N-Type
The majority of devices are fabricated on n-type float zone material with a crystal orientation of <100>. This material has a high resistivity typically in the range 3 – 20 KΩ cm. Specials can be offered up to 70 KΩ cm
P-Type
P-type silicon processing can be offered on all designs where segmentation isolation is possible.
NTD
Neutron transmutation doped n-type silicon is offered for applications where low resistivity variation across the wafer is required. This material has a much higher depletion voltage that regular high resistivity n-type material.
Epitaxy
Epitaxy (also called epi wafer, epi-wafer, or epiwafer) is a process in which an additional monocrystalline silicon layer is deposited on to the polished crystal surface of a silicon wafer. This process makes it possible to select the material properties independently of the polished substrate. This consequently can be used to create wafers which have different properties in the substrate and the epitaxial layer
Silicon Thickness / Wafer Size
The wafer size corresponds to the standard* silicon thicknesses that the device can be processed on.
|
WAFER SIZE |
STANDARD SILICON THICKNESSES (µm) |
| 4-inch | 20, 30, 40, 50, 65, 80, 100, 140, 250, 300, 500, 1000, 1500 |
| 6-inch | 150, 200, 300, 400, 500, 675, 1000 |
*Other non standard and R&D silicon thicknesses are available on request.
Metallisation Options
The coverage of the metal over the active area can be suited to the sensors application and to compliment the dead layer of the implant. The metal coverage refers to both the junction side and ohmic sides
|
METAL COVERAGE |
DESCRIPTION |
|
M |
A continuous metal coverage of standard thickness over the whole active area regions. |
|
G |
Grid coverage, typically 3 %, of standard thickness metallisation over the whole active area and contact pads for wire bonding. |
|
P |
A periphery metal band, typically 30 mm wide, around the edge of the active areas and contact pads for wire bonding. The majority of the active area metal coverage free. |
|
T |
A standard periphery coverage, as described above, for good electrical contact, and a thin metal coverage typically 0.1 -0.3 mm over the majority of the active area. |
|
D |
Double metal process to track signal in a direction different to the active area elements. |
|
E |
An equipotential metal band array used on PSD devices. |
Metallisation Type
The standard metallisation scheme is 100 % sputtered aluminium of thickness 0.5 µm for good ultra sonic wire bonding connections.
The evaporated metal system Ti/Ni/Au is also available on request. Gold ohmic contacts are used for high operating temperature detectors +55o to +120o required for military applications
Ohmic / Junction Window Type
Range of dead layer windows available with in-house ion implanters. Window types refer to the junction of a device, but can also be achieved on the ohmic side upon request.
|
WINDOW TYPE |
DEAD LAYER (µm) |
MINIMUM ENERGY THRESHOLD |
|
|
Electron (KeV) |
Proton (KeV) |
||
|
2 |
0.5 |
4 |
90 |
|
7 |
0.3 |
2 |
70 |
|
9 |
0.1 |
1 |
20 |
|
9.5 |
0.05 |
0.5 |
10 |
|
10 |
0.01 |
0.1 |
1 |
|
PSD |
0.03 |
0.3 |
5 |
Sensor Package Options
The silicon chips can be delivered as chip only or assembled in a standard or custom package. The majority of packages are made from standard FR4 material or on black FR4 material where light transmission through the package needs to be minimized. Many of the designs currently offered on FR4 material can be modified and transferred onto ceramic 96% alumina or aluminium nitride) for operation in ultra high vacuum environments. Other package materials such as polyamide and kapton for high density readouts are also available on request. Assemblies have been designed where the detector is mounted on a heat conducting substrate with the readout ASIC amplifiers connected directly to the support, see MSA127 detector assembly.
The connector type (straight or 90 degree) and orientation (exiting the junction or ohmic side) can also be changed to suit the experimental arrangement. Where a common pitch is used it may also be possible to request a specific connector part. The choice of connector is critical as it often occupies valuable space in an experiment. It is also important to ensure that the insertion force of a mating connector does not stress or damage the detector assembly.
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