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Pulsed Laser Deposition

Available Systems

NANO PLD | PLD/MBE Systems | PLD 2000 / 3000 | PLD 5000 | PLD 8000 | MAPLE |
PS/PLD | Coated Conductor PLD | Combinatorial Thin Films

PLD Components

UHV Target Manipulators | PLD Intelligent Window | Optical Trains

Overview

PVD Products offers PLD systems for substrates ranging in size from 50 mm up to 200 mm in diameter. All systems consist of a user-friendly electro-polished SS box chamber with a front mounted hinged door. This door provides excellent access to the inside of the deposition chamber. Both substrates and targets are quickly transferred through the door in a matter of minutes. No flanges need to be removed for either target or substrate changes. Our systems can handle substrates from 10 mm square up to 200 mm in diameter. PVD Products would be happy to assist in the selection of the proper laser for your particular application.

The Chamber

Each chamber is bolted to a support frame with casters and leveling pads. The frames can have either one or two standard 19” wide racks to house the various electronic components.

Besides the hinged access door the chambers have several extra ports for user diagnostics or other applications. These include both target and substrate view ports, ports for Atomic Absorption or emission spectroscopy, a pair of ports for in-situ ellipsometry, as well as incorporation of an ion gun or magnetron sputter source into the chamber. Ports are also available for the addition of a load-lock, RGA, ion probe, or other diagnostics as well. Each chamber comes with a pressure relief valve so that the chamber pressure cannot exceed that of atmosphere by more than 2 PSIA.

This photo displays the view of a PLD 3000 load-locked system with the main door opened. Note the dual set of Viton O-rings which are differentially pumped to yield a base pressure below 5 x 10^-8 Torr. This pressure is defined by the outgassing of the large diameter oxide targets. A set of reflecting shields has been removed to expose the substrate spinner assembly which has been lowered to the substrate exchange position. Note that the black body style substrate heater includes a complete water cooled housing unit. Also seen is one of the target pedestals which is exposed by simply removing a cover plate. Targets can be easily changed through this cutout with out removal of any flanges. Also seen in this figure is a shutter used for pre-cleaning targets as well as the target manipulator gear set and bearing carousel.

The Substrate

Close up of a substrate exchange through the hinged door of a PLD 3000 unit. No flanges or gaskets need to be removed for target changes in any of the PVD systems. Once the system is vented and the door is opened, one set of reflecting shields is removed to expose the substrate spinner assembly. Substrate changes are accomplished with a pair of tweezers. Note that substrates are held in a ring only at the edges - no thermal paste or clamps are necessary. No cold spots are produced with this approach and very uniform film properties are achieved.

Large area systems give you the opportunity to coat a variety of substrate sizes and shapes. The photograph above shows various substrate holders available for our PLD 5000 system. Any substrate from 3 inches up to 5 inches can be coated along with multiple 2 inch or smaller samples. Custom holders can be made to accommodate your specific substrate sizes and needs for all of our PLD systems.

Pumps

The systems come with turbo molecular pumps backed by rotary vane rough pumps. Rotary vane pumps are prepped with Fomblin^TM for applications where oxygen will be routinely pumped. All valves on the system are electropneumatic and will automatically close to a safe position on power failure. A standard Mass Flow Control unit provides for precise and reproducible process gas during deposition. Deposition pressure is monitored and controlled using a heated capacitance manometer whose output it fed into a closed loop butterfly valve. The process pressure can be controlled from 1 to 500 mTorr. The capacitance manometer is connected to a tube that extends into the substrate heater box where it measures the pressure inside the deposition region, and not at the chamber wall. These pressures can vary significantly as the substrate is heated and the gas density and pressure directly in front of the substrate changes from that of the rest of the chamber. Base vacuum is measured with a Bayard Alpert Ion gauge. Chamber pressure and rough line pressure are also monitored with Convectron^TM gauges.

Target Manipulators

Each of our systems comes with a multi-target manipulator as outlined in the table below:

Our target manipulators use a dual axis, magnetically coupled rotary feedthrough and are further described in the Target Manipulator section.

In order to achieve uniform film properties the laser beam is rastered across the large diameter targets using a programmable optical train. The beam is rastered across the whole target to minimize cone formation and reduce the number of particles in the ablated films.

Targets

As noted in the table above, all of our PLD systems use large diameter targets. Thus the laser beam path length varies as it is scrolled from one edge of the target to the other and thus the laser fluence will change. In our PLD 2000 and 3000 systems the variation in fluence on the target surface is less than that of the pulse-to-pulse stability of the excimer laser. The two larger systems however, come with a special constant fluence optical train. Here the focus lens is mounted on a programmable stage whose position is slaved to that of the raster mirror. As the raster mirror scrolls the laser beam from one end of the target to the other the focus lens is moved in such a way that the beam path and thus the focused spot size remain constant.

Changing targets is a very simple, one-minute process because of the PVD box chamber design: simply vent the chamber, open the hinged door and remove two thumbscrews that attach the target shield. Then, remove the target and replace it with a new one.

If more than one target needs to be exchanged, one needs to index the target manipulator so that the next target to be exchanged is exposed. When all the targets are exchanged, the cover shield is replaced and the two thumbscrews put back in place. No flanges, gaskets, or water lines need to be removed from any PVD system for this process.

All of PVD Products PLD systems use large diameter targets, as they are necessary for producing large-area films. Laser beam rastering over large diameter rotating targets yields excellent film uniformity and does not require constant “resurfacing” the way small diameter targets do on a routine basis.

Optical Train

All of our PLD systems come with a complete optical train. This includes an optical breadboard positioned on the surface of one of the two electronic racks. The optical train consists of a focus lens, mirror set, kinematic mirror mounts, and PVD’s Intelligent Window. All of the optical components are AR coated for either 248 nm (KrF) or 193-nm (ArF). Other wavelengths are available as well. A computer is supplied to control the rastering of one of the kinematic mirror mounts so that the laser can be scrolled completely across a target diameter. A constant fluence optical train is supplied with our PLD 5000 and PLD 8000 systems. Here the focus lens position is slaved to that of the raster mirror so that the beam path length does not change as the laser beam is rastered across the 150 mm or 300 mm diameter targets.

The optical train is completely enclosed in a Plexiglas box that provides both eye protection as well as an excellent dust cover. The box is sufficiently airtight so that it can be purged with nitrogen to minimize ozone formation when using 193 nm (ArF) excimer laser radiation. A large hinged door on the front of the Plexiglas box allows for easy adjustment of all of the optical components.

Substrate Heaters

All of our PLD systems utilize our proprietary blackbody substrate heater design. Bonding of the substrate to a heated back plate is not required with our heaters.

We use banks of custom designed IR heat lamps and are able yield substrate temperatures of 850°C for materials such as sapphire and LaAlO₃. Silicon or other absorbing materials can be heated to 950°C. A thermocouple in close proximity to the substrate spinner and a programmable closed-loop temperature control unit are used to provide the user with the desired level of substrate temperature control during the entire film growth process. The blackbody heater can also be used for post-deposition annealing of YBCO films up to pressures of 300 Torr of O₂.

Substrates are held only at the edges and are not clamped in any way. They are heated by radiation alone and yield very uniform temperature profiles. The heaters and substrate rotation stage are completely surrounded by copper water-cooled shields (visible in the substrate change image) that minimize the thermal load on the vacuum chamber walls. Slots machined into the water-cooled shields provide for laser beam access to the target surface as well as the ability to observer the laser plume and substrate during the deposition process.

Substrate changes are very easy with our substrate heater and spinner design. Substrates are simply placed into a substrate holder ring and then slipped into the spinner. The spinner is then retracted up into the upper section of the heater housing using a motor controlled linear transfer stage. A variety of substrate shapes and sizes can be handled with custom substrate holders. For instance, our PLD 5000 unit can handle three 50 mm diameter LaAlO₃ substrates along with four 1-cm square substrates at one time as seen in the photograph.

Load-lock Compatibility

All of PVD Products vacuum chamber and substrate spinner assemblies are completely load-lock compatible. Substrates can be inserted into the main chamber through a gate valve using a magnetic transfer arm. Substrates can then easily placed into the spinner through a cutout in the front heat shield using a second transfer arm.

Load-lock compatible chambers come with a pair of differentially pumped Viton O-rings on the front door sealing surface and base pressures below 5 x 10^-8 Torr are readily obtainable.

Throw Distance = Target to Substrate distance. This distance is adjustable (~65 mm) using the spinner translation stage. However, maximum substrate temperature and temperature uniformity will vary slightly as the throw distance is reduced.