Deposition rate monitoring quartz crystal monitors

The deposition rate is often an important processing variable in PVD processing. Not only can the rate affect the film growth along with the deposition time, it is often used to determine the total amount of material deposited. The quartz crystal deposition rate monitor (QCM) is the most commonly used in situ, real-time deposition rate monitor for PVD processing. 

Deposition rate monitors include devices such as quartz crystal monitors and RHEED tools that measure the rate of deposition of a film on a surface and... 

Monoatomic copper vapor was generated by directly heating a tungsten-rod assembly around which copper wire was wrapped. The rate of metal atom deposition (10-12 K) was continuously monitored with use of an in situ quartz-crystal microbalance assembly. Cu(C2H2) and Cu(C2H2)2 were detected by spectroscopic methods. 

Thickness controllability (Table 9.1, no. 6) and reproducibility in OVPD is achieved by accurate adjustment of the flow of carrier gas by means of mass-flow controllers whereas in VTE quartz crystal monitors are used to control the rate of deposition by adjustment of the evaporation temperature. In VTE small deviations of the evaporation temperature are known to affect the stability of the deposition rate and consequently the layer thickness, which may also affect the roughness and morphology of the VTE-deposited layer. 

The rotatable reactor can also be used for reactions in fluids having suitably low (< 10"3 Torr) vapor pressure. In this mode, metal atoms are evaporated upwards into the cold liquid, which is spun as a thin band on the inner surface of the flask. Reactions with dissolved polymers can then be studied. Specially designed electron gun sources can be operated, without static discharge, under these potentially high organic vapor pressure conditions (6). Run-to-nin reproducibility is obtained by monitoring the metal atom deposition rate with a quartz crystal mass balance (thickness monitor). 

Silver evaporations were done in the same preparation chamber using an inhouse-constructed evaporation assembly containing a resistively heated tungsten basket. Ag coverages were controlled by a quartz crystal thickness monitor. The deposition rates were typically 0.01 to 0.1 A/s depending on the desired coverage. Coverages were subsequently calibrated by XPS analysis of the Ag 3d and polymer core level (C Is and O Is) intensities as compared to known standards, and by neutron activation analysis (111. 

When argon is used as the plasma gas, the sputtering rate measured by the deposition rate of aluminum on a quartz crystal thickness monitor was found to be linearly proportional to Wjp as depicted in Figure 9.9 [15]. In the domain of glow discharge, W increases by the increase of current at nearly constant discharge voltage, and Wjp could replace Vjp. 

The separation properties of the membranes vary not only with the thickness of the plasma polymer coatings but also with the conditions of LCVD. One such plot of the variation is shown in Figure 34.21 [14]. The upper portion of this figure shows how the specific conversion parameter, DRjFM, varies as a function of the composite energy input parameter, WjFM. DR is the nominal deposition rate of plasma polymer film on the surface of a quartz crystal thickness monitor located in the plasma reactor, adjacent to the hollow fibers. 

Similarly, partial reaction currents in electroless copper-plating solution can be extracted using electrochemical quartz crystal microgravimetry (EQCM) to in situ monitor the rate of copper deposition under open-circuit conditions and as a function of the electrode potential... 

An optical monitor and/or a quartz crystal monitor is used to control the film thickness and deposition rate. Quarter-wave films in the visible range can be deposited within 3-4 min. 

For control of the rate of deposition, a quartz crystal monitor can additionally be used. Because of the importance of this method, it will be treated in more details in the next section. 

The difference between Cf and C f is easy to calculate. For a mass corresponding to a 2% shift in starting frequency, the difference in areal density using C f instead of C, is about 4%. For accurate mass determinations, this variable sensitivity has to be considered. The quartz crystal monitor can also record the rate of deposition, as already mentioned above. Rate measurements are very important especially in reactive deposition. The rate is obtained by electronic differentiation of the mass-dependent frequency change with respect to time. The slightly varying mass sensitivity with increasing mass load need not be considered for rate measurements. 

In practice, however, the attained sensitivity is in the 10 7 g cm 2 range. This accuracy of quartz-crystal microbalances for mass determination is by far sufficient for most requirements in thin-film deposition. Commercially available thickness and rate monitors use quartz crystals with a frequency of 5 or 6 MHz. Fig. 6a shows the Leybold IC/4 Plus thickness and rate monitor and Fig. 6b shows the various types of quartz crystal holders. 

The deposition rate of the polymer films was monitored by quartz crystal oscillating technique and controlled by multiple beam interferometry according to Tolansl s... 

The wet disks are immediately immersed into the vapor of refluxing isopropanol. Once they reach the reflux temperature, as noted by a reduction in the rate of alcohol condensation on the disks, they are removed into the room air where they rapidly become dry and slowly cool to room temperature. At this point, the disks are individually weighed to the nearest 0.1 mg. The disks are then loaded into a metal tray with large circular regions on their bottom faces exposed and the tray placed in the load lock of a vacuum chamber. The load lock is pumped to about 10 torr and then the tray is translated into the chamber and the load lock sealed off from the chamber. The chamber is pumped to about 10 torr with a cryopump. The major residual gas is water from the rotatable rubber seal used between the evacuated space in the chamber and the water flow path into and out of the rotatable copper crucible mentioned below. Titanium vapor is sublimed from a Ti ingot by bombardment with about 8 keV electrons while the periphery of the ingot is cooled by sparse physical contacts with the water-cooled copper crucible in which it rests. The Ti vapor condenses in the line of sight from the source onto the exposed bottoms of the disks. The thickness of the deposited titanium, is monitored by a calibrated quartz crystal balance close to the quartz disks. Typically (iji 5 x 10 cm. 

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