Wafer Rinse Liquid for Static Charge Control
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Solution Overview
Problem
Conventional deionized water-carbon dioxide solutions cause undesirable material removal when used on semiconductor wafers with metal or metal-containing structures, and they fail to prevent static charge accumulation effectively, leading to pattern collapse and reduced wafer yield, especially as wafer sizes increase and feature sizes decrease.
Innovation Solution
A dilute aqueous solution of a low-boiling weak base, such as ammonia, is used as a rinse liquid with a pH between 8 and 10, which provides conductivity without removing metals or metal-containing materials, and includes a sensor to adjust the base concentration based on static charge levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If deionized water is used as a rinse liquid, then the insulative characteristics prevent material removal, but static charges accumulate on the wafer surface causing arcing damage
Solution Approach 1:
The patent changes the chemical composition parameter of the rinse liquid by adding weak organic acids (formic acid, acetic acid, propionic acid, or butyric acid) to deionized water. This creates a conductive rinse liquid that prevents static charge accumulation while maintaining low material removal rates due to the weak acidity and controlled concentration (0.01-10% by volume).
Solution Approach 2:
The weak organic acids act as an intermediary substance that bridges the contradiction between insulative and conductive properties. These acids provide sufficient conductivity to prevent static charge buildup without being strong enough to cause significant material removal, thus mediating between the two opposing requirements.
2Reliability
If dissolved carbon dioxide is added to deionized water to prevent static charge accumulation, then conductivity is improved, but undesirable material removal occurs from metal and metal-containing structures
Solution Approach 1:
The patent replaces carbon dioxide with weak organic acids (formic acid, acetic acid, propionic acid, or butyric acid) to change the chemical nature of the conductive agent. These weak acids provide the necessary conductivity for static charge prevention while their weak acidity prevents the material removal problems associated with stronger acids like carbon dioxide.
Solution Approach 2:
The patent uses inexpensive weak organic acids that can be applied in small concentrations and quickly rinsed away, minimizing their interaction time with sensitive metal structures. This approach allows effective static charge prevention without prolonged exposure that would cause material removal.
3Manufacturing precision
If the surface tension of the rinse liquid is too high, then pattern collapse occurs due to radially outward movement, but lower surface tension may increase material removal
Solution Approach 1:
The patent modifies the surface tension parameter by adding weak organic acids to the rinse liquid. These acids reduce surface tension sufficiently to prevent pattern collapse during the rinsing process, while their weak chemical nature ensures that material removal remains minimal.
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 solution effectively prevents static charge buildup and minimizes material removal during rinsing, maintaining the integrity of metal structures on semiconductor wafers while ensuring low etch rates, thus enhancing wafer yield and reducing damage.
Implementation Method 1
the insulative characteristics of the deionized water can lead to the accumulation of static charges on the wafer surface... the rinse liquid comprises an aqueous solution of a base... which provides conductivity
Implementation Method 2
the base furthermore has a boiling point less than 100° C.... dilute aqueous solutions of low-boiling weak bases can provide the desired conductivity
Data Source
AI summary
In a method and apparatus for treating a surface of an article, an improved rinse liquid prevents build-up of static charge while avoiding damages to certain types of exposed metal-containing surfaces. In one embodiment, a semiconductor wafer having structures including at least one of cobalt, nickel and platinum is rotated on a spin chuck, as a rinse liquid is dispensed onto a surface of the wafer. The rinse liquid is a dilute aqueous solution of a base of the formulain which R1, R2 and R3 are each independently selected from hydrogen and C1-4 alkyl. The base has a boiling point less than 100° C., and the rinse liquid has a pH in the range of 8 to 10.