JPH0566725B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a cleaning technique, particularly a technique for ultra-high cleaning, and relates to a technique effective for cleaning wafers in the manufacture of semiconductor devices, for example. .

[Background Art] When cleaning a wafer in the manufacture of semiconductor devices, it is conceivable to immerse the wafer in running water for cleaning.

However, the inventor of the present invention has found that such a cleaning technique has a problem in that foreign matter remaining in the fine deep grooves formed in the wafer cannot be sufficiently cleaned.

An example of a technique that describes the technique of cleaning wafers with running water is the "Electronic Materials November 1982 Special Edition" published by Kogyo Research Association Co., Ltd., November 10, 1982.
There are P95 to P102.

[Purpose of the invention]

An object of the present invention is to provide a cleaning technique that can sufficiently clean the inside of minute deep grooves.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the object to be cleaned is immersed in a liquid and the object to be cleaned is made cathodic, so that the object to be cleaned is cleaned using the cleaning action of hydrogen gas bubbling caused by electrolysis.

〔Example〕

FIG. 1 is a longitudinal sectional view showing a wafer cleaning apparatus embodying the cleaning method of the present invention, and FIG. 2 is an enlarged partial sectional view showing the portion shown in FIG. 1.

In this embodiment, this cleaning apparatus is configured to clean a wafer 1 made of a silicon substrate. On the main surface of the wafer 1, which is the object to be cleaned,
For example, in a metal oxide semiconductor (MOS), a fine deep groove 2 for forming a capacitor is cut, and an insulating layer 3 made of a silicon oxide film, a silicon nitride film, etc. is formed on the surface.

This wafer cleaning apparatus includes a water tank 4 capable of accommodating a wafer 1, and the water tank 4 holds a liquid 5 that performs a cathode hydrogen gas bubbling action by electrolysis. As the liquid 5, it is preferable to use pure water containing a very small amount of electrolyte to the extent that it substantially only performs the bubbling action of the cathode hydrogen gas through electrolysis.

An anode electrode 6 and a cathode electrode 7 made of a material insoluble in the liquid 5 such as platinum (Pt) or gold (Au) are disposed in the liquid 5, and the cathode electrode 7 is connected to the wafer. 1 by suitable means. A power source 8 is electrically connected to both electrodes 6 and 7 so as to be able to cathode the wafer 1, and thus the power source 8 constitutes a power supply means for making the wafer 1 a cathode. At the outer bottom of the water tank 4, an ultrasonic generator 9 is installed so as to be able to apply ultrasonic vibrations into the liquid 5.

Next, the method of use and effect will be explained.

A wafer 1, which is an object to be cleaned, is immersed in a liquid 5, and a cathode electrode 7 is electrically connected to the wafer 1. Next, both electrodes 6,
At the same time, the ultrasonic generator 9 applies ultrasonic vibrations to the liquid 5 .

When a voltage is applied to both electrodes 6 and 7, since the wafer 1 is exposed to the liquid 5 in the deep groove 2 and is in electrical contact with it, a reaction as shown in the following equation (1) occurs. In the deep groove 2, hydrogen gas bubbles due to electrolysis.

2 x H cations + 2 x electrons = hydrogen gas... (1) As shown in Fig. 2, the bubbles 10 generated inside the deep grooves 2 are caused by the following actions: The surface will be cleaned.

(1) Foaming stirs the liquid 5 inside the deep groove 2 and washes away foreign substances 11 such as polymer residues attached during etching.

(2) The bubbles 10 trap contamination in the grooves with their surfaces (trap effect) and transfer them to the outside of the grooves 2.

(3) The bubbles 10 peel off the foreign matter 11 attached to the surface of the deep groove 2.

(4) When bubble 10 collapses or rises, foreign matter 11
Mechanically destroys foreign substances, making them easier to peel off, capture, and transport.

By the way, if the generated hydrogen gas bubbles 10 continue to adhere to the surface of the deep grooves 2 of the wafer 1, it is conceivable that the bubbling effect will be suppressed.

In this embodiment, an ultrasonic vibration generator 9 is attached, and by applying ultrasonic vibrations into the liquid 5, the generated bubbles 10 are removed from the surface of the deep groove 2 into the liquid 5.
We are trying to get them to leave as quickly as possible.
That is, when energized with ultrasonic vibration energy,
The bubbles 10 are forcibly separated from the deep grooves 2.

In this way, when bubbles are generated and released at the same time,
Since the surface of the deep grooves 2 comes into immediate contact with the liquid 5, the foaming action due to electrolysis occurs continuously and effectively. Furthermore, since the ultrasonic vibration imparts mechanical energy to the foam 10, it also acts to promote the cleaning actions (1) to (4) described above due to foaming. Moreover, the ultrasonic vibration itself also performs a cleaning action.

As a means of promoting foaming by separating the bubbles from the surface of the deep grooves as quickly as possible, there is a means of utilizing an electrochemical reaction.

For example, sodium (Na) and potassium (Ka)
By using as the liquid 5 an electrolytic solution containing a very small amount of positive ions, it is possible to suppress the enlargement of the hydrogen gas bubbles 10 and to attract and separate the ionically neutralized bubbles 10.

Note that it is desirable that the other surfaces of the wafer 1 be covered with an insulating layer so that foaming can occur effectively inside the deep grooves 2.

〔effect〕

While a wafer having minute deep grooves is immersed in a liquid, hydrogen gas bubbles are generated from the surface of the deep grooves by electrolysis, and the bubbles generated on the surface of the deep grooves are applied to the liquid with ultrasonic vibration energy. Since hydrogen gas bubbles can be formed on the surface of the deep grooves using ultrasonic vibration energy, hydrogen gas bubbles can be formed on the surface of the deep grooves using ultrasonic vibration energy. The bubbles can be agitated within the deep grooves while being separated, and together with the foaming promotion effect of ultrasonic vibration, the insides of the fine deep grooves can be thoroughly cleaned.

Although the invention made by the present inventor has been specifically explained based on Examples above, the present invention is not limited to the Examples described above, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say.

For example, the water tank is not limited to one that stops and stores liquid, but may be one that has a flow.

Pure water as a liquid may contain impurities to the extent that they do not adversely affect the object to be cleaned.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a wafer cleaning apparatus embodying the cleaning method of the present invention, and FIG. 2 is an enlarged partial sectional view showing the portion shown in FIG. 1. 1...Wafer (object to be cleaned), 2...Deep groove, 3...
... Insulator layer, 4 ... Water tank, 5 ... Liquid, 6 ... Anode electrode, 7 ... Cathode electrode, 8 ... Power supply (power supply means), 9 ... Ultrasonic vibration generator, 10 ...
...Bubble, 11...Foreign object.

Claims (1)

[Scope of Claims] 1. A cleaning method for cleaning a wafer having fine deep grooves and whose surface other than the deep grooves is covered with an insulating material, wherein the wafer is immersed in a water tank holding liquid. , electricity is passed between the wafer and an anode disposed in the liquid using the wafer as a cathode to generate hydrogen gas bubbles by electrolysis on the surface of the deep groove, and A cleaning method characterized in that the bubbles generated in the liquid are caused to separate from the surface by applying ultrasonic vibration energy to the liquid. 2. The cleaning method according to claim 1, wherein the liquid is pure water. 3. The cleaning method according to claim 1, wherein the liquid contains a component that promotes separation of generated bubbles from the surface of the deep grooves.