JP3057533B2 - Cleaning method for semiconductor wafer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer cleaning method for cleaning a semiconductor wafer in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, there is a step of cleaning a semiconductor wafer in order to remove organic and inorganic contamination on the surface of the semiconductor wafer which has been subjected to a pre-process or handling. As this cleaning method, cleaning using a mixed cleaning solution of hydrochloric acid and hydrogen peroxide solution is known. This mixed cleaning solution is often used for the purpose of removing impurities such as metal components and organic components on the wafer surface by oxidation and decomposition.

In this mixed cleaning solution, the solubility of hydrochloric acid in metals, the oxidizing effect of hydrogen peroxide on metals, the oxidizing effect of hydrogen peroxide on organic matter, and the hypochlorous acid generated by mixing hydrochloric acid and hydrogen peroxide ( HClO) has a cleaning effect.

When using a mixed solution of hydrochloric acid and aqueous hydrogen peroxide, a cleaning effect is promoted by accelerating the decomposition reaction of hydrogen peroxide and generating a large amount of oxygen (O ₂ ) serving as an active cleaning factor (oxidizing agent). Is generally used under the following conditions in order to improve Liquid temperature 50 ° C. to 80 ° C. Liquid composition ratio HCl (36% by weight): H ₂ O ₂ (30% by weight): H ₂ 0 = 1: 1: 1 to 1: 1: 10 (volume ratio) Concentration HCl is 3 ～5.1 wt% H ₂ O ₂ is from 2.5 to 4.3% by weight remainder H ₂ O

FIG. 7 shows an example of a conventional method for cleaning a semiconductor wafer. As shown in FIG. 7A, hydrochloric acid, hydrogen peroxide solution, and water are supplied to the treatment tank 1 at the above-described liquid composition ratio. Next, as shown in FIG. 7B, the liquid is sufficiently mixed by the stirrer 2 to obtain a hydrochloric acid-hydrogen peroxide mixed cleaning liquid 3. next,
As shown in FIG. 7C, the mixed cleaning liquid 3
Is heated to 50 ° C. to 80 ° C., and thereafter, the semiconductor wafer 6 stored in the cassette 5 is immersed in the mixed cleaning liquid 3 together with the cassette 5 to perform a cleaning process.

[0006]

However, under the above-mentioned conditions of use, there are the following problems. It is necessary to heat the hydrochloric acid-hydrogen peroxide mixed cleaning solution to 50 ° C. to 80 ° C., and a heating facility for that is required. Hydrochloric acid (HCl) evaporates when the temperature of the mixed cleaning solution is increased, and hydrogen peroxide (H ₂ O ₂ ) is decomposed. Therefore, the loss of active ingredients such as hydrochloric acid and hydrogen peroxide is reduced before the mixed cleaning solution is used. growing. The decomposition rate of hydrogen peroxide at operating temperature is slow,
Low cleaning effect due to oxidation and decomposition. Since the decomposition reaction rate is low, unreacted hydrogen peroxide remains after the cleaning treatment. Therefore, there is a possibility of reacting after the waste liquid, and in order to prevent the danger of heat generation and foaming, the waste liquid cannot be treated until the unreacted hydrogen peroxide is sufficiently reduced, and the waste liquid treatment requires a long time.

SUMMARY OF THE INVENTION In view of the above, the present invention provides a method for cleaning a semiconductor wafer, which eliminates the need for raising the temperature of a cleaning solution, can efficiently clean in a short time, and simplifies waste liquid treatment after cleaning. .

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for cleaning a semiconductor wafer using a mixed cleaning solution of hydrochloric acid and hydrogen peroxide solution, the method comprising the steps of: The ratio is 0.1% by weight.
8: 1 to 12: 1, and the total pure concentration of hydrochloric acid and hydrogen peroxide is set to 28 to 35.4% by weight.

[0009]

In the present invention, when mixing hydrochloric acid and hydrogen peroxide solution, the mixing ratio of pure hydrochloric acid: hydrogen peroxide is set to 0.8: 1 to 12: 1 by weight, and hydrochloric acid and hydrogen peroxide are mixed. By setting the total concentration of pure hydrogen peroxide to 28 to 35.4% by weight, the decomposition reaction of hydrogen peroxide is promoted at room temperature,
Also, the heat of the decomposition reaction raises the temperature of the mixed cleaning solution to accelerate the decomposition reaction of hydrogen peroxide, and the synergistic effect of decomposition → heating → decomposition promotes the high concentration of oxygen (O ₂ ), which is an effective cleaning component, in a short time. And the semiconductor wafer is cleaned in a short time.

Since there is no need to raise the temperature of the mixed cleaning solution, a heating apparatus is not required, and there is no evaporation of hydrochloric acid and decomposition of hydrogen peroxide at the time of heating as in the prior art. Less loss of active ingredients.

Further, since the decomposition reaction of the mixed cleaning liquid is completed at the end of the cleaning processing, the waste liquid processing after the cleaning is completed is simplified.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

When a cleaning solution is obtained by mixing hydrochloric acid and aqueous hydrogen peroxide, under the above-described concentration conditions which have been conventionally used as the cleaning solution, heat generation and foaming due to the decomposition reaction hardly occur. However, by mixing both chemicals of hydrochloric acid and hydrogen peroxide with a specific range of concentration and composition ratio (mixing ratio), the decomposition reaction of hydrogen peroxide (see Chemical Formula 1) can be promoted.

[0014]

Embedded image

In this embodiment, as shown in FIG. 1, hydrochloric acid (HCl), hydrogen peroxide solution (H ₂ O ₂ ) and water (H ₂ O) are supplied to the treatment tank 11 to supply hydrochloric acid-hydrogen peroxide. A mixed cleaning solution 12 of water is obtained (FIG. 1A). At this time, the mixing ratio and concentration of hydrochloric acid and hydrogen peroxide are set as follows.

That is, HCl: H ₂ O in the mixed cleaning solution
₂ of pure content mixing ratio of 0.8 wt%: 1% to 12% by weight: as well as to 1 wt% of the range, HCl and H ₂ O ₂
Is set in the range of 28 to 35.4% by weight (the remaining components are H ₂ O). More preferably, HC
l: H ₂ O ₂ = 1% by weight: 1% to 5% by weight: 1% by weight (1.2% by weight: 1% by weight is best), and the total pure concentration of HCl and H ₂ O ₂ is 30 Up to 35.4% by weight is acceptable.

Here, when the mixing ratio of the pure hydrochloric acid is less than 0.8% by weight or exceeds 12% by weight, the decomposition reaction and heat generation described below do not occur. If the total concentration of hydrochloric acid and hydrogen peroxide is less than 28% by weight, no decomposition reaction or heat generation occurs. In addition, the same pure concentration 3
5.4% by weight is the upper limit of the concentration normally obtained.

By setting the mixing ratio of the pure components of HCl and H ₂ O ₂ and the total pure component concentration in the above ranges to prepare the mixed cleaning liquid 12, the decomposition reaction of H ₂ O ₂ occurs at room temperature, and FIG.
As shown in FIG. 1B, the cleaning solution 12 is diffused by the bubbling of oxygen (O ₂ ), and similarly, as shown in FIG.
2 is heated. Oxygen (O ₂ ) acting as an active cleaning factor is generated by the decomposition reaction of hydrogen peroxide, and the heat of the decomposition reaction raises the temperature of the cleaning solution 12 to accelerate the decomposition reaction of hydrogen peroxide. A lot of oxygen (O
₂ ) occurs. Therefore, by immersing the semiconductor wafers 6 stored in the cassette 5 in the mixed cleaning liquid 12, the semiconductor wafers can be efficiently cleaned in a short time.
The temperature of the cleaning liquid 12 is adjusted by the amount of water (H ₂ O) used for dilution.

The rise in the temperature of the cleaning liquid 12 due to the synergistic effect of the decomposition reaction of hydrogen peroxide and the heat generated by the cleaning liquid 12 and the heat generated by the cleaning liquid 12 accelerating the decomposition reaction of hydrogen peroxide is shown by the curve I in FIG. after an induction period T ₁ from the liquid temperature immediately after mixing (room temperature) soared in the decomposition reaction of rapid hydrogen peroxide, until decomposition reaction is complete. The decomposition reaction is completed at the maximum temperature, and thereafter, the temperature of the solution decreases due to heat radiation. The decomposition reaction is completed in a few minutes. T ₂ are an exploded reaction period.

Since H ₂ O ₂ is changed to H ₂ O or O ₂ by the same decomposition reaction, unreacted H ₂ O
₂ O ₂ does not remain in the cleaning solution. The decomposition reaction occurs even when both the hydrochloric acid and the hydrogen peroxide solution are mixed at room temperature.

As shown in FIG. 2, there is an induction period T ₁ from the mixing of the cleaning solution to the start of the rapid decomposition reaction.
The induction period T ₁ is somewhat affected by the mixing and stirring method when the temperature and concentration of the cleaning liquid 12 immediately after mixing are high, but the induction period T ₁ when the both solutions of hydrochloric acid and hydrogen peroxide at room temperature are vigorously stirred. ₁ is about 2 to 4 minutes.

Next, the reaction on the samples [1] to [10] of the mixed cleaning solution in which the total pure concentration of hydrochloric acid and hydrogen peroxide shown in Table 1 and the mixing ratio of hydrochloric acid: hydrogen peroxide were changed. FIG. 3 shows changes in the temperature over time and the temperature of the cleaning liquid. Curves (1), (2), (3), (4), (5), (6),
(7), (8), (9), and (10) are samples [1],
[2], [3], [4], [5], [6], [7],
[8] and

Each corresponds to [9].

[0023]

[Table 1]

From Table 1 and FIG. 3, samples [1], [2], [3], [4] and [5] whose maximum temperatures exceeded 40 ° C.
(Pure content concentration, pure content mixing ratio) are recognized as conditions under which it can be determined that the decomposition reaction of hydrogen peroxide is promoted and the cleaning effect on the semiconductor wafer is improved. The maximum temperature can be adjusted by changing the concentration of the pure component. That is, the lower the pure concentration, the lower the maximum temperature.

The cleaning method according to the present invention can be applied to dip type cleaning, spin type single wafer type cleaning, spray type batch type cleaning and the like. In the dip cleaning, as shown in FIG. 4, a hydrochloric acid-hydrogen peroxide mixed cleaning solution 12 set to the above-described pure component mixing ratio and the pure component concentration is supplied into a treatment tank 11, and a cassette is added to the mixed cleaning solution 12. Semiconductor wafer 6 housed in 5
For washing. After the cleaning, the chemical solution is removed in a pure water rinsing tank (not shown).

In the spin-type single-wafer cleaning, as shown in FIG. 5, a semiconductor wafer 6 set on a wafer carrier 14 is rotated at a high speed while a cleaning liquid 12 containing a mixture of hydrochloric acid, hydrogen peroxide and water is sprayed from a spray nozzle 15. Inject and wash. After that, pure water rinsing is performed.

As shown in FIG. 6, the spray type batch cleaning is performed by a carrier 18 rotatably disposed in a cleaning chamber 17.
A plurality of wafers 6 are held, and the mixed cleaning liquid 12 from the mixing chamber 20 is injected into the wafers 6 through a spray nozzle 19 arranged along the central axis of the carrier 18 to perform cleaning. Thereafter, pure water rinsing is performed.

According to the above-described embodiment, in the method for cleaning the semiconductor wafer 6 using the mixed cleaning solution 12 of hydrochloric acid-hydrogen peroxide solution, the cleaning solution 12 has a pure hydrochloric acid: hydrogen peroxide mixture ratio, and a mixture of hydrochloric acid and hydrogen peroxide. By specifying the total pure oxide concentration of hydrogen oxide within the above range, the semiconductor wafer surface can be cleaned in a short time (several minutes).

That is, the decomposition reaction of hydrogen peroxide is accelerated, and oxygen (O ₂ ), which is an effective cleaning component, can be generated at a high concentration in a short time, and the cleaning effect is improved. At the same time, a decomposition reaction occurs at room temperature, and the temperature of the cleaning liquid 12 sharply rises due to the heat generated by the decomposition reaction. Therefore, HCl evaporation and H The loss of cleaning active components such as decomposition of ₂ O ₂ is reduced.

Further, since the temperature of the mixed cleaning liquid 12 is raised by the heat of decomposition reaction, there is no need to raise the temperature from the outside, so that a conventional heating and heating period is unnecessary, and a heating equipment is not required. The cleaning liquid 12 contains oxygen (O ₂ ) generated by the decomposition reaction of H ₂ O _{2.
Since the} liquid is diffused by the foaming of ₂ ), the cleaning liquid 12 is sufficiently mixed without using a stirring device.

Further, since the decomposition reaction of H ₂ O ₂ is completed at the maximum temperature, there is no unreacted H ₂ O ₂ after the completion of the washing. Therefore, the waste liquid treatment after the completion of the washing is easy. I can do it.

[0032]

According to the present invention, the mixing ratio of pure hydrochloric acid to hydrogen peroxide and the total pure concentration of hydrochloric acid and hydrogen peroxide in the mixed cleaning solution of hydrochloric acid and hydrogen peroxide are set within the above-mentioned specific ranges. The reaction between both components (exothermic, foaming)
, The surface of the semiconductor wafer can be cleaned in a short time, and the waste liquid treatment after the completion of the cleaning can be simplified. Further, since there is no need to raise the temperature of the cleaning liquid, it is possible to eliminate the need for a heating device such as a heater. Therefore,
The cleaning effect and safety in the cleaning process of the semiconductor wafer can be improved, and the equipment cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a cleaning method according to the present invention.

FIG. 2 is a graph showing an outline of a decomposition reaction of a cleaning solution according to the present invention.

FIG. 3 is a graph showing the relationship between the passage of time and the temperature of the cleaning liquid for each material (cleaning liquid) in Table 1 when hydrochloric acid and hydrogen peroxide are mixed.

FIG. 4 is an explanatory diagram in the case where the cleaning method of the present invention is applied to a dip type cleaning.

FIG. 5 is an explanatory diagram in the case where the cleaning method of the present invention is applied to a spin-type single-wafer cleaning.

FIG. 6 is an explanatory diagram when the cleaning method of the present invention is applied to a spray-type batch cleaning.

FIG. 7 is an explanatory view of a conventional cleaning method.

[Explanation of symbols]

 1, 11 treatment tank 2 stirrer 3, 12, mixed cleaning solution of hydrochloric acid-hydrogen peroxide solution 4 heater 5 cassette 6 semiconductor wafer

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/304

Claims (1)

(57) [Claims] 1. A semiconductor wafer cleaning method for cleaning a semiconductor wafer using a mixed cleaning solution of hydrochloric acid and hydrogen peroxide solution, wherein the mixing ratio of pure hydrochloric acid to hydrogen peroxide in the mixed cleaning solution is 0.1% by weight. 8: 1 to 12: 1, and the total pure concentration of hydrochloric acid and hydrogen peroxide is 28 to
A method for cleaning a semiconductor wafer, wherein the method is set at 35.4% by weight.