Patent Publication Number: US-2013248611-A1

Title: Epitaxial Deposition Apparatus, Gas Injectors, and Chemical Vapor Management System Associated Therewith

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35USC§119(e) of U.S. provisional patent application 61/418,104 filed on Nov. 30, 2011, the specification of which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The technical field relates to an epitaxial deposition apparatus and, more particularly, to an epitaxial deposition apparatus for vapor phase epitaxy (VPE) and its associated chemical vapor management system and gas injector. It also relates to a method for epitaxial deposition and gas supply during epitaxial deposition processes. 
     BACKGROUND 
     Epitaxial growth of semiconductor thin films has been used to fabricate systems for a wide variety of applications in electronics and photonics, over many years. The techniques that are used to produce nucleation of crystalline materials over the surface of a crystalline substrate are numerous. For instance, vapor phase epitaxy (VPE) processes provide high level of purity and film quality. VPE uses chemical molecules or atoms in gaseous form for deposition over the surface of a heated substrate during the epitaxy process. Thin layers of high purity materials are deposited on the crystalline substrate. The deposited layer has the same structure than the substrate surface, i.e. the deposited layer atoms are aligned with the substrate atoms. 
     In VPE and more particularly ultra-high vacuum (UHV)-based epitaxial growth techniques, the substrate is inserted in a vacuum chamber. Gases are extracted from the chamber with pumps until the pressure within the chamber is in a high or ultra-high vacuum range (High vacuum range: about 1×10 −3  Torr to about 1×10 −9  Torr 100 mPa to 100 nPa; Ultra-high vacuum range: about 1×10 −9  Torr to about 1×10 −12  Torr; 100 nPa to 100 pPa). In these pressure ranges, the ambient pressure is so low and gas is so rarified that the gas molecules remaining in the chamber do not collide or very rarely do so and travel in the chamber along a substantially straight line. Some molecules hit the substrate surface. The epitaxy process requires that the quantity of molecules that hit the substrate surface is substantially uniform along the substrate surface. Typically the industry standard requires a variation below 1% for several parameters over the surface of the substrate. 
     There is always a need to reduce the production costs while simultaneously maintaining or increasing the resulting product quality. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore an aim of the present invention to address the above mentioned issues. 
     According to a general aspect, there is provided an epitaxial deposition apparatus comprising: a deposition chamber with at least one gas injector having a gas injection surface and a substrate support having a deposition surface; and at least one vacuum pump having an aperture in fluid communication with the deposition chamber and aligned with the gas injection surface of the at least one gas injector, the substrate support being interposed between the at least one gas injector and the aperture of the at least one vacuum pump. 
     According to another general aspect, there is provided an epitaxial deposition gas injector comprising: a circular hollow body having a gas inlet located at a proximal end of the body and an opposed distal end and defining an internal gas conduit; at least one partition wall extending in the internal conduit and dividing the internal gas conduit into a conduit section and an outer conduit section, the partition wall being configured to divide an inlet gas flux into two gas flux portions traveling separately towards the distal end in the outer conduit and back towards the proximal end in the conduit. 
     According to still another general aspect, there is provided an epitaxial deposition apparatus having a reactive gas injector in combination with a gas supply and handling system, the gas supply and handling system comprising: at least two gas supplies, each one of the gas supplies having a first gas conduit connected and in fluid communication with a respective one of the gas supplies; and a gas injector conduit operatively connected to the reactive gas injector, the gas conduit injector being in fluid communication with the first gas conduits. 
     According to a further general aspect, there is provided a gas supply and handling system for an epitaxial deposition apparatus having a gas injector, the gas supply and handling system comprising: a housing defining a chamber and having a partition wall extending therein and separating the chamber into two sections; at least one gas supply mounted in a first one of the chamber section having a gas conduit connected thereto and extending through the partition wall, the gas conduit being in a controllable fluid communication with the gas injector of the epitaxial deposition apparatus; a heating system configured to heat air contained in the chamber; and a control system operatively connected to the heating system and configured to maintain the temperature of the first one of the chamber section at a first temperature and the temperature of the second one of the chamber section at a second temperature higher than the first temperature. 
     According to a further general aspect, there is provided a gas supply and handling system for a gas supply and handling system for an epitaxial deposition apparatus having a gas injector, the gas supply and handling system comprising: a housing defining a chamber; a gas supply and handling assembly including at least one gas supply and at least one gas conduit connected to the gas supply mounted in the chamber, the gas conduit being in fluid communication with the gas injector of the epitaxial deposition apparatus; and a heating system configured to heat air contained in the chamber and the at least one gas conduit extending in the chamber. 
     According to another general aspect, there is provided an epitaxial deposition apparatus comprising: a deposition chamber with at least one gas injector having a gas injection surface and a substrate support having a deposition surface; and at least one vacuum pump having a gas aperture in fluid communication with the deposition chamber and facing the gas injection surface of the at least one gas injector, the substrate support being interposed between the at least one gas injector and the gas aperture of the at least one vacuum pump. 
     According to still another general aspect, there is provided an epitaxial deposition apparatus comprising: a deposition chamber with at least one gas injector configured to propel a gas along a gas flux path in the deposition chamber, and a substrate support having a deposition surface; and at least one vacuum pump having a gas aperture in fluid communication with the deposition chamber, the gas flux path being directed towards the gas aperture of at least one vacuum pump with the substrate support being mounted in the gas flux path between the gas injector and the vacuum pump. 
     In an embodiment, the at least one gas injector propels a gas flux in the deposition chamber along a gas flux path and the gas aperture of the at least one vacuum pump is positioned to accept a majority of the gas flux traveling along the gas flux path. The gas aperture of the at least one vacuum pump can be positioned to accept substantially an entirety of the gas flux traveling along the gas flux path. 
     In an embodiment, the at least one gas injector propels a gas flux with at least one of a normal incidence injection and a grazing incidence injection with respect to the deposition surface of the substrate support. At least one of the gas injector(s) can propel a gas flux with a normal incidence injection wherein the injection surface of the gas injector is substantially parallel to the deposition surface of the substrate support. The gas injector can be positioned substantially centered with at least one of the deposition surface of the substrate support and the gas aperture of the vacuum pump. At least one of the gas injectors can propel a gas flux with a grazing incidence injection wherein the injection surface of the gas injector defines an angle above 0° and below 90° with the deposition surface of the substrate support. Furthermore, at least one of the gas injectors can propel a gas flux with a normal incidence injection wherein the injection surface of the injector is substantially parallel to the deposition surface of the substrate support and at least one of the gas injectors can propel a gas flux with a grazing incidence injection wherein the injection surface of the injector defines an angle above 0° and below 90° with the deposition surface of the substrate support. 
     In an embodiment, at least one gas injector comprises an elongated nozzle. 
     In an embodiment, the gas injector comprises a gas injection surface defined by a plurality of gas injection apertures and the gas flux path extends between the gas injection surface and the gas aperture of the at least one vacuum pump. The gas aperture of the vacuum pump can face the gas injection surface of the at least one gas injector. 
     According to still another general aspect, there is provided a method of epitaxial deposition, comprising: injecting a flux of gas along an injected gas path in a deposition chamber with a gas injector; depositing molecules contained in the injected gas flux on a substrate positioned in the injected gas path; and withdrawing at least a fraction of a remainder of the gas flux with a vacuum pump having a gas aperture facing the injected gas path and mounted downstream of the substrate along the injected gas path. 
     In an embodiment, the gas aperture of the vacuum pump faces a gas injection surface of the gas injector. 
     In an embodiment, the step of “injecting” comprises directing the gas flux towards the gas aperture of at least one vacuum pump. In an embodiment, the step of “injecting” is carried out with at least one of a normal incidence injection and a grazing incidence injection with the substrate. The step of “injecting” can be carried out with a normal incidence injection wherein a gas injection surface of the gas injector is substantially parallel to the substrate. The gas injector can be positioned substantially centered with at least one of the substrate and the gas aperture of the vacuum pump. The step of “injecting” can be carried out with a grazing incidence injection wherein an injection surface of the injector defines an angle above 0° and below 90° with the substrate. 
     According to another general aspect, there is provided an epitaxial deposition gas injector comprising: a body having a gas inlet located at a proximal end of the body and an opposed distal end and defining an annular internal gas conduit; and at least one partition wall extending in the internal gas conduit and dividing the internal gas conduit into at least one inner gas conduit section and at least one outer gas conduit section, the partition wall being configured to divide an inlet gas flux into two gas fluxes traveling along separated paths towards the distal end and back towards the proximal end. 
     According to still another general aspect, there is provided an epitaxial deposition gas injector comprising: a body defining an annular gas channel therein and a gas injection surface, the body having at least one gas inlet in fluid communication with the annular gas channel and at least one partition wall separating the annular gas channel into at least two gas conduit sections to provide a substantially uniform gas flux injected from the injection surface. 
     In an embodiment, the body is toroidally shaped. 
     In an embodiment, the internal gas conduit is divided into at least two inner gas conduit sections and at least two outer gas conduit sections and the gas fluxes travel separately in one of the outer gas conduit sections and the inner gas conduit sections towards the distal end and in the other one of the outer gas conduit sections and the inner gas conduit sections towards the proximal end. The internal gas conduit can be divided into two inner gas conduit sections and two outer gas conduit sections and the gas fluxes can travel separately in the outer gas conduit sections towards the distal end and in the inner gas conduit sections towards the proximal end. 
     In an embodiment, a first one of the gas fluxes travels in the outer gas conduit section towards the distal end and back towards the proximal end and a second one of the gas fluxes travels in the inner gas conduit section towards the distal end and back towards the proximal end. The outer gas conduit section and the inner gas conduit section can be substantially annular shaped. 
     In an embodiment, the gas inlet is radial to the partition wall. 
     In an embodiment, the gas fluxes are separated at the distal end. 
     In an embodiment, the epitaxial deposition gas injector further comprises elongated injection apertures provided along an injection surface of the gas injector to produce a substantially uniform injected gas flux intensity. 
     In an embodiment, the at least one partition wall divides the annular gas channel into at least one inner gas conduit section and at least one outer gas conduit section and wherein at least two gas fluxes travel along separated paths between a first end of the body towards a second end of the body and back to the first end. 
     In an embodiment, the at least one partition wall divides the annular gas channel into at least two inner gas conduit sections and at least two outer gas conduit sections and two gas fluxes travel separately in one of the outer gas conduit sections and the inner gas conduit sections towards a distal end of the body and in the other one of the outer gas conduit sections and the inner gas conduit sections towards a proximal end of the body, opposed to the distal end. The at least one partition wall can divide the annular gas channel into two inner gas conduit sections and two outer gas conduit sections and the gas fluxes can travel separately in the outer gas conduit sections towards the distal end and in the inner gas conduit sections towards the proximal end. 
     In an embodiment, the at least one partition wall divides the annular gas channel into an outer gas conduit section and an inner gas conduit section and a first gas flux travels in the outer gas conduit section from a proximal end of the body towards a distal end of the body, opposed to the proximal end, and back towards the proximal end and a second gas flux travels in the inner gas conduit section from one of the proximal end and the distal end towards the other one of the proximal end and the distal end and back towards the one of the proximal end and the distal end. The second gas flux can travel from the proximal end towards the distal end and back towards the proximal end in the inner gas conduit section. 
     According to another general aspect, there is provided a method for injecting a gas flux with a gas injector, the method comprising: injecting gas in the gas injector at a proximal end thereof; separating the gas into at least two separated gas fluxes upon entrance into the gas injector, the at least two gas fluxes traveling separately along separated gas paths from the proximal end towards an opposed distal end and back towards the proximal end; and expelling gas along the gas paths. 
     In an embodiment, the gas injector comprises a toroidal gas injector body. 
     In an embodiment, the gas is expelled substantially continuously along the gas paths. 
     In an embodiment, a first one of the gas fluxes travels in an inner gas conduit defined in the gas injector and a second one of the gas fluxes travels in an outer gas conduit defined in the gas injector. 
     In an embodiment, the fluxes travel separately towards the distal end in one of outer gas conduit sections and inner gas conduit sections, concentric with the outer gas conduit sections, and back towards the proximal end in the other one of the outer gas conduit sections and the inner gas conduit sections. 
     In an embodiment, the gas is injected radially in the gas injector. 
     According to another general aspect, there is provided a gas nozzle in combination with an epitaxial deposition gas injector, the gas nozzle comprising an elongated nozzle body having a proximal end securable to the gas injector, a distal end opposed to the proximal end and defining a gas output, at least two spaced-apart and elongated tubular walls defining therebetween an elongated gas channel extending along the nozzle body and in fluid communication with the gas injector. 
     According to still another general aspect, there is provided an epitaxial deposition gas injector for deposition on a substrate, the epitaxial deposition gas injector comprising: an injector body having an annular gas channel defined therein and an injection surface; and a nozzle body mounted to the injector body and having at least one elongated gas channel extending therein and a gas output oriented towards the substrate and at a distal end of the at least one elongated gas channel, the at least one elongated gas channel being in fluid communication with the annular gas channel through the injection surface. 
     In an embodiment, the elongated tubular walls comprise a proximal section wherein the elongated tubular walls extend substantially parallel to one another and a distal section wherein the elongated tubular walls are inclined towards a center of the nozzle body. The proximal and the distal sections of the elongated tubular walls can be contiguous. In the distal section, an outer one of two adjacent elongated tubular walls defining one of the gas channel can be less inwardly inclined than an inner one of the two adjacent elongated tubular walls. 
     In an embodiment, the gas injector comprises a plurality of concentric gas conduit sections and the nozzle comprises a plurality of elongated gas channels and each one of the gas conduit sections being in register with a respective one of the elongated gas channels. 
     In an embodiment, the elongated gas channel has an annular shape. 
     In an embodiment, the gas injector comprises at least one gas inlet, and a gas flux direction in the at least one gas inlet is substantially normal to a gas flux direction in the elongated gas channel of the nozzle body 
     In an embodiment, the elongated tubular walls of the nozzle body are concentric with one another. 
     In an embodiment, a length of the nozzle body is longer than a diameter of the nozzle body or the diameter of the gas injector body. 
     In an embodiment, the nozzle body comprises at least two concentric elongated gas channels and the injector body comprises at least one partition wall dividing the annular gas channel into at least two concentric gas conduit sections and each one of the at least two concentric gas conduit sections being in fluid communication with a respective one of the at least two elongated gas channels defined in the nozzle body. 
     In an embodiment, the nozzle body comprises a proximal end mounted to the gas injector body, a distal end opposed to the proximal end and defining the gas output, at least two spaced-apart and elongated tubular walls defining therebetween the at least one elongated gas channel. The elongated tubular walls can comprise a proximal section wherein the elongated tubular walls extend substantially parallel to one another and a distal section wherein the elongated tubular walls are inclined towards a center of the nozzle body. 
     In an embodiment, the at least one elongated gas channel has an annular shape. 
     According to another general aspect, there is provided a method for injecting a gas flux with a gas injector, the method comprising: injecting gas in the gas injector; separating the gas into at least two separated gas fluxes upon entrance into the gas injector, the two gas fluxes traveling separately along separated paths in the gas injector; expelling the gas along the gas paths in a nozzle having at least one elongated channel and being contiguous to the gas injector; and expelling the gas at a distal end of the nozzle towards a substrate. 
     In an embodiment, the method further comprises concentrating said gas prior to expelling gas towards the substrate. 
     In an embodiment, the gas fluxes travel in separated elongated gas channels in the nozzle. 
     In an embodiment, the nozzle comprises at least two concentric and elongated gas channels and the gas fluxes of the gas injector are partially combined in the at least two elongated gas channels of the nozzle and at least two gas fluxes travel separately in the at least two elongated gas channels. 
     In an embodiment, a gas flux direction in the gas injector is substantially normal to a gas flux direction in the at least one elongated channel of the nozzle. 
     According to another general aspect, there is provided a gas supply and handling system for an epitaxial deposition apparatus having a gas injector, the gas supply and handling system comprising: a housing defining a chamber and having a partition wall extending therein and separating the chamber into two chamber sections; at least one gas supply mounted in a first one of the chamber sections and having a gas conduit connected thereto and extending through the partition wall in the second one of the chamber sections, the gas conduit being in fluid communication with the gas injector of the epitaxial deposition apparatus; a heating system configured to heat ambient air contained in the chamber; and a control system operatively connected to the heating system and configured to maintain the temperature of the first one of the chamber section at a first temperature and the temperature of the second one of the chamber section at a second temperature. 
     In an embodiment, the second temperature is higher than the first temperature. 
     In an embodiment, the gas conduit extends through an aperture defined in the partition wall. 
     In an embodiment, the gas supply and handling system further comprises at least one blower in fluid communication with at least one of the chamber sections. 
     In an embodiment, the gas conduit is in controllable fluid communication with the gas injector of the epitaxial deposition apparatus. 
     In an embodiment, the second one of the chamber sections comprises at least two gas conduits extending therein and at least two of the gas conduits extending in the second one of the chamber sections are connected together and merge into a single gas conduit in fluid communication with the gas injector. 
     According to still another general aspect, there is provided a gas supply and handling system for an epitaxial deposition apparatus having a gas injector, the gas supply and handling system comprising: a housing defining a chamber; a gas supply and handling assembly including at least one gas supply and at least one gas conduit connected to the gas supply, the gas conduit being in fluid communication with the gas injector of the epitaxial deposition apparatus and extending in the chamber; and a heating system configured to heat ambient air contained in the chamber. 
     In an embodiment, the chamber of the housing houses at least one of a proximal section of the gas conduit being operatively connected to a respective one of the at least one gas supply and a distal section of the gas conduit. The proximal section of the gas conduit and the at least one gas supply can be surrounded by an ambient air having a first ambient air temperature, and the distal section of the gas conduit can be surrounded by an ambient air having a second ambient air temperature, wherein the second ambient air temperature can be maintained above the first ambient air temperature. The chamber of the housing can comprise at least two chamber sections separated by a partition wall and wherein the at least one gas supply is located in a first one of the chamber sections with a proximal section of the gas conduit being operatively connected to a respective one of the at least one gas supply and extending in the first one of the chamber section and a distal section of the gas conduit extending in a second one of the chamber sections and being in gas communication with the proximal section of the gas conduit. The gas conduit can extend through an aperture defined in the partition wall. The gas supply and handling system can further comprise a control system operatively connected to the heating system and configured to maintain a first ambient air temperature in the first one of the chamber sections at a first temperature and a second ambient air temperature in the second one of the chamber sections at a second temperature. It can further comprise a control system operatively connected to the heating system and configured to maintain a temperature difference between a first ambient air temperature in the first one of the chamber sections and a second ambient air temperature in the second one of the chamber sections. The second ambient air temperature can be higher than the first ambient air temperature. 
     In an embodiment, the gas supply and handling system further comprises at least one blower in gas communication with the chamber. 
     According to still another general aspect, there is provided a method for supplying gas to an epitaxial deposition apparatus, the method comprising: controlling an ambient air temperature in a first chamber housing a distal section of a gas conduit to be higher than an ambient air temperature in a second chamber housing at least one gas supply container in gas communication with a proximal section of the gas conduit, the proximal section of the gas conduit being in gas communication with the distal section of the gas conduit; and supplying gas contained in the at least one gas supply container to a gas injector of the epitaxial deposition apparatus through the proximal section and the distal section of the gas conduit. 
     In an embodiment, the method further comprises controlling the ambient air temperature in the second chamber. 
     In an embodiment, the method further comprises circulating air contained in at least one of the first chamber and the second chamber. 
     In an embodiment, the step of “controlling” comprises heating air contained in at least one of the first chamber and the second chamber. 
     In an embodiment, the step of “controlling” comprises controlling a difference of ambient air temperature between the first chamber and the second chamber. 
     In an embodiment, the method further comprises combining gas circulating in at least two distal sections of gas conduits extending in the first chamber into a single gas conduit in gas communication with the gas injector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a vapor phase epitaxy (VPE) apparatus in accordance with an embodiment; 
         FIG. 2  is a top plan view of the vapor phase epitaxy (VPE) apparatus shown in  FIG. 1 ; 
         FIG. 3  is a sectional view along section lines  3 - 3  of the vapor phase epitaxy (VPE) apparatus shown in  FIG. 2  and wherein a housing including a substrate support is spaced-apart from a vacuum pump assembly; 
         FIG. 4  is a schematic view of a vapor phase epitaxy (VPE) apparatus in accordance with an embodiment; 
         FIG. 5  is a schematic view of a vacuum pump alignment with a normal incidence injection in accordance with an embodiment; 
         FIG. 6  is a schematic view of a vacuum pump alignment with a grazing incidence injection in accordance with an embodiment; 
         FIG. 7  is a schematic view of an apparatus including two gas injectors and two vacuum pumps and combining normal and grazing incidence injections in accordance with an embodiment; 
         FIG. 8  includes  FIGS. 8   a  and  8   b ,  FIG. 8   a  is a perspective view of a toroidal injector with two concentric internal conduit sections in accordance with a first embodiment and  FIG. 8   b  is a perspective view of the toroidal injector with two concentric internal conduit sections in accordance with a second embodiment; 
         FIG. 9  is a perspective view of the toroidal injector shown in  FIG. 8   a  with a base and a corresponding face plate defining an injection surface in accordance with an embodiment; 
         FIG. 10  is a perspective view of a nozzle mounted to a gas injector in accordance with an embodiment; 
         FIG. 11  is a side elevation view of the nozzle mounted on the gas injector shown in  FIG. 10 ; 
         FIG. 12  is a cross-sectional view along section lines  12 - 12  of the nozzle mounted on the gas injector shown in  FIG. 11 ; and 
         FIG. 13  is a perspective view of a housing for enclosing and heating a gas transport conduit network in accordance with an embodiment. 
     
    
    
     It will be noted that throughout the appended drawings, like features are identified by like reference numerals. 
     DETAILED DESCRIPTION 
     Referring now to the drawings and, more particularly, referring to  FIGS. 1 to 3 , a vapor phase epitaxy (VPE) apparatus  20  for chemical beam epitaxy (CBE) and related high and ultra-high vacuum based epitaxial growth techniques will be described. 
     The VPE apparatus  20  has a main housing  22  with a plurality of external components which will be described in more details below. The housing  22  defines a deposition vacuum chamber  24  which is configured substantially vertically. 
     Referring now to  FIGS. 3 and 4 , there is shown that the deposition chamber  24  is configured to receive and support a substrate (or sample) (not shown) on which the gas molecules will be deposited. The sample is mounted on a substrate support (or platen)  26  which can be provided with a rotation system  29  to rotate the sample during the deposition process as it will be described in more details below and a heating system  30  to heat the sample during the deposition process. 
     The deposition chamber  24  is linked to and, more particularly, in gas communication with a gas supply and handling system  32 , which will be described in more details below in reference to  FIG. 13 . In the embodiment shown in  FIG. 4 , gases are injected in the deposition chamber  24  through two injection systems, each one including a gas injector. For instance, the first injection system  34  can be used to inject a first gas such as and without being limitative ammonia (NH 3 ) and the second injection system  36  can be used to inject the other reactive gases. 
     One skilled in the art will appreciate that the apparatus  20  can include one or a plurality of injection systems. Several gases can be injected through the same injector, as it will be described in more details below. 
     In the embodiment shown in  FIG. 4 , the first injection system  34  for ammonia gas ends with a showerhead injector, which includes a disk with a large number of orifices spread around its surface. In an embodiment, the first injector  34  is made of a transparent material to let light through, for instance quartz. This type of injector procures a collimated beam of molecules, directed towards the sample. The other reactive gases (OM) are sent towards the sample through another injector  36  which, in a particular embodiment, is a toroidal injector including several injection apertures defined in an injection surface facing the substrate as it will be described in more details below in reference to  FIGS. 8 and 9 . The different gases are supplied and controlled with the gas supply and handling system  32 . 
     The deposition chamber  24  is also equipped with a suite of in-situ temperature monitoring instruments  38 . One skilled in the art will appreciate that other parameters can also be monitored during the epitaxial deposition process. 
     The sample heating system is usually made of a high temperature heating element mounted in close proximity to the sample support back surface and, more particularly, to the sample back surface. 
     A vacuum pump  42  is mounted behind the sample and the sample support  26 , in the lower portion of the apparatus  20 , i.e. the substrate support  26  is mounted in the gas flux path  28  between the gas injector  34 ,  36  and the vacuum pump  42 . The vacuum pump  42  is mounted downstream of the gas injector(s)  34 ,  36  with respect to the gas flux path  28 . The vacuum pump  42  is in fluid communication with the deposition chamber  24  through a vacuum pump aperture  46  (or gas aperture) and removes the gaseous chemicals from the deposition chamber  24 . To increase the pumping power in the deposition chamber  24 , the vacuum pump aperture  46  is located in direct line with the injected gas molecules trajectory, i.e. the sample support  26  and the vacuum pump  42  are mounted along the gas flux path  28  with the sample and its sample support  26  being interposed between one or more of the injector(s)  34 ,  36  and the vacuum pump  42 . Therefore, a fraction of the molecules that do not reach the sample surface are quickly pumped away and do not increase the background pressure in the deposition chamber  24 . This configuration improves the vacuum pump efficiency. Typically, 20 to 50 wt % of the molecules that do not reach the sample surface are removed through the pump  42 . This percentage is higher than with a conventional configuration wherein the aperture  46  of the vacuum pump  42  is laterally mounted with respect to the substrate, i.e. the aperture  46  is not mounted in the gas flux path  28 . 
     In the embodiments shown in  FIGS. 3 to 7 , the substrate support  26  is spaced-apart from a vacuum pump assembly  42 . In an embodiment (not shown), a valve such as a gate valve and a pendulum valve can be mounted in the deposition chamber  24 , between the substrate support  26  is spaced-apart from a vacuum pump assembly  42 . 
     In an embodiment, the injection surface  44  of the injectors  34 ,  36  is aligned with the withdrawal aperture  46  of the vacuum pump  42  in a manner such that gas molecules expelled from or propelled by the injector  34 ,  36  and traveling in a substantially straight line are directed in the aperture  46  of the vacuum pump  42  if they do not hit the substrate  50 . In the embodiment shown in  FIG. 5 , the gas injector  37  is positioned substantially centered and in line with the deposition surface  48  of the substrate support  50  and the gas aperture  46  of the vacuum pump  42 . However, in an alternative embodiment (not shown), one skilled in the art will appreciate that the injection surface  44  of the injector  34 ,  36  is not compulsorily centered on the aperture  46  of the vacuum pump  42 . The injected molecules that do not directly reach the substrate  50  are directed directly to the main pump and a fraction thereof is removed from the vacuum chamber, without increasing the background pressure. 
     The gas injection surface  44  of the gas injector  34 ,  36  is defined by a plurality of gas injection apertures. In the deposition chamber  24 , the gas flux path  28  extends between the gas injection surface  44  and the gas aperture  46  of the vacuum pump  42 , wherein the vacuum pump  42  is mounted downstream of the substrate  50  along the injected gas path. The gas aperture  46  of the vacuum pump  42  faces the injected gas path. 
     Thus, the gas aperture  46  of the vacuum pump  42  is configured to receive a majority of the incident gas flux  28  that is propelled in the deposition chamber  24  by one or both injectors  34 ,  36 . In an embodiment, the gas aperture  46  of the vacuum pump  42  is theoretically configured to receive substantially the entire gas flux  28 , except the molecules which deposit on the substrate  50 . Thus, a fraction of the remainder of the gas flux  28  is withdrawn from the deposition chamber  24  with the vacuum pump  42  and, more particularly, through the gas aperture  46  of the vacuum pump  42 . 
     As shown in the accompanying figures, the gas flux path  28  can be frusto-conically shaped. The aperture  46  of the vacuum pump  42  should be sufficiently large to cover a majority and substantially all the gas flux  28  which is directed towards the substrate and the vacuum pump  42  and which is not deposited on the substrate. One skilled in the art will appreciate that even if the aperture  46  of the vacuum pump  42  is sufficiently large to cover all the gas flux  28  which is directed towards the substrate and the vacuum pump  42 , only a fraction of the molecules are typically removed from the deposition chamber  24 . 
     In the apparatus  20 , the injectors  34 ,  36  and, more particularly, their injection surfaces  44  have optical access to the sample deposition surface  48  and the vacuum pump  42 . 
     The injectors  34 ,  36  are spaced apart from the substrate  50  to provide a substantially uniform gas flux  28  towards the deposition surface  48  of the substrate  50 . One skilled in the art will appreciate the distance between the injectors  34 ,  36  and the substrate  50  can be varied. 
     Referring to  FIG. 5 , there is shown a first embodiment of a vacuum pump alignment with a normal incidence injection, i.e. the injection surface  44  of the injector  37 , which can be any type of injector, is substantially parallel to the deposition surface  48  of the substrate  50 . In other words, the gas molecule flux injected by the injector  37  is substantially perpendicular to the substrate  50 . In the embodiment shown, the injection surface  44  of the injector  37  is also substantially parallel to the aperture  46  of the vacuum pump  42 . In the embodiment shown, the gas injector  37  is positioned directly in front of the deposition surface  48  of the substrate  50 . In some applications, substrate rotation can be eliminated since the resulting deposition can be substantially uniform. The vacuum pump  42  is positioned directly behind the substrate  50  and the heating unit, if any. A portion of the gas flux  28  molecules will reach the deposition surface  48  of the substrate  50  and a fraction of the remaining portion will directly enter vacuum pump aperture  46 . 
     One skilled in the art will appreciate that the path of injected gas between the injection surface  44  of the injector  37  and the gas aperture  46  of the vacuum pump  42  is substantially frusto-conical. In the normal incidence injection, the molecules located about centrally in the gas flux  28  are propelled substantially perpendicular to the substrate  50 . As mentioned above, the resulting gas flux being frusto-conically shaped, the pump aperture  46  should be large enough to accept a large proportion, substantially the entirety, of the incident gas flux  28 . 
     One skilled in the art will appreciate that the configuration of the vacuum pump  42  can differ from the one shown. For instance, in an alternative embodiment (not shown), the aperture  46  of the pump can define an angle with at least one of the injection surface  44  of the injector  37  and the deposition surface  48  of the substrate  50 . 
     Referring to  FIG. 6 , there is shown a second embodiment of the vacuum pump alignment with a grazing incidence injection, i.e. the injection surface  44  of the injector  37  is angled (between greater than 0° (parallel) and below 90° (perpendicular)) relatively to the deposition surface  48  of the substrate  50 . In other words, the injection surface  44  of the injector  37  and the deposition surface  48  of the substrate  50  are neither parallel nor perpendicular to one another. 
     In the embodiment shown, the injection surface  44  of the injector  37  is also angled (between above 0° (parallel) and below 90° (perpendicular)) relatively to the aperture  46  of the vacuum pump  42 . In the embodiment shown, the deposition surface  48  of the substrate  50  is substantially perpendicular to the aperture  46  of the vacuum pump  42 . 
     One skilled in the art will appreciate that the configuration of the vacuum pump  42  can differ from the one shown. For instance, the aperture  46  of the pump can define an angle (between above 0° (parallel) and below 90° (perpendicular)) with the deposition surface  48  of the substrate  50 . 
     Gas injection at grazing incidence minimizes the size of the injected gas cone and relaxes the requirements for a large gas aperture  46  of the vacuum pump  42 . 
     Referring to  FIG. 7 , there is shown a third embodiment of the apparatus  20  wherein the apparatus  20  includes two gas injectors  37   a ,  37   b  and two vacuum pumps  42   a ,  42   b  and combining normal and grazing incidence injections. Thus, two gas fluxes  28  are injected by the two gas injectors  37   a ,  37   b , each having its own injection surface  44   a ,  44   b , which are deposited on one substrate  50 . The gas injector  37   a  is a toroidal gas injector wherein only a proximal end and a distal end are shown, as it will be described in more details below. A portion of the gas fluxes  28  are recovered by the vacuum pumps  42   a ,  42   b  through their apertures  46 ,  46   b . One skilled in the art will appreciate that the apparatus  20  can include any combination and number of gas injector(s) and vacuum pump(s). Furthermore, the apparatus can be configured to provide normal incidence injection, grazing incidence injection, and combinations of both. 
     The combined normal and grazing incidence injections can be suitable for specific applications. 
     For all injection embodiments described above and illustrated, the deposition surface  48  of the substrate  50  is pointing upwards in the deposition chamber  24 . The injected gas molecules arrive on the deposition surface  48  from above. However, one skilled in the art will appreciate that all these configurations can be flipped vertically for applications where it is desired to have the substrate deposition surface  48  pointing downwards to avoid particulates, for instance. Furthermore, one skilled in the art will appreciated that the substrate, the aperture of the vacuum pump and the gas injector can be oriented in any configuration including orientations wherein the substrate is vertically mounted. 
     One skilled in the art will appreciate that various vacuum pumps can be used. For instance and without being limitative, a turbomolecular (drag) pump, a diffusion pump, an ion pump, a Ti sublimation pump, a cryogenic pump, a rotary pump, a scroll pump, and a diaphragm pump can be used. 
     One skilled in the art will appreciate that various injectors can also be used. For instance and without being limitative, simple injectors with or without nozzle, multi-nozzle injectors, injectors including a low or high temperature preheating, injectors without preheating or spray-shower injectors can be used. 
       FIGS. 8   a  and  8   b  show two embodiments of a section of a toroidal injector  36 , without a face plate  74  (shown in  FIG. 9 ), including a circular hollow shaped body  56  defining an internal conduit and a partition wall  58  dividing the internal conduit into an outer conduit section  60  and an inner conduit section  62  in accordance with an embodiment. The outer and the inner conduit sections  60 ,  62  are concentric. In the embodiments shown, the injector  36  is toroidal shaped with a gas inlet  64  radially oriented with respect to the hollow shaped body  56  and the partition wall  58  at a proximal end  68  thereof. 
     One skilled in the art will appreciate that the gas injector can include more than one gas inlet. Furthermore, the gas inlet can be oriented to another angle than radially with the partition wall. 
     In the embodiment shown in  FIG. 8   a , upon entrance in the injector  36 , gas splits in two spaced-apart fluxes in the outer conduit  60  of the injector  36  and travel along separated paths to an opposed distal end  66  of the injector  36 . Then, the gas fluxes enter in the inner conduit sections  62  of the injector  36  and travel back to the first proximal end  68  still along separated paths. 
     In the embodiment shown in  FIG. 8   b , upon entrance in the injector  36 , gas splits in two spaced-apart fluxes. A first one of the fluxes travels to the opposed distal end  66  and back to the first proximal end  68  in the outer conduit  60  of the injector  36 . A second one of the fluxes travels to the opposed distal end  66  and back to the first proximal end  68  in the inner conduit  60  of the injector  36 . Thus, the incoming flux is separated into two fluxes which travel separately to an opposed distal end  66  of the injector  36  and back to the first proximal end  68 . 
     One skilled in the art will appreciate that alternative embodiments can be foreseen. For instance and without being limitative, in an alternative embodiment, upon entrance in the injector, gas can split in two spaced-apart fluxes in the inner conduit  60  of the injector  36  and travel along separated paths to an opposed distal end  66  of the injector  36 . Then, the gas fluxes enter in the outer conduit sections  62  of the injector  36  and travel back to the first proximal end  68  still along separated paths. 
     For both embodiments ( FIGS. 8   a  and  8   b ), along the gas flux paths in the gas conduit sections, the gas pressure lowers. In other words, when the gas enters the injector  36 , the gas pressure is relatively high. When the gas fluxes reach the distal end  66 , the gas pressure is relatively medium. Finally, when the gas fluxes return to the proximal end  68 , the gas pressure is relatively low in comparison with the pressure at entrance. The toroidal injector  36  with double internal conduits  60 ,  62  provides a substantially uniform gas flux injected from the injection surface  44  since relatively high pressure zones are adjacent to relatively relatively low pressure zones while a relatively middle pressure zone is adjacent to another relatively middle pressure zone. This zone combination provides a substantially uniform gas flux for the entire injection surface  44  of the injector  36 . Thus, the partition wall  58  divides the annular gas channel defined in the body  56  of the gas injector  36  in a manner such that the injected gas flux in the deposition chamber  24  is substantially uniform over the injection surface  44  of the gas injector  36 . Thus, the inner and outer conduit sections are provided in a manner such that the injection surface  44  of the gas injector  36  injects a substantially uniform or equal gas flux in the deposition chamber  24 . 
     In an alternative embodiment, the injector  36  can be donut shaped, toroid shaped, torus shaped, quoit shaped or disk shaped with a plurality of internal conduits  60 ,  62  defined therein to equalize the gas flux injected in the deposition chamber. 
     In an alternative embodiment, one skilled in the art will appreciate that the toroidal injector  36  can include more than two internal conduit sections  60 ,  62 . In an embodiment, the toroidal injector  36  includes an even number of concentric internal conduit sections. In an embodiment, the cross-sectional area of each one of the internal conduit sections, i.e. its diameter, can be the same or can be varied to equalize the injected gas flux. 
     Injection apertures  70  are provided along both internal conduit sections  60 ,  62  of the toroidal injector  36  defined in the injection surface of the gas injector. Gas is expelled from the injector  36  through the injection apertures  70  and towards the substrate  50 . In an embodiment, the injection apertures  70  are conically shaped and provided successively along both internal conduits  60 ,  62 . In another embodiment, the injection apertures  70  are elongated slot shaped as shown in  FIG. 9  with inclined inner walls, i.e. the aperture surface close to the inner conduits is smaller than the aperture surface at the injection surface  44  (or outer surface) of the injector  36 . One skilled in the art will appreciate that the shape, number and configuration of the injection apertures can vary from the one described above in reference to the drawings. For instance and without being limitative, the apertures can be of any shape such as conical, cylindrical, rectangular and the like. 
     In  FIG. 9 , the injector  36  of  FIG. 8   a  includes two main components: a base  72  and a face plate (or cover)  74 . The base  72  has peripheral walls  76  that define an annular gas channel and partition walls  58  that divide the annular gas channel into the internal conduits  60 ,  62  of the injector  36 . The face plate  74  is superposable and securable over the base  72  to partially close the internal conduits  60 ,  62  and control gas release. The face plate  74  defines the injection surface  44  of the injector  36 . In the embodiment, the injection apertures  70  defined in the face plate  74  are quarter annular shaped. As mentioned above, a person skilled in the art will appreciate that the shape of the apertures can vary from the embodiment shown in  FIG. 9 , as mentioned above. 
     The toroidal injector  36  provides a substantially uniform gas flux intensity on a circular surface, without requiring rotation of the substrate  50 . Furthermore, the toroidal injector  36  ensures that a significant portion of the injected gas reaches directly the deposition surface, thereby improving the process efficiency. 
     One skilled in the art will appreciate that several toroidal injectors can be mounted in a concentric relationship. 
     In an alternative embodiment, the injector can have a circular body with substantially annular shaped internal channel defined therein and divided into at least two gas conduit sections. 
     In an alternative embodiment (not shown), the gas injector can have more than one gas inlet. For instance, the gas injector can include two gas inlets mounted at opposed ends of the gas injector body, i.e. one gas inlet is provided at a proximal end of the gas injector body and the other gas inlet is provided at a distal end of the gas injector body. The gas injector body can be similar to the configuration shown in either one of the embodiments shown in  FIGS. 8   a  and  8   b . In a configuration similar to the embodiment shown in  FIG. 8   a , gas flowing from a first one of the gas inlets can travel from a first end (close to its respective gas inlet) towards a second end, opposed to the first end, and back towards the first end, opposed to the first end, in adjacent gas conduit sections. Gas flowing from a second one of the gas inlets can travel from a first end (close to its respective gas inlet) towards a second end, opposed to the first end, and back towards the first end in adjacent gas conduit sections. In a configuration similar to the embodiment shown in  FIG. 8   b , gas flowing from the gas inlets can travel in substantially annular shaped gas conduits, concentric with one another. Thus gas flowing from a first one of the gas inlet flows from a first end (close to its respective gas inlet) towards a second end, opposed to the first end, and back towards the first end in an inner gas conduit. Gas flowing from a second one of the gas inlets can travel from a first end (close to its respective gas inlet) towards a second end, opposed to the first end, and back towards the first end in an outer gas conduit, adjacent and concentric with the inner gas conduit. 
     Referring now to  FIGS. 10 to 12 , there is shown an elongated nozzle  75  mounted to a gas injector, which can be a conventional gas injector or a toroidal gas injector such as the one shown in  FIGS. 8   a ,  8   b , and  9 . In the embodiment shown in  FIGS. 10 to 12 , the gas injector is a toroidal gas injector  36 . 
     The nozzle  75  has an elongated body  77  defined by a plurality of substantially concentric elongated tubular walls  78 ,  79 ,  80   a ,  80   b . More particularly, in the embodiment shown, the nozzle  75  has a tubular and elongated outer wall  79  which extends from a proximal end  83  mounted to the gas injector  36  to an opposed distal end  85 , which corresponds to the gas output of the nozzle  75 . It also includes a tubular and elongated inner wall  78  which also extends from the proximal end  83  to the opposed distal end  85 . The inner wall  78  is spaced apart and concentric with the outer wall  79 . In the embodiment shown, the nozzle  75  also includes two elongated and internal partition walls  80   a ,  80   b , each one of the partition walls  80   a ,  80   b  being associated with a respective one of the inner wall  78  and the outer wall  79  and defining therewith an elongated and annular gas channel  87   a ,  87   b . Thus, the nozzle  75  has an elongated and annular inner gas channel  87   a  which is defined between the inner wall  78  and the innermost one  80   a  of the elongated and internal partition walls  80   a ,  80   b . The nozzle  75  also has an elongated and annular outer gas channel  87   b  which is defined between the outer wall  79  and the outermost one  80   b  of the elongated and internal partition walls  80   a ,  80   b.    
     In the embodiment shown, the two elongated and internal partition walls  80   a ,  80   b  are spaced-apart from one another and concentric with one another and with the inner and outer walls  78 ,  79 . One skilled in the art will appreciate that in an alternative embodiment, the nozzle  75  can include only one partition wall and the partition wall defines the inner gas channel and the outer gas channel with a respective one of the inner wall  78  and the outer wall  79 . 
     In the embodiment shown, the inner gas channel  87   a  of the nozzle  75  is mounted in register with the inner conduit  62  (or conduit sections) of the gas injector  36 . Thus gas flowing in the inner conduit  62  (or conduit sections) of the gas injector  36  then flows in the inner gas channel  87   a  of the nozzle  75  towards the gas output. The inner gas channel  87   a  of the nozzle  75  and the gas injector  36  are thus in fluid communication. Similarly, the outer gas channel  87   b  of the nozzle  75  and the outer conduit section  60  of the gas injector  36  are in fluid communication and mounted in register. Gas flowing in the outer conduit section  60  (or conduit sections) of the gas injector  36  then flows in the outer gas channel  87   b  of the nozzle  75  towards the gas output. 
     If the nozzle  75  is operatively connected to a gas injector similar to the one shown in  FIG. 8   a , the gas expelled from the injector while flowing in the outer gas conduit sections  60  flows in the outer gas channel  87   b  while the gas expelled from the injector while flowing in the inner gas conduit sections  62  flows in the inner gas channel  87   a.    
     The central section of the gas injector  36  is in register with the central elongated channel of the nozzle  75  and no gas flows therein. 
     One skilled in the art will appreciate that several alternative embodiments can be foreseen. For instance and without being limitative, the nozzle  75  can be partition wall free and thus include only one elongated gas channel defined between the inner and the outer elongated walls  78 ,  79 . Moreover, the nozzle  75  can include any number of partition walls and thus any number of gas channels defined therebetween. Thus, the nozzle  75  can include two or more substantially concentric and elongated gas channels. 
     The elongated gas channels can be contiguous or separated by another channel in which no gas flows. 
     In the embodiment shown, the nozzle  75  comprises an elongated channel extending between the inner and outer gas channels  87   a ,  87   b  and defined by the adjacent inner and outer partition walls  80   a ,  80   b . In the embodiment shown, no gas flows in this intermediate channel. However, in alternative embodiments (not shown), the inner and outer gas channels  87   a ,  87   b  can be contiguous to one another with no elongated channel extending therebetween or gas can flow in the intermediate elongated channel. One skilled in the art will appreciate that the configuration of the gas injector  36  will be adjusted accordingly. 
     Similarly, in the embodiment shown, no gas flows in the central channel defined inwardly of the inner wall  78 . However, in alternative embodiments (not shown), the central channel can be filled or gas can flow therein. One skilled in the art will appreciate that the configuration of the gas injector  36  will be adjusted accordingly. 
     In the embodiment shown, the walls  78 ,  79 ,  80   a ,  80   b  are elongated tubular members with a circular cross-section. In alternative embodiments, the  78 ,  79 ,  80   a ,  80   b  can be tubular members having a non-circular cross-section. For instance and without being limitative, their cross-sections can be square, rectangular, triangular, and the like. 
     The gas flow direction in the inner and outer gas channels  87   a ,  87   b  of the nozzle  75  is oriented normal to the gas flow direction in the inner and outer gas conduits  62 ,  60  of the gas injector  36 . Thus, gas flowing in the gas conduits  62 ,  60  of the gas injector  36  flows in a substantially perpendicular direction in the downstream nozzle  75 . The gas channels  87   a ,  87   b  of the nozzle  75  are also oriented substantially normal to the injector gas inlet  64 . Similarly, gas flow direction in the gas inlet  64  is substantially normal (or perpendicular) to the gas flow direction in the gas channels  87   a ,  87   b  of the nozzle  75 . 
     In the embodiment shown, the nozzle  75  is mounted to the original injection surface  44  of the injector body  56 . It replaces the face plate  74  shown in  FIG. 9 . However, in an alternative embodiment (not shown), the nozzle  75  can be mounted to the gas injector  36  including the face plate  74 . 
     The inner, outer, and partition walls  78 ,  79 ,  80   a ,  80   b  can be divided into two sections: a first and substantially straight section  89  (or proximal section) extending from the proximal end  83  towards the distal end  85  and a second and inwardly inclined section  91  (or distal section) extending from the distal end  85 . The first and second sections  89 ,  91  are contiguous. In the first section  89 , the inner, outer, and partition walls  78 ,  79 ,  80   a ,  80   b  extend substantially parallel to one another. In the second section  91 , the inner, outer, and partition walls  78 ,  79 ,  80   a ,  80   b  are inclined towards the center of the nozzle  75 . The second section  91  of the walls  78 ,  79 ,  80   a ,  80   b  are deflectors which direct the gas flow towards the substrate  50  which is mounted downstream of the nozzle  75 . The second section  91  of the walls  78 ,  79 ,  80   a ,  80   b  further concentrates the gas flow towards the substrate  50 . 
     In the embodiment shown, the second section  91  of the innermost wall defining one of the gas channels  87   a ,  87   b  is more inclined inwardly than the second section  91  of the outermost wall defining the respective one of the gas channels  87   a ,  87   b . More particularly, the second section  91  of the outermost partition wall  87   b  is more inclined inwardly than the second section  91  of the outer wall  79 . Similarly, the second section  91  of the inner wall  78  is more inclined inwardly than the second section  91  of the innermost partition wall  87   a.    
     For instance, the angle defined between the walls of the first section  89  and the walls of the second section  91  can range between 25 and 50 degrees and, in a particular embodiment, the angle ranges between 30 and 40 degrees. 
     The length of walls  78 ,  79 ,  80   a ,  80   b  can be similar or different. For instance, in the embodiment shown, the outer walls are longer than the inner walls (including the partition walls). More particularly, the outer wall  79  is the longest wall while the outer partition wall  80   b  is longer than the inner partition wall  80   a  and the inner wall  78  but shorter than the outer wall  79 . Similarly, the inner partition wall  80   a  is longer than the inner wall  78  but shorter than the outer wall  79  and the outer partition wall  80   b . Finally, the inner wall  78  is the shortest wall. 
     Furthermore, the length of each section  89 ,  91  for each one of the walls  78 ,  79 ,  80   a ,  80   b  can vary. In the embodiment shown, the walls  78 ,  79 ,  80   a ,  80   b  are divided by pairs with the outer wall  79  and the outer partition wall  80   b  forming a first one of the pairs and the inner wall  78  and the inner partition wall  80   a  forming a second one of the pairs. The walls  79 ,  80   b  of the first one of the pairs have a longer first section than the walls  78 ,  80   a  of the second one of the pairs. Thus, the inner gas channel  87   a  is shorter than the outer gas channel  87   b.    
     The gas output of the nozzle  75  is closer to the substrate  50  than the gas injector  36 . Thus, the gas flux expelled by the gas injector  36  having an elongated nozzle  75  mounted thereto is more directed and concentrated towards the substrate  50  and enhances the deposition. 
     The length of the inner, outer, and partition walls  78 ,  79 ,  80   a ,  80   b  and the corresponding elongated gas channels  87   a ,  87   b  of the nozzle  75  are longer than its diameter, which substantially corresponds to the diameter of the corresponding gas injector  36 . Thus, the nozzle  75  directs and concentrates the injected gas flux towards the substrate  50 . 
     In the embodiment shown, the nozzle  75  and the gas injector  36  are two components assembled together. However, one skilled in the art will appreciate that in an alternative embodiment, the nozzle  75  and the gas injector  36  can be a single component mounted in the deposition chamber  24 . 
     For high performance deposition, the apparatus  50  must be able to supply very stable and predictable amounts of gas to the sample surface  48 . It should be able to switch the gas flux on and off within a fraction of a second. This level of control can be achieved through the use of a pressure control scheme  82 , where the gas flux is obtained by maintaining a constant pressure inside a control volume that is linked to the vacuum chamber  24  by an orifice that acts as a calibrated leak. 
     Since several different types of reactive process gases are necessary for the operation of the apparatus, it must include several lines with pressure control cells. One problem that can occur during the operation is condensation of the process gases on the line walls and the formation of droplets. Gas condensation must be avoided since it causes harder control of the reactive gas flux. To prevent gas condensation, all metallic surfaces in contact with the reactive gases should be maintained at a temperature that is several tens of degrees Celsius higher that the gas temperature. 
     In the apparatus  20 , this is obtained by enclosing all gas conduit lines  82  in an evacuated and heated cabinet or housing  84  as shown in  FIG. 13 . This ensures a substantially uniform temperature throughout the gas handling system  32 , but it also facilitates the maintenance by avoiding use of heating tapes applied to the gas conduits, which are often used in such systems. The air contained in the housing  84  is evacuated and directed towards a chimney on a regular basis or continuously. Thus, in case of a gas leak, gases contained in the housing  84  are directed in the chimney instead of the ambient air of the laboratory or the plant. 
     Reactive gases flow from gas supplies  86 , typically pressurized gas bottles, where pressure ranges between 0.001 and 20 atmosphere (atm) to an injection zone where pressure is in the order of 0.00001 atm. One skilled in the art will appreciate that gas supplies can include, without being limitative, compressed or pressurized gas, liquids or solids. If the gas supplies contain a liquid or a solid, the latter are supplied in vapor phase to the gas conduits. 
     In an embodiment (not shown), each one of the gas supplies  86  is connected to an individual gas transport conduit  82  which allows gas/fluid communication between their respective gas supply  86  and the injector(s) (not shown). In other words, the individual gas transport conduits  82  are operatively connected to their respective gas supply  86  and their respective injector(s). 
     Valves and other sensors including pressure gauge can be operatively connected to the transport conduits  82  and are part of the gas transport components. 
     In an embodiment (not shown), each gas transport conduit  82  is operatively connected to an individual injector which is mounted in and releases gases in a vacuum deposition chamber. Therefore, the number of injectors is equal to the number of gas supplies  86 . 
     In an alternative embodiment such as the one shown in  FIG. 13 , to reduce the number of injectors, a gas supply and handling system  32  can have a single common downstream conduit with a high hydraulic conductivity connecting together a plurality of upstream gas conduits, each one of the upstream gas conduits being operatively connected to a respective gas supply, and wherein the single common downstream conduit is operatively connected to a common gas injector. 
     Gas transport is carried out in a rarefied state, i.e. the gas molecules almost never interact together and collisions with the conduit walls in which they circulate are rare. For instance, in the rarified state, the gas pressure is below about 0.01 Torr. Therefore, several gases, which require similar injection conditions, such as and without being limitative similar pressures and flow rates, can share the same conduit  82  and the same injector. 
     To substantially prevent condensation on the gas transport conduits  82 , gas temperature in the gas transport conduits  82  and in the injector must slightly exceed the gas temperature in the gas supply bottles  86 , as mentioned above. 
     Referring now to  FIG. 13 , there is shown that the gas supply and handling system  32  is enclosed in a housing  90  having a plurality of horizontal and vertical frame members  92 , which can be made of aluminum, and panels  94  extending between the frame members  92  for defining a chamber  96  containing the gas supplies  86  and the gas transport components. In the embodiment shown, the gas supplies  86  include pressurized gas supply containers and the gas transport components include, amongst others, gas conduits  82 , valves, pressure gauges, and other sensors. 
     The chamber  96  is vertically divided into two sections  96   a ,  96   b  separated by a horizontally extending partition wall  98  and, more particularly, a plexiglass plate. The horizontally extending plexiglass plate  98  has a plurality of holes or apertures  100  defined therein in which the gas conduits  82  extend. The lower chamber section  96   a  includes a plurality of gas supply bottles  86  and relatively short sections of gas conduits  82 , which are referred to as proximal sections of upstream gas conduits  82  that are operatively connected to a respective one of the gas supply bottles or containers  86 . 
     The upper chamber section  96   b  includes the remaining sections of the upstream gas conduits  82  and other gas transport components such as the valves  88  and the manometers. The remaining sections of the upstream gas conduits  82  are referred to as the distal section of the upstream gas conduits  82  which are in gas communication with the proximal sections housed in the lower chamber section  96   a . Thus, the upstream gas conduits  82  extend continuously between the proximal and the distal sections. 
     In a non-limitative embodiment, the ambient air in the lower chamber section  96   a  is maintained at a temperature close to the ambient temperature. The upper chamber section  96   b  has an ambient temperature higher than the lower chamber section  96   a . In an embodiment, the temperature in the upper chamber section  96   b  is a few tens of degrees Celsius above the temperature in the lower chamber section  96   a . For instance and without being limitative, the ambient air temperature in the upper chamber section  96   b  is about 20 degrees Celsius above the ambient air temperature in the lower chamber section  96   a . The plexiglass partition wall  98  and the panels  94  ensure relative thermal insulation between both chambers and between the ambient air external to the housing  90 . One skilled in the art would appreciate that the panels  88 ,  96  and the frame members  92  can be made of other suitable materials and that the shape and configuration of the housing  90  and the gas transport components can differ from the embodiment shown. For instance, materials with enhanced insulating properties can be used for the panels  94  and the partition wall  98 . 
     In the embodiment shown, heated air is introduced in the upper chamber section  96   b  through an aperture defined in one of the panels  88 . Temperature sensor(s) can be mounted in the chamber  96  to control the heating system and maintain a substantially constant temperature. 
     A ventilation system can also be operatively connected to the chamber  96  to evacuate the gases contained therein, if needed. It can further include a control system configured to control the temperature inside at least one of the chamber sections. For instance, the control system can be operatively connected to the heating system and, optionally to the ventilation system. It can be configured to maintain the ambient air temperature in at least one of the chamber sections  96   a ,  96   b  at a predetermined temperature set-point or to maintain the ambient air temperature difference between both chamber sections  96   a ,  96   b  at a predetermined set-point. Thus, appropriate temperature sensors must be provided in the housing  90  to measure the ambient air temperature in at least one of the chamber sections  96   a ,  96   b.    
     In a non-limitative embodiment, the ambient air temperature is measured in both chamber sections  96   a ,  96   b  and each one of the chamber is maintained at its own temperature set-point. In a non-limitative and alternative embodiment, the ambient air temperature is measured in both chamber sections  96   a ,  96   b  and the difference of temperatures is controlled. For instance, the heating system can be operatively connected to only one of the chamber sections  96   a ,  96   b  and the ambient air temperature in this chamber section is adjusted in a manner such that the difference of temperatures between both chamber sections  96   a ,  96   b  is close to the predetermined set-point. 
     One skilled in the art will appreciate that several embodiments can be foreseen for controlling the relative ambient air temperature in chamber sections  96   a ,  96   b.    
     The housing  90  can further include one or several fan(s) or any other appropriate blower(s) than ensure a substantially uniform ambient air temperature in the chamber sections  96   a ,  96   b . Each one of the chamber sections  96   a ,  96   b  can include its own blower or one blower can be operatively connected to both chamber sections  96   a ,  96   b . The fan(s) can be operatively connected to the control system. 
     As mentioned above, several gases, which require similar injection conditions, can share the same conduit  82  and the same gas injector. As shown in  FIG. 13 , several distal upstream gas conduits  82   b  are connected together and in fluid communication in the upper chamber section  96   b . More particularly, in the embodiment shown, gases flowing from three gas supplies  86  and into a plurality of proximal and distal upstream gas conduits  82   a ,  82   b  combine in a manifold  81  and flows outwardly of the housing  90  into a single upstream gas conduit  82   c  which is in fluid communication with a gas injector of the epitaxial deposition apparatus. Thus the number of gas conduits  82  can be reduced in the chamber section  96   b  housing the distal gas conduits  82   b.    
     In the embodiment shown, the housing includes two chamber sections with the gas supply containers  86  and the proximal sections of the gas conduits  82  housed in the lower chamber section and the distal sections of the gas conduits  82  and the other gas transport components housed in the upper chamber section. However, in an alternative and non-limitative embodiment (not shown), one skilled in the art will appreciate that the lower chamber section can house the distal sections of the gas conduits  82  and the other gas transport components while the upper chamber section can house the gas supply containers  86  and the proximal sections of the gas conduits  82 . Furthermore, in another alternative and non-limitative embodiment (not shown), the two chamber sections can be configured side-by-side or spaced-apart from one another. Furthermore, in still another alternative and non-limitative embodiment (not shown), the gas supply and handling system  32  can include more than two chamber sections. 
     Furthermore, in still another alternative and non-limitative embodiment (not shown), the gas supply and handling system  32  can include only one chamber housing either the gas supply containers  86  and the proximal sections of the gas conduits  82  or the distal sections of the gas conduits  82  and the other gas transport components. If the single chamber houses the gas supply containers  86  and the proximal sections of the gas conduits  82 , the ambient temperature in the chamber is controlled to be below the ambient temperature surrounding the distal sections of the gas conduits  82  and the other gas transport components. In the alternative, if the single chamber houses the distal sections of the gas conduits  82  and the other gas transport components, the ambient temperature in the chamber is controlled to be above the ambient temperature surrounding the gas supply containers  86  and the proximal sections of the gas conduits  82 . 
     In a non-limitative embodiment, the deposition chamber  24  is designed to contain a 50 to 300 mm diameter platen  26 . Several apparatuses  20  can be mounted in a cluster with a plurality of chambers  24 . It is appreciated that when the apparatuses  20  are configured in clusters, they can share several components of the apparatuses, for instance the gas supply and handling system. This modular approach allows for progressive upgrades, along with the increased demand. Furthermore, multiple chambers reduce downtime because single chambers can be taken down for maintenance and repairs, while other chambers are operating. 
     The semiconductor films manufactured with the above-described apparatus can be used in telecommunication technologies (electronics and photonics), liquid crystal display backlighting for cell phones and flat screens, high power LED technologies for lighting applications, blue lasers for high density data storage (Blue ray and others), high efficiency, multi-junction, concentrated solar cells, and high energy density electronics for electrical and hybrid motors, for instance and without being limitative. 
     Several alternative embodiments and examples have been described and illustrated herein. The embodiments of the invention described above are intended to be exemplary only. A person of ordinary skill in the art would appreciate the features of the individual embodiments, and the possible combinations and variations of the components. A person of ordinary skill in the art would further appreciate that any of the embodiments could be provided in any combination with the other embodiments disclosed herein. It is understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. Accordingly, while the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.