JP5873270B2 - Etching method, silicon etchant used therefor, and method for manufacturing semiconductor substrate product - Google Patents

Description

  The present invention relates to an etching method, a silicon etching solution used therefor, and a method for manufacturing a semiconductor substrate product.

  Conventionally, a concave type has been adopted as a capacitor structure of a DRAM. In this structure, the lower electrode film is formed in the cylinder hole, and only the inner side surface functions as an electrode. According to this, the area occupied by the capacitor can surely be reduced, but the diameter of the cylinder hole is inevitably reduced. On the other hand, the capacity required for the device operation of the DRAM must be secured. In order to satisfy both of these requirements, the depth of the cylinder hole is becoming deeper and it is becoming difficult to cope with the fine processing technology. In response to this situation, a crown type capacitor has been proposed that can use not only the inside of the lower electrode of the cylinder structure but also the outside to reduce the aspect ratio of the capacitor (see, for example, Patent Document 1).

  Although efforts have been made to reduce the aspect ratio of the capacitor structure as described above, it is not easy per se to form a fine cylinder structure and its holes with high precision. Usually, this processing is performed by wet etching. That is, the inner and outer members must be removed by the etching solution so that a cylindrical structure having a cylinder wall having a depth of nanometer to submicrometer size is left on the semiconductor substrate. In particular, the removal of the inside of the cylinder hole must be removed so as to remove the material from the enclosed space, which is difficult as a process performed by wet etching. Although it is conceivable to apply a solution having a high etching power with emphasis on the workability, there is a concern that the action may corrode the electrode and other parts.

  There is a combination of nitric acid and hydrofluoric acid as a treatment liquid exhibiting high etching properties with respect to silicon. However, this alone is too reactive with silicon and has problems due to foaming, and the reactivity of single crystal silicon is adjusted by adding a considerable amount of acetic acid, water, or the like as a buffer (see Patent Document 2, etc.). ).

JP 2010-199136 A JP 2006-206374 A

In addition to the capacitor structures that have been adopted recently, the etching solution that enables good removal of silicon and the like has not been sufficiently researched and developed. In particular, the present inventors accurately and rapidly remove silicon and the like, while selectively etching without damaging the remaining electrode members, etc. I thought it was important from the point of view. In particular, studies have been conducted on the etching properties of polycrystalline silicon and / or amorphous silicon whose use has been expanding in recent years.
Therefore, the present invention relates to a silicon etching solution capable of accurately and rapidly removing silicon and the like from polycrystalline silicon and / or amorphous silicon, while maintaining the remaining electrode members and the like without damaging them. An object of the present invention is to provide a conventional etching method and a semiconductor substrate product using the etching method.

The above problem has been solved by the following means.
(1) A silicon etching solution containing an anionic group-containing compound having 3 or more carbon atoms, nitric acid and hydrofluoric acid in an aqueous medium is prepared, and the silicon etching solution is obtained from polycrystalline silicon and / or amorphous silicon. An etching method for forming an uneven shape to be a capacitor by applying to a silicon film,
An etching method comprising at least one selected from a Ti compound, an Hf compound, SiN and W, wherein the concavo-convex shape portion constituting the capacitor structure is not removed even by etching by applying the etching solution.
(2) The etching method according to (1), wherein the compound having 3 or more carbon atoms having an anionic group is an amino acid compound or an anionic surfactant.
(3) The etching method according to (1) or (2), wherein the concentration of the compound having 3 or more carbon atoms having an anionic group in the total amount of liquid is 20% by mass or less.
(4) The etching method according to any one of (1) to (3), wherein the compound having 3 or more carbon atoms having an anionic group is a basic amino acid compound or an anionic surfactant having 10 or more carbon atoms. .
(5) The etching method according to any one of (1) to (4), wherein the concentration of the nitric acid in the silicon etching solution is more than 30% by mass.
(6) The etching method according to any one of (1) to (5), wherein a concentration of the hydrofluoric acid in the silicon etching solution is 6% by mass or less.
(7) The etching method according to any one of (1) to (6), wherein the uneven portion has a cylinder hole that is removed by the silicon etchant.
(8) The ratio (R _Si / R _Ti ) between the etching rate (R _Si ) of the silicon film and at least one etching rate (R _Ti ) selected from the Ti compound, Hf compound, SiN and W is 100 or more. The etching method according to any one of (1) to (7).
(9) The etching method according to any one of (1) to (8), wherein the Ti compound is TiN.
(10) The etching method according to (7), wherein the cylinder hole has an aspect ratio of 15 or more.
(11) The anionic surfactant is at least one selected from the group consisting of a carboxylic acid compound having 10 or more carbon atoms, a sulfonic acid compound having 10 or more carbon atoms, and a phosphonic acid compound having 10 or more carbon atoms (2 The etching method as described in.
(12) The etching method according to (2), wherein the amino acid compound is arginine or histidine.
(13) The etching method according to any one of (1) to (12), wherein the temperature of the etching solution is 20 to 80 ° C.
(14) forming a multilayer film structure having a silicon film made of a polycrystalline silicon film and / or an amorphous silicon film on a semiconductor substrate and forming irregularities in the multilayer film structure having the silicon film ;
Forming a conductive film on at least the upper surface of the irregular surface and the wall surface of the recess;
Providing a buried film on the conductive film and filling the recess with the buried film;
Removing a portion of the conductive film portions are applied to the upper surface and the buried layer, and a step of exposing the silicon layer of the semiconductor substrate, then
An etching solution is applied to the semiconductor substrate to leave the exposed silicon film and the embedded film while leaving the conductive film on the wall surface of the recess,
The manufacturing method of the semiconductor substrate product which uses the silicon etching liquid which contains a C3 or more compound which has the said anionic group, nitric acid, and hydrofluoric acid in an aqueous medium as said etching liquid.
(15) The method for producing a semiconductor substrate product according to (14), wherein the conductive film is at least one selected from the group consisting of a Ti compound, an Hf compound, and W.
(16) was prepared to have a substantially flat surface as the semiconductor substrate, the etchant applied to the surface of the silicon layer, and removing said buried layer and said silicon film, is its removal The method of manufacturing a semiconductor substrate product according to (14) or (15), wherein the portion is a concave portion, and the convex portion including the conductive film left in the substrate is a capacitor electrode.
(17) A silicon etching solution for removing a polycrystalline silicon film and / or an amorphous silicon film, the compound having 3 or more carbon atoms having an anionic group, nitric acid, and hydrofluoric acid in an aqueous medium A silicon etching solution containing nitric acid in a concentration of more than 30% by mass.
(18) The silicon etching solution according to (17), wherein the concentration of the hydrofluoric acid is 0.5 to 2% by mass.
(19) The silicon etching solution according to (17) or (18), wherein the concentration of the compound having 3 or more carbon atoms having an anionic group is 0.001% by mass or more and 20% by mass or less.
(20) The compound having 3 or more carbon atoms having the anionic group is selected from the group consisting of a carboxylic acid compound having 10 or more carbon atoms, a sulfonic acid compound having 10 or more carbon atoms, and a phosphonic acid compound having 10 or more carbon atoms. The silicon etching solution according to any one of (17) to (19), which is at least one kind.
(21) A silicon etching solution for removing a polycrystalline silicon film and / or an amorphous silicon film, which contains an amino acid compound having 3 or more carbon atoms, nitric acid, and hydrofluoric acid in an aqueous medium. liquid.
(22) The silicon etching solution according to (21), wherein the concentration of hydrofluoric acid is 0.5 to 2% by mass.
(23) The silicon etching solution according to (21) or (22), wherein the concentration of the amino acid compound is 0.001% by mass or more and 20% by mass or less.
(24) The silicon etching solution according to any one of (21) to (23), wherein the concentration of nitric acid is more than 30% by mass.
(25) The silicon etching solution according to any one of (21) to (24), wherein the amino acid compound is arginine or histidine.

  According to the present invention, the constituent material of polycrystalline silicon and / or amorphous silicon can be removed accurately and at high speed. Furthermore, if necessary, it is possible to cope with a capacitor structure composed of an electrode having a cylinder structure, and selectively remove the polycrystalline silicon film and / or the amorphous silicon film while suppressing damage to the electrode member and the like. It has an excellent effect of being able to.

It is sectional drawing which shows typically the example of a manufacturing process of the capacitor structure applied to this invention. It is sectional drawing which shows typically the example of a manufacturing process of the capacitor structure applied to this invention (continuation of FIG. 1). It is sectional drawing which shows typically the example of a manufacturing process of the capacitor structure applied to this invention (continuation of FIG. 2). FIG. 4 is a cross-sectional view schematically showing a manufacturing process example of a capacitor structure applied to the present invention (continuation of FIG. 3). It is sectional drawing which shows typically another example of the capacitor structure applied to this invention. It is sectional drawing which shows typically the example of a manufacturing process of the capacitor structure applied to this invention. It is a plane sectional view of the capacitor structure applied to the present invention.

[Formation of capacitor structure]
First, before describing the etching solution according to the present invention, a manufacturing example of a capacitor structure that can be suitably employed in the present invention will be described with reference to the accompanying drawings. In the following detailed description, the formation of the capacitor structure will be mainly described, but the present invention is not construed as being limited thereto.

(Process a)
In the manufacturing example of the present embodiment, the first molded film 1 and the second molded film 2 are formed on the silicon wafer 3. The first molding film 1 is an etching stopper film when the cylinder hole is opened, and is a film having an etching rate ratio with the second molding film 2 by an anisotropic dry etching process. Examples of the first molded film 1 include a nitride film formed by an LP-CVD (Low-pressure Chemical Vapor Deposition) process. On the other hand, the second molded film 2 may be a polycrystalline silicon film or an amorphous silicon film. Further, although not shown, a protective film may be provided.
Although the silicon wafer 3 is greatly simplified and shown as a single layer, a predetermined circuit structure is usually formed here. For example, those using an isolation insulating film, gate oxide film, gate electrode, diffusion layer region, polysilicon plug, silicon oxide film, silicon nitride film, bit line, metal plug, nitride film, plasma oxide film, BPSG film, etc. (For example, refer to Patent Document 1). Moreover, in FIGS. 1-6, although it does not show in particular with hatching, the cross section of each member is shown.

(Process b)
Next, after patterning the photoresist 4 using a photolithography process, holes are formed by anisotropic dry etching (concave portion Ka). As for the photoresist 4 and the dry etching method at this time, a normal object or method applied to this type of product may be applied.

(Process c), (Process d)
Furthermore, after opening, along the wall surface Wa of the recess Ka and the upper surface Wb of the molding film (silicon film) 2, the conductive film 5 made of TiN and the embedded film 6 for protecting the conductive film 5 (for example, polycrystalline silicon or amorphous A silicon film is sequentially formed. At this time, a recess formed intermediately (after formation of the conductive film 5) is shown as Kb.

(Process e)
After the buried film 6 is formed, a part of the buried film 6 and the conductive film 5 (FIGS. 2 and 3) on the wafer surface is removed by CMP (Chemical Mechanical Polishing), and the etch back line E is exposed. Here, the second molding film 2 and the embedded film 6 are removed by wet etching. In the present invention, this step is important, and an etching solution according to the present invention described later exhibits a high effect. Through this step, the lower electrode (cylinder wall) 50 (FIG. 3) of the capacitor having the cylinder hole Kc is formed. The depth h ₂ of the cylinder bore wall is not particularly limited, considering the conventional construction of such a device, it is practical that a 500-2000 nm. Note that the etching solution of the present invention is preferably applied to the surface smoothed by the etch back or the like as described above, and it is preferable that the buried film is removed therefrom to form a trench structure.

(Process f)
After the formation of the lower electrode 50 of the capacitor formed as described above, the capacitor insulating film 9 is formed, and then the plate electrode (upper electrode) (not shown) is sequentially formed to form the capacitor structure 10. In this specification, the capacitor structure may be a capacitor itself or a structure part constituting a part of the capacitor. In the example shown in FIG. 4, the lower electrode 50, the capacitor insulating film 9, The capacitor structure 10 is shown as comprising. In the figure, the lower electrode 50 and the wafer 3 are shown as being separated from each other by the molding film 1. However, if necessary, the lower electrode 50 and the wafer 3 are electrically connected at the cross section or at different positions in the figure. May be interpreted as For example, a plug structure or damascene structure may be formed in the molding film 1 to ensure conduction, or the lower electrode 50 may be formed so as to penetrate the molding film 1. Further, the capacitor insulating film may be formed not only on the lower electrode 50 but also on other substrate surfaces.

FIG. 5 shows a modification of the capacitor structure of the above embodiment. In this example, the bottom 81 and the main part 82 of the lower electrode (cylinder structure) are made of different materials. For example, the bottom 81 is made of Si ₃ N ₄ and the main part 82 is made of TiN.

(Process a ')
FIG. 6 shows a modification of the manufacturing example of the above embodiment. A first molding film 1, a second molding film 2, a third molding film 21 and a fourth molding film 31 are sequentially formed on the silicon wafer 3. The first molding film 1 is an etching stopper film when the cylinder hole is opened, and the second molding film 2 is a film having an etching rate ratio in an anisotropic dry etching process. Examples of the first molded film 1 include a nitride film formed by an LP-CVD process. The second molded film 2, the third molded film 21, and the fourth molded film 31 have a combination of films that do not have an etching rate ratio by anisotropic dry etching and can obtain an etching rate ratio by isotropic etching. Further, it is preferable to form the second molding film 2, the third molding film 21, and the fourth molding film 31 with a film that can be removed at once with the same wet etching solution at the time of capacitor formation.
The etching rate ratio in the isotropic etching is such that the second molding film 2 and the fourth molding film 31 have the same etching rate, and the third molding film 21 has the second molding film 2 and the fourth molding film 31. A film having a higher etching rate than the molded film 31 is preferable. Further, the second molded film 2 and the fourth molded film 31 may be the same film or different films. Further, although not shown, a protective film may be provided. The silicon wafer 3 is greatly simplified and shown as a single layer, but as described above, a predetermined circuit structure is usually formed here. Moreover, in FIG. 6, although not shown in particular with hatching, the cross section of each member is shown, and the top view is shown in FIG.

(Process b ')
Next, after patterning the photoresist 4 using a photolithography process, holes are formed by anisotropic dry etching (concave portion Ka). As for the photoresist 4 and the dry etching method at this time, a normal object or method applied to this type of product may be applied.
After the opening, isotropic etching is performed to form the recess Va in the portion of the third molding film 21, and then the electrode protection film 7 is grown. The electrode protective film 7 is a molded film having a sufficient etching rate ratio with respect to the etching solution used for removing the second molded film 2, the third molded film 21, and the fourth molded film 31 at the time of capacitor formation. Further, it is preferable that the film can be formed uniformly over the entire recess Ka, and the recess 7 formed in the middle of the recess Ka can be completely embedded. Examples thereof include a nitride film using an ALD (Atomic Layer Deposition) method and a tantalum pentoxide (Ta ₂ O ₅ ) film.
After the growth of the electrode protective film 7, the electrode protective film 7 is removed by isotropic etching. At this time, the electrode protective film 7 in the recess Va remains without being removed.

(Process c ')
In the same manner as in the above steps (c) to (f), the lower electrode (cylinder wall) 50 of the capacitor having the cylinder hole Kc is formed. In the same manner as in the above manufacturing example, after the capacitor lower electrode 50 is formed, the capacitor insulating film 9 is formed, and then the plate electrode (upper electrode) (not shown) is sequentially formed to form the capacitor structure. In this specification, the capacitor structure may be a capacitor itself or a structure part constituting a part of the capacitor.

[Silicon etchant]
Next, a preferred embodiment of the silicon etching solution of the present invention that can be used extremely effectively for the wet etching described in the step e will be described. In the etching solution of the present embodiment, by applying nitric acid, hydrofluoric acid, and the following specific surface protective agent, formation of a capacitor structure having an uneven shape as described above without damaging members such as electrodes. This makes it possible to accurately remove the polycrystalline silicon film or the amorphous silicon film. In particular, according to the present invention, a polycrystalline silicon film or an amorphous silicon film having a high aspect ratio as shown in FIGS. 3 and 6 and a deep cylinder hole Kc or a complicated etching shape such as Kd in FIG. Can be accurately removed.

(nitric acid)
The content of nitric acid is preferably contained in the range of more than 30% by mass and 70% by mass or less, and more preferably 50 to 65% by mass with respect to the total amount of the etching solution of the present embodiment. By setting it to the above lower limit or more, it is preferable in terms of securing a sufficient etching rate in consideration of industrial productivity for polycrystalline silicon and amorphous silicon. In particular, the present embodiment is preferable because the etching property is dramatically improved with the lower limit as a boundary. The use of a relatively large amount of nitric acid in this manner is particularly suitable for the etching of polycrystalline silicon or amorphous silicon in the present embodiment, and is characterized by being applied in a small amount like the etching of an aluminum-based metal described later. It is a different point.
By setting it to the upper limit value or less, it is preferable in that it exhibits a corrosion prevention effect on the concave and convex capacitor, and more effectively exhibits high etching selectivity such as etching of polycrystalline silicon or amorphous silicon.

(Hydrofluoric acid)
The content of hydrofluoric acid is preferably contained within a range of 6% by mass or less, more preferably 0.5 to 2.0% by mass, with respect to the total amount of the etching solution of the present embodiment. preferable. It is preferable that the upper limit is not more than the above upper limit because a more outstanding etching selectivity can be realized and it can be handled safely. By setting it to the above lower limit or more, it is preferable in that it exhibits an anticorrosive effect on a concave-convex capacitor and exhibits high etching selectivity more effectively, such as etching polycrystalline silicon or amorphous silicon.

(Surface protectant)
In the present invention, a silicon etching solution applied to a silicon film made of polycrystalline silicon and / or amorphous silicon is a compound having 3 or more carbon atoms having an anionic group as a surface protecting agent for an electrode member or the like (hereinafter simply referred to as anionic). A group-containing compound). In the present invention, the anionic group is not particularly limited, but typically means a functional group having a hydrophilic group in the molecule dissociated in an aqueous solution to become an anion or anionic. Here, the compound having an anionic group may be present as an acid accompanied by a hydrogen atom, or may be a dissociated anion, or a salt thereof. As long as it is anionic, it may be non-dissociable and includes acid esters. The compound having an anionic group in the present invention is preferably an anionic surfactant or an amino acid compound. Note that having an anionic group means that it has at least one anionic group and may contain a plurality of anionic groups.

(Anionic surfactant)
The silicon etching liquid as the first form contains an anionic surfactant as a surface protecting agent for electrode members and the like. In the present invention, the anionic surfactant is not particularly limited, but typically has a hydrophilic group and a lipophilic group in the molecule, and the hydrophilic group portion is dissociated in an aqueous solution to become an anion, or It means an anionic compound. Here, the anionic surfactant may be present as an acid with a hydrogen atom, or may be a dissociated anion, or a salt thereof. As long as it is anionic, it may be non-dissociable and includes acid esters.

The anionic surfactant in the present embodiment has 3 or more carbon atoms, preferably 5 or more carbon atoms, and more preferably an anionic surfactant having 10 or more carbon atoms. Although there is no upper limit in particular, it is practical that it is 20 or less carbon atoms. By setting it as more than the lower limit of the said carbon number, it is preferable at the point from which effective etching selectivity is obtained.
Specific examples of the anionic surfactant having 10 or more carbon atoms include carboxylic acid compounds having 10 or more carbon atoms, phosphonic acid compounds having 10 or more carbon atoms, and sulfonic acid compounds having 10 or more carbon atoms. Among them, alkyl sulfonic acid, alkyl benzene sulfonic acid, alkyl naphthalene sulfonic acid, alkyl diphenyl ether sulfonic acid, fatty acid amide sulfonic acid, polyoxyethylene alkyl ether carboxylic acid, polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl ether propionic acid, alkyl phosphone Acids, fatty acids and their salts are preferred.
Specific examples include Emar E-27C, Neoperex GS (above, manufactured by Kao Chemical Co., Ltd.), W004, W005, W017 (above, manufactured by Yusho Co., Ltd.), and the like. Among these, anionic surfactants composed of sulfonic acid compounds having 10 or more carbon atoms are preferred, and among them, alkylsulfonic acid, alkylsulfonic acid salt, alkylbenzenesulfonic acid, alkylbenzenesulfonic acid salt, and alkylphosphonic acid are more preferred. 10-16 alkyl sulfonic acids or alkyl sulfonates are more particularly preferred. Examples of the “salt” include ammonium salt, sodium salt, potassium salt, and tetramethylammonium salt.

The anionic surfactant in the present invention exhibits an anticorrosive effect for electrode members and the like. Although the detailed reason includes an unclear point, it is presumed as follows.
First, it is conceivable that polycrystalline silicon or amorphous silicon is oxidized by nitric acid, and hydrofluoric acid dissolves the oxide. At this time, nitric acid and hydrogen fluoride similarly dissolve a considerable amount of electrode members such as TiN (see Comparative Example c11 described later). On the other hand, in the present invention, the anionic surfactant is adsorbed on the surface of the charged electrode member via the hydrophilic group, thereby forming a protective film therewith, and thereby using nitric acid or hydrofluoric acid. Presumably plays a role in preventing dissolution. In addition, by adding an anionic surfactant to the etching solution, the viscosity of the etching solution is optimized, and if necessary, the advantage of further improving the in-plane uniformity of etching is expected. Although there is an etching solution in which nitric acid, hydrofluoric acid, a surfactant, cupric oxide and the like are mixed (Japanese Patent Publication No. 5-30914), this etches an aluminum-based metal. In addition, as described above, there is an example in which a considerable amount of acetic acid is contained in nitric acid and hydrofluoric acid (Japanese Patent Laid-Open No. 2006-206374). From the results disclosed therein, polycrystalline silicon or amorphous silicon is used. It cannot be predicted whether etching can be performed effectively and selective etching with TiN or the like can be achieved.

The content of the anionic surfactant is preferably 20% by mass or less, more preferably 10% by mass or less, and more preferably 0.001 to 1.0% by mass with respect to the total amount of the etching solution of the present embodiment. It is more preferable to make it contain within the range, It is more preferable to contain 0.001-0.1 mass%, It is especially preferable to contain 0.005-0.05 mass%. It is preferable to set it to the upper limit or less because the etching rate and etching selectivity are further improved and foaming can be suppressed. It is preferable to set it to the above lower limit value or more from the viewpoint of suppressing corrosion of the member.
These anionic surfactants can be used singly or in combination of two or more.

In the present specification, when the term “compound” is added to the end or indicated by a specific name or chemical formula, it is used in the meaning including its salt, complex, and ion in addition to the compound itself. Moreover, it is the meaning including the derivative modified with the predetermined form in the range with the desired effect. In addition, in the present specification, a substituent that does not specify substitution / non-substitution means that the group may have an arbitrary substituent. This is also synonymous for compounds that do not specify substitution / non-substitution. Preferred substituents include the following substituent T.
(Substituent T)
An alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, such as methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.), alkenyl A group (preferably an alkenyl group having 2 to 20 carbon atoms, such as vinyl, allyl, oleyl, etc.), an alkynyl group (preferably an alkynyl group having 2 to 20 carbon atoms, such as ethynyl, butadiynyl, phenylethynyl, etc.), A cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.), an aryl group (preferably an aryl group having 6 to 26 carbon atoms, for example, Phenyl, 1-naphthyl, 4-methoxyphenyl, -Chlorophenyl, 3-methylphenyl, etc.), heterocyclic groups (preferably heterocyclic groups having 2 to 20 carbon atoms, such as 2-pyridyl, 4-pyridyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2 -Oxazolyl etc.), an alkoxy group (preferably an alkoxy group having 1 to 20 carbon atoms, such as methoxy, ethoxy, isopropyloxy, benzyloxy etc.), an aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms) , For example, phenoxy, 1-naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy, etc.), alkoxycarbonyl groups (preferably C2-C20 alkoxycarbonyl groups such as ethoxycarbonyl, 2-ethylhexyloxycarbonyl, etc.) ), Amino group (preferably carbon Amino group having 0 to 20 children, such as amino, N, N-dimethylamino, N, N-diethylamino, N-ethylamino, anilino, etc.), sulfonamide group (preferably sulfonamide having 0 to 20 carbon atoms) A group such as N, N-dimethylsulfonamide, N-phenylsulfonamide, etc., an acyloxy group (preferably an acyloxy group having 1 to 20 carbon atoms such as acetyloxy, benzoyloxy, etc.), a carbamoyl group (preferably A carbamoyl group having 1 to 20 carbon atoms, such as N, N-dimethylcarbamoyl, N-phenylcarbamoyl, etc.), an acylamino group (preferably an acylamino group having 1 to 20 carbon atoms, such as acetylamino, benzoylamino, etc.) , A cyano group, or a halogen atom (eg, fluorine atom, chlorine atom, bromine atom) More preferably an alkyl group, alkenyl group, aryl group, heterocyclic group, alkoxy group, aryloxy group, alkoxycarbonyl group, amino group, acylamino group, cyano group or halogen atom, Particularly preferred are an alkyl group, an alkenyl group, a heterocyclic group, an alkoxy group, an alkoxycarbonyl group, an amino group, an acylamino group, and a cyano group.

(Amino acid compound)
The silicon etching liquid as the second form of the present embodiment contains an amino acid compound as a specific surface protecting agent. The number of carbon atoms of the amino acid is 3 or more, preferably 3 to 12, and more preferably 4 to 9. By setting it as more than the lower limit of the said carbon number, it is preferable at the point from which effective etching selectivity is obtained. The upper limit is typically determined by the normal carbon number of the amino acid.
As the amino acid compound, a commonly used amino acid compound can be used. Specific examples include lysine, arginine, histidine aspartic acid, glutamic acid, serine, threonine, asparagine, glutamine, alanine, glycine, valine, isoleucine, leucine, phenylalanine, tyrosine, tryptophan, methionine, cysteine, proline, ornithine. It is done. Basic amino acid compounds are particularly preferred, and specific examples include lysine, arginine, and histidine. Among these, histidine and arginine are preferable, and histidine is more preferable.
The content of the amino acid compound is preferably 20% by mass or less, more preferably 0.01 to 20% by mass with respect to the total amount of the etching solution of the present embodiment. It is more preferable to make it contain 1-10 mass%, and it is especially preferable to contain 0.5-5 mass%. By setting it to the upper limit or less, it is preferable because silicon solubility can be secured and the etching rate and etching selectivity are further improved. It is preferable to set it to the above lower limit value or more from the viewpoint of suppressing corrosion of the member.
These amino acid compounds can be used singly or in combination of two or more.

  The amino acid compound in this invention shows the anticorrosion effect of an electrode member. The detailed reason includes an unclear point and is presumed as follows. The mechanism by which nitric acid and hydrofluoric acid dissolve polycrystalline silicon and amorphous silicon is the same as that described in the section of the anionic surfactant. At this time, it is presumed that the amino acid compound adheres to the surface of the electrode member or the like and forms a protective film on the electrode surface in some kind of adsorption mode (not necessarily the same as the anionic surfactant). Moreover, it is the same as that of the anionic surfactant that the amino acid compound contributes to optimization of the viscosity of the etching solution.

(Aqueous medium)
The etching solution of the present invention is preferably an aqueous liquid composition using an aqueous medium as a medium. An aqueous medium refers to an aqueous solution in which water and a water-soluble solute are dissolved. The solute does not include the nitric acid, hydrofluoric acid, and the surface protecting agent, and examples thereof include alcohols and salts of inorganic compounds. However, even when the solute is applied, it is preferable that the amount is suppressed within a range in which a desired effect is obtained. The aqueous composition means that the aqueous medium is the main medium. The majority of the medium other than the solid content is preferably an aqueous medium, more preferably 70% by mass or more, and 90% by mass. The above is particularly preferable.

  In addition, in this specification, the liquid which combined the specific agent (component) means the liquid composition containing the said agent, and mixes and uses each agent or the liquid containing it before use. The meaning as a kit is included. Further, the term “semiconductor substrate” is used to mean not only a wafer but also the entire substrate structure having a circuit structure formed thereon. A semiconductor substrate member refers to the member which comprises the semiconductor substrate defined above, and may consist of one material or may consist of several materials. Note that a processed semiconductor substrate is sometimes referred to as a semiconductor substrate product, and a chip that is further processed and diced and taken out as necessary, and the processed product are referred to as a semiconductor element.

  Note that the upper and lower sides of the semiconductor substrate need not be particularly defined, but in this specification, based on what is illustrated, the side of the wafer 3 is a lower (bottom) direction and the conductive film 5 is an upper ( The direction of the top.

(PH)
The silicon etching solution of the present invention is acidic and is preferably adjusted to pH 5 or lower. This adjustment can be performed by adjusting the amount of nitric acid and hydrofluoric acid added. However, as long as the effects of the present invention are not impaired, other pH adjusting agents may be used to adjust the pH within the above range. The pH of the silicon etching solution is further preferably 3 or less, and more preferably 1 or less. When this pH is not more than the above upper limit, a sufficient etching rate can be obtained. Although there is no lower limit in particular in the said pH, it is practical that it is -2 or more. In the present invention, unless otherwise specified, pH is a value measured at room temperature (25 ° C.) with F-51 (trade name) manufactured by HORIBA.

(Other ingredients)
-Addition of organic solvent In the silicon etching solution of the present invention, a water-soluble organic solvent may be further added. This is effective in that the uniform etching property within the wafer surface can be further improved. Water-soluble organic solvents are alcohols (for example, ethylene glycol, glycerin, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, propylene glycol, furfuryl alcohol, 2-methyl-2,4 -Pentanediol), glycols (eg, diethylene glycol, dipropylene glycol, dipropylene glycol methyl ether, propylene glycol monopropylene glycol), dimethyl sulfoxide, ethers (eg, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetra Ethylene glycol dimethyl ether and propylene glycol dimethyl ether) are preferred. The addition amount is preferably 0.1 to 20% by mass, and more preferably 1 to 15% by mass with respect to the total amount of the etching solution. When this amount is not less than the above lower limit, the above-described etching uniformity can be effectively improved. On the other hand, it is possible to ensure wettability with respect to a polycrystalline silicon film, an amorphous silicon film, or other metal film by being below the upper limit.

-Addition of surfactant The silicon etching solution of the present invention may further contain another surfactant. As the surfactant, nonionic surfactants, cationic surfactants, and amphoteric surfactants can be used.

Nonionic surfactants include, for example, polyalkylene oxide alkylphenyl ether surfactants, polyalkylene oxide alkyl ether surfactants, block polymer surfactants composed of polyethylene oxide and polypropylene oxide, and polyoxyalkylene distyrenation. Examples include phenyl ether surfactants, polyalkylene tribenzylphenyl ether surfactants, and acetylene polyalkylene oxide surfactants.
Examples of the cationic surfactant include quaternary ammonium salt surfactants and alkylpyridium surfactants.
Examples of amphoteric surfactants include betaine surfactants, amino acid surfactants, imidazoline surfactants, and amine oxide surfactants.

  The content of the surfactant is preferably 0.0001 to 5% by mass and more preferably 0.001 to 1% by mass with respect to the total mass of the silicon etching solution. It is preferable because the viscosity of the silicon etching solution can be adjusted by adding a surfactant to the silicon etching solution, and the wettability to the object to be etched can be improved. It is preferable also from the point of being more excellent. Such surfactants are generally commercially available. These surfactants may be used alone or in combination.

(Workpiece)
Any material can be etched by applying the etching solution of the present embodiment, but examples of a substrate material used for manufacturing a general capacitor include polycrystalline silicon and amorphous silicon. On the other hand, the electrode material forming the core of the capacitor structure is titanium nitride (TiN). That is, the etching solution of the present embodiment preferably has a large ratio (R _Si / R _Ti ) between the etching rate (R _Si ) of the substrate material and the etching rate (R _Ti ) of the electrode material. The specific ratio value is not particularly limited because it depends on the type and structure of the material, but R _Si / R _Ti is preferably 100 or more, more preferably 200 or more. In this specification, using an etchant to etch a semiconductor substrate is referred to as “application”, but the embodiment is not particularly limited. For example, the etching may be performed by being immersed in a batch type, or may be performed by discharging a single wafer type.

The shape and dimensions of the capacitor structure to be processed are not particularly limited. However, when the cylinder structure as described above is used, the aspect ratio (h ₂ / d _c ) of the cylinder hole Kc (FIG. 3) is 5 or more. In some cases, the high effect of the etching solution of the present embodiment is utilized, which is preferable. From the same viewpoint, the aspect ratio is preferably 15 or more, and more preferably 20 or more. Although there is no upper limit in particular, it is practical that it is 50 or less. But not limited opening diameter d _c in particular of the cylinder bore Kc, are effective exerted in this embodiment, in consideration of the miniaturization of the recent capacitor structure, it is preferable in 20 to 80 nm.
The distance d _d is not particularly limited between the lower electrode, considering the miniaturization of recent capacitor structure, it is preferable in 20 to 200 nm.
The concave and convex shape of the capacitor in the present specification is not particularly limited, but may be a hole shape such as a cylinder (columnar) hole, a quadrangular prism shape, a taper shape, or a reverse taper shape.

Furthermore, from the above viewpoint, in the present invention, while leaving an electrode film made of Ti compound (for example, TiN, Ti, etc.), Hf compound (for example, HfOx, etc.), SiN or W at least on the wall surface of the concavo-convex structure, It is preferable to perform etching on the polycrystalline silicon film or the amorphous silicon film.
Further, a semiconductor substrate having a substantially flat surface having the polycrystalline silicon film or the amorphous silicon film is prepared, and the etching liquid is applied to a surface of the semiconductor substrate, and the polycrystalline silicon film or the amorphous silicon film and It is preferable that the embedded film is removed, the removed portion is a recess, and the protrusion remaining in the substrate is a capacitor. At this time, an electrode film such as TiN is preferably present on the wall surface of the recess.
The etching method of the present invention is not applied only to these manufacturing processes, and can be used for various etching without particular limitation.

(Etching method)
Although it does not specifically limit as an etching apparatus used by this invention, A single wafer type and a batch type can be used. The single wafer method is a method in which wafers are etched one by one. One of the single-wafer embodiments is a method of performing etching by spreading an etching solution over the entire wafer surface with a spin coater. The batch method is a method of etching several to several tens of wafers at a time. One of the batch-type embodiments is a method of etching by immersing a plurality of wafers in a tank filled with an etching solution.
The liquid temperature of the etching liquid, the spray discharge amount of the etching liquid, and the rotation speed of the wafer of the spin coater are selected and used as appropriate values depending on the selection of the wafer to be etched.

  In this embodiment, the etching conditions are not particularly limited, but may be spray (single-wafer) etching or batch (immersion) etching. In spray etching, the semiconductor substrate is conveyed or rotated in a predetermined direction, and an etching solution is sprayed into the space to bring the etching solution into contact with the semiconductor substrate. If necessary, the etching solution may be sprayed while rotating the semiconductor substrate using a spin coater. On the other hand, in batch-type etching, a semiconductor substrate is immersed in a liquid bath made of an etching solution, and the semiconductor substrate and the etching solution are brought into contact in the liquid bath. These etching methods may be properly used depending on the structure and material of the element.

  In the case of a spray type, the environmental temperature at which etching is performed is preferably 15 to 100 ° C., and more preferably 20 to 80 ° C. The etching solution is preferably 20 to 80 ° C., more preferably 30 to 70 ° C. By setting it to the above lower limit value or more, a sufficient etching rate for the metal layer can be secured, which is preferable. By making it not more than the above upper limit value, etching selectivity can be secured, which is preferable. The supply rate of the etching solution is not particularly limited, but is preferably 0.05 to 1 L / min, and more preferably 0.1 to 0.5 L / min. By setting it to the above lower limit value or more, uniformity in the etching plane can be secured, which is preferable. By setting it to the upper limit value or less, it is preferable because stable selectivity can be secured during continuous processing. When the semiconductor substrate is rotated, although it depends on its size and the like, it is preferably rotated at 50 to 400 rpm from the same viewpoint as described above.

  In the case of the batch type, the liquid bath is preferably 20 to 80 ° C, more preferably 30 to 70 ° C. By setting it to the lower limit value or more, the etching rate can be secured, which is preferable. By making it not more than the above upper limit value, etching selectivity can be secured, which is preferable. The immersion time of the semiconductor substrate is not particularly limited, but is preferably 0.5 to 30 minutes, more preferably 1 to 10 minutes. By setting it to the above lower limit value or more, uniformity in the etching plane can be secured, which is preferable. By setting it to the upper limit value or less, it is preferable because stable selectivity can be secured during continuous processing.

In general, examples of the silicon material include single crystal silicon, polycrystalline silicon (polysilicon), and amorphous silicon (amorphous silicon). Of these, polycrystalline silicon or amorphous silicon is used in the present invention.
Single crystal silicon is a silicon crystal in which the orientation of atoms is aligned throughout the crystal, but in reality, various defects exist when observed at the atomic level.
Polycrystalline silicon is block or layered silicon composed of a large number of single crystal grains having different crystal orientations. It may be made of only Si, or may be doped with boron or phosphorus. In addition, various defects and impurities may be present as described above within a range in which a desired effect is achieved. The manufacturing method is not particularly limited, and examples thereof include those formed by a CVD method.
Amorphous silicon refers to an amorphous semiconductor whose constituent element is silicon. Specifically, it is silicon that does not have a long-range periodic structure as described below. It includes those in which some arrangement order is maintained locally, rather than atomic arrangements that are not connected in any disorder. Since the bonds are disordered, the silicon atom loses the covalent bond partner, and there is a dangling bond occupied by electrons not involved in the bond. This dangling bond bonded with hydrogen (hydrogenated) is called hydrogenated amorphous silicon and has a stable solid shape. In this specification, although simply referred to as amorphous silicon, it refers to both cases of non-hydrogenated amorphous silicon and hydrogenated amorphous silicon.

As will be described again, in the present invention, polycrystalline silicon or amorphous silicon is targeted for etching. The meaning is described here.
First, single crystal silicon has surface selectivity and a high etching rate on a specific surface. On the other hand, the etching rate is very slow or not etched on surfaces other than a specific surface. Although there is no such surface selectivity in the etching rate in polycrystalline silicon or amorphous silicon, in general, the etching rate tends to be slower than a specific surface where the etching rate of single crystal silicon is high. The silicon etching solution of the present invention can be etched at a high speed even with a polycrystalline silicon film or an amorphous silicon film by an etching mechanism different from that of single crystal silicon, and is selectively etched with TiN or the like. Can be achieved.

<Example 1, comparative example 1>
An etching solution was prepared by containing the components shown in Table 1 below and the composition (mass%) shown in the following formulation.

<Etching test>
Test wafer: A wafer of polycrystalline silicon having a thickness of 500 nm or amorphous silicon having a thickness of 500 nm formed on a single crystal <100> silicon was prepared. As the TiN substrate, SVM standard 200 mm Test wafers 5000A SiO ₂ / 3000A TiN +/− 5% was prepared. For these, etching was performed under the following conditions using a single wafer type apparatus (manufactured by SPS-Europe BV, POLOS (trade name)), and an evaluation test was performed. The cross section of the wafer was photographed with SEM (Scanning Electron Microscope), the remaining film thickness was measured, and the etching rate was obtained.
・ Chemical temperature: 30 ℃
・ Discharge rate: 1 L / min.
・ Wafer rotation speed: 500rpm

  From the above results, according to the etching solution of the present invention, it is possible to etch polycrystalline silicon and / or amorphous silicon sufficiently industrially, and to suppress the etching of titanium nitride. You can see that Note that c13 corresponds to the etching solution disclosed in Japanese Patent Laid-Open No. 2006-206347.

(Example 2, comparative example 2)
Next, an etching solution was prepared by containing the components shown in Table 2 below and the composition (mass%) shown in the following prescription. An etching test similar to that of Example 1 was performed using the obtained etching solution. The results are shown in Table 2 below.

  From the above results, according to the etching solution of the present invention, even in the embodiment using the amino acid compound, polycrystalline silicon and / or amorphous silicon can be etched industrially sufficiently fast, and titanium nitride It can be seen that the etching selectivity is excellent to suppress etching. In addition, as a comparative example, c11-c13 of Table 1 corresponds to it, and it can contrast with these.

  As shown in the above table, in the comparative example containing no anionic surfactant or amino acid compound, selective etching of TiN could not be performed. According to the silicon etching solution of the present invention, a high etching rate was exhibited with respect to polycrystalline silicon and amorphous silicon, while high etching selectivity was exhibited such that TiN was not damaged.

DESCRIPTION OF SYMBOLS 1 1st shaping | molding film 2 2nd shaping | molding film 3 Silicon wafer 4 Photoresist 5 Conductive film 6 Buried film 7 Electrode protective film 9 Capacitance insulating film 10 Capacitor structure 21 3rd shaping | molding film 31 4th shaping | molding film 50 Lower electrode (Cylinder wall)

Claims (25)

A silicon etching solution containing an anionic group-containing compound having 3 or more carbon atoms, nitric acid and hydrofluoric acid in an aqueous medium is prepared, and the silicon etching solution is made of polycrystalline silicon and / or amorphous silicon Is an etching method for forming an uneven shape to be a capacitor,
An etching method comprising at least one selected from a Ti compound, an Hf compound, SiN and W, wherein the concavo-convex shape portion constituting the capacitor structure is not removed even by etching by applying the etching solution.   The etching method according to claim 1, wherein the compound having 3 or more carbon atoms having an anionic group is an amino acid compound or an anionic surfactant.   The etching method according to claim 1 or 2, wherein a concentration of the compound having 3 or more carbon atoms having an anionic group in a total amount of liquid is 20% by mass or less.   The etching method according to any one of claims 1 to 3, wherein the compound having 3 or more carbon atoms having an anionic group is a basic amino acid compound or an anionic surfactant having 10 or more carbon atoms.   The etching method according to any one of claims 1 to 4, wherein a concentration of the nitric acid in the silicon etching solution is more than 30% by mass.   The etching method according to claim 1, wherein the concentration of the hydrofluoric acid in the silicon etchant is 6% by mass or less.   The etching method according to any one of claims 1 to 6, wherein the uneven portion has a cylinder hole formed by being removed by the silicon etching solution. A ratio (R _Si / R _Ti ) between an etching rate (R _Si ) of the silicon film and at least one etching rate (R _Ti ) selected from the Ti compound, Hf compound, SiN and W is 100 or more. Item 8. The etching method according to any one of Items 1 to 7.   The etching method according to claim 1, wherein the Ti compound is TiN.   The etching method according to claim 7, wherein the cylinder hole has an aspect ratio of 15 or more.   3. The anionic surfactant is at least one selected from the group consisting of a carboxylic acid compound having 10 or more carbon atoms, a sulfonic acid compound having 10 or more carbon atoms, and a phosphonic acid compound having 10 or more carbon atoms. Etching method.   The etching method according to claim 2, wherein the amino acid compound is arginine or histidine.   The etching method according to any one of claims 1 to 12, wherein a temperature of the etching solution is set to 20 to 80 ° C. Forming a multilayer film structure having a silicon film composed of a polycrystalline silicon film and / or an amorphous silicon film on a semiconductor substrate, and forming irregularities in the multilayer film structure having the silicon film ;
Forming a conductive film on at least the upper surface of the irregular surface and the wall surface of the recess;
Providing a buried film on the conductive film and filling the recess with the buried film;
Removing a portion of the conductive film portions are applied to the upper surface and the buried layer, and a step of exposing the silicon layer of the semiconductor substrate, then
An etching solution is applied to the semiconductor substrate to leave the exposed silicon film and the embedded film while leaving the conductive film on the wall surface of the recess,
The manufacturing method of the semiconductor substrate product which uses the silicon etching liquid which contains a C3 or more compound which has the said anionic group, nitric acid, and hydrofluoric acid in an aqueous medium as said etching liquid.   The method of manufacturing a semiconductor substrate product according to claim 14, wherein the conductive film is at least one selected from the group consisting of a Ti compound, an Hf compound, and W. The prepared those having a substantially planar surface as the semiconductor substrate, the etchant applied to the surface of the silicon layer, and removing said buried layer and said silicon film, the concave portion and the removed portion 16. The method of manufacturing a semiconductor substrate product according to claim 14, wherein the convex portion including the conductive film left in the substrate is used as an electrode of a capacitor.   A silicon etching solution for removing a polycrystalline silicon film and / or an amorphous silicon film, which contains the compound having 3 or more carbon atoms having an anionic group, nitric acid, and hydrofluoric acid in an aqueous medium. A silicon etching solution in which the concentration of nitric acid is more than 30% by mass.   The silicon etching solution according to claim 17, wherein the concentration of hydrofluoric acid is 0.5 to 2 mass%.   The silicon etching solution according to claim 17 or 18, wherein the concentration of the compound having 3 or more carbon atoms having an anionic group is 0.001% by mass or more and 20% by mass or less.   The compound having 3 or more carbon atoms having the anionic group is at least one selected from the group consisting of carboxylic acid compounds having 10 or more carbon atoms, sulfonic acid compounds having 10 or more carbon atoms, and phosphonic acid compounds having 10 or more carbon atoms. The silicon etching solution according to any one of claims 17 to 19.   A silicon etching solution for removing a polycrystalline silicon film and / or an amorphous silicon film, which contains an amino acid compound having 3 or more carbon atoms, nitric acid, and hydrofluoric acid in an aqueous medium.   The silicon etching solution according to claim 21, wherein the concentration of the hydrofluoric acid is 0.5 to 2 mass%.   The silicon etching solution according to claim 21 or 22, wherein the concentration of the amino acid compound is 0.001 mass% or more and 20 mass% or less.   24. The silicon etching solution according to any one of claims 21 to 23, wherein the concentration of nitric acid is more than 30% by mass. The silicon etching solution according to any one of claims 21 to 24, wherein the amino acid compound is arginine or histidine.

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