Patent Publication Number: US-9837258-B2

Title: Ion trap with variable pitch electrodes

Description:
STATEMENT OF GOVERNMENT RIGHTS 
     This invention was made with Government support under contract: W911NF-12-1-0605, awarded by the U.S. Army. The Government has certain rights in this invention. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to methods, devices, and systems for positional control of ions in an ion trap. 
     BACKGROUND 
     An ion trap can use a combination of electrical and magnetic fields to capture one or more ions in a potential well. Ions can be trapped for a number of purposes, which may include mass spectrometry, research, and/or controlling quantum states, for example. 
     Ions can be transported along a path in some regions of an ion trap, and can have their motion restricted in other regions of an ion trap. As an example, electric and/or magnetic fields can be used to transport and/or capture ions (e.g., charged particles). Some ion traps make use of electrodes to transport and/or capture ions, for example, by providing static and/or oscillating electric fields that can interact with the ion. 
     It may be desirable to provide differing degrees of positional control to such ions as they move through different regions of an ion trap; however, providing differing degrees of positional control over ions in an ion trap can be problematic using conventional methods, which can employ electrodes of uniform pitch to provide positional control. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  provides an illustration of an example ion trap. 
         FIG. 2  illustrates a portion of an example ion trap. 
         FIG. 3  illustrates an example flow chart of an example method for providing an ion trap with variable pitch electrodes. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments of the present disclosure relate to methods, apparatuses, and systems for design, fabrication, and use of an ion trap with variable pitch electrodes. As described herein, different issues which can arise from the use of some previous approaches to ion trap technology can be overcome. 
     One such issue can arise from use of electrodes that are formed on uniform pitch in an ion trap. Forming electrodes on uniform pitch in an ion trap can limit positional control over ions in an ion trap, for example, by providing a uniform electric field that can interact with the ion. Stated differently, positional control of ions in an ion trap can be limited to a single degree of positional control over the ions if the ions are transported and/or positioned using electrodes that are formed on uniform pitch. 
     In the following detailed description, reference is made to the accompanying figures that form a part hereof. The figures show by way of illustration how one or more embodiments of the disclosure may be practiced. 
     The embodiments are described in sufficient detail to enable those of ordinary skill in the art to practice one or more embodiments of this disclosure. It is to be understood that other embodiments may be utilized and that process, electrical, and/or structural changes may be made without departing from the scope of the present disclosure. 
     As will be appreciated, elements shown in the various embodiments herein can be added, exchanged, combined, and/or eliminated so as to provide a number of additional embodiments of the present disclosure. The proportion and the relative scale of the elements provided in the figures are intended to illustrate the embodiments of the present disclosure, and should not be taken in a limiting sense. 
     It should be noted that although many of the figures provided herein provide visual views of example optical bench configurations and example alignments of optical fibers, the embodiments of the present disclosure can be accomplished by using different configurations, materials, and/or components. Further, as used herein, “a” or “a number of” something can refer to one or more such things. For example, “a number of optical components” can refer to one or more optical components. 
       FIG. 1  provides an illustration of an example ion trap  100  according to the present disclosure. As illustrated in  FIG. 1 , the ion trap  100  can include a plurality of vias  109 - 1 ,  109 - 2 , . . . ,  109 -N (referred to generally herein as “vias  109 ”). A plurality of capacitors  110 - 1 ,  110 - 2 , . . . ,  110 -N (referred to generally herein as “capacitors  110 ”) can be included and positioned such that a respective capacitor  110 - 1 , for example radially encompasses a respective via  109 - 1 , for example. The ion trap  100  can be fabricated using anisotropic and deep reactive ion (DRIE) etching techniques, among other suitable techniques. 
     The plurality of capacitors  110  can be formed on a first pitch  120 - 1 . As used herein, “pitch” refers to a distance between various similar objects. For example, as illustrated in  FIG. 1 , a first capacitor (e.g.,  110 - 1 ) can be formed adjacent to a second capacitor (e.g.,  110 - 2 ), and the distance (e.g., first pitch  120 - 1 ) between the two capacitors in the x-direction is then the pitch on which the two capacitors  110 - 2 ,  110 - 2  are formed. As a further example, a pitch (e.g.,  122 - 1 ) associated with an electrode (e.g.,  112 - 1 ) can be a distance between the rails of the electrode. 
     In the example of  FIG. 1 , the ion trap  100  can include a first region  114  and a second region  116 . In some embodiments, first region  114  can include a plurality of vias  109  and a plurality of capacitors  110 . The second region  116  can include a plurality of electrodes  112 - 1 ,  112 - 1 , . . . ,  112 -N (referred to generally herein as “electrodes  112 ”), and a control region  118 . 
     In some embodiments, respective electrodes among the plurality of electrodes  112  can be formed on a pitch that is different from the first pitch  120 . For example, electrode  112 - 2  can be formed on a second pitch  122 - 1  that is different from the first pitch  120 - 1 . As a further example, electrodes  120 -N can be formed on a pitch  122 -N that is different than the first pitch  120 - 1 . Examples are not so limited; however, and respective electrodes of the plurality of electrodes  112  can be formed at a pitch that is different both from the first pitch  120 - 1  and a pitch (e.g.,  122 - 1 ) on which a different respective electrode is formed. That is, electrode  112 -N can be formed on a pitch  122 -N that is different than the first pitch  120 - 1  and different from pitch  122 - 1 , for example. 
     In some embodiments, the pitch of respective electrodes of the plurality of electrodes  112  can vary along a length of a respective electrode (e.g.,  112 - 1 ). For example, in the first region  114 , an electrode  112 - 1  can have a pitch that is the same as the first pitch  120 - 1 , and a pitch that is different than the first pitch  120 - 1  in the second region  116 . In some embodiments, the rails of a respective electrode  112  can taper continuously from the first pitch to the second pitch. 
     In some embodiments, an apparatus can include an ion trap  100  and a plurality of variable pitch electrodes  112  disposed on the ion trap  100 . A respective electrode (e.g.,  112 - 1 ) of the plurality of electrodes  112  can have a first pitch  121 - 1  in a first region  114  of the ion trap  100  and a second pitch  122 - 1  in a second region  116  of the ion trap  100 . 
     A plurality of capacitors  110  can be disposed in the first region  114 . In some embodiments, a respective capacitor (e.g.,  110 - 1 ) of the plurality of capacitors  110  can be formed on the first pitch  120 - 1 . The capacitors  110  can be trench capacitors, for example. 
     In some embodiments, the first pitch can be between 50 microns and 70 microns, and the second pitch can be less than 50 microns. Embodiments are not so limited; however, and the second pitch can be greater than 70 microns, for example. 
     As discussed in further detail in connection with  FIG. 2 , providing electrodes  112  on a different pitch (e.g.,  121 - 1 , . . . ,  121 -N,  122 - 1 , . . . ,  122 -N) than a pitch  120 - 1  associated with the capacitors  110  can allow for ions to be transported with varying degrees of positional control in the ion trap  100 . For example, coarse positional control over ions in the ion trap  100  can be provided in a first region  114 , while fine positional control over ions in the ion trap  100  can be provided in a second region  116 . 
       FIG. 2  illustrates a portion of an example ion trap  200  according to the present disclosure. In some embodiments, a pitch on which a respective electrode (e.g.,  212 - 1 ) is formed can vary along a length of the respective electrode (e.g.,  212 - 1 ). That is, the pitch of a respective electrode (e.g.,  212 - 1 ) can be tapered such that a pitch at one end of the electrode (e.g.,  212 - 1 ) is different than a pitch at the opposite end of the electrode (e.g.,  212 - 1 ). For example, with respect to electrode  212 - 1 , pitch  221 - 1  can be different than pitch  220 - 1 , and can also be different than pitch  222 - 1 . 
     In some embodiments, the capacitors  210  can be trench capacitors. As an example, trench capacitors  210  can be formed such that a trench region of at least one of the plurality of capacitors  210  extends to a depth of between 200 and 400 microns from the surface of the ion trap. In some embodiments, at least one of the plurality of capacitors  210  can have a capacitance between 50 and 250 picofarads. For example, at least one of the capacitors  210  can have a capacitance of 100 picofarads. 
     In some embodiments, an ion trap apparatus can include an apparatus body, a plurality of vias  209  disposed on the body, and a plurality of electrodes  212 . Each respective electrode (e.g.,  212 - 1 ) can be electrically coupled to a respective capacitor (e.g.,  210 - 2 ). A first pitch  220 - 1  of each respective electrode  212  can be the same as a pitch  220 - 1  of the respective capacitor (e.g.,  210 - 2 ) in a first region  214  of the body, and a second pitch (e.g.,  222 - 1 ) of each respective electrode  212  can be different than the pitch  220  of the respective capacitor  210  in a second region  216  of the body. Advantageously, this can allow for variable positional control of an ion in the different regions. For example, coarse positional control can be provided in first region  214 , and fine positional control can be provided in second region  216  and in the control region  218 . 
     In some embodiments, the pitch of a respective electrode (e.g.,  212 - 1 ) can be tapered from the first pitch  220 - 1  to the second pitch  222 - 1  such that a distance between the rails of the respective electrode (e.g.,  212 - 1 ) changes as a distance from the respective capacitor (e.g.,  210 - 2 ) changes. 
     An example method  330  of fabrication for one or more embodiments contained herein is presented below. In some embodiments, an ion trap can be formed from a plurality of alternating metal and dielectric layers that can be formed together in a sequential order. For instance, anisotropic etching or deep reactive ion etching (DRIE) can be used to form portions of the ion trap. Anisotropic etching and DRIE are different etching techniques in the context of device fabrication. 
       FIG. 3  illustrates an example flow chart of an example method  330  for forming an ion trap with variable pitch electrodes. In this embodiment, the process can include forming a plurality of vias through an ion trap apparatus, at block  332 . For example, in the embodiment of  FIG. 2 , the ion trap includes a plurality of vias  209  that can be formed through the substrate. 
     At block  334 , the method  330  includes forming a plurality of capacitors in the ion trap apparatus such that a respective via (e.g.,  209 ) is substantially encircled by a respective capacitor (e.g.,  210 - 1 ) of the plurality of capacitors  210 . In some embodiments at least one of the capacitors can be a trench capacitor. 
     In various embodiments, the method  330  can include forming a plurality of electrodes, wherein a respective electrode is electrically coupled to the respective capacitor of the plurality of capacitors, and wherein the respective electrode is formed at a first pitch in a first region of the ion trap apparatus and is formed at a second pitch in a second region of the ion trap apparatus. In some embodiments, a pitch associated with a respective electrode can taper from the first pitch to the second pitch such that a distance between the rails of the electrodes changes as a distance from a respective capacitor changes. 
     The method  330  can also include forming at least one of the plurality of capacitors to a depth between 250 and 350 microns below a surface of the ion trap apparatus. In some embodiments, the method can include filling a trench region of at least one of the plurality of capacitors with a doped polysilicon material. For example, the sidewalls of at least one of the plurality of capacitors can be oxidized and subsequently filled with a polysilicon. In some embodiments, the polysilicon can be a boron-doped polysilicon, for example 1.0×10 25  m −3  boron-doped polysilicon. 
     In some embodiments, the method  330  can include forming the plurality of electrodes out of a metal, e.g., gold or other suitable metal. The electrodes can be formed such that a width of a respective rail of an electrode is between 1 micron and 2 microns. 
     The method  330  can include controlling a position of an ion in the ion trap with a first level of positional control in the first region of the trap, and controlling the position of an ion in the ion trap with a second level of positional control in the second region of the trap. In some embodiments, the first level of positional control and the second level of positional control can be different. For example, a comparatively coarse level of positional control over the ion can be provided in the first region of the trap and a comparatively fine level of positional control over the ion can be provided in the second region of the trap. 
     Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art will appreciate that any arrangement calculated to achieve the same techniques can be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments of the disclosure. 
     It is to be understood that the above description has been made in an illustrative fashion, and not a restrictive one. Combination of the above embodiments, and other embodiments not specifically described herein will be apparent to those of skill in the art upon reviewing the above description. 
     The scope of the various embodiments of the disclosure includes any other applications in which the above structures and methods are used. In the foregoing Detailed Description, various features are grouped together in example embodiments illustrated in the figures for the purpose of streamlining the disclosure. Rather, inventive subject matter lies in less than all features of a single disclosed embodiment.