Ceramic Mounting Table Stress Relaxer for Thermal Diffusion
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Solution Overview
Problem
The existing mounting table structures in semiconductor processing apparatuses face issues with thermal diffusion of metal elements like cobalt and nickel, leading to brittle intermetallic compound formation and joint strength reduction, especially at high temperatures.
Innovation Solution
A ceramic-based mounting table structure with a stress relaxing member made of a metal free from cobalt and nickel, or with a boundary layer to prevent diffusion, and a connection terminal made of high-melting-point metals or intermetallic compounds, jointed using brazing materials that do not contain nickel, to maintain joint integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a stress relaxing member containing cobalt and nickel is used to absorb thermal expansion stress, then the stress relaxation function is improved, but thermal diffusion occurs at high temperatures causing brittle intermetallic compound formation and joint strength reduction
Solution Approach 1:
A diffusion barrier layer is introduced as an intermediary between the stress relaxing member and the connection terminal. This barrier layer prevents thermal diffusion of metal elements while allowing the stress relaxing member to continue absorbing thermal expansion stress. The barrier layer acts as a mediator that blocks harmful diffusion paths while maintaining the functional integrity of the joint.
Solution Approach 2:
The joint structure is designed as a composite system consisting of multiple materials with complementary properties: the stress relaxing member (e.g., Kovar alloy) provides thermal expansion compensation, the diffusion barrier layer (e.g., nickel-free brazing material or metal nitride) prevents thermal diffusion, and the connection terminal (e.g., molybdenum) provides electrical connectivity. This composite structure resolves the contradiction by combining materials that individually address different requirements.
2Temperature
If high temperature heat treatment is performed on the mounting table structure, then the wafer processing capability is improved, but metal element diffusion occurs in the joint area causing detachment and brittleness
Solution Approach 1:
The diffusion barrier layer serves as a thermal mediator that allows heat to pass through for wafer processing while blocking the diffusion of metal elements. This enables the system to withstand high temperatures necessary for wafer heat treatment without suffering from thermal diffusion damage in the joint areas.
Solution Approach 2:
The invention converts the harmful effect of high temperature (which causes thermal diffusion) into a beneficial situation by introducing a diffusion barrier layer. The high temperature is necessary for wafer processing, and the barrier layer transforms this potentially harmful condition into an acceptable operating state by preventing diffusion while allowing heat transfer.
3Reliability
If a power-feeding rod with connector portion is inserted into the connection hole to feed electricity, then the electrical connectivity is improved, but the joint structure becomes complex and susceptible to thermal diffusion damage
Solution Approach 1:
The diffusion barrier layer is introduced as an intermediary in the electrical connection path. While this adds a layer to the structure, it significantly simplifies the overall design by eliminating the need for complex stress relaxation mechanisms and protecting against thermal diffusion damage, thereby improving reliability without proportionally increasing complexity.
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
Prevents thermal diffusion of metal elements, thereby maintaining joint strength and preventing detachment issues, ensuring reliable electrical connectivity and mechanical stability under high-temperature conditions.
Implementation Method 1
a stress relaxing member 28 made of an alloy containing Co (cobalt) and/or Ni (nickel), e.g., Kovar (registered trademark) which is a Co—Fe—Ni alloy, is interposed between the power-feeding connector portion 26 and the Mo-containing connection terminal 22 in order to absorb the stress generated by the difference in thermal expansion
Implementation Method 2
The connection terminal 22 and the stress relaxing member 28 are jointed to each other by, e.g., a Ni alloy brazing material 30. Likewise, the stress relaxing member 28 and the power-feeding connector portion 26 are jointed to each other by, e.g., a Ni alloy brazing material 32
Implementation Method 3
a mounting table structure 4 for supporting a semiconductor wafer W on its upper surface is arranged within a cylindrical processing chamber 2... to perform heat treatments on the wafer under predetermined process conditions
Data Source
AI summary
A mounting table body made of ceramic includes power-receiving conductor portions and buried therein. A surface of mounting table body is formed with a recessed connection hole and a connection terminal electrically jointed to the power-receiving conductor portion and exposed into the connection hole, the connection terminal being made of a high-melting-point metal, an alloy thereof or a compound thereof. A power-feeding line member provided with a power-feeding connector portion is inserted at its leading end portion into the connection hole to feed electricity to the power-receiving conductor portion. A stress relaxing member is interposed between the connection terminal and the power-feeding connector portion. The stress relaxing member and the connection terminal are jointed together by a brazing material. The stress relaxing member is made of a metal free from cobalt and nickel or an alloy thereof.