Monoalkyl Tin Triamide Storage for Low Dialkyl Tin Impurities
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Solution Overview
Problem
The synthesis of monoalkyl tin triamides with high purity is challenging due to the formation of dialkyl tin impurities during the preparation process, which can contaminate semiconductor substrates and degrade device performance, particularly in EUV lithography applications, where stringent purity requirements are necessary to prevent off-gassing and optical degradation.
Innovation Solution
A method involving lithiation of a dimethylamine solution with controlled stoichiometry and solvent conditions, followed by filtration and vacuum removal of LiCl salt, and optional distillation, to produce monoalkyl tin triamides with purities of at least 99 mol%, minimizing dialkyl tin and other impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional synthesis methods using lithium dimethylamide and alkyl tin trichloride are employed, then monoalkyl tin triamides can be produced, but significant amounts of dialkyl tin impurities are generated
Solution Approach 1:
The patent applies preliminary action by using excess lithium dimethylamide (at least 3.09 equivalents) in the synthesis reaction before impurities form. This excess reagent prevents comproportionation reactions that would generate dialkyl tin impurities by ensuring complete conversion of alkyl tin trichloride to monoalkyl tin triamide, thereby preventing harmful impurity formation before it occurs
Solution Approach 2:
The patent changes the stoichiometric parameters of the reaction by employing at least 3.09 equivalents of lithium dimethylamide relative to alkyl tin trichloride. This parameter change transforms the reaction outcome from producing significant dialkyl tin impurities to achieving greater than 99 mol% purity by controlling the molar ratios to favor complete substitution without comproportionation
2Ease of operation
If lower temperatures are used during synthesis to slow substitution reaction, then reaction control is improved, but risk of comproportionation increases
Solution Approach 1:
The patent changes the temperature parameter to at least 0°C during the synthesis reaction. This temperature parameter change simultaneously achieves good reaction control (preventing runaway exothermic reactions) while minimizing comproportionation risks, as the elevated temperature favors the substitution reaction pathway over comproportionation while still allowing for controlled addition and heat management
3Reliability
If high purity monoalkyl tin triamides are produced, then semiconductor substrate contamination is prevented, but synthesis complexity increases
Solution Approach 1:
The patent applies preliminary action by incorporating purification steps (filtration to remove LiCl, optional distillation) into the synthesis protocol from the outset. This ensures high purity (>99 mol%) product that prevents semiconductor substrate contamination while managing synthesis complexity through systematic, integrated purification rather than multiple separate complex operations
Solution Approach 2:
The patent uses parameter changes in the form of optional distillation under reduced pressure to achieve the required purity levels. By adjusting pressure and temperature parameters during distillation, high purity product is obtained that prevents device degradation, while the optionality of this step allows flexibility to manage synthesis complexity based on specific purity requirements
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 method achieves monoalkyl tin triamides with purities exceeding 99 mol%, significantly reducing dialkyl tin impurities and other contaminants, ensuring high-quality semiconductor fabrication by preventing off-gassing and optical degradation in EUV lithography.
Implementation Method 1
the synthesis may be performed using lithium dimethylamide and alkyl tin trichloride (amination)
Implementation Method 2
followed by filtration and vacuum removal of LiCl salt
Implementation Method 3
optional distillation, to produce monoalkyl tin triamides with purities of at least 99 mol%
Implementation Method 4
vacuum removal of LiCl salt
Data Source
AI summary
Monoalkyl tin triamide compounds having purity of at least about 99 mol % and the chemical formula RSn(NMe2)3 are described. R1 is selected from RA, RB and RC; RA is a primary alkyl group having about 1 to 10 carbon atoms, RB is a secondary alkyl group having about 3 to 10 carbon atoms, and RC is a tertiary alkyl group having about 3 to 10 carbon atoms; each R2 is independently an alkyl group having about 1 to 10 carbon atoms; and a content of R1Sn(NR22)2(N(R2)CH2NR22) is less than about 1 mol %. Methods for synthesizing, purifying, and storing these compounds are also provided. The monoalkyl tin compounds may be used for the formation of high-resolution EUV lithography patterning precursors and are attractive due to their high purity and minimal concentration of dialkyl tin and other tin impurities.