JP7496253B2 - Silicon nitride film etching solution and method for manufacturing semiconductor device using same - Google Patents

Description

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

Currently, there are various methods for etching silicon nitride films, but dry etching and wet etching are the most commonly used methods.

Dry etching is an etching method that usually uses gas, and has the advantage of being more isotropic than wet etching. However, it is less productive than wet etching and is a more expensive method, so wet etching is becoming more widely used.

A commonly known wet etching method is one that uses phosphoric acid as an etching solution. If only pure phosphoric acid is used to etch the silicon nitride film, as elements become finer, problems such as various defects and pattern abnormalities may occur due to etching of not only the silicon nitride film but also the silicon oxide film. 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.

The present invention aims to provide a silicon nitride film etching solution that prevents particle generation and increases the selectivity ratio of silicon nitride film to silicon oxide film under etching conditions.

The present invention also aims to provide a method for manufacturing semiconductor devices using the silicon nitride film etching solution described above.

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

[Chemical formula 1]

In the above formula 1,
The dotted lines indicate single or double bonds;
Y ₁ is selected from oxygen and sulfur;
_Y2 is selected from oxygen, sulfur, and a hydroxy group (—OH);
X is selected from sulfur and phosphorus;
Z is selected from hydrogen, halogen, an alkoxy group, and a hydroxy group (—OH);
A is 1 to 4.

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

The silicon nitride film etching solution of the present invention contains the compound represented by Chemical Formula 1, which reduces the reactivity with water or acid and prevents the growth of silicon-based particles at room temperature and low temperatures.

In addition, the silicon nitride film etching solution according to the present invention contains the compound represented by Chemical Formula 1, which can increase the etching selectivity of silicon nitride film relative to silicon oxide film.

1A to 1C are cross-sectional views each showing a silicon nitride film removal process using an etching solution according to an embodiment of the present invention;

The advantages and features of the present invention, as well as the methods for achieving them, will become clearer with reference to the following examples. However, the present invention is not limited to the examples disclosed below, and may be embodied in various different forms. However, the examples are provided to fully disclose the present invention and to fully inform those skilled in the art of the present invention of the scope of the invention, and the present invention is only defined by the scope of the claims.

The silicon nitride film etching solution of the present invention is described in detail below.

According to one aspect of the present invention, there is provided a silicon nitride film etching solution that contains an aqueous phosphoric acid solution and a compound represented by the following chemical formula 1.

[Chemical formula 1]

In the above formula 1,
The dotted lines indicate single or double bonds;
Y ₁ is selected from oxygen and sulfur;
_Y2 is selected from oxygen, sulfur, and a hydroxy group (—OH);
X is selected from sulfur and phosphorus;
Z is selected from hydrogen, halogen, an alkoxy group, and a hydroxy group (—OH);
A is 1 to 4.

In this application, alkoxy refers to both -O-(alkyl) and -O-(unsubstituted cycloalkyl) groups having one or more ether groups and 1 to 10 carbon atoms. Specific examples include, but are not limited to, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, tert-butoxy, sec-butoxy, n-pentoxy, n-hexoxy, 1,2-dimethylbutoxy, cyclopropyloxy, cyclobutyloxy, cyclopentyloxy, cyclohexyloxy, and the like.

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

Typically, a silicon additive may be included in the silicon nitride film etching solution to protect the silicon substrate from the phosphoric acid aqueous solution. However, the silane compounds that are mainly used as silicon additives basically have low solubility in etching solutions that contain phosphoric acid. To increase the solubility of silane compounds in etching solutions, silane compounds in which a hydrophilic functional group is bonded to a silicon atom are used.

In this way, when a silane compound in which a hydrophilic functional group is bonded to a silicon atom is used as a silicon additive, the silane compound can have an appropriate solubility in the etching solution, but it can easily decompose and grow into silicon-based particles. When silicon-based particles grow, they become the biggest cause of defects in silicon substrates, and the etching selectivity of silicon nitride film to silicon oxide film decreases.

In addition, in order to ensure the appropriate solubility of the silane compound and to prevent it from being easily decomposed at low temperatures, a silane compound having an alkyl group, a cycloalkyl group, or an aminoalkyl group bonded to a silicon atom can be used. However, the compound is still not decomposed even under high temperature etching conditions, and the passivation layer of the silicon oxide film is not easily decomposed.
As a result, the effect of increasing the etching selectivity of the silicon nitride film to the silicon oxide film is weak.

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

[Chemical formula 1]

In the above formula 1,
The dotted lines indicate single or double bonds;
Y ₁ is selected from oxygen and sulfur;
_Y2 is selected from oxygen, sulfur, and a hydroxy group (—OH);
X is selected from sulfur and phosphorus;
Z is selected from hydrogen, halogen, an alkoxy group, and a hydroxy group (—OH);
A is 1 to 4.

In the above formula 1, the sulfolene or phosphorene group bonded to the silicon atom exhibits polarity. The compound represented by the above formula 1 contains a silicon atom bonded to a polar sulfolene or phosphorene group, thereby ensuring the proper solubility of the silane compound in the etching solution.

In particular, the compound represented by Chemical Formula 1 is not easily decomposed at low temperatures, but is easily decomposed under high-temperature etching conditions.
The phosphoric acid is decomposed into ethyl phosphate (ETA), which bonds with the silicon oxide film to form a protective film, thereby protecting the silicon oxide film from the phosphoric acid solution, increasing the etching rate of the silicon nitride film, and decreasing the etching rate of the silicon oxide film.

As an example, the compound represented by Chemical Formula 1 above may undergo a reaction according to Reaction Scheme 1 or 2 below under high temperature etching conditions.

[Reaction Scheme 1]

[Reaction Scheme 2]

As shown in the above reaction formula 1 and reaction formula 2, the compound represented by Chemical formula 1 has a ring structure and contains a sulfolene group or a phospholene group containing a double bond. The sulfolene group and the phospholene group have a double bond ring structure, and therefore, the ring structure is opened (ring
As the ring structures of the sulfolene and phospholene groups are opened, the silicon atoms of the compounds react with the oxygen atoms in the phosphoric acid solution to decompose into silicic acid, which can then combine with the silicon oxide film to form a protective film.

As an example, the compound represented by Chemical formula 1 may be any of the compounds represented by Chemical formulas 2 to 9 below.

[Chemical formula 2]

[Chemical formula 3]

[Chemical formula 4]

[Chemical formula 5]

[Chemical formula 6]

[Chemical formula 7]

[Chemical formula 8]

[Chemical formula 9]

In the above formulas 2 to 9,
_Y2 is selected from oxygen and sulfur;
Z and _Y1 are as defined above in formula 1.

Here, the compounds represented by Chemical Formulas 2 to 9 contain at least one sulfolene group or phosphorene group bonded to a silicon atom, which can further suppress the formation of siloxane groups formed by polymerization of silicon-hydroxy groups, and can more effectively prevent the growth of silicon-based particles formed by repeated polymerization of siloxane groups.

More specifically, the compound represented by Chemical Formula 1 above may be any of the compounds represented by Compounds 1-1 to 1-21 below.

The compound represented by Chemical formula 1 is preferably present in the silicon nitride film etching solution at 100 to 600,000 ppm. The compound represented by Chemical formula 1 is more preferably 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 expressed in ppm units.

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

When the compound represented by Chemical Formula 1 is present in a silicon nitride film etching solution at less than 100 ppm, the amount of silicon compound may be insufficient under the etching conditions, and the effect of increasing the etching selectivity of silicon nitride film relative to silicon oxide film may be weak.

On the other hand, if the compound represented by Chemical Formula 1 in the silicon nitride film etching solution exceeds 600,000 ppm, the saturation concentration of the silicon additive in the silicon nitride film etching solution increases, which can cause a problem of a large amount of silicon-based particles being generated.

The silicon substrate preferably contains at least a silicon oxide film ( _SiOx ), and may contain both a silicon oxide film and a silicon nitride film (Si _x N _y , SI _x O _y N _z ). In addition, 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 laminated alternately or may be laminated in different regions.

Silicon oxide films are classified into SOD (Spin On Dielectric) films, HDP (High Density
Plasma film, thermal oxide film, BPSG (Borophosphate)
Silicate Glass film, PSG (Phospho Silicate Glass) film, BSG (Boro Silicate
Glass film, PSZ (Polysilazane) film, FSG (Fluorinated Silicate)
Glass) film, LP-TEOS (Low
Pressure Tetra Ethyl Ortho Silicate (PETEOS) film, Plasma Enhanced Tetra
Ethyl Ortho Silicate film, HTO (High Temperature Oxide) film, MTO (Medium
Temperature Oxide film, USG (Undoped 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 may be mentioned.

In one embodiment, it is preferable that the phosphoric acid aqueous solution is contained at 60 to 90 parts by weight per 100 parts by weight of the silicon nitride film etching solution.

If the content of phosphoric acid aqueous solution is less than 60 parts by weight per 100 parts by weight of silicon nitride film etching solution, the etching speed of the silicon nitride film may decrease, and the silicon nitride film may not be sufficiently etched or the efficiency of the silicon nitride film etching process may decrease.

On the other hand, if the content of phosphoric acid aqueous solution exceeds 90 parts by weight per 100 parts by weight of silicon nitride film etching solution, the increase in the etching rate of the silicon oxide film is greater than the increase in the etching rate of the silicon nitride film, which may reduce the etching selectivity of the silicon oxide film to the silicon nitride film and cause defects in the silicon substrate due to etching of the silicon oxide film.

The silicon nitride film etching solution according to one embodiment of the present invention may further contain a fluorine-containing compound to compensate for the reduced etching rate of the silicon nitride film due to the inclusion of the compound represented by Chemical Formula 1 and to improve the efficiency of the overall etching process.

In this application, a fluorine-containing compound refers to any compound in any form that dissociates fluoride ions.

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

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

For example, the fluorine-containing compound may be a compound in the form of an ionic bond between an alkyl ammonium and a fluorine-based anion. Here, the alkyl ammonium is an ammonium having at least one alkyl group, and may have up to four alkyl groups. The definition of the alkyl group is as described above.

In yet another example, the fluorine-containing compound may be an ionic liquid in the form of an ionic bond between an organic cation selected from alkylpyrroleum, alkylimidazolium, alkylpyrazolium, alkyloxazolium, alkylthiazolium, alkylpyridinium, alkylpyrimidinium, alkylpyridazinium, alkylpyrazinium, alkylpyrrolidinium, alkylphosphonium, alkylmorpholinium, dialkylimidazolium, and alkylpiperidinium and a fluorine-based anion selected from fluorophosphate, fluoroalkyl-fluorophosphate, fluoroborate, and fluoroalkyl-fluoroborate.

Compared to hydrogen fluoride or ammonium fluoride, which are commonly used fluorine-containing compounds in silicon nitride film etching solutions, fluorine-containing compounds provided in the form of ionic liquids have a high boiling point and decomposition temperature, and are therefore less likely to change the composition of the etching solution due to decomposition during the etching process, which is carried out at high temperatures.

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

According to this manufacturing method, it is possible to manufacture a semiconductor device by performing a selective etching process on a silicon nitride film (SI _x N _y ) on a silicon substrate including at least the silicon nitride film using the above-mentioned etching solution.

A silicon substrate used in manufacturing a semiconductor device _may include a silicon _nitride film ( _SIxNy ), or may include both a silicon oxide film and a silicon _nitride film ( _SixNy , _SIxOyNz ). In addition, in the case of a silicon substrate including both a silicon oxide film and a silicon nitride film, the silicon oxide film and the silicon _nitride film may be laminated alternately or may be laminated in different regions.

The method for manufacturing a semiconductor device according to the present invention may be applied to the manufacturing process of a NAND device. More specifically, the above-mentioned etching solution can be used in a process step that requires selective removal of a silicon nitride film without loss of a silicon oxide film in a stacked structure for forming a NAND.

As an example, FIG. 1 is a schematic cross-sectional view illustrating the process 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 stacked structure 20 in which silicon nitride films 11 and silicon oxide films 12 are alternately stacked on a silicon substrate 10, and then a trench 50 is formed through an anisotropic etching process.

Referring also to FIG. 1, an etching solution according to the present invention is applied through the trench 50 region formed in the stacked structure 20, thereby etching the silicon nitride film 11 so that only the silicon oxide film 12 and the mask pattern layer 30 remain.

That is, the present invention uses an etching solution with an improved etching selectivity for silicon oxide to silicon nitride, thereby minimizing the etching of the silicon oxide film 12 in the stacked structure 20 and completely and selectively removing the silicon nitride film 11 in a sufficient amount of time. Then, a semiconductor device can be manufactured through a subsequent process including a step of forming a gate electrode in the area where the silicon nitride film 11 has been removed.

Specific examples of the present invention are presented below. However, the examples described below are merely intended to specifically illustrate or explain the present invention, and should not be construed as limiting the present invention.

Example
Preparation of Etching Solution In Examples 1 to 8, the compound represented by Chemical formula 1 was added to an aqueous phosphoric acid solution to prepare an etching solution having an initial group concentration of 150 ppm.

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

[Table 1]

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

[Table 2]

Experimental Example
Measurement of Etching Rate of Silicon Oxide Layer and Silicon Nitride Layer The silicon nitride layer etching solutions according to Examples 1 to 8 and Comparative Examples 1 to 3 were heated at 175° C. to immerse a 500 Å-thick thermal oxide layer and a silicon nitride layer in the etching solutions, and etched for 10 minutes.

The thicknesses of the silicon oxide film and the silicon nitride film before and after etching were measured by ellipsometry (Nano-View, SE
The etching rate was calculated by dividing the difference in thickness between the silicon oxide film and the silicon nitride film before and after etching by the etching time (10 minutes).

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 of silicon oxide films compared to the etching solutions of Comparative Examples 1 to 3, and this confirms that the etching selectivity ratio of silicon oxide films to silicon nitride films is improved.

Although one embodiment of the present invention has been described above, a person having ordinary knowledge in the technical field can modify and change the present invention in various ways by adding, changing, deleting or adding components, etc., without departing from the concept of the present invention described in the claims, and this can also be said to be within the scope of the 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)

an aqueous solution of phosphoric acid; and
The compound represented by the following formula 1 is included:
Silicon nitride etching solution:
[Chemical formula 1]

In the above formula 1,
The dotted lines indicate single or double bonds;
Y ₁ is selected from oxygen and sulfur;
_Y2 is selected from oxygen, sulfur, and a hydroxy group (—OH);
X is selected from sulfur and phosphorus;
Z is selected from hydrogen, halogen, an alkoxy group, and a 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 formula 2]

[Chemical formula 3]

[Chemical formula 4]

[Chemical formula 5]

[Chemical formula 6]

[Chemical formula 7]

[Chemical formula 8]

[Chemical formula 9]

In the above formulas 2 to 9,
_Y2 is selected from oxygen and sulfur;
Z and _Y1 are as defined above in formula 1. The silicon nitride film etching solution contains the compound represented by Chemical Formula 1 in an amount of 100 to 600,000 ppm.
The silicon nitride film etching solution according to claim 1 . The silicon nitride film etching solution further includes at least one fluorine-containing compound selected from hydrogen fluoride, ammonium fluoride, ammonium bifluoride, and ammonium bifluoride;
The silicon nitride film etching solution according to claim 1 . The silicon nitride film etching solution further includes a fluorine-containing compound having an ionic bond between an organic cation and a fluorine-based anion.
The silicon nitride film etching solution according to claim 1 . The organic cation is at least one selected from alkylimidazolium, dialkylimidazolium, alkylpyridinium, alkylpyrrolidinium, alkylphosphonium, alkylmorpholinium, and alkylpiperidinium;
The silicon nitride film etching solution according to claim 5 . The fluorine-based anion is at least one selected from the group consisting of fluorophosphate, fluoroalkyl-fluorophosphate, fluoroborate, and fluoroalkyl-fluoroborate;
The silicon nitride film etching solution according to claim 5 . A method for manufacturing a semiconductor device, comprising an etching step performed using the silicon nitride film etching solution according to claim 1.

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