Semiconductor Wafer Wet-Start Cleaning for Lower Center Defects
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Solution Overview
Problem
Existing methods for cleaning semiconductor wafers often result in defect patterns, particularly in the center of the wafer, which can negatively impact the manufacturing process for microelectronic components.
Innovation Solution
A multi-step cleaning process involving pre-cleaning with increasing ozonated water concentration, followed by sequential steps with ozonated water, HF treatment, and drying in a nitrogen atmosphere, while maintaining specific rotational speeds and nozzle alignment, is employed to minimize defect occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-wafer cleaning process is used, then the cleaning process is simple and fast, but defect patterns occur in the center of the wafer
Solution Approach 1:
The cleaning process is divided into multiple sequential steps (pre-cleaning, first cleaning, second cleaning, third cleaning, rinsing, drying) with different chemical treatments and parameter settings. Each step targets specific contamination types and addresses the defect formation issue at different stages, transforming a single problematic process into a segmented multi-step procedure that eliminates center defects.
Solution Approach 2:
A pre-cleaning step is introduced before the main cleaning steps to prepare the wafer surface. This preliminary action removes initial contaminants and conditions the surface, preventing defect formation during subsequent cleaning steps. The pre-cleaning establishes a clean baseline that prevents the center defect pattern from developing.
2Reliability
If multiple cleaning steps with different chemicals are used, then defect patterns are reduced, but the process time and complexity increase
Solution Approach 1:
The multiple cleaning steps are designed to proceed continuously without interruption, with each step immediately following the previous one. The wafer rotates continuously through different chemical environments (SC1, HF, SC2 solutions) in sequence, maintaining continuous useful action throughout the process. This continuous multi-step approach achieves defect reduction while minimizing idle time between steps.
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 method significantly reduces radial defect density in the center of the semiconductor wafer, enhancing the reliability of the wafer's behavior in subsequent manufacturing processes.
Implementation Method 1
a first cleaning step for cleaning with ozonized water... a second cleaning step comprising a treatment step with ozonized water... a third cleaning step for cleaning with ozonized water
Implementation Method 2
a treatment step with a liquid containing HF... wherein the second cleaning step may be repeated several times
Implementation Method 3
a semiconductor wafer is set into rapid rotation around its central axis... the liquids are applied to the rotating semiconductor wafer and accelerated by centrifugal force towards the wafer edge, causing the liquids to flow outwards
Implementation Method 4
During subsequent drying with further rotation of the semiconductor wafer, for example with the addition of a vapor that reduces the surface tension of the liquid film (e.g. isopropanol), the liquid film flows completely outwards
Data Source
Figure 1
AI summary
A method for cleaning one side of a semiconductor wafer comprising, in a given sequence: (1) a first cleaning step for cleaning with ozonated water followed by a rinsing step with purified water, (2) a second cleaning step comprising a treatment step with ozonated water followed by a treatment step with an RF-containing liquid, wherein the second cleaning step can be repeated multiple times, (3) a third cleaning step for cleaning with ozonated water followed by a rinsing step with purified water, (4) a drying step in which the side of the semiconductor wafer is dried, characterized in that a pre-cleaning step with water is performed directly before the first cleaning step, so that one side of the semiconductor wafer is still wet when the first cleaning step begins.