Multi-Electrode Capacitive Wafer Bow Measurement
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Solution Overview
Problem
Conventional methods for measuring semiconductor wafer planarity, such as laser interferometry and capacitive sensing, are either expensive or time-consuming, and capacitive sensing techniques can only obtain measurements from one location at a time, reducing throughput.
Innovation Solution
A capacitive measurement tool with a non-contact capacitive sensor unit featuring a plurality of electrodes that simultaneously obtain capacitance measurements from multiple locations on the wafer surface, allowing for improved throughput and accuracy by calculating wafer bow using a controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser interferometry is used to measure wafer planarity, then measurement precision is improved, but device complexity and measurement time increase
Solution Approach 1:
The patent replaces the optical mechanical system of laser interferometry with a capacitive sensing system. The capacitive sensor unit uses electrical field interaction between electrodes and wafer surface to measure planarity, eliminating complex optical components like beam splitters, mirrors, and photodetectors while achieving comparable or superior measurement precision.
Solution Approach 2:
The capacitive sensor unit is designed to perform multiple functions: it can measure wafer planarity, detect wafer bow, and map surface topology simultaneously using the same electrode array, replacing the need for separate specialized measurement systems.
2Device complexity
If conventional capacitive sensing is used to measure wafer planarity, then device complexity is reduced, but productivity decreases due to sequential measurements
Solution Approach 1:
The sensor unit is segmented into multiple electrodes arranged in a grid pattern across the wafer surface. Each electrode independently measures capacitance at its location, allowing parallel measurement of multiple points simultaneously rather than sequentially scanning across the wafer.
Solution Approach 2:
The patent transitions from one-dimensional sequential scanning (moving the sensor across the wafer surface line by line) to two-dimensional simultaneous measurement (using an array of electrodes covering the entire wafer surface at once), dramatically increasing measurement throughput.
3Device complexity
If a single electrode is used for capacitive measurement, then device complexity is minimized, but measurement precision and data collection capability are limited
Solution Approach 1:
Multiple individual capacitive sensing elements (electrodes) are merged into a single integrated sensor unit that functions as one measurement device. The electrode array is electrically connected to a readout circuit that processes signals from all electrodes simultaneously, combining the capabilities of multiple simple sensors into one sophisticated unit.
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 capacitive measurement tool enhances throughput and measurement accuracy by simultaneously collecting data across the wafer surface, providing precise wafer bow measurements and enabling efficient 3D mapping, which can be used to enhance wafer patterning and mitigate stress regions.
Implementation Method 1
obtain a plurality of capacitance values from the plurality of electrodes by measuring a capacitance between each electrode and a respective opposing area on the surface of the semiconductor wafer
Data Source
AI summary
Systems and methods are provided herein for determining the planarity of a semiconductor wafer. The systems and methods described herein utilize a capacitive measurement tool to detect and characterize the bow of a semiconductor wafer. The capacitive measurement tool disclosed herein utilizes a non-contact, capacitive sensor unit to measure wafer bow. Unlike conventional capacitive sensing techniques used to measure wafer bow, the capacitive sensor unit disclosed herein uses a plurality of electrodes for simultaneously obtaining a plurality of capacitance measurements from the wafer at various locations on the wafer surface. By including a plurality of electrodes within the capacitive sensor unit, the techniques described herein increase the amount of data collected across the wafer surface at any given time to improve the throughput and measurement accuracy of the capacitive measurement tool.