Semiconductor Device with Segmented Heat Treatment for Oxide Transistors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor devices using oxide semiconductor transistors face challenges in achieving stable resistance reduction of source and drain regions and purification of the channel formation region, leading to normally-on characteristics due to impurities like water or hydrogen.
Innovation Solution
A semiconductor device structure is developed with a specific layer configuration and insulating layers containing nitrogen and metal elements, along with a self-aligned sidewall insulating layer, to reduce the resistance of source and drain regions and purify the channel formation region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is performed in an oxygen atmosphere to reduce resistance of source and drain regions, then the resistance is reduced, but the channel formation region becomes contaminated with impurities causing normally-on characteristics
Solution Approach 1:
The patent divides the heating process into two distinct stages: first heating the metal film to form alloy regions at source and drain without oxygen exposure, then separately heating the oxide semiconductor film in oxygen atmosphere to reduce resistance. This segmentation prevents impurity diffusion into the channel region while still achieving the desired resistance reduction.
Solution Approach 2:
The patent performs preliminary heating of the metal film before the oxide semiconductor film to create alloy regions with reduced resistance. This preliminary action is taken before the oxygen exposure step, ensuring that the metal film structure is established first, then oxygen is supplied to reduce resistance without causing impurity contamination.
2Reliability
If metal film is formed over source and drain regions to reduce resistance, then resistance is reduced, but the metal film extracts oxygen from the oxide semiconductor film causing degradation
Solution Approach 1:
The patent forms the metal film and performs preliminary heating to create alloy regions before supplying oxygen to the oxide semiconductor film. This sequence ensures that the metal film is already in place to serve as a resistance-reducing element without extracting oxygen, as oxygen is supplied after the metal film formation.
Solution Approach 2:
The patent changes the temperature parameter during different process steps: first heating to form alloy regions at lower temperature, then heating at higher temperature in oxygen atmosphere to reduce resistance. This parameter change sequence prevents oxygen extraction while achieving resistance reduction.
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
The proposed solution enables the creation of semiconductor devices with favorable electrical characteristics, allowing for miniaturization, high integration, and high productivity, while preventing diffusion of impurities and maintaining low off-state current.
Implementation Method 1
heat treatment is performed on the metal film in an oxygen atmosphere. By performing the heat treatment, a constituent element of the metal film enters the source region and the drain region of an oxide semiconductor film as a dopant, whereby the resistance is reduced.
Implementation Method 2
purification of the channel formation region (a reduction in impurities such as water or hydrogen, typically dehydration or dehydrogenation) is not performed
Implementation Method 3
By performing the heat treatment in an oxygen atmosphere, the conductive film is oxidized, whereby the resistance of the conductive film is increased.
Implementation Method 4
a transistor using an oxide semiconductor (Oxide Semiconductor transistor; hereinafter referred to as an OS transistor) has an extremely low leakage current in an off state
Data Source
AI summary
A semiconductor device that can be highly integrated is provided.The semiconductor device includes a semiconductor layer, a first insulating layer, a second insulating layer, a third insulating layer, and a first conductive layer. The third insulating layer is positioned over the semiconductor layer and includes a first opening over the semiconductor layer. The first conductive layer is positioned over the semiconductor layer, the first insulating layer is positioned between the first conductive layer and the semiconductor layer, and the second insulating layer is provided in a position that is in contact with a side surface of the first opening, the semiconductor layer, and the first insulating layer. The semiconductor layer includes a first portion overlapping with the first insulating layer, a pair of second portions between which the first portion is sandwiched and which overlap with the second insulating layer, and a pair of third portions between which the first portion and the pair of second portions are sandwiched and which overlap with neither the first insulating layer nor the second insulating layer. The first portion has a smaller width than the first opening and has a thinner shape of the semiconductor layer than the second portions, and the second portions have a thinner shape of the semiconductor layer than the third portions.