High-resolution, high-throughput interrogation schemes are essential for the advancement of nanotechnology. In particular highly reliable, high-throughput characterization techniques with high spatial resolution and sensitivity are needed for profiling advanced semiconductor devices to enable future scaling. Continued device scaling will require new device architectures, smaller feature sizes and new materials. Innovation in physical characterization techniques will be critical to advance this field. Existing techniques like transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are limited in 2D resolution or 3D imaging capability. Moreover, some of those techniques require extensive sample preparation time, which limits throughput.
New devices require new microscopy techniques for device dimension characterization and defect identification. Scanning probes are becoming increasingly attractive for these applications. The primary advantages of scanning-probe based metrology are the ultrahigh spatial resolution that is possible down to the atomic scale, high throughput operation via parallel-probe operation, low cost, small form factor, nondestructive sample profiling, 3D imaging capability and the ability to sense multiple device properties such as topography, capacitance, resistance and thermal conductance, among others.
IBM Research - Zurich has long-standing expertise in scanning-probe technology, starting from the inception of the scanning tunneling microscope (STM) in the mid-80s, which has pioneered the field of atomic scale imaging and manipulation. Over the past few years, we have made significant additional contributions to scanning-probe technology [10]. Subnanometer-scale topography sensing capability has been demonstrated using thermo-electric sensors, with which we have also demonstrated 3D imaging capability with multi-scale resolution [9]. Alternative schemes based on magnetic sensing are being developed for high-resolution topography sensing in the Megahertz regime [8]. We are also engaged in the development of novel conductive probes for high-resolution conductance mapping of surfaces [5-7]. Techniques akin to conductive probe microscopy are currently employed for the characterization of semiconductor devices at the nanometer scale.
Nanopositioning is a key enabling tool for scanning-probe technology. We have made several key contributions to the emerging field of nanopositioning [11-13,16]. We pioneered the use of robust control techniques for nanopositioning and developed several schemes for the characterization of the performance of nanopositioning systems. Using the concept of directed shaping of noise sensitivity transfer function, positioning accuracies far below the noise levels of the employed position sensors have been achieved [12,13]. We pioneered the concept of employing multiple sensors for repeatable and hence absolute positioning capability in large scan areas with nanometer-scale precision [16]. We are currently pursuing schemes for ultrafast nanopositioning using scanning signal transformation concepts [11].
These capabilities, supported by continuous advancement in related techniques, are enabling the development of advanced metrology tools for future semiconductor technology generations.
