Deposition
Thin film deposition processes can be broadly classified into two groups: those that involve a chemical reaction, and those that are deposited by means of physical sputtering.
Some of the more specific types of deposition processes commonly used in semiconductor technology are Chemical Vapor Deposition (CVD), Epitaxy, Atomic Layer Deposition (ALD), and Physical Vapor Deposition (PVD). At each device level during the manufacturing cycle the wafer typically undergoes multiple process steps that deposit films of various materials such as oxide, nitride, polysilicon, and single-crystal silicon, each with different material properties such as crystalline structure and chemical composition.
Industry Challenges
The quality and thickness control of the thin films is critical to the chip performance and reliability. Furthermore, it can define the performance of the subsequent processing steps, making it essential that key characteristics of the deposition process are monitored and controlled. For example, film thickness uniformity after deposition impacts the performance of subsequent chemical mechanical planarization (CMP) steps. With tightening process windows, thickness control is needed both at deposition and at CMP steps.
Another example where the monitoring and control of film properties is essential relates to the transistor channel consisting of silicon and silicon germanium layers. For some devices these layers are measured on planar stacks, but for others they must be measured on complex 2D or 3D structures. In addition, germanium content in the silicon germanium layers must be controlled—a measurement made even more challenging for those devices that have multiple silicon germanium layers, each with a different germanium concentration. Nova’s in-line x-ray and optical solutions address these challenges using precise, accurate, and non-destructive metrology.
Nova’s Solutions
Nova’s in-line x-ray-based metrology solutions are used to extract post-deposition dimensional and material information from structures. For example, our surface-sensitive x-ray photoelectron spectroscopy (XPS) systems can measure thickness and chemical composition of ultra-thin films. Nova’s in-line XPS is a key enabling metrology in many modules across logic, 3D NAND, and DRAM devices. Our XPS systems can measure film stacks with multiple dielectric and metal layers having nanometer-level thicknesses, without layer-to-layer cross-talk that can negatively affect accuracy.
In addition, our in-line low-energy x-ray fluorescence (LE-XRF) technology supplements our XPS metrology by providing additional thickness and material information by quantifying the amount of various atomic species present in a structure. This can be used for more complex multi-layer applications such as silicon germanium nanosheet stacks used for advanced logic devices.
Nova’s in-line optical metrology technologies offer a wide range of planar, 2D, and 3D application solutions for current and next-generation deposition challenges. Our stand-alone scatterometry platforms offer high performance solutions with maximum application flexibility. Nova also offers Integrated Metrology (IM) solutions for complex deposition applications of planar and patterned structures that require wafer-to-wafer or within-wafer feedforward (FF) or feedback (FB) control.
By maximizing the extraction of information from optical spectra, our NovaFit solutions can be used to extend our optical metrology capabilities by minimizing the effects of structural complexity and providing a direct link to reference metrology, such as electrical test measurements.
For the most challenging deposition applications, our hybrid metrology solutions combine the strengths of two or more metrology technologies to provide results superior to what each technology can obtain individually.
