KR100875586B1 - Semiconductor substrates drying method using surfactants in supercritical carbon dioxide after wet etching - Google Patents

Abstract

The semiconductor substrate drying method is provided to reduce the dry time by providing the surfactant containing much water in the residue elimination process. The method for removing the acid substance remaining on substrate after the wet etching process includes as follows. The first stage is for performing a rinsing process after the wet etching process. A second step is for manufacturing the rinse liquid by injecting the liquid carbon dioxide into the reactive cell - 1(4) by the pressure supply method(3). The third step is for flowing the rinse liquid of the reactive cell -1 to the reactive cell -2 and completely removing the water of the substrate having within the reactive cell -2. A four step is for increasing the temperature of the high pressure drying container and removing residues in the supercritical carbon dioxide state.

Description

Method for Drying Semiconductor Substrate Using Surfactant in Supercritical Carbon Dioxide After Wet Etching {SEMICONDUCTOR SUBSTRATES DRYING METHOD USING SURFACTANTS IN SUPERCRITICAL CARBON DIOXIDE AFTER WET ETCHING}

The present invention provides a method for removing acidic water remaining on a substrate after wet etching using an aqueous hydrofluoric acid solution, the method of effectively removing water using a acid-resistant, low molecular weight partially fluorinated block copolymer surfactant in supercritical carbon dioxide. It is about.

In recent years, as the size of metal oxide semiconductor high density integrated circuits (MOSLSIs) increases, the size of chips and the miniaturization of LSI manufacturing patterns have been promoted, and patterns having a line width of 100 nm or less are currently being formed. to be. And narrowing the line width means that a pattern with a large aspect ratio (height / width) is formed as a result.

However, typical aqueous processing processes strongly resist important properties such as porous, low-k dielectric materials, where aqueous solutions include mechanical strength, water absorption, thermal expansion coefficient, and adhesion to other substrates. There is an important drawback that affects.

Korean Patent 2005-0008844 is a batch type which is used by immersing in a detergent containing appropriately diluted ammonium fluoride, corrosion inhibitor, surfactant, chelating agent, etc. to remove residue after etching with hydrofluoric acid solution. A single-leaf method of rotating the substrate or semiconductor structure and supplying the cleaning composition to the surface has been proposed, but in particular, the water-based cleaning in a high aspect ratio pattern not only wets the cleaning materials but also wet cleaning the entire wafer. Conversely, there is a disadvantage in that contamination reattaches or collapses the ultrafine pattern due to the high capillary pressure of water. In addition, it consumes a large amount of chemical or pure water, and at the same time emits a large amount of waste liquid and exhaust gas, which is not good in terms of manufacturing cost reduction or environmental conservation.

The problem caused by capillary force can be solved by using a rinse liquid with a small surface tension. To solve this problem of pattern collapse, a rinse liquid with zero surface tension is required, and carbon dioxide close to zero Recently, it has been spotlighted as a suitable cleaning solvent in the electronics industry.

This is the cleanliness and high diffusion of carbon dioxide, so that the solvent can penetrate to a depth of less than a micron and there is no capillary force during drying, so no pattern collapse occurs. This advantage is also key to microelectromechanical systems technology that integrates three-dimensional microstructures, circuits, sensors, and actuators on silicon substrates.

However, if the supercritical carbon dioxide is to be used in the drying process after the aqueous process, an appropriate surfactant is required for mixing the residual water and carbon dioxide fluid. In particular, in order to effectively remove the residual water as a carbon dioxide fluid after the wet etching process, the surfactant must be resistant to hydrofluoric acid, which is a strong acid present in the remaining water, so that the chemical structure is not changed during the treatment and the performance can be maintained. In addition, the surfactant must have a dissolving power in the supercritical carbon dioxide and excellent hydration ability to completely remove the water. Conventional salts of the conventional salt form has the disadvantage of losing the properties of the surfactant by decomposition or protonation (protonation) in a strong acid atmosphere.

The semiconductor manufacturing industry and microelectromechanical system technology consist of a variety of ultra-fine fabrication processes that use large amounts of toxic chemicals and expensive ultrapure water. In addition to environmental necessity, supercritical carbon dioxide solvent technology is being actively researched because it is difficult to control the ultrafine structure with the existing technology.

Carbon dioxide is nontoxic, flame retardant, inexpensive and environmentally friendly. Carbon dioxide can be obtained as a by-product of many chemical processes or collected from the atmosphere. And the carbon dioxide used is recycled over 99%. Therefore, the ultrafine processing process technology using a carbon dioxide solvent minimizes the use of toxic chemicals, eliminates the consumption of expensive ultrapure water, and reduces the process steps.

In addition, carbon dioxide has a relatively low critical temperature and critical pressure (31.1 ℃, 1070 psi) has the advantage that it can easily reach the supercritical state, when the supercritical state has a low viscosity and close to zero surface tension It is effective for cleaning and drying complex structures with fine patterns because of the same density as the liquid, which shows the same diffusivity, penetration and solvent strength.

In order to achieve the above object, the selection of a surfactant that is acid-resistant, good solubility in carbon dioxide and excellent in the water hydration ability and using it with supercritical carbon dioxide to remove acidic water with a short time, a small amount of surfactant cleanly It is done.

In order to achieve the above object, it provides a surfactant that is acid-resistant, good solubility in carbon dioxide and excellent in the water hydration ability.

Specifically, the surfactant carbon dioxide component in the surfactant of the present invention is provided by a partially fluorinated polymer, and the small carbon dioxide component is a low molecular weight block copolymer provided by polyethylene glycol, wherein the polyethylene glycol component has a hydration ability and acid resistance at the same time. Have It also allows for surfactant performance control because the polymer composition can be changed freely.

Moreover, the solubility in carbon dioxide increases as the content of carbon dioxide increases, but using a low molecular weight polyethylene glycol having an affinity for carbon dioxide can reduce the size of the partial fluorinated block, which is a carbon dioxide component, with the same solubility. The surfactant can be implemented.

As a preferred embodiment of the present invention, the present invention provides a surfactant represented by the formula (1).

Formula 1

Wherein m is from 10 to 455, n is from 2 to 100, and R is CH ₂ CF ₂ CF ₂ CF ₃ (dihydro fluorobutyl methacrylate, FBMA), CH ₂ CF ₂ CF ₂ CF ₂ CF ₃ (dihydro fluoropentyl methacrylate, FPMA), CH ₂ CH ₂ (CF ₂ ) ₅ CF ₃ (tetrahydro fluorooctyl methacrylate, 1H2H-FOMA) _, CH ₂ (CF ₂ ) ₆ CF ₃ (dihydro fluorooctyl methacrylate, 1H-FOMA) _, CH ₂ CH ₂ (CF ₂ ) _3-12 CF ₃ (zonyl TM).

The above-described invention provides a structure of a surfactant that reacts with a poly (ethylene oxide) macroinitiator and a partially fluorinated monomer to be a carbon dioxide and retaining pollutant cleaning ability.

The surfactant is acid resistant and designed and manufactured with a low molecular weight to hydrate a large amount of water even in a small amount to simply remove the water remaining on the substrate.

Surfactants are required to effectively remove contaminants from substrates in carbon dioxide fluids, suggesting the use of non-toxic, non-flammable, inert, inexpensive and environmentally harmless carbon dioxide to remove water from the substrate, The surfactants in this study show very good performance in terms of acid resistance, drying effect and economics.

For example, conventional surfactants have a relatively large molecular weight and are difficult to remove contaminants in fine cracks, but the surfactants of the present study are designed to have a low molecular weight so that they can penetrate into the fine parts and leave no residue after drying. There is no advantage.

Unlike conventional surfactants, which are difficult to use due to their lack of affinity with water, the surfactants in this study exhibit good properties of being well soluble in carbon dioxide and absorbing water.

The present invention utilizes a surfactant in a carbon dioxide fluid to separate water from the substrate, and the substrate described above may be in any form, such as a wafer, an aluminum-aluminum oxide substrate, a gallium arsenide substrate, a ceramic substrate, a copper substrate, or the like.

In a preferred embodiment of this aspect, it may be gaseous, liquid or supercritical, preferably liquid and supercritical.

In addition, the carbon dioxide fluid may be used alone, or may be used together with additives such as water, alcohol, and acid base.

Carbon dioxide fluids can be used with 0.1 to 10 percent by weight of additives, which can improve the drying effect when used alone.

The present invention is to develop a surfactant for more effective drying in the carbon dioxide fluid, these materials can be a surface active agent in the carbon dioxide fluid to disperse the materials having a relatively low solubility in the carbon dioxide fluid described above. .

In general, the surfactant is present at the boundary between the contaminant and the carbon dioxide phase, thereby lowering the internal tension between the two components, and as a result, the contaminant is well exported to the carbon dioxide, and the surfactant is usually 0.001 to 30% by weight in the carbon dioxide. Used as a percentage.

In the step of removing water after wet etching of the present invention, FIG. 1 shows a conceptual diagram of a drying apparatus for explaining a method of removing water after wet etching according to the present invention.
As shown in FIG. 1, the semiconductor substrate drying apparatus according to the present invention includes a carbon dioxide supply means 1 and a valve 2 for controlling carbon dioxide flow in and out from the carbon dioxide supply means, and a pressure of carbon dioxide supplied from the carbon dioxide supply means. The pressure supply means (3) to control, the reaction cell-1 (4), the reaction cell-1 (4) prepared by mixing the surfactant to the carbon dioxide adjusted from the pressure supply means by using a magnetic bar (7) The carbon dioxide supply line 5 to which the rinse liquid is moved, the reaction cell-2 (8) and the reaction cell-2 (8) which remove water from the substrate using the rinse liquid prepared in the reaction cell-1 (4). It consists of a temperature control means 9 that can adjust the temperature.
In the present invention, after rinsing (treating with water) after the wet etching process, the reaction cell is placed in the reaction cell-2 (8) while the water is attached to the substrate, and the surfactant is placed in the reaction cell-1 (4). The carbon dioxide supplied from the carbon dioxide supply means 1 is injected into the pressure supply means 3 at a pressure of 1000 to 3000 psi and a temperature of 25 to 28 ° C. and then injected into the reaction cell-1 (4), followed by a magnetic stirrer ( 6) using a magnetic bar (7) to prepare a rinse liquid. At this time, the most preferable conditions are 28 ℃, 3000psi. The rinse liquid is injected into the reaction cell-2 (8) to remove water adhering to the substrate. The temperature is then raised to remove supernatant carbon dioxide while flowing carbon dioxide at a rate of 5 ml per minute as a supercritical carbon dioxide. The supercritical carbon dioxide temperature is 31 ℃ ~ 100 ℃, the pressure is suitable 1070psi ~ 7250psi range, the most preferred conditions are 40 ℃, 3000psi.

delete

As such, the present invention can cleanly remove residual water after wet etching by using an acid resistant surfactant in an eco-friendly supercritical carbon dioxide fluid. The surfactant is designed and manufactured at a low molecular weight, so that it is well dissolved in carbon dioxide even in a small amount and is excellent in water hydration ability, and it may contain a large amount of water in the process of removing residues, which may shorten the drying time. In addition, there is an effect to easily separate the removed water from the semiconductor substrate.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1

PEO after wet etching _2K - b -PZonylTM _8K Removal of Water Using Surfactants

Two stainless steel reactors, connected by a high-pressure syringe pump, consisted of a vessel mixing 4 ml of surfactant and carbon dioxide and a vessel drying 3 ml of substrate.

The substrate drying vessel was a high pressure vessel, and transparent sapphire glass was attached to the outside, and the Teflon-coated magnetic bar was mixed in the surfactant and carbon dioxide mixing vessel so that the mixing was possible.

The carbon dioxide temperature and pressure were set at 28 ° C. and 3000 psi, respectively, and the PEO _2K - b- PZonylTM _8K surfactant added an excess of solubility in carbon dioxide.

The wet etched semiconductor wafer specimen was subjected to a cleaning reaction by immersing a 1 × 1 cm sensitizer piece into a drying vessel before drying. After that, the carbon dioxide and surfactant rinse solution were treated at 3000 psi pressure at 5 ml / min until water disappeared, and the water observed inside the vessel disappeared after 10 minutes.

After 2 to 3 more minutes, the supply of carbon dioxide and surfactant rinse solution was stopped, the carbon dioxide solution was injected to release the internal solution, replaced with a pure carbon dioxide solution, and the temperature was raised to 40 ° C. and treated with supercritical carbon dioxide. Finally, the vessel outlet valve was opened, dried at a rate of 5 ml per minute, and observed by SEM.

As a result, a clean pattern without expansion and collapse was obtained.

Comparative example  One

After wet etching Supercritical Carbon Dioxide  Water removal

As a result of the experiment using only supercritical carbon dioxide without a surfactant in the above-described method, the result was that water was not dried at the same time, and it was found that the hydration ability of the surfactant was important to shorten the time.

Comparative example  2

F- after wet etching AOT  Removal of Water Using Surfactants

Experiments using the F-AOT surfactant in the above-described method resulted in the decomposition of the surfactant and the decomposition of the surfactant on the substrate, resulting in the presence of more residues. This was important.

1 is a conceptual diagram of a drying apparatus for explaining a method for removing water after wet etching according to the present invention.

* Description of the symbols for the main parts of the drawings *

1: CO2 supply means, 2: Valve, 3: Pressure supply means, 4: Reaction cell-1, 5: CO2 supply line, 6: Magnetic stirrer, 7: Magnetic bar, 8: Reaction cell-2, 9: Temperature control means

Claims (9)

delete After the wet etching process, the acidic water remaining on the substrate is removed. (a) a first step of rinsing (treating in water) after the wet etching process; (b) after the first step, while the water is attached to the substrate, the liquid carbon dioxide supplied into the reaction cell-2 (8) and supplied from the carbon dioxide supply means 1 and controlled by the pressure supply means 3 is reacted with the reaction cell-1. Injecting (4) to prepare a rinse liquid; (c) a third step of completely removing the water in the substrate in the reaction cell-2 (8) by flowing the rinse solution of the reaction cell-1 (4) to the reaction cell-2 (8) after the second step; And (d) a substrate drying method comprising at least a fourth step of increasing the temperature inside the high-pressure drying vessel after the third step to remove the residue by treating in a supercritical carbon dioxide state; Surfactant is a substrate drying method characterized in that the acid resistance, excellent solubility in carbon dioxide and excellent ability to hydrate the water represented by the formula (1). Formula 1

Wherein m is 10 to 455, n is 2 to 100, R is CH ₂ CF ₂ CF ₂ CF ₃ (dihydro fluorobutyl methacrylate, FBMA), CH ₂ CF ₂ CF ₂ CF ₂ CF ₃ (dihydro fluoropentyl methacrylate, FPMA), CH ₂ CH ₂ (CF ₂ ) ₅ CF ₃ (tetrahydro fluorooctyl methacrylate, 1H2H-FOMA) _, CH ₂ (CF ₂ ) ₆ CF ₃ (dihydro fluorooctyl methacrylate, 1H-FOMA) _, CH ₂ CH ₂ (CF ₂ ) _3-12 CF ₃ (zonyl TM). The method of claim 2, wherein the surfactant is designed and manufactured at a low molecular weight in the range of 1,500 to 70,000 to remove residues in a small amount of about 0.001 weight percent in carbon dioxide. The process of removing the residue by completely removing water by using the liquid carbon dioxide and the surfactant mixture of claim 2 and then raising the temperature in a supercritical carbon dioxide state, the liquid carbon dioxide conditions are 25 ~ 28 ℃ temperature, pressure 1070 ~ 3000 psi, supercritical carbon dioxide conditions are 31 to 100 ℃ temperature, the substrate drying method, characterized in that the pressure is 1070 ~ 7250 psi. The method according to claim 2, wherein the surfactant is saturated with carbon dioxide set to an appropriate pressure by the pressure supply means (3) in the reaction cell-1 (4) to continue flowing water into the reaction cell-2 (8). A method of drying a substrate, characterized in that a constant amount of surfactant is supplied to reaction cell-2 (8) during removal and drying. The method of claim 2, wherein the substrate is used in a cleaning method including a wafer, an aluminum-aluminum oxide substrate, a gallium arsenide substrate, a ceramic substrate, a copper substrate, and the like. The method of claim 2, wherein the carbon dioxide may be used alone or in a cleaning method used as a carbon dioxide fluid with additives such as water, alcohols, acids, and bases. 8. The method of claim 7, wherein the carbon dioxide fluid can be used with 0.1 to 10 percent by weight of the additive when used in combination with an additive. The method of claim 2, wherein the surfactant is used in 0.001 to 30% by weight in carbon dioxide.

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