JPS59116146A - Glass for adhering silicon semiconductor element - Google Patents

Abstract

PURPOSE:To obtain the titled glass having a coefft. of thermal expansion close to that of silicon and a low glass transition temp. by providing a specified composition consisting of SiO2, B2O3, Al2O3, Na2O, K2O, Li2O, V2O5, CuO, PbO, As2O3 and Sb2O3. CONSTITUTION:This glass has a composition consisting of, by weight, 65-75% SiO2, 15-25% B2O3, 1.0-3.5% Al2O3, 2.0-4.0% Na2O, 0-2% K2O, 0-1% Li2O (Na2O+K2O+Li2O=2.0-5.0%), 0.1-2% V2O5, 0-2% CuO (V2O5+CuO=0.1- 2.5%), 0-5% PbO, 0.2-0.5% As2O3 and 0-0.5% Sb2O3. The glass has 33- 36X10<-7>/ deg.C average coefft. of thermal expansion close to about 34X10<-7>/ deg.C average coefft. of thermal expansion of silicon, and it has <=500 deg.C glass transition temp. and can be adhered to silicon at a temp. below the limit of heat resistance of Al.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to the composition of glass that adheres to semiconductor elements such as silicon pressure sensors.

[Prior art and its problems]

Special measures are required when attaching a semiconductor device pellet, such as a silicon pressure-sensitive device, which is sensitive to residual stress, to a substrate or the like. That is, it is necessary to strictly match the thermal expansion of the base and silicon. However, in order to airtightly attach this element to the object to be measured, a mounting part is required, and metal such as stainless steel, glass, etc. are used for that part. Since these materials usually do not match the thermal characteristics of silicon elements, a silicone beret is provided between the mounting portion and the beret, and a structure as shown in FIG. 1, for example, has been used.

However, this structure has disadvantages such as (1) high material cost and molding cost for the silicon pellet 1, and (2) many bonding steps. A method has been proposed in which a glass 4 that can be thermally matched with the pellet 1 is bonded directly to the pellet 1. The glass material used is hard borosilicate glass, well known under trade names such as Virex, and for bonding, the mirror-polished element and the bonding surface of the glass are pressed together under load, and then heated to a temperature above the transition temperature of the glass. The pressure welding method is used. The pressure welding method is well suited for the purpose of reducing residual stress because there is no intervening adhesive layer of different nature, but the above-mentioned commonly available glass materials have a glass transition temperature of 5.
It is necessary for adhesion to exceed 50'0. This is higher than the melting point of aluminum, which is commonly used as an electrode and wiring material for semiconductor devices, and therefore requires other electrode materials. The reality is that it is extremely difficult to obtain electrode materials suitable for use in semiconductor devices with heat resistance.

[Purpose of the invention]

The purpose of the present invention is to match the thermal expansion with a silicon semiconductor element,
Moreover, it is an object of the present invention to provide a glass particle material that can be pressure-welded at a temperature below the melting point of aluminum.

[Summary of the invention] The glass material according to the present invention has a coefficient of thermal expansion of 33 to 36.
It is required that the glass transition temperature be in the range of X 10 /C and that the glass transition temperature be 500°C or less. The coefficient of thermal expansion of silicon is approximately 34×10′/”C. It has been found that when the coefficient of thermal expansion of glass is within the above range, residual stress in silicon can be ignored.

In addition, pressure bonding between glass and silicon may vary slightly depending on the bonding conditions, but it is usually 50 to 100 "0" below the glass transition temperature.
The upper limit of the above transition temperature is determined because high heat treatment is required and even in that case the heat resistance limit of the aluminum electrode (600'0 or less) is not exceeded.

As a result of searching for a composition that could achieve these thermal properties and produce high-quality glass using normal melting methods, 5i026
5-76, B2O31,5-25, Al2O3
1-3.5, Na2O:2-4, K2O0-2
, Li2O0~1, but 2Q for Na20+
+Li2OQ ~5, V2O50,1~2, C
uOO~2 However, V2O5+ Cll00.1~2.5
, PbOO~5 + AS2030~0.5, 5b
It was found that a range of 2020 to 2005 by weight was appropriate. This glass belongs to the range of so-called alkali borosilicate glasses, and the relationship between the basic composition of this glass and its glass transition temperature and coefficient of thermal expansion is known. Also Al 203
The relationship between additives such as and these thermal properties and chemical properties is also known. However, even if glass compositions were carefully examined based on these known facts in order to satisfy the above-mentioned thermal property conditions, no material that could be put to practical use could be obtained. The biggest problem was residual foam and decreased chemical durability due to increased high temperature viscosity.

More specifically, according to the above-mentioned known literature, in order to lower the transition temperature while keeping the thermal expansion low in this type of glass, it is necessary to lower the alkali concentration and increase the B2O3 concentration. be. However, even when glass with this composition is melted at 1600"C, which is the practical limit, many residual bubbles remain, and the chemical durability is such that the surface weathers to white after being left in the air for a few days. In order to overcome this problem, we examined the basic composition and additives, and as a result, we obtained the above composition. 5i02 is the basic composition of glass, and below 65wt, the expansion coefficient is low. It deviates from the above range or has poor chemical durability.Moreover, if it exceeds 75wt, the bath melting temperature becomes high and defoaming becomes difficult.O B2O3 is also a basic component of glass,
If it is lower than 25 wt.%, the glass transition temperature cannot be lowered to 500° C. or less, and if it exceeds 25 wt.%, the chemical durability of the glass becomes unsuitable for practical use.

AI 203 is a semi-basic component that improves the chemical durability of glass, but when added in an increased amount, it increases the high temperature viscosity of glass and makes defoaming difficult. The effect becomes clear at 1 wt% or more, but the concentration limit is 3 wt%.

Alkali oxides are also basic components of glass, and although they lower the melting point of glass and improve chemical durability, they have the disadvantage of increasing the coefficient of thermal expansion. The effect varies somewhat depending on the type of alkali. Based on Na2Q, 20 has a small tendency to increase thermal expansion but is poor in low melting ability, and Li2O has a high ability to reduce high temperature viscosity but has a small effect on improving chemical durability.

The total alkali concentration is suitably in the range of 2 to swt%; if it is lower than this, the chemical durability will deteriorate, and if it is higher than this, it will be out of the range of thermal expansion. This glass is characterized by the addition of V2O5 as an essential component that lowers the high-temperature viscosity of the glass and facilitates defoaming. The effect appears above 0.1 wt '4, but when it exceeds 2 wt%, the glass becomes phase split,
Impairs chemical durability. CuO has a similar effect, and V
It can be used as an auxiliary component of 2O5. It is preferable to add PbO as a component to improve the low melting properties and chemical durability of the glass, but if it exceeds 5 wt%, problems such as an increase in the coefficient of thermal expansion will occur. As2O3,5b203 is used as an antifoaming agent and is preferably 0.2-0.5 wt%.

These glasses can be manufactured using conventional glass manufacturing methods. That is, silica sand, boric acid, soda carbonate, aluminum hydroxide, and the corresponding metal oxides are prepared and mixed as raw materials,
It is melted and refined using an electric furnace or gas furnace at a melting temperature of 1600° or less. It can also be easily molded using normal methods.
Can be processed.

Adhesion to the silicon element is performed by the following method.

That is, glass having the above composition range is formed, for example, into a tubular shape, and one end of the tubular shape is polished. A silicone pellet with a mirror-polished adhesive surface was brought into contact with this end, and a load (50g/
rtnl J or higher) to a temperature 50 to 100° C. higher than the transition temperature of the glass, for example in an electric furnace, a strong bond can be obtained.

1 Effects of the Invention The glass according to the present invention has a thermal expansion coefficient well matched to that of silicon, and has a temperature m lower than the heat resistance limit of aluminum.
Since it can be bonded to silicon with l, if used in pressure sensors, etc., it is possible to limit the residual strain of the device and reduce costs.

[Embodiments of the invention]

A crow with the composition shown in Cloth-1 was prepared. Glass raw materials include refined silica sand, boric acid, alumina, sodium nitrate, soda carbonate, potassium carbonate, red lead, lithium carbonate, copper oxide, vanadium pentoxide, etc. The melt weighed approximately 1 kg, and was melted in a platinum crucible at 1500-1600°0 in an oxygen-city gas furnace. The mixture was poured onto a welded stainless steel plate for 6 hours, solidified, and then slowly cooled to produce a glass plate. Table 1 shows the thermal expansion coefficient and transition temperature of the obtained glass. The obtained glass was ground into a cube with 5 mm on each side, and a mirror-finished silicon substrate (n-type 3 (ltx), surface orientation <111>, I$300μ
> was cut into 5 am x 5 mm pieces and placed on the above glass cube, and the temperature was lowered by 5 am below the glass transition temperature under a load of 2 kg.
When heated for 1 hour at a temperature 0°C higher, good adhesion was obtained in all cases. These glasses did not change in quality even after being left indoors for more than a month.

We prepared a pressure resistance sensor that utilizes the piezoresistive effect of silicon. This element has additional electrodes made of aluminum, and the pellet size is 8ml + IX8”
, the diameter of the central diaphragm was 1.5 mm. Clothes-1
Select 6 glasses, outer diameter 61 mm, inner diameter 2 mm, length 301 mm.
An 11 m thick tube was molded. The end face of the glass and the bonding surface of the silicon pellet are mirror polished. The adhesive surface of the silicon pellet was placed on the sharp surface of the glass, a load of 1 kg was placed on the glass, and the glass was heated at 530° 0 for 10 minutes. The published adhesive could be maintained up to a vacuum level of 10 Torr, and no deterioration was observed in the aluminum wiring. In addition, the pressure sensor thus obtained had good initial value fluctuations and linearity of sensitivity, and no difference was observed from conventional products bonded to a silicon substrate with gold-silicon eutectic.

Margin below

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views of a silicon pressure sensor that utilizes the piezoresistive effect. 1: Silicon pellet, 2: Silicon substrate, 3: Metal tube, 4 Niglass tube, 5: 9 body, 6: Lead, 7: Electrode. Agent: Patent attorney Kensuke Chika (and 1 other person)

Claims (1)

[Claims] 5iOz65~75wtqlD, B2O315~25
wt, A1203 1.0-3.5 wt%,
NazO2, 0-4.0%, K2OQ ~2 wt
% +Li 200~1 wt% However, Na2O and 2
The sum of 0 and Li2O is 2.0-5. Owt%, V
2O50,1~2wtZ, Cu00~2wt%
. However, the sum of CuO and V2O5 is 0.1 to 2.5 wt.
%, Pb00~5wt%, As2O30,2~0
．． 5 wt%, 5b2030-0.5 wt 96 composition range, average thermal expansion coefficient 33-36 x 10
``/'O, a glass for bonding silicon semiconductor devices, characterized in that the glass transition temperature is 500°C or less.