DIAGNOSTIC METROLOGY

Design Considerations

With the greater challenges of Advanced technology nodes, for the process engineer, the need for greater insight and knowledge of the real effects of wafer process steps becomes essential if yields and performance are to be competitive. WaferMasters needed this information, as well, to develop thermal process solutions.  Work on WaferMasters’ suite of Diagnostic Metrology tools, developed over the last 6 years (Micro-Raman Spectroscopy, Photoluminescence, Surface Profiling), was guided by the challenges of current technology nodes. The need for stability, repeatability, low signal-to-noise resolution capability and measurements at different depths into the silicon, all on a non-contact basis, demanded new instrument designs and disciplines.

How WaferMasters Achieves Superior Measurement Performance

Superior Measurement Stability and Reproducibility – No moving parts and Fixed Optics where possible. No discernable drift wafer to wafer, or week to week.

Greater Measurement Resolution – Long focal length with minimum “folding” for greater linear deflection per wavenumber and special monochromator design.

Virtual Drill Down Capability –  Multi-wavelength capability for different penetration depths by selectable, multi-line laser with fixed optics.

Intuitive Display Functionality –  Data displayed with versatile display parameters to conceptualize statistically analyzed results.

 

EVERY process affects the physical condition of the silicon lattice. CVD and etch processes can induce compressive or tensile forces which can put the wafer, or the silicon crystal lattice, under stress. Implant can cause “damage” to the lattice sites and affect “crystallinity” (crystal quality). RTP can significantly modify the crystal quality of the lattice, as well as stress or strain levels of the wafer. And ALL of these can affect chip performance.

WaferMasters has developed a suite of complementary tools (MRS-300, MPL-300 and OSP-300) to help process engineers understand what their POR’s (Processes of Record) are really doing to the wafer. While several techniques, such as TEM (Transmission Electron Microscopy) and XRD (X-ray Diffraction), are frequently used, most of these are either invasive or limited in spatial resolution.  The MRS-300 (Multi-Wavelength Raman Spectrometer), MPL-300 (Multi-Wavelength Photoluminescence System)and OSP-300 (Optical Surface Profilometer) are non-contact and non-destructive and can offer new insights (including depth profiling) into effective process control and optimization.

Wafer Level

Stress during wafer processing causes shape and flatness aberrations which can affect die yield, performance and reliability. Tensile and Compressive forces often co-exist, and  in close proximity.  These characteristics and anomolies can be be measured at the wafer level by the OSP-300 platform (Optical Surface Profilometer).  Vector mapping, convoluted intensity plots, and micro contour analysis are but a few of the software generated analytical report techniques.

Chip/Die Level

At the micro-level, wafer stress and dopant non-uniformities can affect the performance of strained silicon and advanced semiconductors at the transistor level.  The MRS-300 platform (Multi-Wavelength Raman Spectrometer) uses shift, curve shape (full-width at half max) and intensity to analyze lattice characteristics (micro stress and uniformity) as a function of depth.  Every wafer process can, and does, influence and impact the physical state of the semiconductor.  Innovative data mapping displays, compressive/tensile stress metrics, uniformities and more, are used in an “exploded view” mode for depth comparison.

Probing Depths

WaferMasters’ MRS-300 and MPL-300 multiwavelength architecture allows selecting and changing laser frequency for different penetration depths with no change of sample position or instrument setting. This unique virtual drill down capability allows consistent analysis of the sample at a variety of depths.