Uniformity control circuit for use within an impedance matching circuit

Patent metadata

Field	Value
Publication number	US-9761414-B2
Application number	US-201514878666-A
Country	US
Kind code	B2
Filing date	Oct 8, 2015
Priority date	Oct 8, 2015
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

An impedance matching circuit (IMC) is described. The IMC includes a first circuit that includes a first plurality of tuning elements defined along a path. The first circuit has an input coupled to a kilohertz (kHz) radio frequency (RF) generator. The first circuit is coupled to an output. The IMC further includes a second circuit having a second plurality of tuning elements. The second circuit has an input coupled to a megahertz (MHz) RF generator and is coupled to the output. The IMC includes a uniformity control circuit (UCC) defined from at least one of the plurality of tuning elements of the first circuit. The UCC is connected serially along the path of the first circuit to define a capacitance that at least partially influences a radial uniformity profile in an etch rate produced by a plasma chamber.

First claim

The invention claimed is:

1. An impedance matching circuit comprising:
a first circuit including a first plurality of tuning elements defined along a path, the first circuit having an input coupled to a kilohertz (kHz) radio frequency (RF) generator, wherein the first circuit is coupled to an output;
a second circuit having a second plurality of tuning elements, wherein the second circuit has an input coupled to a megahertz (MHz) RF generator and is coupled to the output;
wherein the output of the first and second circuits is coupled to an input of an RF transmission line that is coupled to an electrode of a plasma chamber used for processing semiconductor substrates, and
a uniformity control circuit defined from at least one of the plurality of tuning elements of the first circuit, wherein the uniformity control circuit is connected serially along the path of the first circuit to define a capacitance that at least partially influences a radial uniformity profile in an etch rate produced by the plasma chamber, wherein a change in the capacitance causes an adjustment in the radial uniformity profile, wherein the kHz RF generator is configured to operate in a range of 50 kHz to less than 1000 kHz.

2. The impedance matching circuit of claim 1 , wherein the change in the capacitance causes an adjustment in an RF rod potential at the RF transmission line simultaneous with causing the adjustment in the radial uniformity profile.

3. The impedance matching circuit of claim 1 , wherein the capacitance is defined to provide a pre-determined level of isolation from a MHz RF signal transferred through the second circuit and to achieve a pre-determined level of power delivered to the electrode of the plasma chamber.

4. The impedance matching circuit of claim 3 , wherein the first circuit is coupled to a probe via an RF cable, wherein the probe is used to calculate an amount of power that is delivered via the first circuit, wherein the amount of the power delivered and the pre-determined level of power are used to set the capacitance of the uniformity control circuit.

5. The impedance matching circuit of claim 3 , wherein the first circuit is coupled to a power sensor, wherein the second circuit is coupled to a power sensor, wherein the power sensors are used to calculate an amount of isolation of a kHz RF transferred via the first circuit from the MHz RF signal transferred via the second circuit, wherein the calculated amount of isolation and the pre-determined level of isolation are used to set the capacitance of the uniformity control circuit.

6. The impedance matching circuit of claim 3 , wherein the first circuit is coupled to a probe via an RF cable, wherein the probe is used to calculate an amount of power that is delivered via the first circuit, wherein the amount of the power delivered is used to set the capacitance of the uniformity control circuit,
wherein the first circuit is coupled to a power sensor, wherein the second circuit is coupled to a power sensor, wherein the power sensors are used to calculate an amount of isolation of the kHz signal transferred via the first circuit from the MHz signal transferred via the second circuit, wherein the calculated amount of isolation and the pre-determined level of isolation are used to set the capacitance of the uniformity control circuit.

7. The impedance matching circuit of claim 1 , wherein the capacitance is defined by one or more capacitors.

8. The impedance matching circuit of claim 7 , wherein the capacitance is adjusted by replacing the one or more capacitors with one or more replacement capacitors.

9. The impedance matching circuit of claim 7 , wherein the capacitance is adjusted by dynamically varying a variable control of one or more of the capacitors.

10. The impedance matching circuit of claim 1 , wherein the first circuit includes one or more series circuit elements and one or more shunt circuit elements, wherein the second circuit includes one or more series circuit elements and one or more shunt circuit elements, wherein the uniformity control circuit is coupled serially with the one or more series circuit elements of the first circuit, wherein the uniformity control circuit is not a shunt circuit element.

11. The impedance matching circuit of claim 1 , wherein the uniformity control circuit includes one or more capacitors having a capacitance ranging from 600 picoFarads to 15000 picoFarads.

12. The impedance matching circuit of claim 1 , wherein the uniformity control circuit includes a variable capacitor, the capacitance is controlled by a host system via an actuator.

13. The impedance matching circuit of claim 1 , wherein the uniformity control circuit includes a fixed capacitor.

14. The impedance matching circuit of claim 1 ,
wherein the electrode of the plasma chamber is configured to be coupled to a measurement electrode, wherein the measurement electrode is configured to generate a signal representative of wafer direct current (DC) bias, wherein the wafer DC bias is used to set the capacitance of the uniformity control circuit,
wherein the electrode of the plasma chamber is coupled to the impedance matching circuit via a radio frequency (RF) transmission line, wherein the RF transmission line is configured to be coupled to a voltage sensor, wherein the voltage sensor is configured to measure an RF rod potential of the RF transmission line, wherein the RF rod potential is used to set the capacitance of the uniformity control circuit,
wherein the plasma chamber is configured to remove materials deposited on a wafer, wherein a removal rate of removing the materials is measured using an optical thickness measurement device and a host system, wherein the removal rate is used to set the capacitance of the uniformity control circuit,
wherein the plasma chamber is configured to receive a probe for collecting ion current within the plasma chamber for generating an electrical signal, wherein the probe is configured to connect to a current sensor for measuring an amount of current from the electrical signal, wherein the host system is configured to measure ion saturation current density from the amount of current, wherein the ion saturation current density is used to set the capacitance of the uniformity control circuit.

15. A system comprising:
a kilohertz (kHz) radio frequency (RF) generator for generating and supplying a kHz RF signal, wherein the kHz RF generator is configured to operate in a range of 50 kHz to less than 1000 kHz;
a megahertz (MHz) RF generator for generating and supplying a MHz RF signal;
a first RF cable connected to an output of the kHz RF generator for receiving the kHz RF signal;
a second RF cable connected to an output of the MHz RF generator for receiving the MHz RF signal;
an impedance matching circuit coupled to the kHz RF generator via the first RF cable, wherein the impedance matching circuit is coupled to the MHz RF generator via the second RF cable, wherein the impedance matching circuit has an output and includes:
a first circuit including a first plurality of tuning elements located along a path for transferring the kHz RF signal;
a second circuit having a second plurality of tuning elements for transferring the MHz RF signal, wherein the first and second circuits are coupled to the output; and
a uniformity control circuit defined from at least one of the tuning elements of the first plurality,

an RF transmission line coupled to the impedance matching circuit;
a plasma chamber including an electrode, wherein the electrode is connected to the RF transmission line,
wherein the uniformity control circuit is located seri

Assignees

• Lam Res Corp

Inventors

• Marakhtanov Alexei
• Kozakevich Felix
• Lucchesi Kenneth
• Holland John Patrick

Classifications

• H10P50/242

  of Group IV materials · CPC title

• H01J2237/334

  Etching · CPC title

• H01J37/32532

  Electrodes · CPC title

• H01J37/32449

  Gas control, e.g. control of the gas flow · CPC title

• H01J37/32091 Primary

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