JPH03234045A - Aluminum nitride board and semiconductor module with aluminum nitride board - 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 [Object of the Invention (Industrial Application Field) The present invention relates to an aluminum nitride substrate and a semiconductor module in which a semiconductor element is mounted on the aluminum nitride substrate.

(Prior Art) As semiconductor devices become more highly integrated and output, the amount of heat generated from the devices tends to increase, and accordingly, ceramic substrates used are required to have high heat dissipation properties.

Therefore, instead of the conventionally used ceramic substrates using alumina, ceramic substrates using aluminum nitride are attracting attention.

Aluminum nitride substrates have high thermal conductivity and are convenient as substrates for mounting semiconductor devices that dissipate a large amount of heat, such as power transistors.In addition, they have a coefficient of thermal expansion similar to that of silicon, which is the material for semiconductor devices. Therefore, there is also the advantage that there is almost no risk of defects such as cracks occurring in the solder layer or metallized layer on the component side even if thermal cycles are repeated.

Furthermore, when manufacturing semiconductor modules using ceramic substrates, metallized layers are formed on both sides of the alumina substrate, a semiconductor chip is mounted on one metalized layer, and the other metalized layer is soldered to form a heat sink. However, by using the above aluminum nitride substrate as a circuit board for semiconductor modules, it is no longer necessary to form a metallized layer on both sides of the substrate, and it is possible to bond silicone resin or the like to a heat dissipating container made of aluminum or the like. Direct bonding using an agent is performed.

(Problems to be Solved by the Invention) As described above, by using an aluminum nitride substrate as a circuit board for a semiconductor module, metallization treatment on one side can be omitted and it can be bonded to a heat sink. There is a problem in that connection with the heat sink must be taken into consideration.

That is, when bonding an aluminum nitride substrate to another member, in order to obtain high adhesiveness, it is preferable that the bonding surface of the aluminum nitride substrate has a certain degree of roughness.
Roughness of about 5 to 2.0 μm is required.

However, this roughness is too rough on the side to which a semiconductor chip is bonded as a semiconductor module, and sufficient bonding strength between the metallized layer and the aluminum nitride substrate cannot be obtained.

That is, when manufacturing a semiconductor module using an aluminum nitride substrate, it is necessary to separately control both sides of the aluminum nitride substrate.

The present invention has been made to solve these problems, and includes an aluminum nitride substrate in which the surface condition of the amphiphilic surface is controlled according to each purpose, and reliability improved by using such an aluminum nitride substrate. The purpose is to provide a semiconductor module with improved performance.

[Structure of the Invention] (Means for Solving the Problems) The aluminum nitride substrate of the present invention has a surface roughness Ra of less than 0.5μ on one main surface of the aluminum nitride substrate, and It is characterized in that the surface roughness Ra on the main surface is 0.5 to 2.0 μm.

Further, the semiconductor module of the present invention includes: an aluminum nitride substrate whose one main surface has a surface roughness Ra of 0.5 μm or less; a metallized layer bonded to the one main surface of the aluminum nitride substrate; The semiconductor element mounted on the metallized layer and the aluminum nitride substrate, which is the other main surface opposite to the metallized layer and has a surface roughness Ra of 0.5 to 2.0 μ■, are bonded using an organic heat-resistant adhesive. It is characterized by being equipped with a bonded heat sink.

In the present invention, the centerline average roughness (that is, indicated by Ra) is used as the surface roughness.

In the present invention, one main surface of the aluminum nitride substrate is a surface to which parts such as semiconductor chips are bonded, and the surface roughness thereof is made by grinding or the like to less than RaO, 5 μm.

When RaO exceeds 5 μ-, the bonding strength with the metallized layer decreases.

The other main surface of the aluminum nitride substrate is the surface to be bonded to the heat sink with an adhesive, and its surface roughness can be adjusted to Ra of 0.5 to 2 by machining such as honing or chemical treatment such as alkali etching. .0μm.

For surfaces to be bonded with adhesive, if the surface roughness is too small, the surface area for the adhesive to penetrate is small, resulting in insufficient bonding strength, while if it is too large, voids are likely to occur in the four parts, reducing heat dissipation. will be invited.

Note that this heat sink bonding surface may have a moderate surface roughness even when the aluminum nitride is sintered as it is. It is only necessary to treat the surface (on the loading side).

(Function) In the present invention, the aluminum nitride substrate is treated so that the degree of surface roughness differs between one main surface and the other main surface.

Therefore, the metallized layer on the semiconductor chip mounting side and the heat sink are both bonded in a more optimal state.

Therefore, the reliability of the bonding strength of the semiconductor module is greatly improved.

(Example) Next, embodiments of the present invention will be described using the drawings.

Embodiment FIG. 1 is a sectional view showing a semiconductor module according to an embodiment of the present invention.

In the figure, 1 is a ceramic substrate made of an aluminum nitride sintered body. One main surface 1a of this aluminum nitride substrate 1 is polished to a surface roughness R by a method such as grinding.
aO, 3 μs, and the other main surface 1b is honed to have a surface roughness Ra of 1.0 μI.

Here, the surface roughness Ra represents the centerline average roughness determined by the hull according to the measurement method according to the JIS standard.

Such an aluminum nitride substrate 1 is first prepared with a main surface 1
After adjusting a to a predetermined roughness, the main surface 1a is masked to protect it from further roughness, and the masked aluminum nitride substrate is further honed.
It is obtained by etching or the like to further roughen the other main surface 1b.

A metallized layer 2 made of molybdenum with a predetermined circuit pattern (not shown) is formed on the main surface 1a of the aluminum nitride substrate 1, and is plated, and a semiconductor element 4 is bonded to the main surface 1a via a solder layer 3.

This semiconductor element 4 is electrically connected to the circuit of the metallized layer 2 by a bonding wire 5.

On the other hand, the other main surface lb side of the aluminum nitride substrate 1 with respect to the main surface 1a is bonded to a heat sink 7 made of aluminum using an organic heat-resistant adhesive 6.

These constitute a semiconductor module M.

The organic heat-resistant adhesive 6 is applied to the aluminum nitride substrate 1.
The material is selected in consideration of wettability and thermal conductivity with respect to the heat sink 7.

Note that the heat-resistant adhesive referred to here does not need to soften or decompose when heat is dissipated from the semiconductor element, and is usually 150% adhesive.
It is sufficient that the material has a heat resistance temperature of about 0.degree.

For example, when a heat dissipating container made of aluminum is used as the heat sink 7, silicone resin is used as the heat-resistant adhesive 6 because of its excellent wettability with aluminum nitride or aluminum and its excellent thermal conductivity. Adhesives are suitable.

Silicone resin adhesives generally have a heat resistance temperature of about 180°C and a thermal conductivity of about 5vlIK to 15w/-.

Further, in order to improve thermal conductivity, it is more preferable to use a silicone resin adhesive containing fine thermal conductive powder as a filler.

Next, a specific manufacturing example of the semiconductor module M having the above configuration and evaluation results of its characteristics will be described.

First, a pair of main surfaces of an aluminum nitride sintered body containing an appropriate amount of sintering aid are treated to have respective surface roughnesses.

Next, a metallized layer is formed on the main surface on the semiconductor element mounting portion side, which has a small surface roughness, and the semiconductor element is further bonded and mounted by soldering.

On the other hand, silicone resin adhesive ES E-32 is used as an organic heat-resistant adhesive on the main surface on the heat sink joint side.
2 (trade name: manufactured by Toshiba Silicone Co., Ltd.), 120
The heat sink and the aluminum nitride substrate are bonded by leaving it for 2 hours at ℃.

Using the semiconductor module obtained in this way, we conducted characteristic tests on bonding strength and heat dissipation, and found that the bonding strength was 0.5.
It had good Kgf'/lxm2 and excellent heat dissipation.

Comparative Example 1 Both surfaces of aluminum nitride substrate have surface roughness R
A semiconductor module was manufactured in the same manner as in the example except that a was treated to be 0.3 μι.

When we conducted a characteristic test using this semiconductor module under the same conditions as in the example, we found that the heat dissipation did not deteriorate significantly, but the bonding strength was 0.2 KgC/s+s2, and the heat sink and aluminum nitride substrate The bonding condition was not sufficient.

Comparative Example 2 The main surface of the aluminum nitride substrate on the semiconductor element mounting side was processed to have a surface roughness Ra of 0.3 μm, and the other main surface was processed to have a surface roughness Ra of 2.5 μm.

A semiconductor module was manufactured in the same manner as in the example except that.

When a characteristic test was conducted using this semiconductor module under the same conditions as in the example, the bonding strength was 0.2 Kgr/lll1
The result was 12, indicating that the bonding state between the heat sink and the aluminum nitride substrate was not sufficient, and that large voids were generated in the four parts, resulting in a decrease in heat dissipation.

As is clear from these results, the semiconductor module according to this example can obtain sufficient bonding strength with each bonding member by controlling the surface roughness of the aluminum nitride substrate, and has high heat dissipation. was able to be granted.

[Effects of the Invention] As explained above, according to the present invention, the surface of the aluminum nitride substrate is treated in a state suitable for each member to be joined, so that the joint strength at each joint part is good. , a highly reliable semiconductor module can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a semiconductor module according to an embodiment of the present invention. 1... Aluminum nitride substrate 2... Metallized layer 3... Solder layer 4... Semiconductor element 5... Bonding wire 6... ... Organic heat-resistant adhesive 7 ... Heat sink M ... Semiconductor module

Claims (2)

[Claims] (1) Surface roughness Ra on one main surface of the aluminum nitride substrate is less than 0.5 μm, and surface roughness Ra on the other main surface of the aluminum nitride substrate is 0.5 to 2.0 μm. aluminum nitride substrate. (2) an aluminum nitride substrate whose one main surface has a surface roughness Ra of less than 0.5 μm; a metallized layer bonded to the one main surface of the aluminum nitride substrate; and a heat sink bonded to the aluminum nitride substrate, the other main surface of which is opposite to the metallized layer and has a surface roughness Ra of 0.5 to 2.0 μm, using an organic heat-resistant adhesive. A semiconductor module characterized by: