Deposition Method Mitigating Wafer Thickness Non-Uniformity
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Solution Overview
Problem
Conventional Low Pressure Chemical Vapor Deposition (LPCVD) methods result in uneven thin-film thickness on semiconductor wafers, with periphery films being thicker than center films due to temperature gradients in the reaction chamber.
Innovation Solution
A deposition method involving a first constant-temperature deposition followed by a cool-down process during which a second low-temperature deposition occurs, adjusting the deposition times based on deposition rates and desired thickness to achieve uniform film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional constant-temperature deposition is conducted in a heated reaction chamber, then deposition can be performed efficiently, but the thin-film thickness becomes non-uniform with periphery films thicker than center films due to temperature gradients
Solution Approach 1:
The patent applies dynamics by transitioning from static constant-temperature deposition to dynamic temperature-changing deposition. The reaction chamber temperature is continuously lowered during the deposition process, creating a time-dependent temperature profile that compensates for the spatial temperature gradient. This dynamic approach allows the periphery (which is always hotter) to deposit at effectively lower temperatures as the overall chamber cools, achieving uniform film thickness while maintaining high deposition efficiency.
Solution Approach 2:
The patent employs parameter changes by modifying the temperature parameter during the deposition process. Instead of maintaining a constant temperature, the chamber temperature is continuously reduced from an initial high value to a final lower value. This parameter change strategy transforms the fixed temperature gradient problem into a controllable process where the evolving temperature profile balances the spatial variations, resolving the thickness uniformity issue while preserving productivity.
2Quantity of substance
If pressure and flow rate are adjusted to control overall deposition thickness, then deposition rate can be modified, but the thickness discrepancy between periphery and center regions remains unresolved
Solution Approach 1:
The patent identifies temperature as the critical parameter to change during deposition, rather than adjusting pressure or flow rate. By continuously lowering the chamber temperature, the process dynamically compensates for spatial temperature gradients. This parameter change approach affects the deposition kinetics in a way that balances the inherent periphery-center thickness discrepancy, achieving both controlled quantity and improved uniformity simultaneously.
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 ensures more uniform thin-film thickness, improving homogeneity by at least 50% compared to conventional methods, as the temperature gradient is mitigated during the cool-down process.
Implementation Method 1
Low Pressure Chemical Vapor Deposition (LPCVD) of a thin-film deposition process
Implementation Method 2
due to heat radiation from heated reaction chamber, in a constant-temperature deposition, the temperature near a wall of the reaction chamber is higher than that at the center of the reaction chamber
Implementation Method 3
conducting a cool-down process on the reaction chamber
Data Source
AI summary
A deposition method relating to semiconductor technology is presented. The deposition method includes: conducting a first deposition in a reaction chamber at a first deposition temperature; conducting a cool-down process on the reaction chamber, and conducting a second deposition during the cool-down process. In the first deposition, the thin-films deposited on the periphery of a wafer are thicker than those deposited on the center of a wafer, while in the second deposition, the thin-films deposited on the periphery of a wafer are thinner that those deposited on the center of a wafer. Therefore the thin-films deposited by this deposition method are more homogeneous in thickness that those deposited with conventional methods.