Measuring and controlling wafer potential in pulsed RF bias processing

Patent metadata

Field	Value
Publication number	US-9659757-B2
Application number	US-201213663393-A
Country	US
Kind code	B2
Filing date	Oct 29, 2012
Priority date	Sep 20, 2006
Publication date	May 23, 2017
Grant date	May 23, 2017

Abstract

Apparatus and methods are provided for monitoring a pulsed RF bias signal applied to a chuck in a processing chamber. One method includes operations for detecting voltage values of individual pulses of the pulsed RF bias voltage, and for determining the time for sampling the value of each individual detected pulse. At the sampling time for each pulse, a particular voltage value of the respective individual detected pulse is sampled and the particular voltage value is held. Each particular voltage value represents a characteristic peak-to-peak voltage value of each individual detected pulse. A feedback signal representing the characteristic peak-to-peak voltage value for a voltage envelope of one of the individual detected pulses is generated, and the voltage of the pulsed RF bias voltage signal applied to the chuck is adjusted according to a difference between the feedback signal and a desired voltage value of the pulsed RF bias voltage signal.

First claim

What is claimed is:

1. A method for processing a semiconductor wafer in a plasma chamber, the method comprising:
generating an envelope signal of a pulsed RF bias voltage signal applied to a chuck of the plasma chamber, the envelope signal being defined from a plurality of peak-to-peak voltage values that define amplitudes for the envelope signal;
determining a sampling time at which to sample the envelope signal to obtain a maximum voltage value associated with at least one of the peak-to-peak voltage values in the envelope signal;
generating a feedback signal for the obtained maximum voltage value; and
adjusting a voltage of the pulsed RF bias voltage signal applied to the chuck based on the obtained maximum voltage value received from the feedback signal and a reference voltage value of the pulsed RF bias voltage.

2. The method as recited in claim 1 , further including:
generating an output signal by holding constant the obtained maximum voltage value.

3. The method as recited in claim 1 , wherein adjusting the voltage of the pulsed RF bias voltage is based on a difference between the feedback signal and the reference voltage value.

4. The method as recited in claim 1 , wherein electrical characteristics of a plasma are held steady during processing to compensate for a variation of an impedance presented to the chuck.

5. The method as recited in claim 1 , wherein adjusting a voltage of the pulsed RF bias voltage further includes:
averaging a plurality of sampled values of the envelope signal corresponding to a plurality of pulses of the pulsed RF bias voltage.

6. The method as recited in claim 1 , wherein the pulsed RF bias voltage comprises RF cycles, each RF cycle having an ON mode where an RF voltage is provided and an OFF mode where no RF voltage is provided.

7. The method as recited in claim 1 , further including:
fabricating at least part of an integrated circuit in a plasma chamber having the chuck utilizing the adjusted pulsed RF bias voltage signal applied to the chuck.

8. A method for processing a semiconductor wafer in a plasma chamber, the method comprising:
generating an envelope signal of a pulsed RF bias voltage signal applied to a chuck of the plasma chamber, the envelope signal being defined from a plurality of peak-to-peak voltage values that define amplitudes for the envelope signal;
determining a sampling time at which to sample the envelope signal to obtain a maximum voltage value associated with at least one of the peak-to-peak voltage values in the envelope signal;
repeating the generating and the determining for a plurality of RF cycles, each RF cycle having an ON mode and an OFF mode, such that said pulsed RF bias voltage signal is applied during said ON mode;
generating a feedback signal for a plurality of obtained maximum voltage values, the plurality of obtained maximum voltage values being averaged to define a maximum voltage value; and
adjusting a voltage of the pulsed RF bias voltage signal applied to the chuck based on the maximum voltage value received from the feedback signal and a set point voltage signal, the set point voltage signal representing a desired voltage value for the pulsed RF bias voltage signal applied to the chuck.

9. The method of claim 8 , wherein the plurality of obtained maximum voltage values are averaged for the ON mode and does not include values sampled during the OFF mode.

10. The method of claim 9 , further comprising,
holding the sampled envelope signal captured during the ON mode while in the OFF mode.

11. The method of claim 8 , wherein determining the sampling time includes,
detecting a rising edge of each of pulse of the pulsed RF bias voltage signal; and
determining a delay time for the rising edge so that the sampling time corresponds to the obtained maximum voltage values.

Assignees

• Lam Res Corp

Inventors

• Kuthi Andras
• Hwang Stephen
• Vetter James C
• Eilenstine Greg
• Wang Rongping
• Ngo Tuan

Classifications

• H10P74/238

  comprising acting in response to an ongoing measurement without interruption of processing, e.g. endpoint detection or in-situ thickness measurement · CPC title

• H10P74/00

  Testing or measuring during manufacture or treatment of wafers, substrates or devices · CPC title

• H10P50/242

  of Group IV materials · CPC title

• H01J37/32174

  Circuits specially adapted for controlling the RF discharge · CPC title

• H01J37/321

  the radio frequency energy being inductively coupled to the plasma · CPC title