JP2021072436A - Silicon nitride film etching solution and method of producing semiconductor element using the same - Google Patents

Abstract

To provide a silicon nitride film etching solution which is hardly decomposed at low temperature but easily decomposed under an etching condition at high temperature, and which prevents growth as silicon-based particles and can increase a selection ratio of a silicon nitride film to a silicone oxide film.SOLUTION: The silicon nitride film etching solution comprises a phosphoric acid aqueous solution and at least one of compounds represented by the formula in the figure. In the formula, each X1 is independently selected from nitrogen, oxygen and sulfur; each Y1 is independently selected from hydrogen, halogen, alkoxy group, amine and a hydroxy group; and each a is independently from 1 to 4.SELECTED DRAWING: None

Description

The present invention relates to a silicon nitride film etching solution and a method for manufacturing a semiconductor device using the same. More specifically, the present invention is a silicon nitride film that prevents the generation of particles and increases the selectivity of the silicon oxide film to the silicon nitride film. The present invention relates to an etching solution and a method for manufacturing a semiconductor device using the etching solution.

Currently, there are various methods for etching a silicon nitride film, but a dry etching method and a wet etching method are mainly used.

The dry etching method is usually an etching method using a gas, and has an advantage that it is more isotropic than a wet etching method. However, the dry etching method has a limitation in the etching pattern, is too inferior in productivity to the wet etching method, and is an expensive method. Therefore, the wet etching method is being widely used.

Generally, as a wet etching method, a method using phosphoric acid as an etching solution is well known. At this time, when only pure phosphoric acid is used for etching the silicon nitride film, not only the silicon nitride film but also the silicon oxide film is etched as the device becomes finer, so that various defects and patterns are formed. Therefore, it is necessary to form a protective film on the silicon oxide film to further reduce the etching rate of the silicon oxide film.

An object of the present invention is to provide a silicon nitride film etching solution that prevents the generation of particles and increases the selectivity of the silicon oxide film with respect to the silicon nitride film under etching conditions.

Another object of the present invention is to provide a method for manufacturing a semiconductor device, which is performed by using the above-mentioned silicon nitride film etching solution.

In order to solve the above-mentioned technical problems, according to one aspect of the present invention, the silicon nitride film etching solution contains at least one of a phosphoric acid aqueous solution and a compound represented by the following Chemical formula 1 or Chemical formula 2. ..

In the above-mentioned 1 and the above-mentioned 2
X ₁ and X ₂ are independently selected from nitrogen, oxygen and sulfur, respectively.
Y ₁ and Y ₂ are independently selected from hydrogen, halogen, alkoxy group, amine, and hydroxy group, respectively.
a and b are 1 to 4 independently of each other.

Further, according to another aspect of the present invention, there is provided a method for manufacturing a semiconductor device, which is performed by using the above-mentioned silicon nitride film etching solution.

Since the silicon nitride film etching solution according to the present invention contains at least one of the compounds represented by Chemical formula 1 or Chemical formula 2, the reactivity with water or acid is lowered at a low temperature, and the silicon nitride film etching solution grows as silicon-based particles. Can be prevented.

Further, the silicon nitride film etching solution according to the present invention contains at least one of the compounds represented by Chemical formula 1 or Chemical formula 2, and is easily decomposed under high temperature etching conditions to form silicon with respect to the silicon oxide film. The etching selectivity for the nitride film can be increased.

FIG. 5 is a cross-sectional view schematically showing a step of removing a silicon nitride film using an etching solution according to an embodiment of the present invention.

The advantages and features of the present invention, and the methods for achieving them, will be clarified with reference to the examples described later. However, the present invention is not limited to the examples disclosed below, and is embodied in various forms different from each other. However, the present embodiment is provided to complete the disclosure of the present invention and to fully inform a person having ordinary knowledge in the technical field to which the present invention belongs the scope of the invention, and the present invention is claimed. It is only defined by the category of terms.

Hereinafter, the silicon nitride film etching solution according to the present invention will be described in detail.

According to one aspect of the present invention, there is provided a silicon nitride film etching solution containing an aqueous phosphoric acid solution and at least one of the compounds represented by Chemical formula 1 or Chemical formula 2 below.

In the above-mentioned 1 and the above-mentioned 2
X ₁ and X ₂ are independently selected from nitrogen, oxygen and sulfur, respectively.
Y ₁ and Y ₂ are independently selected from hydrogen, halogen, alkoxy group, amine, and hydroxy group, respectively.
a and b are 1 to 4 independently of each other.

Alkoxy in the present application means both an -O- (alkyl) group and an -O- (unsubstituted cycloalkyl) group, and is one or more ether groups and 1 to 10 carbon atoms. .. Specifically, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, tert-butoxy, sec-butoxy, n-pentoxy, n-hexoxy, 1,2-dimethylbutoxy, cyclopropyloxy, cyclobutyloxy, cyclopentyl. Although it contains, but is not limited to, oxy, cyclohexyloxy, and the like.

Halogen in the present application means fluoro (-F), chloro (-Cl), bromo (-Br) or iodine (-I).

Generally, a silicon additive may be contained in the silicon nitride film etching solution in order to protect the silicon substrate from the aqueous phosphoric acid solution. However, the silane compound mainly used as a silicon additive basically has low solubility in an etching solution containing phosphoric acid. In order to increase the solubility of a silane compound in an etching solution, a silane compound in which a hydrophilic acting group is bonded to a silicon atom is used.

As described above, when a silane compound in which a hydrophilic acting group is bonded to a silicon atom is used as a silicon additive, the proper solubility of the silane compound in the etching solution can be ensured, but it is easily decomposed at a low temperature. , Can grow as silicon-based particles. When silicon-based particles grow, they act on the biggest cause of defective silicon substrates.

More specifically, the silane compound in the form in which a hydrophilic acting group is bonded to a silicon atom may be reacted by the following reaction formula 1.

[Reaction formula 1]

As in the above reaction formula 1, a silane compound in which a hydrophilic acting group is bonded to a silicon atom is easily decomposed at a low temperature by an intramolecular rearrangement reaction to form a silicon-hydroxy group (-Si-OH). ) Can be formed. The silicon-hydroxy group can form a siloxane (-Si-O-Si-) group in which silicon atoms and oxygen atoms are alternately bonded by polymerization to form a random chain structure. As a result, the silane compound grows and precipitates as silicon-based particles, which causes a problem of lowering storage safety.

In addition, a silane compound in which an alkyl group or a heteroalkyl group is bonded to a silicon atom can be used so as to ensure proper solubility of the silane compound and prevent it from being easily decomposed at a low temperature. As an example, the silane compound may be in the form of methane, ethane, propane, octane, isopropyl or t-butyl bonded to a silicon atom.

However, the compound is still not decomposed even under high temperature etching conditions, and the passivation of the silicon oxide film is performed.
The layer) cannot be sufficiently formed, and this causes a problem that the effect of increasing the etching selectivity with respect to the silicon nitride film with respect to the silicon oxide film is weak.

As an example, a silane compound in the form of an octane group bonded to a silicon atom is silicic under high temperature etching conditions.
It is hard to be decomposed into acid). Therefore, it is difficult to form a protective film by combining the silicon oxide film and silicic acid, and the effect of protecting the silicon oxide film from the phosphoric acid aqueous solution and increasing the selectivity of the silicon oxide film with respect to the silicon nitride film is weak. The problem arises.

The silicon nitride film etching solution according to one embodiment of the present invention secures proper solubility and is not easily decomposed, and under etching conditions, it is easily decomposed to prevent growth as silicon-based particles and to the silicon oxide film. In order to increase the selectivity for the silicon nitride film, it contains at least one of the compounds represented by Chemical formula 1 or Chemical formula 2 below.

In the above-mentioned 1 and the above-mentioned 2
X ₁ and X ₂ are independently selected from nitrogen, oxygen and sulfur, respectively.
Y ₁ and Y ₂ are independently selected from hydrogen, halogen, alkoxy group, and hydroxy group, respectively.
a and b are 1 to 3 independently of each other.

In Chemical formulas 1 and 2 above, the substituent containing nitrogen, oxygen or sulfur bonded to the silicon atom exhibits polarity. The compounds represented by Chemical formulas 1 and 2 contain a silicon atom to which the polar substituent is bonded, so that the proper solubility of the silane compound in the etching solution can be ensured.

Further, in the compounds represented by Chemical formulas 1 and 2, the formation of bonding silicon-hydroxy group (-Si-OH) was suppressed, and the siloxane group formed by the polymerization of the silicon-hydroxy group was repeatedly polymerized. Growth as silicon-based particles can be suppressed.

In particular, the compounds represented by Chemical formulas 1 and 2 are easily decomposed under etching conditions. The etching conditions may be 100 ° C. or higher. Under the etching conditions, the compound is decomposed into silicic acid and combined with the silicon oxide film to form a protective film, thereby protecting the silicon oxide film from the phosphoric acid aqueous solution and the etching rate of the silicon nitride film. Can be increased to reduce the etching rate of the silicon oxide film.

The compound represented by Chemical formula 1 can be decomposed into silicic acid by a rearrangement reaction under etching conditions, and silicic acid can be combined with a silicon oxide film to form a protective film. As a result, by protecting the silicon oxide film from the aqueous phosphoric acid solution, there is an effect of increasing the etching selectivity of the silicon oxide film with respect to the silicon nitride film.

Further, as an example, the compound represented by Chemical formula 1 may be the compound represented by Chemical formula 3 below.

In the above-mentioned 3
Y ₁ and a are as defined above of 1.

Further, as an example, the compound represented by Chemical formula 2 may be the compound represented by Chemical formula 4 below.

In the above 4
Y ₂ and b are as defined in Chemical formula 2 above.

The compound represented by Chemical formula 1 described above is preferably present at 100 to 500,000 ppm of the silicon nitride film etching solution. Further, the compound represented by Chemical formula 1 described above is more preferably present at 1,000 to 150,000 ppm of the silicon nitride film etching solution. Here, the content of the additive is the amount of the compound represented by Chemical formula 1 dissolved in the silicon nitride film etching solution, and is shown in units of ppm.

For example, the fact that the compound represented by Chemical formula 1 is present in the silicon nitride film etching solution at 5,000 ppm means that the compound represented by Chemical formula 1 dissolved in the silicon nitride film etching solution is present at 5,000 ppm. It means that there is.

When the compound represented by Chemical formula 1 is present in the silicon nitride film etching solution in an amount of less than 100 ppm, the amount of the silicon compound is insufficient under the etching conditions, and the etching selectivity of the silicon oxide film to the silicon nitride film is high. The increasing effect can be weak.

On the other hand, when the compound represented by Chemical formula 1 exceeds 500,000 ppm in the silicon nitride film etching solution, the proportion of water contained in the phosphoric acid aqueous solution in the silicon nitride film etching solution decreases under the etching conditions. As a result, particles may be generated at a high temperature, and there may be a problem that the etching selectivity for the silicon nitride film is lowered with respect to the silicon oxide film.

The silicon substrate may contain a silicon nitride film (Si _x N _y ), or may contain both a silicon oxide film (SiO _x ) and a silicon nitride film (Si _x N _y). Further, in the case of a silicon substrate containing both a silicon oxide film and a silicon nitride film, the silicon oxide film and the silicon nitride film may be alternately laminated or may be laminated in different regions.

Silicon oxide films include SOD (Spin On Dielectric) films and HDP (High Density) depending on the application and the type of material.
Plasma) film, thermal oxide film, BPSG (Borophosphate)
Silicate Glass (Silicate Glass) Membrane, PSG (Phospho Silicate Glass) Membrane, BSG (Boro Silicate) Membrane
Glass) film, PSZ (Polysilazane) film, FSG (Fluorinated Silicate)
Glass) film, LP-TEOS (Low)
Pressure Tera Ethyl Ortho Silicate) Membrane, PETEOS (Plasma Enhanced Tetra)
Ethyl Ortho Silicate) Membrane, HTO (High Temperature Oxide) Membrane, MTO (Medium)
Temperature Oxide (Temperature Oxide) Membrane, USG (Unloaded Silicate Glass) Membrane, SOG (Spin On Glass) Membrane, APL (Advanced Development)
Layer) membrane, ALD (Atomic Layer)
Deposition membrane, PE-oxide membrane (Plasma Enhanced oxide) or O _3- TEOS (O _3- Tetra Ethyl)
Ortho Silicate) and the like.

In one example, the phosphoric acid aqueous solution is preferably contained in an amount of 60 to 90 parts by weight with respect to 100 parts by weight of the silicon nitride film etching solution.

If the content of the phosphoric acid aqueous solution is less than 60 parts by weight with respect to 100 parts by weight of the silicon nitride film etching solution, the etching rate of the silicon nitride film decreases and the silicon nitride film is not sufficiently etched or silicon nitrided. The efficiency of the film etching process may decrease.

On the other hand, when the content of the phosphoric acid aqueous solution exceeds 90 parts by weight with respect to 100 parts by weight of the silicon nitride film etching solution, the etching selectivity of the silicon oxide film with respect to the silicon nitride film may decrease, and the silicon oxide film may have a lower etching selectivity. It can cause defects in the silicon substrate due to etching.

The silicon nitride film etching solution according to an embodiment of the present invention compensates for the etching rate of the silicon nitride film, which is lowered by containing the compound represented by Chemical formula 1, and improves the efficiency of the overall etching process. , A fluorine-containing compound may be further contained.

Fluoride-containing compounds in the present application refer to any compound in any form that dissociates fluorine ions.

In one example, the fluorine-containing compound is at least one selected from hydrogen fluoride, ammonium fluoride, ammonium fluoride, and ammonium hydrogen fluoride.

Further, in another embodiment, the fluorine-containing compound may be a compound in which an organic cation and a fluorine anion are ionically bonded.

For example, the fluorine-containing compound may be a compound in which an alkylammonium and a fluorine-based anion are ionically bonded. Here, the alkylammonium is an ammonium having at least one alkyl group and may have up to four alkyl groups. The definition for the alkyl group is as described above.

In yet another example, the fluorine-containing compounds are alkylpyrrolium, alkylimidazolium, alkylpyrazolium, alkyloxazolium, alkylthiazolium, alkylpyridinium, alkylpyrimidinium, alkylpyridazinium, alkylpyra. Organic cations selected from dinium, alkylpyrrolidinium, alkylphosphonium, alkylmorpholinium, dialkylimidazolium, and alkylpiperidinium, and fluorophosphates, fluoroalkyl-fluorophosphates, fluoroborates, and It may be an ionic liquid in the form of an ionic bond with a fluorine-based anion selected from fluoroalkyl-fluoroborate.

Among the silicon nitride film etching solutions, the fluorine-containing compound provided in the form of an ionic liquid has a higher boiling point and decomposition temperature than hydrogen fluoride or ammonium fluoride which is usually used as a fluorine-containing compound, and thus has a high temperature. There is an advantage that there is little possibility of changing the composition of the etching solution due to decomposition during the etching step performed in 1.

According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor device, which is carried out using the above-mentioned silicon nitride film etching solution.

According to this manufacturing method, it is possible to manufacture a semiconductor device by performing a selective etching step on a silicon nitride film using the etching solution described above on a silicon substrate containing at least a silicon nitride film.

The silicon substrate used for manufacturing the semiconductor element may include a silicon nitride film, or may contain both a silicon oxide film and a silicon nitride film. Further, in the case of a silicon substrate containing both a silicon oxide film and a silicon nitride film, the silicon oxide film and the silicon nitride film may be alternately laminated or may be laminated in different regions.

The method for manufacturing a semiconductor device according to the present invention can be applied to a manufacturing process for a NAND device. More specifically, by using the etching solution described above in a process step in which the selective removal of the silicon nitride film is required without loss to the silicon oxide film among the laminated structures for forming the NAND. It can be carried out.

As an example, FIG. 1 is a schematic cross-sectional view for explaining a step of removing a silicon nitride film using an etching solution according to the present invention.

Referring to FIG. 1, a mask pattern layer 30 is formed on a laminated structure 20 in which a silicon nitride film 11 and a silicon oxide film 12 are alternately laminated on a silicon substrate 10, and then a trench is formed through an anisotropic etching step. 50 is formed.

Further, referring to FIG. 1, the etching solution according to the present invention is injected through the trench 50 region formed in the laminated structure 20, whereby the silicon nitride film 11 is etched, and the silicon oxide film 12 and the mask are used. Only the pattern layer 30 remains.

That is, the present invention minimizes the etching of the silicon oxide film 12 in the laminated structure 20 by using an etching solution having an improved etching selectivity for the silicon nitride film with respect to the silicon oxide film, and silicon in a sufficient time. The nitride film 11 can be completely and selectively removed. After that, the semiconductor device can be manufactured through a subsequent step including a step of forming a gate electrode in the removed region of the silicon nitride film 11.

Hereinafter, specific examples of the present invention will be presented. However, the examples described below are merely for exemplifying or explaining the present invention, and the present invention should not be restricted by this.

Example
Production of Etching Solution In Example 1, the compound represented by Chemical formula 1 was added, and in Example 2, the compound represented by Chemical formula 2 was added to the phosphoric acid aqueous solution so that the initial concentration was 500 ppm. Manufactured.

The etching solution composition according to Examples 1 and 2 is as shown in Table 1.

The etching solution composition according to Comparative Examples 1 to 3 is shown in Table 2.

Experimental example
Measurement of Average Diameter of Silicon-based Particles The average diameter of silicon-based particles present in the etching solutions of Examples 1 and 2 and Comparative Examples 2 and 3 was measured over time at room temperature (25 ° C.). The average diameter of the silicon-based particles was measured using PAS (particle size particle). The average diameter of the measured silicon particles is shown in Table 3 below.

As shown in Table 3 above, it can be confirmed that the etching solutions of Examples 1 and 2 have almost no silicon-based particles even after a lapse of time.

On the other hand, as shown in Table 3 above, in the etching solutions of Comparative Examples 2 and 3, it can be confirmed that silicon-based particles having a diameter of 5 μm or more are present over time.

Measurement of Etching Rate of Silicon Oxide Film and Silicon Nitride Film The silicon nitride film etching solution according to Examples 1 and 2 and Comparative Examples 1 to 3 is applied to a silicon oxide film (thermal oxide layer) having a thickness of 500 Å at 175 ° C. Was immersed in a heated etching solution and etched for 10 minutes.

Before and after etching, the thickness of the silicon oxide film and the silicon nitride film is determined by ellipsometry (Nano-View, SE).
It is measured using MG-1000; Ellipometry), and the etching rate is a numerical value calculated by dividing the difference in thickness between the silicon oxide film and the silicon nitride film by the etching time (10 minutes) before and after etching. Is.

The measured etching rates are shown in Table 4 below.

As shown in Table 4 above, the etching solutions of Examples 1 and 2 can reduce the etching rate with respect to the silicon oxide film as compared with the etching solutions of Comparative Examples 1 to 3, thereby forming a silicon oxide film. On the other hand, it can be confirmed that the etching selectivity for the silicon nitride film is improved.

In the above, one embodiment of the present invention has been described, but any person having ordinary knowledge in the technical field can add components within the range not deviating from the idea of the present invention described in the claims. The present invention can be modified and changed in various ways by modification, deletion, addition, etc., and it can be said that this is also included in the scope of rights of the present invention.

10 Silicon substrate 11 Silicon nitride film 12 Silicon oxide film 20 Laminated structure 30 Mask pattern layer 50 Trench

Claims (9)

Phosphoric acid aqueous solution;
Containing at least one of the compounds represented by Chemical formula 1 or Chemical formula 2 below;
Silicon nitride film etching solution:

In the above-mentioned 1 and the above-mentioned 2
X ₁ and X ₂ are independently selected from nitrogen, oxygen and sulfur, respectively.
Y ₁ and Y ₂ are independently selected from hydrogen, halogen, alkoxy group, amine, and hydroxy group, respectively.
a and b are 1 to 4 independently of each other. The compound represented by Chemical formula 1 is characterized by being a compound represented by Chemical formula 3 below, or is characterized by being a compound represented by Chemical formula 3.
The silicon nitride film etching solution according to claim 1:

In the above-mentioned 3
Y ₁ and a are as defined above of 1. The compound represented by the above-mentioned Chemical formula 2 is a compound represented by the following Chemical formula 4.
The silicon nitride film etching solution according to claim 1:

In the above 4
Y ₂ and b are as defined in Chemical formula 2 above. Among the silicon nitride film etching solutions, the compound represented by the above-mentioned Chemical formula 1 is characterized by being contained in an amount of 100 to 500,000 ppm.
The silicon nitride film etching solution according to claim 1. The silicon nitride film etching solution further contains at least one fluorine-containing compound selected from hydrogen fluoride, ammonium fluoride, ammonium bicarbonate, and ammonium hydrogen fluoride.
The silicon nitride film etching solution according to claim 1. The pre-silicon nitride film etching solution further contains a fluorine-containing compound having an ion-bonded form of an organic cation and a fluorine-based anion.
The silicon nitride film etching solution according to claim 1. The organic cations include alkyl-imidazolium, dialkyl-imidazolium, alkyl-pyridinium, alkylpyrrolidinium, alkylphosphonium, and alkylphosphonium. It is characterized in that it is at least one selected from alkylmorpholinium (Alkyl-morpholinium) and alkylpiperidinium (Alkyl-piperidinium).
The silicon nitride film etching solution according to claim 6. The fluorine-based anion is at least one selected from fluorophosphate, fluoroalkyl-fluorophosphate, fluoroborate, and fluoroalkyl-fluoroborate. Characterized by being one,
The silicon nitride film etching solution according to claim 6. A method for manufacturing a semiconductor device, which comprises an etching step performed by using the silicon nitride film etching solution according to claim 1.

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