KR20080043444A - Method for cleaning a substrate - Google Patents

Abstract

A substrate cleaning method is provided to compose an azeotropic mixture having surface tension smaller than surface tension of deionized water and water by using an in-line static mixer installed at a dispenser. A substrate(102) is rotated. A cleaning solution is dispensed onto a surface of the rotating substrate. An azeotropic mixture is generated by mixing a solution having surface tension smaller than surface tension of deionized water and water. The azeotropic mixture is dispensed onto the surface of the rotating substrate. The substrate is dried by supplying inert gases onto the substrate. A melting point of the azeotropic mixture is lower than a melting point of the deionized water and the solution. The solution having the surface tension smaller than the surface tension of the water is isopropyl alcohol.

Description

Substrate cleaning method {METHOD FOR CLEANING A SUBSTRATE}

1 is a cross-sectional view showing an example of a single substrate cleaning apparatus to which a substrate cleaning method according to the present invention is applied.

2 is a cross-sectional view showing an example of a substrate holding apparatus used in the single substrate cleaning method according to the present invention.

3 is a cross-sectional view showing an example of an in-line static mixer used in a single substrate cleaning apparatus for mixing a deionized water with isopropyl alcohol to form an azeotropic mixture according to the present invention.

※ Explanation of codes for main parts of drawing

100 substrate fixing device 102 substrate (or wafer)

104, 106: Dispenser 108: In-Line Static Mixer

110, 114: flow meter 112, 116: spike pump

120: chamber

The present invention relates to a method for cleaning a substrate or a wafer during a semiconductor process, and more particularly, to a method for preparing azeotropic mixtures for cleaning a substrate and cleaning the substrate using the azeotropic mixture. will be.

The performance, reliability and production yield of integrated circuits are affected by physical and chemical unnecessary impurities present on the wafer used during fabrication or on the device surface after fabrication. As the minimum line width of the device becomes smaller and reaches the submicron region, the importance of the technique of cleanly cleaning the wafer surface before oxidation and pattern formation among them becomes more important. The technology for cleaning the semiconductor wafer surface can be largely divided into wet chemical cleaning method, dry cleaning method, steam method, etc., the traditional wafer cleaning method is a wet chemical cleaning method, the most widely used method is standard cleaning 1 RCA cleaning including (standard clean 1: SC-1) and standard clean 2: SC-2. Typically, wet cleaning of silicon wafers is performed by immersing approximately 50-100 wafers in a cleaning solution such as SC-1 or SC-2 in a batch and then rinsing them in DI water. However, the process of immersing the wafers in the cleaning liquid collectively is inherently slow because it depends on the flow rate along the stationary wafer for wafer rinsing.

Thus, shorter periods of time are required in the manufacture of semiconductor integrated circuits, thereby increasing the need to quickly clean and rinse a single wafer.

Accordingly, US patent application Ser. No. 09 / 892,130 discloses a method for improving wafer rinse in a single wafer cleaning apparatus.

According to this method, after exposing the wafer to the cleaning solution, the cleaning solution is removed from the wafer by rotating the wafer at high speed and dispensing or spraying deionized water onto the wafer in rotation. The centrifugal force of the rotating wafer further improves the rinse of the wafer.

However, even when the wafer is rotated at high speed, the deionized water swells due to the lack of centrifugal force and the surface tension of the deionized water at the center of the wafer.

At this time, the high concentration of chemical diffuses very quickly in deionized water, so rinsing by deionized water is effective at the initial stage of rinse, but the diffusion rate decreases with time, and the deionized water that swells in the center of the wafer is maintained as it is. There was a problem.

In order to solve this problem, US patent application Ser. No. 09 / 892,130 also discloses a solution having a lower surface tension than water, for example, isopropyl alcohol (IPA) after chemical and / or deionized water dispensing. Also disclosed is a method of dispensing on a wafer in liquid or gaseous form. According to this method, in the initial stage of rinsing of the wafer, the chemical is removed using deionized water having high solubility in the chemical, and at the end of the rinse stage, the IPA is used to reduce the layer of deionized water that swells in the center of the wafer. Accelerates diffusion

In another embodiment, before dispensing deionized water for rinsing after chemical dispensing, eject the IPA vapor or liquid, or in another embodiment administering the IPA solution to one point of the wafer through one nozzle and simultaneously Disclosed is a method of dispensing deionized water at another point on a wafer through a nozzle.

Also disclosed is a method of heating deionized water to a temperature higher than room temperature, such as 60 to 70 ° C, to provide thermal energy to the deionized water to improve the diffusion of the chemical.

In addition, a method of rotating a wafer at a higher speed than wafer rinsing or adding nitrogen gas for drying the wafer after the rinsing step is disclosed.

However, the prior art discloses a method of using a liquid having a lower surface tension than deionized water and water, for example, an isopropyl alcohol liquid, for cleaning the substrate, but by appropriately formulating a mixing ratio of deionized water and isopropyl alcohol. It has not been disclosed how to facilitate the drying process during substrate cleaning even at room temperature.

On the other hand, the present inventors rinse and dry the substrate even at room temperature when the azeotropic mixture produced by mixing a deionized water and a liquid having a lower surface tension than water, in particular, isopropyl alcohol in an appropriate composition ratio, is used. It has been found that this can be done effectively.

Accordingly, according to the present invention, the mixing ratio of a mixture of deionized water and a liquid having a surface tension less than that of water applied during the semiconductor cleaning process is appropriately adjusted to make the mixture into an azeotropic mixture, and the substrate is effectively cleaned at room temperature. Provide a method.

An object of the present invention is to adjust the composition ratio of deionized water and a liquid having a surface tension smaller than that of water used for semiconductor cleaning to form an azeotropic mixture which is easier to evaporate at a lower temperature than the evaporation temperature of deionized water and IPA. It is to provide a method for effectively cleaning the.

Another object of the present invention is to use an in-line static mixer mounted on a dispenser of a semiconductor cleaning device to effectively clean a substrate by forming an azeotropic mixture of deionized water with a constant composition ratio and a liquid having a lower surface tension than water. To provide a way.

In order to achieve the object of the present invention as described above, the present invention is easy to evaporate even at room temperature by properly adjusting the mixing ratio of deionized water (DIW) and a liquid having a surface tension less than water to rinse the substrate surface during substrate cleaning After the azeotropic mixture is made, the mixture is dispensed onto the wafer to provide a method of cleaning the wafer.

The method for cleaning a substrate according to the present invention comprises the steps of rotating the substrate, dispensing the cleaning liquid on the surface of the rotating substrate, mixing deionized water and a liquid having a surface tension smaller than water to generate an azeotropic mixture, and Dispensing the azeotropic mixture on the surface of the rotating substrate, wherein the boiling point of the azeotropic mixture is lower than the boiling point of the deionized water and the mixing liquid.

Preferably, the substrate cleaning method according to the present invention further comprises the step of dispensing an azeotropic mixture, followed by dispensing the vapor of a solution having a lower surface tension than water on the center of the rotating substrate with a gas or a rotating substrate. Include.

Preferably, the substrate cleaning method according to the present invention further includes the step of simultaneously dispensing the vapor and the vapor of a solution having a surface tension less than water onto the rotating substrate after dispensing the azeotropic mixture.

Preferably, the azeotropic mixture according to the substrate cleaning method according to the invention is produced and supplied by an in-line static mixer.

Preferably, according to the substrate cleaning method of the present invention, by supplying nitrogen gas from the upper portion of the chamber along the circumference of the chamber in which the cleaning of the substrate is performed to form the nitrogen gas film, it is possible to prevent the inflow of impurity particles from outside the chamber. have.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1 is a cross-sectional view showing an example of a single substrate cleaning apparatus to which a substrate cleaning method according to the present invention is applied.

As shown in Fig. 1, the substrate cleaning apparatus 10 used for substrate cleaning according to the present invention is a substrate fixing apparatus 100 (also called a chuck) for fixing and rotating a substrate 102 thereon, a substrate being rotated. Liquids (eg, deionized water and isopropyl alcohol) connected to the dispensers 104 and 106 and the dispenser 106 for dispensing cleaning liquid, deionized water for rinse, etc., on the surface of the substrate 102. In-line static mixer (108) for mixing a mixture to form an azeotropic mixture, a flow meter connected to the in-line static mixer to control the flow rate of the liquid flowing into the in-line static mixer ( 110, 114, spike pumps 112 and 116 for supplying liquid to the in-line static mixer, and chamber 120 to allow substrate cleaning to be performed in an atmosphere isolated from the external environment. have.

In addition, nitrogen gas is supplied from the upper portion of the chamber 120 along the circumference of the chamber 120 where the substrate is cleaned, thereby forming a curtain film of nitrogen gas. It is blocked by the curtain curtain.

Hereinafter, an example of the substrate fixing apparatus 100 used for the substrate cleaning apparatus 10 which concerns on this invention is demonstrated concretely with reference to FIG.

2 shows an example of a substrate holding apparatus used in a single wafer cleaning apparatus according to the present invention.

As shown in FIG. 2, the substrate holding apparatus 200 (chuck) according to an embodiment of the present invention includes a top plate (including a porous plate 23 in which a plurality of holes 25 are irregularly and uniformly distributed). 21, a lower plate 22, a substrate (not shown), which is coupled to the lower portion of the upper plate 21 to form a gas storage portion 26 that stores gas introduced from the outside of the chuck 200 through a spindle (not shown). A sensing member (not shown) including a wafer support 24 for tightly fixing the substrate in close contact with the side of the substrate), and a sensor for sensing the presence and the approximate position of the wafer at the central portion of the porous plate 23. The circular porous plate 23 is located at the center of the upper plate 21 in a circular shape.

At this time, gas, for example, nitrogen gas, from the gas reservoir 25 formed between the upper plate 21 and the lower plate 22 to the outside through the plurality of holes 25 of the porous plate 23 toward the substrate. When ejected, the substrate mounted on the upper plate 21 is supported by the pressure of the ejected gas, and the side of the supported substrate is fixed by the substrate support 24.

In addition, as shown in Fig. 2, the plurality of holes 25 formed in the porous plate 23 are irregularly and uniformly distributed in the shape of a foam sponge. The porous plate 23 is a highly functional plastic having the best chemical resistance and is made of Poly Tetra Fluoro Ethylene (PTFE), commonly referred to as "Teflon," and thus has no reactivity with the chemical used in wafer processing. Also, no impurities are generated.

The size and quantity of the holes 25 formed in the porous plate 23 can be adjusted, the size is preferably 5 ~ 800 ㎛, the volume of the holes 25 is 5 ~ 90% of the volume of the porous plate 23 Is preferred. In addition, the gas ejected through the plurality of holes 25 is injected with an unspecific orientation to the wafer.

In this embodiment, the top plate 21 is provided with only one circular porous plate 23, but the shape of the porous plate 23 may be any shape such as polygon, and the plurality of porous plates may be provided in the chuck 10. It may be arranged in a point symmetrical form with respect to the center of.

According to the substrate cleaning method according to the present invention, first, the nitrogen gas is blown out through the porous plate 23 using the chuck 100 as described above to support the substrate 102 to rotate the substrate 102. Typically, SC-1 and SC-2 are used as semiconductor cleaning liquids, which are sprayed onto the surface of the rotating substrate 102 and then rinse the substrate surface. According to the substrate cleaning method according to the present invention, the process of adding a cleaning liquid to the substrate 102 and rinsing it is performed in the same apparatus 10.

According to one embodiment of the substrate cleaning method of the present invention, for rinsing the substrate 102, first, while rotating the substrate 102 to which the cleaning liquid, such as SC-1 and SC-2, is applied, using the chuck 100, The dispenser 106 is used to dispense a mixed liquid of deionized water (DIW) and isopropyl alcohol (IPA) in an azeotropic mixture state to the surface of the substrate 102.

Typically, deionized water has a high solubility in ionic contaminants and is inexpensive to purchase and process, so that at the initial stage of substrate rinsing, high concentrations of chemicals remaining on the substrate are rapidly diffused and reduced in deionized water. Its use is effective for removing contaminants and is widely used for substrate cleaning.

However, when deionized water is applied to the substrate to rinse the substrate coated with the cleaning liquid or the etching solution, the thickness of the deionized water film formed on the surface of the substrate is reduced to the edge because the centrifugal force due to the rotation of the substrate increases toward the edge of the substrate. Increasingly, the centrifugal force is relatively small at the center of the substrate, so that the film of deionized water swells at the center. That is, the centrifugal force caused by the rotation of the substrate thins the membrane of deionized water toward the edge of the substrate, whereas the center of the substrate having the small centrifugal force is inflated by the surface tension of the deionized water.

As described above, as time passes, the diffusion of contaminants into deionized water gradually decreases, and deionized water swells in the center of the substrate. It is necessary to reduce the convex portion of the deionized water formed.

Therefore, according to the substrate cleaning method of the present invention, after the deionized water liquid (l) and the isopropyl alcohol (IPA: (CH3) 2CHOH) liquid (l) are formulated in an appropriate mixing ratio for rinsing the substrate, This azeotropic mixture is added to the surface of the substrate to rinse the substrate.

Isopropyl alcohol is less soluble to ionic contaminants than water, while the surface tension is less than water, so that when mixed with deionized water, the overall surface tension of the mixture is less than water, resulting in the center of the substrate by the surface tension. It serves to reduce the convex portion of the deionized water formed in the.

In addition, isopropyl alcohol can make azeotropic mixtures which cannot be made pure by removing moisture by distillation. Azeotropic mixtures refer to liquid mixtures in solution in which azeotropic mixtures can occur. In general, the composition of the vapor in equilibrium with the solution in which the two liquid components are mixed differs from that of the solution. This fact applies to the fractionation of a mixed solution of liquid into the component liquid by distillation. In general, when distilling a solution, the composition of the vapor is different from that of the original solution, and only one of the two components of the liquid is increased. Therefore, the composition of the solution itself is gradually increased in the concentration of the other component, accordingly, the boiling point of the solution is continuously changed and changed.

However, in a solution of a specific composition, the composition of the solution and the composition of the vapor are the same at the time of distillation, so that the components of the solution do not change, so that boiling continues at a constant temperature. As described above, boiling at a constant temperature without changing the composition in the liquid mixture solution is referred to as "air boiling", and a certain temperature (boiling point) at which azeotropic boiling occurs is called "azeo boiling point".

As mentioned above, a liquid mixture solution of a specific composition in which azeotropic light occurs is called an azeotropic mixture, which is the "lowest azeotropic mixture" at which the azeotropic boiling occurs at the lowest boiling point of the solution system and at the highest boiling point. It can be divided into two types, "best azeotropic mixture".

According to the present invention, an azeotropic mixture is formed between 10-90: 90-10 with an isopropyl alcohol liquid and deionized water. Preferably, when isopropyl alcohol: deionized water is approximately 95.6: 4.4, water ( Boiling point 99.97 ° C.) and isopropyl alcohol (boiling point 82.3 ° C.) result in azeotropy at 1 atm, 80.4 ° C., which is the lowest azeotropic mixture of deionized water and isopropyl alcohol.

Therefore, when the azeotropic mixture of isopropyl alcohol and deionized water is dispensed onto the rotating substrate for cleaning the substrate, the following three effects further improve the cleaning of the substrate, particularly the rinsing and drying of the substrate. That is, first, the coating film of deionized water and isoflavol alcohol liquid formed on the surface of the substrate becomes thinner toward the edge of the substrate by centrifugal force by the rotation of the substrate.

Next, since isopropyl alcohol has a smaller surface tension than water, the total surface tension of deionized water and isopropyl alcohol becomes smaller, and as a result, the thickness of the film formed on the substrate surface by the mixture of deionized water and isopropyl alcohol is desorbed. It becomes smaller than the thickness of the film formed only with ionized water, and in particular, it is possible to reduce the thickness of the convex portion of the film formed at the center of the substrate. In addition, when deionized water and isopropyl alcohol are mixed at an appropriate composition ratio, evaporation is made easier at room temperature because azeotropes having a lower boiling point are formed. As a result, the rinsing and drying of the substrate during the cleaning of the substrate are further improved.

Further, according to the substrate cleaning method according to the present invention, since a small amount of isopropyl alcohol is used, it is also suitable for the use of isopropyl alcohol, which is expensive to purchase and process.

Further, according to the substrate cleaning method according to the present invention, the use of a small amount of isopropyl alcohol can effectively prevent the generation of water marks remaining on the substrate.

Preferably, as shown in FIG. 1, according to the substrate cleaning method according to the present invention, after the azeotropic mixture of deionized water and isopropyl alcohol is dispensed onto the surface of the substrate 102, the substrate is dispensed using the dispenser 104. The method may further include charging nitrogen gas at the center of the 102. According to this, the physical force can be applied to the convex portion of the center of the substrate by the price of nitrogen gas, so that the thickness of the convex portion formed at the center of the substrate can be reduced together with the isopropyl alcohol liquid mixed with the deionized water.

In addition, preferably, after dispensing an azeotrope of deionized water and isopropyl alcohol on the surface of the substrate 102, the dispenser 104 is used to reduce the thickness of the convex portion formed at the center of the substrate 102. Vapor of isopropyl alcohol may be applied to the center of the substrate 102. At this time, isopropyl alcohol applied to the center of the substrate 102 is dissolved in deionized water to reduce the surface tension, and as a result, the thickness of the center of the substrate surface is reduced.

In addition, preferably, after dispensing an azeotrope of deionized water and isopropyl alcohol on the surface of the substrate 102, the dispenser 104 is used to reduce the thickness of the convex portion formed at the center of the substrate 102. Nitrogen gas and vapor of isopropyl alcohol can be applied simultaneously to the center of the substrate 102.

3 is a cross-sectional view showing an example of an in-line static mixer used in a single substrate cleaning apparatus for mixing a deionized water with isopropyl alcohol to form an azeotropic mixture according to the present invention. .

As shown in FIG. 3, the in-line static mixer 108 is supplied by the spike pump 112 and the spike pump with isopropyl alcohol liquid IPA (l) controlled by the flow meter 110. A deionized water (DIW (l)) supplied by 116 and whose flow rate is controlled by the flow meter 114 is supplied and mixed to form an azeotropic mixture.

If the pre-mixing system is pre-configured outside the unit to mix and supply deionized water and isopropyl alcohol, deionized water and isopropyl as the equipment grows in size and over time in the mixing tank of the unit. Differences occur in the vapor pressure of the alcohol, which results in a change in the composition ratio of deionized water and isopropyl alcohol.

As a result, since the optimum composition ratio of deionized water and isopropyl alcohol cannot be maintained, a problem arises in that an azeotropic mixture having the lowest boiling point cannot be formed. Thus, as shown in FIG. 1, the apparatus 10 used in the substrate cleaning method according to the present invention is an in-line static mixer 108 capable of mixing deionized water and isopropyl alcohol in the apparatus 10. Equipped with.

Typically, the in-line static mixer 108 has a series of elements 302 fixed in the pipe in a lateral direction to convert continuous laminar fluid into the flowing fluid while converting the laminar fluid into a turbulent fluid. It is a device that effectively mixes two or more fluids, gases, and powders. When using this in-line static mixer 108, the three roles of dividing, reversing, and mixing are continuously mixed during the conveying in the pipe while dividing the fluid flow, changing the flow direction, and inverting the flow. can do. As a result, the in-line static mixer 108 improves productivity by reducing process time such as shortening, simplifying and sequencing the mixing process, and reducing production cost (energy saving power cost), and attaching the device 10 to any position. Also effective mixing effect can be obtained.

The substrate cleaning method according to the present invention employs the in-line static mixer 108 as described above, thereby maintaining a constant surface ratio of the azeotropic mixture of deionized water and isopropyl alcohol, despite the passage of time. By dispensing the azeotropic mixture in, the substrate cleaning can be effectively performed.

 The foregoing description of the disclosed embodiments is provided to enable any person skilled in the art to make use of the invention. Many variations of these embodiments will be apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Accordingly, the invention is not limited to the embodiments disclosed herein, and the invention is given the broadest scope consistent with the principles and novel features disclosed herein.

According to the present invention, by adjusting the composition ratio of the deionized water and the liquid having a lower surface tension than the water used in the semiconductor cleaning, the azeotropic mixture which is easy to evaporate even at a lower temperature than the evaporation temperature of the deionized water and the liquid to form a wafer Can be effectively cleaned.

In addition, according to the present invention, by using an in-line static mixer mounted on the dispenser of the semiconductor cleaning apparatus, by forming an azeotropic mixture of deionized water with a constant composition ratio and a liquid having a lower surface tension than water, the wafer can be effectively cleaned. Can be.

Claims (10)

In a method for cleaning a substrate, Rotating the substrate; Dispensing a cleaning liquid onto a surface of the rotating substrate; Mixing deionized water with a liquid having a surface tension less than that of water to produce an azeotropic mixture; Dispensing the azeotropic mixture on the surface of the rotating substrate; And Supplying an inert gas (N 2, Ar, Ne, etc.) to the substrate to complete drying; The boiling point of the azeotropic mixture is lower than the boiling point of the deionized water and the liquid. The method of claim 1, The liquid having a lower surface tension than water is isopropyl alcohol. The method of claim 1, And the azeotropic mixture is produced and supplied by an in-line static mixer. The method of claim 1, And supplying nitrogen gas from the top of the chamber along a circumference in the chamber in which the cleaning of the substrate is performed to form a film of nitrogen gas. The method according to any one of claims 1 to 4, After dispensing the azeotropic mixture, further comprising striking the center of the rotating substrate with a gas. The method of claim 5, wherein Wherein the gas is nitrogen gas The method according to any one of claims 1 to 4, After dispensing the azeotropic mixture, dispensing vapor of a solution having a surface tension less than water onto the rotating substrate. The method of claim 7, wherein The solution of less surface tension than water is isopropyl alcohol (IPA). The method according to any one of claims 1 to 4, After the dispensing the azeotropic mixture, further comprising simultaneously dispensing a vapor of a solution of less than water and a gas onto the rotating substrate. The method of claim 9, Wherein said gas is nitrogen gas and said solution is isopropyl alcohol.

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