TWI361451B - Method for cleaning a substrate - Google Patents

Description

1361451 IX. Description of the Invention: [Technical Field] The present invention relates to a method for cleaning a substrate or a wafer in a semiconductor manufacturing process, and more specifically, to a method for producing an azeotrope and using the same to clean a substrate . [Prior Art]

The performance, reliability, and throughput of an integrated circuit are affected by the wafers used in the manufacturing process or by unwanted physical/chemical impurities that remain on the surface of the component after the production process. When the minimum line width of an element becomes small enough to reach a sub-micron level, it is more important to clearly clean the surface of the wafer prior to oxidation and patterning. The technique for cleaning the surface of a semiconductor wafer is roughly classified into a wet chemical cleaning method, a dry cleaning method, a vapor method, and the like, and a wet chemical cleaning method is most often used. In the wet chemical cleaning method, an RCA cleaning method including standard cleaning (parent-1) and quasi-cleaning 2 (SC-2) is most widely used. In general, wet wafer cleaning is performed by immersing approximately 5 〇 1 晶圆 wafers together in a cleaning solution such as SC4 or 5 (:_2, and rinsing them in deionized water (9) 2 ). However, there is a problem in the process of immersing the wafers together in the cleaning solution. Since the process relies on the flow of water through the intermittent wafer to be rinsed, slowness is unavoidable. Therefore, there is an increasing demand for faster cleaning and rinsing of wafers because it takes less time to fabricate semiconductor integrated circuits. Therefore, U.S. Patent Application Serial No. _92,13G discloses a method for improving wafer rinsing in which a single wafer is cleaned in a device. According to this method, 5 1361451 wafers are exposed to a cleaning solution that spins at high speed and then applies or sprays a deionized water onto the rotating wafer to remove the cleaning fluid from the wafer. The centrifugal force of the rotating wafer further improves wafer rinsing. However, even when the wafer is rotated at a high speed, the deionized water is still raised in the wafer, because of the weak centrifugal force and the surface tension of the deionized water, and because of the centrifugal force, the deionized water film is thinner around the wafer.

At this point, high-concentration chemicals diffuse very quickly in deionized water; therefore, although it is effective to use deionized water at the beginning of the rinsing process, the diffusion rate will decrease over time and bulge in the center of the wafer. Ionized water still exists. In order to solve the above problems, U.S. Patent Application Serial No. 09/892,130 teaches a method of applying a solution having a surface tension lower than the surface tension of water (whether in liquid or gaseous form) after application of the chemical and/or application of deionized water. ) to the wafer, such as isopropyl alcohol (ΙΡΑ). According to this method, the chemical is removed from the deionized water with high solubility in the initial stage of the rinsing, and the deionized water layer bulging in the center of the wafer is reduced by the enthalpy in the final stage of rinsing. Accelerate the spread. Another embodiment discloses a method of applying deionized water for rinsing. Another embodiment discloses applying a isopropyl alcohol liquid at one point and deionized water at another point. The method of spraying an isopropanol vapor or liquid method before applying the chemical 'through a nozzle while the wafer is simultaneously exposed through the other nozzle on the wafer - a method of heating at a temperature higher than room temperature Deionized water, such as 60 pins, accelerates the diffusion of chemical 1361451 by supplying thermal energy to deionized water. It also discloses a method of spinning the wafer at a higher speed than during wafer rinsing or applying nitrogen to the wafer after rinsing to dry the wafer.

However, although the prior art has revealed a method of cleaning a substrate using deionized water and a liquid having a surface tension lower than the surface tension of water (for example, isopropyl alcohol), it has not been disclosed by appropriately adjusting the substrate at room temperature. A mixing ratio of deionized water to isopropanol to simplify the drying process. In this regard, the inventors have discovered that the process of cleaning, rinsing, and drying the substrate can be carried out more efficiently at room temperature by using an azeotrope during the cleaning of the substrate, which is aborted It is produced by mixing a deionized water with a liquid having a surface tension lower than the surface tension of water (especially isopropanol). Thus, the present invention provides a method of producing an azeotropic mixture in which a deionized water applied during cleaning of a semiconductor and a liquid having a surface tension lower than that of water are mixed in an appropriate ratio, and the resulting total is used. The mixture is more efficiently cleaned at room temperature. SUMMARY OF THE INVENTION [Technical Problem] An object of the present invention is to provide a method for producing an azeotrope which can be easily evaporated at a temperature lower than a temperature at which deionized water and isopropanol evaporate, by appropriately adjusting A mixing ratio of deionized water for cleaning a semiconductor to a liquid having a surface tension lower than a surface tension of water' and a method for efficiently cleaning a substrate using the azeotrope 1361451 Another object of the present invention is to provide a Method for producing an azeotrope mixture consisting of a liquid having a fixed composition ratio of deionized water and a surface tension lower than the surface tension of water by using an applicator attached to the semiconductor cleaning device The on-axis coaxial static mixer' uses the azeotrope to effectively clean the substrate. [Technical Answers]

In order to achieve the above object, the present invention provides a method for producing an azeotrope mixture which can be easily evaporated at room temperature. The formula is to appropriately adjust a deionized water and a liquid having a surface tension lower than the surface tension of water. The mixing ratio 'is used to rinse the substrate surface during cleaning. Furthermore, the present invention further provides a method of cleaning a wafer by applying the azeotrope to the wafer. The substrate cleaning method according to the present invention comprises the steps of: rotating a substrate; applying a cleaning liquid to the surface of the rotating substrate; producing an azeotrope mixture by mixing a deionized water with a liquid having a surface tension lower than that of water; And applying the azeotrope to the surface of the rotating substrate, wherein the boiling point of the azeotrope is lower than the boiling point of the deionized water to be mixed with the liquid. The substrate cleaning method according to the present invention preferably further comprises, after the step of applying the mutual acid mixture, using a gas to blow the center of the rotating substrate or applying a vapor of a liquid having a surface tension lower than the surface tension of the water to the rotating substrate. Step by step. The substrate cleaning method according to the present invention preferably further comprises the step of simultaneously applying a gas and a vapor of a liquid having a surface tension lower than the surface tension of water to the rotating substrate after the step of applying the composition of the monument #1361451. The azeotrope applied by the substrate cleaning method in accordance with the present invention is preferably produced and provided by a coaxial static mixer. The substrate cleaning method according to the present invention preferably prevents a foreign matter from entering the room by a nitrogen film which is formed by supplying nitrogen gas from above the room around the room where the substrate cleaning is performed.

[Advantages] The present invention can effectively clean a wafer by using an azeotropic mixture which can be easily evaporated at a temperature relatively lower than the temperature at which the deionized water and the liquid evaporate, and the azeotrope is appropriately adjusted to clean the substrate. The composition ratio of deionized water to a liquid having a surface tension lower than the surface tension of water produces 0. The present invention uses a mixture of deionized water having a fixed composition ratio and a liquid having a surface tension lower than that of water. The boiling mixture 'is effectively cleaned the wafer, which is produced by a coaxial static mixer attached to the applicator of the semiconductor cleaning apparatus. [614] [Embodiment] Hereinafter, a more preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view showing an embodiment of a single substrate cleaning apparatus used in a substrate cleaning method in accordance with the present invention.

As shown in FIG. 1, the substrate cleaning apparatus 10 used in the substrate cleaning method according to the present invention includes: a substrate fixing device 1 (also referred to as "chuck") for fixing the upper substrate 102 and rotating it; And a gamma for applying a cleaning liquid, deionized water for rinsing, etc. onto the surface of the rotating substrate; a coaxial static mixer (10) connected to the applicator 106 for mixing to be applied to the surface of the substrate 102 Liquid (such as deionized water and isopropanol) to produce a mixture; flow meters 110, 114, which are connected to the i-axis static mixer to adjust the flow rate of the liquid 2 flowing into the coaxial static mixer; short pulse pump 112, 116' is used to supply liquid to the coaxial 1, mixer; and a room 120 separate from the external environment for performing substrate cleaning. 9 Further, nitrogen is supplied from the room around the inside of the room where the substrate is cleaned to form a "' nitrogen film curtain, thereby preventing the intrusion of impurities outside the room. An embodiment of the fixing device 100, which is used in the substrate cleaning apparatus 10 according to the present invention, will be described with reference to FIG. Apparatus = 2 剖面 A cross-sectional view of an embodiment of a substrate fixing apparatus used in the substrate cleaning apparatus of the present invention. According to an embodiment of the present invention, the substrate fixing device δ @上板 21 '纟 includes a perforated plate 23, and 1361451 has a plurality of holes thereon for irregular and uniform distribution; a plate 22, which is connected To the bottom end of the upper plate 21, to form a gas storage zone, gas flowing in from the outside of the chuck 100 through a mandrel is stored therein; a wafer holder 24' is attached to the side of the substrate by being tightly attached a method for fixing a substrate; and a sensing element including a sensor for sensing the presence of the wafer and a general position of the wafer at the center of the porous plate 23, wherein the perforated plate 23 is circular, and Located at the center of the upper plate 21.

When a gas, for example, nitrogen gas, flows from the gas storage region between the upper plate 21 and the lower plate 22 through the plurality of holes of the perforated plate 23 to the substrate, the substrate attached to the top end of the upper plate 21 is subjected to the pressure of the outflowing gas. The upper side floats while the side of the floating substrate is held by the substrate holder 24. Further, as shown in Fig. 2, a plurality of holes formed on the perforated plate 23 are distributed in an irregular and uniform manner like the shape of a foam sponge. The perforated plate 23 is composed of a highly functional plastic that exhibits the most superior chemical resistance, namely a polytetrafluoroethylene (PTFE), commonly referred to as "Teflon"; therefore, it does not interact with the chemistry used to process the wafer. The product reacts and does not produce any impurities. The size and number of the holes formed in the perforated plate 23 can be adjusted; the size of the holes is preferably from 5 to 800 Å, and the volume is preferably from 5 to 90% by volume of the perforated plate 23. Furthermore, the gas flowing out through the holes is sprayed onto the wafer in an irregular direction. In the present embodiment, the upper plate 21 includes only one circular perforated plate 23, but the outer plate 23 may take any shape such as a polygon or the like, and further, a plurality of points may be arranged in a point symmetrical form with respect to the center of the chuck 10. Multiwell plate. π 1361451 According to the substrate cleaning method of the present invention, the above-described chuck 100 is used to allow nitrogen gas to flow out through the perforated plate 23, and the crucible & 1〇2 floats upward and rotates » SC-1 and SC-2 are generally used as semiconductor cleaning liquids. In use, these liquids are sprayed onto the surface of the rotating substrate 102 to rinse the surface. The process of applying the cleaning liquid to the substrate 1 以及 2 and the process of rinsing the substrate according to the substrate cleaning method of the present invention are carried out in the same apparatus 10. According to an embodiment of the substrate cleaning method of the present invention, in order to rinse the substrate 102, a mixed solution of deionized water (DIW) and isopropyl alcohol (IPA) in an azeotrope state is controlled by an applicator 1〇6. It is applied to the surface of the substrate 1〇2 while the substrate 100 of the cleaning liquid such as sc_2 is sprayed by the chuck 100.

In general, 'deionized water has high solubility in ionic contaminants and is inexpensive to purchase and process, and it is effective in eliminating contaminants' because of the high concentration of chemistry remaining on the substrate during the initial steps of rinsing The article is quickly dispersed in deionized water and reduced. For this reason, deionized water is widely used in the cleaning process of substrates. However, 'when deionized water is applied to a substrate to which a cleaning liquid or an etching solution or the like has been applied for rinsing, the centrifugal force generated by rotating the substrate becomes stronger around the substrate' and thus deionization is formed on the surface of the substrate. The water film is thinner around; however, the centrifugal force in the center of the substrate is relatively weak, which is why the deionized water film is raised in the center. That is, the centrifugal force of the rotating substrate makes the deionized water film thinner around the substrate, and the centrifugal force is weak. The center of the substrate is bulged by the surface tension of the deionized water. As described above, as time passes, the contaminant is dispersed in the deionized water 12 1361451, and the deionized water will bulge in the center of the substrate. Therefore, in order to more effectively rinse and dry the substrate, it is necessary to reduce the raised portion of the deionized water formed in the center of the substrate. According to the substrate cleaning method of the present invention, the deionized water liquid (1) and isopropanol (IPA) are mixed at an appropriate ratio. : (CH3)2CH0H) Liquid (1) to formulate a mutual acid mixture' and apply this azeotrope to the surface of the substrate to rinse the substrate. Although isopropanol has a lower solubility in ionic contaminants than water, its surface tension is lower than the surface tension of water; therefore, when isopropyl alcohol is mixed with deionized water, the overall surface tension of the mixture is lower than that of water. The embossed portion formed by the deionized water at the substrate can be reduced. Furthermore, isopropyl alcohol produces an azeotropic mixture that cannot be converted to a pure product by distillation. Azeotrope refers to a liquid mixture that is in a solution state and that produces an azeotrope. In general, the vapor in the same state as the solution in which the two liquid components are mixed has a composition different from that of the solution itself. This fact is applied when the liquid mixture solution is distilled into each component liquid. When a solution is distilled, the composition of the vapor is usually different from the composition of the original solution, and one component exceeds the other. Therefore, with regard to the composition of the solution itself, the concentration of the other component is gradually increased, and the boiling point of the solution is thus continuously increased. However, a solution having a composition exhibits a pure liquid property; that is, during the distillation, the composition of the solution is the same as that of the vapor, so that the composition of the constituent solution remains unchanged and continues to boil at a specific temperature. Similarly, in the case of a liquid mixture solution, the boiling which occurs at a certain temperature without changing the neon 13 1361451 is called "azeotropic", and the temperature at which azeotropy occurs (boiling point) is referred to as "azeotropic point". As mentioned above, a liquid mixture solution having a specific composition and capable of generating an azeotrope is referred to as an "azeotropic mixture", and the azeotrope is classified into a "minimum co-stagnation mixture" whose azeotropy occurs at the lowest boiling point of the solution system, and "The highest total mixture", its azeotropy occurs at the highest boiling point. According to the present invention, an azeotropic mixture is produced by mixing the ratio of isopropanol liquid to deionized water, wherein the mixing ratio is between 1 〇 -9 〇: 9 〇 1 〇; when the isopropyl alcohol liquid is deionized water The ratio is about 95 6 : 4.4, at a barometric pressure, azeotropy occurs at 80. 4 〇c, its boiling point is lower than the boiling point of water (99. 97 °c) and the boiling point of isopropanol (82 3〇c), which is the lowest azeotropic mixture of deionized water and isopropanol. Therefore, the process of cleaning the substrate, especially the rinsing and drying, by applying an azeotropic mixture of isopropyl alcohol and deionized water to the rotating substrate, can be greatly improved by the following three effects. Specifically, first, the film of deionized water and isopropyl alcohol liquid formed on the surface 0 of the substrate becomes thinner around the substrate due to the centrifugal force of the rotating substrate. Next, the surface tension of isopropyl alcohol is lower than the surface tension of water, resulting in a decrease in the overall surface tension of the mixture of deionized water and isopropyl alcohol; as a result, the film formed by deionized water and isopropyl alcohol on the surface of the substrate is only deionized. The film formed by water is thinner, in particular, the thickness of the film ridge portion appearing in the center of the substrate can be reduced. "When deionized water is used in an appropriate ratio with isopropanol·' σ, a lower point is produced. The co-stagnation mixture is therefore more susceptible to evaporation at room temperature. As a result, the rinsing and drying of the cleaning substrate was further improved by the process of 1361,451. Further, according to the substrate cleaning method of the present invention, only a small amount of isopropyl alcohol is used, so that a somewhat expensive isopropanol can be selected. Further, according to the substrate cleaning method of the present invention, the use of a small amount of isopropyl alcohol can effectively prevent the watermark from remaining on the substrate. As shown in Fig. 1, after the step of applying the azeotropic mixture of deionized water and isopropanol to the surface of the earth plate 102, the substrate cleaning method of the present invention preferably has a 'φ. further comprising blowing nitrogen gas through an applicator. The step to the center of the substrate 102. Blowing out nitrogen increases the physical stress to the raised portion of the substrate, thereby reducing the thickness of the raised portion of the central portion of the substrate, as well as the isopropanol liquid mixed with deionized water. Further, after applying an azeotropic mixture of deionized water and isopropyl alcohol to the surface of the substrate 102, it is preferable to add the vapor of isopropyl alcohol to the center of the substrate 102 by means of an applicator 1〇4 to lower the center of the substrate. The thickness of the raised portion formed. At this time, the isopropyl alcohol added to the center of the substrate 1〇2 was dissolved in 9 deionized water, whereby the surface tension was lowered, and as a result, the thickness at the center of the substrate surface was reduced. Further, after applying an azeotropic mixture of deionized water and isopropyl alcohol to the surface of the substrate 102, it is preferable to simultaneously add a vapor of nitrogen and isopropyl alcohol to the center of the substrate 102 by means of an applicator 1〇4, so that The thickness of the raised portion formed in the center of the substrate is lowered. Figure 3 is a cross-sectional view of an embodiment of a coaxial static mixer for mixing deionized water with isopropanol to produce an azeotrope in a single substrate cleaning apparatus. Figure 1 15 1361451 As shown in Figure 3, 'Coaxial Static Mixer 1' 8 is a device for generating a mixture of buds' by receiving an isopropanol liquid (IPA (1)) supplied by a short pulse pump 112 and controlled by a flow rate meter 110, and by a short pulse pump. 116 is supplied and the flow rate is deionized water (DIff (1)) controlled by a flow meter Π4, and the two are mixed. In the case where a premixing system is employed and a mixture of deionized water and isopropyl alcohol is supplied from outside the apparatus, a larger sized device is required, and with the passage of time in the mixing tank of the 纟 device, the vapor pressure of the deionized water It becomes different from the vapor pressure of isopropyl alcohol; therefore, the composition ratio of deionized water to isopropyl alcohol will change. The result is no 35, maintaining the optimum composition ratio of deionized water to #@帛, thus failing to produce an azeotropic mixture having the lowest boiling point. Therefore, as shown in Fig. 1, the apparatus 10 used in the substrate cleaning method of the present invention is equipped with a coaxial static mixer 108 for mixing in the apparatus 10.

Deionized water and isopropanol. § Ask the glaze static mixer 108 that several elements 3 are continuously fixed from right to left within β, producing a continuous mixing action for the passing fluid' while converting the laminar fluid into a turbulent fluid for effective mixing of the species or fluids. , gas, and powder. The coaxial static mixer plays: the role 'is distinguishing, reversing direction, and mixing, the way is to distinguish the fluid from its direction and change during the transmission within the tube, thereby achieving good Ί so 'using coaxial static mixing stomach 1 〇 8 can Helping to improve health, while achieving better mixing results, it also simplifies '...and reduces time and reduces production costs (for example, by saving energy 16 1361451, making the management of the overall mixing process easier. And regardless of coaxial static mixing) By using the above-mentioned coaxial static mixer, the substrate cleaning method according to the present invention can clean the substrate more efficiently by applying a mixture of the mixture to the substrate surface while maintaining deionized water. The composition ratio of the azeotrope with isopropanol is fixed regardless of the passage of time.

The description of the examples provided herein will allow those skilled in the art to practice the invention freely. Various changes to the embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the embodiments disclosed herein, but all equivalents that conform to the principles of the present invention and the innovative features are included.

17 1361451 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing an embodiment of a single substrate cleaning apparatus used in a substrate cleaning method according to the present invention. Fig. 2 is a cross-sectional view showing an embodiment of a substrate fixing device used in the substrate cleaning method according to the present invention.

Figure 3 is an illustration of an embodiment of a coaxial static mixer used to mix deionized water with isopropanol to produce an azeotrope. [Main component symbol description] 100: Substrate fixing device 102: Substrate (or wafer) 104, 106: Applicator 108: Coaxial static mixer 110, 114: Flowmeter 112, 116: Short pulse pump 120: Room 18

Claims (1)

1361451 X. Patent application scope: 1. A method for cleaning a substrate, rotating a substrate; applying a cleaning liquid to the surface of the rotating substrate by mixing a deionized (DI) water with a tension liquid to produce an azeotrope at 10-90: 90-10; applying an azeotropic mixture to the rotating substrate by providing an inert gas to the substrate (the working 'the boiling point of the liquid in which the surface of the mixture is at the surface tension of the water. 2. The surface tension in the first item of the patent application scope The surface tension lower than water is CnH2n+10H (n=l~10). 3. The azeotrope in the first item of the patent application is from the same wheel. 4. Further included in the first item of the patent application. Nitrogen gas is supplied from above the execution substrate cleaning to form a nitrogen gas. 5. The scope of the application is further included in the center of the application of the rotating substrate. 6. The gas in the fifth aspect of the patent application is nitrogen. 1 '. 7 EI Correction Replacement Page This method consists of the following steps: Surface surface tension is lower than the surface of the water's azeotrope mixture ratio surface; and nitrogen, argon,氖)) to complete drying lower than deionized water and low surface tension 0 The method of cleaning the substrate, the liquid is a protic solvent, especially the method of cleaning the substrate, provided by a static mixer. The method for cleaning a substrate, the method for cleaning the substrate described in the room 4 of the room interior, and the method for cleaning the substrate by a gas, 19 1361451 7. Patent application The method of cleaning a substrate according to any of the items 1 to 4, further comprising applying a vapor of the liquid having a surface tension of less than the surface tension of the water to the rotating substrate after applying the mixture. 8. The method of cleaning a substrate according to claim 7, wherein the liquid having a surface tension lower than a surface tension of water is isopropyl alcohol. 9. The method of cleaning a substrate according to claims 1 to 4, further comprising applying a vapor of a gas and a surface tension lower than a surface tension of the water to the rotating substrate after applying the azeotrope. 10. The method of cleaning a substrate according to claim 9, wherein the gas is nitrogen, and the liquid having a surface tension lower than the surface tension of the water is a protic solvent, especially CnH2n+10H (n=l~l ( Hey.