JP2648556B2 - Surface treatment method for silicon 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 method for treating a silicon wafer with hot pure water, which can reduce particle contamination in a cleaning step of cleaning a silicon wafer to be a semiconductor substrate using a chemical cleaning solution such as hydrofluoric acid.

[0002]

2. Description of the Related Art Generally, in a manufacturing process of a silicon wafer (hereinafter, referred to as a wafer) as a semiconductor substrate, when a heat treatment is performed in a state where a wafer surface and a natural oxide film are contaminated with particles or heavy metals, particles are generated. As a result, unevenness of the thermal oxide film, crystal defects caused by heavy metals, and the like occur, which significantly lowers the yield rate of the wafer.

Therefore, conventionally, a natural oxide film itself is removed by performing cleaning using a solution obtained by diluting hydrofluoric acid with pure water (hereinafter referred to as hydrofluoric acid cleaning), whereby the wafer surface and the natural oxide film are removed. Removal of heavy metals therein is performed.

That is, in hydrofluoric acid cleaning, a wafer is immersed for a predetermined time in a hydrofluoric acid cleaning tank prepared by mixing hydrofluoric acid diluted to a specified amount with pure water, and then another rinse tank to which pure water is supplied. Then, the wafer was rinsed for a predetermined time, and the wafer pulled up from the rinsing tank was dried by a drying means such as a spinner.

[0005]

However, in the above-described conventional wafer cleaning method, hydrofluoric acid cleaning is very effective for removing heavy metals, but is ineffective for removing particles. In other words, according to the hydrofluoric acid cleaning, the natural oxide film is removed, and conversely, the wafer surface becomes very hydrophobic to which particles are easily attached, and therefore, when the wafer is pulled from the hydrofluoric acid cleaning tank. And
When the wafer is pulled from the pure water rinsing tank, particles adhere to the surface of the wafer and become contaminated, resulting in a problem that the yield rate of the wafer decreases.

Further, in order to suppress particle contamination when the wafer is pulled out of the hydrofluoric acid cleaning tank, pure water is supplied while the wafer is kept in the tank after the hydrofluoric acid cleaning is completed, so that hydrofluoric acid is supplied in the same tank. It is also conceivable to perform washing and rinsing with pure water, and then pull up the wafer from inside the tank after rinsing is completed, but in this case also, since the wafer surface is hydrophobic, after rinsing is completed, As described above, when the wafer is pulled up, the wafer surface is contaminated with particles, and the yield rate of the wafer is reduced.

Further, for the same reason as described above, there is a problem that such particle contamination is very likely to occur even when storing the wafer after cleaning with hydrofluoric acid.

Accordingly, the present invention provides a treatment for rendering the hydrophobic wafer surface after hydrofluoric acid cleaning hydrophilic.
It is an object of the present invention to provide a surface treatment method for a silicon wafer that removes heavy metals on the wafer surface, is resistant to particle contamination, and can improve quality.

[0009]

According to a first aspect of the present invention, there is provided a method for treating a surface of a silicon wafer after cleaning for removing a natural oxide film and heavy metals from a silicon wafer by using a chemical cleaning liquid. The chemical cleaning solution is replaced with pure water while the silicon wafer that has been cleaned in the cleaning tank is kept in the cleaning tank, and then hot pure water is supplied into the same cleaning tank, and the silicon wafer is immersed in hot pure water at a temperature of 40 ° C. or higher for 10 minutes. This is the surface treatment method for a silicon wafer configured to be dipped.

[0010]

Therefore, according to the present invention, the surface of a silicon wafer washed with a chemical cleaning solution such as hydrofluoric acid is oxidized by dissolved oxygen in warm pure water, and a natural oxide film grows on the surface of the silicon wafer by this oxidation. As a result, the surface of the silicon wafer changes from hydrophobic to hydrophilic, making it difficult for particles to adhere thereto. As a result, it becomes possible to manufacture a silicon wafer from which heavy metals are removed and which is resistant to particle contamination. Incidentally, in hot pure water at a temperature of 30 ° C., the same action as in the present invention cannot be achieved unless immersed for 24 hours or more. In addition, since the silicon wafer is processed while remaining in the cleaning tank, it is possible to avoid a situation in which particles are attached to the surface of the wafer and contaminated when the tank is moved as in the related art.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view showing a cleaning apparatus for performing the wafer surface treatment method of the present embodiment.

As shown in FIG. 1, the cleaning apparatus 1 includes a cleaning tank 4 for cleaning and rinsing a wafer 2 as a cleaning object with hydrofluoric acid, a pure water supply pipe 5 for supplying pure water to the cleaning tank 4, and
A hot pure water supply pipe 6 for supplying hot pure water to the cleaning tank 4, and a hot pure water heater 7 interposed in the hot pure water supply pipe 6 to make hot pure water from pure water. Each of the supply pipes is connected to a pure water supply source (not shown). In the figure,
Reference numeral 3 denotes a carrier for accommodating a plurality of wafers 2 and immersing the wafers in the cleaning tank 4.

Next, a case where a wafer is cleaned using the above-mentioned warm cleaning apparatus will be described.

[0014] First, meet the washing bath 4 in pure water supply pipe 5 with pure water cleaning tank 4 is supplied with pure water, to prepare a hydrofluoric acid cleaning solution by adding hydrofluoric acid to pure water this filled . Then, the wafers 2 stored in a plurality of clean carriers 3
Is immersed together with the carrier 3 in a hydrofluoric acid cleaning solution in the cleaning tank 4. By immersing in the hydrofluoric acid cleaning solution for a specified time, the natural oxide film on the surface of the wafer 2 is etched by hydrofluoric acid, and the heavy metal in the surface of the wafer 2 and the natural oxide film is removed. The surface of the wafer 2 is in a state where Si is exposed. At this point, the surface of the wafer 2 is hydrophobic.

Next, with the wafer 2 held in the cleaning tank 4, the inside of the cleaning tank 4, the surface of the wafer 2, and the carrier 3 are fixed.
In order to replace the surface with pure water, overflow rinse is performed by supplying pure water from a pure water supply pipe 5. In this case, when the replacement with the pure water is sufficiently completed, the supply of the pure water is stopped.

Further, after the replacement with the pure water is completed, the hot pure water heated by the hot pure water heater 7 is continuously supplied from the hot pure water supply pipe 6 into the washing tank 4. In this case, in the cleaning tank 4, pure water is gradually replaced by hot pure water, the periphery of the wafer 2 is also filled with hot pure water, and the surface of the wafer 2 where Si is exposed is oxidized by dissolved oxygen in the hot pure water. Due to this oxidation, a natural oxide film grows on the surface of the wafer 2 over time, and the surface of the wafer 2 changes from hydrophobic to hydrophilic as the natural oxide film grows.

When the surface of the wafer 2 changes to hydrophilic, the supply of hot pure water from the hot pure water supply pipe 6 is stopped, and then pure water is supplied from the pure water supply pipe 5 so that the cleaning tank 4 Is replaced with pure water, and the washing tank 4, the wafer 2 and the carrier 3 are cooled.

Thereafter, when the cooling of the cleaning tank 4, the wafer 2, and the carrier 3 is completed, the wafer 2 is removed from the carrier 3.
The carrier 3 is pulled up from the pure water in the washing tank 4 with the carrier 3 inserted therein, and the moisture of the wafer 2 and the carrier 3 is blown off by a centrifugal force by a drying means such as a spinner to dry, and the washing process is completed.

The inventor carried out hydrofluoric acid cleaning on the wafer (P type, crystal axis <100>) by the above method, then performed surface treatment with hot pure water at various temperatures, and measured the contact angle after the treatment. Then, the result shown in FIG. 2 was obtained.

From this result, when the surface treatment was performed with hot pure water of 40 ° C. or more for 10 minutes or more, the contact angle of the wafer surface after hydrofluoric acid cleaning was set to a low angle side, that is, the wafer surface was changed to a hydrophilic surface. It can be seen that it can be changed to When the temperature of the hot pure water is higher than 80 ° C., clouding tends to occur on the wafer surface after the surface treatment, and the processing temperature with the hot pure water is 40 ° C. or higher, preferably 40 to 80 ° C. 10 minutes or more is appropriate.

In order to confirm the effect of the hot pure water treatment, the present inventor produced 10 wafers each of which had been subjected to the hot pure water treatment and which had not been subjected to the hot pure water treatment, using the same wafer as described above. Then, the wafer was left in a passage in a clean room, and the standing time and the amount of increase in particles on the wafer surface were measured. The results shown in FIG. From this result, it is clear that there is a difference in the amount of increased particles depending on the presence or absence of the hot pure water treatment, and it can be confirmed that performing the hot pure water treatment has an effect of greatly reducing particle contamination.

In the above-described embodiment, pure water is heated and supplied using a hot pure water heater, but the present invention is not limited to this, and a cleaning apparatus as shown in FIG. 4 can be used.

The cleaning apparatus shown in FIG. 4 uses a heating heater 8 in place of the hot pure water supply pipe and the hot pure water heater of the above embodiment. Then, when performing the hot pure water immersion treatment, the pure water filled in the cleaning tank 4 is heated to the hot pure water by the heating heater 8, whereby the surface of the wafer 2 is oxidized by dissolved oxygen in the hot pure water,
A natural oxide film is formed on the surface of the wafer 2, and a hydrophilic wafer 2 surface is formed.

In the above-mentioned surface treatment method,
Although hydrofluoric acid treatment and surface treatment were performed in the same cleaning tank, two tanks, a hydrofluoric acid treatment tank and a surface treatment tank using hot pure water, were provided, and the wafer was moved from the hydrofluoric acid treatment tank to the surface treatment tank in a highly clean environment. If the transfer is performed, the same effect as described above can be obtained even if two tanks are used.

Further, this surface treatment method can be used for the surface treatment of a washed wafer even when a natural oxide film on the wafer surface is removed using a chemical other than hydrofluoric acid.

[0026]

As described above, the present invention relates to a method for treating the surface of a silicon wafer after cleaning for removing a natural oxide film and heavy metals of a silicon wafer by using a chemical cleaning liquid. A configuration in which the chemical cleaning liquid is replaced with pure water while the wafer is held in the cleaning tank, and then the pure water is supplied into the same cleaning tank, and the silicon wafer is immersed in hot pure water at a temperature of 40 ° C. or higher for 10 minutes or more. Therefore, according to the present invention, according to the present invention, the silicon wafer surface washed with a chemical cleaning solution such as hydrofluoric acid is oxidized by dissolved oxygen in warm pure water. Natural oxide film grows on the silicon wafer surface changes from hydrophobic to hydrophilic and particles are difficult to adhere It becomes, as a result, heavy metals are removed, and it is possible to produce a strong silicon wafer to particle contamination. In addition, since the silicon wafer is processed while remaining in the cleaning tank, it is possible to avoid a situation in which particles are attached to the surface of the wafer and contaminated when the tank is moved as in the related art.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a cleaning apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the processing time and the contact angle at the hot pure water temperature in the hot pure water processing.

FIG. 3 is a diagram showing a difference in particle contamination with or without hot pure water treatment.

FIG. 4 is a schematic sectional view showing a cleaning apparatus according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cleaning apparatus 2 Silicon wafer 3 Carrier 4 Cleaning tank 5 Pure water supply pipe 6 Hot pure water supply pipe

Claims (1)

(57) [Claims] In a method for treating a surface of a silicon wafer after cleaning for removing a natural oxide film and heavy metals from the silicon wafer with a chemical cleaning liquid, the silicon wafer cleaned with the chemical cleaning liquid is cleaned.
Replace the chemical cleaning solution with pure water while keeping it in the tank, and
After that, supply hot pure water into the same
A method for surface treating a silicon wafer, comprising immersing the wafer in hot pure water at a temperature of 40 ° C. or more for 10 minutes or more.