What is a Probe Station? Design, Types & Applications

As devices shrink to microscopic scales, the ability to accurately measure and characterize their electrical properties becomes increasingly challenging. A probe station is a specialized tool designed to help conduct precise electrical measurements on small devices or sensitive materials. It allows engineers, researchers, and technicians to probe, test, and characterize the electrical properties of organic semiconductors, wafers, microchips, MEMS devices, and other small-scale electronic components. The main benefit of probe stations is they allow you to position testing probes with a high level of accuracy, repeatability, and stability to avoid damaging your sample.

Probe Station Components

At its core, a probe station consists of several key components, which work together with measurement instruments to analyze electrical parameters, enabling highly accurate testing.

Probe Station

Coming soon!

Fine-Tipped Probes

Fine-tipped probes are important for making precise contact with the device under test (DUT). Their tips, typically 1 µm to 200 µm in diameter, allow for probing minute features on modern electronic components and materials.

The probe material choice affects its mechanical durability and electrical conductivity, which in turn dictates which applications it is best suited for. Tungsten and tungsten carbide are widely valued for their durability and hardness, making them ideal for repetitive probing and general-purpose DC measurements. For applications requiring high levels of electrical conductivity, Beryllium-Copper alloy (BeCu) is a good choice, especially for low-resistance measurements. However, these probes are softer than Tungsten so require more careful handling. Additionally, probes are often gold-plated – typically over a core of tungsten, BeCu, or even nickel. This combines the base material's mechanical properties with gold's excellent electrical conductivity and resistance to oxidation, making such probes highly suitable for sensitive, low-noise measurements or when probing gold contact pads to ensure stable and reliable contact.

Besides common single-needle probes, other specialized types are available for advanced measurements. RF probes, for example, are designed with controlled impedance for accurate high-frequency device characterization, from MHz to GHz. For simultaneous testing numerous identical devices, such as in wafer-level screening or production environments, Probe Cards offer a custom assembly of multiple fixed probes. For highly accurate low-resistance measurements, Kelvin probing techniques, also known as four-point probe measurements, are used. This often involves using specialized probe needles where each tip has two electrical contacts (a "force" line for sourcing current and a "sense" line for measuring voltage) very close to the point of contact with the device. Using two such dual-contact probes (or four carefully placed individual probes) in a four-wire configuration allows for the measurement of voltage directly at the DUT, effectively eliminating the influence of probe and lead resistance from the result.

Micromanipulators

Most probe stations use several micromanipulators to position these electrodes or probes with high spatial resolution. These systems allow probe needles to be positioned precisely on tiny contact points of a sample, often with micron or sub-micron accuracy. While various designs exist, they primarily fall into a few categories:

• Manual Micromanipulators:

  These offer direct, hands-on control and are widely favored for their intuitive feel, straightforward operation, and cost-effectiveness. They provide excellent tactile feedback, allowing researchers to carefully guide probes into position.

• Motorized Micromanipulators:

  These provide automated movement, often programmable for repetitive tasks or remote operation. They can be beneficial for more complex probe patterns, reducing manual effort and potentially improving throughput for certain routines.

• Piezoelectric Micromanipulators:

  For applications needing extremely high spatial resolution (often in the nanometer range), piezoelectric manipulators offer exceptionally fine and smooth motion control. They are typically used with manual or motorized stages to facilitate coarser positioning.

Each type presents a different balance of precision, speed, automation capabilities, and cost. For many research applications requiring precise and reliable probe placement, manual micromanipulators offer an excellent solution. The Micromanipulator provides fine XYZ axis control with a positioning accuracy of 10 µm, ensuring stable and repeatable contact. It's also easy to use and and easy to integrate into different experimental setups, complementing essential measurement equipment.

Micromanipulator

Request a quote or buy now

Optical Microscope

An optical microscope will provide visual feedback to aid in positioning both the sample and probes. These microscopes need a long working distance so there is enough space between the lens and the sample for the probes and manipulators.

Common choices include stereo microscopes, which offer direct eyepiece viewing with excellent depth perception. These are highly beneficial for intuitive manual probe alignment. For screen-based viewing, many probe stations use monocular zoom lens systems coupled with digital cameras, displaying a high-magnification image directly onto a monitor. This digital approach can be more comfortable for operators during long sessions and allows for easy shared viewing. It also improves operator safety when testing active optoelectronic devices such as LEDs or lasers, as it prevents direct eye exposure to the magnified emitted light. Regardless of the specific optical setup, achieving clear and uniform illumination across the sample area is important for effective navigation and reliable probe placement.

Wafer Chuck

The wafer chuck is an important part of the probe station, acting as the stable platform for the DUT. Its characteristics directly impact the quality and type of measurements possible. Key dimensional specifications for any chuck include its diameter (to accommodate various sample or wafer dimensions), flatness, and planarity. These features help ensure consistent probe contact across the sample.

Various chuck types are available. Vacuum chucks hold samples in place by applying a vacuum to holes or grooves on the chuck surface. Thermal chucks enable temperature-dependent measurements. Chucks can be electrically conductive and have a separate connection to measurement instruments like a parameter analyzer. Alternatively, they can be electrically insulating, used when you need to electrically isolate the DUT. Choosing the right chuck type and material is important for accurate and reliable measurement.

Positioning Stage

The positioning stage is the mechanical assembly that holds and moves the sample chuck. It allows for precise alignment of the DUT relative to the probes. Typically, stages offer movement in at least three linear axes – X, Y (for planar movement across the sample) and Z (for vertical adjustment to make or break probe contact) – and often a rotational R (theta) axis for fine angular alignment of the sample with respect to the probes or features.

Stages can be:

• Manual:

  Offering direct, hands-on adjustment via micrometers or lead screws. These are often preferred for simpler setups or when frequent, varied adjustments are needed.

• Motorized:

  Driven by stepper or servo motors, these stages allow for automated, high-precision, and repeatable positioning, often controlled via software. This is beneficial for wafer mapping, automated test sequences, and remote operation.

Key performance characteristics of a stage include its travel range, positioning resolution, repeatability, and stability.

Vibration Isolation

Many electrical measurements, especially those involving very small contact points, low currents, or high frequencies, are extremely sensitive to mechanical vibrations. External vibrations from lab equipment, foot traffic, or building HVAC systems can cause probe tips to skate across contact pads or damage delicate samples and probes. This leads to noisy data, inaccurate results, and poor measurement repeatability.

Vibration isolation is therefore an important factor for reliable probing. Maybe probe stations include or require vibration isolation equipment– like specialized optical tables, active cancellation systems, or built-in dampers – to stablize probe contact.

Probe Station Applications

Probe stations are integral in fields like semiconductor manufacturing, electronics research, telecommunications, and automotive and aerospace industries.

Wafer-Level Testing

Probe stations are essential for wafer-level testing in fields like semiconductor manufacturing. Before a wafer is diced into individual chips, it undergoes testing to assess the performance of each die. This early-stage testing helps manufacturers identify faulty dies, reducing waste and improving overall production efficiency.

Device Characterization

Probe stations are also used to measure a wide range of electrical parameters, including DC characteristics like current-voltage (I-V) curves and capacitance-voltage (C-V) curves, as well as RF characteristics such as S-parameters. By analysing these measurements, engineers can gain insights into the device's performance, reliability, and suitability for specific applications.

Failure Analysis

When a device malfunctions, a probe station can be used to pinpoint the root cause of the failure. By systematically probing different parts of the device, engineers can identify defective components or faulty connections. This information is crucial for improving future designs and manufacturing processes.

Research and Development (R&D)

In R&D environments, probe stations are used to test new materials, device structures, and fabrication processes. Researchers can use them to explore the electrical properties of novel materials like organic semiconductors, 2D materials, and nanostructures.

Optoelectronic Testing Stations

In addition to electrical testing, probe stations can be used to test optoelectronic devices, such as photodiodes, LEDs, and laser diodes. By integrating optical sources and detectors into the setup, engineers can measure the performance of devices that interact with light, which is crucial for applications in fibre optics, solar cells, and display technologies.

Life Sciences

These instruments are also crucial in electrophysiology, where they are used to position microelectrodes with extreme precision to record electrical activity from individual neurons or muscle cells. This allows researchers to study ion channel behaviour, synaptic transmission, and neural circuitry in real-time. In cell biology, micromanipulators are used for various tasks, such as injecting biological molecules into cells, performing patch-clamp experiments, or isolating specific cells for further analysis. They are also employed in genetic engineering for microinjection of DNA or RNA into embryos or cells, and in microdissection to manipulate or dissect small tissue samples under a microscope.

Specialized Probe Stations

Beyond basic setups, specialized probe stations are available for advanced testing techniques:

• RF Probe Stations and Microwave Probe Stations: These systems are designed for high-frequency testing of devices like amplifiers, oscillators, and antennas. Special RF probes and equipment are used to measure parameters like S-parameters and impedance at high frequencies, making probe stations essential for the development of 5G technology and other high-speed communication systems.
• Microscale & Nanoscale Probe Stations: With the increasing miniaturization of electronic components, probe stations can be equipped with micromanipulators that allow for precise positioning of probes on very small features, such as micron-sized or nanometre-sized structures. This is essential for testing MEMS (Micro-Electro-Mechanical Systems) devices, nanowires, and other small-scale components. These systems require high precision micromanipulators and high resolution microscopes.
• Cryogenic & Temperature-Dependent Probe Stations: Some probe stations come with thermal chucks that allow testing at different temperatures. This is important for understanding how devices perform under various thermal conditions, such as in high-temperature or cryogenic environments. Temperature-dependent testing is particularly useful for automotive electronics and space applications, where devices must operate reliably under extreme conditions.
• Vacuum Probe Stations:  Some probe stations are designed to operate in vacuum chambers or controlled atmospheres (e.g., within a glove box) to test devices that are sensitive to air or moisture. This is particularly important for testing organic semiconductors, such as non-fullerene acceptors, 2D materials, and other delicate structures that may degrade when exposed to the environment.

Supercharge your research with the right experimental setup, contact us to discuss discuss your requirements and find out more about our probe station products!

NamePlease fill the field

Email Please enter valid email address

Message Please enter your message

Learn More

Micromanipulator Drift and Other Common Errors

The performance of a micromanipulator can suffer from various mechanical issues, including drift, backlash, side play, and sticking. Understand these issues and how our engineers have implemented solid design principles to avoid potential movement issues from the start.

Read more...

Connecting the Micromanipulator to the Source Measure Unit

This guide gives an overview of how to use the Ossila Micromanipulators with the Source Measure Unit, as well as some general tips and tricks for getting the most out of sensitive electrical probing measurements.

Read more...