JP3154184B2 - 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 sulfuric acid and hydrogen peroxide solution is known. This mixed cleaning liquid is particularly effective in removing organic substances from contamination.

[0003] In a mixed treatment solution of sulfuric acid and hydrogen peroxide solution, the hydrogen peroxide component is decomposed and consumed as shown in the following formula 1 with the rise in temperature and the passage of time. Oxygen (O ₂ ) is generated during this decomposition reaction, and this oxygen acts as an active cleaning factor (oxidizing agent).

[0004]

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[0005] The decomposition reaction is an exothermic reaction, and the temperature of the mixed cleaning solution rises as the decomposition occurs.

[0006] At the time of cleaning a semiconductor wafer, the decomposition reaction of Chemical Formula 1 has a great effect on the effect of removing metals and organic components on the wafer surface. That is, the semiconductor wafer is
When immersing in a mixed cleaning solution of hydrogen peroxide for cleaning, the more vigorous the decomposition reaction of hydrogen peroxide, the better the cleaning effect. This effect is particularly apt to occur during the resist stripping process on the wafer surface.

For this reason, in a normal semiconductor wafer cleaning process, a mixed cleaning solution of sulfuric acid-hydrogen peroxide is used at 60 ° C. to 1 ° C.
By heating to about 50 ° C., the above-mentioned decomposition reaction is promoted and the cleaning effect is improved.

[0008]

However, the conventional cleaning method using a mixed cleaning solution of sulfuric acid and hydrogen peroxide has the following problems.

It takes 30 to 90 minutes to heat the mixed cleaning solution to a predetermined temperature. During the heating of the mixed cleaning solution, hydrogen peroxide as a cleaning active ingredient is considerably decomposed and consumed. The decomposition rate of hydrogen peroxide is slow, and it takes much time to clean the wafer by, for example, immersion. Unreacted hydrogen peroxide remains in the liquid after using the mixed cleaning liquid. Therefore, there is a possibility of reacting after the waste liquid, and in order to prevent the risk 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.

In view of the above, the present invention provides a method for cleaning a semiconductor wafer, which eliminates the need to raise the temperature of a cleaning liquid, can efficiently clean in a short time, and simplifies waste liquid treatment.

[0011]

According to the method for cleaning a semiconductor wafer of the present invention, a semiconductor wafer is cleaned by adding a decomposition accelerator such as nitric acid to a mixed cleaning solution of sulfuric acid and hydrogen peroxide.

[0012]

In the present invention, the decomposition reaction of hydrogen peroxide is induced and promoted by adding a decomposition accelerator to the mixed washing solution of sulfuric acid and hydrogen peroxide solution. At the same time, the temperature of the mixed cleaning liquid increases due to the heat of the decomposition reaction, and the decomposition reaction of hydrogen peroxide is promoted. The cleaning effect on the wafer surface is improved by two factors, the induction of the decomposition reaction and the increase in the liquid temperature due to the heat of the decomposition reaction.

Further, the addition of a decomposition accelerator increases the decomposition rate of hydrogen peroxide, and at the same time further promotes the decomposition reaction by raising the temperature of the mixed cleaning solution due to the heat of reaction, so that oxygen (O ₂₎ as an active cleaning factor ) Occurs at a high concentration 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 device is not required, and the decomposition and consumption of hydrogen peroxide during heating as in the prior art is avoided.

Furthermore, since the decomposition reaction of hydrogen peroxide is completed in a short time, waste liquid treatment after washing is simplified.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic principle of the present invention is that a strong oxidizing agent is generated by adding a decomposition accelerator to a mixed cleaning solution of sulfuric acid and hydrogen peroxide to induce a decomposition reaction of hydrogen peroxide. The cleaning effect on the surface of the semiconductor wafer is improved by two factors, that is, oxygen and a rise in liquid temperature due to the heat of decomposition reaction.

The greater the effect of the decomposition accelerator, the more
Since the decomposition rate of hydrogen peroxide is increased and oxygen can be generated and the temperature of the cleaning solution can be increased in a short time, the cleaning time of the semiconductor wafer can be reduced.

Examples of the decomposition accelerator include nitric acid and heavy metals, with nitric acid (about 70 wt%) being particularly preferred. With the addition of a few drops of nitric acid, the decomposition reaction of hydrogen peroxide is completed within minutes.

The decomposition promoting effect of the addition of nitric acid is hardly affected by the temperature of the mixed cleaning solution of sulfuric acid and hydrogen peroxide.
Therefore, it is desirable to maintain the mixed cleaning solution at room temperature during a period in which the cleaning process of the semiconductor wafer is not performed (so-called standby) as much as possible in order to prevent unnecessary decomposition and consumption of hydrogen peroxide. Further, as a component of the cleaning liquid after the cleaning, hydrogen peroxide is almost consumed by decomposition, so that only sulfuric acid is contained. Therefore, waste liquid treatment can be performed by dilution with water.

Next, an embodiment will be described with reference to the drawings.
The method for cleaning a semiconductor wafer according to the present invention is applicable to any of dip-type cleaning, spin-type single-wafer cleaning, and spray-type batch-type cleaning.

FIG. 1 shows an example applied to dip type cleaning. In this example, a treatment tank 2 containing a mixed cleaning solution 1 of sulfuric acid and hydrogen peroxide solution is prepared (see FIG. 1A). The semiconductor wafer 3 to be cleaned at room temperature in the processing tank 2
Immerse. Here, the entire cassette 4 containing a plurality of semiconductor wafers 3 is immersed in the processing tank 2 (see FIG. 1B).

Next, nitric acid 5 as a decomposition accelerator is added to the mixed cleaning solution 1 in the processing tank 2 (see FIG. 1C). By the addition of the nitric acid 5, the decomposition reaction of hydrogen peroxide in the mixed cleaning liquid 1 is promoted, and at the same time, heat is generated to increase the liquid temperature of the mixed cleaning liquid 1 (see FIG. 1D). The synergistic effect of this decomposition reaction → heating → decomposition reaction enhances the cleaning effect and cleans the semiconductor wafer surface.

After the cleaning, the semiconductor wafer 3 is taken out of the processing tank 2 together with the cassette 4 (see FIG. 1E), and then the semiconductor wafer 3 is immersed in a rinsing processing tank 6 containing pure water 7 for rinsing (see FIG. 1). 1F). After the completion of the cleaning process, the hydrogen peroxide is completely decomposed, and the cleaning solution 1 containing only sulfuric acid is diluted with water to be subjected to a waste liquid treatment.

FIG. 2 shows another example of the dip cleaning. In this example, a treatment tank 11 containing nitric acid 5 and a sulfuric acid-
A treatment tank 2 containing a mixed cleaning solution 1 of a hydrogen peroxide solution and a rinsing treatment tank 6 containing a pure water 7 are prepared.

Then, first, the semiconductor wafer 3 stored in the cassette 4 is immersed in the nitric acid 5 in the processing tank 11, and the cleaning surface of the wafer is wetted with the nitric acid 5. Since nitric acid 5 has a lower viscosity and lower surface tension than sulfuric acid, it can easily penetrate into fine parts and uniformly wet the wafer surface.

Next, the semiconductor wafer 3 is taken out of the processing tank 11 and immersed in the cleaning solution 1 containing sulfuric acid and hydrogen peroxide in the processing tank 2. At this time, a decomposition reaction of hydrogen peroxide rapidly occurs on the wafer surface to which the nitric acid 5 is adhered, and the wafer surface is cleaned. After the cleaning, the semiconductor wafer 3 is immersed in a rinsing tank 6 of pure water to rinse the chemical on the wafer surface.

In the example shown in FIG. 2, the semiconductor wafer 3 is first immersed in nitric acid 5 to wet the wafer surface.
When immersed in the next cleaning solution 1 containing sulfuric acid and hydrogen peroxide, hydrogen peroxide undergoes a decomposition reaction from the wafer surface. In contrast, in the example of FIG. 1 in which the semiconductor wafer 1 is immersed in the sulfuric acid-hydrogen peroxide mixed cleaning solution 1 and then nitric acid 5 is dropped,
The decomposition reaction occurs from the liquid surface of the mixed cleaning liquid and sequentially proceeds to the wafer surface. Therefore, the embodiment of FIG. 2 has a better cleaning effect.

FIG. 3 shows an example in which the present invention is applied to a spin type single wafer type cleaning. In this example, the wafer carrier 1
While rotating the semiconductor wafer 3 set at 3 at high speed, sulfuric acid (H ₂ SO ₄ ), hydrogen peroxide solution (H ₂ O ₂ ),
Each of nitric acid (HNO ₃ ) chemicals is spray nozzles 14, 1
Cleaning is performed by injecting the wafer into the wafer surface from 5 and 16.

In FIG. 3, a spray nozzle 14 for sulfuric acid, a spray nozzle 15 for hydrogen peroxide solution, and a spray nozzle 16 for nitric acid are separately provided, and sulfuric acid and hydrogen peroxide solution are mixed on the wafer 3. , Nitric acid is added. Alternatively, sulfuric acid and hydrogen peroxide may be injected onto the wafer 3 from one spray nozzle.

The order of injection of the chemical solution may be such that nitric acid is injected first, and then sulfuric acid and hydrogen peroxide solution are injected, or vice versa.

FIG. 4 shows another example in which the present invention is applied to a spin type single wafer type cleaning. In this example, instead of mixing each chemical solution of sulfuric acid, hydrogen peroxide solution and nitric acid on the wafer surface,
The premix is injected onto the wafer surface in a supply line leading to a spray nozzle.

That is, a tank 17 containing sulfuric acid, a tank 18 containing hydrogen peroxide solution, or a tank 19 containing a mixed solution of sulfuric acid and hydrogen peroxide solution is provided instead of these as shown by the dashed line. A mixed solution of sulfuric acid and hydrogen peroxide is supplied to the spray nozzle 21 from the tank 17, 18, or 19 through the supply line 20, and nitric acid from the tank 22 is supplied through the supply line 20. The mixed solution of nitric acid-sulfuric acid-hydrogen peroxide solution is injected onto the surface of the semiconductor wafer 3 rotating at a high speed to perform a cleaning process. Here, the nitric acid 22 can be injected into the supply line 20 at a position as close as possible to the spraying portion (that is, the nozzle 21).

FIG. 5 shows an example in which the present invention is applied to spray-type batch cleaning. A carrier 25 holding a plurality of semiconductor wafers 3 in a cleaning chamber 24 is rotatably arranged about a rotation shaft 26, and the above-mentioned respective chemicals from a chemical solution supply unit 27 are transferred to the carrier 25.
The semiconductor wafer 3 is injected into the semiconductor wafer 3 through a spray nozzle 28 disposed along the center of the substrate, and is cleaned. Thereafter, a pure water rinsing process is performed. The method of injecting each chemical is the same as in the case of the spin-type single wafer cleaning described above.

According to the above-mentioned embodiment, the surface of the semiconductor wafer is short-time (within several minutes) by adding, for example, nitric acid, which is a decomposition accelerator, to the mixed cleaning solution of sulfuric acid and hydrogen peroxide.
Can be washed.

That is, the decomposition reaction of hydrogen peroxide is accelerated, the decomposition product of hydrogen peroxide, ie, oxygen, which is an effective cleaning component, is rapidly generated, and the temperature of the mixed solution increases due to the heat of the reaction. Oxygen as an active ingredient can be generated at a high concentration in a short time, and the cleaning effect is improved. With decomposition reaction at room temperature occurs at the same time, since the temperature of the washing solution rises rapidly in heat generation at the decomposition reaction, H ₂ at time conventional heating heating
O ₂ decomposition, consumption is avoided.

Further, since it is not necessary to heat the mixed cleaning liquid, a heating and heating period as in the conventional case is not required, and a heating apparatus is not required.

Since the decomposition reaction is completed in about 2 minutes by the addition of nitric acid, it is possible to shorten the wafer immersion time conventionally required for 30 to 90 minutes or more. Since the decomposition reaction of H ₂ O ₂ is completed in a short time, H ₂ O ₂
There is no unreacted component of No. ₂ , so that waste liquid treatment after washing is easily performed.

[0038]

According to the present invention, the decomposition reaction in a mixed cleaning solution of sulfuric acid and hydrogen peroxide is promoted, the surface of the semiconductor wafer can be cleaned in a short time, and the waste liquid treatment after the cleaning is completed is simplified. be able to. Further, since there is no need to raise the temperature of the mixed cleaning liquid, a heating and temperature raising facility can be eliminated. 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 a diagram illustrating an example of a case where a cleaning method according to the present invention is applied to dip type cleaning.

FIG. 2 is an explanatory view of another example in which the cleaning method according to the present invention is applied to dip-type cleaning.

FIG. 3 is a diagram illustrating an example of a case where the cleaning method according to the present invention is applied to a spin-type single-wafer cleaning.

FIG. 4 is an explanatory view of another example in which the cleaning method according to the present invention is applied to a spin-type single-wafer cleaning.

FIG. 5 is an explanatory diagram when the cleaning method according to the present invention is applied to a spray-type batch cleaning.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sulfuric acid-hydrogen peroxide mixed washing liquid 2, 6, 11 Processing tank 3 Semiconductor wafer 4 Cassette 7 Pure water 14, 15, 16, 21 Spray nozzle 17, 18, 19 Tank

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/304 647 H01L 21/30 572

Claims (1)

(57) [Claims] 1. A method for cleaning a semiconductor wafer, comprising adding a decomposition accelerator to a mixed cleaning solution of sulfuric acid and hydrogen peroxide solution to perform a cleaning treatment on the semiconductor wafer.