Turbomolecular Vacuum Pumps

Magnetically levitated turbopumps use a 5-axis magnetic bearing system to keep the rotor in constant suspension without physical contact between the rotor and the pump housing. Also known as active magnetic bearing, this technique leverages the advantages of electromagnetism: It uses the forces of electromagnets combined with distance sensors to stabilize and set the rotor in motion. A digital electronic control system adjusts the electromagnetic field through the present magnets in real time to keep the rotor centered and balanced. This active stabilization compensates for imbalances and minimizes vibration.

As the rotor never touches the pump housing, there is no mechanical friction, eliminating the need for lubrication and ensuring oil-free operation inside the pump. Magnetically levitated turbopumps are ideal for high and ultra-high vacuum applications in semiconductor manufacturing, coating, as well as research and development.

This advanced magnetic bearing technology offers several key benefits.

Turbopumps with hybrid bearings combine two bearing concepts within one pump. On the forevacuum side, a ceramic ball bearing protects the rotor from external vibrations. This bearing type is also found in mechanical turbopumps such as the HiPace 10 Neo, making the pump a robust option for tasks like mobile vacuum experiments.

On the high vacuum side, a permanent magnetic bearing keeps the rotor suspended without contact with the pump housing, just like in magnetically levitated turbopumps. This combination provides a robust rotor bearing arrangement for the extreme rotational speeds of ultra-high vacuum generation down to 10^-11 hPa (mbar). Although the ball bearing is minimally lubricated, the pump generates an oil-free vacuum, because the ball bearing is located at the forevacuum side and is therefore isolated from the high vacuum side of the pump. Thanks to this design feature and the compression ratio of the turbo rotor, oil contamination in the vacuum chamber is avoided. Hybrid bearing turbopumps are a reliable solution for a wide range of processes, including analytical applications, research and development as well as space simulation.

Hybrid bearing turbopumps offer a variety of benefits:

Turbopumps belong to the group of kinetic vacuum pumps. They are displacing the pumped medium by accelerating the molecules into the pumping direction. The turbomolecular vacuum pump was designed to achieve something what was previously thought to be nearly impossible – vacuum of such unparalleled purity that it would unlock new frontiers in science and technology. In 1958, Dr Willi Becker, a scientist at Pfeiffer Vacuum+Fab Solutions, invented the very first turbopump. Thanks to their groundbreaking technology, these vacuum pumps can achieve high, ultra-high, and even extremely high vacuum levels down to 10^-11 hPa (mbar).

Today, turbopumps are used to explore the frontiers of knowledge, from simulating the vacuum of space for astrophysics research to testing materials for their performance in extreme environments. In semiconductor manufacturing, these specialized vacuum pumps maintain the ultra-clean, controlled environments needed to produce microchips. The applications for turbopumps in various industries are virtually endless.

At its core, a turbomolecular vacuum pump operates on the principle of kinetic energy transfer. The design is similar to that of a turbine: A multi-stage rotor with disks rotates in a housing. Mirror-inverted bladed stator disks are interposed between the rotor disks, creating a series of stages that compress and transport gas molecules. Turbopump rotors spin at speeds of up to 90,000 revolutions per minute (rpm). This is far more than the engines of a jumbo jet, which only rotate at a maximum of 30,000 rpm.

Turbomolecular pumps require a backing pump to operate effectively. While the turbopump is responsible for generating high and ultra-high vacuum levels, it cannot exhaust gas directly to atmospheric pressure. Instead, it relies on a backing pump to maintain sufficiently low pressure at the outlet, ensuring stable and efficient operation.

Vacuum generation of turbopumps explained in three steps

Modern turbopumps can reach speeds of up to 90,000 rpm. The kinetic energy, therefore, is correspondingly high, resulting in extreme forces acting on the pump housing and anchoring within fractions of a second in the event of malfunction. To ensure the safety of your processes and equipment, Pfeiffer has worked with TÜV Rheinland to develop a safety certification that includes dual protection against excess rotational speed to prevent mechanical failure.

Additionally, as part of the certification, the outer casing of the turbopumps is tested to withstand kinetic rotor energy. Pfeiffer turbopumps are also certified to UL 61010 and Semi S2 standards, ensuring that the equipment meets stringent safety and performance requirements in laboratory and industrial environments, as well as in semiconductor fabs.

Turbomolecular vacuum pumps from Pfeiffer are available in a hybrid and mechanical bearing as well as a magnetically levitated version, offering several advantages:

The hybrid bearing was invented by Pfeiffer Vacuum+Fab Solutions more than 40 years ago. It consists of a permanent magnetic bearing and a ceramic ball bearing.

On the high vacuum side of the pump, a magnetic bearing suspends the rotor without physical contact, minimizing friction and eliminating wear. On the forevacuum side ceramic ball bearings stabilize the rotor in both the radial and axial directions, making it resilient to strong shocks such as atmospheric vents and external vibrations. Although the ball bearing is minimally lubricated, the pump generates an oil-free vacuum, because the ball bearing is located at the forevacuum side and is therefore isolated from the high vacuum side of the pump. Thanks to this design feature and the compression ratio of the turbo rotor, oil contamination in the vacuum chamber is avoided. The circulating lubricant also absorbs heat generated by the ball bearings during operation.

Hybrid bearing turbopumps are suitable for a wide range of processes, including analytical applications, research and development as well as space simulation.

Magnetically levitated turbopumps use a 5-axis magnetic bearing system to keep the rotor in constant suspension without physical contact between the rotor and the pump housing. This bearing technique leverages the advantages of electromagnetism: It uses the forces of electromagnets combined with distance sensors to stabilize and set the rotor in motion. Electromagnetic bearings are also called “active magnetic bearings” because the rotor position is monitored and continuously adjusted. This ensures a wear-free, low-vibration operation by automatically compensating for imbalances. As a result, maintenance- and lubricant-free operation is ensured over the entire service life.

Magnetic bearings are therefore particularly suitable for applications where low wear, clean and dry conditions as well as high pumping speeds are required – such as in high and ultra-high vacuum generation for semiconductor manufacturing, coating as well as research and development.

The rotor of a turbopump rotates at up to 90,000 revolutions per minute. At such speeds, the slightest imbalance can have a major impact on the operation and safety of the pump. Precise balancing of the rotor is therefore relevant both for smooth running and for years of damage-free and secure operation of the turbopump.

To address this, Pfeiffer has developed and patented Laser Balancing, a technology that enables highly precise rotor balancing. Unlike conventional methods that require adding weights or drilling holes, Laser Balancing uses laser ablation to remove material from specific areas of the rotor.

This process is carried out during production in an automated balancing system, which improves both accuracy and repeatability. Laser Balancing improves the balance quality of turbopump rotors by 20% compared to traditional methods. This leads to reduced vibration and noise levels and enhances overall pump performance. These benefits are particularly valuable in vibration-sensitive applications, such as electron microscopy.

Hybrid bearing turbopumps combine a ball with a magnetic bearing. Thanks to the contactless operation of the permanent magnetic bearing, hybrid bearing turbopumps require only minimal maintenance. This bearing technology ensures that the rotor is held in suspension without physical contact on one side of the pump, minimizing friction and wear. However, in every vacuum pump, certain components are subject to high mechanical stress. In hybrid bearing turbomolecular vacuum pumps the operating fluids and ball bearings should be replaced after four to five years, depending on the design and size of the turbopump. Such maintenance work prevents the consequences of far-advanced wear and failures or irreparable damage to the pump.

To learn more about our service offer for turbopumps, visit our service page.

Pfeiffer is recognized as one of the leading manufacturers of turbomolecular vacuum pumps due to several key factors:

1. Pioneering innovation: Pfeiffer invented and patented the first turbomolecular vacuum pump in 1958.

2. Comprehensive product portfolio: Pfeiffer offers a complete range of turbomolecular vacuum pumps, including mechanically levitated and hybrid bearing turbopumps. This comprehensive portfolio ensures that a suitable solution is available for various applications and industries.

3. High-quality engineering: Known for engineering excellence, Pfeiffer ensures that all of its products meet the highest standards of quality and reliability. Our turbopumps are designed to efficiently handle high speeds and kinetic energy efficiently, thus ensuring excellent performance and longevity.

4. Customer-centric approach: Pfeiffer is committed to providing exceptional customer service and support. We offer comprehensive training for operators and product services with maintenance tailored to turbopump technology to ensure that our customers receive the best possible vacuum solutions and support.

A backing pump, also known as a roughing pump, is a special type of vacuum pump used to work in combination with a high vacuum pump, such as a turbomolecular vacuum pump. It reduces the pressure in a system so that a high vacuum pump can operate and can be thought of as a "start-up aid" for the main pump.

A backing pump is the first stage in a vacuum system. It is responsible for evacuating the system and vacuum chamber from atmospheric pressure to a level that is low enough to allow the high vacuum pump to operate effectively.

It is important that the backing pump has sufficient pumping speed to meet the requirements of the high vacuum pump. Typical backing pumps are for example, rotary vane, diaphragm or scroll vacuum pumps. Optionally, vacuum booster s can be integrated into the fore-vacuum system if a higher pumping speed is required.

Why do turbopumps need a backing pump?
Turbomolecular vacuum pumps belong to the category of kinetic vacuum pumps moving gas molecules from the inlet to the exhaust by means of momentum transfer. They are high-performance devices that generate extremely low pressures, i.e. high or even ultra-high vacuum. To avoid back streaming of transferred gases from the exhaust of the turbopump into the vacuum chamber, they need a backing pump to help them discharge the molecules through the fore-vacuum line.

The backing pump and the turbopump are typically started simultaneously and evacuate the vacuum system together. When the turbopump is installed directly on the vacuum chamber (see figure), the backing pump evacuates the system through the turbopump.

Once a certain backing pressure is achieved, the turbopump starts working at full speed, generating high to ultra-high vacuum. Even then, the backing pump continues to operate and removes the gas molecules being pumped by the high vacuum pump. This ensures that the turbopump can maintain its operating pressure and won’t overheat.

The backing pump performs several important tasks at the same time: