JP5731295B2 - Capacitor structure forming method and silicon etching solution used therefor - Google Patents

Description

  The present invention relates to a method for forming a capacitor structure and a silicon etching solution used therefor.

  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. Further, in a portion where the cylinder structure is dense, etching is difficult even outside the hole due to the same situation. Although it is conceivable to apply a solvent having a high etching power with emphasis on workability, there is a concern that the action may corrode the electrode and other parts. Further, in order to increase the aspect ratio, the filler material tends to be changed from SiO ₂ to polycrystalline silicon or amorphous silicon, and good etching corresponding to this tends to be possible.

JP 2010-199136 A

  By the way, the formation of the capacitor structure may be performed by a batch type cleaning apparatus or a single wafer type cleaning apparatus. In any method, since the etching process is performed for a certain time under a predetermined temperature condition, it is desirable that the activity of the etching solution is maintained during that time. In particular, in the case of a single wafer type, the etching solution is used for cleaning in a circulated state. Therefore, the processing capacity is not lowered even by the circulation holding at the predetermined temperature, that is, a long life is required. Is done.

  Therefore, the present invention is capable of accurately and efficiently removing amorphous silicon or polycrystalline silicon so as to form a concavo-convex shape on a semiconductor substrate, and is silicon etching that maintains its activity for a long time under the conditions under which the etching is performed. An object is to provide a liquid and a method for forming a capacitor structure using the same.

The above problem has been solved by the following means.
(1) A method of forming a capacitor structure having a lower electrode of a cylinder or trench structure made of titanium nitride, a capacitive insulating film covering the lower electrode, and an upper electrode. In forming the lower electrode,
A silicon etching solution containing ammonia and at least one specific basic compound selected from the group consisting of a hydroxylamine compound, a basic organic compound, and a metal-containing basic compound under the following conditions (a) to (c): The single wafer processing apparatus is applied to a polycrystalline silicon film or an amorphous silicon film and a titanium nitride (TiN) film at a liquid temperature of 50 ° C. to 90 ° C., and the polycrystalline silicon film or the amorphous silicon film. By selectively removing at least a portion of the titanium nitride film with the following selection ratio,
A method of forming a capacitor structure that forms an uneven shape to be a capacitor.
Condition (a): Condition (b) in which the content ratio (M _A / M _SB ) of the mass (M _A ) of the ammonia and the mass (M _SB ) of the specific basic compound is 0.1 to 10 (C): the concentration of the specific basic compound is 1-25% by mass The selectivity: the etching rate (ERe) of titanium nitride and the polycrystalline silicon film or amorphous silicon (2) The specific basic compound is selected from the group consisting of tetramethylammonium hydroxide, potassium hydroxide, hydroxylamine compounds and alkanolamines. The ratio (ERs / ERe) of the etching rate (ERs) of the film is 100 or more. The forming method according to (1), which is at least one kind.
(3) The forming method according to (1) or (2), wherein the etching solution is composed of an A agent containing ammonia and a B agent containing a specific basic compound, and the A agent and the B agent are mixed at the time of use.
(4) At least a part of the polycrystalline silicon film or amorphous silicon film is removed by the silicon etchant to form a cylinder or trench structure having an aspect ratio (depth / opening width) of 10 or more (1) to ( The forming method according to any one of 3).
(5) The polycrystalline silicon film or the amorphous silicon film is etched while leaving an electrode film made of titanium nitride so as to form an uneven structure, and any one of (1) to (4) The forming method described in 1.
(6) The polycrystalline silicon film or the amorphous silicon film is removed, the removed portion is used as a recess, and the projecting portion made of titanium nitride left in the substrate is used as the lower electrode of the capacitor (1) The formation method as described in any one of-(5).
(7) An etching solution for forming the following capacitor structure through a step of removing at least a part of the polycrystalline silicon film or the amorphous silicon film with respect to the titanium nitride film at the following selectivity, And at least one specific basic compound selected from the group consisting of a hydroxylamine compound, a basic organic compound, and a metal-containing basic compound in combination under the following conditions (a) to (c): Etching solution.
Capacitor structure: Structural condition in which a lower electrode of a cylinder or trench structure made of titanium nitride, a capacitive insulating film covering the lower electrode, and an upper electrode are arranged (a): mass of the ammonia (M _A ) and a specific basic compound Condition (b) where the content ratio (M _A / M _SB ) to the mass (M _SB ) is 0.1 to 10: Condition (c) where the ammonia concentration is 5 to 25% by mass: the specific base Ratio of the active compound is 1 to 25% by mass: the ratio (ERs / ERe) of the etching rate (ERs) of the titanium nitride and the etching rate (ERs) of the polycrystalline silicon film or amorphous silicon film is 100 or more there (8) the specific basic compound, etching according to the metal-containing basic compound, and characterized in that it is selected from the group consisting of an alkanolamine (7) Liquid.
( 9 ) The etching solution according to (7) or (8) , which is used in a single wafer processing apparatus.
( 10 ) Any one of (7) to ( 9 ), characterized in that the kit comprises an agent A containing ammonia and an agent B containing a specific basic compound, and is used by mixing both agents at the time of use. The etching liquid as described in one.
( 11 ) The etching solution according to any one of (7) to ( 10 ), wherein the polycrystalline silicon film or the amorphous silicon film is selectively removed with respect to titanium nitride (TiN).

  According to the silicon etchant of the present invention and the method of forming a capacitor structure using the same, it is possible to remove amorphous silicon or polycrystalline silicon accurately and efficiently so as to form a concavo-convex shape on a semiconductor substrate. There is an excellent effect that the activity is maintained for a long time under the conditions. In addition, according to the present invention, if necessary, removal of etching residues can be achieved at the same time, and the process can be made more efficient.

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 another manufacturing process of the capacitor structure applied to this invention. It is sectional drawing of the VII-VII line arrow cross section shown in FIG.

[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 FIGS. 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 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 FIG. 1-5, although it does not show in particular with hatching, the cross section of each member is shown (the lower figure of FIG.3 (f) is a top view).

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

(Process e)
After the formation of the buried film 6, the buried film 6 and the conductive film 5 (FIGS. 2 and 3) on the wafer surface are partially removed by CMP and exposed to the etch back line E. Here, the second insulating film 2 and the buried 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. 4 and 5, the structure is shown as an end view.

Next, based on FIG. 6, FIG. 7, the modification (form with the protection part 7) of the said embodiment is demonstrated. In the present embodiment, the electrode protective film 7 is formed. The electrode protective film is desirably an insulating film having sufficient resistance to the wet etching solution used for removing the silicon material when forming the capacitor structure. Furthermore, it is desirable that a film can be formed uniformly over the entire cylinder hole Ka. For example, a nitride film using an ALD (Atomic Layer Deposition) method, a tantalum pentoxide (Ta ₂ O ₅ ) film, or the like can be given. Although the procedure for forming this is not particularly limited, the electrode protective film is removed after the growth of the electrode protective film by isotropic etching. Specifically, first, the molding film 2 is configured to have a three-layer structure including the molding layer 21 (FIG. 6A). This is etched, but the molded film 21 is easily etched in isotropic etching. Therefore, a recess Va is formed in this portion by isotropic etching (FIG. 6B). Thereafter, when a protective film (not shown) is formed, the surface including the depression formed on the wall surface of the recess Ka is covered with the protective film. That is, the electrode protective film is filled in the recess. Thereafter, when isotropic etching is performed, only the protective part 7 is left. Thereafter, the lower electrode 50 can be formed by applying the conductive film 5 as in the above embodiment. Next, when the silicon film and the buried film are removed with the etching solution of the present embodiment, when the lower electrode 50 described later is formed, a protruding electrode protection portion (not shown) can be formed there (FIG. 6 ( c)). The structure and advantages of this electrode protecting projection are disclosed in detail in Japanese Patent Application Laid-Open No. 2010-199136.
In this modification, not only is it difficult to remove the embedded film from the cylinder hole Kc, but also the protective part 7, so it is difficult to remove the molded film 2 from the gap (concave part) Kd between the electrodes 50. Rather, the protective part 7 protruding outward functions like a weir, and it may make it difficult to remove and release the molded film below it. Since the etching solution of the present invention exhibits a particularly high effect in such an aspect that is difficult to remove, its application is preferable.

[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 ammonia and a specific basic compound in combination, the polycrystalline silicon according to the formation of the capacitor structure having the uneven shape as described above without damaging members such as electrodes The film or amorphous silicon film can be accurately removed. Although the detailed reason includes an unclear point, it is estimated as follows. That is, ammonia has a low molecular weight and a low pKb, so that many hydroxyl groups can be included in the system. Therefore, a high silicon etching rate can be realized. However, ammonia tends to volatilize, and the period of manifestation of its effect tends to be very short. Although details are unknown, it is considered that by combining a specific basic compound, a hydroxyl group can be retained in the system for a long time, and a high etching rate can be retained for a long time.
In addition, in this specification, the liquid which combined the specific agent means the liquid composition containing the said agent, and also as a kit which mixes and uses each agent or the liquid containing it before use. The meaning is included.

(ammonia)
The etching solution of this embodiment contains ammonia as an essential component. The ammonia concentration is preferably 5 to 25% by mass, and more preferably 10 to 20% by mass. A high etching rate is realizable by setting it as the said lower limit or more. In addition, when the upper limit value is not exceeded, the decay over time of the etching rate can be moderated.

(Specific basic compounds)
The etching solution of this embodiment contains a specific basic compound other than ammonia together with ammonia. The specific basic compound is selected from the group consisting of a hydroxylamine compound, a basic organic compound, and a metal-containing basic compound.

-Basic organic compound It is preferable to have carbon and nitrogen as a constituent element of a basic organic compound, and it is more preferable to have an amino group. Specifically, the basic organic compound is preferably at least one compound selected from the group consisting of organic amines and quaternary ammonium hydroxides. The organic amine means an amine containing carbon as a constituent element.

  The organic amine used as the organic alkali compound of the etching solution of the present embodiment includes monoethanolamine, diethanolamine, triethanolamine, diethylene glycolamine, alkanolamines such as N-hydroxylethylpiperazine, and / or ethylamine, benzylamine, Diethylamine, n-butylamine, 3-methoxypropylamine, tert-butylamine, n-hexylamine, cyclohexylamine, n-octylamine, 2-ethylhexylamine, o-xylenediamine, m-xylylenediamine, 1-methylbutylamine, Ethylenediamine (EDA), 1,3-propanediamine, 2-aminobenzylamine, N-benzylethylenediamine, diethylenetriamine, triethylenetetramine, etc. It includes organic amine having no hydroxy group. Alkanolamine is preferable from the viewpoint of effectively exhibiting the above action, and monoethanolamine, diethanolamine, triethanolamine, diethylene glycolamine, ethylenediamine (EDA), 1,3-propanediamine, diethylenetriamine, and triethylenetetramine are particularly preferable. . In addition, in the description of a compound and a group (atomic group) in this specification, the description which does not describe substitution and non-substitution includes what has a substituent with what does not have a substituent. For example, the “alkyl group” includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).

The quaternary ammonium hydroxide used as the alkali compound is preferably a tetraalkylammonium hydroxide, more preferably a tetraalkylammonium hydroxide substituted with a lower (1 to 4 carbon atoms) alkyl group. Examples include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), and tetrabutylammonium hydroxide (TBAH). Furthermore, examples of the quaternary ammonium hydroxide include trimethylhydroxyethylammonium hydroxide (choline), methyltri (hydroxyethyl) ammonium hydroxide, tetra (hydroxyethyl) ammonium hydroxide, and benzyltrimethylammonium hydroxide (BTMAH). In addition, a combination of ammonium hydroxide and one or more quaternary ammonium hydroxides can also be used. Among these, TMAH, TEAH, TPAH, TBAH, and choline are more preferable, and TMAH and TBAH are particularly preferable.
These organic amines and quaternary ammonium hydroxides 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.

-Hydroxylamine compound In this invention, a hydroxylamine compound can be used as a specific basic compound. Examples of the hydroxylamine compound include hydroxylamine and salts of hydroxylamine. Examples of the salt of hydroxylamine include hydroxylamine nitrate (also referred to as HAN), hydroxylamine sulfate (also referred to as HAS), hydroxylamine phosphate, hydroxylamine hydrochloride and the like. An organic acid salt of hydroxylamine can also be used for the etchant, and examples include hydroxylamine citrate and hydroxylamine oxalate. Among these salts of hydroxylamine, inorganic acid salts such as hydroxylamine nitrate, hydroxylamine sulfate, hydroxylamine phosphate, and hydroxylamine hydrochloride are preferable because they are inert to metals such as aluminum, copper, and titanium. In particular, hydroxylamine nitrate and hydroxylamine sulfate are preferred. These hydroxylamine compounds can be used singly or in combination of two or more.

-Metal-containing basic compound Examples of the metal-containing basic compound include potassium hydroxide, sodium hydroxide, lithium hydroxide, cesium hydroxide, and calcium hydroxide. Among them, potassium hydroxide and sodium hydroxide are preferable, Potassium hydroxide is more preferred.

  In the present invention, it is preferable that the etching solution contains ammonia and two or more specific basic compounds. The combination of two or more kinds of specific basic compounds is preferably a combination of at least hydroxylamine and a basic organic compound and / or a basic inorganic compound, and in particular, at least hydroxylamine and quaternary ammonium hydroxide. The combination with a product is more preferable, and the combination of at least hydroxylamine and TMAH and / or MEA is particularly preferable.

The content of the specific basic compound is preferably contained within a range of 1 to 25% by mass, and more preferably 1 to 15% by mass with respect to the total mass of the etching solution of the present embodiment. It is preferable to set it to the upper limit value or less and the lower limit value or more because a high etching rate can be maintained. In addition, since performance is saturated, it is sufficient to cope with the above upper limit from the viewpoint.
It is preferable that the content ratio of the mass _{(M SB)} of a specific basic compound with ammonia in the mass _{(M A) (M A /} M SB) is 0.1 to 10, is 0.3 to 5 It is more preferable. Since the etching rate can be maintained by setting the upper limit value or less, it is preferable. Since it can obtain a high etching rate by setting it as the said lower limit or more, it is preferable. In addition, a specific basic compound may be used 1 type, or may be used in combination of 2 or more type.
As described above, a salt composed of an anion may be used as the specific basic compound such as a hydroxylamine salt. However, in the present invention, when using a salt of an anion derived from a strong acid, the pH in the system is adjusted to that of the basic compound. It is preferable to keep it alkaline by addition or the like.

(PH)
The silicon etching solution of the present invention is alkaline and is adjusted to pH 11 or higher. This adjustment can be performed by adjusting the addition amounts of the alkali compound and the hydroxylamine compound. 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 preferably 9 or more, more preferably 11 or more. When this pH is equal to or higher than the lower limit, a sufficient etching rate can be obtained. There is no particular upper limit to the pH, but it is practical that it is 14 or less.

(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 a surfactant. As the surfactant, nonionic, anionic, cationic surfactants, and amphoteric surfactants can be used. The content of the surfactant in the antioxidant liquid is preferably 0.0001 to 5% by mass and more preferably 0.0001 to 1% by mass with respect to the total mass of the antioxidant liquid. It is preferable to add a surfactant to the antioxidant solution because the viscosity can be adjusted and further improvement in in-plane uniformity of etching can be improved. Such surfactants are generally commercially available. These surfactants may be used alone or in combination.

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 distyrene. Phenyl ether surfactants, polyalkylene tribenzylphenyl ether surfactants, and acetylene polyalkylene oxide surfactants.
Anionic surfactants include alkyl sulfates, alkyl sulfonic acids, alkyl benzene sulfonic acids, alkyl naphthalene sulfonic acids, alkyl diphenyl ether sulfonic acids, polyoxyethylene alkyl ether carboxylic acids, polyoxyethylene alkyl ether acetic acids, polyoxyethylene alkyl ethers. Examples include propionic acid and salts thereof.
Examples of the cationic surfactant include a quaternary ammonium salt surfactant and an alkyl pyridium surfactant.
Examples of amphoteric surfactants include betaine surfactants, amino acid surfactants, imidazoline surfactants, and amine oxide surfactants.

  The content of the surfactant in the etching solution is preferably 0.0001 to 5% by weight, more preferably 0.0001 to 1% by weight, based on the total mass of the etching solution. It is preferable because the viscosity of the cleaning composition can be adjusted by adding a surfactant to the cleaning composition, and the wettability to the object to be cleaned 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.

(Aqueous medium)
The etching solution of this embodiment 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. Examples of the solute include alcohols and salts of inorganic compounds. However, even when the solute is applied, it is preferable that the amount thereof be suppressed within a range where a desired effect is exhibited. 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 this specification, the term “semiconductor substrate” is used to include 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.

(kit)
The etching solution of the present invention comprises an agent A and an agent B, and may be a kit in which the agent A and the agent B are mixed immediately before use. In this case, for example, the agent A includes ammonia, and the agent B includes a specific basic compound such as tetramethylammonium hydroxide. Dividing into two kits in this way is preferable from the viewpoint of manufacturing cost.
In such an embodiment, only one agent may be added during the chemical solution circulation of the single wafer processing apparatus. By doing in this way, a high etching rate is expressed longer.

[Etching conditions]
In this embodiment, the etching conditions are not particularly limited, but may be spray type, wafer spin type (single wafer type) etching, or batch type (immersion type) etching. In spray-type (wafer spin-type) etching, a 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. 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 the wafer spin method, the environmental temperature for etching is preferably 15 to 100 ° C., more preferably 20 to 80 ° C. The etching solution is preferably 20 to 100 ° C, more preferably 30 to 95 ° C, and particularly preferably 50 to 90 ° 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 2 L / min, and more preferably 0.1 to 1 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, depending on its size and the like, it is preferably rotated at 0 to 500 rpm, more preferably 10 to 400 rpm, from the same viewpoint as described above.

  In the case of the batch type, the liquid bath is preferably 15 to 90 ° C, more preferably 20 to 80 ° 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 the present invention, it is preferable to perform etching with a single wafer processing apparatus, where etching is performed one by one, and the circulating etching solution is sequentially discharged and used. In the present invention, the single-wafer type is preferable because the etching solution has a long life and the etching performance is less likely to decrease during circulation. The above conditions are preferable for the treatment temperature. Further, the processing rotation speed is preferably the above condition. The treatment may be either spin cleaning or paddle cleaning. The rinsing includes water, IPA (isopropyl alcohol), perfluoroether, and the like, and an appropriate process can be selected.

(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 (ERs / ERe) between the etching rate (ERs) of the substrate material and the etching rate (ERe) of the electrode material. The specific ratio value is not particularly limited because it depends on the type and structure of the material, but ERs / ERe 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, if the cylinder structure as described above is used, the etching liquid of this embodiment is particularly high when the aspect ratio of the cylinder hole is 5 or more. The effect is utilized and preferable. From the same viewpoint, the aspect ratio is preferably 10 or more, and more preferably 20 or more. Although there is no upper limit, it is practical that the aspect ratio is 1000 or less. But not limited opening diameter d _c in particular of the cylinder bore, the effect is exhibited in the present embodiment, in consideration of the miniaturization of the recent capacitor structure, it is preferable in 20 to 80 nm. In the present specification, the trench or its structure is not particularly limited as long as it has a concave shape in a specific cross section, and not only a groove shape but also a hole shape, and conversely a needle shape structure. The circumference | surroundings etc. which many parts protruded may be sufficient. Taking FIG. 3 as an example, the cylinder hole Kc corresponds to the hole-shaped trench structure, in which the concave portion Kd corresponds to a trench structure including a large number of needle-shaped structure portions protruding therefrom. Aspect ratio, the cylinder bore Kc is a value obtained by dividing the depth h ₂ of the width d _c of the concave portion. The aspect ratio of the concave portion Kd forming the periphery of the needle-like structures many projects, for example, a value obtained by dividing the depth h ₁ of the concave portion in the width d _d.

  From the above viewpoint, it is preferable to etch the polycrystalline silicon film or the amorphous silicon film while leaving at least the electrode film made of TiN, Ti, or W on the wall surface of the concavo-convex structure with the etching solution of the present invention. Also, a semiconductor substrate having a substantially flat surface having the polycrystalline silicon film or the amorphous silicon film is prepared, and the etching solution is applied to a surface of the semiconductor substrate, and the polycrystalline silicon film or the amorphous silicon film is formed. It is preferable to perform a process of removing the removed portion as a concave portion and the convex portion remaining in the substrate as a capacitor. At this time, it is more preferable that the TiN film remains on the wall surface of the recess.

The process requirements relating to the preferred method for manufacturing a semiconductor substrate product in the present invention are described below.
(1) preparing a semiconductor substrate having a silicon film made of a polycrystalline silicon film or an amorphous silicon film, and applying a specific etching solution to the semiconductor substrate to etch at least a part of the silicon film. .
(2) In the step of preparing the semiconductor substrate, a multilayer film structure including the silicon film is formed, and irregularities are formed on the semiconductor substrate,
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 the conductive film portion applied to the upper surface and a part of the embedded film to expose the silicon film of the semiconductor substrate, and
In the silicon film etching step, the etching solution is applied to the semiconductor substrate to remove the exposed silicon film and the embedded film while leaving the conductive film on the wall surface of the recess.
(3) A semiconductor substrate having a substantially flat surface is prepared, the etching solution is applied to the surface of the semiconductor substrate, the silicon film and the embedded film are removed, and the removed portion Is a concave portion, and the convex portion including the conductive film left in the substrate is a capacitor electrode.

According to the preferable etching method of the present invention, residues of dry etching and ashing performed before that can be effectively removed. Thereby, wet etching of silicon and cleaning of residues can be performed at a time, which contributes to a significant improvement in manufacturing efficiency.
In the manufacturing process of a semiconductor element, there is a step of etching a metal layer or the like on a semiconductor substrate by plasma etching using a resist pattern or the like as a mask. Specifically, a metal layer, a semiconductor layer, an insulating layer, or the like is etched to pattern the metal layer or the semiconductor layer, or an opening such as a via hole or a wiring groove is formed in the insulating layer. In the plasma etching, a residue derived from a resist used as a mask, a metal layer to be etched, a semiconductor layer, and an insulating layer is generated on the semiconductor substrate. In the present invention, such a residue generated by plasma etching is referred to as “plasma etching residue”.
Further, the resist pattern used as a mask is removed after etching. For removing the resist pattern, as described above, a wet method using a stripper solution or a dry method by ashing using, for example, plasma or ozone is used. In the ashing, a residue obtained by altering a plasma etching residue generated by plasma etching or a residue derived from a resist to be removed is generated on the semiconductor substrate. In the present invention, the residue generated by ashing in this way is referred to as “ashing residue”. Further, a generic term for what should be cleaned and removed on a semiconductor substrate through processing such as plasma etching residue and ashing residue may be simply referred to as “residue”.
It is preferable that the plasma etching residue and the ashing residue, which are the residues after etching (Post Etch Residue), are removed by cleaning using a cleaning composition. The etching solution of this embodiment can also be applied as a cleaning solution for removing plasma etching residues and / or ashing residues. Especially, it is preferable to use it for removing a plasma etching residue and an ashing residue after plasma ashing performed following plasma etching.

<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 capacitor height (corresponding to h ₁ in FIG. 3) was prepared a test pattern wafer for forming an amorphous silicon crown DRAM structure 6000 Å. On the other hand, etching is performed under the following conditions with a single wafer type apparatus (manufactured by SPS-Europe BV, POLOS (trade name)), and the etching rate is compared between 0 minutes and 60 minutes after the start of etching. evaluated. In this apparatus, the etching liquid is circulated in the apparatus, which means that the liquid temperature is maintained at the following temperature for the above time.
・ Chemical solution temperature: 80 ℃
・ Tank capacity: 40L
・ Discharge rate: 1 L / min.
・ Wafer rotation speed: 500rpm

c17: Japanese Patent Laid-Open No. 2006-351813 equivalent to Example 1 c18: Japanese Patent No. 3,994,992 equivalent to Example 1
TMAH: Tetramethylammonium hydroxide
HA: Hydroxylamine
MEA: Monoethanolamine
Initial: Silicon etching rate (Å / min.) When processing is disclosed
Time: Silicon etching rate after 60 minutes (Å / min.)

As shown in the above table, according to the silicon etching solution of the present invention, it can be seen that a sufficient etching rate is realized corresponding to amorphous silicon, and the decrease in the etching rate is very small even after 60 minutes. Furthermore, it was confirmed that the silicon etching solution of the present invention caused very little damage to each film such as TiN, SiN, and SiO ₂ which are electrode materials of the device.
The test No. 1 of Comparative Example 1 was used. In c11, the speed reduction was remarkably large, and in c12 to c16, the etching speed was not sufficient although there was no speed reduction.
Moreover, when the residue of silicon | silicone was also evaluated, each Example resulted in few residues compared with the comparative example.

<Example 2>
When the wafer was changed to a test pattern wafer using polycrystalline silicon and the same evaluation as in Example 1 was performed, all of the silicon etching solutions of the present invention achieved a sufficient etching rate, and etching after 60 minutes had elapsed. There was very little reduction in speed.

<Example 3 >
An etching solution consisting of the following agent A and agent B was prepared, and the agent A and agent B were mixed immediately before use and evaluated in the same manner as in Example 1. As a result, a sufficient etching rate was achieved and 60 minutes. The decrease in the etching rate after the lapse was very small.
(A agent)
Ammonia 15% by mass
Water balance (B agent)
Tetramethylammonium hydroxide 10% by mass
Water balance

DESCRIPTION OF SYMBOLS 1 1st insulating film 2 2nd insulating film 3 Silicon wafer 4 Photoresist 5 Conductive film 6 Buried film 7 Protection part 9 Capacitance insulating film 10 Capacitor structure 50 Lower electrode (cylinder wall)

Claims (11)

A method of forming a capacitor structure having a lower electrode of a cylinder or trench structure made of titanium nitride, a capacitive insulating film covering the lower electrode, and an upper electrode. In forming the lower electrode,
A silicon etching solution containing ammonia and at least one specific basic compound selected from the group consisting of a hydroxylamine compound, a basic organic compound, and a metal-containing basic compound under the following conditions (a) to (c): The single wafer processing apparatus is applied to a polycrystalline silicon film or an amorphous silicon film and a titanium nitride (TiN) film at a liquid temperature of 50 ° C. to 90 ° C., and the polycrystalline silicon film or the amorphous silicon film. By selectively removing at least a portion of the titanium nitride film with the following selection ratio,
A method of forming a capacitor structure that forms an uneven shape to be a capacitor.
Condition (a): Condition (b) in which the content ratio (M _A / M _SB ) of the mass (M _A ) of the ammonia and the mass (M _SB ) of the specific basic compound is 0.1 to 10 (C): the concentration of the specific basic compound is 1-25% by mass The selectivity: the etching rate (ERe) of titanium nitride and the polycrystalline silicon film or amorphous silicon The ratio (ERs / ERe) of the etching rate (ERs) of the film is 100 or more   The formation method according to claim 1, wherein the specific basic compound is at least one selected from the group consisting of tetramethylammonium hydroxide, potassium hydroxide, a hydroxylamine compound, and an alkanolamine.   The forming method according to claim 1 or 2, wherein the etching solution comprises an A agent containing ammonia and a B agent containing a specific basic compound, and the A agent and the B agent are mixed at the time of use.   The cylinder or trench structure having an aspect ratio (depth / opening width) of 10 or more is formed by removing at least a part of the polycrystalline silicon film or the amorphous silicon film with the silicon etchant. 2. The forming method according to item 1.   5. The method according to claim 1, wherein the polycrystalline silicon film or the amorphous silicon film is etched while leaving an electrode film made of titanium nitride so as to form an uneven structure. 6. .   6. The polycrystalline silicon film or the amorphous silicon film is removed, the removed portion is used as a concave portion, and the convex portion made of titanium nitride left in the substrate is used as a lower electrode of the capacitor. The forming method according to any one of the above. An etching solution for forming the following capacitor structure through a step of removing at least a part of the polycrystalline silicon film or the amorphous silicon film with respect to the titanium nitride film at the following selection ratio: ammonia and hydroxylamine A silicon etching solution comprising at least one specific basic compound selected from the group consisting of a compound, a basic organic compound, and a metal-containing basic compound in combination under the following conditions (a) to (c).
Capacitor structure: Structural condition in which a lower electrode of a cylinder or trench structure made of titanium nitride, a capacitive insulating film covering the lower electrode, and an upper electrode are arranged (a): mass of the ammonia (M _A ) and a specific basic compound Condition (b) where the content ratio (M _A / M _SB ) to the mass (M _SB ) is 0.1 to 10: Condition (c) where the ammonia concentration is 5 to 25% by mass: the specific base Ratio of the active compound is 1 to 25% by mass: the ratio (ERs / ERe) of the etching rate (ERs) of the titanium nitride and the etching rate (ERs) of the polycrystalline silicon film or amorphous silicon film is 100 or more is there The etching solution according to claim 7, wherein the specific basic compound is selected from the group consisting of a metal-containing basic compound and an alkanolamine. The etching solution according to claim 7 or 8 , which is used in a single wafer processing apparatus. The kit according to any one of claims 7 to 9 , wherein the kit comprises an agent A containing ammonia and an agent B containing a specific basic compound, and is used by mixing both agents at the time of use. Etching solution. The etching solution according to any one of claims 7-10 for selectively effect removal of the polycrystalline silicon film or amorphous silicon film with respect to titanium nitride (TiN).

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