Semiconductor device manufacturing: process – Bonding of plural semiconductor substrates – Subsequent separation into plural bodies
Reexamination Certificate
2002-03-11
2003-11-25
Chaudhuri, Olik (Department: 2823)
Semiconductor device manufacturing: process
Bonding of plural semiconductor substrates
Subsequent separation into plural bodies
C438S459000, C438S977000
Reexamination Certificate
active
06653207
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the production of a thinned electric part. Specifically, the process is characterized in that a resin composition containing a swelling inorganic compound (WC) is used for part or the whole of an adhesion layer and a separation is promoted due to a decrease or loss in the adhesive strength of the adhesion layer by making the swelling inorganic compound (WC) absorb a liquid after the completion of a treatment step of a back surface. In particular, the process enables a separation in cases where the separation is extremely difficult, such as a case in which an adhesive strength is strengthened by a treatment step such as a treatment step essentially requiring a high temperature step.
BACKGROUND OF THE INVENTION
In recent years, electronic devices have been desired to be decreased in thickness or in weight. As is typified by a portable telephone or an IC card, electric devices are decreasing in thickness. From the viewpoint of a speed-up or a decrease in electric power consumption, it is required to decrease the thickness of a semiconductor.
When electric circuits are formed on only one surface of a semiconductor wafer, a ceramic substrate and etc. (to be generically referred to as “substrate” hereinafter) which have been already thinned, warps or distortions occur due to a thermal expansion coefficient difference of approximately 5~15×10
−6
K
−1
between a material for the formation of circuits, particularly a metal such as aluminum, copper or gold, and the silicon wafer or the ceramic substrate. Due to the occurrence of warps or distortions, it becomes impossible to form circuits on its back surface and furthermore it becomes also impossible to carry out even all steps of the front surface in some cases. For this reason, it is substantially impossible to use a substrate which has been already thinned.
Thus, conventionally, when electric circuits are formed on only one surface, there is adopted a method in which an electric-circuits-forming step essentially requiring a high temperature is performed mainly on one surface (front surface) of a substrate having a thickness, generally at least 200 &mgr;m, sufficient for retaining the shape thereof, then the front surface is bonded to a holding substrate to protect the front surface, and the opposite surface (back surface) is polished to thin the substrate.
Conventionally, as a thinning method, there is proposed a fixation method with a wax or a tape.
As a fixitation method using a wax, there is proposed a method in which a wax is applied on a dummy wafer (holding substrate) under heat, a wafer is bonded to the dummy wafer, the wafer is ground and further polished and then the wafer is separated from the dummy wafer by melting the wax under heat and slipping the wafer sideways or by cooling the wax and breaking the wax which has become fragile by means of an impact breakdown. However, the wax fixation has problems about thickness accuracy, parallelism and flatness.
As a tape fixation method, there is a method in which a back-grinding tape is affixed to a front surface of a substrate and an opposite surface is polished to thin the substrate.
When it is required to form a metal thin layer on the back surface of a thinned wafer or a thinned substrate, generally, there is required a high-temperature treatment step at a temperature of from 250 to 450° C. for from 30 minutes to 1 hour, which high-temperature treatment includes, for example, a pretreatment with fluoric acid, nitric acid or the like, a metal deposition such as aluminum or gold, and a calcination treatment thereof.
However, it is impossible to carry out these steps under the state where a substrate is bonded to a holding substrate with a wax or a back-grinding tape. In the method using a wax or a tape for thinning, after a substrate is thinned, it is separated from a holding substrate and then subjected to a high-temperature treatment step. The thinned substrate is very fragile. And, since semiconductor circuits different in thermal expansion coefficient from the substrate exist on one surface of the thinned substrate, a defective fraction considerably increases because of distortion or breakage. Further, when the thickness is thin or approximately 50 &mgr;m, it is difficult to subject the thinned substrate to a high-temperature treatment step.
If electric circuits can be efficiently formed on a thinned substrate having a large work size, electric parts having a decreased thickness, a high speed and a decreased electric power consumption can be practically produced.
Thus, the present inventors have proposed a method in which a substrate is bonded to a holding substrate, the substrate is thinned, the thinned substrate bonded to the holding substrate is subjected to a high temperature treatment step or other steps as it is and, after the completion of these steps, the substrate is separated from the holding substrate by using water or the like (JP-A-2001-77304, Japanese Patent Application Nos. 2001-30746, 2000-401077, 2000-401078, etc.).
However, in the above method, when a treatment step at more than 400° C. is present, the separation is substantially impossible.
Further, even when no high temperature treatment step is present, depending on a surface-treatment method of a substrate, it is very difficult in some cases to find a resin composition for bonding which has an adhesion reliability sufficient for enduring a processing step of a back surface and allows an easy separation after the completion of the step.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a resin composition for bonding which can be easily decreased in adhesive strength by a simple means even when an adhesion is strengthened by a high-temperature treatment step or even when it is difficult to find an easily-separable resin composition for bonding, and provide its use.
According to the present invention, there is provided a process for the production of an electric part, comprising performing a circuit-parts-forming step including the introduction of impurities on one surface (surface A) of a semiconductor substrate, then bonding the surface A to a holding substrate, performing a back surface treatment step essentially including a polishing of an exposed surface (surface B) of the semiconductor substrate to a thickness of 100 &mgr;m or less to obtain an electric-part-formed thinned substrate and separating the thinned substrate from the holding substrate, wherein a resin composition containing a swelling inorganic compound (WC) is used for an adhesion layer and in the separating step the thinned substrate is separated from the holding substrate after decreasing the adhesive strength of the thinned substrate and the holding substrate by swelling the swelling inorganic compound (WC).
Further, in the process provided according to the present invention, preferably, the swelling inorganic compound (WC) is a fine powder having an average particle diameter of from 0.05 to 3 &mgr;m.
Further, in the process provided according to the present invention, preferably, the swelling inorganic compound (WC) contains substantially no particles having a particle diameter of 10 &mgr;m or more.
Further, in the process provided according to the present invention, preferably, the swelling inorganic compound (WC) is a swelling clay mineral, a swelling phyllosilicate or a swelling carbon.
Further, in the process provided according to the present invention, preferably, the content of the swelling inorganic compound (WC) in the resin composition is 1 to 30% by weight.
DETAILED DESCRIPTION OF THE INVENTION
The constitution of the present invention will be explained hereinafter.
The present invention is characterized in that a resin composition containing a swelling inorganic compound (WC) is used in an adhesive layer.
The swelling inorganic compound (WC) is an inorganic compound which gets swollen by absorbing water, an organic solvent, steams of these, etc. Generally, the above inorganic compound has a layered crystal s
Nobukuni Takeshi
Ohya Kazuyuki
Otsu Kazuhiro
Chaudhuri Olik
Mitsubishi Gas Chemical Company Inc.
Nguyen Khiem
Wenderoth , Lind & Ponack, L.L.P.
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