High Purity Thermal Spray Powder for Dense Ceramic Liners
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Solution Overview
Problem
Conventional plasma spraying methods for creating ceramic liners in semiconductor etching chambers result in porous liners with high porosity, which are not resistant to corrosive environments and have impurities due to the use of fine powders and sintered agglomerates, leading to inefficiencies and liner degradation over time.
Innovation Solution
A powder with over 95% rare earth metal oxide, hafnium oxide, or yttrium-aluminum oxide composition, characterized by high circularity, controlled particle size distribution, and low porosity, is developed for plasma spraying, which is produced through a process involving granulation, injection into a plasma jet, and controlled cooling to achieve a dense and pure liner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fine powders are used directly from chemical or pyrolytic manufacturing processes, then the powder can be easily obtained, but the resulting liner exhibits high porosity (2-3%) which is insufficient for protecting semiconductor etching chambers
Solution Approach 1:
The patent applies preliminary consolidation by sintering the fine powders before plasma spraying to form dense agglomerates with controlled porosity. This pre-processing step creates feedstock particles that will form dense liners upon spraying, resolving the contradiction between ease of manufacture and liner density precision.
Solution Approach 2:
The patent changes the physical and chemical parameters of the powder through controlled sintering processes, adjusting temperature, time, and atmosphere to achieve optimal density while maintaining sprayability. This transforms the powder characteristics to simultaneously satisfy both manufacturing ease and liner density requirements.
2Ease of operation
If sintered agglomerates are used as feed powder, then the powder can be sprayed with good fluidity, but the liner still exhibits porosity and results in particle release over time when exposed to corrosive environments
Solution Approach 1:
The patent creates composite structures within the agglomerates by combining sintered particles with binders or other ceramic materials, forming multi-phase feedstock that produces liners with improved integrity. The composite nature allows simultaneous achievement of sprayability and resistance to particle release in corrosive environments.
3Reliability
If rare earth metal oxides, hafnium oxide, or yttrium-aluminum oxides are used, then the liner exhibits good intrinsic resistance to chemical attacks, but the high melting temperature and low thermal diffusion make it difficult to obtain a very dense liner by plasma spraying
Solution Approach 1:
The patent applies preliminary melting and consolidation of these refractory oxides before spraying, creating pre-densified feedstock particles. This pre-processing overcomes the difficulty of achieving density during spraying by already establishing the dense structure before the material is deposited onto the substrate.
Solution Approach 2:
The patent modifies the thermal and mechanical parameters during processing, using elevated temperatures and pressure treatments to enhance densification of these high-melting-point materials. These parameter changes enable the refractory oxides to achieve the required density while maintaining their chemical resistance properties.
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 solution results in a very dense and pure liner with reduced porosity, improved resistance to corrosive environments, and enhanced spraying productivity, achieving a bulk density of 2.3 g/cm3 and porosity below 1.5%, effectively addressing the limitations of existing methods.
Implementation Method 1
injection of a powder formed of granules, via a carrier gas, through an injector as far as a plasma jet generated by a plasma gun, so as to obtain molten droplets
Implementation Method 2
more than approximately 90% of the particles of starting material can be completely or partially converted into the liquid form
Implementation Method 3
cooling said molten droplets, so as to obtain a feed powder according to the invention
Data Source
AI summary
Powder of particles, more than 95% by number of said particles exhibiting a circularity greater than or equal to 0.85, wherein said powder contains more than 99.8% of a rare earth oxide and/or of hafnium oxide and/or of yttrium aluminum oxide, as percentage by weight relative to the oxides, and has: a median particle size D 50 of between 10 and 40 microns and a size dispersion index (D 90−D 10)/D 50 of less than 3; a percentage by number of particles having a size less than or equal to 5 μm which is less than 5%; an apparent-density dispersion index (P<50−P)/P of less than 0.2, the cumulative specific volume of the pores which have a radius of less than 1 μm being less than 10% of the apparent volume of the powder, in which the percentiles Dn of the powder are the particle sizes corresponding to the percentages, by number, of n %, on the curve of cumulative distribution of the particle size of the powder, the particle sizes being classified in increasing order, the density P<50 being the apparent density of the fraction of particles having a size less than or equal to D50, and the density P being the apparent density of the powder.