# US 2018/0323038 A1 · Methods and apparatus for controlling plasma in a plasma processing system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0323038 A1 - Document ID: US20180323038A1 - Status: Published application - Kind: A1 - Application number: 16/024,602 - Filed: 2018-06-29 - Published: 2018-11-08 - Earliest claimed: 2012-02-22 - Assignees: Lam Research Corporation - Applicants: Lam Research Corporation - Inventors: John C. Valcore, JR.; Bradford J. Lyndaker - Web page: https://patentgrep.com/patent/US20180323038A1 ## CPC - H01J 37/32091: {the radio frequency energy being capacitively coupled to the plasma} - B44C 1/22: Removing surface-material, e.g. by engraving, by etching {(for multi-layer articles B44C3/005)} - H01J 37/32165: {Plural frequencies} - H01J 37/32935: {Monitoring and controlling tubes by information coming from the object and/or discharge} - H01J 37/3467: {Pulsed operation, e.g. HIPIMS} - H03L 5/00: Automatic control of voltage, current, or power - H05H 2242/26: Matching networks - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) - B44C: PRODUCING DECORATIVE EFFECTS (processes for applying liquids or other fluent materials to surfaces, in general B05D; shaping of plastics or substances in a plastic state B29C; printing processes to produce transfer pictures B41M3/12; thermographic duplication or marking methods B41M5/00); MOSAICS; TARSIA WORK (imitation of mosaic or tarsia work patterns B44F11/04); PAPERHANGING {(labels G09F; multi-step processes for making paper labels or tags B31D1/02)} - H03L: AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES (generation of oscillations H03B) - H05H: PLASMA TECHNIQUE (apparatus or processes specially adapted for producing X-rays H05G2/00); PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS ## Abstract Methods and apparatus for processing a substrate in a multi-frequency plasma processing chamber are disclosed. The base RF signal pulses between a high power level and a low power level. Each of the non-base RF generators, responsive to a control signal, proactively switches between a first predefined power level and a second predefined power level as the base RF signal pulses. Alternatively or additionally, each of the non-base RF generators, responsive to a control signal, proactively switches between a first predefined RF frequency and a second predefined RF frequency as the base RF signal pulses. Techniques are disclosed for ascertaining in advance of production time the first and second predefined power levels and/or the first and second predefined RF frequencies for the non-base RF signals. ## Claims ### Claim 1 A system comprising: a base radio frequency (RF) generator; a non-base RF generator; a control circuit coupled to the base RF generator and the non-base RF generator, wherein the control circuit is configured to: control the base RF generator to generate a base RF signal that pulses between a first base power level and a second base power level; and synchronize the non-base RF generator with the base RF generator to generate a non-base RF signal that pulses between a first pre-determined non-base power level and a second pre-determined non-base power level, wherein the non-base RF signal is pulsed to achieve the first pre-determined non-base power level simultaneous with achievement of the first base power level and to achieve the second pre-determined non-base power level simultaneous with achievement of the second base power level, wherein the first pre-determined non-base power level and the second pre-determined non-base power level are achieved without detection of a change in a plasma impedance, wherein each of the first pre-determined non-base power level and the second pre-determined non-base power level is configured to reduce a disturbance in the plasma impedance caused by the pulsing of the base RF signal. ### Claim 2 (depends on 1) The system of claim 1, wherein the base RF generator is a 2 megahertz (MHz) RF generator and the non-base RF generator is a 27 MHz or a 60 MHz RF generator. ### Claim 3 (depends on 1) The system of claim 1, wherein the first base power level includes a range of power values of the base RF signal and the range of power values is exclusive of a range of power values of the second base power level of the base RF signal. ### Claim 4 (depends on 1) The system of claim 1, wherein the first pre-determined non-base power level facilitates achievement of a process result and the second pre-determined non-base power level facilitates achievement of another process result. ### Claim 5 (depends on 1) The system of claim 1, wherein to synchronize the non-base RF generator, the control circuit is configured to send a control signal to the non-base RF generator to facilitate a generation of the first pre-determined non-base power level with the generation of the first base power level and a generation of the second pre-determined non-base power level with the generation of the second base power level. ### Claim 6 (depends on 1) The system of claim 1, wherein to synchronize the non-base RF generator, the control circuit is configured to: send a control signal to the non-base RF generator to achieve the second pre-determined non-base power level without identifying the change in the plasma impedance, wherein the change in the plasma impedance is caused by a transition from the first base power level to the second base power level; and send a control signal to the non-base RF generator to achieve the first pre-determined non-base power level without identifying another change in the plasma impedance, wherein the other change in the plasma impedance is caused by a transition from the second base power level to the first base power level. ### Claim 7 (depends on 1) The system of claim 1, further comprising a computer configured to calculate the first pre-determined non-base power level and the second pre-determined non-base power level from one or more measurements of a plasma processing chamber parameter, wherein the first pre-determined non-base power level and the second pre-determined non-base power level are calculated to achieve a process parameter associated with a substrate within the plasma chamber. ### Claim 8 (depends on 7) The system of claim 7, wherein the plasma processing chamber parameter is a chuck bias and the process parameter is a deposition rate. ### Claim 9 (depends on 1) The system of claim 1, further comprising a computer configured to calculate the first pre-determined non-base power level and the second pre-determined non-base power level before the base RF generator is controlled to generate the base RF signal and before the non-base RF generator is synchronized with the base RF generator to generate the non-base RF signal. ### Claim 10 (depends on 1) The system of claim 1, wherein both the base RF generator and the non-base RF generator are configured to be coupled to an electrode of a plasma chamber via an impedance matching network, wherein another electrode of the plasma chamber is configured to be coupled to a ground potential, wherein the other electrode is configured to face the electrode. ### Claim 11 (depends on 1) The system of claim 1, wherein the achievement of the first pre-determined non-base power level and the second pre-determined non-base power level occurs during processing of a substrate in a plasma chamber, wherein the change in the plasma impedance is not detected during the processing of the substrate. ### Claim 12 A system comprising: a base radio frequency (RF) generator; a non-base RF generator; a control circuit coupled to the base RF generator and the non-base RF generator, wherein the control circuit is configured to: control the base RF generator to generate a base RF signal that pulses between a first base power level and a second base power level; and synchronize the non-base RF generator to generate a non-base RF signal that pulses between a first pre-determined non-base frequency and a second pre-determined non-base frequency, wherein the non-base RF signal is pulsed to achieve the first pre-determined non-base frequency simultaneous with achievement of the first base power level and to achieve the second pre-determined non-base frequency simultaneous with achievement of the second base power level, wherein the first pre-determined non-base frequency and the second pre-determined non-base frequency are achieved without detection of a change in a plasma impedance. ### Claim 13 (depends on 12) The system of claim 12, wherein the first base power level includes a range of power values of the base RF signal and the range of power values is exclusive of a range of power values of the second base power level of the base RF signal. ### Claim 14 (depends on 12) The system of claim 12, wherein to synchronize the non-base RF generator, the control circuit is configured to: send a control signal to the non-base RF generator to achieve the second pre-determined non-base frequency without identifying the change in the plasma impedance, wherein the change in the plasma impedance is caused by a transition from the first base power level to the second base power level; and send a control signal to the non-base RF generator to achieve the first pre-determined non-base frequency without identifying another change in the plasma impedance, wherein the other change in the plasma impedance is caused by a transition from the second base power level to the first base power level. ### Claim 15 (depends on 12) The system of claim 12, further comprising: a computer configured to calculate the first pre-determined non-base frequency and the second pre-determined non-base frequency to increase efficiency of power delivered by the non-base RF generator. ### Claim 16 (depends on 12) The system of claim 12, further comprising: a computer configured to calculate the first pre-determined non-base frequency and the second pre-determined non-base frequency before the base RF generator is controlled to generate the base RF signal and before the non-base RF generator is synchronized to generate the non-base RF signal. ### Claim 17 (depends on 12) The system of claim 12, wherein the base RF generator and the non-base RF generator are configured to be coupled to an electrode of a plasma chamber via an impedance matching network, wherein the plasma chamber includes another electrode that is configured to be coupled to a ground potential, wherein the other electrode is configured to face the electrode. ### Claim 18 (depends on 12) The system of claim 12, wherein the achievement of the first pre-determined non-base frequency and the second pre-determined non-base frequency occurs during processing of a substrate in a plasma chamber, wherein the change in the plasma impedance is not detected during the processing of the substrate. ### Claim 19 A system comprising: a plasma chamber configured to process a substrate; an impedance matching circuit (IMC) coupled to the plasma chamber; a base radio frequency (RF) generator coupled to the IMC and configured to generate a pulsed base RF signal that pulses in synchronization with a control signal; and a non-base RF generator coupled to the IMC and configured to generate a pulsed non-base RF signal, wherein the non-base RF signal pulses between a first pre-determined parameter level and a second pre-determined parameter level synchronous with the pulsed base RF signal. ### Claim 20 (depends on 19) The system of claim 19, wherein the first pre-determined parameter level is a power level and the second pre-determined parameter level is a power level. ### Claim 21 (depends on 19) The system of claim 19, wherein the first pre-determined parameter level is a frequency and the second pre-determined parameter level is a frequency. ### Claim 22 (depends on 19) The system of claim 19, wherein the second pre-determined parameter level is achieved without detecting a change in a plasma impedance in the plasma chamber caused by a transition from a first base power level of the pulsed base RF signal to a second base power level of the pulsed base RF signal, and the first pre-determined parameter level is achieved without detecting a change in the plasma impedance in the plasma chamber caused by a transition from the second base power level to the first base power level.