Patent Application
20080160171
The invention relates to electron beam physical vapor deposition apparatus and, more particularly, to independent spatial position stabilization of a target in an electron beam physical vapor deposition apparatus.
Chemical variations, e.g., lamination, across the cross-section of multi-component condensates are one of the main problems encountered when utilizing Electron-Beam Physical Vapor Deposition (EB-PVD) techniques. These chemical variations are caused by instability in EB-PVD process parameters. For instance, one main parameter whose instability can cause such significant chemical variations is the relative level of the molten pool within the EB-PVD chamber. Theoretically, when the molten pool level is maintained at a fixed height throughout the EB-PVD process, lamination may be significantly reduced or eliminated. However, in current EB-PVD apparatus, the molten pool level is maintained manually by the EB-PVD operator. As a result, the relative level of the molten pool remains a potentially instable operating parameter.
Therefore, there exists a need for an EB-PVD apparatus equipped with an independent system designed to monitor and maintain a constant relative level of the molten pool within the EB-PVD chamber.
In accordance with one aspect of the present invention, process for adjusting a feed rate in an electron-beam physical vapor deposition apparatus broadly comprises positioning a target at a first height within a chamber of an electron-beam physical vapor deposition apparatus; feeding the target at a rate into a beam of electrons generated by an electron gun of the electron-beam physical vapor deposition apparatus; evaporating the target with the beam of electrons; monitoring the first height by measuring a difference between a first light intensity and a second light intensity of at least one image of the target using an optical sensor disposed proximate to the chamber; determining a change in the first height; and adjusting a target feed rate.
In accordance with another aspect of the present invention, an electron beam physical vapor deposition apparatus broadly comprises a chamber housing the following: a target station; means for moving the target station; and a window; an optical sensor disposed in connection with the chamber and proximate to the window, wherein the optical sensor comprises means for measuring a difference between a first light intensity and a second light intensity of at least one image of a target; an electron gun disposed in connection with the chamber; and an electron module connected to the optical sensor and the means for moving the target station.
In accordance with yet another aspect of the present invention, a process for manufacturing multi-component condensates free of lamination using an electron-beam physical vapor deposition apparatus broadly comprises positioning a multi-component target at a first height within a chamber of an electron-beam physical vapor deposition apparatus; feeding the multi-component target at a rate into a beam of electrons generated by an electron gun of the electron-beam physical vapor deposition apparatus; evaporating the multi-component target with the beam of electrons into at least a first component evaporant and a second component evaporant; monitoring the first height by measuring a difference between a first light intensity and a second light intensity of at least one image of the multi-component target using an optical sensor disposed proximate to the chamber; determining a change in the first height; adjusting a multi-component target feed rate to evenly deposit the first component evaporant and the second component evaporant upon a substrate; and forming a multi-component condensate free of lamination.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference numbers and designations in the various drawings indicate like elements.
Referring now to
The optical sensor 22 may comprise a gas dynamic filter 36, a focusing lens 38, a separating prism 40, and a first photodetector 41 and a second photodetector 43, each connected to a preamplifier 44. The gas dynamic filter 36 may be a substantially tubular structure having a grid disposed therein. The structure may be about 150 mm in length with an internal diameter of about 25 mm. The grid disposed within the structure may possess a mesh thickness of about 0.1 mm to about 0.15 mm. The gas dynamic filter 36 may provide a filter optical transmission of about 0.02 nm to about 0.05 nm during the course of evaporating at least a target of one (1) meter in length.
The gas dynamic filter 36 and focusing lens 38 are coupled together and mounted to an exterior surface of the chamber 12. Preferably, the gas dynamic filter 36 is positioned against the window 14 of the chamber 12 at an angle of about 3 degrees to about 7 degrees outward from the exterior surface of chamber 12 and in the line-of-sight of the target station 16. The focusing lens 30 may be any one of a number of focusing lenses known to one of ordinary skill in the art. Preferably, the focusing lens 38 may be about 29 millimeters to about 30 millimeters in diameter, or about 29.5 mm to about 29.9 mm in diameter, or about 29.8 mm to about 29.9 mm in diameter, or about 29.9 mm in diameter, and have a focal distance of about 45 mm to about 55 mm, or about 49 mm to about 51 mm, or about 50 mm. The separating prism 40 may be any one of a number of separating prisms as known to one of ordinary skill in the art, and preferably is a 100% reflecting prism with a right angle at the apex and having a base size of about 10 mm by about 10 mm located within a hollow rectangle of about 30 mm by about 30 mm by about 20 mm. Each photodetector 41, 43 may be disposed within a vertical plane at opposing sides of the separating prism 40.
The optical sensor 22 captures at least one image of the target within the target station 16 through the window 14. The gas dynamic filter 36 as known to one of ordinary skill in the art prevents dusting of the window 14 during the target evaporation process. The focusing lens 38 reduces the image passing through the window 14 and gas dynamic filter 36, and projects the image upon the apex of the separating prism 40. The separating prism 40 reflects a reflected image of the original image upon a first photodetector 41 and also refracts a refracted image of the original image upon a second photodetector 43. Each photodetector 41, 43 measure the intensity of light of the reflected image and the intensity of light of the refracted image. The difference in intensity or absence of a difference in intensity is registered and displayed by the preamplifier 44. In addition, the difference in intensity or absence of a difference in intensity is also communicated as at least one output signal from the optical sensor 22 to the electron module 20.
The difference in intensity or absence of a difference in intensity may be determined by comparing the light intensity measurements of the photodetectors 41, 43. The output signal produced by the optical sensor 22, and based upon the difference in intensity, indicates whether the height of the target station 16 is higher or lower than an optimal height required for stabilizing the target surface and optimal evaporation of the target. If the light intensity measurements of each image are equal, the optical sensor 22 outputs a signal equal to zero (0). This indicates the two images of the target within the target station 16 are the same, and the height of the target station remains constant and unchanged. When referring to the height of the target station 16, the surface of the molten liquid contained within the target station is the point at which the height is measured.
If the light intensity measurements of each image are not equal, this indicates the two images of the target are not the same, and the height of the target station has changed. If the second photodetector 43 measures a light intensity value greater than that of the first photodetector 41, then the height of the target station 16 is lower than an optimal height required for stabilizing the target surface and optimal evaporation of the target. In response, the system will raise the target station 16 and in turn increase the feeding rate, that is, evaporation, of the target by the electron beam of the EB-PVD apparatus. If the second photodetector 43 measures a light intensity value less than that of the first photodetector 41, then the height of the target station 16 is higher than an optimal height required for stabilizing the target surface and optimal evaporation of the target. In response, the system will lower the target station 16 and in turn reduce the feeding rate of the target by the electron beam of the EB-PVD apparatus.
Referring now to
The amplifier 28 receives the output signal from the optical sensor 22. The amplifier 28 increases the output signal from about −20 decibels (dB) to about 20 dB, and provides the amplified output signal to the pulse-width modulator 30. The pulse-width modulator 30 may be utilized to control the supply of the amplified output signal, that is, suppresses the current flow, to the galvanic isolator 32. The galvanic isolator 32 serves to isolate functional sections of the electrical system of the electron module 20. For example, galvanic isolator 32 may be designed to electrically isolate the optical sensor circuitry shown in
In response to receiving the translated, modulated output signal, the means for moving the target station 18 receives the output signal and moves the surface of the target within the target station 16 upward or downward at an angle perpendicular to the floor 48 of the chamber 12. The means for moving the target station 18 may be powered using the mechanism power supply 33 of the electron module 20. The means for moving the target station 18 may be any mechanism capable of moving the target station in the aforementioned directions at a rate of at least 0.2 mm per second to about 0.4 mm per second.
The driving generator 26 may be any driving generator capable of operating at a frequency of about 9 kHz to about 10 kHz as known to one of ordinary skill in the art. The power supply 24 may be any power supply capable of providing about 10,000 volts (V), or 10 kV, of power as known to one of ordinary skill in the art.
The Pool Level Closed Loop Control (PLCLC) system described herein may be employed to manufacture multi-component condensates free of lamination. A multi-component target may be positioned at a first height within a chamber of the electron-beam physical vapor deposition apparatus. The multi-component target may be fed at a rate into a beam of electrons generated by the electron gun. Using the electron beam, the multi-component target may be evaporated into at least a first component evaporant and a second component evaporant. The first height of the multi-component target may be monitored using the optical sensor by measuring a difference between a first light intensity and a second light intensity of the images. Once a the optical sensor registers a change in the first height, the means for moving the target station may actuate the target station and in turn adjust the multi-component target feed rate to evenly deposit the first component evaporant and the second component evaporant upon a substrate and prevent lamination from occurring.
Referring now to
As experiments show, lamination is significantly reduced or eliminated at all when the pool level is kept fixed during the process using the Pool Level Closed Loop Control (PLCLC) system described herein. As illustrated in the microphotograph of
One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.
