JPH0724271B2 - Semiconductor device - Google Patents

Description

The present invention relates to a semiconductor wafer, an electrode member in contact with the wafer, an internal buffer member in contact with the electrode member, and a pressure applied to each member. The present invention relates to a semiconductor device having a post that makes contact.

[Conventional technology]

In the semiconductor rectifier or semiconductor controlled rectifier,
A structure in which a cooling body is brought into contact with both sides of a semiconductor wafer having a rectifying action or a switching action and heat generated in the semiconductor wafer is dissipated to conductors or cooling bodies on both sides of the semiconductor wafer is as shown in FIG.

In the figure, 1 is a semiconductor wafer having a plurality of pn junctions, 2
Is provided below the semiconductor wafer 1, and the semiconductor wafer 1
A molybdenum plate or a molybdenum plate is used as a supporting plate having a coefficient of thermal expansion almost equal to that of the supporting plate, and a brazing material 13 made of aluminum is bonded between the supporting plates. Reference numeral 3 is an Al electrode member provided on the semiconductor wafer 1, 6 is an internal buffer member provided on the Al electrode member 3 and having a thermal expansion coefficient substantially equal to that of the semiconductor wafer 1, and a Mo plate or a W plate is used. Has been. Four
And 5 are copper anode and cathode posts that dissipate heat, 9 and 9'are flexible metal plates joined to both posts 4 and 5,
11 is a cylindrical insulating ring that is airtightly bonded between the flexible metal plates 9 and 9 ', 7 and 8 are cooling bodies, 12 is a bolt for tightening the cooling bodies 7 and 8, and 10 is elastic. It is the body.

In this type of apparatus, the contact surfaces of the semiconductor wafer 1, the Al electrode member 3 and the internal buffer member 6 on the semiconductor wafer 1 are heated by the heat generated in the semiconductor wafer 1 under pressure. There is a drawback that it causes welding and deteriorates the characteristics of the apparatus. That is, because of the heat generated in the semiconductor wafer 1, the semiconductor wafer 1, the Al electrode member 3, and the internal buffer member 6, which are in pressure contact with each other by the posts 4 and 5, thermally expand, The coefficient of thermal expansion of the Al electrode member 3 is several times larger than the coefficient of thermal expansion of the semiconductor wafer 1 and the internal buffer member 6. Therefore, when the contact surfaces are welded to each other due to heat and friction and cannot slide on each other, the semiconductor wafer 1 is subjected to an alternating load of tension and compression due to the thermal cycle generated during the operation of the apparatus. Has the problem of finally cracking.

Conventionally, a method of forming a W-Ni, W-Co, Mo-Co layer on the semiconductor wafer side and the post side by plasma welding or plating to prevent the welding (Japanese Patent Publication No. 30428/1975, Japanese Patent Laid-Open No. 52-52). Five
No. 5862), or a method of forming a metal plating of an iron group element on the semiconductor wafer side and further performing a sulfurating treatment to prevent welding (JP-A-48-21423). All of these have complicated manufacturing processes,
It has the drawback of soiling the surface of the Si wafer, which is the most important of the semiconductor devices.

Further, a method of interposing a metal layer of Mo, W, V, Rh, Hf or the like between the Al electrode member and the cathode post (Japanese Patent Laid-Open No. 55-98835), metal-fiber composite material as the cathode post and anode post materials. Method using (Cu-C) (JP-A-56-14)
2645, 59-21033, 59-31034 and 59-31035) are proposed.

[Problems to be solved by the invention]

As described above, between the electrode member mainly composed of Al provided on the semiconductor wafer and the internal buffer member, slight sliding occurs due to thermal expansion and contraction under high pressure contact, and the material currently used. However, there is a problem that a welding phenomenon occurs between the electrode member and the internal buffer member, and the semiconductor wafer below the electrode member is cracked.

An object of the present invention is to provide an internal buffer member that eliminates the above-mentioned drawbacks and minimizes welding on the contact surface.

[Means for solving problems]

The present invention relates to a semiconductor device comprising a semiconductor wafer, an electrode member in contact with the wafer, an internal buffer member in contact with the electrode member, and a post for press-contacting each member with each other. The lubricant member should be made of molybdenum compound, tungsten compound, boron nitride or titanium nitride.
It is characterized in that it is made of a sintered body made of a tungsten plate or a molybdenum plate containing 0.05 to 5.0% by weight, and the density ratio of the sintered body is 98% or more.

Here, the molybdenum compound is preferably MoS ₂ , MoSe ₂ or MoTe ₂ , and the tungsten compound is preferably WS ₂ , WSe ₂ or WTe ₂ .

The tungsten plate or molybdenum plate is preferably formed by molding each component having a particle size of 0.5 to 40 μm and sintering it by HIP (hot isostatic pressing). Here, it is preferable that at least one of Cr, Co, and Ni is contained as a sintering aid in a proportion of 1% by weight or less.

[Action]

It is premised on the discovery of the fact that when Mo compounds, W compounds, BN or TiN are mixed in as an internal buffer member, compared with the case where Mo or W materials are used as a single material, lubricity is improved. It will be. That is, to form an internal buffer member comprising a sintered body composed of a Mo plate or a W plate mixed with a lubricant such as a Mo compound in an amount of 0.05 to 5.0% by weight, and having a density ratio of the sintered body of 98% or more. Due to
A slight slide with the Al electrode member will become smooth,
Therefore, welding development is prevented.

The voids in the sintered body are used while pressing the internal buffer member against the semiconductor element, but in this case, stress concentration occurs around the holes, and there is a high possibility that they will become fracture starting points. In the case of fine sliding, it is desirable that a uniform load be applied to the semiconductor element, but if holes are present, the load becomes non-uniform and welding easily occurs. Therefore, the present invention is characterized in that a sintered body is prepared by using HIP (hot isostatic pressing) in order to reduce voids as much as possible.

Mo compounds, W compounds, or BN or TiN as nitrides are used as the sliding component of the internal buffer member. By using the Mo plate or the W plate containing and dispersed, the fine sliding can be smoothly performed. In detail, Mo-0.05 to 5 wt% MoS _2, Mo-0.05~5
Wt% MoSe _2, Mo-0.05~5 wt% MoTe _2, Mo-0.05~5
Wt% BN or W-0.05 to 5 wt% WS ₂ , W-0.05 to
5 wt% WSe _2, W-0.05~5 wt% WTe _2, W-0.05~5
The purpose can also be achieved with a wt% BN, or a W-0.05 to 5 wt% TiN or other Mo-W compound, a combination of W-Mo compounds, and a dispersant containing a plurality of lubricants.

These metal plates or internal buffer members are
By subjecting the sintered body to HIP (hot isostatic pressing) for higher density, a metal plate with a density ratio of 98% or more close to 100% can be obtained.

The manufacturing method of the sintered body is as follows.
Mix Mo compound powder, W compound powder or BN, TiN. At this time, since the powders to be mixed have different densities, wet mixing is used to prevent non-uniform mixing. The effective molding pressure of the molded product after mixing is 0.5 to 4 ton / cm ² . Molding becomes unstable at 0.5ton / cm ² or less, 4ton / cm ²
The above causes cracks in the sintered body.

The content of the Mo compound powder, the W compound powder, or the BN and TiN powder with respect to the W powder or the Mo powder is 0.05 to 5% by weight. When the content is 0.05% by weight or less, the effect of smoothly performing fine sliding with the electrode member or the post hardly appears, and the semiconductor wafer is cracked. On the other hand, Mo compounds, W compounds, BN, T
It is more effective if the content of lubricating components such as iN is large,
The upper limit of the semiconductor device parts is 5% by weight. The reason is that if the content is 5% by weight or more, the electric conductivity (I
・ A ・ C ・ S%) is the electric conductivity of Mo or W single material
It falls to 10% or less compared to 30 to 35%, which causes an increase in electric resistance or a rise in temperature inside the device. Further, the thermal expansion coefficient also increases by 15% or more when the content is 5% by weight or more, which leads to an increase in the minute sliding distance, which makes it unsuitable as a semiconductor component. Further, a mixture containing 5% by weight or more of a lubricating component has poor moldability, is not molded regardless of molding pressure, and collapses.

The particle size of the powder used as each component of the internal buffer member according to the present invention is 0, from the viewpoint of uniform mixing or moldability.
The optimum size is 5-40 μm. If this particle size is 0.5 μm or less, agglomerates of particles are generated, and uniform mixing is almost impossible even after mixing for a long time. From the results of the friction test, it was confirmed that when the dispersed particle size was 0.5 μm or less, the dispersed particles were covered by the fluidized bed of the base material due to friction and the dispersing effect was not exhibited. On the other hand, in the case of coarse particles having a particle size of 40 μm or more, the density ratio of the sintered body does not reach 90% or more, resulting in insufficient strength as an internal buffer member.

In order to improve the sinterability, it is effective to add Ni, Cr or Co in an amount of 1% by weight or less as a sintering aid. By adding the sintering aid, the sintering temperature is lowered and a dense and high-strength sintered body is obtained. If the addition amount is 1% by weight or more, a compound with a matrix element is formed, which causes deterioration of electrical characteristics and mechanical strength, which is not effective.

〔Example〕

Example 1 A method for manufacturing a sintered body used for the internal buffer member of the present invention will be described below. First of all, the sintering of the molded body is
The temperature was 1200 to 1450 ° C. in an H ₂ atmosphere.

The density ratio of the sintered body thus obtained decreases as the content of Mo compound, W compound or BN, TiN increases, but it is 92% in the sintered body containing 5% by weight and the mixed composition No change was observed. Next, these sintered bodies
The density ratio is further increased by the HIP treatment. The above-mentioned sintered body was put into a HIP-treated capsule made of mild steel (SS41 material) having a thickness of 3 mm, which was vacuum-exhausted and degassed while heating and vacuum-sealed. The above HIP-treated capsule is set in the pressure vessel of the HIP treatment apparatus, the inside of the pressure vessel is deaerated in vacuum, and then Ar gas is isotropically pressurized through the high-pressure gas inlet, and at the same time the temperature inside the pressure vessel is raised by the heater. Temperature 1200, pressure 1500kg / c
As a result of HIP treatment under the condition of m ² , the density ratio of the sintered body containing 5% by weight reached 98-99%, which was close to 100%. Moreover, no difference in the density ratio depending on the composition was observed.

FIG. 2 shows the results of examination by friction tests of the welding limit surface pressures of the internal buffer member obtained in the present invention and the conventionally used internal buffer member (a single material of Mo). It is a thing. The test piece of the Al electrode member used as the mating material was a Si wafer on a W plate with a diameter of 21 mm and a plate thickness of 5 mm.
l Adhesive with brazing filler metal, Al is 10 to 15 μm on the surface of this Si wafer.
It is vapor-deposited to the thickness of. The rubbing method is to bring the end surfaces of a cylindrical movable test piece and a fixed test piece into contact with each other and to bring them into contact rotary friction. The friction velocity is 75 μm / s, and the friction atmosphere is N ₂ gas. The load pressure method is the initial load
The coefficient of friction was measured from 1 kg by increasing it by 1 kg every 30 minutes thereafter, and was continued until the coefficient of friction rapidly increased.

As shown in the figure, in the conventional internal buffer member, the friction coefficient starts to increase from a load of about 2 kg and increases to 0.3 to 0.35 at a load of 4 kg, and the friction surface is completely welded. On the other hand, the internal buffer member according to the present invention
Mo-0.1 wt% BN21 and W-0.1 wt% BN22 materials are
There is no welding up to 5 kg, and the coefficient of friction is as low as 0.2 or less. Further, it can be seen that even with Mo-0.1 wt% MoS ₂ 23 and W-0.1 wt% MoS ₂ 24, no welding was observed even under a load of 10 kg, and the coefficient of friction was as low as 0.08. The internal buffer member according to the present invention uses a powder component having a particle diameter of 40 μm, 0.5% by weight of Ni is added to the sintering aid, and the plate thickness is 0.8 mm.
The plate was sintered and molded. The surface was mirror-polished with a roughness of 0.8S.

Example 2 FIG. 3 shows the results of a constant load, long-time friction test for an internal buffer member according to the present invention and a conventional internal buffer member (a single Mo material). Al electrode member used as mating material and friction method,
The friction speed, the friction atmosphere, etc. are the same as those in the first embodiment. The load was constant at 5 kg.

As shown in the figure, the conventional internal buffer member has a friction coefficient of 0.3 or more at a friction distance of 20 mm,
The friction surface is welded. On the other hand, the internal buffer member Mo-0.1 wt% BN21, W-0.1 wt% according to the present invention
BN22, Mo-0.1 wt% MoSe ₂ 23 and W-0.1 wt% MoSe ₂ 2
4 is a friction distance of 700 mm, converted to actual machine micro-sliding, the coefficient of friction is as low as 0.1 or less even after about 80,000 cycles,
Almost no welding was observed on the friction surface.

Example 3 The contact area of the internal buffer member according to the present invention is 28.2.
The internal buffer member surface was observed when it was incorporated into a rectifier of cm ² and a current of 500 A was repeatedly turned on and off, and when energization and cooling were repeated so that the difference in temperature change of the semiconductor substrate was 150 ° C. As a result, the conventional internal buffer member was confirmed to be welded 30,000 to 40,000 times. On the other hand, the internal buffer member according to the present invention did not cause welding even after 50,000 cycles or more, and the characteristics were not deteriorated.

〔The invention's effect〕

According to the present invention, since the internal buffer member is formed of a Mo plate or a W plate mixed with a lubricant, the lubricant smoothly causes a slight sliding of the contact surface with the electrode member due to thermal expansion and contraction. Since the density ratio of the sintered body is high and there are very few holes on the surface of the sintered body, cracks originating from the holes on the surface of the sintered body do not easily occur during use, and repeated heat A semiconductor device having a long life which can endure a cycle can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor device, FIG. 2 is a view showing a result of welding limit measurement, and FIG. 3 is a view showing a result of a long-term friction test. 1 ... Semiconductor wafer, 3 ... Electrode member, 4,5 ... Post, 6 ... Internal buffer member.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuroku Sakurada 3-1-1, Saiwaicho, Hitachi, Ibaraki Hitachi Ltd. Hitachi factory (56) References JP-A-52-119167 (JP, A) ) Japanese Patent Laid-Open No. 50-68777 (JP, A) Japanese Patent Laid-Open No. 58-157903 (JP, A) Japanese Utility Model No. 57-93153 (JP, U) Japanese Patent Publication No. 44-9013 (JP, B1) Japanese Patent Publication No. 43- 8377 (JP, B1)

Claims (4)

[Claims] 1. A semiconductor device comprising: a semiconductor wafer; an electrode member in contact with the wafer; an internal buffer member in contact with the electrode member; and a post for pressing each member into pressure contact with each other. The null buffer member is made of a sintered body made of a tungsten plate or a molybdenum plate containing 0.05 to 5.0% by weight of a lubricant made of at least one of a molybdenum compound, a tungsten compound, boron nitride and titanium nitride, and a density ratio of the sintered body. Is 98%
A semiconductor device having the above. _2. A semiconductor device according to claim 1, wherein the molybdenum compound is MoS ₂ , MoSe ₂ or MoTe ₂ , and the tungsten compound is WS ₂ , WSe ₂ or WTe ₂ . 3. The tungsten plate or molybdenum plate according to claim 1, wherein the particle size of each component is 0.5 to 40.
A semiconductor device that is made by molding and HIP (hot isostatic pressing) with a size of μm. 4. A semiconductor device according to claim 3, wherein at least one of Cr, Co and Ni is contained as a sintering aid in a proportion of 1% by weight or less.