Semiconductor Contact Barrier with High Heat of Formation Layer
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Solution Overview
Problem
In semiconductor devices with three-dimensional memory cells, the high temperature conditions during memory cell formation can cause the diffusion of impurities from the source and drain layers into the metal contacts through the barrier metal film, leading to increased contact resistance.
Innovation Solution
Incorporating a conductive film with a higher heat of formation than the barrier metal film between the barrier metal film and the diffusion region, such as zirconium nitride or hafnium nitride, to prevent impurity diffusion and maintain low contact resistance even under high temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If contacts are produced prior to memory cells under high temperature conditions, then the contact formation process is simplified and can be performed earlier in the manufacturing sequence, but impurity diffusion from source and drain layers into the metal contacts increases, leading to increased contact resistance
Solution Approach 1:
A conductive film with higher heat of formation than the barrier metal film is introduced as an intermediary layer between the barrier metal film and the diffusion region. This conductive film acts as a mediator that allows the contact to be formed early in the manufacturing process while simultaneously preventing impurity diffusion into the metal contact during subsequent high-temperature memory cell formation, thus resolving the contradiction between manufacturing efficiency and contact reliability
Solution Approach 2:
The contact structure is designed as a composite multi-layer system comprising a metal film, a barrier metal film, and a conductive film with specific thermal properties. This composite structure combines materials with different heat of formation characteristics, where the conductive film has higher heat of formation than the barrier metal film, creating a hierarchical barrier system that effectively prevents impurity diffusion while maintaining low contact resistance
2Reliability
If a barrier metal film is used to prevent impurity diffusion, then contact resistance can be maintained low, but under high temperature conditions impurities still diffuse through the barrier metal film into the metal contacts
Solution Approach 1:
The invention changes the thermal parameter (heat of formation) of the barrier system by introducing a conductive film with higher heat of formation than the barrier metal film. This parameter change creates a thermal gradient that prevents impurity diffusion, as impurities prefer to diffuse into materials with lower heat of formation, thus effectively blocking impurity migration into the metal contact while maintaining the barrier function
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 conductive film with higher thermal resistance effectively prevents impurity diffusion into the metal contacts, ensuring low resistance and reliable electrical connections in the semiconductor device.
Implementation Method 1
a conductive film provided between the barrier metal film and the diffusion region and including a conductive material having a higher heat of formation than a heat of formation of the barrier metal film
Data Source
AI summary
A semiconductor device according to an embodiment includes: a semiconductor substrate having a diffusion region including an impurity; and a contact provided on the diffusion region. The contact includes a metal film, a barrier metal film covering the metal film, and a conductive film provided between the barrier metal film and the diffusion region and including a conductive material having a higher heat of formation than a heat of formation of the barrier metal film.