Semiconductor device manufacturing: process – Chemical etching – Liquid phase etching
Reexamination Certificate
2000-12-15
2004-10-12
Chen, Kin-Chan (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Liquid phase etching
C438S746000, C205S157000, C205S640000
Reexamination Certificate
active
06803322
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to alloy-semiconductor radiation detectors with rectifying junction contacts, the formation of rectifying junction contacts on alloy-semiconductors using photo-electrochemical etching, the use of such alloy-semiconductor devices with rectifying junction contacts in PIN ionization detector devices, and systems and methods for revealing surface morphology of such alloy-semiconductors.
2. Description of the Related Art
Several methods have been developed for the external formation of P- and N-type contacts on CdTe and CdZnTe for Positive-Intermediate-Negative (PIN) devices. For example, X. Li, et al., “Effect of nitric-phosphoric acid etches on material properties and back-contact formation of CdTe-based solar cells,”
Journal of Vacuum Science Technology A
, 17(3), May/June, 1999; R. Sudharsanan et al., “Fabrication and characterization of CdZnTe radiation detectors with a new P-I-N design,” presented at the 1996 U.S. Workshop on the Physics and Chemistry of II-VI Materials, 1996; A. Khusainov et al., “Performance of a high resolution CdTe and CdZnTe P-I-N detectors,”
Nuclear Instruments and Methods in Physics Research A
, 380, 245-251, 1996; T. Narita et al., “Development of prototype pixellated PIN CdZnTe detectors,” Proceeding of the SPIE, 3446, 1998; S. U. Egarievwe et al., Proceeding of SPIE, 3768, 1999; T Narita et al., “Development of IMARAD CZT detectors with PIN contacts,” Proceeding of SPIE, 3768, 1999; M. Niraula et al., “Fabrication of CdTe detectors in a P-I-N design for gamma-ray spectroscopy,” Proceeding of SPIE, 3768, 1999; M. Niraula et al., “Fabrication and performance of P-I-N CdTe radiation detectors,”
Nuclear Instruments and Methods in Physics Research A
, 436, 132-137, 1999; and T. Takahashi et al., “High-resolution Schottky CdTe diode for hard X-ray and gamma-ray astronomy,”
Nuclear Instruments and Methods in Physics Research A
, 436, 111-119, 1999, all describe various methods for forming an external P-type and/or N-type contacts on CdTe and CdZnTe for PIN semiconductor devices.
However, all these methods suffer from several shortcomings. First, these conventional methods all involve sophisticated vacuum deposition equipment. This necessarily entails that production of semiconductor devices using such methods are expensive and difficult. Second, these conventional methods also require high temperature heating during formation of the contacts, which heating can cause degradation of semiconductor's material properties. Third, because the metal used in the metal deposition process may be impure, the semiconductor device can become contaminated during the metal deposition process. Fourth, it is possible that the interface between the deposited metal and semiconductor device may have an oxide layer that can degrade device performance. Thus, there remains a need for an improved system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices. There also remains a need for a PIN ionization detector device utilizing such alloy-semiconductor devices with rectifying junction contacts. Further, there remains a need for an efficient and inexpensive method for revealing surface morphology of alloy-semiconductors. These advantages have been obtained with the present invention.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a more efficient system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices using photo-electrochemical, etching.
It is another object of the present invention to provide a more efficient system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices in which there is no external contamination arising from impurities in the metal being deposited.
It is a further object of the present invention to provide a more efficient system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices in which there is no oxide layer to degrade device performance.
It is still another object of the present invention to provide a more efficient system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices, which method employs a room temperature process.
It is another object of the present invention to provide a more efficient system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices in which fine contacts are produced easily.
It is a further object of the present invention to provide a more efficient system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices in which there is lower leakage between adjacent contacts because the etch is recessed.
It is still another object of the present invention to provide a more efficient system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices in which higher internal electric fields are possible, thereby improving charge collection.
It is another object of the present invention to provide a more efficient system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices in which there is lower leakage current, producing an improved detector.
It is a further object of the present invention to provide a more efficient system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices which results in lower production costs.
It is still another object of the present invention to provide a method for revealing surface morphology of alloy-semiconductors.
It is a further object of the present invention to provide a method for revealing surface morphology of such alloy-semiconductors such that high yields of single crystalline material can be obtained.
It is still another object of the present invention to provide a method for revealing surface morphology of such alloy-semiconductor which provides for visual mapping of the areas of maximum electron transport, which is closely related to good charge collection within a detector.
These objects, among others, have been obtained by means of a more efficient system and method for forming rectifying junction contacts in PIN alloy-semiconductor devices using photo-electrochemical etching. The present invention provides a means of creating rectifying junction contacts on alloy-semiconductor devices such as CdTe and CdZnTe, among others. In addition, the present invention also provides a simple and low cost method for revealing wafer surface morphology of alloy-semiconductors, thus providing an efficient and effective means for selecting single grain semiconductor substrates. Further, the present invention provides nuclear detectors employing such alloy-semiconductor devices having improved rectifying junctions as the detector element.
REFERENCES:
patent: 4369099 (1983-01-01), Kohl et al.
patent: 4710589 (1987-12-01), Meyers et al.
patent: 5320736 (1994-06-01), Stickney et al.
patent: 5338416 (1994-08-01), Mlcak et al.
patent: 5401986 (1995-03-01), Cockrum et al.
patent: 5578502 (1996-11-01), Albright et al.
X. Li et al., “Effect of Nitric-Phosphoric Acid Etches on Material Properties and Back-Contact Formation of CdTe-Based Solar Cells,” Journal of Vaccuum Science Technology A, 17(3), May/Jun., 1999.
R. Sudharsanan et al., “Fabrication and Characterization of CdZnTe Radiation Detectors with a New P-I-N Design,” presented at the 1996 U.S. Workshop on Physics and Chemistry of II-VI Materials, Oct., 1996.
A. Khusainov et al., “Performance of a High Resolution CdTe and CdZnTe P-I-N Detectors,” Nuclear Instruments and Methods in Physics Research A, 380, 245-251, Oct., 1996.
T. Narita et al., “Development of Prototype Pixellated PIN CdZnTe Detectors,” Proceeding of SPIE, 3446, Jul., 1998.
S.U. Egarievweet al., “Study of Au/CdZnTe/CdS m-i-n detectors fabricated by sputtering technique,” Proceeding of SPIE, 3768, Jul., 1999.
T. Narita et al., “Development of IMARAD CZT Detectors with PIN Contacts,” Proceeding of SPIE, 3768, Jul., 1999.
M. Niraula et
Chen Kuo-Tong
Polichar Raulf M.
Chen Kin-Chan
Kilpatrick Strockton LLP
Science Applications International Corporation
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