TiSi2 Heater Electrode for Ceramic Chuck Thermal Uniformity
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Solution Overview
Problem
Ceramic heaters produced by low-temperature firing face issues with particle detachment, uneven electrical resistance, and thermal uniformity during plasma etching due to the 'reversal of temperature-dependence of resistivity' phenomenon, particularly when using molybdenum-based materials.
Innovation Solution
Incorporating TiSi2 as the main component in the heater electrode to suppress the reversal of temperature-dependence of resistivity and in-plane variation of electrical resistivity, while using an alumina ceramic base with magnesium fluoride to reduce thermal expansion coefficient differences and facilitate low-temperature firing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If low-temperature firing is used to produce ceramic heater, then production cost and energy consumption are reduced, but particle detachment occurs and electrical resistance cannot be measured
Solution Approach 1:
The invention changes the chemical composition parameters of the heater electrode material from traditional WC-based paste to a specific mixed powder containing Mo, Ni, and Cu in controlled proportions. This material parameter change enables the electrode to achieve sufficient densification and electrical properties at low firing temperatures (1,120-1,300°C) without particle detachment, resolving the contradiction between low-energy production and reliable electrical resistance measurement
Solution Approach 2:
The invention uses a composite material system consisting of Mo as the base metal powder, Ni as a sintering aid, and Cu as an electrical conductivity enhancer. This composite powder mixture synergistically achieves low-temperature sintering capability while maintaining adequate electrical resistance for heater operation, solving the problem of particle detachment and unmeasurable resistance at low firing temperatures
2Manufacturing precision
If WC and alumina mixed powder is used as paste for low-temperature firing, then densification is improved, but sufficient electrical properties are not obtained
Solution Approach 1:
The invention changes the material composition parameters by replacing WC with Mo and adding specific proportions of Ni and Cu. This parameter change allows the electrode to achieve both adequate densification and sufficient electrical conductivity at low firing temperatures, resolving the contradiction between manufacturing precision and electrical property reliability
Solution Approach 2:
The invention introduces Ni and Cu as intermediary elements that facilitate both densification and electrical property development. Ni acts as a sintering aid promoting particle bonding, while Cu enhances electrical conductivity. These intermediary materials enable the Mo-based electrode to achieve dual objectives of densification and electrical performance at low temperatures
3Adaptability or versatility
If molybdenum paste is used as heater electrode material, then alternative to WC is achieved, but reversal of temperature-dependence of resistivity occurs
Solution Approach 1:
The invention changes the compositional parameters by adding Ni and Cu to the Mo-based paste in specific proportions. This modification suppresses the formation of molybdenum carbide and prevents the reversal phenomenon, maintaining consistent positive temperature coefficient behavior across different operating temperatures. The result is simplified temperature control without sacrificing material versatility as a WC alternative
Solution Approach 2:
The invention converts the potential harm of molybdenum carbide formation (which causes resistivity reversal) into a benefit by adding Ni and Cu that suppress carbide formation. The Ni and Cu act as protective additives that prevent the harmful chemical reaction between Mo and carbon from the die, transforming the material system to eliminate the reversal phenomenon while maintaining the advantages of Mo as a WC alternative
4Device complexity
If molybdenum containing titanium component is used, then reversal phenomenon is suppressed, but in-plane variation of electrical resistivity increases
Solution Approach 1:
The invention changes the compositional parameters by replacing Ti with Cu in the Mo-based alloy system. This parameter change achieves both suppression of the reversal phenomenon and maintenance of in-plane resistivity uniformity. Cu provides similar benefits to Ti in preventing carbide formation while avoiding the in-plane variation problem, thus resolving the contradiction between temperature control simplicity and manufacturing precision
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 use of TiSi2 in the heater electrode effectively addresses the reversal of temperature-dependence of resistivity and in-plane resistivity variation, ensuring improved thermal uniformity and stability of the ceramic heater, even at low firing temperatures.
Implementation Method 1
the phenomenon of reversal of temperature-dependence of resistivity was improved
Implementation Method 2
conducting firing at a low firing temperature of 1,120° C. to 1,300° C.
Implementation Method 3
a heater electrode embedded in the ceramic base
Data Source
AI summary
An electrostatic chuck 10 includes a disc-shaped alumina ceramic base 12, and a heater electrode 14 and an electrostatic electrode 16 that are embedded in the alumina ceramic base 12. An upper surface of the alumina ceramic base 12 functions as a wafer-receiving surface 12a. The heater electrode 14 is formed in a pattern shape, for example, in the manner of a single brush stroke so as to be arranged over the entire surface of the alumina ceramic base 12. When a voltage is applied to the heater electrode 14, the heater electrode 14 generates heat, and heats a wafer W. This heater electrode 14 contains TiSi2 as a main component.