Methods of forming semiconductor structures with sulfur dioxide etch chemistries

Methods of forming a semiconductor device structure and sulfur dioxide etch chemistries. The methods and chemistries, which may be plasma chemistries, include use of sulfur dioxide and a halogen-based compound to form a trimmed pattern of a patterning material, such as a resist material, at a critical dimension with low feature width roughness, with low space width roughness, without excessive height loss, and without substantial irregularities in the elevational profile, as compared to trimmed features formed using conventional chemistries and trimming methods.

FIELD

The present disclosure, in various embodiments, relates generally to semiconductor device design and fabrication. More particularly, this disclosure relates to semiconductor fabrication involving patterning methods.

BACKGROUND

In semiconductor fabrication, integrated circuit (IC) devices are becoming smaller, faster, and more efficient, leading toward higher densities of IC devices on chips. As this trend continues, reducing critical dimension (CD) is often important. The critical dimension is the dimension of the smallest feature (e.g., interconnect line, contact, trench) that can be formed during semiconductor device fabrication. Lowering critical dimensions facilitates formation of smaller components and, therefore, increased device density. Accordingly, achieving a desired critical dimension is often a goal of patterning processes.

FIGS. 1 and 2illustrate a stage in a conventional patterning process. According to the process, photolithography techniques are used to define a pattern in a patterning material112formed above a base material114, which may be supported by a substrate116, to be patterned. In some instances, the substrate116may have patterning material112located directly thereon for patterning of the substrate116. The patterning material112is selectively exposed to an energy source, such as an actinic energy, to alter the material characteristics of the patterning material112in select regions such that the altered regions will be more or less susceptible to development by a developer. Such susceptibility and the response of the patterning material112to exposure depend upon the patterning material chemistry. For example, if the patterning material112is formulated as a positive tone photoresist material, exposed regions become more susceptible to development while unexposed regions (e.g., masked regions) remain less susceptible. However, if the patterning material112is formulated as a negative tone photoresist material, exposed regions become less susceptible to development, and the unexposed regions (e.g., masked regions) remain susceptible. Post exposure, the development-susceptible regions are selectively removed to define a pattern, referred to herein as an “initial pattern”118, of initial features120, which may be elongate features. As illustrated inFIGS. 1 and 2, the initial features120of the initial pattern118may be separated from one another by trenches122, each of which may expose an upper surface124of the base material114. Each initial feature120may be formed so as to define an initial width Wiand an initial height Hi. The initial width Wimay be of the smallest dimension achievable due to limitations of the photolithography process employed. Nonetheless, the initial width Wimay not be small enough to accommodate patterning of the base material114at a desired critical dimension. For example, the initial width Wimay be on the order of about 40 nm to about 50 nm, while the desired critical dimension may be on the order of about 20 nm to about 30 nm. Accordingly, the initial pattern118of the plurality of initial features120may be subjected to a trimming process to reduce the width of the initial features120.

During a conventional trimming process, the initial features120may be exposed to an etchant, referred to herein as a “trimming chemistry.” The trimming chemistry may be used to remove material laterally and vertically from the initial features120at sidewalls126and a top surface128, respectively, to form, as illustrated inFIGS. 3 and 4, a trimmed pattern130of trimmed features132(also referred to herein as a “pattern of trimmed features”). In embodiments in which the initial features120are elongate features, the trimmed features132may also be elongate features, but with a narrower width (i.e., a smaller lateral dimension). The trimmed features132may be spaced from one another by enlarged trenches134exposing more of the upper surface124of the base material114than was exposed by the trenches122prior to the trimming process.

Each of the trimmed features132defines a trimmed width Wtand a trimmed height Ht. Theoretically, the trimmed width Wtmay correspond to a desired critical dimension, and each of the trimmed features132includes trimmed sidewalls136that define a smooth, vertical, elevational profile terminating at a 90° angle with a planarized, trimmed top surface138. In actual practice, however, conventional trimming chemistries and processes often lead to formation of trimmed features132having rough (non-uniform) trimmed sidewalls136that are not straight and vertical and that do not meet a planarized top surface138at a 90° angle. As illustrated inFIG. 5, the trimmed sidewalls136may include peaks and valleys that contribute to a nonuniform feature width roughness (e.g., line width roughness (LWR)) and nonuniform space width roughness (SWR). Thus, at various points along a length of a trimmed feature132, the trimmed width Wtmay vary; hence, as illustrated inFIG. 5, trimmed widths Wt1, Wt2, Wt3, and Wt4are not uniform. Likewise, at various points along a length of the enlarged trenches134, a trench width (e.g., Tt1, Tt2, Tt3, and Tt4) varies.

As illustrated inFIGS. 6A through 6J, conventional trimming chemistries and processes may also lead to formation of trimmed features132A-132E and trimmed patterns130E-130J having undesirable cross-sectional profiles that exhibit one or more defects. Conventional trimming chemistries include, for example, sulfur dioxide alone (i.e., SO2, which may produce trimmed pattern130F ofFIG. 6F), sulfur dioxide and oxygen (i.e., SO2and O2, which may produce trimmed pattern130G ofFIG. 6G), oxygen and a halogen-based compound without sulfur dioxide (e.g., Cl2and O2, which may produce trimmed pattern130H ofFIG. 6H), oxygen with a halogen-based compound and an organohalogen compound, but without sulfur dioxide (e.g., Cl2, O2, CF4, and CH2O2, which may produce trimmed pattern130I ofFIG. 6I), or oxygen with an organohalogen compound and without sulfur dioxide (e.g., CF4and O2, which may produce trimmed pattern130J ofFIG. 6J). As such, conventional trimming chemistries may produce trimmed features having slanted profiles (e.g., trimmed features132A,132E and trimmed patterns130F,130J), sloped sidewalls (e.g., trimmed features132A,132B and trimmed pattern130I), top coating material140overhang regions142(e.g., trimmed feature132C), line collapse or wobbling (e.g., trimmed feature132D and trimmed pattern130J), top tapering (e.g., trimmed features132A,132E and trimmed patterns130E-130I), bottom tapering (e.g., trimmed feature132B and trimmed pattern130I), and excessive height loss (e.g., trimmed feature132E and trimmed patterns130F,130G). Each of the imperfections with regard to feature width roughness, space width roughness, trimmed feature profile, and feature height may lead to formation of errors in structures formed in the base material114when the trimmed pattern130is transferred to the base material114. It is contemplated that avoiding such imperfections may present even more of a challenge as critical dimensions decrease.

DETAILED DESCRIPTION

Methods of forming a semiconductor device structure and sulfur dioxide etch chemistries are disclosed. The disclosed methods and chemistries utilize sulfur dioxide and a halogen-based compound, which enable formation of a pattern of trimmed features of a resist or other patterning material at a desired critical dimension while being less prone to high feature width roughness, high space width roughness, high feature height loss, and irregular cross-sectional profiles, such as profiles that are slanted, tapered, or include overhang regions. Consequently, the resulting pattern of trimmed features may be transferred to a base material with more reliability to pattern the base material with precision at even small dimensions.

As used herein, the term “substrate” means and includes a foundation material or construction upon which components, such as those within memory cells as well as other semiconductor device structures, are formed. The substrate may be a semiconductor substrate, a base semiconductor material on a supporting structure, a metal electrode, or a semiconductor substrate having one or more materials, structures, or regions formed thereon. The substrate may be a conventional silicon substrate or other bulk substrate including a semiconductive material. As used herein, the term “bulk substrate” means and includes not only silicon wafers, but also silicon-on-insulator (“SOI”) substrates, such as silicon-on-sapphire (“SOS”) substrates or silicon-on-glass (“SOG”) substrates, epitaxial layers of silicon on a base semiconductor foundation, or other semiconductor or optoelectronic materials, such as silicon-germanium (Si1-xGex, where x is, for example, a mole fraction between 0.2 and 0.8), germanium (Ge), gallium arsenide (GaAs), gallium nitride (GaN), or indium phosphide (InP), among others. Furthermore, when reference is made to a “substrate” in the following description, previous process stages may have been utilized to form materials, regions, or junctions in or on the base semiconductor structure or foundation.

As used herein, the term “base material” refers to a material that is to be patterned by transferring an overlying, defined pattern in a patterning material. The base material may comprise one or more of a hard mask material, a conductive material, a dielectric material, an antireflective coating material, or other known materials utilized in semiconductor device structures. In some instances, the material of a substrate of semiconductor material may, itself, comprise a base material.

As used herein, the terms “fluorine-based compound,” “chlorine-based compound,” “bromine-based compound,” and “iodine-based compound” refer to a chemical compound comprising a fluorine (F) atom, a chlorine (Cl) atom, a bromine (Br) atom, and an iodine (I) atom, respectively. The terms are not mutually exclusive. For example, CF3I is within the definition of both the “fluorine-based compound” term and the “iodine-based compound” teen as used herein.

As used herein, the term “organohalogen compound” refers to a chemical compound comprising at least one carbon atom bonded to at least one halogen atom. For example, and without limitation, an organohalogen compound may include one or more of an organofluorine compound, an organochlorine compound, an organobromine compound, and an organoiodine compound. Again, these terms are not mutually exclusive.

As used herein, the term “trim” refers to removal of material from at least a vertically-oriented surface of the material being “trimmed.” In this sense, a “vertically-oriented” surface is one that defines a plane essentially perpendicular to a plane defined by a primary surface of the substrate over which the material being trimmed is located.

As used herein, the term “top coating material” refers to a material of a composition formulated to protect a photoresist material in photolithography processes. A top coating material may be formulated to inhibit leaching of acid or base from the photoresist. For example, and without limitation, a top coating material may include a polymer material, such as, e.g., a perfluoro alkyl polyether, a perfluoro alkyl amine, or other resist top coating material known in the art.

As used herein, reference to an element as being “on” or “over” another element means and includes the element being directly on top of, adjacent to, underneath, or in direct contact with the other element. It also includes the element being indirectly on top of, adjacent to, underneath, or near the other element, with other elements present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

The illustrations presented herein are not meant to be actual views of any particular material, feature, structure, region, segment, or fabrication stage, but are merely idealized representations that are employed to describe embodiments of the present disclosure.

Embodiments are described herein with reference to the accompanying drawing figures. Variations from the shapes of the structures depicted in the figures as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein are not to be construed as being limited to the particular shapes or regions as illustrated but include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as box shaped may have rough and/or nonlinear structures. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and do not limit the scope of the present claims.

The following description provides specific details, such as material types and processing conditions, in order to provide a thorough description of some embodiments of the disclosed devices and methods. However, a person of ordinary skill in the art will understand that the embodiments of the methods may be practiced without employing these specific details. Indeed, the embodiments of the methods may be practiced in conjunction with conventional semiconductor fabrication techniques employed in the industry.

The fabrication processes described herein do not form a complete process flow for processing semiconductor device structures. The remainder of the process flow is known to those of ordinary skill in the art. Accordingly, only the methods and structures necessary to understand embodiments of the present devices and methods are described herein.

Unless the context indicates otherwise, the materials described herein may be formed by any suitable technique including, but not limited to, spin coating, knife coating, dip coating, blanket coating, chemical vapor deposition (“CVD”), atomic layer deposition (“ALD”), plasma enhanced ALD, and physical vapor deposition (“PVD”). Alternatively, the materials may be grown in situ. Depending on the specific material to be formed, the technique for depositing or growing the material may be selected by a person of ordinary skill in the art.

Unless the context indicates otherwise, the removal of materials described herein may be accomplished by any suitable technique including, but not limited to, etching, abrasive planarization, and other methods.

Reference will now be made to the drawings, where like numerals refer to like components throughout. The drawings are not necessarily drawn to scale.

The methods disclosed herein may be used to form semiconductor device structures. As nonlimiting examples, the methods may be used to pattern hard masks for semiconductor device fabrication or to form conductive contacts, conductive interconnects, transistors, and memory devices, including, for example, in dynamic random access memory (DRAM) cells, non-volatile memory cells, and NAND flash memory.

With reference toFIGS. 7 and 8, a trimmed pattern230may be formed by exposing a patterning material, such as an exposed and developed patterning material112comprising features to be trimmed before being transferred to base material114, to a trimming chemistry. Prior to exposing the patterning material112to the trimming chemistry, the patterning material112may be formed over a base material, e.g., the base material114, which may be supported by a substrate, e.g., the substrate116. The patterning material112may be patterned, e.g., by a photolithography process, to form an initial pattern, such as the initial pattern118(FIGS. 1 and 2). Patterning the patterning material112may include selectively removing regions of the patterning material112to define the initial features120(FIG. 1) (e.g., initial resist features, such as elongate resist features) separated from one another by the trenches122(FIG. 2). The upper surface124of the base material114may be exposed through the trenches122(FIG. 2).

Exposing the initial pattern118(FIGS. 1 and 2) of the initial features120to the trimming chemistry may be used to broaden the trenches122(FIG. 2) by at least removing material from the sidewalls126of the initial features120(e.g., laterally etching the initial features120) to form a trimmed pattern230of trimmed features232(e.g., trimmed resist features, such as trimmed elongate resist features) spaced from one another by enlarged trenches234and having trimmed sidewalls236and a trimmed top surface238. The trimmed features232define a trimmed width Wt′ and a trimmed height Ht′. Further, the trimmed features232define a cross-sectional profile (i.e., a side view through the width of the feature), e.g., the profiles illustrated inFIG. 8. The cross-sectional profile of the trimmed features232may be less slanted, may be less prone to line collapse or wobbling, may include more vertically aligned trimmed sidewalls236, and may include a less tapered trimmed top surface238, without excessive height loss, as compared to the elevational profiles of trimmed features132formed using conventional trimming chemistries, e.g., trimmed features132A-132E (FIGS. 6A through 6E).

With reference toFIG. 9, the resulting trimmed features232may include trimmed sidewalls236exhibiting less feature width roughness (e.g., less line width roughness) than that of the trimmed sidewalls136of the trimmed features132farmed using a conventional trimming chemistry. Therefore, for example, feature widths taken along various points along the trimmed features232, e.g., feature widths Wt1′, Wt2′, Wt3′, and Wt4′, as well as trench widths taken along various points along the enlarged trenches234, e.g., trench widths Tt1′, Tt2′, Tt3′, and Tt4′, may vary less, on average, than the feature widths taken along various points along the trimmed features132(FIG. 5), e.g., feature widths Wt1, Wt2, Wt3, and Wt4, vary from one another and the trench widths taken along various points along the large trenches134(FIG. 5), e.g., trench widths Tt1, Tt2, Tt3, and Tt4, vary from one another, respectively.

The trimmed pattern230of trimmed features232may be transferred to the base material114by selectively removing portions of the base material114exposed in the enlarged trenches234. Methods for removing the base material114, e.g., a hardmask material, are known in the art and therefore are not described in detail.

The trimmed features232may be formed using the trimming chemistry in a dry etching process. For example, the patterning material112may be exposed to the trimming chemistry within an etching chamber, such as an etching chamber configured to provide an RF source power via transformer coupled plasma (“TCP”), inductively coupled plasma (“ICP”), an electron cyclotron resonance (“ECR”) plasma source, or capacitively coupled plasma with high frequency RF power. Thus, the trimming chemistry may be in the fora of a plasma during the trimming process, wherein the plasma includes the sulfur dioxide and a halogen-based material.

The trimming chemistry may be introduced into the chamber and may be used to form the plasma that acts upon the patterning material112to trim the initial features120and to widen the trenches122to form the enlarged trenches234. Source power or top power (e.g., power from a TCP source), also referred to herein as “RF” power, may be applied at a level of about 150 W to about 1000 W, e.g., about 380 W. Selecting the appropriate top power level may depend upon the composition of the trimming chemistry, the equipment used, and the patterning material112to be exposed.

Accordingly, disclosed is a method of forming a semiconductor device structure. The method comprises forming a resist material over a base material. Portions of the resist material are selectively removed to define trenches in the resist material. The resist material is exposed to a plasma to widen the trenches. The plasma comprises sulfur dioxide and at least one of a fluorine-based compound, a chlorine-based compound, and a bromine-based compound.

Substantial bias power may not be applied during the trimming process, such that the bias voltage does not exceed about 10 V. In other embodiments, bias power may be applied at, for example, below about 50 V. As discussed below, selecting the appropriate bias power level may depend, at least in part, on the composition of the patterning material112to be exposed as well as whether the trim chemistry is employed to both pattern and trim features in the patterning material as described below

The patterning material112over the substrate116may be exposed to the trimming chemistry for a duration of between about 5 seconds and about 50 seconds, e.g., about 25 seconds. Again, the exposure time (also referred to herein as the “throughput time”) selected may depend at least in part on the patterning material112to be exposed, the composition of the trimming chemistry, and the desired critical dimension and cross-sectional profile of the resulting trimmed features232.

The chamber temperature may be maintained at about 25° C. to about 70° C., e.g., about 50° C. In other embodiments, the chamber temperature may be adjusted during the process. Pressure within the chamber may be maintained at about 2 mTorr to about 100 mTorr, e.g., about 8 mTorr. The pressure may be stabilized within the chamber prior to striking RF power to generate the plasma and prior to beginning the trimming. The pressure may be maintained throughout the trimming process. However, in other embodiments, the pressure may be adjusted during the process. The pressure conditions may be selected depending, at least in part, on the composition of the trimming chemistry, the composition of the patterning material112to be exposed, and the desired critical dimension and elevational profile of the resulting trimmed features232.

Thus, the duration time, the chamber pressure, the source power, and the bias power (e.g., bottom) may be selected to tune the trimming process to form the trimmed features232from the patterning material112to a desired critical dimension and a desired elevational profile while still achieving low feature width roughness and space width roughness. For example, a “low” feature width roughness may be a feature width roughness of less than about 40 Å with a three sigma distribution, e.g., less than about 30 Å with a three sigma distribution. The trimming process conditions and the composition of the trimming chemistry may be selected based at least in part on the composition of the patterning material112to be trimmed. For example, the trimming chemistries discussed below may be formulated to trim a 193 nm resist material. The same trimming chemistries, with possible adjustments as to relative concentrations and process conditions, may alternatively be used to trim a 248 nm resist, a 157 nm resist, or both. The 193 nm resist material, the 248 nm resist material, or the 157 nm resist material may be a conventional photoresist material, such as a conventional positive tone or negative tone photoresist material.

The trimming chemistry to which the initial pattern118of the initial features120(FIG. 1) is exposed to form the trimmed pattern230(FIG. 7) of the trimmed features232may be a chemistry comprising sulfur dioxide and a halogen-based compound. For example, and without limitation, the trimming chemistry may include sulfur dioxide and at least one of a halogen-based compound (e.g., a fluorine-based compound, a chlorine-based compound, a bromine-based compound), such as an organohalogen compound. More specifically, for example and without limitation, the trimming chemistry may include sulfur dioxide and at least one of CF4, C3F8, C4F8, C4F6, CHF3, CH2F2, SF6, NF3, ClF3, HBr, Cl2, BCl3, and CF3I.

Accordingly, disclosed is a sulfur dioxide etch chemistry comprising a plasma. The plasma comprises sulfur dioxide and a halogen-based compound.

Without being limited to any one theory, it is contemplated that the combination of the sulfur dioxide and the halogen-based compound within the same trimming chemistry provides the benefits of low feature width roughness and space width roughness while enabling achievement of a desired critical dimension without excessive feature height loss and without excessive irregularities in the elevational profile. It is contemplated that, in the trimming chemistry, several reactions may take place, such as etching of resist material, halogenization of resist components, sulfurization (e.g., cross-linking) of resist components, and deposition of polymers. The halogen within the trimming chemistry may halogenize the resist material (i.e., enable a chemical reaction between the halogen of the trimming chemistry and a component of the patterning material112, e.g., carbon), resulting in different chemical and mechanical properties of the resist material (e.g., the patterning material112). Such property change may depend upon the halogen species in the trimming chemistry and the polymerizing (e.g., cross-linking) tendency of the gases within the trimming chemistry. Sulfur dioxide (SO2), on the other hand, contains both an aggressive etching component, i.e., oxygen (O), and a moderate depositing and cross-linking component, i.e., sulfur (S). The halogen species in the trimming chemistry (e.g., in the plasma) may also affect the degree of disassociation of the sulfur dioxide. Fluorine radicals may be the most aggressive halogen species in this regard, i.e., in breaking of bonds between sulfur and oxygen in the sulfur dioxide. Because there may be an intrinsic bias voltage (which may be less than about 8 V) in a plasma trimming chemistry, even when using a 0 W bias power setting during the trimming process, it is contemplated that the sulfurization (i.e., chemical reaction between sulfur of the trimming chemistry and a component of the patterning material112, e.g., carbon) and halogenization take place on the top surface128(FIG. 2) of the initial features120(FIG. 2), where there is ion bombardment because of the intrinsic bias voltage. This bias voltage may enhance the penetration depth of the halogen or sulfur species into the resist (e.g., the patterning material112). However, on the sidewalls126(FIG. 2) of the initial features120(FIG. 2), there may be no ion bombardment. Therefore, compared to the top surface128(FIG. 2), there may be less halogenization and sulfurization on the sidewalls126(FIG. 2) but more deposition (e.g., when the gases of the trimming chemistry are formulated to enable polymerization). As such, a larger remaining resist height (e.g., greater final trimmed height Ht′ (FIG. 8)) may be attributable to factors, including, (1) that halogenized or sulfurized resist material (e.g., patterning material112) may have more physical strength than non-halogenized and non-sulfurized resist material and may, therefore, be able to better withstand the heat of the plasma, resulting in less melt-down of the resist material, and (2) halogenized or sulfurized resist material (e.g., patterning material112) may be more etch-resistant than non-halogenized and non-sulfurized resist material, such that a topside trim rate (e.g., vertical etch rate) may be reduced more than a sidewall trim rate (e.g., horizontal etch rate) is reduced due to the occurrence of more halogenization, sulfurization, or both on the top surface128(FIG. 2) than on the sidewalls126(FIG. 2) of the initial features120(FIG. 2). Additionally, post trim feature width roughness (e.g., line width roughness) may be impacted by factors, including, (1) the feature width roughness of the initial features120(FIG. 2), i.e., the starting feature width roughness; (2) the trimming chemistry's etch selectivity to various components of the patterning material112during the trimming process; (3) the composition of the patterning material112, including, for example, how components of the patterning material112are connected to one another; and (4) the mechanical strength of the patterning material112under the heat of a plasma trimming chemistry, wherein a patterning material112with a relatively higher mechanical strength may be less prone to wobbling than a patterning material112with a relatively lower mechanical strength. Both halogenization and sulfurization may enhance mechanical strength and may improve the evenness of the patterning material, which may result in less feature width roughness in the trimmed features132than the feature width roughness of conventionally trimmed features. Therefore, the final trimmed height Ht′ and feature width roughness may be tuned by tailoring the composition (e.g., gaseous species) within the trimming chemistry and the flow rates of the components relative to that of the sulfur dioxide.

In some embodiments, the trimming chemistry may be formulated to provide trimmed features232exhibiting low feature width roughness, low space width roughness, and elevational profiles having few imperfections while also having little feature height loss. Such trimming chemistries so formulated may include, for example, sulfur dioxide and a non-polymerizing gas at least one component consisting of two elements, one of the two elements being fluorine, and the other element being, e.g., carbon, nitrogen, sulfur, or chlorine. These “type I trimming chemistries” may include, for example, CF4, NF3, SF6, C3F8, ClF, and ClF3. Such type I trimming chemistries may be useful for trimming resist materials or carbon-based materials to post-trim line critical dimensions that are very small (e.g., fewer than 25 nm) and the trimmed features need to be tall enough for subsequent processing acts. Type I trimming chemistries may yield a single-side lateral trim rate (e.g., lateral etch rate) that is about 40 percent to about 70 percent that of a vertical trim rate (e.g., vertical etch rate). For example, an initial feature120(FIG. 2) of a top-coated (with top coating material140) resist patterning material112, having an initial height Hiof about 900 Å, an initial width Wiof about 460 Å, and an initial feature width roughness of about 55 Å with a three sigma distribution, exposed to a type I trimming chemistry comprising SO2and NF3to reduce (e.g., shrink) the width of the initial feature120to a final trimmed width Wt′ of about 190 Å, may form a trimmed feature232(FIG. 8) having a final trimmed height Ht′ of about 700 Å (e.g., about 730 Å) and a feature width roughness of about 28 Å. As another example, exposing an initial feature120(FIG. 2) of a top-coated (with top coating material140) resist patterning material112, having an initial height Hiof about 900 Å, an initial width Wiof about 460 Å, and an initial feature width roughness of about 55 Å with a three sigma distribution, exposed to a type I trimming chemistry comprising SO2and CF4to reduce (e.g., shrink) the width of the initial feature120to a final trimmed width Wt′ of about 190 Å, may form a trimmed feature232(FIG. 8) having a final trimmed height Ht′ of about 700 Å (e.g., about 670 Å) and a feature width roughness of about 28 Å.

In some embodiments, the trimming chemistry may be formulated to provide trimmed features232exhibiting low feature width roughness and low space width roughness, though with more feature height loss than features formed using the type I trimming chemistries. Such trimming chemistries so formulated may include, for example, sulfur dioxide and one or more relatively polymerizing gases with at least one of CHF3, CH2F2, C4F8, C4F6, and C5F8(referred to herein as a “type II trimming chemistry”). The organohalogen compounds within the type II category may include at least one of one or more hydrogen atoms (e.g., as in CHF3and CH2F2), double- or triple-bonded carbon atoms (e.g., in some isomers of C4F8, C4F6, or C5F8), and a carbon ring (e.g., in some isomers of C4F8, C4F6, or C5F8). Such type II trimming chemistries may have slower lateral etch rates than those of type I trimming chemistries. They may be used in trimming processes in which trimmed features232of shorter resist heights than those formed using type I trimming chemistries are needed for or do not negatively impact subsequent processing acts. Type II trimming chemistries may also be used if formation of fluorocarbon polymers on surfaces of the patterning material112are desired or beneficial. For example, an initial feature120(FIG. 2) of a top-coated (with top coating material140) resist patterning material112, having an initial height Hiof about 900 Å, an initial width Wiof about 460 Å, and an initial feature width roughness of about 55 Å with a three sigma distribution, exposed to a type II trimming chemistry comprising SO2and CH2F2to reduce (e.g., shrink) the width of the initial feature120to a final trimmed width Wt′ of about 190 Å, may form a trimmed feature232(FIG. 8) having a final trimmed height Ht′ of less than about 520 Å and a feature width roughness of about 29 Å.

In other embodiments, the trimming chemistry may be formulated to provide trimmed features232exhibiting low feature width roughness and low space width roughness, though with more feature height loss than features formed using type I and type II trimming chemistries. Such trimming chemistries so formulated may include a halogen other than fluorine (i.e., a “non-fluorine halogen”), e.g., chlorine, bromine, or iodine. These “type III trimming chemistries” may include, for example, sulfur dioxide and at least one of Cl2, HBr, BCl3, and CF3I. Type III trimming chemistries may achieve superior feature width roughness and superior etch selectively over DARC (dielectric antireflective coating), compared to other types of trimming chemistries. Type III trimming chemistries may also provide a relatively larger process window in which to achieve low feature width roughness or space width roughness. Also, type III trimming chemistries may exhibit a vertical etch rate that is at least about three times greater than a lateral etch rate. For example, an initial feature120(FIG. 2) of a top-coated (with top coating material140) resist patterning material112, having an initial height Hiof about 900 Å, an initial width Wiof about 460 Å, and an initial feature width roughness of about 55 Å with a three sigma distribution, exposed to a type III trimming chemistry comprising SO2and Cl2to reduce (e.g., shrink) the width of the initial feature120to a final trimmed width Wt′ of about 190 Å, may form a trimmed feature232(FIG. 8) having a final trimmed height Ht′ of less than about 570 Å and a feature width roughness of about 27 to about 28 Å (e.g., about 27.5 Å).

FIG. 10depicts a photomicrograph of resulting trimmed features232′ defining a trimmed pattern230′ resulting from exposing a 193 nm photoresist material to a type I trimming chemistry. As shown, the trimmed features232′ have more remaining resist height (as compared to, e.g.,FIGS. 6F and 6G), less top tapering (as compared to, e.g.,FIGS. 6F-6I), less bottom tapering (as compared to, e.g.,FIG. 6I), a more vertically aligned cross-sectional profile (as compared to, e.g.,FIG. 6J), and substantially no slanting or wobbling (as compared to, e.g.,FIG. 6J), at a small lateral dimension (which may be smaller than that of, e.g.,FIG. 6I). For example, exposing an initial feature120(FIG. 2) of a top-coated (with top coating material140) resist patterning material112, having an initial height Hiof about 900 Å, an initial width Wiof about 460 Å, and an initial feature width roughness of about 55 Å with a three sigma distribution, to conventional trimming chemistries may form trimmed features having higher resist height loss, higher feature width roughness, or both compared to trimmed features232(FIG. 8) formed using trimming chemistries disclosed herein (e.g., the aforementioned example type I trimming chemistry comprising SO2and NF3, the aforementioned example type I trimming chemistry comprising SO2and CF4, the aforementioned example type II trimming chemistry comprising SO2and CH2F2, and the aforementioned example type III trimming chemistry comprising SO2and Cl2). For example, exposing such initial feature to a conventional trimming chemistry of Cl2and O2may form a trimmed feature having more than 340 Å in height loss with a final feature width roughness of about 28.5 Å; exposing such initial feature to a conventional trimming chemistry of Cl2, O2, CF4, and CH2F2may form a trimmed feature having about 260 Å of height loss with a final feature width roughness of about 30.0 Å; exposing such initial feature to a conventional trimming chemistry of CF4and O2may form a trimmed feature having about 170 Å of height loss with a final feature width roughness of about 34.0 Å; exposing such initial feature to a conventional trimming chemistry of Cl2, HBr, and O2may form a trimmed feature having more than about 380 Å of height loss with a final feature width roughness of about 28.5 Å; exposing such initial feature to a conventional trimming chemistry of SO2alone may form a trimmed feature having more than about 450 Å of height loss with a final feature width roughness of about 29.0 Å; and exposing such initial feature to a conventional trimming chemistry of SO2and O2may form a trimmed feature having more than about 500 Å of height loss with a final feature width roughness of about 29.5 Å.

Accordingly, also disclosed is method of forming a semiconductor device structure, the method comprising patterning a photoresist material to form resist features. The resist features are exposed to an etchant comprising sulfur dioxide and a halogen-based compound to reduce a width of each the resist features.

The concentration of components within the trimming chemistry may be described in terms of relative flow rates or, alternatively, in terms of parts. The trimming chemistry may include about 5 sccm to about 500 sccm of SO2, e.g., about 30 sccm to about 300 sccm SO2, while the halogen-based compound may be present at a range of, for example, about 0.1 parts (e.g., 0.1 sccm) to about 10 parts (e.g., 10 sccm) of the halogen-based compound per about 1 part (e.g., 1 sccm) of the SO2. For example, without limitation, the trimming chemistry may comprise, for every 1 part of SO2, at least one of about 0.2 parts to about 10 parts CF4, about 0.2 parts to about 10 parts SF6, about 0.2 parts to about 10 parts NF3, about 0.2 parts to about 5 parts ClF3, about 0.2 parts to about 10 parts Cl2, about 0.1 parts to about 5 parts CHF3, and about 0.1 parts to about 2 parts CH2F2. In the foregoing, the “parts” may be volumetric measurements, such as, for example, a volumetric flow rate (e.g., “sccm”) or volumes themselves (e.g., “cm3,” or “L” (at chamber operating pressure and temperature)).

More particular examples of trimming chemistries, wherein compositions listed are in terms of flow rates of each component, are as follows:

Type I Trimming Chemistry Examples

Type II Trimming Chemistry Examples

Type III Trimming Chemistry Example

The trimming chemistries above may be utilized in a trimming process at conditions of about 25 seconds throughput time, about 8 mTorr chamber pressure, about 380 W source RF power, about 0 V bias RF power, and about 50° C. electrostatic chuck (ESC) temperature, wherein the structure subjected to the trimming chemistry may be supported by the ESC.

Each of the foregoing trimming chemistry examples may additionally include, where not already listed, one or more additive gases such as, for example, argon (Ar), helium (He), nitrogen (N2), and oxygen (O2). Inert additive gases, such as Ar and He, may be included in the trimming chemistry to maintain a proper chamber pressure or to achieve certain etch uniformity. Reactive additive gases, such as N2and O2, may be included in the trimming chemistry to increase the rate of material removal (e.g., the etch rate). However, selecting an amount of such reactive additive gases may be dependent upon tuning the trimming chemistry to achieve a desired elevational profile and feature height. When included, the additive gases may be included in the trimming chemistry in a ratio of about 1 part (e.g., about 1 sccm) for every about 0.1 part to about 15 parts (e.g., about 0.1 sccm to about 15 sccm) SO2.

Exposing initial features120(FIG. 1) of a 193 nm photoresist material with a top coating material140thereon, the initial features120exhibiting initial widths Wiof approximately 580 Å, initial heights Hiof about 980 Å, and an initial feature width roughness of about 55 Å with a three sigma distribution, to one of the type I trimming chemistries at the conditions discussed above, the resulting trimmed features232may have the cross-sectional profile of the trimmed features232illustrated inFIG. 8and may be photomicrographed as shown inFIG. 10. The trimmed features232may have a feature width roughness (e.g., a line width roughness) of about 28 Å with a three sigma distribution, a final trimmed height Ht′ of about 600 Å to about 800 Å (e.g., about 750 Å, using a type I trimming chemistry including SO2and CF4, or about 600 Å, using a type I trimming chemistry including SO2and CH2F2), and a final trimmed width Wt′ of less than about 400 Å (e.g., about 360 Å). In such embodiments, therefore, the desired critical dimension (CD) may be equal to the resulting trimmed width Wt′(e.g., about 36 nm).

The trimmed feature232may be achieved using the trimming chemistry to remove material laterally from the resist material at a rate (e.g., at a lateral etch rate) of about 4 Å/s to about 7 Å/s (e.g., about 6 Å/s) and to remove material vertically from the resist material at a rate (e.g., a vertical etch rate) of about 1.8 times faster than the lateral material removal rate, i.e., about 7.2 Å/s to about 12.6 Å/s (e.g., about 10.8 Å/s).

Generally, a trimming chemistry formulated to yield a high trim rate ratio (i.e., the ratio of a lateral material removal rate to a vertical material removal rate) may be desirable, so as to achieve minimized reduction of the height of the patterning material112, when removing material from the initial features120to form the trimmed features232. For example, a “high” trim rate ratio may be greater than about 0.5, e.g., about 0.55 (i.e., a trim rate ratio of about 1 Å/s of lateral etching to about 1.8 Å/s of vertical etching). The trim rate ratio may be increased by increasing the relative amount (e.g., flow rate) of the non-polymerizing fluorine-based gases (e.g., CF4, NF3, SF6, ClF3), by increasing amount of sulfur dioxide relative to the other active gases (e.g., polymerizing gases (e.g., CH2F2and C4F6)), or by decreasing the amount of aggressive carbon-etching gases (e.g., O2) within the trimming chemistry relative to the other active components (e.g., the halogen-based compound or other etchant compounds). However, conventional trimming chemistries comprising a high concentration of sulfur dioxide or of sulfur dioxide and oxygen, without a halogen-based compound, often lead to extensive vertical material removal and tapering in the resulting trimmed features (e.g., trimmed features132E (FIG. 6E) and trimmed patterns130F (FIG. 6F) and 130G(FIG. 6G)). Accordingly, the ratio of sulfur dioxide to the halogen-based compound and other active compounds may be tailored to achieve a high trim rate ratio without excessive height loss and elevational profile tapering.

Without limitation, it is theorized that the inclusion of a halogen compound with the sulfur dioxide may enable halogenations and sulfurization (or cross-linking) of the resist or carbon material within the patterning material112. Such halogenization (e.g., fluorination from CF4, NF3, SF6, or ClF3) and cross-linking may strengthen the patterning material112and may enhance its etch resistance, particularly on the top surface128(FIG. 2) of the initial features120(FIG. 2). Accordingly, a trimming chemistry comprising sulfur dioxide and at least one of, e.g., CF4, NF3, SF6, ClF3, C3F8, C4F8, C4F6, CHF3, and CH2F2may achieve a higher trim rate ratio than that achievable by a chemistry lacking a halogen compound. Therefore, for example, it is contemplated that a trimming chemistry comprising SO2and CF4may have a higher trim rate ratio compared to a trimming chemistry comprising SO2alone or one comprising SO2and O2without a organohalogen compound.

Accordingly, disclosed is a method of forming a semiconductor device structure, the method comprising forming a patterning material over a base material. At least a portion of the patterning material is removed to define a plurality of features in the patterning material. The patterning material is exposed to a chemistry comprising sulfur dioxide and a halogen-based compound to alter a lateral dimension of the features of the plurality of features and form a pattern of trimmed features.

The trim rate ratio may also be impacted by the presence or absence of bias power. For example, application of a bias power of more than about 50 W during the trimming process may increase a vertical material removal rate, thereby decreasing the trim rate ratio. In some embodiments, such as those in which a tall trimmed feature232(i.e., a trimmed feature232having a final trimmed height Ht′ of at least about 600 Å) is not vital to precise pattern transfer to the base material114, a bias power may be applied during the trimming process.

Because application of bias power may promote material removal in the vertical direction, it is contemplated that the patterning material112, before patterning or other material removal, may be exposed to the trimming chemistry in the presence of applied bias power to pattern the patterning material112to form the initial pattern, e.g., initial pattern118of initial features120(FIGS. 1 and 2). The bias power may then be substantially stopped and the initial pattern118of initial features120exposed to the trimming chemistry in the substantial absence of the bias power to trim the initial features120to form the trimmed features132. Therefore, one chemistry may be used to both pattern and then to trim the patterning material112, stopping the bias power therebetween. In such an embodiment, lowering the bias power during the trimming process may lower the vertical material removal rate while increasing the trim rate ratio.

Using the trimming chemistry during the application of bias power may also enable selective removal (e.g., trimming) of a material other than a conventional resist material. In such embodiments, the patterning material112may include, or consist of, a hardmask material. Accordingly the same trimming chemistry may be used to trim a photoresist material, in the substantial absence of a bias power, and to trim a hardmask material, in the presence of a bias power. Therefore, the methods and chemistries of the present disclosure are not limited to use with only resist materials.

The trimming chemistry, according to embodiments of the disclosure, may be formulated to accomplish isotropic etching during the trimming process. For example, the type I and type II trimming chemistries discussed above may be formulated for isotropic etching of a 193 nm resist material.

The trimming process may, optionally, further include a curing act prior to exposure of the initial features120to the trimming chemistry. For example, the initial features120of the patterning material112may be exposed to a curing chemistry comprising HBr for about 30 seconds to about 70 seconds prior to exposure to the trimming chemistry. The curing act may be used to smooth the initial features120and to densify the patterning material112within the initial features120. The use of curing may further facilitate formation of trimmed features232exhibiting low feature width roughness.

The trimming chemistries comprising the sulfur dioxide and the halogen-based compound may selectively etch carbon-based material relative to oxide and nitride materials, e.g., when in the substantial absence of bias power. That is, the trimming chemistries may remove carbon-based material faster than they remove oxide and nitride materials when no substantial bias power is applied. Accordingly, the base material114may include a dielectric antireflective coating (DARC), such as, for example, silicon dioxide, silicon oxynitride, or combinations thereof. In such embodiments, the trimming process may trim the initial features120of the patterning material112to form the trimmed features132without substantially removing the base material114.

The trimming chemistry may alternatively or additionally be formulated to enable selective removal (e.g., etching) of non-carbon-based materials with application of substantial bias power, such as, for example, a bottom-antireflective coating (BARC). The same trimming chemistry may be formulated to enable selective removal (e.g., etching or trimming) of oxide-containing or nitride-containing material from, for example, the base material114, with the application of bias power, e.g., a bias power of less than about 50 V.

According to some conventional photolithography techniques used to pattern a resist material, a top coating material140(FIG. 6C) may be applied over a top surface of the resist material (e.g., over a top surface of the patterning material112), prior to patterning the patterning material112to form the initial features120(FIG. 1). In such embodiments, the presence of the top coating material140(FIG. 6C) on the initial features120may lead to feature width roughness and an other-than-vertical profile after initial patterning or after trimming with a conventional trimming chemistry, such as a conventional trimming chemistry comprising CF4and O2. Conventional trimming chemistries may remove resist material along the sidewalls126of the initial features120faster than the top coating material140is removed, leading to formation of an overhang region142(FIG. 6C). In embodiments of the present methods and chemistries, when used with initial features120including top coating material140thereon, the trimming chemistry may be tailored to substantially remove the top coating material140during the trimming process, which may enable formation of the trimmed features132with a vertical elevational profile and without an overhang region142. Tuning the trimming chemistry may include selecting a relative amount of sulfur dioxide and halogen-based compound, such as CF4, that removes as much of the top coating material140as needed to avoid formation of the overhang region142but not removing so much of the top coating material140and portions of the top surface128to form a tapered (e.g., rounded) trimmed top surface (e.g., as inFIGS. 6A and 6E). Increasing the amount (e.g., flow rate) of the sulfur dioxide relative to the halogen-based compound (e.g., CF4) within the trimming chemistry may increase the rate at which the top coating material140is removed. On the other hand, increasing the amount (e.g., flow rate) of the halogen-based compound (e.g., CF4) relative to the sulfur dioxide within the trimming chemistry may decrease the rate at which the top coating material140is removed. Accordingly, the composition of the trimming chemistry can be tailored to tune the resulting elevational profile of the trimmed features232.

It is contemplated that if the cross-sectional profile of an initial feature120including a top coating material140is substantially vertical, the trimming chemistry according to embodiments of the present disclosure may be tailored to not substantially remove the top coating material140during the trimming process. In such embodiments, given the vertical cross-sectional profile of the initial feature120, removing the top coating material140may not be necessary to achieve a vertical elevational profile in the trimmed feature132.

Even in embodiments in which a top coating material140is not utilized, the trimming chemistries and methods of embodiments of the present disclosure may achieve formation of the trimmed features232at a desired critical dimension with low feature width roughness, with more vertical elevational profiles, and without excess height loss. Accordingly, the present methods and chemistries are configured and formulated, respectively, for use with both patterning material112alone and patterning material112over which a top coating material140has been formed.

Because the trimming chemistries, according to embodiments of the present disclosure, enable formation of trimmed features232at a desired critical dimension with low feature width roughness, low feature height loss, and with about vertical elevational profiles, the trimming chemistries are formulated for use in patterning processes used for fabricating semiconductor device structures at very small dimensions, e.g., at critical dimensions of less than about 25 nm. Accordingly, the trimming chemistries may be used as part of a pitch multiplication process (e.g., pitch doubling, pitch tripling), as illustrated inFIGS. 11 through 14. Pitch multiplication processes are used to form at least two features in a target material for each feature that may be formed in an overlying material, such as a patterning material, from an initial patterning process. Examples of various pitch multiplication processes are described in, for example, U.S. Pat. No. 7,709,390, issued May 4, 2010, and U.S. Pat. No. 7,989,307, issued Aug. 2, 2011.

With reference toFIGS. 11 and 12, illustrated is a pitch multiplication process act following the fabrication process act illustrated inFIGS. 7 and 8. The trimmed features232may be formed to define a starting pitch, labeled inFIG. 11as “X.” A spacer material is formed over the trimmed features232, and an upper surface thereof may be planarized to form spacers240between which are exposed planarized top surfaces242of the trimmed features232. Neighboring spacers240define an opening244of width X1.

The trimmed features232of the patterning material112may then be removed while leaving the spacers240, as illustrated inFIGS. 13 and 14. Methods for removing the patterning material112, such as a photoresist material, of the trimmed features232without removing a spacer, such as spacer240, are known in the art and therefore are not described in detail. The remaining spacers240define other openings246of width X2. Depending on the thicknesses of the trimmed features232and the spacers240, in some embodiments, the width X1of openings244may be about equal to the width X2of other openings246. The remaining openings244and the other openings246define a masking pattern248of the spacers240, which masking pattern248may be transferred to the base material114to form two features in the base material114for every one of the trimmed features232formed prior to the pitch multiplication process.

Notably, widths X1and X2are, together, less than the starting pitch X. Because the dimensions of the masking pattern248are so small, forming the spacers240precisely is often important. Because the spacers240are formed on the trimmed sidewalls236(FIG. 8) of the trimmed features232, it is therefore often important to form the trimmed features232with precision, e.g., with minimized feature width roughness, with a precise elevational profile, and with sufficient height. Accordingly, utilizing the trimming chemistries and methods of embodiments of the present method may be well suited for use in pitch multiplication processes.

The forgoing methods and chemistries may be used not only for achieving critical dimensions with fewer imperfections in the resulting formed patterning material features, they can also be used for trimming other carbon-based materials and for cleaning surfaces of carbon-based materials (e.g., polymer “descumming”).

While the present disclosure is susceptible to various modifications and alternative forms in implementation thereof, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, the present disclosure is not intended to be limited to the particular forms disclosed. Rather, the present disclosure encompasses all modifications, combinations, equivalents, variations, and alternatives falling within the scope of the present disclosure as defined by the following appended claims and their legal equivalents.