JPS6223114A - Monitoring for ultraviolet cleaning - Google Patents

Abstract

PURPOSE:To enable the judgement of the completion of cleaning about an individual matter to be cleaned by a method wherein the organic substance film on the surface of the matter to be cleaned is decomposed by oxidation utilizing the ozone generated by ultraviolet rays and the cleaned state of the matter is monitored by an in-line using the gas produced by this decomposition. CONSTITUTION:Oxygen gas 2 introduced in a cleaning tank 1 from a gas introducing port 1a is irradiated with an ultraviolet lamp 3 to generate ozone and the resist on an Si semiconductor wafer 4 set up in parallel to the lamp 3 is decomposed by oxidation. Moreover, the ozone absorbs the ultraviolet rays emitted from the ultraviolet lamp 3 and is decomposed into excited oxygen atoms richer in an oxidative reaction than the ozone and the resist on the Si semiconductor wafer 4 is decomposed by oxidation in the same manner as the ozone. A component produced by this oxidation decomposition scatters on the Si semiconductor wafer 4 in a gaseous state and is exhausted through an exhaust vent 1b, while infrared rays A emitted from an infrared light source 5 are absorbed in the decomposition gas on the semiconductor wafer 4, the absorption strength is measured by an infrared detector 6, and at the same time, the measured value is monitored by a recording meter 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for monitoring the cleaning state of an apparatus for cleaning organic substances on the surface of an object to be cleaned with ultraviolet rays, and in particular a non-contact and non-destructive method for monitoring the cleaning and removal state of an object to be cleaned. This relates to a monitoring method that can be used for monitoring.

[Background of the invention]

Conventional ultraviolet cleaning equipment, as described in JP-A-59-94823 and JP-A-59-94824, has an ultraviolet intensity X185 at a wavelength of 185 nm and an ultraviolet light intensity X185 at a wavelength of 25 j n
The ratio of m to the ultraviolet lamp 254 (185/T25
4) Irradiate with a light source set in the range of = 008 to a3,
In addition, the radiation intensity of the workpiece 165 on the surface of the object to be cleaned is 3 mW/
K is configured so that the cleaning is completed when the object to be cleaned on the belt conveyor finishes passing under the ultraviolet lamp by irradiating the object with a light source set so as to be more than -.

However, the determination as to whether or not the above-mentioned cleaning has been completed is determined based on the relationship between the pre-caulking cleaning time and the cleanliness of the surface of the object to be cleaned. For this reason, it is not impossible to actually measure the cleaning and removal status of each individual object;
Sometimes cleaning and removal is insufficient. No consideration was given to confirming that the totoro had been washed and removed.

[Purpose of the invention]

The present invention solves the above problems, oxidizes and decomposes organic matter on the surface of the object to be cleaned using ozone generated by ultraviolet rays, and monitors the cleaning state in-line using the gas generated by the decomposition. It is an object of the present invention to provide an ultraviolet cleaning sonitor method.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention provides a cleaning tank which contains an object to be cleaned and an ultraviolet lamp, and which is equipped with a means for generating infrared light on one side and a means for detecting infrared light on the other side. Oxygen gas is introduced into the cleaning tank, and the organic components on the surface of the object to be cleaned are oxidized and decomposed by the ozone generated in the cleaning tank, and the infrared absorption intensity of the gas generated by the oxidative decomposition is continuously measured. The present invention is characterized in that the state of cleaning and removal of the organic matter is evaluated by doing so.

[Embodiments of the invention]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before explaining one embodiment of the present invention with reference to the drawings, the principle thereof will be explained in detail below.

Oxygen 02 and UV II! The ozone Os generated by irradiation acts on organic matter, for example, CnHmOk (where n and m are natural numbers), and reacts as shown in fl) to (3) 2 below.

hv(184,?nm)+Oz→0+0・・・・・・
(1)02+0 →Os ・・・・・・・・・ (
2) Os + Cn Hm Ok -1(1:o(ga
s), Co2 (gas).

H2O (gull B)...(3) As shown in the above (11 (212), K, oxygen 02 and 184.
When irradiated with light hv around 9 nm, the light energy is absorbed and ozone Os is generated. Since the ozone O1 has a strong oxidizing effect, it combines with carbon C and hydrogen H of organic matter on the surface of the object to be cleaned, and decomposes carbon monoxide Go, carbon dioxide Co2, and water vapor Hx OK as shown in (3) 2 above. .

On the other hand, Ozone O! Light around 254.7 nm reacts as shown in +4115)2 below.

h'v (254,7nm) +Os →oz +O*
−・−・−・−(410*+CnHmOk−+Co(g
as), Co2 (gas), H2O (gas)...
...(5) However, the * mark indicates an excited state.

As shown in equation (4) above, 254.7 n of ozone Os
When it is irradiated with light h'v k near m, it absorbs the light energy and generates excited oxygen atoms O*, which have a stronger oxidizing effect than ozone Os. As shown in the above formula (5), the # atom Os combines with C1H of an organic substance like ozone,
Decomposes into gases of CO1CO2 and H2O.

GO, C produced by the reaction formula shown in +31 f5) 2 above
By continuously measuring the infrared absorption intensity of each gas, Oz and H2O, on the surface of the object to be cleaned, it is possible to monitor the state of cleaning and removal of organic matter on the surface of each object to be cleaned during cleaning. .

Next, an organic matter is decomposed by ozone generated by ultraviolet rays, and a spectrum that can be used as a monitor from an infrared absorption spectrum of a gas produced by the decomposition will be explained with reference to FIG.

The figure shows the infrared absorption spectrum, with the wave number (cR-') on the horizontal axis and the transmittance (2) on the vertical axis.

As clearly shown in Figure 1, the above infrared absorption spectrum is
In carbon dioxide Cow, the spectrum based on antisymmetric vibration is 2300 to 2380 cIIL-'.

Also, the spectrum based on double degenerate vibration is 620-7Q.
Qcm'. On the other hand, for water vapor H20, the spectrum based on fully symmetric and antisymmetric stretching vibrations is 3600-39
0.0 CII-', and the spectrum based on fully symmetric bending vibration is 1400 to 1780 c111-'. However, the absorption spectrum of the spectrum 2050 to 2250cII-', which is based on the stretching vibration of -carbon oxide CO, is not detected because the amount produced is relatively small.

Furthermore, in addition to the above, the absorption spectrum of ozone Os generated by ultraviolet irradiation of oxygen is 970-1070α
-1 and 206.0 to 2130-'.

Therefore, the infrared absorption spectrum of carbon dioxide or water vapor, which is a gas decomposed and produced by ultraviolet rays, does not overlap with the infrared absorption spectrum of ozone, which is a gas produced other than decomposition. By continuously measuring the intensity, the cleaning removal status can be monitored.

FIG. 2 shows the main structure of this embodiment based on the above-mentioned principle. In the same figure, a cleaning tank with an inlet 1a and an outlet 1b for oxygen gas, ultraviolet rungs arranged in parallel at the top and bottom of the cleaning tank 1, and objects to be cleaned, such as semiconductors, are shown. It's a wafer. An infrared light source and an infrared detector are disposed on one side (left side) and the other side (right side) of the five- and six-tube cleaning tank 1, respectively, and 7 is a recorder connected to the infrared extractor 6.

Next, the operation of this embodiment configured as described above will be explained.

Oxygen gas 2 introduced into the cleaning tank 1 from the gas inlet 1a
The wavelength of 184.9 nm emitted from the ultraviolet lamp 3
The lamp 3 generates ozone by being irradiated with nearby ultraviolet rays.
The resist (
(not shown) is oxidized and decomposed.

In addition, the ozone absorbs ultraviolet light with a wavelength of around 254.7 nm emitted from the ultraviolet lamp 3, and the ozone
Decomposes into excited oxygen atoms, which are rich in oxidation reactions.

Similar to the ozone, the resist on the KSi semiconductor wafer 4 is oxidized and decomposed. Components generated by the oxidative decomposition, 81
The gas scatters on the semiconductor wafer 4 and is exhausted from the exhaust port 1b.

On the other hand, an infrared ray is emitted from an infrared light source 5.

It is absorbed by the decomposed gas on the Si semiconductor substrate 4, and its absorption intensity is measured by an infrared detector 6, and the measured value is monitored by a recorder 7.

FIG. 3 is a diagram showing the results of measuring changes over time in the infrared absorption intensity of decomposed carbon dioxide, with the horizontal axis representing cleaning time and the vertical axis representing absorption intensity. That is, the absorption intensity in the infrared absorption spectrum 2349>-' of the carbon dioxide was continuously measured.

As is clear from this figure, the amount of carbon dioxide on the S1 semiconductor wafer 4 increases at the same time as cleaning starts, and reaches a constant concentration after several minutes, and the cleaning speed also stabilizes. Furthermore, as the resist on the wafer 4 decreases, the concentration of carbon dioxide decreases, so the absorption intensity at a wave number of 2549 cm-' also decreases, and the cleaning is completed when the absorption intensity becomes zero. I understand.

[Effects of the Invention] As explained above, according to the present invention, the cleaning state of organic matter on the surface of the object to be cleaned by ultraviolet rays can be improved without the influence of ozone.
Not only can non-contact and non-destructive in-line monitoring be possible, but it is also possible to determine whether or not cleaning has been completed for each object to be cleaned.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the infrared absorption spectrum of gas generated by the decomposition of organic matter by ultraviolet rays, Figure 2 is a block diagram of an ultraviolet cleaning equipment to which the cleaning monitoring method of the present invention is applied, and Figure 6 is a diagram showing the decomposition products. FIG. 2 is a diagram showing the results of measuring changes over time in the infrared absorption intensity of carbon dioxide. 1...Cleaning tank, 3...Ultraviolet lamp, 4...Object to be cleaned. 5... Infrared light source, 6... Detector. １、、＋轡、

Claims (1)

[Claims] Oxygen gas is introduced into a cleaning tank that contains the object to be cleaned and an ultraviolet lamp, and is equipped with a means for generating infrared light on one side and a means for detecting infrared light on the other side. The organic matter on the surface of the object to be cleaned is oxidized and decomposed by the ozone generated by the process, and the infrared absorption intensity of the gas generated by the oxidative decomposition is continuously measured to evaluate the state of cleaning and removal of the organic matter. Characteristic ultraviolet cleaning monitoring method.