KR20040060087A - Real-time monitoring system and method for cleaning the surface of materials by laser beam - Google Patents

Abstract

PURPOSE: An apparatus and method for monitoring the cleaning degree of a surface in real time using laser beam are provided to be capable of simplifying a monitoring process without using surface analysis equipment by simultaneously measuring the reflected and transmitted light of the laser beam and comparing with each other. CONSTITUTION: An apparatus for monitoring the cleaning degree of a surface in real time using laser beam is provided with a light source part(110) for generating laser beam, a light path control part(112) for irradiating the laser beam to a sample(106), and a first detection part(130a) for detecting the transmitted light of the laser beam through the sample. The apparatus further includes a second detection part(130b) for detecting the reflective light of the laser beam from the sample, and a comparison and display part(140) for comparing the signals supplied from the first/second detection parts with each other and displaying the cleaning state of the sample.

Description

Real-time monitoring system and method for cleaning the surface of materials by laser beam}

The present invention relates to a system and method for real-time monitoring of the degree of cleaning in a cleaning process that removes contaminants adhering to the surface of the base material.

Generally, wet cleaning using chemical solvents has been used as a method for cleaning semiconductor surfaces, but interest in dry cleaning has increased due to environmental pollution. Dry cleaning method uses a laser or a lamp to directly irradiate the UV beam (or laser beam) to the surface to generate organic cleaning and laser cleaning (ultraviolet cleaning) to generate a vacuum plasma and radicals to react with contaminants Plasma cleaning to remove, and carbon dioxide snow cleaning to make a surface of the carbon dioxide to make a strong injection to clean the surface.

That is, in the conventional method for measuring the contaminants present on the surface of the base material, the contaminant form is divided into a particle form and a film form. Conventionally, in the case of a contaminant in the form of a thin film, a method of measuring the degree of cleaning of the contaminant is measured by using an apparatus for analyzing the surface state of the base material before and after cleaning. The analysis equipment used here includes an electron microscope (SEM) for measuring the shape of the surface, an atomic force microscope (AFM) for measuring the shape of the surface, and an X-ray diffraction analysis device (XRD) for identifying the components and structures. . In addition, the apparatus for measuring the thickness and characteristics of the thin film during the surface cleaning process includes a device for measuring the characteristics and thickness of the thin film through the characteristics of the light reflected by irradiating the monitoring light to the surface at a constant angle.

However, the above-described conventional devices do not measure the surface state of the base material in which the cleaning process is being performed, but collect each sample before and after the cleaning process and place the sample in the analysis equipment, and measure the physical characteristics thereof. In addition, the device for accurately measuring the characteristics or thickness of the thin film is measured by measuring the reflected light and its properties, in the case of a rough surface sample is difficult to measure and has a problem of inferior accuracy. In addition, when the thickness of the contaminant is small compared to the roughness of the sample surface, it is almost impossible to measure the degree of desorption of the contaminant.

The present invention has been proposed in order to solve the above problems, by monitoring the degree of cleaning of the surface during the dry cleaning process by using a ratio of the intensity of the light reflected from the surface and the light passing through the base material to the surface of the base material It is an object of the present invention to provide a surface cleaning monitoring apparatus and method using light that can quantitatively measure the degree of desorption of contaminants adhering to the surface.

The present invention has the advantage that the surface roughness of the base material is larger than the thickness of the contaminant and the reflected light is very weak, and the extent of the transmitted light is measured by measuring the change in the intensity of transmitted light in the sample whose cleaning degree is not known in the process. .

1 is a block diagram showing the configuration of a surface cleaning monitoring system according to the present invention;

2A and 2B are diagrams for explaining a surface cleaning monitoring concept according to the present invention;

3 is a flow chart illustrating a surface cleaning monitoring procedure in accordance with the present invention.

* Explanation of symbols for main parts of the drawings

102: laser for cleaning 104: laser for monitoring

106: Sample 108: Sample Support

110: laser generator for monitoring 112: total reflection mirror

120a, 120b: interference filter 130a, 130b: photodetector

140: computer

In order to achieve the above object, the device of the present invention, the light source for generating a laser light for monitoring; Optical path control means for irradiating the sample with the monitoring laser light; Transmitted light detecting means for detecting the intensity of light transmitted through the sample; Reflected light detecting means for detecting an intensity of light reflected from the sample; And comparing and displaying means for comparing each signal input from the transmitted light detecting means and the reflected light detecting means to display a cleaning state.

In order to achieve the above object, the method of the present invention includes a laser generating step for monitoring; Irradiating the sample surface with the generated monitoring laser; Detecting light reflected from the sample and transmitted light; And displaying the process state by comparing the detected reflected light with the intensity of the transmitted light.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing the configuration of a surface cleaning monitoring system according to the present invention.

As shown in FIG. 1, the surface cleaning monitoring system according to the present invention includes a laser generator 110 for monitoring, a total reflection mirror 112, interference filters 120a and 120b, photo detectors 130a and 130b, and a computer 140. It is possible to monitor the degree to which the contaminants 106a of the cleaning sample 106, which are arranged on the sample attachment table 108, and are cleaned by the cleaning laser 102.

Referring to FIG. 1, in a dry cleaning process, a base material (sample) 106 for cleaning is placed on a sample mounting table 108, and the base material is formed by a laser beam 102 generated from a cleaning laser source (not shown). Remove contaminants 106a attached to the surface of 106.

In this case, the surface cleaning monitoring system according to the present invention generates the monitoring laser beam 104 from the monitoring laser generator 110, and then firstly totally reflects to the sample side by the total reflection mirror 112 and transmits the sample to the interference filter. The light is converted into an electrical signal by the transmitted light photodetector 130a via 120a, and the light reflected from the sample is reflected by the total reflection mirror 112, and then is reflected by the reflected light photodetector 130b via the interference filter 120b. Is converted into an ordinary signal.

The computer 140 loads and executes an application program for predetermined measurement and monitoring while comparing the data input from the transmitted light photodetector 130a with the data input from the reflected light photodetector 130b to clean the sample 106. The degree is displayed in real time.

FIG. 2A is a diagram illustrating a concept of surface cleaning monitoring according to the present invention, and FIG. 2B is a graph showing the intensity of transmitted and reflected light measured during the cleaning process according to the present invention.

Referring to FIG. 2A, the monitoring laser light 104 is incident on the sample 106 side, partly reflected by the pollutant 106a, and partly transmitted through the sample. At this time, by comparing the intensity of the reflected light (104b) and the intensity of the transmitted light (104a) it is possible to monitor the degree of removal (that is, the cleaning state) of the contaminant 106a on the sample 106. For example, when there are many contaminants, the intensity of the reflected light 104b is greater than that of the transmitted light 104a, and as the contaminants are gradually removed, the intensity of the transmitted light 104a becomes larger than the reflected light 104b. .

2B, the horizontal axis of the graph represents the time axis and the vertical axis represents the intensity of light. According to the graph shown, when there are many pollutants, the intensity 104b of the reflected light is greater than the intensity 104a of the transmitted light, and as the contaminants are removed as time passes by the cleaning process, the intensity 104a of the transmitted light gradually increases. It can be seen that the increase and the intensity 104b of the reflected light decrease. At this time, when the intensity of the transmitted light reaches the threshold (Th), the contaminants are all removed and the cleaning process is terminated. 2B is only a graph conceptualizing the characteristics of the present invention. In practice, since the degree of contamination of the sample before washing is different and the permeation characteristics of the sample itself are also different, the characteristics may be represented by different types of graphs.

Thus, according to the present invention it is possible to monitor the state of the process more accurately by displaying the degree of removal of contaminants in real time during the cleaning process.

3 is a flow chart illustrating a surface cleaning monitoring procedure in accordance with the present invention.

As discussed in the prior art, the current technology for measuring the degree of cleaning of the base material of the wet and dry cleaning devices is a technique for analyzing the surface state of the base material before and after cleaning. On the other hand, in the present invention, in the case of the base material having the light transmissive property and the reflective property, the reflection light 104b and the transmitted light 104a can be simultaneously measured as shown in FIG. 2A to more precisely measure the degree of removal of contaminants on the surface. Particularly, in the case of a base material having a roughness of several tens of micrometers, measurement by reflected light on the surface is impossible, and thus the degree of contamination removal may be monitored by the intensity of transmitted light. That is, the intensity of transmitted light is changed by the change in the thickness of the contaminant removed until the contaminant on the surface is removed several tens of micrometers from the surface, so the degree of removal of the contaminant is measured by measuring the change of the intensity with the photodetector 130a at the bottom of the sample. Can be calculated.

According to the present invention, the laser light 104 irradiated to monitor the degree of cleaning of the surface uses a He-Ne laser or a diode laser in the visible region, and the incident angle of the surface is located on the photo detector 130a located behind the sample. Incident close to the vertical direction to be incident to. When the degree of contamination is large, the intensity of the reflected light is stronger than that of the transmitted light, so the ratio of the reflected light and the transmitted light is continuously measured during the cleaning process to monitor the change of the intensity until the contaminant is completely removed. Techniques mainly used for dry cleaning for surface cleaning are laser light, CO 2 gas, plasma, and the like. In an embodiment of the present invention, laser light is irradiated onto a surface of a sample and cleaned.

Referring to FIG. 3, when monitoring is required by the process manager, the laser 104 is generated from the monitoring laser source 110, which is almost perpendicular to the surface of the sample to which the cleaning laser light is irradiated through the total reflection mirror 112. Incidentally (301 to 303).

The sample 106 placed on the sample mounting plate is moved at right angles to the cleaning laser 102 light irradiation direction to change the position of the cleaning site, and the reflected light is again reflected from the reflected light and transmitted from the cleaning site. After filtering by the interference filter 120b through 120b, the light is input to the reflected light detector 130b, and the transmitted light is filtered by the interference filter 120a and then incident to the transmitted light detector 130a. As described above, the filtering by the interference filters 120a and 120b removes interference of external noise light (laser, etc.) other than transmitted light and reflected light, and passes only the wavelength of monitoring light (304 to 307).

The electric signal of the transmitted light detected by the transmitted light detector 130a and the electric signal of the reflected light detected by the reflected light detector 130b are input to the computer 140. The computer 140 compares the two detection signals and then By displaying a graphic or a letter to display the progress of the cleaning process in real time, and when the ratio of the transmitted light and the reflected light reaches the reference value, it is determined that the cleaning is completed (308 ~ 311).

As described above, according to the present invention, the monitoring data during the cleaning process may be usefully used for analyzing and improving the cleaning process because the data is managed in a database.

In the above embodiment, the dry cleaning process has been described as an example, but the present invention can be applied in the same manner to a surface coating process different from the dry cleaning, and the technical spirit of the present invention can be applied to other embodiments as it is.

As described above, according to the present invention, unlike the conventional method, the degree of cleaning during dry cleaning of surface contaminants is measured by using the monitoring light before and after the cleaning. The degree of cleaning can be measured during the cleaning process by changing the light intensity ratio. In particular, the present invention has an advantage that the degree of cleaning can be estimated only by measuring the intensity change of the transmitted light even when the intensity of the reflected light is difficult due to the roughness of the base material surface.

Claims (3)

A light source unit generating a monitoring laser light; Optical path control means for irradiating the sample with the monitoring laser light; Transmitted light detecting means for detecting the intensity of light transmitted through the sample; Reflected light detecting means for detecting an intensity of light reflected from the sample; And And a comparison and display means for comparing the respective signals inputted from said transmitted light detection means and said reflected light detection means to display a cleaning state. The method of claim 1, wherein the monitoring device, An interference filter for filtering only the monitoring light from the transmitted light, and an interference filter for filtering only the monitoring light from the reflected light, the surface cleaning monitoring apparatus using the laser light. Monitoring laser generation step; Irradiating the sample surface with the generated monitoring laser; A filtering step of extracting only monitoring light from light reflected from the sample and light transmitted through the sample; Detecting the monitoring reflected light and transmitted light as an electrical signal; And And comparing the detected reflected light with the intensity of the transmitted light to display a process state.