Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Utility Patent
1998-08-28
2001-01-02
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S311000
Utility Patent
active
06168905
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for etching a multi-level terraced structure in a semiconductor substrate, especially to a method to prepare a multi-level terraced structure in a semiconductor substrate, using only one photomask and one etching step. This invention also discloses a photo mask suited for the etching method of this invention and the product therefrom.
BACKGROUND OF THE INVENTION
The multi-level structure is widely used in the fields of the optical system and the microelectromechanical system. Good examples include diffractive lens used in the micro optical system. In the conventional art, a multi-level structure is prepared with a “terraced” structure wherein a semiconductor substrate is burned-off with laser beams or etched in an etchant so that a terraced structure is prepared to function as a multi-level structure. Among the approaches in the preparation of the terraced structure, etching is welcome by the industry due to its relatively low preparation costs.
In the conventional art, a terraced or multi-level structure is prepared with a plurality of etching processes, using a plurality of photomasks. A first photomask is used to form a first etching mask prepared with a photoresist on the semiconductor substrate. After etching the substrate in an etchant, a two-level terrace is formed. Then a second photomask is used to form a second etching mask on the semiconductor substrate, whereby a four-level terrace is formed. And so on. After n etching processes, a 2
n
-level terrace is prepared. If the material of the substrate is silicon or germanium, the multi-level terraced structure may function as a diffractive lens for the infrared application.
As described above, in the conventional art, a plurality of photomasks and etching steps are used to prepare a multi-level terraced structure. This approach is not only labor, time and material consuming but also creates problems in the alignment of each photomasks. U.S. patent application Ser. No. 08/909,089 relates to “Diffractive leans and preparation method thereof”. In this invention disclosed is a method for the preparation of a multi-level terraced structure using one single photomask and one single etching step. According to this invention, the widths of the masked areas and their intervals of the pattern in the photomask are decided such that a multi-level terraced structure may be prepared with one single photomask under one single etching step and that the widths and heights of the levels of the terraced structure may be decided accordingly.
Although the above-said invention enables the preparation of a multi-level terraced structure with one single photomask and under one single etching step, the design of the pattern for the photomask requires complicated calculations. Many factors are taken for consideration so that a multi-level terraced structure with required widths and heights of all levels may be prepared.
it is thus a need in the industry to have a simplified etching method for multi-level terraced structures such that multi-level terraced structures with decided widths and heights of all levels may be prepared with one single photomask under one single etching step.
OBJECTIVES OF THE INVENTION
The objective of this invention is to provide a novel etching method for multi-level terraced structure whereby multi-level terraced structures with decided widths and heights of all levels may be prepared with one single photomask under one single etching step.
Another objective of this invention is to provide a simplified etching method for multi-level terraced structure whereby multi-level terraced structures with decided widths and heights of all levels may be prepared with one single photomask under one single etching step.
Another objective of this invention is to provide a photomask suited in the above-said etching method for multi-level terraced structure.
SUMMARY OF THE INVENTION
According to the etching method for multi-level terraced structure of this invention, a photomask with a plurality of regions is disclosed. Widths of the masked areas of the pattern on the photomask are so decided that the etching rate of the etchant to respective parts of the substrate may be controlled, whereby a multi-level terraced structure with decided widths and heights of all levels may be prepared with one single photomask under one single etching step. This invention also discloses the photomask used in the etching method and products prepared according to the etching method.
These and other objectives and advantages of this invention may be clearly understood from the detailed description by referring to the following drawings.
REFERENCES:
patent: 5866281 (1999-02-01), Guckel et al.
Vangbo, Mattias and Backlund, Ylva, Terracing of (100) Si with one mask and one etching step using misaligned V-grooves, Journal of Micromechanics and Microengineering, vol. 6, No. 1, p. 39-41, Mar. 1996.*
Chung Chen-Kuei
Lee Chien-Chih
Wu Ching-Yi
Bacon & Thomas
Huff Mark F.
Industrial Technology Research Institute
Mohamedulla Saleha R.
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