Bromine and iodine etch process for silicon and silicides

DETAILED DESCRIPTION Objects In view of the above discussion, it is one object of the present invention to provide a silicon etch process that is suitable for reproducibly forming deep narrow silicon trenches with a controlled profile.
In particular, it is an object of the present invention to provide a process for etching single crystal silicon and polysilicon that consistently and reproducibly produces deep narrow silicon trenches having a U-shaped profile that is characterized by vertical sidewalls and rounded bottom edges.
It is another object of the present invention to provide an etching process using brominate and gas chemistry for forming deep, narrow, high aspect ratio trenches or grooves at a high etch rate in silicon and without problems such as bowing, trenching or black silicon.
It is also an object of the present invention to provide an etch process which accomplishes the above objectives and is an inherently clean process.
It is still another object of the present invention to provide a process for etching silicides and polycides which accomplishes the above objectives.
SUMMARY In one aspect, the present invention is embodied in, and the above objects are achieved by a process which comprises exposing a silicon or silicide body in a vacuum chamber to plasma formed from a reactive gas mixture comprising a preselected quantity of gas selected from brominate gas and iodinate gas.
Preferably, a magnetic field is applied parallel to the surface of the body to control etch rate, profile and ion bombardment.
The reactive gas mixture comprises the brominate etching gas hydrogen bromide or CF.
sub.
2 Br.
sub.
2, which may be doped with a preselected flow of fluorinate gas such as silicon tetrafluoride, or the iodinate gas hydrogen iodine, which may be doped with a preselected flow of chlorinated gas such as chlorine, silicon tetrachloride or hydrogen chloride.
The dopant also can be a mixture of fluorinate plus chlorinate gas such as CF.
sub.
2 Cl.
sub.
2, or SiCl.
sub.
4 plus SiF.
sub.
4.
The reactive gas mixture may include a diluent gas such as helium, argon, nitrogen and hydrogen to improve the process results or minimize damage to the process results