Transfer Chamber Metrology for LED Epitaxial Yield
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Solution Overview
Problem
The challenge in the semiconductor industry is the difficulty in controlling the epitaxial growth of thin material layers in LED stacks, particularly due to the dependence of device properties on material and physical characteristics, which is exacerbated by the inability to perform in-situ metrology in the epitaxy chamber, leading to significant yield loss when growth processes deviate from specifications.
Innovation Solution
Implementing a multi-chambered cluster tool with a transfer chamber for metrology, where substrates pass through a metrology-equipped chamber between growth operations, allowing for measurements such as PL, thickness, resistivity, and roughness assessment, and using temperature correction based on emission from a known base layer or absorbance band edge to control epitaxial growth parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If in-situ metrology is performed in the epitaxy chamber, then real-time measurement capability is improved, but the epitaxy chamber environment obscures observation of material properties
Solution Approach 1:
The patent introduces a transfer chamber as an intermediary environment between the epitaxy chamber and the measurement system. The transfer chamber provides a controlled atmosphere that allows optical access for metrology while maintaining the vacuum or inert environment needed for epitaxial growth. This mediator enables measurements to be performed on substrates without exposing them to air or contaminants that would interfere with both growth and observation.
Solution Approach 2:
The system is divided into separate functional chambers: an epitaxy chamber for material growth, a transfer chamber for substrate handling and metrology, and a measurement system. This segmentation allows each chamber to be optimized for its specific function - the epitaxy chamber maintains growth conditions while the transfer chamber provides the transparent environment needed for optical measurements.
2Manufacturing precision
If post-manufacture metrology is performed, then manufacturing control is improved, but the control point is too downstream to avoid significant yield loss
Solution Approach 1:
The transfer chamber metrology system performs measurements after epitaxial growth but before subsequent processing steps. This preliminary measurement allows detection of growth deviations early in the manufacturing sequence, enabling corrective actions to be taken before additional materials and processing steps are applied, thereby minimizing yield loss.
Solution Approach 2:
The metrology system provides feedback on the quality and characteristics of epitaxially grown layers. This feedback loop enables real-time monitoring and control of growth processes, allowing manufacturers to adjust parameters for subsequent wafers or process steps based on measured deviations, thereby maintaining manufacturing precision while reducing waste.
3Extent of automation
If a multi-chambered cluster tool with transfer chamber is implemented, then real-time control capability is improved, but device complexity increases
Solution Approach 1:
The transfer chamber serves multiple functions: it acts as a transition zone between epitaxy and measurement chambers, provides a controlled environment for metrology, and enables substrate handling without exposure to air. This multi-functionality reduces the need for additional separate systems, thereby limiting the increase in overall device complexity while maintaining real-time control capabilities.
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 enables real-time control of epitaxial growth processes, reducing yield loss by allowing for immediate adjustments based on metrology data, thereby improving the consistency and quality of LED film stacks.
Implementation Method 1
PL measurement of a group III-V film grown in a first chamber while a substrate is at an elevated (high) temperature
Implementation Method 2
temperature correction based on emission from a known base layer or absorbance band edge
Data Source
AI summary
Apparatus and method for control of epitaxial growth parameters, for example during manufacture of light emitting diodes (LEDs). Embodiments include PL measurement of a group III-V film following growth while a substrate at an elevated temperature is in a transfer chamber of a multi-chamber cluster tool. In other embodiments, a film thickness measurement, a contactless resistivity measurement, and a particle and/or roughness measure is performed while the substrate is disposed in the transfer chamber. One or more of the measurements performed in the transfer chamber are temperature corrected to room temperature by estimating the elevated temperature based on emission from a GaN base layer disposed below the group III-V film. In other embodiments, temperature correction is based on an absorbance band edge of the GaN base layer determined from collected white light reflectance spectra. Temperature corrected metrology is then used to control growth processes.