JPS62281431A - Method and device for ultrasonic cleaning - Google Patents

Abstract

PURPOSE:To clean a wafer after causing washings to thoroughly flow into such complicate and deep grooves as are possessed by fluted capacitor cells by cleaning the wafer to be cleaned, thereby causing the wafer to be immersed in the washings which are adjusted at a temperature within permitted limit for cleaning and also making the temperature-controlled washings to deliver ultrasonic oscillations. CONSTITUTION:Washings in a washing tank 12 are adjusted at a temperature within permitted limit and a cleaned object 16 is immersed in the above washings 14 and then, the cleaned object 16 is cleaned with the ultrasonic oscillations of the temperaturecontrolled washings. In addition, an ultrasonic cleaning device 1 is composed of the following components; cleaning part 10 to be filled with the washings 14, ultrasonic oscillation generating part 20 which permits the washings to make ultrasonic oscillations as well as temperature regulating part 30 which adjusts the temperature of washings within permitted limit for cleaning. Further, for example, the above ultrasonic oscillation generating part 20 consists an ultrasonic generator 22 and oscillator 24 and futhermore, the above temperature regulating part 30 consists of a heating means 36 and temperature sensor 32 as well as temperature regulator 34.

Description

[Detailed description of the invention] 3. Detailed description of the invention [Industrial application field] The present invention relates to an ultra-single-wave cleaning method and a cleaning device.

More specifically, the present invention relates to an ultrasonic cleaning method that cleans a wafer by ultrasonic vibration while heating a cleaning liquid, and an ultrasonic cleaning apparatus used to carry out the method.

[Prior Art] In order to improve the performance and reliability of 1' conductor substrates, cleaning treatment holds a major key. Since semiconductor surfaces are very sensitive, minimizing contamination of the element surface significantly improves the stability of the element's properties. For this reason, in order to prevent contaminants that adhere to the conductor surface during the wafer manufacturing process from remaining in the finished product, diffusion,
oxidation, CVI), 2nd place, etc. (11-
must be removed deliberately.

2I on the surface, dyeing is generally molecular and ionic.

Can be classified into atoms.

Examples of molecular contaminants include wax, resin, photoresist, ura, and residues of solvents.

Fingerprint fat also falls into this category. Molecular two-dimensional dyes are attached to the surface of the Noyo board by weak static electricity. Double dyeing with organic matter causes polarization and ionic drift due to proton movement, especially in the MO8 structure, which is sensitive to the surface.

If water-insoluble organic matter is attached, the substrate surface becomes water-repellent, making it difficult to remove ionic or metallic contaminants that have absorbed nitrogen.

Ionic contaminants are physically or chemically adsorbed, but chemically adsorbed ions are more difficult to remove than physically adsorbed ions. Chemical reactions must be used to remove this. Among ionic contaminants, alkali ions such as Na1 are particularly harmful, and BT treatment causes threshold voltage drift and formation of an inversion layer9.
Causes surface leakage current generation.

Original r-shaped zl; Dyeing can include heavy metals such as Au, Ag+Cu. These segregate into crystal defects and p
This lowers the n-junction breakdown voltage and affects the lifetime of minority carriers, surface conduction, and other device parameters. In order to remove these metals, they are ionized using a liquid that dissolves the metals to prevent them from settling on the surface.

Generally, all three types of contaminants mentioned above are deposited on the substrate surface. Therefore, first the large organic residues that cover the surface and make it water repellent must be removed, and then the remaining organic, ionic and atomic contaminants must be removed.

[Problems to be solved by the invention] Conventionally, such an i-conductor element or silicon wafer was
Cleaning has been carried out only by a chemical method called wet cleaning.

This cleaning method can be used for fA and Tp on a patterned surface where the wafer surface has a heavy phase or relatively small steps. However, when the process involves, for example, a llvg type capacitor cell, the problem of wettability between the air in the groove and the cleaning liquid prevents the cleaning liquid from completely reaching the inside of the groove, making it impossible to clean the cell.

If cleaning is incomplete, subsequent diffusion, oxidation, and CVD may occur.

Otherwise, problems may occur to the extent that the debossing occurs, which may reduce the product quality of the wafer or the manufacturing yield.

[Purpose of the Invention] Accordingly, the object of the present invention is to provide a method for cleaning a wafer by allowing a cleaning solution to completely penetrate into the complex and deep grooves of a trench-type capacitor cell, and for use in implementing the method. The objective is to provide a device that can

[Means for Solving the Problems] As a second step to solving the above-mentioned problems and achieving the object of the invention, the present invention provides a method for controlling the cleaning liquid in the cleaning tank at a temperature within the permissible 1M degree range for cleaning processing. The object to be cleaned is immersed in the cleaning solution at a temperature of J4, and the temperature exceeds the J4 cleaning solution) N
An ultrasonic cleaning method characterized by cleaning the object to be cleaned while vibrating it with waves, and 1. A cleaning section filled with washing ffi'/& used for carrying out the contact method, and an ultra 1'°~° for ultrahigh vibration of the cleaning liquid in the cleaning section
/g1. 111 volumes of cleaning processing for the vibration generating part and the cleaning branch? !
,,l ID:,Provides a super cleaning device consisting of 1 piece and 4 pieces for adjusting the temperature within the range.

[Operations] As described above, the ultrasonic cleaning method and apparatus of the present invention can be used in conventional chemical unit cleaning θ by heating the cleaning solution to 7F.
J, J! The wafer, which is the object to be cleaned, is ultrasonically cleaned by applying ultra-high vibration at 4L.

As a result, compared to the case where the cleaning liquid is used at room temperature, the cleaning effect is dramatically improved when the cleaning liquid is heated and used at a controlled temperature.

In addition, in the conventional chemical wet cleaning 1, the object to be cleaned is static 11.
, it was carried out under the following conditions. In contrast, in the method and apparatus of the present invention, the cleaning liquid and the object to be cleaned are vibrated ultrasonically. Unable to stay there, he comes over. Then, by removing the air that had been a barrier, the cleaning liquid can enter the area.

In addition, the wettability of the wafer surface with fA and the purifying solution is also extremely high. The single-wave vibration causes the wafer and the cleaning solution to constantly repeatedly collide with each other, resulting in extremely good results, and the cleaning solution comes into contact with the entire wall surface of the groove without any interference, achieving a high degree of cleaning.

In any case, in conventional chemical wet cleaning, attempts have been made to increase the cleaning effect of wafers such as groove-shaped capacitor cells by heating and controlling the temperature of the cleaning solution and applying ultrasonic vibrations, thereby improving the wafer manufacturing yield. For the first time, success has been achieved by the inventor.

[Example 1] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram of an apparatus used to carry out the wafer cleaning method of the present invention.

As shown in FIG. 1, the cleaning device 1 of the present invention is roughly divided into a cleaning section 10. It consists of an ultrasonic vibration generation section 20 and a cleaning liquid heating/temperature adjustment section 30.

75V, the node 10 consists of a circular or square cleaning tank 12. 15 and the cleaning part 12 can be made of, for example, quartz or the like. Other materials can of course also be used.

The cleaning tank 12 is filled with cleaning '$L14.

The cleaning liquid 14 may be water alone, but in order to enhance the cleaning effect, chemicals that do not adversely affect the wafer 16 may be used.

For example, acetone, isopropyl alcohol.

Solvents such as ethyl alcohol, ortho-xylene, carbon tetrachloride, tetrachloroethylene, trichlene, methyl alcohol, etc. can be used.

Processing solutions for acid cleaning include sulfuric acid, nitric acid, and hydronic acid.

Examples include hydrochloric acid, hydrogen peroxide, and ammonia. Sulfuric acid has a strong dehydrating effect and is effective in removing organic contamination. Nitric acid, hydrochloric acid, or a mixture of these (tap water) is used to remove heavy metals. Hydrofluoric acid is used to remove the Si oxide film.

Various like this? Due to the difference in a' ability for lj dyed fabrics, using a suitable combination of these treatment solutions produces a great cleaning effect.

For example, a mixed solution of H20/H202/NH40H in a ratio of 5:■=1 to 7:2:1 (volume ratio) removes organic contamination using the dissolving action of ammonia hydroxide and the oxidizing power of hydrogen peroxide. Ammonia hydroxide is also C u +
It also has the ability to remove metals such as N i+ A g.

Historically H20/H202/HC1 8:1:l to 8:2
:1 (volume ratio) mixed solution is effective in removing heavy metals.
These heavy metals are made into 1-1f soluble ions to prevent irG deposition from the solution.

It is preferable that several to several dozen wafers 16 are arranged in a wafer cassette jig 18 and immersed in the cleaning liquid.

The ultrasonic vibration generator 20 includes an ultrasonic oscillator 22 and a vibrator 24
Consisting of 26 is a cable connecting the oscillator 22 and the vibrator 24.

The ultrasonic oscillator 22 is a variable output type 9 frequency variable type;
Types well known to those skilled in the art, such as multi-frequency types, can be used. The vibrator 24 is of an immersion type.

Any type, such as an external type or an embedded type, can be used.

What is shown in the figure is an external l town "1 vibration γ, super-°
In order to transmit one-wave vibration to the cleaning liquid in one washing tank, two pieces of water are placed inside.
A heating ultrasonic bath 29 filled with 8 is used. When using an immersion type or implantable type transducer, the ultrasonic bath as shown in the small figure in the figure functions as a 1M bath. Super rr'6Jt
The cleaning effect changes depending on the frequency, but generally 30
Frequencies around kHz are used.

+Ii7 addition tJ+↓super? The tank 29 can be made of, for example, stainless steel coated with Teflon.

A heat insulating material 40 (for example,
(neoprene sponge, etc.).

Other insulation materials can also be used.

The temperature sensor 32 determines whether or not the medium water 28 in the ultrasonic tank 29 is at the temperature set in the temperature controller 34, and the heating means 36 is activated thereby to heat up or heat the medium water 28. d.

W n. This medium water 28 is pumped by a pump 38 to
It is circulated between the wave tank 29 and the heating means 36 and maintained at a set degree of uniformity. In this state, the object to be cleaned (wafer) 50 is placed in a cleaning tank and cleaned.

Add cleaning solution! ! It is preferable to set the % temperature at a temperature that is within the allowable temperature range for cleaning processing and that provides the highest cleaning effect, taking into consideration the components and composition used.

Such temperatures can be readily determined by those skilled in the art through repeated experiments under the conditions of use.

The cleaning time varies depending on the components and composition of the cleaning liquid used, the set temperature, the frequency used, etc., but is generally about a few minutes to several minutes. Therefore, the cleaning time itself is not an essential requirement of the present invention. It is preferable to immediately quench with pure water after ai.

The heating means is, for example, a heat exchanger such as an electronic cooling type or a heating type, or a gas heater.

An electric wire heater etc. can be used.

l &! By changing the set temperature of the JJI device 34 and cleaning it, the 15V effect can be increased by 15V.

Instead of the pump circulation type cleaning liquid heating/temperature control mechanism as shown in the figure, a heating means such as an immersion heater or a heating jacket may be used,
A method of stirring the medium water inside with a propeller type stirrer to maintain the medium water at a uniform temperature can also be used.

If you continue cleaning, the cleaning solution will gradually lose 7fi as time passes. If you continue wiping the cleaning solution while it is still dirty, the wafer cleaning effect will decrease, so please remove the cleaning solution. It is preferable to replace part or all of it after it has been used for a predetermined period of time.For this purpose, a discharge port is provided at the bottom of the cleaning tank 12, and the Vibro 0 is connected to this. A valve 62 is provided.In this way, part or all of the tji, turbid, and θ wash in the cleaning tank 12 can be discarded.The cleaning tank 12 is replenished with fresh cleaning liquid from the cleaning liquid replenishing section 64.

The on-off valve 62 is used when replacing the cleaning liquid with another type.
．． Two. In fact, depending on the wafer, the cleaning effect may be enhanced by changing the composition of the cleaning r'p group.

The cleaning solution may contain a surfactant and/or other agents capable of enhancing the cleaning effect, which are well known to those skilled in the art, within a range that does not adversely affect the wafer.

[Effects of the Invention - 1] As explained above, the ultrasonic cleaning method and apparatus of the present invention perform ultrasonic cleaning while heating and controlling the temperature of the cleaning solution in conventional chemical wet cleaning. A wafer, which is an object to be cleaned, is subjected to ultrasonic cleaning 1 by applying η-wave vibration. As a result, compared to the case where the cleaning liquid is used at room temperature, when the cleaning liquid is heated and used at a controlled temperature, the cleaning effect is significantly reduced.

Furthermore, conventional chemical cleaning has been carried out with the object to be cleaned lying still. On the other hand, in the method and apparatus of the present invention, the cleaning liquid and the object to be cleaned are vibrated ultrasonically. Unable to stay, he grows bitter. Then, by removing the air that had been a barrier, /'A
, RP liquid becomes infiltrated by one knife.

In addition, the rlM resistance between the wafer surface and the cleaning solution is also 1.
The wafer and cleaning solution constantly collide with each other due to wave vibration, resulting in extremely good cleaning, and the cleaning solution comes into even contact with the entire wall surface of the groove, achieving a high degree of cleaning.

In any case, in the conventional chemical cleaning process, heating the cleaning solution and applying ultrasonic vibration improves the cleaning effect of wafers such as groove-shaped capacitor cells, and improves the wafer manufacturing yield. The present inventor was the first to succeed in his attempt to achieve this.

[Brief explanation of the drawing]

The first is a schematic diagram of an apparatus used to carry out the wafer cleaning method of the present invention. 1... Wafer cleaning device, 10... Cleaning section, 12...
・Washing tank, 14...Cleaning liquid, 16...Wafer, 18...Wafer cassette jig, 20...Ultrasonic vibration generator, 22...Ultrasonic oscillation, 24...Vibration r
129...Heating ultrasonic bath, 30...a Purified liquid heating I-
Control section, 32...1jIA degree seven sensor, 34...Temperature controller, 36...Heating means, 38...Pump, 40...
insulation material

Claims (5)

[Claims] (1) Adjust the temperature of the cleaning liquid in the cleaning tank to within the allowable temperature range for cleaning processing, immerse the object to be cleaned in the temperature-controlled cleaning liquid, and immerse the object to be cleaned while ultrasonically vibrating the temperature-controlled cleaning liquid. An ultrasonic cleaning method characterized by cleaning. (2) The ultrasonic cleaning method according to claim 1, characterized in that the temperature of the cleaning liquid is adjusted to a temperature at which the cleaning effect is maximized. (3) Claim 1, wherein the object to be cleaned is a wafer.
The ultrasonic cleaning method according to item 1 or 2. (4) A cleaning section filled with cleaning liquid, an ultrasonic vibration generating section for ultrasonic vibration of the cleaning liquid in the cleaning section, and a temperature control section for adjusting the temperature of the cleaning liquid to within the allowable temperature range for cleaning processing. Ultrasonic cleaning equipment consisting of. (5) The ultrasonic cleaning apparatus according to claim 4, wherein the ultrasonic vibration generation section includes an ultrasonic oscillator and vibration, and the temperature control section includes a heating means, a temperature sensor, and a temperature regulator.