Combinatorial thin film deposition (K1 - K3)

Combinatorial thin film deposition (K1 - K3)

The Chair for MEMS Materials has specialized in applying the combinatorial technique to make and screen novel materials systems. Therefore, thin films are deposited by physical vapor deposition (PVD). There are currently 3 PVD chambers available (DCA, Finnland; AJA, USA), all designed to handle 100mm (4") silicon wafer substrates:

(1) K1 is a cryopumped UHV linear chamber, where 6 magnetron cathodes (3x DC/bipolar pulsed DC and 3x RF) are arranged along a straight arm that is translated back and forth to sequentially deposit layered films on a substrate. Shutters located near to the substrate surface can be positioned to confine the coated area by shadowing, or moved during the deposition to create wedge-shaped thickness gradients across the substrate.This chamber has a substrate table that can be RF biased, heated up to 1000°C and can have a magnetic field imposed at the substrate level during deposition or annealing.

(2) K2 is a cryopumped UHV circular chamber with 5 confocal cathodes (1x DC/bipolar pulsed DC, 3x RF). When the substrate is rotated about an axis through the focal point, atomic-scale mixtures of the sputtered materials are deposited. This yields nonequilibrium solid solutions and metastable alloy phases having identical surface and bulk composition without annealing, which would lead to thermodynamically stable phases, diffusion, segregation, and possible changes in bulk and surface compositions. Alternatively, substrate rotation can be stopped, leading to thickness and composition wedges coming from the deposition profile of the cathodes being used. The substrate in this chamber can be heated up to 1000°C during deposition or annealing, and either RF or DC biased.

(3) K3 is a turbopumped HV chamber with 3 confocal cathodes (1x each DC, RF, bipolar pulsed DC). This chamber is designed for depositing films of oxides and nitrides, and has a heater capable of going to 850°C in oxygen or nitrogen environments, as well as RF bias on the substrate.

A multipin stage can be mounted to any of the deposition chambers, which has 100 independent, spring-loaded electrical contacts arranged to press against the substrate around its periphery. This has been used for example to measure resistivity in situ during film growth, and for powering arrays of micro-hotplates during deposition or annealing.

A cooling stage can also be mounted to any of the deposition chambers. Liquid nitrogen can flow through this stage, with the temperature monitored by a built-in PT100 thermocouple.
Integrated with the UHV central handling transfer chamber, is a mask and storage module. Up to 6 wafers and/or shadow masks can be stored in low 10-9 mbar vacuum conditions. A handling mechanism allows the shadow masks to be placed, removed or rotated (in 90° increments) on a substrate wafer without leaving UHV.

Each deposition chamber is independently software controlled, so that for instance 2 chambers can be in use while target change or maintenance work is going on with the 3rd. Wafer and mask movement is computer controlled for chambers K1 and K2, while it is manually done for K3.