Bonded Wafer Cleaning via NF3 Gas and Sacrificial Oxidation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The ion implantation delamination method for manufacturing SOI wafers generates small particles (65 nm) from the delamination surface, which are difficult to remove and lead to contamination, causing productivity issues in the cleaning line, especially when ultrasonic cleaning is used.
Innovation Solution
A method that prevents the generation of 65 nm particles by performing cleaning without ultrasonic application in each bath step, followed by a flattening process using sacrificial oxidation or vapor phase etching to remove damage-remaining parts, and optionally includes a second cleaning step with ultrasonic or a third physical action step to address larger particle contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If ultrasonic cleaning is applied to remove particles from the delamination surface, then particle removal capability is improved, but generation of new small particles (65 nm) occurs due to mechanical action on the damaged layer
Solution Approach 1:
The patent replaces the mechanical ultrasonic cleaning system with a chemical cleaning system using NF3 gas. The NF3 gas chemically reacts with and removes particles from the delamination surface without the mechanical vibration that causes damaged layer fragmentation, thus eliminating particle generation while achieving particle removal
Solution Approach 2:
The patent changes the cleaning method from mechanical (ultrasonic) to chemical (NF3 gas treatment). This parameter change in the cleaning mechanism fundamentally alters how particles are removed, avoiding the generation of new particles from the damaged layer while still achieving effective particle removal
2Shape
If touch polishing is performed to remove the damaged layer, then surface roughness is improved, but film thickness uniformity of the SOI layer deteriorates due to non-uniform stock removal
Solution Approach 1:
The patent replaces the mechanical touch polishing process with chemical cleaning using NF3 gas. This substitution eliminates the mechanical removal action that causes non-uniform stock removal, thereby preserving the film thickness uniformity achieved during ion implantation while still improving surface quality by removing particles and damaged layer material
Solution Approach 2:
The patent changes the surface treatment parameter from mechanical polishing to chemical cleaning. This fundamental parameter change allows removal of the damaged layer and particles without the non-uniform material removal inherent in mechanical polishing, thus maintaining the precise film thickness uniformity
3Shape
If high-temperature heat treatment is applied to improve surface roughness, then surface quality is improved, but additional process steps and time are required
Solution Approach 1:
The patent extracts the surface treatment function from the high-temperature heat treatment process and implements it separately using NF3 gas cleaning. This allows particle and damaged layer removal without requiring the extended high-temperature processing time, thereby reducing overall process time while achieving surface quality improvement
Solution Approach 2:
The patent changes the surface treatment method from thermal processing to chemical cleaning. This parameter change enables effective removal of particles and damaged layer material without the time-consuming high-temperature heat treatment, thus reducing process time while maintaining or improving surface quality
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 effectively controls and reduces particles of 65 nm or more, improving cleaning line productivity and ensuring the removal of damage-remaining parts, thereby suppressing particle generation in subsequent processes.
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 the ion implantation layer (also referred to as a micro bubble layer or 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 so that the bond wafer is separated into a thin film
Implementation Method 3
another heat treatment (a bonding heat treatment) is then performed to strengthen a bond between the wafers
Implementation Method 4
introduction of NF3 gas into a cleaning bath for cleaning particles from a surface of the bonded wafer
Data Source
Figure 1
AI summary
The present invention is a method for manufacturing a bonded wafer comprising: producing a bonded wafer having a thin-film on its base wafer by an ion implantation delamination method, and reducing a film thickness of the thin-film, wherein the step of reducing the film thickness comprises a stage of reducing the film thickness by sacrificial oxidation treatment or vapor phase etching, wherein the method for manufacturing a bonded wafer further comprises a cleaning step of cleaning the bonded wafer exposing the delamination surface just before the step of reducing the film thickness, wherein the cleaning step includes a stage of performing a wet cleaning by successively dipping the bonded wafer to plural of cleaning baths, and wherein the wet cleaning is performed without applying ultrasonic in each of the cleaning baths in the wet cleaning. The method enables to clean a bonded wafer exposing a delamination surface remaining damage of ion implantation using a cleaning line in a strict control level.