Abstract:
A method for fabricating a semiconductor apparatus includes setting a semiconductor substrate in a process chamber, increasing an internal temperature of the process chamber to a predetermined temperature for pyrolyzing a source gas, supplying the source gas to the inside of the process chamber and pyrolyzing ions of the source gas to remain on the semiconductor substrate, and forming the ohmic contact layer by supplying a reaction gas to the inside of the process chamber, wherein the reaction gas is reacted with non-metal ions pyrolyzed from source gas.

Description:
CROSS-REFERENCES TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 U.S.C. 119(a) to Korean application No. 10-2014-0031047, filed on Mar. 17, 2014, in the Korean intellectual property Office, which is incorporated by reference in its entirety as set forth in full. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    Various embodiments of the inventive concept relate to a method for fabricating a semiconductor apparatus, and more particularly, to a method for fabricating a semiconductor apparatus including a uniform metal silicide layer having a thin thickness. 
         [0004]    2. Related Art 
         [0005]    The penetration rate of digital apparatuses is increasingly growing and there are demands for memory devices with ultra-high integration, ultra-high speed, and ultra-low power, which are built in digital apparatuses in order to process large amounts of data at high speed in a limited area. 
         [0006]    To meet the demands, variable resistive memory devices using a resistance material as a memory medium have been suggested. Typical examples of variable resistive memory devices are ferroelectric random access memories (FRAMs), magnetoresistive RAMs (MRAMs), or phase-change RAMs (PCRAMs). 
         [0007]    A variable resistive memory device may be typically formed of a switching device and a resistance device, and may be implemented with a single-level cell (SLC) or a multi-level cell (MLC). 
         [0008]    In particular, PCRAM includes a phase-change material layer which is stabilized to either a crystalline state or an amorphous state by heat, and switched between the two different resistance states. 
         [0009]    Hereinafter, a general structure of a PCRAM will be described with reference to the accompanying drawings. 
         [0010]    The PCRAM has a structure in which a switching device layer, an ohmic contact layer, a lower electrode, a phase-change material layer, and an upper electrode are sequentially formed on a semiconductor substrate. 
         [0011]    The ohmic contact layer in the PCRAM structure is provided to reduce the electric contact resistance between the switching device layer and the lower electrode, and may generally include a metal silicide layer. 
         [0012]    The metal silicide layer may be formed through a physical vapor deposition (PVD) method or a direct current plasma-assisted chemical vapor deposition (CVD) method. 
         [0013]    A metal silicide layer produced through the PVD method may be formed by thickly depositing a metal layer, and performing a post-heat treatment process on the metal layer. However, the post-heat treatment makes it difficult to form a uniform metal silicide layer. 
         [0014]    When the metal silicide layer is formed through the direct current plasma-assisted CVD method, the metal is grown by a vapor reaction and simultaneously the metal silicide layer is formed by a reaction with the silicon (Si) surface. As the metal reaction is increased by plasma or high-temperature deposition, the direct-current plasma-assisted CVD method makes it difficult to form a uniform metal silicide layer due to poor step coverage. 
       SUMMARY 
       [0015]    According to an exemplary embodiment of the present invention, a method for fabricating a semiconductor apparatus including an ohmic contact layer is provided. The method may include setting a semiconductor substrate in a process chamber, increasing the internal temperature of the process chamber to a predetermined temperature for pyrolyzing a source gas, remaining pyrolyzed ions of the source gas on the semiconductor substrate by supplying the source gas to the inside of the process chamber and pyrolyzing ions of the source gas, and forming the ohmic contact layer by supplying a reaction gas to the inside of the process chamber and supplying an inert gas to the process chamber to form a plasma atmosphere, wherein the reaction gas is reacts with non-metal ions pyrolyzed from the source gas in a plasma atmosphere. 
         [0016]    According to an exemplary embodiment of the present invention, a method for fabricating an ohmic contact layer on a switching device layer of a phase changeable random access memory (PCRAM) is provided. The method may include providing a chemical vapor deposition (CVD) chamber, setting a substrate on which the switching device layer is formed in the CVD chamber, increasing the temperature of the CVD chamber to a first temperature, supplying a source gas including a metal material and other materials to the CVD chamber, wherein the source gas is pyrolyzed by the first temperature of the chamber, supplying a reaction gas and an inert gas to the CVD chamber, wherein the reaction gas reacts with the other materials on the switching device to be removed therefrom, and purging the inside of the chamber using a purge gas. 
         [0017]    According to an exemplary embodiment of the present invention, a method for fabricating a semiconductor apparatus is provided. The method may include supplying a source gas including a metal material at a predetermined temperature to a semiconductor substrate in a chamber and depositing the source gas on the semiconductor substrate, and removing materials deposited on the semiconductor substrate other than the metal material by reacting a reaction gas with deposited materials. 
         [0018]    These and other features, aspects, and embodiments are described below in the section entitled “DETAILED DESCRIPTION”. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The above and other aspects, features and other advantages of the subject matter of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0020]      FIG. 1  is a schematic cross-sectional view illustrating a semiconductor apparatus according to an embodiment of the inventive concept; 
           [0021]      FIG. 2  is a flowchart illustrating a method for fabricating a semiconductor apparatus according to an embodiment of the inventive concept; 
           [0022]      FIG. 3  is a schematic diagram illustrating fabrication equipment where an ohmic contact layer fabrication method of a semiconductor apparatus is performed according to an embodiment of the inventive concept; and 
           [0023]      FIG. 4  is a waveform diagram illustrating a supply pattern of process gas in a fabrication method of a semiconductor apparatus according to an embodiment of the inventive concept. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Exemplary embodiments are described herein with reference to schematic illustrations of exemplary embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, exemplary embodiments should not be construed as limited to the particular shapes illustrated herein but may include deviations in shapes that result, for example, from manufacturing. In the drawings, lengths and widths of layers and regions may be exaggerated for clarity. Like reference numerals in the drawings denote like elements. It is also understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other or substrate, or intervening layers may also be present. It is also noted that in this specification, “connected/coupled” refers to one component not only directly coupling another component but also indirectly coupling another component through an Intermediate component. In addition, the singular form may include a plural form, and vice versa, as long as it is not specifically mentioned. 
         [0025]    The inventive concept is described herein with reference to cross-section and/or plan illustrations of embodiments of the inventive concept. However, embodiments of the inventive concept should not be construed as limiting the inventive concept. Although a few embodiments of the inventive concept will be shown and described, it will be appreciated by those of ordinary skill in the art that changes may be made in these exemplary embodiments without departing from the principles and spirit of the inventive concept. 
         [0026]    Hereinafter, an exemplary embodiment of the inventive concept, for example, a PCRAM will be described.  FIG. 1  illustrates a semiconductor apparatus according to an embodiment of the inventive concept. 
         [0027]    Referring to  FIG. 1 , a semiconductor apparatus  10  according to an embodiment of the inventive concept may include a switching device layer  120  formed on a semiconductor substrate  110 , an ohmic contact layer  130  formed on the switching device layer  120 , a lower electrode  140  formed on the ohmic contact layer  130 , a phase-change material layer  150  formed on the lower electrode  140 , and an upper electrode  160  formed on the phase-change material layer  150 . 
         [0028]    The ohmic contact layer  130  in a structure of the semiconductor apparatus  10  is provided to reduce electrical resistance between the switching device layer  120  and the lower electrode  140 . The ohmic contact layer  130  may be provided to cover an upper surface and a sidewall of the switching device layer  120  which is formed on the semiconductor substrate. The switching device layer  120  may have a pillar structure and include a silicon material. This is because the ohmic contact layer  130  increases the contact area with the lower electrode  140  to reduce contact resistance with the lower electrode  140 , and to increase an ON current due to reduction in the contact resistance. 
         [0029]    The ohmic contact layer  130  may include a metal silicide layer. For example, the ohmic contact layer  130  may be formed of a titanium silicide layer. 
         [0030]    The reference numerals  111 ,  113 , and  115  denote a gate insulating layer, a gate electrode, and an inter-dielectric layer, respectively. 
         [0031]    A process for forming an ohmic contact layer of a semiconductor apparatus according to an embodiment of the inventive concept will be described with reference to  FIGS. 1 to 3 . 
         [0032]    First, the semiconductor substrate  110  including the switching device layer  120  is arranged in a process chamber  20  (S 110 ). The process chamber  20  may be a chemical vapor deposition (CVD) chamber. 
         [0033]    Next, in the temperature is raised in the process chamber  20  (S 120 ). For example, the inside of the process chamber  20  may be set to a temperature of 450° C. to 1000° C. at a rate of 5 to 20° C./sec. The temperature may be a pyrolyzing temperature of a source gas for forming a metal silicide layer. Further, the pressure of the process chamber  20  may be about 0.5˜20 Torr. 
         [0034]    The source gas G 1  is supplied to the inside of the process chamber  20  for through a first pipe L 1  (S 130 ). The source gas G 1  may be selected from the group consisting of gases containing a metal precursor and an organic metal precursor. For example, the source gas G 1  may be TiCl 4  gas, and may be provided to the inside of the process chamber  20  at a flow rate of 1 to 1000 sccm. 
         [0035]    When the source gas G 1  is supplied as a high-temperature environment is created in the process chamber  20  as described above, a precursor of the source gas G 1  may be pyrolyzed into metal ions and non-metal ions inside of the process chamber  20 , and the metal ions and non-metal ions may be deposited on the switching device layer  120 . For example, when the source gas G 1  includes TiCl 4  gas, Ti metal ions and Cl ions may be pyrolyzed and absorbed on the semiconductor substrate  110  having the switching device layer  120 . 
         [0036]    Next, a reaction gas G 2  is supplied to inside the process chamber  20  for a given time through a second pipe L 2  (S 140 ), and simultaneously a plasma atmosphere is created in the process chamber  20  (S 150 ). The reaction gas G 2  may Include at least one selected from the group consisting of H 2  gas, NH 3  gas, and F gas. 
         [0037]    The reaction gas G 2  may react with one of the ions remaining on the semiconductor substrate  110  in the plasma atmosphere. For example, when the reaction gas G 2  includes H 2  gas, the H 2  gas may react with Cl ions (Cl − ) remaining on the semiconductor substrate  110  in the plasma atmosphere, and the Cl ions may be removed. Only non-reacted Ti metal ions are left on the semiconductor substrate  110 . 
         [0038]    In the above-described process, to create the plasma atmosphere in the process chamber  20 , an inert gas G 3  may be supplied through a third pipe L 3 . The inert gas G 3  may include one selected from the group consisting of Ar, He, Ne, Kr, Xe, and Rn gas. 
         [0039]    The Cl ions reacted with the reaction gas G 2 , that is, HCl gas and the inert gas G 3  may be vented by continuously pumping them out of the process chamber  20 . 
         [0040]    Next, a purge gas G 4  is supplied to inside of the process chamber  20  through a fourth pipe L 4  (S 160 ). When the purge gas G 4  is supplied, a reduction in temperature inside the process chamber  20  may occur. 
         [0041]    The above-described sequences S 120  to S 160  may suppress a vapor reaction of the reaction gas G 2  and the source gas G 1  and react the reaction gas G 2  with non-metal ions (Cl ions) of the source gas G 1  on a surface of the semiconductor substrate  110  to uniformly form a metal silicide layer (Ti metal ions) on the semiconductor substrate  110  including the switching device layer  120 . 
         [0042]    Referring to  FIGS. 2 and 4 , a thin metal silicide may be smoothly formed by repeatedly performing the above-described sequences. That is, when the sequences S 120  to S 160  are defined as one cycle, the metal silicide layer having a predetermined thickness may be formed by repeatedly performing the cycle. 
         [0043]    For example, when a process of forming a metal silicide layer having a thickness of 10 Å is defined as one cycle, 10 cycles may be repeatedly performed to form a metal silicide layer with a thickness of 100 Å. In the embodiment, a process of forming a thin metal silicide layer may be repeatedly performed to form a uniform metal silicide layer having a predetermined thickness. 
         [0044]    As described above, in the embodiment, ions of the source gas G 1  are deposited on the semiconductor substrate  110  by pyrolyzing the source gas G 1  in the process chamber  20  at high temperatures, and the uniform metal silicide layer may be formed using the metal ions deposited on the semiconductor substrate  110  by reacting the reaction gas G 2  with the deposited non-metal ions in a plasma atmosphere. 
         [0045]    The embodiment may smoothly form a thin but uniform metal silicide layer having a predetermined thickness by repeatedly performing the above-described process. 
         [0046]    The above embodiment of the present invention is illustrative and not limitative. Various alternatives and equivalents are possible. The invention is not limited by the embodiments described herein, nor is the invention limited to any specific type of semiconductor device. Other additions, subtractions, or modifications are obvious in view of the present disclosure and are intended to fall within the scope of the appended claims.