WO1999045574A1

WO1999045574A1 - Method for changing a processing medium contained in a processing tank and system for carrying out the method

Info

Publication number: WO1999045574A1
Application number: PCT/EP1999/001285
Authority: WO
Inventors: Mostafa Sabet
Original assignee: Mostafa Sabet
Priority date: 1998-03-02
Filing date: 1999-02-27
Publication date: 1999-09-10
Also published as: EP1101243A1

Abstract

The invention relates to a method for changing a processing medium for the wet chemical processing of silicon wafers, said processing medium being contained in a processing tank (12). According to the invention, a quantity of the contaminated processing medium is extracted and replaced by an equivalent quantity of non-contaminated processing medium at predetermined intervals and/or after a predetermined number of silicon wafers have been processed. Said quantity (ΔV) corresponds to a fraction of the overall quantity (Vmax) of processing medium (14) contained in the processing tank (12). The invention also relates to a system for the wet chemical processing of silicon wafers (16), comprising a processing tank (12), a tank supply line (26) and a tank discharge line (46). The inventive system is characterised in that a dosing pump (30, 56) is provided in the tank supply line (26) and in the tank discharge line (46) and in that a control device (80) is allocated to said dosing pumps. Said control device (80) enables the processing medium to be extracted from or introduced into the processing tank.

Description

Process for changing a treatment medium contained in a treatment basin and system for carrying out the process

The invention relates to a method for changing a treatment medium contained in a treatment basin for a wet chemical treatment of silicon wafers, wherein a quantity of the contaminated treatment medium and a corresponding quantity of a non-contaminated treatment medium are drawn off at predefinable time intervals and / or after the treatment of a predefinable number of silicon wafers is introduced. Furthermore, the invention relates to a system for the wet chemical treatment of silicon wafers, with a treatment basin for receiving a treatment medium, a basin inlet line and a basin outlet line. In the production of semiconductors, wet-chemical methods for treating silicon wafers, also referred to below as wafers, are usually used. The wet chemical processes are used, for example, to clean or etch the wafers. Until it is finished, the wafer is subjected to a number of different treatments in succession. A conventional system for the wet chemical treatment of wafers therefore comprises a multiplicity of treatment basins which are filled with a treatment medium or a treatment liquid (hereinafter also simply referred to as a liquid), for example phosphoric acid. The entire system is divided into so-called chemistry modules, with each chemistry module comprising a treatment basin, treatment basin inlet and outlet lines and the necessary infrastructure. One or more such chemistry modules are referred to as a wet bench.

During operation of the system, the treatment basin is first filled with the treatment medium (approximately 50 1 volume) in one operating cycle. Before this, however, this treatment medium is brought to a preselectable temperature in a so-called reservoir tank with a corresponding holding volume (approximately 501), so that it is not necessary to heat the treatment medium in the treatment basin in order to shorten the treatment idle times. Instead, a heater assigned to the treatment tank only has to maintain the operating temperature of the treatment medium. As soon as the treatment basin is filled, lots of silicon wafers are introduced into the treatment basin for a predetermined treatment time. Due to an increasing contamination of the treatment medium during a cycle, its effect diminishes, which leads to a deterioration in the treatment result. For this reason, after a certain time or after the treatment of a certain number of silicon wafer lots, it is necessary to drain the treatment medium and to replace it with a fresh treatment medium, so that the cycle described above can start again.

In general, hot modules, i.e. in the case of modules receiving a hot treatment medium, the treatment medium is drained from the treatment basin into a cooling tank and held therein until the temperature has dropped to a value specified by the manufacturer. The treatment medium is then either discarded or reprocessed.

The disadvantage of this method is in particular that the treatment results fluctuate within a wide range and are therefore not reproducible. To reduce this fluctuation range, the time interval between filling and draining the treatment medium would have to be shortened, but this would lead to a significant increase in the cost of the method and an increase in idle times.

In addition, this system for the wet chemical treatment of silicon wafers requires a large amount of space, since each treatment pool is preceded by a reservoir tank. Since such systems are installed in expensive clean rooms, this high space requirement also leads to correspondingly high costs. Against this background, the object of the invention is to provide a method which permits the treatment of silicon wafers with reproducible results and furthermore minimizes the service life, ie the idle time of the system. Furthermore, the task is to create a system that requires less space or clean room space and thus enables cost savings.

The object on which the invention is based is achieved by a method of the type mentioned at the outset, which is distinguished in that the amount corresponds to a fraction of the total amount of the treatment medium present in the treatment basin.

This advantageously makes it possible to minimize the fluctuation range of the impurities present in the treatment medium and thus to make the treatment results uniform during one cycle and thus to make them reproducible. Because only a small amount, for example 5 liters, of the treatment medium is exchanged after one cycle, the idle time of the system is also reduced or returns to zero.

In an advantageous development of the invention, the amount of the withdrawn and the amount of the introduced treatment medium is metered by metering pumps, the treatment medium preferably being first withdrawn and then introduced.

The use of metering pumps has the advantage that a very precise metering of even small amounts of the introduced and withdrawn treatment medium can be achieved with simple means. In an advantageous development of the invention, the introduced treatment medium, which is preferably mixed beforehand from different media, is heated in the treatment basin. This has the advantage that an upstream heating of the introduced treatment medium is no longer necessary. Since the treatment medium introduced corresponds to a fraction of the total amount in the treatment basin, only a small amount of energy is required to heat this fraction. Usually, the heating assigned to the treatment basin, which is designed to maintain the temperature, should be sufficient for this.

In an advantageous development of the invention, the treatment medium is delivered directly from a supply unit assigned to a plurality of treatment basins.

This has the advantage that it is possible to simplify the construction of the system. It also reduces the risk of leaks that can occur in the template tanks or mixing tanks described above. These are no longer necessary due to the central supply of the treatment basins via a supply unit, a line coming from the supply unit leading directly to the treatment basin and there preferably into the overflow collar.

In an advantageous development of the invention, the contamination of the treatment medium is measured and, depending on this measured value, the supply and the withdrawal of the treatment medium are controlled. This has the advantage that a further improvement and optimization of the method and thus the treatment results is possible.

In an advantageous development of the invention, the liquid contained in the treatment basin is circulated, the liquid being heated and filtered.

This has the advantage that the quality of treatment can be increased.

In a particularly advantageous manner, the method according to the invention makes it possible to dispense with heating and / or filtering when circulating; this leads to a significant simplification of the procedure.

The object on which the invention is based is also achieved by a system of the type mentioned at the outset, which is characterized by a metering pump arranged in each case in the basin inlet line and in the basin outlet line, and a control device assigned to the metering pumps, which detach and introduce a fraction of the total amount of the medium from or into the treatment basin.

The fact that only a fraction of the total amount of the medium present in the treatment basin is introduced and removed during one cycle means that the supply tanks assigned to the treatment basin are unnecessary. In particular, the upstream heating of the medium to be introduced into the treatment basin can be dispensed with. This also eliminates the heating units provided on the supply tanks. Instead of- It is possible to supply fresh treatment medium directly from a central supply unit. The system can thus be constructed in a more space-saving manner, which leads to significant cost advantages.

In an advantageous development of the invention, the basin drain line (in the case of hot modules) is connected to a cooling tank, the receiving volume (for example 51) of which is smaller than the volume of the medium which can be accommodated in the treatment basin (for example 801).

This has the advantage that the dimensions of the cooling tank can be reduced, so that the space requirement for the system is reduced, which leads to further cost advantages.

In an advantageous development of the invention, at least one mixing tank is connected upstream of the treatment basin.

Since the amount of the treatment medium to be introduced into the treatment basin is small, the mixing tank can be constructed with small dimensions, so that the required space is significantly less than that of the tanks previously used in the prior art.

In an advantageous development of the invention, the treatment basin is assigned a heater for heating the treatment medium.

This has the advantage that an additional heater associated with the supply tank can be dispensed with. It is only necessary to keep the temperature constant dimensioned heating of the treatment basin so that heating of the introduced amount of treatment medium is also possible. Since this amount is small, the necessary measures are not very expensive, so that there are significant cost advantages compared to the installation of an extra heater.

In an advantageous development of the invention, the treatment pool is assigned a sensor for detecting the contamination of the treatment medium, the sensor being connected to the control device.

This has the advantage that the treatment results can be optimized with little resources.

In an advantageous further development of the invention, the treatment basin has an overflow chamber and a treatment chamber, both chambers being connected via a circulation circuit. The circulating circuit preferably comprises a pump, a water heater and a filter. However, it is particularly preferred to dispense with the instantaneous water heater and / or the filter, so that the circulation circuit comprises only one pump and the corresponding lines.

This has the advantage that the system is further simplified in terms of its structure, which has both a positive influence on the system price and on the running costs.

Further advantages and refinements of the invention result from the description and the accompanying drawing. It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the combination indicated in each case, but also in other combinations or on their own without departing from the scope of the present invention.

The invention will now be explained in more detail using an exemplary embodiment with reference to the drawing. Show:

Fig. 1 is a schematic representation of a treatment basin and the connected components, and

2 shows a diagram to illustrate the method, the volume being plotted on the abscissa and the amount of impurities in the liquid being plotted on the ordinate.

In Fig. 1, a chemistry module is identified by reference number 10. As already stated, such a chemistry module is part of a system for the wet-chemical treatment of silicon wafers, one or more chemistry modules forming a wet bench. The system itself usually includes a wet bench.

The chemistry module 10 has a treatment basin 12 which is designed to receive a treatment medium or a treatment liquid 14. Several silicon wafers 16 are shown purely schematically, which are completely immersed in the treatment liquid 14 and are held by a schematically indicated carrier 18. Several of these silicon wafers 16 are referred to below as a lot. 10

The treatment basin 12 has two chambers 20, 22, the chamber 20 forming the treatment space and the chamber 22 forming an overflow space.

The treatment basin 12 further comprises a heater 24, which is arranged within the treatment room 20 in the floor area.

To fill the treatment basin 12, an inlet line 26 is provided, which is connected on the one hand to a supply unit V, not shown, and on the other hand opens into the overflow space 22. A valve 28 and a metering pump 30 downstream thereof are arranged in the feed line 26. In order to compensate for supply fluctuations in the supply unit, a buffer tank 27 can be connected to the feed line 26, the capacity of which, however, is significantly less than that of a storage tank.

Sensors 31a to 31c are assigned to treatment room 20, and sensors 31d to 31e are assigned to overflow chamber 22, which provide signals dependent on the level of the liquid. The three sensors 31a to 31c assigned to the treatment room 20 enable statements to be made about the level levels full, minimal and empty, while the two sensors 31d, 31e assigned to the overflow room 22 only provide signals about the level levels full and minimal.

These level signals are used both during the filling phase and during operation of the system in order to prevent that too much or too little liquid 14 is present in the treatment basin 12. 11

The chemistry module 10 further comprises a circulation circuit 32 which connects the overflow space 22 to the treatment space 20 via a line 34. In this line 34 - seen downstream - a pump 36, a water heater 38 and a filter 40 are provided. In a particularly preferred embodiment, however, the instantaneous water heater and / or the filter are dispensed with.

In the floor area of the treatment room 20 and the overflow room 22, a line 42 or 44 is connected, both of which open into a common drain line 46. Both lines 42, 44 each include a valve 48 and 50, respectively. A valve 54 and a metering pump 56 are introduced into the common drain line 46 downstream.

1 also shows that a line 58 is branched off from the outlet line 46 upstream of the valve 54. A valve 60 and a pump 62 are introduced in this line downstream. Downstream of the pump 62, the line 58 branches into two lines 64, 66, each of which comprises a valve 68 or 70. Line 64 opens into a tank, not shown, which stores medium that can no longer be used and disposed of, while line 66 opens into a tank in which medium to be recycled is collected.

1 further shows a line 72 which is connected on the one hand to the line 58 in the area between the valve 60 and the pump 62 and on the other hand to the cooling tank 52. A valve 74 is provided to shut off the line 72. 12

The chemistry module 10 further comprises a control unit 80, which is connected to control the pumps 30, 36, 56 and 62 and the valves 28, 48, 50, 54, 60, 68, 70 and 74 via corresponding lines. For reasons of clarity, only lines 82, 84 are shown in FIG. 1, line 82 creating a connection with pump 30 and line 84 creating a connection with valve 28. Depending on the application, the cables are designed as electrical or pneumatic cables.

To measure impurities in the liquid 14 contained in the treatment room 20, a sensor 86 is provided, which is connected via a line 88 to the control device 80 for transmitting measured values. The sensors 31a-e are also connected to the control device 80.

The chemistry module 10 now performs the following function:

Before the chemistry module 10 is started up, the treatment basin 12 is filled with the liquid 14. This is done via line 26, valve 28 being opened and pump 30 being activated. During this process, the overflow space 22 fills first, and by activating the circulation circuit 32, the liquid 14 is then pumped into the treatment space 20. Of course, the filling is also possible in another way. As soon as a predetermined level is reached, the pump 30 is deactivated and the valve 28 is closed. By means of the heater 24, the liquid 14 present in the treatment room 20 is then brought to a predeterminable operating temperature and kept at this temperature level. 13

The first treatment cycle then begins with the introduction of the silicon wafer lot to be treated. After a predetermined treatment time has expired, the silicon wafer lot is transported out of the treatment pool 12.

The treatment of the silicon wafer lot leads to contamination of the liquid 14 present in the treatment room 20. The process of the contamination of the liquid 14 is shown graphically in FIG. 2. At the beginning of the start of operation of the chemistry module 10, the treatment basin 12 contains a volume V _{max of} a non-contaminated liquid 14, which therefore has a contamination level of zero. This point is marked with A in the diagram. After the treatment of the first batch, the amount of contamination increases by a value Δm. This point is marked with B. With the treatment of further lots of silicon wafers, the amount of contamination increases slowly until it reaches a value m ₂ which is marked with C. This amount of contamination can be determined, for example, with the sensor 86. Alternatively, the amount of contamination can also be estimated from the number of lots treated.

When this amount of contamination m ₂ is reached, the metering pump 56 is activated via the control device 80 after the valves 48 and 54 have been opened. A quantity .DELTA.V of the liquid 14 is then withdrawn from the treatment room 20 and introduced into the cooling tank 52. The amount .DELTA.V of the liquid 14 corresponds to a fraction of the total liquid 14 contained in the treatment tank 12. After the amount .DELTA.V has been subtracted, the two valves 48, 54 are closed again. This process of withdrawing a quantity of liquid ΔV is shown in the diagram in FIG. 2 by connecting the two points C and 14

D marked. By withdrawing an amount ΔV of the contaminated liquid 14, the amount of the contaminants has decreased from the value m ₂ to the value ₁ . The valve 28 is then opened via the control device 80 and the metering pump 30 is activated in order to introduce a corresponding amount ΔV of a fresh liquid 14 into the treatment basin 12. Since the introduced liquid 14 contains no impurities, the amount of impurities m _λ does not change during this process. In the diagram shown in FIG. 2, this is characterized by the connecting line of the points D and E. After the total quantity V _{max has been reached} in the treatment basin 12, the metering pump 30 is deactivated and the valve 28 is closed again.

This process, ie the application of a certain amount .DELTA.V of the contaminated liquid 14 and the introduction of a corresponding amount of .DELTA.V of a clean liquid 14, is repeated whenever the amount of contaminants in the treatment tank 12 reaches the value m ₂ . It follows from this that during operation of the chemistry module 10, the amount of impurities in the treatment tank 12 fluctuates in the range between the values m _x and m ₂ .

During the entire operation of the chemistry module 10, the circulation circuit 32 is activated, so that liquid is transported from the overflow space 22 through the pump 36 into the treatment room 20, the liquid depending on the configuration of the circulation circuit, the flow heater 38 and / or the filter 40 happens. If the amount contained in the treatment room 20 reaches a certain level, the excess liquid runs off into the overflow room 22. 15

After a certain cooling time, the liquid contained in the cooling tank 52 is pumped via line 72 with the aid of pump 62 either via line 64 into the recycling tank or via line 66 into a disposal tank, the corresponding valves 74 and 68 and 70 being opened for this purpose become. To empty the entire treatment basin 12, the two valves 48, 50 and the valve 60 and one of the two valves 68 and 70 are opened and the pump 62 is activated, the temperature of the liquid 14 in the treatment basin 12 having previously dropped to the required value.

As already mentioned, the advantage of the previously described method is that the amount of impurities contained in the liquid 14 only fluctuates in a small range m ₂ -m _l , so that the treatment results also fluctuate only within a small range and are therefore reproducible. In addition, the chemistry module 10 does not require a receiver tank which holds the total amount V _{max of} the liquid 14 and preheats it to a certain value.

The quantity .DELTA.v is preferably set such that the sum of the quantities .DELTA.v introduced during a previously usual liquid change cycle corresponds exactly to the total quantity in the treatment room. Of course, other quantities Δv can also be set. E.g. these can also be changed over time. Since the quantities .DELTA.v are introduced during the treatment of wafers, the operation of the system for changing the liquid no longer has to be interrupted, in contrast to previously.

Claims

16 patent claims

1. A method for changing a treatment medium contained in a treatment basin (12) for a wet chemical treatment of silicon wafers, with a quantity of the contaminated treatment medium being withdrawn and a corresponding quantity of a non-contaminated one being withdrawn at predefinable time intervals and / or after the treatment of a predefinable number of silicon wafers Treatment medium is introduced, characterized in that the amount (ΔV) corresponds to a fraction of the total amount (V _max ) of the treatment medium (14) present in the treatment tank (12).

2. The method according to claim 1, characterized in that the amount (ΔV) of the withdrawn and introduced treatment medium (14) is metered by metering pumps (30, 56).

3. The method according to claim 1 or 2, characterized in that first the contaminated treatment medium is applied and then or while the clean treatment medium is introduced.

4. The method according to any one of the preceding claims, characterized in that the introduced treatment medium is previously mixed from different treatment media.

5. The method according to any one of the preceding claims, characterized in that the introduced treatment medium in the treatment basin (12) is heated. 17

6. The method according to any one of the preceding claims, characterized in that the treatment medium from a plurality of treatment tanks (12) associated supply unit (V) is delivered directly.

7. The method according to any one of the preceding claims, characterized in that the contamination of the treatment medium is measured and the supply and withdrawal of the treatment medium is controlled depending on this measured value.

8. The method according to any one of the preceding claims, characterized in that the treatment medium (14) contained in the treatment tank (12) is circulated.

9. The method according to claim 8, characterized in that heating and filtering of the circulated treatment medium takes place during the circulation.

10. Plant for wet chemical treatment of silicon wafers (16), with a treatment basin (12) for receiving a treatment medium (14), a basin inlet line (26) and a basin outlet line (46), characterized by one in each of the basin inlet line (26) and in the dosing pump (30, 56) arranged in the basin drain line (46), and a control device (80) assigned to the dosing pumps (30, 56), which enables the treatment medium to be drawn off and introduced into or into the treatment basin. 18th

11. Plant according to claim 10, characterized in that the basin drain line (46) is connected to a cooling tank (52) whose receiving volume is smaller than the volume of the treatment medium (14) absorbable in the treatment basin (12).

12. Plant according to claim 10 or 11, characterized in that the basin inlet line (26) with a central supply device (V) is directly connected.

13. Plant according to claim 10, 11 or 12, characterized in that the treatment tank (12) is connected upstream of at least one mixing tank.

14. Plant according to one of claims 10 to 13, characterized in that the treatment basin (12) is associated with a heater (24) for heating the treatment medium (14).

15. Plant according to one of claims 10 to 14, characterized in that the treatment basin (12) is assigned a sensor (86) for detecting the contamination of the treatment medium (14), the sensor (86) being connected to the control device (80) is.

16. Plant according to one of claims 10 to 15, characterized in that the treatment tank (12) has an overflow chamber (22) and a treatment chamber (20), both chambers (20, 22) being connected via a circulation circuit (32). 19

17. Plant according to claim 15, characterized in that the circulating circuit (32) comprises a pump (36), a water heater (38) and a filter (40).