Metal Bellows made from super alloys for use in Ultrahigh vacuum conditions

Metal bellows can withstand severe conditions where other parts hardly can. It makes them suitable for implementing in semiconductor fabrication to control pressure, vacuum and movement. Semiconductor units and various vacuum conditions are hard on various components. These components are subjected to extreme media of gases or liquids and the system used in these conditions hardly withstands the contamination.

Metal bellows has several applications in the semiconductor industries for their frequent positioning capabilities and potential to work in the extreme media.

The metal bellows normally has he physical form of a versatile, spring like accordion however it changes as soon as it fills with liquid or gas under atmospheric or vacuum conditions and its ends are sealed. The bellows become susceptible to different kinds of forces, offering a predictable, frequent and active reaction.  

In semiconductor wafer processing area, ultrahigh vacuum (UHV) or ultrahigh purity treatment, vacuum and pressure bellows can handle different kinds of functions. They can be found in semiconductor clean rooms where they can establish and retain specific atmospheres. In optical equipments, they can accurately position filters and lenses utilized to monitor light in the manufacturing process of semiconductor. Moreover they can be utilized as flexible, hermetically sealed feedthroughs in process chambers to retain high pressure or vacuum when an executive positions different equipments while the production of semiconductor chips.

Various factors of processing media that feature UHV processes can develop rare challenges for metal bellows. Particularly, these bellows should be made with small dimensions and exacting function specifications for high consistency. Moreover, they should be made with low spring rates and highest leak tightness.

Electrodeposited bellows

In the same manner, the requirements of semiconductor processing conditions

describe the metal bellows that can be produced from the specific set of alloys. For instance, some semiconductor applications need bellows produced from a non-magnetic alloy whilst in others, the presence of corrosive process media can limit the need of materials. Normally, the metal bellows are made from one of the three main methods: electrodeposition, edge welding and hydroforming. Every method has advantages and drawbacks. From the production methods used, electrodeposition and edge welding are commonly used to develop the bellows required for semiconductor production and ultrahigh vacuum applications.

Electrodeposited bellows are made by plating metal usually copper, nickel or nickel alloy onto a bellows-shaped form and thereafter discarding the mandrel utilizing chemical or physical methods. These methods can allow manufacturers to vigilantly control the bellows wall thickness and develop bellows with small diameters and extremely thin walls. In these dimensions, the received tiny bellows are very susceptible and perfect for precision instrument applications. They also offer big deflections to an application of small forces.

If electrodeposited nickel is not an alternative then gold can be used for surface coating. For bellows made from nonmagnetic material, electrodeposited nickel will not be significant., here copper can be useful.

In the specialized cases, nickel can be replaced by copper. In such conditions when the apparatus treats as a heat sink, copper is used. 

Hastelloy made bellows are perfect for precision apparatus. They are flawless

and nonporous that is essential for semiconductor based applications that are based on contamination resistance.

The edge-welded bellows are made from several materials such as stainless steel, Inconel, Hastelloy and titanium and others. These bellows have high strength and excellent durability. Although the edge welding cannot develop bellows with tiny diameters or thin walls.  They have good stroke length and outstanding compression capabilities, permitting extensive expansion and contraction while in use. With large number of metallurgical options available, edge welded metal bellows can also handle extreme liquid and gas conditions and temperatures.

Design factors

Talking about metal bellows, compatibility problems occur with metal selection. In various semiconductor manufacturing procedures, the availability of corrosive gases develops special requirements or factors that limit the type of metal that will be similar to engineered bellows. The final specification will be described by site-specific criteria, the materials suitable for electrodeposited bellows are nickel and copper. The materials for edge-welded bellows are stainless steel 316l, 304l, Inconel 625, Inconel 718 super alloy, Hastelloy C276 and Titanium metal.

Electron-beam welding can be utilized to discard the use of solders and epoxies. In various industrial applications, solders link the metal bellows within the machine assembly.

Edge welding can produce bellows for semiconductor applications

 For the versatility of electrodeposited nickel, stainless steel 304l and 316l can

be e-beam welded to the bellows. The steel transition piece is laser welded to steel components in the machine assembly. Electron-beam welding takes place by using automated computer controls and the welding technique offers localized energy to the sample, decreasing distortion of thin components. It also develops very clean welds in applications cannot handle contamination or volatile outgassing. This workaround solution would need adequate pace where the bellows assembly should fit, or need special design factors at the time the bellows is fabricated.

Suitable fabrication can ensure tight spring rate tolerances and reduces stroke. The metal bellows utilized in several semiconductor applications should meet specific design tolerances. With suitable manufacturing, bellows can be fabricated with spring rates about ±10%. The semiconductor processes include tough cleaning methods that have a steep effect on the bellows fabrication and/or material. Various cleaning protocols include ultrasonic cleaning in a fluid condition for components that are installed into a semiconductor apparatus.

Small size demands are also critical. As the requirement for nominal manufacturing rises, device geometry shrinks. This develops ongoing challenges in tight space factors. Modern latest electrodeposited technology that metal bellows is manufactured in various sizes. In Ultrahigh vacuum applications, stainless steel is the sole material that is reliable.