Contacting your Semiconductor Device to make electrical measurements using probe tips, multi-contact wedges and probe cards
One of the main purposes of a probe system – analytical or production is to allow the user to make mechanical contact with the device to allow electrical measurements to be performed. The number of probe contacts could be one or two, under fifty, over a hundred or a few thousand. It depends on the device being tested.
Most semiconductor devices and materials must be characterized. The devices could be diodes, transistors, capacitors, resistors, integrated circuits and more. The devices could be fabricated using a variety of materials such as Silicon, Germanium, GaAs, GaN, SiC and others. The final product could be a device fabricated for a myriad of applications - MEMS, High Frequency, Optoelectronic, High Power and more.
Contacting the device pads is often done using individual manipulators with a single probe, or with a multi-contact wedge or with a probe card mounted to a probe card holder. Most probe system platen designs will allow the user to use manipulators, probe cards or both at the same time. It is usually easy to exchange between the contact methods – manipulator to probe card or vice versa.
Probe Station Probes - PS4L Probe System Platen with a probe card holder and a High Frequency probe card
Probe Station Probes - PS4L Probe System Platen with fourteen (14) MA-9000 programmable manipulators around the platen opening.
Manual or programmable manipulators can often be used on a probe system. Manual manipulators usually have three axis movements – X, Y and Z. Each axis is moved with a thumbscrew or micrometer – 40, 50, 80 or 100 TPI versions. In most cases it gets difficult to use > 12 manipulators on a probe system platen due to space constraints on the paten and easy axis to the manipulator controls. Programmable manipulators are usually provided as three axis or up to six axis versions (hexapods). Their axes are controlled via high precision motors that provide local or remote control. Most analytical probe system suppliers provide 3 axis programmable manipulators. Companies like Physik Instruments, SmartAct, Newport, Thorlabs and more provide hexapods that are integrated into the analytical or production probers. Hexapods are often used for optoelectronic probing applications.
Probe Station Probes - MA-9000 Manual Manipulator
Probe Station Probes - Physik Instruments (PI) Hexapods – 6 axis
Probe Station Probes - MA-9000 Programmable Manipulator – 3 axis
Manual MA-8005 manipulator with a coaxial probe arm inserted into the adjustable faceplate.
Manual MA-9000 manipulator with a 10 KV Keysight coaxial probe arm and connector
Programmable MA-9000 manipulator with a High Frequency and an Optical Fiber Holder arm combined
Manual MA-9000 manipulator with a triaxial probe arm
Manual MA-8005 manipulator with a coaxial probe arm inserted into the adjustable
Probe arms are mounted to the manipulators, and the designs are application specific. They can be fabricated using a variety of cable types – coaxial, triaxial, high voltage, high current and more. On one end of the probe arm is the mechanical clamping of the probe tip. The other end of the probe arm is inserted into the faceplate of the manipulator body. The adjustable faceplate allows the user to place the probe arm in a few locations to provide larger Z movement without limiting out the thumbscrew travel. The cable usually protrudes out of the probe arm and is connected to an interconnect panel or directly to the test instrumentation. In some cases, the cables are connected directly to the probe (HF, multi-contact wedge and more). Most probe arm terminations are BNC (coaxial or triaxial), but others are used – banana, HV coaxial, HV triaxial, SHV and more. The probe arms, cables and connectors selected depend on the application and the desired measurements to be made.
Coaxial Probe Arm – clamping collet holding the probe tip (needle)
Coaxial Probe Arm – clamping collet on one end and a BNC male connector on the othercfaceplate.
Using a multi-contact wedge that is mounted to a manipulator probe arm is one way to probe multiple contacts at the same time without having to use a probe card. It all depends on how the device pad layout is configured. If the pads are in a linear array around the device, then it is quite possible to use four (4) wedges mounted on high frequency probe arms to simultaneously contact multiple pads.
Multi-Contact wedges often combine multiple DC and RF probes – DC to 40, 50, 67 and 110 GHz. Several wiring configurations are available for DC and High Frequency needles. Cables used to connect to the test instrumentation are usually coaxial, ribbon and hook up wire. The connectors most often used are BNC, SMA, Banana Plug and D-Subminiature (9, 15, 25 and 37) or Amp-Latch Receptacles (20 or 26 pin). The Amp-Latch Receptacles have a double row of contacts on 0.1” centers and can receive 0.025” square or round pins. Other connector types are also available.
Multi-Contact Wedge with DC and RF needles and cables terminates with BNC male and SMA connectors.
Multi-Contact Wedge with DC needles and coaxial cable terminated with BNC coaxial male connectors.
Multi-Contact Wedge with DC needles and ribbon cable with a D-Subminiature connector
Common Multi-Contact Wedge dimensions that are mounted to a manipulator using a high frequency probe arm – West/East or North/South
Multi-Contact Wedge with several DC needles
Multi-Contact Wedge for High Current measurements
Multi-Contact Wedge for High Current measurements
Multi-Contact wedges are manufactured by several worldwide manufacturers of probe cards such as GGB Industries, Accuprobe, American Probe, Wentworth, Formfactor, MPI and more. They are used for a variety of applications – DC, High Frequency, High current and more.
Probe cards are used on analytical and production probing systems. They are usually rectangular shaped or round. The rectangular shaped probe cards, also referred to a blade cards or cantilever probe cards, are usually manufactured in widths of 4.5” (114.3 mm) or 6.5” (165.1 mm). The lengths can vary significantly based on what is added to them – bias circuitry, cable connections and more. The rectangular shaped probe cards are inserted into a probe card holder and clamped in place when in position. Probe card holders often have probe car levelling and theta rotation capabilities.
Rectangular Card – with DC needles
Rectangular Probe Card – with DC and HF probe needles
Rectangular Probe Card Blanks – lengths and blade density varies by design
The rectangular probe cards are often used on the analytical probe systems – R&D, Product Development, Device Characterization, Failure Analysis, Pilot Production. In some applications they are used in production.
The round probe cards are often used in high volume production probing applications because of significantly more capacity to manage many probe needles (blades) – cantilever, vertical spring, pogo and more with ultra fine pitch requirements. They are often interfaced with a load board. Sometimes they are designed for one-touchdown testing on a 300 mm wafer with high needle contact with test heads. The overall size can be large.
Round boards also have different types of probe needles that can be used. Metal blades are the most popular and are available in a variety of sizes and types. Ceramic blades are also used in applications at high frequency or low-level sensitive measurements – leakage, capacitance, voltage, and more. Pogo pins, spring loaded, are also used for applications testing devices with planarity issues, substrates, PCB, high current and more. MEMS technology is often used to fabricate sophisticated probe cards and probes.
Metal Blades - cantilever
Ceramic Blade - cantilever
There are multiple worldwide suppliers of probe cards that can provide simple to sophisticated solutions. A partial list is Accuprobe, Formfactor, Micronics Japan (MJC), Japan Electronics Materials (JEM), Feinmetal, IST Group, MPI, STAR Technologies, T.I.P.S and more.