Cryo-Implanted Wafer Heating Under Vacuum to Prevent Condensation
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Solution Overview
Problem
The challenge in integrated circuit fabrication is the potential contamination from condensation that forms on wafers during the ion cryo-implantation process due to differences in vacuum levels, leading to wafer-to-wafer inconsistency and contamination.
Innovation Solution
A heating stage is integrated into the implantation system, maintaining the same vacuum level as the processing chamber to heat wafers post-implantation, eliminating condensation and ensuring consistent wafer stability by preventing moisture condensation under heavy vacuum conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If wafers are heated in the outgoing load lock after ion cryo-implantation, then wafers can be warmed to processing temperature, but condensation forms on the cold wafer surface due to vacuum level differences causing contamination
Solution Approach 1:
The system is divided into separate functional zones: the implantation chamber maintained at high vacuum (10^-6 to 10^-8 Torr) and the outgoing load lock at lower vacuum (10^-3 to 10^-1 Torr). The heating stage is positioned within the implantation chamber, allowing wafer heating to occur in the high vacuum environment before the wafer is transferred to the load lock, thus preventing condensation contamination.
Solution Approach 2:
The heating stage acts as an intermediary device that enables temperature change of the wafer while maintaining the high vacuum environment. By heating the wafer in place within the implantation chamber before transfer, the system avoids the harmful interaction between cold wafer surfaces and the lower vacuum environment of the load lock that would cause condensation.
2Productivity
If wafers are transferred directly from implantation chamber to load lock without heating, then process time is reduced, but wafer-to-wafer consistency deteriorates due to condensation
Solution Approach 1:
The heating stage performs the heating action preliminarily, before the wafer is transferred to the outgoing load lock. By heating the wafer to near-processing temperature while still in the high vacuum environment, the system eliminates the condensation problem that would otherwise occur during transfer, ensuring wafer-to-wafer consistency without significant delay to throughput.
3Object-affected harmful factors
If the heating stage is integrated into the implantation chamber at the same vacuum level, then condensation is eliminated, but device complexity increases
Solution Approach 1:
The heating stage is merged with the implantation chamber structure, sharing the same high vacuum environment. This integration allows the heating function to be performed within the existing vacuum system without requiring a separate vacuum chamber, thus adding functionality while minimizing the increase in overall system complexity.
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 approach reduces contamination and enhances wafer-to-wafer consistency by maintaining the same vacuum level throughout the process, preventing condensation and ensuring the integrity of implanted species.
Implementation Method 1
a heating stage configured to heat the wafer after implantation to a second temperature that corresponds to a processing temperature
Implementation Method 2
a cooling stage configured to cool a wafer to a first temperature prior to ion implantation, the first temperature corresponding to a cryogenic temperature
Implementation Method 3
an implantation platen configured to retain the wafer during an ion implantation process
Data Source
AI summary
Embodiments of an ion cryo-implantation process utilize a post implantation heating stage to heat the implanted wafer while under the heavy vacuum used during cryo-implantation. The implanted wafer is then transferred to load locks which are held at a lesser vacuum than the heavy vacuum.