Abstract:
There is described an apparatus, a tubular laminar flow, plug flow reactor, for making silylamines and particularly trisilylamine (TSA) in high yields from ammonia gas and a monohalosilane gas. The apparatus can be a tubular flow reactor comprising a first portion of the reactor defining a gas entry zone, a second portion of the reactor defining a reaction zone and a third portion of the reactor defining a separation zone, the reaction zone providing a reactant contacting region. Trisilylamine can be recovered in the separation zone in a cold trap collection vessel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of U.S. Provisional Patent Application Ser. No. 61/184,148, entitled “Apparatus And Method For The Production Of Trisilylamine,” filed on Jun. 4, 2009, which is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a reactor for synthesizing silylamines and particularly disilylamine and trisilylamine. 
       BACKGROUND OF THE INVENTION 
       [0003]    Trisilylamine is a useful molecule for use in semiconductor manufacturing. It is stable once produced, but is susceptible to decomposition from excessive reaction conditions and synthesis by products. Dussarrat, et al. U.S. Pat. No. 7,192,626 demonstrated that a stable Silicon nitride film is formed on a substrate by feeding trisilylamine and ammonia into a CVD reaction chamber that contains a substrate. 
         [0004]    Wells and Schaeffer ( J. Am. Chem. Soc.,  88:1, 37 (1996)) discuss a batch method of preparing trisilylamine by the reaction silyl chloride with ammonia. They report the yields of trisilylamine varied depending on the method of mixing and the purity of the reactants. Wells and Schaeffer allowed the reactants to mix in the gas phase by introducing the ammonia from below into a 1 liter bulb containing silylchloride. After introducing the gaseous ammonia very slowly, the reaction bulb and contents were allowed to remain at room temperature for 15 min. Copious amounts of white solid were precipitated on the walls of the bulb as soon as mixing occurred. The product was removed and the trisilylamine recovered. The process yield was about 77% of the theoretical amount of trisilylamine. 
         [0005]    In the batch reactor process, all of monohalosilane is charged into the reactor vessel. Batch size is limited by this initial charge and the size of the vessel. Ammonia gas is then very slowly added into the flask. Reaction conditions will vary in the vessel depending on the initial concentrations of monohalosilane and ammonia and the efficiency of turbulent mixing in the vessel. The mixing is affected by vessel size as well as the efficiency of the mechanical mixing device if one is employed. In addition, during the batch process the silylamines produced are in contact with ammonium halide which is also a product of the reaction. Ammonium halides such as ammonium chloride are catalysts and will disproportionate TSA into silane and other degradation products thereby lowering the yield of TSA. The reaction of silyl halide and ammonia produces heat thereby exacerbating the degradation conditions in a closed reactor vessel. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention is directed to a tubular flow reactor and a process for the synthesis of silylamines which have been found to produce high volumes, at high yield efficiencies of silylamines. The reactor has a unique combination of characteristics found in plug flow and laminar flow devices. This combination of properties results in a high volume high efficiency synthesis of silylamines. The primary silylamine of interest is trisilylamine. Production of disilylamines in commercial quantities is also within the scope of the present invention. 
         [0007]    The present invention is directed to a tubular laminar flow, plug flow gas reactor for synthesis of silylamine comprising: 
         [0000]    (a) a first portion of the tubular laminar flow reactor defining a gas entry zone, a second portion of the tubular laminar flow reactor defining a reaction zone and a third portion of the tubular laminar flow reactor defining a separation zone, the reaction zone providing a reactant contacting region;
 
(b) one or more conduits positioned substantially parallel to the central, longitudinal axis of the flow reactor extending into the gas entry zone and terminating in the reaction zone, the one or more conduits directing a laminar flow of a first reactant gas into the reaction zone;
 
(c) one or more gas entry conduits positioned upstream of the one or more conduits directing a flow of a second reactant gas into the gas entry zone to form a flow of the second reactant gas which passes into the reaction zone;
 
(d) a reaction zone wherein the first reactant gas and the second reactant gas come in contact with one another forming a reactant stream;
 
(e) a gas exit port directing the flow of the reactant stream from the reaction zone to a collection zone;
 
(f) a collection zone comprising a collector removing reaction product from the reactant stream.
 
         [0008]    The internal reactor pressure is maintained at about one atmosphere or less. Preferably the reactor is has an internal pressure of about 100 torr to about 400 torr. 
         [0009]    The present invention is also directed to a process for preparing silylamines in a tubular laminar flow, plug flow gas reactor, comprising: 
         [0000]    (a) directing a flow of a first reactant gas into a reaction zone region of a tube reactor;
 
b) passing a second reactant gas through a conduit into the reaction zone region of the tube reactor containing the first reactant gas thereby forming a laminar flow and plug flow reaction stream wherein the first reactant gas and the second reactant gas react to form silylamines;
 
(c) passing the reaction stream containing silylamines into a collection zone of the flow tube reactor;
 
(d) separating the silylamines from the reaction stream; and
 
(e) maintaining the reactor at a pressure of about one atmosphere or less.
 
Preferably maintaining the reactor internal pressure at about 100 torr to about 400 torr.
 
         [0010]    The complete reaction is: 
         [0000]      4NH 3 +3SiH 3 X→3NH 4 X+(SiH 3 ) 3 N 
         [0011]    It is believed that the silylamines of the present invention are produced in accord with the following reaction sequence: 
         [0000]      2NH 3 +SiH 3 X →NH 4 X+SiH 3 NH 2    
         [0000]      2SiH 3 NH 2 →NH 3 +(SiH 3 ) 2 NH 
         [0000]      3(SiH 3 ) 2 NH→NH 3 +2(SiH 3 ) 3 N 
         [0000]      X=Cl, F, Br, I 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Specific embodiments of the invention are described below with reference to the following. 
           [0013]      FIG. 1  is a cross section view of the tubular reactor and a collection vessel. 
           [0014]      FIG. 2  is a cross section view of the gas entry zone and the reaction zone. 
           [0015]      FIG. 3  is a cross section view of the gas entry zone and the reaction zone. 
           [0016]      FIG. 4  is a cross section view of the tubular reactor with multiple gas entry conduits. 
           [0017]      FIG. 5  is a cross section view of the gas entry zone with multiple gas entry conduits and the reaction zone. 
           [0018]      FIG. 6  is a view of the solids accumulator, load lock gate valve, entry zone and reaction zone. 
           [0019]      FIG. 7  is a simplified schematic diagram of a flow reactor of the invention. 
           [0020]      FIG. 8  is a photograph of the inside of the reaction zone after the process has been run. 
           [0021]      FIG. 9  is a gas chromatogram of the reaction product of the invention taken from the collection vessel when the vessel temperature was about −78° C. 
           [0022]      FIG. 10  is a gas chromatogram of the reaction product of the invention taken from the collection vessel when the vessel temperature was allowed to warm to about 20° C. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    The invention relates to a flow reactor and a process that promotes reaction conditions suitable for a high volume high efficiency synthesis of silylamines. The primary silylamine of interest is trisilylamine. Production of disilylamine in commercial quantities is also within the scope of the present invention. 
         [0024]    The reactants are contacted in a manner that optimizes reaction conditions thereby avoiding excessive reaction conditions which can result in product decomposition and the formation of synthesis byproducts, notably silane and silazane polymers. For example, the tubular reactor causes the ammonium halide product of the reaction to stay in the tube while the gaseous products such as disilylamine and trisilylamine flow out of the reactor and are collected in a cold trap vessel substantially free of ammonium halide. The ammonium halide byproduct of the synthesis is crystalline under reaction conditions, so it generally deposits on the side wall of the reactor or falls to the bottom of the reactor while the gaseous products continue to travel up the reactor, that is down stream, and out of the reactor. The reactor tube may be positioned horizontal or vertical with vertical positioning being preferred. 
         [0025]    In the present process, the reaction stream is initially not homogeneous and is gradually heated within the reaction zone as the reaction products form as the reaction is exothermic. At first, as the reactant gases enter the reaction zone, the initial flow is laminar. The reaction rate is controlled by the rate of diffusion across the barrier between the first reactant entering from the conduit at the beginning of the reaction zone and the second reactant which entered the reactor from the conduit in the gas entry zone. As the reaction occurs, particulate ammonium halide, gaseous silylamines and heat are produced which combine to cause mixing of reactants to occur. During this reaction caused mixing process, the reacting gases continue to move along the length of the reaction zone in a plug flow manner to the collection zone in a unilateral rather than a turbulent flow. The ammonium halides produced during the reaction fall out of the gas stream as they are formed. An optional filter at the down stream end of the reactor or optionally in the tubing connecting the reactor to the collection vessel removes all residual fine particulates from the gas stream as the gases leave the reactor reaction zone. Removing ammonium halide from the product stream eliminates the catalytic degradation of TSA by ammonium halide in the collection vessel. As the mixing reactants progress through the reaction zone, the concentrations of both of the reactant gases decreases thereby avoiding detrimental side reactions from occurring as the result of the formation of a large excess of one reactant coming in contact with the other reactant. 
         [0026]    In contrast, in a batch reactor, the reactant entering the reactor will have the same concentration at the beginning of the batch process as at the end of the batch process. However, the concentration of reactant initially charged into the batch reactor will continually drop as the reaction continues. The resulting localized concentration inequities of the reactants may cause detrimental side reactions to occur causing low yields and making product purification more difficult. 
         [0027]    Referring to the drawings, in  FIG. 1  there is a flow reactor  100  vertically disposed and having a generally tubular configuration. A flow reactor can provide continuous production. The reaction zone  110  commences down stream of the opening  104  of the second conduit  102 , which is positioned in the upstream inlet zone  109  of the flow reactor and substantially parallel to the central longitudinal axis of the flow reactor, and continues to the reaction zone exit  106  where the gaseous products flow into the separation zone through opening  107  into tube  111  into the collection vessel  112  which is sitting in a cold bath  114 . The silylamine reaction products  113  are collected in the collection vessel  112 . The downstream end of the reaction zone  110  may optionally contain a filter  105  for the removal of particulates such as ammonium halide from the gas stream. Optional filter  105  may be any non-reactive filter media. Typical filter media useful in the present invention include and are not limited to glass frits, metal frits, glass wool, gas permeable membranes and the like. A preferred type of filter useful in the present invention is the GasShield® POU filters, all metal filters for removal of particulates from a gas stream. GasShield filters are available from the Mott Corporation, Farmington, Conn. A GasShield® POU filter and similar filters would be placed after the reactor exit  107  and before the collection vessel  112 . Non-reactive filter media is defined as a filter media that does not interact with the carrier gases, reactants, reaction products including the silylamine products of the reaction thereby consuming a portion of the reactants or silylamine products reducing yield and/or causing the final product to be contaminated with impurities caused by a chemical reaction between the filter media and the carrier gases, reactants or products of the reaction. 
         [0028]      FIG. 2  illustrates an embodiment of the present tubular flow reactor wherein the inlet conduit  101  enters the inlet zone at the end  108  of the reactor tube. Inlet conduit  102  is positioned to pass through the upstream end  108  of the reactor tube and extend into the reactor tube. The internal end of conduit  102  is the point at which the reaction zone  110  of the tubular reactor begins and the inlet zone  109  ends. The conduit  102  is substantially parallel to the central longitudinal axis of the flow reactor. 
         [0029]    Flow rates of the gases passing through the reactor will depend on the diameter of the reactor as well as the number of inlet conduits used and the internal pressure of the reactor during operation and the length of the reactor. Optimal flow rates for a given reactor configuration may be determined by determining the percent of theoretical yield for a series of synthesis runs with increasing flow rates. Both reactant gases enter the reactor through conduits. The conduits may enter the reactor tube through the side wall of the reactor or through the base. 
         [0030]    The reactor is run at reduced pressure to assure that the reaction products, disilylamine and trisilylamine remain in the gas state until collected in the cold collection vessel. The reactor may be operated at ambient pressure if the reactor and exit conduits are heated sufficiently to maintain the reaction products, disilylamine and trisilylamine, in the gas state until collected in the cold collector vessel. The boiling point of trisilylamine is 52 degrees Celsius. 
         [0031]      FIG. 3  illustrates an embodiment of the present tubular flow reactor wherein the inlet conduit  301  enters the inlet zone at the upstream end  108  of the reactor tube. Inlet conduit  302  is positioned to pass into and through conduit  301  through the upstream end of the reactor tube  108  and extend into the reactor tube  300 . The internal end  303  of conduit  302  is the point at which the reaction zone  110  of the tubular reactor begins and the inlet zone  109  ends. The conduit  302  is substantially parallel to the central longitudinal axis of the flow reactor. Conduits  301  and  302  are preferably concentric. 
         [0032]      FIG. 4  illustrates an embodiment of the tubular flow reactor wherein the inlet conduit  401  enters the inlet zone at the upstream end  408  of the tube reactor  400 . Inlet conduits  402  A, B and C enter the reactor through the side wall of the reactor and have corresponding openings  404  A, B and C. The three conduit outlets  404  A, B and C also called nozzles are positioned so that the reactant outlets are substantially parallel to the central longitudinal axis of the flow reactor. 
         [0033]    The reactant gas entering through each of conduits  402  A, B and C may be the same reactant gas or different reactant gases or different concentrations of reactant gases or different flow rates of the reactant gases. The reaction zone  410  has a wider diameter commencing down stream of the conduit opening  404  A. The wider diameter of the tube reactor may commence at any point downstream of the inlet zone. The gaseous reaction products flow through reaction zone  410  through optional filter  405  into the separation zone through tube  411 . The filter  405  removes particulate ammonium halide, which forms during the reaction, from the gas stream. Optional filter  405  may be any non-reactive filter media. Typical filter media useful in the present invention include and not limited to glass frits, metal frits, glass wool, gas permeable membranes and the like. Non-reactive filter media is a filter media that does not interact with the carrier gases, reactants or silylamine products of the reaction thereby consuming a portion of the reactants or silylamine products reducing yield and/or causing the final product to be contaminated with impurities caused by a chemical reaction between the filter media and the carrier gases, reactants or products of the reaction. The filter may be placed in the down stream end of the reactor tube or may be placed outside of the reactor in the exit conduit  411 . A preferred type of filter useful in the present invention is the GasShield® POU filter. 
         [0034]      FIG. 5  illustrates an embodiment of the inlet portion of present tubular flow reactor invention wherein the inlet conduit  501  enters the tubular reactor through the side wall  505 . The first reactant is delivered through conduit  501  into a chamber  507  at the upstream end of the reactor  500 . Holes  503  in wall  506  which separates chamber  507  from the remainder of the reactor allow the first reactant to pass into the entry zone  509 . Second conduit  502  with openings  504  which are positioned down stream of holes  503  and are substantially parallel to the central longitudinal axis of the flow reactor. 
         [0035]    The diameter of the reactor tube is selected based on the amount of product to be made per hour. Larger tubes may produce more product. Shape of the reactor tube is not critical. Cylindrical reactors are preferred and are easier and less expensive to fabricate. Non-limiting examples of cross section tube shapes useful in the present invention include circular, oval, elliptical, square and rectangular. Reactor tubes may be made out of materials that do not react with the reactants or products of the synthesis of silylamines. Non-limiting examples of reactor materials are steel, glass, &amp; polymers such as Teflon (tetrafluoroethylene) &amp; Kel-F (polychlorotrifluoroethylene). 
         [0036]      FIG. 6  illustrates an embodiment of the inlet portion of present tubular flow reactor with the reactor tube being substantially vertical further comprising a solids accumulator vessel  606  for collecting particulate ammonium halide  607  reaction product. During the course of the reaction to form silylamines, ammonium halide is formed. The ammonium halide  607  is crystalline and has been observed to adhere to the sidewalls of the reaction zone and collect on the bottom of the reactor. The reservoir  606  is connected to the upstream base (bottom) of the reactor either directly or with a gate valve  605 . During operation of the reactor with a gate valve, the gate valve may be opened or closed. Ammonium halide  607  will accumulate at the bottom of the reactor, in reservoir  606 , during operation of the reactor. Accumulation of the ammonium halide in the reservoir will permit longer operation of the reactor between cleanings. The accumulated ammonium halide is removed from the reactor between runs to avoid clogging. 
         [0037]      FIG. 7  is a flow diagram of the flow through reactor set to produce silylamines from ammonia gas and a monohalosilane. Ammonia gas in tank  701  is fed through conduit  703  to flow controller  705  through valve  707  into the upstream end of rector  711 . The monohalosilane in tank  702  is fed through conduit  704  to flow controller  706  through valve  708  into the upstream end of reactor  711 . The silylamine product leaves the reactor in conduit  716  through valves  715  and  717  into the cold trap collection vessel  718 . The silylamines are captured in cold trap  718 . The effluent from collection vessel  718  can be vented through conduits  719  and  727 . Optionally, the effluent of collection vessel  718  may be passed into collection vessel  721 . Vessel  721  is a cold trap maintained a temperature colder than about −140° C. Vessel  718  is maintained at a temperature of about 20° C. to about −110° C., preferably from about −50° C. to about −110° C. Pressure gages  703  A,  704 A,  712 ,  714  and  728  monitor pressure throughout the system. Conduit  710  is the manifold vacuum line. Conduits  722 ,  723 ,  727 , and  724  are used to control the pressure in the reactor. Prior to operation, the system is purged with a flow of gas that is not reactive with the reagents such as hydrogen, nitrogen and helium or the like. The purge gas may enter the system through the ammonia or monohalosilane input lines or both. Once the system is purged, pressure in the system is reduced and controlled by opening valves  709 ,  720 ,  725  and  726  until the desired internal pressure in the reactor is achieved. Conduit  710  is a vacuum line when the reactor is being run at reduced pressure. Typically, the reactor is run at a pressure from about 100 torr to about 400 torr, preferably from about 200 torr to about 300 torr. The reactor may be run at ambient pressure if the reactor  711  and exit conduits  716  and  717  are heated sufficiently to keep the silylamine reaction products in the gas state. 
         [0038]      FIG. 8  is a photograph of the inside of the reaction zone of the tubular reactor after a synthesis run to produce trisilylamine from ammonia and monochlorosilane. The photograph shows a deposit of crystalline ammonium chloride on the inside walls of the reaction zone. 
         [0039]    The present invention is also directed to a process for preparing silylamines in a tubular laminar flow plug flow gas reactor comprising: 
         [0000]    (a) directing a flow of a first reactant gas into the reaction zone of a tube reactor;
 
b) passing a second reactant gas through a conduit into the reaction zone of the tube reactor containing the first reactant gas thereby forming a laminar flow plug flow reaction stream wherein the first reactant gas and the second reactant gas react to form silylamines;
 
(c) passing the reaction stream containing silylamines into a collection zone;
 
(d) separating the silylamines from the reaction stream; and
 
e) maintaining the reactor at a pressure of about one atmosphere or less.
 
         [0040]    Preferably maintaining the reactor internal pressure at about 100 torr to about 400 torr. 
         [0041]    Ammonia and monohalosilane are metered into a vertical tubular reactor from the bottom. The gases are fed through different conduits to avoid premature reaction in the conduits. An excess of about 2 mole % to about 20 mole % of monohalosilane is normally used. The pressure is maintained at a value of about 100 to about 400 torr. If the reactor is heated, either externally or by capturing the heat of reaction, the pressure in the reactor may be raised accordingly. The boiling point of TSA is 52° C. at 1 atmosphere. Heating the reactor and outlet tubing to 60° C. would be sufficient to avoid TSA condensation in the reactor and outlet tubing when the reactor is run at 1 atmosphere. In addition, running the reactor at about 1 atmosphere, allows the TSA product to be in a collector vessel maintained at about 0° C. to about 20° C. The reaction is exothermic and hence the walls of the reactor get warm as the process progresses. The gases react to form substantially disilylamine and trisilylamine and ammonium halide. The waste product, ammonium halide, is a solid and partially sticks to the reactor walls or falls to the bottom of the reactor. Disilylamine and trisilylamine exit through the top of the reactor then move to a collection vessel, kept in a cold bath—dry ice/isopropyl alcohol (IPA) or liquid nitrogen (LN2). Disilylamine, trisilylamine and excess monohalosilane and any reaction by-products are collected in the collection vessel. It has been found that a slight excess of monohalosilane prevents or reduces formation of unwanted by-products such as higher molecular weight silazanes and silane. Upon standing in the receiver container, the condensed disilylamine produced in the reaction converts to trisilylamine. This conversion reaction is fast at temperatures at or above about 0° C., &amp; is believed to proceed via: 
         [0000]      3(SiH 3 ) 2 NH→NH 3 +2(SiH 3 ) 3 N 
         [0042]    Aylett and Hakim,  Inorg. Chem.,  1966, 5 (1), p 167, reported that in the gas state, at about 150° C. for 3 hours, DSA did not convert to TSA and that in the liquid state, at about 0° C. DSA converted to TSA in about 80% yield in 72 hours, Monohalosilanes useful in the present invention include monofluorosilane, monochlorosilane, monobromosilane and monoiodosilane. Monochlorosilane is preferred. 
         [0043]    In an embodiment of the invention, ammonia and monochlorosilane (MCS) are metered into a vertical tubular reactor from the bottom. The gases are fed through different conduits and through different nozzles to avoid premature reaction in the delivery conduits. A slight excess of about 2 mole % to about 20 mole % of MCS is normally used. The pressure is maintained at a value below the room temperature vapor pressure of TSA (258 torr @ 20° C.) usually about 100 torr to about 200 torr. The gases react to form disilylamine, trisilylamine and ammonium chloride. The waste product, ammonium chloride, is a solid and effectively sticks to the reactor walls or falls to the bottom of the reactor. Disilylamine and trisilylamine exit through the top of the reactor to a collection vessel, kept in a cold bath—dry ice/isopropyl alcohol (IPA) or liquid nitrogen (LN2). The silylamines are collected in the receiver container. The reaction between ammonia and MCS is exothermic and hence the walls of the reactor get warm as the process progresses. It has been found that a slight stoichiometric excess of monohalosilane to ammonia prevents or reduces formation of unwanted by-products such as silazanes and silane. Preferably, the molar ratio of monohalosilane to ammonia is about 1 to about 1.2. The preferred monohalosilane is monchlorosilane. 
       Example 1 
       [0044]    23 gm of Ammonia and 87 gm of monochlorosilane (MCS) are metered into a vertical tubular reactor from the bottom. The gases were fed through different lines and through different nozzles, as illustrated in  FIGS. 1 and 7 , to avoid premature reaction in the delivery lines. Ammonia was fed into the reactor at a rate of 0.38 gm/min. Monochlorosilane was fed into the reactor at a rate of 1.45 gm/min. This is an excess of about 29 mole % of MCS. The total run time was 60 minutes. The pressure in the reactor was maintained at about 100 to about 200 torr. The gases react to form disilylamine, trisilylamine and ammonium chloride. The reaction is exothermic and hence the walls of the reactor became warm as the process progressed. The gaseous reaction products exited through the top of the reactor to a collection vessel. The collection vessel is kept in a cold bath—dry ice/isopropyl alcohol (IPA) which creates a temperature of about −78° C. Disilylamine, trisilylamine are collected in the collection vessel. The yield of was greater than 95% of the theoretical. 
         [0045]      FIG. 9  is a chromatogram of the product in the gas flowing in the line between the reactor outlet and the cold trap inlet at 20 minutes after the start of the run described in Example 1. A large peak  901  of disilylamine can be seen at a retention time of about 5.5 minutes a much smaller peak  902  of trisilylamine can be seen at a retention time of about 6.2 minutes. Monochlorosilane  903 , which was added in excess to the reactor, is at a retention time of about 3.6 minutes while silane, an impurity from MCS, is at a retention time of about 2.9 minutes. In  FIGS. 9 and 10 , time is increasing, left to right, on the X axis and detector response, Y axis, is increasing from bottom to top. 
         [0046]    After the reaction was completed, the collection vessel was allowed to warm to about 20° C., this took 85 minutes, and a second chromatogram was then determined,  FIG. 10 . In the chromatogram of  FIG. 10 , only a trace of disilylamine  1001  (&lt;0.1%), can be seen at a retention time of about 5.7 minutes a much larger peak  1002  of trisilylamine can be seen at a retention time of about 6.4 minutes. Monochlorosilane  1003 , which was added in excess to the reactor, is at a retention time of about 3.8 minutes while silane, an impurity from MCS, is at a retention time of about 3.1 minutes. The appearance of the double peak of TSA is an artifact caused by detector saturation. The yield of Example 1 was greater than 95% of the theoretical. 
         [0047]    The chromatograms of  FIGS. 9 and 10  were determined under the following conditions: 
         [0048]    Column: Rtx-1, 105 meter, 0.53 mm ID, 5 micron film. 
         [0049]    Chromatograph: GC-MS system consisting of a Hewlett-Packard 5890 gas chromatograph using helium carrier gas and thermal conductivity and a Hewlett-Packard 5970 mass spectrometer. 
         [0050]    Temperature program: 35 C/5 minutes initial hold time, 70 C/minute ramp, 175 C/10 minutes final hold time. 
         [0051]    Sample introduction: 6-port Valco gas sample valve, 1 ml sample loop, sample pressure 50 torr. 
         [0052]    Chromatograms,  FIGS. 9 and 10 , are plotted as increasing time from left to right and increasing total ion current increasing from bottom to top. 
       Example 2 
       [0053]    139 gm of Ammonia and 450 gm of monochlorosilane (MCS) are metered into a vertical tubular reactor from the bottom. The gases were fed through different lines and through different nozzles, as illustrated in  FIGS. 1 and 7 , to avoid premature reaction in the delivery lines. Ammonia was fed into the reactor at a rate of 0.93 gm/min. Monochlorosilane was fed into the reactor at a rate of 3.0 gm/min. This is an excess of about 10.6 mole % of MCS. The total run time was 150 minutes. The pressure in the reactor was maintained at about 100 to about 200 torr. The gases react to form disilylamine, trisilylamine and ammonium chloride. The reaction is exothermic and hence the walls of the reactor became warm as the process progressed. The gaseous reaction products exited through the top of the reactor to a collection vessel. The collection vessel is kept in a cold bath—dry ice/isopropyl alcohol (IPA) which creates a temperature of about −78° C. Disilylamine, trisilylamine are collected in the collection vessel. The yield was greater than 95% of the theoretical. 
       Example 3 
       [0054]    353 gm of Ammonia and 1063 gm of monochlorosilane (MCS) are metered into a vertical tubular reactor from the bottom. The gases were fed through different lines and through different nozzles, as illustrated in  FIGS. 1 and 7 , to avoid premature reaction in the delivery lines. Ammonia was fed into the reactor at a rate of 1.47 gm/min. Monochlorosilane was fed into the reactor at a rate of 4.43 gm/min. This is an excess of about 2.6 mole % of MCS. The total run time was 240 minutes. The pressure in the reactor was maintained at about 100 to about 200 torr. The gases react to form disilylamine, trisilylamine and ammonium chloride. The reaction is exothermic and hence the walls of the reactor became warm as the process progressed. The gaseous reaction products exited through the top of the reactor to a collection vessel. The collection vessel is kept in a cold bath—dry ice/isopropyl alcohol (IPA) which creates a temperature of about −78° C. Disilylamine, trisilylamine are collected in the collection vessel. The yield was greater than 95% of the theoretical. 
         [0055]    The description of illustrative and preferred embodiments of the present invention is not intended to limit the scope of the invention. Various modifications, alternative constructions and equivalents may be employed without departing from the true spirit and scope of the appended claims.