Patent Application
20080057211
Following are brief descriptions of exemplary drawings. They are mere exemplary embodiments and the scope of the present invention should not be limited thereto.
This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation.
The enclosure 210 is operable toward the plating cell 220. In some embodiments, the enclosure 210 is connected with the plating cell 220 as shown in
The plating cell 220 comprises a space (not shown) for accommodating the plating solution 225 so that a plating process can be performed therein. In some embodiments, the plating cell 220 comprises at least one valve (not shown) coupled to a delivery system (not shown) for introducing and/or draining the plating solution 225 into and/or from the plating cell 220. The plating solution 225 comprises chemical of a material that is to be plated over the surface 215c of the substrate 215. In some embodiments, the plating solution may comprise a catholyte solution including a desired amount of acid, halides, supporting electrolyte, additives and/or other components.
The substrate holder 230 is disposed within the enclosure 210 and operable facing toward the plating cell 220. The substrate holder 230 comprises, for example, a clamp, knob clamp, clip, electrostatic chuck, or other device that is adapted to fasten the substrate 215 to the substrate holder 230. The shaft 235 is configured to move (translate), rotate and/or tilt the substrate holder 230.
The actuator 240 is coupled to the shaft 235. The actuator 240 can be, for example, a motor driving device to move (i.e., translate), rotate and/or tilt the substrate holder 215. In some embodiments, the actuator 240 comprises, for example, a motor (not shown) to actuate the shaft 235. The actuator 240 is adapted to actuate the shaft 235 to move the substrate holder 215 toward the plating cell 220 with a relative speed of about 100 millimeters per second (mm/s) or more in the directions indicated by double-sided arrow 245, for example.
In some embodiments, the plating apparatus 200 further comprises a rotational speed controller 250. The rotational speed controller 250 is coupled to the actuator 240 and can transmit a signal to the actuator 240 to rotate the substrate holder 230 (about a normal to a surface of the substrate) with a rotational speed between about 5 revolutions per minute (rpm) and about 90 rpm in the direction indicated by arrow 265, for example. In some embodiments, the plating apparatus 200 further comprises an angle controller 260. The angle controller 260 is coupled to the actuator 240 and can transmit a signal to the actuator 240 to tilt the substrate holder 230 to an angle between about 1° and about 5° with respect to the surface of the plating solution in the directions indicated by double-sided arrow 255, for example. In some embodiments, the plating apparatus 200 further comprises a power supply 270. The power supply 270 may be coupled to the substrate holder 230 via the shaft 235, for example. The power supply 270 may provide a current density between about 2.8 milliamperes per square centimeter (mA/cm2) and about 14 mA/cm2 to the substrate holder 230 for electrical plating.
In step 310, the actuator 240 (shown in
In step 320, the angle controller 260 transmits a signal to the actuator 240 to actuate the shaft 235 to tilt the substrate holder 230 so that the surface 215c of the substrate 215 facing the plating solution 225 has an angle between about 1° and about 5° with respect to the top surface of the plating solution 225.
In step 330, the rotational speed controller 250 transmits a signal to the actuator 240 to actuate the shaft 235 to rotate the substrate holder 230 so that the substrate 215 is rotated about a normal to a surface of the substrate with a speed between about 5 revolutions per minute (rpm) and about 90 rpm.
In some embodiments, the sequence of steps 310-330 is adjustable. For example, step 330 may be performed before step 320. In other embodiments, at least two of the three steps can be performed at approximately the same time. In some embodiments, steps 320 and 330 are not performed until the substrate 215 contacts or is immersed into the plating solution 225.
In step 340, the substrate 215 is immersed into the plating solution 225 for plating. In some embodiments, the immersion speed of the substrate 215 held by the substrate holder 230 is about 100 mm/s or more, as soon as at least one portion, e.g., portion 215a, of the substrate 215 contacts the plating solution 225. The portion 215a of the substrate 215 may be, for example, a point or small area at which the substrate 215 contacts the top surface of the plating solution 225. The immersion speed of the substrate 215 can be, for example, gradually increased from the speed, e.g., of about 50 mm/s, described in step 310 to the speed of about 100 mm/s or more. The substrate 230 is then completely immersed into the plating solution 225 with the speed of about 100 mm/s or more until the last portion, e.g. portion 215b, of the substrate 215 is immersed under the top surface of the plating solution 225.
In some embodiments, the immersion speed of the substrate 215 is between about 100 mm/s and about 120 mm/s during the period between the time the portion 215a of the substrate 215 begins contacting the top surface of the plating solution 225 and the time when the whole surface 215c of the substrate 215 is immersed under the top surface of the plating solution 225. In some embodiments of electrical plating, the power supply 270 provides a current density between about 4.2 mA/cm2 and about 8.4 mA/cm2 during this period. Because the immersion speed of the substrate 215 is higher than about 100 mm/s, the period during which current crowds on the portion 215a of the substrate 215 is sufficiently short so that the hazy phenomenon described above can be effectively reduced or prevented. In some embodiments, the hazy phenomenon can be further reduced or prevented by rotating the substrate 215 with a speed between about 5 revolutions per minute (rpm) and about 90 rpm. By rotating the substrate 215, the portion of the substrate 215 contacting the plating solution 225 is rotated so that the charge carriers will not crowd at the same region, i.e., the hazy phenomenon will not occur at the same area.
In some embodiments, the substrate 215 is titled by the shaft 235 so that the surface 215c of the substrate 215 has an angle between about 1° and about 5° with respect to the surface of the plating solution 225, while the portion 215a contacts the top surface of the plating solution 225. The substrate 215 is tilted to reduce or prevent bubbles within the plating solution 225 from being blocked under the surface 215c of the substrate 215. The bubbles may be created by, for example, a plating solution delivery system (not shown) which introduces the plating solution 225 into the plating cell 220. The bubbles may be blocked under the surface 215c of the substrate 215, while the substrate 215 is being immersed into the plating solution 225. The bubbles may adversely affect physical uniformity and/or electrical characteristics of the material plated on the surface 215c of the substrate 215, specifically at a region where devices or circuits with feature sizes are formed. In still other embodiments, the substrate 215 is immersed into the plating solution 225 in such a way that the surface 215c of the substrate 215 is substantially parallel to the top surface of the plating solution 225 as long as the bubbles within the plating solution 225 are not a concern.
In some embodiments, the immersion speed of the substrate 215 is between about 120 mm/s and about 400 mm/s during the period between the time when the portion 215a of the substrate 215 begins contacting the top surface of the plating solution 225 and the time when the whole surface 215c of the substrate 215 is immersed under the top surface of the plating solution 225. For electrical plating, the power supply 270 may provide a current density between about 4.2 mA/cm2 and about 8.4 mA/cm2 to the substrate 215, for example. In some embodiments, the surface 215c of the substrate 215 may be substantially parallel to the top surface of the plating solution 225 because the immersion speed of the substrate 215 is sufficiently high so that bubbles within the plating solution 225 may not be blocked under the surface 215c of the substrate 215. Accordingly, the substrate 215 is not tilted.
Further, due to the high immersion speed, e.g., between about 120 mm/s and about 400 mm/s, rotation of the substrate 215 may be omitted, because the substrate 215 can be immersed into the plating solution 225 in a short period of time, so that current crowding described above can be reduced or prevented. Accordingly, the hazy phenomenon described above can be effectively reduced or prevented. In these embodiments, steps 320 and 330 described above are omitted.
In other embodiments, the substrate 215 fastened by the substrate holder 230 is rotated between about 5 rpm and about 90 rpm in order to reduce or prevent current crowing effect as described above. In still other embodiments, the substrate 215 may be tilted so that the surface 215c of the substrate 215 has an angle between about 1° and about 5° with respect to the surface of the plating solution 225. The inventor has determined that in some embodiments, for a given motor, the tilt angle of the substrate 215 is correlated with the immersion speed of the substrate 215. For example, assume the tilt angle is 2° and the immersion speed is 300 mm/s. If the substrate 215 is tilted to an angle of about 4°, the immersion speed is reduced to 150 mm/s, i.e., the larger the tilt angle, the slower the immersion speed. Accordingly, a large tilt angle, e.g., more than 5°, may affect the immersion speed of the substrate 215.
In step 350, the actuator 240 stops moving the substrate 215 so that the substrate 215 is immersed in the plating solution 225 for plating. During the period that the whole surface 215c of the substrate 215 is immersed under the top surface of the plating solution 225, and the moving of the substrate 215 stops, the immersion speed of the substrate 215 can be gradually reduced to zero, for example. In other embodiments, after being immersed in the plating solution 225, the actuator 240 maintains substantially the same immersion speed applied to the substrate 215 as set forth in connection with step 340 for a period of time, and then the immersion speed of the substrate 215 is gradually reduced to zero.
In step 360, after a desired layer of material is plated over the substrate 215, the actuator 240 removes the substrate 215 from the plating solution 225.
Although the present invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly to include other variants and embodiments of the invention which may be made by those skilled in the field of this art without departing from the scope and range of equivalents of the invention.
