Abstract:
A heat lamp which has captured fasteners that can attach the lamp inside a radiantly heated semiconductor processing reactor. The fasteners are captured within eyelet terminals on each end of the lamp, thereby rotatably securing the fasteners to the lamp. The eyelet terminals may have threaded apertures which screw into the threaded portion of the fasteners. Alternatively, the terminals may be adapted with tabs, conductor extensions or housing assemblies which fold over the top of a fastener inserted through the terminal. In another embodiment, the terminals may be adapted with notched projections which engage a circular dovetail in a fastener inserted through the terminal.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to heat lamps suitable for semiconductor processing reactors. 
     BACKGROUND OF THE INVENTION 
     Chemical vapor deposition (CVD) is a very well known process in the semiconductor industry for forming thin films of materials on substrates, such as silicon wafers. In a CVD process, gaseous molecules, including constituents of the material to be deposited, are supplied to wafers to form a thin film of that material on the wafers by chemical reaction. Typically, CVD processes are conducted at elevated temperatures to accelerate the chemical reaction and to produce high quality films. 
     Substrates (e.g., silicon wafers) can be heated using resistance heating, induction heating or radiant heating. Among these, radiant heating is the most efficient technique and, hence, is the currently favored method for certain types of CVD, particularly for cold wall reactors, where rapid heating is desired in each heating cycle. Similarly, radiant heating is favored in numerous other types of semiconductor processing reactors, such as rapid thermal anneal (RTA), rapid thermal processors (RTP), etch tools, etc. Radiant heating involves positioning infrared lamps within high-temperature ovens, called reactors. Currently, lamps are fastened into the reactor with brass washers and screws. Because of the confined space in the reactor, these screws are difficult to install and/or replace and often are lost within the hardware of the reactor itself. Lost screws have the potential to damage the reactor or cause electrical short-circuits, and, consequently, time is sacrificed locating and replacing them during lamp changes. 
     Accordingly, a need exists for a means of fastening heating lamps in a semiconductor processing reactor which avoids the aforementioned problems of the prior configuration. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention, there is provided a lamp for semiconductor processing. The lamp includes a lamp body, a filament within the lamp body, a captured fastener assembly, and a conductive connector which provides electrical connection from the filament to the captured fastener. 
     It is contemplated that the captured fastener may take one of several forms. In a preferred embodiment, the captured fastener includes a threaded eyelet terminal. A threaded screw is threaded through the eyelet terminal. The threads in the upper portion of the screw&#39;s shank are relieved so that the screw may rotate freely once the threaded portion has passed through the threaded eyelet. In another embodiment, the conductive wire lead of the lamp is extended through the crimped portion of the eyelet such that it retains the screw in the eyelet. In another embodiment, a screw with an annular groove is inserted through an eyelet terminal. A retaining snap ring is subsequently engaged onto the annular groove. In yet another embodiment, a screw is inserted through an eyelet terminal and tabs on the top of the eyelet terminal are engaged over the head of the screw. In still another embodiment, a screw is inserted through an eyelet terminal with a housing assembly, hingedly connected to the terminal by an arm, is folded over the head of the screw. In still another embodiment, a screw with a circular dovetail in the bottom of the head is inserted through an eyelet terminal. The eyelet terminal has a notched projection extending from the top surface which engages the circular dovetail. 
     In accordance with another aspect of the invention, a method is provided for maintaining a screw within an eyelet terminal of a lamp for a semiconductor processing reactor. The method includes providing a screw comprising a head and an elongated shank portion, where the elongated shank portion has a threaded portion. The screw is inserted into the eyelet terminal. The screw is captured in the eyelet terminal to prevent removal of the screw from the eyelet terminal. 
     In accordance with another aspect of the invention, a chemical vapor deposition reactor is provided. The reactor includes a lamp, a fastener for securing the lamp inside the reactor, and means for retaining the fastener on the lamp after the lamp is removed from the reactor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These are other aspects of the invention will be readily apparent from the description below and the appended drawings, in which like reference numerals refer to similar parts throughout, which are meant to illustrate and not to limit the invention. 
         FIG. 1  is a side view of a prior art lamp with a conventional eyelet terminal which is mounted into the reactor with a screw and washer. 
         FIGS. 2A and 2B  are side views of a screw captured by a threaded eyelet terminal or an extended conductor wire lead, respectively, constructed in accordance with two preferred embodiments of the present invention. 
         FIGS. 3A and 3B  are perspective views of the eyelet terminals in  FIGS. 2A and 2B , respectively. 
         FIG. 4  is a side view of a screw captured by a retaining snap ring, constructed in accordance with another embodiment of the present invention. 
         FIG. 5  is a side view of the screw and a perspective view of the retaining snap ring in  FIG. 4 . 
         FIG. 6  is a side view of a screw captured by bendable tabs on the eyelet terminal, constructed in accordance with still another embodiment of the present invention. 
         FIG. 7  is a top plan view of the screw and bendable tabs in  FIG. 6 . 
         FIG. 8  is a side view of the screw and eyelet terminal in  FIG. 6  before the tabs have captured the screw. 
         FIG. 9  is a side view of the screw and eyelet terminal in  FIG. 6  after the tabs have captured the screw. 
         FIG. 10  is a perspective view of an alternative configuration for the embodiment shown in  FIG. 6 , where compliant tabs are fixed. 
         FIG. 11  is a perspective view of a housing assembly on the eyelet terminal, constructed in accordance with yet another embodiment of the present invention. 
         FIG. 12  is a top plan view of the eyelet terminal and housing shown in  FIG. 11 . 
         FIG. 13  is a perspective view of an alternative configuration for the embodiment shown in  FIG. 11 , where there is no notch and catch assembly. 
         FIG. 14  is a perspective view of an alternative configuration for the embodiment shown in  FIG. 11 , where the catch engages directly on the housing assembly. 
         FIG. 15  is a side view of a fastener with a circular dovetail captured by a compliant tong on the eyelet terminal, constructed in accordance with still another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  depicts a prior art lamp  10  as might be typically found in a reactor. The illustrated lamp  10  generally comprises two eyelet terminals  12 , made of a conductive metal, disposed at opposite ends of a tube  14 , which is typically made of quartz or some other transparent material. A filament  16  extends though the tube  14 , and is electrically connected to each of the eyelet terminals  12 . Each eyelet terminal  12  is fastened to the reactor with a brass screw  18  (illustrated as a Philips head) and washer  20 . Thus, when a power source is connected across the terminals  12 , the filament  16  receives current and provides a source of radiant energy in a manner generally known to those of ordinary skill in the art. Unfortunately, the confined space inside the reactor makes removal and retrieval of the screw  18  and washer  20  difficult. Because these lamps are consumed in their operation, they must frequently be replaced with new lamps. This constant replacement increases the potential for the fasteners to be dropped and lost. In addition, a typical reactor contains over 20 lamps (40 eyelets and fasteners), which further increases the potential for dropped fasteners. 
     One proposed solution to this problem is to capture the fastener with the eyelet terminal. As shown in a preferred embodiment,  FIGS. 2A and 3A , a quartz lamp  30  is attached to an eyelet terminal  32  by a wire or conductive connector  34 . An aperture  36  of the eyelet terminal  32  is internally threaded. In this preferred embodiment, a fastener or screw  38  can be tightened with an alien wrench, such that a hexagonal socket is provided in the button head  40 . Of course, alternative drive mechanisms could be used; therefore, any type of screw or bolt could be substituted. An elongated shank portion extends from the button head  40 . The shank has an undercut unthreaded cylindrical middle portion  42  and a threaded end portion  44  terminating in a blunt tip. The captured screw is assembled by threading the screw  38  through the threaded eyelet  32 . After assembly, the unthreaded middle portion  42  freely rotates within the eyelet  36  but the screw  38  is unable to escape the threaded eyelet  32  without deliberate unscrewing. In installing the lamp  30  into the reactor, the threaded end portion  44  can be screwed into the reactor electrodes while the unthreaded middle portion  42  freely rotates within the eyelet  36 . 
     An exemplary semiconductor processing reactor, in which lamps in accordance with  FIG. 1  and in accordance with the embodiments of  FIGS. 2A-15  are employed, is the Epsilon® chemical vapor deposition reactor, commercially available from ASM America, Inc. of Phoenix, Ariz. A description of one configuration of a heating system for the Epsilon® chamber is in U.S. Pat. No. 4,975,561, issued Dec. 4, 1990, entitled “Heating System for Reaction Chamber of Chemical Vapor Deposition Equipment,” the disclosure of which is incorporated herein by reference. For such a context, the lamps described herein preferably each have a 6 kW to 10 kW capacity. 
       FIGS. 2B and 3B  illustrate a modified embodiment, in which the conductive connector  34  includes an extended braided wire lead that aids keeping the screw  38  biased downwardly in contact with the eyelet terminal  32 . The conductive connector  34  is extended through a retaining portion of the eyelet terminal  32 , which is then crimped, such that the extended portion contacts and helps retain the head  40  of the screw  38 . As shown, the eyelet terminal  32  of this embodiment need not have internal threads. 
       FIGS. 4 and 5  show a captured fastener assembly, in accordance with another embodiment of the present invention. The fastener or screw  38  has a button head  40  and an elongated shank portion extending from the head  40 . The shank has an undercut unthreaded cylindrical middle portion  42  and a threaded end portion  44  terminating in a blunt tip. An annular groove  46  ( FIG. 5 ) is provided adjacent the proximal end of the threaded end portion  44 . For retaining the screw member in a captured rotatable relationship with the eyelet, there is provided a retaining snap ring  48  (e.g., E-ring, C-ring). The retaining snap ring  48  includes an annular peripheral rim  50  with a spaced gap  52 . The rim  50  provides engagement within the annular groove  46  of the screw member. The captured screw is assembled by inserting the screw  38 , with or without a washer, through the eyelet terminal  32 . The screw member is captured by having the rim  50  of the retaining snap ring  48  engage in the annular groove  46  of the screw  38 , the ring  48  being positioned on the underside of the eyelet terminal  32 . 
       FIGS. 6 and 7  are a side view and top view, respectively, of a captured fastener assembly, in accordance with still another embodiment of the present invention. The quartz lamp  30  is attached to the eyelet terminal  32  by a conductive connector  34 . The fastener or screw  38  has a hexagonal socket button head  40  and a threaded portion  44  terminating in a blunt tip. Because the eyelet terminal  32  is unthreaded, the screw  38  need not include any unthreaded portion. For retaining the screw  38  in a captured rotatable relationship with the eyelet terminal  32 , the eyelet  32  has an integrated capture portion with three upwardly protruding rectangular tabs  60  spaced evenly around the diameter of its top surface. Instead of the illustrated three bendable tabs, one or more bendable tabs may be used. As shown in  FIGS. 8-9 , the captured screw is assembled by inserting the screw  38 , with or without a washer, through the eyelet terminal  32 . The screw  38  is captured by bending the tabs  60  over the head  40  of the screw  38 . As shown in  FIG. 10 , instead of the illustrated bendable tab configuration, it will be understood that the tabs may be fixed with a compliant shape, for instance, sinuate, that allows the tabs  60  to snap around the screw member head  40  when engaged. 
       FIGS. 11 and 12  are a side view and a top down view, respectively, of a captured fastener assembly, in accordance with yet another embodiment of the present invention. For retaining a screw in a captured rotatable relationship with the eyelet terminal  32 , the eyelet terminal  32  is modified by adding a housing assembly  74 . The housing assembly  74  comprises a conical cap member  76  hingedly connected to the eyelet terminal  32  by an arm  78 . The arm portion  78  is bendable about a radius adapted to place the housing assembly over the eyelet portion in order to capture the screw member head  40  when engaged. A through bore  80  is provided in the top of the cap for screwdriver access to the head of the screw member. The diameter of the bore  80  is selected to be large enough to permit the selected size of a tightening mechanism (not shown) to reach and manipulate the screw, but small enough to prevent lifting of the screw out of the eyelet terminal  32 . 
     In the present example, a catch assembly  82  is provided on the conical cap  76  member to secure it when the cap is engaged, but as an alternative, shown in  FIG. 13 , the catch assembly may be omitted. Returning to  FIGS. 11 and 12 , the catch assembly  82  comprises a fixed rectangular tab  84  outwardly extended from the side of the conical cap member  76  and having a notch  86  at the distal end. The catch assembly  82  further comprises a tab  88  with a compliant catch  90  upwardly extending from the eyelet terminal  32 . As shown in  FIG. 14 , note that the illustrated notch  86  may be omitted such that the catch  90  engages directly to the conical housing assembly  74 . 
     The captured screw is assembled by inserting a screw  38  or screw and washer through the eyelet terminal  32 . The screw member is captured by folding the conical cap member  76  over the head of the screw. If a catch assembly  82  is used, the notched tab  84  of the conical cap  76  engages in the compliant catch  90  of the eyelet terminal  32 . In other arrangements, instead of the illustrated conical cap configuration, it will be understood that the cap may have other geometries, e.g., ring-shaped. 
       FIG. 15  is a side view of a captured fastener assembly, in yet another embodiment of the present invention. The fastener or screw  38  has a hexagonal socket button head  40  and an elongated shank portion extends from the head  40 . The shank has an undercut unthreaded cylindrical middle portion  42  and a threaded end portion  44  terminating in a blunt tip. A circular dovetail  100  concentrically formed around the shank is recessed into the bottom surface of the screw head  40 . Note that the inner diameter of the circular dovetail  100  is smaller than the diameter of the eyelet terminal  32 , but larger than the major diameter of the shank. The eyelet terminal has a generally cylindrical collar  102  upwardly extending from the top surface. The inner diameter of the collar aligns with the inner diameter of the eyelet terminal  32 . The collar  102  has a compliant notch  104  extending radially outward from the top surface. The captured screw is assembled by inserting the screw  38  through the eyelet terminal  32 . The screw member  38  is captured by engaging the circular dovetail  100  of the screw member into the compliant notch  104  of the collar extension  102 . In other arrangements, instead of the illustrated notched collar, it will be understood that the compliant notched engaging member could have other configurations, such as two or more notched tabs, upwardly extending from the top surface of the eyelet terminal. 
     In each of the foregoing embodiments, a screw is captured in an eyelet terminal in the sense that the screw cannot be vertically lifted from the eyelet without deliberate modification to release the screw. However, the screw freely rotates within the eyelet for ready attachment to a corresponding terminal or electrode within a radiantly heated semiconductor reactor. 
     It will be appreciated by those skilled in the art that various modifications and changes may be made without departing from the scope of the invention. Such modifications and changes are intended to fall within the scope of the invention, as defined by the appended claims.