High-speed high-accuracy fiber optic low-coherence interferometry for in situ grinding and etching process monitoring

Abstract

We present design of novel tool for characterization of wafer thickness and wafer topography employing fast low coherence fiber optic interferometer, which optical length of the reference arm of the interferometer is monitored by secondary long coherence length interferometer.

Fiber optics low-coherence IR interferometry for defense sensors manufacturing

“…We have reported use of this type of the apparatus for in-situ and ex-situ monitoring of semiconductor wafer grinding and chemical etching [5]. We reported both silicon [3], and compound materials applications [9], [12].…”

“…We reported both silicon [3], and compound materials applications [9], [12]. In past several systems were reported including multi-probe systems [8], and fast systems enabling applications capable to measure wafer thickness during grinding process [4,5]. Finally, the reference plane solutions have been invented allowing to reduce dependence of the measured signal on temperature variations [10].…”

“…In past the alternative technique was presented, which did not suffer from above discussed limitations. Figure 1 represents a single probe Michelson interferometer similar to that used and described earlier [2,3,[5][6][7][8][9][10][11][12][13][14]. Light emitted by a light source LS is transmitted to and split into two portions by a single mode optical fiber to a 2x2 coupler BS.…”

“…Low coherence optical interferometry [1] has been proven to be an effective tool for characterization of thin and ultrathin semiconductor Si wafers, compound materials, MEMs, detector structures, light emitting devices and others [2][3][4][5][6][7][8][9][10][11][12][13][14]. The commonly employed tools for wafer thickness metrology are based on capacitance or air pressure methods.…”

Real-Time and Long-Distance Measurement of Displacement Based on Optoelectronic Oscillator

“…The optical interferometric techniques using Mach-Zehnder interferometer configuration [14] and Michelson interferometer configuration [15] can be realized in the time domain, namely, white-light interferometry (WLI), or in the frequency domain, namely, optical coherence tomography (OCT). The WLI approach based on low-coherence light sources and two arms is usually used as a slow distance or a slow displacement sensor [16] for the measurements of the thickness of silicon wafers [17] and distance in machine-made industrial [18]. To improve the measurement speed, the OCT approach is presented.…”