Semiconductor device manufacturing: process – Bonding of plural semiconductor substrates – Thinning of semiconductor substrate
Reexamination Certificate
1998-04-28
2001-02-20
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Bonding of plural semiconductor substrates
Thinning of semiconductor substrate
C438S455000, C438S458000
Reexamination Certificate
active
06191007
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of priority from Japanese Patent Applications No. H. 9-111284 filed on Apr. 28, 1997, No. H. 9-117780 filed on May 8, 1997, No. H. 9-126738 filed on May 16, 1997, No. H. 9-139890 filed on May 29, 1997, No. H. 9-185022 filed on Jul. 10, 1997, NO. H. 9-189745 filed on Jul. 15, 1997, No. H. 9-224280, filed on Aug. 5, 1997, No. H. 9-251944 filed on Sep. 17, 1997, No. H. 9-260592 filed on Sep. 25, 1997, No. H. 9-268688 filed on Oct. 1, 1997, and No. H. 9-349151 filed on Dec. 18, 1997, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for manufacturing a semiconductor substrate having a semiconductor layer, in which a semiconductor element is formed, on a supporting substrate with an insulating film interposed therebetween, and particularly to a method for manufacturing a semiconductor substrate having a patterned structure for a buried electrode below the semiconductor layer.
2. Description of the Related Art
As a semiconductor substrate provided with a semiconductor layer for forming a semiconductor element therein on a supporting substrate interposing an insulating film therebetween, there is for example a SOI (Silicon On Insulator) substrate. The SOI substrate is made by forming an oxide film as an insulating film on a silicon substrate serving as a supporting substrate and forming a monocrystalline silicon thin film on the oxide film. When this kind of semiconductor substrate is used, not only does it become unnecessary to provide a separate step for insulating the semiconductor layer from the substrate but also the insulation performance is good and it is possible to form semiconductor elements on the monocrystalline silicon thin film with a high density to make integrated circuits.
In a semiconductor substrate having this kind of SOI structure, to form an element such as a double gate MOSFET, the idea of forming on the lower face of the oxide film or in the oxide film a buried electrode pattern to constitute a back gate or interconnection pattern has been being considered. However, in a conventional semiconductor substrate having a pattern structure for a buried electrode of this kind, manufacturing technology for sharply increasing the film thickness uniformity of the SOI layer (the monocrystalline silicon thin film) and greatly enhancing the film thickness controllability of when this SOI layer is formed as an extremely thin film has not been completed, and the development of this kind of manufacturing technology has been being awaited.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for manufacturing a semiconductor substrate having a semiconductor layer for forming a semiconductor element therein on a supporting substrate with an insulating film therebetween and a pattern structure for a buried electrode, with which it is possible to sharply increase the film thickness uniformity of the semiconductor layer and it is possible to greatly enhance the film thickness controllability of when this semiconductor layer is formed as an extremely thin film. As a result, improvements in quality and characteristics of the semiconductor layer can be achieved and the deployment of such semiconductor substrates to various uses is made possible.
To achieve this object and other objects, the invention provides a manufacturing method wherein, after an insulating film forming step of forming on a first semiconductor substrate an insulating film eventually to provide insulation between a supporting substrate and a semiconductor layer is carried out, an electrode pattern forming step of forming, in a predetermined region on the insulating film, an electrode pattern eventually to become a buried electrode is performed. Also, an insulating material depositing step of depositing an insulating material on the insulating film in such a state that it covers the electrode pattern as well as the insulating film, a flattening process material depositing step of depositing a flattening process material on the insulating material in such a state that it covers the same, and a flattening step of flattening the surface of this flattening process material are carried out in order. Thereafter, a first laminating step of laminating the first semiconductor substrate to the supporting substrate with the flattening process film therebetween is performed.
After that, in a substrate forming step, the first semiconductor substrate laminated to the supporting substrate is removed to expose the entire surface of the insulating film. As a result, a buried electrode substrate including the supporting substrate and the electrode pattern on the under face of the insulating film exposed at its surface is thereby formed. That is, in a buried electrode substrate formed in this way, a flattening process material, an insulating material, an electrode pattern and an insulating film are disposed in this order on the supporting substrate.
Meanwhile, separately from the formation of this buried electrode substrate, an ion implantation step of forming an ion-implanted layer for detachment use by implanting ions to a predetermined depth is carried out on a second semiconductor substrate. Following to the ion implantation step, a second laminating step of laminating the ion implantation side face of the second semiconductor substrate to the insulating film on the buried electrode substrate is carried out.
After that, a detaching step of performing heat treatment on the buried electrode substrate and the second semiconductor substrate thus laminated together in the second laminating step and thereby detaching the second semiconductor substrate from the buried electrode substrate at a defective layer part formed by the ion-implanted layer is carried out. At the time of this heat treatment, in the second semiconductor substrate, microbubbles coalesce in the defective layer region to form macrobubbles. This causes detachment of the second semiconductor substrate along the defective layer.
By executing the steps described above it is possible to manufacture a semiconductor substrate having a basic structure wherein a semiconductor layer is formed on a supporting substrate interposing an insulating film therebetween (equivalent to an SOI structure) and also having an electrode pattern for a buried electrode formed on the underside of the insulating film.
With this manufacturing method, the film thickness of the semiconductor layer formed on the supporting substrate interposing the insulating film therebetween is determined by the depth of the ion-implanted layer formed in the second semiconductor substrate in the ion implantation step. This depth can be accurately set by controlling the ion implantation energy of that ion implantation step. Therefore, even when the semiconductor layer is to be formed as an extremely thin film, it is possible to greatly increase its film thickness controllability and it is possible to easily manufacture a semiconductor substrate having the film thickness of the semiconductor layer set to a desired dimension. Hence, the semiconductor substrate can be deployed to various applications.
Because the face of the second semiconductor substrate from which the ion implantation is carried out can be flattened in advance extremely easily, by carrying out the ion implantation step with this face so flattened it is possible to form the ion-implanted layer exactly parallel with the insulating film. As a result, the film thickness uniformity of the semiconductor layer can be greatly increased and it is possible to realize improvements in the quality and characteristics of the semiconductor substrate finally obtained.
Furthermore, since the second semiconductor substrate is only consumed by an amount corresponding to the film thickness of the part thereof left on the supporting substrate side each time the detaching step is carried out, and can be repeatedly reused, it becomes possible
Asai Akiyoshi
Enya Takeshi
Matsui Masaki
Ohshima Hisayoshi
Onoda Kunihiro
Denso Corporation
Lattin Christopher
Niebling John F.
Pillsbury Madison & Sutro LLP
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