Equipment Plasma reactor

FIG. 35. Vertical cross section of the reaction chamber equipped with the mass spectrometer system. Indicated are QMF. the quadmpole mass filter ESA. the electrostatic analyzer CD, the channeltron detector DE, the detector electronics DT, the drift tube lO, the ion optics TMP, the turbomolecular pump PR, the plasma reactor and MN. the matching network. 

Ihe equipment used in this study (Figure 1) consisted of a capacitively-coupled plasma reactor similar to the apparatus described by Poulsen 3) for the plasma etching of integrated circuits. This arrangement resulted in uniform depositions over a range of flow rates and improved utilization of monomer. 

Important plasma diagnostics include Langmuir probes, optical emission spectroscopy, laser induced fluorescence, absorption spectroscopy, mass spectrometry, ion flux and energy analysis, and plasma impedance analysis. A plasma reactor equipped with several of these diagnostics is shown in Fig. 51 [35, 160]. A capacitively coupled plasma is sustained between the parallel plates of the upper (etching) chamber. The lower (analysis) chamber is differentially pumped and communicates with the etching chamber through a pinhole on the lower electrode. 

Figure 2.1 shows a schematic diagram of the CVD equipment. A commercial low-pressure microwave (2.45 GHz) plasma reactor, Model AX5400 (ASTeX Coip., Wohurn, MA) was used (Fig. 2.2). This unit consists of a vacuum system, a microwave generating system and a gas supply system.

As in any process that uses cheniicals and electronic and mechanical equipment, a concerted safety effort is required in plasma etching. Proper shielding of reactors and power supplies to minimize operator exposure to rf radiation is imperative. An exposure level below 1 mW/cm has been suggested as a safe operating point (150). 

All plasma experiments were performed with an LMP reactor which has been described elsewhere in detail (5). The reactor is equipped with a heatable, rotating platen, 15 cm. in diameter, to which are fastened specimens for surface modification. The reactor operates at 2.45 GHz frequency and at power in the range 0.1 - 2.5 kW. 

The equipment used in the unit operations is complex and microprocessor controlled to allow the execution of process recipes. However, advanced control schemes are rarely invoked. The microprocessor adjusts set points according to some sequence of steps defined by the equipment manufacturer or the process operator. Flows, pressures, and temperatures are regulated independently by off-the-shelf proportional-integral-derivative controllers, even though the control loops interact strongly. For example, fluorine concentration, substrate temperature, reactor pressure, and plasma power all influence silicon etch rates and uniformity, but they are typically controlled independently. 

All plasma exposures were carried out in an IPC (International Plasma Corporation) 2005 capacitance-coupled barrel reactor at 13.56MHz. The reactor was equipped with an aluminum etch tunnel and a temperature controlled sample stage. Pressure was monitored with an MKS capacitance manometer RF power was monitored with a Bird R.F. power meter and substrate temperature was measured with a Fluoroptic thermometer utilizing a fiber optic probe which was immune to R.F. noise. 

The plasma polymerization reactor used is schematically shown in Figure 5.5. Parallel electrodes, equipped with magnetic enhancement, by a 10-kHz power source created glow discharge of the monomer. A thickness monitor sensor is placed at the projected circumference of electrodes intercepting the midelectrode plane. The electrodes are 13.2 cm in diameter and 6.1cm apart. The thickness monitor surface is perpendicular to the plane parallel to the electrodes. 

The step of evaluating the technical and economic merit of a proposed process requires selection of the type of equipment and processing conditions to be employed. However, too little is known about the factors controlling the plasma reaction to apply kinetic theory to aid in the selection. As a result, reaction studies have been empirical. However, as this series of papers shows, there is extensive research being undertaken. What is needed is a means of correlating the results reported for the various discharge reactor systems used so as to guide future research and to obtain answers for the many questions yet unresolved. 

RIE equipment is usually parallel plate reactors in which both plasma and DC bias voltage are... 

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