Patent Publication Number: US-2006000719-A1

Title: Method and apparatus for feeding chips to a deposition location in a coating system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of U.S. Provisional Patent Application No. 60/565,293, filed Apr. 26, 2004, the entirety of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to coating systems, in particular, to an apparatus for feeding chips to a deposition location in a coating system. The present invention also relates to an apparatus for feeding chips to a measurement device in a system in which thin layers are deposited onto substrates. The present invention further relates to a method of feeding chips to a deposition location in a coating system.  
     BACKGROUND OF THE INVENTION  
      There are a wide variety of technologies which employ articles having one or more thin layers of materials. Such thin layers can be formed in any of a variety of ways. For example, thin films for use in the field of optics as well as other applications are typically created through deposition processes such as chemical vapor deposition (CVD) and physical vapor deposition (PVD).  
      In a CVD process, a source material is decomposed by heat within a chamber of vacuum or low pressure. The material is subsequently condensed onto a target substrate, which has been biased to attract the vaporized material at a controlled rate to form a film of a specified thickness.  
      In a PVD process, the source material can be vaporized either through sputtering or evaporation. Sputtering methodologies include DC sputtering and RF sputtering. Sputtering involves the bombardment of the source material with a plasma or ion beam. Evaporation methods include thermal evaporation and electron beam evaporation. As with CVD processes, PVD processes occur within a chamber of vacuum or low pressure and the vaporized source material is condensed onto a biased or non-biased substrate at a controlled rate to form a film of a specified thickness.  
      CVD and PVD are just examples of a wide variety of methods employed for depositing a material; the present invention is applicable to any method for depositing a material.  
      In many such devices which include such thin films, it is necessary to precisely monitor one or more parameters of the film or films as they are being deposited, e.g., in many devices, it is important to control the thickness of the thin film or films during the deposition process in order to achieve the desired properties. Therefore precise measurement techniques are required in situ and in real time. For example, in many cases it is important to monitor the thin film growth rate and thickness and to ensure that the deposition process is stopped when the thin film reaches the desired thickness.  
      Microbalances make use of the properties of a piezoelectric material, e.g., a quartz crystal (microbalances are just one example of a type of system to which the present invention is applicable). When a physical force is applied to a piezoelectric material, electric charges build on opposite faces, thereby producing an electric field. By changing these physical forces at a specific rate, an oscillating voltage can be produced. Conversely, when a voltage is applied, the piezoelectric material will deform. Reversal of the polarity of the applied voltage will cause the piezoelectric material to deform in the opposite direction. Therefore, by applying a voltage from an alternating source, the material can be made to oscillate. When a voltage of a specific frequency is applied, the quartz will oscillate with minimal resistance. This frequency is referred to as the resonant frequency.  
      As a thin film is deposited on a piezoelectric crystal through a deposition process, the thickness added by the thin film to the crystal causes the resonant frequency to decrease. By closely monitoring changes in resonant frequency, resolutions of a few angstroms of thickness can be realized. Typically, where such a microbalance is employed, the microbalance is placed near the article or articles being produced, and the conditions to which the microbalance is subjected are caused to be as similar as possible to the conditions to which the article or articles being produced are subjected, so that the thickness or thickness growth detected by the microbalance can be assumed to be approximately similar to the thickness or thickness growth occurring in the article or articles being produced (alternatively, where conditions differ, a tooling factor can be employed).  
      Crystals employed in a microbalance are designed to function effectively for as long as possible, but they all fail eventually; some fail prematurely (sometimes catastrophically). Such failure can occur because the thickness of the material deposited on the crystal just becomes so large that the crystal can no longer function as accurately as needed or desired. Sometimes a crystal cracks or otherwise fails before such a large thickness of material is deposited.  
      In a typical microbalance, microprocessor controlled source voltage and oscillation sensors are connected to the crystal. The source voltage is applied so as to cause the crystal to oscillate at its resonant frequency. As the thin film is deposited on the crystal, the corresponding decrease in the resonant frequency is sensed by the microprocessor through the oscillation sensor. The microprocessor then converts the change in frequency to a deposition rate and thickness.  
      Thin film structures have greatly increased in complexity. Currently, it is not unusual for high-speed optical communications systems to demand stacks of alternating refractive index films which comprise up to 256 layers.  
      The need to shut down a deposition process in order to replace a chip (e.g., a crystal) used in monitoring a deposition process (e.g., thickness of deposited coating or rate of such thickness growth) is certainly a drawback, usually a serious drawback, especially when it occurs during the course of a sequence of depositing a large number of layers.  
      Attempts have been made, with varying success, to provides ways by which a monitoring procedure can be switched from monitoring using one chip to monitoring using another chip without having to shut down a deposition process. There exists, however, an ongoing need for improvements in dealing with situations where there is a desire or need to switch from monitoring using one chip to monitoring using a different chip. This need is particularly critical in light of the ever-increasing complexity of the structures being produced and the ever-increasing degrees of accuracy desired. Moreover, there is an ongoing need for devices which make it possible to switch from monitoring using one chip to monitoring using a different chip in which the chips are reliably positioned with excellent precision. There is further a need for such improvements while minimizing increases in the size of the devices.  
     BRIEF SUMMARY OF THE INVENTION  
      In accordance with a first aspect of the present invention, there is provided a device for storing and feeding chips to a deposition location in a coating system, the device comprising:  
      a holder stack comprising a plurality of holders including at least a first holder and a last holder, the first holder being positioned at a loading position, the last holder being positioned at an opposite end of the stack relative to the first holder, each of the plurality of holders being in contact with at least one other of the holders, any holder in the stack other than the first holder and the last holder being in contact with two others of the holders;  
      a biasing element which applies a force in a first direction to the last holder, thereby applying a force to each of the holders by virtue of the contact among the plurality of holders; and  
      a pushing element which, when actuated, will push the first holder from the loading position to a deposition location where the first holder will be adjacent to or in contact with a portion of an interior surface of a deposition opening defining element, the deposition opening defining element having an opening, the opening being substantially circumscribed by a boundary of the first holder when the first holder is in the deposition location.  
      Preferably, in this aspect of the invention, the device further comprises at least one electrode, a portion of the electrode being located at a contact location such that when the first holder is located at the deposition location and a chip is contained within the first holder, the chip contained within the first holder will make contact with the portion of the electrode.  
      Preferably, in this aspect of the invention, a chip is located within each holder, and each chip comprises a piezoelectric element, a first electrical contact and a second electrical contact, the first and second electrical contacts being spaced from each other and each being in contact with the piezoelectric element, or each chip comprises a glass element, a first electrical contact and a second electrical contact, the first and second electrical contacts being spaced from each other and each being in contact with the glass element.  
      In a further preferred aspect, the device further comprises a deposition system which, when activated, deposits material on a chip located in the first holder when the first holder is positioned in the deposition location.  
      In accordance with a second aspect of the present invention, there is provided a device for storing and feeding chips to a deposition location in a coating system, the device comprising:  
      a housing which defines a holding space;  
      a holder stack positioned within the holding space, the holder stack comprising a plurality of holders including at least a first holder and a last holder, the first holder being positioned at a loading position, the last holder being positioned at an opposite end of the stack relative to the first holder, each of the plurality of holders being in contact with at least one other of the holders, any holder in the stack other than the first holder and the last holder being in contact with two others of the holders;  
      a biasing element which applies a force in a first direction to the last holder, thereby applying a force along the first direction to each of the holders by virtue of the contact among the plurality of holders, the first holder having a first surface which is pushed into contact with a first surface of the holding space by virtue of the force applied in the first direction, the first surface of the holding space being substantially perpendicular to the first direction; and  
      a pushing element which, when actuated, will push the first holder from the loading position along the first surface of the holding space in a direction substantially perpendicular to the first direction to a deposition location where the first holder will be adjacent to or in contact with a portion of an interior surface of a deposition opening defining element, the deposition opening defining element having an opening, the portion of the interior surface substantially circumscribing the opening, the interior surface of the deposition opening defining element being substantially coplanar with the first surface of the holding space, whereby when the pushing element pushes the first holder from the loading position to the deposition location, the first holder will slide substantially smoothly along the first surface of the holding space and the interior surface of the deposition opening defining element.  
      Preferably, in this aspect of the invention, as with the first aspect of the present invention, the device further comprises at least one electrode, a portion of the electrode being located at a contact location such that when the first holder is located at the deposition location and a chip is contained within the first holder, the chip contained within the first holder will make contact with the portion of the electrode.  
      Preferably, in this aspect of the invention, as with the first aspect of the present invention, a chip is located within each holder, and each chip comprises a piezoelectric element, a first electrical contact and a second electrical contact, the first and second electrical contacts being spaced from each other and each being in contact with the piezoelectric element, or each chip comprises a glass element, a first electrical contact and a second electrical contact, the first and second electrical contacts being spaced from each other and each being in contact with the glass element.  
      In a further preferred aspect, the device further comprises a deposition system which, when activated, deposits material on a chip located in the first holder when the first holder is positioned in the deposition location.  
      In accordance with a third aspect of the present invention, there is provided a method of feeding chips to a deposition location in a coating system, the method comprising:  
      loading a plurality of holders into a holding space, each of the holders containing a chip, so that the plurality of holders are in the form of a holder stack including at least a first holder and a last holder, the first holder being positioned at a loading position, the last holder being positioned at an opposite end of the stack relative to the first holder, each of the plurality of holders being in contact with at least one other of the holders, any holder in the stack other than the first holder and the last holder being in contact with two others of the holders, a force being applied to the last holder by a biasing element whereby a force is applied to each of the holders by virtue of the contact among the plurality of holders; and  
      actuating a pushing element to push the first holder from the loading position to a deposition location, where the first holder is in contact with a portion of an interior surface of a deposition opening defining element, the deposition opening defining element having an opening and the opening being substantially circumscribed by a boundary of the first holder.  
      Preferably, the method further comprises applying current through a chip contained in the first holder, between the portion of the interior surface of the deposition opening defining element and at least one electrode in contact with the first chip, and the method further comprises depositing a deposition material onto a surface of the chip by passing a deposition material through the opening and then into contact with the chip.  
      Preferably, in the method of the third aspect of the present invention, when the first holder is moved from the loading position to the deposition location, a second holder is moved by the force of the biasing element to the loading position, and preferably the method further comprises at a later time actuating the pushing element to push the first holder from the deposition location to a spent location, and then actuating the pushing element to push the second holder from the loading position to the deposition location.  
      The invention may be more fully understood with reference to the accompanying drawings and the following detailed description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       FIG. 1  is a sectional view taken along line  1 - 1  in  FIG. 2  and inverted.  
       FIG. 2  is a top view of a device in accordance with the present invention (when the device is in use, it is preferably inverted, i.e., such that the structure shown in  FIG. 2  faces downward).  
       FIG. 3  is a front view of the device.  
       FIG. 4  is a close-up view of a portion of  FIG. 1 .  
       FIGS. 5 and 8  are perspective views of the device of  FIG. 1 , with a housing cover  23  and a cartridge cover  24  (see  FIG. 3 ) removed.  
       FIG. 6  is a perspective view of the device of  FIG. 1 .  
       FIG. 7  is a perspective view of the device of  FIG. 1  with the housing cover  23 , the cartridge cover  24  and the cartridge  25  (see  FIG. 3 ) removed.  
       FIG. 9  is a view of an interior surface of the cartridge cover  24 .  
       FIGS. 10 and 11  are back and front views, respectively, of an embodiment of a preferred holder in accordance with the present invention.  
       FIG. 12  is a side view of the holder shown in  FIGS. 10 and 11 .  
       FIG. 13  is a perspective view of the holder shown in  FIGS. 10-12 .  
       FIG. 14  is a sectional view along the line  14 - 14  in  FIG. 10 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      As noted above, in accordance with a first aspect of the present invention, there is provided a device for storing and feeding chips to a deposition location in a coating system, the device comprising a holder stack, a biasing element and a pushing element.  
      Throughout the present specification, the expression “substantially” is used to mean at least 95% correspondence, e.g., where two planes are characterized as being “substantially parallel”, an angle defined by such planes is not more than about 4.5 degrees, a surface which is “substantially circumscribed” by one or more curves means that the one or more curves include 95% of the length of a curve which circumscribes the surface, “substantially perpendicular” means that an angle defined by a pair of surfaces is within the range of from 85.5 degrees to 94.5 degrees, “substantially coplanar” means that an angle defined by a pair of surfaces is not more than about 4.5 degrees, and/or that 95% of the area of each surface lies within a single plane.  
      The holder stack comprises a plurality of holders including at least a first holder positioned at a loading position and a last holder positioned at an opposite end of the stack relative to the first holder. Preferably, each of the holders has a first surface consisting of one or more sections located in a first plane, a second surface consisting of one or more sections in a second plane, and an outer peripheral edge consisting of one or more sections extending from the first surface to the second surface, the first surface and second surface preferably being of substantially similar shapes and dimensions, the first plane preferably being substantially parallel to the second plane and being spaced from the second plane by a distance which is much smaller than the dimensions of the first and second surfaces, whereby the holders can be substantially aligned in the holder stack, i.e., such that the holder stack has a front surface (the first surface or the second surface of the first holder), a rear surface (the first surface or the second surface of the last holder) and one or more flat or curved side surfaces made up of the outer peripheral edges of each of the holders in the holder stack (that is, where the outer peripheries of each of the first and second surfaces of the respective holders are substantially square with rounded corners, the overall shape of the holder stack is substantially square cylindrical with rounded edges).  
      In a specifically preferred embodiment of a holder in accordance with the present invention, the holder comprises a first surface and a second surface, an opening being located in an interior of the first surface and extending toward the second surface, at least one lip portion having a lip surface positioned between the first surface and the second surface, the lip surface extending into and blocking a portion of the opening, whereby a chip can be inserted into the opening through the first surface and the chip is prevented from passing through the holder by the at least one lip portion.  
      Preferably, one chip is located within each holder. Preferably, each chip fits in the opening with relatively small tolerances, e.g., the largest distance between a periphery of the chip and a surface of the opening is less than 1/10 of the largest dimension of the chip, more preferably less than 1/20 of the largest dimension of the chip, more preferably less than 1/40 of the largest dimension of the chip, even more preferably less than 1/60 of the largest dimension of the chip. Preferably, the tolerance is small enough that the chip is restrained, to at least some degree, from falling out of the opening (in the direction opposite to the lip surface(s)) by virtue of contact between a peripheral edge of the chip and a peripheral edge of the opening.  
      A chip can be generally any article which can be employed in a device which can be employed for monitoring a deposition of material in a coating system.  
      For example, in one embodiment of chips for use according to the present invention, the chips each comprise a piezoelectric element, a first electrical contact and a second electrical contact, the first and second electrical contacts being spaced from each other and each being in contact with the piezoelectric element (such a chip can be used to monitor deposition of material in a coating system by applying current to cause the piezoelectric element to vibrate, and monitoring changes in the resonant frequency of such vibration). Such chips typically have at least one substantially convex or substantially concave surface and/or at least one substantially flat surface. Typically, each such chip can be oriented with either of its two major surfaces facing the deposition material, i.e., the material can be deposited on either surface.  
      In another embodiment of chips for use according to the present invention, the chips each comprise a glass element, a first electrical contact and a second electrical contact, the first and second electrical contacts being spaced from each other and each being in contact with the glass element (such a chip can be used to monitor deposition of material in a coating system by measuring resistivity across a chip as material is being deposited on the chip). For example, such chips can be used as an in situ resistance monitor, which measures the sheet resistance of a film (usually a thin film) during its deposition. Such measurement is critical for manufacturing a number of articles, e.g., flat panel display devices, semiconductors and similar thin film technologies. An example of an in situ resistance monitor is an IRM-4, an in situ four point probe consisting of a square piece of glass (of any suitable size, e.g., up to 2 inches by up to 2 inches by up to 0.1 inch thick, such as about ½ inch by ½inch by 0.020 inch thick or ½ inch by 1.5 inch by 0.020 inch thick), having a deposited pattern which gives a sheet resistance reading when hooked to a power supply-such sensors can generally only be used once per run, making the device according to the present invention particularly useful in connection with such sensors.  
      The biasing element applies a force in a first direction to the rear surface of the holder stack, i.e., to the last holder in the holder stack, thereby applying a force to each of the holders by virtue of the contact among the plurality of holders. The biasing element can include any biasing device or combination of biasing devices, e.g., a spring (linear, torsion or leaf), a piston-cylinder device, a bladder supplied with fluid under pressure, a diaphragm to which pressure is applied, etc. For example, a preferred embodiment of a biasing element for use in accordance with the present invention comprises a linear compression spring, one end of which abuts a fixed structure and the other end of which abuts a first surface of a pressing plate, the pressing plate having a second surface (opposite to the first surface) which applies force to the last holder in the stack. Preferably, the biasing element applies force continuously, although it is possible to construct a device in which the biasing element applies force non-continuously (for example, the biasing element can include a bladder containing fluid to which pressure is applied non-continuously), e.g., only just before the pushing element begins to push a holder from the loading position to the deposition position and while the pushing element pushes a holder from the loading position to the deposition.  
      Preferably, the device includes a housing which defines a holding space having a first end, a second end and one or more sidewalls extending from the first end to the second end, in which the holder stack is positioned. Preferably, the holding space has interior dimensions such that the outer peripheral edges of the holders in the holder stack fit within the holding space with a relatively tight tolerance (e.g., the distance from the outer peripheral edges of each holder to the nearest sidewall of the holding space is less than ⅕ of the largest dimension of the holders, preferably less than ⅛ of the largest dimension of the holders, more preferably less than 1/12 of the largest dimension of the holders, even more preferably less than 1/20 of the largest dimension of the holders). Preferably, the front surface of the holder stack (i.e., the first or second surface of the first holder) abuts the first end of the holding space, and preferably, the force exerted by the biasing element pushes the front surface of the holder stack against the first end of the holding space. Preferably, the biasing element exerts force between the second end of the holding space and the rear surface of the holder stack (i.e., the first or second surface of the last holder in the holder stack). For example, where the biasing element comprises a biasing device (e.g., a compression spring) and a pressing plate, preferably, the biasing device exerts force between the second end of the holding space and the first surface of the pressing plate, and the second surface of the pressing plate is in contact with the rear surface of the holder stack.  
      The device can accommodate at least two holders, preferably at least seven holders, more preferably at least twelve holders, even more preferably about twenty holders (or even more). As holders are fed from the holder stack to the deposition location, the holder stack can be replenished at any suitable time. For example, when the last holder in the holder stack has been fed to the deposition location and needs to be replaced, the holder stack needs to be replenished in order to supply a new holder to the deposition location. Preferably, however, the holder stack is replenished before the last holder is used, preferably at times when the deposition process is shut down, e.g., after completion of a run (that is, when completed products are removed from the coating system).  
      The pushing element, when actuated, will push the first holder from the loading position to the deposition location. For example, in an embodiment which includes a housing which defines a holding space, the pushing element preferably displaces the first holder by being pushed against the first holder, such that an end of the pushing element moves into and occupies the loading position; after actuation of such a pushing element, a first surface of the pushing element preferably will be adjacent to or in contact with the first end of the holding space, a second surface of the pushing element (the second surface of the pushing element being substantially parallel to and opposite the first surface of the pushing element) preferably being in contact with a first surface of a next holder (the first surface of the next holder having been in contact with the second surface of the first holder before the pushing element was actuated), the first surface of the next holder preferably being pushed, by virtue of the force applied to the rear surface of the holder stack by the biasing element, against the second surface of the pushing element (the next holder may also be the last holder, in which case the next holder has a second surface, opposite the first surface of the next holder, which is the rear surface of the holder stack).  
      When positioned at the deposition location, the first holder will be adjacent to or in contact with a portion of an interior surface of a deposition opening defining element. The deposition opening defining element has an opening which is preferably substantially circumscribed by a boundary of the first holder when the first holder is in the deposition location and/or which is preferably substantially circumscribed by the portion of the interior surface to which the first holder is adjacent or with which the first holder is in contact. The opening is provided such that material being deposited can pass through the opening and deposit onto a surface of a chip positioned inside the first holder.  
      The interior surface of the deposition opening defining element is preferably substantially coplanar with the first surface of the holding space, whereby when the pushing element pushes the first holder from the loading position to the deposition location, the first holder will slide substantially smoothly along the first surface of the holding space and the interior surface of the deposition opening defining element.  
      Preferably, there is further provided a deposition system which, when activated, deposits material on a deposition surface of a chip located in the first holder when the first holder is positioned in the deposition location, and which deposits material on one or more other structures contained within a deposition chamber, the deposition location being exposed to the activity in the deposition chamber through the opening in the deposition opening defining element.  
      The device preferably further comprises at least one electrode, a portion of the electrode being located at a contact location such that when the first holder is located at the deposition location and a chip is contained within the first holder, a back surface of the chip contained within the first holder will make contact with the portion of the electrode. Preferably, the at least one electrode is biased, such that the portion of the electrode is urged toward the portion of the electrode. Specifically preferred electrodes for use in accordance with the present invention are pogo pins (such electrodes are well known to those of ordinary skill in the art). Preferably, one or more pogo pins are mounted such that for each pogo pin, a contact portion of the pogo pin extends to an extended location when no external force is applied to the pogo pin, and as a holder is pushed into the deposition location, the pogo pin(s) are retracted due to the force applied by the holder (i.e., in a direction opposite to the direction of the force exerted by the pogo pins) to allow the holder to occupy the deposition location and such that the contact portion of each pogo pin is in contact with a back surface of a chip contained within the holder, and such that each pogo pin exerts a force against the back surface of the chip, thereby maintaining contact between each pogo pin and the back surface of the chip. In a specific preferred embodiment of the present invention, four pogo pins are provided at locations which ensure that regardless of the orientation of the chip within the holder, at least one of the pogo pins is in contact with a contact portion on the chip (i.e., an electrode), thereby ensuring electrical contact between at least one of the pogo pins and the back surface of the chip.  
      Preferably, at least a part of the portion of the interior surface of the deposition opening defining element is an electrical contact. Preferably, the front surface of the chip within the holder in the deposition location is in contact with the electrical contact on the interior surface of the deposition opening defining element. In embodiments where the at least one electrode is biased such that the electrode is urged toward the back surface of the chip contained within the first holder, e.g., where the at least one electrode is one or more pogo pins in contact with the back surface of the chip, as described above, the biasing force preferably pushes the chip on the back surface thereof so that the deposition surface of the chip is pressed against the electrical contact on the interior surface of the deposition opening defining element.  
      Preferably, the electrical contact on the interior surface of the deposition opening defining element and the at least one electrode are electrically connected, e.g., via respective circuitries, to opposite sides of a power source, whereby an electrical circuit is defined by the electrode, the chip in the holder at the deposition location and the electrical contact. Any suitable circuitries can be employed for completing such circuit, and persons of skill in the art can readily select any of a wide variety of suitable circuitries; all such circuitries are within the scope of the present invention.  
      Preferably, e.g., when the chip in the first holder is no longer able to provide the desired degree of accuracy, the pushing element can be further actuated to push a holder from the deposition location to a discard location. The pushing element is retractable, so that it can then be retracted so that the second surface of the pushing element will no longer be in contact with the front surface of the holder stack (i.e., the first surface of the next holder), whereby the holder stack will be pushed by the biasing element such that the next holder is in the loading position, i.e., the next holder occupies substantially the space which was occupied by the first holder prior to the first holder being pushed by the pushing element into the deposition location. In such a way, one-by-one, each of the holders in the holder stack can be moved, in sequence, to the loading position, from the loading position to the deposition location, and, after the chip in the holder has performed its sensing function in the deposition system, from the deposition location to the discard location. As noted above, the holder stack can be replenished, i.e., one or more holders can be inserted, at any time, preferably in between deposition runs.  
      Alternatively, instead of the pushing element first pushing a holder from the deposition location to the discard and then pushing a holder from the loading position to the deposition location, the pushing element can push a holder from the loading position to the deposition location, that holder simultaneously pushing another holder from the deposition location to the discard location.  
      As noted above, in accordance with a third aspect of the present invention, there is provided a method of feeding chips to a deposition location in a coating system, the method comprising:  
      loading a holder stack into a holding space, each of the holders containing a chip, a first holder being positioned at a loading position, a force being applied to the last holder by a biasing element whereby a force is applied to each of the holders by virtue of the contact among the plurality of holders;  
      actuating a pushing element to push the first holder from the loading position to a deposition location.  
      The descriptions of suitable holder stacks, holding spaces, chips, holders, loading positions, biasing elements, pushing elements and deposition locations set forth above are applicable to this aspect of the present invention as well.  
      The method according to the third aspect of the present invention preferably further comprises applying current through a chip contained in the first holder, between the portion of the interior surface of the deposition opening defining element and at least one electrode in contact with the chip.  
      As noted above, the method preferably further comprises passing a deposition material through the opening and then into contact with the chip, on which the deposition material deposits. The depositing can be carried out according to any deposition process, a wide variety of which are well known to those of skill in the art, and can be carried in any deposition chamber or other coating apparatus, a wide variety of which are well known to those of skill in the art, and the present invention encompasses all such deposition processes and coating apparatuses.  
      In accordance with a preferred modification according to the present invention, the chips themselves can be handled as holders, i.e., instead of a holder stack, there can be provided a chip stack, and each chip can be moved through the device in the way that the holders are moved in accordance with the description set forth above. This modification is especially effective in cases where the chips are in situ resistance monitors as described above.  
      A preferred embodiment of a device for storing and feeding chips to a deposition location in a coating system in accordance with the present invention is shown in  FIGS. 1-8 .  FIG. 1  is a sectional view taken along line  1 - 1  in  FIG. 2  and inverted.  FIG. 2  is a top view of a device in accordance with the present invention (when the device is in use, it is preferably inverted, i.e., such that the structure shown in  FIG. 2  faces downward).  FIG. 3  is a front view of the device.  FIG. 4  is a close-up view of a portion of  FIG. 1 .  FIGS. 5 and 8  are perspective views of the device, with a housing cover  23  and a cartridge cover  24  (see  FIG. 3 ) removed.  FIG. 6  is a perspective view of the device.  FIG. 7  is a perspective view of the device with the housing cover  23 , the cartridge cover  24  and the cartridge  25  (see  FIG. 3 ) removed.  FIG. 9  is a bottom view of the cartridge cover  24 .  
      Referring to  FIG. 1 , there is shown a holder stack  10  comprising a plurality of holders  11 - 19  (more easily seen in  FIG. 3 ), including a first holder  11  and a last holder  19 . The holder stack  10  is positioned within a holding space  50 . The first holder  11  is in the loading position. The last holder  19  is positioned at an opposite end of the stack  10  relative to the first holder  11 , and each of the plurality of holders  11 - 19  is in contact with at least one other of the holders. The holders  12 - 18  are each in contact with two others of the holders.  
      A biasing element  20  applies a force in a first direction (downward in the perspective shown in  FIG. 1 ) to the last holder  19 , thereby applying a force to each of the holders  11 - 19  by virtue of the contact among the plurality of holders. Referring to  FIG. 7 , the biasing element  20  comprises a compression spring  21  and a pressing plate  22 . The biasing element thereby exerts force which presses the first surface  51  (see  FIG. 4 ) of the first holder  11  against the first surface  52  of the holding space  50  or against the pushing element  26  (as shown in FIG.  4 ).  
      The pushing element  26  is connected via a connector bar  27  and an actuator  28  to a stepper motor  34  which moves the actuator  28 , the connector bar  27  and the pushing element  26  between a first position (shown in  FIG. 8 ) where the pushing element  26  is to the left (in the perspective shown in  FIG. 1 ) of the loading position, a second position where the pushing element  26  has moved to the right (in the perspective shown in  FIG. 1 ) sufficiently far that the first holder is moved from the loading position to the deposition location (i.e., the arrangement as shown in  FIGS. 1 and 4 ), and a third position where the pushing element  26  has moved to the right (in the perspective shown in  FIG. 1 ) sufficiently far that the first holder is moved from the deposition location to the discard location  28 .  
      The device includes four pogo pin electrodes  29  (see  FIG. 5 ), which are connected electrically, via a plate  30  to a pair of electrical conductors  31  (see  FIGS. 5 and 1 ), which terminate in contacts which electrically connect with a pair of pogo pin electrodes  32  when the cartridge  25  is installed on the base  33  (see  FIG. 7 ). As a holder is pushed by the pushing element  26  from the loading position to the deposition location, the pogo pin electrodes  29  are pushed inward (i.e., toward the plate  30 ) to allow the holder to move into the deposition location, and the biasing of the pogo pin electrodes  29  forces the pogo pin electrodes  29  toward the holder (i.e., away from the plate  30 ) such that the ends of the pogo pin electrodes  29  press against one surface of the chip  35  within the holder. The chip  35  is thereby biased toward an interior surface  37  (see  FIG. 9 ) of the cartridge cover  24 . The exterior surface  38  of the cartridge cover  24  is shown in  FIG. 2 . The interior surface  37  of the cartridge cover  24  includes a contact area  39  which surrounds an opening  40  (see  FIGS. 9 and 2 ) which extends from the interior surface  37  to the exterior surface  38 . The chip  35  is biased (as noted above) and is thereby pressed against the contact  39 .  
      The pogo pin electrodes  32  are electrically connected to contacts through which electrical connection can be made to circuitry exterior to the device. Similarly, the contact  39  is electrically connected to contacts through which electrical connection can be made to circuitry exterior to the device. Accordingly, a circuit can be completed by connecting opposite ends of a source of electrical power to the respective contacts, i.e., one end of the source of electrical power to the contacts which are electrically connect to the pogo pin electrodes  32 , and the other end of the source of electrical power to the contact which is connected to the contact  39 , such circuit being completed by the electrical connection from the contact  39  to the chip  35 , and through the chip  35  to the pogo pin electrodes  32 . The chip  35  has a diameter which is larger than that of the opening  40 . In this embodiment, the interior surface  37  of the cartridge cover  24  functions as the interior surface of a deposition opening defining element as described above, the deposition opening defining element having an opening  40 , the opening  40  being circumscribed by a boundary of a holder which is in the deposition location, and the portion of the interior surface with which such a holder is in contact circumscribing the opening  40 .  
      As a holder is pushed by the pushing element  26  from the loading position to the deposition location, the holder slides smoothly along the interior surface  37  of the cartridge cover  24 . After the holder has been pushed by the pushing element  26  from the deposition location to the discard location  28 , the holder is then free to move, typically by the force of gravity, into an adjacent first discard space  41  formed in the cartridge cover  24  or into an adjacent second discard space  42  (see  FIG. 5 ) formed in the cartridge  25 .  
      The exterior surface  38  of the cartridge cover  24  has a cone-shaped structure  49  into which, during a deposition process, material being deposited passes on its way to coating the exposed surface of the chip (i.e., the surface of the chip which faces the opening  40 ).  
      The cartridge  25  is removably held in place on the base by tightening a set screw  36 . The housing cover  23  and the cartridge cover  24  are removably mounted on the. base  33  and the cartridge  25 , respectively.  
       FIGS. 10 and 11  are back and front views, respectively, of an embodiment of a preferred holder in accordance with the present invention. Referring to  FIG. 10 , the holder has a first surface including regions  43  and  44 ; referring to  FIG. 11 , the holder has a second surface  45 . The holder has an opening  46 . As seen in  FIG. 11 , the holder has first and second lip surfaces  47  and  48  which are on opposite sides of respective lip portions with respect to regions  43  and  44 . In use, a chip is placed in the opening  46  of the holder such that the chip rests on the lip surfaces  47  and  48 . Preferably, the distance from the lip surfaces  47  and  48  to the second surface  45  is greater than the thickness of the chip, such that when a plurality of holders, each containing one chip, are stacked, each chip is in contact with only the lip surfaces  47  and  48  of the corresponding holder.  FIG. 12  is a side view of the holder shown in  FIGS. 10 and 11 ,  FIG. 13  is a perspective view of the holder shown in  FIGS. 10-12 , and  FIG. 14  is a sectional view along the line  14 - 14  in  FIG. 10 . The holder shown in  FIGS. 10-14  thus has a first surface consisting of two sections  43  and  44  located in a first plane, a second surface consisting of one section  45  in a second plane, and an outer peripheral edge  53  consisting a plurality of sections extending from the first surface to the second surface, the first surface and second surface being of substantially similar shapes and dimensions, the first plane being parallel to the second plane and being spaced from the second plane by a distance which is much smaller than the dimensions of the first and second surfaces. A plurality of such holders can therefore be substantially aligned in the holder stack, i.e., such that the holder stack has a front surface (the first surface or the second surface of the first holder), a rear surface (the first surface or the second surface of the last holder) and one or more flat or curved side surfaces made up of the outer peripheral edges of each of the holders in the holder stack. The overall shape of such holder stack will be substantially square cylindrical with rounded edges.  
      Cooling fluid (e.g., water) inlet and outlet pipes  54  are shown in  FIG. 2 , and the construction of such pipes, used to control the temperature of components within the device, in particular, the chips, are well known to those of skill in the art.  
      The various components of the devices according to the present invention can be made of any suitable material, and persons of skill in the art can readily make appropriate selections from among a wide variety of such suitable materials, all of which choices are encompassed by the present invention. For example, the cooling fluid pipes may be formed of stainless steel, the body of the base may be formed of stainless steel or aluminum, the body of the cartridge may be formed of aluminum, the body of the cartridge cover may be formed of aluminum, and the body of the housing cover may be formed of aluminum.  
      Any two or more structural parts of the devices described above can be integrated. Any structural part of the devices described above can be provided in two or more parts which are held together, if necessary. Similarly, any two or more functions can be conducted simultaneously, and/or any function can be conducted in a series of steps.