Plasma etching reactors

Step 2. A dual-armed robot (e g., an Endura VHP robot by Applied Materials) transfers one wafer to the plasma-etch reactor in 20 s. The robot is encased within a transport module that is evacuated to 1 torr. Based upon the Trikon Sigma fxp Deposition Cluster, it is estimated that 35.1 ft2 of 100-level clean room area are required. 

Figure 8. Configurations for plasma etch reactors, (a) barrel or volume loaded 0)) parallel plate or surface loaded (c) downstream etcher.

Kushner, MJ. A kinetic study of the plasmaetching process I. A model for the etching of Si and Si02 in CnFm/H2 and CnFm/02. J. Appl. Phys. 1982, 53, 2923-2938 IBID, A kinetic study of the plasma-etching process II. Probe measurements of electron properties in an RF plasma-etching reactor. J. Appl. Phys. 1982, 53, 2939-2946. 

Hargis, P. J., Jr., and M. J. Kushner. Detection of CF2 radicals in a plasma etching reactor by a laser induced fluorescence spectroscopy. 

GL 16] [R 12] [P 15] By a plasma etch process (see description in ]R 12]), a highly porous surface stmcture can be realized which can be catalyst coated [12]. The resulting surface area of 100 m is not far from the porosity provided by the catalyst particles employed otherwise as a fixed bed. In one study, a reactor with such a waU-porous catalyst was compared with another reactor having the catalyst particles as a fixed bed. The number of channels for both reactors was not equal, which has to be considered in the following comparison. 

The steam reformer is a serpentine channel with a channel width of 1000 fim and depth of 230 fim (Figure 15). Four reformers were fabricated per single 100 mm silicon wafer polished on both sides. In the procedure employed to fabricate the reactors, plasma enhanced chemical vapor deposition (PECVD) was used to deposit silicon nitride, an etch stop for a silicon wet etch later in the process, on both sides of the wafer. Next, the desired pattern was transferred to the back of the wafer using photolithography, and the silicon nitride was plasma etched. Potassium hydroxide was then used to etch the exposed silicon to the desired depth. Copper, approximately 33 nm thick, which was used as the reforming catalyst, was then deposited by sputter deposition. The reactor inlet was made by etching a 1 mm hole into the end... 

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). 

Three different dry etch techniques were investigated isotropic O2 plasma etching in a Tegal 200 reactor, R.I.E. in a parallel-plate in-house modified Tegal AOO reactor and R.I.M. in a Veeco, Model RG-830. The conditions of operation for each system were as follows where time is the time to etch 1.2 p of fully cured polyimide. 

Like CVD units, plasma etching and deposition systems are simply chemical reactors. Therefore, flow rates and flow patterns of reactant vapors, along with substrate or film temperature, must be precisely controlled to achieve uniform etching and deposition. The prediction of etch and deposition rates and uniformity require a detailed understanding of thermodynamics, kinetics, fluid flow, and mass-transport phenomena for the appropriate reactions and reactor designs. 

Figure 7. Configuration for plasma etch and deposition reactors, (a) parallel-plate or surface-loaded design with wafers positioned horizontally (h) parallel-plate design with vertical electrodes with a furnace tube (c) external coupling, downstream (d) external coupling, (a Reproduced from reference 2. Copyright 1983 American Chemical Society, b-d Reproduced with permission from reference 46. Copyright 1983 American Society for Testing and Materials.)...

Studies were also performed with an artificial fixed bed composed of an array of microstructured columns made by a plasma etch process. These columns were made porous to increase the surface area to 100 m2, which is not far from the porosity of catalyst particles in fixed beds, and then coated with a catalyst [278]. The performance of such catalytic microcolumns was compared with that of a catalytic fixed bed reactor. When normalized to the metal content, the reaction rates of the columnar and the particle-containing reactor are similar with 6.5 x 10 5 and 4.5 x 10-5 mol/(minm2), respectively. 

Fig. 6. IR transmission (a-c) and difference (d.e) spectra of O, plasma etched PBTMSS films hst m Table II. Samples I - RIE -400 V 2 - SME 3 - high-pressure RIE - high-bias RIE, 5 - barrel reactor etched. Curves a are for the initial film b for the film treated as given, n Table I, c after additional RIE at 20 mTorr and -400 V for 10 min. Curves d-b-a, e-c a.

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. 

Plasma Etching. The glow discharge reactor used in oxygen plasma etching of POP film was described previously ( ). The reactor pressure was monitored with a capacitance manometer (MKS... 

Besides the nitrogen contamination due to pollution of the carrier gas, the diamond films obtained by chemical vapour deposition (CVD) are usually contaminated with silicon. This contamination originates from the plasma etching of the silica walls of the reactor and of the commonly used silicon substrates [37]. 

Fig. 3. Panorama of plasma etching using silicon etching with chlorine as an example. This figure also shows the disparate length scales involved from the reactor, to the sheath, to the microfeature, to the atomic scale. Cl radicals and CIJ ions are generated in the plasma by electron impact of gas molecules (a). Ions accelerate in the sheath and bombard the wafer along the vertical direction (b), thereby inducing anisotropic etching of microscopic features to yield SiCU, a volatile product (c). Ion bombardment creates a modified layer at the surface where Cl is mixed within the Si lattice (d).

In what follows, the fundamentals of plasma engineering are discussed with emphasis on plasma etching. Discussion pertains to the kind of plasmas used in electronic materials processing. Similarities and differences with electrochemical reactor engineering are pointed out along the way, and are summarized in Section 8. 

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