Thin film deposition by pulsed laser ablation
Researcher: Daniel Marconi
Keywords: physical vapor deposition, pulsed laser deposition, thin films, thermoelectric materials
Description
Thin films are structures that have one dimension much smaller than the other two (10 nm ÷ 100 nm). They are intensively used because of the properties that nanostructuring confers: enhanced charge transport, increased toughness and, in the case of semiconductor thin films, enhanced charge carrier motion in the plane of the thin film compared to the plane perpendicular to the film.
Pulsed Laser Deposition (PLD) is a physical thin film deposition technique using a high power pulsed laser beam. It strikes a target of the material to be deposited, vaporizes it, and displaces it from the target (in a plasma cone) onto a substrate (such as a target-facing silicon wafer) on which it is subsequently deposited as a thin film. This process can take place in high vacuum (10-9 mbar) or in the presence of a gas, such as oxygen which is commonly used for oxide deposition.
The processing of thin film materials allows easy further integration into different types of devices, and we now find them as component parts in transistors, capacitors, nonvolatile memories, sensors, thermo-, ferro- or piezoelectric materials or photovoltaic materials.
Applications
Application areas: thin films obtained by PLD – metals, semiconductors, oxides, organic materials, polymers, hybrid materials with organic and inorganic components – are used in optical engineering, optoelectronics, electronics, energy, magnetic applications, sensors or biomedicine.
Systems: thermoelectric devices, solar cells, electronic circuits, sensors, sensors, transistors, diodes, anti-reflection coatings, corrosion protection coatings.
Industries: energy industry, electronic circuits industry, semiconductor systems industry.
Infrastructure
The thin film deposition system by pulsed laser ablation is located in the clean room ISO-8 class 100000 at the CETATEA Center for Research and Advanced Technologies for Alternative Energies, INCDTIM Cluj-Napoca. The system includes:
- 16″ cylindrical deposition chamber
- load-lock sample and target introduction chamber
- high vacuum up to 5 – 10-9 mbar obtained by a vacuum pump system composed of a 90 L/min preliminary pump and a 700 L/min turbomolecular pump
- real time deposition rate monitoring by a Refraction High Energy Electron Diffraction (RHEED) system for in-situ operation
- 5 port carousel for 1″ targets with automatic movements in all three directions
- heating mode for substrate temperatures up to 1000ºC and automatic substrate movements in all three directions
- 850 mJ Q-smart 850 mJ Nd:YAG laser in the wavelength range 670-2600 nm
- KrF excimer laser with wavelength 248 nm and energy 400 mJ
- process gas flow control system, bake-out system, integrated electronics and software for deposition process automation
Advantages
The versatility of the PLD technique offers a wide range of advantages, of which we can point out a few, namely:
High flexibility in the choice of deposition parameters
Precise control of growth rate and deposited layer thickness
Thin film deposition of any type of material, including materials in metastable states, which cannot be deposited by other techniques
Fabrication of mixed layers due to the built-in multi-target system
Material stoichiometry is preserved in the transfer from target to substrate
Deposition on substrates up to 50 mm in diameter
Deposition can take place in both high vacuum and reactive oxygen atmosphere
The radiation source is external to the deposition chamber
Estimated costs
The price for pulsed laser deposition thin film will include the price of the deposition material and the substrate used, the KrF gas used by the laser, the sample preparation operation, as well as the system operating time and labor.