Development of chemically assisted dry etching methods for magnetic devicestructures

There is a strong need for advanced pattern transfer methods for magnetic d evices such as magnetic random access memories, sensors for avionics and mi ne detection, and read/write heads for high density information storage. As the critical dimensions in these devices are decreased, the use of ion mil ling for pattern transfer presents major obstacles, including sidewall rede position (which degrades magnetic performance) and poor mask selectivity. M ost magnetic materials do not form volatile etch products in conventional r eactive ion etching. We have recently found that high density plasmas provi de efficient ion-assisted desorption of metal chloride etch products, provi ded that the etch production formation and removal are balanced by correct choice of ion/neutral ratio. We have completed the survey of plasma chemist ries for etching of giant magnetoresistance (GMR) (NiFe, NiMnSb) and collos sal magnetoresistance (CMR) (LaCaMnO3,LaSrMnO3,PrBaCaMnO3) materials. The o ptimum choices are Cl-2/Ar for CMR oxides, SF6/Ar for NiMnSb Heusler alloys and either Cl-2/Ar or CO/NH3 for GMR multilayers. We have also addressed t he issue of postetch cleaning for corrosion prevention, by combining simple water rinsing with in situ plasma cleans involving H-2, O-2, or F-2. Under optimized conditions, there is excellent long-term stability of both the m echanical and magnetic properties of the multilayer structures. (C) 1999 Am erican Vacuum Society. [S0734-211X(99)06206-X].