Semiconductor Dopant Introduction via Halogen and Flash Lamp Heating
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Solution Overview
Problem
Conventional dopant introduction methods for semiconductor substrates face challenges in achieving efficient and defect-free dopant activation, particularly in three-dimensional structures, due to issues with ion implantation damage and the limitations of short-time heat treatment processes like flash lamp annealing, which struggle to diffuse dopants through native oxide films and result in low activation rates and excessive dopant diffusion.
Innovation Solution
A method involving the formation of a thin film containing a dopant on a semiconductor substrate, followed by heating with a continuous halogen lamp to diffuse the dopant, and subsequent flash lamp irradiation to activate it, while maintaining a low oxygen atmosphere and controlling pressure, effectively introducing and activating the dopant without causing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flash lamp annealing is used for short-time heat treatment, then heat capacity is reduced and processing speed is improved, but dopant diffusion through oxide film is insufficient and activation rate is low
Solution Approach 1:
The heat treatment process is divided into two distinct stages: first, a relatively long-time heat treatment to diffuse dopant through the oxide film, followed by a short-time flash lamp annealing to activate the dopant. This segmentation allows each stage to optimize for its specific function, resolving the contradiction between processing speed and activation rate.
Solution Approach 2:
The preliminary long-time heat treatment pre-diffuses the dopant through the oxide film into the semiconductor substrate before the flash lamp annealing. This preliminary action ensures that sufficient dopant is positioned in the substrate, enabling the subsequent short-time treatment to achieve high activation rates without excessive diffusion.
2Manufacturing precision
If spike RTA is used for longer-time heat treatment to diffuse dopant through oxide film, then dopant diffusion is improved, but activation rate becomes low and excessive dopant diffusion occurs
Solution Approach 1:
The process segments the heat treatment into two phases with different duration and temperature characteristics: a longer first phase for controlled diffusion, and a shorter second phase for activation. This prevents the excessive diffusion problem while maintaining high activation rates.
Solution Approach 2:
The heat treatment parameters are dynamically adjusted between stages: the first heat treatment uses moderate temperature for extended duration to achieve controlled diffusion, while the second flash lamp annealing uses high temperature for very short duration to activate dopant without excessive diffusion. This dynamic parameter adjustment resolves the contradiction.
3Productivity
If ion implantation is used for dopant introduction, then dopant introduction efficiency is improved, but crystal defects are generated in the semiconductor substrate
Solution Approach 1:
The mechanical ion implantation process is replaced with a thermal diffusion process. Instead of physically bombarding the substrate with ionized dopant atoms, the patent uses heat treatment to drive dopant diffusion from the oxide film into the substrate. This substitution eliminates the crystal damage caused by ion implantation while maintaining effective dopant introduction.
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 high dopant activation rates while preventing excessive diffusion, ensuring efficient and defect-free dopant introduction into semiconductor substrates, even in three-dimensional structures, by combining the benefits of continuous and flash heating techniques.
Implementation Method 1
irradiating the semiconductor substrate with light from a continuous lighting lamp to heat the semiconductor substrate to a first temperature
Implementation Method 2
diffusing the dopant from the thin film into the surface of the semiconductor substrate
Implementation Method 3
irradiating the semiconductor substrate with a flash of light from a flash lamp to heat the surface of the semiconductor substrate to a third temperature
Implementation Method 4
activating the dopant
Data Source
AI summary
A thin film containing a dopant is deposited on a surface of a semiconductor wafer. The semiconductor wafer on which the thin film containing the dopant is deposited is rapidly heated to a first peak temperature by irradiation with light from halogen lamps, so that the dopant is diffused from the thin film into the surface of the semiconductor wafer. The thermal diffusion using the rapid heating achieves the introduction of the necessary and sufficient dopant into the semiconductor wafer without producing defects. The surface of the semiconductor wafer is heated to a second peak temperature by further irradiating the semiconductor wafer with flashes of light from flash lamps, so that the dopant is activated. The flash irradiation which is extremely short in irradiation time achieves a high activation rate without excessive diffusion of the dopant.