CVD Susceptor Assembly for HTS Tape Thermal Control
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Solution Overview
Problem
Existing heated susceptors in CVD processes for HTS production face challenges with high temperature gradients, errant deposition on susceptor surfaces, and difficulty in maintaining precise thermal control, which affects the quality and continuity of HTS film deposition.
Innovation Solution
A susceptor assembly with a longitudinal susceptor block, refractory elements, a radiation shield, and heater elements, along with channels to collect errant deposition material, is designed to provide improved thermal control and minimize errant deposition, thereby enhancing the quality and continuity of HTS film deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a hot block susceptor is used to heat the substrate tape, then the deposition temperature can be maintained, but high temperature gradients are created within the reactor and on the susceptor surface
Solution Approach 1:
The susceptor block is segmented into multiple heating zones with independent temperature control, allowing different regions to be optimized for their specific functions. The top surface is segmented to prevent errant deposition while side surfaces are heated to maintain structural integrity without causing excessive temperature gradients.
Solution Approach 2:
Different surfaces of the susceptor are given different thermal properties and heating characteristics. The top deposition surface is designed with specific emissivity and thermal conductivity to maintain uniform temperature, while side surfaces have different properties to minimize errant deposition. Heating elements are strategically positioned to provide localized heating where needed.
2Productivity
If the showerhead is positioned close to the deposition surface (5-30 mm spacing), then deposition efficiency is improved, but illumination intensity cannot be maintained at required levels and temperature gradients increase
Solution Approach 1:
The susceptor top surface is designed with specific radiative properties (emissivity) to maintain uniform temperature distribution despite the close proximity of the showerhead. The surface geometry and material properties are optimized to distribute heat evenly across the deposition area, compensating for the temperature gradients that would otherwise result from the small spacing.
3Quantity of substance
If precursor and carrier gases flow from the showerhead, then reactant delivery is achieved, but the cooler gases cool both the susceptor and substrate, making the deposition process sensitive to temperature changes
Solution Approach 1:
The susceptor is pre-heated to the target deposition temperature before precursor introduction, and heating continues throughout the process to compensate for cooling from gas flow. The heating system is designed to anticipate and counteract the cooling effect of the precursor and carrier gases, maintaining temperature stability within the required 5-10°C range.
4Manufacturing precision
If the susceptor operates at high temperature (800-900°C), then HTS film growth occurs, but errant deposition builds up on exposed surfaces of the susceptor and other reactor components
Solution Approach 1:
The harmful hot surfaces that cause errant deposition are removed or isolated. The susceptor design minimizes exposed hot surfaces to only those necessary for substrate heating. Side surfaces and other exposed areas are either shielded, insulated, or kept at lower temperatures through separate heating control, extracting the problem-causing elements from the system.
Solution Approach 2:
Different surfaces of the susceptor have different temperature profiles and heating characteristics. The top surface that contacts the substrate is heated to 800-900°C for proper film growth, while side and exposed surfaces are maintained at lower temperatures or have reduced heating to prevent errant deposition. This localized thermal control allows HTS film quality to be maintained while minimizing material loss to errant deposition.
5Duration of action of moving object
If long process times are used for HTS tape manufacturing, then production continuity is achieved, but errant deposition on the susceptor builds up to exceed tape thickness
Solution Approach 1:
The susceptor design removes or minimizes the exposed surfaces that accumulate errant deposition. By configuring the susceptor geometry and thermal fields, surfaces prone to buildup are either eliminated, shielded, or maintained at temperatures below the errant deposition threshold (400-450°C), allowing continuous operation without frequent cleaning interruptions.
Solution Approach 2:
The temperature parameters of exposed susceptor surfaces are changed and maintained below the errant deposition threshold (400-450°C) while the top deposition surface remains at the required 800-900°C. This parameter differentiation allows long process runs by preventing buildup on exposed surfaces that would otherwise require periodic cleaning.
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 susceptor assembly effectively reduces temperature gradients and errant deposition, allowing for precise thermal control and improved HTS film quality, enabling longer continuous process runs and higher-quality HTS tape production.
Implementation Method 1
a heater element coupled to the susceptor block, with at least a portion of the heater element extending to an exterior of the susceptor assembly
Implementation Method 2
a radiation shield surrounding one or more sides of the refractory element
Implementation Method 3
a longitudinal susceptor block for heating at least one longitudinal substrate tape
Implementation Method 4
In the manufacturing of High Temperature Superconductors (HTS) via chemical vapor deposition (CVD) or metal-organic chemical vapor deposition (MOCVD) processing
Data Source
AI summary
A thermally stable susceptor assembly used in a deposition reactor provides heat input and controls the temperature of a substrate tape as well as minimizes the build-up of errant deposition material. The susceptor heats a substrate tape within the reactor upon which one or more thin films are deposited, particularly high temperature superconductor (HTS) thin films produced in a MOCVD reactor.