Etching resistivity of AlN ceramics surface

The etching resistivity of aluminum nitride (AlN) surface was investigated on properties of pull-out for AlN ceramics grain and uneven dissolution in chemical agents. Maximum step irregularity (MSI) of AIN with Y/sub 2/O/sub 3/ finally reaches to 7/spl times/10/sup -7/m at 10 k s at 50/spl deg/C in the aqueous solution of 2.5 mol KCN. This value is below the grain size of AlN, 4/spl times/10/sup -6/m. AlN grains did not begin to pullout, when the MSI value was below the AlN grain size. MSI of AlN with CaO reached to 2/spl times/10/sup -2/m at 3 ks in the same solution. This value is equal to the limit value of 2/spl times/10/sup -4/m. No pit was observed on the surface of AIN with Y/sub 2/O/sub 3/ until 10 ks from SEM result. However, many pits were observed at the grain boundary even at 30 s on the surface of AlN with CaO. The etching resistivity for AlN with Y/sub 2/O/sub 3/ is about 300 times as long as that with CaO. The surface of AlN ceramics with Y/sub 2/O/sub 3/ was confirmed to be stable against the KCN aqueous solution. The surface of AlN with CaO received a great deal of damage in etching solution. The AlN with Y/sub 2/O/sub 3/ is suitable choice for a MCM substrate with wet etching process.