Abstract:
A filter connectable to an external circulating system, the circulating system being included by a substrate treatment apparatus which etches a substrate with an H 3 PO 4  solution, the filter includes:  
     a chemical feeding port which permits feed of H 3 PO 4  solution containing particles deposited due to etching of a substrate;  
     an H 2 O adding port which permits the addition of H 2 O;  
     a filter film which removes the particles from the H 3 PO 4  solution whose heat distribution is made ununiform by the addition of H 2 O; and  
     a protection member which is disposed between the H 2 O adding port and the filter film and which protects the filter film from bumping of the H 3 PO 4  solution that is causable by the addition of H 2 O.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims benefit of priority under 35USC §119 to Japanese Patent Application No. 2004-73204, filed on Mar. 15, 2004, the contents of which are incorporated by reference herein.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a filter, a substrate treatment apparatus and a substrate treatment method, and is intended for, for example, etching of a substrate to form a micropattern thereon.  
         [0004]     2. Related Background Art  
         [0005]     In etching a SiN film of a semiconductor substrate, it has been known that repetitive use of the same chemical solution would increase silica dust on a wafer after treatment with increase of the number of treatment batches. Therefore, it is necessary to exchange a dirty H 3 PO 4  solution to a fresh one or to replace a filter in which a certain amount of silica is deposited, when a predetermined number of treatment batches and a predetermined amount of dissolved silica have been exceeded.  
         [0006]     Various attempts have heretofore been made to reduce the silica dust in the H 3 PO 4  solution. There have been mainly three methods to reduce the dissolved silica. The first method is to separate silica dissolved into the H 3 PO 4  solution in a heat exchange area and then remove it with a filter, as described in, for example, Japanese laid open (kokai) 2002-299313 and Japanese laid open (kokai) 09-219388 (1997). The second method is to add H 2 O which extremely drops temperature and reduces solubility, thereby separating the silica dust onto the filter for removal. Further, the third method is to add HF to the H 3 PO 4  solution so that dissolved silica will be a gas of Sif 4  to be removed from the solution, as described in, for example, Japanese laid open (kokai) 09-45660 (1997), 07-86260 (1995), 10-50682 (1998) and 08-83792 (1996).  
         [0007]     However, the problem associated with the first and second methods is that because the temperature of the H 3 PO 4  solution is extremely decreased, reheating needs to be performed by a heater which requires costs. The third method also has a problem that the solution has to be adequately heated to remove the added HF from the H 3 PO 4  solution.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     According to a first aspect of the present invention, there is provided a filter connectable to an external circulating system, the circulating system being included by a substrate treatment apparatus which etches a substrate with an H 3 PO 4  solution, the filter comprising:  
         [0009]     a chemical feeding port which permits feed of H 3 PO 4  solution containing particles deposited due to etching of a substrate;  
         [0010]     an H 2 O adding port which permits the addition of H 2 O;  
         [0011]     a filter film which removes the particles from the H 3 PO 4  solution whose heat distribution is made ununiform by the addition of H 2 O; and  
         [0012]     a protection member which is disposed between the H 2 O adding port and the filter film and which protects the filter film from bumping of the H 3 PO 4  solution that is causable by the addition of H 2 O.  
         [0013]     According to a second aspect of the present invention, there is provided a substrate treatment apparatus comprising:  
         [0014]     a treatment tank which receives a substrate to etch the substrate with an H 3 PO 4  solution;  
         [0015]     a circulating system which takes in the H 3 PO 4  solution containing particles deposited in the treatment tank and which removes the particles and returns the H 3 PO 4  solution to the treatment tank;  
         [0016]     a pump attached to the circulating system to circulate the H 3 PO 4  solution in the circulating system;  
         [0017]     a filter attached to the circulating system, the filter including a chemical feeding port which permits the feed of the H 3 PO 4  solution containing particles deposited by the etching, and a filter film which removes the particles from the H 3 PO 4  solution;  
         [0018]     an H 2 O adder attached on an upstream side of the filter film of the filter to add H 2 O to the H 3 PO 4  solution so that a concentration of the H 3 PO 4  solution is maintained within an arbitrary range and to impart an ununiform temperature distribution to the H 3 PO 4  solution; and  
         [0019]     a heater attached to the circulating system to heat the H 3 PO 4  solution so that the H 3 PO 4  solution at the arbitrary temperature is supplied to the treatment tank.  
         [0020]     According to a third aspect of the present invention, there is provided a substrate treatment method using a substrate treatment apparatus which comprises a treatment tank which etches with an H 3 PO 4  solution a substrate to be treated; a circulating system which takes in the H 3 PO 4  solution containing particles deposited by the H 3 PO 4  solution in the treatment tank and which removes the particles and returns the H 3 PO 4  solution to the treatment tank; a pump attached to the circulating system to circulate the H 3 PO 4  solution in the circulating system; a filter which includes an attachment part to be attached to the circulating system and a filter film to remove the particles from the H 3 PO 4  solution; and a heater attached to the circulating system to heat the H 3 PO 4  solution so that the H 3 PO 4  solution at an arbitrary temperature is supplied to the treatment tank, the treatment method comprising:  
         [0021]     adding H 2 O to the H 3 PO 4  solution on an upstream side of the attachment part of the filter in the circulating system to maintain a concentration of the H 3 PO 4  solution within an arbitrary range and to impart an ununiform concentration distribution to the H 3 PO 4  solution. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     In the accompanying drawings:  
         [0023]      FIG. 1  is a block diagram showing a schematic configuration in a first embodiment of a substrate treatment apparatus according to the present invention;  
         [0024]      FIG. 2  is a block diagram showing a schematic configuration in a second embodiment of the substrate treatment apparatus according to the present invention;  
         [0025]      FIG. 3  is a block diagram showing essential parts of one embodiment of a filter according to the present invention; and  
         [0026]      FIG. 4  is a block diagram showing a schematic configuration in a third embodiment of the substrate treatment apparatus according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]     (1) First Embodiment  
         [0028]      FIG. 1  is a block diagram showing a schematic configuration in a first embodiment of a substrate treatment apparatus according to the present invention. An etching apparatus  1  shown in  FIG. 1  comprises a treatment tank  10 , a circulation line L 0 , a pump  12 , a heater  14 , two filters F 1 , F 2 , cleaning lines L 1 , L 2 , H 2 O replenishing lines PL 1 , PL 2 , and valves VL 1  to VL 10  to adjust the amount of replenishment chemical solution or H 2 O.  
         [0029]     The treatment tank  10  receives a semiconductor wafer W under manufacture to selectively remove by an H 3 PO 4  solution all or part of a film formed in a surface layer or on a surface of the wafer W. Consequently, silica dust is dissolved into the H 3 PO 4  solution, and the H 3 PO 4  solution containing the silica dust is sucked by the pump  12  and then flows in the circulation line L 0 . The two filters F 1 , F 2  are connected in parallel to each other and placed immediately before an upstream side of the heater  14 , and remove the silica dust in the H 3 PO 4  solution. The heater  14  heats the H 3 PO 4  solution filtered by the filters F 1 , F 2  and returns it to the treatment tank  10 .  
         [0030]     The valves VL 3 , VL 4  are provided between a branch point Nu of the parallel connection on the upstream side of the filters F 1 , F 2  and the respective filters, and they adjust an inflow amount of the H 3 PO 4  solution into the respective filters. Similarly, the valves VL 5 , VL 6  are provided between the branch point Nd of the parallel connection on the downstream side of the filters F 1 , F 2  and the respective filters, and they adjust an outflow amount of the H 3 PO 4  solution from the respective filters. Further, an HF solution feed line L 1  for cleaning is connected via the valves VL 7 , VL 8  to the circulation line L 0  between the downstream valve VL 5  and the filter F 1  and to the circulation line L 0  between the downstream valve VL 6  and the filter F 2 , respectively. Moreover, an HF solution discharging line L 2  is connected via the valves VL 1 , VL 2  to the circulation line L 0  between the upstream valve VL 3  and the filter F 1  and to the circulation line L 0  between the upstream valve VL 4  and the filter F 2 , respectively.  
         [0031]     The H 2 O replenishing lines PL 1 , PL 2  are connected on the upstream side of the filters F 1 , F 2  to the circulation line L 0  immediately before the respective filters F 1 , F 2  via the valves VL 9 , VL 10 , respectively, and replenish H 2 O to the H 3 PO 4  solution to maintain a concentration of the H 3 PO 4  solution within an arbitrary range thereof.  
         [0032]     Thus, according to the etching apparatus  1  in the present embodiment, since H 2 O is added to the H 3 PO 4  solution immediately before the respective filters, the temperature of the H 3 PO 4  solution rapidly drops, the silica dust is deposited due to a decrease in solubility, and the filter which immediately follows removes the silica dust before different temperatures are uniformed. Thus, according to the etching apparatus  1  in the present embodiment, the H 3 PO 4  solution can be cleaned by the filters with high efficiency while the concentration of the H 3 PO 4  solution is held at an arbitrary value. Further, the filters F 1 , F 2  connected in parallel are disposed immediately before the heater  14  at which the temperature of the H 3 PO 4  solution is the lowest, and H 2 O is added immediately before these filters, thereby creating a state in which particles are easily deposited. In this state where H 2 O is locally added into the H 3 PO 4  solution and the particles are deposited, the particles are removed from the H 3 PO 4  solution, allowing elongation of the life of the chemical solution.  
         [0033]     A distance D between each connection point of the H 2 O replenishing line PL 1 , PL 2  and the circulation line L 0 , and the filter F 1 , F 2  is set within a range where the H 3 PO 4  solution reaches a filter film in each filter until an ununiform temperature distribution caused in the H 3 PO 4  solution when H 2 O at room temperature is added to the H 3 PO 4  solution at a high temperature (e.g., 160° C.) is uniformed.  
         [0034]     As described above, since the etching apparatus  1  in the present embodiment comprises the two filters F 1 , F 2  connected in parallel, the filters can be efficiently cleaned without stopping a cleaning treatment of the H 3 PO 4  solution. A specific method thereof will be described below.  
         [0035]     First, the valves VL 3 , VL 5  are opened while the other valves remain closed so that the H 3 PO 4  solution is passed through and filtered by the filter F 1 . When the time comes to clean the filter F 1 , the valves VL 4 , VL 6  are opened and the valves VL 3 , VL 5  are closed. In this way, the H 3 PO 4  solution can be filtered by the filter F 2  without stopping the cleaning treatment of the H 3 PO 4  solution. Subsequently, the valves VL 7 , VL 1  are opened to pass an HF solution from the valve VL 7  side into the filter F 1  through the HF solution feed line L 1 , and the HF solution is discharged from the valve VL 1  side to the HF solution discharging line L 2 . When the cleaning of the filter F 1  is completed, the valves VL 7 , VL 1  are closed. Subsequently, when the time comes to clean the filter F 2 , the valves VL 3 , VL 5  are opened, and then the valves VL 4 , VL 6  are closed to switch the filter F 2  to the filter F 1 . To clean the filter F 2 , the valves VL 2 , VL 8  are opened so that the HF solution flows from the valve VL 8  side. The above operation is repeated, so that the filters can be efficiently cleaned withou 2 t stopping the cleaning treatment of the H 3 PO 4  solution at the time when the filter is to be cleaned or replaced. Thus, semiconductor devices can be etched at high throughput. Moreover, as the filters can be frequently cleaned, the filters can be less frequently replaced.  
         [0036]     (2) Second Embodiment  
         [0037]     In the first embodiment described above, the H 2 O replenishing line PL 1 , PL 2  are connected to the circulation line L 0  in the vicinity of the respective filters on the upstream side of the respective filters. The present embodiment is described in such a manner that the H 2 O replenishing lines PL 1 , PL 2  are connected not to the circulation line L 0  but directly to the respective filters.  
         [0038]      FIG. 2  is a block diagram showing a schematic configuration in a second embodiment of the substrate treatment apparatus according to the present invention. An etching apparatus  2  shown in  FIG. 2  comprises filters F 3 , F 4  as one embodiment of the filters according to the present invention, instead of the filters F 1 , F 2  which the etching apparatus  1  shown in  FIG. 1  comprises, and the H 2 O replenishing line PL 1 , PL 2  are directly connected to these filters F 3 , F 4 . The configuration in other parts of the etching apparatus  2  shown in  FIG. 2  is substantially the same as that of the etching apparatus  1  shown in  FIG. 1 .  
         [0039]      FIG. 3  is a block diagram showing essential parts of the filter F 3  (F 4 ) which the etching apparatus  2  in the present embodiment comprises. The filter F 3  (F 4 ) shown in  FIG. 3  comprises a filter cover  50  provided with a chemical feeding port  62 , a chemical discharging port  66  and an H 2 O adding port  64 ; a filter film  52  contained in the filter cover  50 ; and a protective barrier  68 . The H 2 O adding port  64  is provided in the vicinity of the chemical feeding port  62 , so that H 2 O at room temperature is added to the H 3 PO 4  solution at a high temperature, and immediately after this, the H 3 PO 4  solution is introduced into the filter film  52  with the ununiform temperature distribution and efficiently filtered.  
         [0040]     In the first embodiment described above, H 2 O is added to the H 3 PO 4  solution in the vicinity of the filters F 1 , F 2 , but in this case, the H 3 PO 4  solution could cause bumping due to a temperature difference between the H 3 PO 4  solution and H 2 O, in which case the filter films of the filters F 1 , F 2  might be damaged. As shown in  FIG. 3 , the filter F 3  (F 4 ) in the present embodiment comprises the protective barrier  68  provided between the filter film  52  and the filter cover  50 , so that the filter film  52  can be protected from the damage when bumping occurs. This provides the filters with high filter efficiency and long life. The length of the protective barrier  68  may be such that the filter film  52  is not affected by the bumping.  
         [0041]     (3) Third Embodiment  
         [0042]      FIG. 4  is a block diagram showing a schematic configuration in a third embodiment of the substrate treatment apparatus according to the present invention. As apparent from contrast with  FIG. 1 , an etching apparatus  3  shown in  FIG. 4  is characterized in that it further comprises a bypass line which is provided in a circulating system so as to couple the connection points Nu, Nd of the parallel connection of the filters F 1 , F 2  and which does not have filters, and that a waste solution line L 4  to exchange the H 3 PO 4  solution is provided between the connection point Nu and the pump  12 . Valves VL 11 , VL 12  are respectively provided between a bypass line L 3  and the connection points Nu, Nd, and these valves adjust the amount of H 3 PO 4  solution passing through the bypass line L 3 . The configuration in other parts of the etching apparatus  3  shown in  FIG. 4  is substantially the same as that of the etching apparatus  1  shown in  FIG. 1 . Therefore, in the filters F 1 , F 2  connected in parallel, a method of switching the filters during the cleaning of the respective filters is the same as in the etching apparatus  1 .  
         [0043]     According to the etching apparatus  3  of the present embodiment, when the H 3 PO 4  solution is exchanged, the bypass line without filters is used to enable smooth circulation of the exchanged H 3 PO 4  solution. This will be described below.  
         [0044]     For example, it is assumed that the exchange of the H 3 PO 4  solution is needed when the valves VL 3 , VL 5  are opened whereas the other valves are closed and the chemical H 3 PO 4  solution is passing through the filter F 1 . In order to exchange the chemical solution, a valve VL 20  is opened to start drawing off the H 3 PO 4  solution from the circulation line L 0  through the waste solution line L 4 .  
         [0045]     With regard to the open/close state of the valves at this moment, the valves VL 3 , VL 5  may be closed and the valves VL 11 , VL 12  may be opened immediately before the exchange of the chemical solution, or the valves VL 3 , VL 5  may be closed and the valves VL 11 , VL 12  may be opened when the chemical solution is completely drawn off. The fresh solution fed in the treatment tank  10  circulates sequentially from the treatment tank  10  to the pump  12  and the heater  14  without being subjected to the resistance of the filter F 1  or F 2 . In this regard, the cleaning of the filter F 1  which has been used until just before the exchange of the H 3 PO 4  solution may be carried out in parallel with the circulation of the fresh H 3 PO 4  solution. Specifically, the valves VL 1 , VL 7  are opened so that the HF solution flows from the valve VL 7  side by way of the HF solution feed line L 1 . When the cleaning is finished, the valves VL 1 , VL 7  may be closed.  
         [0046]     In this way, as the etching apparatus  3  of the present embodiment comprises the bypass line L 3  on which filters are not placed, even the H 3 PO 4  solution whose temperature is low and whose viscosity is high immediately after the exchange can be supplied to the treatment tank  10  after efficiently and uniformly heated without being subjected to the resistance of the filter.