JP2775848B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device formed on an SOI structure substrate, which aims at suppressing potential floating of each element and preventing a temperature rise. And a method of manufacturing a semiconductor device in which a metal is diffused into the support-side substrate of the SOI structure substrate including the support-side substrate, the insulating layer, and the element-side substrate on which the element is formed, and the support-side substrate is alloyed. .

[Industrial applications]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device formed on an SOI structure substrate.

As a high-speed, high-density, radiation-resistant LSI substrate, an SOI substrate with a Si layer / oxide film / Si structure is useful.

In recent years, as the system becomes larger and faster, it is required to improve the degree of integration and operating speed of the LSI. In order to satisfy this requirement, the power consumption of the chip is significantly increased, and how to suppress the temperature rise due to the heat generation of the elements is a major problem for the improvement of the degree of integration and the operation speed.

[Conventional technology]

Conventionally, in a LSI substrate, a cooling mechanism is added to the outside of the package to prevent a temperature rise due to heat generation of an element. However, in an SOI substrate with an oxide film between the Si layer forming the device and the supporting substrate, the thermal conductivity of the oxide film is small, so the temperature of the device is more likely to rise than in a normal bulk substrate. To improve the efficiency of heat transfer,
After the elements are formed, the supporting side substrate is made as thin as possible and die-bonded to a metal package.

In order to prevent the temperature of the device from rising, the thinner the supporting substrate is, the better. However, the mechanical strength of Si is not so large, so the limit for lapping is about 200 μm.

In order to further reduce the thermal resistance by reducing the thickness, it is necessary to increase the mechanical strength of the supporting substrate. Further, it is also effective to increase the thermal conductivity of the supporting substrate.

Further, in the SOI structure, since each element is completely separated from the supporting substrate by the insulating layer, each element is in an electrically floating state.
Therefore, each element may malfunction due to external or internal noise. To prevent this, it is necessary to increase the electrical conductivity of the supporting substrate and fix the potential of each element by capacitive coupling with the supporting substrate.

However, the mechanical strength, thermal conductivity, and electrical conductivity of the supporting substrate have hardly been studied.

[Problems to be solved by the invention]

Therefore, in order to realize the high-performance LSI by exhibiting the features of the SOI structure based on the above-mentioned problems, a large electrical conductivity, a large thermal conductivity, and a large mechanical strength must be realized on the supporting substrate. Is required.

An object of the present invention is to provide a method for manufacturing a semiconductor device having an SOI structure that meets these problems.

[Means for solving the problem]

The above object is to diffuse the metal into the support-side substrate made of single-crystal silicon, the insulating layer, and the support-side substrate of the SOI structure substrate composed of the single-crystal silicon element-side substrate on which the element is formed, thereby forming the support-side substrate. The problem is solved by a method of manufacturing a semiconductor device to be alloyed.

[Action]

In the present invention, the supporting substrate 1 is alloyed by diffusing a metal into the supporting substrate 1 to improve the electrical conductivity, the thermal conductivity, and the mechanical strength of the supporting substrate 1.

By improving the mechanical strength, the support-side substrate 1 can be made thinner. This makes the effect of removing heat generated from the element effective in combination with the improvement of the thermal conductivity.

The improvement in the electric conductivity has an effect of suppressing the element from being in an electrically floating state.

Further, since the step of diffusing the metal into the support-side substrate 1 is performed after forming the element on the element-side substrate 3, there is no fear that the element-side substrate 3 is contaminated by the metal. If a step of diffusing a metal into the supporting substrate 1 is performed before the element is formed, the element-side substrate 3 may be contaminated by the metal during the element forming process.

Embodiments FIGS. 1A to 1E are diagrams for explaining an embodiment of the present invention, in which 1 is a supporting substrate, 1a is a supporting substrate having a reduced thickness, and 2 is an insulating layer. Reference numeral 3 denotes an element-side substrate on which elements are formed, 4 denotes a metal layer, 5 denotes an alloy layer, and 5a denotes an alloy layer having a reduced thickness.

The embodiment will be described below with reference to FIGS. 1 (a) to 1 (e).

As shown in FIG. 1 (a), an element of an SOI structure substrate composed of a supporting side substrate 1, an insulating layer 2, and an element side substrate 3 on which two 6-inch Si wafers each having an SiO ₂ film formed thereon as an insulating layer 2 are bonded. An LSI is formed on the side substrate 3 by a normal process.

 The thickness of each part is as follows.

1. Support-side substrate (Si) 0.6 mm 2. Insulating layer (SiO ₂ ) 1 μm 3. Element-side substrate (Si) 0.6 mm See FIG. 1 (b). Wrap up. 1a represents a supporting-side substrate whose thickness has been reduced to about 0.3 mm.

Referring to FIG. 1 (c), a metal layer 4 is formed by depositing copper (cu) to a thickness of about 2 μm on the supporting side substrate 1a having a reduced thickness.

Referring to FIG. 1 (d), a heat treatment is performed at 400 ° C. for 10 hours. Copper (Cu) diffuses into the reduced support-side substrate 1a and alloys with Si of the support-side substrate 1a, and the reduced-support-side substrate 1a becomes an alloy layer 5 of Si and Cu.

Referring to FIG. 1 (e), the alloy layer 5 is wrapped to a thickness of about 0.1 mm to form an alloy layer 5a having a reduced thickness. At the time of this lapping, the mechanical strength of the support-side substrate is increased by the formation of the alloy layer 5, so that the substrate is not broken.

Then, it is cut into chips and die-bonded to a package.

In this manner, a semiconductor device having an SOI structure having a supporting substrate having high thermal conductivity and high electrical conductivity is realized.

In addition to copper (Cu), gold (Au), barium (Ba), etc.
There can be metals that alloy with silicon (Si) at temperatures below ° C. If the heat treatment temperature for alloying exceeds 450 ° C., Al in the wiring reacts with Si to cause disconnection or break the pn junction, which is not desirable.

When depositing copper on the support-side substrate 1a having a reduced thickness, the support-side substrate 1a may be heated to 450 ° C. or lower, and the deposition and alloying may be performed simultaneously.

〔The invention's effect〕

As described above, according to the present invention, the mechanical strength of the supporting substrate is increased, the thickness of the supporting substrate can be reduced by lapping, and the thermal conductivity of the supporting substrate can be increased to improve the device performance. It is possible to reduce the thermal resistance to the generated heat flow and prevent the temperature of the element from rising.

In addition, by improving the electrical conductivity of the support-side substrate, floating of the potential of each element can be suppressed, and malfunction of the element due to noise can be prevented.

[Brief description of the drawings]

FIG. 1 shows an embodiment. In the figure, 1 is a support side substrate and a silicon substrate, 1a is a support side substrate having a reduced thickness, 2 is an insulating layer and an SiO ₂ film, and 3 is an element side substrate on which an element is formed and is a silicon substrate. The substrate, 4 is a metal layer and is a Cu layer, 5 is an alloy layer, and 5a is an alloy layer with reduced thickness.

Claims (1)

(57) [Claims] An SOI structure substrate comprising a support-side substrate made of single-crystal silicon, an insulating layer, and a single-crystal silicon device-side substrate on which elements are formed. And a method for manufacturing a semiconductor device.