JPH05129265A - Cleaning method - Google Patents

Abstract

PURPOSE:To provide a method which allows high cleaning effects and that reduces the quantity of metal impurities adsorbed on a substrate for cleaning the substrate of a semiconductor, etc. CONSTITUTION:A subject to be cleaned is cleaned in pure warm water flow and the cleaning time is permitted to be shorter than a time that permits the ion concentration or the resistivity of the pure warm water to restore to a value before the cleaning subject is impregnated. Then, the cleaning subject is cleaned in pure water which is cooler than the pure warm water. The temperature of the pure water (2) which is cooler than the pure warm water is set at 60 deg.C or below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate cleaning method in a manufacturing process of semiconductor devices, liquid crystal display devices and the like.

In recent years, in the manufacturing process of highly integrated semiconductor devices, it is necessary to reduce contamination by metal impurities in order to improve device reliability.

[0003]

2. Description of the Related Art Ultrapure water is used for conventional substrate cleaning. In particular, recently, with the increase in the diameter of substrates, hot pure water, which has a high cleaning effect, has been used.

[0004]

However, the cleaning with hot pure water has a problem that metal impurities in the pure water are easily adsorbed on the substrate.

It is an object of the present invention to provide a method having a high cleaning effect and reducing the amount of metal impurities adsorbed on a substrate.

[0006]

[Means for Solving the Problems] 1)
The object to be cleaned is washed in a stream of warm pure water, and the cleaning time is set to be less than the time for recovering the hydrogen ion concentration or the specific resistance of the warm pure water to the value before the immersion of the cleaner, This can be achieved by a cleaning method of cleaning with pure water, or 2) the cleaning method of 1) above, wherein the temperature of pure water lower than the warm pure water is 60 ° C. or lower.

[0007]

In the present invention, the washing time with warm pure water is high resistance value (neutral) which is the original resistance (or hydrogen ion concentration) of warm pure water.
Before the recovery, it is washed with pure water at room temperature.

The Si surface usually has a -OH group in an aqueous solution, and the surface charge depends on the hydrogen ion concentration (PH) in the aqueous solution.
It becomes 0 near 2. Therefore, by suppressing the PH of pure water to a low level, adsorption of metal impurities charged in pure water can be reduced. This prevents the amount of metal impurities in the hot pure water from adsorbing to the substrate.

In the latter-stage cleaning, the pH of the metal impurities is suppressed from adsorbing to the substrate by lowering the temperature of the pure water (the adsorption of the metal impurities is experimentally confirmed above 60 ° C.). Until the original is recovered.

FIG. 1 is a diagram for explaining the principle of the present invention.
The mechanism will be explained using the experimental results shown in. First, high-purity hydrochloric acid (36%) for semiconductors was added to hot pure water at 80 ° C, and the PH of hot pure water was adjusted to 7, 6.2, 6, 5.9, 5.7, 4 respectively.
And

After cleaning the Si substrate for 30 minutes with each of the hot pure water and drying, the native oxide film on the substrate surface was dissolved and recovered with hydrofluoric acid, and each metal element (Ca, Mg, Al, Ni, Zn, Mn) were analyzed. At this time,
The concentration of each metal element in pure water was about 1 ppb.

Each of the illustrated metal elements has a small adsorption amount on the substrate surface when the pH is low. On the other hand, the adsorbed amount of each metal element increases as the PH increases, reaching its peak at PH = 7.

The hot pure water cleaning is used for rinsing after the acid solution treatment. In this case, in the present invention, since the acid solution is brought into the cleaning layer together with the object to be cleaned, the PH of the hot pure water is lowered. I used this.

[0014]

EXAMPLE 2 FIG. 2 is an explanatory diagram of Example 1 of the present invention. In the figure, 1 is an acid solution tank, 2 is a rinse tank for cleaning with pure water,
Reference numeral 3 is a pure water supply line control system, 4 is a hot pure water supply line (for example, ° C), 5 is a room temperature pure water supply line, 6 is a conductivity meter for measuring specific resistance, and 7 is a thermometer.

Hot pure water is supplied to the rinse tank 2 following the acid solution tank 1, and the specific resistance and temperature are measured. These values are sent to the control system 3 to control the flow rates of hot pure water and room temperature pure water. When the Si substrate, which is the object to be cleaned, is transferred from the acid solution tank 1 to the rinse tank 2, the resistivity of the hot pure water in the rinse tank drops sharply and then recovers little by little over time. Next, just before the specific resistance recovers to the high specific resistance before the substrate was loaded,
Switch to room temperature pure water. Pure water is supplied from the bottom of the tank and overflowed from the top.

In this case, the temperature of the pure water in the rinse tank may be gradually lowered by changing the flow rate ratio between the hot pure water and the normal temperature pure water. FIG. 3 is an explanatory diagram of the second embodiment of the present invention.

In this example, two rinse tanks following the acid solution tank 1 are provided, warm pure water is supplied to the rinse tank 21 at the front stage, and rinse tank 22 at the rear stage.
At room temperature, pure water is supplied from the bottom of the tank and overflowed from the top.

The cleaning time in the rinse tank 21 at the preceding stage is set to be before the specific resistance of pure water in the tank is completely recovered. Although the specific resistance of pure water is used for monitoring in the above embodiments, the pH may be directly monitored with a positive correlation.

[0019]

According to the present invention, a method having a high cleaning effect and reducing the amount of metal impurities adsorbed on the substrate was obtained. As a result, we were able to contribute to the improvement of manufacturing yield and reliability of semiconductor devices.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is an explanatory diagram of Embodiment 1 of the present invention.

FIG. 3 is an explanatory diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1 Acid solution tank 2, 21, 22 Rinse tank for cleaning with pure water 3 Control system of pure water supply line 4 Hot pure water supply line 5 Normal temperature pure water supply line 6 Conductivity meter 7 for measuring specific resistance 7 Thermometer

Claims (2)

[Claims] 1. The object to be cleaned is cleaned in a stream of warm pure water, and the cleaning time is less than the time for recovering the hydrogen ion concentration or specific resistance of the warm pure water to the value before immersion of the cleaned material, and then A cleaning method comprising cleaning with pure water having a temperature lower than that of warm pure water. 2. A pure water temperature lower than the warm pure water
The cleaning method according to claim 1, wherein the temperature is 60 ° C. or lower.