KR102378930B1 - Etchant composition for etching nitride layer and method of forming pattern using the same - Google Patents

Abstract

The nitride layer etching composition of the present invention includes phosphoric acid, a silane ammonium-based compound in which two or more ammonium groups are bonded per one silicon (Si) atom, and excess water. The nitride layer can be etched with a high selectivity by using the nitride layer etching composition without damage to the oxide layer and re-adsorption of etch residues.

Description

Nitride etching composition and pattern formation method using the same

The present invention relates to a nitride layer etching composition and a pattern forming method using the same. More particularly, it relates to a nitride film etching composition including an acid solution and a pattern forming method using the same.

For example, in manufacturing a semiconductor device, various insulating films such as a silicon oxide film and a silicon nitride film may be stacked on a substrate. A selective etching process of the silicon nitride layer may be required according to the necessity of forming various patterns included in the semiconductor device.

When the silicon nitride layer is etched through the wet etching process, as the etching process progresses, the etching rate may decrease and the selectivity of the silicon nitride layer to the silicon oxide layer may also decrease.

In addition, silicon-based by-products are generated from the etch target layer, which may inhibit the etching rate and cause aggregation or adsorption problems.

For example, Korean Patent Laid-Open Publication No. 10-2005-0003163 discloses an etchant for a nitride film of a semiconductor device containing phosphoric acid and hydrofluoric acid. However, when hydrofluoric acid is included in the etchant, the silicon oxide film is also removed, so it is difficult to secure a sufficient etching selectivity of the nitride film to the oxide film.

Accordingly, research on an etchant capable of suppressing defects caused by etching by-products while improving the etch selectivity of the nitride film compared to the silicon oxide film is continuously being conducted.

Korean Patent Laid-Open Publication No. 10-2005-0003163 (2005.01.10.)

An object of the present invention is to provide a nitride layer etching composition having improved etching properties for a silicon nitride layer.

An object of the present invention is to provide a pattern forming method using a nitride layer etching composition having improved silicon nitride layer etching properties.

1. Phosphoric acid; a silane ammonium compound containing two or more ammonium groups and two or more hydroxyl groups; and excess water, a nitride film etching composition.

2. The nitride layer etching composition according to the above 1, wherein the hydroxyl groups are bonded to molecular terminals of the silane ammonium-based compound.

3. The nitride layer etching composition according to the above 1, wherein the silane ammonium-based compound includes a compound represented by the following Chemical Formula 1:

[Formula 1]

(In Formula 1, R ^a and R ^b are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms, and n is an integer of 1 to 4).

4. The composition of the above 3, wherein R ^a and R ^b are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms.

5. In the above 1, among the total weight of the composition,

70 to 99% by weight of phosphoric acid; 0.01 to 10% by weight of the silane ammonium-based compound; and excess water, a nitride film etching composition.

6. The nitride layer etching composition of 1 above, wherein the silane ammonium-based compound includes at least one selected from the group consisting of ammonium silane, tetramethylammonium silane, tetraethylammonium silane, and tetrapropylammonium silane.

7. forming an oxide film and a nitride film on the substrate; and

A method of forming a pattern, comprising the step of at least partially removing the nitride layer using the nitride layer etching composition of any one of claims 1 to 6 above.

8. The method according to 7 above, wherein the oxide layer includes silicon oxide, and the nitride layer includes silicon nitride.

9. In the above 7, a nitride film pattern is formed from the nitride film,

The method further comprising etching the oxide layer or the substrate using the nitride layer pattern as a mask.

As described above, according to embodiments of the present invention, the nitride layer etching composition may include phosphoric acid and an ammonium silane compound. The ammonium silane compound may passivate the silicon oxide layer to suppress corrosion and damage to the silicon oxide layer during the nitride layer etching process.

In addition, the ammonium silane compound may act as a barrier to silica by-products generated during the etching process to block re-adsorption of by-products to the silicon oxide layer.

The nitride etching composition according to the embodiments of the present invention may be effectively used in, for example, manufacturing a semiconductor device using a silicon nitride layer and a silicon oxide layer, or forming a pattern of the semiconductor device.

1 to 5 are cross-sectional views for explaining a pattern forming method according to example embodiments.

The nitride film etching composition according to the embodiments of the present invention may be used for selective etching of a silicon nitride film applied to, for example, a semiconductor device or a display device. For example, the nitride layer etching composition may be supplied on a structure including an oxide layer and used to etch only the silicon nitride layer with high selectivity without substantially damaging the oxide layer or causing a thickness change.

Hereinafter, embodiments of the present invention will be described in detail. However, these are preferred examples, and the spirit and scope of the present invention are not necessarily limited thereto. When there is an isomer of the compound represented by the formula used in the present application, the compound represented by the formula means the representative formula including the isomer.

<Nitride layer etching composition>

The nitride layer etching composition according to embodiments of the present invention may include phosphoric acid, an ammonium silane compound, and excess water.

Phosphoric acid may be represented by the chemical formula of, for example, H ₃ PO ₄ , and may act as a main etching component for etching the nitride layer. In example embodiments, the nitride layer etching composition may include phosphoric acid in an amount of about 70 to about 99 wt% expressed as a weight percent of the total weight of the composition.

When the phosphoric acid content is less than about 70 wt %, the overall nitride layer etching rate may be reduced. When the phosphoric acid content exceeds about 99% by weight, the etching rate of the nitride layer as well as the oxide layer, the semiconductor layer, or the metal layer increases together, so that the etching selectivity for the nitride layer may be reduced.

In some embodiments, phosphoric acid may be included in an amount of about 80 to 90 wt% in consideration of the etching efficiency and the etching selectivity of the nitride layer.

The ammonium silane compound may be included as an etch control agent for suppressing etch damage to an oxide film such as a silicon oxide film. For example, the surface of the silicon oxide layer may be passivated by the ammonium silane compound to be protected from etching damage. Accordingly, when a wet etching process is performed using the nitride layer etching composition, the etch selectivity for the nitride layer (eg, silicon nitride layer) may be significantly improved.

According to exemplary embodiments, the silane ammonium-based compound may include two or more ammonium groups and two or more hydroxyl groups. The ammonium group may be bonded in the form of a salt through an oxygen atom or an oxygen anion bonded to a silicon atom (Si).

In some embodiments, the hydroxyl groups may be bonded to both ends of the silane ammonium-based compound molecule. In this case, two hydroxyl groups may be included per molecule of the silane ammonium-based compound.

The hydroxyl group may function as an adsorption hand adsorbing to the silicon oxide film. Accordingly, passivation of the silicon oxide layer may be formed by the ammonium silane compound.

In some embodiments, the ammonium silane compound may include a compound represented by Formula 1 below.

[Formula 1]

In Formula 1, R ^a and R ^b may each independently represent hydrogen or an alkyl group having 1 to 5 carbon atoms. n may be an integer from 1 to 4.

During a wet etching process for a silicon nitride layer, a silica by-product may be generated as an etching residue. For example, the silica by-product may be hydrated in the etchant composition to produce silica hydrate. Since the silica hydrate has a high affinity for the silicon oxide film, it may be re-adsorbed on the surface of the silicon oxide film.

However, according to exemplary embodiments, the ammonium silane compound is adsorbed to the silicon oxide layer to form passivation, and an ammonium group may be exposed from the surface of the silicon oxide layer.

For example, since a hydroxyl group having affinity for the silica hydrate is disposed at the end of the silane ammonium-based compound and adsorbed to the silicon oxide, only the ammonium group may be exposed to the surface of the silicon oxide layer.

Accordingly, the relatively bulky ammonium group acts as a barrier to block the silica hydrate, and re-adsorption to the silicon oxide layer can be suppressed.

Therefore, while the etching and erosion of the silicon oxide layer are prevented, re-adsorption of the etching residue may be blocked together. Accordingly, the profile and thickness of the silicon oxide layer are maintained substantially unchanged, and a highly selective wet etching process of only the silicon nitride layer, which is an etch target layer, can be implemented.

In some embodiments, in Formula 1, R ^a and R ^b may each independently be an alkyl group having 1 to 3 carbon atoms. When the number of carbon atoms of R ^a and R ^b exceeds 4, aggregation between neighboring silane ammonium-based compounds may occur due to an increase in dispersing power. In this case, the adsorption blocking efficiency of the etching residue may be reduced.

In addition, in Formula 1, when n is 5 or more, the ratio of adsorption hands per molecule may decrease, so that a sufficient passivation effect may not be realized.

For example, the silane ammonium-based compound may include ammonium silane, tetramethylammonium silane, tetraethylammonium silane, or tetrapropylammonium silane. These may be used alone or in combination of two or more.

In addition, since the ammonium silane compound contains hydroxyl groups, it has high solubility and can reduce the generation of particles or additional etching byproducts.

In example embodiments, the nitride layer etching composition may include about 0.01 to 10% by weight of the silane ammonium-based compound based on the total weight of the composition.

When the content of the phosphorus-containing silane-based compound is less than about 0.01 wt %, a sufficient effect of preventing damage to the silicon oxide film and preventing re-adsorption of silica hydrate may not be realized. When the content of the ammonium silane compound exceeds about 10% by weight, etching by-products or particles may be generated due to aggregation of the ammonium silane compound, and etching efficiency of the nitride layer may be reduced.

In some embodiments, the content of the ammonium silane compound may be adjusted to about 0.05 to 0.5 wt % in consideration of the improvement of the nitride etch selectivity and the etching efficiency.

The excess water included in the nitride layer etching composition may include, for example, distilled water or deionized water (DIW).

In some embodiments, the nitride layer etching composition may further include an additive such as an etch enhancer. The etch enhancer may include, for example, a sulfuric acid-based compound or an ammonium acid-based compound. The etch enhancer may be added to improve the overall etching rate of the nitride layer etching composition, and may be added in a small amount not to decrease the etch selectivity for the nitride layer.

Examples of the sulfuric acid-based compound include sulfuric acid or methanesulfonic acid. Examples of the ammonium acid-based compound include ammonium sulfate, ammonium persulfate, ammonium acetate, ammonium phosphate, and the like. These may be used alone or in combination of two or more.

In addition, additional components such as surfactants and corrosion inhibitors may be further included within a range that does not inhibit the action of the ammonium silane compound.

In some embodiments, in order to protect the silicon oxide layer and the semiconductor layer, the hydrofluoric acid-based or fluorine-based (eg, fluorine-containing silane-based) compound may be excluded from the nitride layer etching composition.

In an embodiment, the composition for etching the nitride layer may include only the above-described silane ammonium-based compound as a silane-based compound, and may not include other silane compounds (eg, oxime silane, silyl sulfate, TEOS, etc.). In the case of the other silane compounds, the protection of the silicon oxide film may be inhibited rather than the silicon oxide layer through competition with the ammonium silane-based compound according to exemplary embodiments, and particles may be generated due to a decrease in solubility.

As described above, the nitride layer etching composition according to exemplary embodiments of the present invention may include an ammonium silane compound together with phosphoric acid. The ammonium silane compound may selectively increase the etching rate of the nitride layer while having excellent solubility. In addition, it may function as an adsorption barrier for etch residues while substantially imparting an anti-corrosion effect to the silicon oxide layer. Accordingly, a wet etching process with high reliability and high selectivity can be implemented while preventing deformation and denaturation of the silicon oxide layer.

<Pattern Forming Method>

Embodiments of the present invention provide a pattern forming method using the above-described nitride layer etching composition.

1 to 5 are cross-sectional views for explaining a pattern forming method according to example embodiments. The pattern forming method is used to encompass a nitride film pattern forming method and a method for forming a predetermined structure through removal of the nitride film.

Referring to FIG. 1 , an oxide layer 110 and a nitride layer 120 may be formed on a substrate 100 .

The substrate 100 may include a semiconductor material such as single crystal silicon or single crystal germanium, and may be formed to include polysilicon.

According to example embodiments, the first oxide layer 110 may be formed to include silicon oxide, and the nitride layer 120 may be formed to include silicon nitride. The first oxide film 110 and the nitride film 120 may be formed through, for example, a chemical vapor deposition (CVD) process, a sputtering process, a physical vapor deposition (PVD) process, an atomic layer deposition (ALD) process, etc. can In one embodiment, the first oxide film 110 may be formed through a thermal oxidation process on the upper surface of the substrate 100 .

Referring to FIG. 2 , the nitride layer 120 may be partially etched to form a nitride layer pattern 125 . In example embodiments, the etching process may be performed using the above-described composition for etching a nitride layer.

As described above, the composition for etching the nitride layer includes phosphoric acid and an ammonium silane compound, and prevents corrosion and damage of the first oxide layer 110 by the ammonium silane compound, and prevents etching residues such as silica hydrate. Adsorption to the first oxide layer 110 may be blocked.

Accordingly, only the nitride layer 120 may be substantially etched without modification or deformation of the first oxide layer 110 .

In some embodiments, the etching process may be performed in a temperature range of about 150 to 170 ^o C. Preferably, the etching process is about 155 to 165 It can be carried out in the temperature range of ^o C. In the above temperature range, the activity of phosphoric acid and passivation or barrier formation by the silane ammonium-based compound may be promoted. When the etching temperature is excessively increased, the ammonium silane compound and/or phosphoric acid may be dissociated or decomposed before contacting the nitride layer or the oxide layer.

Referring to FIG. 3 , the trench 130 may be formed by etching the first oxide layer 110 and the substrate 100 using the nitride layer pattern 125 as an etching mask. The etching process for forming the trench 130 may include a dry etching process.

Referring to FIG. 4 , a second oxide layer 135 filling the trench 130 may be formed. The second oxide layer 135 may be formed through a deposition process such as a CVD process to include silicon oxide.

Referring to FIG. 5 , the nitride layer pattern 125 may be removed. In some embodiments, the nitride layer pattern 125 may be removed using the nitride layer etchant composition according to the above-described exemplary embodiments.

Accordingly, the nitride layer pattern 125 may be selectively removed without damage or increase in thickness of the second oxide layer 135 .

Thereafter, a cleaning process for removing etching by-products or a polishing process for the second oxide layer 135 may be additionally performed.

Hereinafter, experimental examples including specific examples and comparative examples are presented to help the understanding of the present invention, but these are merely illustrative of the present invention and do not limit the appended claims, the scope and description of the present invention It is apparent to those skilled in the art that various changes and modifications to the embodiments are possible within the scope of the spirit, and it is natural that such variations and modifications fall within the scope of the appended claims.

Examples and Comparative Examples

A nitride layer etching composition having the composition and content (wt%) shown in Table 1 was prepared.

division phosphoric acid
(H ₃ PO ₄ ) silane compound ammonium
sulfate water
(DIW) A-1 A-2 A-3 A-4 A-5 A-6 Example 1 85 0.05 - - - - 14.95 Example 2 85 0.1 - - - - 14.9 Example 3 85 - 0.05 - - - 14.95 Example 4 85 - 0.1 - - - 14.9 Example 5 85 - - 0.1 - - 14.9 Example 6 85 - - - 0.1 - 14.9 Example 7 85 0.6 - - - - 14.4 Example 8 85 1.0 - - - - 14.0 Comparative Example 1 85 - - - - - - - 15 Comparative Example 2 85 - - - - 0.1 - - 14.9 Comparative Example 3 85 - - - - 0.1 - 0.1 14.8 Comparative Example 4 85 - - - - - 0.1 - 14.9

Specific names or structures for the silane compound are as follows.

A-1: ammonium silane

A-2: tetramethylammonium silane (TMAS)

A-3: Tetrabutylammonium Silane (TBAS)

A-4:

A-5: tetramethoxysilane (TMOS)

A-6: methyltrimethoxysilane (MTMOS)

Experimental example

(1) Silicon Nitride (SiN) Etch Rate (E/R) Measurement

A silicon nitride film (SiN) 5000Å thick wafer was cut to a size of 2x2cm ² to prepare a sample, and the sample was immersed in the compositions of Examples and Comparative Examples described in Table 1 at a temperature of 160° C. for 3 minutes. Thereafter, after washing and drying with deionized water (DIW), the film thickness was measured with a scanning electron microscope (SEM) to measure the etching rate (Å/min).

(2) silicon oxide film (SiO ₂ ) etch rate measurement

A silicon oxide film (SiO ₂ ) A 400 Å thick wafer was cut to a size of 2x2 cm ² to prepare a sample, and the sample was immersed in the compositions of Examples and Comparative Examples described in Table 1 at a temperature of 160° C. for 30 seconds. Thereafter, after washing and drying with deionized water (DIW), the etch rate (Å/min) was measured by measuring the film thickness with an ellipsometer.

(3) Measurement of resorption on silicon oxide film

The same silicon nitride film sample and silicon oxide film sample as those used in items (1) and (2) were immersed together in the compositions of Examples and Comparative Examples shown in Table 1 at a temperature of 160° C. for 60 minutes. Thereafter, after washing and drying with deionized water (DIW), an increase in the thickness of the silicon oxide film was measured with an ellipsometer to evaluate the resorption prevention properties. The evaluation criteria are as follows.

◎: less than 1Å

○: 1Å~5Å

△: 5Å~10Å

X: greater than 10 Å

The measurement results are shown in Table 2 below.

division SiN E/R
(Å/min) SiO ₂ E/R
(Å/min) etching
selection fee Prevention of re-adsorption Example 1 78.7 0.7 112.4 ◎ Example 2 72.5 0.3 241.7 ◎ Example 3 76.4 0.9 84.9 ◎ Example 4 71.9 0.4 179.8 ◎ Example 5 71.4 0.5 142.8 ○ Example 6 70.5 0.6 117.5 ○ Example 7 68.5 0.3 228.3 ◎ Example 8 64.3 0.3 214.3 ◎ Comparative Example 1 61.2 2.1 29.1 △ Comparative Example 2 57.8 1.7 34.0 X Comparative Example 3 56.7 1.5 37.8 △ Comparative Example 4 54.2 1.8 30.1 X

Referring to Table 2, in the case of Examples including the above-described silane ammonium-based compound, the etching rate of the silicon oxide layer was lowered, and excellent anti-readsorption properties were exhibited.

In the case of Examples 5 and 6, the anti-readsorption properties were somewhat decreased compared to Examples 1 to 4 due to the aggregation of the silane ammonium-based compound.

In Examples 7 and 8 in which the silane ammonium-based compound was contained in a rather excessive amount, the etching rate for the silicon nitride layer was reduced compared to Examples 1 to 4.

In the case of Comparative Examples in which the silane ammonium-based compound was not included, the silicon oxide film thickness was increased by re-adsorption while the etching of the silicon oxide film increased.

100: substrate 110: oxide film
120: nitride film 125: nitride film pattern
130: trench 135: second oxide film

Claims (9)

phosphoric acid;
Ammonium silane compound represented by Formula 1; and
A nitride film etching composition comprising excess water:
[Formula 1]

(In Formula 1, R ^a and R ^b are each independently hydrogen or an alkyl group having 1 to 5 carbon atoms, and n is an integer of 1 to 4).
delete delete The composition of claim 1 , wherein R ^a and R ^b are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms.
The method according to claim 1, wherein in the total weight of the composition,
70 to 99% by weight of phosphoric acid;
0.01 to 10% by weight of the silane ammonium-based compound; and
A nitride film etching composition comprising excess water.
delete forming an oxide film and a nitride film on a substrate; and
A method of forming a pattern, comprising the step of at least partially removing the nitride layer using the nitride layer etching composition according to claim 1 .
The method of claim 7 , wherein the oxide film includes silicon oxide, and the nitride film includes silicon nitride.
The method according to claim 7, wherein a nitride film pattern is formed from the nitride film,
The method further comprising etching the oxide layer or the substrate using the nitride layer pattern as a mask.

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