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Magnetron Enhanced Reactive Ion Etching

IP.com Disclosure Number: IPCOM000047954D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 4 page(s) / 42K

Publishing Venue

IBM

Related People

Grebe, KR: AUTHOR [+3]

Abstract

Magnetron-enhanced etching greatly increases the etch rate of many materials in both reactive ion etching (RIE) and sputter etching modes. At plasma-concentrated regions, the sputter etching rate of metal can be more than 1 micron/min. and the RIE rate of polymers can be more than 2 microns/min. With relative motion between magnets and the substrate holder, etching uniformity across the substrate holder may be achieved. This process is appropriate for scaling up to substrate holder dimensions more than 1 meter. Therefore, it is a manufacturable process and is particularly applicable for large parts and for high throughputs. This process is applicable to stripping of resist, via etching of holes, formation of trenches, etch-back for planarization, removal of metals, etc.

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Magnetron Enhanced Reactive Ion Etching

Magnetron-enhanced etching greatly increases the etch rate of many materials in both reactive ion etching (RIE) and sputter etching modes. At plasma-concentrated regions, the sputter etching rate of metal can be more than 1 micron/min. and the RIE rate of polymers can be more than 2 microns/min. With relative motion between magnets and the substrate holder, etching uniformity across the substrate holder may be achieved. This process is appropriate for scaling up to substrate holder dimensions more than 1 meter. Therefore, it is a manufacturable process and is particularly applicable for large parts and for high throughputs. This process is applicable to stripping of resist, via etching of holes, formation of trenches, etch-back for planarization, removal of metals, etc. There has been increasing interest in achieving high etch rates of various materials by dry processes. The implication of high etch rate is shortened process time and hence reduced production cost. Materials requiring high etch rates are usually thicker than 1 micron. This situation often happens in packaging processes, although it can also happen in chip processes. Examples are polyimide (2-10 microns), glass, sputtered quartz, epoxy, KAPTON* (one form of polyimide), RISTON*, silicon etc.

Most of the materials can be etched in oxygen or CF4-containing plasma, by laser, or by combinations. Compared to wet etching processes, etching in plasma is severely limited by the availability of active etching species. This is primarily due to low ion densities in the conventional plasma etching and RIE modes. The etch rate in a plasma process is usually proportional to the input power to the plasma. Because of the limitation of plasma current, high power density implies high bias voltage which causes physical sputtering of electrode/substrate materials in addition to heating.

In oxygen RIE of photoresist (Shipley AZ1350J), for example, the etch rate usually is about 40-45 nm/min(0.1 W/cm2) at 50 mT oxygen if the etching is not flow limited. The corresponding RF bias voltage on the cathode at 0.3 W/cm2 is about 800-900 volts (peak-to-peak). One way to increase the power density without substantial increase of voltage is to increase the plasma current or the ion density. This can be achieved by microwave enhancement. Microwave-enhanced plasma etching and RIE have been demonstrated and are currently under further investigation and development; another known way to increase plasma intensity is by magnetic field. This article demonstrates magnetron enhancement to the RIE. Operation Principle The development of magnetron sputter deposition was driven by the reason that conventional DC or RF sputter deposition rates were limited by ion density. The externally applied magnetic field (mostly parallel to the target surface) modifies the electron trajectory and hence increases the electron-neutral atom (molecule) collision probability before the e...