JPH0812854B2 - Wet etching equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet etching apparatus that circulates an etching solution and updates the etching solution while etching.

[0002]

2. Description of the Related Art As semiconductor integrated circuits become highly integrated, the requirements for cleaning the surface of semiconductor wafers have become more severe. For example, in order to remove a thermal oxide film or a natural oxide film of a semiconductor wafer, a semiconductor wafer is etched by immersing it in a hydrofluoric acid-containing etching solution using a wet etching device. Metal ions with low ionization tendency (Cu, Au
Etc.) are often included. If such metal ions are contained, these metal ions adhere to the surface of the semiconductor wafer and adversely affect the electrical characteristics.
Therefore, in this type of wet etching apparatus, various removal methods for removing the metal ions have been proposed.

As a method for removing the harmful metal ions, a wet etching apparatus utilizing a method for removing metal ions by using metal-deposited silicon particles as an adsorbent is publicly known.
It disclosed in 91-8033 JP open Technical Report.

FIG. 4 is a schematic sectional view of a conventional wet etching apparatus. The wet etching apparatus disclosed in Published Technical Report 91-8033 is shown in FIG.
As shown in FIG. 3, an overflow tank 20 for storing the etching solution 14 overflowing from the etching tank 19, a circulation pipe 15 for connecting the overflow tank 20 and the etching tank 19 to circulate the etching solution 14, and the overflow tank 20 to the etching tank 19 are provided. Further, a pump 16 for pumping the etching liquid 14 is provided, and a metal impurity removal column 17 and a filter 18 that are installed in series with the circulation pipe 15 in the subsequent stage of the pump 16 are provided.

In this wet etching apparatus, the etching solution 14 overflowing from the etching tank 19 is temporarily stored in the overflow tank 20, and when the predetermined level is reached, the pump 16 pumps the etching solution 19 under pressure.
By flowing the etching solution through the circulation pipe 15, the metal impurities removing column 17 adsorbs and removes the metal ions in the solution, and the filter 18 removes the fine particles. Then, the purified etching solution is returned to the etching tank 19.

As described above, the dirty etching solution in the overflow tank 20 is removed from the metal impurity removing column 17 and the filter 1.
It was circulated to the etching tank 19 through 8 to supply a cleaned etching solution to the etching tank 19 to reduce the amount of newly added etching solution to reduce the operating cost of the apparatus.

[0007]

In the above-described wet etching apparatus, although the metal impurities are completely removed by the metal impurity removal column, the entire amount of the etching solution to be fed becomes a circulation system that passes through the metal impurity removal column. since it is, the flow rate of the circulation system line the metal impurity removal
It is determined by the maximum flow rate of the column (flow rate at which adsorption capacity is obtained), and one circulation cycle time of the etching solution is limited, and there is a drawback that it cannot be made faster. This has a problem that the throughput of the etching process cannot be improved. Also, when pure water is flown to clean the circulation system piping, the pure water flows into the metal impurity removal column,
There is also a problem that the metal impurities adsorbed on the metal-deposited silicon particles are eluted during cleaning and reuse, and the etching liquid is contaminated.

[0008] Therefore, an object of the present invention is to provide a wet etching apparatus in which the regeneration cycle of the etching solution is further accelerated to improve the throughput, and contamination is not caused by the re-elution of metal impurities.

[0009]

The features of the present invention are that an overflow tank for storing an etching solution overflowing from an etching tank, a circulation pipe connecting the overflow tank and the etching tank, and the overflow tank to the etching tank. A pump for pumping the etching solution, a metal impurity removal column that is attached to the upstream side of the circulation pipe via a first flow rate adjusting valve and that is filled with metal-deposited silicon particles, and the circulation pipe. A bypass pipe connected to the upstream side portion and branched from the first flow rate adjusting valve and the metal impurity removal column; a first opening / closing valve attached to the liquid discharge side of the metal impurity removal column; Wet etching provided with an opening / closing valve of the above and a filter attached to a circulation pipe section that joins with the bypass pipe It is the location. Preferably, the content of metal impurities in the etching solution discharged from the overflow bath is detected, and the first impurity is detected according to the content.
It is to control the flow rate adjusting valve.

[0010]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing a first embodiment of a wet etching apparatus of the present invention. As shown in FIG. 1, this wet etching apparatus includes a bypass pipe 6 that branches a circulation pipe 15a that discharges an overflowing etching solution, and a flow rate control valve that is attached to the branched metal impurity removal column 3 on the liquid inflow side. 4 and an on-off valve 8 attached to the liquid discharge side are respectively provided, the opening degree of the flow rate adjusting valve 4 is changed, and the flow rate of the etching solution flowing into the metal impurity removal column 3 is changed.

Next, the circulation operation of the etching solution in this wet etching apparatus will be described. For ease of explanation, it is assumed that the total amount of the etching liquid is 40 liters, the discharge amount of the pump 16 is 12 liters / minute, and the maximum flow rate of the metal impurity removal column 3 is 6 liters / min.

First, the etching solution 14 that has overflowed
Is discharged from the circulation pipe 15a by the operation of the pump 2. Next, it is estimated from the specified value of the content of metal impurities, the flow control valve 4 is closed by the valve control unit 7, and the etching solution is not allowed to flow into the metal impurity removal column 3. As a result, the etching solution is flowed at a flow rate of 12 liters / minute and the bypass pipe 6
To the etching tank 9 through the filter 5.

Next, as the etching operation progresses, the concentration of metal impurities in the etching solution increases, so the content of metal impurities is measured after a predetermined number of circulation cycles. If the content of metal impurities is more than the specified value, for example,
If it exceeds 20%, the valve control unit 7 opens the flow rate adjusting valve 4 to a predetermined opening, and, for example, the etching solution 1
4 is passed through the metal impurity removal column 3 at a flow rate of 3 l / min, and the remaining etching solution 14 is passed through the bypass pipe 6 at a flow rate of 9 l / min. Next, the metal impurity content is measured again, and if the measured value is equal to or less than the specified value, the opening of the flow rate adjusting valve 4 is left unchanged and the etching operation is continued. If it exceeds the specified value, the opening of the flow rate adjusting valve 4 is expanded according to the exceeded value to increase the flow rate of the etching solution flowing through the metal impurity removal column 3.

As described above, the flow rate of the etching liquid flowing through the metal impurity removing column 3 is changed according to the content of the metal impurities, and the remaining etching liquid is caused to flow through the bypass pipe 6, so that the object to be etched is not affected. By suppressing the metal impurity concentration to some extent and increasing the flow rate of the etching solution flowing through the circulation line, it is possible to speed up the conventional circulation cycle.
Incidentally, one circulation cycle is 40 liters / 12 liters / minute = 3 minutes 20 seconds in this apparatus, which is twice as fast as 40 liters / 6 liters = 6 minutes 40 seconds in the conventional apparatus.

When the circulation line of this wet etching apparatus is washed with pure water by exchanging the etching solution or the like, the on-off valve 8 and the flow rate adjusting valve 4 are closed and the metal impurity removal column 3 is separated from the circulation line. Bypass piping
Pure water can be washed by flowing pure water into only 6. By this,
When the metal impurity removal column 3 was washed without separation
Of metal impurities from the column 3
Re-elution can be prevented, and the circulation that was generated during the circulation line cleaning
It was possible to eliminate the pollution of the loop line. Further, the saturated adsorption amount of the metal-precipitated silicon particles in the metal impurity removal column can be estimated by periodically measuring the metal impurity concentration of the etching solution. It also has the advantage that it can be delayed until it reaches.

FIG. 2 is a schematic sectional view showing a second embodiment of the wet etching apparatus of the present invention. As shown in FIG. 2, this wet etching apparatus is equipped with an overflow tank 1
The metal ion detector 1 for measuring the content of the metal impurities in the etching solution 14 discharged from 0 is provided, the content of the metal impurities is measured for each circulation cycle, and the measured value is input to the valve control unit 7a, The opening degree of the flow rate adjusting valve 4 is changed according to the measured value to control the flow rate of the etching liquid flowing into the metal impurity removal column 3. Other than that is the same as the above-mentioned embodiment.

This wet etching apparatus measures the metal impurities for each circulation cycle, and the metal impurity removal column 3 is used.
Since the flow rate of the etching solution is controlled, there is an advantage that the cleanliness of the etching solution can be controlled more precisely than in the above-described embodiment.

FIG. 3 is a schematic sectional view showing a third embodiment of the wet etching apparatus of the present invention. In this wet etching apparatus, as shown in FIG. 3, a flow rate adjusting valve 4a is provided on the inflow side of the bypass pipe 6 and an opening / closing valve 8a is provided on the outflow side. Other than that is the same as the above-mentioned embodiment.

In this wet etching apparatus, the flow rate of the etching liquid 14 flowing in the bypass pipe 6 is adjusted by the flow rate adjusting valve 4
By narrowing a, it is possible to reduce the bypassed etching solution and reduce the metal impurities contained in the etching solution 14. In other words, in consideration of the content of the metal impurities that affect the object to be etched, the flow rate of the etching liquid flowing through the bypass pipe 6 is appropriately reduced, and the flow rate to the metal impurity removing column 3 is increased to obtain an appropriate amount of the metal impurities. The following control is performed to make the circulation cycle efficient. Of course, the operation described in the above embodiment can be performed by setting the flow rate adjusting valve 4a to the maximum opening and changing the flow rate adjusting valve 4.
Further, by closing the flow rate adjusting valve 4a and the opening / closing valve 8a, as described in the conventional example, a wet etching apparatus having a wide range of application that can completely remove metal impurities can be obtained.

Even if there is a slight difference between the flow resistance of the etching liquid 14 to the bypass pipe and the flow resistance of the pipe to the metal impurity removal column 3 due to the difference in the actual pipe system, these two flow control valves By adjusting 4, 4a independently, there is an advantage that the flow rate of the etching liquid flowing through the bypass pipe 6 and the metal impurity removal column 3 can be accurately set.

[0022]

As described above, the present invention is provided with the bypass pipe for branching the metal impurity removal column and the flow rate adjusting valve for adjusting the flow rate of the etching solution flowing into the bypass pipe and the metal impurity removal column, By setting the flow rate of the etching solution that flows into the bypass pipe and the metal impurity removal column according to the content of the metal impurities to the extent that it does not affect the object to be etched, the metal impurities can be efficiently removed and a faster etching solution can be obtained. It is possible to obtain the circulation cycle of and improve the throughput. In addition, by providing an open / close valve that shuts off the circulation line of the metal impurity removal column,
It can be separated from the circulation line, so the circulation line
When purging with pure water, flow pure water only through the bypass piping.
Re-elution of metal impurities from the column for removing metal impurities
This has the effect of eliminating the contamination of the circulation line and the etching liquid.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of a wet etching apparatus of the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of the wet etching apparatus of the present invention.

FIG. 3 is a schematic sectional view showing a third embodiment of the wet etching apparatus of the present invention.

FIG. 4 is a schematic sectional view of a wet etching apparatus showing a conventional example.

[Explanation of symbols]

 1 Metal Ion Detector 2,2a, 16 Pump 3,17 Metal Impurity Removal Column 4,4a Flow Rate Control Valve 5,5a, 18 Filter 6 Bypass Piping 7,7a, 7b Valve Control Section 8,8a Open / Close Valve 9,19 Etching Tank 10,20 Overflow tank 14 Etching solution 15,15a, 15b Circulation piping

Claims (3)

[Claims] 1. An overflow tank for storing an etching solution overflowing from an etching tank, a circulation pipe connecting the overflow tank and the etching tank, a pump for pumping the etching solution from the overflow tank to the etching tank, A metal impurity removal column that is attached to the upstream side of the circulation pipe via a first flow rate adjusting valve and that is filled with metal-deposited silicon particles; and a column connected to the upstream side of the circulation pipe and No. 1 flow control valve and a bypass pipe branching from the metal impurity removal column, a first opening / closing valve attached to the liquid discharge side of the metal impurity removal column, and the first opening / closing valve and the bypass pipe. A wet etching apparatus, comprising: a filter attached to a circulation pipe section. 2. The content of metal impurities in the etching liquid discharged from the overflow tank is detected, and the first flow rate adjusting valve is controlled according to the content. Wet etching equipment. 3. A second flow rate adjusting valve is attached to the liquid inflow side of the bypass pipe, and a second on-off valve is attached to the liquid outflow side of the bypass pipe.
The content of metal impurities in the etching liquid discharged from the overflow tank is detected, and the first flow rate adjusting valve and the second flow rate adjusting valve are controlled according to the content. Item 1. The wet etching apparatus according to item 1.