초록 ▼

A method is provided to optimize the channel characteristics of thin film transistors (TFTs) on polysilicon films. The method is well suited to the production of TFTs for use as drivers on liquid crystal display devices. Regions of polycrystalline silicon can be formed with different predominant cry

A method is provided to optimize the channel characteristics of thin film transistors (TFTs) on polysilicon films. The method is well suited to the production of TFTs for use as drivers on liquid crystal display devices. Regions of polycrystalline silicon can be formed with different predominant crystal orientations. These crystal orientations can be selected to match the desired TFT channel orientations for different areas of the device. The crystal orientations are selected by rotating a mask pattern to a different orientation for each desired crystal orientation. The mask is used in connection with lateral crystallization ELA processes to crystallize deposited amorphous silicon films.

대표청구항 ▼

1. A method of forming polycrystalline regions on a substrate comprising the steps of :a) directing a laser beam through a mask to irradiate the substrate; b) orienting the mask at an initial angle over an initial region on the substrate; c) annealing the initial region using a lateral crystallizati

1. A method of forming polycrystalline regions on a substrate comprising the steps of :a) directing a laser beam through a mask to irradiate the substrate; b) orienting the mask at an initial angle over an initial region on the substrate; c) annealing the initial region using a lateral crystallization process; d) reorienting the mask at a second angle over a second region on the substrate; and e) annealing the second region using a lateral crystallization process. 2. The method of claim 1, wherein the step of reorienting the mask to the second angle reorients the mask such that the second angle is substantially ninety degrees relative to the initial angle. 3. The method of claim 1, wherein the mask is mounted to a mask holder, which is rotatable, and the step of reorienting the mask is achieved by rotating the mask holder. 4. The method of claim 1, wherein the substrate is placed on a stage, which is rotatable, and the step of reorienting the mask is achieved by rotating the stage whereby the substrate is rotated relative to the mask. 5. The method of claim 1, wherein the mask is mounted to a mask holder, which is rotatable, and the substrate is mounted to a stage, which is rotatable, and the step of reorienting the mask is achieved by rotating the mask holder and the stage in combination. 6. A method of processing a substrate comprising the steps of:a) depositing amorphous silicon on a substrate; b) annealing a first region on the substrate using a lateral crystallization ELA process to form a first polycrystalline region having elongated grain structures with a first orientation; c) annealing a second region on the substrate using a lateral crystallization ELA process to form a second polycrystalline region having elongated grain structures with a secon d orientation, which is different from the first orientation; d) forming a first TFT having a channel oriented substantially parallel to the elongated grain structures of the first polycrystalline region; and e) forming a second TFT having a channel oriented substantially parallel to the elongated grain structures of the second polycrystalline region. 7. The method of claim 6, wherein the second orientation is substantially ninety degrees relative to the first orientation. 8. The method of claim 6, wherein the first orientation is produced by a mask pattern. 9. The method of claim 8, wherein the second orientation is produced by rotating the mask pattern. 10. The method of claim 9, wherein the mask is mounted to a mask holder, which is rotatable. 11. The method of claim 9, wherein the substrate is mounted to a stage, which is rotatable. 12. The method of claim 9, wherein the mask is mounted to a mask holder, which is rotatable, and the substrate is mounted to a stage, which is rotatable. 13. A method of processing an LCD substrate comprising the steps of:a) depositing amorphous silicon on a substrate; b) forming row drivers by annealing a first plurality of regions on the substrate using a lateral crystallization ELA process to form polycrystalline regions having elongated grain structures with a first orientation and forming a first plurality of TFT structures having channels oriented substantially parallel to the elongated grain structures with the first orientation; and c) forming column drivers by annealing a second plurality of regions on the substrate using a lateral crystallization ELA process to form polycrystalline regions having elongated grain structures with a second orientation, which is different from the first orientation and forming a seco nd plurality of TFT structures having a channel oriented substantially parallel to the elongated grain structures of the second polycrystalline region. 14. The method of claim 13, wherein the second orientation is substantially perpendicular to the first orientation. 15. The method of claim 13, further comprising forming a pixel region. 16. The method of claim 15, wherein the pixel region is formed by annealing a region on the substrate using a lateral crystallization ELA process to form polycrystalline regions having elongated grain structures with the first orientation. 17. The method of claim 15, wherein the pixel region is formed by annealing a region on the substrate using a lateral crystallization ELA process to form polycrystalline regions having elongated grain structures with the second orientation. 18. A liquid crystal display (LCD) device comprising:a) a transparent substrate; b) a layer of semiconductor material having polycrystalline regions overlying the transparent substrate, wherein at least two different predominant crystal orientation regions are present; c) a first set of thin film transistors having channels oriented substantially parallel to the predominant crystal orientation of a first polycrystalline region; and d) a second set of thin film transistors having channels oriented substantially parallel to the predominant crystal orientation of a second polycrystalline region. 19. The LCD device of claim 18, wherein the transparent substrate is quartz, glass or plastic. 20. The LCD device of claim 18, wherein the semiconductor material is silicon. 21. The LCD device of claim 18, wherein the first polycrystalline region and the second polycrystalline region have predominant crystal orientations substantially perpendicular to each other.