Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2005-Mar-25
This article describes a non-saturated BHF etch solution prepared from NH4F and HF solutions, in which the NH4F concentration has been changed from 40 to 37 percent.
describes a non-saturated BHF etch solution
prepared from NH4F and HF solutions, in which the NH4F concentration
has been changed from 40 to 37 percent.
conventional solutions, i.e., mixtures of NH4F 40 percent
and HF 49 percent (BHF 39.9/.1), the etch rates of wet tanks open to
the atmosphere are subject to changes caused by variations in the
concentrations of the initial solutions and the composition of the
mixture during the lifetime of the bath.
By adding a
small amount of water, the etch rate of the mixture
remains almost unchanged, while the strong initial etch rate
variations are avoided. In addition, the particle performance is
about a factor 2 better than that of the common solutions.
The figure shows the change of the NH4F and
concentration during the lifetime of the bath both for the common
(BHF 39.9/.1) and the new (BHF 37.0/.1) solution.
With the new
solution, both species, NF4F and HF, increase
during the lifetime of the bath. This indicates that there is little
or no sedimentation and/or other reaction of NH4F resulting from