Output of the matching network is connected to an impedance and power monitoring device such as a V/I probe before it is connected to the plasma chamber as shown in Figure 3. The communication between RF generator and matching network is usually established with optical communication for immunity to electromagnetic interference. RF generator power output is connected to an automated matching network using half a wavelength RF coax cable at the operational frequency. In the system shown, RF power is provided at the desired power level and the operational frequency is set by the user via a host computer that communicates with the generator using series type communication such as RS-232 or RS-485. Typical RF delivery systems consist of an RF generator, matching network, impedance and power measurement device, which are illustrated in Figure 3. Impedance and power measurement devices such as a V/I probe 8 can be included in the system to give users the ability to monitor several important parameters such as the level of RF energy, chamber impedance and the corresponding RF frequency.įigure 4 Wafer size transitions and corresponding cost per watt. RF energy is applied via RF generators that are connected to process chambers with matching networks. As a result, the level of RF energy, RF signal purity, RF interface impedance, application frequency and RF wave shape applied carry great importance to accomplish selective wafer processing including uniformity, etch rate, anisotropy, etc. RF waves are used to provide energy to target materials (typically insulators) and bias substrates in processes where plasma is required. The generation and sustaining of a plasma inside the process chamber is possible with the RF energy. Inside the process chamber, partially ionized gas with a combination of free electrons, ions, radicals and neutral species called plasma is used to accomplish the processes described including deposition, etching and cleaning. The typical illustration of the process chamber for semiconductor wafer processing with its surrounding components is illustrated in Figure 2. Related Resourcesįigure 2 Illustration of process chamber with surrounding components for semiconductor wafer processing. All the processes described take place when the wafer is placed inside a chamber which is also commonly called as a process or plasma chamber. There is conductor etching and dielectric etching depending on the application. 7 The process of etching is also used in manufacturing ICs mainly to remove the unwanted material from the wafer. 6 The main categories of PVD processing are classified as evaporation and sputtering. Layers can be added by deposition that can be implemented by chemical vapor deposition (CVD) 5 or physical vapor deposition (PVD). 1-4 Layers consist of insulators, semiconductors or conductors. Fabrication processes of ICs involve many steps including layering, patterning, doping and heat treatment. Bare and patterned silicon wafers are illustrated in Figure 1. The area on the wafer occupied by the discrete device or IC is called a chip or die. Devices or ICs are formed, for the most part, on the typical silicon wafer surface where 200 to 300 identical devices are formed on each wafer. In fact, the state of technology in semiconductor wafer processing is a driving force for the invention and development of new electronic devices due to enhanced features of the manufactured ICs. Semiconductor wafer processing is used to manufacture integrated circuits (IC) that are components in the most sophisticated electronic products that are used in everyday life. Matching networks and RF amplifier topologies used in RF delivery systems are also discussed. Radio frequency power levels, frequency allocation and operational modes are studied. Subcomponents of the RF generators including RF power amplifiers, combiners, couplers and filters are presented. This article provides an overview of radio frequency (RF) delivery systems including RF generators and matching networks, which are one of the most critical surrounding components of the plasma chamber in wafer processing.
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