Granted Patent
Utility
US 4,711,989 · App. 06/864,676
Diffusion furnace multizone temperature control
Inventor:
Chorng-Tao Yu
Patented Case
View Patent ↗
Granted: Dec 8, 1987
Filed: May 19, 1986
Inventor
Chorng-Tao Yu
Assignee (at issue)
Thermco Systems, Inc.
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.