Abstract:
Provided is a method and structure for utilizing advance channel substrate materials in semiconductor manufacturing. Advanced channel substrate materials such as germanium and Group III-V channel substrate materials, are advantageously utilized. One or more capping films including at least a nitride layer are formed over the channel substrate prior to patterning, ion implantation and the subsequent stripping and wet cleaning operations. With the capping layers intact during these operations, attack of the channel substrate material is prevented and the protective films are easily removed subsequently. The films are dimensioned in conjunction with the ion implantation operation to enable the desired dopant profile and concentration to be formed in the channel substrate material.

Description:
TECHNICAL FIELD 
       [0001]    The disclosure relates, most generally, to integrated circuit fabrication processes, and more particularly to new materials used as channel substrates for integrated circuit and other semiconductor devices and methods for processing the new materials. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    In the advancing semiconductor manufacturing industry, new substrate materials are being developed in response to the demand for greater electron and hole mobility and work function tuning. Materials such as germanium, SiGe and Group III-V materials such GaAs, InP and InGaAs are being proposed because of their lattice structures and inherent stresses which have been found to enhance electron and hole mobility in integrated circuit and other semiconductor devices. The use of these materials is particularly advantageous as device processing technologies continue to advance and devices are formed in the 10 nanometer regime. 
         [0003]    A challenge faced in the development of these new materials as channel substrate materials lies in the incompatibility between the new channel substrate materials and conventional wet chemical processes used in semiconductor manufacturing. Wet chemical cleaning operations are commonly used in semiconductor manufacturing for various purposes including the cleaning operations that follow dry photoresist stripping operations. Wet chemical operations are also used to remove oxide layers and for other purposes. Wet chemical operations are typically used multiple times in the sequence of processing operations used to manufacture a semiconductor device. Commonly used chemicals used for wet chemical processing operations include HCl, HF, HNO 3 , H 2 SO 4 , NH 4 OH, APM, HPM and Caros acid (SPM). Additional chemicals are also used in other conventional wet chemical processing operations. 
         [0004]    The new substrate materials such as Ge, SiGe and Group III-V materials are susceptible to attack by these wet chemicals used in semiconductor manufacturing. The wet chemical processing operations induce a significant amount of substrate film loss and also damage the substrate materials by roughening the surfaces to unacceptable levels. This undesirable surface morphology adversely affects subsequent processing operations. 
         [0005]    It would therefore be desirable to formulate processing operations that are compatible with the new substrate materials that provide the aforementioned advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0006]    The present disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawing. It is emphasized that, according to common practice, the various features of the drawing are not necessarily to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Like numerals denote like features throughout the specification and drawing. 
           [0007]      FIG. 1  is a cross-sectional view showing an exemplary protective film structure of the disclosure; 
           [0008]      FIG. 2  is a cross-sectional view showing an exemplary protective film structure of the disclosure on a FinFET substrate; 
           [0009]      FIG. 3  is a cross-sectional view showing another exemplary protective film structure according to the disclosure; 
           [0010]      FIG. 4  shows a processing sequence according to the disclosure and includes two cross-sectional views; and 
           [0011]      FIG. 5  illustrates a processing sequence of the disclosure performed on a FinFET structure according to the disclosure and also includes two cross-sectional views. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    A channel substrate material is provided for use in semiconductor device manufacturing. The channel substrate may be used as a substrate for the formation of various integrated circuit and other semiconductor devices used in various applications, it may be used in various processing technologies and it may come in various sizes used in the semiconductor manufacturing industry. The channel substrate material may be Ge, SiGe, GaAs, InP, InGaAs or other Group III-V semiconductor materials. The channel substrate may be a relatively thick layer formed over another substrate commonly used in the semiconductor fabrication industry, e.g. over a silicon wafer. In another exemplary embodiment, the wafer itself may be formed of the channel substrate material with the channel substrate referring to the upper portion of the substrate, in which the transistor channels will be formed. The disclosure provides for forming a film structure including at least a nitride material layer over the channel substrate to protect the channel substrate during wet chemical cleaning operations commonly used in the semiconductor manufacturing industry, particularly cleaning operations and oxide removal operations. These protective layers protect the channel substrate material from being attacked and therefore losing film thickness or becoming undesirably and unacceptably roughened. 
         [0013]    The protective film structure may advantageously be utilized early in the fabrication sequence and may remain in place over the channel substrate during one or a plurality of processing operations including a sequence of ion implantation processing operations that include the formation of a photoresist pattern, an ion implantation operation, and the removal of the photoresist pattern after the ion implantation operation followed by a wet cleaning operation. The protective film structure may advantageously be formed and utilized multiple times during the sequence of fabrication operations used to form a semiconductor device. The protective film or films are easily removed after they are utilized to prepare the channel substrate for further processing operations. 
         [0014]      FIG. 1  is a cross-sectional view showing channel substrate  2 . Channel substrate  2  may simply comprise an upper portion of a wafer, i.e. substrate formed of the channel substrate material or it may be a layer formed over a substrate formed of a further material such as a silicon or other wafer and, according to this exemplary embodiment, channel substrate  2  may include a thickness ranging from about 1000-2500 angstroms. Other suitable thicknesses may be used in other exemplary embodiments. Channel substrate  2  may be formed of a material that may be Ge, SiGe, GaAs, InP, InGaAs or other Group III-V materials which find utility as channel substrate materials in semiconductor manufacturing because they enhance device performance by enhancing electron and hole mobility due to the strain effect resulting from their lattice structures. A Group III-V material should be understood to be a material formed of a combination of elements from Group III and Group V of the periodic table of elements. 
         [0015]    Channel substrate  2  is planar in the illustrated embodiment of  FIG. 1  and includes planar surface  4 . STI, shallow trench isolation, structure  6  is formed in channel substrate  2  and extends downwardly from planar surface  4  and may be produced using conventional or other means. The presence of STI structure  6  within channel substrate  2  indicates that the protective film structure of the disclosure is formed over and after the formation of STI structure  6  in this embodiment. In the illustrated embodiment, two films are formed over channel substrate  2 . Lower oxide film  8  may be various oxide materials and may include a thickness of about 5-15 angstroms in one exemplary embodiment, but other thicknesses may be used in other exemplary embodiments. Lower oxide film  8  may be formed using thermal oxidation processes, CVD, ALD or other deposition processes. In other exemplary embodiments, lower oxide film  8  may be a chemical oxide film such as may be formed in a chemical processing operation that uses ozone in conjunction with deionized water, DIW. Various other oxide formation techniques may be used to form lower oxide film  8 . Nitride film  10  is formed over lower oxide film  8  and may include a thickness ranging from about 5-50 angstroms in one exemplary embodiment, but other thicknesses may be used in other exemplary embodiments. Nitride film  10  may be stoichiometric Si 3 N 4  or it may be other stoichiometric nitride layers or it may be silicon oxynitride or other nitride materials in other exemplary embodiments. Nitride layer  10  may be formed using thermal processes, CVD, ALD or other suitable film deposition techniques. 
         [0016]      FIG. 2  shows an embodiment in which channel substrate  2  includes fins  14 . Fins  14  formed from channel substrate  2  will be used in the formation of FinFET, fin-type field effect transistor devices as commonly used in the semiconductor manufacturing industry. Lower oxide film  8  and nitride film  10  are as described above, as are STI structures  6 . Fins  14  may be formed using known methods and to various dimensions. 
         [0017]      FIG. 3  shows the planar channel substrate of  FIG. 1  with a different protective film structure formed over planar surface  4  of channel substrate  2 . Single cap layer  18  may be a nitride material such as silicon oxynitride, SiO x N y  or other suitable nitride materials. Cap layer  18  may be formed to a thickness within the range of about 10-50 angstroms but other thicknesses may be used in other exemplary embodiments. In one exemplary embodiment, the silicon oxynitride layer may also be formed by first forming an oxide layer then using suitable nitridation techniques such as an N 2  plasma or a thermal operation using NH 3  to introduce nitrogen into the initially formed oxide. Other techniques for nitridizing an originally formed oxide film may also be used. In another exemplary embodiment, a silicon nitride layer may be formed initially and the film may be bombarded, implanted, or otherwise aggressively treated with oxygen such as by using an O 2  plasma, to form a silicon oxynitride layer. Other techniques may be used in other exemplary embodiments to form silicon oxynitride or other materials suitably used as cap layer  18 . 
         [0018]    Although the embodiments illustrated in  FIGS. 1 and 2  include a two layer protective film structure and the embodiment illustrated in  FIG. 3  includes a one layer protective film structure, the protective film structure may include multiple layers including at least one nitride layer, according to other exemplary embodiments of the disclosure. 
         [0019]      FIGS. 4 and 5  each illustrate the same sequence of processing operations and exhibit the utility of the protective film structure according to the disclosure.  FIGS. 4 and 5  differ in that  FIG. 4  shows the sequence of processing operations carried out on a planar substrate and  FIG. 5  shows the sequence of processing operations being carried out on a channel substrate including fins such as suitable for FinFET technology. While the sequence of processing operations illustrates the exemplary embodiment in which a composite film structure of lower oxide film  8  and nitride film  10  are used, it is pointed out that the same sequence of processing operations may be used according to the exemplary embodiments in which the protective film structure includes multiple layers, or a single capping layer such as capping layer  18  shown in  FIG. 3 . 
         [0020]    Now referring to  FIGS. 4 and 5 , patterned photoresist  20  has been formed and is disposed over the exemplary protective film structure of lower oxide film  8  and nitride film  10 . Various photoresist materials and various suitable patterning techniques may be used.  FIGS. 4 and 5  show an ion implantation operation taking place with arrows  22  indicating the presence and direction of ions being implanted into channel substrate  2  at step  24 . Patterned photoresist  20  protects channel substrate  2  from being subjected to implanted ions where present. Lower oxide film  8  and nitride film  10  are formed to a thickness chosen in conjunction with the ion implantation process or processes to be carried out with lower oxide film  8  and nitride film  10  in place. The illustrated ion implantation process may be any of various types of implantation operations such as but not limited to n-well ion implantation operations and p-well ion implantation operations. Other exemplary implantation operations may involve channel formation or channel adjustment implantation operations. The film thicknesses are chosen such that the ion implantation process implants ions through lower oxide film  8  and nitride film  10  and into channel substrate  2  at suitable depths. The number type and thicknesses of protective films may be tuned for the particular device and the type and number of implantation operations that will take place with the protective film or films in place. 
         [0021]    After the ion implantation operation has been carried out, a dry ashing operation is carried out at step  26 . The dry ashing operation removes patterned photoresist  20 . Various plasma ashing operations may be carried out. Wet chemical cleaning operation is next carried out at step  30 . The wet chemical cleaning operation of step  30  is used to remove residual photoresist and to further clean and prepare the channel substrate for further processing. The wet chemical cleaning operation may be a Caros acid clean in one exemplary embodiment. A Caros clean is also known as piranha or an SPM clean and involves a mixture of H 2 SO 4  and H 2 O 2  typically in a 1:4 ratio. Other cleaning operations may be used in other exemplary embodiments. Other cleaning solutions include HCl in various compositions, HF, an HF/HCl mixture, HNO 3 , H 2 SO 4 , NH 4 OH, APM (ammonium hydrogen peroxide mixture) and HPM, (an HCl, hydrogen peroxide mixture) and the APM and HPM mixtures may consist of various ratios. After the dry ashing operation of step  26  and wet chemical cleaning operation of step  30 , all residual photoresist and other debris is removed and channel substrate  2  with lower oxide film  8  and nitride film  10  is clean as shown in step  32 , the right-hand side of  FIGS. 4 and 5 . 
         [0022]    According to one exemplary embodiment, a further patterned photoresist material may be formed over the cleaned structure illustrated in step  32  of  FIGS. 4 and 5  and a further sequence of ion implantation processing operations, as described infra, may be carried out. In various exemplary embodiments, multiple such sequences of ion implantation processing sequences may be carried out using the same film structure. 
         [0023]    The illustrated sequence of processing operations shown in  FIGS. 4 and 5  is exemplary only and in other exemplary embodiments, various wet chemical cleaning operations may be used subsequent to various preceding processing operations with the protective film structure in place. The wet chemical cleaning operation need not necessarily follow a dry ashing operation that removes photoresist, for example. 
         [0024]    Moreover, the structure illustrated in  FIGS. 4 and 5  undergoing the ion implantation operation in step  24  is intended to be exemplary only. In other exemplary embodiments, polysilicon gate structures may be formed over the channel substrate  2  illustrated in  FIGS. 4 and 5 , and the film structure  8 ,  10  or capping film  18 , may be formed thereover. In one exemplary embodiment, lower oxide film  8  and nitride film  10  or capping layer  18  may be formed over channel substrate  2  including over polysilicon gates formed over channel substrate  2 , and a photoresist pattern may be formed to define self-aligned gate source/drain regions. An implantation operation may then take place and be followed by dry ashing and wet chemical cleaning operations prior to the removal of the protective films, nitride layer  10 , lower oxide layer  8 . 
         [0025]    Nitride layer  10 , lower oxide layer  8  and capping layer  18  may be easily removed using conventional wet stripping operations after the films have been utilized. The wet etching of nitride films is often performed in concentrated hot orthophosphoric acid, H 3 PO 4  but other methods may also be used. Various wet etching oxide removal operations are known and available. In addition to the films being usable for multiple patterning implantation and cleaning operations taking place using the same set of films, the protective films of the disclosure may be formed and removed multiple times in the formation of a semiconductor device such as at an early processing stage for well definition and ion implantation and later for source/drain patterning and ion implantation after the formation of polysilicon leads on channel substrate  2 . 
         [0026]    According to one aspect, a method for forming a semiconductor device is provided. The method comprises providing a channel substrate of a substrate material being one of Ge, SiGe, GaAs, InP and InGaAs and a further Group III-V semiconductor material, forming a film structure comprising a nitride layer over the channel substrate, performing a plurality of ion implantation processing sequences, removing the film structure, and performing further processing operations. 
         [0027]    According to another aspect, a further method for forming a semiconductor device is provided. The method comprises: providing a channel substrate of a substrate material being one of Ge, SiGe, GaAs, InP, InGaAs and a further Group III-V semiconductor material; forming a film structure comprising a nitride layer over the channel substrate; performing a plurality of ion implantation processing sequences; and, removing the film structure. The method further comprises: forming polysilicon gate structures over the channel substrate; forming a further film structure comprising a further nitride layer over the channel substrate including over the polysilicon gate structures; forming a photoresist pattern and performing a source/drain ion implantation; removing the photoresist layer; performing a wet chemical cleaning operation using at least one of HCl, HF, HNO 3 , H 2 SO 4 , APM, HPM and Caros acid; and removing the further film structure. 
         [0028]    The preceding merely illustrates the principles of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes and to aid the reader in understanding the principles of the disclosure and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. 
         [0029]    This description of the exemplary embodiments is intended to be read in connection with the figures of the accompanying drawing, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. 
         [0030]    Although the disclosure has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the disclosure, which may be made by those skilled in the art without departing from the scope and range of equivalents of the disclosure.