Precise production of pin structures in Zerodur and SiC wafer chucks
No change in material properties through the use of
ultra-short pulse lasers
Surface roughness in the base Ra <= 3 – 4 µm
Precise Pin structures in Wafer chucks for the Semiconductor Industry
Wafer chucks are an important basis for the high-precision processing of wafers in the semiconductor industry. These holding devices enable the secure fixing of wafers during various process steps such as lithography, etching or inspection. The ever smaller structure sizes (nodes) in EUV or nanoimprint lithography are increasing the demands on the evenness of the fixation of the wafer on the wafer chuck.
Pin structures on the surface of the wafer chucks play a decisive role in ensuring ideal planarity of the wafers in lithography and inspection processes.
The pins are defined contact points for the wafer. By applying a vacuum between the wafer and the pin structures, uneven wafers are straightened, thus creating the basis for homogeneous process results in the individual processing steps. The homogeneity of the pin structures plays an important role here.
By minimizing the contact surface, the deformation of the wafer is effectively reduced. In this demanding environment, materials such as silicon carbide (SiC) and Zerodur are becoming increasingly important due to their special properties.
Laser-produced pin structure on a SiC surface.
© Pulsar Photonics GmbH.
Silicon carbide is characterized by high thermal conductivity, excellent stability and resistance in harsh environments. Zerodur, on the other hand, is characterized by extremely low thermal expansion. These properties are necessary to avoid deformation of the wafers during processing.
Laser ablation with USP lasers for the Production of pin structures
in SiC and Zerodur
The production of high-precision pin structures in wafer chucks in both materials requires manufacturing technologies that can achieve high precision with minimal influence on the material properties.
Laser micromachining with ultrashort pulse lasers offers advantages compared to traditional mechanical methods. Due to the localized material evaporation and the minimal heat-affected zone, the process enables the precise, contour-accurate production of pin structures. Processing typically begins on the lapped or polished wafer chuck surface.
As an ablative process, the material surrounding the pins to be produced is selectively removed. This gives the pin surfaces the same roughness and flatness as achieved in the previous polishing or lapping step. Special attention is paid to surface contamination and the surface roughness at the base.
With the UKP laser, surface roughness values of Ra < 3–4 µm can be achieved, depending on the material.
Any residues from the laser processing can be removed through appropriate post-processing.
Microscopic image of a SiC planar surface with pin and circular structures. © Pulsar Photonics GmbH.
PULSAR PHOTONICS covers the complete process chain
Your Personal Contact person
Dennis Pechner
Technical Sales, Laser Application Center