Crystallization and doping of amorphous silicon on low temperature plastic
First Claim
1. A method for improving the crystallinity of a thin film of amorphous silicon directly deposited on a low temperature plastic substrate incapable of withstanding sustained processing temperatures higher than about 180°
- C. and sustained processing time periods longer than about 105 nanoseconds, comprising the steps of;
positioning the deposited thin film in a controlled atmosphere; and
applying at least one pulse from a pulsed high energy source onto the thin film for a time period sufficient to change the crystallinity of the thin film without heating the substrate above a temperature of about 180°
C. for more than about 105 nanoseconds.
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Abstract
A method or process of crystallizing and doping amorphous silicon (a-Si) on a low-temperature plastic substrate using a short pulsed high energy source in a selected environment, without heat propagation and build-up in the substrate. The pulsed energy processing of the a-Si in a selected environment, such as BF3 and PF5, will form a doped micro-crystalline or poly-crystalline silicon (pc-Si) region or junction point with improved mobilities, lifetimes and drift and diffusion lengths and with reduced resistivity. The advantage of this method or process is that it provides for high energy materials processing on low cost, low temperature, transparent plastic substrates. Using pulsed laser processing a high (>900° C.), localized processing temperature can be achieved in thin films, with little accompanying temperature rise in the substrate, since substrate temperatures do not exceed 180° C. for more than a few microseconds. This method enables use of plastics incapable of withstanding sustained processing temperatures (higher than 180° C.) but which are much lower cost, have high tolerance to ultraviolet light, have high strength and good transparency, compared to higher temperature plastics such as polyimide.
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Citations
24 Claims
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1. A method for improving the crystallinity of a thin film of amorphous silicon directly deposited on a low temperature plastic substrate incapable of withstanding sustained processing temperatures higher than about 180°
- C. and sustained processing time periods longer than about 105 nanoseconds, comprising the steps of;
positioning the deposited thin film in a controlled atmosphere; and applying at least one pulse from a pulsed high energy source onto the thin film for a time period sufficient to change the crystallinity of the thin film without heating the substrate above a temperature of about 180°
C. for more than about 105 nanoseconds. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
- C. and sustained processing time periods longer than about 105 nanoseconds, comprising the steps of;
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20. A process for producing at least one region of doped polycrystalline or micro-crystalline silicon in a thin film of amorphous silicon deposited on a substrate composed of commercial-grade plastic incapable of withstanding processing;
- temperatures of higher than 180°
C. for longer than about 35 nanoseconds, comprising the steps of;forming the substrate from material selected from the group of E-CTFE, E-TFE, PES, PVDF, PTFE, FEP, and HDPE; depositing a thin film of amorphous silicon on the substrate; positioning the thus formed structure in a controlled environment selected from the group of vacuum (<
1 mT), 50 torr BF3, and 50 torr PF5 ; anddirecting at least one pulse of 308 nm light from a XeCl laser onto the thin film of amorphous silicon for providing irradiation energy in the range of about 150 mJ cm-2 to about 800 mJ cm-2. - View Dependent Claims (21, 22, 23, 24)
- temperatures of higher than 180°
Specification