KR20170078238A - Method of refining etching composition - Google Patents

Abstract

The present invention relates to a method for purifying an etchant comprising the step of supplying steam to an etchant containing phosphoric acid used for etching a silicon nitride film to remove fluorinated compounds contained in the etchant, And the lifetime of the etching solution can be increased.

Description

[0001] METHOD OF REFINING ETCHING COMPOSITION [0002]

The present invention relates to an etching solution purification method capable of increasing the process efficiency of the silicon nitride film etching process and the etchant purification process and extending the life of the etching solution.

Silicon nitride (Si ₃ N ₄ ) is a very important compound as a material for ceramics and semiconductors. In a semiconductor manufacturing process, a step of selectively etching a silicon nitride film without damaging the silicon oxide film is required. For the etching of the silicon nitride film, a wet etching method in which an etching solution composed of 85H ₃ PO ₄ .5H ₂ O is heated at a temperature of 163 to 175 ° C is used. However, phosphoric acid has a disadvantage in that the silicon oxide film is damaged when used at a high temperature of 150 ° C or higher, and that the byproducts such as insoluble silicon compounds produced after wet etching of the silicon nitride film are precipitated. Further, in order to increase the process efficiency, it is necessary to increase the etching rate of the silicon nitride film. In this case, a fluorinated compound is added to the etching composition.

However, the fluorinated compounds volatilize at high temperatures, which results in a change in etch composition and is discarded after one use. In view of process efficiency and economics, there is a need for a process for removing fluorinated compounds in the etching composition and reusing phosphoric acid. However, the conventional method of removing the fluorinated compound at a high temperature of 170 占 폚 or more is inefficient because it takes a long time to remove the fluorinated compound. Accordingly, there has been a need to develop a method for regenerating phosphoric acid which can efficiently remove fluorinated compounds in the etching composition at a high temperature of 170 ° C or higher to increase process efficiency.

Korean Patent Publication No. 2001-0027001 Japanese Patent Laid-Open No. 1996-083792

The present invention provides a method for purifying an etchant comprising the step of supplying steam to an etchant composed of an aqueous phosphoric acid solution used for etching a silicon nitride film to remove fluorinated compounds contained in the etchant.

In order to achieve the above object, the present invention provides a method for purifying an etchant comprising the step of supplying steam to an etchant containing phosphoric acid used for etching a silicon nitride film to remove a fluorinated compound contained in the etchant.

The etchant may include phosphoric acid, a fluorinated compound, and a silicon-based compound.

The fluorinated compound may be silicon fluoride (SiF 4) and / or hydrogen fluoride (HF).

The fluorinated compound is contained in an amount of 100 to 3000 ppm in the etchant to be purified, and may be contained in the etchant after the purification in an amount of 0.1 to 5 ppm.

The method of refining the etchant may include extracting the etchant from the etchant, supplying steam to the etchant to purify the etchant, and circulating the etchant through the etchant.

The steam may be supplied in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the etching solution.

The steam may be supplied at a pressure of 1 to 20 bar at a steam flow of 100 to 1000 ° C at a flow rate of 0.2 to 20 cc / min to 200 cc of the etching solution.

The steam supply may be conducted for 10 to 24 hours.

At the time of supplying the steam, nitrogen bubbles (N ₂ Bubble) may be additionally supplied.

The nitrogen gas bubbles may be supplied at a flow rate of 5 to 10 L / min.

The present invention provides a method for efficiently and stably removing a fluorinated compound contained in an etchant composed of an aqueous phosphoric acid solution used for etching a silicon nitride film using the method for purifying an etchant according to the present invention.

It is possible to increase the process efficiency of the silicon nitride film etching process and the etching solution purification process by using the etchant refining method and to enable the reuse of the aqueous phosphoric acid solution as the silicon nitride film etching solution, thereby reducing the economic cost and environmental pollution.

1 is a schematic view showing a process for purifying an etchant according to an embodiment of the present invention.

The present invention is capable of various modifications and various embodiments and is intended to illustrate and describe the specific embodiments in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present invention, terms such as comprise, having, or the like are intended to designate the presence of stated features, integers, steps, operations, elements, parts or combinations thereof, and may include one or more other features, , But do not preclude the presence or addition of one or more other features, elements, components, components, or combinations thereof.

As used herein, the term " combination thereof " means that two or more substituents are bonded to each other through a single bond or a linking group, or two or more substituents are condensed and connected.

The present invention relates to a method for purifying an etchant by removing a fluorinated compound added to selectively etch a silicon nitride film in a high temperature phosphoric acid process and a silicon byproduct produced during the etching process.

The fluorinated compounds contained in the etchant are volatilized at high temperatures, resulting in a change in the etching composition content, which is discarded after one use. In addition, when the silicon compound produced at the etching is contained in the aqueous solution of phosphoric acid at a certain concentration or more, particles adhered to the semiconductor wafer are formed to lower the process efficiency. When the silicon additive and the etching process by- And it has remained as an inhibiting factor for the reuse of phosphoric acid. There is a problem that it is difficult to apply it industrially because the economical efficiency is low due to the above problems. In order to solve this problem, the present invention provides a method for purifying an etchant comprising the step of supplying steam to an etchant containing phosphoric acid used for etching a silicon nitride film to remove fluorinated compounds contained in the etchant.

The etchant includes phosphoric acid, a solvent, and a silicon compound, and further includes a fluorinated compound to increase the etching rate. The etchant may be used alone or in combination with a solvent and / or a silicone compound in phosphoric acid.

The solvent may be any one selected from the group consisting of water, alcohol, glycol ether, ether, ester, ketone, carbonate, amide, and combinations thereof.

(SiH ₄ , SinH _{2n + 2} ), siloxane (H ₂ SiO, (H ₃ Si) _{2 O,} (H ₂ SiO) _6, halide SiX ₄ (X = F, Cl, Br, I), Si ₂ X ₆ (X═Cl, Br, I), SiX ₂ (X = 1) boron SiB _{3 ,} SiB _{6 ,} carbide SiC, oxide SiO _{2 ,} SiO _{2 ,} siloxane Si ₆ O ₃ H _{6 , a} nitride Si ₃ N _4, and a mixture thereof, and may be silicon dioxide (SiO ₂ ) or silicon nitride (Si ₃ N ₄ ).

In the present invention, steam is supplied to the etchant to remove the fluorinated compound contained in the etchant.

The steam is a gaseous state of pure water and has no organic and inorganic contents.

In the semiconductor etching process according to the present invention, impurity control is essential. Impurities should be controlled to a few ppb or less. When using general water other than steam, it is difficult to control the impurity level required in the semiconductor process because organic matter and inorganic matters are contained. Therefore, it is preferable to use steam.

In addition, since steam is injected at a high temperature of 100 ° C or more, it is easy to maintain the high temperature (170 ° C or more) of the purification.

The fluorinated compound may be silicon fluoride (SiF 4) and / or hydrogen fluoride (HF).

The silicon fluoride and hydrogen fluoride may be added to increase the etching rate and be a by-product discharged in the etching process.

The fluorinated compound is contained in an amount of 100 to 3000 ppm of the etchant to be refined and is contained in an amount of 0.1 to 5 ppm in the etchant after the refinement.

The steam supply may be performed in parallel with the etching process of the silicon nitride film, or may be performed by collecting the etchant after the etching process. It can be selected according to the etching object and the condition among the above methods.

In detail, the steam supply is sprayed into the etching solution at the upper part in the wet etching process of the silicon nitride film to perform the etching process, and when the etching solution obtained through the etching process is collected at the lower part, the tube is immersed in the lower used etching solution to supply the steam have.

Since the steam is supplied in the presence of the object to be etched, there is a limitation in the setting range of the etchant injection speed and the heating temperature. However, the method has an advantage that the operating rate of the apparatus can be increased.

Alternatively, when the etching process of the silicon nitride film is performed in the etching bath, the etching solution obtained through the etching process is collected from the etching bath, the steam is supplied to the collected etching solution, and the purified etching solution is circulated in the etching bath again .

Since the method supplies steam in a state in which a semiconductor wafer or the like as an etching target material is not present, precise management of the etching solution concentration and heating temperature is not required, but the operating rate of the apparatus is not high.

The steam may be supplied in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the etching solution.

The steam may be supplied at a pressure of 1 to 20 bar at a steam flow of 100 to 1000 ° C at a flow rate of 0.2 to 20 cc / min to 200 cc of the etching solution.

More preferably, the steam is 100 to 300 ° C, and most preferably 100 to 200 ° C. It is most advantageous to maintain the high temperature (170 deg.

If less than 0.2 cc / min of steam per 200 cc of etching solution is supplied, the fluorinated compound may not be sufficiently removed. If the amount exceeds 20 cc / min, the temperature of the purification process may rise excessively, The composition may be deteriorated.

The ideal addition amount of the steam may be varied depending on various conditions such as the shape of the apparatus, the heating temperature of the etching liquid, the amount of heat added, the amount of water evaporated, the amount of the fluorinated compound remaining in the etching solution, and the residual additive amount.

The mechanism for removing the fluorinated compound is represented by the following formula (1).

[Chemical Formula 1]

H ₃ PO ₄ + 18HF + Si ₃ N ₄ ? -Si + HF? SiF ₄ (1)

3SiF ₄ + 2H ₂ O? 2H ₂ SiF _6? + SiO ₂ (2)

Moisture is evaporated from the heated high-temperature etchant and discharged to the top of the etch bath. The silicon tetrafluoride and fluorosilicic acid are removed from the system together with the evaporating moisture. It is possible to prevent the filter from being clogged due to precipitation of the silicon compound which is the particulate matter.

When supplying the steam, nitrogen bubbles (N ₂ Bubble) may be additionally supplied.

The nitrogen gas bubbles are the same as the steam supply method, and can be performed simultaneously with the supply of the steam, or after supplying the steam, the nitrogen gas bubbles alone can be supplied.

The nitrogen gas bubbles are preferably supplied at a flow rate of 5 to 10 L / min.

Nitrogen gas bubbles are inert gases that do not react with the compound upon removal of the fluorinated compound and are effective in increasing the removal rate of the fluorinated compound.

1 is a schematic view showing a process for purifying the etchant.

Referring to FIG. 1, the etching solution in the etching bath 10 is transferred to the etching bath 20. At this time, the transfer of the etchant may be performed using a pump 61. In the purification step (20), a refining step of supplying the steam (30) to the supplied etchant to remove the fluorinated compound contained in the etchant is performed. When the steam 30 is supplied, the nitrogen gas bubble 40 may be further supplied. A heater (50) for heating the etchant may be connected to the purification process (20). The etchant having undergone the refining step in the refining step 20 is circulated back to the etch bath 10 using a pump 62 or the like.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[ Manufacturing example ]

A phosphoric acid aqueous solution and a fluorinated compound was prepared. Silicon fluoride and hydrogen fluoride were added to aqueous phosphoric acid solution and contained 900 ppm of hydrogen fluoride. The silicon nitride film was wet-etched for 1 hour using the etching solution. After etching, 200 cc of etching solution was collected from the etching bath to purify the etching solution.

< Comparative Example  1>

200 cc of the etching solution was heated at a high temperature of 170 DEG C for 24 hours.

< Example  1>

The tube was immersed in the etching solution at 200 cc and heated at a high temperature of 170 캜 while continuously supplying steam at 170 캜 into the etching solution at a flow rate of 3 cc / min.

< Example  2>

Steam was supplied to the etchant at 200 cc in the same manner as in Example 1, and a nitrogen gas bubble was supplied at a flow rate of 5 L / min and heated at a high temperature of 170 캜.

[ Experimental Example  One: Etching  Speed and selection ratio measurement]

The etching rate and selectivity of the silicon nitride film of the etchant prepared in the above Preparation Example were measured and purified by the method according to Examples 1 and 2 and Comparative Example 1. The etching rate and selectivity of the silicon nitride film of the etchant were measured, Respectively.

[ Experimental Example  2: Measurement of concentration of hydrogen fluoride]

The concentration of hydrogen fluoride in the etchant prepared in the above Preparation Example was measured and the concentration of hydrogen fluoride in the etchant was measured after purification by the method according to Examples and Comparative Examples.

division Refining time Silicon nitride etching rate (Å / min) Silicon oxide etching rate (Å / min) Selection ratio
(Silicon nitride film / silicon oxide film) Hydrogen fluoride content
(ppm) Comparative Example 1 - 243.11 12.83 18.9 900 2 197.52 36.47 5.4 - 4 180.15 60.15 3.0 - 6 165.37 53.80 3.1 - 8 150.82 48.19 3.1 - 10 132.69 44.67 3.0 - 24 95.61 40.15 2.4 50.7 Example 1 - 241.39 13.04 18.51 900 2 190.17 36.67 5.19 - 4 160.18 50.17 3.19 - 6 126.47 36.17 3.50 - 8 98.17 29.18 3.36 - 10 84.98 25.78 3.30 1.8 24 - - - - Example 2 - 242.18 12.98 18.66 900 2 133.47 34.67 3.85 - 4 85.16 25.48 3.34 0.5 6 - - - - 8 - - - - 10 - - - - 24 - - - -

In Comparative Example 1 shown in Table 1, hydrogen fluoride was not completely removed even after evaporation at a high temperature of 170 캜 for 24 hours, indicating that phosphorus reusable was impossible.

It was confirmed that the hydrogen fluoride content after the purification in Examples 1 and 2 was significantly lower than that of Comparative Example 1. Particularly, the purification effect was further enhanced in Example 2 using steam and nitrogen gas bubbles at the same time.

[ Experimental Example  3: Depending on the number of phosphorus reuse Etching  Speed and selection ratio]

The etchant was reused by the method described in Example 1, and the etch rate and selectivity were measured each time, and the results are shown in Table 2 below.

Reuse of phosphoric acid Silicon nitride film etch rate
(Å / min) Silicon oxide etch rate
(Å / min) Selection ratio
(Silicon nitride film / silicon oxide film) - 241.67 12.88 18.8 One 243.16 13.07 18.6 2 242.67 12.96 18.7 3 242.78 12.87 18.9 4 241.67 12.89 18.7

As shown in Table 2, phosphoric acid could be reused in Example 1 because the etching rate of the silicon nitride film and the silicon oxide film did not change even when the phosphoric acid reuse process was repeated four times.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

10: etching bath
20: Purification
30: Steam
40: nitrogen gas bubble
50: heater
61, 62: pump

Claims (10)

And supplying steam to the etchant containing phosphoric acid used for etching the silicon nitride film to remove the fluorinated compound contained in the etchant. The method according to claim 1,
Wherein the etchant comprises phosphoric acid, a fluorinated compound, and a silicon-based compound. The method according to claim 1,
Wherein the fluorinated compound is silicon fluoride (SiF 4) and / or hydrogen fluoride (HF). The method according to claim 1,
Wherein the fluorinated compound is contained in an amount of 100 to 3000 ppm in the etchant to be refined,
Wherein said refining is contained in an amount of 0.1 to 5 ppm in the etchant after said refining. The method according to claim 1,
The etching solution is taken out from the etching bath, steam is supplied to the etching solution taken out, and the purified etching solution is circulated in the etching bath again. The method according to claim 1,
Wherein the steam is supplied in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the etching solution. The method according to claim 1,
Wherein the steam supply is performed at a pressure of from 1 to 20 bar at a steam flow rate of from 100 to 1000 占 폚 at a flow rate of 0.2 to 20 cc / min with respect to 200 cc of the etching solution. The method according to claim 1,
Wherein the steam supply is carried out for 10 to 24 hours. The method according to claim 1,
Wherein during the steam supply, a nitrogen gas bubble (N ₂ Bubble) is further supplied. 10. The method of claim 9,
Wherein the nitrogen gas bubbles are supplied at a flow rate of 5 to 10 L / min.

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