Copper Wiring Barrier Structure for Stable Semiconductor Transistors
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Solution Overview
Problem
The processing of copper, aluminum, gold, silver, and molybdenum in semiconductor wiring is difficult, leading to diffusion into semiconductor films, causing impurities and poor electrical characteristics in transistors, such as increased resistance and threshold voltage variations.
Innovation Solution
A semiconductor device design featuring a stacked-layer structure of protective and conductive films, where the second protective films are positioned outside the conductive films, reducing exposure to plasma and preventing diffusion of metal elements into the semiconductor film, and using materials like titanium, tantalum, or their nitrides for the protective films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper, aluminum, gold, silver, or molybdenum is used as wiring material, then electrical conductivity is improved, but the metal elements diffuse into the semiconductor film causing impurity contamination
Solution Approach 1:
A protective film is introduced as an intermediary layer between the conductive film containing copper, aluminum, gold, silver, or molybdenum and the semiconductor film. This protective film prevents direct contact and diffusion of metal elements into the semiconductor film, thereby eliminating impurity contamination while maintaining the electrical conductivity benefits of the conductive materials.
Solution Approach 2:
The electrode structure is segmented into multiple distinct layers: a conductive film for electrical conductivity and a separate protective film for preventing diffusion. This segmentation allows each layer to perform its specific function independently, with the conductive film providing low resistance and the protective film acting as a diffusion barrier.
2Object-generated harmful factors
If protective films are added to prevent metal diffusion, then impurity concentration is reduced, but device structure becomes more complex
Solution Approach 1:
The protective film serves multiple functions simultaneously: it acts as a diffusion barrier to prevent metal element contamination, serves as an etching mask during fabrication processes, and provides structural support. This multi-functionality reduces the need for additional separate components, thereby minimizing the increase in device complexity.
Solution Approach 2:
The protective film is integrated directly with the conductive film in a stacked configuration, merging the electrical conduction function and the protective function into a unified electrode structure. This integration streamlines the overall device architecture while achieving both conductivity and contamination prevention.
Data Source
AI summary
The stability of steps of processing a wiring formed using copper or the like is increased. The concentration of impurities in a semiconductor film is reduced. Electrical characteristics of a semiconductor device are improved. A semiconductor device includes a semiconductor film, a pair of first protective films in contact with the semiconductor film, a pair of conductive films containing copper or the like in contact with the pair of first protective films, a pair of second protective films in contact with the pair of conductive films on the side opposite the pair of first protective films, a gate insulating film in contact with the semiconductor film, and a gate electrode overlapping with the semiconductor film with the gate insulating film therebetween. In a cross section, side surfaces of the pair of second protective films are located on the outer side of side surfaces of the pair of conductive films.