SPI Supplies™ Brand of Plasma Etchers, Cleaners, and Ashers

Chemistry of the plasma and what can be etched

When they're gone, they're gone!

For over 20 years the Plasma Prep II system and its family have been top selling low-temperature etcher/cleaner/ashers, used in many research labs. Now the system has been replaced by the Plasma Prep III solid-state system and its family of etchers and cleaners. We will continue to sell the Plasma Prep II systems until they are gone, and we are getting close to that point. Be assured that SPI Supplies will still support these systems for as long as we can provide the RF tubes and other spare parts.

In the meantime, check out our Plasma Prep III system.

Introduction:
What can be etched at any given time will dependent on the feed gas being used for the etching (hereafter, when we refer to "etching", one could substitute "ashing" or even "cleaning") because it is the chemistry of the plasma that determines just what will be etched. For example, just about anything carbonaceous, including diamond and most other polymers including PFTE and polyimide can be etched readily with pure oxygen.

Most metal oxides can be etched with argon. Passivation layers such as SiO₂ or Si₃N₄ can be removed only with CF₄ or 90% CF₄/10% O₂. Silicon can be etched with SiF₄. Aluminum can be etched with BCl₃.

For some polymers the etching at room temperature can be painfully slow, even with pure oxygen so if one can keep the sample heated

As indicated above, the SPI Plasma Prep II is also widely used to remove organic residues and/or contaminants from non-flat surfaces that can become trapped in difficult-to-reach areas such as on newly manufactured (non-polymeric) prosthetic devices. A quick treatment with oxygen, for example, will remove such residues or other layers of carbonaceous composition and there will be an immediate improvement in wettability and overall adhesion characteristics.

One can speed up greatly the etching rate by keeping the sample at an elevated temperature. This can be readily done by taking a small piece of ceramic, for example one that might be a block that is 50 mm x 50 mm x 10 mm thick, first putting it into an oven at some temperature, for example, 200° C, and then transferring the hot ceramic block to the plasma etcher and then placing the sample to be etched onto the heated ceramic block. In the case of polyimide for example, a plasma etch in a mixture of 30% CF₄/70% O₂ at 250° C, will remove 8 µm of hard baked polyimide in about 4 minutes.

In general, the etch rate can be increased, sometimes dramatically if the sample is heated as described above.

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Thursday February 09, 2012 © Copyright 2012. By Structure Probe, Inc.
Contacting SPI Supplies and Structure Probe, Inc.
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