Patent Application
20080157455
1. Field of the Invention
Embodiments of the invention generally relate to a method or an apparatus for holding a semiconductor substrate.
2. Description of the Related Art
Integrated circuits have evolved into complex devices that can include millions of components (e.g., transistors, capacitors and resistors) on a substrate (e.g., semiconductor wafer). Millions of micro-electronic field effect transistors (e.g., complementary metal-oxide-semiconductor (CMOS) field effect transistors) that are formed on the substrate and cooperate to perform various functions within the circuit. Typically, thousands of or even more process steps are performed to form the components on the substrate. During device manufacturing, it is occasionally necessary to hold one or more substrates in a vertical orientation during and/or between process steps. For example, a substrate holding assembly may be used in a measuring system to provide a transfer platform for staging substrates prior to and/or after inspection. In another example, a substrate holding assembly may be used in a wet clean system to provide a platform on which multiple substrates. Examples of processes that may need and use substrate holding assemblies include wet bench processing systems, dry cleaning processing systems, ion implanting process, photomask manufacturing process, and other different types of semiconductor processing systems.
Therefore, there is a need for an improved substrate holding assembly.
Methods and an apparatus for holding substrate are provided. In one embodiment, an apparatus, such as a compliant substrate holding assembly, includes a base plate, a finger disposed on the base plate having a substrate receiving slot and two arms disposed on opposite end of the base plate, and each arm having a substrate receiving slot formed therein.
In another embodiment, a compliant substrate holding assembly includes a substrate supporting structure biased to a first position above a base plate and a sensor arranged to detect a change in position of the substrate supporting structure.
In yet another embodiment, a compliant substrate holding assembly includes a base plate having at least two arms extending upward from opposite sides of the base plate, a resilient finger disposed between the arms, and a sensor arranged to detect a change in position of the finger.
In still another embodiment, a method for holding a substrate on a compliant substrate holding assembly includes providing a substrate supporting structure having a finger disposed on a base plate, setting a substrate on the substrate supporting structure, and detecting a change in position of the finger.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
The present invention provides a method and an apparatus for holding a substrate in a vertical orientation. In one embodiment, the substrate holding assembly has a substrate supporting structure that moves to accommodate substrates of various dimensions and materials, thereby substantially preventing substrate improper positioning, misalignment, and substrate lean. The substrate holding assembly provides three substrate contact points. In another embodiment, a sensor may be provided to accurately detect the presence of a substrate in the holding assembly. The presence of the substrate may be triggered by a change in position of a structure that supports the substrate. Since the change in position of the substrate supporting structure is indicative of the presence of the substrate in the substrate holding assembly, opaque or transparent substrates may be reliably detected.
The substrate supporting structure 302 moves to accommodate substrates 304 having different thicknesses and diameters while maintaining the substrate securely in a vertical orientation within the assembly 300. In one embodiment, the base plate 310, the substrate supporting structure 302 and the two arms 312, 314 may be fabricated by a plastic material, such as perfluoroalkoxy (PFA), Telfon®, polyetherimide, Ultem®, or other suitable materials. In another embodiment, the assembly 300 may be fabricated by other suitable types of ceramic, metal or polymer materials.
In embodiment where the substrate holding assembly 300 is fabricated by a conductive material, such as metals, an electrically conductive ground path may be provided to eliminate static electricity from building on the assembly 300 or substrates positioned therein. The conductive ground path may be created by utilizing a conductive material, such as foils, wires, connecting the substrate holding assembly 300 at a first end and routing to the ground at a second end. In one embodiment, the conductive material may have a first end coupled to the base plate 310, the substrate supporting structure 302, the two arms 312, 314, or other suitable location in the substrate holding assembly 300 and a second end routed to the ground.
In one embodiment, the substrate supporting structure 302 includes a plurality of fingers 306 configured to hold separate substrates. Each finger 306 extends from a body 328 to form a comb-like structure.
A tip 408 is formed on a distal end of the finger 306. A sensor 406 is disposed proximate to the first end 312 of the base plate 310 and has a notch 410 configured to allow the tip 408 to pass therethrough upon deflection of the finger 306. The sensor 406 provides a light beam transmitting across the notch 410 which detects the presence of the tip 408, which corresponds to the presence of the substrate. Other sensors suitable for detecting the change in position of the tip 408 due to deflection of the finger 306 may be utilized. Since the sensor 406 is triggered by the change in position of finger 306 due to the substrate, the sensing mechanism is insensitive to materials of the substrate 304, and as such, the presence of transparent and other hard to detect substrates may be reliably sensed in the assembly 300.
The arms 312, 314 and support structure may have additional slots 402, 404 formed therein to hold additional substrates. Although the assembly 300 is shown configured to hold two substrates, it is contemplated that the assembly may be configured to hold any number of substrates.
The flexible and compliant character of the finger 306 provides a compensation and accommodation for multiple sources of substrate misalignment including from parts tolerances, assembly error, substrate warping due to age or thermal expansion, or dimension variation. The compliant finger 306 also acts to reduce the forces applied to the substrate during transfer from a cassette (e.g., FOUP) to the substrate supporting structure 302 or from the substrate supporting structure 302 to a processing station.
The V-shaped configuration of the slot 308 formed on the finger 306 along with the V-shaped slots 402, 404 formed in the two arms 314, 312 provides a stable and adjustable contact points to accommodate the substrate with different dimensions positioned within the slots. As the substrates with different thickness may rest on the finger 306 with different third contact points (e.g., higher or lower contact points within the slot 308) at and around substrate's 6 o'clock position, the two substrate edges at its 3 and 9 o'clock position in contact with the slots on the arms may create different first and second contact points as well. The V-shaped configuration of the slots 308, 322, 324 enables the substrate being placed in the slots to have three contact points. The three contact points provide a secure and stable position that allows the substrate to be in place within the substrate supporting structure 302 without leaning forward or backward from the vertical plane, thereby efficiently preventing and reducing the cross-substrate damage or misplacement. The V-shaped configuration of the slots accommodate and compensate substrates with dimension variation to be upstraightly held thereupon and allows the substrates to touch the V-shaped configuration at different contact points with different depth within the slots.
Thus, methods and apparatus for holding substrate in a substrate holding assembly are provided. The compliant structure formed in the substrate holding assembly advantageously provides compliance or flexible motion to substrate with various dimensions and materials positioned in the assembly, thereby preventing substrate improper positioning, misalignment, and substrate lean.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
