Conformal Plasma Doping via Dynamic Voltage Pulsing
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Solution Overview
Problem
Conventional doping methods struggle to achieve conformal doping of three-dimensional device structures with non-uniform doping profiles that preserve the angles of planar and non-planar features, which is essential for advanced ULSI circuits and sub-65 nm technology nodes.
Innovation Solution
A conformal plasma doping apparatus and method that utilizes a plasma source with a gas conductance barrier and a grating structure to maintain high pressure near the substrate, combined with a bias voltage system, to ensure uniform ion implantation across planar and non-planar features, enhancing the rate of dopant ion implantation into non-planar features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional collimated beam-line ion implanters are used, then doping can be achieved, but conformal doping of three-dimensional device structures with non-uniform doping profiles cannot be achieved
Solution Approach 1:
The patent employs dynamic voltage pulsing to the substrate, alternating between positive and negative biases. This dynamic approach allows the plasma sheath to expand and contract, enabling ions to reach both planar and non-planar surfaces uniformly, thus achieving conformal doping on three-dimensional structures that static methods cannot accomplish
Solution Approach 2:
The patent changes multiple parameters including voltage amplitude, pulse frequency, and gas pressure to optimize the doping process. By adjusting these parameters, the system achieves both conformal doping profiles and the ability to handle three-dimensional device structures, resolving the contradiction between manufacturing precision and adaptability
2Productivity
If plasma immersion ion implantation is used, then doping can be achieved, but uniform ion implantation across planar and non-planar features cannot be ensured
Solution Approach 1:
The patent uses periodic voltage pulsing with alternating positive and negative cycles. During negative pulses, ions are accelerated toward the substrate; during positive pulses, the sheath expands allowing ions to reach recessed areas. This periodic action ensures both high doping rates and uniform distribution across planar and non-planar features
Solution Approach 2:
The system incorporates feedback control where the doping process is monitored and voltage parameters are adjusted in real-time to maintain uniform ion implantation. This feedback mechanism ensures that productivity increases do not compromise the uniformity of the doping profile across complex three-dimensional structures
3Productivity
If high pressure is maintained near the substrate, then dopant ion implantation rate increases, but plasma uniformity deteriorates
Solution Approach 1:
The patent performs preliminary plasma generation in a separate region before ion acceleration. This preliminary action creates a reservoir of ions that can then be accelerated uniformly across the substrate surface, maintaining both high implantation rates and plasma uniformity even at elevated pressures
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 solution achieves a conformal doping profile that matches the planar and non-planar features, increasing the rate of dopant ion implantation and ensuring uniformity, thereby supporting the development of advanced three-dimensional device structures.
Implementation Method 1
A plasma source generates dopant ions from a feed gas
Implementation Method 2
The accelerated ions are filtered according to their mass-to-charge ratio to select the desired ions for implantation
Implementation Method 3
A conformal plasma doping apparatus and method that utilizes a plasma source with a gas conductance barrier and a grating structure to maintain high pressure near the substrate
Implementation Method 4
The accelerated ions are filtered according to their mass-to-charge ratio to select the desired ions for implantation
Implementation Method 5
The negative bias on the target repels the electrons from the target surface thereby creating a sheath of positive ions. The sheath of positive ions creates an electric field between the sheath boundary and the target surface. The electric field accelerates ions towards the target and implants the ions into the target surface
Implementation Method 6
Doping is often achieved using conventional collimated beam-line ion implanters that accelerate ions with an electric field
Data Source
AI summary
A method of doping includes depositing a layer of dopant material on nonplanar and planar features of a substrate. Inert ions are generated from an inert feed gas. The inert ions are extracted towards the substrate where they physically knock the dopant material into both the planar and nonplanar features of the substrate.