Semiconductor Contact Plug With Barrier Layer For Copper Silicide Prevention
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Solution Overview
Problem
The reliability of semiconductor devices using copper contacts is compromised due to the risk of copper silicide formation, which can lead to voids or disconnection in the contact plug, especially when Ta and/or TaN barrier layers are insufficient in thickness.
Innovation Solution
A semiconductor device and method that incorporates a first contact plug with a Ti and/or TiN barrier layer and a tungsten layer on source and drain regions, and a second contact plug with a Ta and/or TaN barrier layer and a conductive layer, such as copper, on both the metal gate and the first contact plug, to reduce the likelihood of reaction between the conductive layer and the metal silicide, enhancing device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper contact plug is used to reduce contact resistance, then the electrical performance is improved, but the reliability deteriorates due to copper silicide formation causing voids or disconnection
Solution Approach 1:
The patent introduces a barrier layer (Ta or TaN) between the copper contact plug and the metal silicide layer. This intermediary layer prevents direct contact between copper and metal silicide, thereby preventing copper silicide formation while maintaining low contact resistance. The barrier layer acts as a mediator that allows electrical connection without harmful chemical reactions.
Solution Approach 2:
The contact structure uses a composite material approach by combining multiple layers with different properties: copper for high conductivity, Ta/TaN for barrier properties, and metal silicide for adhesion and contact properties. This composite structure leverages the strengths of each material while mitigating their individual weaknesses.
2Device complexity
If the barrier layer thickness is reduced to minimize process complexity, then the manufacturing precision is improved, but the protective function deteriorates as it can hardly achieve effective separation
Solution Approach 1:
The patent optimizes the barrier layer thickness parameter to achieve the minimum effective thickness that provides sufficient protection against copper diffusion while maintaining process simplicity. By carefully controlling this parameter, the patent balances protective function with manufacturing ease.
Solution Approach 2:
The barrier layer is applied selectively only where copper contacts may occur (at the interface with metal silicide), rather than uniformly throughout the entire structure. This localized application provides protection exactly where needed while minimizing overall process complexity and material usage.
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 configuration reduces the risk of reaction between the conductive layer and the metal silicide, thereby enhancing the reliability and performance of the semiconductor device by sandwiching the tungsten and barrier layers between the conductive layer and the metal silicide on source and drain regions, and directly connecting the conductive layer to the metal gate with only a barrier layer in between.
Implementation Method 1
Ta and/or TaN has already been used in the copper contact technique to form the barrier layer 40 for preventing copper from diffusing into the metal silicide 20
Implementation Method 2
a second contact plug comprising a second barrier layer arranged on both of the metal gate and the first contact plug and a conductive layer arranged on the second barrier layer, wherein the conductivity of the conductive layer is higher than that of the tungsten layer
Data Source
AI summary
The present invention provides a semiconductor device. The semiconductor device comprises contact plugs that comprise a first contact plug formed by a first barrier layer arranged on the source and drain regions and a tungsten layer arranged on the first barrier layer; and second contact plugs comprising a second barrier layer arranged on both of the metal gate and the first contact plug and a conductive layer arranged on the second barrier layer. The conductivity of the conductive layer is higher than that of the tungsten layer. A method for forming the semiconductor device is also provided. The present invention provides the advantage of enhancing the reliability of the device when using the copper contact technique.