Nanofabrication

Equipment

Fabrication:

Lithography

The backbone of the cleanroom is the lithography capability, the techniques by which design patterns are transferred to a sensitive resist as the initial stage of a fabrication process. In the Centre, the lithography is a mixture of photolithography, using UV mask aligners for pattern resolutions of down to 0.5?m, and electron beam lithography for smaller feature sizes. The Centre also has alternative nanopatterning techniques available such as microcontact printing and Nano Imprint Lithography.

The mask aligners operate in contact or proximity modes and can handle a wide range of substrate sizes from small pieces up to 200mm wafers. The Centre also has an extensive and versatile facility for resist processing, including a spray coater/developer for non-planar surfaces and the normal range of equipment such as spinners. The types of resist that are standard in the Centre is similarly extensive, from photoresists, ebeam resists through to thick film resists such as SU-8 and laminatable epoxy and acrylllic materials. More details can be found below:

EVG6200 Infinity - robotic mask aligner

This is a fully automated, rapid, double-sided mask aligner, which is capable of high precision and high throughput processing of wafer sizes up to 200mm.

EVG 620 TB - double sided mask aligner

This is a high precision, automated mask aligner capable of aligning both top and bottom side patterns on wafer sizes up to 150mm. It is also paired with the EVG 520 bonder to provide the ability to precision align wafer stacks prior to bonding.

EVG 620 TB - rapid prototyping

This second high precision, automated mask aligner is located in the rapid fabrication Bio area of the cleanroom, handling up to 150mm wafer sizes.

EVG 620 T - single side mask aligner

A standard automated mask aligner providing straightforward mask alignment and patterning options.

EVG 150 - robotic resist processing station

An automated resist processing station, providing both resist deposition on a range of surfaces and topographies and development, using spray technology. Capable of handling substrates up to 200mm in size from a cassette loading point.

EVG 510 - laminate thick film resist station

Align and Bond

Associated with the Centre interests in MEMs, microfluidics and packaging technology, there is a facility for wafer to wafer precision aligning and bonding. The alignment functions is provided by specially designed tools for the double sided aligner, which are then transferred to the bonder. We have the capability for thermal compression bonding, anodic bonding, fusion bonding and UV exposure bonding on wafer sizes up to 150mm. For R&D purposes, the machines are also capable of operating on pieces down to 15mm in size.

EVG 620 TB - double sided mask aligner

This is a high precision, automated aligner capable of aligning wafers (up to 150mm) on both top and bottom side features. Automated top and bottom alignment using specially designed marks is also possible.

EVG 520 TB - bonder

This a thermal bonder, capable of producing contact forces up to 10000N and temperatures in excess of 500?C, with an excellent degree of uniformity and stability across wafer sizes up to 150mm.

Thermal Evaporation

Sputtering

PECVD

OPT Plasmalab System 100 PECVD: amorphous silicon deposition

This system is used to deposit amorphous and polycrystalline silicon, germanium and silicon-germanium. The material can be doped either n-type (phosphorus) or p-type (boron) during deposition (i.e. in-situ doping). A deposition temperature up to 650C can be used, allowing the silicon to be deposited as polycrystalline (~600C and above) or amorphous (<540C) material. For silicon-germanium slightly lower temperatures can be used and for germanium slightly lower still. The deposition rate for amorphous silicon is >25nm/min and for polysilicon is >40nm/min. The system can accept wafers up to 200mm in diameter and can do depositions on small pieces of silicon placed on a larger wafer. This is recommended to minimize cost when doing lots of trial depositions to set up a new process.

OPT Plasmalab System 100 liquid source PECVD: nitride & oxide deposition

This system is used to deposit silicon dioxide, silicon nitride and rare earth doped oxides. The machine has two liquid precursors, one for TEOS and one for rare earth doped oxides. For high vapour pressure liquid sources, argon is bubbled through the liquid precursor to provide a vapour for the PECVD, whereas for low vapour pressure liquid sources the bottle is just open to the deposition chamber. TEOS is used to deposit silicon dioxide at 350-400C and has good planarising properties for metallization. The system has a low frequency and high frequency (RF) plasma source and the two sources can be combined to deposit layers with low stress. For TEOS the deposition rate is >40nm/min. Silicon dioxide can also be deposited using SiH4/N2O/N2 at 300C with a deposition rate of >40nm/min. Silicon nitride is deposited using SiH4/NH3/N2 at 300C with a deposition rate of >10nm/.min. The system can accept wafers up to 200mm in diameter and can do depositions on small pieces of silicon placed on a larger wafer. This is recommended to minimize cost when doing lots of trial depositions to set up a new process.

OPT Nanofab 1000 agile: nanotube & wire deposition

This system is used to deposit carbon nanotubes and silicon, silicon-germanium and germanium nanowires. Catalyst nanoparticles are needed to initiate nanotube or wire growth, which usually takes the form of metal nanoparticles generated on the surface of the wafer prior to deposition. If the nanoparticles are omitted, the system can be used to produce silicon, silicon-germanium, germanium and SiC films. The nanowires can be doped either n-type (phosphorus) or p-type (boron) during deposition (i.e. in-situ doping). A deposition temperature up to 1000C can be used, allowing the silicon to be deposited as polycrystalline (~600C and above) or amorphous (<540C) material. For silicon-germanium slightly lower temperatures can be used and for germanium slightly lower still. The system can accept wafers up to 200mm in diameter and can do depositions on small pieces of silicon placed on a larger wafer. This is recommended to minimize cost when doing lots of trial depositions to set up a new process.

OPT FlexAl RPX: Atomic Layer Deposition

This system is equipped with four liquid precursor modules and hence can deposit up to four different ALD layers in the same run. It can be used to deposit HfO2, TiN, ZnO and Al2O3 using TEMAH, TiCl4, DEZ and TMA precursors respectively. The deposition rate is typically between 0.2 and 1.5 angstrom per cycle. The system can accept wafers up to 200mm in diameter and can do depositions on small pieces of silicon placed on a larger wafer. This is recommended to minimize cost when doing lots of trial depositions to set up a new process.

LPCVD

LPCVD is a technique for depositing a variety of materials that are commonly used in the semiconductor industry. The reactants are gases and energy is provided by heating the substrate to a high temperature (typically 500-700C). Since the reactants are gases, deposition can be performed in principle on any substrate.

Tempress LPCVD Poly Furnace

This furnace can be used to deposit undoped amorphous and polycrystalline silicon. A deposition temperature of around 625C is typically used to deposit polycrystalline silicon and 540C to deposit amorphous silicon. The wafer throughput is very high and the furnace can accept wafers up to 200mm in diameter.

Tempress LPCVD Nitride Furnace

This furnace can be used to deposit silicon nitride using a deposition temperature of around 740C. If deposition at lower temperatures is required, plasma enhanced chemical vapour deposition can be used. The wafer throughput is very high and the furnace can accept wafers up to 200mm in diameter.

Anneal

High temperature annealing is needed for a number of applications, including the repair of implantation damage, the densification of deposited insulators, the diffusion of dopants, for silicide formation etc. Anneals are usually done at a high temperature (900C or above) and in a nitrogen ambient. However, if a completely inert anneal is required, anneals can also be performed in an argon ambient. The most common anneal method uses a furnace at a high temperature and an anneal time of typically one hour. However, shorter anneals are often required to minimise dopant diffusion and in this case a rapid thermal annealer can be used.

Tempress Anneal Furnaces

For silicon and other clean processes, several anneal furnaces are available, including a 200mm anneal furnace and a 150mm anneal furnace. For general processes, a 150mm anneal furnace is available. These furnaces allow automated loading of up to 25 wafers in a quartz boat and provide oxidations at temperatures between 600 and 1150C. Temperature accuracy can be controlled to better than ?1C. For alloying of metal contacts, a low temperature anneal furnace is available which uses forming gas (a mixture of hydrogen and nitrogen). An alloy anneal is typically performed at 420C for about 15 minutes and has the dual functions of providing a low resistance ohmic contact and of hydrogen passivation of the interface between silicon dioxide and silicon.

Jipelec Jetfirst 200 Rapid Thermal Annealers

Where very thin silicon dioxide layers are required, rapid thermal annealing can be used. Rapid thermal oxidation is a technique that provides a short (typically 30 seconds) anneal at a high temperature using fast lamp heaters. Two Jipelec Jetfirst 200 rapid thermal annealers are available in the clean room, one for clean silicon processing and one for general use. Temperatures between 400 and 1200C can be reached and the anneal time can be varied from 5 seconds to 10 minutes, with a ramp-up rate of 150C/s. Absolute temperature can be controlled to within ?5C. Temperature is generally measured using a pyrometer, but a thermocouple can also be used.

Growth

Growth of silicon dioxide is performed using thermal oxidation, either in a dry or a wet ambient. For the highest quality oxides, such as gate oxides, dry oxidation is preferred. Advantages are a slow oxidation rate, good control of the oxide thickness in thin oxides and high values of breakdown field. For thicker oxides, such as a field oxide in CMOS technology, wet oxidation is preferred. The main advantage is a fast oxidation rate, so that a thick oxide (around 0.5 micron) can be produced in a reasonable period of time (around an hour). The main disadvantage of oxidation is that a high temperature is required of typically 900C or above. For applications requiring a silicon dioxide layer produced at a lower temperature, plasma enhanced chemical vapour deposition can be used.

Tempress Oxidation Furnaces

For silicon and other clean processes, several oxidation furnaces are available, including a 200mm dry oxidation furnace, a 150mm dry oxidation furnace and a 150mm wet oxidation furnace. For other processes, a 150mm dry oxidation furnace is available. These furnaces allow automated loading of up to 25 wafers in a quartz boat and provide oxidations at temperatures between 600 and 1150C. Temperature accuracy can be controlled to better than ?1C.

Jipelec Jetfirst 200

Where very thin silicon dioxide layers are required, rapid thermal oxidation can be used. Rapid thermal oxidation is a technique that provides a short (typically 30 seconds) oxidation at a high temperature using fast lamp heaters. Two Jipelec Jetfirst 200 rapid thermal oxidation systems are available in the clean room, one for clean silicon processing and one for general use. Temperatures between 400 and 1200C can be reached and the oxidation time can be varied from 5 seconds to 10 minutes, with a ramp-up rate of 150C/s. Absolute temperature can be controlled to within ?5C. Temperature is generally measured using a pyrometer, but a thermocouple can also be used

Dry Etch

The cleanroom has an extensive range of dry etch systems for various research interests in silicon processing, metal etching, dielectric machining, thin film processing and other semiconductor materials (Type II, III, V, and N). High resolution pattern transfer features from micron to nano scale is done through reactive gas chemistry and plasma etch technology. There are six machines based in the main cleanroom:

RIE - Reactive Ion Etching

The etch mechanism of RIE is achieved by using the reactive gas plasma generated by strong RF source (13.56 MHz) to chemically ion etch the material of the samples. Depending on the process recipe, the material's etched profile can achieve high anisotropy. There are two Plasmalab systems:

  • Plasmalab 80 plus - Fluorine-based chemistry etching, alternatively argon and oxygen. Ideal for silicon (amorphous, poly), silica, silicon nitride, polymer, metal and resist residue cleaning.

  • Plasmalab 80 plus - Chlorine-based chemistry etching. Ideal for metal etching and suitable for III-V semiconductor materials.

ICP - Inductively Coupled Plasma Etching

The etching plasma is created by an RIE RF source and RF induction magnetic coil to produce high plasma densities. The results are high etch rate, high aspect ratio, and anisotropic etching of material of the samples. In addition, the systems can operate in ICP or RIE mode separately. The ICP systems are:

  • Plasmalab System 100 - Fluorine-based chemistry etching. Ideal for deep oxide etching, BPSG, TEOS, rare earth oxide, poly-silicon, polymer and diamond based material.

  • Plasmalab System 100 - Chlorine/bromine-based chemistry etching. Ideal for metal etching, poly-silicon gate, platinum, III-V and III-N based semiconductor materials.

RIBE - Reactive Ion Beam Etching

Working on the similar principle as the reactive ion etcher but is assisted by an energised ion beam for the etching mechanism. This can achieve very high aspect ratio profiles, high etch rate and uniformity over a large sample. The system can handle up to 200 mm diameter wafer and sample can be tilted to perform angular etch.

  • Ionfab 300 plus - Configured for MEMS and NEMS structures, silicon-based material, silica, quartz and deep etch structures.

DSE - Deep Silicon Etcher

This system utilises the Advanced Silicon Etch (ASE) Technology, based on the Bosch process, to achieve very deep silicon etch profile and smooth sidewall. This etching process is particularly suitable for silicon-based MEMS and NEMS devices where anisotropic profiles are essential.

  • STS LPX Pegasus - Configured for fluorine-based chemistry to etch silicon-based materials.

Wet Etch

Wet etching provides a simple and cheap method of pattern transfer after photolithography. Its advantage is excellent selectivity (usually 100%), but its main disadvantage is that it gives little control over the etch profile. This means that wet etched windows tend to be bigger than their as-drawn size and wet etched lines tend to be smaller. If good control of window size or linewidth is required, dry etching can be used, which allows the etch profile to be varied from anisotropic to isotropic. Wet etches, such as the Secco, Sirtl or Wright etches (Journal of the Electrochemical Society, vol 124, No. 5, p757, 1977) can also be used for delineating crystallographic defects in silicon.

Wet Etch Room

The wet etch room provides a safe environment for wet etching of a wide variety of materials. The standard wet etch processes are given below.

Dice Bond Packaging

The Centre has a range of finishing technologies available for post-fabrication packaging or characterisation. The normal semiconductor scribe and dice facilities are available, as well a precision wire-bonding machine. We also have the capability for prototype novel processes, including wafer-wafer polymer/glue bonding or microfluidic system encapsulation.

Scriber - Mitsuboshi Diamond MS300A-CE

The MS300A meets the requirements for scribing of silicon, glass, and brittle materials in two directions with an automatic alignment function. Handles wafer sizes is up to 300 mm.

Dicing Saw - Loadpoint Microace Series 3

A complete micro-dicing solution for the precision dicing, scribing and grinding needs. It is capable of processing a wide range of materials including silicon, glass, germanium, PZT and sapphire up to 6 inch/150 mm in diameter.

Bonder - Innovative Microelectronic Production Systems 4524 Ball Bonder

A multi process ball bonder with individual bonding parameters control. It has versatile operation modes from manual to fully-automated, for gold wire of 18 to 76 mm in diameter and provides fine control and consistency of ball size. It would be widely used for bonding applications from simple discrete devices to complex hybrid and microwave devices. Bonding area is up to 152 X 152mm (6 X 6 inch).

 

Characterisation:

Nanometrology

Focused Ion Beam System

This system has the dual functions of sample preparation using the focussed ion beam column and sample imaging using the electron column (field emission scanning electron microscopy). Typical applications are cross-section imaging of samples and thin foil preparation for transmission electron microscopy. The system is also equipped with a Rutherford backscattering detector for the analysis of material composition.

Helium Ion Microscope

This microscope is able to perform high resolution imaging of specimen surfaces and Rutherford backscattering analysis of specimen composition. It has a better depth of focus, a higher resolution and better material contrast than a scanning electron microscope and hence is ideal for nanostructure characterisation.

Field Emission Scanning Electron Microscope

The field emission electron microscope (FESEM) provides somewhat higher resolution imaging than the environmental SEM. Its primary application is for specimen imaging after electron beam lithography.

Environmental Scanning Electron Microscope

This microscope is able to image biological specimens in liquid and hence avoids problems arising from the drying or freezing of the specimens. The microscope is also equipped with X-ray fluorescence (XRF) for analysis of trace elements down to 50ppm (element dependent) with a resolution of around 50um. Higher resolution elemental analysis can be performed using the Xradia nanoXFi, which has a sub-100nm resolution. A Gatan X-ray computed tomography attachment provides 2D and 3D imaging of specimens.

Ellipsometer & Profilometer

The ellipsometer is used to measure film thickness and refractive index after material deposition. The spot size is 150um, so this information can usually be obtained from wafer scribe lanes. The profilometer uses a mechanical stylus to measure step heights after etching.

SPM

High Resolution SPM

This microscope can visualise single-walled carbon nanotubes, semiconductor nanowires and single proteins. Atomic lattices can be investigated by tunnelling current from the probe to the surface of a suitable material and examining the local density of electronic states. The system modes include atomic force microscopy (AFM), scanning tunneling microscopy (STM), force distance curves, lateral force microscopy (LFM), Kelvin probe microscopy (KFM) and scanning capacitance microscopy (SCM).

Integrated SPM-Raman System

This is an integrated microscopy system consisting of a high performance SPM and laser Raman spectrometer. The system is able to work separately in SPM mode or in very high resolution confocal Raman spectroscopy. Integration of both systems provides users the opportunity to perform tip-enhanced Raman spectroscopy (TERS) on nanoscale structures. The system is also capable of performing atomic force microscopy (AFM), scanning near-field optical microscopy (SNOM) and phase imaging.

Integrated Cryogenic SPM System

This system is designed and configured for high vacuum scanning probe microscopy and device characterisation in very low temperature environments. The system is cooled to a temperature of less than 10 K by liquid helium and capable of performing all standard atomic force microscopy (AFM) modes, scanning near-field optical microscopy (SNOM), conductive AFM, confocal microscopy and is integrated to a multi laser Raman spectrometer system. This system is ideal for low temperature semiconductor device research such as quantum nanodots, nanowire electronics and photonics.

Standard SPM System

This is an entry level SPM system designed for routine microscopy and also constitutes an educational tool for undergraduate and postgraduate projects. The stand-alone system is capable of producing high resolution topography images at the nanometer scale and can handle wafers of any size. This is ideal for routine analysis of nanofabricated structures by atomic force microscopy (AFM).

Electrical & RF

Magneto-resistance System

The Lakeshore EMTTP4 Cryogenic Probe Station with in-plane Magnetic Field is a versatile probe station which will allow magneto-resistance measurements from 10K and 300K without the necessity of bonding the contacts. It is perfectly suitable for nanodevices, such as carbon Nanotube transistors where liquid nitrogen temperatures will reveal most of the effects and very suitable for low temperature I-V characterisation on MOSFETs and other electronic devices.

Single-Electron Transistor System

The Cryogenic Ltd Cryogen free cryomagnet system is perfectly suitable for single and few electron device measurements and other fundamental research on nanoscale devices. The large magnetic field allows a variety of Coulomb blockade measurements.

Deep Level Transient Spectroscopy (DLTS) System

The Sula DLTS with Janis Optical Cryostat in a turn-key system for deep level transient spectroscopy which will allow unique electronic characterisation of materials. It has an optical window for photo-induced DLTS and a fast pulse interface. The combination of charge and current transient spectroscopy allows the system to function on both semiconductors and more insulating materials.

Micro-Electro Mechanical System (MEMS) Tester

The MSA-400 Micro System Analyser provides measurements of structural vibrations and surface topology in microstructures such as MEMS, by means of a microscope integrated with Scanning Laser-Doppler Vibrometry, Stroboscopic Video Microscopy and White light Interferometry.

Radio-Frequency (RF) Semi-automatic Prober

The Cascade SUMMIT 12000B Semi-Automatic probe station with Agilent N5250A 67GHz Vector Network Analyzer allows S-parameter measurements and other RF measurements to a high precision. It has a micro chamber, providing a dry, shielded wafer enclosure for reduced EMI and RFI interference and access to the 4 RF positioner controls even when system is electrically sealed.

DC and low frequency Current-Voltage (IV) System

The Cascade R32 REL3200 Probe-Station is the work horse of the electronic characterisation laboratory and is excellent for any top-contact electron device such as MOSFET Characterisation. It is associated with a Agilent 4155C. It has a vibration isolation table, a light tight enclosure and the SEIWA stereo zoom microscope allows probing on ads down to 10 microns. We also have a Cascade M150 Probe Station with a triaxial chuck which allow more precise I-V and C-V measurements with the back of the wafer as one of the contacts. It also has a temperature dependent chuck which will allow above room temperature measurements.

Four point Probe Station

A Jandel Four Point Probe System is available for resistivity measurements on wafers up to 8 inch (similar to v/d Pauw measurements)