JP2000279792A - Vacuum load locking mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the desorption of particles from filters and to suppress the adhesion of the particles to a sample by providing the two opposite points of the spaces enclosing the sample with the filters and arranging these filters in such a manner that the directions of the air flow at the time of vacuum evacuation and at the time of restoration to the atmospheric pressure are the same. SOLUTION: A load locking chamber 3 is separated to the three spaces 11 to 13 by two sheets of the air permeable filters 14 and 15 for blocking dust. A vacuum pump 5 is connected via a valve 7 to the low-pressure chamber 12 and air piping 10 is connected via a valve 9 to the high-pressure chamber 13. The middle chamber 11 is mounted with a valve 8 on the vacuum side and a valve 6 on the atmospheric side, respectively. At the time of the vacuum evacuation of the load locking chamber, the respective valves 6, 8 and 9 are closed and the valve 7 is opened. At this time, the air flows toward an arrow. Then, the particles soaring up in the middle chamber 11 are removed by the filter 14. The particles soaring up in the high-pressure chamber 13 are blocked by the filter 15 and cannot infiltrate the inside of the middle chamber 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum load lock mechanism for moving a sample between the atmosphere and a vacuum.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, particles adhering to a wafer surface cause defects in an element structure. This problem has become more serious due to recent miniaturization and high integration of ULSI patterns. In many cases, the sample is treated in a down-flow atmosphere through a filter to avoid particle adhesion to the sample. However, when a sample is processed in a vacuum, the following problems occur.

FIG. 4 shows an example of the configuration of an electron beam writing apparatus. An electron optical column 1 for generating an electron beam to draw a pattern on a sample, a drawing container 2 for holding a sample 4 being drawn, and moving the sample 4 from the atmosphere to a vacuum or returning the sample 4 from the vacuum to the atmosphere. The load lock chamber 3 is connected to a pump 5 for evacuating the load lock chamber, and a gas pipe 10 for introducing air into the load lock chamber. The connection and cutoff are performed by valves 6 to 9, respectively.
The following procedure is performed when pattern writing is performed on the sample 4. First, with the valves 6 to 8 closed, the valve 9 is opened and air is introduced until the load lock chamber 3 reaches atmospheric pressure. The valve 6 is opened at the time when the gasification is performed, and the sample 4 is moved to the load lock chamber. Thereafter, the valves 6 and 9 are closed, the valve 7 is opened, and the load lock chamber is evacuated.
When the pressure in the load lock chamber is sufficiently reduced, the valve 8 is opened to move the sample 4 to the drawing container 2, and the valve 8 is closed to start drawing. After the drawing is completed, the valve 8 is opened to move the sample to the load lock chamber. With the valves 7 and 8 closed, the valve 9 is opened to introduce air. After the load lock chamber is evacuated, the valve 6 is opened and the sample 4 is taken out of the apparatus. Here, when the sample 4 is evacuated from the atmosphere and returned to the atmosphere from the vacuum, a turbulent airflow is generated in the load lock chamber, and particles adhering to the inner wall of the load lock chamber 3 are removed from the wall by the air flow. Sample 4 after detachment
May adhere to the surface.

In order to cope with this problem, the turbulence of the air flow is reduced by performing evacuation or atmosphericization for a very long time. However, it takes too long time to evacuate or atmosphericize. Greatly reduces manufacturing efficiency. In addition, when evacuation is performed over a long period of time, the sample is cooled due to adiabatic expansion of the air, which causes a dimensional change of the sample, which causes a deterioration in accuracy in an electron beam lithography apparatus requiring high accuracy. On the other hand, an invention has recently been proposed in which a sample is placed in a small container with a filter, and the entire container is evacuated and atmosphericized (Japanese Unexamined Patent Application Publication No. Hei 1 (1999)).
0-261560). According to this, even if an air current is seen at the time of evacuation and atmosphericization at high speed, the adhesion of particles from the wall surface of the vacuum vessel to the sample can be reduced. However, this method can also cause the following problem. That is, in the present invention, the particles adhered at the time of assembling the small container filter may be detached from the filter during atmosphericization and adhere to the sample.

[0005]

As described above, the load lock mechanism considered up to now has a problem that particles adhere to the sample when evacuating and atmosphericizing in a practical time.

[0006]

In the load lock mechanism included in the present invention, filters are provided at two opposing positions in the space surrounding the sample, so that the direction of the air flow at the time of evacuation and at the time of atmosphericization are the same. It is like. [Operation] In the above-mentioned load lock mechanism, since the direction of the air flow with respect to the filter is the same between when the vacuum is evacuated and when the gas is atmosphericized, there is no detachment of the particles from the filter, and the adhesion of the particles to the sample can be suppressed.

[0007]

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. Shows a first embodiment of the present invention. FIG. 1 shows the configuration of the load lock chamber 3. The load lock chamber 3 is separated into three spaces 11 to 13 by two air-permeable dust blocking filters 14 and 15. Hereinafter, they will be referred to as a middle chamber, a low pressure chamber, and a high pressure chamber, respectively. The vacuum pump 5 is connected to the low-pressure chamber 12 via a valve 7, and the air pipe 10 is connected to the high-pressure chamber 13 via a valve 9. In the middle chamber 11, the valve 8 is attached to the vacuum side, and the valve 6 is attached to the atmosphere side. When evacuating the load lock chamber, the valve 6,
8, 9 are closed and valve 7 is opened. At this time, the air flow is in the direction indicated by the arrow in the figure.

[0008] Therefore, the particles soared in the inner chamber 11 are taken in by the filter 14. The particles soared in the high pressure chamber 13 are filtered by the filter
Do not enter 1. When the load lock chamber 3 is evacuated, the valves 6, 7, 8 are closed and the valve 9 is opened.
Also in this case, the flow of the air is almost in the direction indicated by the arrow. Here, an auxiliary pump 17 is connected to the low-pressure chamber 12 via a valve 16, and the valve 16 is opened so that the low-pressure chamber always has a slightly lower pressure than the middle chamber 11. It is desirable to control the flow to be in the direction of the arrow. By doing so, the filters 14, 1
In contrast, the air flow is the same in both directions during evacuation and atmosphericization, so that desorption of particles from the filter 14 can be minimized. From the viewpoint of system operation, it is desirable to repeat the atmosphericization of the load lock chamber 3 and the evacuation beforehand, and to introduce the sample 4 after the soaring of particles in the middle chamber 11 is sufficiently reduced.

FIG. 2 shows a second embodiment. In this embodiment, the sample 4 is a container 18 provided with filters 14 and 15.
Put in. A removable bottom plate 19 is provided at the lower part of the container 18.
Are fixed, and the sample 4 is placed on the bottom plate 19. The procedure for moving the sample 4 into a vacuum is as follows.
The container 6 is moved to the load lock chamber 3 by opening the valve 6. Here, on the ceiling side of the load lock chamber, the packing 20 works to reach the upper portion of the container 18 and divides the load lock chamber into three spaces. In this state, the valve 6 is closed, the valve 7 is opened, and the load lock chamber is evacuated.

At this time, the air flows from the space 22 to the space 23 as shown in FIG. An elevator mechanism 21 is provided below the load lock chamber 3, and lowers the sample 4 together with the bottom plate 19 into the evacuated elevator chamber 24. The sample 4 is taken out in the elevator room 24. The elevator chamber 24 is connected to an exhaust pipe (not shown) and an atmospheric pipe, and is evacuated when the load lock chamber is evacuated.
The sample 8 can be carried to the vacuum side by opening the valve 8. Thereafter, the elevator mechanism 21 moves up, and the bottom plate 19 is fixed to the container 18. The procedure for removing the sample 4 into the atmosphere is as follows. The elevator mechanism 21 is lowered to remove the bottom plate 19 from the container 18. The sample is moved to the bottom plate 19 by opening the valve 8. Elevator mechanism 21
Is raised and fixed to the container 18. After closing the valve 8, the valve 9 is opened to evacuate the load lock chamber 3. At this time, it is desirable to control the direction of the airflow as in the example of FIG. After the load lock chamber and the elevator chamber 24 are evacuated, the valve 6 is opened and the container 18 is taken out.

The mechanism can be used not only when the apparatus is moved between the atmosphere and vacuum, but also when the sample is moved to a gas atmosphere or between different gas atmospheres like an etching apparatus. It is clear.
In this case, it is possible to perform gas replacement while adjusting the direction of air flow by operating the auxiliary pump, but it is desirable to introduce the gas after once evacuating the sample environment to vacuum.

[0012]

As is apparent from the above description, according to the present invention, particles can be prevented from adhering to the sample when the sample moves between the atmosphere and the vacuum.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a load lock mechanism of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a container used in another embodiment.

FIG. 3A is a cross-sectional view showing a load lock chamber containing a small container. (B) Sectional view with the elevator mechanism lowered.

FIG. 4 is a sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electro-optical column 2 Drawing container 3 Load lock room 4 Sample 6, 7, 8, 9 Valve 10 Gas piping 11 Middle room 12 Low pressure room 13 High pressure room 14, 15 Dust prevention filter 16 Valve 17 Auxiliary pump 18 Container 19 Bottom plate 21 elevator mechanism 24 elevator room

Claims (2)

[Claims] 1. A load lock mechanism for moving a sample between airtightly partitioned spaces, and filters A and B for preventing air-permeable dust from passing through at least two places in a space surrounding the sample. Are provided so as to substantially oppose each other in the space, and the space is evacuated from the filter A side, and gas is introduced from the filter B side. 2. A vacuum load lock mechanism for putting a sample containing a container into and out of the apparatus, wherein filters are provided at two positions of the container. Vacuum load lock mechanism.