JPH01111337A - Wafer cleaning apparatus - Google Patents

Abstract

PURPOSE:To remove an organic contaminant adhered to the surface of a semiconductor water by a method wherein a chemical cleaning operation by using a cleaning liquid, oxygen in the air and ultraviolet rays is executed and, in addition, a physical cleaning operation by superposing the cleaning liquid from a spray nozzle on an ultrasonic vibration is executed. CONSTITUTION:A semiconductor wafer 4 is held on a wafer-holding stage 5 by a vacuum chuck system; said holding stage 5 is turned by using a driving motor 6. An ultrasonic spray nozzle 2 is equipped with an ultrasonic oscillator 7 and is controlled by an ultrasonic wave generator 8; while ultrasonic waves are superposed on a jet chemical-liquid stream, a required chemical liquid is fed from a chemical-liquid supply pipe 9. In addition, two or more ultraviolet lamps 10 used to radiate ultraviolet rays are installed above the wafer-holding stage 5; the whole surface of the wafer 4 is irradiated with the ultraviolet rays. By a multiplied action of a chemical cleaning action and a physical cleaning action, a very small amount ot organic contaminant adhered to the surface of the semiconductor wafer 4 can be effectively removed.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention relates to a wafer cleaning device, and relates to a device for removing surface contaminants from semiconductor wafers, and in particular to a device for removing surface contaminants from semiconductor wafers. It is used in wafer cleaning equipment.

(Conventional technology) As semiconductor devices become more sophisticated and denser, surface contaminants such as particulate matter and film-like deposits that get mixed in during the wafer process deteriorate processing accuracy and reduce the reliability of device characteristics. Therefore, removal of these surface contaminants is essential for improving device yield.

(Problems to be Solved by the Invention) Wafer cleaning has traditionally been carried out using a combination of chemical solutions such as organic solvents, oxidizing acids, alkalis, and surfactants, and the cleaning equipment has also been designed to suit this purpose. It has been put into practical use. However, this conventional cleaning method was unable to sufficiently remove organic surface contaminants. That is, even if a semiconductor wafer is immersed in an organic solvent, firmly attached surface contaminants cannot be completely removed only by physical cleaning/desorption or dissolution performed by the organic solvent. In addition, the organic solvent itself used for cleaning and the contamination of paid components in the series of cleaning steps that follow, such as organic substances in acids and alkalis, and carbon components attached due to organic contamination from the surrounding environment, can be removed using conventional methods. cannot be removed sufficiently. Particularly when cleaning a wafer with a fine pattern with unevenness such as a trench structure, it is difficult to remove residual organic matter by immersing the wafer in a chemical solution alone.

On the other hand, carbon atoms attached to semiconductor wafers may precipitate on crystals, oxide films, or the interface between oxide films and substrates, or form crystal defects or carbon compounds such as SiC, leading to a decrease in dielectric strength and leakage current. This results in increase in bonding properties and deterioration of bonding properties. Further, crystal distortion occurs around the SiC, and heavy metals are fixed in this area, resulting in poor characteristics. Since the presence of carbon atoms causes a decrease in the reliability of semiconductor devices, it is necessary to completely remove them.

An object of the present invention is to provide a wafer cleaning apparatus that can effectively remove minute amounts of organic contaminants attached to the surface of a semiconductor wafer.

[Structure of the invention] (Means and effects for solving the problem) The present invention includes a spray nozzle that is equipped with an ultrasonic vibrator and discharges a cleaning liquid, and a semiconductor wafer onto which the cleaning liquid is sprayed is held and rotated. This wafer cleaning apparatus is characterized by comprising a rotation driving means, an ultraviolet irradiation means for irradiating the semiconductor wafer with ultraviolet rays, and a cleaning tank for cleaning the wafer using the nozzle and each means. That is, the present invention includes an ultrasonic spray nozzle that superimposes ultrasonic waves on a chemical solution for cleaning semiconductor wafers and sprays it onto the wafer, an ultraviolet irradiation device, and a wafer rotation drive device. It is designed to completely remove minute amounts of organic contaminants adhering to the wafer surface.

(Example) An example of the present invention will be described below with reference to the drawings. 1st
The figure shows the configuration of a wafer cleaning apparatus that is an embodiment of the present invention. This cleaning device is equipped with a cleaning tank 1 for cleaning semiconductor wafers, and various required chemical solutions are supplied from an ultrasonic spray nozzle 2 disposed above the cleaning tank 1, and a high-pressure jet-like liquid is supplied from a high-pressure pure water supply port 3. Can supply pure water. A semiconductor wafer 4 is held by a wafer holder 5 using a vacuum chuck method, and the outer holder 5 is rotationally driven by a drive motor 6 . The ultrasonic spray nozzle 2 includes an ultrasonic oscillator 7 and is controlled by an ultrasonic generator 8 to superimpose ultrasonic waves on the ejected liquid flow.

A chemical liquid supply pipe 9 is connected to the ultrasonic spray nozzle 2, and a required chemical liquid is fed into the ultrasonic spray nozzle 2. Furthermore, a wafer holding table 5
The upper part of the mI! which irradiates ultraviolet rays! ! UV lamps 10 are provided, and the entire surface of the wafer 4 is irradiated with ultraviolet light.

Semiconductor wafers are cleaned using organic solvents,
It is carried out by a combination of oxidizing and alkali chemicals,
The chemical liquid necessary for the series of cleaning steps is supplied from the chemical liquid supply nozzle 2 of the wafer cleaning apparatus. Further, between a series of cleaning steps, pure water is supplied from the high-pressure pure water supply port 3 to perform pure water washing in order to remove the chemical solution in the previous step. Of course, it is also possible to supply pure water from the chemical liquid supply nozzle 2.

Removal of organic contaminants attached to the surface of semiconductor wafers is
This is carried out in the series of cleaning steps described above; for example, a dilute solution of persulfuric acid is supplied from the chemical supply nozzle 2, and the semiconductor chip 4 is irradiated with ultraviolet light from the ultraviolet lamp 10. Furthermore, ultrasonic waves from the ultrasonic transducer 7 are superimposed on the persulfuric acid diluted solution.

During this time, the semiconductor wafer 4 is rotated by the rotation drive device N6.

In the above manner, the organic contaminants attached to the surface of the semiconductor wafer 4 are removed by the activation effect of ultraviolet rays, active oxygen generated by a chemical reaction of oxygen caused by ultraviolet irradiation, and persulfuric acid generated by ultraviolet rays. It is completely removed by the synergistic action of the chemical cleaning action of active sulfate groups generated by a chemical reaction caused by irradiation with the physical cleaning action of ultrasonic vibration. At this time, the rotation applied to the semiconductor wafer 4 uniformizes the cleaning of its surface. To explain the above-mentioned cleaning action in more detail, as shown in the following formula (1), persulfate ions in persulfuric acid become active fii11i1 groups with high oxidation reactivity when irradiated with ultraviolet rays. Also below (21゜(
As shown in formula a, oxygen in the surrounding atmosphere undergoes a chemical reaction when irradiated with ultraviolet rays to produce oxygen, which has an oxidizing effect. Further, as shown in equation (4) below, organic contaminants adhering to the surface of the semiconductor wafer 4 are excited by ultraviolet rays. In this way, this excited organic contaminant is oxidized by the active sulfur Wi group of the following formula (1) and the oxygen of the generator of the following formula (3) as in the following formulas (5) and (0), and the organic contaminant is removed. The constituent carbon becomes carbon dioxide gas and is removed.

52o82-+hν→2S04″″・ (1)02
+h v-+03 (2)03+h
ν→02+[O] (3)R+hν→R″
(4) R″+2804− ・+
820-+n CO2+...R' + [0] 4j
l CO2+-' (5) Between these cleaning steps, pure water cleaning is performed to remove the chemical solution and the like.

. Pure water is supplied from a high-pressure pure water nozzle 3. In the above formula, hv represents light energy, R represents an organic substance, n represents a positive integer or fraction, and [0] represents atomic oxygen. Second
Figure (a) shows that using the wafer cleaning apparatus of the above embodiment, a silicon wafer is treated with a mixture of ammonia water, hydrogen peroxide solution, and pure water in a ratio of 1:1:6, and then treated with pure water. Then, mix hydrochloric acid, hydrogen peroxide, and pure water in a ratio of 1:1.
After treatment with a mixed solution mixed at a ratio of 6, treated with pure water, further superimposed ultrasonic waves on a 30% persulfuric acid diluted solution, sprayed on the wafer, and treated by irradiating it with ultraviolet rays. shows the cleaning results when treated with pure water. The oxide film breakdown voltage on the horizontal axis in this figure is 12Oi thick on a silicon wafer.
It is known that the oxide film breakdown voltage distribution reflects the surface cleanliness of the semiconductor wafer. For comparison purposes, FIG. 2(b) shows the cleaning results of a conventional cleaning sequence that does not include persulfuric acid diluted solution cleaning among the above-mentioned series of cleaning sequences. As shown in both figures, it can be seen that high pressure resistance has been achieved as a result of the tool cleaning using this apparatus. That is, it can be seen that the distribution shifts to the right in FIG. 2(a) compared to FIG. 2(b), and the breakdown voltage is 5.

[Effects of the Invention] As explained above, according to the present invention, a spray nozzle is provided on a semiconductor wafer set in a cleaning tank, and an ultraviolet irradiation device is provided that sprays a cleaning liquid discharged from the spray nozzle and irradiates it with ultraviolet rays. It is configured to perform a chemical cleaning effect using the cleaning liquid, oxygen in the surrounding atmosphere, and ultraviolet rays, as well as a physical cleaning effect by superimposing ultrasonic vibrations on the cleaning liquid from the spray nozzle. Due to the synergistic effect of the physical and chemical cleaning effects, organic contaminants adhering to the surface of the semiconductor wafer could be completely removed, and the yield of semiconductor devices could be improved.

[Brief explanation of the drawing]

15A is a block diagram of a wafer cleaning apparatus which is an embodiment of the present invention, and FIGS. 2(a) and 2(b) show the cleaning effect of the wafer cleaning apparatus shown in FIG. 1 above, and the conventional cleaning method. It is a figure showing a cleaning effect. 1...Cleaning tank, 2...Ultrasonic spray nozzle, 3.
...High pressure pure water nozzle, 4...Semiconductor wafer, 5...
- Wafer holding table, 6... Drive motor, 7... Ultrasonic sensor, 8... Ultrasonic generation power source, 9... Chemical solution supply pipe, 10... Ultraviolet irradiation device. Applicant Representative Patent Attorney Takehiko Suzue Taiman (Mv/cm) fI-jFf- (MV/cm)

Claims (1)

[Claims] a spray nozzle equipped with an ultrasonic vibrator and discharging a cleaning liquid; a rotation drive means for holding and rotating a semiconductor wafer onto which the cleaning liquid is sprayed; an ultraviolet irradiation means for irradiating the semiconductor wafer with ultraviolet rays;
A wafer cleaning apparatus comprising a cleaning tank for cleaning the wafer using each of the means.