  The half quantum vortex(HQV) in condensate has been studied, since it was
predicted by Salomaa and Volovik in superfluid $^3$He-A phase. However, an
experimental evidence for its existence has not been reported so far. Motivated
by a recent experimental report by Yamashita et al\cite{yamashita}, we study
the HQVs in superfluid $^3$He confined between two parallel plates with a gap D
$\sim$ 10 $\mu$m in the presence of a magnetic field H $\sim$ 26 mT
perpendicular to the parallel plates. We find that the bound HQVs are more
stable than the singular vortices and free pairs of HQVs, when the rotation
perpendicular to the parallel plates is below the critical speed, $\Omega_c
\sim$ 2 rad/s. The bound pair of HQVs accompanies the tilting of ${\hat
d}$-vector out of the plane, which leads to an additional absorption in NMR
spectra. Our study appears to describe the temperature and rotation dependence
of the observed satellite NMR signal, which supports the existence of the HQVs
in $^3$He.
