Wafer Metrology Electrostatic Force Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing semiconductor wafer metrology techniques face challenges in accurately measuring wafer mass due to errors caused by atmospheric buoyancy, electrostatic forces, and air currents, which are difficult to simultaneously minimize using conventional methods.
Innovation Solution
The use of a grounded Faraday cage to isolate and measure electrostatic forces, combined with precise monitoring of atmospheric conditions, allows for correction of weight measurements by subtracting the electrostatic force's effect, thereby improving mass measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a housing (weighing chamber) is used to reduce air current effects, then measurement stability is improved, but electrostatic forces from surrounding materials increase
Solution Approach 1:
A Faraday cage is introduced as an intermediary structure between the wafer and the chamber walls. The cage is made of conductive material and connected to ground, creating an electrostatic shield that blocks electric field lines from reaching the wafer. This mediator allows the chamber to maintain its stabilizing function while preventing harmful electrostatic forces from acting on the measurement object.
2Object-affected harmful factors
If surrounding materials are placed far from the wafer to reduce electrostatic forces, then electrostatic interference is reduced, but the space required for the housing increases
Solution Approach 1:
The Faraday cage acts as a compact intermediary shield that can be positioned close to the wafer without requiring large spacing. The conductive mesh structure of the cage provides effective electrostatic shielding while occupying minimal space, allowing the housing to maintain a compact form factor while still protecting against electrostatic forces.
3Object-affected harmful factors
If ionization devices are used to reduce static electricity, then surface charges are neutralized, but residual charges remain due to unbalanced ion streams
Solution Approach 1:
The grounded Faraday cage serves as a passive intermediary shield that blocks electrostatic forces without requiring active ionization. By providing a conductive barrier connected to ground, the cage prevents both positive and negative charge accumulation on the wafer surface, avoiding the residual charge problem associated with unbalanced ion streams from ionization devices.
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 significantly reduces measurement errors, achieving high repeatability and accuracy in determining the mass of semiconductor wafers by compensating for both electrostatic and buoyancy forces, resulting in improved quality control during production.
Implementation Method 1
placing the wafer on a sensing element of a first weighing instrument, the sensing element being inside a grounded faraday cage
Implementation Method 2
Electrostatic attraction forces arise when there is a voltage potential difference between the wafer and surrounding material
Implementation Method 3
A common method of obtaining mass measurements is to use a very sensitive force sensor to measure the force (weight) due to gravity
Implementation Method 4
The wafer therefore displaces a volume of this atmosphere, which causes an up thrust force. The up thrust force depends on the atmospheric (air) density
Data Source
AI summary
A semiconductor wafer metrology technique which corrects for the effect of electrostatic forces on an atmospheric buoyancy compensated weight force measurement of a semiconductor wafer. In one aspect a wafer is weighed in a faraday cage whose is measured independently. A change in the measured weight of the faraday cage can be used to correct the measure weight the wafer. In another aspect a direct electrostatic measurement can be converted into a weight correction using a predetermined correlation between an electrostatic charge measured by the charge meter and a weight error force. In another aspect the electrostatic measurement may be indirect, e.g. derived from varying the distance between the wafer and a grounded plate parallel to the wafer to effect a change in an electrostatic force between the grounded plate and the wafer.