Technical_Requirements-Combinatorial_PLD_System.doc

Technical Requirements for Pulsed Laser Deposition System The following is a list of the Technical Requirements (MTRs) for a pulsed laser deposition (PLD) system including high pressure reflection high-energy electron diffraction (RHEED) package, UHV compatible deposition chamber and system frame, multi-target carousel system, rotating substrate heater, vacuum pumping package, gas flow control system, computer-controlled system software, and combinatorial synthesis system capable of continuous composition variation of binary and ternary phases.

1. The PLD system shall be combined with a combinatorial approach to deposit thin films and heterostructures with continuously varying composition across a 2–inch diameter substrate using two targets (binary phase variation) or three targets (ternary phase variation).

2. The combinatorial approach shall integrate both hardware (target and substrate indexing/rotation and heating) and software (laser pulse triggering/rastering) of the PLD system and shall be demonstrated successfully at the customer’s site after installation.

3. The PLD system shall consist of an ultra-high-vacuum (UHV) compatible, stainless steel 18-inch diameter spherical chamber and shall be designed to easily accommodate future upgrades consisting of: a load-lock for loading substrates into the heater without venting the main chamber, DC ion guns, and RF/DC sputtering sources.

4. The deposition chamber shall consist of two vertically aligned 8-inch conflat (CF) ports for the substrate heater (top) and multi-target assembly (bottom), one 6-inch CF port for the incident laser window, one 6-inch CF port for the load-lock (upgrade), one 6-inch port for the vacuum pump, three 6-inch CF ports for future RF/DC Sputtering and DC ion guns (upgrade), and two 2.75-inch CF ports for the gas inlet.

5. The incident laser beam shall be focused onto the target at 45 degrees with respect to the target normal.

6. The ‘x and y’ dimensions of the incident laser spot on the target shall be similar.

7. The position and rastering speed of the incident laser beam on the target and the target rotation shall be controlled by hardware and software to produce uniform erosion of the target surface.

8. The laser entrance window shall be equipped with a sacrificial ultraviolet (UV) grade fused silica liner, which can be removed for cleaning, in order to minimize coating of the laser window.

9. The PLD chamber shall integrate an automated multi-target carousel system that accommodates six 1-inch diameter targets or three 2-inch diameter targets.

10. The target carousel system shall be installed in an 8-inch CF flange and shall be mounted from the bottom of the chamber so that the target faces the top.

11. The target selection, target rastering, and target rotation shall be controlled by the system software.

12. The substrate heater shall be installed in an 8-inch CF flange and mounted from the top of the chamber so that the substrate surface faces bottom.

13. A moveable shutter (in-situ) shall be included to protect the substrate and heater.

14. The substrate heater shall be capable of heating a substrate up to 850˚C, either in vacuum or in high oxygen pressure (up to 1 atm) with temperature uniformity of +/- 2% across a 2-inch diameter substrate.

15. The substrate heater shall be 360 degree rotatable by a motor with an adjustable speed (1-10 rpm).

16. The heater temperature shall be controlled by a programmable PID controller with a K-type thermocouple.

17. The PLD system shall accommodate substrate sizes up to 2-inch diameter and shall include a substrate carrier for smaller substrate sizes. The substrate carrier shall be compatible with a load-lock upgrade.

18. The target-to-substrate distance shall be adjustable from 5 cm to 12 cm.

19. The PLD chamber shall be pumped by a turbomolecular pump with a pumping speed higher than 240 l/s and an oil-free, dry scroll pump. The pumping system shall provide a minimum base pressure in the chamber of 7 x 10-7 Torr within 30 minutes.

20. One mass flow controller shall be integrated for fine regulation of process gas flow with a maximum flow rate of 100 SCCM for oxygen. The maximum process pressure for oxygen shall be up to 400 mTorr.

21. The system software shall communicate with a temperature controller on the PLD system to control the substrate heater temperature by ramp time, ramp rate, dwell time, and/or set-point control.

22. The system software shall communicate with the turbo pump, vacuum gauge, and mass flow controllers in order to adjust turbo pump speed and flow rate of the process gas to establish optimum process gas pressure.

23. The system software shall externally trigger the laser with a user specified repetition rate and number of pulses.

24. The PLD system shall be integrated with a RHEED system to deposit high quality epitaxial films and interfaces with film growth control at the atomic level. The deposition chamber shall be designed to have one 6-inch CF port for a RHEED gun and one 6-inch CF port for a RHEED screen. Both ports shall be aligned to have the same azimuth of the PLD chamber and parallel to the substrate.

25. The angle of the RHEED gun shall be adjustable to point at an incident angle of 2-5˚ with respect to the sample surface and an angular deflection of at least ± 6° shall be adjustable with X-Y axes control during use. Both incident angle and azimuth angles shall be controlled by the system controller.

26. The RHEED gun system shall provide high energy electron beams with a voltage range (0-30 keV), a current range (1- 100 µA), and a spot size of less than 50 microns diameter at a maximum working distance of 150 mm.

27. The metal shielding shall be integrated to protect the RHEED gun from any magnetic fields. Leaded-glass shields shall be provided for all view ports to protect from X-ray radiation.

28. The RHEED electron gun shall be capable of operating at high oxygen pressures (200 – 400 mTorr) using a differential pumping system.

29. The RHEED data acquisition system shall include a 12 bit CCD camera, real-time frame grabber, zoom lens, and optical and hardware components for optimized RHEED imaging. The RHEED data acquisition system shall be capable of reading and controlling external devices.

30. The RHEED software shall include single or multiple image acquisition and analysis, growth rate analysis via RHEED intensity oscillations, real time live zoom video, and image filtering system.

31. For future upgrades, the deposition chamber shall be designed to accommodate three 6-inch CF ports for RF/DC sputter sources or a DC ion gun. These sources will be used for RF/DC sputtering and ion-assisted PLD (or ion cleaning of the substrate surface). Theses sputtering sources must lie at an angle of 45 degrees with respect to the substrate normal.