Semiconductor Wafer Cleaning via Chemical Oxidation
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Solution Overview
Problem
Conventional cleaning methods for semiconductor wafers after tungsten etch back or chemical mechanical polish fail to effectively remove small-sized defects and particles, and can damage the surface by scratching, especially when trying to remove top excess portions of tungsten plugs, leading to reduced yield and performance issues.
Innovation Solution
A cleaning method involving a combination of hydrogen peroxide and dilute hydrofluoric acid, optionally with ammonium hydroxide, is used to contact the wafer surface, where hydrogen peroxide oxidizes and ammonium hydroxide helps in removing the top excess portions and particles, while dilute hydrofluoric acid ensures minimal damage to the dielectric and metal barrier layers, with controlled temperature and sonic shaking for enhanced effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If DNS (Dai Nippon Screen brush) cleaner is used to brush clean the surface of tungsten plugs and metal barrier layer, then defects and particles can be removed, but the surface of tungsten plugs and metal barrier layer is scratched
Solution Approach 1:
The patent replaces the mechanical brushing system (DNS cleaner with physical brushes) with a chemical cleaning system using hydrogen peroxide and ammonium hydroxide solution. This chemical substitution eliminates mechanical contact that causes scratching while effectively removing organic contaminants and particles through oxidation and chemical dissolution.
Solution Approach 2:
The patent changes the cleaning parameters by using a specific chemical composition (hydrogen peroxide and ammonium hydroxide in deionized water) with controlled temperature (20-70°C) and exposure time (1-10 minutes). These parameter optimizations enable effective cleaning without the mechanical damage inherent in traditional brushing methods.
2Productivity
If conventional cleaning methods are used after tungsten etch back or chemical mechanical polish, then some cleaning is achieved, but small-sized defects and particles are not effectively removed
Solution Approach 1:
The patent employs hydrogen peroxide, a strong oxidant, to rapidly oxidize and remove organic contaminants and small particles from the wafer surface. The oxidation process is accelerated by heating the solution to 20-70°C, which significantly enhances the cleaning effectiveness for small-sized defects that conventional methods miss.
Solution Approach 2:
The cleaning process uses periodic action through sonic shaking during the immersion step, which creates micro-turbulence and enhances the contact between the cleaning solution and the wafer surface. This periodic mechanical agitation complements the chemical action and improves removal of stubborn particles.
3Reliability
If top excess portions of tungsten plugs are removed to prevent electrical short circuits, then device reliability is improved, but cleaning complexity increases
Solution Approach 1:
The cleaning solution serves multiple functions simultaneously: it oxidizes and removes organic contaminants, dissolves inorganic particles, and etches away top excess portions of tungsten plugs. This multi-functionality is achieved through the combination of hydrogen peroxide (oxidation), ammonium hydroxide (complex formation and dissolution), and controlled temperature, eliminating the need for separate processing 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 effectively removes top excess portions and defects from tungsten plugs and metal barrier layers without causing damage, improving the yield and reliability of semiconductor devices by ensuring precise and efficient cleaning.
Implementation Method 1
hydrogen peroxide oxidizes and ammonium hydroxide helps in removing the top excess portions and particles
Implementation Method 2
optionally with ammonium hydroxide, is used to contact the wafer surface, where hydrogen peroxide oxidizes and ammonium hydroxide helps in removing the top excess portions and particles, while dilute hydrofluoric acid ensures minimal damage to the dielectric and metal barrier layers, with controlled temperature and sonic shaking for enhanced effectiveness
Data Source
AI summary
A novel cleaning method for preventing defects and particles resulting from post tungsten etch back or tungsten chemical mechanical polish is provided. The cleaning method comprises providing a stack structure of a semiconductor device including a tungsten plug in a dielectric layer. The tungsten plug has a top excess portion. A surface of the stack structure is then contacted with a cleaning solution comprising hydrogen peroxide. Next, the surface of the stack structure is contacted with dilute hydrofluoric acid. The cleaning solution and hydrofluoric acid are capable of removing the top excess portion and particles on the surface of the stack structure.