Active control of radial etch uniformity

Patent metadata

Field	Value
Publication number	US-10916409-B2
Application number	US-201816011442-A
Country	US
Kind code	B2
Filing date	Jun 18, 2018
Priority date	Jun 18, 2018
Publication date	Feb 9, 2021
Grant date	Feb 9, 2021

Abstract

Systems and methods for active control of radial etch uniformity are described. One of the methods includes generating a radio frequency (RF) signal having a fundamental frequency and generating another RF signal having a harmonic frequency. The harmonic frequency, or a phase, or a parameter level, or a combination thereof of the other RF signal are controlled to control harmonics of RF plasma sheath within a plasma chamber to achieve radial etch uniformity.

First claim

The invention claimed is:

1. A method for controlling radial etch uniformity, comprising:
generating, by a first radio frequency (RF) oscillator of a single RF generator, a first RF signal having a fundamental frequency and a first phase;
generating, by a second RF oscillator of the single RF generator, a second RF signal having an (n−1)th harmonic frequency and a second phase based on the fundamental frequency and the first phase respectively, wherein n is an integer greater than two;
generating, by a third RF oscillator of the single RF generator, a third RF signal having an nth harmonic frequency and a third phase based on the fundamental frequency and the first phase respectively;
receiving, by a single RF match, the first, second, third RF signals, wherein the first RF signal is used to output a first modified signal within the single RF match, the second RF signal is used to output a second modified signal within the single RF match, and the third RF signal is used to output a third modified signal within the single RF match;
combining, within the single RF match, the first modified signal, the second modified signal, and the third modified signal to output a combined RF signal, wherein the combined RF signal is output based on the fundamental frequency and the first phase, the (n−1)th harmonic frequency and the second phase, and the nth harmonic frequency and the third phase;
providing, by the single RF match, the combined RF signal to an electrode of a plasma chamber to control the radial etch uniformity across a surface of a substrate during an etch operation;
receiving, from a sensor within the single RF match, a measured parameter signal;
determining a measured phase of the fundamental frequency, a measured phase of the (n−1)th harmonic frequency, and a measured phase of the nth harmonic frequency from the measured parameter signal;
adjusting, by the single RF generator, the second phase of the second RF signal based on the measured phase of the fundamental frequency and the measured phase of the (n−1)th harmonic frequency; and
adjusting, by the single RF generator, the third phase of the third RF signal based on the measured phase of the fundamental frequency and the measured phase of the nth harmonic frequency.

2. The method of claim 1 , wherein the first RF signal is a high RF signal, the method further comprising:
generating a low RF signal;
receiving, by the RF match, the low RF signal, wherein the combined RF signal is output based on the first, second, and third RF signals, and the low RF signal.

3. The method of claim 1 , wherein the (n−1)th harmonic frequency is locked with the fundamental frequency and the nth harmonic frequency is locked with the fundamental frequency, wherein the second phase is locked with the first phase and the third phase is locked with the first phase, wherein the first RF signal has a first parameter level, the second RF signal has a second parameter level, and the third RF signal has a third parameter level, wherein the second parameter level is locked with the first parameter level and the third parameter level is locked with the first parameter level.

4. The method of claim 1 , wherein the measured parameter is signal is an electrical signal, the method further comprising:
analyzing data within the electrical signal to identify a measured fundamental frequency, a measured (n−1)th harmonic frequency, and a measured nth harmonic frequency;
calculating a first difference between the measured (n−1)th harmonic frequency and the measured fundamental frequency;
calculating a second difference between the measured nth harmonic frequency and the measured fundamental frequency;
comparing at least one of the first difference with a first pre-determined threshold and the second difference with a second pre-determined threshold;
modifying at least one of the fundamental frequency of the first RF signal and the (n−1)th harmonic frequency of the second RF signal in response to determining that the first difference is greater than the first pre-determined threshold; and
modifying at least one of the fundamental frequency of the first RF signal and the nth harmonic frequency of the third RF signal in response to determining that the second difference is greater than the second pre-determined threshold.

5. The method of claim 1 , wherein the measured parameter signal is an electrical signal, the method further comprising:
calculating a first difference between the measured phase of the (n−1)th harmonic frequency and the measured phases at the fundamental frequency;
calculating a second difference between the third one of the measured phases at the nth harmonic frequency and the first one of the measured phase of the fundamental frequency;
comparing at least one of the first difference with a first pre-determined threshold and the second difference with a second pre-determined threshold,
wherein said adjusting the second phase includes modifying the second phase of the second RF signal in response to determining that the first difference is greater than the first pre-determined threshold, and
wherein said adjusting the third phase includes modifying the third phase of the third RF signal in response to determining that the second difference is greater than the second pre-determined threshold.

6. The method of claim 1 , wherein the first RF signal has a first parameter level, the second RF signal has a second parameter level, and the third RF signal has a third parameter level, wherein the measured parameter signal is an electrical signal, the method further comprising:
analyzing data within the electrical signal to identify a measured parameter level at the fundamental frequency, a measured parameter level at the (n−1)th harmonic frequency, and a measured parameter level at the nth harmonic frequency;
calculating a first difference between the measured parameter level at the (n−1)th harmonic frequency and the measured parameter level at the fundamental frequency;
calculating a second difference between the measured parameter level at the nth harmonic frequency and the measured parameter level at the fundamental frequency;
comparing at least one of the first difference with a first pre-determined threshold and the second difference with a second pre-determined threshold;
modifying at least one of the first parameter level of the first RF signal and the second parameter level of the second RF signal in response to determining that the first difference is greater than the first pre-determined threshold; and
modifying at least one of the first parameter level of the first RF signal and the third parameter level of the third RF signal in response to determining that the second difference is greater than the second pre-determined threshold.

7. The method of claim 1 , wherein the (n−1)th harmonic frequency is a second harmonic frequency and the nth harmonic frequency is a third harmonic frequency.

8. The method of claim 1 , wherein at least one of the first RF signal, the second RF signal and the third RF signal is a continuous wave signal.

9. The method of claim 1 , wherein said receiving the first, second and third RF signals comprises receiving the first RF signal at a first input of the single RF match, the second RF signal at a second input of the single RF match, and the third RF signal at a third input of the RF single match.

10. A system for controlling radial etch uniformity, comprising:
a single radio frequency (RF) generator including:
a first RF oscillator configured to generate a first RF signal having a fundamental frequency and a first phase;
a second RF oscillator configured to generate a second RF signal having an (n−1)th harmonic frequency and

Assignees

• Lam Res Corp

Inventors

• Marakhtanov Alexei
• Kozakevich Felix Leib
• Holland John
• Ji Bing
• Lucchesi Kenneth

Classifications

• H10P72/0421

  for drying etching · CPC title

• H10P50/242

  of Group IV materials · CPC title

• H01J37/32165 Primary

  Plural frequencies · CPC title

• H01J37/32183 Primary

  Matching circuits · CPC title

• H01J37/32091 Primary

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