Laser-irradiated thin films having variable thickness

Abstract

A crystalline film includes a first crystalline region having a first film thickness and a first crystalline grain structure; and a second crystalline region having a second film thickness and a second crystalline grain structure. The first film thickness is greater than the second film thickness and the first and second film thicknesses are selected to provide a crystalline region having the degree and orientation of crystallization that is desired for a device component.

1 . A device comprising:
 a plurality of thin film transistors (TFT), each TFT having a thin film active channel;   wherein at least a first TFT active channel has a first thickness and at least a second TFT active channel has a second thickness that is greater than the first thickness and the mobility of the second active channel is greater than the mobility of the first active channel.   
   
   
       2 . A device of  claim 1 , wherein the first TFT active channel comprises an active channel for an integration area TFT. 
   
   
       3 . A device of  claim 1 , wherein the second TFT active channel comprises an active channel for a pixel area TFT. 
   
   
       4 . A device of  claim 1 , wherein the film comprises a semiconductor material. 
   
   
       5 . A device of  claim 1 , wherein the first and/or second crystalline regions comprise a single crystal subregion having a dimension large enough to accommodate an active channel of a TFT. 
   
   
       6 . A system for processing a film comprising:
 a laser source capable of producing a pulsed laser beam;   one or more optical elements capable of generating a first laser beam and a second laser beam having different beam characteristics from the pulsed laser beam, wherein the first laser beam has a first energy density to melt a first region of a film to be crystallized to form a first crystalline region having a first grain structure and the second laser beam has a second energy density sufficient to melt a second region of the film to be crystallized to form a second crystallized region having a second grain structure, wherein the first energy density is greater than the second energy density;   a stage configured to support and position a film to be crystallized such that the first laser beam is directed to and irradiates a first portion of the stage and a second laser beam is directed to and irradiates a second portion of the stage; and   a computer for controlling the laser source, optical elements, and stage to facilitate the delivery of the first laser beam and the second laser beam to portions of the stage corresponding to first and second regions of a film to be crystallized.   
   
   
       7 . The system of  claim 6 , comprising a film positioned on the stage. 
   
   
       8 . The system of  claim 7 , wherein the first laser beam irradiates a first region of the film and the second laser beam irradiates a second region of the film. 
   
   
       9 . The system of  claim 8 , wherein the irradiations of the first region of the film and the second region of the film occur substantially at the same time. 
   
   
       10 . The system of  claim 8 , wherein the irradiations of the first region of the film and the second region of the film occur sequentially. 
   
   
       11 . The system of  claim 7 , wherein the first region has a first thickness and the second region has a second thickness. 
   
   
       12 . The system of  claim 11 , wherein the first thickness and the second thickness are different. 
   
   
       13 . The system of  claim 11 , wherein the first thickness is greater than the second thickness. 
   
   
       14 . The system of  claim 7 , wherein the film comprises a semiconductor material. 
   
   
       15 . The system of  claim 6  further comprising a first mask for masking the first laser beam and a second mask for masking the second laser beam. 
   
   
       16 . The system of  claim 15 , wherein the first mask and the second mask have the same masking configuration. 
   
   
       17 . The system of  claim 15 , wherein the first mask and the second mask have different masking configurations. 
   
   
       18 . The system of  claim 6 , wherein the optical element comprises a beam steering element to receive the pulsed laser beam and direct the pulsed laser beam along a first optical path generating the first laser beam and along a second optical path generating the second laser beam. 
   
   
       19 . The system of  claim 18 , wherein the beam steering element comprises a beam splitter. 
   
   
       20 . The system of  claim 18 , wherein the beam steering element comprises a mirror.