JPS5945618B2 - Glass composition for coating and method of using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glass composition for coating semiconductors, and more particularly to a glass composition suitable for coating electronic components such as semiconductor devices, and a method for using the same.

Generally, in the manufacture of various electronic components such as diodes, resistors, and capacitors, glass coating materials are often used for the purpose of surface protection or passivation, or for hermetic sealing. has been done.

For example, in manufacturing a semiconductor device having a pn junction, coating the pn junction surface with a glass film is an effective method for stabilizing the device characteristics and increasing reliability.
It is widely used. Usually, the glass composition for coating is adhered to the surface to be coated in a powder state, and is fixed to the surface to be coated by being fired in an oxidizing atmosphere.
In this case, an oxidizing atmosphere is used because the absence of oxygen causes a phenomenon in which the electrical characteristics of the object to be coated are deteriorated. For example, the characteristics of glass-coated semiconductor devices vary significantly depending on the presence or absence of oxygen in the glass firing atmosphere. In fact, when glass is fired in an oxygen-free atmosphere, the leakage current of the element increases and the withstand voltage decreases (for example, from 800V to 500V). However, when the glass firing process is performed in such an oxidizing atmosphere, the electrode members and other oxidizable parts are undesirably oxidized, which makes it difficult to solder them smoothly in the subsequent soldering process. First, another problem arises in that the product yield is reduced.

Therefore, an object of the present invention is to solve these problems and provide a novel coating glass composition that can be fired in a non-oxidizing atmosphere.

Another object of the present invention is to provide a method for coating various electronic components, particularly semiconductor devices, with glass at a high yield without undesirably oxidizing electrode members and the like.

According to one feature of the invention, an oxide capable of releasing oxygen during glass firing, preferably at a temperature just before the start of melting of the glass, is incorporated into the glass composition as a minor component.

Since such coating glass compositions release oxygen during firing in the coating process, it is possible to use a non-oxidizing atmosphere as the firing atmosphere, and the property deterioration of the coated object due to the use of a non-oxidizing atmosphere can be avoided. be avoidable. The proportion of the oxide to be mixed is preferably about 0.1 to 30% by weight.

If the proportion of the oxide added exceeds 30% by weight, the fluidity of the glass deteriorates, causing a practical problem. Also, the amount added is 0
．． If it is less than 1% by weight, the oxygen release effect will be small and the degree of increase in leakage current will be considerably large. Examples of oxides that release oxygen include the following: In addition,
The temperature in parentheses below indicates the temperature at which oxygen release occurs. As a result, dirt and other organic substances in the glass are decomposed and disappear into gas.

In addition, when a silicon semiconductor substrate is coated by a sintering operation of the glass composition according to the present invention, oxygen released during sintering oxidizes the silicon surface or is adsorbed to the silicon surface, and the wettability of the glass to the silicon surface increases. can be made good. In this case, the effect of reducing traps caused by oxygen deficiency at the silicon-glass interface can also be obtained. The invention will now be described in detail with reference to embodiments shown in the accompanying drawings.

FIGS. 1a to 1c show each process of an embodiment in which the present invention is applied to manufacturing a glass-sealed diode.

First, as shown in a, a number of diode chips D selected to obtain a desired withstand voltage, for example 22, were stacked with their polarities aligned, and dummy chips DML and DM2 were fixed to both ends of the diode chips D, respectively. A diode chip stack 10 is prepared.

Each diode chip D is made by diffusing phosphorus from one side of an n-type silicon wafer and boron from the other side, and then pelletizing the wafer.
-np structure silicon chip, and each dummy chip is made of a silicon chip highly doped with impurities and exhibiting low resistance. The laminate 10 is created by depositing brazing material layers 14, 14a, 14b such as A1 on both sides of each wafer from which these silicon chips are obtained, and then stacking a predetermined number of these layers and heat-treating the wafers. This can be done by fixing the wafers together and then cutting the wafer stack into predetermined sizes. Note that a known etching process may be applied to remove the strained layer caused by cutting at this time and to clean the surface. Next, as shown in b, slag leads 12a and 12b, each consisting of a molybdenum slug S and a copper lead L welded to it, are placed coaxially opposite each other, and the laminate 10 is fixed between them.

This fixing process is performed by applying appropriate heat treatment to the end brazing material layer 14.
This is easily accomplished by melting a and 14b and then solidifying them. Furthermore, as shown in C, a diode chip stack 10 and a slug lead 12 sandwiching it
A glass sealing body 16 that surrounds and airtightly seals the slug portions a and 12b is formed according to the present invention.

The glass composition used in this example contains ZnO=63%, B
It has a composition of 2O3 = 21%, SiO2 = 10%, PbO -5%, and SnO2 = 1%, and contains 95% crystalline glass with a softening point of 630°C, and 5% PrO2 as an oxide. . When the structure shown in FIG. 1b rotates around the axis of its leads, a slurry made by adding water to the glass powder having such a composition is used to form a slurry, and when the structure shown in FIG. The coating is applied by winding it around the surface, then dried and fired at about 700° C. in nitrogen gas. In this firing process, the glass is melted and wetly attached to the element structure in the shape shown in FIG. 1C, and then cooled and solidified. The reverse characteristics of the diode manufactured through the above process are as shown in curve B in Figure 2, which indicates that the same type of crystalline glass without the addition of oxygen-releasing oxide is placed in an oxidizing atmosphere. It is clear that the leakage current level is low and the withstand voltage is high when compared with the reverse direction characteristic A of the diode obtained when the diode is fired in a diode and coated on the same type of diode structure.

Further, in the diode obtained by the above process of the present invention, no oxidation was observed in the leads or other electrode parts.

The reason why the coating composition according to the present invention was able to achieve the remarkable effect of not causing oxidation phenomena in parts that come into contact with the outside air, such as electrode parts, and having a low leakage current level and a high withstand voltage, is because the coating composition according to the present invention is sintered. This is thought to be due to the fact that glass can be fired in a non-oxidizing atmosphere because it contains components that sometimes release oxygen.

FIG. 3 shows another embodiment of the present invention, in which n+-p
The mesa transistor chip 20 having a -n-n+ structure is made of silicon, for example, and has one surface covered with gold.
A collector electrode 24 made of a nickel layer is formed, and an emitter electrode 24 made of aluminum, for example, is formed on the other surface.
6 and a base electrode 28 are formed.

The emitter and base region surfaces excluding the electrode forming portion are made of Si.
The mesa groove, which is covered with an insulating film 22 such as O2 and which surrounds a predetermined emitter and base region and crosses the base-collector Pn junction, is formed using the glass composition according to the present invention. Layer 30 has been applied. FIG. 4 shows still another embodiment of the present invention, in which a bevel-type thyristor chip 40 with a pn-pn structure made of silicon has an anode electrode 44 made of tungsten on one main surface. In addition, a cathode electrode 46 and a gate electrode 48 made of aluminum are provided on the opposite main surface.
has.

A glacivation layer 50 formed using a glass composition according to the present invention is deposited on the bevel surface where the Pn junction that provides the breakover voltage terminates. Gracivation layers 30, 5 as illustrated in FIGS. 3 and 4
0, ZnO-B2O mixed with an oxygen-releasing oxide is used as described above with reference to FIG.
A method may be used in which a slurry of crystalline glass containing 3-SiO2 as a main component is coated by screen printing or other suitable method, and then dried and fired.

As another method for attaching glass particles or powder to a predetermined portion of the transistor chip 20 or thyristor chip 40 prior to firing, known electrophoresis method or centrifugal sedimentation method can also be used. After adhering the glass powder to the surface to be coated in this way, when performing a firing treatment, the heat treatment can be performed in a non-oxidizing atmosphere, such as a nitrogen atmosphere, as in the previous example. Oxidation of the collector electrode 24, the anode electrode 44, the aluminum electrodes 26, 28, 46, 48, etc. can be avoided, and a decrease in yield in the subsequent soldering process etc. can be prevented. Furthermore, despite the firing process in a non-oxidizing atmosphere, there is hardly any deterioration in collector reverse breakdown voltage (in the case of FIG. 3) or forward voltage blocking characteristics (in the case of FIG. 4). Although the present invention has been described above in detail based on preferred embodiments, it is natural that the present invention is not limited to these. In the above example, mainly ZnO-B2O
Although reference has been made to crystalline glass containing 3-SiO2 as a main component, the present invention can also be applied to other glass compositions such as amorphous glass containing PbO-SiO2-B2O3 as a main component. Further, the coating glass according to the present invention is
Not only can it be used for sealing or passivation of ICs related to various semiconductor devices or combinations thereof other than the above-mentioned types, but it can also be effectively used to cover other electronic components such as resistors, capacitors, and IC boards. It is something. The excellent effects obtained by the present invention are summarized as follows.

(1) Since oxygen is supplied during firing, stable device characteristics are ensured even during firing in a non-oxidizing atmosphere.

(2) Since firing is possible in a non-oxidizing atmosphere, oxidation of electrodes and other metal parts can be prevented.

[Brief explanation of the drawing]

1a-c are cross-sectional views showing the manufacturing process of a glass-sealed diode according to an embodiment of the present invention, and FIG. The graphs shown in comparison with the reverse characteristics of the diode shown in FIG. Explanation of symbols, 10...Semiconductor chip laminate, 1
2a, 12b...Slag lead, 14, 14a
, 14b... Brazing material layer, 16... Glass sealing body, 20... Mesa type transistor chip, 30, 50... Gracivation layer, 40...
...Bevel type thyristor chip.

Claims (1)

[Claims] 1. Tl_2O_3, N
i_2O_3, PrO_2, Mn_2O_3, Bi_2
At least one oxide selected from O_3, Ru_2O_5, Pb_3O_4 on the condition that it releases oxygen in the firing temperature range during semiconductor coating treatment with the glass is mixed in a proportion of 0.1 to 30% by weight. A glass composition for coating semiconductors. 2 Tl_2O_3, N to glass powder for semiconductor coating
i_2O_3, PrO_2, Mn_2O_3, Bi_2
A glass composition in which at least one oxide selected from O_3, Ru_2O_5, Pb_3O_4 is mixed in a proportion of 0.1 to 30% by weight on the condition that it releases oxygen in the firing temperature range during semiconductor coating treatment with the glass. A glass composition for covering a semiconductor, comprising the steps of: depositing powder on the surface of a semiconductor; and melting and fixing the deposited glass powder to the semiconductor surface by firing in a non-oxidizing atmosphere. How to use things. 3. The method according to claim 2, wherein the semiconductor is comprised of a semiconductor element pellet to which a metal electrode is attached prior to the step of applying the glass composition. How to use glass compositions.