An inspection apparatus and a semiconductor device manufacturing method using the same. The inspection apparatus is used for defect inspection, line width measurement, surface potential measurement or the like of a sample such as a wafer. In the inspection apparatus, a plurality of charged particles is delivered from a primary optical system to the sample, and secondary charged particles emitted from the sample are separated from the primary optical system and introduced through a secondary optical system to a detector. Irradiation of the charged particles is conducted while moving the sample. Irradiation spots of the charged particles are arranged by N rows along a moving direction of the sample and by M columns along a direction perpendicular thereto. Every row of the irradiation spots of the charged particles is shifted successively by a predetermined amount in a direction perpendicular to the moving direction of the sample.

Inspection system by charged particle beam and method of manufacturing devices using the system

The present invention provides an electron beam apparatus for irradiating a sample with primary electron beams to detect secondary electron beams generated from a surface of the sample by the irradiation for evaluating the sample surface. In the electron beam apparatus, an electron gun has a cathode for emitting primary electron beams. The cathode includes a plurality of emitters for emitting primary electron beams, arranged apart from one another on a circle centered at an optical axis of a primary electro-optical system. The plurality of emitters are arranged such that when the plurality of emitters are projected onto a straight line parallel with a direction in which the primary electron beams are scanned, resulting points on the straight line are spaced at equal intervals.

Electron beam apparatus and method of manufacturing semiconductor device using the apparatus

In an optical scanning system for detecting particles and pattern defects on a sample surface, a light beam is focused to an illuminated spot on the surface and the spot is scanned across the surface along a scan line. A detector is positioned adjacent to the surface to collect scattered light from the spot where the detector includes a one- or two-dimensional array of sensors. Light scattered from the illuminated spot at each of a plurality of positions along the scan line is focused onto a corresponding sensor in the array. A plurality of detectors symmetrically placed with respect to the illuminating beam detect laterally and forward scattered light from the spot. The spot is scanned over arrays of scan line segments shorter than the dimensions of the surface. A bright field channel enables the adjustment of the height of the sample surface to correct for errors caused by height variations of the surface. Different defect maps provided by the output of the detectors can be compared to identify and classify the defects. The imaging function of the array of sensors combines the advantages of a scanning system and an imaging system while improving signal/background ratio of the system.

Optical scanning system for surface inspection

A high throughput surface inspection system with enhanced detection sensitivity is described. The acquired data is processed in real time at a high rate of below 50 MHZ thereby reducing the cost for data processing. Anomalies are detected and verified by comparing adjacent repeating patterns and the height of the surface (40) is monitored and corrected dynamically to reduce misregistration errors between adjacent repeating patterns. Local thresholds employing neighborhood information are used for detecting and verifying the presence of anomalies. The sampled point spread function of the combined illumination (22) and collection system (90, 92, 111b) is exploited for anomaly detection and verification.

Surface inspection system

A high sensitivity and high throughput surface inspection system directs a focused beam of light at a grazing angle towards the surface to be inspected. Relative motion is caused between the beam and the surface so that the beam scans a scan path covering substantially the entire surface and light scattered along the path is collected for detecting anamolies. The scan path comprises a plurality of arrays of straight scan path segments. The focused beam of light illuminates an area of the surface between 5-15 microns in width and this system is capable of inspecting in excess of about 40 wafers per hour for 150 millimeter diameter wafers (6-inch wafers), in excess of about 20 wafers per hour for 200 millimeter diameter wafers (8-inch wafers) and in excess of about 10 wafers per hour for 300 millimeter diameter wafers (12-inch wafers).

Scanning system for inspecting anamolies on surfaces

Low‐voltage scanning electron microscopes enjoy many advantages over light microscopes for both dimensional measurements and the analysis of small features. Their combination of high‐resolution and large depth‐of‐focus has made them a standard instrument in the semiconductor industry. However, until now, they have been many orders of magnitude too slow to be used for automated wafer inspection. In this article, the authors will determine the optical requirements of high‐speed inspection at low voltage and show how this leads to a novel optical system design. This optical system shares similarities with a 20 keV column designed for an x‐ray mask inspection system [W. D. Meisburger, A. Desai, and A. D. Brodie, J. Vac. Sci. Technol. B 9, 3010 (1991)]. However, the objective lens and electron detection system are unique. The objective lens combines superimposed electric and magnetic fields to decelerate the primary beam from 20 keV to ∼800 eV, and to effectively collimate and reaccelerate the resulting secondary electrons. Auxiliary electrodes are used to control the electric field on the semiconductor’s surface. A Wien filter is used to separate the secondary electrons from the primary beam. A second Wien filter is used to cancel the transverse chromatic aberration of the first filter. This optical system is capable of producing current densities of 1000 A/cm2 at 800 eV into spots as small as 50 nm. Images are acquired at a rate of 100 million pixels/second. Both theoretical and experimental performance results for this system will be presented.

Low‐voltage electron‐optical system for the high‐speed inspection of integrated circuits

Production viable inspection of x‐ray masks requires the resolution of a scanning electron microscope (SEM) at an imaging rate approximately 1000 times that of commercially available systems. This article analyzes the inspection task for x‐ray masks and compares the requirements for beam‐current density and imaging efficiency necessary to achieve reasonable throughput with technologies available on current SEM and electron‐beam lithography systems. The resulting specifications have been translated into an electron‐optical column with many novel features. The gun, which contains six thermal field‐emission sources mounted on a turret, produces a Gaussian profile beam that is scanned over a continuously moving substrate. Dual electrostatic icosapole deflectors provide high speed telecentric deflection. Secondary electrons are separated from the primary beam by a Wien filter and accelerated into a semiconductor electron detector. An analog optical‐fiber link is used to transmit the signal to the image compute...

Requirements and performance of an electron‐beam column designed for x‐ray mask inspection

SEMSpec is a scanning electron‐beam inspection system designed for high‐resolution die‐to‐die inspections of conductive x‐ray masks, wafer prints, or stencil masks in a production environment. The inspection sensitivity can be varied from 97% detection of 50‐nm defects, at a rate of 27 min cm−2, to 97% detection of 250‐nm defects at 1 min cm−2. A thermal‐field‐emission source produces a Gaussian profile electron beam that is moved by electrostatic deflectors over the continuously moving substrate that is being inspected. Secondary electrons from the substrate are collected in a high‐speed detector and the resulting digitized image data is stored in a specialized memory system. Pairs of images to be compared are continuously transferred from the memory to a high‐speed defect processor for analysis. Defect reports from the defect processor are analyzed during inspection and stored for subsequent review. We describe the overall system including the electron‐beam column with its six‐emitter field‐emission gun...

An electron‐beam inspection system for x‐ray mask production

The design and performance of an X–Y stage for fast electron‐beam inspection of wafers and x‐ray masks is described. The inspection technique involves the comparison of images that are acquired by the raster scan acquisition of long swath images recorded while the stage moves at constant velocity. Pairs of images acquired serially must remain registered to about 0.05 μm net accuracy, requiring interferometer controlled motion with very low vibration. The system design requires high‐vacuum compatible, nonmagnetic construction, with provision for electron and light optical elements above the stage, and additional electron optics and substrate loading elements below it. Accordingly, an open frame stage with internal linear motors and bearings was selected. High stiffness and particular attention to smooth motion results in very low vibration with a relatively large moving mass. The stage is driven by brushless linear motors inside a 20 Hz bandwidth servo loop closed around high‐resolution λ/256=2.5 nm interferometers. Smooth motion contributes to accurate short term position measurement, allowing residual errors to be corrected by beam deflection. Long range accuracy relies largely upon occasional re‐registration using features on the die patterns. At the end of swaths, programmed turnaround trajectories employing position and acceleration feedback allow serpentine paths with a minimum acceleration and overhead time. Using several complementary measurement techniques, overall registration accuracy was shown to be sufficient for detection of 0.05 μm defects.

W. D. Meisburger

Papers

Low‐voltage electron‐optical system for the high‐speed inspection of integrated circuits

Requirements and performance of an electron‐beam column designed for x‐ray mask inspection

An electron‐beam inspection system for x‐ray mask production

Dynamic performance of a scanning X-Y stage for automated electron-beam inspection

Application of the SEMSpec electron-beam inspection system to in-process defect detection on semiconductor wafers