Underlying Metal Film Composition for Semiconductor Interconnects
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Solution Overview
Problem
Semiconductor devices require materials for gate electrodes and interconnects that balance high melting point with low resistance, but tungsten and molybdenum, commonly investigated for these applications, have higher bulk resistivity compared to copper, which is typically used for low-resistance interconnects.
Innovation Solution
The use of tantalum-aluminum, tungsten-zirconium, tungsten-titanium, and tungsten films as underlying metal films, with specific composition ranges and crystal orientations, to form metal films that have lower specific resistance and suitable melting points for semiconductor memory devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If tungsten or molybdenum is used for gate electrode or interconnect, then high melting point is achieved, but bulk resistivity increases compared to copper
Solution Approach 1:
The patent uses composite material structures including tungsten-zirconium alloy films, tungsten-titanium alloy films, and multi-layer combinations (e.g., tungsten barrier film with molybdenum interconnect film). These composite structures allow optimization of both melting point and resistivity by combining materials with complementary properties, achieving lower resistivity than pure tungsten/molybdenum while maintaining high melting points suitable for semiconductor processing.
Solution Approach 2:
The patent systematically varies composition parameters (e.g., zirconium content of 1-20 at%, titanium content of 1-50 at%, aluminum content of 50-85 at%) and crystal orientation parameters ((100), (110), or (111) orientation) to optimize the balance between melting point and resistivity. By controlling these parameters, the invention achieves specific resistance values lower than conventional tungsten/molybdenum while maintaining sufficient melting points for memory device fabrication.
2Reliability
If copper is used for low-resistance interconnect, then resistivity is reduced, but melting point becomes insufficient for high-temperature processing
Solution Approach 1:
The patent introduces tungsten barrier films and tungsten-zirconium/tungsten-titanium alloy films as intermediary layers between copper interconnects and surrounding structures. These intermediary layers have high melting points that protect the copper from diffusion and degradation during high-temperature processing, while the copper core maintains low resistivity for electrical performance.
Solution Approach 2:
The invention creates composite interconnect structures combining copper (for low resistivity) with tungsten-based barrier and capping layers (for high melting point). This multi-material composite approach allows simultaneous achievement of copper's electrical advantages and tungsten's thermal stability, solving the contradiction between low resistivity and high melting point requirements.
Data Source
AI summary
According to one embodiment, a semiconductor device includes an underlying metal film and a metal film. The underlying metal film is a tantalum-aluminum film having an aluminum content of more than 50 atomic % and less than 85 atomic %, a tungsten-zirconium film having a zirconium content of less than 40 atomic %, a tungsten-titanium film having a titanium content of less than 80 atomic %, or a tungsten film. The metal film is provided on the underlying metal film and in contact with the underlying metal film. The metal film contains at least one of tungsten and molybdenum, and has a main orientation of (100) or (111).