Thin Layer Transfer Heating Profile for Low-Roughness Separation
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Solution Overview
Problem
Existing SMART CUT™ technology for transferring thin films in SOI structures exhibits significant variability in surface roughness, particularly due to spontaneous separation in the buried brittle plane, leading to high and low-frequency roughness variations that degrade the final quality of the transferred thin films.
Innovation Solution
A transfer method involving a fracture heat treatment with a rapid temperature rise-rate (>1°C/s) and a controlled temperature gradient between the central and peripheral regions of the bonded structure, combined with pre-annealing to ripen microcracks, followed by in situ smoothing at high temperatures, to achieve early and repeatable separation with improved surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If spontaneous separation is used in the buried brittle plane, then the transfer process is simple and efficient, but the surface roughness of the transferred thin film becomes highly variable with significant microroughness and rippling
Solution Approach 1:
The patent applies a controlled temperature gradient (varying between 40°C and 120°C between central and peripheral regions) and rapid heating rate (>1°C/s) during fracture heat treatment to modify the separation process parameters, achieving early and repeatable separation with improved surface roughness
Solution Approach 2:
The patent performs pre-annealing treatment before the fracture heat treatment to ripen microcracks in the buried brittle plane, preparing the structure for controlled separation and reducing surface roughness variability
2Ease of manufacture
If conventional fracture heat treatment is used, then the separation process is straightforward, but the temperature control is insufficient to achieve repeatable early separation with low surface roughness
Solution Approach 1:
The patent implements dynamic temperature control with a rapid heating rate (>1°C/s) and a controlled temperature gradient that varies between 40°C and 120°C, enabling precise control over the separation timing and surface roughness outcome
Solution Approach 2:
The patent uses inspection tools to measure surface roughness and haze, providing feedback that allows optimization of the temperature gradient and heating rate parameters to achieve the desired separation characteristics
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 ensures low microroughness and minimal dense zones, significantly enhancing the surface quality of the transferred thin films by reducing mottling and ripple defects, thereby improving the overall quality of the stacked structure.
Implementation Method 1
applying a fracture heat treatment to induce spontaneous separation along the buried brittle plane, associated with the growth of microcracks in the plane through thermal activation
Implementation Method 2
a temperature rise-rate in excess of 1° C./s, at least between an initial temperature lower than 250° C. and a level temperature greater than or equal to 500° C.
Implementation Method 3
a temperature profile such that the bonded structure is subjected to a temperature gradient varying between 40° C. and 120° C. between a central region and a peripheral region
Implementation Method 4
The assembly is advantageously carried out by direct bonding, by molecular adhesion, that is, without involving adhesive material: a bonding interface is thus established between the two assembled substrates
Data Source
AI summary
A method of transferring a thin layer onto a support substrate comprises the following steps: —supplying a bonded structure comprising a donor substrate and the support substrate, assembled by direct bonding at the respective front faces thereof along a bonding interface, the donor substrate comprising a buried brittle plane, —applying a fracture heat treatment to the bonded structure to induce spontaneous separation along the buried brittle plane, associated with the growth of microcracks in the plane through thermal activation, the separation leading to the transfer of a thin layer from the donor substrate to the support substrate. The fracture heat treatment exhibits: —a temperature-rise rate in excess of 1° C./s, at least between an initial temperature lower than 250° C. and a plateau temperature greater than or equal to 500° C., and —a temperature profile such that the bonded structure is subjected to a temperature gradient varying between 40° C. and 120° C. between a central region and a peripheral region.