TiSix Contact Layer Formation on C-Containing Si Substrates
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Solution Overview
Problem
The challenge in forming a contact layer on semiconductor substrates, particularly those containing carbon, is that the reaction between the Ti film and the Si substrate is difficult, leading to increased resistance and limitations due to the narrowing diffusion layer with miniaturization, especially when using C-containing Si substrates.
Innovation Solution
A method involving the use of a film forming apparatus that converts Ti and Si source gases into plasma to form a TiSix film or react a Ti film with an Si film, forming a contact layer within the contact hole, independent of the substrate conditions, using specific gas flow rates, pressures, and temperatures to ensure low resistance and high reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Ti film is formed on the Si substrate and reaction is allowed to grow TiSix layer, then good ohmic contact is obtained on pure Si substrate, but on C-containing Si substrate the reaction becomes difficult and resistance increases
Solution Approach 1:
An Si film is formed on the substrate surface before forming the Ti film, preparing a reactive interface that ensures reliable TiSix layer formation regardless of substrate composition. This preliminary Si film deposition modifies the substrate surface to be more reactive with Ti, solving the compatibility issue with C-containing substrates.
Solution Approach 2:
The Si film acts as an intermediary layer between the substrate and Ti film, facilitating the reaction to form TiSix. This intermediate Si film mediates the interaction between Ti and the substrate, ensuring consistent reaction behavior whether the substrate is pure Si or C-containing Si.
2Reliability
If contact area is formed by reaction with base Si substrate, then good ohmic resistance is achieved, but with miniaturization the diffusion layer narrows and this method becomes limited
Solution Approach 1:
The Si film is deposited in advance on the substrate before Ti film formation, creating a controlled reactive layer that does not depend on the narrow diffusion layer. This preliminary action enables sufficient reaction area even when the substrate diffusion layer is narrowed due to miniaturization.
Solution Approach 2:
The method changes the reaction interface from substrate-based to film-based by introducing a deposited Si film. This parameter change in the reaction system allows the contact layer formation to proceed independently of the substrate diffusion layer dimensions, accommodating miniaturized device structures.
3Ease of manufacture
If Ti film reacts with C-containing Si substrate, then contact layer formation is attempted, but C is introduced into contact area and resistance increases
Solution Approach 1:
The Si film serves as an intermediary barrier that prevents direct contact between Ti and the C-containing substrate. This intermediate layer allows Ti to react with Si to form TiSix while blocking carbon atoms from migrating into the contact area, thereby eliminating carbon contamination.
Solution Approach 2:
The harmful carbon element is effectively extracted or isolated from the contact layer formation process by introducing the Si film intermediate. The Si film separates the Ti reaction zone from the carbon source in the substrate, removing the harmful effect of carbon introduction.
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 enables the formation of a contact layer with low impurity content and good ohmic contact, regardless of the substrate conditions, effectively addressing the resistance issues and miniaturization challenges in semiconductor devices.
Implementation Method 1
converting the Ti source gas, the reducing gas and an Si source gas into plasma to form a TiSix film on the substrate
Implementation Method 2
converting the Ti source gas, the reducing gas and an Si source gas into plasma to form a TiSix film on the substrate
Implementation Method 3
reacting the Ti film with the Si film, thereby forming a contact layer consisting of TiSix in the bottom of the contact hole
Data Source
AI summary
A method of forming a contact layer on a substrate having a contact hole to make a contact between the substrate and a buried metal material, includes disposing the substrate in a chamber, introducing a Ti source gas, a reducing gas and an Si source gas into the chamber, and converting the Ti source gas, the reducing gas and the Si source gas into plasma to form a TiSix film on the substrate. A portion of the TiSix film in a bottom of the contact hole corresponds to the contact layer.