Bonded Wafer Surface Flattening via RTA and Sacrificial Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The ion implantation separation method for manufacturing SOI wafers results in a damage layer and surface roughness, which can lead to increased bulk micro defect (BMD) density, causing misalignment issues in photolithography due to the combination of rapid thermal annealing (RTA) and sacrificial oxidation processes.
Innovation Solution
A method involving RTA under specific temperature conditions, with a retention start temperature of 1175°C to 1250°C and a retention end temperature of 1100°C to 1150°C, followed by a sacrificial oxidation process, to inhibit the formation of new BMD nuclei and flatten the surface of the thin film, thereby reducing BMD density and surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If RTA and sacrificial oxidation processes are performed to remove the damage layer and flatten the surface, then surface roughness is improved, but BMD density increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the RTA temperature profile (heating rate, peak temperature, holding time, and cooling rate) and oxidation conditions to achieve surface flattening while minimizing BMD formation. By optimizing these parameters, the process removes the damage layer and flattens the surface without excessively increasing BMD density
Solution Approach 2:
The patent applies local quality by creating a controlled oxidation environment where oxidation occurs preferentially at the surface to remove damaged layers, while the bulk material is protected from excessive oxidation that would generate BMDs. The differential treatment of surface versus bulk material allows surface improvement without harmful bulk effects
2Shape
If touch polishing is performed to remove the damage layer, then surface roughness is improved, but uniformity of SOI layer thickness is degraded
Solution Approach 1:
The patent replaces the mechanical touch polishing system with a thermal-chemical system (RTA and sacrificial oxidation). Instead of using mechanical abrasion to remove the damage layer, the process uses controlled thermal oxidation to chemically remove damaged material, thereby avoiding the nonuniform material removal inherent in mechanical polishing and preserving SOI layer thickness uniformity
Solution Approach 2:
The patent uses parameter changes in the thermal and chemical fields to achieve surface improvement. By controlling temperature, oxidation atmosphere composition, and processing time, the method removes damaged layers uniformly without the mechanical contact that causes nonuniform polishing, thus maintaining precise control over SOI layer thickness
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 produces a bonded wafer with low BMD density and improved surface smoothness, preventing deformation and misalignment during device processes, ensuring high-quality photolithography for advanced integrated circuits.
Implementation Method 1
gas ions such as hydrogen ions or rare gas ions are implanted from a front surface of one of the silicon wafers (a bond wafer) to form a micro bubble layer (an enclosed layer) in the interior of the wafer
Implementation Method 2
a heat treatment (a delamination heat treatment) is then performed to cleave one of the wafers (the bond wafer) along the micro bubble layer
Implementation Method 3
performing rapid thermal annealing (RTA) under an atmosphere containing hydrogen on the bonded wafer after separating the bond wafer
Implementation Method 4
subsequently performing a sacrificial oxidation process to reduce a thickness of the thin film
Data Source
Figure 1~3
Figure 4~6
Figure 7(a)~7(g)
AI summary
The present invention provides a method of manufacturing a bonded wafer, including performing RTA under an atmosphere containing hydrogen on a bonded wafer after separating the bond wafer constituting the bonded wafer, and subsequently performing a sacrificial oxidation process to reduce the thickness of the thin film, wherein the RTA is performed under conditions of a retention start temperature of more than 1150°C and a retention end temperature of 1150°C or less. The invention can inhibit the BMD density from increasing and sufficiently flatten the surface of a thin film when the thin film of the bonded wafer is flattened and thinned by the combination of the RTA and sacrificial oxidation processes.