Thin Film Transistor Side Wing Contacts Reduce Channel Length
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Solution Overview
Problem
Conventional thin film transistors with an etch stop layer (ESL) structure have a large channel length, which affects their performance due to overlay tolerance and resolution errors during the manufacturing process.
Innovation Solution
The design incorporates a thin film transistor structure with side wing contacts between the active layer and the source/drain electrodes, eliminating the need for contact holes on the ESL, thereby reducing channel length and improving ion current by using a single patterning process to form the active layer and ESL, and a similar process for the source and drain electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contact holes are formed on the ESL to connect the active layer and source/drain electrodes, then electrical connection is achieved, but the channel length becomes large due to overlay tolerance and resolution errors
Solution Approach 1:
The invention extracts the ESL from the contact region by designing the ESL pattern to exclude the contact hole areas. The ESL is formed only in regions where it is needed for etch stopping, while deliberately leaving openings in the contact regions. This allows contact holes to be formed directly down to the active layer without being constrained by the ESL, thereby reducing the channel length while maintaining the ESL's protective function in other areas.
Solution Approach 2:
The ESL pattern is segmented into multiple regions: regions where the ESL is present (for etch stop function) and regions where the ESL is absent (for contact holes). This segmentation is achieved through specific patterning processes that create the ESL only in certain areas, allowing the contact holes to bypass the ESL and directly reach the active layer, thus reducing the channel length.
2Device complexity
If a single patterning process is used to form the active layer and ESL, then manufacturing complexity is reduced, but manufacturing precision deteriorates due to resolution errors
Solution Approach 1:
The invention uses a preliminary patterning action where the active layer pattern is first formed, and then the ESL pattern is formed in a subsequent step using the same or different patterning process. The ESL pattern is designed to be formed after considering the active layer pattern, allowing the ESL to be precisely positioned relative to the active layer while using standard patterning processes. This preliminary action approach maintains manufacturing simplicity while achieving the required precision through careful process sequencing.
Data Source
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AI summary
A thin film transistor (TFT) according to the present disclosure may include an active layer, an etch stop layer (ESL), a source electrode and a drain electrode. The active layer may include at least one first active portion, a second active portion and a third active portion located on both sides of the first active portion and connected to the first active portion. The at least one first active portion may be overlaid by the ESL, and a longitudinal width of the at least one first active portion may be less than those/that of the second active portion and/or the third active portion. The second active portion and the third active portion may be overlaid by a horizontally-extending portion of the ESL on the first active portion. A side wing contact may be formed between the second active portion and one electrode of the source electrode and the drain electrode, and/or a side wing contact may be formed between the third active portion and the other electrode of the source electrode and the drain electrode.