Bits & Chips Benelux RF Conference 29. May 2024 Nijmegen

Lecture Sajjad Ahmed | Focus Microwaves: Sub-THz load pull and characterization of noise parameters

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Motorised and semi-automatic Probe Station series CheckMate

The CheckMate series is a powerful sampler platform that can handle almost any task in the semiconductor lab with the highest quality up to a wafer size of 300mm.

CheckMate Probe Stations are available in the following configurations:

  • Manual samplers: CM-21X for 200 mm wafer, CM-31X for 300 mm wafer
  • Motorised manual samplers: CM-22X for 200 mm wafer, CM-32X for 300 mm wafer
  • Semi-automatic samplers with DC motor: CM-23X for 200 mm wafer, CM-33X for 300 mm wafer
  • Semi-automatic samplers with servo motor: CM-25X for 200 mm wafer, CM-35X for 300 mm wafer

The most important features are:

  • Climate chamber for testing at temperatures from -65 to +300 °C with chiller
  • Thermo chucks for temperatures from +30 to +300 °C
  • Low noise shielding for parameter analysis
  • Shielding chamber for darkening for testing light-sensitive components
  • Protective chamber with interlock protection for testing at high voltages and currents

The manual samplers are also available motorised. Therefore, operation can be effected from the joystick with a view of a monitor, which shows the test object via the microscope with video system. This has the advantage that the operator can remotely control the test sequence in a comfortable working position.

Semi-automatic machines are used for the SW automated measurement of many chips on a wafer. We call these Probe Stations semi-automatic, because they always measure a whole wafer automatically (a fully automatic machine has a robotic system to automatically load and test several wafers from a cassette). The semi-automatic machines have a higher accuracy than the motorised manual samplers and are equipped with extensive SW functions:

  • Automatic angular orientation of the wafer (theta auto alignment)
  • Creation of a wafer map (electronic representation of the configuration of the chips on the wafer)
  • Measurement of distances on the test object with the video system
  • Travels to coordinates or differential distances
  • Automatic stepping of all chips on the wafer with contacting and contact separation of the probes (contact/separation)
  • Video recognition of structures or pads on the test object
  • Automatic scan of the height profile over the wafer (z-profiling)
  • Remote control of the Probe Station with GPIB interface and a suitable command set

Semi-automatic Probe Station type CM250 for 200 mm wafer

A stable optical table for mechanical isolation of vibrations and interferences is the indispensable basis for safe and reliable test procedures. Our Probe Stations are preferably combined with optical tables by TMC, which have an ergonomically designed work surface and allow comfortable work with joystick, PC, keyboard and mouse next to the Probe Station. The image shows a CM250 semi-automatic machine, in the lower part of the optical table, motor control unit and PC are located.

For the characterisation of semiconductors tests over a wide temperature range are necessary. Therefore, the CheckMate Probe Stations are equipped with a climate chamber which is flooded with dry nitrogen to prevent icing at temperatures below the dew point. Typical achievable temperatures at the chuck range from -65 °C to +300 °C. The example in the picture also has the low noise shielding for measurements of currents in the fA range.

The SW interface offers a clear and easy to use menu interface. All important modules can be displayed at the same time, which allows safe and easy learning the operation of the automatic CheckMate Probe Station.

Most common standard application: test of a wafer with coaxial or triaxial connected DC-needles or with RF probes, which are wired with amplitude and phase stable coaxial cables. The image shows how a performance semiconductor component on a wafer is contacted with triaxially applied test needles.

Application of test adapters with needle cards (probe cards). In this example a probe card is adjusted to the chip. In addition, DC probe needles are used to contact additional pins.

If printed circuit boards or modules (e.g. made of ceramic or softboard material) are to be contacted, a universal sample holder can be mounted on the xy table instead of the chuck. Various screw and clamping elements are then used to fasten the test object.

Motorised manipulators are available for special tasks requiring high-precision adjustment. Therefore, in addition to the other movement units (xyz-theta stage), a test needle or RF probe may be adjusted with the help of a joystick and microscope image. With the CAP-946 manipulator a resolution of only 50 nm is achieved.