Patent GB-1341759-A (GB)
Title: Film deposition
IPC: C23C14/22
Filed: 1971-05-19
Abstract: 1341759 Sputtering and evaporation apparatus WHITTAKER CORP 19 April 1971 [20 March 1970] 23343/71 Heading C7F [Also in Division H1] Apparatus for depositing a film 21 upon a substrate 22 comprises an ion source 10, a deposition chamber 20 having holder means (not shown) for containing the substrate 22, an apertured constricting member 26 between said ion source 10 and deposition chamber 20, and an apertured extracting electrode 24 situated between said constricting member 26 and said means for containing the substrate 22. To deposit a silicon film 21 on a single crystal silicon substrate 22, the ion source electrodes 14 and 15 are made of silicon and are connected across a power supply 34 to establish a discharge. A neutral gas such as A, H or He, or a more active gas such as N or O, or a mixture thereof, is introduced through a pipe 12 and ionized to sputter or vaporize atoms of silicon from the cathode electrode into the discharge where they are ionized. Electron paths are constrained by the magnetic field of a coil 30 to increase the likelihood of ionizing the silicon atoms. Pressure in the ion source is determined by a vacuum pump connected to pipe 13. The main function of the member 26 is to separate the higher pressure source chamber 10 from the deposition chamber 20 which is maintained at a pressure of about 10<SP>-6</SP> torr, by a vacuum line 29. Deposition of compounds, e.g. aluminium oxide, silicon dioxide, or silicon nitride can be achieved either by using electrodes of Si or Al and introducing the necessary O or N gas through the pipe 12, or by making the electrodes 14 and 15 of the necessary materials e.g. silicon oxide or nitride. Tungsten carbide can be deposited by using W and C electrodes or by introducing a tungsten compound in gaseous form and a hydrocarbon gas into the chamber 10. Insulating films of carbon in diamond-like form can be deposited by using C electrodes and a hydro-carbon gas, e.g. methane. Electrode 24 is biased positively with respect to the source 10 by a supply 36 and operates as an anode to extract electrons from the source. The electric field generated by the extracted electrons pulls positive ions along with them. Electrode 26 is connected to a potential divider comprising resistors 40 and 42 connected across supply 36, or may be left floating. A discharge restricting insulating shield 17 in the source 10 may also be left floating. A focussing electrode 19 is shown connected to the anode 24 but may be connected to a separate biasing supply. An A.C. or R.F. voltage from an oscillator 54 is superimposed by a transformer 52 on to the D.C. supply 50 to the substrate 22 to prevent the build up of a positive charge when the deposited film or the substrate is an insulator. In a modified form of the apparatus Fig. 2 (not shown) a vaporizing source of the material to be deposited is located in the deposition chamber. This may be a sputtering source, a crucible type source, or a resistively heated ribbon. Atoms from this source impinging on the substrate are then energized by a beam of gaseous ions, e.g. A, from the source 10.