Alternating Epitaxial Stack Deposition for Thick 3D DRAM Layers
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Solution Overview
Problem
The challenge in semiconductor manufacturing lies in maintaining low stress in thick epitaxial stacks, which is crucial for 3D DRAM devices, as stress relaxation can occur with increased thickness, affecting processing and integration.
Innovation Solution
A method involving alternating deposition cycles with different reaction gas mixtures to form epitaxial layers with controlled lattice parameters, reducing stress relaxation and enabling the growth of thick epitaxial stacks on multiple substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the epitaxial stack is increased to provide higher density and improved device performance, then the device performance and density are improved, but stress relaxation occurs in the stack
Solution Approach 1:
The patent applies parameter changes by alternating between different deposition conditions (first and second reaction gas mixtures) to form layers with different lattice parameters. This alternation allows control of internal stress in the epitaxial stack, enabling growth of thick stacks without stress relaxation while maintaining high density and performance.
Solution Approach 2:
The patent creates a composite epitaxial structure with alternating layers (first and second epitaxial layers) having different compositions and lattice parameters. This composite structure enables stress management throughout the thick stack, allowing increased height while preventing stress relaxation that would otherwise occur in uniform thick layers.
2Productivity
If multiple substrates are processed simultaneously to improve manufacturing throughput, then productivity is improved, but maintaining consistent stress control across all substrates becomes more difficult
Solution Approach 1:
The patent employs a universal deposition process that can be applied simultaneously to multiple substrates in a single process chamber. The alternating deposition cycles with different reaction gas mixtures function uniformly across all substrates, ensuring consistent stress control and lattice parameter management throughout the entire batch, thereby maintaining both high productivity and precision.
3Reliability
If alternating deposition cycles with different reaction gas mixtures are used to control stress, then stress relaxation is reduced, but the process complexity increases
Solution Approach 1:
The patent implements periodic action through alternating deposition cycles that switch between first and second reaction gas mixtures. This periodic alternation creates a repeating pattern of layer formation with controlled lattice parameters, effectively managing stress throughout the thick epitaxial stack while maintaining a systematic and controllable process sequence.
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
This method allows for the formation of thick epitaxial stacks with reduced stress relaxation, improving process throughput and enabling the manufacturing of 3D DRAM devices with enhanced etch selectivity between layers.
Implementation Method 1
The first deposition pulse may comprise a provision of a first reaction gas mixture to the process chamber, thereby forming the first epitaxial layer having a first lattice parameter
Implementation Method 2
The second deposition pulse may comprise a provision of a second reaction gas mixture to the process chamber, thereby forming the second epitaxial layer having a second lattice parameter
Implementation Method 3
The first lattice parameter may lie in a range within 1.5% larger than and 0.9% smaller than the second lattice parameter
Data Source
AI summary
A method for forming an epitaxial stack on a plurality of substrates comprises providing a plurality of substrates to a process chamber and executing deposition cycles, wherein each deposition cycle comprises a first deposition pulse and a second deposition pulse. The epitaxial stack comprises a first epitaxial layer stacked alternatingly and repeatedly with a second epitaxial layer, the second epitaxial layer being different from the first epitaxial layer. The first deposition pulse comprises a provision of a first reaction gas mixture to the process chamber, thereby forming the first epitaxial layer having a first native lattice parameter. The second deposition pulse comprises a provision of a second reaction gas mixture to the process chamber, thereby forming the second epitaxial layer having a second native lattice parameter, wherein the first native lattice parameter lies in a range within 1.5% larger than and 0.9% smaller than the second native lattice parameter.