JP4042412B2 - Cleaning and drying method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for cleaning and drying an object to be processed. More specifically, the object to be processed is cleaned with a large cleaning and drying effect without damaging the microstructure of the object to be processed and without risk of ignition. It relates to a method of drying.
[0002]
[Prior art]
In the process of manufacturing a microstructure such as a semiconductor device or a micromachine, after the process such as an etching process, the cleaning liquid is used for cleaning and removing the etching liquid or the etching residue. The cleaning process and the drying process are necessary.
The microstructure includes a microstructure having no movable part and a microstructure having a movable part. A microstructure having no movable part is a microstructure having a large ratio of opening pattern height and width called aspect ratio (height / width), such as a semiconductor substrate having an LSI fine pattern, or a fine pattern. A fine structure such as a photomask. In addition, a microstructure having a movable portion is a microstructure having a movable portion supported by a substrate while maintaining a narrow space between the substrate and a stationary substrate, for example, a minute driving component called a micromachine. It is a micro structure.
[0003]
Speaking of microstructures that have no moving parts, with the recent increase in the size of MOS LSIs, the miniaturization of LSI patterns has progressed, and now patterns with a line width of 100 nm or less, that is, patterns with a large aspect ratio are formed. It is becoming.
When forming a pattern on a substrate, a resist film is formed on the pattern formation layer, and a processing mask is formed by photolithography. Next, after the pattern forming layer is etched from above the processing mask, a pattern is formed through a cleaning process using a cleaning liquid, followed by a rinsing cleaning process using pure water, and then a drying process.
Also when forming the processing mask, after the development of the resist film by photolithography, a drying process is performed through a cleaning process using a rinse solution. In order to form a fine pattern of an LSI, a processing mask having a fine pattern is required, and thus the resist pattern of the processing mask necessarily has a high aspect ratio.
In other words, the opening pattern of the microstructure having no movable part is increasingly having a high aspect ratio.
[0004]
In addition, miniaturized structures having movable parts such as micromachines are increasingly miniaturized. Here, with reference to FIG. 7, a structure of a microstructure having a movable part such as a micromachine will be described.
As shown in FIG. 7C, the microstructure 40 includes a substrate 42 and a beam structure layer 44 formed on the substrate 42. The beam structure layer 44 is fixed on the substrate 42 by a beam structure layer main body, that is, a plurality of beam structure fixing portions (column portions) 48 formed integrally with a beam structure movable portion 46 described later. The beam portion between the beam structure fixing portions 48 constitutes a beam structure movable portion 46 that approaches and separates toward the substrate. The beam may be a continuous beam or a single beam. Such a beam shape is often used for sensor contacts, vibrators, minute springs, optical elements, and the like.
[0005]
Even when the microstructure 40 is manufactured, an etching process, a cleaning process, and a drying process are necessary.
First, as shown in FIG. 7A, a sacrificial layer (first layer) 50 is formed on the substrate 42 in a predetermined shape. The sacrificial layer 50 is not limited as long as it can be selectively etched with respect to the substrate 42 and the structure layer formed on the sacrificial layer 50. For example, when a Si substrate is used as the substrate 42, SiO 2₂PSG (phosphorus doped glass) and polysilicon are commonly used.
[0006]
Next, as shown in FIG. 7B, a structural layer (second layer) 52 is formed on the entire surface of the substrate 42. In the formation of the structural layer 52, the portion 48 to be the beam structure fixing portion of the microstructure 40 is brought into direct contact with the substrate 42, and the portion 46 to be the beam structure movable portion between the beam structure fixing portions 48. Is stacked on the sacrificial layer 50 to form a laminated body having a beam structure.
The structural layer 52 of the laminated body is patterned into a predetermined shape by a dry etching method, for example, RIE (reactive ion etching) method, and the structural layer 52 is formed on the substrate 42 as shown in FIG. To do.
The material of the structural layer 52 may be anything as long as the sacrificial layer 50 can be selectively etched after the structural layer 52 is formed. Depending on the purpose of the microstructure 40, a metal film, an oxide film, a semiconductor film, or the like may be used. Although used, a SiN layer, a polysilicon layer, or the like formed by using a low pressure CVD method is generally used because of its good mechanical properties and ease of film forming process.
[0007]
Next, the sacrificial layer 50 is removed by a wet etching method using an etchant such as a hydrofluoric acid (HF) aqueous solution to form a microstructure 40 as shown in FIG. Thereafter, a rinsing process with rinsing water is performed to wash away the etchant, and then a drying process is performed.
Alternatively, the sacrificial layer 50 may be removed by dry etching to form the microstructure 40 as shown in FIG. At the time of dry etching, an etching residue remains. Therefore, the etching residue is removed with an acid cleaning solution or an alkaline water-soluble cleaning solution, and a rinsing step is performed to remove the cleaning solution, and then a drying step is performed.
[0008]
[Problems to be solved by the invention]
By the way, when manufacturing a microstructure having no movable part, for example, a semiconductor device, a pattern forming layer was etched by a dry etching method to form a high aspect ratio pattern, it was used immediately after etching or as an etching mask. In many cases, after the resist mask is peeled off, a minute foreign substance remains on the bottom of the groove portion constituting the pattern.
For example, in a semiconductor device such as an LSI, the remaining minute foreign matter affects the performance of the semiconductor device and causes variations in characteristics. Therefore, it is necessary to remove the remaining minute foreign matters in the cleaning process. And when a washing | cleaning process is implemented, a drying process is needed.
[0009]
However, the cleaning and removing process of the dry etching residue of a fine pattern having a large aspect ratio and the drying process have the following problems.
The first problem is that cleaning and drying are difficult. Since the cleaning liquid such as water has a large surface tension, it is difficult to enter the bottom of the pattern groove portion having a high aspect ratio. For this reason, it has been difficult to remove minute foreign matters with the cleaning liquid. Further, even if the cleaning liquid was cleaned, it was difficult to rinse the cleaning liquid with pure water or the like and discharge the rinse water from the groove to the outside to dry the microstructure.
[0010]
The second problem is that the pattern collapses, that is, the pattern is damaged. Pattern collapse is caused by bending force (surface tension or capillary force) caused by the pressure difference between the rinse liquid remaining between patterns and the external air when the semiconductor device is dried, and this capillary force is generated between patterns. Depends on the surface tension of the rinse liquid generated at the gas-liquid interface. This capillary force not only causes the pattern collapse of the resist mask, but also may distort the pattern formed on the silicon substrate or the like of the semiconductor device. Therefore, the magnitude of the surface tension of the rinsing liquid is an important reason for selecting an important rinsing liquid. Pattern collapse occurs when the rinsing liquid is dried, and is more noticeable in high aspect ratio patterns.
[0011]
In addition, there are the following problems in the wet etching process, the cleaning process, and the drying process of the microstructure having the movable part.
The first problem is that the movable part is damaged during the cleaning / drying process. For example, when the sacrificial layer 50 is selectively etched in the production of the microstructure 40 described above, the etching etchant after the etching is rinsed and removed, and the drying process is used in a normal semiconductor device manufacturing process. When the rinsing process and the drying process with pure water are performed as described above, the structural layer 52 held on the substrate 42 is often fixed to the substrate or destroyed via the gap after the sacrificial layer 50.
[0012]
This phenomenon is a drying process in which the rinse liquid used for cleaning / removing the etchant is evaporated from the microstructure 40, and the rinse liquid remaining between the minute gaps between the structural layer 52 and the substrate 42 is evaporated. As the volume is reduced, a suction force is generated between the substrate 42 and the structural layer 50 due to the surface tension of the rinsing liquid. When the rigidity of the structural layer 50 is insufficient, the structural layer 50 is fixed to the substrate 42. This is a phenomenon that the structural layer 50 itself is destroyed.
[0013]
The second problem is that the microstructure itself is damaged. Since the microstructure 40 formed on the substrate 42 is extremely small and mechanically fragile, it is destroyed in the wet etching process and the rinsing process by the pressure of the etchant or the water pressure by stirring in the rinsing solution. It is.
[0014]
Because of the above problems, there is a cleaning and drying method comprising rinsing with pure water and drying with a spin dryer after rinsing or vapor drying with an organic solvent such as isopropyl alcohol, as used in conventional semiconductor processes. It is actually difficult to apply to the etching process of the sacrificial layer of the microstructure.
[0015]
In the above description, the formation of a fine pattern such as an LSI pattern and the production of a micromachine have been described as examples. However, the above problem is not only a problem of formation of a pattern or production of a micromachine, but a micro structure. This problem is applicable to all objects to be processed.
[0016]
Accordingly, an object of the present invention is to provide a large cleaning and drying effect that is safe and free from danger of igniting and the like without damaging the microstructure of the object to be processed and when drying the object having a microstructure. The object is to provide a method of cleaning and drying the object to be processed.
[0017]
[Means for Solving the Problems]
In the course of the present inventors' research into the cause of damage to the microstructure during cleaning and drying of the microstructure, the following was found.
(1) In the cleaning and drying of the microstructure having the movable portion described above, if the rinse is performed using a rinse liquid having a small surface tension, pattern collapse or damage to the movable portion is unlikely to occur. For example, the surface tension of water is about 72 dyn / cm, but the surface tension of methanol is about 23 dyn / cm. Therefore, it is better to dry the methanol after replacing the water with methanol than to directly dry the water. In addition, it is possible to suppress the pattern collapse and the occurrence of damage to the movable part. However, the surface tension of methanol is also quite high, so it is not a complete solution to the problem.
[0018]
(2) A complete solution to the problem of preventing damage due to surface tension is to make the rinsing liquid a fluid with zero surface tension, or replace the rinsing liquid with a fluid with zero surface tension and dry. A liquid having a surface tension of zero is a supercritical fluid.
A supercritical fluid is a fluid in a phase state that occurs at a temperature and pressure above the critical temperature and pressure that are inherent to the fluid substance. In the supercritical state, the fluid substance has a dissolving power in other liquids and solids. Has a unique property that its viscosity is remarkably small and its diffusion coefficient is extremely large, though it is almost equivalent to the liquid state of the substance. In other words, it can be said to be a liquid having gas properties.
[0019]
As a result, the supercritical fluid does not form a gas-liquid interface, so the surface tension becomes zero. Therefore, if it is dried in a supercritical state, the concept of surface tension disappears, so that pattern collapse and movable part damage do not occur at all.
In supercritical drying, usually, a liquefied fluid is introduced and heated to become a supercritical fluid under temperature and pressure conditions above the critical point, and then the supercritical fluid is discharged and then dried under reduced pressure. Supercritical fluid gasifies quickly when the pressure drops below the critical pressure.
[0020]
As the supercritical fluid, many substances that have been confirmed to be in a supercritical state, such as carbon dioxide, ammonia, water, alcohols, low molecular weight aliphatic saturated hydrocarbons, benzene, diethyl ether, etc. are used. be able to.
Among them, carbon dioxide having a supercritical temperature of 31.3 ° C., which is close to room temperature, is one of the preferable materials for the supercritical fluid because it is easy to handle and the sample does not need to be heated to a high temperature.
[0021]
(3) By the way, since supercritical carbon dioxide has properties like a nonpolar organic solvent, its dissolution performance is capable of removing low molecular weight organic substances, but etching residues made of inorganic organic polymer compounds. It is not necessarily effective for removing contaminants such as inspection and removing oxide films.
For this reason, before performing drying with supercritical carbon dioxide, wet cleaning with a chemical solution (cleaning solution) having a proven track record and excellent in dissolving power and oxidative decomposition power is necessary. After cleaning with the cleaning liquid, the object to be processed is transferred from the chemical solution (cleaning liquid) to the rinsing water without being exposed to the atmosphere, and the target object is washed with rinsing water to remove the cleaning liquid, and then supercritical carbon dioxide. It is necessary to replace the rinse water with.
[0022]
(4) Since supercritical carbon dioxide and water or liquid carbon dioxide and water are difficult to dissolve each other, it is not easy to replace water with supercritical carbon dioxide or liquid carbon dioxide. Even if the replacement can be performed, the replacement takes a very long time.
In view of this, it has been proposed to use lower alcohols (having 4 or less carbon atoms) or glycol ethers as a replacement liquid from water to supercritical carbon dioxide by JP-A-9-43587 and JP-A-9-139374. ing.
However, alcohols are designated as dangerous goods category 4 of the Fire Service Act and are flammable. Glycol ethers are highly toxic and difficult to dispose of waste liquids. Both are unsuitable for use at production sites in the mass production stage from the viewpoint of safety.
Moreover, the time required for washing or drying is increased and the cost is increased by adding one replacement step with the replacement liquid.
[0023]
Therefore, the present inventor has conceived a cleaning and drying method according to the following procedure, repeated experiments to confirm the effectiveness of the idea, and came to invent the present invention.
First, the sacrificial layer is wet-etched with an etchant to form an object to be processed having a microstructure in which the movable part is separated from the substrate, and then the etchant is washed and removed with a washing solution, and then replaced with another substitution solution. To do.
Subsequently, the object to be processed is brought into contact with the supercritical fluid in a state where the replacement liquid is attached to the surface of the object to be processed, and the replacement liquid is dissolved in the supercritical fluid and removed.
Next, while maintaining the temperature of the supercritical fluid at or above the critical temperature, the pressure is reduced below the critical pressure, the supercritical fluid is gasified, the object to be treated is dried, and taken out into the atmosphere.
The same procedure is also applied to an object to be processed on which a finely processed pattern having a large aspect ratio is formed by wet etching.
[0024]
Since the surface tension of the supercritical fluid is extremely small, when the supercritical fluid is removed from the surface of the microstructure in the drying process, the stress applied to the object to be processed by the surface tension is negligible. Therefore, the microstructure of the object to be processed is not deformed or broken.
Thereby, for example, in the manufacture of a semiconductor device, it is possible to effectively remove the cleaning liquid or the like adhering during processing.
[0025]
  In order to achieve the above object, based on the above-mentioned knowledge, the cleaning and drying method according to the present invention (hereinafter referred to as the first invention method) is to clean a target object having a microstructure with a cleaning liquid, A method of drying with a supercritical fluid, a cleaning step of cleaning the object accommodated in a processing chamber of a cleaning / drying apparatus with a cleaning liquid, a hydrofluoroether and a hydrophobic ether having a carbon number of 4 or less. A step of substituting the liquid mixture with alcohol or the fluorinated alcohol alone as a replacement liquid and replacing the cleaning liquid with the replacement liquid;Carbon dioxideAnd a step of replacing with a supercritical fluid.
[0026]
Another cleaning and drying method according to the present invention (hereinafter referred to as the second invention method) is a method of cleaning a target object having a microstructure with a cleaning liquid and then drying with a supercritical fluid,
A cleaning step of cleaning the object to be processed contained in a processing chamber of a cleaning / drying apparatus with a cleaning liquid;
A liquid mixture of hydrofluoroether and a small amount of alcohol having 4 or less carbon atoms than the hydrofluoroether, or a step of replacing the cleaning liquid with the replacement liquid using a fluorinated alcohol alone as a replacement liquid;
Converting the replacement liquid in the processing chamber into a supercritical fluid;
It is characterized by having.
[0027]
In the first and second invention methods, the cleaning liquid / rinsing water can be easily removed after the cleaning process and before the supercritical fluid is supplied and dried, and the replacement liquid has a high affinity for the supercritical fluid. It is replaced with.
For example, by using hydrofluoroether and a small amount of added isopropyl alcohol as the replacement liquid, isopropyl alcohol reduces the surface tension of the substrate surface, making it easier for the cleaning liquid / rinsing water to be separated from the substrate, so that surface tension is not generated on the substrate. Then, the cleaning liquid / rinsing water is removed so that the hydrofluoroether wraps the cleaning liquid / rinsing water.
When the added alcohol is isopropyl alcohol, the addition rate of the isopropyl alcohol to the hydrofluoroether is 1% by volume or more and 10% by volume or less.
A mixture of hydrofluoroether and a trace amount of isopropyl alcohol and fluorinated alcohol have no flash point, so they can be processed without the risk of ignition, and the ozone depletion potential is zero, the global warming potential is relatively small, Environmental impact is also small.
[0028]
Still another cleaning and drying method according to the present invention (hereinafter referred to as a third invention method) is a method of cleaning a target object having a microstructure with a cleaning liquid and then drying with a supercritical fluid,
A cleaning step of cleaning the object to be processed contained in a processing chamber of a cleaning / drying apparatus with a cleaning liquid;
Replacing the cleaning liquid with liquefied carbon dioxide to which a terpene solvent has been added;
Converting the liquefied carbon dioxide into a supercritical fluid;
It is characterized by having.
[0029]
In the third invention method, the second petroleum terpene solvent as a compatibilizer is added to carbon dioxide in a small amount in advance, so that the risk of ignition is small compared to alcohol or glycol ether, and the third fluid ( Without using the replacement liquid), the cleaning liquid / rinsing water can be directly replaced with a supercritical fluid such as supercritical carbon dioxide.
A terpene is a general term for a multimer having a unit of 5 carbon atoms based on the isoprene rule, and is often present in plant essential oils. Among them, volatile oils extracted from pine resin and orange peel are called turpentine oil and orange terpene, respectively, and are already used on many industrial scales. These essential oils are mainly called a terpene hydrocarbon because they are mainly composed of a hydrocarbon compound having 10 carbon atoms and have a unique chemical structure.
The terpene solvent is a solvent that is soluble in a nonpolar solvent and water, and the addition rate is 1% by volume or more and 10% by volume or less.
Some terpene-based solvents contain about 90% limonene, have low toxicity and high biodegradability, so that waste liquid treatment is easy.
[0030]
By applying the first to third invention methods, the movable part is destroyed or the movable part is stuck to the substrate due to the difference in stress between the selective etching and the drying that occurs in the conventional sacrificial layer etching method. In addition, it is possible to prevent sticking, and to manufacture a microstructure having a movable portion on a substrate with a high yield by a simple process with high safety and low cost. In addition, when patterning a semiconductor device having a fine pattern, pattern formation can be performed without causing pattern collapse that has conventionally occurred.
[0031]
  In the first to third invention methods, when the object to be processed has a movable part supported by the substrate while maintaining a narrow gap with the substrate, for example, the movable part is already on the object by dry etching. Are formed in a supercritical fluid by introducing a gas into the processing chamber before the step of cleaning with the cleaning liquid, and the object to be processed is immersed in the supercritical fluid, and hydrofluoroether + carbon number 4 A step of substituting a supercritical fluid with a replacement liquid using a mixed liquid of the following alcohols or a fluorinated alcohol as a replacement liquid;Cleaning liquidAnd substituting with. In this embodiment, the gas-liquid interface does not occur in the replacement process or the drying process, so that the movable part is not damaged.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail based on exemplary embodiments with reference to the accompanying drawings.
First, with reference to FIG. 1, the structure of the processing apparatus 10 used when implementing the method of Embodiment 1 to 5 is demonstrated. FIG. 1 is a schematic diagram showing the configuration of a processing apparatus used when carrying out the method of this embodiment.
The processing apparatus 10 is a batch type cleaning / drying processing apparatus that stores a plurality of microstructures W as described above in a cassette and performs cleaning / drying processing.
[0033]
As shown in FIG. 1, the processing apparatus 10 has an opening 12 at an upper portion thereof, a chamber 15 having a processing chamber 14 in which a microstructure introduced through the opening 12 is accommodated, and an opening 12. And a lid 16 for sealing the fluid, a fluid supply source 18 for supplying a processing fluid to the processing chamber 14, a fluid supply means for introducing the processing fluid from the fluid supply source 18 into the processing chamber 14, and a microstructure. The fluid discharge means for discharging the processed fluid from the processing chamber 14 and the heating means 20 for heating the processing fluid introduced into the processing chamber 14 are provided.
The processing fluid is an etchant that dissolves the sacrificial layer of the microstructure, a cleaning solution and rinsing water that removes the etchant or etching residue, a supercritical fluid that dries the microstructure, and so on. , Called processing fluid.
[0034]
The microstructure is carried into and out of the processing chamber 14 through the opening 12. An O-ring 22 is disposed as a seal member between the opening edge of the opening 12 of the processing chamber 14 and the lid 16 so that the opening 12 can be sealed with the lid 16. The lid 16 is connected to the processing chamber 14 by a fastening tool 24 such as a screw, and seals the processing chamber 14. That is, the inside of the processing chamber 14 can be completely sealed by fastening the lid 16 via the O-ring 22 with the fastening tool 24.
In addition, a holding cassette 26 for placing and holding a plurality of microstructures can be disposed inside the processing chamber 14.
[0035]
The fluid supply means includes a pressure / temperature control means 28 for controlling the processing fluid to a predetermined pressure and a predetermined temperature, and a fluid supply port 30 disposed in the processing chamber 14. A processing fluid controlled to a predetermined pressure and temperature by the pressure / temperature control means 28 is introduced into the processing chamber 14 through the port 30.
The fluid discharge means includes a fluid discharge port 32 provided in the processing chamber 14, a discharge pressure valve 34, and a discharge separation device 36 connected to the fluid discharge port 32 via the discharge pressure valve 34.
[0036]
The exhaust pressure valve 34 opens when the internal pressure of the processing chamber 14 exceeds a set pressure, and has a function of discharging the processing fluid introduced into the processing chamber 14. That is, the pressure in the processing chamber 14 can be maintained at a predetermined pressure by the exhaust pressure valve 34.
The discharged liquid separator 36 is a gas / liquid separator, and reduces the discharged processing fluid into a gas component and a liquid component by reducing the pressure to atmospheric pressure. The gas component is a vaporized solvent and / or other substance of the processing fluid, and is recovered as an exhaust gas by a gas recovery device (not shown). The liquid component is obtained by separating the remaining medium composed of the replacement liquid or the additive phase solvent as a liquid, and is recovered as a discharge liquid.
The recovered exhaust gas is carbon dioxide or the like and can be reused. The recovered effluent can be reused as well.
[0037]
Further, the side wall 15a of the chamber 15 is provided with a heating unit 20 that heats the processing fluid introduced into the processing chamber 14 and maintains the processing fluid at a predetermined temperature.
The heating means 20 is composed of a heating medium such as a heating wire, and controls the power supplied to the heating wire from a power source (not shown) provided outside the processing chamber 14 so that the temperature of the heating means 20 is predetermined. A temperature control device 38 for controlling the temperature is provided.
[0038]
In the following, the processing apparatus 10 is used to etch the microstructure by a wet etching method using an etchant, then rinse and then dry using a supercritical fluid, that is, from the processing step, rinse water is replaced. A replacement step with a liquid, or a replacement step with a replacement liquid into a supercritical fluid, followed by a replacement step with a replacement liquid or rinse water from the supercritical fluid will be described.
Processing process
In forming the microstructure, when the sacrificial layer is dissolved, the holding cassette 26 storing a plurality of microstructures is first accommodated in the processing chamber 14 from the opening 12 of the processing chamber 14.
Next, the lid 16 is closed to seal the processing chamber 14. Subsequently, a predetermined processing fluid, that is, an etchant is introduced into the processing chamber 14 from the fluid supply source 18. Then, the microstructure is held in the processing chamber 14 at a predetermined temperature for a predetermined time, and the sacrificial layer is etched.
[0039]
Replacement process
For example, in the replacement step with the supercritical fluid, the processing fluid supplied from the processing fluid supply source 18 is set to a predetermined pressure and a predetermined temperature by the pressure / temperature control means 18, and enters the processing chamber 14 via the supply port 30. Introduce. At this time, the processing fluid introduced into the processing chamber 14 by the heating means 20 is heated, and the processing fluid in the processing chamber 14 is heated to a predetermined temperature to become a supercritical fluid.
The temperature of the processing fluid is controlled by the temperature control device 38. When the internal pressure of the processing chamber 14 becomes equal to or higher than a certain pressure, the exhaust pressure valve 34 is opened, and the processing fluid is discharged out of the system via the discharged liquid separator 36. The fluid to be discharged is an etchant, rinse water, supercritical fluid, or the like depending on the fluid to be replaced in the replacement step. The generated waste liquid is separated and recovered and regenerated as necessary.
As described above, by appropriately discharging the processing fluid filled in the processing chamber 14, the pressure and temperature in the processing chamber 14 can be kept constant.
[0040]
Supercritical drying process
For example, when carbon dioxide is used as the supercritical fluid, the temperature is increased to 31.1 ° C. or higher after the carbon dioxide is converted to a supercritical fluid at 31.1 ° C. or higher and 7.38 MPa or higher in the supercritical drying step. While maintaining, the pressure is reduced to atmospheric pressure. Next, the temperature is lowered from 31.1 ° C. or higher to room temperature (for example, 20 ° C.). When the process chamber is depressurized to discharge carbon dioxide and cooled, the substrate is filled with gaseous carbon dioxide, the rinse water or the replacement liquid is removed together with the carbon dioxide, and the inside of the process chamber 14 is dried.
By passing through the supercritical drying step, the microstructure having a beam shape or the fine pattern of the semiconductor device can be dried without breaking.
[0041]
The processing fluid that has entered the effluent separator 36 through the evacuation valve 24 is gas-liquid separated when the pressure is reduced to atmospheric pressure. For example, the substitution liquid and the compatibilizer, which are media, are separated as a liquid and collected as an exhaust liquid. A substance such as carbon dioxide as a solvent is separated as a gas, exhausted, and collected.
The recovered effluent and exhaust gas can be reused. Since the terpene solvent contains limonene, it can be reused for disposal of waste materials such as plastics if its purity is poor and it cannot be regenerated.
[0042]
The above-described processing apparatus 10 and the procedure of the cleaning and drying method can also be applied when the microstructure is provided on the object to be processed by dry etching and then the etching residue is removed.
Further, the above-described processing apparatus 10 can be used as a single wafer type for cleaning / drying the microstructures one by one. Moreover, the procedure of the washing and drying method is the same as that described above.
[0043]
Embodiment 1
This embodiment is an example of an embodiment in which the cleaning and drying method according to the first invention method is applied to wet etching of a sacrificial layer of a microstructure, and subsequent cleaning and drying. FIG. It is a flowchart which shows the procedure of the washing | cleaning and drying method of an example.
In the present embodiment example, first, the processing step and then the replacement step are performed, and then the process proceeds to the supercritical drying step.
(1) Processing process
Step S₁Then, the microstructure is placed in the processing chamber 14, immersed in a processing fluid (etchant), and the sacrificial layer is removed by a wet etching method.
(2) Replacement process
Step S₂Then, in a state where the microstructure is immersed in the processing fluid in the processing chamber 14, the processing fluid is discharged while supplying the rinsing water to the processing chamber 14, and the processing fluid is gradually diluted. Replace with rinse water.
The processing fluid discharged as the waste liquid is separated by the discharged liquid separation device 36, and is recovered and regenerated as necessary.
[0044]
Step S_ThreeThen, in a state where the microstructure is immersed in the rinse water, the rinse water is discharged while supplying a mixed liquid of hydrofluoroether + 5% by volume isopropyl alcohol (hereinafter referred to as IPA) to the treatment chamber 14 as a replacement liquid. The rinse water is gradually diluted and replaced with a replacement solution. Hydrofluoroether +5 vol% IPA is sold by Sumitomo 3M as Novec HFE71IPA.
IPA reduces the surface tension of the surface of the microstructure so that the rinsing water can be easily separated from the surface, and surface tension is not generated on the surface. The hydrofluoroether encloses the rinse water and removes the rinse water. Thereby, the microstructure is filled with the hydrofluoroether.
Instead of a mixed liquid of hydrofluoroether + 5% by volume IPA, a fluorinated alcohol may be used as a replacement liquid. Fluorinated alcohol is used in various products as a refrigerant.
[0045]
The mixed waste liquid of hydrofluoroether / 5% IPA and water, or the mixed waste liquid of fluorinated alcohol and water is separated by the discharge liquid separation device 36 and recovered and regenerated as necessary.
[0046]
Step S_FourThen, the processing chamber 14 is pressurized to a predetermined pressure of 5 Mpa or more while the microstructure is immersed in the replacement liquid, and the predetermined pressure is maintained.
Hydrofluoroethers and fluorinated alcohols are highly volatile, so it is necessary to control the pressure precisely so that they volatilize and no gas-liquid interface is formed.
Step S_FiveThe replacement liquid is discharged while supplying liquefied carbon dioxide to the processing chamber 14 maintained at a predetermined pressure, and the replacement liquid is gradually diluted and replaced with liquefied carbon dioxide.
The waste liquid of the replacement liquid is separated by the drain liquid separator 36 and is recovered and regenerated as necessary.
[0047]
(3) Supercritical drying process
Step S₆Then, the carbon dioxide in the processing chamber 14 is pressurized to 7.38 Mpa or more, and then step S₇To 31.1 ° C. or higher to bring carbon dioxide into a supercritical state.
Specifically, carbon dioxide is supplied from the processing fluid supply source 18 and introduced into the processing chamber 14 through the supply port 30 at a predetermined pressure of 7.38 Mpa or higher at a predetermined temperature by the pressure / temperature control means 18. . Further, the carbon dioxide introduced into the processing chamber 14 by the heating means 20 is heated to 31.1 ° C. or higher, so that the carbon dioxide in the processing chamber 14 is brought into a supercritical state, and this state is maintained. The temperature control of the carbon dioxide is performed by the temperature control device 38.
[0048]
Step S₈When the processing chamber 14 is depressurized to discharge carbon dioxide and cooled, the microstructure is filled with gaseous carbon dioxide and dried.
The recovered carbon dioxide is liquefied by compression cooling.
[0049]
Embodiment 2
This embodiment is an example in which the cleaning and drying method according to the second invention method is applied to wet etching of a sacrificial layer of a microstructure and subsequent cleaning and drying. FIG. 3 shows this embodiment. It is a flowchart which shows the procedure of the washing | cleaning and drying method of an example.
Also in the present embodiment example, the treatment process and the replacement process are performed, and then the process proceeds to the supercritical drying process.
First, as in the first embodiment, step S is performed.₁Next, step S₂And step S_ThreeThe rinsing water is removed from the processing chamber 14 and the microstructure is filled with a mixture of hydrofluoroether + 5 vol% IPA or fluorinated alcohol.
[0050]
In this embodiment, the process then proceeds to the supercritical drying process. In the supercritical drying process, as shown in FIG._FourThus, the pressure in the processing chamber 14 is increased to 3.2 MPa or more. Then, step S_FiveThen, while maintaining the pressure, the temperature in the processing chamber 14 is raised to 195.9 ° C. or higher to bring the mixed solution or the fluorinated alcohol itself into a supercritical state.
Step S₆Thus, when the pressure in the processing chamber 14 is lowered, the mixed solution or the fluorinated alcohol evaporates, so that the microstructure covered with the mixed solution or the fluorinated alcohol is dried.
The collected mixed liquid or fluorinated alcohol is liquefied by compression cooling.
[0051]
Embodiment 3
This embodiment is another example of an embodiment in which the cleaning and drying method according to the third invention method is applied to wet etching of a sacrificial layer of a microstructure and subsequent cleaning and drying. These are the flowcharts which show the procedure of the washing | cleaning and drying method of this embodiment.
Also in the present embodiment example, the processing step and then the replacement step are performed, and then the process proceeds to the supercritical drying step.
First, as in the first embodiment, step S is performed.₁Processing steps and step S₂The replacement process is performed so that the processing fluid in the processing chamber 14 is replaced with rinsing water.
[0052]
In this embodiment, the process then proceeds to the supercritical drying process. In the supercritical drying process, step S_ThreeThen, the rinse water in the processing chamber 14 is heated to 31.1 ° C. or higher.
Then step S_FourThen, the pressure in the processing chamber 14 is increased to 7.38 Mpa or more, and the rinsing water is gradually discharged while introducing liquefied carbon dioxide in which the terpene solvent has been pressurized and dissolved in advance into the processing chamber 14. Is diluted and replaced with liquefied carbon dioxide. In order to perform the replacement quickly, a terpene solvent is added to the liquefied carbon dioxide as a compatibilizer.
Step S_FiveWhen the processing chamber 14 is depressurized to discharge carbon dioxide and cooled, the microstructure is filled with gaseous carbon dioxide and dried.
Further, the terpene solvent is separated from the carbon dioxide discharged from the processing chamber 14 and recovered and reused, and the recovered carbon dioxide is liquefied by compression cooling.
Incidentally, as a terpene solvent to be added in advance to liquefied carbon dioxide, Nippon Alpha Metals' terpene cleaner EC series and Yashara Chemical's Woody River are commercially available.
[0053]
When the sacrificial layer is etched by the dry etching method instead of the wet etching method, in the first to third embodiments, after the etching process, the microstructure is placed in the processing chamber 14 and the etching residue is removed by an acid cleaning solution or an alkali cleaning solution. Then, the substrate is rinsed with the above procedure without being exposed to atmospheric pressure, followed by a replacement step and a supercritical drying step.
[0054]
Embodiment 4
The present embodiment is an example of an embodiment in which the cleaning and drying method according to the first invention method is applied to the cleaning and drying of a microstructure that has been dry-etched. FIGS. It is a flowchart which shows the procedure of the washing | cleaning and drying method of embodiment.
In the microstructure to which this embodiment is applied, the sacrificial layer has already been removed by dry etching, and a beam structure is formed, but etching residues remain. If such a microstructure is accommodated in the processing chamber 14 and the cleaning liquid is introduced, the beam structure may be damaged when the cleaning liquid contacts the beam structure. Therefore, it is necessary to supply a supercritical fluid from the beginning. There is.
In view of this, in the present embodiment example, the liquid immersion process, the replacement process, and the supercritical drying process are performed.
[0055]
(1) Liquid immersion process
First, the holding cassette 26 storing a plurality of microstructures to be subjected to the cleaning and drying processes for the beam structure is stored in the processing chamber 14 through the opening 12, and the lid 16 is closed to seal the processing chamber 14.
Then step S₁Then, gaseous carbon dioxide is introduced from the fluid supply source 18 into the processing chamber 14. Step S₂Then, the carbon dioxide in the processing chamber 14 is heated to 31.1 ° C. or higher and pressurized to 7.38 Mpa or higher to obtain a supercritical state.
Then step S_ThreeThus, the phase of carbon dioxide in the processing chamber 14 is lowered to change the phase from supercritical carbon dioxide to liquefied carbon dioxide.
Next, step S_FourThen, hydrofluoroether + 5% IPA or fluorinated alcohol is supplied to the processing chamber 14 as a replacement agent, the microstructure is wetted with a cleaning solution, and is cleaned while reducing the pressure as necessary to remove etching residues. To do.
Step S after washing_FiveThus, the processing chamber 14 is depressurized and returned to normal pressure, and the process proceeds to the replacement step.
[0056]
(2) Replacement process
In the replacement process, step S of Embodiment 1 is performed.₂To step S_FiveIn the same manner as shown in FIG.₆To step S₉Perform the operation.
Next, in the supercritical drying process, Step S of Embodiment 1 is performed.₆To step S₈As shown in FIG. 6, as shown in FIG._TenTo step S₁₂Perform the operation.
[0057]
Embodiment 5
The present embodiment is an example of an embodiment in which the cleaning and drying method according to the third invention method is applied to cleaning and drying of a microstructure that has been dry-etched.
As in the fourth embodiment, the method of the present embodiment includes a liquid immersion process, a replacement process, and a supercritical drying process.
First, in the present embodiment example, step S of the embodiment example 4 is performed.₁To step S_FiveIn the same manner as described above, the liquid immersion process is performed.
Next, in the replacement step, step S of Embodiment 3 is performed.₂The rinsing water replacement step is performed in the same manner as described above.
Subsequently, in the supercritical drying process, Step S of Embodiment 3 is performed._ThreeTo step S_FiveProcess in the same way.
[0058]
In Embodiments 1 to 5 described above, since the gas-liquid interface does not pass through the beam structure of the microstructure, the microstructure is destroyed by surface tension during rinsing with pure water after etching or etching residue removal. There is nothing.
In this embodiment, a microstructure having a minute movable part called a micromachine is taken as an example, and a wet etching process, a cleaning / drying process, or a cleaning / drying process after dry etching is described. However, the first to fifth embodiments are not limited to cleaning / drying of a microstructure having a movable part, but include a microstructure such as a semiconductor device having no movable part, for example, pattern formation with a high aspect ratio of a large scale integrated circuit. It can be similarly applied to formation of holes and resist patterns, formation of photomasks, and the like.
[0059]
【The invention's effect】
  As described above, according to the first invention method, a cleaning liquid is replaced with a replacement liquid using a mixture of hydrofluoroether and alcohol having a carbon number of 4 or less less than hydrofluoroether, or a fluorinated alcohol alone as a replacement liquid. And replace the solutionCarbon dioxideBy substituting with the supercritical fluid, it can be dried with the supercritical fluid without risk of ignition, and thus the object to be processed having a microstructure can be cleaned and dried with a great cleaning and drying effect. In addition, since the ozone depletion coefficient is zero and the global warming index is relatively small, there is little environmental impact.
  Further, according to the second invention method, by replacing the cleaning liquid, a mixture of hydrofluoroether and alcohol having a carbon number of 4 or less smaller than hydrofluoroether, or fluorinated alcohol alone is converted into a supercritical fluid, Further, the same effects as those of the first invention method can be obtained with a smaller number of steps.
[0060]
According to the third invention method, the cleaning liquid is replaced with liquefied carbon dioxide to which a terpene solvent is added, and the liquefied carbon dioxide is converted into a supercritical fluid without using the third fluid as a replacement liquid. Since the cleaning liquid can be directly replaced with supercritical carbon dioxide, the object to be processed having a microstructure can be cleaned and dried with a small number of steps, a low cost, and a safe cleaning and drying effect.
The terpene-based solvent is a dangerous material class 4 second petroleum under the Fire Service Law, and is less flammable than alcohols and glycol ethers, so that the apparatus can be handled easily. Terpene solvents are highly biodegradable and have low toxicity, so they are highly safe and easy to handle.
[0061]
By applying the first to third invention methods, the movable part is destroyed or the movable part is stuck to the substrate due to the difference in stress between the selective etching and the drying that occurs in the conventional sacrificial layer etching method. In addition, it is possible to manufacture a microstructure having a movable portion on a substrate with a high yield by a simple process which prevents sticking and is high in safety and low in cost. In addition, when patterning a semiconductor device having a fine pattern, pattern formation can be performed without causing pattern collapse that has conventionally occurred.
By applying the method of the present invention, it is possible to improve quality such as electrical and mechanical characteristics of a fine semiconductor device or micromachine, and to improve product yield.
[0062]
  In addition, when the object to be processed has a movable part supported on the substrate while maintaining a narrow gap with the substrate, for example, when the movable part is already formed on the object to be processed by dry etching, the cleaning liquid Before the step of cleaning with (3), a gas is introduced into the processing chamber to form a supercritical fluid, the object to be processed is immersed in the supercritical fluid, and then a hydrofluoroether and a hydrocarbon having a carbon number of 4 or less less than the hydrofluoroether. A mixed liquid or a fluorinated alcohol simple substance as a replacement liquid,Supercritical fluidBy substituting with a replacement liquid, the object to be processed can be replaced without being exposed to the atmosphere, so that a beam-shaped movable part can be formed without being destroyed by the influence of the surface tension generated at the gas-liquid interface. In this embodiment, the gas-liquid interface does not occur in the replacement process or the drying process, so that the movable part is not damaged.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of a processing apparatus used when carrying out a method of an embodiment.
FIG. 2 is a flowchart showing a procedure of a cleaning and drying method according to Embodiment 1;
FIG. 3 is a flowchart showing a procedure of a cleaning and drying method according to Embodiment 2;
FIG. 4 is a flowchart showing a procedure of a cleaning and drying method according to Embodiment 3;
FIG. 5 is a flowchart showing a procedure of a cleaning and drying method according to Embodiment 4;
FIG. 6 is a flowchart illustrating the procedure of the cleaning and drying method according to the fourth embodiment, following FIG. 5;
FIGS. 7A to 7C are cross-sectional views for each process when a microstructure is manufactured. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Processing apparatus, 12 ... Opening part, 14 ... Processing chamber, 15 ... Chamber, 16 ... Lid, 18 ... Fluid supply source, 20 ... Heating means, 22 ... O-ring, 24 ... Tightening tool, 26 ... holding cassette, 28 ... pressure / temperature control means, 30 ... fluid supply port, 32 ... fluid discharge port, 34 ... discharge pressure valve, 36 ... discharge separator, 38 ... temperature control Device: 40 ... Microstructure, 42 ... Substrate, 44 ... Beam structure layer, 46 ... Beam structure movable part, 48 ... Beam structure fixing part (column part), 50 ... Sacrificial layer, 52: Structural layer.

Claims (7)

A method of cleaning a workpiece having a microstructure with a cleaning liquid and then drying with a supercritical fluid,
A cleaning step of cleaning the object to be processed contained in a processing chamber of a cleaning / drying apparatus with a cleaning liquid;
A liquid mixture of hydrofluoroether and a small amount of alcohol having 4 or less carbon atoms than the hydrofluoroether, or a step of replacing the cleaning liquid with the replacement liquid using a fluorinated alcohol alone as a replacement liquid;
And a step of replacing the replacement liquid with a supercritical fluid of carbon dioxide . A method of cleaning a workpiece having a microstructure with a cleaning liquid and then drying with a supercritical fluid,
A cleaning step of cleaning the object to be processed contained in a processing chamber of a cleaning / drying apparatus with a cleaning liquid;
A liquid mixture of hydrofluoroether and a small amount of alcohol having 4 or less carbon atoms than the hydrofluoroether, or a step of replacing the cleaning liquid with the replacement liquid using a fluorinated alcohol alone as a replacement liquid;
And a step of converting the substitution liquid in the processing chamber into a supercritical fluid. A method of cleaning a workpiece having a microstructure with a cleaning liquid and then drying with a supercritical fluid,
A cleaning step of cleaning the object to be processed contained in a processing chamber of a cleaning / drying apparatus with a cleaning liquid;
Replacing the cleaning liquid with liquefied carbon dioxide to which a terpene solvent has been added;
And a step of converting the liquefied carbon dioxide into a supercritical fluid. When the object to be processed has a movable part supported by the substrate while maintaining a narrow gap with the substrate, before the cleaning step, a gas is introduced into the processing chamber to form a supercritical fluid, said to a step of immersing the object to be processed in the supercritical fluid, a mixture of a small amount of 4 or less carbon atoms of the alcohol from the hydrofluoroether and hydrofluoroethers, or a fluorinated alcohol alone as substitution fluid, the supercritical fluid The cleaning and drying method according to any one of claims 1 to 3 , further comprising a step of replacing the replacement liquid with the cleaning liquid, and a step of replacing the replacement liquid with the cleaning liquid. It said alcohol is a isopropyl alcohol, any one of claims 1, 2 and 4, characterized in that the addition rate for the hydrofluoroether of the isopropyl alcohol is 10% by volume or less than 1 volume% 1 The cleaning and drying method according to Item. When the object to be processed has a first layer and a second layer formed on a substrate, the first layer is selectively removed by a wet etching method in the processing chamber before the cleaning step. Etching to form a microstructure having a movable part made of the second layer supported on the substrate while maintaining a narrow space between the substrate and the substrate. The cleaning and drying method according to any one of claims 1 to 5 . The cleaning and drying method according to any one of claims 1 to 6 , wherein in the cleaning step, rinsing with rinsing water is performed at the end of the cleaning step.

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