Patent Application
20140308456
The present disclosure relates to an apparatus and method for controlling the deposition of particles on a substrate and increasing the density of the particles on the substrate to allow for measurement of the size of the deposited particles with transmission electron microscopy.
In order to accurately calibrate the inspection and metrology equipment used in the integrated circuit industry, such as scanning surface inspection systems (SSIS), precise knowledge of the size of the particles used to calibrate such equipment is needed. One way of precisely measuring particles is to deposit an aerosol of uniformly sized, or mono-dispersed, particles on a film or a substrate and measure the size of the particles using transmission electron microscopy (TEM). Once the size of the deposited particles is known, the film or the substrate with the deposited particles can be used to calibrate inspection and metrology equipment.
However, in order to measure particle sizes using TEM, there must be sufficient particle density on the film or substrate. At particle densities lower than the required threshold, it is too difficult to find and measure a particle. Current systems use a charged nozzle and large, planar, oppositely charged electrode beneath the receiving film or substrate to direct the flow of uniformly sized particles from the nozzle to the film or substrate, but are only capable of achieving particle densities of approximately 105/mm2, which is far below the approximately 108/mm2 particle density required for measurement via TEM.
Currently, the only way to achieve the particle densities required by TEM is to apply unfiltered, non-uniformly sized particles in the form of a colloidal liquid onto the film or substrate. However, the range of sizes of such unfiltered particles is very large using this deposition method, typically 30-50% in full width at half maximum, which is 3-10 times larger than the variance in the sizes of the particles in the uniformly sized particle aerosol described above. Due to this variance, the actual sizes of the particles used for the calibration are unknown, as they may be of a different size than the particles measured via TEM.
According to aspects illustrated herein, there is provided an apparatus for the controlled deposition of particles onto a film or a substrate, including: a frame arranged to support a film or a substrate having first and second surfaces facing in first and second opposite directions, respectively; a nozzle arranged to emit a stream of particles charged with a first polarity toward the first surface; and an electrode: charged with a second polarity, opposite the first polarity, and located adjacent the second surface; and arranged to attract the stream of particles to a region of the first surface. A line orthogonal to the first surface passes through the region and the electrode.
According to aspects illustrated herein, there is provided an apparatus for the controlled separation of particles, including: a frame with an aperture; a nozzle arranged to emit a stream of particles comprising particles charged with a first polarity and having a non-uniform quality toward the frame; a collecting vessel; and an electrode charged with a second polarity, opposite the first polarity, and located adjacent the second surface and arranged to attract the stream of particles toward the aperture in the frame, separate first particles having a predetermined quality from the stream of particles and direct the first particles through the aperture in the frame and into the collecting vessel.
According to aspects illustrated herein, there is provided a method for controlled deposition of particles onto a film or a substrate, including: disposing a nozzle to face a first surface of a film or a substrate, the first surface facing in a first direction; disposing an electrode proximate a second surface facing in a second direction, opposite the first direction, of the film or the substrate; charging the electrode with a first polarity; streaming, from the nozzle, a plurality of particles, charged with a second polarity, opposite the first polarity; attracting the plurality of particles to a region of the first surface; and depositing the plurality of particles on the region of the first surface.
According to aspects illustrated herein, there is provided method for controlled separation of particles, including: emitting, using the nozzle, a stream of particles charged with the first polarity and having a non-uniform quality towards a frame; positioning an electrode adjacent an aperture in the frame; charging the electrode with a second polarity opposite the first polarity; attracting, with the electrode, the stream of particles toward the aperture in the frame; separating, with the electrode, first particles having a predetermined quality from the stream of particles; and directing, with the electrode, the first particles through the aperture in the frame and into the collecting vessel.
Various embodiments are disclosed, by way of example only, with reference to the accompanying schematic drawing in which:
At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the embodiments set forth herein. Additionally, it should be understood that the disclosure as claimed is not limited to the disclosed aspects.
Furthermore, it is understood that this patent is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present disclosure.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. It should be understood that any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure.
As further described below, electrode 106 is arranged to attract the stream of particles to region 109 of surface 111. As further described below, electrode 106 helps define a location, shape, and size of region 111, for example, line L1 orthogonal to the surface 111 passes through region 109 and the electrode. In an example embodiment, nozzle 101 has a diameter in the range of 1 mm to 5 mm and is between a few mm to tens of cm away from film or substrate 103. Although stream of particles 102 is depicted by dashed arrows in
In an example embodiment, electrode 106 is formed so that the profile of the electrode facing second surface 112 is the shape of a circle, ellipse, a square, a rectangle, a polygon, and/or a combination of straight and curved lines, including complex composite shapes. In an example embodiment, electric field 107 is in the range of 0 kV to 30 kV. In an example embodiment, nozzle 101 is tapered and the end of electrode 106 adjacent to second surface 112 is substantially rounded, i.e., substantially hemispherical, in order to reduce the gradient of the strength of electric field 107 and, thus, the risk of electrical arcing between nozzle 101 and electrode 106.
As the profile of electrode 106 which is adjacent to second surface 112 is relatively small compared to the width of nozzle 101, electric field 107 tends to deflect the individual particles in stream of particles 102 from their respective initial courses from nozzle 101 to the region of first surface 111 wherein a line orthogonal to first surface 111 passes through the region and electrode 106, thereby increasing the density of particles deposited within this region on film or substrate 103. In an example embodiment, this region of particle deposition on first surface 111 is between 0.1 mm and 1 mm in diameter, which diameter is generally equivalent to the diameter of the profile of electrode 106. In an example embodiment, the area of the region of particle deposition on first surface 111 is generally smaller than the area of nozzle 101 which is coplanar to first surface 111. This concentrating effect allows for particle densities on the targeted region of the film or substrate of approximately 108/mm2, which is sufficient to measure the size of the deposited particles using TEM.
In an example embodiment, one or more focusing electrodes are used to “defocus” stream of particles 102 by increasing the region of deposition on film or substrate 103, either through the position of the focusing electrodes or by charging the focusing electrodes with a polarity equivalent to the polarity of electrode 106. Focusing electrode 121 is in the form of a ring coaxial to electrode 106 and adjacent to second surface 112. Focusing electrode 122 is in the form of a disk with an aperture, through which aperture electric field 107 passes and stream of particles 102 is directed. In an example embodiment, focusing electrodes 121 and 122 take the form of cylinders with through-bores, tubes, or plates, with or without apertures. In an example embodiment, focusing electrodes 121 and 122 may generate a magnetic field in order to direct the direction of stream of particles 102. Any number, combination, configuration, and location of the types and shapes of focusing electrodes described above are possible.
At least one actuator 131 is connected to frame 104 and arranged to translate frame 104 and film or substrate 103 relative to the path of stream of particles 102. In an example embodiment, multiple actuators are used to provide translation in multiple directions. This translation changes the region of first surface 111 onto which particles are deposited. By translating frame 104 and film or substrate 103, it is possible to create patterns of particle deposition on film or substrate 103. These patterns may be arrays of simple points, lines, or complex shapes.
Flow control mechanism 141 is arranged to adjust the rate of flow of stream of particles 102 from nozzle 101. By adjusting the rate of flow of stream of particles 102, it is possible to finely control the density of particles deposited on film or substrate 103. Furthermore, in combination with the translation of film or substrate 103 by actuator 131, it is possible to create patterns of particle deposition on film or substrate 103 that vary in particle density, such that particle density varies as a function of location on film or substrate 103. These complex patterns can then be used to test the sensitivity of the inspection and metrology equipment being calibrated with film or substrate 103.
In an example embodiment, nozzle 101 is electrically grounded and the charge on electrode 152 creates an electrostatic field (not shown to preserve the clarity of
Electric field 107 and the electrostatic field are arranged to generally direct stream of particles 102 to the aperture in frame 104. The strength of electric field 107 or the electrostatic field determines how strongly electric field 107 and the electrostatic field are able to deflect the individual particles in stream of particles 102 from their respective initial course from nozzle 101 to the aperture in frame 104. Furthermore, certain qualities of the particles in stream of particles 102, such as mass, electric charge, and size, affect how strongly electric field 107 or the electrostatic field are able to deflect the individual particles in stream of particles 102. Therefore, by varying the strength of electric field 107 or the electrostatic field are, it is possible to ensure that only particles 156 possessing one or more predetermined qualities, such as a specific size, are deflected enough to enter the aperture in frame 104 adjacent electrode 152 and travel through the channel in frame 104 to collection vessel 151. In an example embodiment, collection vessel 151 contains a liquid to capture particles 156 possessing the predetermined quality or qualities. These captured particles can then be gathered from the liquid via physical or chemical enrichment processes, such as evaporation or dielectrophoresis.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/810,632, filed Apr. 10, 2013, which application is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61810632 | Apr 2013 | US |
