Etching barrel

The remaining spectra in Figure 6 show evidence of similar formation of SiO for the different passivation treatments. The extent of oxide formation as judged from the intensity of the peak at 1070 cm" depended on the particular passivation treatment as did stability to an additional 10 min. "standard" RIE. For example, SME resulted in a much greater extent of oxide formation (curve 2d) than high-bias (curves 3d and 4d) or barrel etching (curve 5d). 

Figure 11 shows an RBS spectrum of a PBTMSS film after O2 RIE (1 min, —800 V, 20 mTorr). The substrate signal in this and other spectra is markedly lower and it is similar to the simulated spectrum which indicates that oxygen plasma treatment makes the film more radiation resistant. In addition, the surface layer of plasma treated films does not contain measurable amounts of sulfur. The thickness of this sulfur-free layer, estimated by comparison with simulated spectra, is about 50 A after RIE and SME and 25 A after the barrel etching. The data also show that the same layer is enriched in oxygen and silicon which was confirmed by simulation. These results compare favorably with those obtained from AES spectra. 

Barrel etching Chemical Excellent anisotropic Isotropic 100... 

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

The resist has been used as a mask in wet etching and in lift-off processes, and more recently in etching chromium films in a chlorine-oxygen-helium plasma. In the latter, the etch rates have ranged from 4 to 5.5nm/min at lOOW power in a barrel type reactor. Chromium etches at about 6.5nm/min under these conditions. The etch rate of the resist appears to be independent of the degree to which it has been cured before exposure, so the sensitive form described here is just as effective a mask as the highly cross-linked resists described earlier, at least in the chromium etching process. 

Very little will be said here concerning the equipment aspects of plasma etching. There are three basic types of equipment which have been used a) barrel systems, b) planar systems, and c) systems in which the wafers are located downstream from the plasma to be referred to in this paper as downstream etching systems. These plasma etching configurations are shown schematically in Fig. 3.1. Often the barrel systems are used with a perforated metal tube called an etch tunnel which is shown in Fig. 3.1 a and b. The purpose of the etch tunnel is to protect the wafers from the energetic ion and electron bombardment to which waters immersed directly... 

Fig. 3.1. Plasma etching systems, a and b Barrel system with etch tunnel, c Planar system, d Planar system (reactive ion etching or reactive sputter etching mode), e Downstream system...

Barrel etcher with etch tunnel Arbitrary between wafers Division Not applicable 83... 

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. 

Resist films were also etched in a barrel-type plasma reactor (Plasmod, March Instruments, Inc.) operating at 13.56 MHz at a power density of approx. 0.007 W/cm and with an oxygen pressure of 0.85 Torr. 

Fig. 3. Thickness of PBTMSS after etching in a barrel plasma reactor (A) (po 850 mTorr) versus time. The samples were then etched for 10 min. under O2 RIE conditions (B) (poj 20 mTorr, U —400 V).

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.

Fig. 9. AES atomic concentration depth profile for a PBTMSS film on Au/Si. Film etched for 1 min. in a barrel reactor at 850 mTorr O2.

Contrary to the observations reported by Bagley et al. (7) on the etching of an organosilsesquioxane in a barrel reactor, the PBTMSS etching process does not proceed beyond the surface layer, probably because much higher elasticity of the PBTMSS network causes collapse of the micropores through which the active species diffuse into the film. 

C for 30 minutes in a vacuum oven. Plasma development was carried out either in a barrel etcher or a planar etcher. For the barrel etcher, 02 (oxygen) was used as the etch gas. In Figure 4, the normalized film thickness remained after development vs exposure dose is plotted for two different bake temperatures. It appears from the figure that 60° bake has produced a more sensitive resist but 100° bake has produced a thicker resist at high dose. The exposed patterns were 10 micron by 500 micron rectangles. 

The volume-loaded barrel reactor shown in Fig. 19c, is not used for applications that require anisotropic etching. A typical example is photoresist stripping. High... 

Fig. 19. Schematic of common plasma reactor configurations besides the one shown in Fig. 3a. Reactive ion etching (RIE) (a), magnetically enhanced reactive ion etching (MERIE) (b), barrel (c), and downstream etching (d) reactors. In the barrel and downstream reactors etching is purely by neutral radical...

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