Curvature Measurement via Laser Beam Alignment on Process Chamber Window
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Solution Overview
Problem
Current curvature measurement techniques in substrate processing apparatuses suffer from decreased accuracy due to temperature gradients in the film forming chamber, causing refractive index variations in the window, which affect the alignment of laser beams and result in incorrect curvature measurements.
Innovation Solution
The substrate processing apparatus aligns the incident points of the first and second laser beams along the long side direction of a long-shaped window, minimizing temperature gradient effects and ensuring consistent refractive indexes, thereby improving curvature measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two laser beams are irradiated in parallel to a substrate via a window in the film forming chamber, then curvature measurement can be performed, but temperature gradient in the window causes refractive index variation leading to measurement inaccuracy
Solution Approach 1:
The patent applies local quality by positioning the two laser beam incident points at locations on the window where temperature gradients are minimized. Specifically, the incident points are arranged symmetrically with respect to the center of the window in the short-side direction, ensuring that both points experience similar thermal conditions and refractive index variations, thereby canceling out the differential effect on measurement accuracy.
Solution Approach 2:
The patent employs asymmetry in the arrangement of laser beam incident points relative to the window geometry. The incident points are positioned at specific asymmetric locations that account for the temperature distribution pattern in the window, optimizing the measurement configuration to minimize the impact of thermal gradients on refractive index variations.
2Temperature
If the window is exposed to high temperature during film formation, then film formation process can proceed, but temperature difference between window edges and center causes temperature gradient and refractive index variation
Solution Approach 1:
The patent addresses refractive index stability by selecting specific local regions on the window for laser beam incidence. The incident points are positioned where temperature gradients are least severe, ensuring that the refractive index at these locations remains relatively stable during high-temperature film formation, thus maintaining measurement reliability.
Solution Approach 2:
The patent applies equipotentiality by positioning the two laser beam incident points at locations with equivalent thermal potentials on the window. By arranging the points symmetrically with respect to the window center in the short-side direction, both points experience comparable temperature and refractive index conditions, eliminating differential effects that would compromise measurement accuracy.
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 configuration prevents changes in the incident position interval of the laser beams due to refractive index differences, enhancing the accuracy of curvature measurements and preventing errors caused by factors other than substrate warping.
Implementation Method 1
the refractive index of the window varies along the short side direction due to this temperature gradient in the short side direction
Implementation Method 2
detects the positions of two laser beams reflected by the substrate
Data Source
AI summary
A substrate processing apparatus has a process chamber, a long-shaped window on a wall surface of the process chamber, an irradiator configured to irradiate a first laser beam and a second laser beam to a substrate in the process chamber via the long-shaped window so that incident points of the first and second laser beams are aligned substantially along a long side direction of the window, a detector configured to have a light reception surface receiving the first and second laser beams reflected by the substrate and passing through the window, the detector being configured to detect incident positions of the first and second laser beams on the light reception surface, and a calculator configured to calculate a curvature of the substrate by using a relative position of the first laser beam and the second laser beam which are detected by the detector.