Abstract
Methane (CH4) concentration distribution in a semiconductor process chamber was controlled using the measurement of computed tomography-tunable diode laser absorption spectroscopy (CT-TDLAS) and the feedback control toward the feeding CH4 concentrations and flow rates. CH4 diluted with nitrogen was fed into the chamber through a shower head having three separate and concentric areas. Thirty-two laser paths were configured in the chamber to collect the infrared absorption spectra for the CT-TDLAS measurement. The computed tomography calculation using the 32 spectra reconstructed the two-dimensional CH4 concentration distribution in the chamber. The measured concentration distribution was updated once per second. Based on the measured concentration distribution, the feedback control algorithm determined the feeding CH4 concentration and flow rate of each shower head area. In this work, we set the target distribution as a ring shape. In the control algorithm, first the feeding CH4 flow rate of each shower head area was adjusted to match the concentration peak radius in the measured distribution to the radius in the target distribution. Then, the feeding CH4 concentration of each area was adjusted in sequence to match the measured average concentration of each area to the corresponding concentration in the target distribution. The algorithm worked successfully, and the concentration distribution reached the target distribution. The extension of the application and its limitations were also discussed.
Highlights
As temperature distribution on a wafer plays an important role in the profile variation, a multiple temperature-zone electrostatic chuck has been well studied and attained some progress in the manufacturing yields
The infrared absorption spectra for multiple laser paths passing through the measured region of the inner chamber are collected, and the computed tomography (CT) calculation reconstructs gas concentration and temperature distributions using the spectra
In Ref. 19, we showed the feasibility of controlling gas concentration distribution by adjusting the feeding gas flow rate of each inlet port
Summary
Variation of etched feature profiles is a critical issue in semiconductor fine structure fabrications.1–3 As temperature distribution on a wafer plays an important role in the profile variation, a multiple temperature-zone electrostatic chuck has been well studied and attained some progress in the manufacturing yields.4–6 Etching gas concentration distribution over the wafer is another important factor that affects the profile variation. In Ref. 19, we showed the feasibility of controlling gas concentration distribution by adjusting the feeding gas flow rate of each inlet port. The concentration distribution control requires adjusting the feeding gas concentrations and flow rates, while the temperature scitation.org/journal/adv distribution control requires the susceptor heater adjustment.
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