plate thickness of the flat glass,
The Ra value of the surface roughness of the first side surface portion is 0.1 to 10 nm, the Rmax value is 0.1 to 30 nm, the Ra value of the surface roughness of the second side surface portion is 0.01 to 5 nm, Rmax. The value is 0.01 to 20 nm, a cover glass for a solid-state imaging device. 2. The cover glass for a solid-state imaging device according to claim 1, wherein the linear internal transmittance of visible light having a wavelength of 500 nm and the linear internal transmittance of visible light having a wavelength of 600 nm are each 95% or more. SiO ₂ 50-70%, Al ₂ O ₃ 0.5-20%, B ₂ O ₃ 5-20% RO 0.1-30% (RO = MgO + CaO + ZnO + SrO + BaO), ZnO 0-9%, MO The cover glass for a solid-state imaging device according to claim 1, comprising 1 to 20% (MO = Li ₂ O + Na ₂ O + K ₂ O). Containing _{SiO 2 50~70%, Al 2 O} 3 0.5~20%, B 2 O 3 5~20% RO 0.1~30% (RO = MgO + CaO + ZnO + SrO + BaO), the 0 to 9% ZnO represented by mass% The cover glass for a solid-state imaging device according to any one of claims 1 to 3 , wherein the cover glass does not substantially contain an alkali metal oxide. According to the standard of JIS-R3502, the alkali elution amount is 0.1 mg or less, the density is 2.8 g / cm ³ or less, the specific Young's modulus is 27 GPa / g · cm ⁻³ or more, and the Vickers hardness is 500 kg / mm ² or more. a solid-state imaging device cover glasses according to any one of claims 1, wherein the 4.