KR102311328B1 - Silicon nitride film etching method and manufacturing method of semiconductor device using the same - Google Patents

Abstract

The present invention relates to a silicon nitride film etching method and a method for manufacturing a semiconductor device using the same, and more particularly, to a silicon nitride film etching method using an etching composition containing a fluorine-containing compound in order to maintain a stable etching rate at a high temperature.

Description

BACKGROUND ART Silicon nitride film etching method and manufacturing method of semiconductor device using the same

The present invention relates to a silicon nitride film etching method and a method for manufacturing a semiconductor device using the same, and more particularly, to a silicon nitride film etching method using an etching composition containing a fluorine-containing compound in order to maintain a stable etching rate at a high temperature.

In a semiconductor manufacturing process, _{an oxide film such as a silicon oxide film (SiO 2} ) and a nitride film such as a silicon nitride film (SiN _x ) are used as representative insulating films, either singly or by alternately stacking one or more layers. The silicon nitride film is deposited through a chemical vapor deposition (CVD) process in a structure in contact with a silicon oxide film, a polysilicon film, and the surface of a silicon wafer, etc., which is removed through dry etching and wet etching. Etching is widely used.

In a wet etching process for removing the silicon nitride layer, a mixture of phosphoric acid and deionized water is generally used. The deionized water is added to prevent a decrease in an etch rate and a change in etch selectivity for the oxide film, but there is a problem in that a defect occurs in the etching removal process of the nitride film even with a slight change in the amount of deionized water supplied. In addition, phosphoric acid is a strong acid and has a corrosive property, so it is difficult to handle.

An object of the present invention is to provide a silicon nitride film etching method in which an etching rate is stably maintained in an etching process performed at a high temperature and the selectivity of a silicon nitride film/oxide film is not reduced during the etching process.

An object of the present invention is to provide an etching composition used in the etching method.

An object of the present invention is to provide a method of manufacturing a semiconductor device using the etching method.

The present invention comprises the steps of: a) preparing an etching composition comprising a fluorine-containing compound represented by the following formula (1);

[Formula 1]

CF ₃ (CF ₂ ) _n CH ₂ -R ₁

In Formula 1,

n is an integer from 1 to 10,

R ₁ is —OH or —NH ₂ ,

b) heating the etching composition; and

c) providing a silicon nitride layer etching method comprising the step of adding silver nitrate (AgNO _{3 ) to the heated etching composition:}

The present invention provides an etching composition used in the etching method.

The present invention provides a method of manufacturing a semiconductor device using the etching method.

The present invention provides a silicon nitride film etching method in which an etching composition including a fluorine-containing compound is prepared, heated, and silver nitrate is added to the heated etching composition, whereby fluorine ions are released even at high temperatures to maintain etching performance do.

In addition, the present invention provides the silicon nitride film etching method, so that the etching rate is maintained stably even in the etching process performed at a high temperature, the nitride film/oxide film selectivity is high, and the silicon nitride film etching method is excellent in the rapid etching of the nitride film and the etching suppression efficiency of the oxide film provides

Hereinafter, the present invention will be described in detail.

The embodiments described below are only for helping the understanding of the present invention, and the present invention is not construed as being limited to the following embodiments, and may be implemented in various different forms.

Conventionally, a technique for removing a nitride layer using an etching composition containing phosphoric acid (H ₃ PO ₄ ) and hydrofluoric acid (HF) or nitric acid (HNO ₃ ), etc. has been known, but rather the etching of the nitride layer and the oxide layer due to an increase in the etching rate of the oxide layer Problems that impede the selection ratio appear.

In addition, when an etching composition containing fluorine ions such as ammonium fluoride (NH ₄ F) or ammonium bifluoride (NH ₄ HF ₂ ) is used, the fluorine ions have poor stability at high temperatures. The phosphoric acid etching composition is used in a high-temperature process of 150 to 170. Although water molecules prevent the evaporation of hydrofluoric acid through hydrogen bonding, it is decomposed into ammonia and hydrofluoric acid as soon as it exceeds about 120 and evaporation occurs. Accordingly, as the temperature increases, the concentration of fluorine ions decreases, and the composition of the etching composition continues to change, thereby decreasing the etching rate and at the same time significantly reducing the silicon nitride/oxide layer selectivity.

In order to solve this problem, the present invention provides a silicon nitride film etching method comprising the following steps.

a) preparing an etching composition including a fluorine-containing compound represented by the following Chemical Formula 1;

[Formula 1]

CF ₃ (CF ₂ ) _n CH ₂ -R ₁

In Formula 1, n is an integer of 1 to 10, R ₁ is -OH or -NH ₂

b) heating the etching composition; and

c) A silicon nitride film etching method comprising the step of adding silver nitrate (AgNO _{3 ) to the heated etching composition.}

The fluorine-containing compound represented by Formula 1 has a high boiling point and is a stable compound that is not easily thermally decomposed at high temperatures. In addition, the fluorine-containing compound has a _{low dissociation constant because the conventional ammonium fluoride (NH 4} F), ammonium bifluoride (NH ₄ HF ₂ ), and the like do not release the fluorine component even at a high temperature. Therefore, until the etching composition is heated to a temperature for etching and silver nitrate is added, the fluorine component in the etching composition is not present. However, when silver nitrate is added when the etching composition is heated to reach a desired temperature, Chemical Formula 1 reacts with silver nitrate to start emitting a fluorine component.

That is, in the present invention, since the fluorine component does not exist in the composition while the etching composition is heated, there is no concern that the fluorine component necessary for etching is lost while the etching composition is heated. In addition, when the etching composition reaches a desired temperature, the fluorine component starts to dissociate from the moment the nitric acid reacts with the fluorine-containing compound is added, so that the concentration of the fluorine component can be maximized at a desired time point.

The present invention maximizes the concentration of the fluorine component in the heated etching composition, thereby having excellent etching ability and high selectivity for nitride/oxide layers.

In one embodiment of the present invention, in the fluorine-containing compound represented by Formula 1, n is an integer of 1 to 5, R ₁ may be —OH or —NH ₂ , and preferably R ₁ may be —OH. have. R ₁ may be easily dissolved in the etching composition by having a polar group.

In one embodiment of the present invention, the fluorine-containing compound represented by Formula 1 is 2,2,3,3,3-pentafluoro-1-propanol, 2,2,3,3,3-pentafluoropropane -1-amine and combinations thereof, preferably 2,2,3,3,3-pentafluoro-1-propanol.

In one embodiment of the present invention, the etching composition of step a) contains phosphoric acid containing the fluorine-containing compound represented by Formula 1 at a concentration of 100 to 3000 ppm, preferably at a concentration of 300 to 700 ppm with respect to the entire etching composition. It may be a solution.

When the content of the fluorine-containing compound is less than 100 ppm, the etching rate of the silicon nitride layer is not improved or the stability of the etching process is not maintained at a high temperature, so that there is a risk of generating foreign substances.

In addition, when the content of the fluorine-containing compound exceeds 3000 ppm, there is a problem of inhibiting the etching selectivity between the nitride layer and the oxide layer due to an increase in the etching rate of the oxide layer.

At this time, the phosphoric acid solution can be prepared as follows.

The fluorine-containing compound is added to phosphoric acid. In this case, the concentration of the fluorine component is determined according to how many fluorine atoms are included in the molecule of the fluorine-containing compound. For example, when 5 fluorine atoms are included in the molecule of the fluorine-containing compound, the concentration of the fluorine component may be expressed as 5 times the concentration of the compound.

The etching composition is mixed at room temperature for 10 minutes to 3 hours, preferably for 30 minutes to 1 hour. Then, the phosphoric acid is heated to 120 to 200, preferably to 145 to 185.

When the etching composition is heated to a desired temperature, silver nitrate is added, and the concentration of the added silver nitrate may be from 1 to 100 ppb, but is preferably from 5 to 15 ppb.

The etching composition may include 80 to 90 wt% of the phosphoric acid, preferably 85 to 90 wt%.

When the phosphoric acid is included in an amount of less than 80 wt %, there is a fear that foreign substances may be generated or the etching rate of the silicon nitride film may be lowered, so that the nitride film may not be easily removed.

In addition, when the phosphoric acid is included in an amount exceeding 90% by weight, the concentration of phosphoric acid is excessively high, thereby slowing the etching effect.

Therefore, when the compound containing phosphoric acid and fluorine is included in the weight % range according to the present invention, the etching composition can implement a high silicon oxide/nitride film selectivity and an improved silicon nitride film etching rate while maintaining an appropriate level of stability during semiconductor processing. It enables the etching process.

In one embodiment of the present invention, the etching composition of step a) may further include other additives for improving the etching rate.

The other additives refer to any additives commonly used in the art to improve etching performance, such as surfactants, metal ion sequestrants, and corrosion inhibitors.

In particular, when other additives for improving the etching rate are included, it is preferable to include 85 wt% or more of the fluorine-containing compound represented by Chemical Formula 1 in view of implementing a high selectivity.

In one embodiment of the present invention, in the silicon nitride film etching method, when the etching composition is heated to 145 to 185° C. in step b), silver nitrate (AgNO ₃ ) may be added in step c).

In one embodiment of the present invention, the concentration of silver nitrate may be from 1 to 100 ppb, but is preferably from 5 to 15 ppb.

When the content of the silver nitrate (AgNO ₃ ) is less than 1 ppb, the fluorine ion is not smoothly supplied at a high temperature, so that the etching rate of the silicon nitride film is not improved or there is a risk of generating foreign substances.

In the present invention, since the concentration of fluorine ions is maintained for a long time in a high-temperature etching process, the composition of the etching composition does not change as the process time progresses. Therefore, when phosphoric acid and fluorine-containing compounds are included in the above range, the etching composition can implement a high silicon oxide/nitride film selectivity and an improved silicon nitride film etching rate while maintaining an appropriate level of high-temperature stability during semiconductor processing, thereby enabling a stable etching process. make it

The present invention is an etching composition added to the silicon nitride film etching method, and may be an etching composition including a fluorine-containing compound represented by the following Chemical Formula 1:

[Formula 1]

CF ₃ (CF ₂ ) _n CH ₂ -R ₁

In Formula 1, n is an integer of 1 to 10, and R ₁ is -OH or -NH ₂ .

The present invention may be a method of manufacturing a semiconductor device including the silicon nitride etching method.

In one embodiment of the present invention, the etching composition of step a) may further include a silicon-containing additive for preventing particle aggregation.

Particles are a typical contaminant on the wafer surface during the semiconductor device process. When a silicon-containing additive is used to prevent particle aggregation, the silicon-hydroxy group is converted into the form of silicon-oxygen-carbon instead of silicon-oxygen-silicon. It can be changed to prevent particle generation.

In another embodiment of the present invention, a _{method for storing silica (SiO 2} ) particles and a silica solution, which is a composition for storing silica particles, may be provided.

The storage method is to suppress aggregation and oxidation reaction of silica particles, and by including a fluorine-containing compound at a pH of 2 to 6 of a silica solution made of SOL-GEL, the silica particles are modified with fluorine to cause agglomeration and / or to prevent precipitation.

Conventionally, a small amount of methanol is contained in the storage of silica (SiO ₂ ) particles to prevent the formation and aggregation of uniform particles. There was a problem in forming

Therefore, by adjusting the pH of the silica solution made of SOL-GEL to 2-6 and including a fluorine-containing compound, the silica particle surface is modified with Si-F to prevent the formation of Si-O-Si bonds, thereby preventing particle aggregation ( aggregation) can be prevented.

In this case, the pH of the silica solution is 2 to 6, preferably 4 to 5.

According to an embodiment of the present invention, the fluorine compound included in the silica solution may be HF, NH ₃ F, or the like.

Hereinafter, specific embodiments of the present invention are presented. However, the present invention may be embodied in several different forms and is not limited to the experimental examples described herein.

Experimental example

Example One / comparative example 1 to 3: etching Preparation of the composition

As shown in [Table 1] below, the etching compositions of Examples 1 and Comparative Examples 1 to 3 were prepared by adding a fluorine-containing compound to phosphoric acid.

The etching compositions prepared in Example 1 and Comparative Examples 1 to 3 were heated, and in Example 1, silver nitrate (AgNO ₃ ) was added to the heated etching composition. At this time, the conditions for each step are described in [Table 1] below.

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 fluorine-containing compound of step a) 2,2,3,3,3-pentafluoro-1-propanol (500 ppm) Ammonium fluoride
(500ppm) 2,2,3,3,3-pentafluoro-1-propanol (500 ppm) Ammonium fluoride
(500ppm) b) step Heat the etch composition to 165 °C Heat the etch composition to 165 °C Heat the etch composition to 165 °C Heat the etch composition to 165 °C c) step Add 10ppb silver nitrate Add 10ppb silver nitrate - -

[Measurement of physical properties]

In the etching compositions of Examples 1 and Comparative Examples 1 to 3 prepared according to [Table 1], the concentration of fluoride ions according to the time (1, 2, 3 hours) for each temperature based on the time when silver nitrate was added was measured. measured. The results are shown in [Table 2] below.

division Amount of fluoride ions (ppm) 140 160 180 1 hours 2 hours 3 hours 1 hours 2 hours 3 hours 1 hours 2 hours 3 hours Example 1 480 438.4 396.6 459.4 398.6 345.8 421.4 366.2 307.4 Comparative Example 1 420 378 311 387 326 248 364 309 249 Comparative Example 2 0 0 0 0 0 0 0 0 0 Comparative Example 3 418 369 315 390 318 250 367 310 231

As shown in [Table 2], it can be seen that in the etching composition according to the etching method of Example 1, a high concentration of fluorine ions is present at a high temperature.

On the other hand, it can be seen that the etching composition by the etching method of Comparative Example 2 does not emit fluoride ions at high temperature, and the etching composition by the etching method of Comparative Examples 1 and 3 does not maintain the concentration of fluoride ions at high temperature. Able to know.

[Measurement of stability of silica (SiO _{2 ) storage solution]}

Example 2 / comparative example 4 to 6: Determination of whether silica particles are agglomerated

Examples 2 and Comparative Examples 4 to 6 were prepared as shown in [Table 3] using _{800 nm silica (SiO 2} ) particles made of 12% SOL-GEL.

condition HF pH Comparative Example 4 1L of sealed system 500ppm 7 Comparative Example 5 1L of open system 500ppm 7 Comparative Example 6 1L of open system 0ppm 4.3 Example 2 1L of open system 500ppm 4.3

The size of _{silica (SiO 2} ) aggregated particles according to time of Comparative Examples 4 to 6 and Example 2 was measured in Table 4 below.

1 hours 24 hours 120 hours Comparative Example 4 796 nm, 801 nm 798 nm, 803 nm 799 nm, 801 nm Comparative Example 5 795 nm, 803 nm 825 nm, 851 nm 825 nm, 1,100 nm, 1,500 nm Comparative Example 6 812 nm, 831 nm 1,100 nm, 1,500 nm 1,700 nm, 2,100 nm Example 2 779 nm, 810 nm 791 nm, 815 nm 795 nm, 811 nm

In Example 2, the hydrolysis reaction was inhibited through the reaction of silicon and fluorine at low pH, and _{it was confirmed that silica (SiO 2} ) particles did not agglomerate.

On the other hand, in Comparative Examples 5 and 6, the hydrolysis reaction proceeded with the passage of time, and it was confirmed that the size of the _{silica (SiO 2 ) particles was not kept constant.}

Claims (9)

a) preparing an etching composition including a fluorine-containing compound represented by the following Chemical Formula 1;
[Formula 1]
CF ₃ (CF ₂ ) _n CH ₂ -R ₁
In Formula 1, n is an integer of 1 to 10, R ₁ is -OH or -NH ₂
b) heating the etching composition; and
c) A silicon nitride film etching method comprising the step of adding silver nitrate (AgNO _{3 ) to the heated etching composition.}
The method of claim 1,
In the fluorine-containing compound represented by Formula 1, n is an integer of 1 to 5, and R ₁ is -OH.
The method of claim 1,
The fluorine-containing compound represented by Formula 1 is 2,2,3,3,3-pentafluoro-1-propanol, 2,2,3,3,3-pentafluoropropan-1-amine, and combinations thereof A silicon nitride film etching method, characterized in that selected from the group consisting of.
4. The method according to any one of claims 1 to 3,
The etching composition of step a) is based on the entire etching composition.
A silicon nitride film etching method, characterized in that it is a phosphoric acid solution containing the fluorine-containing compound represented by Formula 1 at a concentration of 100 to 3000 ppm.
4. The method according to any one of claims 1 to 3,
An additive for improving an etching rate is further included in the etching composition of step a), the silicon nitride film etching method.
4. The method according to any one of claims 1 to 3,
When the etching composition in step b) is heated to 145 to 185 °C,
In step c), silver nitrate (AgNO ₃ ) is added, a silicon nitride film etching method.
4. The method according to any one of claims 1 to 3,
The silver nitrate (AgNO ₃ ) is characterized in that added at a concentration of 1 to 100 ppb, silicon nitride etching method.
delete A method of manufacturing a semiconductor device using the silicon nitride film etching method according to any one of claims 1 to 3.