Process for the production of electronic parts

Details Process for the production of electronic parts Process for the production of electronic parts

2000-06-28

2002-01-08

Niebling, John F. (Department: 2812)

Semiconductor device manufacturing: process

Coating of substrate containing semiconductor region or of...

C438S690000, C438S715000, C438S719000, C438S724000

Reexamination Certificate

active

06337288

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a process for the production of electronic parts, in which electronic circuits are formed on both the surfaces of a semiconductor substrate, the electronic circuits being for attaining an intended function. More specifically, it relates to a process for the production of electronic parts, which process uses a heat-resistant thermoplastic for supporting a semiconductor substrate on one surface of which electronic circuits are formed, so that the process can be applied to an electronic part production process including the step of processing (polishing and forming circuits on) exposed surfaces of the semiconductor substrate at a high temperature of 350° C. or higher.
PRIOR ART OF THE INVENTION
In recent years, it is increasingly required to decrease electronic machines and equipment in thickness and weight, and these machines and equipment are decreasing in thickness further and further, as is typically found in cellular phones and IC cards.
As a thin printed wiring board, printed wiring boards using a wholly aromatic polyamide paper or a polyimide film as a substrate are increasing in number.
Further, ceramic substrates are also available, and they are required to have a thickness of 0.2 mm or less, or they are required to have a smaller thickness of 0.1 mm, 0.05 mm, 0.03 mm or the like. However, a ceramic is generally hard and not deformable, and it has a defect that it is liable to break when decreased in thickness, unless it is a flexible thin glass sheet. For this reason, a ceramic substrate according to a thin film method has a thickness of 0.2 mm and a size of 50 mm×50 mm as a largest work size.
Similarly, electronic parts per se are decreasing in size according to demands for a decrease in size and higher functions.
With regard to silicon wafers, developments for increasing the work size from 20.32 cm to 30.48 cm are actively under way from the viewpoint of an increase in productivity. However, it is difficult to handle silicon wafers when they are decreased in thickness. Further, there is found no process in which metal-containing electronic circuits are formed on both the surfaces of a substrate at the same time, and in a presently available production process, an electronic circuit is formed on one surface and then an electronic circuit is formed on the other surface. Since the thermal expansion coefficient of metals such as copper and aluminum greatly differs from that of a semiconductor substrate by 10 to 15×10
−6
K
−1
, a substrate warps when the substrate is decreased in thickness, and the substrate may break in some cases.
In the production of an electronic part having a thin semiconductor substrate and electronic circuits formed on both the surfaces of the substrate, therefore, it is required to employ, for example, a method in which semiconductors and other electronic circuit portions whose formation requires high temperatures are formed on one surface (e.g., front surface) of a semiconductor substrate having a general thickness, the substrate is supported by a supporting substrate by attaching the surface (in which semiconductors and other electronic circuit portions are formed) to the supporting substrate, the other surface (reverse surface) is ground and polished to decrease the substrate in thickness, electronic circuits are formed on the reverse surface, the substrate is peeled from the supporting substrate, and the substrate is separated into individual electronic parts.
In the step of forming electronic parts on the reverse surface, processing at a high temperature is not required so long as metallizing is carried out to such an extent that a difference between the thermal expansion coefficients is balanced. However, when semiconductor circuits are formed, a substrate is required to have durability against a high temperature of approximately 350° C. or higher and a vacuum degree at which plasma processing or ion plating can be carried out at such a temperature.
Then, it is required to employ a method in which the thin and fragile semiconductor substrate in which a number of electronic circuit parts are formed is peeled off from the supporting substrate with taking care not to break the substrate, and the substrate is separated into individual electronic parts.
It is therefore required to provide a supporting substrate which can be used in the above steps and can be used repeatedly to some extent and which has a thermal expansion coefficient substantially equivalent to the thermal expansion coefficient of a semiconductor substrate, an adhesive which serves to support the semiconductor substrate on the supporting substrate and which permits peeling the semiconductor substrate off from the supporting substrate, and a method of use of these.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method which endures the step of grinding and polishing and the step of processing semiconductor circuits at a temperature of 350° C. or higher and can separate electronic parts. In this object, it is to provide a supporting substrate which endures a repeated use, a method of supporting by bonding and a separation method of, electronic parts.
According to the present invention, there is provided a process for the production of electronic parts, comprising the steps of
forming semiconductor circuits in one surface (surface A) of a semiconductor substrate (SEC) having a thickness of at least 0.2 mm,
supporting the semiconductor substrate on a supporting substrate (BP) by bonding (AS) of said surface A to the supporting substrate (BP),
grinding and polishing the exposed other surface (surface B) of the semiconductor substrate (SEC) by a physical method, a chemical method or a method of combination of these methods, to decrease the thickness of the semiconductor substrate (SEC) to less than 0.2 mm,
forming semiconductor circuits in the polished surface, to obtain an electronic-circuits-possessing semiconductor substrate (PSE), and
peeling (PS) the electronic-circuits-possessing semiconductor substrate (PSE) off from the supporting substrate (BP),
wherein the step of polishing the surface B or the step of forming electronic parts in the surface B includes the step of processing the surface B at a high temperature of at least 350° C., and the bonding (AS) uses a heat-resistant thermoplastic (RF).
In the present invention, preferably, a difference between the thermal expansion coefficient of the semiconductor substrate (SEC) and the thermal expansion coefficient the supporting substrate (BP) is 2×10
−6
K
−1
or less, the heat-resistant thermoplastic (RF) is selected from the group consisting of polyimide, polyetherimide, polyamideimide, polyesterimide, polyether ether ketone, polyester and polyamide, the bonding (AS) is carried out by thermal pressing under conditions of a temperature of 150 to 400° C., a pressure of 0.1 to 5 MPa and a time period of 3 to 90 minutes, the peeling (PS) is carried out after treatment with water, an amine or a mixture of water with an amine, an ultrasonic treatment at 28 kHz to 150 kHz is also carried out in combination for the peeling (BS), and the supporting substrate (BP) is a resin composite inorganic substrate prepared by impregnating an inorganic substrate selected from the group consisting of an aluminum nitride-boron nitride (AlN-h-BN) substrate, an aluminum nitride-silicon carbide-boron nitride (AlN—SiC—h—BN) substrate, an alumina-boron nitride (Al
2
O
3
—h—BN) substrate, a substrate made of a &bgr;-silicon carbide porous material, an amorphous carbon substrate and a carbon-fiber-reinforced carbon substrate with a heat-resistant resin and curing the resin.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be explained in detail hereinafter.
Semiconductor Substrate (SEC) Having a Thickness of at least 0.2 mm
The semiconductor substrate (SEC) for use in the present invention is typified by a silicon (Si) wafer. In addition, the semiconductor substrate (SEC) includes a semiconductor substrate containing

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