Development of a detachable high speed miniature scanning probe microscope for large area substrates inspection

Abstract

We have developed a high speed, miniature scanning probe microscope (MSPM) integrated with a Positioning Unit (PU) for accurately positioning the MSPM on a large substrate. This combination enables simultaneous, parallel operation of many units on a large sample for high throughput measurements. The size of the MSPM is 19 × 45 × 70 mm(3). It contains a one-dimensional flexure stage with counter-balanced actuation for vertical scanning with a bandwidth of 50 kHz and a z-travel range of more than 2 μm. This stage is mechanically decoupled from the rest of the MSPM by suspending it on specific dynamically determined points. The motion of the probe, which is mounted on top of the flexure stage is measured by a very compact optical beam deflection (OBD). Thermal noise spectrum measurements of short cantilevers show a bandwidth of 2 MHz and a noise of less than 15 fm/Hz(1/2). A fast approach and engagement of the probe to the substrate surface have been achieved by integrating a small stepper actuator and direct monitoring of the cantilever response to the approaching surface. The PU has the same width as the MSPM, 45 mm and can position the MSPM to a pre-chosen position within an area of 275×30 mm(2) to within 100 nm accuracy within a few seconds. During scanning, the MSPM is detached from the PU which is essential to eliminate mechanical vibration and drift from the relatively low-resonance frequency and low-stiffness structure of the PU. Although the specific implementation of the MSPM we describe here has been developed as an atomic force microscope, the general architecture is applicable to any form of SPM. This high speed MSPM is now being used in a parallel SPM architecture for inspection and metrology of large samples such as semiconductor wafers and masks.

Non-contact distance measurement and profilometry using thermal near-field radiation towards a high resolution inspection and metrology solution

“…Great steps are taken in this direction by miniaturization of the OBD systems, 44 but further size reduction can be achieved using piezoresistive cantilevers. 45,46 Combined with the development of miniature thermocouples and integrated heaters in the probes, 23 a large part of the measurement system can be reduced to chip level.…”

Automated Cantilever Exchange and Optical Alignment for High-Throughput Parallel Atomic Force Microscopy

“…2 The advantage of this technique over other clamp methods 13 is that the vacuum clamp does not add mass to the moving parts of the vertical (z) scanning stage; therefore, the clamp will not limit the vertical (z) scanning stage control bandwidth. Furthermore, the vacuum principle allows for a compact design, which is more difficult to achieve with mechanical clamp solutions.…”

“…The motion of the cantilever is measured using optical beam deflection (OBD), 1 which is converted to a topography measurement of the surface. 2,3 Due to its atomic resolution and the ability to measure mechanical, 4 physical 5 and chemical 6 parameters, AFM has attracted great interest in several industrial applications, such as semiconductor metrology, 7,8 biological and medical applications, 5 material science 9 and data storage. 10 Industrial applications with high-volume manufacturing characteristics require high-throughput, fully automated instruments.…”

“…The instrument for this procedure is specifically designed for use in the recently developed parallel AFM. 2,7,16 The automatic cantilever exchange and alignment instrument is capable of exchanging 22 cantilevers in parallel in only 6 seconds and includes OBD alignment for a high signal-to-noise ratio (SNR). No intermediate holder is used, maximizing the performance of the z-scanner and rendering the method compatible with any type of AFM cantilever.…”

Analysis of contact stiffness in ultrasound atomic force microscopy: three-dimensional time-dependent ultrasound modeling

“…Atomic force microscopy (AFM) was initially developed for topographic imaging [1][2][3]. In AFM, a vibrating cantilever with a sharp tip scans a sample surface, which in turn, influences the deflection of the same cantilever.…”