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  Plasma generation and control using a dual frequency rf sourceUSPTO Application #: 20070006971Title: Plasma generation and control using a dual frequency rf source Abstract: A method and apparatus for generating and controlling a plasma in a semiconductor substrate processing chamber using a dual frequency RF source is provided. The method includes the steps of supplying a first RF signal from the source to an electrode within the processing chamber at a first frequency and supplying a second RF signal from the source to the electrode within the processing chamber at a second frequency. The second frequency is different from the first frequency by an amount equal to a desired frequency. Characteristics of a plasma formed in the chamber establish a sheath modulation at the desired frequency. (end of abstract) Agent: MoserIPLaw Group / Applied Materials, Inc. - Shrewsbury, NJ, US Inventors: Steven C. Shannon, Alex Paterson, Theodoros Panagopoulos, John P. Holland, Dennis Grimard, Yashushi Takakura USPTO Applicaton #: 20070006971 - Class: 156345280 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070006971. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of co-pending U.S. patent application Ser. No. 10/843,914, filed May 12, 2004, which claims benefit of U.S. Provisional Application No. 60/495,523 filed Aug. 15, 2003. Each of the aforementioned related patent applications is herein incorporated by reference in their entirety. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention generally relates to semiconductor substrate processing systems and, more particularly, to plasma generation and control using a dual frequency RF source. [0004] 2. Description of the Related Art [0005] Plasma enhanced semiconductor processing chambers are widely used to manufacture integrated circuit devices. In most plasma enhanced chambers, multiple radio frequency (RF) sources are utilized to form and control the plasma. For example, an RF source with a high frequency is typically used for plasma formation and ion dissociation. Additionally, an RF source with a lower frequency is often used to modulate the plasma sheath in order to control the accumulation of a DC voltage (i.e., bias voltage) on the substrate. The cost of the various sources and their related matching circuits are quite substantial and contribute to the high cost of the equipment needed to fabricate integrated circuits. Reducing the RF infrastructure without sacrificing any process benefit would result in significant cost savings. [0006] Therefore, there is a need for an improved method and apparatus for plasma generation and control in a plasma enhanced semiconductor substrate processing. SUMMARY OF THE INVENTION [0007] The present invention is a method and apparatus for generating and controlling a plasma in a plasma enhanced semiconductor substrate processing chamber. The method includes the steps of supplying a first RF signal from the source to an electrode within the processing chamber at a first frequency and supplying a second RF signal from the source to the electrode within the processing chamber at a second frequency. The second frequency is different from the first frequency by an amount equal to a desired frequency. Characteristics of a plasma formed in the chamber establish a sheath modulation at the desired frequency (i.e., the frequency difference between the first and second frequency). BRIEF DESCRIPTION OF THE DRAWINGS [0008] So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. [0009] FIG. 1 depicts an exemplary block diagram of a plasma enhanced semiconductor processing chamber having a dual frequency RF source; [0010] FIG. 2 is a graph of the frequency spectrum of an input waveform on the electrode; [0011] FIG. 3 is a graph of the frequency spectrum of the sheath voltage; [0012] FIG. 4A is a graph of reflection coefficient magnitude versus frequency; [0013] FIG. 4B is a Smith chart for the match element model; [0014] FIG. 5 is a simplified schematic of one embodiment of a processing chamber having a dual frequency RF source; and [0015] FIG. 6 is a simplified schematic of another embodiment of a processing chamber having a dual frequency RF source. [0016] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. DETAILED DESCRIPTION [0017] The present invention is a method and apparatus for forming and controlling a plasma in a plasma enhanced semiconductor processing chamber using a dual frequency RF source. Plasma enhanced semiconductor processing chambers generally utilize power fed at two frequencies: a high frequency for plasma excitation and ion dissociation; and a low frequency for plasma sheath modulation. In one embodiment, the present invention utilizes two high frequency inputs generated from a single RF source to generate the plasma. The sheath modulation is controlled by utilization of a wave packet phenomenon that creates a low frequency component in the plasma sheath equivalent to the difference in frequency between the two input signals. [0018] FIG. 1 depicts a simplified block diagram of a plasma enhanced semiconductor processing chamber having a dual frequency RF source. A plasma enhanced processing chamber 100 according to the present invention includes a chamber 102, a dual frequency RF power source 104, and a single matching circuit 106. The chamber 102 includes a powered electrode 108 that is coupled to the source 104 through the matching circuit 106 and a grounded electrode 110. The chamber 102 is otherwise similar to a conventional plasma enhanced processing chamber with the exception of the reduced RF infrastructure. [0019] The source 104 is an RF generator with dual frequency excitation. The source 104 is generally capable of generating two frequencies in the range of from about 100 KHz to about 200 MHz. The source 104 is also generally able to produce up to 5000 W of either continuous or pulsed power. In one specific embodiment, the source produces both about 13 MHz and about 14 MHz, each frequency at about 3 KW. Continue reading... Full patent description for Plasma generation and control using a dual frequency rf source Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Plasma generation and control using a dual frequency rf source patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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