Semiconductor device manufacturing: process – Bonding of plural semiconductor substrates
Reexamination Certificate
2002-03-07
2003-11-11
Chaudhuri, Olik (Department: 2823)
Semiconductor device manufacturing: process
Bonding of plural semiconductor substrates
C438S456000, C438S458000, C438S464000
Reexamination Certificate
active
06645830
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a method for exfoliating a detached member, and in particular, a transferring method for exfoliating a transferred layer comprising a thin film such as functional thin film and for transferring it onto a transfer member such as a transparent substrate. Also, the present invention relates to a transferring method of a thin film device, a thin film device, a thin film integrated circuit device, and a liquid crystal display device produced using the same.
2. Description of Related Art
Production of liquid crystal displays using thin film transistors (TFTs), for example, includes a step for forming thin film transistors on a transparent substrate by a CVD process or the like.
The thin film transistors are classified into those using amorphous silicon (a-Si) and those using polycrystalline silicon (p-Si), and those using polycrystalline silicon are classified into those formed by a high temperature process and those formed by a low temperature process.
Since the formation of such thin film transistors on a substrate involves treatment at a relatively high temperature, a heat resistant material, that is, a material having a high softening point and a high melting point must be used as the transparent substrate. At present, in the production of TFTs by high temperature processes, transparent substrates composed of quartz glass which are sufficiently resistive to a temperature of approximately 1,000° C. are used. When TFTs are produced by low temperature processes, the maximum process temperature is near 500° C., hence heat-resisting glass which is resistive to a temperature near 500° C. is used.
As described above, a substrate for use in forming thin film devices must satisfy the conditions for producing these thin film devices. The above-mentioned “substrate” is, however, not always preferable in view of only the steps after fabrication of the substrate provided with thin film devices is completed.
For example, in the production process with high temperature treatment, quartz glass or heat-resisting glass is used, however, they are rare and very expensive materials, and a large transparent substrate can barely be produced from the material.
Further, quartz glass and heat-resisting glass are fragile, easily broken, and heavy. These are severe disadvantages when a substrate provided with thin film devices such as TFTs is mounted into electronic units. There is a gap between restriction due to process conditions and preferred characteristics required for products, hence it is significantly difficult to satisfy both the restriction and characteristics.
SUMMARY OF THE INVENTION
The present invention has been achieved in view of such a problem, and has an object to provide an exfoliating method, which permits easy exfoliation regardless of characteristics of the detached member and conditions for exfoliating, and transferring to various transfer members. Another object is to provide a novel technology which is capable of independently selecting a substrate used in production of thin film devices and a substrate used when the product is used (a substrate having preferable properties for use of the product). A further object is to provide a novel technology not causing deterioration of characteristics of thin film devices which are transferred onto a substrate, by decreasing the optical energy radiated to the separable layer causing ablation in the transferring process.
DISCLOSURE OF INVENTION
1. First, method for exfoliating a detached member or a transferred layer form a substrate for production is disclosed. The inventions are as follows: (1) An exfoliating method in accordance with the present invention is a method for exfoliating a detached member, which is present on a substrate with a separation layer therebetween, from the substrate, wherein the separation layer is irradiated with incident light so as to cause exfoliation in the separation layer and/or at the interface, and to detach the detached member from the substrate.
(2) A method for exfoliating a detached member, which is present on a transparent substrate with a separation layer therebetween, from the substrate, wherein the separation layer is irradiated with incident light from the side of the substrate so as to cause exfoliation in the separation layer and/or at the interface, and to detach the detached member from the substrate.
(3) A method for exfoliating a transferred layer formed on a substrate with a separation layer therebetween from the substrate and transferring the transferred layer onto a transfer member, wherein after the transfer member is adhered to the opposite side of the transferred layer to the substrate, the separation layer is irradiated with incident light so as to cause exfoliation in the separation layer and/or at the interface, and to detach the transferred layer from the substrate to transfer onto the transfer member.
(4) A method for exfoliating a transferred layer formed on a transparent substrate with a separation layer therebetween from the substrate and transferring the transferred layer onto a transfer member, wherein after the transfer member is adhered to the opposite side of the transferred layer to the substrate, the separation layer is irradiated with incident light from the side of the substrate so as to cause exfoliation in the separation layer and/or at the interface, and to detach the transferred layer from the substrate to transfer onto the transfer member.
(5) An exfoliating method includes a step for forming a separation layer on a transparent substrate, a step for forming a transferred layer on the separation layer directly or with a given interlayer therebetween, a step for adhering the transfer member to the opposite side of the transferred layer to the substrate, and a step for irradiating the separation layer with incident light from the side of the substrate so as to cause exfoliation in the separation layer and/or at the interface, and to detach the transferred layer from the substrate to transfer onto the transfer member.
In connection with these inventions, the following inventions are disclosed.
After transferring the transferred layer onto the transfer member, a step for removing the separation layer adhering to the side of the substrate and/or transfer member may be provided.
A functional thin film or a thin film device may be used as the transferred layer. Particularly, a thin film transistor is preferably used as the transferred layer. Preferably, the transfer member is a transparent substrate.
When the maximum temperature in the formation of the transferred layer is Tmax, it is preferred that the transfer member be composed of a material having a glass transition point (Tg) or softening point which is lower than Tmax. Particularly, it is preferred that the transfer member be composed of a material having a glass transition point (Tg) or softening point which is lower than 800° C.
It is preferable that the transfer member be composed of a synthetic resin or glass.
It is preferable that the substrate has thermal resistance. In particular, when the maximum temperature in the formation of the transferred layer is Tmax, it is preferred that the substrate be composed of a material having a distortion point which is lower than Tmax.
In the above-mentioned exfoliating methods, the exfoliation of the separation layer is caused by an elimination of or a decrease in the adhering force between atoms or molecules in the constituent substances in the separation layer.
It is preferable that the incident light be laser light. Preferably, the laser light has a wavelength of 100 nm to 350 nm. Alternatively, the laser light has a wavelength of 350 nm to 1,200 nm.
It is preferable that the separation layer is composed of amorphous silicon. Preferably, the amorphous silicon contains 2 atomic percent or more of hydrogen (H).
The separation layer may be composed of a ceramic. Alternatively, the separation layer may be composed of a metal. Alternatively, the separation layer may be composed of an organic po
Inoue Satoshi
Miyazawa Wakao
Shimoda Tatsuya
Brewster William M.
Chaudhuri Olik
Oliff & Berridg,e PLC
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