Oxide Semiconductor TFT Pixel Electrode Contact Hole Design
Solution Overview
Problem
The voltage applied to the pixel electrode in oxide semiconductor TFTs can influence the channel region, leading to variations in the threshold voltage of the TFT, making the TFT characteristics unstable.
Innovation Solution
A semiconductor device with a thin film transistor structure where the pixel electrode is arranged not to overlap the channel region, with a contact hole design that exposes a portion of the metal oxide layer to the pixel electrode, allowing it to contact only the drain contact region, thereby isolating the channel region from the pixel electrode's voltage influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the pixel electrode is arranged to be in direct contact with the oxide semiconductor layer (as in Patent Document No. 1), then the manufacturing process is simplified and the pixel aperture ratio can be increased, but the voltage applied to the pixel electrode influences the channel region causing threshold voltage variations and unstable TFT characteristics
Solution Approach 1:
The oxide semiconductor layer is segmented into distinct functional regions: a channel formation region and a drain contact region. The pixel electrode is configured to contact only the drain contact region through a contact hole, while being spatially separated from the channel formation region. This segmentation prevents voltage influence from the pixel electrode from affecting the channel region, thereby stabilizing TFT characteristics while maintaining direct contact configuration benefits.
Solution Approach 2:
Different regions of the oxide semiconductor layer are assigned different functional qualities: the channel formation region is optimized for charge transport with specific thickness and material properties, while the drain contact region is optimized for electrical contact with the pixel electrode. This local differentiation allows the pixel electrode to contact the semiconductor layer directly at the drain region without causing voltage-induced threshold shifts in the channel region.
2Area of moving object
If the pixel electrode overlaps the channel region, then the pixel aperture ratio can be increased, but the voltage from the pixel electrode influences the channel region causing threshold voltage variations
Solution Approach 1:
The oxide semiconductor layer is divided into a channel formation region and a drain contact region. The pixel electrode contacts only the drain contact region through a contact hole, creating spatial separation between the electrode and the channel formation region. This segmentation enables the pixel aperture ratio to be maximized while preventing voltage influence from affecting the channel region, thus maintaining threshold voltage stability.
Solution Approach 2:
The contact between the pixel electrode and oxide semiconductor layer is achieved through a contact hole in the vertical dimension, while maintaining horizontal spatial separation between the electrode and channel region. This dimensional approach allows the pixel electrode to extend over the pixel region for high aperture ratio while the contact hole provides selective vertical access only to the drain contact region, preventing lateral voltage influence on the channel.
Data Source
AI summary
A semiconductor device includes a TFT (101), the TFT including a gate electrode (12), a gate insulating layer (14) covering the gate electrode, a metal oxide layer (16A) including a channel region (16c), a source contact region (16s) and a drain contact region (16d), a first electrode (18A) in contact with the source contact region, an insulating layer (22) formed on the metal oxide layer and the first electrode, the insulating layer having a first opening (22p) therein through which a portion of the metal oxide layer is exposed, and a light-transmissive second electrode (24) formed on the insulating layer and in a contact hole including the first opening, wherein the second electrode (24) is in contact with the drain contact region (16d) in the contact hole, the drain contact region (16d) is a portion of a region (17) of the metal oxide layer (16A) that is exposed through the contact hole, and as seen from a direction normal to a substrate (11), the second electrode (24) does not overlap the channel region (16c).