Abstract:
Micromachine systems are provided. An embodiment of such a micromachine system includes a substrate that defines a trench. First and second microelectromechanical devices are arranged at least partially within the trench. Each of the microelectromechanical devices incorporates a first portion that is configured to move relative to the substrate. Methods also are provided.

Description:
BACKGROUND OF THE INVENTION 
     Summary of the Invention 
     Briefly described, the present invention relates to micromachines. In this regard, embodiments of the invention may be construed as micromachine systems. An embodiment of such a micromachine system includes a substrate that defines a trench. First and second microelectromechanical devices are arranged at least partially within the trench. Each of the microelectromechanical devices incorporates a first portion that is configured to move relative to the substrate. 
     Other embodiments of the invention may be construed as methods for forming arrays of micromachines. In this regard, an embodiment includes the steps of providing a substrate and forming a trench in the substrate. First and second microelectromechanical devices are arranged at least partially within the trench. Each of the microelectromechanical devices includes a first portion that is configured to move relative to the substrate. 
     Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such features and advantages be included herein within the scope of the present invention, as defined in the appended claims. 
     FIELD OF THE INVENTION 
     The present invention generally relates to micromachines and, more specifically, to systems and methods that provide high density packing of micromachines on a substrate. 
     DESCRIPTION OF THE RELATED ART 
     Micromachines, such as microelectromechanical system (MEMS) devices, are becoming prevalent in numerous applications. These devices are able to provide mechanical functionality on an extremely small scale. For example, a typical micromachine can be formed on the scale of tens of nanometers to millimeters. 
     Oftentimes, micromachines are formed on substrates, e.g., a semiconductor wafer. A single substrate can include hundreds of micromachines or more. The number of micromachines that are able to be provided per unit area of substrate, i.e., the packing density of the micromachines, is influenced by several factors. For example, the size of the micromachines and spacing provided between adjacent micromachines affect the packing density of the micromachines. 
     Since there is a seemingly perpetual desire to increase the packing density of micromachines, there is a need for systems and methods that address this and/or other desires. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The present invention, as defined in the claims, can be better understood with reference to the following drawings. The drawings are not necessarily to scale, emphasis instead being placed on clearly illustrating the principles of the present invention. 
     FIG. 1 is a schematic diagram depicting a portion of a substrate including a representative arrangement of micromachines. 
     FIG. 2 is a schematic diagram depicting the micromachines of FIG.  1 . 
     FIG. 3 is a schematic diagram depicting a representative arrangement of micromachines. 
     FIG. 4 is a schematic diagram depicting a representative arrangement of micromachines. 
     FIG. 5 is a schematic diagram depicting a portion of a substrate including an representative arrangement of micromachines. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the figures wherein like reference numerals indicate corresponding components throughout the several views, FIG. 1 depicts an embodiment of a micromachine system  100 . As described in greater detail hereinafter, embodiments of the micromachine system of the present invention can employ various techniques for providing high density packing of micromachines. 
     In FIG. 1, micromachine system  100  includes multiple micromachines  110  that are provided on a substrate  111 . By way of example, substrate  111  can be a semiconductor wafer. Each micromachine  110  incorporates a micromover component (“micromover”)  112 . Micromovers  112  are adapted to move relative to at least a portion of substrate  111 . In other embodiments of the invention, various types of micromachines other than micromovers can be used. However, in the description that follows, embodiments of the invention will be described with reference to micromovers. This is done merely for ease of description and not for the purpose of limitation. 
     Micromovers  112  preferably are spaced from each other so that adjacent micromovers  112  do not interfere with each other. More specifically, if adjacent micromovers were permitted to contact each other, either or both of the micromovers could be inhibited from performing their intended functions and/or could be damaged. Spacing between adjacent micromachines is accommodated by arranging each micromover within a corresponding trench  116 . Preferably, each trench is defined by material of substrate  111 . More specifically, the material of the substrate forms a longitudinal barrier  118  between adjacently disposed micromovers of a row  120  of micromovers. A transverse barrier  122  is formed between adjacently disposed micromovers of a column  124  of micromovers. Trenches  116  can be formed by either removing material of the substrate in the desired area of the trench, such as by etching, and/or by forming a raised area about the desired area of the trench, such as by deposition of material. 
     In the embodiment depicted of FIG. 1, micromovers  112  are substantially retained within their respective trenches by flexures  130 . Multiple flexures  130  engage each micromover  112 . The flexures tend to maintain a micromover within its trench while permitting the micromover to move, e.g., micromover  112  moves relative to substrate  111 . Representative examples of flexures include springs and micro-fabricated beams. 
     Each flexure  130  is affixed to an anchor  132 . Anchor  132  can be formed as a component affixed to the substrate or as a portion of the material of the substrate. 
     Micromachines can be fabricated by a variety of micromachining processes. In a typical process, the device material is silicon that is provided in the form of a wafer. The micromover, flexure, and anchor system are defined in the silicon wafer by a masking layer, which can be formed of a photoresist, for example. A deep silicon reactive ion etch may be used to transfer the mask shape into the silicon wafer. A typical etch depth may be 10 to 100 m. The etch depth is often set by an etch-stop layer that is provided in the silicon wafer before micromachining fabrication is begun. The etch-stop layer can be formed of silicon dioxide, for example. The etch-stop layer is used as a sacrificial layer to facilitate the release of the micromover from the substrate. Release refers to a process by which constraints on the MEMS part, e.g., the micromover, are removed. This allows the micromover to move freely relative to the substrate. In the embodiment of FIG. 1, for example, flexures and anchors serve to constrain the motion of the released micromover to the desired degrees of freedom. 
     An isotropic etch of the sacrificial layer is performed to remove the sacrificial material from about the micromachine components in desired areas. The sacrificial layer may be 1 μm thick, for example. The duration of the etch step will determine which structures are released from the substrate. For instance, the longer the etch time, the more sacrificial material typically is removed during the etch. By removing more material during the etch, typically a larger structure, i.e., the structure defined in the masking step, can be released. Given sufficient time, the release etch can completely remove sacrificial material formed underneath a micromover and its flexures. In contrast, anchors are not released by the etch. To prevent release of the anchors, the anchors are formed sufficiently wide so that they are not undercut by the etch to a degree that permits release. 
     Referring now to FIG. 2, it is shown that several discrete dimensions affect the packing density of the micromachines  110 , i.e., the number of micromachines per unit area. More specifically, each micromachine  110  exhibits a length (MX) and a width (MY), with MX and MY including both the dimensions of the physical device and its operating range. Each micromachine  110  is spaced from an adjacent micromachine by a length (SX), i.e., SX is the distance between adjacent micromachines of the same row, and a width (SY), i.e., SY is the distance between adjacent micromachines of the same column. Thus, in the embodiment depicted in FIG. 2, the total area associated with a micromachine  110  is defined by: 
     MX+(2)( ½ SX), in the X dimension; and    
     MY+(2)( ½ SY), in the Y dimension.    
     An alternative embodiment of micromachine system  100  is depicted in FIG.  3 . As shown in FIG. 3, longitudinal barriers, which are shown in the embodiment of FIGS. 1 and 2, are not provided between adjacent micromovers  110 . In this configuration, an increased packing density of the micromachines is achieved compared to the embodiment of FIGS. 1 and 2. More specifically, each micromachine  110  of FIG. 3 requires a length of MX1, i.e., in some embodiments, MX1&lt;MX+(2)(½ SX). 
     Another embodiment of micromachine system  100  is depicted in FIG.  4 . As shown therein, separators  410  are provided between adjacently disposed micromachines. The separators  410  are adapted to prevent direct contact of adjacent micromovers. Preferably, each separator  410  is formed as a distinct component, i.e., the separator is not formed entirely of the material of the substrate. For example, separator  410  could be a micro-fabricated beam that is similar to that of flexure  130 . 
     In FIG. 4, anchors  420  are used to secure multiple flexures  130 . In particular, each anchor  420  is arranged between an adjacent pair of micromovers and is used to affix at least one flexure from each of the pair of micromovers. Each anchor  420  also can secure one or more separators  410 . Tn embodiments incorporating anchors for fixing multiple components, such as flexures and/or separators, an increased packing density can be achieved. More specifically, in some embodiments, MX2&lt;MX1&lt;MX+(2)(½ SX). 
     In FIG. 5, micromachine system  100  includes multiple micromachines  502  that are provided on a substrate  504 . Micromachines  502  preferably are spaced from each other so that adjacent micromovers  506  do not interfere with each other. Flexures  508  of the micromachines are affixed to anchors. The anchors, being raised from a surface  510  of the substrate, define a trench  512  that is arranged about the anchors. 
     In FIG. 5, four types of anchors are depicted, i.e., anchors  514 ,  516 ,  518  and  520 . More specifically, anchors  514  are adapted to affix a flexure from a single micromover. Typically, such a micromover is arranged at a corner of the array of micromachines. In regard to anchors  516 , these anchors are adapted to affix flexures from at least two micromachines. Since micromachine system  100  of FIG. 5 includes columns  522  of micromachines, anchors  516  typically are provided only along the outer edge of a column of micromachines. 
     Anchors  518  also are adapted to affix flexures from at least two micromovers. Anchors  518  typically are provided only along the outer edge of a row  524  of micromachines. Similar to anchors  516 , anchors  518  are adapted to affix flexures from at least two micromachines. However, unlike anchors  516 , each of which engages flexures on opposing sides of the anchor, each anchor  518  typically engages the flexures along one side of the anchor. 
     Anchors  520  typically are provided at locations other than the outer periphery of an array of micromachines. As shown in FIG. 5, anchors  520  are adapted to affix flexures from at least four micromovers. In particular, one side of an anchor is adapted to affix flexures of adjacently disposed micromovers of a first row, and the other side of the anchor is adapted to affix flexures of adjacently disposed micromovers of a second row. 
     Although not shown in FIG. 5, separators also can be provided between at least some of the adjacently disposed micromovers of the micromachine system  100  depicted therein. 
     The foregoing description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Modifications or variations are possible in light of the above teachings. The embodiment or embodiments discussed, however, were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. 
     For example, spacing between adjacently disposed micromachines may not be required for micromachines that are intended to move together. In these embodiments, a further increase in packing density can be achieved by configuring these micromachines so that they engage each other. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly and legally entitled.