Abstract:
A method including introducing a precursor in the presence of a circuit substrate, and forming a film including a reaction product of the precursor on the substrate, wherein the precursor includes a molecule comprising a primary species of the film and a modifier. A method including introducing a precursor in the presence of a circuit substrate, the precursor including a primary species and a film modifier as a single source, and forming a film on the circuit substrate. An apparatus including a semiconductor substrate, and a film on a surface of the semiconductor substrate, the film including a reaction product of a precursor including a molecule comprising a primary species and a modifier.

Description:
BACKGROUND  
       [0001]     1. Field  
         [0002]     Circuit processing.  
         [0003]     2. Background  
         [0004]     Advanced circuit structures demand precision in the processing techniques that are used to form them. Advanced transistor structures, for example, require precisely doped semiconductor (e.g., silicon) layers that may serve, for example, as source/drain regions, tips, and channels. As device (e.g., transistor) geometries shrink, these layers become thinner and the composition of the layer must increasingly be more carefully controlled. Ion implantation remains one of the leading techniques to dope silicon, but as layers becomes thinner, ion implantation lacks the precision to dope some of the more delicate structures. In terms of depositing semiconductor layers, epitaxial deposition is often used. Doping of epitaxial layers may be accomplished by ion implantation or by separately introducing a semiconductor precursor and a doping precursor in the formation of the epitaxial layer.  
         [0005]     In addition to electrically active layers such as described above, integrated circuits use dielectric layers to isolate individual devices on a chip. These dielectric materials include materials such as silicon dioxide (SiO 2 ), phosphosilicate glass (PSG), silicon carbide (SiC), fluorinated silicate glass (FSG), and carbon doped oxide (CDO). A dielectric material is selected in one regard for its dielectric properties as well as its parasitic capacitance. As the parasitic capacitance is reduced, the cross-talk (e.g., a characterization of the electric field between adjacent interconnections) is reduced, as is the resistance-capacitance (RC) time delay and power consumption (e.g., with respect to signals conducted along interconnections). The property of a dielectric material, notably its dielectric constant, may be altered by dopants or changes in porosity. Thus, the ability to precisely control a dopant concentration and/or porosity within a layer becomes critical as circuit performance is maximized for semiconductor and dielectric materials. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     Features, aspects, and advantages of embodiments will become more thoroughly apparent from the following detailed description, appended claims, and accompanying drawings in which:  
         [0007]      FIG. 1  shows a schematic side view of a system for depositing film.  
         [0008]      FIG. 2  shows one example of a silicon-germanium precursor in the form of a germanium hydride.  
         [0009]      FIG. 3  shows another example of a silicon-germanium precursor in the form of a germyl silane.  
         [0010]      FIG. 4  shows one example of a silicon-phosphorous precursor in the form of a phosphine.  
         [0011]      FIG. 5  shows another example of a silicon -phosphorous precursor in the form of a phosphine.  
         [0012]      FIG. 6  shows an example of a dielectric precursor in the form of a silane substituted with hydrazine moeties.  
         [0013]      FIG. 7  shows another example of a dielectric precursor in the form of a silane substituted with hydrazine moeties.  
         [0014]      FIG. 8  shows one example of a dielectric material precursor in the form of a cyclic silazane.  
         [0015]      FIG. 9  shows another example of a dielectric material precursor in the form of a cyclic silazane.  
         [0016]      FIG. 10  shows another example of a dielectric material precursor in the form of a cyclic silazane.  
         [0017]      FIG. 11  shows another example of a dielectric material precursor in the form of a cyclic silazane.  
         [0018]      FIG. 12  shows another example of a dielectric material precursor in the form of a cyclic silazane.  
         [0019]      FIG. 13  shows one example of a dielectric material precursor in the form of an azidosilane.  
         [0020]      FIG. 14  shows one example of a dielectric material precursor in the form of a tetraazadisilacyclohexane.  
         [0021]      FIG. 15  shows another example of a dielectric material precursor in the form of a tetraazadisilacyclohexane. 
     
    
     DETAILED DESCRIPTION  
       [0022]     In one embodiment, a method is described. The method relates to forming a film or films on a circuit substrate, such as a semiconductor substrate. Suitable films include, but are not limited to, active layer films that may contain one or more components of a device (e.g., source/drain, tips, channels, etc.) and dielectric films such as might be used between the substrate and various interconnection metal layers formed on the substrate.  
         [0023]      FIG. 1  shows a system that may be suitable for depositing a film. System  100  may be utilized with any of various deposition techniques including, but not limited to, a system employing deposition through a vertical diffusion furnace (VDF), a chemical vapor deposition (CVD) technique, a plasma enhanced CVD (PECVD, including remote plasma) technique, an atomic layer deposition (ALD) technique, and an electrospray deposition technique. System  100  includes chamber  110  that has volume  115  of a size suitable to contain a substrate, such as a 200 millimeter (mm) or 300 mm wafer.  FIG. 1  shows wafer  120  within volume  115  in chamber  110 . In other embodiments, chamber  110  may have volume  115  to contain several wafers.  
         [0024]     Referring to  FIG. 1 , chamber  110  is of a material suitable for the desired deposition technique. Connected to chamber  110  are various sources. Included among the sources are inert gas source  130 , such as a nitrogen gas source. Additional sources are selected for a particular deposition. In one embodiment, source  140  contains a precursor including a primary species of the film to be formed and a modifier. System  100  may also include first supplemental source  150  and second supplemental source  160 . First supplemental source  150  is, for example, a source containing the primary species of the film to be formed on substrate  120 . Second supplemental source  160  contains, for example, a modifier for the film to be formed on substrate  120 . A modifier includes in this context, a dopant or a porogen. Each of the sources (e.g., inert gas source  130 , precursor source  140 , first supplemental source  150 , and second supplemental source  160 ) is contained in a suitable tank. Connected to each tank is a release valve. Each release valve is connected to processor  170 . In one embodiment, processor  170  includes machine readable program instructions to execute a method to open a release valve and release a source gas into volume  115  of chamber  110 .  
         [0025]     Although illustrated as a single tank source (e.g., gas source), suitable combination precursors may be delivered to a chamber (e.g., chamber  110  of  FIG. 1 ) according to various techniques. Representatively, the combination precursor may be in various forms and delivered via vapor draw, direct liquid injection, or bubbling. The combination precursor can be delivered to the reaction chamber separately or as a pre-mixed precursor cocktail. In the embodiment where a primary species of the film is silicon, for example, the combination precursor can be delivered to a reaction chamber (e.g., chamber  110  of  FIG. 1 ) separately or as a pre-mixed precursor cocktail consisting of a silicon-modifier precursor (precursor source  140 ), a silicon source (e.g., supplemental source  150 ), a modifier source (e.g., supplemental source  160 ), and/or an appropriate solvent (which can be any appropriate organic solvent, including, but not limited to, hexanes, octanes, and nonanes). In another embodiment, the combination precursor may be introduced alone or with one of the noted other sources.  
         [0026]      FIG. 1  also shows pressure gauge  180  connected to processor  170 . Pressure gauge  180  is, for example, a BARATROM™ pressure sensor capable of monitoring a pressure within volume  115  and relaying a signal representative of the pressure in volume  115  to processor  170 . System  100  also includes temperature sensor  190  within volume  115  of chamber  110 . Temperature sensor  190  is capable of measuring a temperature within volume  115  of chamber  110  and sending a signal representative of that temperature to processor  170 . It is appreciated that a suitable chamber may contain multiple pressure and temperature sensors. Processor  170  includes machine readable program instructions to monitor and establish a pressure and temperature necessary for a particular film formation process within chamber  110 .  
         [0027]     In one embodiment, a precursor is delivered to chamber  110  that includes a primary species of a film to be formed and a modifier (a “combination precursor”). The primary species and the modifier are introduced through a single source such as precursor source  140  in system  100  of  FIG. 1 . The primary species and the modifier may be part of a single molecule.  
         [0028]     In terms of active layer film formation, one type of combination precursor that may be delivered to volume  115  of chamber  110  in  FIG. 1  is a silicon-germanium precursor.  FIG. 2  shows an example of a silicon-germanium precursor as a single molecule. Precursor  200  has the general formula: 
 
GeR t (SiR x   3 ) 3  
 
 where R x  and R y  are selected from a hydrogen, an amine, a halogen, an alkyl, an aryl, a silyl, a substituted form of the noted groups or other organic ligand containing, in one embodiment, from one to 20 carbons. Each R x  and R y  may be the same or different (e.g., independent). One example of a silicon-germanium precursor source as a single molecule as precursor  200  is tris(trimethylsilyl)germanium hydride, where R y  is a hydrogen and each R x  is an alkyl (a methyl group). 
 
         [0029]     A second type of silicon-germanium precursor is shown in  FIG. 3 . Precursor  300  has the general formula: 
 
SiR x   3 (GeR y   3 ) 
 
 where R x  and R y  may be selected from a hydrogen, an amine, a halogen, an alkyl, an aryl, a silyl, a substituted form of the noted groups or other organic ligand containing, in one embodiment, from one to 20 carbons. Each R may be the same or different (e.g., independent). One example of a silicon-germanium precursor as precursor  300  is trimethyl(trimethylgermyl)silane, where each R x  and each R y  is an alkyl (a methyl group). 
 
         [0030]     Another type of modifier to be combined with a primary species in the form of a precursor for forming a film is a dopant. Representatively, P- and N-type dopants are used to modify a semiconductor such as silicon in the formation of active films. A typical dopant for a P-type semiconductor substrate is boron. Typical dopants for an N-type semiconductor material are arsenic or phosphorous. In one embodiment, a combination precursor includes a molecule including a primary species of the film (e.g., silicon) and a dopant.  FIG. 4  shows one example of a silicon phosphorous precursor. In this embodiment, the precursor as a single molecule has the general formula: 
 
R x JSi z R y  
 
 where R x  and R y  may be the same or different (e.g., independent) and may be selected from a hydrogen, an amine, a halogen, an alkyl, an aryl, a silyl, a substituted form of the noted groups or other organic ligand containing, in one embodiment, from one to 20 carbons. In this example, x+z=3, and R x  may also be nothing at all (i.e., z=3). J may be phosphorous and boron. One example of this precursor is precursor  400  where x is zero and J is phosphorous. An example of this type is tris(trimethylsilyl)phosphine, where each R y  is an alkyl (a methyl group). 
 
         [0031]      FIG. 5  shows a second example of a molecule including a primary species (e.g., silicon) of a film and a dopant of phosphorous. Precursor  500  is a dimethyl(trimethylsilyl)phosphine. In this embodiment, the precursor again is a single molecule having the general formula: 
 SiR y   3 (JR x   2 ).  
 where each R x  and R y  is an alkyl (a methyl group) and J is phosphorous. 
 
         [0032]     The above embodiments describe forming active films (e.g., layers) using a combination precursor. The combination precursor technique may also be used in the formation of dielectric layers. In one embodiment, it is desired to deposit precursors (e.g., dielectric film precursors) at a relatively low temperature, such as less than 500° C. In certain instances, it is also desirous to form films having dielectric constants less than silicon dioxide (SiO 2 ) (low k dielectrics). One way low k dielectrics may be formed is by doping an SiO 2  film. Another technique is to form porous films.  
         [0033]      FIG. 6  and  FIG. 7  show examples of combination precursors as single molecules that may be utilized to form a dielectric film.  FIG. 6  and  FIG. 7  show examples of substituted hydrazine moieties. A silane substituted with hydrazine moieties may have the general formula: 
 Si(N 2 R 2 ) x R y    
 where R is a ligand including, but not limited to, hydrogen, alkyl, aryl, or amine and each R may be the same or different (e.g., independent). The silane substituted with hydrazine moieties may be introduced at a temperature (e.g., a temperature within volume  115  of chamber  110 ) in the presence of oxygen. The combination precursor reacts with oxygen to form an oxide film. Molecule  600  of  FIG. 6  is bis (2,2-dimethyl-hydrazino)ethylsilane and molecule  700  of  FIG. 7  is bis (2,2-dimethyl-hydrazino)diethylsilane. Although illustrated as an alkyl (e.g., methyl), the R groups may be independent and selected from H, other alkyls, aryls, amines, etc. 
 
         [0034]     A second group of precursor compounds for a dielectric film is shown in  FIGS. 8-12 . These compounds consist of cyclic silazanes (e.g., four or six membered rings with alternating silicon and nitrogen atoms). In one embodiment, cyclic silazanes are represented by the following formulas: 
 
Si 2 N 2 R 6  Si 3 N 3 R 9  
 
 where R in each molecule is a ligand including, but not limited to, hydrogen, alkyl, aryl, or amine and the different R groups in each molecule may be the same or different (e.g., independent). 
 
         [0035]      FIG. 8  shows precursor molecule  800  that is cyclodisilizane.  FIG. 9  shows precursor molecule  900  that is 1-tertiarybutylamino-2,4-ditertiarybutylcyclodisilazane,  FIG. 10  shows precursor molecule  1000  that is 1,3-ditertiarybutylamino-2,4-ditertiarybutyl-cyclodisilazane.  FIG. 11  shows precursor molecule  1100  that is 2,2,4,4,6,6-hexamethylcyclotrisilazane.  FIG. 12  shows precursor molecule  1200  that is 2,4,6-trimethyl-2,4,6-trivinyl-cyclotrisilazane.  
         [0036]     Another family of precursor compounds that may be suitable to form a dielectric film include azidosilanes. A molecular feature of this family of compounds includes at least one azide ligand (N 3 ) bound to silicon (e.g., a silane, disilane, or some other variation such as noted in the previous chemical families).  FIG. 13  shows one example of an azidosilane. Molecule  1300  is trimethylazidosilane. Other alkyls or other noted R groups may be substituted for the methyl groups and may be the same or different.  
         [0037]     Another family of compounds suitable as precursors for forming a dielectric film include precursor molecules based on 1,2,4,5-tetraaza-3,6-disilacyclohexane, a six membered ring containing two silicon and four nitrogen atoms with the general formula: 
 
Si 2 N 4 R 8  
 
 where R is a ligand, including, but not limited to, hydrogen, an alkyl, an aryl, and an amine and each R may be similar or different (e.g., independent).  FIG. 14  and  FIG. 15  illustrate two examples of precursor molecules.  FIG. 14  shows molecule  1400  of a 3,6-bis(dimethylamino)-1,4-ditertiarybutyl-2,5-dimethyl-1,2,4,5-tetraaza-3,6-disilacyclohexane.  FIG. 15  shows precursor molecule  1500  of 3,6-bis(tertiarybutylamino)-1,4-ditertiarybutyl-1,2,4,5-tetraaza-3,6-disilacyclohexane. 
 
         [0038]     In the preceding paragraphs, specific embodiments are described. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.