Unisearch Limited

Massachusetts Institute of Technology

Christopher M Horwitz

Stephen Boronkay

The present invention relates in particular to electrostatic holding devices for holding semiconductor wafers and other materials during processing operations, such as vacuum sputtering, for example. One problem with such holding devices is that a residual electrostatic charge tends to build up on the surface of the device. This can lead to problems in the release of the wafer when processing is completed, as this electrostatic charge will tend to grip the wafer. The present invention overcomes this problem by determining a value of drive voltage to be applied to the electrostatic chuck to cancel out the holding effects of at least most of the residual electrostatic charge and thus enable release of the wafer. The value of drive voltage to be applied to allow release is determined by monitoring motion of the wafer as the drive voltage is varied, the motion of the wafer being indicative of whether it is being gripped by the body or not.

Electrostatic chuck with improved release

Electrostatic chuck using A.C. field excitation

A new logic circuit construction in which gates are formed by appropriate interconnections of complementary current-mirror cells. With a signal applied, the resulting logic circuit draws a current drain which rises with power supply voltage, as does the speed of the circuit. With no signal the current drain of the circuit is small. Clocked circuits using this logic can use one clock line. With three states available in the clock line, a non-overlapping two-phase clock is automatically obtained with a simple oscillating signal. This logic circuit is also capable of providing a weighted input or output, enabling threshold logic ('multiple-valued logic') to be performed.

Complementary current mirror logic

There is disclosed a dry process etching or deposition chamber which allows an improvement in process speed and control of directionality over prior art dry process chambers. The etching or deposition chamber is provided with a hollow cathode electrode comprising two parallel electrode surfaces which are maintained at substantially the same electrical potential while a radio frequency potential is applied between the hollow cathode electrode and an anode electrode which is also located within the chamber. During the etching or deposition process, a partial vacuum is maintained in the dry process chamber and a gas is introduced into the chamber to provide a source of halogen ions and carbon or silicon ions under radio frequency excitation these ions forming a chemically reactive plasma. Products of the etching or deposition process can be pumped out of the chamber during the processing step if greater performance is required.

Hollow cathode sputter etcher

A process for selectively etching an aluminum-containing coating in preference to a masking material on a surface of the aluminum-containing coating by positioning a patterned masking material on the aluminum-containing coating in a radio frequency plasma etching chamber and introducing an etchant gas and a source of oxygen and silicon to the interior of the chamber under conditions where silicon dioxide is deposited selectively on masking material layer while the unmasked aluminum-containing coating is etched.

Gas mixtures for aluminum etching

Selective etching of aluminum

A process is provided for selectively etching silicon by means of a plasma etching composition wherein an etching target is connected to a radio frequency voltage and a source of silicon and oxygen is provided with the plasma etching composition in order to minimize etching of a masking composition.

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Summer Hill, Australia

Christopher M Horwitz