Optical Lift Pin Wafer Field Sensing Without Plasma Disturbance
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Solution Overview
Problem
Conductive materials in existing electric field measuring apparatuses disrupt the uniform distribution of plasma in plasma chambers, leading to inaccurate measurements of the electric field strength of wafers.
Innovation Solution
An electric field measuring apparatus using a non-conductive lift pin with an electro-optical crystal probe and optical waveguide, which changes refractive index in response to the electric field, allowing for accurate measurement by comparing light signals at different vertical positions without contacting the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conductive material is used in the measuring apparatus, then the measurement capability is improved, but the plasma distribution uniformity deteriorates
Solution Approach 1:
The patent replaces the conventional conductive electrical measurement system with an optical measurement system. The probe uses electro-optical crystals that interact with the electric field through optical means rather than direct electrical contact, thereby avoiding plasma disruption while maintaining measurement capability through detection of optical signal changes caused by the electric field.
Solution Approach 2:
The patent changes the measurement parameter from direct electrical signal to optical signal. By using electro-optical crystals whose refractive index changes in response to the electric field, the system translates electrical field information into optical domain, enabling measurement without conductive materials that would disrupt plasma.
2Object-affected harmful factors
If a non-conductive probe is used, then the plasma distribution uniformity is improved, but the measurement precision deteriorates
Solution Approach 1:
The patent substitutes electrical detection mechanism with optical detection mechanism. The non-conductive probe incorporates electro-optical crystals that respond to electric fields through changes in refractive index, which are then detected optically, maintaining measurement precision without requiring conductive materials.
Solution Approach 2:
The probe uses composite structure incorporating electro-optical crystals within a non-conductive housing. This composite design enables the non-conductive probe to sense electric fields through the electro-optical effect while maintaining plasma compatibility, thus achieving both measurement precision and plasma uniformity.
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
Enables precise, non-contact measurement of electric field strength on wafers without disrupting plasma distribution, ensuring reliable dechucking and preventing damage during wafer separation.
Implementation Method 1
a probe in the lift pin and having a refractive index changed by an electric field of the wafer, the probe including an electro-optical crystal
Implementation Method 2
an optical waveguide configured to form at least one internal path of light having a polarization characteristic changed by the changed refractive index between the probe and the wafer
Implementation Method 3
an electrostatic chuck provided with a through hole and configured to hold a wafer using an electrostatic force
Data Source
AI summary
An electric field measuring apparatus includes an electrostatic chuck with a through hole and holding a wafer, a lift pin picking up the wafer, a driver vertically moving the lift pin along the through hole, a probe in the lift pin and having a refractive index changed by an electric field of the wafer, the probe including an electro-optical crystal, an optical waveguide forming at least one internal path of light having a polarization characteristic changed by the changed refractive index between the probe and the wafer, and a control module controlling the lift pin and the driver. The lift pin moves to first and second positions. The control module calculates a strength of the electric field of the wafer, using electric field data measured using the probe at each of the first and second positions.