JPH09260345A - Filtration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make approximately const. the recovery time taken for recovery of a stationary state after removal of foreign matter from an etching liq., irrespective of the number of foreign matter carried with a wafer by controlling the flow rate in a circulation pump, based on data from a dust counter to measure the number of foreign matter in the etching liq. SOLUTION: This system comprises a dust counter for measuring the number of foreign matter in an etching liq. 2, circulation pump 3 for circulating this liq. and means 8 for controlling the flow rate in the pump 3. For example, an arithmetic circuit and pump flow rate controller 8 are mounted on the counter 5. When a max. number of foreign matter becomes large, the number of strokes of the pump 3 is increased to increase the flow rate so that the recovery time taken for recovering a stationary state may be const., irrespective of the change of the max. number of foreign matter in the etching liq. Thus, it is possible to make const. the progress time to the next step to improve the throughput.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filtration system provided in a wet processing apparatus for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In a filtration system attached to a conventional wet processing apparatus, an etching solution is constantly circulated at a constant flow rate. Therefore, when the number of foreign particles brought into the wafer is small, the recovery time for the etching liquid to recover (removing the foreign materials) and return to a steady state is short,
When the number of foreign matters brought in on the wafer is large, the recovery time for the etching solution to recover and return to a steady state is long.

[0003]

However, if the recovery time until the etching solution is recovered and returns to the steady state depends on the number of foreign particles brought in on the wafer, the transition time to the next process is increased. If the value is constant, the foreign matter removal may proceed to the next step with insufficient removal, and the yield may deteriorate.On the other hand, if the foreign matter removal is sufficiently performed before proceeding to the next step, There is a problem that the transition time to the next process becomes uneven and the throughput deteriorates.

The present invention has been made by paying attention to such problems of the prior art, and the recovery time until the foreign substances in the etching solution are removed and the state returns to the steady state regardless of the number of foreign substances brought into the wafer. Is almost constant, and the yield can be improved by sufficiently removing foreign matter in the fixed time, and the throughput can be improved by keeping the transition time to the next step constant by sufficiently removing foreign matter in the fixed time. The purpose is to provide a filtration system that can.

[0005]

A filtration system according to the present invention for solving the above-mentioned problems includes a dust counter for measuring the number of foreign matters in an etching solution, and a circulation system for circulating the etching solution. A circulation pump and control means for controlling the flow rate of the circulation pump based on the data from the dust counter are provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, the circulation flow rate of the filtration system can be changed in accordance with the number of foreign matter carried into the wafer. Therefore, the etching solution can always be sufficiently recovered even if the transition time to the next step is constant, and the yield can be significantly improved and a highly accurate semiconductor product can be obtained. Also,
In the present invention, since the recovery time of the etching solution is constant, the transition time to the next step can be constant, and the throughput can be greatly improved.

Embodiment 1 The first embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, 1 is an etching treatment tank with a recovery tank, 2 is an etching solution, 3 is a filtration system bellows pump, 4 is a filter, 5 is a submerged dust counter, 6 is a foreign matter measurement sample suction tube, and 7 is A sample drainage tube for which foreign matter has been measured, 8 is a pump flow rate controller that controls the flow rate of the pump, and 9 is a cable that sends a signal from the pump flow rate controller 8 to the pump 3.

As shown in (1) of FIG. 2, the foreign matter recovery characteristics of the filtration system are as follows: logarithm logn (t) of foreign matter number n (t) on the horizontal axis and time t _{1 on} the vertical axis, From the steady state N ₀₀ , the maximum number of foreign matters N ₀ is reached during the processing and after the processing time to, and then linearly recovers, and then returns to the steady state at the time t ₁ . In terms of the formula,

When t ₀ <t <t ₁ , logn (t) = − (t−t ₀ ) / A + logN ₀ n (t) = N ₀ exp [− (t−t ₀ ) / A]. Where A is the recovery time constant, which is the flow rate of the pump,
The amount depends on the size of the tank. When the size of the tank is constant, A is determined by the flow rate of the pump. When the flow rate is large, A is small and when the flow rate is small, A is large.

If the flow rate of the pump is constant as in the conventional case, the maximum foreign matter number N ₀ becomes large as shown in (2) of FIG. 2 (N ' ₀ > N ₀ ), and A is constant. time slope back to the same steady state becomes longer as _{t 2 (t 2> t 1} ).

Therefore, an arithmetic circuit and a pump flow controller 8 are attached to the dust counter 5 in the liquid, and the number of strokes of the pump can be adjusted even if N ₀ increases and N ′ ₀ according to the maximum foreign substance number N _0. The flow rate is increased by increasing (the stroke length remains constant) and A is decreased to t ₁ . In this way, even if the maximum number of foreign substances in the etching solution changes, the recovery time for returning to the steady state can be made constant. Therefore, the etching liquid can always be sufficiently recovered even if the time for the transition to the next step is constant. Further, since the etching solution can be sufficiently recovered in a constant time, the time required for the transition to the next step can be made constant, and the throughput can be greatly improved.

Embodiment 2. In the first embodiment described above,
The number of strokes of the pump is changed according to the maximum number of foreign matters in the etching liquid 2 (the stroke length remains constant). On the other hand, in the second embodiment, the pump 3
The number of strokes is kept constant, and the stroke length is changed according to the maximum number of foreign matters in the etching liquid 2 measured by the dust counter 5. Therefore, according to the second embodiment as well, the recovery time for returning to the steady state can be made constant regardless of the change in the maximum number of foreign matters in the etching solution, and thus the same effect as that of the first embodiment can be realized. be able to.

Embodiment 3 Embodiment 1 or 2 described above
Then, the stroke number or stroke length of the circulation pump is changed according to the maximum number of foreign matters in the etching liquid 2. On the other hand, in the third embodiment, the number of strokes or the stroke length of the pump 3 remains constant, and the pressure of the circulation pump 3 is set to the maximum foreign matter in the etching liquid 2 measured by the data from the dust counter 5. I try to change it according to the number. Therefore, the third embodiment
Also by this, the recovery time for returning to the steady state can be made constant regardless of the change in the maximum number of foreign matters in the etching solution, so that an effect similar to that of the first or second embodiment can be realized.

Embodiment 4 In the first, second or third embodiment described above, the number of strokes, the stroke length or the pressure of the circulation pump 3 is changed according to the maximum number of foreign matters in the etching solution 2. On the other hand, the fourth embodiment
Then, a plurality of circulation pumps 3 having different flow rates are provided in advance, and the plurality of pumps having different flow rates are set in accordance with the maximum number of foreign matters in the etching solution 2 measured by the data from the dust counter 5. I am trying to switch between them. Therefore, according to the fourth embodiment as well, the recovery time for returning to the steady state can be made constant irrespective of the change in the maximum number of foreign matters in the etching solution, and therefore, it is almost the same as the first, second or third embodiment. The effect can be realized.

[0015]

As described above, according to the present invention, the circulation flow rate of the filtration system is controlled in accordance with the number of foreign matters carried into the wafer. Therefore, even if the transition time to the next process is constant, the etching liquid can always be sufficiently recovered (removal of foreign substances) regardless of the number of foreign substances brought into the etching liquid of the wafer, and the yield is greatly improved. As a result, highly accurate semiconductor products can be obtained. Further, in the present invention, the recovery time of the etching solution can be made constant at all times regardless of the number of foreign particles brought into the etching solution of the wafer, so that the transition time to the next process can be made constant, and the throughput can be improved. Will be greatly improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a filtration system of a wet apparatus according to Embodiment 1 of the present invention.

FIG. 2 is a graph showing the relationship between the maximum number of foreign matters in the etching solution and the recovery time.

[Explanation of symbols]

1 Etching tank with recovery tank. 2 Etching solution. 3 Bellows pump for filtration system. 4 filter. 5 Liquid dust counter. 6
Foreign material measurement sample suction tube. 7 Sample drainage tube with foreign matter measured. 8 Pump flow controller. 9 cables

Claims (1)

[Claims] 1. A filtration system for removing foreign matter in an etching solution, which is provided in a semiconductor wet processing apparatus, comprising: a dust counter for measuring the number of foreign matter in the etching solution; A filtration system comprising: a circulation pump for circulation; and control means for controlling a flow rate of the circulation pump based on data from the dust counter.