JP2000031109A - Method of drying - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dry a silicon wafer by removing humidity, remove water molecules from a silicon wafer surface having no oxide film, and simultaneously promote hydrogen termination of silicon atoms, by drying the semiconductor with inert gas that contains hydrogen radicals. SOLUTION: Hydrogen is added to inert gas to generate hydrogen radicals by using a heated metallic catalyzer to promote hydrogen termination after the drying. Usable catalyzer has a catalytic effect for the radical generation, for which nickel, platinum or the like are listed; however more preferable one in terms of the catalytic capability is platinum. In using the metallic catalyzer, its form preferably has as large surface area as possible, and a form of filter is preferable to increase effective contact area between the metallic catalyzer and hydrogen. The gas is required to be heated to approximately a temperature of blowing the wafer. The position of drying the wafer is preferably close to the point where the gas has just been released from the metallic catalyzer, because of short lifetime of the irradiating radicals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for drying a semiconductor manufacturing process, and more particularly to a method for drying a wafer using hydrogen radicals generated in a gas.

[0002]

2. Description of the Related Art In a wet process of a semiconductor manufacturing process, a step of removing moisture adhering to a wafer in an earlier process is performed as a final step. The drying process includes methods such as spin drying, IPA (2-propanol) vapor drying, and Marangoni drying, all of which have only the effect of removing water.

[0003] In a wet cleaning step of a silicon substrate, the substrate surface after cleaning with a cleaning solution containing hydrofluoric acid has a structure in which silicon atoms on the outermost surface are linked to hydrogen atoms and the outermost surface is terminated by hydrogen atoms. This hydrogen-terminated silicon surface is said to be a chemically very stable surface. However, not all silicon atoms are bonded to hydrogen atoms, and it has been confirmed that silicon atoms are present in the unbonded state as they are on the surface as well as silicon atoms to which fluorine atoms are bonded. Such a silicon atom is a site that is extremely unstable chemically and is susceptible to oxidation.

In a wet cleaning process for a silicon substrate, the substrate after cleaning with a cleaning solution containing hydrofluoric acid has no oxide film on the surface. However, the substrate in this state tends to cause adhesion of various particles. Therefore, although a cleaning solution in which ozone is added to hydrofluoric acid has been developed, it has been found that the amount of hydrogen termination is weaker than the conventional cleaning process using only hydrofluoric acid.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a drying method for drying moisture and promoting hydrogen termination of silicon atoms in a semiconductor drying step.

[0006]

A drying method according to the present invention is characterized in that in a wafer drying step of a semiconductor manufacturing process, drying is performed with an inert gas containing hydrogen radicals. By using a gas containing hydrogen radicals for drying, water molecules are eliminated from the silicon surface without an oxide film, and at the same time, hydrogen termination is promoted.

[0007]

According to the present invention, hydrogen is first added to an inert gas, and hydrogen radicals are generated by using a heated metal catalyst to promote the termination of hydrogen after drying. The catalyst used here can be used as long as it has a catalytic effect for generating radicals. Examples include nickel, platinum and the like, but platinum is more preferred as the catalytic ability.

[0008] When used as a metal catalyst, the shape is preferably as large as possible in surface area. For example, it is better to use a filter-shaped material than a tube-shaped material and increase the effective contact area between the metal catalyst and hydrogen.

It is necessary to raise the temperature of the gas up to the vicinity of blowing the gas onto the wafer. Further, it is preferable that the position where the wafer is dried be as close as possible to the gas coming out of the metal catalyst. This is because the lifetime of the radical irradiated on the wafer is short. In particular, there is almost no effect if it is 30 mm away from the gas outlet.

[0010] The temperature of the gas blown to the wafer is 150
Although the effect is seen more than ℃, more preferably 200
It is higher than or equal to 350 ° C. In particular, in the high temperature part, the hydrogen termination is destroyed by the hydrogen termination due to the effect of the radical, and the reaction proceeds toward the formation of the oxide film.

It has been found that the hydrogen concentration is more effective than 0.05%. Further, the upper limit of the hydrogen concentration is desirably not more than a hydrogen explosion limit of 4.1%.

The inert gas and hydrogen used here are as free from moisture and oxygen as possible, especially 1 pp.
b or less is preferable.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples, but it goes without saying that the present invention is not limited to these examples.

(Example 1) An n-type (100) silicon substrate having a resistivity of 3 to 7 Ω / cm was washed with a chemical solution in which 97% sulfuric acid and 30% hydrogen peroxide were mixed at a volume ratio of 4: 1 for 10 minutes. After rinsing with ultrapure water at a flow rate of 1 L / min,
Treated with 0.5wt% hydrofluoric acid for 1 minute, and flow rate 1L /
Rinsing with ultrapure water for one minute.

After rinsing, dry with nitrogen at a gas flow rate of 10 L / min and dry with hydrogen radicals using a nickel filter (effective filtration area: 13.5 cm ² ) as a metal catalyst (gas composition ratio: hydrogen: nitrogen = 0.1%: 99). .9%) for 20 seconds.

Immediately, the substrate is sized 50 mm × 20 mm.
Si-H peaks were observed by a multiple reflection method using a Fourier transform infrared spectrometer using a parallelogram type germanium crystal having a 60 mm angle (thickness: 2 mm) cross section as a prism. The results are shown in Tables 1 and 2.

[0017]

[Table 1]

[0018]

[Table 2]

Example 2 An n-type (100) silicon substrate having a resistivity of 3 to 7 Ω / cm was washed for 10 minutes with a chemical solution in which 97% sulfuric acid and 30% hydrogen peroxide were mixed at a volume ratio of 4: 1. After rinsing with ultrapure water at a flow rate of 1 L / min,
Treated with 0.5wt% hydrofluoric acid for 1 minute, and flow rate 1L /
Rinsing with ultrapure water for one minute.

After rinsing, use a nickel filter (effective filtration area 13.5 cm) as a metal catalyst at a gas flow rate of 10 L / min.
² ) The hydrogen radical drying of 300 was performed by changing the gas composition ratio.
C. for 20 seconds.

Immediately, this substrate is sized 50 mm × 20 mm.
Si-H peaks were observed by a multiple reflection method using a Fourier transform infrared spectrometer using a parallelogram type germanium crystal having a 60 mm angle (thickness: 2 mm) cross section as a prism. Table 3 shows the results.

[0022]

[Table 3]

Example 3 An n-type (100) silicon substrate having a resistivity of 3 to 7 Ω / cm was washed for 10 minutes with a chemical solution in which 97% sulfuric acid and 30% hydrogen peroxide were mixed at a volume ratio of 4: 1. After rinsing with ultrapure water at a flow rate of 1 L / min,
The mixture was treated with a mixed solution of ppm ozone and 0.5 wt% hydrofluoric acid for 1 minute, and rinsed again with ultrapure water at a flow rate of 1 L / min.

After rinsing, use a nickel filter (effective filtration area: 13.5 cm) as a metal catalyst at a gas flow rate of 10 L / min.
² ) Hydrogen radical drying (gas composition ratio: hydrogen: nitrogen =
0.1%: 99.9%) at 300 ° C. for 20 seconds.

Immediately, this substrate is sized 50 mm × 20 mm.
Si-H peaks were observed by a multiple reflection method using a Fourier transform infrared spectrometer using a parallelogram type germanium crystal having a 60 mm angle (thickness: 2 mm) cross section as a prism. Table 4 shows the results.

[0026]

[Table 4]

[0027]

According to the present invention, the following effects can be obtained.
In addition to the conventional drying step, a function of chemically stabilizing the dried silicon surface can be provided.

Continued on the front page. (72) Inventor Tadahiro Omi, 1-17-1, Yonegabukuro, Aoba-ku, Sendai-shi, Miyagi 301 (72) Inventor Yuhisa Nitta 4- 1-7 Hongo, Bungo-ku, Tokyo Ultra Clean Co., Ltd. Technology Development Laboratory

Claims (1)

[Claims] 1. A method of drying a wafer in a semiconductor manufacturing process, wherein drying is performed with an inert gas containing hydrogen radicals.