Source: http://www.google.com/patents/US8067297?dq=6,272,646
Timestamp: 2014-09-21 16:21:28
Document Index: 635486667

Matched Legal Cases: ['Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 2002', 'Application No. 2002', 'Application No. 2007']

Patent US8067297 - Process for deposition of semiconductor films - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsChemical vapor deposition processes utilize higher order silanes and germanium precursors as chemical precursors. The processes have high deposition rates yet produce more uniform films, both compositionally and in thickness, than films prepared using conventional chemical precursors. In preferred embodiments,...http://www.google.com/patents/US8067297?utm_source=gb-gplus-sharePatent US8067297 - Process for deposition of semiconductor filmsAdvanced Patent SearchPublication numberUS8067297 B2Publication typeGrantApplication numberUS 11/642,167Publication dateNov 29, 2011Filing dateDec 20, 2006Priority dateFeb 12, 2001Also published asDE60223662D1, DE60223662T2, DE60227350D1, EP1374290A2, EP1374290B1, EP1374291A2, EP1374291B1, EP1421607A2, US6716713, US6716751, US6743738, US6821825, US6900115, US6958253, US6962859, US7186582, US7273799, US7285500, US7547615, US7585752, US7893433, US8360001, US20020168868, US20020173113, US20020197831, US20030022528, US20030068851, US20030068869, US20030082300, US20050048745, US20050064684, US20050208740, US20050250302, US20070102790, US20080014725, US20080073645, US20100012030, WO2002064853A2, WO2002064853A3, WO2002065508A2, WO2002065508A3, WO2002065516A2, WO2002065516A3, WO2002065516A8, WO2002065517A2, WO2002065517A3, WO2002080244A2, WO2002080244A3, WO2002080244A9Publication number11642167, 642167, US 8067297 B2, US 8067297B2, US-B2-8067297, US8067297 B2, US8067297B2InventorsMichael A. ToddOriginal AssigneeAsm America, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (107), Non-Patent Citations (24), Classifications (119), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetProcess for deposition of semiconductor filmsUS 8067297 B2Abstract Chemical vapor deposition processes utilize higher order silanes and germanium precursors as chemical precursors. The processes have high deposition rates yet produce more uniform films, both compositionally and in thickness, than films prepared using conventional chemical precursors. In preferred embodiments, trisilane is employed to deposit SiGe-containing films that are useful in the semiconductor industry in various applications such as transistor gate electrodes.
1. A SiGe film in an integrated circuit,
wherein the integrated circuit comprises a transistor,
wherein the transistor comprises at least one electrode comprising a plurality of films over a substrate,
wherein the plurality of films comprises the SiGe film,
wherein the SiGe film directly overlies a gate dielectric,
wherein the SiGe film has a compositional non-uniformity of about 22% or less, and
wherein the SiGe film has an as-deposited thickness non-uniformity of less than 5%.
3. The SiGe film as claimed in claim 1, wherein the gate dielectric has a dielectric constant greater than 5.
4. The SiGe film as claimed in claim 1, wherein the gate dielectric has a dielectric constant greater than 10.
5. The SiGe film as claimed in claim 1, wherein the gate dielectric comprises a material selected from the group consisting of aluminum oxide, hafnium oxide and zirconium oxide.
6. The SiGe film as claimed in claim 1, the SiGe film having an as-deposited thickness non-uniformity of about 2% or less.
7. The SiGe film as claimed in claim 1, wherein the SiGe film is contained in a heterojunction bipolar transistor.
8. A SiGe film in an integrated circuit, the SiGe film having an as-deposited thickness non-uniformity of less than 5%, wherein the SiGe film is graded and has a compositional non-uniformity of less than 22% across a plane of the SiGe film.
9. The SiGe film as claimed in claim 8, wherein the SiGe film comprises a central portion having a substantially constant Ge concentration, the central portion being sandwiched between graded portions in which the Ge concentration varies.
10. The SiGe film as claimed in claim 1, the SiGe film having a compositional non-uniformity of about 17% or less.
11. The SiGe film as claimed in claim 1, the SiGe film having a compositional non-uniformity of about 12% or less.
12. A SiGe film in an integrated circuit, the SiGe film having an as-deposited thickness non-uniformity of less than 5%, and the SiGe film having a compositional non-uniformity of less than about 10%.
13. The SiGe film as claimed in claim 1, wherein the SiGe film is amorphous.
14. The SiGe film as claimed in claim 1, wherein the SiGe film is epitaxial.
15. The SiGe film as claimed in claim 1, wherein the SiGe film is polycrystalline.
RELATED APPLICATION INFORMATION This application is a divisional of U.S. patent application Ser. No. 11/124,340, filed on May 6, 2005 now U.S. Pat. No. 7,186,582 which is a continuation of U.S. patent application Ser. No. 10/074,534, filed on Feb. 11, 2002 (now U.S. Pat. No. 6,958,253), which claims priority to: U.S. Provisional Application No. 60/268,337, filed Feb. 12, 2001; U.S. Provisional Application No. 60/279,256, filed Mar. 27, 2001; U.S. Provisional Application No. 60/311,609, filed Aug. 9, 2001; U.S. Provisional Application No. 60/323,649, filed Sep. 19, 2001; U.S. Provisional Application No. 60/332,696, filed Nov. 13, 2001; U.S. Provisional Application No. 60/333,724, filed Nov. 28, 2001; and U.S. Provisional Application No. 60/340,454, filed Dec. 7, 2001; all of which are hereby incorporated by reference in their entireties.
This application is related to and incorporates by reference in their entireties, co-owned and U.S. patent application Ser. Nos.: 10/074,563 (now U.S. Pat. No. 6,821,825); 10/074,149 (now U.S. Pat. No. 6,716,751); 10/074,722 (now U.S. Pat. No. 7,026,219); 10/074,633 (now U.S. Pat. No. 6,900,115); and 10/074,564 (now U.S. Pat. No. 6,962,859).
Japanese Patent Application Disclosure Number S60-43485 discloses the use of trisilane to make amorphous thin films at 300� C., apparently for photovoltaic applications. Japanese Patent Application Disclosure Number H5-62911 discloses the use of trisilane and germane to make epitaxial thin films at 500� C. or less. Japanese Patent Application Disclosure Number H3-91239, H3-185817, H3-187215 and HO2-155225 each disclose the use of disilane, some also mentioning trisilane.
In another aspect of this invention, methods are taught for making graded SiGe-containing films by thermal CVD by using a deposition gas containing amounts of trisilane and a germanium precursor that are varied during the deposition. In a preferred embodiment, the amount of trisilane in the deposition gas is effective to incorporate germanium into the graded Si�Ge film in an amount that is a substantially linear function of the amount of germanium precursor.
FIG. 4 schematically illustrates a preferred Ge concentration profile in an epitaxial Si�Ge layer for the base layer of a heterojunction bipolar transistor.
FIG. 5 is a plot of film composition and deposition rate as a function of germane flow rate using silane at 600� C.
FIG. 6 is a plot of film composition and deposition rate as a function of germane flow rate using silane at 625� C.
FIG. 7 is a plot of film composition and deposition rate as a function of germane flow rate using silane at 650� C.
FIG. 8 is a plot of film composition and deposition rate as a function of germane flow rate using silane at 700� C.
FIG. 9 is a plot of film composition and deposition rate as a function of germane flow rate using trisilane at 600� C. at a H2 flow rate of 20 slm.
FIG. 10 is a plot of film composition and deposition rate as a function of germane flow rate using trisilane at 600� C. at a H2 flow rate of 30 slm.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Dynamic temperature variations, due to limitations in heating and temperature control systems, play a significant role in the non-uniformity of film deposition on substrate surfaces by CVD. It is generally desirable for the deposited film to be as uniform as possible in both thickness and elemental composition, but existing processes tend to produce films that are non-uniform to varying degrees. Such non-uniformities often result from temperature variations across the surface of the substrate because under typical CVD process conditions the surface temperature of the substrate influences the deposition rate and the composition of the resulting film. Imperfect control over other process parameters, including gas flow rates and total pressure, are also believed to contribute to non-uniformities in film physical properties.
Uniformity is often sought by empirically tuning the deposition conditions e.g., gas flow rate, rotation speed of substrate, power distribution to heating elements, etc., to achieve an overall uniform thickness for the desired film. This is done by first depositing a large number of films on different substrates, each under a different pre-selected set of deposition conditions. The thickness variations within each film are then measured and the results analyzed to identify conditions that would eliminate the thickness variations. The inventor has realized, however, that such empirical tuning does not necessarily achieve uniform temperature distributions throughout the process; rather, conventionally tuning effectively time-averages the thickness variations produced by the temperature variations for a specific reaction temperature �set-point�.
As will be appreciated by the skilled artisan, the temperature range for the mass transport limited regime can be determined for a given precursor and set of reaction conditions, and illustrated in an Arrhenius plot. For the chemical precursor trisilane, the transition point from temperature-dependent deposition rates to temperature-independent deposition rates is much lower than the transition point for silane or disilane, as illustrated in the Arrhenius plot shown in FIG. 16. The lower region of the plot up to the transition has a significant upward linear slope, indicating that silicon deposition by flowing trisilane within this temperature range is a strong function of temperature and therefore not within the mass transport limited regime. For example, FIG. 16 shows that silicon deposition using trisilane is not mass transport limited (i.e., is within the kinetic regime) at temperatures less than about 525� C., under the conditions used (25 sccm flow rate, 40 Torr pressure). In contrast, the region of the plot above the transition point is substantially flat, indicating that deposition using trisilane within this temperature range is independent of temperature and therefore within the mass transport limited regime. For example, FIG. 16 shows that trisilane deposition is clearly mass transport limited at temperatures of about 620� C. or greater. It will be understood that the transition occurs over a range of temperatures in which the declining slope of the Arrhenius plot indicates that the deposition of trisilane within this temperature range is substantially independent of temperature, near the mass transport limited regime. For example, FIG. 16 shows that trisilane deposition is substantially mass transport limited at temperatures of about 525� C. or greater. It will be understood that the transition point may increase somewhat at higher flow rates, and decrease somewhat at lower flow rates. For example, it has been determined experimentally that the transition point from temperature-dependent deposition to substantially mass transport limited deposition shifts to higher temperatures when the trisilane flow rate is increased. Accordingly, the use of trisilane enables substantially mass transport limited deposition at temperatures that are desirable for other reasons in contemporary fabrication (e.g., conservation of thermal budgets for maintaining crystal properties, controlling dopant profiles, etc.).
Selection of the deposition temperature can also depend partly upon the desired crystallinity in the layer being deposited. For example, predominantly crystalline silicon can be deposited in the range of about 620� C. to 800� C., which is clearly within the mass transport limited regime, as discussed above. More preferably, polycrystalline layer deposition is conducted between 650� C. and 750� C. Lower temperatures can be used for amorphous layer deposition, but preferably temperatures are selected to remain at least substantially mass transport limited (i.e., preferably at higher than 525� C. for the preferred conditions). Epitaxial deposition is largely dependent upon the purity of the surface upon which deposition is to take place. Namely, as will be recognized by the skilled artisan, an extremely clean single-crystal surface, such as the upper surface of a previously-deposited epitaxial layer or the upper surface of a single crystal wafer, enables epitaxial deposition at a large range of temperatures, depending upon flow rates, pressure, etc. Typically, epitaxial deposition upon a suitable surface can take place between 500� C. and 1160� C. It is preferred to employ the lower temperature ranges, such as from about 500� C. to about 750� C., for reasons of consideration of thermal budgets.
A suitable manifold may be used to supply feed gas(es) to the CVD chamber. Experimental results described herein were conducted in a CVD chamber with horizontal gas flow, and preferably the chamber is a single-wafer, horizontal gas flow reactor, preferably radiantly heated. Suitable reactors of this type are commercially available, and preferred models include the Epsilon� series of single wafer epitaxial reactors commercially available from ASM America, Inc. of Phoenix, Ariz. While the processes described herein can also be employed in alternative reactors, such as a showerhead arrangement, benefits in increased uniformity and deposition rates have been found particularly effective in the horizontal, single-pass, laminar gas flow arrangement of the Epsilon� chambers.
The chemical precursors are preferably supplied to the CVD chamber in the form of a feed gas or as components of a feed gas, at the temperatures and pressures used for deposition. The total pressure in the CVD chamber is preferably in the range of about 0.001 Torr to about atmospheric pressures, more preferably in the range of about 0.1 Torr to about 200 Torr, most preferably in the range of about 1 Torr to about 80 Torr. Surprisingly, the processes described herein obtain extremely high uniformity despite being conducted well above conventional low pressure CVD (LPCVD) pressure ranges (typically in the milliTorr range). The partial pressure of each Si- and/or Ge-containing chemical precursor is preferably in the range of about 1�10−6% to about 100% of the total pressure, more preferably about 1�10−4% to about 100%, same basis. The partial pressure of each carbon source, if any, is preferably in the range from 0% to about 1% of the total pressure, more preferably about 1�10−6% to about 0.1%, same basis. If used, the partial pressure of the carbon source is preferably effective to provide the resulting Si-containing and/or Ge-containing film with a carbon content of about 20% or less (10% or less for single crystal materials), even more preferably about 10% or less (5% or less for single crystal materials), where the percentages are by weight based on total film weight.
Dopant precursors include diborane, deuterated diborane, phosphine, and arsine. Silylphosphines [(H3Si)3-xPRx] and silylarsines [(H3Si)3-xAsRx] where x=0-2 and Rx=H and/or D are preferred dopant sources of phosphorous and arsenic. SbH3 and trimethylindium are preferred sources of antimony and indium, respectively. Such dopants and dopant sources are useful for the preparation of preferred films such as boron-, phosphorous-, antimony-, indium-, and arsenic-doped silicon, SiGe and SiGeC films, by the methods described herein. The dopant concentration in these materials, when doped, is preferably in the range of from about 1�1014 to about 1�1022 atoms/cm3. Dopants can be incorporated using very low concentrations of the dopant sources, e.g., as mixtures in hydrogen with concentration ranging from about 1 ppm to about 1%, by weight based on total. These diluted mixtures can then be delivered to the reactor via a mass flow controller with set points ranging from 10 to 200 standard cubic centimeters per minute (sccm), depending on desired dopant concentration and dopant gas concentration. The dopant source is also preferably further diluted in the carrier gas delivered to the reactor with the silicon/germanium/carbon sources. Since flow rates often range from about 20 standard liters per minute (slm) to about 180 slm, the concentration of the dopant used in a typical process is usually very small.
The relative partial pressures of the chemical precursors (and carbon source, if any) can be held relatively constant over the course of depositing the Si-containing and/or Ge-containing film, or can be varied to produce a graded film that has differing amounts of Si and/or Ge as a function of depth within the thickness of the film. Preferably, the film has a thickness in the range of about 10 Å to about 5,000 Å. The elemental composition of the film may vary in a stepwise and/or continuous fashion. Film thickness may be varied as suitable for the intended application, by varying the deposition time and/or gas flow. As discussed below, the use of mixtures containing germanium precursor(s) and higher order silane(s) allows for the deposition of higher quality, better controlled graded films. Whether constant or graded, compound and doped films deposited by the methods described herein have relatively constant composition across a plane at any particular given depth. The �plane� in this sense may undulate if the film is deposited over a patterned substrate.
Graded films having improved properties may be prepared using preferred chemical precursors (particularly trisilane). For example, FIG. 4 illustrates a preferred Ge concentration profile for an epitaxial SiGe film, in the context of the base layer in a heterojunction bipolar transistor (�HBT�). In the illustrated embodiment, the Si�Ge film layer includes a central portion have a substantially constant Ge concentration that is sandwiched between graded portions in which the Ge concentration varies as a function of film thickness.
For example, the effect of changing the amount of Ge precursor during CVD deposition using a silane-containing deposition gas is shown in FIGS. 5-8. During the illustrated depositions, the amount of Ge precursor (germane) in the deposition gas was varied by changing the germane flow rate. The effect of changing the germane flow rate on the amount of Ge incorporated into the film and on the deposition rate of the film was measured as described in the Examples below. At a deposition temperature of 600� C., FIG. 5 shows that the amount of germanium incorporated into the resulting film (left-hand axis) is not a linear function of the amount of germane in the deposition gas. Thus, a linear ramp-up or ramp-down in germane flow during deposition does not produce a Si�Ge film in which the Ge concentration has a correspondingly linear profile under these deposition conditions.
Deposition is further complicated by the non-linear effect of changing Ge precursor flow on deposition rate. FIG. 5 also shows that the deposition rate of the Si�Ge film (right-hand axis) increases non-linearly as a function of increasing germane flow, with a degree of non-linearity that is significantly different from the degree of non-linearity in Ge incorporation shown on the left-hand axis. This greatly complicates the task of depositing a smoothly graded Si�Ge film having a specified thickness and a specified Ge content because of the additional difficulties associated with simultaneously compensating for the observed non-linearities in both Ge concentration and film deposition rate.
FIGS. 6-8 show that concentration and deposition rate non-linearities for thermal CVD using silane/germane are similarly observed at higher deposition temperatures. This means that the deposition problems encountered at 600� C. are not eliminated by increasing the deposition temperatures to 625� C. (FIG. 6), 650� C. (FIG. 7), or even 700� C. (FIG. 8). In fact, since the shapes of the plots are different at each temperature, these plots indicate that relatively small temperature variations across the surface of a substrate are likely to further complicate deposition using silane/germane.
The use of a deposition gas that contains trisilane greatly simplifies the task of depositing a graded Si-containing film using thermal CVD. For example, the effect of changing the amount of Ge precursor during CVD deposition using a trisilane-containing deposition gas is shown in FIGS. 9-10. The data shown in FIGS. 9-10 were obtained under the conditions described in the Examples below. In contrast to the non-linearities apparent in FIGS. 5-8, FIG. 9 shows that the Ge incorporation into the film is a substantially linear function of the germane flow rate. FIG. 9 also illustrates preferred linearity in the deposition rate as a function of the germane flow rate. The data is taken over a large range of Ge concentrations and Ge deposition rates of interest in IC fabrication contexts. It is preferred that both Ge incorporation and deposition rate be substantially linear functions of flow rate in order to facilitate the process of depositing graded Si�Ge films. Those skilled in the art will appreciate that data such as that shown in FIGS. 9 and 10 can be used to determine preferred conditions for the deposition of graded films, preferably graded Si�Ge films. FIG. 10 also illustrates preferred linearity of Ge incorporation and deposition rate for trisilane/germane under higher H2 flow rate conditions and a different germane concentration than illustrated in FIG. 9, demonstrating that the advantages of using trisilane are not limited to the specific conditions used to obtain the data in FIG. 9.
It will be apparent to those skilled in the art that the use of a deposition gas that comprises a higher-order silane (particularly trisilane) and a germanium precursor provides additional significant advantages for the deposition of Si�Ge films. For example, the use of such higher-order silanes allows for higher deposition rates and greater control over film thickness and composition, preferably resulting in higher device quality and improved manufacturing yield and throughput. It will also be apparent that the deposition gas may optionally further comprise silane, higher-order silane(s), and germanium precursor(s), along with dopant precursor(s), carbon source(s) and carrier gases. Preferably, the ratio of higher-order silane to silane in any such mixture is about 1:1 or greater, more preferably about 4:1 or greater, most preferably about 9:1 or greater, by weight based on total amount of silane and higher-order silane. Preferably, the higher-order silane is trisilane, and most preferably the mixture is substantially free of silane. Preferably, the Si�Ge layer is doped with boron, arsenic, phosphorous or antimony. The ability to deposit high quality doped Si�Ge layers at relatively low temperatures enables strained heteroepitaxial Si�Ge films containing higher amounts of Ge to be made, a significant advantage for the production of HBTs.
The amount of germanium precursor and/or the flow rate during deposition can affect the crystallinity of the resulting SiGe-containing film. Under a given set of deposition conditions, films having lower degrees of crystallinity are generally produced as deposition temperatures are lowered. In a preferred embodiment, deposition temperatures are selected so that the resulting SiGe-containing film (including carbon-doped SiGe) is amorphous. Preferred deposition temperatures are about 600� C. or lower, more preferably about 550� C. or lower. Since higher deposition rates are usually preferred, deposition is preferably conducted at a temperature of about 450� C. or higher, more preferably about 525� C. or higher, although lower temperatures may occasionally be suitable. Deposition of amorphous films is preferably conducted at a temperature in the range of about 450� C. to about 600� C., more preferably about 475� C. to about 575� C., most preferably about 525� C. to about 575� C.
In another preferred embodiment, deposition temperatures are selected so that the resulting SiGe-containing film (including carbon-doped SiGe) is at least partially crystalline. Greater crystallinity is favored at higher deposition temperatures, for a given set of deposition conditions. Preferred deposition temperatures are about 575� C. or higher, more preferably about 600� C. or higher. Since preservation of thermal budget is usually important, deposition temperatures are preferably about 800� C. or below, more preferably about 700� C. or below, although higher temperatures can be used if needed. Deposition is preferably conducted at a temperature in the range of about 575� C. to about 750� C., more preferably about 600� C. to about 700� C.
Preferably, polycrystalline SiGe-containing films, obtained by depositing over non-single crystal materials such as gate dielectric materials, have a surface roughness of about 10% or less, more preferably about 5% or less, based on the mean thickness of the film, as measured by atomic force microscopy on a 10 micron�10 micron scan area. When deposition is conducted as described herein, polycrystalline SiGe films can be obtained that have surface roughness values that are much less than comparable SiGe films deposited using silane in place of trisilane, as demonstrated in Examples 88-89 and FIGS. 12-15. Preferred amorphous SiGe-containing films are also very smooth, and preferably have a surface roughness of about 10% or less, more preferably about 5% or less, even more preferably about 2% or less, based on the mean thickness of the film, as measured by atomic force microscopy on a 10 micron�10 micron scan area.
Process variables such as gas flow rate, gas flow distribution, partial pressure and gas composition are preferably varied in processes similar to that described above for identifying the temperature set point, or during the same experiments, in order to identify the desired deposition conditions for each layer. Preferably, experimental design methods are used to determine the effect of the various process variables and combinations thereof on uniformity and/or deposition rate. Experimental design methods per se are well-known, see e.g., Douglas C. Montgomery, �Design and Analysis of Experiments,� 2nd Ed., John Wiley and Sons, 1984. For a particular process, after the effect of the various process variables and combinations thereof on layer uniformity and/or deposition rate has been determined by these experimental design methods, the process is preferably automated by computer control to ensure batch-to-batch or wafer-to-wafer consistency. Most preferably, the process improvements result from in-situ, stepwise or dynamic adjustments to the process variables mentioned above. This empirical method of tuning process variables to individually improve the properties of the layers has been found to improve the properties of the overall single structural or functional film (comprising multiple layers from a process standpoint) regardless of any theory expressed herein. Therefore, the functioning of this embodiment does not depend on the correctness or incorrectness of any theory.
Preferred Si-containing chemical precursors include higher order silanes as described elsewhere herein, as well as conventional chemical precursors such as silane. Preferably at least one of the first Si-containing chemical precursor and the second Si-containing chemical precursor is selected from the group consisting of silane, disilane and trisilane. At least one of the first gas, second gas and third gas includes an additional germanium and/or other dopant source, preferably a compound selected from the group consisting of germane, digermane, trigermane, NF3, monosilylmethane, disilylmethane, trisilylmethane, tetrasilylmethane, and an electrical dopant precursor, as described elsewhere herein. Preferably, the amount of each Si-containing chemical precursor Xn, for X1%, X2%, X3%, X4%, etc., in the gas is independently in the range of about 1�10−6% to about 100%, preferably about 1�10−4% to about 100%, by volume based on total volume, at any particular stage of the deposition process.
The substrate preferably has a temperature of about 350� C. or higher, more preferably in the range of 450� C. to about 700� C. The CVD chamber is preferably a single-wafer, horizontal gas flow reactor. The resulting multiple layer Si-containing film is preferably selected from the group consisting of a microdot, a SiGe film, a SiGeC film, a SiN film, a silicon-oxygen film, a silicon-carbon-nitrogen film, and a silicon-oxygen-nitrogen film. Such films can be doped with, e.g., P, As or B.
Methods of determining film uniformity and deposition rates are well-known. Deposition rates may be determined by measuring the average thickness of the film as a function of time and can be expressed in units of angstroms per minute (Å/min.). Preferred deposition rates are about 20 Å/min. or greater, more preferably about 50 Å/min. or greater, most preferably 100 Å/min. or greater. Suitable methods for measuring film thickness include multiple-point ellipsometric methods. Instruments for measuring film thickness are well known and commercially available and preferred instruments include the NanoSpec� series of instruments from Nanometrics, Inc., Sunnyvale, Calif.
The term �uniformity,� as used herein to refer to the uniformity of deposited films, is used to refer to both thickness uniformity and compositional uniformity. Film thickness uniformity is preferably determined by making multiple-point thickness measurements, determining the mean thickness, and determining the average amount that the multiple measurements differ from the mean. To enable comparisons, the result can be expressed as percent non-uniformity. More particularly, when comparing the results of different layers, thickness uniformity is to be measured by the following standard: a randomly selected diameter across a wafer is employed and 49 points along that diameter are measured for deposited layer thickness. No measurements are taken within a 3 mm exclusion zone at the wafer periphery. The range in thickness measurements (e.g., �6 Å) over those 49 points is then divided by the sum of the maximum thickness measurement plus the minimum thickness measurement from among the 49 points. When measuring thickness uniformity of a film having a surface that is not accessible to such a measurement, e.g., a film onto which one or more additional layers have been applied, or a film contained within an integrated circuit, the film is cross sectioned and examined by electron microscopy. The film thickness is measured at the thinnest part of the cross sectioned film and at the thickest part, and the range in thickness measurements (e.g., �6 Å) between these two points is then divided by the sum of the two measurements. This non-uniformity is expressed as a percentage herein. Preferably, the percent non-uniformity is about 10% or less, more preferably about 5% or less, most preferably about 2% or less.
Compositional uniformity may be determined using electrical measurements (i.e. 4-point probe), SIMS (Secondary Ion Mass Spectrometry), RBS (Rutherford Backscattering Spectroscopy), Spectroscopic Ellipsometry and/or high resolution X-ray diffractometry (HR-XRD). When comparing one Si-containing film to another, or one deposition process to another, compositional uniformity is measured using SIMS across a circular wafer substrate onto which the Si-containing has been deposited. SIMS measurements are made at three locations: one at the center of the wafer, one at a point midway between the center and the edge (�r/2�), and one at a point 3 millimeters from the edge (�3 mm edge exclusion�). For each non-silicon element in question, the amount of that element at each location is then determined from the SIMS data, and the resulting value expressed in atomic % based on total. The three values are then averaged, and the standard deviation determined. For a given Si-containing film or deposition process, compositional non-uniformity is the standard deviation divided by the sum of the maximum and minimum measured values, and the result expressed as a percentage. For example, if all three values are the same, the compositional non-uniformity is 0%, because the standard deviation is zero; if the three values are 3 atomic %, 5 atomic %, and 10 atomic %, the compositional non-uniformity is 28% (3.6/13=28%) because the standard deviation is 3.6 and the sum of the maximum (10) and minimum (3) values in 13; etc.
Another preferred embodiment provides an apparatus for depositing a Si-containing material on a surface. This apparatus comprises a CVD chamber, a vessel containing trisilane, a feed line operatively connecting the vessel to the CVD chamber to allow passage of the trisilane from the vessel to the CVD chamber, and a temperature controller operatively disposed about said vessel and maintained at a temperature in the range of about 10� C. to about 70� C., preferably about 15� C. to about 52� C., to thereby control the vaporization rate of the trisilane. Examples of suitable temperature controllers include thermoelectric controllers and/or liquid-filled jackets. Preferably, the CVD chamber is a single-wafer, horizontal gas flow reactor. Preferably, the apparatus is also comprised of a manifold operatively connected to the feed line to control the passage of the trisilane from the vessel to the chemical vapor deposition chamber. Preferably, a heat source is operatively disposed about the feed line and the gas lines are heated to about 35� C. to about 70� C., more preferably between about 40� C. and about 52� C., to prevent condensation at high gas flow rates. Preferably, trisilane is introduced by way of a bubbler used with a carrier gas to entrain trisilane vapor, more preferably a temperature-controlled bubbler, most preferably a temperature-controlled bubbler in combination with heated gas lines to deliver trisilane.
Examples 1-4 Si-containing films were deposited using trisilane as a chemical precursor according to the parameters shown in Table 1. The deposition temperature was 700� C., well within the mass transport limited regime for trisilane. However, the resulting films were not uniform and instead had a concave deposition profile (thin in middle and thicker at edges) because the trisilane flow rate was inadequate (under these particular deposition conditions that were tuned for silane-based deposition) to provide a uniform film.
Examples 5-15 Si-containing amorphous films were deposited using trisilane and silane as chemical precursors and diborane as a dopant precursor according to the parameters shown in Table 1. About 120 sccm of 1% B2H6 in H2 was diluted in 2 slm H2 and 120 sccm of this mixture was introduced into the reactor where it was mixed with 20 slm H2 and trisilane or silane at the flow rate shown in Table 2. These results show that much higher deposition rates were generally obtained at a given temperature using trisilane, as compared to silane, even when the flow rate for trisilane was lower than that for silane.
Examples 16-19 Si-containing films were deposited using trisilane and silane as chemical precursors, according to the parameters shown in Table 3. Deposition times were adjusted so that the films each had an average thickness of about 500 Å. Deposition rates were determined by measuring average film thickness using a Nanometrics ellipsometer and then dividing this number by the deposition time. Film thickness non-uniformity was determined from a 49-point thickness map of the film thickness. The results show that a much more uniform film was obtained at a much higher deposition rate by using trisilane at the indicated temperature in place of silane. This is true at 550� C., but dramatically more so at 600� C.
Examples 40-48 (Comparative) A series of films was deposited using the ASM Epsilon 2000� horizontal flow epitaxial reactor system described above. Silane (20 sccm) and germane (1.5% in H2) were introduced into the reactor, mixed with 20 slm H2, and used to deposit a film onto a rotating substrate at a pressure of 80 torr and a temperature of 600� C., under the germane flow rate conditions shown in Table 4 below. The Ge concentrations in the resulting films were determined by Rutherford Backscattering Spectroscopy (RBS). Deposition rates were determined by measuring average film thickness using a Nanometrics ellipsometer and then dividing this number by the deposition time. The Ge concentration and deposition rate data are shown in Table 4 below and plotted in FIG. 5.
GeH4 Flow
Atomic % Ge
Examples 49-57 (Comparative) A series of films was deposited under the conditions described above for Examples 40-48 under the flow rate conditions shown in Table 5 below, except that the deposition temperature was 625� C. The Ge concentrations in the resulting films and the deposition rates were determined as described above for Examples 40-48. The Ge concentration and deposition rate data are shown in Table 5 below and plotted in FIG. 6.
Examples 58-67 (Comparative) A series of films was deposited under the conditions described above for Examples 40-48 under the flow rate conditions shown in Table 6 below, except that the deposition temperature was 650� C. The Ge concentrations in the resulting films and the deposition rates were determined as described above for Examples 40-48. The Ge concentration and deposition rate data are shown in Table 6 below and plotted in FIG. 7.
Examples 68-76 (Comparative) A series of films was deposited under the conditions described above for Examples 40-48 under the flow rate conditions shown in Table 7 below, except that the deposition temperature was 700� C. The Ge concentrations in the resulting films and the deposition rates were determined as described above for Examples 40-48. The Ge concentration and deposition rate data are shown in Table 7 below and plotted in FIG. 8.
Examples 77-80 A series of films was deposited under the conditions described above for Examples 40-48 under the flow rate conditions shown in Table 8 below, except that trisilane was used in place of silane, the pressure was 40 torr, and the germane concentration in the H2 was 10%. Trisilane was supplied to the reactor via a H2 bubbler at a flow rate set point of 25 sccm. The Ge concentrations in the resulting films and the deposition rates were determined as described above for Examples 40-48. The Ge concentration and deposition rate data are shown in Table 8 below and plotted in FIG. 9.
Examples 81-86 A series of films was deposited under the conditions described above for Examples 77-80 under the flow rate conditions shown in Table 9 below, except that the germane concentration in the H2 was 1.5% and the H2 flow rate was 30 slm. The Ge concentrations in the resulting films and the deposition rates were determined as described above for Examples 40-48. The Ge concentration and deposition rate data are shown in Table 9 below and plotted in FIG. 10.
Example 87 A Si-containing film having a mean thickness of 1,038 Å was deposited onto a SiO2 substrate (without a nucleation layer) using trisilane and germane as chemical precursors at a deposition temperature of 650� C. and a pressure of 40 torr. The set points for gas flow injectors had been empirically tuned in the usual manner in a series of previous runs. The resulting SiGe film had a thickness non-uniformity of 0.37% (range of 8 Å) as measured by a 49 point linear diameter scan with 6 mm edge exclusion. FIG. 11 is a plot of film thickness as a function of measurement site for this film.
Example 88 (Comparative) A SiGe-containing film was deposited onto a SiO2 substrate (without a nucleation layer) at a temperature of 600� C. using silane and germane as precursors. The surface roughness of the resulting SiGe film (as measured by atomic force microscopy) was 226 Å for a 10 micron�10 micron scan area. Scanning electron microscopy (SEM) of the SiGe film revealed pyramidal, faceted grains indicative of an island-type deposition, as demonstrated in the SEM micrographs shown in FIGS. 12 and 13.
Example 89 A SiGe-containing film was deposited at 600� C. as described in Example 88, but trisilane and germane were used in place of silane and germane as precursors. The surface roughness of the resulting SiGe film (as measured by atomic force microscopy) was 18.4 Å for a 10 micron�10 micron scan area. SEM of the SiGe film revealed a much more uniform surface, as demonstrated in the SEM micrographs shown in FIGS. 14 and 15 (same magnifications and tilt angles as FIGS. 12 and 13, respectively).
Examples 90-110 A series of Si-containing films were deposited onto a SiO2 substrate (without a nucleation layer) at a pressure of 40 torr using trisilane and germane. The trisilane flow rate was constant at 77 sccm (hydrogen carrier, bubbler) for the examples of Table 9. Germane flow (10% germane, 90% H2) and deposition temperature were varied as shown in Table 9. Germanium concentration (atomic %) and thickness of the resulting SiGe films were determined by RBS, and surface roughness was determined by atomic force microscopy (AFM). The results shown in Table 9 demonstrate that highly uniform films can be prepared over a range of temperatures and flow rate conditions, particularly over a large range of germane concentration. High deposition rates are achieved at relatively low temperatures without sacrificing uniformity.
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Res. & Dev., vol. 46, No. 2/3, Mar./May 2002.Classifications U.S. Classification438/478, 438/603, 257/E21.09, 438/680, 438/503, 438/507International ClassificationH01L21/20, H01L21/8238, H01L31/20, H01L21/316, H01L21/425, C23C16/24, H01L21/205, C23C16/42, H01L21/331, H01L27/092, C23C16/02, C30B25/02, H01L29/78, H01L21/28, H01L21/337, H01L21/469, H01L29/737, H01L29/51, H01L21/285, H01L31/18Cooperative ClassificationY10S438/933, Y02E10/547, H01L21/0243, C23C16/325, H01L21/02598, C30B29/06, H01L31/202, H01L21/02576, H01L29/517, C23C16/56, H01L29/66242, H01L29/127, H01L21/28556, C23C16/345, H01L29/51, H01L21/02595, H01L29/518, H01L21/02422, C30B25/02, H01L21/0251, H01L29/66181, H01L21/0262, C23C16/36, H01L21/02592, H01L21/0245, H01L28/84, H01L21/02579, C23C16/308, C23C16/30, H01L21/02667, H01L31/182, H01L21/02529, C23C16/22, Y02E10/546, C23C16/24, H01L21/28035, H01L21/28044, H01L31/1804, H01L21/02532, H01L21/28194, H01L21/3185, H01L21/28525, H01L21/32055, H01L21/2257, B82Y10/00, B82Y30/00, C23C16/0272European ClassificationC23C16/30, H01L21/02K4B1A3, H01L21/02K4B5L7, H01L21/02K4C1A3, H01L21/02K4C3C2, H01L21/02K4E3C, H01L21/02K4C3C1, H01L21/02K4C1A2, H01L29/66M6T2H, H01L31/18C5, H01L29/66M6D6, B82Y30/00, H01L21/3205N, H01L21/20B, C23C16/36, C23C16/30E, H01L21/02K4C5M2, H01L21/28E2C2D, H01L21/205B, C30B25/02, C23C16/32B, H01L21/285B4H, C23C16/24, H01L28/84, H01L29/12W4, H01L21/285B4B, H01L21/02K4C5M1, H01L21/02K4A5S, C23C16/02H, H01L21/02K4C5M3, H01L21/28E2B2P, C23C16/34C, H01L21/225A4F, C23C16/56, H01L21/205, H01L21/20C, H01L21/02K4A1K, H01L31/20B, B82Y10/00, C23C16/22, H01L31/18C, H01L29/51, H01L21/28E2B2, H01L29/51M, C30B29/06, H01L21/318BLegal EventsDateCodeEventDescriptionApr 17, 2012CCCertificate of correctionDec 20, 2006ASAssignmentOwner name: ASM AMERICA, INC., ARIZONAFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:TODD, MICHAEL A.;REEL/FRAME:018732/0187Effective date: 20020422RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google