microfab Service GmbH

microfab your MEMS Manufactory

MANUFACTORING SERVICE

Fabrication Services

microfab is service provider in the field of silicon-based micro-systems technology. Our production lines, located in two Class 10 to 100 cleanrooms, feature state-of-the-art facilities that permit wafers of 100 to 150mm to be processed.
We can provide standard MEMS production technologies like surface micromachining, bulk micromachining, silicon deep etching (DRIE, Bosch process), wafer bonding as well as 3D microforming.

In this section please find detailed information about fabrication services microfab offers:

Thin films

Thin Film Deposition

Thin film deposition techniques are used to deposit a wide variety of materials on the wafer surface. This films can be used for their electrical, electrochemical, thermal, piezoelectric, magnetic or mechanical properties. They are usually either selectively deposited (i.e. lift off) or selectively etched away after deposition to form patterned thin films. Commonly deposited layer thickness ranges between tens of nanometers to a few microns.

Numerous techniques exist for thin film deposition. Commonly used in micromachining are:
Silicon Oxidation CMOS-compatible quartz furnace processes (Centrotherm), try and wet oxidation 100 and 150mm wafer size.

Thin film sputtering Sputtering and evaporation are both physical vapor deposition techniques used at microFAB to form metal and compounds.

PECVD The PECVD technology is used for deposition of dielectric layers at low temperature.

LPCVD LPCVD technology is used for uniform, double side deposition of 100 and 150mm size silicon wafers with dielectric layers.

Electroplating Electroplating of pure metals, such as gold, nickel and copper, as well as alloys of gold and nickel are available.

Diffusion & Doping

Diffusion & Annealing

Quartz furnace processes (Centrotherm) under inert gas (N2) atmosphere for 100 and 150mm wafer size, batch quantity: up to 25 wafers per run dedicated furnace stacks for p- and n-type dopants and metallization layers are available.

The following standard processes are available:

  • annealing after ion implantation (boron/arsen/phosphorus) @ 950°C, 30 min
  • diffusion (dopant drive in) after ion beam implantation (boron/arsen/phosphorus) @ 1100°C, time variable (process time based TESIM simulation results)
  • post-sputter annealing of Al-Si contacts @ 350/400°C, 30 min

A dedicated tube on our Centrotherm furnace system is installed for saturation-level doping with phosporus (POCl3 source). Low sheet resistances of 11 to 20 Ohm/ can be achieved in a batch process with 100 and 150mm wafer

Lithography

Photolithography

microfab´s Photolithography department is located in a class 10 clean room cell. Several positive photoresist systems in the thickness range between 1.1 and 60 µm are available. One fully automated SSE Spin and Coat Module (Maximus) and two Convac spinners are set up for resist coating. All layouts are on 5 or 7 inch chrome-on-glass masks.

Two SUSS mask aligners (MA150, MA6) and two Electronic Vision (AL6, AL4) mask aligners are available for alignment & exposure. Backside alignment ( ± 2 µm overlay accuracy) is possible. The maximum resolution of 0.8 µm (lines/spaces) is achived with a 1.1 µm AZ1518 positive resist. Resist developement is done on the Dainippon track system or the Convact tools. Thick positive resist (AZ4562) is used for microform application with thicknesses of 20, 30, 40, and 60 µm and aspect ratios of up to 6:1.

Standard Litho Processes
The following standard processes are available:
Resist thickness [µm]
Resist Type
Resolution lines/spaces [µm]
Aspect ratio
min. linewidth [µm]
Application
1.1
AZ1518
0.8
 
0.8
Thin film patterning
1.8
AZ1518
2.0
1:1
2.0
Thin film patterning, implant masking, shallow Si etch
6.5
AZ4562
4.0
1.5:1
4.0
galvanoforming
20
AZ4562
 
4:1
5.0
Galvanoforming
30
AZ4562
 
5:1
6.0
Galvanoforming
40
AZ4562
 
6:1
8.0
Galvanoforming
60
AZ4562
 
6:1
10.0
 

Wet Etching

Wet Chemical Etching

Wet chemical etching is commonly used for uniform stripping or patterning through a mask of dielectric and metallization layers. In contrast to RIE all processes are more or less isotropic and mask underetching is present. Selectivities toward mask and substrate materials are usually much better than with RIE processes. Another special wet etching process used in bulk micromaching technology is the anisotropic, crystal-oriented, KOH or TMAH etch. Standard RCA process (SC1, SC2, HF-dip) is used for wafer cleaning. Special Solvent bathes are available for resist stripping. All standard etch bathes are SPC controlled (etch rate monitoring).

Standard Processes
The following standard processes are available:

  • BOE (buffered oxide etch, NH4F/HF/H2O) Used for etching of thermal oxide, LPCVD oxide (LTO), PECVD oxide, and PECVD. Patterning can be done using a positive AZ resist of 1.2, 1.8 or 6.5 µm thickness.
  • TMAH and KOH silicon etch Used for crystal oriented anisotropic etching of mono silicon. Thermal oxide or LPCVD nitride masks are commonly used for patterning
  • HF-dip Used for etching of thin silicon oxide (gate oxides, native oxide layers)
  • Phosphoric acid (H3PO4) Used for uniform stripping of silicon nitride layers (LPCVD nitride/LOCOS process, PECVD nitrides).
  • Aluminum etch A special mixture of acids is in use for etching of aluminum layers (e.g., interconnection lines)
  • Polysilicon etch A mixture of HF and HNO3 is in use for isotropic etching of polysilicon layers
  • Special etch application There are many further reagents in use for etching of metal layers (Au, Cr, Ni, Cu, Ti).

Dry Etching

Plasma Dry Etching

Ion Beam & Plasma Etching
Dry etching techniques (RIE, ion beam and plasma etching) are intensively used at microfab for patterning of dielectrics, polysilicon and metal layers. Further important applications are the photoresist stripping and the anisotropic deep silicon trench etching.

State-of-the-art monochromatic end point detection is applied with most RIE processes, ensuring a minimum of substrate loss due to overetching. Various etch masks (photoresist, SiO2, Ti, Cr, plasmanitride) can be combined, depending on the materials to be etched.

All processes were optimized regarding troughput, etch rate selectivity toward mask and substrate, CD loss (undercut), and etch profile (taper).

At the present time, microfab operates ten dry etching systems of which there are five RIE systems (STS multiplex, Alcatel 601E and AMS200) for dielectrics and metal etch and for deep silicon trench etching, one physical ion beam etcher (STS 340 PC) for noble metal etch, and four plasma etchers for resist strip processes (two Tepla barrel type etchers).

Standard RIE Processes
There are several standard processes available:
  • RIE/ICP deep silicon trench etching (ASE process, up to 300 µm, aspect ratio 50:1)
  • anisotropic RIE of dielectric layers (SiO2, Si3N4, Si:ON), up to 2000 nm
  • anisotropic RIE of polysilicon (up to 2000 nm)
  • isotropic RIE of polysilicon (up to 2000 nm)
  • anisotropic RIE of Al and AlSiTi metal layers (up to 3000 nm)
  • anisotropic RIE of bulk mono silicon (up to 5000 nm)
  • isotropic RIE of Cr, Ti and WTi10 metal layers (up to 500 nm)
  • anisotropic ion beam etching of Au and Pt layers (up to 500 nm)
  • anisotropic RIE of polyimide and photoresist (up to 10 µm)
  • isotropic strip of photoresist (up to 100 µm)

Deep Trenches

Deep Reactive Ion Etching - DRIE

DRIE is a high aspect ratio, deep trench silicon etching process (Bosch process). The principle of the deep trench silicon etching process is an alternating fluorine based etching and passivation of the structures. This results in sidewall profiles of 90°±1° with aspect ratios of up to 40:1. Masking layers can be made of photo resist or silicon oxide.

There are currently four Alcatel 601E/AMS200 systems and one STS/ICP system installed, which brings the total number of production tools to five.

Main Benefits of DRIE
  • etch rate of up to 10 µm/min
  • aspect ratio up to 40:1
  • selectivity to positive resist > 75:1
  • selectivity to silicon oxide >150:1
  • etch depth capability 10 to 675 µm (through wafer etching)
  • sidewall profile 90°±1°
  • feature size 1 to >500 µm

Alcatel AMS200 & 601E
Alcatel's deep plasma etch technology is designed to deliver superior process performance and maximum process flexibility to meet the needs of a broad range of deep silicon etch applications.
  • Applications in MEMS and microsystems fabrication include: high aspect ratios, etch depths of as great as 675 µm, etching through-the-wafer, etching into a buried cavity in the wafer, or etching onto buried oxide.
  • Applications in deep trench isolation include: etching bulk silicon or silicon-on-insulator (SOI) structures with vertical or positive profiles with very high etch rates for high throughput.

Wafer Bonding

Wafer Level Bonding
microfab is able to do direct, face-to-face bonding of silicon and pyrex (glass) wafers. The following standard processes are available:
  • Silicon direct bonding (SDB)
  • Anodic bonding of silicon to pyrex wafers
  • Glass frit bonding
  • Eutectic bonding
  • High temperature fusion bonding of silicon wafers

SUSS SB6 Thermocompression and Anodic Bonder
The SUSS Bonder SB6 is a semiautomatic, computer-controlled, stand-alone substrate bonder equipped with a vacuum/pressure chamber and a loading arm. The machine processes aligned and unaligned 100 and 150mm wafers. The alignment accuracy of this tool is listed as being 3 µm (3 σ).

All bonding pair alignment is done on the SUSS BA6 Bond Alignment tool, the substrate stacks are mechanically clamped using the transport fixture, and then transported and bonded in the SB6 chamber. Triple stack bonding is possible.

Back End

Back end processes

For prototyping and small series production
microfab offers Back end services as following. For larger numbers microfab recommend to outsource services to one of our Packaging Partners. wafer dicing microfab back end services An automatic wafer dicing machine allows the separation of different materials such as silicon, glas or ceramic. Substrate dimensions up to 150mm of diameter and thicknesses up to 2mm can be diced.

die bonding An epoxy die bonder allows to apply different glue materials, soldering and glas pastes which can be dispensed precisely. The possibility to position the die accurately to a carrier or socket is given as well. A preform/die attach machine allows the use of different preform materials for soldering and eutectic die attachment.

wire bonding microfab offers two different possibilities for wire bonding: Ball-Wedge and Wedge-Wedge bonding with different wires. Gold and aluminium wires are used in a diameter range from 25µm to 50µm. Quality control of bond connections can be done by a pulltest machine.

For larger numbers microfab recommend to outsource services to one of our Packaging Partners.

For more and detailed information please don´t hesitate to contact our production team