Specific Process Knowledge/Thin film deposition/Lesker

Film quality optimization

By Bjarke Thomas Dalslet @Nanotech.dtu.dk

The Lesker CMS 18 sputter system can produce films in a wide range of qualities. The quality of a film depends strongly on the substrate (lattice matching), but also on the energy the sputtered material can utilize for annealing.

Strain estimations was done on 30 nm Ni$_{81}$Fe$_{19}$ thin films using low angle x-ray diffraction, for various substrates. It was found that the strain of the film influenced the resistance (R) and anisotropic magneto resistance (AMR) of the films (this relationship is also documented in literature); A Ta interface layer reduced R and increased AMR on both Si and SiO$_{2}$ substrates while reducing strain.

This study was then done on 30 nm Ni$_{81}$Fe$_{19}$ thin films deposited on 3 nm Ta on top of a SiO$_{2}$ substrate, using R and AMR as an indication of strain. As seen in the tables, applying a substrate bias increases AMR and conductance (1/R). An equivalent effect is seen when heating the substrate during deposition. This heating can also be done after deposition without loosing the effect.

Name	Substrate bias (W)	AMR	1/R (S)	Crystal strain
0029 NiFe3_stack_RF20	20	0.02724278	1.308044474
0018_NiFe1_stack_RF	10	0.025850358	0.898311175
0030 NiFe3_stack	0	0.020103598	0.71772052	0.8

Name	Temperature (C)	AMR	1/R (S)	Crystal strain
0030 NiFe3_stack	25	0.020103598	0.71772052	0.8
BDT-NiFe1-blank30	200	0.019319002	1.095770327
BTD-NiFe-Blank22	250	0.021768497	1.047668937
BTD-NiFe-Blank14	300	0.02983617	1.724137931
BTD-NiFe-Blank13	350	0.033944331	1.887504719
BTD-NiFe-Blank15	400	0.031176801	1.655903295	0.2
BTD-NiFe-Blank16	450	0.030843457