JP2003188450A - Cover glass for optical semiconductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cover glass for optical semiconductor which allows the sufficient transmission of a semiconductor laser beam of wider wavelength up to a near infrared beam from a short wavelength such as blue and does not deteriorates a material such as coloration or the like. <P>SOLUTION: The cover glass for optical semiconductor is composed of a multiple element system oxide glass substantially not including alkali metal oxide. The content of Fe<SP>3+</SP>is 0.03 mass% or less with a conversion value of Fe<SB>2</SB>O<SB>3</SB>, a wavelength is 320 nm in a thickness of 0.3 mm or less and the light transmitting coefficient of wavelength 400 nm is 70% or more but 90% or less. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cover glass for an optical semiconductor used in a package containing an optical semiconductor.

[0002]

2. Description of the Related Art In general, a cover glass used for an optical semiconductor, for example, a light emitting element such as a semiconductor laser or a light receiving element such as a photodiode, transmits a large-capacity optical signal at a predetermined error rate or less or an SN ratio or less. High light transmission characteristics are required for high-speed passage. In recent years, in optical semiconductor devices such as DVD (digital versatile disc) devices, there has been a demand for a high-density technique capable of processing large-capacity data such as video signals at high speed. In such an optical semiconductor device, as shown in FIG. 1, a semiconductor laser 3 is located in a metal cap 2 of a light emitting device 1, and the metal cap 2 is made of a metal such as Kovar and has a light transmitting hole 2a. A cover glass 4 that allows light to pass therethrough is fixed via a sealing material 5. As the cover glass 4 used in this way, a commonly used borosilicate glass or the like is used.

Further, the oscillation wavelength of the semiconductor laser 3 used for reading and writing an optical disc for recording a large amount of information at a high density has shifted to a short wavelength. Specifically, D which has been put to practical use as an optical disc system
In VD, a red semiconductor laser having a wavelength of 650 nm is currently used, but in the next-generation DVD, an optical semiconductor device using a blue-violet semiconductor laser having a wavelength of 350 to 460 nm is put to practical use in order to further increase the capacity. Is being done. When such a blue-violet semiconductor laser is used, it is possible to read and write four times as much data as in the case where a red semiconductor laser is used for an optical disk having the same area.

[0004]

However, as the oscillation wavelength becomes shorter, the cover glass 4 made of the conventional borosilicate glass has a problem that the light transmittance for light having a short wavelength of 300 to 400 nm is low. Has occurred. Further, since such a short-wavelength laser has high energy, there is a problem of material deterioration in that the glass is colored and the light transmittance is lowered with the passage of time.

On the other hand, since metal, ceramics and resin are used as a package for accommodating an optical semiconductor,
The cover glass for optical semiconductors is desired to have a smaller coefficient of thermal expansion than that of the package so that compressive strain may be applied to the glass side from the viewpoint of strength.

Further, if the surface of such a cover glass is eroded and deteriorated during long-term use and loses transparency, it impedes the transmission of light and impairs the characteristics of the optical semiconductor. Therefore, these cover glasses are required to have excellent weather resistance. When an alkali metal oxide component is contained in the glass, these components may elute on the glass surface, or the elution component may crystallize, causing deterioration of the glass surface called so-called bluish or white burnt. . If such deterioration of the glass occurs, the transmittance of the glass decreases, which is not preferable as a cover glass for an optical semiconductor. Therefore, it is preferable that the glass contains as little alkali oxide component as possible.

Further, a cover glass for an optical semiconductor may be subjected to chemical treatment such as plating after being sealed in a package, and if the cover glass is eroded by the chemical treatment and loses its light transmitting property, the optical semiconductor is removed. It becomes a problem as a device. Therefore, the acid resistance to concentrated sulfuric acid used in the plating solution and the like becomes important, and the chemical resistance of the glass to various cleaning solutions such as alkaline solutions used in the process of manufacturing and using these glasses becomes important.

An object of the present invention is to provide a cover glass for optical semiconductors which realizes a highly reliable package for optical semiconductors, which is capable of sufficiently transmitting a semiconductor laser light having a short wavelength such as blue color and which is free from material deterioration such as coloring. Is to provide.

[0009]

The cover glass for optical semiconductors of the present invention comprises a multi-component oxide glass which is substantially free of alkali metal oxides and has a Fe ³⁺ content of Fe.
₂ O ₃ conversion value is 0.03 mass% or less, and the thickness is 0.3
The light transmittance at wavelengths of 320 nm and 400 nm at 70 mm or less is 70% or more and 90% or more, respectively.

The cover glass for optical semiconductors of the present invention has a total Fe content of 0.03 mass% or less in terms of Fe ₂ O ₃ and a thickness of 0.5 mm or less and wavelengths of 320 nm and 400 nm. Light transmittance of 70% or more, 90
% Or more.

The cover glass for optical semiconductors of the present invention has a coefficient of thermal expansion of 2 in the temperature range of 30 to 380 ° C.
It is characterized in that it is 0 to 50 × 10 ⁻⁷ / K.

The cover glass for optical semiconductors of the present invention has a mass% of SiO _{2 of} 50 to 70% and an Al ₂ O ₃ 9 content.
_{~25%, B 2 O 3 3~25} %, 0~5% MgO, C
aO 0-12%, BaO 0-15%, SrO 0-1
2%, ZnO 0-5%, ZrO ₂ 0-5%, TiO ₂
It is characterized by having a glass composition of 0 to 2% and P ₂ O ₅ 0 to 5%.

Furthermore, the cover glass for optical semiconductors of the present invention is characterized in that the optical semiconductor emits or receives light having a wavelength of 300 to 460 nm.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Since the cover glass for optical semiconductors of the present invention has a light transmittance of 70% or more at a wavelength of 320 nm and a light transmittance of 90% or more at a wavelength of 400 nm, it has the highest transmittance in the ultraviolet region. It is important to suppress Fe ³⁺ , which is a component that lowers the Fe content, to 0.03 mass% or less in terms of Fe ₂ O ₃ .

Further, the factor that determines the ultraviolet transmittance of glass is not simply determined by the Fe ³⁺ (Fe ₂ O ₃ ) content. The alkali metal oxide in the glass exists as a modified oxide in the glass and cuts the bonds of oxygen forming a network in the glass to be bonded to the oxygen, forming so-called non-crosslinked oxygen. Since the presence of such non-crosslinked oxygen has a function of lowering the ultraviolet transmittance of glass, it is desirable that such an element is not included as much as possible.

In the non-alkali glass made of a multi-component oxide glass as in the present invention, an alkaline earth metal oxide is contained instead of an alkali metal oxide, and Al ₂ O ₃ and B are added. _{By including 2} O ₃ in an appropriate amount in a coexisting manner, properties required for product performance such as environment resistance, chemical resistance, heat resistance, and thermal expansion coefficient, and devitrification resistance, meltability, etc. The properties required for substrate glass production can be adjusted to desired values. Further, the coexistence of Al ₂ O ₃ and B ₂ O ₃ also has the effect of increasing the transmittance of the alkali-free glass in the ultraviolet region, so that it is desirable to essentially contain these components.

The coloring of glass by ultraviolet rays (ultraviolet ray solarization) depends largely on the content of Fe ³⁺ ions. Fe in glass coexists in two proportions, Fe ²⁺ and Fe ³⁺ , but when Fe ²⁺ in glass causes a valence change to Fe ³⁺ due to the influence of ultraviolet rays, Is colored. Therefore, in order to prevent the coloring of the glass by ultraviolet rays, it is necessary to regulate not only Fe ³⁺ but also the total Fe content. Since the ratio of Fe ²⁺ and Fe ³⁺ of ordinary glass in certain percentage of the content of Fe ³⁺ Fe ₂
By controlling the content of O ₃ to 0.03% by mass or less, the total Fe content can be suppressed to such an amount that coloring does not occur, but the total Fe content is 0.03% by mass or less in terms of Fe ₂ O _3. It is more desirable to keep Further, the alkali component in the glass forms a coloring center by irradiation with ultraviolet rays, and thus causes ultraviolet solarization. Since the ultraviolet solarization can be suppressed by not containing the alkali metal oxide, non-alkali glass is desirable for the glass of the present invention.

The package for accommodating the optical semiconductor is made of metal such as Kovar (coefficient of thermal expansion: 45 to 55 × 10 ^-7 /
K), 42 iron nickel alloy (65 × 10 ^-7 / K), etc., and alumina (about 80 × 10 ^-7 / K), etc. are used as ceramics. Glass smaller than the coefficient is used.

Further, since the optical semiconductor device can record with high precision and high density by using a short wavelength,
Optical defects in the cover glass become fatal defects, bubbles,
There is a demand for highly homogenous glass with almost no scratches or striae.

In order to melt and mold such glass, it is necessary that the glass has high meltability and excellent devitrification resistance.

Further, if the smoothness of the glass surface is impaired,
Since the light transmittance of the glass decreases, the surface of the cover glass must be smooth and transparent like an optically polished surface. Such glass can be obtained by cutting from a block-shaped glass and polishing, but the cost is very high, and there is an unavoidable possibility that dirt such as an abrasive will adhere to the glass surface. Therefore, these cover glasses are as they are drawn on the glass substrate from the glass melting furnace,
It is most desirable in terms of cost and surface quality that a so-called as-drawn surface can be obtained so that a smooth surface can be obtained without polishing. As a molding method for obtaining a smooth surface required for the cover glass of the present invention, for example, a downdraw method or a float method can be considered. It is possible to obtain a particularly smooth surface at a thin plate thickness of 0.3 mm.
Downdraw methods such as the overflow method. For example, in the overflow method, the glass is slowly cooled to a relatively low molding temperature range of 1200 ° C. or less, and thus devitrifying foreign matter is likely to occur on the substrate. Therefore, the devitrification resistance of glass is a very important property. Further, in the float method and other downdraw methods, the devitrification resistance of glass is very important, though not so much as the overflow method.

The reason why the composition of the cover glass for optical semiconductors of the present invention is limited as described above will be described below.

First, SiO ₂ is a main component of glass and has an effect of improving weather resistance and chemical resistance. If its content is less than 50% by mass, its effect is small.
If it exceeds 70%, it becomes difficult to melt the glass and the devitrification resistance deteriorates.

Al ₂ O ₃ coexists with B ₂ O ₃ to suppress the absorption of ultraviolet rays. Further, it has an effect of improving the weather resistance and chemical resistance of glass, but if the content is less than 9% by mass, the effect is small. On the other hand, if the content exceeds 25% by mass, the meltability and devitrification resistance of the glass deteriorate.
A more preferable range of Al ₂ O ₃ is 10 to 20% by mass, and a most preferable range is 10 to 18% by mass.

B ₂ O ₃ lowers the viscosity of the glass and improves the meltability. Since the alkali-free glass as in the present invention does not contain an alkali component that enhances the meltability of the glass, it is necessary to add a component such as B ₂ O ₃ as a flux to improve the meltability. When the meltability of the glass becomes high, the homogeneity of the glass material to be produced becomes high, and a preferable glass having less striae can be obtained. Also,
Since B ₂ O ₃ acts as a network-forming oxide that constitutes the glass structure, it also has the function of improving the devitrification property of the glass, particularly in the composition system of the present invention. If the B ₂ O ₃ content is less than 3% by mass, the above effect is small, while if it exceeds 25% by mass, the chemical resistance and weather resistance of the glass are significantly deteriorated and the glass tends to undergo phase separation. Not preferable. Further, the amount of volatilization at the time of melting increases, and it becomes difficult to obtain a homogeneous glass. The more preferable range of B ₂ O ₃ is 3 to 20% by mass, and the most preferable range is 5 to 15% by mass.

MgO has the function of lowering the viscosity at high temperature and improving the meltability of glass, but if its content exceeds 5%, the liquidus temperature rises.

CaO has the function of lowering the viscosity at high temperature and improving the meltability of glass, but if its content exceeds 12%, the weather resistance of the glass decreases and the coefficient of thermal expansion becomes too high.

BaO and SrO are both components that improve the devitrification resistance and chemical resistance of the glass, but when contained in large amounts, the thermal expansion coefficient of the glass increases, so each content is 15% by mass. It is desirable to control the content to be not more than 12 mass%.

ZnO has the effect of lowering the viscosity without changing the coefficient of thermal expansion, but if its content is more than 5% by mass, the weather resistance of the glass decreases and the devitrification resistance deteriorates.

ZrO ₂ is a component that improves the chemical resistance, particularly acid resistance, of the glass and lowers the viscosity at high temperature to improve the meltability, but when it is more than 5% by mass, the devitrification of zircon or zirconia is caused. It tends to occur.

TiO ₂ improves chemical resistance, particularly acid resistance, and also lowers high temperature viscosity and meltability, but if it is more than 2% by mass, ultraviolet transmittance decreases.

P ₂ O ₅ has a function of improving the devitrification resistance of the glass in the composition system of the present invention, but its content is 5
When the content exceeds 100% by mass, the glass tends to undergo phase separation,
Acid resistance is significantly deteriorated.

In the present invention, in addition to the above components, As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , chloride, Clarifying agents such as fluorides and sulfates and melting accelerators can be included. In addition, Y ₂ O ₃ and La
Components such as ₂ O ₃ and Nb ₂ O ₅ can be contained in small amounts. By adding these components little by little, the devitrification resistance of the glass may be further enhanced. Further, since a reducing agent such as Al or Si has a function of changing Fe ³⁺ in the glass of the present invention to Fe ²⁺ , it is possible to enhance the ultraviolet transmittance and, if necessary, can be appropriately contained. is there. However, the use of the reducing agent component affects the clarity of the glass, and the foam quality of the product may be deteriorated.

The glass having the above composition has a thickness of 0.
Since the light transmittances at wavelengths 320 and 400 nm at 3 mm are 70% or more and 90% or more, respectively,
It is suitable for use as a cover glass for a short-wavelength semiconductor laser such as blue that emits and receives light of 460 nm.

[0035]

EXAMPLES The cover glass for an optical semiconductor of the present invention will be described in detail below based on examples.

Table 1 shows cover glasses for optical semiconductors (hereinafter referred to as cover glasses) of Examples (Sample Nos. 1 to 11).
Table 2 shows the cover glasses of Comparative Examples (Sample Nos. 12 to 17).

[0037]

[Table 1]

[0038]

[Table 2]

The cover glass in the table was prepared as follows.

First, a batch prepared by mixing glass raw materials so as to have the composition shown in the table was put in a platinum crucible and placed in an electric furnace at 1580.
After melting at ℃ for 24 hours, it was cast on a carbon plate to form a plate, and then strained in a slow cooling furnace. The density, thermal expansion coefficient, viscosity, sulfuric acid (H ₂ SO ₄ ) resistance, liquidus temperature, wavelength 320 nm, 400
The light transmittances in nm, 550 nm and 700 nm were measured and shown in the table. In addition, the UV solarization resistance was evaluated in the same manner and is shown in the table.

From Table 1, Sample No. which is the cover glass of the example. 1 to 11 have a thermal expansion coefficient of 32 to 45 × 10 ⁻⁷
/ K shows a suitable value, and the light transmittance is 7 at a wavelength of 320 nm.
5 to 90%, 90 to 92% at a wavelength of 400 nm, 550n
The transmittances at m and 700 nm were also excellent at 91 to 92%. In addition, Example No. The samples Nos. 1 to 11 had good resistance to UV solarization of 1% or less.
Also, its liquidus temperature is as low as 1103 ° C or lower, 10 ^2.5 d
The Pa · s temperature is also 1610 ° C. or lower, which is sufficient meltability,
Combines moldability. Also, the erosion amount of sulfuric acid resistance is 0.
It was excellent at less than 1 mg / cm ² .

Sample No. A cover glass having a thickness of 0.5 mm was prepared using the glasses 3 and 7 and the light transmittances at wavelengths of 320 nm and 400 nm were measured. Light transmittance is 89-90% at wavelength 320nm, wavelength 4
It was excellent at 91 to 92% at 00 nm.

On the other hand, the cover glass of the comparative example 12,
In No. 13, the Fe ₂ O ₃ content was high, the light transmittance at 320 nm was low at 65% and 59%, and the light transmittance at 400 nm was low at 85% and 83%. In addition, the UV solarization resistance was a bad result of 3.2% and 4%. Further, Comparative Example 13 has a coefficient of thermal expansion of 65 ×
It was as high as 10 ^-7 / K. Comparative Example 14 was poor in UV solarization resistance, and Comparative Example 15 was 320 nm.
The transmittance at 400 nm was low and the sulfuric acid resistance was poor. Comparative Example 16 had a high liquidus temperature and a high temperature of 10 ^2.5 dPa · s, was inferior in meltability and moldability, and was also inferior in ultraviolet solarization resistance. Comparative Example 17 was inferior in sulfuric acid resistance.

The densities in the table were measured by the well-known Archimedes method.

As for the thermal expansion coefficient, the average thermal expansion coefficient in the temperature range of 30 to 380 ° C. was measured using a dilatometer.

The strain point and annealing point are ASTM C336-7.
It measured based on the method of 1. The higher these values,
This means that the heat resistance of glass is high. Also high temperature viscosity
10 ^2.5The temperature of dPa · s is measured by the platinum ball lifting method.
It was High temperature viscosity 10^2.5Temperature equivalent to dPa · s
Indicates the melting temperature, and the lower this temperature is, the melting
It is excellent in sex.

The sulfuric acid resistance was evaluated by the following method. First, each glass was processed into a size of 10 × 50 × 0.3 mm, and both surfaces were optically polished to prepare a sample for evaluation. The sample weight before chemical treatment was precisely measured in advance by an analytical balance, and then immersed in a concentrated sulfuric acid chemical solution prepared to have a concentration of 50% by volume at 80 ° C. for 1 hour. After the chemical treatment, the sample weight is precisely measured again, and the weight difference before and after the treatment (mg)
I asked. This is the surface area of the sample (10.36c
It was divided by m ² ) to obtain the erosion amount (mg / cm ² ).

The liquidus temperature was such that each glass sample was crushed and passed through a standard sieve 30 mesh (500 μm), and the glass powder remaining on 50 mesh (300 μm) was put into a platinum boat.
The temperature at which crystals are precipitated is measured by holding the sample in a temperature gradient furnace for 24 hours.

The light transmittance of each glass is 20 short sides × 3 long sides.
300 × 600 nm with a spectrophotometer, which is processed into a size of 0 × 0.3 mm and mirror-polished on both sides.
Of the wavelengths of 320 nm and 40
The evaluation was performed by the value of light transmittance at 0 nm.

UV solarization resistance was evaluated as follows. First, the light transmittance at a wavelength of 400 nm of a sample obtained by optically polishing the surface of a plate glass having a thickness of 0.3 mm was measured. Further, the sample was irradiated with ultraviolet rays having a main wavelength of 253.7 nm for 60 minutes by a 40 W low-pressure mercury lamp, and then the light transmittance at a wavelength of 400 nm was measured again. By determining the difference between the initial transmittance and the light transmittance after irradiation with ultraviolet rays, the decrease in light transmittance due to ultraviolet rays was determined.
At this time, the lower the UV solarization resistance of the glass, the greater the decrease in the light transmittance. In the cover glass for optical semiconductors, which is an application of the present invention, it is required that the resistance to UV solarization by the above test is almost unchanged to 1% or less.

[0051]

The cover glass for optical semiconductors of the present invention is composed of a multi-component oxide glass substantially containing no alkali metal oxide, and has a Fe ³⁺ content of 0 in terms of Fe ₂ O _3. Since it is 0.03 mass% or less and the light transmittances of wavelengths 320 nm and 400 nm at a thickness of 0.3 mm or less are 70% or more and 90% or more, respectively, semiconductor laser light of a short wavelength such as blue is used. It can be used for a read / write device for large-capacity media such as a generation DVD.

Further, the total Fe content is 0.03 mass% or less in terms of Fe ₂ O _3, and the light transmittances at wavelengths of 320 nm and 400 nm at a thickness of 0.5 mm or less are 70% or more and 90%, respectively. According to the cover glass for an optical semiconductor of the present invention having a content of at least%, the optical transmittance of semiconductor laser light having a short wavelength such as blue is high, and stable input / output of optical signals becomes possible.

The cover glass for optical semiconductors of the present invention has a coefficient of thermal expansion of 2 in the temperature range of 30 to 380.degree.
Since it is 0 to 50 × 10 ⁻⁷ / K, the coefficient of thermal expansion is slightly smaller than that of the package in which Kovar, 42 iron nickel alloy, alumina, etc. are used, and the cover glass after sealing comes to have compressive strain. Therefore, the strength of the cover glass can be kept high, and a highly reliable optical semiconductor package can be realized.

Further, the Fe ³⁺ content is 0.03 mass% or less in terms of Fe ₂ O _3, or the total Fe content is 0.03 mass% or less in terms of Fe ₂ O ₃ , and in mass% , SiO ₂
50-70%, Al ₂ O ₃ 9-25%, B ₂ O _{3 3-}
25%, MgO 0-5%, CaO 0-12%, Ba
O 0-15%, SrO 0-12%, ZnO 0-5
%, ZrO ₂ 0 to 5%, TiO ₂ 0 to 2%, P ₂ O ₅
According to the cover glass for an optical semiconductor having a glass composition of 0 to 5%, the cover glass for an optical semiconductor does not substantially contain an alkali metal oxide component that absorbs ultraviolet rays and causes solarization to color the glass, resulting in a decrease in ultraviolet transmittance, and Impurity Fe that causes a decrease in light transmittance due to ultraviolet solarization
₂ O ₃ is suppressed to 0.03 mass% (300 ppm) or less,
The light transmittance of 320 nm is 70% or more and 40 respectively.
Since the light transmittance from 0 nm to 700 nm is 90% or more, and the high light transmittance over almost the entire range of the semiconductor laser light from the near-ultraviolet region to the visible region or the near-infrared region, the conventional semiconductor laser light can be used for the next generation. It can transmit even short wavelength semiconductor laser light such as blue, which is used for reading and writing large capacity media such as DVD, and has no deterioration of material such as UV coloring, and the light transmittance is stable for a long time. Suitable as a next-generation optical semiconductor cover glass.

The cover glass for optical semiconductors of the present invention is suitable as a short-wavelength optical semiconductor cover glass because the optical semiconductor emits or receives light having a wavelength of 300 to 460 nm, and has a large capacity for next-generation DVDs and the like. It is possible to produce a highly reliable optical semiconductor component corresponding to a medium, and it has an excellent effect in practical use.

[Brief description of drawings]

FIG. 1 is a sectional view of a metal cap for a semiconductor laser using a cover glass for an optical semiconductor.

[Explanation of symbols]

1 Light emitting device 2 metal caps 2a Translucent hole 3 Semiconductor laser 4 cover glass 5 Sealing material

Claims (5)

[Claims] 1. A multi-component oxide glass that is substantially free of alkali metal oxides and has a Fe ³⁺ content of F.
e ₂ O ₃ is 0.03 mass% or less in terms of value, thickness 0.
A cover glass for optical semiconductors, which has a light transmittance of 70% or more and 90% or more at wavelengths of 320 nm and 400 nm at 3 mm or less, respectively. 2. The total Fe content is 0.0 in terms of Fe ₂ O _3.
3% by mass or less and a wavelength of 3 at a thickness of 0.5 mm or less
70% light transmission at 20 nm and 400 nm respectively
It is 90% or more above, The cover glass for optical semiconductors of Claim 1. 3. The cover glass for an optical semiconductor according to claim 1, which has a coefficient of thermal expansion of 20 to 50 × 10 ⁻⁷ / K in a temperature range of 30 to 380 ° C. 4. SiO ₂ 50-70% by weight, A
_{l 2 O 3 9~25%, B} 2 O 3 3~25%, MgO 0
~ 5%, CaO 0-12%, BaO 0-15%, S
rO 0-12%, ZnO 0-5%, ZrO ₂ 0-
_{5%, TiO 2 0~2%,} P 2 O 5 0~5% of the optical semiconductor cover glass according to any one of claims 1 to 3, characterized by having a glass composition. 5. The cover glass for an optical semiconductor according to claim 1, wherein the optical semiconductor emits or receives light having a wavelength of 300 to 460 nm.