JPH10284456A - Semiconductor substrate cleaner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the aging deterioration of the etching rate for unwanted films such as natural oxide films due to the reduction of the F ion concn. resulting from the effluence of evaporated HF, and increase the repetition use time of a cleaning liq. to improve the throughput and reduce the cost. SOLUTION: A semiconductor substrate 50 inserted into a cleaning tank 1 through its opening 1c is cleaned with a cleaning liq. prepared by mixing sulfuric acid, hydrogen peroxide water and fluorosulfuric acid fed from a first - third weighing tanks 6a, 6b, 6c to the cleaning tank 1, the opening 1c is closed with a cover 2 and the tank 1 is sealed to suppress the evaporated HF from effluence and the F ion concn. from lowering during cleaning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic substance (including a metal), an organic substance, a particle (such as a fine particle from which a component of a semiconductor substrate has peeled off) or an external substance generated or adhered to the surface of a semiconductor substrate in the process of manufacturing a semiconductor device. Removal of foreign substances such as residues as contaminants from water, or lift-off of unnecessary thin films such as natural oxide films formed during transition from one process to another process (including transport) by slight etching. The present invention relates to an apparatus for cleaning a semiconductor substrate to be removed.

[0002]

2. Description of the Related Art In recent years, the diameter of a semiconductor substrate (silicon wafer) constituting a semiconductor device has been increased from 8 inches (200 mm) to 12 inches (300 mm). Tend to increase. In addition, with the progress of high integration and miniaturization of semiconductor substrates, the foreign substances (inorganic substances, organic substances,
It is necessary to perform a high-performance cleaning process that does not cause residual adhesion of particles and residues) and unnecessary thin films.

Conventionally known high-performance cleaning liquids include sulfuric acid, hydrogen peroxide and fluorine-containing compounds described in, for example, JP-A-4-234118 and JP-A-6-333898. There is a mixture. Sulfuric acid is a typical example of a strongly acidic substance, and removes inorganic substances including metals. Hydrogen peroxide is a typical example of an oxidizing substance, and removes organic substances.

[0004] As the fluorine-containing compound, the technique of the former publication uses hydrofluoric acid (hydrofluoric acid: aqueous solution of hydrogen fluoride) to remove foreign substances such as particles and residues without etching the surface of the semiconductor substrate very much. Remove. As the fluorine-containing compound, the technique of the latter publication uses fluorosulfuric acid or sulfuryl difluoride, and only slightly etches a small amount of unnecessary thin film formed on the surface of the semiconductor substrate by generating fluorine ions. Removes foreign particles such as remaining particles and residues.

In any case, since the surface of the semiconductor substrate is slightly etched, the cleaning effect is high. Since the degree of the etching is a small one on the order of several nm, the physical properties of the semiconductor substrate are not adversely affected.
That is, the expression "etching" used in the present specification does not mean etching (erosion) in a normal sense, but means peeling and removal of an unnecessary thin film only for cleaning. This must be taken into account when considering the detailed description of the invention in interpreting the claims.

[0006] In such a small amount of etching, the amount of surface etching determines the cleaning characteristics. Therefore, during cleaning, it is necessary to make the amount of minute etching on the surface and thus the etching rate substantially constant.

In general, in a semiconductor substrate cleaning apparatus, since cleaning is performed in a state where the cleaning liquid is heated to a relatively high temperature of 80 to 130 ° C., fluorine ions (F ⁻ ) having a surface etching function are produced. Hydrogen fluoride (H
F) tends to evaporate.

[0008] Here, there is experimental data on the evaluation of the concentration of fluorine ions in the evaporation component of a cleaning solution comprising a mixed solution of sulfuric acid, hydrogen peroxide and hydrofluoric acid. In this experiment, two types of cleaning solutions having different sulfuric acid concentrations were prepared. The first cleaning liquid is 24 wt% sulfuric acid and 5 wt%
Of hydrogen peroxide solution, 1 wt% of hydrofluoric acid and water. The second cleaning liquid is composed of 72% by weight of sulfuric acid, 5% by weight of hydrogen peroxide, 1% by weight of hydrofluoric acid and water. Only the weight percentage of sulfuric acid differs. An experiment was conducted by treating each washing solution individually. The cleaning solution was heated to 80 ° C., and the evaporating component from the cleaning solution was collected by the impinger method and analyzed by ion chromatography. As for the first cleaning solution having a sulfuric acid concentration of 24 wt%, the fluorine ion in the evaporating component was The concentration was as low as about 1.0%, and the second cleaning liquid having a sulfuric acid concentration of 72% by weight showed that the fluorine ion concentration in the evaporated component was as high as about 6.2%.
Therefore, in order to remove particles and residues remaining on the surface of the semiconductor substrate, it is preferable to use a cleaning solution having a low sulfuric acid concentration that reduces the amount of evaporation of hydrogen fluoride and thus fluorine ions. However, when the sulfuric acid concentration is reduced, the performance of removing inorganic substances including metal remaining on the surface of the semiconductor substrate is significantly reduced.

In view of this, the technical course of using a cleaning solution having a high sulfuric acid concentration on the premise that the performance of removing inorganic substances is kept sufficiently high and taking measures to suppress fluctuations in the concentration of fluorine ions has been followed. is there. The measure is to add a fluorine-containing compound such as fluorosulfuric acid as a cleaning liquid component.

As a fluorine-containing compound, fluorosulfuric acid (H
In the case of using SO ₃ F), when hydrogen fluoride in the cleaning solution and thus fluorine ions are reduced by evaporation, the reaction of HSO ₃ F + H ₂ O → H ₂ SO ₄ + HF proceeds, and hydrogen fluoride (HF) and fluorine ions ( F ^-) is generated. On the other hand, when the water in the cleaning solution evaporates and the concentration of hydrogen fluoride and thus the concentration of fluorine ions increases, the reaction of HSO ₃ F + H ₂ O ← H ₂ SO ₄ + HF proceeds in the opposite direction, and hydrogen fluoride and Fluorine ions decrease.

In the apparatus for cleaning a semiconductor substrate using a cleaning solution comprising the above components (sulfuric acid, aqueous hydrogen peroxide, and fluorosulfuric acid), as a result of the reversible equilibrium reaction described above, the fluorine ion concentration in the cleaning solution is made substantially constant. They are trying to keep.

[0012]

In a conventional semiconductor substrate cleaning apparatus, a cleaning tank containing a cleaning liquid and immersing the semiconductor substrate set in a carrier in the cleaning liquid for cleaning is provided with an internal pressure of overpressure. It is of the type that is open to the outside in order to prevent negative pressure and negative pressure. A cover may be provided to prevent the washing liquid from scattering, but it does not ensure airtightness, and therefore, outflow of evaporated hydrogen fluoride and moisture is inevitable. In addition, the reversible reaction for automatically maintaining the above-mentioned equilibrium state is merely theoretical.

That is, in the conventional apparatus for cleaning a semiconductor substrate, the processing tank is of an externally open type, and in practice, the fluorination in the cleaning liquid is caused by fluctuations in the absolute amount due to the outflow of evaporation. The concentration of hydrogen, and thus the concentration of fluorine ions, decreases with time, and accordingly, the etching rate also decreases. Incidentally, when a conventional cleaning solution comprising sulfuric acid, hydrogen peroxide solution and hydrofluoric acid is used in an externally open processing tank, the etching rate is relatively high as shown by the broken line characteristic (b) in FIG. There is a problem that the cleaning property is lowered within a short time and the cleaning characteristics become unstable.

The time required for one cleaning treatment depends on the size of the semiconductor substrate, but is usually about 5 to 10 minutes. When the cleaning liquid is repeatedly used, the decrease in the etching rate within the above-mentioned short time becomes a serious problem. That is, cleaning at a reduced etching rate destabilizes the cleaning characteristics. Assuming that the cleaning solution can be reused until the etching rate decreases to 3 nm / min, and the time required for one cleaning process is 10 minutes, the characteristic shown by the broken line in FIG. As shown, it takes about 2 hours (120 minutes) to decrease to 3 nm / min.
Min), the number of times the cleaning solution can be used repeatedly is about 1
The number of cleaning liquids is as small as two, the use cycle of the cleaning liquid is short, and the disposal processing and the generation of the cleaning liquid must be repeated frequently, so that the throughput decreases and the cost required for the cleaning liquid to be used becomes enormous.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a semiconductor substrate cleaning apparatus capable of minimizing a time-dependent decrease in an etching rate of an unnecessary thin film such as a natural oxide film.

[0016]

According to the present invention, there is provided a semiconductor substrate cleaning apparatus for cleaning a cleaning liquid containing a strongly acidic substance and a fluorine-containing compound or a cleaning liquid containing a strongly acidic substance, an oxidizing substance and a fluorine-containing compound. When cleaning the surface of the semiconductor substrate inserted into the cleaning processing tank through the opening with the cleaning liquid, the lid is provided to seal the opening of the cleaning processing tank. It is characterized in that the surface of the semiconductor substrate is cleaned. The opening provided for inserting the semiconductor substrate into the cleaning tank is sealed with a lid, and the cleaning is performed in the sealed cleaning tank. Outflow to the outside can be prevented, and a decrease in the concentration of fluorine ions that contributes to slight etching of the unnecessary thin film can be suppressed. As a result, a temporal decrease in the etching rate of the unnecessary thin film can be suppressed.

Further, the apparatus for cleaning a semiconductor substrate according to the present invention is configured such that components evaporated in the cleaning tank are condensed and liquefied by a condenser, and the liquefied components are collected in the cleaning tank via a recovery pipe. I have. Since the evaporated components are condensed and liquefied, the internal pressure of the cleaning tank is prevented from rising abnormally,
Moreover, since the liquefied component is recovered, there is no loss, and the above-described inhibitory effect is exhibited.

Further, in the semiconductor substrate cleaning apparatus according to the present invention, the oxidizing substance (particularly, hydrogen peroxide solution) is replenished with the oxidizing substance in order to compensate for the evaporated water amount of the generated water. And a means for replenishing the fluorine-containing compound in order to compensate for the evaporated amount of hydrogen fluoride among the hydrogen fluoride generated by the decomposition of the fluorine-containing compound. In this case, there is no need to provide a lid in the cleaning tank, and the insufficient amount of water due to evaporation is compensated for by the decomposition of the oxidized substance that has been replenished. Prevents the semiconductor substrate from being exposed due to a decrease in the liquid level, and pursues the cleaning as expected, while suppressing the decrease in the concentration of fluorine ions that contributes to slight etching of unnecessary thin films by replenishing the fluorine-containing compound. As a result, it is possible to prevent the etching rate of the unnecessary thin film from decreasing over time.

Further, the apparatus for cleaning a semiconductor substrate according to the present invention supplies a cleaning solution containing a strongly acidic substance (particularly sulfuric acid), an oxidizing substance (particularly hydrogen peroxide solution) and a fluorine-containing compound to a cleaning treatment tank, When cleaning the surface of the semiconductor substrate immersed in the cleaning liquid with the cleaning liquid, a decrease in the etching rate due to evaporation of water generated by decomposition of the oxidizing substance (hydrogen peroxide solution) is caused by a strongly acidic substance ( Sulfuric acid)
In order to compensate for the increase in the etching rate due to the decrease in the concentration of, a means for replenishing an oxidizing substance (hydrogen peroxide solution) that generates moisture by decomposition is provided. It is characterized in that the concentration of the strongly acidic substance (sulfuric acid) is reduced by the generation of water. This is because the slight etching characteristics of the unnecessary thin film largely depend on the concentration of the strongly acidic substance (especially sulfuric acid). Above a certain concentration, the lower the concentration, the higher the etching rate. It is based on. Oxidizing substances (particularly aqueous hydrogen peroxide) are decomposed to generate water, and the water evaporates. The fluorine-containing compound is decomposed to generate hydrogen fluoride, and the hydrogen fluoride is also evaporated. Evaporation of hydrogen fluoride tends to lower the etching rate for the unnecessary thin film. The evaporation amount of water is much larger than the evaporation amount of water and the evaporation amount of hydrogen fluoride. Therefore, by supplying a sufficient amount of oxidizing substance (particularly hydrogen peroxide solution), the concentration of the strongly acidic substance (sulfuric acid) is reduced by the water generated by its decomposition, and the etching rate is increased accordingly. To compensate for the decrease in etching rate due to hydrogen fluoride evaporation,
As a result, without replenishment of the fluorine-containing compound, the etching rate is substantially prevented from decreasing over time. From the standpoint of the stability of the cleaning action on the semiconductor substrate, the cleaning effect is stable if the total fine etching amount is constant. The structure is simplified and compact because the means for replenishing the fluorine-containing compound becomes unnecessary.

[0020]

According to a first aspect of the present invention, there is provided an apparatus for cleaning a semiconductor substrate, comprising supplying a cleaning solution containing a strongly acidic substance and a fluorine-containing compound to a cleaning bath, and opening the cleaning bath inside the cleaning bath. In a semiconductor substrate cleaning apparatus for cleaning a surface of a semiconductor substrate inserted from a part with the cleaning liquid, a lid for closing an opening of the cleaning processing tank is provided, and the semiconductor substrate surface is cleaned in a sealed cleaning processing tank. It is characterized by: An inorganic substance containing a metal is removed by a strongly acidic substance, and an unnecessary thin film such as a natural oxide film and foreign substances such as particles and residues are removed by a fluorine-containing compound. The opening provided for inserting the semiconductor substrate into the cleaning tank is sealed with a lid, and the cleaning is performed in the sealed cleaning tank, so that even if the cleaning liquid component evaporates during the cleaning,
It can be prevented from flowing out to the outside, and a decrease in the concentration of fluorine ions contributing to slight etching of the unnecessary thin film can be suppressed, and a decrease in the etching rate of the unnecessary thin film over time can be suppressed.

According to a second aspect of the present invention, there is provided an apparatus for cleaning a semiconductor substrate, comprising: supplying a cleaning solution containing a strongly acidic substance, an oxidizing substance and a fluorine-containing compound to a cleaning tank; In a semiconductor substrate cleaning apparatus for cleaning a surface of a semiconductor substrate inserted from a part with the cleaning liquid, a lid for closing an opening of the cleaning processing tank is provided, and the semiconductor substrate surface is cleaned in a sealed cleaning processing tank. It is characterized by: An inorganic substance containing a metal is removed by a strongly acidic substance, an organic substance is removed by a strongly acidic substance, and an unnecessary thin film such as a natural oxide film and foreign matter such as particles and residues are removed by a fluorine-containing compound. The opening provided for inserting the semiconductor substrate into the cleaning tank is sealed with a lid, and the cleaning is performed in the sealed cleaning tank. Outflow to the outside can be prevented, and a decrease in the concentration of fluorine ions that contributes to slight etching of the unnecessary thin film can be suppressed. As a result, a temporal decrease in the etching rate of the unnecessary thin film can be suppressed.

According to a third aspect of the present invention, there is provided an apparatus for cleaning a semiconductor substrate according to the first or second aspect, wherein a condenser for condensing evaporated components is connected to the cleaning tank. A recovery pipe for collecting components liquefied by the condenser in the cleaning tank is connected to the cleaning pipe. Since the evaporated components are condensed and liquefied in the condenser, the internal pressure of the cleaning tank is prevented from abnormally increasing, and the liquefied components are recovered to the cleaning tank via the recovery pipe, so that there is no loss. Exhibits an inhibitory effect.

According to a fourth aspect of the present invention, there is provided an apparatus for cleaning a semiconductor substrate, comprising supplying a cleaning solution containing a strongly acidic substance, an oxidizing substance, and a fluorine-containing compound to a cleaning tank, and immersing the semiconductor substrate in the cleaning liquid. In a semiconductor substrate cleaning apparatus for cleaning with the cleaning liquid, a means for replenishing the oxidizing substance to compensate for the amount of evaporated water out of the water generated by the decomposition of the oxidizing substance, and the fluorine-containing compound decomposed. Means for replenishing a fluorine-containing compound in order to compensate for the amount of hydrogen fluoride evaporated out of the generated hydrogen fluoride. In this case, it is not necessary to provide a lid in the cleaning tank, and the insufficient amount of water due to evaporation is compensated for by the decomposition of the oxidizing substance (particularly, hydrogen peroxide solution) that has been supplied. Fluoride ions that contribute to slight etching of unnecessary thin films by replenishing fluorine-containing compounds while cleaning is proceeding as expected by preventing the circulation of the cleaning solution from stopping and the level of the cleaning solution dropping to expose the semiconductor substrate. Can be suppressed, and the etching rate of the unnecessary thin film can be prevented from decreasing over time.

According to a fifth aspect of the present invention, there is provided an apparatus for cleaning a semiconductor substrate according to any one of the first to fourth aspects, wherein the strongly acidic substance is sulfuric acid. Sulfuric acid strongly removes inorganic substances including metals.

According to a sixth aspect of the present invention, there is provided an apparatus for cleaning a semiconductor substrate according to any one of the first to fifth aspects, wherein the fluorine-containing compound is fluorosulfuric acid. By using a low concentration of fluorosulfuric acid, slight etching of an unnecessary thin film such as a natural oxide film can be effectively realized, and the unnecessary thin film and foreign matters such as particles and residues can be satisfactorily removed.

According to a seventh aspect of the present invention, there is provided the apparatus for cleaning a semiconductor substrate according to any one of the first to fifth aspects, wherein the fluorine-containing compound is hydrofluoric acid. Hydrofluoric acid also has a function comparable to that of fluorosulfuric acid.

According to an eighth aspect of the present invention, there is provided an apparatus for cleaning a semiconductor substrate according to any one of the first to fifth aspects, wherein the fluorine-containing compound is sulfuryl difluoride. When sulfuryl fluoride is used, a reversible equilibrium reaction for stabilizing the fluorine ion concentration occurs, and the properties of the cleaning solution are stable, so that the etching rate is more stable than in the case of fluorosulfuric acid or hydrofluoric acid.

According to a ninth aspect of the present invention, there is provided an apparatus for cleaning a semiconductor substrate according to any one of the second to eighth aspects, wherein the oxidizing substance is hydrogen peroxide. Hydrogen peroxide strongly removes organic matter.

According to a tenth aspect of the present invention, there is provided the apparatus for cleaning a semiconductor substrate according to any one of the second to eighth aspects, wherein the oxidizing substance is ozone. Ozone strongly removes organic matter.

[0030] According to an eleventh aspect of the present invention, in the apparatus for cleaning a semiconductor substrate according to the first or third aspect, the cleaning solution is a cleaning solution in which a strongly acidic substance is sulfuric acid and a fluorine-containing compound is fluorosulfuric acid. It is characterized by. An inorganic substance including a metal is strongly removed, and slight etching of an unnecessary thin film such as a natural oxide film can be effectively realized, so that the unnecessary thin film and foreign substances such as particles and residues can be satisfactorily removed.

According to a twelfth aspect of the present invention, there is provided the semiconductor substrate cleaning apparatus according to any one of the second to fourth aspects, wherein the strongly acidic substance is sulfuric acid and the oxidizing substance is hydrogen peroxide solution. And a cleaning solution using a fluorine-containing compound as fluorosulfuric acid. Organic substances are strongly removed together with inorganic substances including metals, and slight etching of unnecessary thin films such as a natural oxide film can be effectively realized, and unnecessary thin films and foreign substances such as particles and residues can be satisfactorily removed.

According to a thirteenth aspect of the present invention, there is provided an apparatus for cleaning a semiconductor substrate, comprising supplying a cleaning solution containing a strongly acidic substance, an oxidizing substance, and a fluorine-containing compound to a cleaning bath, and immersing the semiconductor substrate in the cleaning liquid. In the apparatus for cleaning a semiconductor substrate, the etching rate is reduced by the evaporation of moisture generated by the decomposition of the oxidizing substance, and the etching rate is increased by the decrease in the concentration of the strongly acidic substance. For this purpose, a means is provided for replenishing an oxidizing substance which generates water by decomposition, and the concentration of the strongly acidic substance is reduced by the generation of water by the decomposition of the replenished oxidizing substance. this is,
The characteristics of the slight etching of the unnecessary thin film largely depend on the concentration of the strongly acidic substance (especially sulfuric acid), and based on a new finding by the present inventors that the etching rate increases as the concentration decreases above a certain concentration. Things. Oxidizing substances (particularly aqueous hydrogen peroxide) are decomposed to generate water, and the water evaporates. The fluorine-containing compound is decomposed to generate hydrogen fluoride, and the hydrogen fluoride is also evaporated.
Evaporation of hydrogen fluoride tends to lower the etching rate for the unnecessary thin film. The evaporation amount of water is much larger than the evaporation amount of water and the evaporation amount of hydrogen fluoride. Therefore, by supplying a sufficient amount of oxidizing substance (particularly hydrogen peroxide solution), the concentration of the strongly acidic substance (sulfuric acid) is reduced by the water generated by its decomposition, and the etching rate is increased accordingly. As a result, the decrease in the etching rate due to the evaporation of hydrogen fluoride is compensated for, and as a result, the time-dependent decrease in the etching rate is substantially suppressed without replenishment of the fluorine-containing compound. From the standpoint of the stability of the cleaning action on the semiconductor substrate, the cleaning effect is stable if the total fine etching amount is constant. The structure is simplified and compact because the means for replenishing the fluorine-containing compound becomes unnecessary.

According to a fourteenth aspect of the present invention, there is provided a semiconductor substrate cleaning apparatus according to the thirteenth aspect, wherein the strongly acidic substance is sulfuric acid and the oxidizing substance is hydrogen peroxide. Inorganic substances and organic substances can be effectively removed, and the above functions are well exhibited.

According to a fifteenth aspect of the present invention, in the cleaning apparatus of the fourteenth aspect, the fluorine-containing compound is any one of fluorosulfuric acid, hydrofluoric acid, and sulfuryl difluoride. Unnecessary thin films such as a natural oxide film, and foreign substances such as particles and residues can be effectively removed, and the above functions are well exhibited.

According to a sixteenth aspect of the present invention, there is provided the semiconductor substrate cleaning apparatus according to the fourth aspect, the thirteenth aspect, the fourteenth aspect, or the fifteenth aspect, wherein the replenishing means supplies a constant amount every predetermined time. It is characterized by being constituted to supply. This makes it possible to effectively suppress the temporal decrease in the etching rate of the unnecessary thin film.

According to a seventeenth aspect of the present invention, there is provided a semiconductor substrate cleaning apparatus according to any one of the fourth, thirteenth, fourteenth, and fifteenth aspects, wherein the replenishing means determines a replenishing amount per unit time. It is characterized in that it is configured to be supplied continuously at a constant rate. Also in this case, it is possible to effectively prevent the etching rate of the unnecessary thin film from decreasing with time.

Hereinafter, specific embodiments of the semiconductor substrate cleaning apparatus according to the present invention will be described in detail with reference to the drawings.

Embodiment 1 FIG. 1 shows a schematic configuration of a semiconductor substrate cleaning apparatus according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes a cleaning tank composed of an inner tank 1a and an outer tank 1b. The inner tank 1a stores and sets a semiconductor substrate (silicon wafer) 50 to be cleaned together with its carrier 51 and stores a cleaning liquid introduced from the outside. As the carrier 51, an ordinary plastic made of tetrafluoroethylene polymer plastic (Teflon: registered trademark of DuPont) is used. The outer tub 1b is for storing a cleaning liquid like the inner tub 1a, and for collecting pure water overflowing from the inner tub 1a and discharging it to the outside when the inner tub 1a is washed with pure water. An opening 1c is formed in the upper part of the cleaning tank 1 for taking in and out the carrier 51 on which the semiconductor substrate 50 is set. Reference numeral 2 denotes a lid for opening and closing the opening 1c of the cleaning tank 1. Between the lid 2 and the flange of the outer tank 1b of the cleaning tank 1, sufficient airtightness is provided when the lid 2 is closed. Gasket 10 is interposed to maintain the pressure. The gasket 10 is preferably a silicone rubber-based gasket. The lid 2 is pivotally attached to the cleaning tank 1 so as to be rotatable and openable, and is forcibly opened and closed by a lid driving mechanism (not shown) such as an air cylinder. The conventional apparatus does not include the lid 2 for keeping the cleaning tank 1 airtight.

Reference numeral 3 denotes a pressure gauge for measuring the pressure in the cleaning tank 1 with the lid 2 sealed and closed, 4 denotes a forced circulation pump for circulating the cleaning liquid in the cleaning tank 1 and 5
Is a filter for removing inorganic substances, organic substances, foreign substances such as particles and residues, and unnecessary thin films such as a natural oxide film in the circulating cleaning solution. The forced circulation pump 4 and the filter 5 are connected to the bottom of the outer tank 1b. It is provided in a pipe 52 connecting the bottom of the inner tank 1a. 6a is a first weighing tank for weighing and temporarily storing a predetermined amount of sulfuric acid as an example of a strongly acidic substance for removing inorganic substances including metals, 6b
Is a second weighing tank for temporarily weighing and temporarily storing a hydrogen peroxide solution as an example of an oxidizing substance for removing organic substances, and 6c is an unnecessary thin film such as a natural oxide film and particles and residues. This is a third weighing tank for weighing and temporarily storing a predetermined amount of fluorosulfuric acid as an example of a fluorine-containing compound for removing foreign substances. The first weighing tank 6a, the second weighing tank 6b, and the third weighing tank 6c are respectively provided with piping 20a, 20b, 20c and automatic valves 11k, 11m of a pressure feeding system for a large-capacity stock solution tank (not shown). , 11n. Each of the weighing tanks 6a, 6b, and 6c is provided with a liquid level sensor 53a, 53b, and 53c, respectively. 6b and 6c. Each of the liquid level sensors 53a, 53b,
The height of 53c is adjustable, and the height, that is, the volume of the cleaning liquid component stored in each of the tanks 6a, 6b, 6c is adjusted according to the cleaning conditions.

Numeral 54 denotes a common supply pipe for supplying a cleaning liquid component from the bottom of each of the weighing tanks 6a, 6b, 6c to the cleaning tank 1 from the bottom thereof. The bottom and the common supply pipe 54 are connected to the outlet pipes 55a, 55b, 55c and the automatic valves 11e, 1
They are connected via 1f and 11g. Common supply pipe 5
An automatic valve 11a is provided in the middle of 4, and an automatic valve 11h is provided at the drain 7c at the end of the common supply pipe 54. Numerals 19a, 19b, and 19c are connected to the upper portions of the weighing tanks 6a, 6b, and 6c, respectively, and supply the cleaning liquid components in the weighing tanks by sending out nitrogen gas as an example of an inert gas. , 55c
Is a pressure feed pipe for supplying the cleaning treatment tank 1 from the tank via the common supply pipe 54. Reference numerals 22a, 22b, and 22c denote capacitance sensors for detecting that all of the cleaning liquid components in the weighing tanks 6a, 6b, and 6c have individually flowed out, and reference numeral 22d denotes a cleaning tank 1 for all the cleaning liquid components. Is a capacitance sensor for detecting that the supply of the liquid crystal is completed.

Reference numeral 8 denotes an air supply port for introducing a nitrogen gas as an example of an inert gas into an upper portion in the cleaning tank 1, and is provided with an automatic valve 11c. Reference numeral 9 denotes an exhaust port for releasing the pressure by opening the automatic valve 11j when the internal pressure of the cleaning tank 1 becomes higher than a predetermined value. The supply port 8 and the exhaust port 9 are connected to the upper part of the cleaning tank 1. The pressure gauge 3 is a control system 56
It is connected to the.

Reference numeral 21 denotes a heater wound around the outer tank 1b of the cleaning tank 1, 57 denotes a heater driving circuit, 58 denotes a temperature sensor for detecting the temperature of the cleaning liquid in the cleaning tank 1, and a temperature sensor 58 Controls the heater drive circuit 57 via the control system 56 to control the temperature of the cleaning liquid in the cleaning tank 1 at a constant temperature (for example, 100 ° C.).
To).

Reference numeral 7a denotes a drain for discharging the liquid in the outer tank 1b to the outside, which is provided with an automatic valve 11d. Reference numeral 7b denotes a drain for discharging the liquid in the inner tank 1a to the outside.
1b. Reference numeral 23 denotes a pure water supply pipe for supplying pure water for cleaning the inner wall surface of the cleaning tank 1 from the bottom of the inner tank 1a, and is provided with an automatic valve 11i.

It is to be noted that all the automatic valves, the forced circulation pump 4, the heater driving circuit 57, the lid driving mechanism and the like are configured to be controlled by the control system 56.

Next, the operation of the semiconductor substrate cleaning apparatus configured as described above will be described.

First, as a preparation stage, each of the automatic valves 11k, 11m, 11m is controlled by the control operation of the control system 56.
n from each stock solution tank (not shown).
a, 20b, 20c via the weighing tanks 6a, 6
A predetermined amount of undiluted solution is supplied to b and 6c and temporarily stored. That is, the liquid level sensor 53a is provided in the first weighing tank 6a.
Sulfuric acid, which is an example of a strongly acidic substance, is supplied until the operation of the second measuring tank. Hydrogen peroxide water, which is an example of an oxidizing substance, is supplied to the second weighing tank 6b until the liquid level sensor 53b operates. The liquid level sensor 53 is provided in the weighing tank 6c.
Until c operates, fluorosulfuric acid, an example of a fluorine-containing compound, is supplied. Supplied sulfuric acid, hydrogen peroxide solution,
The concentration of fluorosulfuric acid is, for example, about 71 wt%,
It is about 6 wt% and about 0.023 wt%.

Next, the process proceeds to the actual cleaning process. The following sequence operations are all controlled by the control system 56.
First, in a state where the lid 2 is opened, the transfer robot (not shown) is driven by the control operation of the control system 56, and a plurality of semiconductor substrates (silicon wafers) 50 are
Is set in the inner tank 1 of the cleaning tank 1
a is lowered and housed through the upper opening 1c.
When the storage of the carrier 51 is completed and the transfer robot is detected by a sensor (not shown), the cover driving mechanism (not shown) is driven to move the cover 2 to the opening 1 c of the cleaning tank 1. Closed. At this time, the gasket 10 between the lid 2 and the flange of the outer tub 1b is pressed, so that the cleaning tank 1 is kept in a highly airtight state by the lid 2.

When the sensor (not shown) detects that the lid 2 has been closed, the control system 56 controls the cleaning liquid components in the weighing tanks 6a, 6b and 6c into the cleaning tank 1. be introduced. That is, first, the automatic valve 11a of the common supply pipe 54 and the automatic valve 11j of the exhaust port 9 are opened, and the supply of sulfuric acid is started as the first stage. That is, the automatic valve 11e is opened, nitrogen gas is injected from the pressure feeding pipe 19a, and the sulfuric acid stored in the first weighing tank 6a is washed with the pressure through the outlet pipe 55a and the common supply pipe 54. It is introduced into the inner tank 1a of the processing tank 1 from its bottom. When the outflow of sulfuric acid from the first weighing tank 6a is detected by the capacitance sensor 22a, the automatic valve 11e is closed. At this time, since the automatic valves 11f and 11g are closed,
The sulfuric acid is changed to the second weighing tank 6b by the pressure of nitrogen gas.
And does not flow into the third weighing tank 6c. Similarly, the hydrogen peroxide solution in the second weighing tank 6b and the fluorosulfuric acid in the third weighing tank 6c are sequentially supplied to the inner tank 1a. The reason why the automatic valve 11j is opened is to allow the air in the cleaning tank 1 to escape from the exhaust port 9, thereby avoiding a pressurized state due to the inflow of the cleaning liquid component and enabling the inflow of the cleaning liquid component. A cleaning liquid is generated by mixing sulfuric acid, hydrogen peroxide solution, and fluorosulfuric acid supplied to the cleaning tank 1. The total amount of the cleaning liquid is set in advance so as to be an amount that overflows from the inner tank 1a to the outer tank 1b.

When the supply of each cleaning liquid component from each weighing tank 6a, 6b, 6c to the cleaning tank 1 is completed,
That is detected by the capacitance sensor 22d,
The automatic valves 11a and 11j are closed by the control system 56. At this stage, the automatic valves 11e, 11f,
11g, 11h, 11b, 11c, 11d, 11i, 1
1k, 11m, and 11n are in a closed state.

When the capacitance sensor 22d operates as described above, the forced circulation pump 4 and the heater driving circuit 57 are driven by the control operation of the control system 56.
By the operation of the forced circulation pump 4, the cleaning liquid flows into the inner tank 1a from the bottom of the outer tank 1b through the forced circulation pump 4 and the filter 5, and is circulated while overflowing from the inner tank 1a to the outer tank 1b. By this forced circulation, the cleaning liquid components (sulfuric acid, aqueous hydrogen peroxide and fluorosulfuric acid) are uniformly mixed. The heater 21 wound around the outer tub 1 b generates heat by the operation of the heater drive circuit 57, and heats the cleaning liquid in the cleaning tank 1. The temperature sensor 58 detects the temperature of the cleaning liquid, and the temperature of the cleaning liquid is controlled at a constant temperature of about 100 ° C. by temperature control by feedback to the control system 56.

As described above, the cleaning process is performed on the semiconductor substrate 50 by the cleaning solution that is controlled at a relatively high temperature in the cleaning tank 1 and is forcedly circulated. That is, among the components of the cleaning solution, sulfuric acid removes inorganic substances including metal as foreign substances on the surface of the semiconductor substrate 50, hydrogen peroxide removes organic substances, and fluorosulfuric acid slightly removes unnecessary thin films such as natural oxide films. In addition to removing by etching, foreign substances such as particles and residues are also removed. The removed matter is captured by the filter 5 and removed from the circulating washing liquid. Therefore, reattachment to the semiconductor substrate 50 and attachment to the forced circulation pump 4 are prevented.

The internal pressure of the cleaning tank 1 may fluctuate due to a reaction during the cleaning processing. The internal pressure of the cleaning tank 1 is constantly monitored by the pressure gauge 3, and a signal of the detected pressure value is transmitted to the control system 56. If the detected pressure exceeds the set value, the control valve 56 opens the automatic valve 11j to release the excess pressure in the cleaning tank 1 through the exhaust port 9 to the outside. When the internal pressure returns to the set value, the automatic valve 11j
Is closed. Therefore, the internal pressure of the cleaning tank 1 is always kept at a substantially constant value.

Since the semiconductor substrate 50 is cleaned while the cleaning tank 1 is sealed by the lid 2 as described above, as shown by the solid line characteristic A in FIG. As compared with the characteristic B, the characteristic of maintaining the etching rate of the oxide film can be remarkably improved. That is, it is possible to greatly suppress the decrease in the etching rate over time as compared with the conventional case. Specifically, assuming that the cleaning solution can be reused until the etching rate decreases to 3 nm / min, and the time required for one cleaning process is set to 10 minutes, in the conventional case, Since it takes about 2 hours (120 minutes) to decrease to 3 nm / min, the number of times the cleaning solution can be used repeatedly is about 12 times, whereas in the case of the cleaning apparatus of the first embodiment, Since it takes about 105 to 110 hours until the cleaning liquid drops to 3 nm / min, the number of times the cleaning liquid can be used repeatedly becomes about 630 to 660 times, which is about 50 times longer life than the conventional one. The reason for this is as follows.

Hydrogen peroxide water is a chemical solution that is easily decomposed, and is decomposed by light or the presence of metal impurities in the chemical solution to become water and oxygen. Fluorosulfuric acid is decomposed into sulfuric acid and hydrogen fluoride by hydrolysis. Hydrogen fluoride and thus fluorine ions are easily evaporated. Therefore, by closing the cleaning tank 1 with the lid 2, evaporation of hydrogen fluoride can be suppressed sufficiently and the rate of decrease of the concentration of fluorine ions in the cleaning liquid can be suppressed sufficiently low. The rate of the rate over time was greatly suppressed.

The introduction of the sulfuric acid, the hydrogen peroxide solution and the fluorosulfuric acid from the weighing tanks 6a, 6b, 6c into the cleaning tank 1 is carried out individually and sequentially as described above or simultaneously. Good. In the above description, the cleaning process is performed at normal pressure. However, it is preferable that the automatic valve 11c be opened to press the nitrogen gas into the cleaning process tank 1 and perform the cleaning process under a pressurized state. is there. This is because the processing temperature can be increased because the boiling point is increased by pressurization, and the cleaning time can be shortened.

When the cleaning process for the semiconductor substrate 50 is completed, the process is switched to a water cleaning process using pure water. The control valve 56 controls the automatic valve 11a in the common supply pipe 54 and the lead-out pipe 5 of the first weighing tank 6a.
The automatic valve 11e of 5a is opened, and the cleaning liquid in the cleaning tank 1 is collected in the first weighing tank 6a for storage by the weight of the cleaning liquid itself and the pressure of the forced circulation pump 4. At this time, the detection signal from the pressure gauge 3 is controlled by the control system 56 so that the inside of the cleaning tank 1 does not become pressurized and the inside of the first weighing tank 6a does not become negative. While monitoring, supply port 8
Is controlled, and the automatic valve 11k of the first weighing tank 6a is controlled.

When the capacitance sensor 22d detects that the cleaning liquid has flowed out from the cleaning tank 1, the control valve 56 closes the automatic valve 11e of the lead-out pipe 55a. This means that the cleaning liquid used for the cleaning process is collected in the first weighing tank 6a for storage until the start of the cleaning process in the next cycle.

Next, the automatic valve 11i in the pure water supply pipe 23 is opened, and the cleaning treatment tank 1 is connected to the pure water supply pipe 23 through a pure water storage tank (not shown) via a pressure pump (not shown). Pure water flows into the inner tank 1a from the bottom. The pure water flowing into the inner tank 1a overflows to the outer tank 1b. At an appropriate timing, the automatic valve 11d in the drain 7a is opened and the pure water in the outer tank 1b is discharged through the drain 7a. Thus, the inner wall surfaces of the inner tank 1a and the outer tank 1b of the cleaning tank 1 are rinsed and washed with pure water. At this time, the automatic valves 11a,
By opening 11h, pure water is also supplied to the common supply pipe 54 and discharged from the drain 7c, and the common supply pipe 54 is also rinsed and cleaned.

The semiconductor substrate 50 after the foreign matter in the inner tank 1a has been removed by the above-mentioned overflow type pure water washing.
To clean. Because of the overflow-type water washing, foreign substances separated from the semiconductor substrate 50 can be prevented from re-adhering to the semiconductor substrate 50.

In place of the overflow type of water washing,
A large valve may be provided at the bottom of the inner tank 1a of the cleaning tank 1 to perform quick dump rinse (QDR) type water washing. In addition, pure water at room temperature may be used for water washing, but when warm pure water heated above room temperature is used, the washing time can be reduced. Above all, the temperature of pure water is 70 ℃
With the above, the effect of shortening the time is good.

When the rinsing process is completed, the lid driving mechanism (not shown) is driven by the control operation of the control system 56 to open the lid 2. Then, the carrier 51 on which the semiconductor substrate 50 is set is carried out from the inner tank 1a through the opening 1c by the transfer robot. Carried-out carrier 51
Is transferred to a drying device, and the semiconductor substrate 50 is dried. As a drying apparatus, an IPA (isopropyl alcohol) vapor drying method, a spin drying method, or the like can be used as in the related art.

As described above, the semiconductor substrate is loaded, the lid is closed, the cleaning liquid is introduced, the semiconductor substrate is cleaned by circulating the cleaning liquid in a constant temperature control state, the cleaning liquid after the cleaning processing is collected, and the semiconductor is purified with pure water. A series of cycle processes such as washing the substrate surface with water, opening the lid, carrying out the washed semiconductor substrate, and drying the semiconductor substrate are performed. Such a cycle process is repeatedly executed many times,
The collected washing liquid is reused repeatedly until the end of its life.

When the cleaning liquid is introduced for the second time or later, the automatic valves 11a and 11e are opened to wash the cleaning liquid collected in the first weighing tank 6a via the common supply pipe 54 into the cleaning tank. 1, it is needless to say that the operation is not performed for the automatic valves 11f and 11g.

When the life of the repeatedly used cleaning liquid comes to an end, the automatic valve 11b is opened to drain the liquid from the drain 7b. The cleaning tank 1 and the common supply pipe 54 are cleaned with pure water. After the cleaning liquid has been used up, the automatic valves 11k, 11m and 11n are opened again, and the pipes 20a and 20a are connected from the stock solution tanks (not shown).
A predetermined amount of the undiluted solution is supplied to each of the weighing tanks 6a, 6b, and 6c via the b and 20c, and is temporarily stored.

In the first embodiment, an inert gas (eg, argon gas) other than nitrogen gas may be used as the inert gas introduced into the cleaning tank 1 and the weighing tanks 6a, 6b, 6c. Further, as the carrier of the semiconductor substrate, a quartz carrier may be used in addition to the ethylene tetrafluoride-based carrier. Further, a semiconductor substrate guide groove is cut in the inner tank 1a itself of the cleaning tank 1, and the semiconductor substrate is set in the guide groove, that is, the semiconductor substrate is cleaned without using a carrier. May be configured. In the first embodiment, the washing with the pure water is performed after the completion of the collection of the washing liquid. However, when the life of the repeatedly used washing liquid approaches, the pure water is introduced simultaneously with the waste liquid of the washing liquid. It is preferable that the semiconductor substrate be washed with water while avoiding the surface of the semiconductor substrate from being exposed to nitrogen gas and dried. This prevents the minute etching amount from changing from the upper part to the lower part of the semiconductor substrate, and also reliably prevents foreign substances such as particles and residues floating on the surface of the cleaning liquid from re-adhering to the semiconductor substrate surface. It is. Once the cleaning solution after the cleaning process has been collected in the first weighing tank 6a for reuse, it is collected in the second weighing tank 6a.
b or the third weighing tank 6c, or may be collected in another tank. In the first embodiment, three types of cleaning liquid components are introduced from the respective weighing tanks and mixed in the cleaning tank 1 to generate a cleaning liquid. However, the cleaning liquid is generated in one weighing tank or a completely different tank. A cleaning liquid may be generated by mixing three types of cleaning liquid components in advance, and the cleaning liquid may be directly introduced into the cleaning tank 1 in the form of the cleaning liquid. Although only one washing tank 1 is provided, a system in which a plurality of washing tanks having the same structure are arranged and driven simultaneously may be adopted in order to improve the throughput.

Further, in addition to fluorosulfuric acid, hydrofluoric acid (hydrofluoric acid: aqueous solution of hydrogen fluoride HF) is used as a fluorine-containing compound for removing unnecessary thin films such as a natural oxide film and foreign matters such as particles and residues. In this case as well, the effect of suppressing a decrease in the etching rate in the cleaning process with the lid 2 closed is similarly secured.

Further, when the necessity of removing organic substances is sufficiently low, a cleaning solution containing a strongly acidic substance (sulfuric acid), an oxidizing substance (aqueous hydrogen peroxide) and a fluorine-containing compound (fluorosulfuric acid or hydrofluoric acid) is used. Instead of using the mixed solution, the oxidizing substance (hydrogen peroxide solution) may be omitted, and a mixed solution of a strongly acidic substance (sulfuric acid) and a fluorine-containing compound (fluorosulfuric acid or hydrofluoric acid) may be used.

As described above, in the semiconductor substrate cleaning apparatus according to the first embodiment, the semiconductor substrate 50 is cleaned while the cleaning tank 1 is sealed by the lid 2.
The evaporation of hydrogen fluoride (fluorine ions) can be suppressed, and the decrease in the concentration of fluorine ions in the cleaning solution over time can be suppressed over a long period of time. As shown by the solid line characteristic (a) in FIG. Compared with the characteristic (b) indicated by the broken line in the case of (1), the characteristic of maintaining the etching rate of the oxide film can be remarkably improved, and stable cleaning characteristics can be maintained for a long time. Therefore, the number of times the same cleaning liquid can be used repeatedly can be greatly increased (for example, 50 times or more) as compared with the conventional case, and the throughput can be increased and the cost can be reduced.

[Second Embodiment] Regarding the operation in the first embodiment, the internal pressure of the cleaning tank 1 fluctuates due to a reaction during the cleaning processing, and the pressure detected by the pressure gauge 3 exceeds the set value. In this case, by the control operation of the control system 56, the automatic valve 11j is opened to release the excess pressure in the cleaning tank 1 to the outside through the exhaust port 9, and if the detected pressure returns to the set value, It has been described that by closing the automatic valve 11j, the internal pressure of the cleaning tank 1 is always maintained at a substantially constant value.

However, when the excess pressure in the cleaning tank 1 is released to the outside by the exhaust port 9, the evaporated hydrogen fluoride (fluorine ions) flows out to the outside. This causes a decrease in the concentration of fluorine ions, which leads to a temporal decrease in the etching rate of the oxide film.

Embodiment 2 described below solves such inconvenience.

FIG. 3 shows a schematic configuration of an apparatus for cleaning a semiconductor substrate according to the second embodiment of the present invention. In FIG. 3, the same reference numerals as those in FIG. 1 according to the first embodiment denote the same elements in the second embodiment, and a description thereof will be omitted.

A configuration different from the first embodiment (FIG. 1) will be described below.

The cleaning tank 1 under the monitor of the pressure gauge 3
In order to release the pressure by opening the automatic valve 11j when the internal pressure of the exhaust gas exceeds a predetermined value, an exhaust port 9 is connected to the upper part of the cleaning tank 1; And the recovery pipe 31 extending obliquely downward from the lowest portion of the inclined bottom of the condenser 30 is connected to the cleaning tank 1.
It is connected to return. Then, a cooling water pipe 32 is inserted into the condenser 30, and cooling water is supplied to the cooling water pipe 32 from outside. Cooling water piping 32
Is formed in a coil shape in order to secure a large contact area with steam. The end 9a of the exhaust port 9 communicates with the external space.

Next, the operation will be described. When the internal pressure of the cleaning bath 1 fluctuates due to a reaction during the cleaning process on the semiconductor substrate 50 and the pressure detected by the pressure gauge 3 exceeds a set value, the control valve 56 controls the automatic valve 11j to open. Then, the excess pressure in the cleaning tank 1 is released to the outside through the exhaust port 9. When the pressure is released through the exhaust port 9, the evaporating hydrogen fluoride (fluorine ion) and moisture flow in the exhaust port 9. Vessel 3
The heat is taken away by the cooling water pipe 32 in 0 and the volume expands, so that it is condensed and liquefied and dropped on the bottom of the condenser 30, and the liquid hydrogen fluoride and water become liquid via the recovery pipe 31. Collected in the cleaning tank 1. Therefore, a decrease in the concentration of hydrogen fluoride and thus the concentration of fluorine ions in the cleaning solution is suppressed more than in the first embodiment. In addition, the excess pressure is reduced by the condensation, and a part of the pressure escapes from the end of the exhaust port 9 to the outside. When the detected pressure returns to the set value, the internal pressure of the cleaning tank 1 can always be maintained at a substantially constant value by closing the automatic valve 11j.

Since the evaporated hydrogen fluoride (fluorine ions) is recovered in the cleaning tank 1, a decrease in the concentration of fluorine ions in the cleaning solution can be suppressed, and the effect of suppressing the temporal decrease in the etching rate of the oxide film is shown in FIG. The characteristics can be improved over the characteristics of the solid line A. Further, it is possible to prevent a decrease in the amount of the cleaning liquid itself, and to stabilize a good cleaning effect for a long time.

Other operations and conditions are the same as those in the first embodiment, and a description thereof will not be repeated.

When the condensing and liquefaction effect of the condenser 30 and the cooling water pipe 32 is sufficient, the excess pressure itself can be prevented by the condensation itself, so that the end 9a of the exhaust port 9 is closed. It may be.
In this case, the expression “exhaust port” is not appropriate, so it may be replaced with “connection port”. The end of the connection port does not need to protrude outside the condenser 30 like the end 9 a of the exhaust port 9, and the end of the connection port becomes the inlet of the condenser 30.

Alternatively, the pressure gauge 3 via the control system 56
The automatic valve 11j is always opened during the cleaning process, and the end 9a of the exhaust port 9 is communicated with the atmosphere so that the inside of the cleaning tank 1 is maintained at normal pressure. You may.

Note that what is described in the description of the first embodiment still applies to the second embodiment.

[Embodiment 3] In Embodiments 1 and 2 described above, the structure in which the upper opening of the cleaning tank is closed with a lid is used to suppress the evaporation of hydrogen fluoride. As a result, a temporal decrease in the etching rate was sufficiently suppressed. On the other hand, in the case of the third embodiment,
The present invention is based on the premise that an external open type cleaning treatment tank without a lid is used, and sufficiently suppresses a temporal decrease in an etching rate.

FIG. 4 shows a schematic configuration of an apparatus for cleaning a semiconductor substrate according to Embodiment 3 of the present invention. In FIG.
Is a cleaning tank composed of an inner tank 61a and an outer tank 61b, and the cleaning tank 61 is configured to be an open-open type without a lid. 62 is a forced circulation pump for circulating the cleaning liquid in the cleaning tank 61, 63 is for removing inorganic substances, inorganic substances, foreign substances such as particles and residues, and unnecessary thin films such as natural oxide films in the circulating cleaning liquid. The forced circulation pump 62 and the filter 63 are provided in a pipe 64 connecting the bottom of the outer tank 61b and the bottom of the inner tank 61a. 65a is a first weighing tank for temporarily weighing and temporarily storing a predetermined amount of sulfuric acid as an example of a strongly acidic substance for removing inorganic substances including metals, and 65b is an example of an oxidizing substance for removing organic substances. A second weighing tank for weighing and temporarily storing a predetermined amount of aqueous hydrogen peroxide as an example, 65c is an example of a fluorine-containing compound for removing unnecessary thin films such as a natural oxide film and foreign matters such as particles and residues. This is a third weighing tank for weighing and temporarily storing a predetermined amount of fluorosulfuric acid. The first weighing tank 65a, the second weighing tank 65b, and the third weighing tank 65c are respectively connected to a large-capacity stock solution tank (not shown) via a piping (not shown) of a pressure feeding system. I have. Each of the weighing tanks 65a, 65b, 65c is provided with a liquid level sensor 66a, 66b, 66c, respectively, so that the stock solution is supplied to each of the weighing tanks 65a, 65b, 65c until these liquid level sensors operate. It has become. The height of each of the liquid level sensors 66a, 66b, 66c can be adjusted, and the height, that is, the volume of the cleaning liquid component stored in each of the weighing tanks 65a, 65b, 65c is adjusted according to the cleaning conditions. ing.

Reference numerals 67a, 67b and 67c denote supply pipes for supplying a cleaning liquid component from the bottom of the weighing tanks 65a, 65b and 65c to the cleaning tank 1 from above. Automatic valves 68a, 68b, 68c are interposed in the middle of 67c. 6
9a, 69b, and 69c are weighing tanks 65a, 65, respectively.
This is a capacitance sensor for detecting that all of the cleaning liquid components in b and 65c have individually flowed out.

Reference numeral 70 denotes a heater attached to the inner tank 61a of the cleaning tank 61, reference numeral 71 denotes a heater driving circuit, reference numeral 72 denotes a temperature sensor for detecting the temperature of the cleaning liquid in the cleaning tank 61, and reference numeral 72 denotes a control system. The heater driving circuit 71 is controlled via 73 to control the temperature of the cleaning liquid in the cleaning tank 61 at a constant temperature (for example, 100 ° C.).
To).

Reference numeral 81 denotes the semiconductor substrate 50 in the cleaning tank 61.
Is a first cleaning liquid component replenishing means for replenishing the cleaning treatment tank 61 with fluorosulfuric acid during cleaning, and a storage tank 82 of fluorosulfuric acid and a fixed amount of suctioning and sending out a predetermined amount of fluorosulfuric acid from the storage tank 82 It comprises a pump 83 and pump control means 84 having a built-in timer, and the fluorosulfuric acid sent out from the metering pump 83
And supplied to the cleaning tank 61 from above. In the middle of the supply pipe 85, an automatic valve 86
Is provided.

Reference numeral 91 denotes the semiconductor substrate 50 in the cleaning tank 61.
Is a second cleaning liquid component replenishing means for replenishing the cleaning treatment tank 61 with hydrogen peroxide solution during the cleaning of the hydrogen peroxide solution, and a storage tank 92 of the hydrogen peroxide solution and a predetermined amount of the hydrogen peroxide solution from the storage tank 92. Pump 93 and a pump control means 94 having a built-in timer. The hydrogen peroxide solution sent from the pump 93 is supplied to a supply pipe 95.
And supplied to the cleaning tank 61 from above. In the middle of the supply pipe 95, an automatic valve 96 is provided.
Is provided.

Note that all the automatic valves, the forced circulation pump 62, the heater drive circuit 71, the pump control means 84,
94 is configured to be controlled by the control system 73.

Next, the operation of the semiconductor substrate cleaning apparatus configured as described above will be described.

First, as a preparation stage, a predetermined amount of the stock solution is supplied from each stock solution tank (not shown) to each of the weighing tanks 65a, 65b, 65c by the control operation of the control system 73, and is temporarily stored. That is, the first weighing tank 6
5a is supplied with sulfuric acid, which is an example of a strongly acidic substance, until the liquid level sensor 66a operates, and the second weighing tank 65
b is supplied with a hydrogen peroxide solution which is an example of an oxidizing substance until the liquid level sensor 66b operates, and the third weighing tank 65c is an example of a fluorine-containing compound until the liquid level sensor 66c operates. Fluorosulfuric acid is supplied. The concentrations of the supplied sulfuric acid, hydrogen peroxide solution, and fluorosulfuric acid are, for example, about 71 wt%, about 6 wt%, and about 0.02 wt%, respectively.
3 wt%.

Next, the process proceeds to the actual cleaning process. The following sequence operations are all controlled by the control system 73.
First, the cleaning liquid components in the weighing tanks 65a, 65b, and 65c are introduced into the cleaning tank 61 by the control operation of the control system 73. That is, first, the supply pipe 67
The automatic valve 68a is opened, the supply of sulfuric acid is started from the first weighing tank 65a, the automatic valve 68b of the supply pipe 67b is opened, and the second weighing tank 65b is opened.
The supply of the hydrogen peroxide solution is started from, the automatic valve 68c of the supply pipe 67c is opened, and the third weighing tank 65 is opened.
The supply of fluorosulfuric acid is started from c. When it is detected by the capacitance sensor 69a that the outflow of sulfuric acid from the first weighing tank 65a has been completed, the automatic valve 68 is detected.
is closed, and when the capacitance sensor 69b detects that the outflow of the hydrogen peroxide solution from the second weighing tank 65b is completed, the automatic valve 68b is closed, and the third capacitance is detected by the capacitance sensor 69c. Weighing tank 65
When it is detected that the outflow of fluorosulfuric acid from c has been completed, the automatic valve 68c is closed, and the supply of the necessary cleaning liquid component to the cleaning tank 61 is completed. The total amount of the supplied cleaning liquid component is set in advance so as to overflow the inner tank 61a to the outer tank 61b. During this time, the forced circulation pump 62 is driven, and the cleaning liquid components are circulated in the cleaning processing tank 61 and mixed to become the cleaning liquid. Further, the heater 70 is driven through the control of the heater driving circuit 71, and the cleaning liquid is heated. The temperature of the cleaning liquid is monitored by a temperature sensor 72, and by controlling the heater drive circuit 71 via a control system 73, the cleaning liquid is controlled at a constant temperature of about 100 ° C. After the supply of all the cleaning liquid components to the cleaning tank 61 is completed, the control robot 73 drives the transfer robot (not shown) to drive the plurality of semiconductor substrates (silicon wafers) 50. The set carrier 51 is lowered and stored in the inner tank 61a of the cleaning tank 61 from its upper opening, and the cleaning of the semiconductor substrate is started with a cleaning liquid composed of a mixture of sulfuric acid, hydrogen peroxide and fluorosulfuric acid. .

As described above, while the cleaning liquid is circulated by the forced circulation pump 62 in the constant temperature control state of about 100 ° C.,
The semiconductor substrate in the cleaning tank 61 is cleaned with a cleaning liquid. That is, among the components of the cleaning solution, sulfuric acid removes inorganic substances including metals as foreign substances on the surface of the semiconductor substrate, hydrogen peroxide removes organic substances, and fluorosulfuric acid slightly etches unnecessary thin films such as natural oxide films. As well as foreign substances such as particles and residues. What has been removed is captured by the filter 63,
It is removed from the circulating washing liquid. Therefore, reattachment to the semiconductor substrate and attachment to the forced circulation pump are prevented.

In the course of the above-described cleaning process, since the cleaning solution in the cleaning tank 61 is constantly heated, the water in the cleaning solution evaporates, and the volume and concentration of the cleaning solution are reduced. Hydrogen peroxide solution is a cleaning solution that is easily decomposed, and is decomposed into oxygen and water by light or the presence of metal impurities in the cleaning solution. Fluorosulfuric acid is decomposed into sulfuric acid and hydrogen fluoride by hydrolysis, and there is a high possibility that hydrogen fluoride evaporates. On the other hand, sulfuric acid has a high boiling point and is difficult to evaporate. The evaporation amount of water is much larger than the evaporation amount of water and the evaporation amount of hydrogen fluoride.

From the above, it is necessary to replenish fluorosulfuric acid and aqueous hydrogen peroxide. Although it is impossible to determine the decomposition rate of aqueous hydrogen peroxide, the amount of evaporation of water or hydrogen fluoride per unit time is determined uniformly if the temperature and the device configuration are determined. Therefore, a fixed amount of replenishment may be performed at regular intervals. Since the concentration of hydrogen peroxide solution is not so sensitive to the cleaning effect, the shortage of water due to evaporation of water is supplemented by replacement with hydrogen peroxide solution (hydrogen peroxide solution is easily decomposed and produces moisture) ), Make up for the shortage due to the evaporation of hydrogen fluoride by replenishing fluorosulfuric acid.

The control system 73 includes the tanks 65a, 65b,
A signal indicating that the supply of the cleaning liquid component from the cleaning liquid component 65c to the cleaning tank 61 is supplied to the pump control means 84 of the first cleaning liquid component supply means 81 and the pump control means 94 of the second cleaning liquid component supply means 91. Pump control means 84, 94
The built-in timer starts the time counting operation from that point in time, and executes the next replenishing process independently of each other after a predetermined time has elapsed. That is, the first cleaning liquid component replenishing means 8
The pump control means 84 in 1 drives the metering pump 83 and opens the automatic valve 86, draws in a predetermined amount of fluorosulfuric acid from the fluorosulfuric acid tank 82, and supplies it to the cleaning tank 61 via the supply pipe 85. The pump control means 9 in the second cleaning liquid component replenishing means 91
4 drives the metering pump 93 and the automatic valve 96
Is opened, a predetermined amount of hydrogen peroxide solution is drawn from the hydrogen peroxide solution tank 92, and supplied to the cleaning tank 61 via the supply pipe 95.

The replenishment time interval and the replenishment amount are as follows, for example. That is, under the condition that the temperature controlled at a constant temperature is 100 ° C. and the capacity of the cleaning tank 61 is 20 liters, fluorosulfuric acid is, for example, 0.1 cc per minute, and hydrogen peroxide is For example, 2 cc per minute. However, the above replenishment amount depends on the cleaning tank 6.
1 varies depending on the shape of 1, the state of exhaust, the number of lots of the semiconductor substrate 50 to be processed, and the like.

In the above case, a predetermined amount of replenishment is performed at predetermined time intervals. However, instead of such intermittent replenishment, continuous replenishment is performed in a state corresponding to the replenishment amount per unit time. You may comprise so that it may replenish. However, since the replenishment amount of the fluorosulfuric acid is extremely small, the fluorosulfuric acid may be intermittently replenished and only the hydrogen peroxide solution may be continuously replenished.

When the cleaning processing for the semiconductor substrate is completed, unlike the first and second embodiments, the carrier on which the cleaned semiconductor substrate is set is taken out of the cleaning processing tank 61 by the transfer robot, and the water cleaning tank is set. (Not shown). In the washing tank, the washing liquid remaining on the semiconductor substrate is washed away. After washing with water, the semiconductor substrate is dried by a drying means, for example, a spin dryer or an IPA vapor dryer.

The cleaning liquid in the cleaning tank 61 is used repeatedly. That is, the cleaning process in which the carrier on which the next semiconductor substrate is set is immersed is repeated.

As a fluorine-containing compound for removing unnecessary thin films such as a natural oxide film and foreign matters such as particles and residues, hydrofluoric acid (aqueous hydrofluoric acid) can be used in addition to fluorosulfuric acid. Also in this case, intermittent or continuous replenishment of a predetermined amount of hydrofluoric acid and hydrogen peroxide water per unit time suppresses a reduction in the etching rate over time in the cleaning process with the cleaning tank open to the outside. The effect is similarly ensured.

As described above, in the apparatus for cleaning a semiconductor substrate according to the third embodiment, a predetermined amount of fluorosulfuric acid (or hydrofluoric acid) and hydrogen peroxide solution are supplied per unit time while the temperature of the cleaning liquid is controlled. Therefore, the evaporated hydrogen fluoride and water can be compensated for by the amount of evaporation, whereby the decrease of the fluorine ion concentration in the cleaning solution can be suppressed for a long time. Therefore, the number of times that the same cleaning liquid can be used repeatedly can be greatly increased as compared with the related art, so that the throughput can be increased and the cost can be reduced.

Note that the matters described in the first embodiment are also applicable to matters which can be applied in the third embodiment.

[Embodiment 4] In the case of Embodiment 3 described above, hydrogen peroxide solution is supplied to make up for the evaporated water, and fluorosulfuric acid (or hydrofluoric acid) is used to make up for the evaporated hydrogen fluoride. (Hydrofluoric acid). On the other hand, in the case of the fourth embodiment, based on a new finding by the present inventor, instead of replenishing fluorosulfuric acid (or hydrofluoric acid), replenishment of only hydrogen peroxide solution was performed. Thus, a decrease in the etching rate over time is suppressed. The new finding is that the slight etching characteristics of an oxide film largely depend on the concentration of sulfuric acid, and that at a certain concentration or higher, the etching rate increases as the concentration decreases (see FIG. 6). .

FIG. 5 shows a schematic configuration of an apparatus for cleaning a semiconductor substrate according to the fourth embodiment of the present invention. In FIG. 5, the same reference numerals as those in FIG. 4 according to the third embodiment denote the same elements in the fourth embodiment, and a description thereof will not be repeated.

The configuration different from the third embodiment (FIG. 4) is as follows.
As a replenishing means, there is no first cleaning liquid component replenishing means 81 for replenishing fluorosulfuric acid in the case of Embodiment 3, but only a second cleaning liquid component replenishing means 91 for replenishing hydrogen peroxide solution. That is the point. Since the number of replenishing means is one, “second” is omitted, and is simply referred to as cleaning liquid component replenishing means 91. In addition, 92 is a hydrogen peroxide water tank, 93 is a fixed amount pump, 94 is a pump control means having a built-in timer, 95 is a supply pipe, and 96 is an automatic valve.

Next, the operation of the semiconductor substrate cleaning apparatus configured as described above will be described.

In the same manner as in the third embodiment, about 71% by weight of sulfuric acid is supplied from the first weighing tank 65a, and about 6% by weight of hydrogen peroxide is supplied from the second weighing tank 65b.
About 2.3 wt% of fluorosulfuric acid is supplied from the third weighing tank 65 c to the cleaning tank 61, and the forced circulation pump 6
The cleaning liquid is mixed by the circulation of 2 and becomes a cleaning liquid. The cleaning liquid is maintained at about 100 ° C. by the constant temperature control by the temperature sensor 72 and the heater driving circuit 71, and the semiconductor substrate is cleaned in this state. That is, among the components of the cleaning solution, sulfuric acid removes inorganic substances including metal as foreign substances on the surface of the semiconductor substrate 50, hydrogen peroxide removes organic substances, and fluorosulfuric acid slightly removes unnecessary thin films such as natural oxide films. In addition to removing by etching, foreign substances such as particles and residues are also removed. Removed filter 63
And is removed from the circulating wash liquid.

In the course of the above-described cleaning process, since the cleaning solution in the cleaning tank 61 is constantly heated, the water in the cleaning solution evaporates, and the volume of the cleaning solution is reduced and the concentration of the cleaning solution is changed. Hydrogen peroxide solution is a cleaning solution that is easily decomposed, and is decomposed into oxygen and water by light or the presence of metal impurities in the cleaning solution. Fluorosulfuric acid is decomposed into sulfuric acid and hydrogen fluoride by hydrolysis, and there is a high possibility that hydrogen fluoride evaporates. On the other hand, sulfuric acid has a high boiling point and is difficult to evaporate. The evaporation amount of water is much larger than the evaporation amount of water and the evaporation amount of hydrogen fluoride.

By the way, the present inventor has shown by experiment that FIG.
As shown in the figure, the slight etching characteristic of the oxide film strongly depends on the concentration of sulfuric acid, and shows a maximum at about 50 wt%. In a higher concentration range, as the concentration increases, the etching rate sharply decreases, Conversely, the inventors have clarified for the first time the fact that as the concentration decreases, the etching rate sharply increases.

When hydrogen fluoride generated by hydrolysis from fluorosulfuric acid evaporates, the concentration of fluorine ions in the cleaning solution decreases, and the etching rate also decreases. Further, the hydrogen peroxide solution is decomposed into oxygen and water, and a large amount of water evaporates due to the high temperature, so that the concentration of sulfuric acid increases and the etching rate sharply decreases.

However, from the standpoint of the stability of the cleaning action on the semiconductor substrate, it is considered that the cleaning effect is stable if the total amount of fine etching is constant.

Therefore, when replenishing the hydrogen peroxide solution, the replenishing rate per unit time was determined to be higher than that in the third embodiment. Since the replenished hydrogen peroxide solution decomposes to form water, the concentration of sulfuric acid is reduced, but the hydrogen peroxide solution is replenished to such an extent that the reduction is lower than the initial 71 wt%. Then, the etching rate increases with a decrease in the concentration of sulfuric acid.
The increase in the etching rate compensates for the decrease in the etching rate due to the evaporation of hydrogen fluoride, and as a result, keeps the total etching rate constant. In this case, there is no need to replenish fluorosulfuric acid as in the case of Embodiment 3, and the first cleaning liquid component replenishing means 81, which is a facility for replenishing fluorosulfuric acid, becomes unnecessary, and the structure is simplified and compact. Become.

The replenishing operation of the hydrogen peroxide solution is as follows. The control system 73 includes the tanks 65a, 65b, 65c
Is supplied to the pump control means 94 of the cleaning liquid component replenishing means 91 for replenishing the hydrogen peroxide solution. Pump control means 9
The timer built in 4 starts a time counting operation from that point in time, and executes a replenishment process after a predetermined time has elapsed. That is, the pump control means 94 drives the metering pump 93 and opens the automatic valve 96 to draw in a predetermined amount of hydrogen peroxide from the hydrogen peroxide tank 92 and to the cleaning tank 61 via the supply pipe 95. Replenish.

The replenishing time interval and the replenishing amount of the hydrogen peroxide solution are as follows. The supply amount per unit time is set to be larger than that in the third embodiment. Under the condition that the temperature controlled at a constant temperature is 100 ° C., for example,
Hydrogen peroxide solution is replenished at a rate of about 150 cc per minute.

In the above case, a predetermined amount of replenishment is performed every predetermined time. Instead of such intermittent replenishment, continuous replenishment is performed in a state corresponding to the above-described replenishment amount per unit time. It may be configured as follows.

When the cleaning process for the semiconductor substrate is completed, the semiconductor substrate is moved to a washing tank as in the third embodiment, and the cleaning liquid remaining on the semiconductor substrate is washed away. After washing with water, drying means such as spin dryer or IPA
The semiconductor substrate is dried by a steam drying device or the like.

The cleaning liquid in the cleaning tank 61 is used repeatedly. That is, the cleaning process in which the carrier on which the next semiconductor substrate is set is immersed is repeated.

As a fluorine-containing compound for removing unnecessary thin films such as a natural oxide film and foreign matters such as particles and residues, hydrofluoric acid (aqueous hydrofluoric acid solution) can be used in addition to fluorosulfuric acid. Also in this case, the intermittent or continuous replenishment of a predetermined amount of the hydrogen peroxide solution per unit time ensures the same effect of suppressing the etching rate from decreasing over time in the cleaning process with the cleaning tank open to the outside. Is done.

As described above, in the apparatus for cleaning a semiconductor substrate according to the fourth embodiment, an increase in the etching rate sufficient to compensate for a decrease in the etching rate due to evaporation of moisture and hydrogen fluoride under a constant temperature control of the cleaning liquid. The hydrogen peroxide solution is configured to supply a sufficient amount of hydrogen peroxide solution per unit time to cause a decrease in the sulfuric acid concentration that causes sulfuric acid. Lowering the etching rate), eliminating the need for replenishing fluorosulfuric acid, eliminating the need for the first cleaning liquid component replenishing means 81 which is a facility for replenishing fluorosulfuric acid, while simplifying the structure and achieving compactness.
The total etching rate can be kept constant. Therefore, the number of times that the same cleaning liquid can be used repeatedly can be greatly increased as compared with the related art, so that the throughput can be increased and the cost can be reduced.

It is to be noted that the matters described in the description of the first embodiment also apply to matters which can be applied also in the fourth embodiment.

The description of the fourth embodiment has been completed.

In each of the above embodiments, the case where fluorosulfuric acid or hydrofluoric acid is used as the fluorine-containing compound has been described. However, in the present invention, hydrofluoric acid is not limited to this. Instead, sulfuryl difluoride (SO ₂ F ₂ ) may be used. Also, a mixture of fluorosulfuric acid and hydrofluoric acid, a mixture of fluorosulfuric acid and sulfuryl difluoride, a mixture of hydrofluoric acid and sulfuryl difluoride, or a mixture of fluorosulfuric acid and hydrofluoric acid and difluorinated acid It may be mixed with sulfuryl. A mixture of any of these and sulfuric acid and hydrogen peroxide solution is used as a cleaning liquid.

The formula of the reversible equilibrium reaction for stabilizing the fluorine ion concentration when sulfuryl difluoride is used is as follows: SO ₂ F ₂ + OH ⁻ ← → HSO ₃ F + F ⁻ That is, the reaction between sulfuryl difluoride and hydroxyl ion generates fluorosulfuric acid and fluorine ion, and the reverse reaction occurs. Since the mixture of sulfuric acid and hydrogen peroxide is acidic, the concentration of OH ^- ions is low and the above reaction is unlikely to occur. Therefore, fluorosulfuric acid (HSO ₃ F) is mixed with sulfuric acid and hydrogen peroxide. The etching rate is more stable than in the case where it is added.

Further, hydrogen peroxide was used as an oxidizing substance for removing organic substances from the surface of the semiconductor substrate.
Alternatively, ozone may be used. In the case of Embodiment 4, instead of supplying hydrogen peroxide water, hydrogen peroxide water and water may be supplied. By diluting the cleaning solution with the replenished water, the concentration of sulfuric acid is reduced, and the etching rate is increased by an amount corresponding to the decrease in the etching rate due to evaporation of hydrogen fluoride.

[0124]

According to the semiconductor substrate cleaning apparatus of the present invention, a cleaning liquid containing a strongly acidic substance and a fluorine-containing compound or a cleaning liquid containing a strongly acidic substance, an oxidizing substance and a fluorine-containing compound is supplied to the cleaning tank. When supplying and cleaning the surface of the semiconductor substrate with the cleaning liquid inside the cleaning bath,
The opening of the cleaning bath into which the semiconductor substrate is inserted is sealed with a lid, and the surface of the semiconductor substrate is cleaned in the sealed cleaning bath. It is possible to prevent outflow, and to suppress a decrease in the concentration of fluorine ions that contributes to slight etching of the unnecessary thin film, thereby suppressing a temporal decrease in the etching rate of the unnecessary thin film, and significantly increasing the number of times the cleaning liquid is repeatedly used. It is possible to increase the throughput and reduce the cost.

Further, the evaporated component is condensed and liquefied by the condenser, and the liquefied component is collected in the cleaning tank through the recovery pipe, thereby preventing the internal pressure of the cleaning tank from abnormally increasing. By recovering the liquefied component, the loss can be eliminated and the above-mentioned suppressing action can be sufficiently exerted.

The oxidizing substance (especially hydrogen peroxide solution) is replenished with an oxidizing substance in order to compensate for the amount of evaporated water among the water generated by decomposition, and the fluorine-containing compound is generated by decomposition. By replenishing the fluorine-containing compound in order to compensate for the amount of hydrogen fluoride evaporated out of the hydrogen fluoride, it is not necessary to particularly provide a lid in the cleaning tank, and the oxidizing substance which has replenished the amount of water shortaged by evaporation is eliminated. Replenishment by decomposition prevents the cleaning solution from circulating in the cleaning tank or lowering the level of the cleaning solution to expose the semiconductor substrate. By suppressing a decrease in the concentration of fluorine ions contributing to a slight etching of the unnecessary thin film by the above, it is possible to suppress a temporal decrease of the etching rate for the unnecessary thin film. It is possible to perform the function.

A cleaning solution containing a strongly acidic substance (particularly sulfuric acid), an oxidizing substance (particularly hydrogen peroxide solution) and a fluorine-containing compound is supplied to a cleaning tank, and the surface of the semiconductor substrate immersed in the cleaning liquid is cleaned. When cleaning with a cleaning solution,
Decomposition is performed to compensate for the decrease in the etching rate due to the evaporation of water generated by the decomposition of the oxidizing substance (hydrogen peroxide solution) with the increase in the etching rate due to the decrease in the concentration of the strongly acidic substance (sulfuric acid). By replenishing the oxidizing substance (hydrogen peroxide solution) that generates moisture by the generation of water by the decomposition of the replenished oxidizing substance (hydrogen peroxide solution), the concentration of the strongly acidic substance (sulfuric acid) is reduced, The inventor of the present invention has found that the characteristics of slight etching of an unnecessary thin film greatly depend on the concentration of a strongly acidic substance (particularly, sulfuric acid). Above a certain concentration, the etching rate increases as the concentration decreases. Utilize it to replenish a sufficient amount of oxidizing substances (especially hydrogen peroxide solution) and reduce the concentration of strongly acidic substances (sulfuric acid) with the water generated by the decomposition. Raising the etching rate I, compensate a decrease amount of the etching rate due to hydrogen fluoride evaporation, as a result, and without supplementation of fluorine-containing compound, substantially inhibit the temporal decrease in the etching rate,
The cleaning effect is stabilized by keeping the total fine etching amount constant, and the function of suppressing the deterioration of the etching rate for unnecessary thin films with the lapse of time is exhibited. It can be simplified and made compact.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view showing a schematic configuration of a semiconductor substrate cleaning apparatus according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a change over time of an etching rate for an oxide film in the embodiment of the present invention and the conventional technique.

FIG. 3 is a structural explanatory view illustrating a schematic configuration of a semiconductor substrate cleaning apparatus according to a second embodiment of the present invention.

FIG. 4 is a structural explanatory view showing a schematic configuration of a semiconductor substrate cleaning apparatus according to Embodiment 3 of the present invention.

FIG. 5 is a structural explanatory view illustrating a schematic configuration of a semiconductor substrate cleaning apparatus according to a fourth embodiment of the present invention.

FIG. 6 shows a new finding of the present inventors, which is the basis of the invention of the semiconductor substrate cleaning apparatus according to the fourth embodiment, and the slight etching characteristics of the oxide film largely depend on the concentration of sulfuric acid; FIG. 6 is a characteristic diagram showing a relationship between a sulfuric acid concentration and an oxide film etching rate to show the fact that the etching rate increases as the concentration decreases above a certain concentration.

[Explanation of symbols]

Reference Signs List 1 cleaning treatment tank 1a inner tank 1b outer tank 1c opening 2 lid 3 pressure gauge 4 forced circulation pump 5 filter 6a sulfuric acid as a strong acid substance is temporarily stored First weighing tank 6b: A second weighing tank for temporarily storing a hydrogen peroxide solution as an oxidizing substance 6c: A third weighing tank for temporarily storing a fluorosulfuric acid as a fluorine-containing compound 9: Exhaust Port 10 Gasket 21 Heater 23 Pure water supply pipe 30 Condenser 31 Recovery pipe 32 Cooling water pipe 50 Semiconductor substrate 51 Semiconductor substrate carrier 58 Temperature sensor 61 ... Cleaning treatment tank 61a ... Inner tank 61b ... Outer tank 62 ... ... forced circulation pump 63 ... Filter 65a ... First weighing tank 65b for temporarily storing sulfuric acid as a strongly acidic substance ... Oxidizing substance Second weighing tank 65c for temporarily storing hydrogen peroxide solution as a third weighing tank for temporarily storing fluorosulfuric acid as a fluorine-containing compound 70 heater 72 temperature sensor 81 for example fluorosulfuric acid First cleaning liquid component replenishing means 82 for replenishing water 82 tank of fluorosulfuric acid 83... Metering pump 84... Pump control means 91... Second cleaning liquid component replenishing means for replenishing hydrogen peroxide solution or simply cleaning liquid component Replenishing means 92 ... tank of hydrogen peroxide water 93 ... metering pump 94 ... pump control means

Claims (17)

[Claims] A cleaning liquid containing a strongly acidic substance and a fluorine-containing compound is supplied to a cleaning tank, and the surface of the semiconductor substrate inserted into the cleaning tank through an opening thereof is cleaned with the cleaning liquid. A cleaning apparatus for a semiconductor substrate, comprising: a lid for closing an opening of the cleaning tank; and cleaning a surface of the semiconductor substrate in the sealed cleaning tank. 2. A cleaning liquid containing a strongly acidic substance, an oxidizing substance and a fluorine-containing compound is supplied to a cleaning tank, and the surface of the semiconductor substrate inserted into the cleaning tank from an opening thereof is cleaned with the cleaning liquid. An apparatus for cleaning a semiconductor substrate, comprising: a lid for sealing an opening of the cleaning tank; and cleaning a surface of the semiconductor substrate in the sealed cleaning tank. 3. A condenser for condensing the evaporated components is connected to the cleaning tank, and a recovery pipe for collecting the components liquefied by the condenser in the cleaning tank is connected to the cleaning tank. The apparatus for cleaning a semiconductor substrate according to claim 1 or 2, wherein: 4. A cleaning apparatus for a semiconductor substrate, comprising supplying a cleaning solution containing a strongly acidic substance, an oxidizing substance and a fluorine-containing compound to a cleaning tank and cleaning a surface of the semiconductor substrate immersed in the cleaning liquid with the cleaning liquid. Means for replenishing the oxidizing substance in order to compensate for the amount of water evaporated out of the water generated by the decomposition of the oxidizing substance, and evaporating hydrogen fluoride out of the hydrogen fluoride generated by the decomposition of the fluorine-containing compound Means for replenishing a fluorine-containing compound to supplement the amount. 5. The apparatus for cleaning a semiconductor substrate according to claim 1, wherein the strongly acidic substance is sulfuric acid. 6. The apparatus for cleaning a semiconductor substrate according to claim 1, wherein the fluorine-containing compound is fluorosulfuric acid. 7. The apparatus for cleaning a semiconductor substrate according to claim 1, wherein the fluorine-containing compound is hydrofluoric acid. 8. The apparatus for cleaning a semiconductor substrate according to claim 1, wherein the fluorine-containing compound is sulfuryl difluoride. 9. The apparatus for cleaning a semiconductor substrate according to claim 2, wherein the oxidizing substance is aqueous hydrogen peroxide. 10. The apparatus for cleaning a semiconductor substrate according to claim 2, wherein the oxidizing substance is ozone. 11. The semiconductor substrate cleaning apparatus according to claim 1, wherein the cleaning liquid is a cleaning liquid in which the strongly acidic substance is sulfuric acid and the fluorine-containing compound is fluorosulfuric acid. 12. The cleaning solution according to claim 2, wherein the strongly acidic substance is sulfuric acid, the oxidizing substance is aqueous hydrogen peroxide, and the fluorine-containing compound is fluorosulfuric acid. The apparatus for cleaning a semiconductor substrate according to any one of the above. 13. A semiconductor substrate cleaning apparatus for supplying a cleaning liquid containing a strongly acidic substance, an oxidizing substance, and a fluorine-containing compound to a cleaning tank, and cleaning a surface of the semiconductor substrate immersed in the cleaning liquid with the cleaning liquid. In order to compensate for the decrease in the etching rate due to the evaporation of the water generated by the decomposition of the oxidizing substance with the increase in the etching rate due to the decrease in the concentration of the strongly acidic substance, the oxidizing substance that generates water by decomposition is used. An apparatus for cleaning a semiconductor substrate, comprising a replenishing means, wherein the concentration of a strongly acidic substance is reduced by the generation of water by the decomposition of a replenished oxidizing substance. 14. The apparatus for cleaning a semiconductor substrate according to claim 13, wherein the strongly acidic substance is sulfuric acid, and the oxidizing substance is aqueous hydrogen peroxide. 15. The apparatus for cleaning a semiconductor substrate according to claim 14, wherein the fluorine-containing compound is one of fluorosulfuric acid, hydrofluoric acid, and sulfuryl difluoride. 16. The replenishing means is configured to replenish a constant amount at regular time intervals.
The apparatus for cleaning a semiconductor substrate according to any one of the above. 17. The replenishing means is configured to continuously replenish with a constant replenishing amount per unit time. The apparatus for cleaning a semiconductor substrate according to any one of the above.