JP2001035824A - Method of cleaning substrate and apparatus for cleaning substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-temperature cleaning method for semiconductor substrates, whereby the apparatus can be downsized, a high-concentration chemical solution is economized, the amount of pure water consumed is reduced, and mutual contamination is caused less. SOLUTION: The apparatus comprises a rotatable substrate placing table 5 onto which a substrate 1 is fixed, means 2 and 6 for purging an aqueous solution of dissolved hydrogen prepared by adding hydrogen gas to pure water onto one surface of a substrate 1, ultrasonic wave supplying means for supplying ultrasonic waves to the purged aqueous solution of dissolved hydrogen, and pure water purging means 3 for purging pure water onto both the surface and backside of the substrate 1. By purging the room-temperature aqueous solution of dissolved hydrogen to which ultrasonic vibrations are applied onto the substrate 1, particles and contaminants on the substrate 1 can be removed by the micro-bubbling effect of hydrogen. Since this can be done at room temperature, contamination caused by the evaporation of a chemical solution can be reduced. Further, the traditional batch dipping system wherein substrates are dipped into a chemical solution is replaced with a single wafer cleaning system, whereby the amount of the aqueous solution of dissolved hydrogen and pure water consumed can be reduced, and the apparatus can also be downsized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for cleaning a semiconductor substrate.

[0002]

2. Description of the Related Art There are various types of cleaning of a semiconductor substrate before oxidation / heat treatment, before film deposition, and the like. However, it is generally widely used that several tens of substrates called an RCA process are collectively immersed in a batch. There is a washing style of stacking style. As an example of the prior art, a cleaning method of the RCA process will be described with reference to the drawings.

FIG. 2 is a diagram showing a general configuration of a series of cleaning tanks used in the RCA process. The washing tank is filled with a high concentration chemical solution (ammonia / hydrogen peroxide mixture or sulfuric acid / hydrogen peroxide mixture) and heated to a high temperature (usually 70 ° C to 8 ° C).
(0 ° C. or 130 ° C. to 140 ° C.), and each cleaning tank is distinguished by a material to be cleaned formed on a semiconductor substrate. For example, 8 is sulfuric acid / hydrogen peroxide solution (130 ° C. to 1 ° C.) for removing organic substances and metals.
(40 ° C.). The organic substance corresponds to, for example, a resist remaining on a semiconductor substrate after being processed by an asher. Reference numeral 9 denotes a water washing tank after chemical treatment, and reference numeral 10 denotes a hydrofluoric acid tank for removing chemical oxides. Here, chemical oxide refers to a thin oxide film that grows on the surface when a semiconductor substrate is treated with an oxidizing chemical such as sulfuric acid / hydrogen peroxide solution.

Reference numeral 11 denotes a water washing tank after the hydrofluoric acid treatment, and 12 denotes a mixed liquid tank of ammonia / hydrogen peroxide / pure water (70 ° C. to 80 ° C.) for the purpose of removing particles attached to the surface of the semiconductor substrate. Reference numeral 13 denotes a water washing tank after the chemical treatment, 14 denotes a hydrofluoric acid tank for removing chemical oxides, 15 denotes a final water washing tank after the hydrofluoric acid treatment, and 16 denotes a spin dryer for drying.

In the configuration of FIG. 2, the cleaning process can be generally divided into two systems. One is a process for removing and cleaning contamination and the like on the surface of the semiconductor substrate which starts with the cleaning tank 8 and ends with the cleaning tank 11, and the other mainly performs particle removal which starts with the cleaning tank 12 and ends with the cleaning tank 15. It is a process. Various tanks are arranged as described above, but the order of arrangement may be appropriately changed in consideration of the type of semiconductor device, cleaning purpose, operability, and the like.

[0006]

However, in the above-described cleaning system, there are the following problems caused by using a cleaning tank and arranging many of them.

(1) A high concentration chemical solution is put into a cleaning tank and is always kept at a high temperature. Therefore, a cleaning tank adjacent to the tank is contaminated by evaporation of the chemical solution from the liquid surface or the like, or a semiconductor substrate is located near the cleaning tank. When the substrate is left, there is a high possibility that the substrate surface is contaminated with steam. In particular, contamination by ammonia is a specific problem. (2) Further, there is a disadvantage that the consumption of the chemical solution is large. This is remarkable when the diameter of the semiconductor substrate is increased. For example, in the case of processing a 6-inch substrate, the capacity of the tank is 28 liters. (3) A large exclusion facility is required for the above-described evacuation of the evaporative chemical solution, which increases the cost. (4) Since the capacity of the washing tank is large,
The amount of pure water used for washing by overflow after each chemical treatment is also as large as about 30 L / min. (5) In addition, since the apparatus has a chemical tank / wash tank and each processing tank, the apparatus becomes large, and the area occupied by the clean room also increases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve such a problem, to reduce the size of the apparatus, save high-concentration chemicals, reduce the amount of pure water used, and reduce cross-contamination. Another object of the present invention is to provide a substrate cleaning method and a substrate cleaning apparatus related to a low-temperature cleaning method for a semiconductor substrate.

[0009]

According to a first aspect of the present invention, there is provided a method for cleaning a substrate, comprising rotating a substrate and applying ultrasonic waves to dissolved hydrogen water obtained by adding hydrogen gas to pure water. The method includes a step of discharging dissolved hydrogen water to the surface of the substrate while applying the voltage, and a step of discharging pure water to the substrate to remove the dissolved hydrogen water.

As described above, the step of rotating the substrate and applying the ultrasonic wave to the dissolved hydrogen water obtained by adding the hydrogen gas to the pure water, and discharging the dissolved hydrogen water to the surface of the substrate, and the step of discharging the pure water to the substrate Then, a step of removing dissolved hydrogen water is included, so that particles and contaminants on the substrate can be removed by discharging the dissolved hydrogen water at room temperature subjected to ultrasonic vibration to the substrate. At this time, in particular, hydrogen dissolved on the substrate generates an extremely large number of microbubbles having minute dimensions and generates hydrogen radicals by the action of ultrasonic waves. Dissolved hydrogen water also exists around contaminants such as particles / organic matter and metals on the substrate, so micro-bubbling effect creates hydrogen microbubbles and hydrogen radicals around the contaminants, thereby removing the contaminants by lift-off It is thought to be done. Since this can be performed at room temperature, contamination by chemical vapor is reduced. Furthermore, by using a single-wafer cleaning method instead of a conventional batch immersion method in which a chemical solution is immersed in a substrate, the amount of dissolved hydrogen water and pure water used can be reduced, and the apparatus can be downsized.

According to a second aspect of the present invention, there is provided a method of cleaning a substrate.
, The hydrogen concentration of the dissolved hydrogen water is 1.0 to 1.5 pp
m. Thus, when the hydrogen concentration of the dissolved hydrogen water is 1.0
By setting the content to 1.5 ppm, the micro-bubbling effect of hydrogen is improved. That is, when the hydrogen concentration of the dissolved hydrogen water is 1
When the amount is less than ppm, the removal rate becomes poor due to the amount of radical generation, and when the amount is more than 1.5 ppm, a high pressure is required for dissolution. Further, since the particle removal performance is also saturated, the concentration of 1.5 ppm or more is not necessary.

According to a third aspect of the present invention, there is provided a substrate cleaning apparatus, comprising: a rotatable substrate mounting table to which a substrate is fixed; and a dissolved hydrogen water discharging means for discharging dissolved hydrogen water obtained by adding hydrogen gas to pure water to one surface of the substrate. And ultrasonic supply means for supplying ultrasonic waves to the dissolved hydrogen water to be discharged.

As described above, since the low-temperature cleaning method using the dissolved hydrogen water discharging means and the ultrasonic wave supplying means are provided, and the dissolved hydrogen water supplied with the ultrasonic waves is discharged onto one surface of the substrate, the conventional high-pressure cleaning method is used. Particles and contaminants on the substrate can be removed without using a concentration chemical. For this reason, the surface of the substrate is not contaminated by evaporation of the high-concentration chemical solution or the like. Further, in addition to this, the dissolved hydrogen water is discharged one by one onto the substrate, instead of immersing the substrate in the chemical solution as in the related art, so that the usage amount of the chemical solution can be greatly reduced. In addition, the size of the apparatus can be reduced, and the cleaning throughput can be improved.

According to a fourth aspect of the present invention, there is provided a substrate cleaning apparatus, comprising: a rotatable substrate mounting table on which a substrate is fixed; and a dissolved hydrogen water discharge for discharging dissolved hydrogen water obtained by adding hydrogen gas to pure water to the front and back surfaces of the substrate. Means and ultrasonic supply means for supplying ultrasonic waves to the dissolved hydrogen water discharged to the front and back surfaces of the substrate.

As described above, the apparatus is provided with the low-temperature cleaning method using the dissolved hydrogen water discharging means and the ultrasonic wave supplying means, and the dissolved hydrogen water supplied with the ultrasonic waves is discharged to the front and back surfaces of the substrate. Particles and contaminants on the substrate can be removed without using a high concentration chemical solution. For this reason, the surface of the substrate is not contaminated by evaporation of the high-concentration chemical solution or the like. In addition to this, instead of immersing the substrate in the chemical solution as in the past, a single-wafer type double-side cleaning method that discharges dissolved hydrogen water one by one onto the substrate greatly reduces the amount of chemical solution used. Can be reduced. In addition, the size of the apparatus can be reduced, and the cleaning throughput can be improved.

According to a fifth aspect of the present invention, there is provided a substrate cleaning apparatus according to the fourth aspect.
Or in 5, the apparatus was provided with pure water discharging means for discharging pure water to the front and back surfaces of the substrate. As described above, since the apparatus is provided with the pure water discharging means for discharging the pure water to the front surface and the back surface of the substrate, the remaining dissolved hydrogen water used in the cleaning step can be removed.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a sectional view of a single-wafer-type semiconductor substrate cleaning apparatus used when carrying out a substrate cleaning method according to an embodiment of the present invention. The cleaning method of this embodiment is basically a method of cleaning using a liquid called dissolved hydrogen water in which hydrogen gas is dissolved in pure water at a certain concentration. The hydrogen concentration is desirably 1.0 to 1.5 ppm. In FIG. 1, 1 is a semiconductor substrate, 2 is a dissolved hydrogen water discharge nozzle having an ultrasonic supply function and discharging pure water to the surface of the substrate, and 3 is a pure water discharge nozzle for rinsing having an ultrasonic supply function. Reference numeral 4 denotes a drying N ₂ gas discharge nozzle, and reference numeral 5 denotes a substrate mounting table for fixing a semiconductor substrate, that is, a chuck unit. The chuck portion 5 can be rotated around a substantially central portion of the semiconductor substrate as an axis. Reference numeral 6 denotes a nozzle for cleaning the back surface of the semiconductor substrate capable of transmitting ultrasonic waves, and reference numeral 7 denotes a processing chamber. The dissolved hydrogen discharge nozzle 2 and the semiconductor substrate back surface cleaning nozzle 6 discharge dissolved hydrogen water obtained by adding hydrogen gas to pure water to the front and back surfaces of the substrate. In this case, the semiconductor substrate back surface cleaning nozzle 6 can discharge pure water to the substrate back surface separately from the dissolved hydrogen water. Although not shown, the ultrasonic oscillation source is located at a location away from the dissolved hydrogen water discharge nozzle 2, the pure water discharge nozzle 3, and the back surface cleaning nozzle 6, and is connected to these nozzles.

Next, the operation and cleaning process of the semiconductor substrate cleaning apparatus using dissolved hydrogen water configured as described above will be described. First, when the semiconductor substrate 1 is set on the chuck section 5 in the chamber 7, 500 rpm
While the semiconductor substrate 1 is rotated at 1.6 m, the hydrogen concentration at room temperature (25 ° C.) to which ultrasonic vibration of 1.6 MHZ is given.
The surface of the semiconductor substrate 1 is cleaned for a predetermined time while discharging a desired amount of 2 ppm of dissolved hydrogen water from the discharge nozzle 2. During this step, the dissolved hydrogen water discharge nozzle 2 reciprocates at least from the center to the periphery of the semiconductor substrate 1 on the surface of the semiconductor substrate 1, and the nozzle of the semiconductor substrate 1 is moved together with the rotation of the substrate. Dissolved hydrogen water hits the entire surface.

In this process, an extremely large number of microbubbles having a very small size are generated by the action of the ultrasonic waves applied to the discharge nozzles 2, particularly on the semiconductor substrate 1, and hydrogen radicals are generated. Occurs. Semiconductor substrate 1
Dissolved hydrogen water is also present around contaminants such as particles / organic matter and metals on the surface. This micro-bubbling effect creates microbubbles of hydrogen, hydrogen radicals, etc. around the contaminants, thereby removing the contaminants by lift-off. It is thought that. That is, in this embodiment, the cleaning effect of the semiconductor substrate 1 is obtained by the dissolved hydrogen water to which the ultrasonic wave is applied. At this time, a desired amount of dissolved hydrogen water having a hydrogen concentration of 1.2 ppm is also discharged from the fixed back surface cleaning nozzle 6 to which the ultrasonic vibration of 1.6 MHZ is transmitted simultaneously on the back surface side of the semiconductor substrate 1. The back surface is also cleaned at the same time. Further, when the hydrogen concentration of the dissolved hydrogen water is 1 ppm or less, the removal rate becomes poor due to the amount of generated radicals,
When the concentration is above ppm, a high pressure is required for dissolution. Further, since the particle removal performance is also saturated, the concentration of 1.5 ppm or more is not necessary. Therefore, in this embodiment, the hydrogen concentration is set to 1.2 ppm.

Thereafter, the semiconductor substrate 1 is set at 1000 rpm.
And a desired amount of pure water for rinsing is discharged from the pure water discharge nozzle 3 and the back surface cleaning nozzle 6 to remove the remaining dissolved hydrogen water used in the cleaning step onto the semiconductor substrate 1. During this process, the discharge nozzle 3 reciprocates at least from the center to the periphery of the semiconductor substrate 1 on the surface of the semiconductor substrate 1 so that the entire surface of the semiconductor substrate 1 is exposed to pure water for rinsing. Has become. After this,
While the semiconductor substrate 1 is rotated at 1500 rpm, a drying N ₂ gas is discharged from the discharge nozzle 4 to dry the surface of the semiconductor substrate 1, the semiconductor substrate 1 is removed from the chuck portion 5 and taken out from the processing chamber 7.

As described above, in the cleaning method according to this embodiment, first, cleaning is performed with dissolved hydrogen water. In this method, all contaminants such as particles, organic substances, and metals on the semiconductor substrate can be removed with one kind of dissolved hydrogen water, and the method can be performed at room temperature. Chemical termination hardly grows due to hydrogen termination. Therefore, there is no need to remove the oxide using hydrofluoric acid, which has been conventionally required. Needless to say, there is almost no need for conventional high-concentration chemical solutions such as aqueous hydrogen peroxide, ammonia, and sulfuric acid.

Further, since cleaning is performed at room temperature and in dissolved hydrogen water, vapor such as ammonia is not generated, and contamination of the semiconductor substrate, which has been a problem in the past, between chemical solutions or a chemical solution can be prevented. There is no need.

Further, in this embodiment, since the cleaning and rinsing for removing contaminants are performed for each semiconductor substrate, the amount of the cleaning chemical or pure water is smaller than that of the conventional batch immersion method. About 1/10. Accordingly, various cleaning tanks having a large capacity are not required, so that the apparatus itself can be miniaturized, and the occupation area of the installation place can be reduced, which is a great advantage.

Although the back cleaning leaf nozzle also serves as a pure water discharge nozzle, it may be configured separately.

[0025]

According to the method for cleaning a substrate according to the first aspect of the present invention, the substrate is rotated and the dissolved hydrogen water is applied to the substrate while applying ultrasonic waves to the dissolved hydrogen water obtained by adding hydrogen gas to pure water. And a step of discharging pure water to the substrate, and a step of removing dissolved hydrogen water, so that by discharging ultrasonic vibration-imparted room temperature dissolved hydrogen water to the substrate, Particles and contaminants can be removed. At this time, especially the hydrogen dissolved on the substrate is caused by the action of the ultrasonic wave,
A very large number of micro-bubbles of a fine size are generated and hydrogen radicals are generated. Dissolved hydrogen water also exists around contaminants such as particles / organic matter and metals on the substrate, so micro-bubbling effect creates hydrogen microbubbles and hydrogen radicals around the contaminants, thereby removing the contaminants by lift-off It is thought to be done. Since this can be performed at room temperature, contamination by chemical vapor is reduced. Furthermore, by changing from a batch immersion method in which a chemical solution is immersed to a substrate as in the past to a single-wafer cleaning method,
The amount of dissolved hydrogen water and pure water used can be reduced, and the size of the apparatus can be reduced.

In the second aspect, the hydrogen bubbling effect of hydrogen is improved by setting the hydrogen concentration of the dissolved hydrogen water to 1.0 to 1.5 ppm.

According to the substrate cleaning apparatus of the third aspect of the present invention, the substrate cleaning apparatus is provided with a low-temperature cleaning system using a dissolved hydrogen water discharging unit and an ultrasonic supply unit, and the dissolved hydrogen water supplied with the ultrasonic wave is supplied to one of the substrates. Since the liquid is ejected to the surface, particles and contaminants on the substrate can be removed without using a high-concentration chemical solution as in the related art. For this reason, the surface of the substrate is not contaminated by evaporation of the high-concentration chemical solution or the like. Further, in addition to this, the dissolved hydrogen water is discharged one by one onto the substrate, instead of immersing the substrate in the chemical solution as in the related art, so that the usage amount of the chemical solution can be greatly reduced. In addition, the size of the apparatus can be reduced, and the cleaning throughput can be improved. As a result, it is possible to shift from the high concentration / high temperature processing RCA process, which is a conventional semiconductor substrate cleaning method, to a low temperature cleaning process, and it is possible to prevent contamination by a cleaning chemical solution by adopting a single wafer processing, and to use a cleaning chemical solution amount and an exhaust system. There is an effect that cost can be reduced.

According to the substrate cleaning apparatus of the fourth aspect of the present invention, the substrate cleaning apparatus is provided with a low-temperature cleaning system using a dissolved hydrogen water discharging means and an ultrasonic supply means, and the dissolved hydrogen water supplied with the ultrasonic wave is supplied to the surface of the substrate. In addition, since the liquid is discharged to the back surface, particles and contaminants on the substrate can be removed without using a high-concentration chemical solution as in the related art. For this reason, the surface of the substrate is not contaminated by evaporation of the high-concentration chemical solution or the like. In addition to this, instead of immersing the substrate in the chemical solution as in the past, a single-wafer type double-side cleaning method that discharges dissolved hydrogen water one by one onto the substrate greatly reduces the amount of chemical solution used. Can be reduced. In addition, the size of the apparatus can be reduced, and the cleaning throughput can be improved. As a result, a high concentration / high temperature treatment R which is a conventional semiconductor substrate cleaning method as in claim 3 is achieved.
The transition from the CA process to the low-temperature cleaning process can be achieved, and the adoption of the single-wafer processing can prevent contamination by the cleaning chemical solution, thereby reducing the amount of the cleaning chemical solution and reducing the cost of the exhaust equipment.

According to the fifth aspect, since pure water discharging means for discharging pure water to the front surface and the back surface of the substrate is provided, the remaining dissolved hydrogen water used in the cleaning step can be removed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a semiconductor substrate cleaning apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a semiconductor substrate cleaning apparatus using a conventional RCA process.

[EXPLANATION OF SYMBOLS] 1 semiconductor substrate 2 pure water for dissolved hydrogen water discharge nozzle 3 rinse discharge nozzle 4 for drying N ₂ gas discharge nozzle 5 semiconductor substrate chuck portion 6 back surface cleaning nozzle 7 process chamber 8 sulfuric acid / water tank 9 Rinse tank 10 Hydrofluoric acid tank 11 Rinse tank 12 Ammonia / hydrogen peroxide water tank 13 Rinse tank 14 Hydrofluoric acid tank 15 Rinse tank 16 Spin dryer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B08B 3/08 B08B 3/08 A 3/12 3/12 Z

Claims (5)

[Claims] A step of rotating the substrate, applying ultrasonic waves to the dissolved hydrogen water obtained by adding hydrogen gas to the pure water, and discharging the dissolved hydrogen water to the surface of the substrate, and applying the pure water to the substrate. Discharging and removing the dissolved hydrogen water. 2. The hydrogen concentration of the dissolved hydrogen water is 1.0 to 1.5.
3. The method for cleaning a substrate according to claim 2, wherein the amount is ppm. 3. A rotatable substrate mounting table to which a substrate is fixed, dissolved hydrogen water discharge means for discharging dissolved hydrogen water obtained by adding hydrogen gas to pure water to one surface of the substrate, and said dissolved hydrogen water discharged. A substrate cleaning apparatus comprising: an ultrasonic supply unit that supplies ultrasonic waves to water. 4. A rotatable substrate mounting table to which a substrate is fixed, dissolved hydrogen water discharging means for discharging dissolved hydrogen water obtained by adding hydrogen gas to pure water to the front and back surfaces of the substrate, and a surface of the substrate. A substrate cleaning apparatus comprising: an ultrasonic supply unit configured to supply ultrasonic waves to dissolved hydrogen water discharged to a back surface. 5. The substrate cleaning apparatus according to claim 4, further comprising pure water discharging means for discharging pure water to the front and back surfaces of the substrate.