N-type TFT Manufacturing via Grating Light Shielding
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Solution Overview
Problem
Conventional methods for manufacturing N-type thin-film transistors (TFTs) with lightly doped drain (LDD) structures are costly and time-consuming, requiring multiple masks and ion doping operations, and suffer from alignment deviations affecting homogeneity, while also being sensitive to poly-silicon grain size variations.
Innovation Solution
A method involving a light shielding layer with a grating-like patternization to create poly-silicon zones with varying grain sizes, allowing for a single ion doping operation to achieve equivalent LDD effects, reducing manufacturing time and cost by controlling electrical resistivity through grain size differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithographic process with multiple masks is used to form LDD structure, then heavily doped zones and lightly doped zones can be formed, but alignment deviation occurs and manufacturing cost increases
Solution Approach 1:
The light shielding layer is divided into multiple independent light shielding blocks with different widths, where each block corresponds to a different doping region. The first light shielding block has a first width for defining the heavily doped zone, while the second light shielding block has a second width for defining the lightly doped zone, eliminating the need for multiple masks and alignment steps
Solution Approach 2:
The light shielding layer is patterned into blocks of different widths before the doping process begins. This preliminary segmentation allows both the heavily doped zone and lightly doped zone to be defined in a single exposure step, preventing alignment deviation that would occur with sequential masking
2Reliability
If multiple ion doping operations are performed to create LDD structure, then desired doping profile is achieved, but manufacturing time increases
Solution Approach 1:
The light shielding layer is segmented into blocks with different widths that correspond to different doping regions. This allows a single ion doping operation to simultaneously create both the heavily doped zone (where the first light shielding block is present) and the lightly doped zone (where the second light shielding block is present), reducing manufacturing steps while maintaining doping profile control
Solution Approach 2:
Different regions of the poly-silicon layer receive different doping concentrations through the selective blocking of the light shielding blocks. The first region (heavily doped zone) and second region (lightly doped zone) are differentiated by the presence and width of light shielding blocks, enabling local quality variation in a single doping step
3Manufacturing precision
If light shielding layer is used for patternization, then doping regions can be defined, but manufacturing cost increases
Solution Approach 1:
The light shielding layer is segmented into multiple independent blocks with different widths during a single patternization process. This eliminates the need for multiple masks and alignment steps, reducing material costs and process complexity while maintaining precise definition of doping regions
Solution Approach 2:
The light shielding layer serves multiple functions: it defines both the heavily doped zone and lightly doped zone boundaries, acts as a protective layer during doping, and eliminates the need for separate masks. This multi-functionality reduces the total number of manufacturing steps and associated costs
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in an N-type TFT with reduced leakage current and improved reliability, facilitating the production of flexible display devices by saving manufacturing time and cost, and minimizing poly-silicon layer damage.
Implementation Method 1
providing a substrate, depositing a light shielding layer on the substrate, and subjecting the light shielding layer to patternization treatment
Implementation Method 2
subjecting the amorphous silicon layer to dehydrogenation treatment by applying an excimer laser annealing process to convert the amorphous silicon layer into a poly-silicon layer
Implementation Method 3
applying an excimer laser annealing process to convert the amorphous silicon layer into a poly-silicon layer
Implementation Method 4
performing one N-type light doping operation with the gate conductor layer 500 as a shielding layer so as to obtain N-type heavily doped zones 310, N-type lightly doped zones 320
Data Source
AI summary
The present invention provides a method for manufacturing the N-type TFT, which includes subjecting a light shielding layer to a grating like patternization treatment for controlling different zones of a poly-silicon layer to induce difference of crystallization so as to have different zones of the poly-silicon layer forming crystalline grains having different sizes, whereby through just one operation of ion doping, different zones of the poly-silicon layer have differences in electrical resistivity due to difference of grain size generated under the condition of identical doping concentration to provide an effect equivalent to an LDD structure for providing the TFT with a relatively low leakage current and improved reliability. Further, since only one operation of ion injection is involved, the manufacturing time and manufacturing cost can be saved, damages of the poly-silicon layer can be reduced, the activation time can be shortened, thereby facilitating the manufacture of flexible display devices.