Interconnect Deposition at Low Pressure to Minimize Voids
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Solution Overview
Problem
Existing semiconductor fabrication methods face challenges in forming interconnect structures with improved conformity, reduced overhangs at corners, and minimal voids and seams, which affect device performance and increase defects.
Innovation Solution
A low-pressure physical vapor deposition process is used to form conductive features, involving an ignition stage, intermediate pressure reduction, and deposition stage, utilizing a cryopump to enhance pressure control and improve collimation of deposition particles, followed by reflowing the conductive layer to fill openings with minimal overhangs and voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional deposition processes are used to form conductive layers, then the process is simpler and faster, but the conformity and coverage of conductive layers are poor with significant overhangs at corners and voids
Solution Approach 1:
The deposition process is segmented into multiple distinct stages: ignition stage with process gas, intermediate stage with pressure reduction, and deposition stage. This segmentation allows optimization of each stage for specific purposes, improving overall conformity and coverage while managing process complexity through structured breakdown.
Solution Approach 2:
The process performs preliminary actions by first igniting plasma with process gas to prepare the environment, then reducing pressure before deposition. These preliminary steps create optimal conditions for the subsequent deposition stage, ensuring better conformality and reducing defects like overhangs and voids.
2Manufacturing precision
If pressure is not reduced during deposition, then the process is simpler, but particle collimation is poor leading to overhangs and voids
Solution Approach 1:
The pressure is dynamically adjusted during the deposition process - reduced to less than 0.3 mTorr during the deposition stage to improve particle collimation and coverage, then returned to higher pressure after deposition. This dynamic pressure control optimizes manufacturing precision while the automated control system maintains ease of manufacture.
Solution Approach 2:
The process changes the pressure parameter from initial higher pressure during ignition to low pressure (<0.3 mTorr) during deposition, and then returns to higher pressure after deposition. This parameter change optimizes particle transport and deposition quality, achieving better thickness control and coverage.
3Reliability
If DC power is not increased during pressure reduction, then energy consumption is lower, but plasma maintenance becomes difficult at low pressure
Solution Approach 1:
The process applies preliminary action by increasing DC power to greater than 15 kW before and during pressure reduction to greater than 30 kW. This preliminary power increase ensures plasma is maintained and stabilized as pressure drops, preventing plasma extinction and ensuring reliable transition to the low-pressure deposition state.
Solution Approach 2:
The DC power is periodically adjusted in correspondence with pressure changes - increased during pressure reduction, maintained at high level during low-pressure deposition, then reduced after deposition when pressure increases. This periodic power adjustment maintains plasma reliability throughout the pressure cycling process.
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 results in improved device performance and reduced defects by ensuring better thickness control and coverage of conductive layers, minimizing overhangs and voids in interconnect structures.
Implementation Method 1
igniting the process gas into a plasma in the process chamber
Implementation Method 2
reducing a pressure of the process chamber to less than 0.3 mTorr
Implementation Method 3
depositing a conductive layer on a substrate in the process chamber. The conductive layer may be deposited by a low-pressure physical vapor deposition process
Implementation Method 4
reflowed. The conductive layer may be deposited by a low-pressure physical vapor deposition process and reflowed
Data Source
AI summary
Interconnect structures and methods and apparatuses for forming the same are disclosed. In an embodiment, a method includes supplying a process gas to a process chamber; igniting the process gas into a plasma in the process chamber; reducing a pressure of the process chamber to less than 0.3 mTorr; and after reducing the pressure of the process chamber, depositing a conductive layer on a substrate in the process chamber.