Semiconductor Wafer Layer Transfer Hole Density Control
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Solution Overview
Problem
Existing semiconductor wafer layer transfer processes, such as SMART-CUT®, often result in a high density of holes, including through holes, which can compromise the quality of the thin semiconductor layer, particularly in SOI structures, making it challenging to achieve the desired thickness and surface quality.
Innovation Solution
A method is developed to determine a minimum layer thickness for the semiconductor layer to be transferred, with a region of weakness created in the donor substrate by implanting atomic species, followed by a finishing sequence that includes thermal annealing, sacrificial oxidation, and polishing operations to reduce shallow holes and control the density of through holes, ensuring the transferred layer meets the target thickness and surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a thin semiconductor layer is transferred using conventional layer transfer processes, then the desired thin layer thickness is achieved, but the density of holes including through holes increases
Solution Approach 1:
The patent applies preliminary action by determining the minimum layer thickness before the transfer process based on the finishing sequence operations that will be performed afterward. The method calculates the thickness that must be transferred to ensure that after thermal annealing, sacrificial oxidation, and polishing, the final layer meets both the target thickness and acceptable hole density requirements. This preliminary determination prevents transferring layers that are too thin and would result in excessive hole density after finishing operations.
Solution Approach 2:
The patent implements feedback by using the results of finishing sequence operations to adjust and determine the appropriate minimum layer thickness for transfer. The method considers the impact of thermal annealing, sacrificial oxidation, and polishing on hole density and layer thickness, using this information to establish the optimal thickness to transfer initially. This feedback loop ensures that the transferred layer thickness is optimized to achieve the desired final quality after all processing steps.
2Reliability
If the layer thickness is increased to reduce hole density, then the density of through holes decreases, but the target thickness cannot be achieved
Solution Approach 1:
The patent applies parameter changes by systematically varying and optimizing the minimum layer thickness parameter based on the specific finishing sequence operations to be performed. The method adjusts the thickness parameter to account for the material removal and hole density changes that occur during thermal annealing, sacrificial oxidation, and polishing. By changing this critical parameter based on process conditions, the patent achieves the optimal balance between maintaining acceptable hole density and achieving the target final thickness.
Solution Approach 2:
The patent determines the minimum layer thickness in advance before transfer, considering the cumulative effect of all finishing operations. This preliminary determination ensures that the layer is thick enough to maintain acceptable hole density throughout the finishing sequence while still allowing the final thickness to meet the target specification. The method calculates this optimal thickness by working backward from the desired final state through each finishing operation.
3Manufacturing precision
If a finishing sequence is applied to improve surface quality, then the surface quality improves, but the layer thickness is reduced
Solution Approach 1:
The patent applies preliminary action by determining the minimum layer thickness to transfer with consideration of the material removal that will occur during the finishing sequence. The method calculates the required initial thickness by adding the expected material removal from thermal annealing, sacrificial oxidation, and polishing to the target final thickness. This ensures that after all finishing operations remove material, the final layer still achieves the desired thickness while benefiting from improved surface quality.
Solution Approach 2:
The patent uses parameter changes by adjusting the minimum layer thickness parameter based on the specific finishing sequence operations selected. Different finishing sequences remove different amounts of material and have different impacts on surface quality, so the method optimizes the initial thickness parameter to match the chosen finishing sequence. This dynamic parameter adjustment ensures optimal balance between surface quality improvement and final thickness achievement.
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 method effectively reduces the density of through holes and improves the surface quality of the transferred semiconductor layer, achieving the desired thickness and minimizing defects, thereby enhancing the quality of the final semiconductor structure.
Implementation Method 1
After bonding, the donor substrate splits or is cut at the region of weakness
Implementation Method 2
at least one shallow-hole reducing operation that reduces the depth of shallow holes that are present in the transferred layer, which shallow holes extend less than completely through the transferred layer. At least one shallow hole reducing operation can include a thermal annealing operation
Implementation Method 3
The selected finishing sequence can comprise at least one succession of a rapid thermal annealing operation and a sacrificial oxidation operation
Implementation Method 4
The selected finishing sequence can include at least one succession of a first sacrificial oxidation operation, followed by a polishing operation
Data Source
AI summary
A method for configuring a process for treating a semiconductor wafer. A minimum layer thickness of a transferred layer to be provided is determined to obtain a processed layer that has a preselected target thickness and target maximum density of through holes that extend completely therethrough, by conducting a predetermined finishing sequence of operations that improve the surface quality of the layer. The minimum thickness is determined such that the density of through holes remains below the target maximum density after each operation in the finishing sequence.