Abstract:
According to the present invention, there is provided a semiconductor substrate processing apparatus comprising: a processing bath which etches a semiconductor substrate by dipping the semiconductor substrate into a processing solution; an outer bath which is positioned outside said processing bath and receives the processing solution overflowing from said processing bath; a circulation channel which resupplies the processing solution discharged from said outer bath to said processing bath; a heater which adjusts a temperature of the processing solution flowing through said circulation channel; a filter which removes foreign matter in the processing solution flowing through said circulation channel; and a controller which measures, after the semiconductor substrate is loaded into said processing bath, one of the temperature of the processing solution in said processing bath and a time during which the temperature of the processing solution restores a predetermined temperature, calculates a processing time during which the semiconductor substrate is etched on the basis of the measurement result, and etches the semiconductor substrate on the basis of the calculated processing time.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based upon and claims benefit of priority under 35 USC §119 from the Japanese Patent Application No. 2004-298540, filed on Oct. 13, 2004, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a semiconductor substrate processing apparatus and semiconductor device fabrication method.  
         [0003]     There is a semiconductor substrate processing apparatus which etches or cleans a semiconductor substrate by dipping it in a processing solution in a processing bath.  
         [0004]     Outside the processing bath containing the processing solution, this semiconductor substrate processing apparatus has an outer bath for receiving the processing solution overflowing from the processing bath. When discharged from the outer bath, the processing solution is resupplied to the processing bath through a circulation channel.  
         [0005]     The circulation channel has a pump for circulating the processing solution, and a heater for adjusting the temperature of the processing solution which flows through the circulation channel.  
         [0006]     When etching or cleaning for a semiconductor substrate is repeated in the processing bath, particles and the like come off the semiconductor substrate. If these particles are left unremoved, they may reattach to the semiconductor substrate. Therefore, the circulation channel has a filter for removing particles in the processing solution which flows through the circulation channel, and the particles are captured by this filter.  
         [0007]     When the filter is clogged with the air, the circulation flow rate decreases. To prevent the decrease, the filter is connected to a filter air vent line which directly supplies the processing solution to the outer bath, in addition to the circulation channel which supplies the processing solution to the processing bath. When the filter is clogged with the particles, the processing solution is supplied to the outer bath through the filter air vent line at a flow rate corresponding to the decrease.  
         [0008]     When a semiconductor substrate is loaded into the processing bath, the temperature of the processing solution falls under the influence of the semiconductor substrate. This temperature fall of the processing solution decreases the etching rate. Therefore, the heater is turned on to restore the temperature of the processing solution to a temperature suitable for etching. If, however, the flow rate in the filter air vent line has increased owing to clogging of the filter, the time for restoring the temperature of the processing solution in the processing bath prolongs.  
         [0009]     In this case, no desired etching rate can be obtained. Therefore, etching is not actually completed in some cases even after a predetermined time elapses and the processing is terminated. In a case like this, the processed semiconductor substrate must be handled as a defective product or processed again after the filter is replaced. This decreases the throughput or delays the processing.  
         [0010]     The reference concerning the processing of semiconductor substrates is as follows.  
         [0011]     Japanese Patent Laid-Open No. 2001-205158  
       SUMMARY OF THE INVENTION  
       [0012]     According to one aspect of the present invention, there is provided a semiconductor substrate processing apparatus comprising:  
         [0013]     a processing bath which etches a semiconductor substrate by dipping the semiconductor substrate into a processing solution;  
         [0014]     an outer bath which is positioned outside said processing bath and receives the processing solution overflowing from said processing bath;  
         [0015]     a circulation channel which resupplies the processing solution discharged from said outer bath to said processing bath;  
         [0016]     a heater which adjusts a temperature of the processing solution flowing through said circulation channel;  
         [0017]     a filter which removes foreign matter in the processing solution flowing through said circulation channel; and  
         [0018]     a controller which measures, after the semiconductor substrate is loaded into said processing bath, one of the temperature of the processing solution in said processing bath and a time during which the temperature of the processing solution restores a predetermined temperature, calculates a processing time during which the semiconductor substrate is etched on the basis of the measurement result, and etches the semiconductor substrate on the basis of the calculated processing time.  
         [0019]     According to one aspect of the present invention, there is provided a semiconductor device fabrication method which etches a semiconductor substrate by using a semiconductor substrate processing apparatus comprising:  
         [0020]     a processing bath which etches a semiconductor substrate by dipping the semiconductor substrate into a processing solution;  
         [0021]     an outer bath which is positioned outside the processing bath and receives the processing solution overflowing from the processing bath;  
         [0022]     a circulation channel which resupplies the processing solution discharged from the outer bath to the processing bath;  
         [0023]     a heater which adjusts a temperature of the processing solution flowing through the circulation channel; and  
         [0024]     a filter which removes foreign matter in the processing solution flowing through the circulation channel,  
         [0025]     said method comprising:  
         [0026]     measuring, after the semiconductor substrate is loaded into the processing bath, one of the temperature of the processing solution in the processing bath and a time during which the temperature of the processing solution restores a predetermined temperature;  
         [0027]     calculating a processing time during which the semiconductor substrate is etched on the basis of one of the measured temperature and time; and  
         [0028]     etching the semiconductor substrate on the basis of the calculated processing time. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0029]      FIG. 1  is a block diagram showing the arrangement of a semiconductor substrate processing apparatus according to the first embodiment of the present invention;  
         [0030]      FIG. 2  is a graph showing the relationship between the temperature of a processing solution in a processing bath and the etching rate;  
         [0031]      FIG. 3  is a graph showing the relationship between the temperature of the processing solution in the processing bath and the time after a semiconductor substrate is loaded into the processing bath;  
         [0032]      FIG. 4  is a flowchart showing a semiconductor substrate processing sequence according to the first embodiment of the present invention;  
         [0033]      FIG. 5  is a graph showing the relationship between the temperature of the processing solution in the processing bath and the time after a semiconductor substrate is loaded into the processing bath;  
         [0034]      FIG. 6  is a graph showing the relationship between the insufficient etching amount and the additional time;  
         [0035]      FIG. 7  is a flowchart showing the steps of a semiconductor substrate processing method according to the second embodiment of the present invention;  
         [0036]      FIG. 8  is a graph showing the relationship between the temperature of the processing solution in the processing bath and the time after a semiconductor substrate is loaded into the processing bath;  
         [0037]      FIG. 9  is a flowchart showing the steps of a semiconductor substrate processing method according to the third embodiment of the present invention;  
         [0038]      FIG. 10  is a graph showing the relationship between the temperature of the processing solution in the processing bath and the time, for each number of semiconductor substrates loaded.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0039]     Embodiments of the present invention will be described below with reference to the accompanying drawings.  
       (1) First Embodiment  
       [0040]      FIG. 1  shows the arrangement of a semiconductor substrate processing apparatus  10  according to the first embodiment of the present invention. The semiconductor substrate processing apparatus  10  etches or cleans a semiconductor substrate  20  by dipping it in a processing solution in a processing bath  30 .  
         [0041]     Outside the processing bath  30  containing the processing solution, the semiconductor substrate processing apparatus  10  has an outer bath  40  for receiving the processing solution overflowing from the processing bath  30 . When discharged from the outer bath  40 , the processing solution is resupplied to the processing bath  30  through a circulation channel  50 .  
         [0042]     The circulation channel  50  has a pump  60  for circulating the processing solution, a heater  70  for adjusting the temperature of the processing solution flowing through the circulation channel  50 , and a filter  80  for removing particles (foreign matter) which come off the semiconductor substrate  20  and exist in the processing solution flowing in the circulation channel  50 .  
         [0043]     The filter  80  is connected to a filter air vent line  90  capable of directly supplying the processing solution to the outer bath  40 . If the flow rate of the processing solution supplied to the processing bath  30  decreases owing to clogging of the filter  80 , the processing solution is supplied to the outer bath  40  through the filter air vent line  90  at a flow rate corresponding to the decrease.  
         [0044]     A thermometer (not shown) is set in the processing bath  30  and measures the temperature of the processing solution contained in the processing bath  30 . A controller  100  controls the whole of the semiconductor substrate processing apparatus  10 . The controller  100  also monitors the temperature measured by the thermometer set in the processing bath  30 .  
         [0045]     As shown in  FIG. 2 , the etching rate of the semiconductor substrate  20  depends on the temperature of the processing solution contained in the processing bath  30 . That is, when the temperature of the processing solution is low, the etching rate is also low, and, when the temperature of the processing solution is high, the etching rate is also high. Etching data indicating the correspondence of the temperature of the processing solution to the etching rate as described above is prestored in a storage unit  110 .  
         [0046]     The storage unit  110  also stores data (to be referred to as temperature change data hereinafter) indicating the way the temperature of the processing solution in the processing bath  30  changes with time after the semiconductor substrate  20  is loaded into the processing bath  30  when a predetermined filter, e.g., a new filter is used.  
         [0047]     On the basis of the processing solution temperature measured by the thermometer and the temperature change data and etching data stored in the storage unit  110 , the controller  100  calculates a processing time necessary to etch the semiconductor substrate  20 . After this processing time elapses, the controller  100  terminates the etching process by the semiconductor substrate processing apparatus  10 .  
         [0048]     Also, if the controller  100  determines that the calculated processing time will exceed a predetermined upper limit, it activates an alarm  120  to notify the operator that the filter  80  must be replaced. Note that a counter  130  counts the number of semiconductor substrates  20  loaded into the processing bath  30 , and notifies the controller  100  of the number.  
         [0049]      FIG. 3  shows temperature change data of the processing solution after semiconductor substrates  20  are loaded into the processing bath  30 . As shown in  FIG. 3 , immediately after semiconductor substrates  20  are loaded into the processing bath  30 , the temperature of the processing solution largely falls under the influence of the semiconductor substrates  20 . This fall of the temperature of the processing solution decreases the etching rate. Therefore, the temperature of the processing solution is restored to a predetermined temperature by turning on the heater  7 , thereby restoring the original etching rate.  
         [0050]     When the same filter  80  is kept used for a predetermined period, it clogs by capturing particles. Consequently, the flow rate of the processing solution supplied from the filter  80  to the processing bath  30  decreases, and the flow rate of the processing solution supplied to the outer bath  40  through the filter air vent line  90  increases.  
         [0051]     If semiconductor substrates  20  are loaded into the processing bath  30  in this state, the temperature of the processing solution falls more than when a new filter  80  is used. In addition, even after the heater  70  is turned on, the restoration of the temperature of the processing solution is somewhat moderate. This prolongs the restoration time of the temperature of the processing solution.  
         [0052]     In the semiconductor substrate processing apparatus  10  of this embodiment, therefore, a processing time required to etch the semiconductor substrates  20  when a predetermined filter, e.g., a new filter is used is corrected in accordance with the state of the filter  80  actually used, thereby etching the semiconductor substrates  20  until the corrected processing time elapses.  
         [0053]      FIG. 4  shows semiconductor substrate processing sequence RT 10  according to this embodiment.  FIG. 5  shows the temperature change data of the processing solution in the processing bath  30  after semiconductor substrates  20  are loaded into the processing bath  30 , for each of a new filter and a filter currently being used. When semiconductor substrate processing sequence R 10  starts in  FIG. 4 , semiconductor substrates  20  are loaded into the processing bath  30  in step SP 10 . Subsequently, in step SP 20 , the controller  100  measures the temperature of the processing solution in the processing bath  30  at time t 10 .  
         [0054]     In step SP 30 , the controller  100  reads out, from the storage unit  110 , the temperature of the processing solution in the processing bath  30  at time t 10  when a new filter is used, and calculates a temperature difference d 10  between the readout temperature and the temperature of the processing solution in the processing bath  30  currently being used.  
         [0055]     Assuming that the slope when the temperature of the processing solution in the processing bath  30  currently being used restores is the same as the slope when the temperature of the processing solution in the processing bath  30  restores when a new filter is used, the controller  100  calculates, on the basis of the calculated temperature difference d 10 , temperature change data of the processing solution in the processing bath  30  currently being used.  
         [0056]     Then, the controller  100  reads out, from the storage unit  110 , the etching data indicating the correspondence of the temperature of the processing solution to the etching rate. On the basis of this etching data and the temperature change data of the processing solution in the processing bath  30  currently being used, the controller  100  calculates data (to be referred to as etching rate change data hereinafter) indicating the way the etching rate of the processing solution in the processing bath  30  currently being used changes with time.  
         [0057]     In addition, the controller  100  reads out, from the storage unit  110 , the temperature change data of the processing solution in the processing bath  30  when a new filter is used. On the basis of the readout temperature change data and the etching data described above, the controller  100  calculates etching rate change data of the processing solution in the processing bath  30  when a new filter is used.  
         [0058]     The controller  100  integrates this etching rate change data of the processing solution in the processing bath  30  when a new filter is used by a predetermined processing time required for etching, thereby calculating an etching amount required to complete etching.  
         [0059]     At the same time, the controller  100  integrates the etching rate change data of the processing solution in the processing bath  30  currently being used by the same time as the processing time described above, thereby estimating an etching amount when the processing time elapses.  
         [0060]     The controller  100  calculates the difference between the etching amount necessary to complete etching and the estimated etching amount when the processing time elapses, thereby calculating an etching amount to be insufficient (to be referred to as an insufficient etching amount hereinafter).  
         [0061]     As shown in  FIG. 6 , an additional time which is produced, with respect to the processing time required for etching when a new filter used, when the temperature of the processing solution in the processing bath  30  falls depends on the insufficient etching time. For example, when the insufficient etching amount is small, the additional time is short, and, when the insufficient etching amount is large, the additional time is long. Additional time data indicating the correspondence of the insufficient etching time to the additional time is prestored in the storage unit  110 .  
         [0062]     The controller  100  calculates an additional time corresponding to the insufficient etching time on the basis of this additional time data, and corrects the processing time by adding the calculated additional time to it.  
         [0063]     Note that when phosphoric acid (H 3 PO 4 ) is used as the processing solution to etch a silicon nitride film (SiN) by 100 nm at a temperature of 160° C., the processing time is 1,000 sec if a new filter is used. On the other hand, if the filter  80  which has been used for a predetermined period is used, the additional time is 30 sec when temperature difference d 10  is 1.3° C., and 21 sec when it is 1.0° C., when 90 sec elapse after semiconductor substrates  20  are loaded.  
         [0064]     In step SP 40 , the controller  100  checks whether the corrected processing time is equal to or smaller than a predetermined upper limit. If YES in step SP 40 , this indicates that no clogging occurs basically in the filter  80 . If there is clogging to an extent that temperature control of the process is not affected, the controller  100  judges YES. Controller  100  advances to step SP 50  to continue the etching process, and then advances to step SP 60  to terminate processing sequence RT 10 .  
         [0065]     On the other hand, if NO in step SP 40 , this indicates that the filter  80  is beginning to clog, so the controller  100  advances to step SP 70  to activate the alarm  120  to notify the operator that the filter  80  requires replacement, while performing the etching process. After the etching process is completed, the operator replaces or cleans the filter  80 . The flow then advances to step SP 60  to terminate processing sequence RT 10 .  
         [0066]     In this embodiment as described above, etching can be reliably performed by correcting the etching time of the semiconductor substrate  20  in accordance with the fall of the internal temperature of the processing bath  30 , which is caused by clogging of the filter  80 . Accordingly, the yield can be increased.  
         [0067]     If clogging of the filter  80  worsens and the amount of processing solution flowing through the filter air vent line  90  increases, it is sometimes impossible to adjust and restore the temperature of the processing solution in the processing bath  30 . In this case, the processed semiconductor substrate must be handled as a defective product or processed again after the filter is replaced.  
         [0068]     In this embodiment, therefore, the upper limit of the processing time is selected within the range in which the temperature of the processing solution in the processing bath  30  can be adjusted. If the corrected processing time exceeds this upper limit, the operator is notified and promoted to replace or clean the filter  80 . In this manner, it is possible to avoid an event in which clogging of the filter  80  worsens to make the adjustment of the temperature of the processing solution in the processing bath  30  impossible.  
       (2) Second Embodiment  
       [0069]      FIG. 7  shows semiconductor substrate processing sequence RT 20  according to the second embodiment.  FIG. 8  shows temperature change data of a processing solution in a processing bath  30  after semiconductor substrates  20  are loaded into the processing bath  30 , for each of a predetermined filter, e.g., a new filter and a filter currently being used. When semiconductor substrate processing sequence RT 20  starts in  FIG. 7 , semiconductor substrates  20  are loaded into the processing bath  30  in step SP 110 . Subsequently, in step SP 120 , a controller  100  measures time t 20  at which the temperature of the processing solution in the processing bath  30  restores to T 10 .  
         [0070]     In step SP 130 , the controller  100  reads out, from a storage unit  110 , time t 30  at which the temperature of the processing solution in the processing bath  30  restores to T 10  when a new filter is used, and calculates a time difference d 20  between readout time t 30  and time t 20  at which the temperature of the processing solution in the processing bath  30  currently being used restores to T 10 .  
         [0071]     Then, assuming that the slope when the temperature of the processing solution in the processing bath  30  currently being used is the same as the slope when the temperature of the processing solution in the processing bath  30  restores when a new filter is used, the controller  100  calculates, on the basis of the calculated time difference d 20 , temperature change data of the processing solution in the processing bath  30  currently being used.  
         [0072]     After that, in the same manner as in the first embodiment, the controller  100  calculates an additional time, corrects the processing time, and checks in step SP 140  whether the corrected processing time is equal to or smaller than a predetermined upper limit.  
         [0073]     If YES in step SP 140 , the controller  100  advances to step SP 150  to continue the etching process, and then advances to step SP 160  to terminate processing sequence RT 20 .  
         [0074]     On the other hand, if NO in step SP 140 , the controller  100  advances to step SP 170  to activate an alarm  120  while performing the etching process, thereby notifying the operator that a filter  80  requires replacement. After that, the controller  100  advances to step SP 160  to terminate processing sequence RT 20 .  
         [0075]     In this embodiment as described above, etching can be reliably performed by correcting the etching time of the semiconductor substrate  20  on the basis of the increase in restoration time of the internal temperature of the processing bath  30 , which is caused by clogging of the filter  80 . Accordingly, the yield can be increased.  
       (3) Third Embodiment  
       [0076]      FIG. 9  shows semiconductor substrate processing sequence RT 30  according to the third embodiment. When semiconductor substrate processing sequence RT 30  starts in  FIG. 9 , in step SP 200 , a counter  130  counts the number of semiconductor substrates  20  to be loaded into a processing bath  30 , and notifies a controller  100  of the number. In step SP 210 , the semiconductor substrates  20  are loaded into the processing bath  30 . In step SP 220 , the controller  100  measures the temperature of a processing solution in the processing bath  30  at a predetermined timing.  
         [0077]     The degree of the temperature fall of the processing solution in the processing bath  30  after semiconductor substrates  20  are loaded into the processing bath  30  changes in accordance with the number of the semiconductor substrates  20  loaded. That is, as shown in  FIG. 10 , as the number of semiconductor substrates  20  loaded increases, the degree of the fall of the temperature of the processing solution in the processing bath  30  increases. For example, the temperature falls by about 4° C. when the number of semiconductor substrates  20  loaded is  50 .  
         [0078]     In this embodiment, therefore, a storage unit  110  prestores temperature change data of the processing solution in the processing bath  30  after semiconductor substrates  20  are loaded when a predetermined filter, e.g., a new filter is used, for each number of semiconductor substrates  20  loaded.  
         [0079]     In step SP 230 , the controller  100  reads out, from the storage unit  110 , temperature change data corresponding to the number of the semiconductor substrates  20  loaded, and calculates a temperature difference, at the predetermined timing, between the temperature of the processing solution in the processing bath  30  when a new filter is used and the temperature of the processing solution in the processing bath  30  currently being used.  
         [0080]     In this case, the controller  100  may also calculate a time difference between the time before the temperature of the processing solution in the processing bath  30  currently being used restores a predetermined temperature and the time before the temperature of the processing solution in the processing bath  30  restores the predetermined temperature when a new filter is used.  
         [0081]     After that, in the same manner as in the first embodiment, the controller  100  calculates an additional time, corrects the processing time, and advances to step SP 240  to check whether the corrected processing time is equal to or smaller than a predetermined upper limit. Then, the controller  100  performs a processing corresponding to the determination result in step SP 250  or SP 270 , and advances to step SP 260  to terminate processing sequence RT 30 .  
         [0082]     In this embodiment as described above, etching can be reliably performed by correcting the etching time of semiconductor substrates  20  in accordance with the fall of the temperature of the processing solution in the processing bath  30 , which is caused by clogging of a filter  80  and by the number of the semiconductor substrates  20  loaded. Accordingly, the yield can be increased.  
         [0083]     The semiconductor substrate processing apparatuses and semiconductor device fabrication methods of the above embodiments can reliably perform etching and increase the yield.  
       (4) Other Embodiments  
       [0084]     Note that the above embodiments are merely examples and do not limit the present invention. For example, the temperature change data is calculated by assuming that the slope when the temperature of the processing solution in the processing bath  30  currently being used restores is the same as the slope when the temperature of the processing solution in the processing bath  30  restores when a new filter is used. However, it is also possible to assume that these two slopes are different. In this case, the temperature change data of the processing solution in the processing bath  30  currently being used can be calculated by calculating temperature differences at two different timings.  
         [0085]     Also, if the temperature of the processing solution in the processing bath  30  does not largely fall immediately after semiconductor substrates  20  are loaded into the processing bath  30 , and the slope at which the temperature of the processing solution in the processing bath  30  currently being used restores is not linear but rises and falls little by little, the temperature change data of the processing solution in the processing bath  30  currently being used can be calculated by calculating temperature differences at three or more different timings.