Bipolar Electrostatic Chuck Capacitance Abnormality Detection
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Solution Overview
Problem
Conventional methods for inspecting electrostatic chucks of bipolar type cannot determine capacitance abnormalities, which affect the attracting force and proper operation, nor can they identify which electrode has an issue, such as breakage or short circuits.
Innovation Solution
A method involving a bipolar electrostatic chuck with auxiliary electrodes, measuring transient currents when voltages are applied or ceased, and calculating differences between these currents to determine capacitance abnormalities between and around the attracting electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional inspection methods using ammeters are used to measure leakage currents, then insulation failure can be detected, but capacitance abnormalities cannot be determined
Solution Approach 1:
The invention changes the measurement parameter from steady-state leakage current to transient current. By measuring the transient current that flows when voltage is applied to the electrostatic chuck, the system can detect capacitance abnormalities. The transient current contains information about the capacitance state of the dielectric body and attracting electrodes, which is not visible in steady-state measurements.
Solution Approach 2:
The invention replaces the conventional electrical measurement approach (measuring steady-state current) with a different physical measurement approach (measuring transient current response). This substitution allows detection of capacitance properties that cannot be obtained through traditional steady-state electrical measurements alone.
2Reliability
If leakage current magnitude is measured to identify insulation failure, then general insulation issues can be recognized, but the specific location of the abnormality cannot be determined
Solution Approach 1:
The invention segments the measurement into multiple independent transient current measurements. By measuring transient current for each attracting electrode separately when voltage is applied, the system can identify which specific electrode or region has an abnormality. This segmentation of the measurement process provides location information that was lost in conventional unified leakage current measurements.
3Reliability
If steady-state current measurements are performed under no-substrate conditions, then insulation failure can be detected, but capacitance abnormalities affecting attracting force cannot be identified
Solution Approach 1:
The invention changes the measurement parameter from steady-state current to transient current. The transient current measurement captures the capacitive charging behavior of the dielectric body and attracting electrodes, providing information about capacitance abnormalities that affect attracting force. This parameter change enables detection of issues that steady-state measurements cannot detect.
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
Accurately identifies capacitance abnormalities in the electrostatic chuck, determining which electrode is affected and whether there are issues between them, enhancing the reliability of attraction and maintenance by providing detailed capacitance information.
Implementation Method 1
an electrostatic chuck of bipolar type including, in a dielectric body, two attracting electrodes
Implementation Method 2
measuring each of at least three of transient currents obtained when, under a state in which the object to be attracted is not mounted on the electrostatic chuck, the positive direct current voltage and the negative direct current voltage are applied to the electrostatic chuck from the chuck power supply or cease to be applied to the electrostatic chuck from the chuck power supply
Data Source
AI summary
Provided are a method and an apparatus capable of determining which attracting electrode in an electrostatic chuck of bipolar type has a capacitance abnormality occurring in its vicinity. In this inspection method, a positive auxiliary electrode (12) and a negative auxiliary electrode (14) are provided in a dielectric body (6) of an electrostatic chuck (4), and are connected to a ground potential portion. Then, transient currents (I1 to I4) flowing through the attracting electrodes (8 and 10) and the auxiliary electrodes (12 and 14) are measured when direct current voltages (+V and −V) are applied or cease to be applied from a chuck power supply (26) to the electrostatic chuck (4) under a state in which an object (2) to be attracted is not mounted, and a transient current (I5) (=I1−I2 or I3−I4) is calculated. The obtained transient currents are compared to respective predetermined reference values, to thereby determine a capacitance abnormality in the electrostatic chuck (4).