6. RESPONDIENDO A DUDAS DE LAS PERSONAS USUARIAS
6.2. Reclamaciones
3.2.1. Substrate Preparation
Commercially pure grade 1 titanium sheet (Timet, UK) (CPTi) was wire eroded into 10 mm diameter discs with a thickness of 1 mm. Discs were then ground to a mirror finish (Ra = 16 ± 4 nm) using a series of silicon carbide paper (P2407
P1200), polished with a mixture of colloidal silica (Buehler, Germany) and 10 % hydrogen peroxide (Fisher Scientific, UK) and finally water. Discs were cleaned for 30 min in acetone, IMS and distilled water and dried under flowing nitrogen (BOC, UK).
Silicon single crystal (100) orientated Cz wafer (Compart Technology Ltd., UK) was cut into squares approximately 10 x 10 mm in size with a diamond tipped scribe.
3.2.2. Thin Film Deposition
Three different RF magnetron sputtering systems were used in this study. The first system is a bespoke system based on a pair of planar magnetrons arranged parallel to one another as described in section 3.1.2.1. while section 3.1.2.2. details a commercially available system which has been modified for research purposes which is based on 4 vertically mounted magnetrons. A third system, which is described in section 3.1.2.3., was similar to the first system, again based on a dual magnetron setup and used for the production of coatings specifically for characterisation of compositions.
3.2.2.1. Balanced Planar Magnetron (BPM) Deposition Parameters
The rig consisted of a rolled stainless steel cylindrical chamber with internal dimensions of 400 mm diameter and a height of 400 mm. The system was a top loading unit with upper and lower vertically opposed balanced water cooled Ion Tech B325 planar magnetrons. Deposition was carried out using the lower magnetron, requiring targets either 63 or 75 mm in diameter depending on magnetron configuration.
Figure 301. BPM PVD deposition unit.
The chamber was pumped to a base pressure of 1076 Torr (1.3 x 1074 Pa) using an
Edwards RV8 rotary pump and a water cooled Edwards EXT250 Turbomolecular pump. The chamber was then filled with high purity (99.99%) argon (BOC Pureshield, UK) at a user set deposition pressure between 1710 mTorr (0.171.0 Pa). This atmosphere was regulated by a MKS Baratron type 627B temperature controlled capacitive manometer with an operating pressure of 071 Torr (07133.3 Pa) sending data to an MKS 250 pressure controller reading system pressure. The
pressure controller was connected to a MKS 247C 100 sccm mass flow controller allowing a feedback loop to maintain a constant deposition pressure.
The lower magnetron was powered with either a RF Power Products Inc. RF5S 13.56 MHz RF power supply with 50 d matching unit or an ENI RPG750 DC Plasma Generator 5 kW with optional pulse mode.
Substrates were mounted vertically above the lower magnetron with conductive silver dag at a working distance of 50 mm. Before deposition onto substrates, targets were sputter cleaned behind a protective shutter for 30 min to remove surface contamination and oxidants.
For the purpose of this study this rig will be referred to as the balanced planar magnetron (BPM) rig. Details of coatings for all systems described are shown in table 371.
Sample Description Sample Ref. No. HA Magnetron Power Supply Silicon Magnetron Power Supply Frequency (kHz)/Pulse Time (ns) HA Power Density (W cm02 ) Si Power Density (W cm02) Base Pressure (Torr)
Gas Composition % Pressure (Torr) Argon Partial
Oxygen Partial Pressure (Torr) Duration (h) Target Details Estimated Thickness (Om)
HA 7014 Pulsed DC n/a 150/1500 6.8 n/a 4.2 x 1076 100% Argon 2 x 1073 n/a 2 Plasma
sprayed HA 0.2
HA 7017 RF n/a n/a 6.8 n/a 2.1 x 1075 100% Argon 2 x 1073 n/a 2 Plasma
sprayed HA 0.3
HA 7019 RF n/a n/a 11.3 n/a 4.4 x 1076 100% Argon 2 x 1073 n/a 2 Plasma
sprayed HA 0.8
HA 7125 RF n/a n/a 6.8 n/a 4.6 x 1076 87.8% Argon/12.2%
Oxygen 2 x 10
73 2.8 x 1074 2 Plasma
sprayed HA 0.2
HA 7128 RF n/a n/a 4.5 n/a 2.3 x 1075 87.8% Argon/12.2%
Oxygen 2 x 1073 2.8 x 1074 3 sprayed HA Plasma 0.2
HA* 8082 RF Pulsed DC 150/1500 6.8 n/a 2.7 x 1076 87.8% Argon/12.2%
Oxygen 2 x 10
73 2.8 x 1074 2 Plasma
sprayed HA 0.2
HA 8084 RF Pulsed DC 150/1500 6.8 n/a <2 x 1075 87.8% Argon/12.2%
Oxygen 2 x 1073 2.8 x 1074 2 sprayed HA Plasma 0.2
SiHA1 8092 RF Pulsed DC 150/1500 6.8 0.06 4.0 x 1075 87.8% Argon/12.2%
Oxygen 2 x 10
73 2.8 x 1074 2 Plasma
sprayed HA 0.2
SiHA1 8095 RF Pulsed DC 150/1500 6.8 0.06 <2 x 1075 87.8% Argon/12.2%
Oxygen 2 x 1073 2.8 x 1074 2 sprayed HA Plasma 0.2
SiHA2* 8099 RF Pulsed DC 150/1500 6.8 0.17 3.5 x 1075 87.8% Argon/12.2%
Oxygen 2 x 10
73 2.8 x 1074 2 Plasma
sprayed HA 0.2
SiHA2 8102 RF Pulsed DC 150/1500 6.8 0.17 <2 x 1075 87.8% Argon/12.2%
Oxygen 2 x 1073 2.8 x 1074 2 sprayed HA Plasma 0.2
SiHA3 8230 RF Pulsed DC 150/1500 6.8 0.33 5.6 x 1075 87.8% Argon/12.2%
Sample Description Sample Ref. No. HA Magnetron Power Supply Silicon Magnetron Power Supply Frequency (kHz)/Pulse Time (ns HA Power Density (W cm02) Si Power Density (W cm02) Base Pressure (Torr)
Gas Composition % Argon Partial Pressure (Torr) Oxygen Partial Pressure (Torr) Duration (h) Target Details Estimated Thickness
SiHA3 8231 RF Pulsed DC 150/1500 6.8 0.33 2.6 x 1075 87.8% Argon/12.2%
Oxygen 2 x 1073 2.8 x 1074 2 sprayed HA Plasma 0.2
HA BPM RF n/a n/a 8.0 n/a 5 x 1076 100 % Argon 7 x 1073 n/a 6 Sintered HA
powder 0.2
HA CSIRO RF n/a n/a 9.1 n/a 1 x 1076 100 % Argon 8 x 1073 n.a 0.33
Australian Surgical
plasma spray
0.1
3.2.2.2. Uniform Deposition and Plasma Systems (UDP) Deposition
Parameters
Coating deposition was performed in a UDP450/4 Teer Coatings Rig (figure 372) with chamber diameter of 450 mm and height of 570 mm. The chamber’s external wall had a double skin of stainless steel plate with a gap between the layers to allow a flow of cooled water between them. The system had a front opening door to allow for samples to be conveniently loaded. All experiments used 4 magnetrons mounted vertically in the ports in the coating chamber wall. The standard magnetrons are planar and had target dimensions of 220 mm x 134 mm. The magnetron used for the HA target was a 75 mm circular magnetron. The system was configured with the closed field unbalanced magnetron design (figure 373), although the strength of the magnetrons used was different with the silicon target being a stronger magnetron than the HA magnetron. The silicon target was of dimensions 300 x 100 and 0.635 mm.
Before deposition the chamber was pumped to a minimum of 2 x 1075 Torr (2.7 x
1073 Pa). An Edwards 750 diffusion pump provided the vacuum for this system
which is connected to the base of the chamber by an Edwards high7vacuum butterfly valve. This is backed with an Edwards E2M40 rotary pump which achieves a vacuum of approximately 1072 Torr (1.3 Pa) before the high vacuum
valve is opened. Chamber pressure is measured by Edwards Pirani and Penning gauges which operate at < 1073 Torr (0.1 Pa) and > 1074 Torr (0.01 Pa)
respectively. The chamber was then backfilled with either argon or an argon/oxygen mixture using MKS 1179A12CS1BV 100 sccm mass flow controllers. Argon flow was set at 36 sccm for all coatings equating to 2 x 1073
Torr (0.3 Pa). Where used, oxygen was flowed at 5 sccm with a partial pressure of 3 x 1074 Torr (0.04 Pa).
Figure 302. The inside of the deposition chamber of a Teer Coatings UDP450/4 PVD unit.
To alter the composition of HA and SiHA coatings the powder density applied to the targets and the sputtering environment was altered. The HA target was powered by an Advanced Energies RF power supply unit with the silicon target powered by an Advanced Energy Inc DC Pinnacle pulsed DC power supply. Frequency and pulse time was constant at 150 kHz and 1500 ns respectively giving approximately 1500 on cycles per second. The remaining two magnetrons were earthed. A negative bias of 730 V was applied to the substrates.
Figure 303. A Teer Coating Ltd closed field unbalanced magnetron arrangement as in the UDP450/4 rig. With permission from Teer Coatings Ltd.
Samples were mounted on a stainless steel plate as shown in figure 372 with double sided adhesive tape and oscillated at 4 rpm. Before deposition targets were run for a 2 min pre7sputter behind shutters.
For the purpose of this study this rig will be referred to as the UDP rig. Details of coatings for all systems described are shown in table 371.
3.2.2.3. CSIRO Deposition Parameters
Samples were deposited using an in house built rig based at CSIRO, Lindfield, Australia.
The deposition chamber was pumped to a base pressure of 1076 Torr (1.3 x 1074
Pa). Argon was backfilled into the chamber with a MKS 100 sccm mass flow controlled coupled to a MKS throttle type 252 A valve in feedback with a Baratron gauge MKS 127, with a range of 071 Torr (07133.3 Pa).
The target was allowed a 10 min pre7sputter. The sample remained stationary throughout sputtering.
For the purpose of this study this rig will be referred to as the CSIRO rig. Details of coatings for all systems described are shown in table 371.
3.2.2.4. Target Manufacture
Targets used in this study are described below:
Untreated sintered and unsintered HA powder (Plasma Biotal, UK) were used. The powder was loosely compacted onto the magnetron surface and the target was run for 24 h to remove surface contamination and sinter the surfaces. This target type was used for the BPM rig.
HA targets were manufactured by plasma spraying HA powder (Plasma Biotal, UK or Australian Surgical Design, Australia) onto a circular copper backing plate 75 mm in diameter and 5 mm in thickness. The Plasma Biotal method gave targets with a coating thickness of 500 bm whereas the Australian Surgical Design targets had a coating thickness of 400 bm. This target type was used in conjunction with the UDP rig.
Where required, a single 99.999% pure homogeneous silicon target (Kurt J. Lesker, Netherlands) was used which were of dimensions 300 x 100 and 0.635 mm thick were purchased externally.
3.2.3. Post0Deposition Heat Treatments
Post7deposition, thin films were recrystallised by heat treatments at a range of temperatures with a set time of 2 h using a Lenton Thermal Design tube furnace
in an argon atmosphere. Argon was flowed at 100 sccm for 30 min before ramping to temperature at 20°C min71. Mass spectrometry indicated all gases and
water vapour were at untraceable levels before ramping to temperature. Samples were left to cool naturally under argon.