JPS59178736A - Bonded unit of semiconductor body and method of bonding same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the bonding of 1' conductor bodies to thermally conductive substrates, and in particular, but not exclusively, applications in the attachment of lasers to P1-sinks. isn't it.

The method traditionally used to attach lasers to heat sinks has been to use molded pellets of gold-tin eutectic solder. One of the problems with this joining method is that the resolidified solder tends to form raised edges around it. The formation of this edge is believed to be due to a localized increase in the melting point due to changes in the solder composition due to diffusion of gold from the bonded components into the solder. This edge is undesirable because it can be so high that it interferes with the light emitted by the Rayleigh. The second problem is related to the fact that small bubbles are observed in the resolidified solder.

This is thought to be due to the gas content, but if the laser is in a high current density area, it will cause localized high temperature spots that will shorten the life of the laser. A third problem is that the tie floats on the solder, making the exact final height relative to the laser heat sink difficult to control, especially in relation to the edge obstruction problem mentioned above. Zuru.

The object of the invention particularly relates to a joining method that does not use solder moldings.

According to the invention, the surface of the semiconductor body is coated with a diffusion barrier layer coated with a layer of gold, the surface of the substrate is coated with a layer of gold, and one or both of said gold layers are coated with a layer of gold. An alloy with a melting point of 1 degree Celsius is a metal that is a total eutectic, or an alloy that is a metal that forms a total eutectic, and is protected from oxidation by a protective coating of gold if it consists of a metal that forms a total eutectic and is oxidized. A continuous molten metal fitting is coated with a diffusion layer less than 1 micron thick, which completely diffuses into the gold of the gold layer without passing through the layer, covering the bonding area. 2 while the assembly is heated to a temperature at which a melt layer is formed.
The two coated surfaces are brought into abutment d3, providing a method for forming a diffusion metallic bond between the surface of the semiconductor body and the surface of the thermally and electrically conductive substrate.

Bonding of the cliff conductor to the substrate according to a preferred embodiment of the method of the present invention will be described below.

A semiconductor chip 1 such as a GaAeAs or (GaInAsP) laser is connected to a substrate 2 made of silicon, germanium, etc., which has an electrical connection to the laser and a metal coating to dissipate the heat of the laser. It is necessary to join.

The surface of the sheet 1 chip to be bonded to the substrate is coated with a gold vapor deposited layer 3.
Before this, a suitable diffusion barrier layer 4 such as palladium or platinum is applied to prevent the gold from diffusing into the laser beam. (1) Slightly thicker than this, typically about 2 microns, to be deep enough to allow the gold layer to diffuse through without shearing during the subsequent bonding process.

A vapor-deposited tin layer 5 having a thickness of 1 micron or less covers the gold layer 3.
There is. Typically this is about 0.2 microns thick, but since tin is a metal that easily oxidizes, the exposed surfaces of this layer are protected from oxidation by a protective layer 6 of gold. This protective layer is typically 0.02 microns thick.

The substrate 2 is also covered with a vapor-deposited gold layer 7 of similar thickness to layer 3, which has the same function of being able to diffuse through the gold layer of layer 5 during the bonding process. Because there is. A gold layer 7 is placed on a non-metallic sacrifice board 1 such as diamond.
It is typically necessary to provide a metallization to improve the bond between the two. To this end, the diamond substrate is coated with a layer of titanium (not shown) to improve bonding, and this layer is then coated with another layer of platinum (not shown) to prevent continued diffusion of titanium into the gold and platinum. You can do it. Obviously, since no solder is used, the substrate surface does not have to be very flat, which flatness is more easily achieved with diamond between the studs.

Tin suffers from persistent damage from rake or internal diffusion effects (200°C), which is considerably lower than the humidity of about 400°C, where tin suffers from permanent damage from rake or internal diffusion effects.
83° C. is one of the preferred materials for the diffusion layer 5 because it forms a melt at a relatively low temperature with gold at 83°C.
．． It is lightly locked in an appropriate position by a needle tip that applies a force of 2N. Assembly typically takes a few minutes or more (approximately 30
It is heated to 0'C, held at this temperature typically for no more than 30 seconds, and then allowed to naturally cool to room temperature, typically for 5 to 10 minutes. This heating method causes the tin layer 5 to react with some of the gold of layers 3 and 7 to form a continuous molten eutectic layer covering the bonding area. This molten layer consists of layers 3 and 7.
The barrier layer 4 on the substrate 2 is completely diffused without being absorbed.

Several tests of joints made by this method showed that the density of defects was significantly reduced, the joints were highly reliable, and the shapes were more accurate than those made by the solder molding method described above. I wanted to be controlled. Furthermore, since the junction thickness Δ is small and the defect density is low, the thermal impedance is small.

It is easy to incorporate the diffusion layer 5 into the substrate instead of the rake chip and to attach the thin diffusion layer to the pixel element. It is also easy to mix some gold with tin to reduce or eliminate the need for tin.

An example of a metal used in the diffusion layer 5 instead of tin is germanium. Germanium is gold and tin gold J”O1
i product J: A high temperature eutectic is formed, but its temperature +ff is GaAP, AS and (Ga I n As P) (1
) is not too expensive to be used in chip bonding, and the simpler phase diagram of this eutectic may favor the trade of the finished bond.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the depth and substrate assembly before bonding at I8, and FIG. 2 is a cross-sectional view of In1 after bonding. DESCRIPTION OF SYMBOLS 1... Semiconductor depth, 2... Substrate, 3... Gold layer, 4... Diffusion barrier layer, 5... ([Mum diffusion layer, O...
Protective layer, 7... gold layer. Patent Applicant Standard Telephones and Cables Public Page 1 Continued 0 Inventor Arthur Walker 36 Crownhill Rise, Toukuniy, Devon, United Kingdom

Claims (1)

[Claims] (1) The surface of the semiconductor substrate is covered with a diffusion layer V, which is coated with a layer of gold, and the surface of the substrate is covered with a layer of gold, and one of the gold layers or Both are made of an alloy that is a metal-gold eutectic or a metal that forms a metal-gold eutectic with a melting point at a temperature at which the semiconductor body can melt, and in the case of an oxidized metal, a protective coating of gold. The gold layer is covered with a diffusion layer less than 1 micrometer thick, which is protected from oxidation by the gold layer, and it completely diffuses into the interior of the gold layer without passing through the layer, covering the bonding area continuously. The two coated surfaces are brought into contact while the assembly is heated to a temperature at which a total eutectic 4 is formed, forming a thermally and electrically conductive contact with the surface of the semiconductor body. A junction body of a semiconductor body that is J-junctioned to the surface of a substrate. (2) The joined body according to claim 1, wherein the diffusion layer is made of soot or contains tin as a component. (■ The bonded body according to claim 1, characterized in that the diffusion layer is made of germanium or contains germanium as a component. (4) The joined body according to claim 1, characterized in that the diffusion layer is made of germanium or contains germanium as a component. A bonded body according to any one of claims 2 and 3 on page 1j. (5) Claims 1, 2, and 3, characterized in that the semiconductor body is a rake. (6) The semiconductor body (made of GaAR-AS) of Claim 8'F. Section 3,
The zygote according to any one of No. 11 Jj'4 and No. 5. (7) The semiconductor body is characterized in that it consists of (Gii In ASP). The conjugate according to any one of Items 3, 4) and 5. (8) The surface of the semiconductor body is coated with a diffusion barrier layer coated with a layer of gold, the surface of the substrate is coated with a layer of gold, and one or both of the capillary layers has a melting point that exceeds the temperature that the semiconductor body can withstand. Metals to be mixed - Alloys that are all eutectic or the metals -
If it is made entirely of eutectic-forming metals and consists of oxidized metal, it is covered by an expanded layer of less than 1 micron thick, which is protected from oxidation by a protective coating of gold.
The two coatings are heated while the assembly is heated to a temperature at which a continuous molten metal-metal layer is formed that completely diffuses into the metal of the down payment layer without penetrating the layer and covers the Sakuradai region vi. The surface of the semiconductor body is brought into abutment by a method of bonding the semiconductor body by means of a diffusion metal bond between the surface of the semiconductor body and the surface of the thermally and electrically conductive substrate. (9) The bonding method according to claim 8, wherein the diffusion layer is made of tin or contains tin as a component. (10) The bonding method according to claim m1, wherein the diffusion layer is made of germanium or contains germanium as a component. (11) The bonding method according to claim 8, page 91, or claim 10, wherein the diffusion layer is made of an elemental metal. (12) The semiconductor body is a laser. Items 8, 9, and 10 of the Claims 1. The bonding method according to any one of Item 11. (13) The semiconductor body is made of GaAeAs. Claims 8, 91, negative, 10, 11, and 12 are the bonding method according to claim 1. (14) The semiconductor body has (Gal++ΔSP>) Claim 83 r(H,
l', 9 ]L The joining method according to item 1, each of item 10, item 11, and item 12.