JPH07245281A - Cleaning liquid and cleaning method - Google Patents

Abstract

PURPOSE:To provide cleaning liquid and a cleaning method whereby stubborn dirt can be removed from silicon semiconductors. CONSTITUTION:A cleaning liquid is the aqueous alkaline oxidizing solution including both hydroxide of alkaline metals whose gram molecule per liter is not smaller than 0.05mol/l and is not larger than 5mol/l and the hydrogen peroxide whose gram molecule per liter is not smaller than 0.02mol/l and is not larger than 0.5mol/l. Further, in this cleaning liquid, a surface-active agent whose gram molecule per liter is not smaller than 0.0001mol/l and is not larger than 0.01mol/l can be included allowably. As the surface-active agent, an alkyl benzen sulfonate can be used allowably. Moreover, a ultrasonic vibration can be used allowably together with this cleaning liquid.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In manufacturing a semiconductor device or a semiconductor wafer, a cleaning process is performed before and after various processes. As a cleaning solution for these wafers, for example, for a silicon wafer, an alkaline solution containing no oxidant or a solution containing a surfactant added thereto is used for strong contamination, and hydrogen peroxide / So-called SC using an alkaline cleaning solution of ammonia / water mixture
One wash solution has been used.

However, in both cases, very strong pollution,
For example, complex contamination such as fingerprints cannot be completely removed, which causes a decrease in yield.

Therefore, there is a demand for the development of a cleaning liquid having a stronger cleaning power than the cleaning liquids used so far.

[0005]

As described above, the cleaning liquids used so far lack the cleaning ability against strong contamination, which leads to a reduction in yield.

Therefore, it is an object of the present invention to provide a cleaning liquid and a cleaning method having an extremely excellent cleaning ability.

[0007]

The cleaning solution of the present invention is a solution of
05 mol / l or more and 5 mol / l or less alkali metal hydroxide, and 0.02 mol / l or more and 0.5 mol / l
It is an alkaline oxidizing aqueous solution containing 1 or less hydrogen peroxide, and is characterized by reducing the contamination of the surface of the silicon semiconductor, which is the object to be cleaned, by cleaning.

The cleaning liquid may contain 0.0001 mol / l or more and 0.01 mol / l or less surfactant in addition to the alkali metal hydroxide and hydrogen peroxide,
Furthermore, alkylbenzene sulfonate may be used as a surfactant.

Further, the cleaning method of the present invention is characterized in that cleaning is performed using the cleaning liquid. For cleaning, ultrasonic shaking may be used together.

[0010]

The principle of decontamination by the cleaning solution and the cleaning method of the present invention is not clear, but it is presumed as follows.

First, hydrogen peroxide acts on the surface of a silicon semiconductor to form a thin film of silicon dioxide. As a result, the contaminants directly attached to the surface of the silicon semiconductor are deposited on the silicon dioxide thin film.

The thin film of silicon dioxide is then etched with alkali. At this time, contaminants are considered to be removed together with silicon dioxide.

In the cleaning solution of the present invention, the alkali concentration and the hydrogen peroxide concentration are set within a range in which the above reaction uniformly and relatively slowly progresses so as to prevent uneven etching due to an increase in reaction rate.

As is clear from the examples shown in Table 1, by cleaning the silicon semiconductor with the cleaning solution of the present invention, strong contamination represented by fingerprints can be removed.

The cleaning liquid and the cleaning method of the present invention may be carried out in combination with other cleaning steps.

Further, in the cleaning method of the present invention, it is desirable to completely immerse the object to be cleaned in the cleaning liquid in order to prevent uneven cleaning, and it is further desirable to mechanically shake.

The washing temperature is preferably 50 ° C. or higher and 90 ° C. or lower. The cleaning time is preferably 30 seconds or more and 30 minutes or less.

As will be apparent to those skilled in the industrial field related to the present invention, these cleaning conditions have many factors, such as cleanliness of the object to be cleaned before cleaning, surface properties, manufacturing cost, throughput, etc. Because it is influenced by

In the cleaning solution of the present invention, the alkali metal hydroxide is used to realize alkalinity, and it is possible to obtain a high pH with a small amount as compared with the conventionally used ammonia or organic ammonium compounds. Because it is possible and cheap.

In the cleaning liquid of the present invention, the concentration of the alkali metal hydroxide is 0.05 mol / l or more and 5 mol / l or more.
The reasons for the following are as follows. Comparative example 2 in Table 1
As can be seen in 0 and 21, when the alkali metal hydroxide content is less than 0.05 mol / l, the ability to remove contaminants decreases.

It is considered that this is because the etching action of the surface by alkali is lowered.

Further, as seen in Comparative Examples 22 and 23 in Table 1, when the alkali metal hydroxide exceeds 5 mol / l, the contamination is removed but the surface is roughened.

It is considered that this is because the surface etching effect by the alkali becomes too strong and uneven etching occurs.

For the above reasons, in the cleaning liquid of the present invention, the alkali metal hydroxide concentration is 0.05 mol / min.
It was 1 or more and 5 mol / l or less.

In the cleaning liquid of the present invention, hydrogen peroxide is used for the purpose of imparting an oxidizing property, because the oxidizing power of hydrogen peroxide is different from other oxidizing agents such as sodium hypochlorite and potassium permanganate. It is weaker and easier to control.

Further, hydrogen peroxide has the advantages that it is inexpensive and that the waste liquid after use does not contain heavy metals and the waste liquid treatment is easy.

The reason why the concentration of hydrogen peroxide in the cleaning liquid of the present invention is 0.02 mol / l or more and 0.5 mol / l or less is as follows. As can be seen in Comparative Examples 24 and 26 in Table 1, hydrogen peroxide is 0.02 mol /
When it is less than 1, contamination is removed but surface roughness occurs.

It is considered that this is because the thin film of silicon dioxide formed by hydrogen peroxide becomes thin, and as a result, the rate of the etching reaction by the alkali increases and non-uniform etching occurs.

Further, as seen in Comparative Examples 25 and 27 in Table 1, when the hydrogen peroxide content exceeds 0.5 mol / l, the decontamination ability is lowered.

This is because the silicon dioxide film formed by hydrogen peroxide becomes thicker, and as a result, the etching reaction due to alkali is less likely to occur.

For the above reasons, in the cleaning liquid of the present invention, the concentration of hydrogen peroxide is 0.02 mol / l or more and 0.5 or more.
It was set to mol / l or less.

In the cleaning liquid and cleaning method of the present invention,
The action of the surfactant is to prevent the redeposition of the contaminant by encapsulating the contaminant once removed by the hydrophobic group of the surfactant and solubilizing it in the solution. It is clear from the examples in Table 1 that this improves the ability to remove contaminants.

The reason why the concentration of the surfactant in the cleaning liquid of the present invention is 0.0001 mol / l or more and 0.01 mol / l or less is as follows.

As can be seen from Example 8 in Table 1, the decontaminating ability when the concentration of the surfactant is less than 0.0001 mol / l is the same as when the surfactant is not contained.

This is because the surfactant needs to have a certain concentration or more to exert its ability.

Further, as shown in Example 12 in Table 1, the decontaminating ability when the concentration of the surfactant exceeds 0.01 mol / l is 0.0001 mol of the surfactant.
/ L or more and 0.01 mol / l or less, it is rather worse.

It is presumed that this is because the surfactant of high concentration is adsorbed on the surface of the silicon semiconductor to interfere with the formation reaction of silicon dioxide by hydrogen peroxide or the etching reaction by alkali.

For the above reasons, the concentration of the surfactant in the cleaning liquid of the present invention is set to 0.0001 mol / l or more and 0.01 mol / l or less.

The reason why the surfactant in the cleaning liquid of the present invention is an alkylbenzene sulfonate is as follows.

As can be seen from Example 10 in Table 1, when an anionic alkylbenzene sulfonate is used as the surfactant and when a nonionic polyoxyethylene alkyl ether is used (Example 7). compared,
The ability to remove contaminants is slightly improved.

This is because, when alkaline, the alkylbenzene sulfonate is completely dissociated and ionized,
This is because the hydrophilicity of the hydrophilic group is improved and the surface activity becomes stronger than that of the nonionic surfactant.

For the above reasons, the surfactant is alkylbenzene sulfonate.

In the cleaning liquid and cleaning method of the present invention,
The action of ultrasonic vibration assists the removal of contaminants by etching and allows the contaminants to be removed quickly.

It is clear from Examples 16 and 17 in Table 1 that this improves the ability to remove contaminants.

[0045]

EXAMPLE A method for evaluating the surface decontamination ability will be described. A silicon wafer whose surface was roughly polished was prepared. A finger was pressed against the surface of this wafer to attach a fingerprint.

The fingerprint was selected because the fingerprint is a strong complex contamination containing both organic and inorganic substances and cannot be removed by the conventional cleaning liquid.

Further, in some cases, the oil / fat is adhered by immersing it in a solution in which the abrasive powder is dissolved to adhere the abrasive powder or by pressing animal oil / fat.

The wafer thus intentionally attached with the contaminants was washed under the conditions shown in the examples or comparative examples of Table 1. Then, it was rinsed with pure water. At this point it cannot be determined visually whether the contaminants have been removed.

Therefore, etching with mixed acid was further performed. Since the etching rate is different between the portion where the contaminant remains and the portion where the contaminant does not remain, a slight step is formed.

Then, by observing this wafer with a condenser lamp, residual contamination was detected as a step. The degree of residual was visually determined based on the unwashed wafers shown in Examples and Comparative Examples in Table 1.

Table 1 shows a summary of the examples in which the contamination residue after cleaning with the cleaning solution or the cleaning method of the present invention was evaluated (Nos. 1 to 19).

In addition, as a comparative example, the results of the same evaluation in the case where the concentration of the alkali metal hydroxide or hydrogen peroxide is different from that of the cleaning solution of the present invention are also shown in Table 1 (numbers 20 to 27). .

According to the cleaning method using the cleaning liquid of the present invention, contaminants can be effectively removed.

On the other hand, in the comparative example, not only the contaminants could not be sufficiently removed, but also side effects such as surface roughness were observed in some cases.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

As described in detail above, if the cleaning liquid of the present invention is used for cleaning, it is possible to remove strong contamination that could not be removed in the manufacturing of semiconductor devices or semiconductor wafers. The yield improvement is realized and contributes to the development of the industry.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication H01L 21/308 G // B08B 3/08 A 2119-3B (72) Inventor Kenichi Uemura Kouichi Shimada 3434 Shin Nippon Steel Co., Ltd.Hikari Steel Works (72) Inventor Hiroyuki Hatanaka Higuchi City Yamaguchi Pref. Shimada 3434 Nittetsu Electronics Co., Ltd. (72) Inventor Shinji Terunaga 3434 Shimada Hikari City, Yamaguchi Prefecture Address Nittetsu Electronic Co., Ltd.

Claims (5)

[Claims] 1. A hydroxide of an alkali metal of 0.05 mol / l or more and 5 mol / l or less, and 0.02 mol / l
A cleaning liquid, which is an alkaline oxidizing aqueous solution containing 0.5 mol / l or less of hydrogen peroxide, and which reduces the contamination of the surface of the object to be cleaned by cleaning. 2. The alkaline aqueous solution contains 0.0001 mo in addition to the alkali metal hydroxide and hydrogen peroxide.
The cleaning liquid according to claim 1, comprising a surfactant in an amount of 1 / l or more and 0.01 mol / l or less. 3. The cleaning liquid according to claim 2, wherein the surfactant is an alkylbenzene sulfonate. 4. Claim 1 or claim 2 or claim 3.
A method for cleaning a silicon semiconductor, which comprises using the cleaning solution according to 1. 5. The method for cleaning a silicon semiconductor according to claim 4, wherein ultrasonic agitation is also used during cleaning.