Patent Application
20150247087
The present invention relates to an etching liquid for a semiconductor substrate, an etching method using the same, and a method of producing a semiconductor device.
Miniaturization and diversification of semiconductor devices have progressed more and more, and a processing method thereof covers a wide range with respect to each of device structures and production steps. As regards etching of the substrate, development of both dry etching and wet etching has been advanced, and a variety of chemical liquids and processing conditions have been proposed depending on kinds and structures of the substrate material.
Above all, when a device structure of CMOS, DRAM or the like is produced, a technique of etching a prescribed material precisely is important and as one of techniques of addressing such problem, a wet etching which utilizes a chemical liquid is exemplified. For example, a precise etching processing is required in the production of circuit wiring of a microscopic transistor circuit, a metal electrode material, or a substrate having a barrier layer, a hard mask, and the like. However, sufficient study has not yet been done on etching conditions and chemical liquids suitable for each of the substrates containing a wide variety of metal compounds. Under these circumstances, efficient removal of a hard mask or the like applied to the device substrate has been laid out as a production problem. Specifically, there are examples of studies on chemical liquids for etching titanium nitride (TiN) (see Patent Literatures 1 to 6).
By the way, in recent semiconductor device production, there is a requirement for a processing technique of wet-etching a metal hard mask (MHM) composed of TiN under the condition of exposed contact plug composed of tungsten (W), copper (Cu) and the like. In the production, a solid hard mask composed of TiN has to be removed without damaging the contact plug composed of metals. That is to say, simply developing of chemical liquids having removal performance for TiN is not enough to respond to such a requirement. In particular, recently the contact plug has increasingly been miniaturized and it still more increases the difficulty of a fine and selective etching using chemical liquids.
On the other hand, the above Patent Literature 6 sets out that, by using a mixture of a hydrogen fluoride and a silane-containing precursor, a metal hard mask can be removed while suppressing dissolution of the above contact plug material. However, there is no disclosure of the specific formula, so that its details are unclear. Even if the mixture of the hydrogen fluoride and the silane-containing precursor (methyl triethoxysilane) disclosed therein is simply used, there is a possibility that sufficient etching properties cannot be obtained depending on the oxygen concentration of the substrate (see Comparative Example C11 described below).
In view of the above, the present invention addresses the provision of an etching liquid which removes a first layer containing TiN selectively and efficiently to a second layer containing a particular metal and further enables achievement of surface uniformity of the TiN layer after etching, an etching method using the same, and a method of producing a semiconductor device. In particular, the present invention addresses the provision of an etching liquid which achieves the above etching selectivity suitably in response to a broad concentration range of oxygen contained in the TiN layer, if needed, an etching method using the same, and a method of producing a semiconductor device.
The above problems can be solved by the following means.
[1] An etching liquid that processes a substrate having a first layer containing titanium nitride (TiN) and a second layer containing a transition metal and thereby removes selectively the first layer, wherein the etching liquid contains a fluorine-containing compound, an oxidizing agent and an organic silicon compound.
[2] The etching liquid described in the item [1], wherein the transition metal of the second layer is at least one selected from Co, Ni, Cu, Ag, Ta, Hf, W, Pt, and Au.
[3] The etching liquid described in the item [1] or [2], wherein the fluorine-containing compound is selected from the group consisting of hydrogen fluoride, ammonium fluoride, tetramethylammonium fluoride, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluorosilicic acid, ammonium tetrafluoroborate, ammonium hexafluorophosphate, and ammonium hexafluorosilicate.
[4] The etching liquid described in any one of the items [1] to [3], wherein the oxidizing agent is nitric acid or hydrogen peroxide.
[5] The etching liquid described in any one of the items [1] to [4], wherein the organic silicon compound is represented by the following formula (S1):
R14Si (S1)
wherein, in the formula, R1 represents an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an acyloxy group having 1 to 10 carbon atoms, an aryloyloxy group having 7 to 25 carbon atoms, an oxime group having 2 to 10 carbon atoms, or a hydrogen atom with the proviso that all of R's represent hydrogen atoms.
[6] The etching liquid described in any one of the items [1] to [5], wherein a rate ratio (R1/R2) of an etching rate (R1) of the first layer and an etching rate (R2) of the second layer is 2 or more.
[7] The etching liquid described in any one of the items [1] to [6], further containing an anticorrosive agent for the second layer.
[8] The etching liquid described in the item [7], wherein the anticorrosive agent is composed of a compound represented by any one of the following formulae (I) to (IX):
wherein, R1 to R30 each independently represent a hydrogen atom or a substituent; in this case, neighbors adjacent to each other may be ring-fused to form a cyclic structure; A represents a hetero atom with the proviso that when A is divalent, there exists none of R1, R3, R6, R11, R24 and R28 by which A is each substituted.
[9] The etching liquid described in the item [7] or [8], wherein the anticorrosive agent is contained in a range of from 0.01 to 10% by mass.
[10] The etching liquid described in any one of the items [1] to [9], wherein the oxidizing agent is contained in an amount of from 0.05 to 10% by mass.
[11] The etching liquid described in any one of the items [1] to [10], wherein the fluorine-containing compound is contained in an amount of from 0.05 to 30% by mass.
[12] The etching liquid described in any one of the items [1] to [11], wherein the organic silicon compound is contained in an amount of from 0.05 to 30% by mass.
[13] The etching liquid described in any one of the items [1] to [8], wherein a pH is from −1 to 5.
[14] The etching liquid described in any one of the items [1] to [13], wherein the substrate has a third layer containing silicon.
[15] The etching liquid described in the item [14], wherein the third layer is a layer containing a metal compound selected from at least one of SiO, SiN, SiOC, and SiON.
[16] The etching liquid described in the item [14] or [15], wherein a rate ratio (R1/R3) of an etching rate (R1) of the first layer and an etching rate (R3) of the third layer is 2 or more.
[17] An etching method comprising the step of:
processing a substrate having a first layer containing titanium nitride (TiN) and a second layer containing a transition metal by applying an etching liquid to the substrate thereby selectively removing the first layer,
wherein the etching liquid comprises a fluorine-containing compound, an oxidizing agent and an organic silicon compound.
[18] The etching method described in the item [17], wherein the first layer containing titanium nitride (TiN) has a surface oxygen concentration of from 0.1 to 10% by mole.
[19] The etching method described in the item [17] or [18], wherein the method of applying the etching liquid to the substrate contains a step of supplying the etching liquid onto the substrate from above the substrate while rotating the substrate.
[20]A method of producing a semiconductor device comprising the step of: removing a first layer containing titanium nitride (TiN) by the etching method described in any one of the items [17] to [19], thereby producing the semiconductor device from the remaining substrate.
By the etching liquid, the etching method, and the method of producing a semiconductor device using the same according to the present invention, a first layer containing TiN is removed selectively and efficiently to a second layer containing a particular metal and further surface uniformity of the TiN layer after etching can be achieved. Further by the present invention, if needed, the above suitable etching selectivity of the first layer containing TiN can be achieved in response to its broad range of the oxygen concentration.
Other and further features and advantages of the invention will appear more fully from the following description, appropriately referring to the accompanying drawings.
First, preferable embodiments of the etching step concerning the etching method of the present invention are explained on the basis of
Note that, when a silicon substrate or a semiconductor substrate, or simply a substrate is mentioned, these are used in the sense of including not only a silicon wafer but also a whole substrate structure provided with a circuit structure. The term “the element of the substrate” refers to an element that constitutes the silicon substrate that is defined above, and may be made of a single material or a plurality of materials. A processed semiconductor substrate is sometimes called as a semiconductor substrate product by a distinction. A tip or a processed product thereof, which has been obtained by further processing the semiconductor substrate, if needed, and then by singulating the same is referred to as semiconductor device or semiconductor equipment. With respect to the direction of the semiconductor, in reference to
Next, a preferable embodiment of the etching liquid of the present invention is explained. The etching liquid of the present embodiment contains a fluorine-containing compound, an oxidizing agent and an organic silicon compound. Hereinafter, each of components including optional ones is explained.
Examples of the oxidizing agent include nitric acid, hydrogen peroxide, ammonium persulfate, perboric acid, peracetic acid, periodic acid, perchloric acid, or a combination thereof. Among them, nitric acid or hydrogen peroxide is particularly preferable.
The oxidizing agent is contained in an amount of 0.05% by mass or more, preferably in an amount of 0.1% by mass or more, and more preferably in an amount of 0.3% by mass or more, with respect to the total amount of the etching liquid of the present embodiment. The upper limit thereof is preferably 10% by mass or less, more preferably 9.5% by mass or less, still more preferably 7.5% by mass or less, still more preferably 5% by mass or less, and particularly preferably 3% by mass or less. Setting to the above-described upper limit or less is preferable from the viewpoint that good protection performance (selective etching) of the second layer can be achieved thereby. By setting to the above-described lower limit or greater, sufficient etching rate of the first layer can preferably be ensured.
As the above-described oxidizing agent, one kind thereof may be used solely, or two or more kinds thereof may be used in combination.
In the present invention, the fluorine-containing compound is not limited in particular, as long as it has fluorine in the molecule. Above all, a compound which dissolves in water to release a fluorine ion is preferable. Specific examples thereof include hydrogen fluoride, ammonium fluoride, tetramethylammonium fluoride, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluorosilicic acid, ammonium tetrafluoroborate, ammonium hexafluorophosphate, and ammonium hexafluorosilicate. As the counter ion, cations other than ammonium, for example, tetramethyl ammonium and the like may also be used.
The fluorine-containing compound is preferably incorporated in an amount of 0.05% by mass or more, more preferably incorporated in an amount of 0.5% by mass or more, and particularly preferably incorporated in an amount of 1% by mass or more, with respect to the total mass of the etching liquid according to the present embodiment. The upper limit thereof is preferably 30% by mass or less, more preferably 10% by mass or less, still more preferably 10% by mass or less, and particularly preferably 3% by mass or less. Setting to the above upper limit or less is preferable from the viewpoint of securing sufficient etching performance of the first layer. Further, by setting this amount to the above lower limit or above, etching selectivity between the first layer and the second layer can preferably be enhanced to a higher degree as well as securement of sufficient etching performance of the first layer.
In relation to the oxidizing agent, the fluorine-containing compound is preferably used in an amount of 1 part by mass or more, and more preferably in an amount of 10 parts by mass or more, with respect to 100 parts by mass of the oxidizing agent. The upper limit thereof is preferably 1000 parts by mass or less, more preferably 500 parts by mass or less, and particularly preferably 300 parts by mass or less. By using the amounts of both compounds in a suitable relation, a good etching performance can be realized and also a high etching selectivity can be achieved together as described above.
As the above-described fluorine-containing compound, one kind thereof may be used solely, or two or more kinds thereof may be used in combination.
In the present invention, the organic silicon compound is not limited in particular, as long as it has a silicon atom (Si) and a carbon atom (C) in the molecule. Above all, a compound represented by the following formula (S1) is preferable.
R14Si (S1)
In the formula, R1 represents an alkyl group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), an alkoxy group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), an aryl group having 6 to 20 carbon atoms (preferably 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms), an aryloxy group having 6 to 20 carbon atoms (preferably 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms), an alkenyl group having 2 to 10 carbon atoms (preferably 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms, preferably a vinyl group, an allyl group), an acyloxy group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), an aryloyloxy group having 7 to 25 carbon atoms (preferably 7 to 15 carbon atoms, more preferably 7 to 11 carbon atoms), an oxime group having 2 to 10 carbon atoms (preferably 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms), or a hydrogen atom. However, all of R's do not represent a hydrogen atom at the same time.
However, the above R1 may have a substituent additionally. The substituent includes the substituent T described below. Specifically, as the substituent, an amino group (preferably, an amino group free of carbon, an alkyl amino group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), an arylamino group having 6 to 24 carbon atoms (preferably 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms)), a hydroxyl group, a carboxyl group, a glycidyl group, an oxetane group, an acyl group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), an alkoxy group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), an alkylketoxime group having 2 to 10 carbon atoms (preferably 2 to 6 carbon atoms, more preferably 2 to 4 atoms), and the like are preferable. These substituents may be linked through any of the linking group L described below.
Note that as regards the optional possession of an additional substituent as described above, the same is true on R2 to R4 as described below and the range thereof is also the same. Further, through R1 to R5, an alkyl group and an alkenyl group may be straight-chain, branched-chain, or cyclic.
Alkoxysilane
Above all, as the organic silicon compound, alkyl (mono, di, tri) alkoxysilane or tetraalkoxysilane (hereinafter, referred to as particular alkoxysilane) is preferable. The particular alkoxysilane is preferably a compound represented by the following formula (S2).
R2m1Si(OR3)m2 (S2)
R2 represents an alkyl group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), an alkenyl group having 2 to 10 carbon atoms (preferably 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms), or an aryl group having 6 to 24 carbon atoms (preferably 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms). When a plurality of R2s exist, these may be the same or different from one another. Above all, an alkyl group is preferable. Specifically, examples thereof include a methyl group, an ethyl group, a propyl group, and an isopropyl group. Further, among these, a methyl group and an ethyl group are preferable and in particular, a methyl group is preferable. Note that the above alkyl group and alkenyl group may have an oxygen atom in the structure thereof. Specifically, in such group, an ether structure may be formed or an epoxy group or oxetane group may be formed by forming a ring. In the case of having an epoxy group, a glycidoxyalkyl group (preferably 2 to 12 carbon atoms, more preferably 4 to 6 carbon atoms), or an epoxycyclohexylalkyl group (preferably 7 to 12 carbon atoms, more preferably 7 to 9 carbon atoms) are preferable.
R3 represents an alkyl group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), or an aryl group having 6 to 24 carbon atoms (preferably 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms). When a plurality of R3s exist, these may be the same or different from one another. Above all, an alkyl group having 1 to 4 carbon atoms is preferable. In particular, from a viewpoint of easiness of controlling the hydrolysis rate, an ethoxy group is preferable. The ethoxy group corresponds to a group that R3 in formula (S2) is an ethyl group.
m1 and m2 are integers of 1 to 3. m1+m2 are 4.
Oximesilane
As the organic silicon compound, specific oximesilanes represented by the following formula (S3) are also preferable.
R4m3Si(ON═CR52)m4 (S3)
R4 represents an alkyl group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), an alkenyl group having 2 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or an aryloxy group having 6 to 20 carbon atoms. When at least two R4s exist, these may be the same or different from one another.
R5 represents an alkyl group having 1 to 10 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms), an aryl group having 6 to 20 carbon atoms (preferably 6 to 14 carbon atoms, more preferably 6 to 10 carbon atoms), or an aralkyl group having 7 to 20 carbon atoms (preferably 7 to 15 carbon atoms, more preferably 7 to 11 carbon atoms). When at least two R5s exist, these may be the same or different from one another.
m3 and m4 are integers of 1 to 3. m1+m2 are 4.
Specific examples of the organic silicon compound include aminopropyltriethoxysilane, aminopropyltrimethoxysilane, aminopropylmethyl diethoxysilane, aminopropylmethyldimethoxysilane, aminoethylaminopropyltrimethoxysilane, aminoethylaminopropyltriethoxysilane, aminoethylaminopropylmethyldimethoxysilane, diethylenetriaminopropyltrimethoxysilane, diethylenetriaminopropyltriethoxysilane, diethylenetriaminopropylmethyldimethoxysilane, diethylenetriaminopropylmethyldiethoxysilane, cyclohexylaminopropyltrimethoxysilane, hexanediaminomethyltriethoxysilane, phenylaminomethyltrimethoxysilane, phenylaminomethyltriethoxysilane, diethylaminomethyltriethoxysilane, (diethylaminomethyl)methyldiethoxysilane, methylaminopropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, glycidoxypropylmethydiethoxysilane and glycidoxypropylmethydimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyl tris(2-methoxyethoxy) silane, methyltrimethoxysilane, methyltriethoxysilane (MTES), tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), tetrapropoxysilane, methyl tris(methylethyl ketoxime)silane (MOS), methyl tris(acetooxime) silane, methyl tris(methylisobutyl ketoxime)silane, dimethyldi(methylketoxime) silane, trimethyl(methylethyl ketoxime)silane, vinyl tris(methylethyl ketoxime) silane (VOS), methylvinyl di(methylethyl ketoxime) silane, methylvinyl di(cyclohexanoneooxime) silane, vinyl tris(methylisobutyl ketoxime) silane, phenyltris(methylethyl ketoxime)silane (POS), methyltriacetoxysilane, tetraacetoxysilane, diethylsilane, and diphenylsilane. Above all, methyltriethoxysilane (MTES) is preferable.
In the etching liquid of the present invention, the content of the organic silicon compound is preferably 0.05% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more, with respect to the total mass of the etching liquid. The upper limit is preferably 30% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, still more preferably 3% by mass or less, and particularly preferably 1% by mass or less. Setting to the above-described upper limit or less is preferable from the viewpoint that sufficient etching performance of the first layer is ensured. Further, by setting this amount to the above-described lower limit or above, etching selectivity between the first layer and the second layer can preferably be enhanced to a higher degree as well as securement of sufficient etching performance of the first layer.
As regards the organic silicon compound, one kind thereof may be used solely, or two or more kinds may be used in combination.
In the etching liquid of the present invention, it is preferable to contain therein an anticorrosive agent which protects a metal of the second layer from corrosion and damage due to etching. The anticorrosive agent includes a 5- or 6-membered heterocyclic compound (the hetero atom includes nitrogen, oxygen, sulfur and the like) and an aromatic compound. The heterocyclic compound and the aromatic compound may be monocyclic or polycyclic. The heterocyclic compound is preferably a 5-membered heteroaromatic compound. Above all, a 5-membered nitrogen-containing heteroaromatic compound is more preferred. The number of nitrogen to be contained at this time is preferably from 1 to 4. As the aromatic compound, a compound having a benzene ring is preferred.
The anticorrosive agent is preferably a compound represented by any one of the following formulae (I) to (IX).
R1 to R30
In formulae (I) to (IX), R1 to R30 each independently represent a hydrogen atom or a substituent. Examples of the substituent include an alkyl group (having preferably 1 to 20 carbon atoms) described below, an alkenyl group (having preferably 2 to 20 carbon atoms), an aryl group (having preferably 6 to 24 carbon atoms), a heterocyclic group (having preferably 1 to 20 carbon atoms), an acyl group (having preferably 2 to 20 carbon atoms), an amino group (having preferably 0 to 6 carbon atoms), a carboxyl group, a hydroxy group, a phosphoric acid group, a thiol group (—SH), and a boronic acid group (—B(OH)2). Note that, as for the aryl group, a phenyl group or a naphthyl group is preferred. The above-described heterocyclic group includes a nitrogen-containing heteroaromatic group. Above all, a 5-membered nitrogen-containing heteroaromatic group is preferred and a pyrrole group, an imidazole group, a pyrazole group, a triazole group, or a tetrazole group is more preferred. Furthermore, these substituents may have a substituent within the scope in which the effect of the present invention is exerted. Note that, among the above-described substituents, an amino group, a carboxyl group, a phosphoric acid group, and a boronic acid group may form their salts. Examples of the counter ion that forms a salt include quaternary ammonium ions such as ammonium ion (NH4) and tetramethyl ammonium ion ((CH3)4N+).
The above-described substituent may be substituted through an arbitrary linking group. The linking group includes an alkylene group (having preferably 1 to 20 carbon atoms), an alkenylene group (having preferably 2 to 20 carbon atoms), an ether group (—O—), an imino group (having preferably 0 to 4 carbon atoms), a thioether group (—S—), a carbonyl group, or a combination thereof. Hereinafter, these linking groups are called “linking group L”. Furthermore, these linking groups may have a substituent within the scope in which the effect of the present invention is exerted.
As R1 to R30, above all, an alkyl group having 1 to 6 carbon atoms, a carboxyl group, an amino group (the number of carbon atoms is preferably 0 to 4), a hydroxyl group, or a boronic acid group is preferred. As described above, these substituents may be substituted through the linking group L.
Further, as for R1 to R30, neighbors adjacent to each other may be linked or ring-fused to form a cyclic structure. Examples of the ring structure to be formed include a pyrrole ring structure, an imidazole ring structure, a pyrazole ring structure, or a triazole ring structure. Furthermore, these ring-structural sites may have a substituent within the scope in which the effect of the present invention is exerted.
Note that, when the ring structure to be formed is a benzene ring, this ring structure is sectionalized into formula (VII) to organize it.
A
A represents a hetero atom, specifically a nitrogen atom, an oxygen atom, a sulfur atom, or a phosphorous atom. However, when A is divalent (an oxygen atom, or a sulfur atom), there exists none of R1, R3, R6, R11, R24 and R28.
The compound represented by the above-described formula (VII) is preferably a compound represented by any of the following formulae (VII-1) to (VI 1-4).
Ra represents an acid group, preferably a carboxyl group, a phosphoric acid group, or a boronic acid group. The above-described acid group may be substituted through the above-described linking group L.
Rb represents an alkyl group having 1 to 20 carbon atoms, an amino group (preferably 0 to 4 carbon atoms), a hydroxyl group, an alkoxy group (preferably 1 to 6 carbon atoms), or an acyl group (preferably 1 to 6 carbon atoms). The above-described substituent Rb may be substituted through the above-described linking group L. When Rb is an alkyl group, a plurality of Rb's may be linked to form a cyclic alkylene (an unsaturated bond may be incorporated in a part thereof). Alternatively, they may be ring-fused to form a polycyclic aromatic ring.
n1 is an integer of 1 to 5. n2 is an integer of 0 to 5. n3 is an integer of 0 to 4.
When each of n1 to n3 is 2 or more, a plurality of substituents defined there may be the same or different from one another.
In the formulae, A has the same definitions as A defined above. Rc, Rd and Re are the same groups as the defined groups for R1 to R30. However, when A is divalent, there exists none of Rc and Re.
Hereinafter, examples of the compounds represented by any of the above-described formulae (I) to (IX) are shown. However, the present invention is not construed as being limited on the basis of these compounds.
Note that, in the following exemplified compounds, the case of showing an example of a tautomer thereof is included. The other tautomer is also included in preferable examples of the present invention. The same is also true on the above-described formulae (I) to (IX) and (VII-1) to (VII-4).
Above all, compounds I-1, I-4, I-6, VII-2-1 and VII-2-2 are preferable.
The content of the anticorrosive agent in the etching liquid, although it is not limited in particular, is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and particularly preferably 0.1% by mass. The upper limit thereof, although it is not limited in particular, is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, and particularly preferably 1% by mass or less. By setting to the above-described lower limit or greater, a suitable protection effect for the metal layer can be preferably obtained. On the other hand, setting to the above-described upper limit or less is preferable from the viewpoint that the anticorrosive agent does not interfere with good etching performance.
As the above-described anticorrosive agent, one kind thereof may be used solely, or two or more kinds thereof may be used in combination.
The etching liquid of the present invention is preferably an aqueous solution in which water (aqueous medium) is applied as a medium and each of components contained therein is uniformly dissolved. The content of water is preferably from 50 to 99.5% by mass and more preferably from 55 to 95% by mass, with respect to the total mass of the etching liquid. Thus, a composition composed primarily of water (50% by mass or more) is sometimes called as an aqueous composition in particular, and preferable in terms of more inexpensive and more adaptable to the environment, compared to a composition with a high ratio of an organic solvent. It is preferable from this viewpoint that the etching liquid of the present invention is an aqueous composition. The water (aqueous medium) may be an aqueous medium containing components dissolved therein in an amount by which the effects of the present invention are not deteriorated, or may contain inevitable small amount of mixed components. Especially, water which has been subjected to a purifying process, such as distilled water, ion-exchanged water and ultrapure water is preferable and the ultrapure water which is used for production of the semiconductor is particularly preferable.
(pH)
In the present invention, the pH of the etching liquid is preferably controlled to −1 or greater, more preferably 0 or greater. As the upper limit, the pH is preferably controlled to be 5 or less, more preferably 4 or less, and still more preferably 3 or less. Setting to the above-described lower limit or greater is preferable from the viewpoint that not only the etching rate of TiN can be increased to a practical level but also the in-plane uniformity can be improved to a higher level. On the other hand, adjustment to the above-described upper limit or less is preferable for corrosive properties for other layers. The pH refers to a value obtained in accordance with equipment and the conditions used for measurement in Examples, unless otherwise indicated.
pH Controlling Agent
In the present embodiment, the pH of the etching liquid is controlled to be within the above-described range and a pH controlling agent is preferably used for the control thereof. As the pH controlling agent, in order to increase the pH, use of quaternary ammonium salts such as tetramethyl ammonium salts, choline and the like, alkali metal hydroxides such as potassium hydroxide and alkali earth metal salts such as calcium hydroxide, or amino compounds such as 2-aminoethanol, guanidine and the like is preferred. In order to decrease the pH, inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid; and organic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methyl butyric acid, n-hexanoic acid, 3,3-dimethyl butyric acid, 2-ethyl butyric acid, 4-methyl pentanoic acid, n-heptanoic acid, 2-methyl hexanoic acid, n-octanoic acid, 2-ethyl hexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, tartaric acid, citric acid, and lactic acid.
The use amount of the pH controlling agent is not particularly limited and an amount necessary to control the pH to the above-described range may be used.
In the etching liquid used in the present invention, a water-soluble organic solvent may further be added thereto. The water-soluble organic solvent is preferably an organic solvent that can be mixed with water in an arbitrary proportion. Adding the water-soluble organic solvent is effective in terms of enabling to improve in-plane uniform etching property of the wafer.
Examples of the water-soluble organic solvent include: alcohol compound solvents, such as methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, 2-butanol, ethylene glycol, propylene glycol, glycerol, 1,6-hexanediol, cyclohexanediol, sorbitol, xylitol, 2-methyl-2,4-pentanediol, 1,3-butanediol, and 1,4-butanediol; ether compound solvents, such as an alkylene glycol alkyl ether including ethylene glycol monomethyl ether, ethylene glycol monobuthyl ether, diethylene glycol, dipropylene glycol, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol, poly(ethylene glycol), propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, diethylene glycol monobutyl ether, and diethylene glycol monobutyl ether.
Among these solvents, preferred are alcohol compound solvents having 2 to 15 carbon atoms and hydroxyl group-containing ether compound solvents having 2 to 15 carbon atoms. More preferred are alcohol compound solvents having 2 to 10 carbon atoms and hydroxyl groups and hydroxyl group-containing ether compound solvents having 2 to 10 carbon atoms. Especially preferred are alkyleneglycol alkylethers having 3 to 8 carbon atoms. The water-soluble organic solvent may be used singly or in combination of two or more kinds appropriately. In the present specification, a compound having a hydroxyl group (—OH) and an ether group (—O—) in the molecule thereof shall be included in the category of the ether compound in principle (not called as the alcohol compound). When a compound having both a hydroxyl group and an ether group is mentioned distinctively in particular, the compound may be preferably called as “hydroxyl group-containing ether compound”.
Especially among these compounds, propyleneglycol and dipropyleneglycol are preferable. The addition amount thereof is preferably from 0.1 to 70% by mass and more preferably from 10 to 50% by mass, with respect to the total mass of the etching liquid. By setting the addition amount to the above-described lower limit or greater, improvement in uniformity of the above-described etching can be effectively realized.
The above-described water-soluble organic solvent is preferably a compound represented by the following formula (0-1).
R11—(—O—R13—)n—O—R12 (O-1)
R11, R12
R11 and R12 are independently a hydrogen atom or an alkyl group having 1 or more and 5 or less carbon atoms. Among these, they are independently preferably an alkyl group having 1 or more and 5 or less carbon atoms, and more preferably an alkyl group having 1 or more and 3 or less carbon atoms.
R13
R13 is a straight-chain or branched-chain alkylene chain having 1 or more and 4 or less carbon atoms. When a plurality of R13's are present, they may be different from one another.
n
n is an integer of 1 or more and 6 or less.
It is noted that in the present specification, the representation of the compound (for example, when the name of a chemical is called by putting the term “compound” at the foot of the chemical name) is used in the sense that not only the compound itself, but also its salt, and its ion are incorporated therein. Further, it is used in the sense that the compound means to include a derivative thereof which is modified in a predetermined part within the range of achieving a desired effect.
In the present specification, a substituent (a linking group is also the same) that is not specified by substitution or non-substitution means that the substituent may have an optional substituent. This is applied to the compound that is not specified by substitution or non-substitution. Preferable examples of the substituent include the substituent T described below.
The substituent T includes the following substituents.
The substituents include an alkyl group (preferably an alkyl group having 1 to 20 carbon atom(s), for example, methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, and 1-carboxymethyl), an alkenyl group (preferably an alkenyl group having 2 to 20 carbon atoms, for example, vinyl, allyl, and oleyl), an alkynyl group (preferably an alkynyl group having 2 to 20 carbon atoms, for example, ethynyl, butadiynyl, and phenylethynyl), a cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms, for example, cyclopropyl, cyclopentyl, cyclohexyl, and 4-methylcyclohexyl), an aryl group (preferably an aryl group having 6 to 26 carbon atoms, for example, phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, and 3-methylphenyl), a heterocyclic group (preferably a heterocyclic group having 2 to 20 carbon atoms, more preferably a 5- or 6-membered heterocyclic group having at least one hetero atom selected from nitrogen, oxygen and sulfur atoms, for example, 2-pyridyl, 4-pyridyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, and 2-oxazolyl), an alkoxy group (preferably an alkoxy group having 1 to 20 carbon atom(s), for example, methoxy, ethoxy, isopropyloxy, and benzyloxy), an aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms, for example, phenoxy, 1-naphthyloxy, 3-methylphenoxy, and 4-methoxyphenoxy), an alkoxycarbonyl group (preferably an alkoxycarbonyl group having 2 to 20 carbon atoms, for example, ethoxycarbonyl and 2-ethylhexyloxycarbonyl), an amino group (preferably an amino group, an alkylamino group or an aryl amino group having 0 to 20 carbon atom(s), for example, amino, N,N-dimethylamino, N,N-diethylamino, N-ethylamino, and anilino), a sulfamoyl group (preferably a sulfamoyl group having 0 to 20 carbon atom(s), for example, N,N-dimethylsulfamoyl, and N-phenylsulfamoyl), an acyl group (preferably an acyl group having 1 to 20 carbon atom(s), for example, acetyl, propionyl, butyryl and benzoyl), an acyloxy group (preferably an acyloxy group having 1 to 20 carbon atom(s), for example, acetyloxy and benzoyloxy), a carbamoyl group (preferably a carbamoyl group having 1 to 20 carbon atom(s), for example, N,N-dimethylcarbamoyl and N-phenylcarbamoyl), an acylamino group (preferably an acylamino group having 1 to 20 carbon atom(s), for example, acetylamino and benzoylamino), a sulfonamide group (preferably a sulfonamide group having 0 to 20 carbon atom(s) for example, methanesulfonamide, benzenesulfonamide, N-methylmethanesulfonamide, N-ethylbenzenesulfonamide), an alkylthio group (preferably an alkylthio group having 1 to 20 carbon atom(s), for example, methylthio, ethylthio, isopropylthio, benzylthio), an arylthio group (preferably an arylthio group having 6 to 26 carbon atoms, for example, phenylthio, 1-naphthylthio, 3-methylphenylthio, 4-methoxyphenylthio), an alkyl- or aryl-sulfonyl group (preferably an alkyl- or aryl-sulfonyl group having 1 to 20 carbon atoms, for example, methylsulfonyl, ethylsulfonyl, benzenesulfonyl), a hydroxyl group, a carboxyl group, a sulfo group, a cyano group, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom). Among them, an alkyl group, an alkenyl group, an aryl group, a heterocyclic group, an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an amino group, an acylamino group, a hydroxyl group, and a halogen atom are more preferable. An alkyl group, an alkenyl group, a heterocyclic group, an alkoxy group, an alkoxycarbonyl group, an amino group, an acylamino group, and a hydroxyl group are particularly preferable.
Further, each of these groups exemplified as the substituent T may be substituted with the above-described substituent T.
In the present specification, as regards each of technical items such as temperature and thickness including choices of substituents and linking groups of the compound, even if lists of the technical items are each independently described, these can be combined mutually.
The etching liquid of the present invention may be constituted as a kit in which the raw materials thereof are divided into multiple parts. Examples of the kit include an embodiment in which, as a first liquid, a liquid composition in which the above-described fluorine-containing compound is contained in an aqueous medium is prepared, and, as a second liquid, a liquid composition in which the above-described oxidizing agent is contained in an aqueous medium is prepared. As an example of the use thereof, preferred is an embodiment in which both liquids are mixed to prepare an etching liquid, and after that, the etching liquid is applied to the above-described etching process on a timely basis. This avoids the etching liquid from causing deterioration of the liquid properties due to decomposition of the oxidizing agent (for example, hydrogen peroxide) whereby a desired etching function can be effectively exhibited. Herein, the term “on a timely basis (timely)” after mixing defines the meaning of a period of time prior to a desired function being lost after mixing. Specifically, the period of time is preferably within 60 minutes, more preferably within 30 minutes, and particularly preferably within 10 minutes. Although there is no lower limit in particular, the period of one second or longer is practical. The above-described anticorrosive agent may be contained in the first liquid, or in the second liquid, or in the third liquid described below.
The concentration of the fluorine-containing compound in the first liquid, although it is not particularly limited, is preferably 0.5% by mass or more and more preferably 1.5% by mass or more. The upper limit thereof is preferably 40% by mass or less and more preferably 30% by mass or less. By setting the concentration to the above-described range, a condition suitable for mixing with the second liquid can be achieved and a favorable concentration region in the above-described etching liquid can preferably be achieved.
The concentration of the oxidizing agent in the second liquid, although it is not particularly limited, is preferably 0.1% by mass or more and more preferably 0.5% by mass or more. The upper limit thereof is preferably 20% by mass or less and more preferably 10% by mass or less. By setting the concentration to the above-described range, a condition suitable for mixing with the first liquid can be achieved and a favorable concentration region in the above-described etching liquid can be preferably achieved.
In the case where the above-described organic silicon compound, the above-described water-soluble organic solvent or anticorrosive agent is used, it is preferable that the organic silicon compound, water-soluble organic solvent or anticorrosive agent is preliminarily added to the first liquid side. Alternatively, a liquid composition in which an organic silicon compound and further a water-soluble organic solvent or an anticorrosive agent have been added to an aqueous medium is preliminarily prepared and the liquid composition may be mixed as a third liquid with the first liquid and the second liquid.
The procedure for mixing the first liquid with the second liquid, although it is not limited, is preferably a method of putting the first liquid and the second liquid into circulation in a separate flow channel and making them converge at the junction portion of the flow channels, thereby mixing them. After that, it is preferable that the etching liquid obtained by convergence is further put into circulation in a flow channel and then discharged or sprayed from a discharge opening, thereby bringing it contact with a semiconductor substrate. In this embodiment, a step of from converging-mixing at the junction portion to contacting with the semiconductor substrate is preferably conducted “on a timely basis (timely)” described above. This is explained below by using
The etching liquid of the present invention (whether it is a kit or not) can be stored, transported and used by filling it into an arbitrary container, as far as corrosion resistance properties and the like are not concerned. Further, for semiconductor application, it is preferred that the container have high cleanness and less elution of impurities therefrom. Examples of available containers include “CLEAN BOTTLE” series manufactured by AICELLO CORPORATION, and “PURE BOTTLE” manufactured by KODAMA PLASTICS Co., Ltd. However, the present invention is not limited to these.
In the present embodiment, the conditions for etching are not particularly limited. Either single wafer type (spray-type) etching or immersion type (batch type) etching may be applicable. In the spray-type etching, a semiconductor substrate is transported or rotated in the prescribed direction and an etching liquid is sprayed into the space, thereby bringing the etching liquid into contact with the semiconductor substrate. On the other hand, in the batch-type etching, a semiconductor substrate is immersed in a liquid bath constituted of an etching liquid, thereby bringing the etching liquid into contact with the semiconductor substrate in the liquid bath. These etching processes may be appropriately used depending on the structure, the material, and the like of a device.
The environmental temperature at which etching is conducted is preferably 15° C. or higher, and particularly preferably 25° C. or higher, in the measurement method of temperature in Examples below. The upper limit thereof is preferably 80° C. or lower, and more preferably 60° C. or lower. By setting to the above-described lower limit or higher, etching selectivity to the TiN layer and the second layer can preferably be ensured. By setting the temperature to the above-described upper limit or lower, stability with age of the etching rate can preferably be maintained. The feeding rate of the etching liquid, although it is not particularly limited, is preferably set within the range from 0.05 to 1 L/min, more preferably from 0.1 to 0.5 L/min. When the feeding rate of the etching liquid is set to a higher level, the feeding rate is preferably set to a range of from 0.1 to 2 L/min. By setting to the above-described lower limit or greater, in-plane uniformity of etching can preferably be secured at more excellent level. By setting to the above-described upper limit or lower, stable selectivity at the time of continuous processing can preferably be secured. In the case of rotating a semiconductor substrate, although it varies depending on the size or the like, from the same viewpoint as the above, it is preferable to rotate the semiconductor substrate at the rate of 50 to 400 rpm. In the case of low rotation, it is preferable to rotate the semiconductor substrate at the rate of from 50 to 400 rpm. When the rotation number is set to a higher level, the rotation number is preferably set to a range of from 100 to 1000 rpm.
In the case of the batch type, it is also preferable to control the liquid bath to the above-described temperature range from the same reason as the above. The immersing time of the semiconductor substrate, although it is not particularly limited, is preferably set to be from 0.5 to 30 minutes and more preferably from 1 to 10 minutes. By setting to the above-described lower limit or longer, in-plane uniformity of etching can preferably be secured. By setting to the above-described upper limit or lower, the performance required for reuse of the etching liquid can be preferably maintained.
In the single wafer type etching according to a preferable embodiment of the present invention, it is preferable to transport or rotate a semiconductor substrate in the prescribed direction and to spray an etching liquid into the space, thereby bringing the etching liquid into contact with the semiconductor substrate. The feeding rate of the etching liquid and the rotation rate of the semiconductor substrate are the same as already described earlier.
In the single wafer type etching equipment configuration according to a preferable embodiment of the present invention, it is preferable to provide an etching liquid while moving a discharge opening (nozzle), as shown in
The moving rate of the discharge opening (nozzle), although it is not particularly limited, is preferably 0.1 cm/s or more, more preferably 1 cm/s or more. On the other hand, the upper limit is preferably 30 cm/s or less, more preferably 15 cm/s or less. The moving-track-line may be a straight line or a curve (for example, arc-like). In each case, the moving rate can be calculated from an actual length of the track-line and the time it takes for movement.
The production process of the semiconductor device may include a step of etching a metal layer or the like on a semiconductor substrate by a plasma etching technique using a resist pattern or the like as a mask. Specifically, etching of the metal layer, a semiconductor layer, an insulating layer, and the like is conducted, thereby patterning the metal layer and the semiconductor layer, or forming, on the insulating layer, an opening portion such as a via hole and a wiring groove. In the plasma etching, a residue derived from the resist used as a mask, and the metal layer, the semiconductor layer, and the insulating layer to be etched may be produced on the semiconductor substrate. In the present invention, the residue produced by the plasma etching as described above is called as “a plasma etching residue”. The “plasma etching residue” includes an etching residue derived from the above-described second layer (Cu, W) and third layer (SiON, SiOC, and the like).
Further, the resist pattern used as a mask is removed after etching. In order to remove the resist pattern, a wet method using a stripper liquid, or a dry method in which ashing is conducted using, for example, plasma or ozone, is used. In the ashing, a converted residue of the plasma etching residue produced by the plasma etching and a residue derived from the resist to be removed are produced on the semiconductor substrate. In the present invention, the residue produced by the ashing as described above is called as an “ashing residue”. Further, as the general term for the residual matter which is produced on the semiconductor substrate and should be removed by washing, such as the plasma etching residue and the ashing residue, they may be simply called as a “residue”.
The plasma etching residue and the ashing residue which are the residue after such etching (Post Etch Residue) are preferably washed and removed using a washing composition. The etching liquid according to the present embodiment can also be applied as a washing liquid for removing the plasma etching residue and/or the ashing residue. Especially, the etching liquid is preferably used to remove both the plasma etching residue and the ashing residue after the plasma ashing which is conducted in succession to the plasma etching.
A material, which is etched by applying thereto the etching liquid according to the present embodiment, may be arbitrarily used. However, it is required that a substrate having a first layer containing TiN is applied. Herein, the term “layer containing TiN (TiN layer)” means that the layer may contain oxygen. When the TiN layer is especially used to distinguish it from a layer which does not contain oxygen, it may be called as a TiON layer or the like. In the present invention, the surface oxygen content of the TiN layer is preferably 10% by mole or less, more preferably 8.5% by mole or less and still more preferably 6.5% by mole or less. The lower limit side is preferably 0.1% by mole or more, more preferably 2.0% by mole or more, and still more preferably 4.0% by mole or more. Such adjustment of the oxygen concentration in the TiN layer in the substrate can be conducted by, for example, adjustment of the oxygen concentration in a processing room for CVD (Chemical Vapor Deposition) at the time of forming the TiN layer. The above-described oxygen concentration can be specified by the method utilized in Examples described below. Note that the first layer contains TiN as a major ingredient and may contain other ingredients within the range in which the effect of the present invention is exerted. This is true on the other layer such as the second layer, the metal layer and the like.
The above-described first layer is preferably subjected to etching at high etching rate. The thickness of the first layer is not particularly limited. However, when compositions of ordinary devices are considered, it is practical that the thickness is approximately from 0.005 to 0.3 μm. The etching rate (R1) of the first layer is not particularly limited. However, considering production efficiency, the etching rate is preferably 50 Å/min or more, more preferably 100 Å/min or more, and particularly preferably 200 Å/min or more. The upper limit is not particularly limited and it is practical that the upper limit is 500 Å/min or less.
In the present invention, it is preferable that Cu, W, Co, Ni, Ag, Ta, Hf, Pt, Au or the like is applied as a constituent element of the second layer (metal layer). Among them, it is preferable that Cu or W is applied as a material of the second layer.
Here, the technical significance of the metal layer is explained on the basis of an example in which copper (Cu) and tungsten (W) are used as a material thereof. Recently, in response to demands for speed-up of the semiconductor device (semiconductor equipment), miniaturization of wiring pattern, and high integration, reduction in capacity between wirings, improvement in electrical conductivity of the wire and improvement in electromigration resistance have been required. As regards the techniques for addressing these requirements, a multilayer-wiring technique of using copper which has high electrical conductivity and excellent electromigration resistance as a wire material and using a low dielectric constant layer (Low-K layer) as an insulation layer between layers has attracted attention. This copper wiring is generally disposed by a Dual Damascene process, on a copper seed layer (for example, dual layer composed of tantalum (Ta) and tantalum nitride (TaN)) which acts as a copper diffusion-preventing film for preventing copper from diffusion in the copper wiring.
On the other hand, contact of the semiconductor device is disposed through a tungsten plug by a single Damascene process in place of the Dual Damascene process which is ordinarily used at the time of forming a copper wiring and a via hole. In such multilayer-wiring technique, a Damascene method of forming a concave portion such as a wiring gutter, a through hole, and the like in a low dielectric constant layer and thereby burying therein copper is adopted. In this case, in order to form the concave portion with accuracy in the low dielectric constant layer by etching, it is necessary to use a mask composed of a material which has an adequately high-selection ratio to the low dielectric constant layer, as a mask to be used when the low dielectric constant layer is etched.
As the above low dielectric constant layer, an organic material is generally used, and as a result, in the case of etching the low dielectric constant layer using, as a mask, a photoresist layer composed of the same organic material as the above, it is presumed that the selection ratio becomes insufficient. In order to dissolve such problem, it has been proposed to use a hard mask layer composed of an inorganic material such as a TiN film, as a mask to be used at the time of etching. Further, removal of this hard mask layer is needed in the process after etching of the low dielectric constant layer. In particular, in the wet etching process, an exact removal of the above hard mask without corroding a metal layer such as tungsten plug and the like, or other wiring and/or low dielectric constant layer materials is desired.
The first layer (TiN) layer which constitutes a hard mask in the embodiment as described above is removed. As a result, the metal layer (second layer) is expected to be located at the bottom of a via-hole or a trench (see
The etching rate [R2] of the second layer (metal layer) is not limited in particular. However, it is preferable that the second layer is not removed to excess. The etching rate is preferably 100 Å/min or more, and more preferably 50 Å/min or more. The lower limit, although it is not limited in particular, is 0.001 Å/min or more for practical purposes.
The exposed width (d in the figure) of the metal layer is not limited in particular. However, from the viewpoint that advantages of the present invention become more remarkable, the exposed width is preferably 2 nm or more, and more preferably 4 nm or more. In a similar way, from the viewpoint of conspicuity of the effect, the upper limit is 1000 nm or less for practical purposes, preferably 100 nm or less, and more preferably 20 nm or less.
In the selective etching of the first layer and the second layer, its etching rate ratio ([R1]/[R2]) is not particularly limited. However, when described based on the premise of a device that needs a high selectivity, the etching rate ratio is preferably 2 or more, more preferably 3 or more, still more preferably 5 or more. The upper limit is not particularly limited and a higher upper limit is more preferable. However, it is practical that the upper limit is 500 or less.
Further, the method of the present invention is also preferably applied to a semiconductor substrate having a third layer containing a metal compound such as SiO, SiN, SiOC, SiON, or the like. Note that in the present specification, when the composition of a metal compound is expressed by a combination of elements thereof, the composition means that compositions having arbitrary percentage of the elements are incorporated in a broad sense. For example, SiO means that it incorporates a thermally-oxidized film of silicon and SiO2, and includes SiOx. This is the common definition in the present specification, so that same applies to other metal compounds. It is preferable that the third layer is also subjected to surface uniformization. The etching rate [R3] of the third layer, although it is not limited in particular, is preferably the same range as the above etching rate [R2] of the second layer. Further, it is preferable that the etching rate ratio ([R1]/[R3]) of the first layer and the third layer is also in the same range as the etching rate ratio ([R1]/[R2]) of the first layer and the second layer.
In the present embodiment, a semiconductor substrate product having a desired structure is preferably produced through a step of providing a semiconductor substrate by forming the above-described first layer and second layer on a silicon wafer and a step of applying the etching liquid onto the semiconductor substrate thereby selectively dissolving the first layer. At this moment, the above-described specific etching liquid is used for etching. It is preferable that the semiconductor substrate (second layer and/or third layer) is subjected, prior to the above-described etching step, to a dry etching or dry ashing step. Further, it is preferable that a residue produced in the step is removed.
Note that, in the present specification, as regards each of the steps involved in the etching and the method of producing the semiconductor substrate, it is allowed to rearrange the order of the steps arbitrarily and to apply them within the range in which the effect of the present invention is exerted. Further, in the present specification, the expression “preparation” means to prepare a particular material by synthesis or blend and in addition, to include procurement of prescribed materials by purchase or the like. Further, to utilize an etching liquid so as to etch each material of the semiconductor substrate is called “application”. The embodiment thereof is not limited in particular. For example, this term is broad enough to include any embodiment of bringing an etching liquid and a semiconductor substrate into contact. Specifically, etching may be carried out by immersion using batch-type equipment, or may be carried out by discharge using single wafer-type equipment.
The present invention will be described in more detail based on examples given below, but the invention is not meant to be limited by these.
Etching liquids were prepared to contain the components shown in the following Table 1 in accordance with the compositions (% by mass) shown in the same table. Each test, measurement of pH, and the like described below were carried out within 1 minute after preparation of the etching liquid. Note that the balance is water (ultra-pure water). All of “%” in the table indicate % by mass. Measurement of the etching rate (ER) of each layer was carried out by ellipsometry (film thickness measuring method using a spectroscopic ellipsometer VASE (trade name), manufactured by J. A. Woollam). Evaluation was carried out based on a mean value of 5 points thereof.
A TiN film having a surface oxygen concentration of less than 0.1% by mole was formed on a commercially available silicon substrate by CVD (Chemical Vapor Deposition). Further, film formation for a second layer substrate was carried out by CVD in the same manner as the above to use it as a test substrate in tables.
Regarding a surface oxygen concentration of the TiN layer, concentration profiles of Ti, O and N in the depth direction from 0 to 30 nm were measured using etching ESCA (Quantera manufactured by ULVAC-PHI, INCORPORATED) and each of the contents at the depth of from 5 to 10 nm was calculated. An average of the oxygen contents was defined as the surface oxygen concentration.
With respect to the above-described test substrates, etching was carried out under the following conditions using single wafer-type equipment (POLOS (trade name) manufactured by SPS-Europe B.V.) and evaluation tests were carried out.
Processing temperature: 25° C.
Discharge rate: 1 L/min.
Wafer rotation number: 500 rpm
A radiation thermometer IT-550F (trade name) manufactured by HORIBA, Ltd. was fixed at the height of 30 cm above the wafer in single wafer type equipment. The thermometer was pointed onto the wafer surface of 2 cm outside of the wafer center, and temperature measurement was conducted while making a chemical liquid flow. The temperature was measured by digital output from the radiation thermometer and continuously recorded on a personal computer. Among them, an averaged value of the temperature during the period of 10 seconds after stabilization of the temperature was used as a temperature on the wafer.
[Evaluation of in-Plane Uniformity]
Condition setting required for the etching depth at the center of a circular substrate was conducted at different time periods whereby the time period required to be 300 å of the etching depth was confirmed. Then, the entire substrate was again etched at the confirmed time period, and at this moment, the measurement of the obtained etching depth was conducted at the centrally-directed position of 30 mm from the periphery of the substrate. Evaluation was conducted on the condition that as the depth is near 300 å, in-plane uniformity becomes high. Specific criteria are as follows.
The following shows a difference between the above two points (center and 30 mm positions) and evaluation was carried out by an average of five point data.
AAA ±5 Å or less
AA ±more than 5 Å and 12 Å or less
A ±more than 12 Å and 15 Å or less
B ±more than 15 Å and 20 Å or less
C ±more than 20 Å and 30 Å or less
D ±more than 30 Å and 50 Å or less
E ±more 50 Å
Note that the surface of the TiN-containing layer (first layer) becomes non-uniform, which causes a partial residue (etching unevenness) after etching.
The pH in Table is a value obtained by measurement at room temperature (25° C.) using F-51 (trade name) manufactured by HORIBA, Ltd.
Tests beginning with C indicate Comparative Examples.
F compound: fluorine-containing compound
Si compound: organic silicon compound
O2 concentration: surface oxygen concentration of TiN layer
MTES: methyltriethoxysilane
The section of Metal compound 1/Metal compound 2 represents an etching rate ratio [R1]/[R2]. The same is true on the following tables.
From the above results, it is found that by the etching liquid of the present invention, both a good etching selectivity such that TiN is preferentially etched in a broad oxygen concentration range of the TiN layer as well as in-plane uniformity are obtained. Note that TiN is destined to be removed in the manufacturing process, and therefore the in-plane uniformity does not directly influence product performance, but it may cause removal unevenness. When reduction in the processing time is considered, the influence of the in-plane uniformity becomes conspicuous. In other words, upgrading of the in-plane uniformity becomes important because it leads to improvement in productivity.
Etching tests were carried out in the same manner as Example 1, except that the kinds, concentrations and the like of the additives to be used were changed as shown in Tables 2 to 7. The results are shown in Tables 2 to 7.
The pH was each adjusted by sulfuric acid, or tetramethyl ammonium. If its reactivity to the metal is low, this pH adjuster may be replaced with other.
In the case where plural compounds are put down together in one sample, this means that these compounds were mixed in an equal amount.
As is apparent from the above results, it is found that according to the present invention, good performances are exerted in various embodiments with respect to each component and its composition, and pH of the solution.
Etching tests were similarly carried out, except that the etching liquid having the following composition and the following substrate were used. The result is shown in following Table.
SWT: Single wafer-type equipment
POLOS (product name) manufactured by SPS-Europe B.V.
Batch type: Batch type equipment
MANUAL WET BENCH (product name) manufactured by Seto Giken Kogyo Co., Ltd.
Swing speed . . . Swing speed of the discharge opening that applies a liquid chemical (See
Liquid-feeding form
Water washing: “Yes” means that free-flowing-type washing was carried out using ultra-pure water after etching.
The wafer surface after etching was observed using a Defect Inspection System (trade name SP-1, manufactured by KLA-Tencor Corporation) and evaluation was conducted with respect to the number of TiN residue on the surface. Measurement was conducted on the condition that when a residue having a size of 0.2 m or greater was present, the defect number was 1.
The defect number in terms of 0.2 m or greater was:
A: less than 50/12 inch wafer surface
B: 50 or more and less than 200/12 inch wafer surface
C: 200 or more/12 inch wafer surface
From the above results, it is found that the production method using single wafer-type equipment, the free-flowing-type washing after etching and adjustment of the swing speed have effects on improvement in the in-plane uniformity and suppression of point defects.
Having described our invention as related to the present embodiments, it is our intention that the invention not be limited by any of the details of the description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-252748 | Nov 2012 | JP | national |
This application is a continuation of PCT/JP2013/080797 filed on Nov. 14, 2013 which claims benefit of Japanese Patent Application No. 2012-252748 filed on Nov. 16, 2012, the subject matters of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2013/080797 | Nov 2013 | US |
| Child | 14713143 | US |
