Abstract:
A method of fabricating printheads each having a plurality of nozzle assemblies positioned on a substrate from a plurality of sets of the nozzle assemblies positioned on the substrate includes the step of applying a guard defining a plurality of recesses to the substrate so that each set is located within a respective recess. The substrate is then segmented.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application a continuation application of U.S. application Ser. No. 10/296,660 filed on Aug. 1, 2003 now U.S. Pat. No. 7,063,993, which is a national phase (371) application of PCT/AU00/00583, filed on May 24, 2000, all of which are herein incorporated by reference. 

   FIELD OF THE INVENTION 
   This invention relates to the fabrication of devices incorporating microelectromechanical systems (MEMS). More particularly, the invention relates to a method of fabricating a MEMS device using at least one UV curable tape. For the sake of brevity, such a device shall be referred to below as a MEMS device and the part of the device comprising the microelectromechanical system shall be referred to as a MEMS layer. 
   CO-PENDING APPLICATIONS 
   Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending applications filed by the applicant or assignee of the present invention simultaneously with the present application:
         PCT/AU00/00518, PCT/AU00/00519, PCT/AU00/00520, PCT/AU00/00521, PCT/AU00/00522, PCT/AU00/00523, PCT/AU00/00524, PCT/AU00/00525, PCT/AU00/00526, PCT/AU00/00527, PCT/AU00/00528, PCT/AU00/00529, PCT/AU00/00530, PCT/AU00/00531, PCT/AU00/00532, PCT/AU00/00533, PCT/AU00/00534, PCT/AU00/00535, PCT/AU00/00536, PCT/AU00/00537, PCT/AU00/00538, PCT/AU00/00539, PCT/AU00/00540, PCT/AU00/00541, PCT/AU00/00542, PCT/AU00/00543, PCT/AU00/00544, PCT/AU00/00545, PCT/AU00/00547, PCT/AU00/00546, PCT/AU00/00554, PCT/AU00/00556, PCT/AU00/00557, PCT/AU00/00558, PCT/AU00/00559, PCT/AU00/00560, PCT/AU00/00561, PCT/AU00/00562, PCT/AU00/00563, PCT/AU00/00564, PCT/AU00/00565, PCT/AU00/00566, PCT/AU00/00567, PCT/AU00/00568, PCT/AU00/00569, PCT/AU00/00570, PCT/AU00/00571, PCT/AU00/00572, PCT/AU00/00573, PCT/AU00/00574, PCT/AU00/00575, PCT/AU00/00576, PCT/AU00/00577, PCT/AU00/00578, PCT/AU00/00579, PCT/AU00/00581, PCT/AU00/00580, PCT/AU00/00582, PCT/AU00/00587, PCT/AU00/00588, PCT/AU00/00589, PCT/AU00/00583, PCT/AU00/00593, PCT/AU00/00590, PCT/AU00/00591, PCT/AU00/00592, PCT/AU00/00584, PCT/AU00/00585, PCT/AU00/00586, PCT/AU00/00594, PCT/AU00/00595, PCT/AU00/00596, PCT/AU00/00597, PCT/AU00/00598, PCT/AU00/00516, PCT/AU00/00517, PCT/AU00/00511, PCT/AU00/00501, PCT/AU00/00502, PCT/AU00/00503, PCT/AU00/00504, PCT/AU00/00505, PCT/AU00/00506, PCT/AU00/00507, PCT/AU00/00508, PCT/AU00/00509, PCT/AU00/00510, PCT/AU00/00512, PCT/AU00/00513, PCT/AU00/00514, PCT/AU00/00515       

   The disclosures of these co-pending applications are incorporated herein by cross-reference. 
   SUMMARY OF THE INVENTION 
   According to the present invention there is provided a method of fabricating MEMS devices, the method including the steps of: 
   providing a substrate and a MEMS layer, the MEMS layer arranged on one side of the substrate; 
   applying a further layer arranged to protect the MEMS layer to said one side of the substrate; 
   separating the substrate into discrete parts by performing at least one operation including a back etching operation from a side of the substrate opposed to the side having the MEMS layer, each discrete part carrying at least one MEMS part of the MEMS layer; 
   subsequent to the step of separating the substrate into discrete parts, applying a holding means to said opposed side of the substrate; 
   defining individual chips by performing at least one operation, including an etching operation on the further layer, each of said chips being composed of one of said discrete parts of the substrate, at least one part of the MEMS layer and a part of the further layer; and 
   causing the individual chips to be released from the holding means for removal from the holding means. 
   Preferably the step of defining individual chips is performed after the step of applying a holding means to the substrate. 
   The method may further include the step of bonding the holding means to the substrate. 
   In a preferred embodiment the holding means is bonded to the substrate by means of an adhesive which is curable by exposure to ultraviolet (UV) light and in which the method further includes the step of exposing localized regions of the holding means to UV light to release one chip at a time from the holding means to enable each chip to be removed individually from the holding means. 
   Preferably the method further includes the step of applying a handling means to the holding means, the handling means being transparent to UV light so that UV light is transmitted through the handling means to cure the adhesive of the holding means. 
   It is advantageous if the method includes the step of removing each chip from the holding means by a transporting means. 
   The step of removing each chip from the holding means may include reciprocating each chip individually over a source of UV light. 
   The holding means may be bonded to the layer by means of an adhesive which is curable by exposure to ultraviolet (UV) light. By “curable” is meant that the adhesive loses its adhesive properties when exposed to UV light. Thus, the method may include exposing localised regions of the holding means to UV light to release one chip at a time from the holding means to enable each chip to be removed individually from the holding means. It will be appreciated that the handling means is transparent to UV light so that UV light is transmitted through the handling means to cure the adhesive of the holding means. 
   The handling means may be in the form of a glass, quartz, alumina or equivalent wafer. 
   The method may finally include removing each chip from the holding means by a transporting means. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is now described by way of example with reference to the accompanying diagrammatic drawings in which: 
       FIGS. 1 to 8  show various stages in a method of fabricating MEMS devices, in accordance with the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In an initial step, illustrated at  10  in  FIG. 1  of the drawings, of a method of fabricating a MEMS device, in accordance with the invention, a layer  10  is provided to be applied to a first surface  12  of a silicon substrate or wafer  14 . 
   The wafer  14  carries a surface macromachined MEMS layer  16  on the first surface  12  of the wafer  14 . The MEMS layer  16  comprises individual MEMS elements  18 . 
   The invention has particular application in the manufacture of ink jet printheads. For ease of explanation, the invention will be described with reference to that application. Thus, the layer  10  is a nozzle guard layer or wafer which is applied to the surface  12  of the silicon substrate  14 . Each individual MEMS element  18  is in the form of a nozzle assembly. Each nozzle assembly  18  comprises an ink ejection nozzle and its associated actuator. The actuator acts on the nozzle for effecting ink ejection, on demand. 
   The purpose of the method of manufacture is to form individual MEMS chips  20  ( FIG. 8 ). 
   Hence, after the nozzle guard layer  10  has been applied to the wafer  14 , the wafer  14  is turned over to expose a reverse side  22  as shown in  FIG. 3  of the drawings. 
   Various operations are then carried out on the wafer  14 . In particular, the wafer  14  is back etched, from the surface  22  towards the surface  12  to separate the silicon wafer into discrete parts  24 . In addition, in this application of the invention, ink inlet apertures  26  are etched through the parts  24 . It is to be noted that each part  24  comprises a plurality of MEMS elements  18  and a bond pad  28 . Also, as shown more clearly in  FIG. 1  of the drawings, the layer  10  has a plurality of struts  30  which support a body  32  of the layer  10  in spaced relationship above the surface  12  of the wafer  14  such that the MEMS elements  18  and the bond pads  28  are protected by the body  32 . The struts  30  define chambers  34  and  36 . The chambers  34  overlie the bond pads  28  while the chambers  36  overlie the array of MEMS elements  18  of each part  24 . 
   A holding means in the form of an adhesive tape  38  is bonded to the surface  22  of the layer  14  as illustrated in  FIG. 5  of the drawings. The tape  38  is bonded to the layer  14  by means of a curable adhesive. The adhesive is curable in the sense that it loses its adhesive properties or “tackiness” when exposed to ultraviolet (UV) light. 
   Depending on the equipment used, a handling means in the form of a glass, quartz, alumina or other transparent handle wafer  40  is secured to an opposite surface of the tape  38 . 
   The wafer  40 , the tape  38 , the silicon wafer  14  and the nozzle guard layer  10  define a laminate  42 . The laminate  42  is then turned over, as shown in  FIG. 7  of the drawings. 
   Predetermined operations are carried out on the layer  10 . More particularly, passages  44  are etched through the layer  10  from an outer surface  46  towards the chambers  36 . In addition, individual nozzle guards  48  are formed by etching to remove material as shown at  50  in  FIG. 7  of the drawings. The removal of this material exposes the bond pads  28  of each chip  20 . Upon completion of this operation, the individual chips  20  are formed. 
   In this embodiment of the invention, each chip  20  has a plurality of MEMS elements  18  in an array formed thereon. 
   The laminate  42  is placed on an xy wafer stage (not shown) which is reciprocated, as illustrated by arrow  52  in  FIG. 8  of the drawings. Each MEMS chip  20 , when it is desired to remove it, is exposed to UV light as indicated by arrows  54  through a mask  56 . This cures the adhesive of the tape  40  locally in a region beneath one particular MEMS chip  20  at a time to enable that MEMS chip  20  to be removed from the tape  38 . The MEMS chip  20  is removed from the tape  38  by means of a transporting means including a vacuum pickup  58 . 
   Hence, it is an advantage of the invention, that a method of fabrication is provided which facilitates the performing of various operations to fabricate the individual MEMS chip  20  and which facilitates removal of the MEMS chips  20  for packaging. It will be appreciated that devices of the kind in question are measured in micron dimensions. Accordingly, the MEMS elements  18  on such devices are extremely fragile. The provision of the nozzle guard layer  10  and the use of the UV curable tape  38  facilitates that the MEMS elements  18  are not touched by solids or liquids after they are released by the release etch. 
   It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.