Ruthenium Thin Film Step Coverage via Segmented Gas Cycles
Solution Overview
Problem
The CVD method for forming thin films in semiconductor devices faces challenges with low temperature step coverage, leading to impurities like carbon and hydrogen, oxidation of Ru films, and poor productivity due to high temperature processing and incubation time issues.
Innovation Solution
A semiconductor device manufacturing method involving alternating cycles of material gas adsorption and reaction with non-oxygen containing gases in the initial film forming step, followed by oxygen-containing gas reactions in the main film forming step, using ALD and CVD techniques to improve step coverage and adhesion, while minimizing impurities and oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If low temperature CVD method is used to improve step coverage, then step coverage is improved, but impurities such as carbon and hydrogen remain in the film causing electrical characteristics to deteriorate
Solution Approach 1:
The film formation process is segmented into two distinct stages: initial film formation at low temperature using non-oxygen-containing reaction gas to ensure good step coverage, followed by main film formation at higher temperature using oxygen-containing reaction gas to purify the film and improve electrical characteristics. This segmentation allows each stage to optimize for its specific purpose without compromise.
Solution Approach 2:
The initial film formation step performs a preliminary action by forming a base film with good step coverage using non-oxygen-containing gas at low temperature. This preliminary film serves as a foundation that is subsequently improved by the main film formation step, which removes impurities and enhances electrical properties through oxygen-containing gas treatment.
2Reliability
If high temperature heat treatment is applied to remove impurities and crystallize the film, then film quality is improved, but oxygen atoms diffuse into the metallic film causing oxidation and high resistance
Solution Approach 1:
The reaction gas composition is changed as a critical parameter between two formation stages. Non-oxygen-containing reaction gas is used in the initial stage to prevent oxidation, while oxygen-containing reaction gas is introduced in the main formation stage to purify the film. This parameter change allows the system to achieve film quality improvement without causing metallic film oxidation.
Solution Approach 2:
The initial film formation is performed in an inert atmosphere using non-oxygen-containing reaction gas, which prevents oxidation of the metallic film. This inert environment protects the metallic film from oxygen diffusion while still allowing impurity removal and crystallization to occur through the subsequent main film formation stage with controlled oxygen introduction.
3Reliability
If high temperature processing is used to remove impurities, then impurity removal is improved, but film shrinkage occurs causing surface irregularities and peeling
Solution Approach 1:
The film formation is segmented into initial and main stages with different temperature and gas conditions. The initial stage at lower temperature with non-oxygen-containing gas forms a stable base film with good adhesion. The main stage then performs aggressive impurity removal at higher temperature with oxygen-containing gas, but the previously formed stable base film prevents shrinkage-induced peeling and surface irregularities.
4Reliability
If extended incubation time is provided for Ru materials, then film formation is achieved, but productivity decreases
Solution Approach 1:
The film formation process maintains continuous useful action by performing both initial and main film formation in a single sequential operation without interruption or intermediate steps. The initial film formation quickly establishes a base layer, and the main film formation immediately follows to complete the high-quality film, eliminating idle incubation time while ensuring complete film formation.
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
This approach enhances step coverage, adhesion properties, and productivity by reducing impurities and oxidation, thereby improving film quality and yield.
Implementation Method 1
a step of supplying a material gas into the processing chamber to adsorb the material gas on the substrate
Implementation Method 2
a step of supplying a first reaction gas not containing oxygen atoms into the processing chamber to cause a reaction with the material gas adsorbed on the substrate in order to form a thin film on the substrate
Data Source
AI summary
Productivity and product yield, as well as the step coverage and the adhesion are improved. A film forming process includes an initial film forming step, and a main film forming step. In the initial film forming step, a step of supplying a material gas into a processing chamber to adsorb the material gas on the substrate, and a step of supplying a first reaction gas not containing oxygen atoms into the processing chamber to cause a reaction with the material gas adsorbed on the substrate in order to from a thin film on the substrate, are repeated multiple cycles to form the thin film with the specified thickness on the substrate. In the main film forming step, a step of supplying a material gas into the processing chamber to adsorb the material gas on the substrate, and a step of supplying a second reaction gas containing oxygen atoms into the processing chamber to cause a reaction with the material gas adsorbed on the substrate in order to form a thin film on the substrate, are repeated multiple cycles, to form the thin film with a specified thickness on the thin film that was formed on the substrate in the initial film forming step.