Method of etching titanium diboride

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates in general to a method of etching titanium diboride and in particular to a method of dry etching a thin film of titanium diboride that has been deposited onto a substrate and patterned using photolithography.

Titanium diboride has become of interest in laboratory research because of its resistance to change or degradation at high temperatures. It also shows promise in acting as a diffusion barrier to other metals.

One of the difficulties involved with working with titanium diboride is that because of its resistance to attack, it is difficult to pattern. In fact, no wet etches have been available to carry out such patterning.

The general object of this invention is to provide a method of etching titanium diboride. A more particular object of this invention is to provide a method of etching a thin film of titanium diboride that has been deposited onto a substrate and patterned using photolithography.

It has now been found that the aforementioned objects can be attained by etching titanium diboride with a dry etch.

More particularly, according to the invention, a thin film of titanium diboride that has been deposited onto a substrate and patterned using photolithography is dry etched by first mounting the substrate bearing the patterned thin film on the lower electrode of pair of electrodes in the etch chamber of a commercial plasma etcher or plasma therm etcher. The etch chamber is evacuated to a pressure of about 10 -6 Torr and a dry etchant as, for example, dichlorodifluoromethane (CCl 2 F 2 ) admitted at a flow rate of about 1 to 100 sccm and a pressure set at about 1 to 500 mTorr. An electric field is applied between the electrodes, the power level set at about 50 to 1000 watts and etching allowed to proceed for the desired time.

Other dry etchants that will etch TiB 2 include a chloride gas, a mixture of a chloride gas with oxygen, a mixture of a chloride gas with nitrogen, a mixture of a chloride gas with a noble gas, a fluoride gas, a mixture of a fluoride gas with nitrogen, a mixture of a fluoride gas with oxygen, and a mixture of a fluoride gas with a noble gas.

After the dry etch, the sample is removed and the etch rate determined by measuring the etch depth and dividing by the etch time.

By adjusting the process parameters, one is able to attain etch rates of 5 to 800 Å/min for TiB 2 . This is useful for patterning TiB 2 as a diffusion barrier or a Schottky contact to semiconductors.

A thin film of TiB 2 is first deposited on a gallium arsenide substrate by e-beam evaporation and the substrate with thin film of TiB 2 then patterned using photolithography.

The substrate bearing the patterned film is then mounted on the lower electrode of a pair of electrodes in the etch chamber of a commercial plasma etcher. The etch chamber with the electrodes inside is then evacuated to a pressure of about 10 -6 Torr. CCl 2 F 2 is then admitted into the etch chamber at a flow rate of about 2 to 40 sccm and the pressure set at 10 to 200 mTorr. An electric field is applied between the electrodes and the power level set at 150 to 400 watts. The etch is allowed to proceed until the TiB 2 is completely removed in the areas exposed by the photolithography.

Other dry etch processes that can be used to etch TiB 2 include reactive ion beam etching (RIBE), chemically assisted ion beam etching (CAIBE), reactive ion etching (RIE), and magetron ion etching (MIE).

I wish it to be understood that I do not desire to be limited to the exact details as described for obvious modifications will occur to a person skilled in the art.