JPS58147087A - Heat sink for semiconductor element - Google Patents

Abstract

PURPOSE:To obtain high reliability and simplify the constitution, by using a conductive diamond for a heat sink. CONSTITUTION:A B added single crystal diamond is cut, then Ti and Au are vapor-deposited on the junction part of this diamond between an element, and it is pressed into a stem made of Cu. A laser light emitting element is thermally compression-bonded on the surface of the diamond. One electrode is taken from the stem via the diamond heat sink, and the other electrode is taken from the element via the bonding wire of an Au wire. Thereby, it is unnecessitated to constitute electrodes by performing a metallizing treatment and a plating treatment onto the diamond, and joining the bonding wire thereto. By using a heat sink, a semiconductor laser light emitting element of high reliability and simple constitution can be obtained, utilizing the high thermal conductivity of a diamond.

Description

DETAILED DESCRIPTION OF THE INVENTION It is well known that diamond has the highest hardness and highest thermal conductivity of all existing materials.

With the rapid development of semiconductor devices in recent years, the heat dissipation structure plays an important role, especially in devices that operate at high electric fields and high current densities, so the use of diamond as a heat sink has been considered, and some have already put it into practical use. has been done.

For example, semiconductor lasers for optical communications and diodes for high-output microwave oscillations have high output and high reliability by using diamond, which has the highest thermal conductivity, as a heat sink.

Another advantage of using diamond as a heat sink for semiconductor devices is that it has a coefficient of thermal expansion that is relatively close to that of the semiconductor device. For example, when copper is used as a heat sink, the coefficient of thermal expansion is several times larger than that of a semiconductor element, so there is a problem that thermal distortion is caused to the element due to temperature changes.

Another advantage of diamond as a heat sink is that it has high hardness and high mechanical strength, and when bonding semiconductor devices, it can be done at high pressure (1.5 cm), which prevents it from deforming like copper heat sinks. Nothing happens.

However, diamond is generally an insulator.

When a heat sink is used, at least one electrode is often connected via the heat sink. Figure 1 shows the schematic structure of a semiconductor device that has been put into practical use. Diamond 1 is subjected to = metallization treatment, and then a conductive metal is plated on top of it. → Plated layer → Electrically connected to one lead wire via bond wire. When copper or Si 2 is used as a heat sink, since these materials have conductivity, the heat sink can be directly connected to the element to form an electrode, which simplifies the structure. As shown in FIG. 1, there is no need to perform the metal quiz treatment or the plating treatment, and the conductivity can be maintained by simply embedding the connection with the stem 5 mechanically.

Conventional diamond heat sinks use diamond as an insulator, so as mentioned above, they require metallization and plating with a metal with good electrical conductivity, as well as leads bonded to this, which complicates the manufacturing process. Since there are restrictions on the position from which the leads can be taken out, there is a drawback that the structure of the element becomes complicated.

The present invention improves these drawbacks of conventional diamond heat sinks. The diamonds traditionally used as heat sinks were processed from naturally occurring rough stones. Among naturally occurring diamonds, there are extremely rare diamonds called nb type diamonds which have semiconductor characteristics, but the resistivity of the nb type diamonds currently reported is approximately lθ to 10 4 Ω·flaw. This has a large resistance when directly connected to a semiconductor element to form an electric circuit, and when used in this way, 1OΩ
- It is necessary to have a resistivity of a or less.

Diamonds are Fee Ni, Co, Cry Mn*
Although it is artificially synthesized under ultra-high pressure and high temperature using a metal solvent such as Ta, conductive diamond can be obtained by adding B during synthesis.

As a result of examining the amount of B added, synthesis conditions, etc., the inventor found that lO
We were able to synthesize diamond with a resistivity of Ω·a or less. In addition, commercially available synthetic diamonds are used as abrasive grains, and contain a large amount of solvent metal used in synthesis, and their size is 0.7JI3L in diameter.
Too small to be used as a heat sink below.

The inventors conducted research on industrially synthesizing high-purity, large-sized diamonds, for example, patent application No. 54-141918.
No., 54-158186, 55-2818, 55-
26651 and 55-44429, and obtained prospects for industrialization.

The present invention was first made possible by this large single crystal synthesis technology. Examples will be described below.

1 carat of B-doped single crystal diamond (200
8F) was used. The amount of B in the crystal is determined by SIMS
Approximately 8
00 atoms P, P, m, were. This diamond was cut to produce a plate with a thickness of 0.5 mm.

When the resistivity was measured using the four-probe method, it showed a value of about 1Ω·ke. Cut this further to make the side length 1jLILX11Kl
)! It was made into a board. Ti and Au were vacuum-deposited on the diamond at the junction with the element, and then pressed into a copper stem. Then, an InGaAsP/InP-based laser emitting element was thermocompression bonded to the surface of the diamond. One electrode was taken from the stem through a diamond heat sink, and the other electrode was taken from the device through an Au wire bond wire. Conventionally, electrodes were constructed by further metallizing and plating the diamond and bonding wires to it, but this is no longer necessary.

(1' and 8 in Figure 1 are unnecessary) CW of this semiconductor laser
The upper limit of operating temperature is greatly affected by thermal resistance, but by using the heat sink of the present application, it is possible to take advantage of the high thermal conductivity of diamond and obtain a semiconductor laser light emitting device with high reliability and a simple configuration.60

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the structure of a conventional semiconductor laser for explaining the present invention in detail. 1 is a diamond heat sink, and 17 is a metallurgical loss layer and a conductive metal plating layer for forming an electrode. 2 is a laser emitting element, 8.4 is a bond wire lead, and each is electrically coupled to the lead wire 6.7. 7 is a laser beam.

Claims (1)

[Claims] (1) A heat sink for a semiconductor device, characterized in that the heat sink, which is bonded to a semiconductor device via a conductive metal or an intermetallic compound and which also serves as at least one electrode forming a circuit, is made of conductive diamond. (2. A heat sink for a semiconductor device according to claim (1), wherein the conductive heat sink is a synthetic diamond containing B and having a resistivity of 1OΩ-α or less.'