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TARGET STAGES

In any Pulsed Laser Deposition System, the materials to be deposited are mounted onto a target stage. The requirements for the target stages depend usually on the application. For multilayer deposition, where very often switching between different materials occurs a target stage that can hosts several targets and that can switch rapidly between these is necessary. Also, automation of the target change can be an importsant issue. Because of the very localised heating by the laser, a deep an small spot on the target would occur if it would be held stationary in the beam. To get a better use of the entire target surface, the target is moved through the beam. In the most simple configuration, the target is spinning with the laser off the centre of the target. This way a circular track results, provided the laser repetition rate and the spin frequency do not correspond. A more sophisticated solution consist of a stage where teh entire target surface is slowly moved through the beam by means of an XY stage. This type of stage is referred to as target scanning, as opposed to the target spinning stage mentioned before. The final issue in target stages is the changeability of the targets. For maximum flexibility, it is desirable to have a stage where the targets can be changed to new ones with different materials, so that the system has maximum flexibility with respect to the materials that can be deposited.

Twente Solid State Technology has developed a number of different target stages that combine a basically simple design with high flexibility. The first design can host 4 different targets simultaneously (i.e. these can be change in-situ) and provides for target spinning. The stage can be mounted on a flange and can be motorised. The motorisation allows for fast switching between targets and automated starting and stopping of target spinning. The second design can host 5 different targets and is developed for target scanning. This target scanning is useful for targets that require minimised wear, e.g. because they are hygroscopic and should be taken out of the vacuum as little as possible. The whole stage is mounted on an XYZ stage with motorisation. These motors are required to provide for the necessary movement that lead to the scanning. Both designs are loadlock compatible, i.e. the so-called target carrousel where the targets are mounted can be taken out through a loadlock. The target holder itself will remain inside the vacuum. All targets are mounted on special mounts that allow fast changing and easy dismounting for grinding.

Additional Options

The system with target spinning can be extended with the following options:

• A complete flange-mounted target system, with rotary drives for selection and spinning.
• The two drives be motorised, and a home switch for position detection can be included.
• Both systems can be completed with steering electronics for the motorised stages.

Technical Specifications

• Up to four 1" targets on the spinning stage, up to five targets on the scanning stage.
• Flange sizes, travel lengths for the motion possibilities a can be adapted to fit the needs of the system and the applications.