In-Situ Temperature Measurement by Means of Etch Pits
Original Publication Date: 1989-Jan-01
Included in the Prior Art Database: 2005-Jan-27
The temperature of a substrate (e.g., a wafer) is determined without any physical contact by measuring the depth of an etch pit provided in the substrate. A laser beam 1 (Fig. 1) is divided by a calcite crystal into a reference beam L1 and a measuring beam L2. The measuring beam passes a parallel plate which directs the beam to an etch pit 3. The light is reflected by the substrate surface and detected by a light amplifier 4. The photometer signal IR (Fig. 2) is a sinusoidal function of the phase difference between L1 and L2 (i.e., the depth of the etch pits). The depths of the etch pits are preferably h1 = g/4 (N 150 nm) and h2 = 500 g+ g/8 (N 300 mm). The reflected signal has a maximum value at position 1 and a minimum value at position 2. The signal at position 3 is highly temperature-sensitive.