In my experience, all optical ion beam sputtered films are compressive... I tried to reduce the compressive stress and preferably get a tensile stress using ion assisted sputtering in a dual ion beam sputtering machine (http://iopscience.iop.org/article/10.1088/0960-1317/25/5/055019/pdf). However, using magnetron sputtering I remember some one varied the deposition pressure to get tensile stress.

Thanks for the info - reducing the stress of both films using the assist ion beam (eg. below ~50MPa) would probably mitigate my problems as well.  

Do you happen to remember where you saw the tensile Magnetron films?  I haven't been able to find this myself.

I couldn't find the exact paper that I was talking about. But the following are some papers that discuss what you are trying to achieve.

1. "Intrinsic stress in dielectric thin films for micromechanical components", Richter, FSchlott, P

2. "Effect of substrate–target distance and sputtering pressure in the synthesis of AlN thin films", Iriarte, G. F., Rodriguez, J. G., Calle, F.

Good luck with you work...

You can resend me the full-text request... I accidently uploaded it online instead of sending it privately, and now I cant find your request again...

Thank to both of you. Anayat, that first paper was extremely helpful!

Chaman, do you have a paper or other documentation of that?  I would love to know more about the parameters and their effect on the stress (eg. how tensile/compressive one could make the ZnO film.).