Matchless plasma source for semiconductor wafer fabrication

Patent metadata

Field	Value
Publication number	US-12484139-B2
Application number	US-202519072952-A
Country	US
Kind code	B2
Filing date	Mar 6, 2025
Priority date	Oct 18, 2017
Publication date	Nov 25, 2025
Grant date	Nov 25, 2025

Abstract

A matchless plasma source is described. The matchless plasma source includes a controller that is coupled to a direct current (DC) voltage source of an agile DC rail to control a shape of an amplified square waveform that is generated at an output of a half-bridge transistor circuit. The matchless plasma source further includes the half-bridge transistor circuit used to generate the amplified square waveform to power an electrode, such as an antenna, of a plasma chamber. The matchless plasma source also includes a reactive circuit between the half-bridge transistor circuit and the electrode. The reactive circuit has a high-quality factor to negate a reactance of the electrode. There is no radio frequency (RF) match and an RF cable that couples the matchless plasma source to the electrode.

First claim

The invention claimed is:

1 . A low impedance radio frequency (RF) generator for use as a matchless plasma source for providing RF power to an electrode of a plasma chamber, comprising:
a controller; a signal generator configured to provide an input RF signal at an operating frequency in response to a setting by the controller; an amplification circuit having an agile direct current (DC) rail that is interfaced with the controller, wherein the amplification circuit is configured to provide an amplified waveform based on the operating frequency; wherein the controller is configured to set voltage values for the agile DC rail to provide the amplified waveform from the amplification circuit in a shaped envelope; and a reactive circuit configured to extract a shaped sinusoidal waveform from the amplified waveform, the shaped sinusoidal waveform being output based on the shaped envelope, wherein the reactive circuit is configured to provide the RF power of the shaped sinusoidal waveform to the electrode for generating a plasma for processing of a substrate.

2 . The low impedance RF generator of claim 1 , wherein a connection between the reactive circuit and the electrode lacks an RF cable.

3 . The low impedance RF generator of claim 1 , wherein a connection between the reactive circuit and the electrode lacks an RF match.

4 . The low impedance RF generator of claim 1 , wherein the reactive circuit has a reactance that is configured to reduce a reactance of the electrode, or a reactance of the plasma when formed within the plasma chamber, or a reactance of a connection that couples the reactive circuit to the electrode, or a combination thereof.

5 . The low impedance RF generator of claim 4 , wherein the plasma chamber is an inductively coupled plasma chamber and the reactive circuit is a capacitor, wherein the capacitor has a capacitance that is controlled to nullify the reactance of the electrode, or the reactance of plasma when formed within the plasma chamber, or the reactance of the connection that couples the reactive circuit to the electrode, or the combination thereof, wherein the electrode is a transformer coupled plasma (TCP) coil.

6 . The low impedance RF generator of claim 4 , wherein the plasma chamber is a capacitively coupled plasma chamber and the reactive circuit is an inductor, wherein the inductor has an inductance that is controlled to nullify the reactance of the electrode, or the reactance of plasma when formed within the plasma chamber, or the reactance of the connection that couples the reactive circuit to the electrode, or the combination thereof, wherein the electrode is a capacitive upper electrode of the plasma chamber.

7 . The low impedance RF generator of claim 1 , further comprising:
a gate driver configured to receive the input RF signal and produce a plurality of signals, wherein the amplification circuit is configured to receive the plurality of signals from the gate driver to generate the amplified waveform.

8 . The low impedance RF generator of claim 7 , wherein each of the plurality of signals received from the gate driver is a waveform that pulses at the operating frequency between a low power level and a high power level.

9 . The low impedance RF generator of claim 1 , wherein the amplification circuit is a transistor circuit, wherein the transistor circuit includes a field-effect transistor or an insulated-gate bipolar transistor.

10 . The low impedance RF generator of claim 9 , wherein the field-effect transistor has a resistance that allows turning off and turning on of the field-effect transistor in a nearly instantaneous manner to reduce delays in the turning on and the turning off.

11 . The low impedance RF generator of claim 10 , wherein the field-effect transistor is turned on or off within a pre-determined time period to be turned on or off in the nearly instantaneous manner.

12 . The low impedance RF generator of claim 11 , wherein the pre-determined time period is less than 10 microseconds.

13 . The low impedance RF generator of claim 11 , wherein the pre-determined time period is between 0.5 microseconds and 10 microseconds.

14 . The low impedance RF generator of claim 1 , wherein the agile DC rail has a DC voltage source, wherein the amplification circuit has a field-effect transistor, wherein the agile DC rail is coupled to a source terminal or a drain terminal of the field-effect transistor depending on whether the field-effect transistor is p-type or n-type.

15 . The low impedance RF generator of claim 1 , wherein the agile DC rail has a DC voltage source that is configured to generate a voltage signal having the voltage values to shape the amplified waveform.

16 . The low impedance RF generator of claim 1 , wherein the shaped envelope is a multi-state pulse-shaped envelope, or a triangular-shaped envelope, or a continuous-shaped envelope, or an arbitrary-shaped envelope.

17 . The low impedance RF generator of claim 1 , wherein the reactive circuit has a quality factor to remove higher-order harmonics of the amplified waveform to generate a fundamental waveform, wherein the shaped sinusoidal waveform is the fundamental waveform having the shaped envelope.

18 . The low impedance RF generator of claim 1 , further comprising:
a voltage probe configured to measure a voltage applied to the plasma chamber, wherein the controller is configured to control the operating frequency of the signal generator or modify one or more of the voltage values for the agile DC rail or a combination thereof to control the RF power of the shaped sinusoidal waveform based on the voltage.

19 . The low impedance RF generator of claim 18 , wherein the amplification circuit has an output that is coupled to the reactive circuit, wherein the voltage is measured at the output of the amplification circuit.

20 . The low impedance RF generator of claim 1 , further comprising:
a current probe configured to measure a current supplied to the plasma chamber, wherein the controller is configured to control the operating frequency of the signal generator or modify one or more of the voltage values for the agile DC rail or a combination thereof to control the RF power of the shaped sinusoidal waveform based on the current.

21 . The low impedance RF generator of claim 20 , wherein the amplification circuit has an output that is coupled to the reactive circuit, wherein the current is measured at the output of the amplification circuit.

22 . The low impedance RF generator of claim 20 , wherein the reactive circuit is coupled to the plasma chamber via a connection, wherein the current is measured at the connection.

23 . The low impedance RF generator of claim 1 , further comprising:
a voltage probe configured to measure a voltage applied to the plasma chamber; a current probe configured to measure a current supplied to the plasma chamber; wherein the controller is configured to determine a phase difference between the voltage and the current, wherein the controller is configured to control the operating frequency of the signal generator or one or more of the voltage values for the agile DC rail to adjust the phase difference to control the RF power of the shaped sinusoidal waveform.

24 . The low impedance RF generator of claim 1 , further comprising:
a voltage probe configured to measure a complex voltage at an output of the amplification circuit; a current probe configured to mea

Assignees

• Lam Res Corp

Inventors

• Long Maolin
• Wang Yuhou
• Marsh Ricky
• Paterson Alex

Classifications

• H05H2242/24

  Radiofrequency or microwave generators · CPC title

• H05H1/4652

  using inductive coupling means, e.g. coils · CPC title

• H05H1/466

  using capacitive coupling means, e.g. electrodes · CPC title

• H03F3/2173

  of the bridge type · CPC title

• H01J37/32174 Primary

  Circuits specially adapted for controlling the RF discharge · CPC title