19 octobre 2010
(fr) - Lithography facilities at the CRISMAT
Lithography is used to shape a thin film in a given geometry without cutting the substrate. The procedure consists of two steps : the geometry is transfered into a protecting film (the resist) which covers the surface of the thin film. Afterwards, the superfluous part of the thin film is removed by an etching step.
The transfer of the geometry into the resist can be done by exposition to UV light through a mask (optical lithography, minimum lateral sizes of around 1µm) or by exposition with a controlled electron beam (e-beam lithography, minimum lateral sizes smaller than 1µm). Both lithography techniques are possible at the CRISMAT.
The lithography facilities are located in a clean room of around 50m² containing two zones : one with a class of 1000 for the exposition step and one with a class of 10000 where the vacuum machines for deposition and the dry etching are located. The equipment is optimized for the use of samples of a size between 5 x 5mm² and 10 x 10mm², but samples as large as 4" can be processed, too.
Optical lithography :
- Mask aligner MJB4 (SÜSS MicroTec)
Our mask aligner can be equipped with a mid-UV filter, allowing the exposition of the resist of geometries with a minimum lateral size of down to 700nm. Both glass or plastic masks can be used. The available mask include microbridges, deep contacts or out-of-plane geometries for transport measurements in thin films. Also, metal contact pads or microstrips for high frequency characterisation are available.
E-beam lithography :
- Scanning electron microscope FEG Mira 3 (Tescan) with writing electronics Tescan
For the e-beam lithography, a lay out of the desired geometry is fed into a computer which controls the deflection coils of the microscope and the beam blanker. The resist is exposed directly with the electron beam, therefore, no masks are needed for this technique.
Side equipment :
- Laminar flow hoods with class 100 for sample preparation
- Spin coater SÜSS MicroTec with Gyrset system for the reduction of inhomogeneous resist thickness at the sides and the corners of the samples related to a small, rectangular size
- Extractor hood for wet etch
- Dry etch by ion beam etching coupled with a secondary ion mass spectrometer (PLASSYS) in order to follow the etched species in real time
- RF Magnetron reactive sputter deposition of SiO2 or Si3N4 (PLASSYS)
Ulrike Lüders CRISMAT