Semiconductor Contact Formation via Pulsed Light Heating
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Solution Overview
Problem
Conventional heat treatment methods for forming semiconductor contacts, especially on silicon carbide substrates, often result in deteriorated interface characteristics due to hydrogen desorption and impurity diffusion, leading to increased contact resistance and process inefficiencies.
Innovation Solution
A semiconductor manufacturing method involving ion implantation, metal layer formation, and brief light emission in a hydrogen-containing forming gas atmosphere to heat the substrate, utilizing a spectral distribution with higher intensity at 300 nm relative to 500 nm to absorb light effectively, and optionally incorporating a light absorbing film to enhance heating, all while maintaining low contact resistance without degrading device characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperature heat treatment is performed for contact formation, then contact resistance decreases, but hydrogen desorption occurs and interface characteristics deteriorate
Solution Approach 1:
The patent applies periodic action by using pulsed light irradiation instead of continuous heating. The light is emitted in short pulses (e.g., 10 ms to 10 seconds) to rapidly heat the substrate to high temperatures for contact formation, then quickly cool it down. This periodic heating-cooling cycle achieves the desired contact resistance reduction while limiting the total exposure time that would cause hydrogen desorption and interface deterioration.
Solution Approach 2:
The patent changes the temperature-time parameters of the heat treatment process. Instead of prolonged heating at moderate temperatures, the invention uses brief exposure to extremely high temperatures via light irradiation. By controlling the light pulse duration and intensity, the process achieves rapid thermal cycles that form low-resistance contacts before hydrogen desorption can significantly occur.
2Reliability
If high temperature heat treatment is performed for contact formation, then contact resistance decreases, but impurity diffusion occurs and device characteristics deteriorate
Solution Approach 1:
The pulsed light irradiation creates rapid heating and cooling cycles that minimize the time available for impurity diffusion. The short duration of each light pulse (10 ms to 10 seconds) provides just enough time for contact resistance reduction while preventing significant impurity migration that would degrade device characteristics.
Solution Approach 2:
The invention rushes through the heat treatment process by using intense, brief light pulses. This rapid heating and immediate cooling 'skips' over the time period where impurity diffusion would occur, achieving the desired electrical contact properties without compromising the compositional stability of the semiconductor structure.
3Reliability
If conventional furnace heat treatment is performed, then contact formation is achieved, but treatment time is long and process efficiency decreases
Solution Approach 1:
The patent replaces the mechanical furnace heating system with an optical system. Instead of using thermal conduction and convection from a furnace environment, the invention uses direct light irradiation (e.g., from LEDs or other light sources) to heat the substrate. This substitution of heating mechanism dramatically reduces the treatment time from minutes to milliseconds or seconds while achieving the same contact formation objective.
Solution Approach 2:
The periodic pulsed light irradiation enables rapid thermal cycles that achieve contact formation in brief intervals. Each pulse delivers the necessary thermal energy for contact formation, then the substrate quickly cools, repeating the cycle if needed. This periodic approach is far more time-efficient than continuous furnace heating.
4Use of energy by moving object
If light absorbing film is added to enhance heating, then heating efficiency increases, but process complexity increases
Solution Approach 1:
The patent applies local quality by adding the light absorbing film only in specific regions where enhanced heating is needed, such as the contact regions or specific zones of the substrate. This localized approach improves heating efficiency where required without unnecessarily complicating the entire device structure or adding global process steps.
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 the formation of low-contact-resistance semiconductor contacts without hydrogen desorption and impurity diffusion, simplifying the process and maintaining device integrity by briefly heating the substrate to high temperatures in a controlled atmosphere.
Implementation Method 1
emitting light to the semiconductor substrate to be supported by the susceptor for one second or less for heating
Implementation Method 2
The temperature on the surface of the semiconductor substrate can be raised without desorbing hydrogen taken for hydrogen termination
Implementation Method 3
hydrogen taken in the vicinity of the interface is desorbed, resulting in deterioration of the interface characteristics
Implementation Method 4
the step (c) is performed in a forming gas atmosphere containing hydrogen
Implementation Method 5
forming a light absorbing film on the metal layer before the step (c). This increases the absorption rate of the emitted light
Data Source
AI summary
Flash light is emitted from flash lamps to the surface of a semiconductor substrate on which a metal layer has been formed for one second or less to momentarily raise temperature on the surface of the semiconductor substrate including the metal layer and an impurity region to a processing temperature of 1000° C. or more. Heat treatment is performed by emitting flash light to the surface of the semiconductor substrate in a forming gas atmosphere containing hydrogen. By heating the surface of the semiconductor substrate to a high temperature in the forming gas atmosphere for an extremely short time period, contact resistance can be reduced without desorbing hydrogen taken in the vicinity of an interface of a gate oxide film for hydrogen termination.