Methods for forming laterally crystallized polysilicon and devices fabricated therefrom
AssigneeMan Wong, The Hong Kong University of Science & Technology
InventorsMan Wong, Tianfu Ma, Zhiguo Meng
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Abstract
The present invention provides a method for forming metal-induced laterally crystallized polysilicon in which the metal residue is reduced. A first low temperature lateral crystallization is performed using a metal crystallization-inducing agent such as nickel or a nickel compound. A second lateral crystallization is then carried out which may be either a low-temperature crystallization using metal residue from the first crystallization as the metal crystallization-inducing agent, or may be a high temperature crystallization that does not require a metal.
Claims14
1 A method of forming laterally-crystallised polysilicon, comprising the steps of:
- (a) providing a layer of amorphous silicon on a substrate,
- (b) providing a metallic crystallization-inducing agent to a part of said layer of amorphous silicon,
- (c) performing a metal-induced first lateral crystallization step at a temperature of between 400° C. and 650° C. to form first regions of metal-induced laterally crystallized polysilicon, and
- (d) performing a second lateral crystallization step to extend said regions of laterally crystallized polysilicon.
2 A method as claimed in claim 1 wherein the part of said layer of amorphous silicon to which said metallic crystallization-inducing agent is applied is removed prior to said second lateral crystallization stop.
3 A method as claimed in claim 2 wherein the second lateral crystallization step is carried out at a temperature of between 400° C. and 650° C.
4 A method as claimed in claim 1 or 2 wherein the second lateral crystallization step is carried out at a temperature of between 650° C. and 1200° C.
5 A method as claimed in claim 1 wherein in step (b) said the part of said amorphous layer is defined by forming a masking layer covering said layer of amorphous silicon except for said part.
6 A method as claimed in claim 5 wherein said metallic crystallization-inducing agent is provided by evaporation onto the surface of said masking layer and said part of the amorphous layer to which said agent is to be applied.
7 A method as claimed in claim 5 wherein said metallic crystallization-inducing agent is applied by ion implantation in said part of the amorphous layer.
8 A method as claimed in claim 1 wherein after step (d) a high-temperature anneal is performed.
9 A method as claimed in claim 1 wherein in step (b) said metallic crystallization-inducing agent comprises nickel, cobalt, palladium, platinum, titanium or combinations thereof or a compound containing one or more of these metals.
10 A method of forming laterally-crystallized polysilicon from amorphous silicon comprising a metal-induced first lateral crystallization step followed by a second lateral crystallization step.
11 A method as claimed in claim 10 wherein said metal-induced first lateral crystallization step is carded out at a temperature of between 400° C. and 650° C.
12 A method as claimed in claim 11 wherein said second lateral crystallization step is a metal-induced crystallization and is carried out at a temperature of between 400° C. and 650° C.
13 A method as claimed in claim 11 wherein said second lateral crystallization step is carried out at a temperature of between 650° C. and 1200° C.
14 A semiconductor device comprising polysilicon wherein said polysilicon is formed from amorphous silicon by performing a metal-induced first lateral crystallization step followed by a second lateral crystallization step.