KR20210033155A - Etching solution for silicon nitride layer and method for preparing semiconductor device using the same - Google Patents

Abstract

The present invention relates to a silicon nitride film etching solution and to a production method of a semiconductor device using the same and, more specifically, to a silicon nitride film etching solution which secures appropriate solubility, is not easily decomposed at low temperature, is easily decomposed under etching conditions to prevent growth as silicon-based particles, and is capable of increasing the selectivity for a silicon nitride film compared to a silicon oxide film, and to a production method of a semiconductor device performed using the same.

Description

Silicon nitride etching solution and a method of manufacturing a semiconductor device using the same {ETCHING SOLUTION FOR SILICON NITRIDE LAYER AND METHOD FOR PREPARING SEMICONDUCTOR DEVICE USING THE SAME}

The present invention relates to a silicon nitride film etching solution and a method of manufacturing a semiconductor device using the same, and more particularly, to a silicon nitride film etching solution that prevents the generation of particles and increases the selectivity for the silicon nitride film compared to the silicon oxide film, and performed using the same. It relates to a method of manufacturing a semiconductor device.

Currently, there are several methods of etching the silicon nitride layer, and dry etching and wet etching are mainly used methods.

The dry etching method is generally an etching method using a gas, and has the advantage of superior isotropy to the wet etching method, but the wet etching method is widely used in that the productivity is much lower than that of the wet etching method and is an expensive method.

In general, as a wet etching method, a method of using phosphoric acid as an etching solution is well known. In this case, if only pure phosphoric acid is used for etching the silicon nitride layer, problems such as various defects and pattern abnormalities may occur as the device is refined, and as the silicon nitride layer as well as the silicon oxide layer is etched, a protective layer is formed on the silicon oxide layer. It is necessary to further lower the etching rate of the silicon oxide film.

An object of the present invention is to provide a silicon nitride etching solution that prevents particle generation and increases a selectivity for a silicon nitride layer compared to a silicon oxide layer under etching conditions.

In addition, an object of the present invention is to provide a method of manufacturing a semiconductor device performed using the above-described silicon nitride etching solution.

In order to solve the above-described technical problem, according to an aspect of the present invention, the silicon nitride film etching solution includes an aqueous phosphoric acid solution and a compound represented by Formula 1 below.

[Formula 1]

In Formula 1,

The dotted line represents a single bond or a double bond,

Y ₁ is selected from oxygen and sulfur,

Y ₂ is selected from oxygen, sulfur and a hydroxy group (-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 addition, according to another aspect of the present invention, a method of manufacturing a semiconductor device performed using the above-described silicon nitride etching solution is provided.

Since the silicon nitride etching solution according to the present invention contains the compound represented by Chemical Formula 1, the reactivity with water or acid is lowered, so that growth of silicon-based particles can be prevented at room temperature and low temperature.

In addition, since the silicon nitride etching solution according to the present invention contains the compound represented by Chemical Formula 1, the etching selectivity for the silicon nitride layer compared to the silicon oxide layer may be increased.

1 is a cross-sectional view schematically illustrating a silicon nitride film removal process using an etching solution according to an embodiment of the present invention.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the following embodiments. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only the present embodiments are intended to complete the disclosure of the present invention, and common knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to those who have, and the invention is only defined by the scope of the claims.

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

According to an aspect of the present invention, there is provided a silicon nitride etching solution including an aqueous phosphoric acid solution and a compound represented by Formula 1 below.

[Formula 1]

In Formula 1,

The dotted line represents a single bond or a double bond,

Y ₁ is selected from oxygen and sulfur,

Y ₂ is selected from oxygen, sulfur and a hydroxy group (-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.

As used herein, alkoxy refers to both an -O-(alkyl) group and an -O-(unsubstituted cycloalkyl) group, and has at least one ether group 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, cyclopentyloxy, cyclohexyloxy, and the like, but are not limited thereto.

Halogen herein means fluoro (-F), chloro (-Cl), bromo (-Br) or iodo (-I).

In general, a silicon additive may be included in the silicon nitride etching solution to protect the silicon oxide layer from the phosphoric acid aqueous solution. However, the silane compound, which is mainly used as a silicone additive, basically has low solubility in an etching solution containing phosphoric acid. In order to increase the solubility of the silane compound in the etching solution, a silane compound in which a hydrophilic functional group is bonded to a silicon atom is used.

When a silane compound in which a hydrophilic functional group is bonded to a silicon atom is used as a silicone additive, an appropriate solubility of the silane compound in the etching solution can be secured, but it can be easily decomposed and grown into silicone-based particles. When the silicon-based particles are grown, it acts as the biggest cause of the failure of the silicon substrate, and the etch selectivity for the silicon nitride layer compared to the silicon oxide layer decreases.

In addition, a silane compound in which an alkyl group, a cycloalkyl group, or an aminoalkyl group is bonded to a silicon atom may be used to ensure proper solubility of the silane compound and to prevent it from being easily decomposed at low temperature. However, the compound still does not decompose even under high temperature etching conditions, so it is not possible to sufficiently form a passivation layer of the silicon oxide layer, and thus, the effect of increasing the etching selectivity for the silicon nitride layer compared to the silicon oxide layer is insufficient. It is done.

The silicon nitride etching solution according to an embodiment of the present invention secures an appropriate solubility, is not easily decomposed at low temperatures to prevent growth as silicon-based particles, and is easily decomposed under high temperature etching conditions, so that the selectivity for the silicon nitride layer is compared to the silicon oxide layer. It includes a compound represented by the following formula (1) in order to increase.

[Formula 1]

In Formula 1,

The dotted line represents a single bond or a double bond,

Y ₁ is selected from oxygen and sulfur,

Y ₂ is selected from oxygen, sulfur and a hydroxy group (-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 Formula 1, a sulfolene or phosphorene group bonded to a silicon atom exhibits polarity. The compound represented by Chemical Formula 1 includes a silicon atom to which a polar sulforene group or a phosphorene group is bonded, thereby ensuring an appropriate solubility of the silane compound in the etching solution.

In particular, while the compound represented by Formula 1 is not easily decomposed at low temperature, it can be easily decomposed under high temperature etching conditions. Under high-temperature etching conditions, the compound is decomposed into silicic acid and combined with the silicon oxide layer to form a protective layer, thereby protecting the silicon oxide layer from the phosphoric acid aqueous solution, increasing the etching rate of the silicon nitride layer, and increasing the etching rate of the silicon oxide layer. Can be lowered.

For example, the compound represented by Formula 1 may be reacted according to the following Reaction Scheme 1 or Scheme 2 under high temperature etching conditions.

[Scheme 1]

[Scheme 2]

As shown in Scheme 1 and Scheme 2, the compound represented by Formula 1 has a cyclic structure and contains a sulfoene group or a phosphorene group including a double bond. Since the sulforene group and the phosphorene group exhibit a double bonded cyclic structure, the cyclic structure can be opened under high temperature etching conditions. As the cyclic structures of the sulforene group and the phosphorene group are opened, the silicon atom of the compound reacts with an oxygen atom in the phosphoric acid aqueous solution to decompose into silic acid, and the silic acid may combine with the silicon oxide film to form a protective film.

In addition, as an example, the compound represented by Formula 1 may be a compound represented by Formulas 2 to 9 below.

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

[Formula 9]

In Chemical Formulas 2 to 9,

Y ₂ is selected from oxygen and sulfur,

Z and Y ₁ are as defined in Chemical Formula 1.

Here, the compounds represented by Chemical Formulas 2 to 9 include at least one sulfoene group or phosphorene group bonded to a silicon atom, so that the formation of a siloxane group formed by polymerization of a silicon-hydroxy group can be further suppressed. In addition, growth as silicon-based particles in which siloxane groups are repeatedly polymerized can be prevented more effectively.

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

The compound represented by Formula 1 is preferably present in an amount of 100 to 600,000 ppm in the silicon nitride etching solution. In addition, it is more preferable that the compound represented by Chemical Formula 1 is present at 1,000 to 150,000 ppm in the silicon nitride etching solution. Here, the content of the additive is the amount of the compound represented by Formula 1 dissolved in the etching solution of the silicon nitride layer, and is expressed as a unit of ppm.

For example, the presence of 5,000 ppm of the compound represented by Formula 1 in the silicon nitride etching solution will mean that the compound represented by Formula 1 dissolved in the silicon nitride etching solution is 5,000 ppm.

When the compound represented by Formula 1 is present in an amount of less than 100 ppm in the silicon nitride etching solution, the amount of the silicon compound is insufficient under the etching conditions, and thus the effect of increasing the etching selectivity for the silicon nitride layer compared to the silicon oxide layer may be insufficient.

On the other hand, when the compound represented by Formula 1 in the silicon nitride etching solution exceeds 600,000 ppm, a problem of generating a large amount of silicon-based particles may occur due to an increase in the saturation concentration of the silicon additive in the silicon nitride etching solution.

The silicon substrate preferably includes at least a silicon oxide film (SiO _x ), and may include a silicon oxide film and a silicon nitride film (Si _x N _y , SI _x O _y N _z ) at the same time. Also. In the case of a silicon substrate including a silicon oxide layer and a silicon nitride layer at the same time, a silicon oxide layer and a silicon nitride layer may be alternately stacked or stacked on different regions.

Silicon oxide film is SOD (Spin On Dielectric) film, HDP (High Density Plasma) film, thermal oxide film, BPSG (Borophosphate Silicate Glass) film, PSG (Phospho Silicate Glass) film, BSG according to the use and type of material. (BoroSilicate Glass) film, PSZ (Polysilazane) film, FSG (Fluorinated Silicate Glass) film, LP-TEOS (Low Pressure TetraEthyl Ortho Silicate) film, PETEOS (Plasma Enhanced Tetra Ethyl Ortho Silicate) film, HTO (High Temperature Oxide) film, MTO (Medium Temperature Oxide) film, USG (Undopped Silicate Glass) film, SOG (Spin On Glass) film, APL (Advanced Planarization Layer) film, 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 embodiment, the phosphoric acid aqueous solution is preferably contained in an amount of 60 to 90 parts by weight based on 100 parts by weight of the silicon nitride etching solution.

When the amount of the phosphoric acid aqueous solution is less than 60 parts by weight based on 100 parts by weight of the silicon nitride etching solution, there is a concern that the silicon nitride layer may not be sufficiently etched or the process efficiency of etching the silicon nitride layer may be deteriorated due to a decrease in the etching rate of the silicon nitride layer.

On the other hand, when the amount of phosphoric acid aqueous solution exceeds 90 parts by weight per 100 parts by weight of the silicon nitride etching solution, the increase in the etching rate of the silicon oxide layer is large compared to the increase in the etching rate of the silicon nitride layer, so that the etching option for the silicon nitride layer is greater than that of the silicon oxide layer. The ratio may be reduced, and defects of the silicon substrate may be caused due to the etching of the silicon oxide layer.

The silicon nitride film etching solution according to an embodiment of the present invention further comprises a fluorine-containing compound to compensate for the etching rate of the silicon nitride film, which decreases due to the containing the compound represented by Formula 1, and to improve the overall efficiency of the etching process. Can include.

Fluorine-containing compounds herein refer to any type of compound capable of dissociating fluorine ions.

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

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

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

In another example, the fluorine-containing compound is alkylpyrrolium, alkylimidazolium, alkylpyrazolium, alkyloxazolium, alkylthiazolium, alkylpyridinium, alkylpyrimidinium, alkylpyridazinium, alkylpyra Organic cations and fluorophosphates selected from genium, alkylpyrrolidinium, alkylphosphonium, alkylmorpholinium, dialkylimidazolium, and alkylpiperidinium, fluoroalkyl-fluorophosphate, fluoro A fluorine-based anion selected from borate and fluoroalkyl-fluoroborate may be an ionic liquid in an ion-bonded form.

Compared to hydrogen fluoride or ammonium fluoride commonly used as fluorine-containing compounds in silicon nitride etching solutions, fluorine-containing compounds, which are provided in ionic liquid form, have a higher boiling point and decomposition temperature, and are decomposed during the etching process performed at high temperatures. Accordingly, there is an advantage that there is little concern about changing the composition of the etching solution.

According to another aspect of the present invention, a method of manufacturing a semiconductor device performed using the above-described silicon nitride etching solution is provided.

According to the present manufacturing method, it is possible to manufacture a semiconductor device by performing a selective etching process on the silicon nitride layer using the above-described etching solution on a silicon substrate including at least a silicon nitride layer (SI _x N _{y ).}

A silicon substrate used for manufacturing a semiconductor device may include a silicon nitride film (SI _x N _y ) or a silicon oxide film and a silicon nitride film (Si _x N _y , SI _x O _y N _z ) at the same time. Also. In the case of a silicon substrate including a silicon oxide layer and a silicon nitride layer at the same time, a silicon oxide layer and a silicon nitride layer may be alternately stacked or stacked on different regions.

The method of manufacturing a semiconductor device according to the present invention can be applied to a manufacturing process of a NAND device. More specifically, it may be performed by using the above-described etching solution in a process step in which the silicon nitride layer is required to be selectively removed without loss of the silicon oxide layer among the stacked structures for NAND formation.

As an example, FIG. 1 is a schematic cross-sectional view illustrating a silicon nitride film removal process using an etching solution according to the present invention.

Referring to FIG. 1, after forming a mask pattern layer 30 on a stacked structure 20 in which a silicon nitride layer 11 and a silicon oxide layer 12 are alternately stacked on a silicon substrate 10, an anisotropic etching process is performed. Through the trench 50 is formed.

In addition, referring to FIG. 1, an etching solution according to the present invention is injected through a region of a trench 50 formed in the stacked structure 20, and accordingly, the silicon nitride layer 11 is etched, and the silicon oxide layer 12 and the mask Only the pattern layer 30 remains.

That is, the present invention minimizes the etching of the silicon oxide layer 12 in the layered structure 20 by using an etching solution having an improved etch selectivity for the silicon nitride layer compared to the silicon oxide layer, and completely and selectively makes the silicon nitride layer 11 for a sufficient time. Can be removed. Thereafter, a semiconductor device may be manufactured through a subsequent process including forming a gate electrode in a region from which the silicon nitride layer 11 has been removed.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only for illustrating or explaining the present invention in detail, and the present invention is not limited thereto.

Example

Etching Preparation of solution

In Examples 1 to 8, an etching solution was prepared so that the initial concentration was 150 ppm by adding the compound represented by Formula 1 to an aqueous phosphoric acid solution.

Etching solution compositions according to Examples 1 to 8 are shown in Table 1.

Etch Solution Composition Compound of formula 1



Example 1 Phosphoric acid aqueous solution
(85% by weight)
+
Compound of formula 1
(0.015
weight%)
+
Balance water

Example 2


"

Example 3



"

Example 4


"

Example 5


"

Example 6


"

Example 7


"

Example 8




"

The etching solution compositions according to Comparative Examples 1 to 3 are shown in Table 2.

Etch Solution Composition additive

Comparative Example 1 Phosphoric acid aqueous solution
(85% by weight)
+
Balance water

-



Comparative Example 2




Phosphoric acid aqueous solution
(85% by weight)
+
additive
(0.015% by weight)
+
Balance water

Comparative Example 3

Experimental example

Silicon oxide film and silicon Nitrided Etching Speed measurement

The silicon nitride layer etching solutions according to Examples 1 to 8 and Comparative Examples 1 to 3 were immersed in a 500 Å-thick silicon oxide layer and a silicon nitride layer in a heated etching solution at 175°C and etched for 10 minutes.

The thickness of the silicon oxide layer and the silicon nitride layer before and after etching was measured using an ellipsometric tree (Nano-View, SE MG-1000; Ellipsometery), and the etching rate was the difference between the thickness of the silicon oxide layer and the silicon nitride layer before and after etching. Is a value calculated by dividing by the etching time (10 minutes).

The measured etching rates are shown in Table 3 below.

/min)Silicon oxide film
Etch rate(

/min) Silicon nitride film
Etch rate(

/min) Etch selectivity
(Silicone nitride film etch rate/ Silicon oxide film etch rate) Example 1 0.11 93.99 854.45 Example 2 0.23 93.23 405.35 Example 3 0.10 94.01 940.10 Example 4 0.13 94.02 723.23 Example 5 0.14 94.05 671.79 Example 6 0.12 94.14 784.50 Example 7 0.13 94.13 724.08 Example 8 0.15 95.02 644.47 Comparative Example 1 5.17 94.33 18.25 Comparative Example 2 4.75 95.11 20.02 Comparative Example 3 2.33 94.83 40.70

As shown in Table 3, the etching solutions of Examples 1 to 8 can lower the etching rate for the silicon oxide layer compared to the etching solutions of Comparative Examples 1 to 3, and accordingly, the etching selectivity for the silicon nitride layer compared to the silicon oxide layer is It can be seen that it is improved.

As described above, one embodiment of the present invention has been described, but those of ordinary skill in the relevant technical field add, change, delete or add components within the scope not departing from the spirit of the present invention described in the claims. Various modifications and changes can be made to the present invention by means of the like, and it will be said that this is also included within the scope 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; And
Including a compound represented by the following formula (1);
Silicon nitride film etching solution:

[Formula 1]

In Chemical Formula 1,
The dotted line represents a single bond or a double bond,
Y ₁ is selected from oxygen and sulfur,
Y ₂ is selected from oxygen, sulfur and a hydroxy group (-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 method of claim 1,
The compound represented by Formula 1 is a silicon nitride film etching solution, characterized in that it is selected from compounds represented by the following Formulas 2 to 9:

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

[Formula 9]

In Chemical Formulas 2 to 9,
Y ₂ is selected from oxygen and sulfur,
Z and Y ₁ are as defined in Chemical Formula 1.
The method of claim 1,
In the silicon nitride layer etching solution, the compound represented by Chemical Formula 1 is contained in an amount of 100 to 600,000 ppm.
Silicon nitride film etching solution.
The method of claim 1,
The silicon nitride etching solution further comprises at least one fluorine-containing compound selected from hydrogen fluoride, ammonium fluoride, ammonium bifluoride, and ammonium hydrogen fluoride,
Silicon nitride film etching solution.
The method of claim 1,
The silicon nitride film etching solution further comprises a fluorine-containing compound having an ion-bonded form of an organic cation and a fluorine-based anion,
Silicon nitride film etching solution.
The method of claim 5,
The organic cations are Alkyl-imidazolium, DiAlkyl-imidazolium, Alkyl-Pyridinium, Alkyl-pyrrolidinium, and Alkylphosphonium (Alkyl-phosphonium), alkylmorpholinium (Alkyl-morpholinium) and alkyl piperidinium (Alkyl-piperidinium) characterized in that at least one selected from
Silicon nitride film etching solution.
The method of claim 5,
The fluorine-based anion is at least one selected from fluorophosphate, fluoroalkyl-fluorophosphate, fluoroborate, and fluoroalkyl-fluoroborate.
Silicon nitride film etching solution.
A method of manufacturing a semiconductor device including an etching process performed using the silicon nitride film etching solution according to claim 1.

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