JP2021048389A - Silicon nitride film etching solution and manufacturing method for semiconductor device using the same - Google Patents

Abstract

To provide silicon nitride film etching solution that in manufacturing a semiconductor device, prevents occurrence of particles and increases a selection ratio of a silicone oxide film with respect to a silicon nitride film on an etching condition.SOLUTION: Silicon nitride film etching solution includes aqueous phosphoric acid solution and a chemical compound of the following formula. In the formula, a dotted line shows a single bond or double bond, Y1 is selected from oxygen and sulfur, Y2 is selected from oxygen, sulfur, and hydroxy group (-OH), X is selected from sulfur and phosphorus, Z is selected from hydrogen, halogen, alkoxy group, and hydroxy group (-OH), and A is 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 although it has an advantage of being more isotropic than the wet etching method, it is too inferior in productivity to the wet etching method and is an expensive method. , 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 an aqueous phosphoric acid solution and the compound represented by Chemical formula 1 below.

[Chemical 1]

In the above 1
Dotted lines indicate single or double bonds
Y ₁ is selected from oxygen and sulfur,
Y ₂ is selected from oxygen, sulfur, and hydroxy groups (-OH).
X is selected from sulfur and phosphorus,
Z is selected from hydrogen, halogen, alkoxy group, and hydroxy group (-OH).
A is 1 to 4.

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 the compound represented by Chemical formula 1, the reactivity with water or acid is lowered, and the growth as silicon-based particles can be prevented at room temperature and low temperature.

Further, the silicon nitride film etching solution according to the present invention can increase the etching selectivity for the silicon nitride film with respect to the silicon oxide film by containing the compound represented by Chemical formula 1.

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 the compound represented by the following Chemical formula 1.

[Chemical 1]

In the above 1
Dotted lines indicate single or double bonds
Y ₁ is selected from oxygen and sulfur,
Y ₂ is selected from oxygen, sulfur, and hydroxy groups (-OH).
X is selected from sulfur and phosphorus,
Z is selected from hydrogen, halogen, alkoxy group, and hydroxy group (-OH).
A is 1 to 4.

Alkoxy in the present application means both an -O- (alkyl) group and an -O- (unsubstituted cycloalkyl) group, which comprises one or more ether groups and 1 to 10 carbon atoms. Have. 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 and silicon is used. It can be grown as a system particle. When silicon-based particles are grown, they act on the biggest cause of defects in the silicon substrate, and the etching selectivity of the silicon oxide film to the silicon nitride film is reduced.

Further, a silane compound in which an alkyl group, a cycloalkyl group, or an aminoalkyl group is bonded to a silicon atom can be used so as to secure appropriate solubility of the silane compound and prevent it from being easily decomposed at a low temperature. 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.

The silicon nitride film etching solution according to one embodiment of the present invention ensures proper solubility, is not easily decomposed at low temperature, prevents growth as silicon-based particles, and is easily decomposed under high temperature etching conditions. The compound represented by the following formula 1 is included in order to increase the selectivity of the silicon oxide film with respect to the silicon nitride film.

[Chemical 1]

In the above 1
Dotted lines indicate single or double bonds
Y ₁ is selected from oxygen and sulfur,
Y ₂ is selected from oxygen, sulfur, and hydroxy groups (-OH).
X is selected from sulfur and phosphorus,
Z is selected from hydrogen, halogen, alkoxy group, and hydroxy group (-OH).
A is 1 to 4.

In the above-mentioned Chemical formula 1, the sulfolene group or the phosphorene group bonded to the silicon atom shows polarity. The compound represented by the above-mentioned Chemical formula 1 contains a silicon atom to which a polar sulfolene group or a phosphorene group is bonded, so that the proper solubility of the silane compound in the etching solution can be ensured.

In particular, the compound represented by Chemical formula 1 is not easily decomposed at a low temperature, but can be easily decomposed under high temperature etching conditions. The compound under high temperature etching conditions is silicic acid.
It is decomposed into acid) and combined with the silicon oxide film to form a protective film, thereby protecting the silicon oxide film from the aqueous phosphoric acid solution, increasing the etching rate of the silicon nitride film, and increasing the etching rate of the silicon oxide film. Can be lowered.

As an example, the compound represented by Chemical formula 1 may be reacted by the following reaction formula 1 or reaction formula 2 under high temperature etching conditions.

[Reaction formula 1]

[Reaction equation 2]

As shown in Reaction Scheme 1 and Reaction Scheme 2, the compound represented by Chemical formula 1 has a ring structure and contains a sulfolene group or a phosphorene group containing a double bond. The sulfolene group and the phosphorene group show a ring structure of a double bond, so that the ring structure is open (ring) under high temperature etching conditions.
opening) is possible. By opening the ring structure of the sulfolene group and the phosphorene group, the silicon atom of the compound reacts with the oxygen atom in the phosphoric acid aqueous solution and is decomposed into silicic acid, and the silicic acid is bonded to the silicon oxide film. A protective film can be formed.

Further, as an example, the compound represented by Chemical formula 1 may be a compound represented by Chemical formulas 2 to 9 below.

[Chemical 2]

[Chemical 3]

[Chemical 4]

[Chemical 5]

[Chemical 6]

[Chemical 7]

[Chemical 8]

[Chemical 9]

In the above-mentioned formations 2 to 9,
Y ₂ is selected from oxygen and sulfur,
Z and Y ₁ are as defined in Chemical formula 1 above.

Here, the compound represented by the above-mentioned compounds 2 to 9 further contains at least one sulfolene group or phosphorene group bonded to a silicon atom to further form a siloxane group formed by polymerization of a silicon-hydroxy group. It can be suppressed, and the growth of silicon-based particles in which siloxane groups are repeatedly polymerized can be prevented more effectively.

More specifically, the compound represented by Chemical formula 1 may be any of the compounds represented by the following compounds 1-1 to 1-21.

The compound represented by Chemical formula 1 described above is preferably present in the silicon nitride film etching solution at 100 to 600,000 ppm. Further, it is more preferable that the compound represented by Chemical formula 1 described above is present in the silicon nitride film etching solution at 1,000 to 150,000 ppm. 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 at 5,000 ppm in the silicon nitride film etching solution means that the compound represented by Chemical formula 1 dissolved in the silicon nitride film etching solution is 5,000 ppm. Means that

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 not sufficient under the etching conditions, and the etching selectivity ratio of the silicon oxide film to the silicon nitride film is insufficient. The increasing effect of is weak.

On the other hand, when the amount of the compound represented by Chemical formula 1 in the silicon nitride film etching solution exceeds 600,000 ppm, a large amount of silicon-based particles are generated due to the increase in the saturation concentration of the silicon additive in the silicon nitride film etching solution. Problems can arise.

The silicon substrate preferably contains at least a silicon oxide film (SiO _x ), and may contain both a silicon oxide film and a silicon nitride film (Si _x N _y , SI _x O _y N _z ). 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 Tera)
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 film, PE-oxide film (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 increase in the etching rate of the silicon oxide film is compared with the increase in the etching rate of the silicon nitride film. The etching selectivity for the silicon nitride film with respect to the silicon oxide film may decrease, and the etching of the silicon oxide film may cause a defect in the silicon substrate.

The silicon nitride film etching solution according to one 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. It may further contain a fluorine-containing compound.

Fluorine-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 generally used as a fluorine-containing compound, and 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, a semiconductor device can be manufactured by performing a selective etching step on a silicon nitride film using the above-mentioned etching solution on a silicon substrate containing at least a silicon nitride film (SI _x N _y). It is possible.

The silicon substrate used for manufacturing a semiconductor device may contain a silicon nitride film (SI _x N _y ), or may contain both a silicon oxide film and a silicon nitride film (Si _x N _y , SI _x O _y N _z ). Good. 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 may 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 silicon nitride films 11 and silicon oxide films 12 are alternately laminated on a silicon substrate 10, and then a trench 50 is formed through an anisotropic etching step. 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, in the present invention, the etching of the silicon oxide film 12 in the laminated structure 20 is minimized by using an etching solution in which the etching selectivity of the silicon nitride film is improved with respect to the silicon oxide film, and the etching is minimized for a sufficient time. The silicon 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 Examples 1 to 8, the compound represented by Chemical formula 1 was added to the aqueous phosphoric acid solution to produce an etching solution so that the initial group concentration was 150 ppm.

The etching solution compositions according to Examples 1 to 8 are as shown in Table 1.

[Table 1]

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

[Table 2]

Experimental example
Measurement of Etching Rate of Silicon Oxide Film and Silicon Nitride Film The silicon nitride film etching solution according to Examples 1 to 8 and Comparative Examples 1 to 3 is heated at 175 ° C. to a silicon oxide film (thermal oxide layer) having a thickness of 500 Å and the silicon nitride film. It was immersed in the 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 3 below.

[Table 3]

As shown in Table 3 above, the etching solutions of Examples 1 to 8 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 (8)

Phosphoric acid aqueous solution;
Including the compound represented by the following Chemical formula 1.
Silicon nitride film etching solution:
[Chemical 1]

In the above 1
Dotted lines indicate single or double bonds
Y ₁ is selected from oxygen and sulfur,
Y ₂ is selected from oxygen, sulfur, and hydroxy groups (-OH).
X is selected from sulfur and phosphorus,
Z is selected from hydrogen, halogen, alkoxy group, and hydroxy group (-OH).
A is 1 to 4. The compound represented by Chemical formula 1 is selected from the compounds represented by Chemical formulas 2 to 9 below.
The silicon nitride film etching solution according to claim 1:
[Chemical 2]

[Chemical 3]

[Chemical 4]

[Chemical 5]

[Chemical 6]

[Chemical 7]

[Chemical 8]

[Chemical 9]

In the above-mentioned formations 2 to 9,
Y ₂ is selected from oxygen and sulfur,
Z and Y ₁ are as defined in Chemical formula 1 above. Among the silicon nitride film etching solutions, the compound represented by the above-mentioned Chemical formula 1 is characterized by being contained at 100 to 600,000 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 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-pyridinium).
The silicon nitride film etching solution according to claim 5. The fluorine-based anion is selected from 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 5. 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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