JP2002143791A - Method and apparatus for cleaning substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly and stably clean a substrate, to save resources, and to reduce waste. SOLUTION: When the substrate is cleaned with the use of a cleaning solution of an aqueous solution containing ammonium fluoride in a ratio of ammonium fluoride (wt.%) to hydrogen fluoride (wt.%) > 50, an ammonia component is added into the cleaning solution with the passage of time during the cleaning. When an aqueous solution containing ammonium fluoride or containing ammonium fluoride and hydrogen fluoride is used as the cleaning solution, the ratio is changed during the cleaning, and the change depends on the ratio. When the ratio is greater than 50, the ratio changes gradually with the passage of time during the cleaning. Accordingly, by adding the ammonia component to convert excess hydrogen fluoride into ammonium fluoride, the concentration of hydrogen fluoride can be kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for cleaning a substrate using an aqueous solution containing ammonium fluoride as a cleaning liquid.
The present invention also relates to a novel substrate cleaning method and a novel substrate cleaning apparatus developed for the purpose of reducing the amount of cleaning liquid used.

[0002]

2. Description of the Related Art An ammonium fluoride aqueous solution (including an arbitrary mixed solution of hydrogen fluoride and ammonia and a solution containing a surfactant) is mixed with hydrogen fluoride or the like to form a semiconductor (mainly silicon oxide). It is widely used in semiconductor and LCD manufacturing processes for the purpose of cleaning and etching a film) substrate and a glass substrate.

In these fields, products have been reduced in weight and size,
For the purpose of reducing power consumption, a fine processing technology with a higher degree of integration is required. For this reason, even when the substrate is washed with an aqueous solution of ammonium fluoride or a mixed solution of the aqueous solution and hydrogen fluoride, a treatment with higher accuracy is desired.

[0004]

By the way, in the above-mentioned cleaning and etching, a chemical component (NH
_{4 F,} since HF) and moisture changes (evaporation) with time, this etching rate for the silicon oxide film and the glass substrate has a problem in that changes (increases) by.

This is because the concentration of the hydrofluoric acid component in the cleaning solution gradually increases with time during use. However, at present, various types of cleaning solution are changed by frequently changing the cleaning solution. Measures were taken for changes in component concentrations.

However, in this measure, a very large amount of the cleaning solution is used. [In particular, since the ammonium fluoride-containing cleaning solution is used at a high concentration of several tens% (eg, about 40% by weight), it is usually used. The amount of chemical consumed per liquid exchange is larger than that of other cleaning liquids used at a concentration of about several percent. In association with this, the amount of use of ammonium fluoride or hydrofluoric acid (chemical cost) increases.

[0007] Further, when the cleaning liquid is used up, a wastewater treatment as shown in FIG. 7 is required. In this case, a large amount of resources (a wastewater treatment agent) is consumed, and accordingly, a large amount of waste is generated. (Drainage and sludge) (see FIG. 8).

FIG. 7 is a view for explaining the waste liquid treatment step of the cleaning liquid. The waste liquid generated from the cleaning tank 81 is carried to a pH adjusting tank 82, where it is neutralized with, for example, a 20% calcium hydroxide solution. . Next, the waste liquid is conveyed to the coagulation tank 83 and coagulated by a chemical such as aluminum sulfate.
At 4, the coagulation / precipitation is carried out by a polymer coagulant such as a polyacrylamide coagulant, and thereafter, it is discharged as sewage or sludge.

In the processing step, as shown in FIG.
2.0 kg of 20% calcium hydroxide and 0.3% of 8% aluminum sulfate per 1 kg of 0% aqueous ammonium fluoride solution
kg, 1.6 kg of polymer flocculant, and a solid content of 70 kg
2.6 kg of sludge and 2.3 kg of sewage drainage are produced.

[0010] In recent years, global environmental problems have become a global concern, and environmental loads during the production of substrates such as semiconductors and LCDs have been regarded as a problem. Not only the purpose, but also social conservation is strongly demanded for environmental conservation such as resource saving, waste reduction, environmental purification and the like.

The present invention has been proposed in view of such a conventional situation, and a substrate cleaning method, a substrate cleaning method capable of performing uniform and stable substrate cleaning, saving resources, reducing waste, and the like. It is an object to provide a cleaning device.

[0012]

In order to achieve the above object, a method for cleaning a substrate according to the present invention comprises ammonium fluoride, and comprises ammonium fluoride (% by weight) / hydrogen fluoride (% by weight).
When the substrate is cleaned using an aqueous solution having a cleaning liquid of> 50 as a cleaning liquid, an ammonia component is additionally replenished to the cleaning liquid as the use time of the cleaning liquid elapses.

Further, the substrate cleaning apparatus of the present invention cleans a substrate using an aqueous solution containing ammonium fluoride and having an ammonium fluoride (wt%) / hydrogen fluoride (wt%)> 50 as a cleaning liquid. Wherein a substrate cleaning treatment tank containing the cleaning liquid and a replenishing means for additionally replenishing the substrate cleaning treatment tank with an ammonia component are provided.

When cleaning or etching a substrate using ammonium fluoride or an aqueous solution containing ammonium fluoride and hydrogen fluoride as a cleaning liquid, the concentration and composition of the cleaning liquid change over time.

According to the experiment of the present inventor, when an aqueous solution containing ammonium fluoride and hydrogen fluoride is used as the cleaning liquid, the manner of change differs depending on the ratio (ammonium fluoride / hydrogen fluoride).

For example, when ammonium fluoride (% by weight) / hydrogen fluoride (% by weight)> 50, the ratio between ammonium fluoride and hydrogen fluoride changes (decreases) with the passage of time.
As a result, the ratio of hydrogen fluoride in the cleaning liquid increases.

Therefore, in the present invention, when cleaning the substrate using an aqueous solution of ammonium fluoride (% by weight) / hydrogen fluoride (% by weight)> 50 as the cleaning liquid, the cleaning liquid is used as the cleaning liquid elapses. The ammonia component will be additionally replenished.

As described above, ammonium fluoride (% by weight)
When the ratio of hydrogen fluoride (% by weight) is greater than 50, the ratio of ammonium fluoride to hydrogen fluoride gradually changes with the lapse of time. It is converted to ammonium fluoride and the concentration of hydrogen fluoride is kept constant.

At the same time, the frequency of liquid exchange of the cleaning liquid is reduced, so that the amount of the cleaning liquid used is reduced. Further, the amount of chemicals required for draining the cleaning liquid is reduced.
It is possible to reduce the amount of wastewater and sludge generated by wastewater treatment.

That is, according to the present invention, uniform and stable cleaning of the substrate can be achieved, and a reduction in the amount of used cleaning liquid and a reduction in the amount of discharged cleaning liquid can be realized.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a substrate cleaning method and a substrate cleaning apparatus to which the present invention is applied will be described in detail with reference to the drawings.

The present invention provides a method for cleaning (or etching) a substrate using an aqueous solution containing ammonium fluoride or ammonium fluoride and hydrogen fluoride according to the cumulative use time of the cleaning solution and the concentration of various components in the cleaning solution. hand,
The cleaning solution is supplemented with an ammonia component.

FIG. 1 shows a mixture of ammonium fluoride and hydrogen fluoride.
Elapsed time and thermal oxide film etching
It shows the relationship with the rate. The composition of the cleaning solution is
NH ₄ F (40%) / HF (50%) = 400/1
Yes, the temperature of the cleaning solution is 25 ° C, and the thermal oxide film is SiO₂ so
is there.

From FIG. 1, it can be seen that the etching rate for the thermal oxide film has increased significantly with the passage of time.

As described above, substrate cleaning using the above-described cleaning liquid is performed.
In, the etching rate changes every moment
In other words, between this etching rate and the elapsed time
Has a very high correlation (proportional relationship). this is,
Moisture and chemicals (NH ₄ F, HF) time
Changes (evaporation) over time, specifically washing
The water and ammonia components in the purified liquid evaporate at a certain rate
HF component in cleaning solution
That the concentration is increasing at a fixed rate.
Means

FIG. 2 shows the change with time of the HF concentration in the cleaning solution.
It can be seen that the concentration of is increasing at a constant rate.

Here, ammonium fluoride and hydrogen fluoride are
With respect to the mixed aqueous solution containing ₄ F component and HF component
Minute ratio [NH₄ F (% by weight) / HF (% by weight)]
We examined how it changes over time. result
Is shown in FIG.

From FIG. 3, it can be seen that there is a difference in the change of components over time depending on the ratio of ammonium fluoride and hydrogen fluoride.

Specifically, ammonium fluoride (% by weight)
/ Hydrogen fluoride (% by weight) ≦ 50, the ratio of both components hardly changes with the passage of time. On the other hand, when ammonium fluoride (% by weight) / hydrogen fluoride (% by weight)> 50, The ratio changes (decreases) over time. This is because when the proportion of ammonium fluoride is large, NH ₄ F → N
As represented by the formula H ₃ア ン モ ニ ア + HF, this is due to the susceptibility to the evaporation of the ammonia component (naturally, in this case, too, the evaporation of water occurs).

As described above, in the cleaning (etching) treatment of a substrate with a mixed solution of ammonium fluoride and hydrogen fluoride, when ammonium fluoride (% by weight) / hydrogen fluoride (% by weight)> 50, the cleaning effect is obtained. In order to keep the (etching rate) constant, it is very effective to replenish the cleaning liquid with an ammonia component as needed.

That is, if the ammonia component is additionally replenished with the lapse of time, an increase in the HF concentration is suppressed, and a constant etch rate can be obtained.

As a result, it is possible to improve the yield of substrates such as semiconductors and liquid crystals, reduce the frequency of liquid exchange, reduce the amount of cleaning liquid and wastewater treatment chemicals, and reduce the amount of sludge and wastewater generated. .

As the ammonia component to be replenished,
It may be gaseous or liquid. Alternatively, water (pure water) and ammonia water diluted at an arbitrary concentration may be used. Further, a solution of a hydrophilic solvent (acetone, various alcohols, etc.) capable of dissolving the ammonia component may be used. Further, it can be used in combination with ammonium fluoride.

Incidentally, in addition to the ammonia component, water is also evaporated from the cleaning liquid. For this reason, in order to maintain exactly the same composition as at the time of initializing, an appropriate amount of water (pure water) may be replenished in addition to the ammonia component. It should be noted that since the etching rate for various films is not significantly affected by moisture (while the HF concentration is greatly affected), there is no particular problem even if only the above-mentioned ammonia component is added. However, in this case, H
The F concentration will be kept constant by replenishing the ammonia component, but the NH ₄ F concentration will gradually increase over time due to the evaporation of water.

Next, a description will be given of a substrate cleaning apparatus to which the present invention is applied.

FIG. 4 shows a configuration example of a substrate cleaning apparatus to which the present invention is applied.

This substrate cleaning apparatus accommodates a cleaning liquid such as a mixed liquid of ammonium fluoride and hydrogen fluoride, and circulates a substrate processing tank 1 for cleaning the substrate and an overflowing cleaning liquid to the substrate processing tank 1. The substrate is provided with a circulation pump 2. For example, a substrate to be processed is accommodated in a substrate carrier, and the substrate is immersed in a substrate processing tank 1 to perform a cleaning (etching) process.

A characteristic feature is that the substrate processing tank 1 is provided with an ammonia water storage tank 7 for supplying an ammonia component, and the control section 4 controls the additional replenishment of the ammonia component. It is.

The means for supplying the ammonia component is not limited to the above, but may be a means such as a metering pump, gravity drop, or pressure feeding with a gas such as air or nitrogen.

As described above, the ratio of the HF component in the cleaning liquid increases with the lapse of time, and the etching rate for the thermal oxide film increases significantly.

Therefore, in this substrate cleaning apparatus, the control unit 4 replenishes the substrate processing tank 1 with ammonia water from the ammonia water storage tank 7 over time to keep the ratio of the HF component constant and the etching rate substantially constant. It is controlled to become.

Regarding the replenishment amount and replenishment timing of the ammonia component, data collection as shown in FIG. 1, FIG. 2, and FIG. 3 is performed, and the HF component increased with time is calculated. The replenishment amount and replenishment timing conditions can be derived.

It is desirable that the amount of the ammonia component to be replenished in the cleaning liquid is replenished with the amount of ammonia for evaporation until an arbitrary time so that the concentration immediately after the cleaning liquid is prepared (initial) can be maintained. For example, the concentration of the washing solution can be monitored continuously or intermittently, and the amount of the ammonia component added can be calculated from the result.

FIG. 5 is a diagram showing a control state of the etching rate and the HF concentration by additionally supplementing the ammonia component. By intermittently replenishing the ammonia component, the etching rate and the HF concentration are kept within certain ranges.

The condition for replenishing the ammonia component may be either continuous replenishment or intermittent replenishment.
In order to maintain a constant concentration, continuous replenishment is preferred.

In the above substrate cleaning apparatus, the timing of additional replenishment of the ammonia component is controlled based on the measurement data. However, as shown in FIG. 6, a concentration measuring device 5 is provided and circulated. It is also possible to measure the concentration of the cleaning liquid and control the additional replenishment of the ammonia component in real time based on this concentration information. The concentration measuring device may be permanently installed in the cleaning device to feed back the measurement result during the linear processing, or may be added to the ammonia component under predetermined conditions without permanent installation, reflecting the result measured at the spot. You may.

Specifically, the concentration of each component (ammonium fluoride, hydrogen fluoride, moisture, etc.) in the cleaning solution is measured by the concentration measuring device 5, and the measurement result is constituted by a computer, a central monitoring panel or the like. The control unit 4 sends a replenishment instruction to the ammonia water supply line (ammonia water storage tank 7) after judging the necessity of replenishment and calculating the required replenishment amount.
Then, whether or not the replenishment was performed as instructed is confirmed by measurement by the concentration measuring device 5.

Here, as a method of measuring the concentration of the constituents in the cleaning solution, it is possible to use the measurement of the absorbance at a predetermined wavelength, the infrared / ultraviolet absorption spectrum, the refractive index, the specific gravity, the transmittance, the conductivity and the like. Alternatively, a measuring instrument such as a Karl Fischer moisture concentration meter or liquid (ion) chromatography may be used.

As described above, by additionally replenishing the ammonia component, judging from the etching rate at the time of each processing and the concentration of various components, the etching processing with the cleaning liquid is made uniform / stabilized (that is, the etching amount for the oxide film is reduced). It is not necessary to frequently change the cleaning liquid as in the related art. As a result, the service life of the cleaning liquid can be prolonged, the consumption of the cleaning liquid can be reduced by reducing the frequency of liquid replacement (resource saving), and the wastewater treatment agent required for wastewater treatment of the cleaning liquid can be reduced (resource saving). Can also contribute. Furthermore, the reduction in the amount of use of these chemicals can contribute to reducing the amount of sludge and wastewater generated during wastewater treatment (reducing the amount of waste generated).

As described above, the present invention not only achieves uniform / stabilized substrate processing, but also contributes to global environmental conservation in terms of resource saving and reduction of waste generation.

[0051]

As described above, by using the method and apparatus of the present invention, when the substrate is cleaned with an aqueous solution containing ammonium fluoride, the processing can be uniformly stabilized, and the cleaning liquid can be used. Since the frequency of replacement can be reduced, it is possible to save resources of chemicals (cleaning liquids and wastewater treatment agents) and significantly reduce the amount of sludge and wastewater generated due to this.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between an elapsed time and an etching rate in a cleaning liquid.

FIG. 2 is a characteristic diagram showing a relationship between an elapsed time and an HF concentration in a cleaning liquid.

FIG. 3 is a characteristic diagram showing a change in a ratio between an NH ₄ F component and an HF component over time.

FIG. 4 is a schematic diagram illustrating an example of a substrate cleaning apparatus to which the present invention is applied.

FIG. 5 is a diagram showing a control state of an etching rate and an HF concentration by additionally supplementing an ammonia component.

FIG. 6 is a schematic view showing another example of the substrate cleaning apparatus to which the present invention is applied.

FIG. 7 is a diagram for explaining a cleaning liquid waste liquid treatment step.

FIG. 8 is a diagram showing resources required for waste liquid treatment of a cleaning liquid.

[Explanation of symbols]

1 substrate processing tank, 2 circulation pump, 4 control unit, 5
Concentration measuring device, 7 ammonia water storage tank

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/304 648 H01L 21/304 648G 21/308 21/308 G F-term (Reference) 3B201 AA02 AA03 AB01 BB04 BB05 BB82 BB92 BB93 BB96 CB01 CC21 CD22 CD42 CD43 4H003 BA12 DA15 EA05 ED02 FA03 FA21 FA23 5F043 AA02 AA29 BB27 DD30 EE23 EE24 EE27

Claims (4)

[Claims] 1. When cleaning a substrate using an aqueous solution containing ammonium fluoride and containing ammonium fluoride (% by weight) / hydrogen fluoride (% by weight)> 50 as a cleaning liquid, the cleaning liquid elapses over time. A substrate cleaning method, characterized by additionally replenishing the cleaning solution with an ammonia component. 2. The method according to claim 1, wherein the concentration of hydrogen fluoride contained in the aqueous solution is less than 1.0% by weight. 3. A substrate cleaning apparatus for cleaning a substrate using an aqueous solution containing ammonium fluoride and containing ammonium fluoride (% by weight) / hydrogen fluoride (% by weight) <50 as a cleaning liquid, wherein the substrate containing the cleaning liquid is provided. A substrate cleaning apparatus comprising: a cleaning tank; and a replenishing means for additionally replenishing water to the substrate cleaning tank. 4. The substrate cleaning apparatus according to claim 3, wherein the concentration of hydrogen fluoride contained in the aqueous solution is less than 1.0% by weight.