Plasma Doping Non-Planar Semiconductor Devices
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Solution Overview
Problem
Achieving uniform dopant profiles across the height of non-planar semiconductor devices, such as FinFETs, is challenging due to the large plasma sheath formed during plasma doping, which can lead to undesirable threshold voltage variations and source/drain punch-through issues.
Innovation Solution
A plasma doping system is used where a first and second bias voltage are generated to implant dopant ions into a non-planar semiconductor device, with the bias voltages differing to control the depth and angle of dopant ion implantation, thereby reducing straggle and improving uniformity across the fin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plasma doping is used to dope non-planar semiconductor devices, then doping can be achieved in complex fin structures, but dopant uniformity across the fin height deteriorates due to large plasma sheath
Solution Approach 1:
The plasma doping process is divided into multiple sequential doping steps, each targeting different regions of the fin structure. The first doping step targets the lower portion of the fin while the second doping step targets the upper portion, thereby achieving uniform dopant distribution across the entire fin height despite the large plasma sheath
Solution Approach 2:
Different doping parameters are used in sequential steps: the first doping step uses a first set of parameters (power, pressure, gas flow, duration) optimized for lower fin regions, while the second doping step uses a second set of parameters optimized for upper fin regions. This parameter variation compensates for the non-uniform plasma sheath effects
2Device complexity
If single bias voltage plasma doping is used, then processing is simple, but dopant distribution uniformity deteriorates with vertical straggle
Solution Approach 1:
The doping process is segmented into multiple steps with different bias voltages. The first bias voltage implants dopants to a first depth while the second bias voltage implants dopants to a second depth, creating overlapping doping profiles that achieve uniform distribution and reduce vertical straggle
Solution Approach 2:
The plasma doping is performed in periodic cycles with alternating bias voltages. Each cycle consists of a first doping phase with first bias voltage followed by a second doping phase with second bias voltage, creating a periodic modulation of dopant implantation depth that achieves uniform distribution
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 allows for more precise control of dopant distribution, reducing horizontal and vertical straggle and achieving better dopant uniformity across the length and height of the fin, thereby minimizing threshold voltage variations and preventing punch-through issues.
Implementation Method 1
A plasma may be formed in the chamber where the plasma may contain dopant ions. A first bias voltage may be generated to implant dopant ions into a region of the non-planar semiconductor body.
Data Source
AI summary
In plasma doping a non-planar semiconductor device, a substrate having a non-planar semiconductor body formed thereon is obtained. The substrate having the non-planar semiconductor body may be placed into a chamber. A plasma may be formed in the chamber and the plasma may contain dopant ions. A first bias voltage may be generated to implant dopant ions into a region of the non-planar semiconductor body. A second bias voltage may be generated to implant dopant ions into the same region. In one example, the first bias voltage and the second bias voltage may be different.