Semiconductor device manufacturing: process – Bonding of plural semiconductor substrates – Subsequent separation into plural bodies
Reexamination Certificate
2000-04-07
2003-11-11
Everhart, Caridad (Department: 2825)
Semiconductor device manufacturing: process
Bonding of plural semiconductor substrates
Subsequent separation into plural bodies
C438S406000, C438S409000, C438S455000, C438S456000
Reexamination Certificate
active
06645833
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing layer-like structures in which a material layer having hollow cavities, preferably a porous material layer, is produced on a substrate consisting, for example, of monocrystalline p-type or n-type Si and in which the layer-like structure, or a part of it, is subsequently provided on the cavity exhibiting or porous material layer, and is subsequently separated from the substrate using the cavity exhibiting or porous layer as a position of intended separation, for example through the generation of a mechanical strain within or at a boundary surface of the cavity exhibiting or porous layer. Furthermore, the invention relates to different substrates which can be produced by this method and to novel semiconductor components which can be manufactured using the substrates of the invention.
2. Description of the Prior Art
A method of the initially named kind is known from several documents.
By way of example, a method of manufacturing a semiconductor body is described in the European patent application with the Publication No. 0 528 229 A1 in which a silicon substrate is made porous, a non-porous, mono-crystalline silicon layer is formed on the porous silicon substrate at a first temperature and in which a surface of the non-porous, monocrystalline silicon layer is bonded to a second substrate having an insulating material at its surface. Thereafter the porous silicon layer is removed by a chemical etching process and a further monocrystalline silicon layer is grown onto the first-named non-porous monocrystalline silicon layer by an epitaxial process at a second temperature.
The sense of this method is to be able to grow monocrystalline silicon on any desired substrate. The method is, however, relatively complicated because the porous silicon layer must be etched away. Similar methods are also apparent from the European patent specifications with the Publications Nos. 0 536 788 A1 and EP 0 449 589 A1.
In EP-A-0 767 486 a method of the initially named kind is described in which the porous layer has a region of increased porosity and the separation of the layer-like structure from the substrate takes place by mechanical separation in the region of increased porosity. The region of increased porosity is produced either by ion implantation or by a changed current density during the manufacture of the porous layer. Even if the method step of the separation can be improved hereby, the method is more complicated and an increased danger exists of undesired separation prior to or during the production of the layer-like structure. A multiple use of the starting substrate is admittedly achieved here; nevertheless one would, in many potential uses, use the expensive monocrystalline substrate in a relatively wasteful manner.
A similar proposal can be found from the non-prior published EP-A-0 797 258.
The manufacture of silicon solar cells at favorable cost requires high-quality silicon, as far as possible single crystal silicon for high photo voltages, thin Si-layers for material saving, but nevertheless adequate absorption, low manufacturing temperatures for energy saving and favorably priced foreign substrates, for example glass for the mechanical stability.
So far as is known, there are no methods which satisfy all these criteria. For example, work is described in some of the above-named European patent applications in which one carries out CVD epitaxy at temperatures above 800° C. on porous silicon and transfers the so-formed epitaxial layers to a glass substrate. The silicon layers are not structured. For the separation, wet chemical processes or processes which destroy the substrate wafer are used. Applications in the photovoltaic field are not discussed.
The paper “Ultrathin crystalline silicon solar cells on glass substrates” by Rolf Brendel, Ralf B. Bergmann, Peter Lötgen, Michael Wolf and Jürgen H. Werner, which appeared in Appl. Phys. Lett. 70(3), Jan. 20, 1997, describes a possibility of manufacturing structured polycrystalline silicon layers which are suitable for use as photocells. The paper is, however, not concerned with single crystal material and requires a complex structuring of the glass substrate and also a complex contacting of the p- and n-layers in order to realize the photocell.
Further documents which are concerned with porous silicon for different purposes include publications from the Research Centre Jülich, which deal with the manufacture of lateral diffraction gratings on the basis of porous silicon and interference filters of porous silicon. The paper “Optical sensors based on porous silicon multi-layers: A prototype” by W. Thei&bgr;, R. Arens-Fischer, S. Hilbrich, D. Scheyen, M. G. Berger, M. Krüger, M. Thönissen, gives further information concerning the manufacture of porous silicon structures and possible applications of the so-produced structures. Thin layer silicon solar cells are moreover described in the publication “Crystalline thin film silicon solar cells by ion-assisted deposition” by S. Oelting, Dr. Martini and D. Bonnet. This publication appeared on the occasion of the “Twelfth European Photovoltaic Solar Energy Conference” from Apr. 11-15, 1994.
SUMMARY OF THE INVENTION
The object of the present invention is to propose a method of the initially named kind which overcomes the above-named problems and enables the manufacture of components, in particular, but not only, silicon solar cells at favorable cost, with high quality silicon, so far as possible single crystal silicon, for photovoltages and thin silicon layers for material saving, but simultaneously achieving enhanced light absorption while using low manufacturing temperatures and cost favorable foreign substrates. In particular a method is aimed at in which the substrate used can be reused, or in which a plurality of like structures can be produced at favorable cost.
It is also an object of the present invention to propose methods for the production of different novel substrates which form the starting point for the production of further structures by means of epitaxial methods. Moreover, it is an object of the present invention to provide a photocell and other semiconductor components using the method of the invention which can be manufactured at favorable cost and which have excellent technical characteristics.
For the solution of this object methodwise, provision is made in accordance with the invention that the surface of the substrate is structured prior to the production of the porous layer or that the surface of the porous layer is structured.
Since the surface of the porous layer is structured, the mechanical separation at the boundary surface to the layer-like structure can apparently be carried out better, without need to produce porous layers with two different porosities. However, not only a mechanical separation comes into question, but rather also other methods which will be explained in more detail later.
Particularly important are the savings of time, effort and material which can be achieved by the use of structured layers, and indeed in particular when the structuring is exploited in the final product. Since the porous layer has a corresponding surface structuring, the layer-like structure can be provided with the same structuring.
In the manufacture of thin components with structured surfaces, only thin layer-like structures need then be produced. If one, however, operates in accordance with the prior art, which aims at planar surfaces, it is first necessary to produce thicker layers which must then be structured in a complicated manner by the removal of material.
That is to say, using the method of the invention, the porous layer can be made relatively thin, preferably in the range of about 100 nm to 10&mgr;, so that relatively little material is lost and the working speed is improved, particularly since the once produced surface structuring of the substrate can be exploited for the manufacture of a plurality of identically structured layer-like structures.
When the s
Everhart Caridad
Malsawma Lex H.
Max-Planck-Gesellschaft zur Foerderung der Wissenschaften e. V.
Townsend and Townsend / and Crew LLP
LandOfFree
Method for producing layered structures on a substrate,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for producing layered structures on a substrate,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for producing layered structures on a substrate,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3154292