Oxide Semiconductor Transistor Resistance and Channel Purification
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Solution Overview
Problem
Existing semiconductor devices using oxide semiconductors face challenges in achieving stable resistance reduction of source and drain regions and purification of the channel formation region, leading to normally-on transistor characteristics and limitations in miniaturization, integration, productivity, data retention, and power consumption.
Innovation Solution
A semiconductor device with a channel formation region using an oxide semiconductor, featuring a transistor structure with specific insulator and conductor layers, and a manufacturing method that includes heat treatment in a nitrogen atmosphere to reduce resistance and purify the channel region, incorporating metal elements and impurities to form regions with varying carrier densities and hydrogen concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment is performed in an oxygen atmosphere to reduce source and drain resistance, then resistance reduction is achieved, but the channel formation region becomes contaminated and transistor exhibits normally-on characteristics
Solution Approach 1:
The heat treatment process is segmented into two distinct stages: first performing resistance reduction heat treatment in a nitrogen atmosphere to avoid contamination, then performing separate purification heat treatment in an oxygen atmosphere. This segmentation allows each treatment to be optimized independently without interfering with the other, resolving the contradiction between resistance reduction and channel purity.
Solution Approach 2:
The resistance reduction heat treatment is performed as a preliminary action before the purification heat treatment. By first reducing the resistance of source and drain regions in a nitrogen atmosphere, then subsequently purifying the channel formation region in an oxygen atmosphere, the process ensures that the channel is purified after any potential contamination has occurred, thereby achieving both goals.
2Reliability
If metal film heat treatment is performed to reduce source and drain resistance, then resistance is reduced, but transistor miniaturization and integration are limited
Solution Approach 1:
The invention changes the atmospheric parameter from oxygen to nitrogen during the resistance reduction heat treatment step. This parameter change allows for effective resistance reduction without the harmful side effects that limit miniaturization, enabling smaller and more integrated transistor designs while maintaining reliable electrical characteristics.
3Reliability
If dopant is introduced through metal film to reduce source and drain resistance, then resistance is reduced, but manufacturing complexity increases
Solution Approach 1:
The invention extracts the dopant introduction function from the metal film heat treatment process. Instead of relying on metal film to serve as both a resistance-reducing layer and a dopant source, the process separates these functions: the metal film is removed after initial resistance reduction, and dopant introduction is performed separately through ion implantation or other dedicated doping methods, thereby simplifying the overall manufacturing process.
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 solution enables semiconductor devices with favorable electrical characteristics, miniaturization, high integration, long data retention, high-speed data writing, reduced power consumption, and improved design flexibility by stabilizing resistance and purifying the channel region.
Implementation Method 1
heat treatment is performed on the metal film so that the resistance of the metal film is increased and the resistance of the source region and the drain region is reduced
Implementation Method 2
a metal film is formed over a source region and a drain region and heat treatment is performed on the metal film so that the resistance of the metal film is increased and the resistance of the source region and the drain region is reduced
Data Source
AI summary
A semiconductor device that can be highly integrated is provided. The semiconductor device includes a transistor, an interlayer film, and a first conductor. The transistor includes an oxide over a first insulator; a second conductor over the oxide; a second insulator provided between the oxide and the second conductor and in contact with a side surface of the second conductor; and a third insulator provided for the side surface of the second conductor with the second insulator therebetween. The oxide includes a first region, a second region, and a third region. The first region overlaps with the second conductor. The second region is provided between the first region and the third region. The third region has a lower resistance than the second region. The second region has a lower resistance than the first region. The interlayer film is provided over the first insulator and the oxide. The first conductor is electrically connected to the third region. The third region overlaps with one of the third insulator, the first conductor, and the interlayer film. A top surface of the third insulator is level with a top surface of the interlayer film.