Patent Publication Number: US-8980752-B2

Title: Method of forming a plurality of spaced features

Description:
RELATED PATENT DATA 
     This patent resulted from a continuation of U.S. patent application Ser. No. 12/749,923, which was filed on Mar. 30, 2010, which issued as U.S. Pat. No. 8,492,278 on Jul. 23, 2013 and is hereby incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     Embodiments disclosed herein pertain to methods of forming a plurality of spaced features, for example in the fabrication of integrated circuitry. 
     BACKGROUND 
     In the fabrication of integrated circuitry, masks may be used when etching into underlying material to form desired feature shapes. Photolithographic processing is one technique used in fabrication of such masks. For example, photoresist may be deposited over a substrate and exposed to patterned radiation followed by developing to form a patterned photoresist mask. The pattern of the photoresist mask may be subsequently transferred to form electronic device components into underlying substrate material that is one or more of electrically conductive, insulative, or semiconductive. In many applications, the photoresist material of the mask is insufficiently robust by itself to serve as a mask while completing etching of the device features. Hardmask material may be used in such instances between the photoresist and the material into which the device features are formed. Accordingly, the photoresist mask pattern is transferred into the hardmask material which is then used as a more robust etching mask than photoresist. In such instances, the photoresist is likely completely removed during etch of the hardmask material or during etch of the material beneath the hardmask material. 
     Integrated circuitry fabrication continues to make ever smaller feature width dimensions to minimize the size of individual device components and thereby increase density of the components within an integrated circuit. One common component in integrated circuits is an electrically conductive line, for example global or local interconnect lines. Other example conductive lines include transistor gate lines that may or may not incorporate charge storage regions which are spaced along individual transistor gate lines. When etching conductive material beneath a hardmask to form conductive lines, it is desirable that the line material have sidewalls which correspond to the longitudinal orientation of the sidewalls of the patterned hardmask material. However, as minimum line widths approached 30 nanometers, the etching may have a tendency to form the line sidewalls that serpentine in a wave-like manner along the longitudinal orientation of the lines. This may not be desirable. 
     For example referring to  FIG. 1 , a top view of a portion of a prior art substrate  10  is shown. Such includes plurality of line constructions  14  which have been patterned over underlying substrate material  12 . Line constructions  14  were formed using pitch multiplication techniques wherein minimum width of individual of the lines was about 25 nanometers, and space between immediately adjacent of the lines was about 30 nanometers. A sacrificial hardmask material (not shown) comprising a highly compressive amorphous carbon layer received over a highly compressive undoped silicon dioxide layer was used as spaced line features of a mask. Such resulted in the depicted undesired depicted line waviness of the sidewalls along the longitudinal orientation of the lines. 
     While the invention was motivated in addressing the above-identified issues, the invention is in no way so limited. Rather, the invention is limited by the accompanying claims as appropriately interpreted in accordance with the doctrine of equivalence. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic top view of integrated circuitry illustrating a problem which motivated some embodiments of the invention. 
         FIG. 2  is a diagrammatic sectional view of a semiconductor substrate in process in accordance with an embodiment of the invention. 
         FIG. 3  is a view of the  FIG. 2  substrate at a processing step subsequent to that shown by  FIG. 2 . 
         FIG. 4  is a view of the  FIG. 3  substrate at a processing step subsequent to that shown by  FIG. 3 . 
         FIG. 5  is a view of the  FIG. 4  substrate at a processing step subsequent to that shown by  FIG. 4 . 
         FIG. 6  is a view of the  FIG. 5  substrate at a processing step subsequent to that shown by  FIG. 5 . 
         FIG. 7  is a top view of  FIG. 6 . 
         FIG. 8  is a diagrammatic sectional view of a semiconductor substrate in process in accordance with an embodiment of the invention. 
         FIG. 9  is a view of the  FIG. 8  substrate at a processing step subsequent to that shown by  FIG. 8 . 
         FIG. 10  is a view of the  FIG. 9  substrate at a processing step subsequent to that shown by  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Embodiments of the invention include methods of forming a plurality of spaced features, for example forming a plurality of spaced electrically conductive lines. Other features may be additionally and/or alternately formed. In some embodiments, the conductive lines which are formed have respective minimum line widths of no greater than 30 nanometers, for example in addressing and reducing line waviness of such narrow lines as identified above in the Background section. 
     The discussion initially proceeds with respect to  FIGS. 2-7  in the fabrication of features which are a plurality of spaced charge storage transistor gate lines having respective minimum line widths of no greater than 30 nanometers, for example as may be used in flash or in other circuitry. Referring to  FIG. 2 , a substrate fragment  20  may be a semiconductive or other substrate. In the context of this document, the term “semiconductor substrate” or “semiconductive substrate” is defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above. Substrate  20  comprises semiconductive material  22  which may comprise, consist essentially of, or consist of silicon. For example, such might comprise bulk monocrystalline silicon lightly background doped with p-type dopant. Semiconductive material  22  may comprise part of a semiconductor-on-insulator substrate or some other substrate whether existing or yet-to-be developed. 
     A tunnel dielectric  24  has been formed over semiconductive material  22 . Such may comprise any suitable composition or combination of compositions, with undoped silicon dioxide being one example. A charge-retaining material  26  has been formed over tunnel dielectric  24 . The charge-retaining material may comprise a floating gate (for example, polycrystalline silicon) or may comprise charge-trapping material (for example, silicon nitride). The charge-retaining material may be homogenous or non-homogenous, and as an example may comprise nanodots imbedded within dielectric material. 
     A blocking dielectric  28  has been formed over charge-retaining material  26 . The blocking dielectric may comprise any suitable composition or combination of compositions. For example, such may comprise, consist essentially of, or consist of one or more of silicon nitride, silicon dioxide, or any of various high k dielectric materials having a dielectric constant greater than that of silicon dioxide. Control gate material  30  has been formed over blocking dielectric  28 . Such is ultimately electrically conductive in the finished circuitry construction and may comprise, consist essentially of, or consist of one or more metals, metal-containing compositions, and conductively-doped semiconductive materials. All material underlying conductive layer  30  may, in one embodiment, be considered as a base. 
     A sacrificial hardmask material  32  has been formed over control gate material  30 . In some embodiments, the sacrificial hardmask material comprises at least two layers of different composition as will be characterized below. Sacrificial hardmask material  32  in  FIG. 2  is depicted as comprising two layers  34  and  36 . More than two layers may be used. Further,  FIG. 2  depicts an example embodiment where sacrificial hardmask material  32  is formed in direct physical touching contact with the conductive material  30 . One or more additional layers may be provided intermediate hardmask material  32  and conductive material  30 . Regardless, in the context of this document, use of “layer(s)” does not require blanketing or complete coverage of such over underlying material. A layer may be discontinuous or only partially received over underlying material. 
     An antireflective coating  38  and photoresist layer  40  have been formed outwardly of sacrificial hardmask material  32 . Any suitable organic or inorganic antireflective coating may be used, or no antireflective coating used. Further, antireflective coating materials may be encompassed as part of the sacrificial hardmask material independent of providing any antireflective effect and/or independent of whether any additional antireflective materials are used outwardly of the sacrificial hardmask material. Photoresist  40  may comprise any suitable existing or yet-to-be developed positive or negative photoresist. Nevertheless, photolithography is not required. 
     Referring to  FIG. 3 , photoresist  40  has been suitably patterned and developed to form the depicted mask line blocks that will be used to form an etch mask of the sacrificial hardmask material. 
     Referring to  FIG. 4 , portions of sacrificial hardmask material  32  have been removed to form a mask  42  comprising a plurality of spaced mask lines  45  that are received over control gate material  30  which, in one embodiment, have respective minimum widths of no greater than 30 nanometers. The respective widths of spaced mask lines  45  may be the same or different relative one another, and the spaced mask lines may be of the same or different shapes relative one another. Further, the width of individual mask lines  45  may not be constant. The  FIG. 4  construction may be produced by using one or more suitable anisotropic etching chemistries. Sacrificial hardmask material  32  is depicted as having been etched completely through to underlying control gate material  30 , although such is not required. Further, some, none, or all of photoresist  40  and antireflective coating  38  may be removed at this point or subsequently in the etching of material underlying sacrificial hardmask material  32 . 
     Regardless, in one embodiment, spaced mask lines  45  comprise at least two layers of different composition, with two layers  34  and  36  being shown. One of the layers of the individual of the spaced mask lines  45  has a tensile intrinsic stress of at least 400.0 MPa, and the individual spaced mask lines each have a total tensile intrinsic stress greater than 0.0 MPa, during an etching of underlying material as will be described below. In the context of this document, tensile intrinsic stress is designated by positive numbers in mega-pascals, compressive intrinsic stress is designated by negative numbers in mega-pascals, and 0.0 MPa designates no intrinsic stress. Further, greater compressive intrinsic stress is designated by larger negative numbers, for example a value of −700 MPa designates greater compressive intrinsic stress than −500 MPa. In one embodiment, the one layer has tensile intrinsic stress of at least 700 MPa, and in one embodiment at least 1 GPa, during the etching. In one embodiment, each of the individual features has a total tensile intrinsic stress during the etching of at least 100.0 MPa, and in one embodiment of at least 800.0 MPa. 
     Certain materials depending upon deposition technique and underlying substrate material may be deposited over a substrate to have tensile intrinsic stress as-deposited, compressive intrinsic stress as-deposited, or neutral/no intrinsic stress as-deposited. Also, the intrinsic stress of a deposited material may be modified after its deposition. For example, heating a substrate will tend to reduce degree of tensile of a tensile intrinsically stressed layer, and increase compressive intrinsic stress of a compressive intrinsically stressed layer. Accordingly, intrinsic stress of the at least two layers of different composition within the sacrificial hardmask material may or may not be the same during etching of underlying material as compared to the as-deposited state(s). 
     In one embodiment, another of the layers of hardmask material  32  of spaced mask lines  45  has compressive intrinsic stress during the etching of underlying material. Such may enable combining the usual high etch resistance of materials having compressive intrinsic stress with at least one additional layer having tensile intrinsic stress of at least 400.0 MPa to provide the individual features to each have a total tensile intrinsic stress which is positive at greater than 0.0 MPa. In one embodiment, the layer having compressive intrinsic stress is of at least −500 MPa, and in one embodiment of at least −1 GPa, during the etching. In one embodiment, a layer of the features has compressive intrinsic stress during the etching of at least −500 MPa, and the individual features each have total tensile intrinsic stress during the etching of at least 500.0 MPa, and in one embodiment of at least 800.0 MPa. Where a compressive intrinsic stress layer is used, such layer may be received elevationally inward or outward of the tensile intrinsic stress layer. Use of spaced mask lines which individually have a total tensile intrinsic stress immediately before and during etch of underlying material may in some embodiments reduce line waviness, for example than would otherwise occur under identical process conditions where the individual spaced mask lines each have total compressive intrinsic stress during the etching. 
     By way of examples only, a thickness range for the layer of tensile intrinsic stress of at least 400.0 MPa is from about 100 Angstroms to about 1,000 Angstroms, with in one embodiment being from about 200 Angstroms to about 500 Angstroms. Example thicknesses for a compressive intrinsic stress layer of spaced mask line features  45  is from about 100 Angstroms to about 1,200 Angstroms, with in one embodiment being from about 700 Angstroms to about 900 Angstroms. 
     Example materials which exhibit compressive intrinsic stress include amorphous carbon, for example amorphous graphitic carbon or tetrahedral amorphous carbon. Such may, for example, have respective compressive intrinsic stresses of −300 MPa and from −700 MPa to 10 GPa. Silicon dioxide deposited by low pressure chemical vapor deposition at a pressure of no greater than 1 Torr (LPCVD) or by plasma enhanced chemical vapor deposition (PECVD) of tetraethylorthosilicate (TEOS) at from 200° C. to 750° C. exhibits compressive intrinsic stress of from −10 MPa to −500 MPa. Fluorinated silicon glass deposited by PECVD at from 200° C. to 750° C. exhibits compressive intrinsic stress of from −5 MPa to −400 MPa. Thermally deposited silicon dioxide formed by furnace oxidation at from 750° C. to 1150° C. exhibits compressive intrinsic stress of from −350 MPa to −900 MPa. 
     Certain materials may exhibit tensile or compressive intrinsic stress depending upon method of deposition, underlying substrate, and processing of the substrate between time of deposition and time of use as a component in a hardmask during etch of material underlying the hardmask. Example materials that may be provided with tensile intrinsic stress of at least 400.0 MPa include nitrides (i.e., tungsten nitride, tantalum nitride, and/or silicon nitride), oxides (i.e., undoped silicon dioxide, fluorine doped silicon dioxide, and/or spin-on dielectrics which include silicon dioxide), silicides (i.e., cobalt silicide, titanium silicide, and/or nickel silicide), W, Ti, Cu, and Ni. For example, the one layer having tensile intrinsic stress may comprise one or more of such materials, or may consist essentially of, or consist of, one of such materials. Further, multiple layers having tensile intrinsic stress may be used. 
     In one embodiment, layer  34  of spaced mask lines  45  comprises a nitride, for example silicon nitride, having tensile intrinsic stress of at least 400.0 MPa and layer  36  comprises carbon having compressive intrinsic stress, yet with the individual spaced mask lines  45  each having a total intrinsic stress greater than 0.0 MPa. In such embodiment, the compositions of layers  34  and  36  may be reversed. 
     As examples, silicon dioxide deposited by chemical vapor deposition at a pressure of at least 3 Torr (CVD) at from 200° C. to 550° C. using SiH 4  as a precursor exhibits intrinsic stress of from −30 MPa to 63 MPa. Undoped silicon glass deposited by subatmospheric or thermal CVD at from 300° C. to 700° C. using TEOS or SiH 4  as a precursor exhibits intrinsic stress of from −300 MPa to 700 MPa. Spin On Dielectric (SOD) subjected to a post-deposition anneal at from 400° C. to 1000° C. exhibits intrinsic stress of from −300 MPa to 700 MPa, with such stress trending in the direction of compressive the higher and longer the temperature of the post-deposition anneal. Silicon nitride deposited by LPVD or PECVD at from 375° C. to 750° C. exhibits intrinsic stress of from −600 MPa to 1800 MPa. Silicon dioxide deposited by LPCVD at from 500° C. to 750° C. using SiH 4  as a precursor exhibits tensile intrinsic stress of from 210 MPa to 420 MPa. Tungsten nitride deposited by physical vapor deposition (PVD) or CVD at from 150° C. to 600° C. exhibits tensile intrinsic stress of from 500 MPa to 1200 MPa. Tantalum nitride deposited by PVD or CVD at from 150° C. to 600° C. exhibits tensile intrinsic stress of from 500 MPa to 1200 MPa. Tungsten deposited by PVD or CVD at from 150° C. to 600° C. exhibits tensile intrinsic stress of from 700 MPa to 1400 MPa. Titanium deposited by PVD or CVD at from 150° C. to 600° C. exhibits tensile intrinsic stress of from 350 MPa to 450 MPa. Cobalt silicide deposited by PVD or CVD at from 150° C. to 600° C. exhibits tensile intrinsic stress of from 700 MPa to 1400 MPa. Titanium silicide deposited by PVD, CVD, or atomic layer deposition (ALD) at from 150° C. to 600° C. exhibits tensile intrinsic stress of from 1500 MPa to 2100 MPa. Nickel silicide deposited by PVD, CVD, or ALD at from 150° C. to 600° C. exhibits tensile intrinsic stress of from 200 MPa to 600 MPa. Copper deposited by PVD or by chemical plating at from 30° C. to 600° C. exhibits tensile intrinsic stress of from 300 MPa to 600 MPa. Nickel deposited by PVD or by chemical plating at from 30° C. to 450° C. exhibits tensile intrinsic stress of from 300 MPa to 800 MPa. 
     Referring to  FIG. 5 , mask  42  has been used while etching through control gate material  30 , blocking dielectric  28 , and charge-retaining material  26 . Thereby, spaced features in the form of a plurality of spaced charge storage transistor gate lines  48  have been formed which, in one embodiment, have respective minimum widths of no greater than 30 nanometers. Tunnel dielectric  24  may also be etched though to semiconductive material  22 , as shown. In one embodiment, the plurality of spaced features may have respective aspect ratios of at least 15:1. Some, none, or all of hardmask material  32  may be etched during the etch of underlying material to produce spaced charge storage transistor gate lines  48 .  FIG. 5  depicts an embodiment wherein portions of each of elevationally innermost layers  34 ,  36  of hardmask material  32  remain.  FIGS. 6 and 7  depict subsequent removal of such portions, for example, by etching. 
     An example alternate embodiment processing with respect to a substrate  20   a  is described with reference to  FIGS. 8-10 . Like numerals from the first described embodiment have been utilized where appropriate, with differences being indicated with suffix “a” or with different numerals.  FIG. 8  depicts processing in sequence corresponding to that of  FIG. 4  of the above-described embodiment in forming a mask  42   a  comprising spaced mask lines  45   a . Such may be fabricated using existing or yet-to-be developed photolithographic or other technique. Hardmask material  32   a  of spaced mask lines  45   a  comprises an additional layer  50  received elevationally inward of layer  34 . An example material is undoped silicon dioxide deposited by decomposition of tetraethylorthosilicate. Regardless, such layer may comprise compressive intrinsic stress during the subsequent etching or tensile intrinsic stress during the subsequent etching. 
     Referring to  FIG. 9 , mask  42   a  has been used while etching into the underlying material to form a plurality of spaced charge storage transistor gate lines  48 .  FIG. 9  depicts an embodiment wherein portions of each of layers  50 ,  34 , and  36  remain at the conclusion of the etching of the underlying material.  FIG. 10  depicts subsequent removal of such portions, for example by etching. 
     The above processing describes example techniques of forming a plurality of spaced features which in the above embodiment comprise a plurality of electrically conductive lines. Other features may be fabricated. Regardless, an example such embodiment includes forming sacrificial hardmask material over underlying material, wherein the sacrificial hardmask material comprises at least two layers of different composition. Portions of the sacrificial hardmask material are removed to form a mask over the underlying material. Individual features of the mask comprise the at least two layers of different composition. One of such layers of the individual features has a tensile intrinsic stress of at least 400.0 MPa, and the individual features each have a total tensile intrinsic stress greater than 0.0 MPa. Such mask is used while etching into the underlying material to form a plurality of spaced features which comprise such underlying material. Any of the above-described example techniques and materials may be used. 
     In one embodiment, a method of forming a plurality of spaced electrically conductive lines having respective minimum widths of no greater than 30 nanometers includes forming a plurality of spaced mask lines over electrically conductive material. Such mask lines have respective minimum widths of no greater than 30 nanometers, and individually have total tensile intrinsic stress immediately before and during etching of the conductive material using such spaced mask lines as a mask. The spaced mask lines may or may not have one layer having tensile intrinsic stress of at least 400.0 MPa. The spaced mask lines are used as an etch mask while conducting etching of the conductive material to form a plurality of spaced electrically conductive lines having respective minimum line widths of no greater than 30 nanometers. 
     An embodiment of the invention constitutes a method of reducing line waviness in etching electrically conductive material to form a plurality of spaced electrically conductive lines having respective minimum line widths of no greater than 30 nanometers. Such a method comprises using an etch mask having spaced mask lines which individually have a total tensile intrinsic stress immediate before and during such etching, and for example independent of the other attributes described above. 
     In compliance with the statute, the subject matter disclosed herein has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the claims are not limited to the specific features shown and described, since the means herein disclosed comprise example embodiments. The claims are thus to be afforded full scope as literally worded, and to be appropriately interpreted in accordance with the doctrine of equivalents.