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US-20260128264-A1 - PARTICLE CONTAMINATION CONTROL IN A PLASMA AFTERGLOW

US20260128264A1US 20260128264 A1US20260128264 A1US 20260128264A1US-20260128264-A1

Abstract

Apparatus, methods, and systems are disclosed for controlling a charge on a particle in a plasma chamber and for controlling a lifting force on a particle in a plasma chamber. Controlling the lifting force, F˜QE, in a plasma afterglow, is achieved using a combination of two separate potentials during the afterglow. These potentials, one for controlling the charge on the panicle and one for controlling the lifting force, are applied to one or more electrodes of the plasma chamber at different times.

Inventors

  • John Goree
  • Neeraj CHAUBEY

Assignees

  • UNIVERSITY OF IOWA RESEARCH FOUNDATION

Dates

Publication Date
20260507
Application Date
20230921

Claims (14)

  1. 1 . A method for controlling a charge on a dust particle during a plasma afterglow, the method comprising: controlling a voltage signal between at least two of a plurality of electrodes included in a plasma chamber after a delay time after a power signal at the at least two of the plurality of electrodes is turned off, to control the charge.
  2. 2 . The method of claim 1 , wherein controlling the voltage signal comprises: for the voltage signal having a polarity and magnitude, controlling the polarity of the voltage signal and controlling the magnitude of the voltage signal.
  3. 3 . The method of claim 2 , wherein the power signal is a radio frequency power signal.
  4. 4 . The method of claim 1 , wherein the delay time is less than about one hundred milliseconds.
  5. 5 . The method of claim 1 , wherein the charge is between about −10e and about +10e per nanometer of diameter or length of the dust particle.
  6. 6 . The method of claim 1 , wherein the plasma chamber is included in an extreme ultraviolet lithography system.
  7. 7 - 23 . (canceled)
  8. 24 . A system for controlling a charge on a particle in a plasma chamber and for controlling a lifting force applied to the particle, the system comprising: a plurality of electrodes included in the plasma chamber; a power control signal generator; a power source coupled to the power control signal generator and to two of the plurality of electrodes; a first delay circuit coupled to the power control signal generator, the first delay circuit to control delivery of a charge control voltage signal to two of the plurality of electrodes, the charge control voltage signal to control the charge on the particle in the plasma chamber; and a second delay circuit coupled to the power control signal generator, the second delay circuit to control delivery of a lifting control voltage signal to two of the plurality of electrodes, the lifting control voltage signal to control a force on the particle in the plasma chamber.
  9. 25 . The system of claim 24 , further comprising: a tube fluidically coupled to the plasma chamber; and a tube control system for controlling a tube lifting force applied to the particle in the tube.
  10. 26 . The system of claim 25 , further comprising: a load-lock fluidically coupled to the tube; and a load lock control system for controlling a load-lock lifting force applied to the particle in the load lock.
  11. 27 . The system of claim 26 , further comprising a gas source fluidically coupled to the plasma chamber; and a pump fluidically coupled to the plasma chamber.
  12. 28 . A method for controlling a charge on a dust particle, the method comprising: delivering a radio frequency power signal to at least two of a plurality of electrodes included in a plasma chamber; and modulating the radio frequency power signal by turning the radio frequency power signal on and off to control the charge on the dust particle.
  13. 29 . The method of claim 28 , wherein modulating the radio frequency power signal by turning the radio frequency power signal on and off to control the charge on the dust particle comprises: modulating the radio frequency power signal by turning the radio frequency power signal on and off to cause the charge to have a positive value.
  14. 30 . The method of claim 29 , further comprising: controlling a voltage signal between at least two of a plurality of electrodes included in a plasma chamber after a delay time after the radio frequency power signal at the at least two of the plurality of electrodes is turned off, to control the charge.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63/408,717, filed 21 Sep. 2022, and to U.S. Provisional Patent Application No. 63/378,662, filed 6 Oct. 2022. The entire content of U.S. Provisional Patent Application No. 63/408,717 and U.S. Provisional Patent Application No. 63/378,662 is hereby incorporated herein by reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH This invention was made with government support under MURI Grant No. W91INF-18-1-0240, awarded by the Army Research Office, Grant No. DE-SC0014566, awarded by the United States Department of Energy, RSA 1663801, 1672641, and 1689926, subcontracts awarded by NASA/JPL, PHY-1740379, awarded by the National Science Foundation. The government bas certain rights in the invention. FIELD The present invention relates to semiconductor manufacturing. More particularly, but not exclusively, the present invention relates to methods and systems for applying and controlling the lifting force of particles in a plasma afterglow. BACKGROUND During semiconductor manufacturing, plasmas are used for processing substrates such as semiconductor wafers. The processing has purposes such as deposition of layers on a substrate using plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), etching of layers on a substrate, production of an ion beam for implantation on a substrate, or lithography using a plasma-generated light source. Generally, gases are introduced into a plasma chamber or plasma chamber and then the plasmas may be initiated by applying a direct current, a radio-frequency (RF) signal, or microwave signals to the gases. Once the power signal that sustains a plasma glow discharge is switched off there is a temporal plasma afterglow. During these plasma processing steps, an unwanted contamination often occurs, by small solid particles, sometimes referred to as dust particles, typically less than one micron in size, falling onto the substrate. The source of these particles can include a release from surfaces or growth in the gas phase by nucleation and coagulation. This substrate is typically positioned at the bottom of a plasma chamber, facing upward. The time that this particulate contamination occurs is in many cases when the plasma is extinguished. Small particles that previously were electrically suspended in the plasma, or in the plasma-boundary region called a sheath, fall down to the substrate, causing defects which result in “yield loss” in the manufacturing process. What is needed are new and improved methods, apparatus, and systems for reducing particulate contamination and therefore yield loss in semiconductor manufacturing processes. SUMMARY Therefore, it is a primary object, feature, or advantage to improve over the state of the art. It is a further object, feature, or advantage to improve semiconductor manufacturing by reducing particulate contamination and yield loss. It is a still further object, feature, or advantage to control lifting force on particles in plasma afterglow. One or more of these and/or other objects, features, or advantages will be apparent from the specification and claims that follow. No single embodiment need exhibit each and every object, feature, or advantage as different embodiments may have different objects, features, and advantages. According to one aspect, a method for controlling the lifting force of particles in plasma afterglow in semiconductor manufacturing is provided. The method includes potentials on at least one electrode, that do not always remain unchanged. In the first step, the potential helps to control a residual charge, Q, that will remain on the particle at later times. The potential in this first step may be a spontaneously generated, e.g., a self-bias potential that was established while the RF plasma was powered, or the potential in the first step may be applied by an external DC power supply. After the first step, there can be one or more potentials applied to further control the residual charge, Q. The final step, will have a potential applied that helps control the lifting force acting on the particle due to its residual charge, by controlling the electric field E that acts on the residual charge Q, to lift the particle in opposition to gravity. The lifting force is a product of a residual charge, Q, and the electric field, E. This final step for controlling the electric field and lifting force may have sub-steps with different potentials applied and/or different electrodes used. Overall, the minimum number of steps is two, with the first step controlling the residual charge and the final step controlling the lifting force. Any additional steps between the first and last step can serve either for controlling the charge, or controlling the lifting force, or a combination of both. In each step, the potential will be applied for a period of time to a particular electrode or electrodes, or other