JPH06341679A - Contaminant-monitoring device for clean room - Google Patents

Abstract

PURPOSE:To obtain a contaminant-monitoring device for a clean room, which is capable of efficiently collecting contaminants contained in the atmosphere without an influence of man-made contamination to accurately and easily monitor the degree of contamination in the clean room in a shorter period of time. CONSTITUTION:A contaminant-monitoring device includes an outer case having a mounting space inside to mount collecting plates 4 and 5 for collecting contaminants, a suction nozzle 1 which makes the outside air strike concentratedly onto the collecting plates 4 and 5 mounted in the mounting space, an exhaust port to allow the suction nozzle 1 to suck the outside air, electric potential setting terminals 6 and 7 through which a voltage is applied to the collecting plates 4 and 5 from a direct current voltage applying device and the collecting plates 4 and 5 are kept at a specified electric potential, a contamination preventing cap 9 for transfer to cover the suction nozzle 1, and a contamination preventing cap 9 for transfer to cover the exhaust port.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clean room pollutant monitoring device for collecting pollutants in order to analyze the concentration of the pollutants in a clean room for semiconductor manufacturing or the like.

[0002]

2. Description of the Related Art A clean room for manufacturing semiconductors is required to have high cleanliness (ultra cleanliness) in order to improve product yield. Therefore, it is necessary to monitor the degree of pollution in the clean room.

As a conventional simple method for monitoring the degree of contamination in a clean room, there is a method of leaving (exposing) a silicon wafer (hereinafter referred to as a wafer) itself in the environment of the clean room. That is, this is a method in which a wafer is put in a plastic container, the lid of the container is opened, the wafer is exposed in a clean room, and the number and diameter of contaminants attached to the wafer are measured by an inspection device. Alternatively, a method of knowing the degree of contamination by exposing an IC test piece and testing its electrical characteristics has been adopted. There is also a method in which after the contaminants are suctioned and collected by the filter, the filter is washed with a solution and the concentration of the contaminant in the solution is measured.

However, since the inside of the clean room is originally an ultraclean space, such a method of waiting for spontaneous attachment of contaminants requires a long time for measurement. Further, if the charge condition of the wafer or the air flow condition in the clean room changes, the rate of trapping contaminants on the wafer changes. Therefore, although such a method is simple, it includes an error and lacks accuracy.

On the other hand, as a method for monitoring the degree of pollution in an environment where the concentration of pollutants is relatively high, there is a method in which the atmosphere in the environment is caused to collide with the collision plate at high speed with a nozzle. that time,
By adjusting the nozzle diameter and the flow velocity, particles in the atmosphere are classified according to the particle diameter and separated and captured. As a collision plate,
A small silicon plate is used. Then, the contaminants captured by the collision plate are analyzed by an electron microscope or X-ray. But according to this method,
Only particles are captured. In addition, the charging condition of the collision plate is not controlled at all, and if the degree of charging changes, the trapping ratio also changes. Therefore, it is not appropriate to use such a method as it is for monitoring the degree of pollution in a clean room.

[0006]

According to the conventional method of monitoring the degree of contamination in a clean room using a wafer, as described above, there is a problem that the monitoring accuracy is insufficient. Further, according to such a method, contaminants in the environment are uniformly captured on the wafer surface, so that the concentration per unit area becomes low. Therefore, when performing qualitative analysis or quantitative analysis of the contaminants captured on the wafer, there is also a problem that the analysis cannot be performed if the concentration is lower than the resolution of the analyzer.
Further, when the wafer is handled, the wafer may be artificially contaminated, and in such a case, the accuracy of monitoring is also deteriorated. Also,
When a filter is used, pretreatment is required before the filter is applied to the inspection device, which increases the number of steps required for the inspection.

The present invention has been made to solve such a problem, and it is efficient and artificial in order to monitor the degree of contamination in a clean room more accurately and easily in a shorter time. An object of the present invention is to provide a pollutant monitoring device for a clean room, which is capable of collecting pollutants in the environment without being affected by various pollutions.

[0008]

A pollutant monitoring device for a clean room according to the present invention is installed in an installation space having an installation space inside which a collection plate for collecting a contaminant is installed, and an installation space. A suction nozzle for intensively colliding the external air with the collecting plate, an exhaust port for sucking the external air to the suction nozzle, a potential setting unit for keeping the collecting plate at a predetermined potential, and a suction nozzle. A pollution prevention cap for closing the exhaust port and a pollution prevention cap for closing the exhaust port are provided.

[0009]

The suction nozzle according to the present invention causes the atmosphere in the clean room to collide with a narrow area of the collecting plate in a concentrated manner, thereby concentrating the collecting area of the pollutant on the collecting plate at a certain position. The potential setting unit keeps the potential of the collection plate constant so that the collection conditions do not change even when time and place change. Then, the contamination prevention cap prevents the collection plate from being contaminated with a substance other than contaminants in the clean room when moving from the clean room to the place where the inspection device is located.

[0010]

FIG. 1 is a sectional view showing the structure of a pollutant monitoring device for a clean room according to an embodiment of the present invention. As shown in the figure, this monitoring device has a structure in which, for example, a suction nozzle 1 is provided on the upper part of a flat cylindrical outer peripheral part 21, and an exhaust port 22 is provided on the lower part.

Inside the outer enclosure 21, installation spaces 31, 32 for installing the collection plates 4, 5 are provided. Although FIG. 1 shows a case where two installation spaces 31 and 32 are provided, the installation space 31 located above is shown.
Is connected to the outlet side of the suction nozzle 1. The lower part of the installation space 31 is connected to the upper part of the installation space 32 located below, and the lower part of the installation space 32 is connected to the exhaust port 22.

The collection plate support 12 is installed in the installation space 31. The collecting plate 4 is placed on the collecting plate support 12. The collection plate support 14 is installed in the installation space 32. The collecting plate 5 is placed on the collecting plate support 14.

Further, potential setting terminals 6, 7 for applying a predetermined potential to the collecting plates 4, 5 from the outer peripheral portion 21.
Has been pulled out. The potential setting terminal 6 is connected to the collecting plate support 12 via a carbon O-ring 11 on the inner side of the outer enclosure 21. Further, the potential setting terminal 7 is connected to the collection plate support base 14 via an O-ring 13 made of carbon on the inner side of the outer enclosure 21. Then, in the outer envelope portion 21,
Is connected to a ground terminal 8 for keeping the terminal at the ground potential.

There is a threaded portion on the outside of the suction nozzle 1, and the transfer contamination prevention cap 3 shown in FIG. 2 is screwed to the threaded portion, and is made of Teflon O provided on the base of the protruding portion of the suction nozzle 1. The ring 10 has a structure capable of sealing the installation spaces 31, 32. Further, the outlet side of the exhaust port 22 is also closed by the moving pollution preventing cap 9.

Next, a pollutant trapping method using this monitoring device will be described. The monitoring device is installed at a predetermined place in the clean room. At that time, the collecting plates 4 and 5 are placed on the collecting plate support bases 12 and 14. As the collecting plates 4 and 5,
The wafer itself handled in the clean room can be used. Hereinafter, a case where wafers are used as the collecting plates 4 and 5 will be described.

From the DC voltage applying device to the potential setting terminals 6, 7
A predetermined voltage is applied via. Therefore, the charged particles can reach the wafer. Further, by always keeping the wafer at a predetermined potential, the wafer capturing environment is always kept constant even if the installation location or installation time of the monitoring device is different. Further, by intentionally increasing the applied voltage, it is possible to intentionally increase the collection rate of pollutants and shorten the time required for monitoring.

Next, the exhaust port 22 is connected to the suction pump and the flow meter. Then, the suction pump is driven to suck the atmosphere while maintaining a predetermined flow velocity by the flow meter. Then, the atmosphere in the clean room is drawn into the suction nozzle 1, and the atmosphere collides with the surface of the wafer from the outlet side of the suction nozzle 1. Then, contaminants in the air adhere to the surface of the wafer. Since the outlet side of the suction nozzle 1 is narrowed toward the central part of the wafer, the contaminants are concentrated on a narrow area on the surface of the wafer. That is, the collection amount per unit area increases.

By adjusting the diameter of the suction nozzle 1 and the flow velocity,
While classifying the particle size of the contaminants, the contaminants can be concentrated and captured in the central portion of the wafer. Further, although the cascade type impactor suction nozzle is shown as the suction nozzle 1 in FIG. 1, the Andersen type impactor suction nozzle 2 shown in FIG. 3 is used instead of the cascade type impactor suction nozzle. You can also

After the predetermined collection time has elapsed, the moving pollution preventing cap 3 is fitted into the suction nozzle 1 and the moving pollution preventing cap 9 is fitted into the exhaust port 22. And
This monitoring device is moved to an inspection device such as an electron microscope or an X-ray device. In this case, since the amount of contaminants collected on the wafer per unit area is large, the contaminants can be easily analyzed. In addition, when quantitative analysis is performed using X-rays, the detection limit is lower than in the conventional case.

As in this embodiment, the collecting plates 4, 5
As a result, when a wafer is used, the object to be worked in the clean room is used as a sensor, and monitoring closer to actual manufacturing control is executed. Moreover, the monitoring time is shorter than that of conventional monitoring.

In this embodiment, the collecting plates 4,
Although the case where a wafer is used has been described as 5,
A metallic material such as a silver plate or a test paper that reacts with gas may be used. In that case, gaseous pollutants other than particles can be collected, and the metal material or test paper can be directly applied to the analyzer.

[0022]

As described above, according to the present invention,
The clean room pollutant monitoring device uses a suction nozzle that causes external air to collide with the collection plate in a concentrated manner, an exhaust port that allows the suction air to suck the external air, and a potential that keeps the collection plate at a predetermined potential. Setting section,
Since it has a structure that includes a suction nozzle and each pollution prevention cap that blocks the exhaust port, it is possible to collect contaminants intensively in the central portion of the collection plate, etc. There is an effect that the substance can be detected. Further, the pretreatment of the inspection is not required, and the inspection device can be immediately applied, and the possibility of contamination of the collecting plate in the pretreatment is eliminated.

Further, since the potential of the collecting plate is kept constant, it is possible to stabilize the trapping ratio of the pollutants, and the pollutant monitoring accuracy is increased. Further, by mounting the pollution prevention cap, there is also an effect that the collecting plate is prevented from being re-contaminated during the movement.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a contaminant monitoring device for a clean room according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a moving pollution preventing cap.

FIG. 3 is a cross-sectional view showing the structure of another type of suction nozzle.

[Explanation of symbols]

 1 Suction nozzle 3 Contamination prevention cap for movement 4,5 Collection plate 6,7 Potential setting terminal 8 Grounding terminal 9 Contamination prevention cap for movement

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G01N 15/02 F

Claims (1)

[Claims] 1. A pollutant monitoring device for a clean room, which is installed in a clean room and collects pollutants in the clean room, wherein the enclosure has an installation space in which a trapping plate for trapping pollutants is installed. A suction nozzle that causes external air to collide with the collecting plate in a concentrated manner; an exhaust port that causes the suction nozzle to suck the external air; and a potential setting unit that keeps the collecting plate at a predetermined potential. A pollutant monitoring device for a clean room, comprising: the suction nozzle and respective pollution prevention caps that close the exhaust port.