Two-Step Molybdenum Film Deposition for Uniform Nucleation
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Solution Overview
Problem
Existing methods for depositing molybdenum films on metal-containing substrates suffer from issues such as nucleation delays, non-uniform growth, and boron contamination, particularly at higher temperatures, which are unsuitable for next-generation semiconductor manufacturing.
Innovation Solution
A two-step thermal deposition process is employed, where a first elemental metal film is formed at temperatures less than or equal to 400°C, followed by a second molybdenum-containing film formed at higher temperatures, using specific precursors and reducing agents to achieve conformal and low-resistivity films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If molybdenum films are deposited at higher temperatures (>400°C) using H2 reduction of molybdenum halide or oxyhalide, then low-resistivity films can be achieved, but nucleation delays and scattered island growth occur on oxide and nitride surfaces
Solution Approach 1:
A thin elemental metal film (tungsten, molybdenum, ruthenium, cobalt, or their combinations) is deposited first on the substrate surface before depositing the molybdenum-containing film. This preliminary layer serves as a nucleation promotion layer that enables uniform molybdenum nucleation and growth, eliminating the scattered island growth and nucleation delays that occur when depositing directly on oxide and nitride surfaces at high temperatures.
2Manufacturing precision
If diborane is used to deposit boron as a nucleation layer, then nucleation can be improved, but boron contamination and nonuniform deposition occur
Solution Approach 1:
The harmful boron element is completely removed from the process by replacing diborane with elemental metal precursors (tungsten, molybdenum, ruthenium, or cobalt). These elemental metals serve as effective nucleation promotion layers without introducing contamination, thereby achieving both improved nucleation quality and elimination of harmful boron contamination.
3Productivity
If a single-step high-temperature deposition is used, then deposition speed can be increased, but film uniformity and compositional control deteriorate
Solution Approach 1:
The deposition process is divided into two distinct steps: (1) depositing a thin elemental metal film at lower temperature to prepare the surface, and (2) depositing the molybdenum-containing film at higher temperature. This segmentation allows each step to be optimized independently - the first step ensures uniform nucleation sites, while the second step achieves fast deposition with good uniformity and compositional control.
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 method enables the formation of conformal molybdenum-containing films with low resistivity, suitable for advanced semiconductor applications, overcoming nucleation delays and contamination issues.
Implementation Method 1
CVD is a chemical process whereby precursors are used to form a thin film on a substrate surface. In a typical CVD process, the precursors are passed over the surface of a substrate (e.g., a wafer) in a low pressure or ambient pressure reaction chamber. The precursors react and/or decompose on the substrate surface creating a thin film of deposited material.
Implementation Method 2
The second film includes a reaction product of a molybdenum-containing precursor with a reducing agent
Data Source
AI summary
Methods of forming molybdenum-containing films are provided. The methods include thermally depositing a first film on a surface of a substrate, for example, at a first temperature less than or equal to about 400° C., and thermally depositing the molybdenum-containing film (second film) on at least a portion of the first film, for example, at a second temperature of greater than about 400° C. The first film can include an elemental metal, for example, tungsten, molybdenum, ruthenium, or cobalt. The second film includes a reaction product of a molybdenum-containing precursor and a reducing agent.