A method of marking a sintered body includes the step of preparing the sintered
body by sintering a mixture of first and second types of powder particles. The
first type of powder particles is made of a first material and the second type
of powder particles is made of a second material that has a different etch susceptibility
from the first material. The method further includes the step of writing ID information
on the surface of the sintered body by forming a first concave region to a depth
of at least about 10 nm under the surface of the sintered body and a second concave
region under the first concave region, respectively. The first concave region is
formed by etching away both the first and second types of powder particles, while
the second concave region is formed by etching away only the first type of powder particles.
