US20050081886A1 - Wafer cleaning method and equipment - Google Patents
Wafer cleaning method and equipment Download PDFInfo
- Publication number
- US20050081886A1 US20050081886A1 US10/932,006 US93200604A US2005081886A1 US 20050081886 A1 US20050081886 A1 US 20050081886A1 US 93200604 A US93200604 A US 93200604A US 2005081886 A1 US2005081886 A1 US 2005081886A1
- Authority
- US
- United States
- Prior art keywords
- cleaning
- wafer
- solution
- resistivity
- value
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/304—Mechanical treatment, e.g. grinding, polishing, cutting
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
- H01L21/67005—Apparatus not specifically provided for elsewhere
- H01L21/67011—Apparatus for manufacture or treatment
- H01L21/67017—Apparatus for fluid treatment
- H01L21/67028—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like
- H01L21/6704—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like for wet cleaning or washing
- H01L21/67057—Apparatus for fluid treatment for cleaning followed by drying, rinsing, stripping, blasting or the like for wet cleaning or washing with the semiconductor substrates being dipped in baths or vessels
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/06—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a liquid
Definitions
- the present invention relates to a wafer cleaning process. More particularly, the invention relates to a wafer cleaning method and equipment in a final wafer cleaning process using cleaning water after cleaning chemical a wafer with a chemical solution.
- a wafer is cleaned with a chemical solution.
- Common chemical solutions used for cleaning a wafer include a mixed water solution of hydrochloric acid and hydrogen peroxide, a mixed water solution of ammonia and hydrogen peroxide, and a mixed solution of dense sulfuric acid and hydrogen peroxide.
- a water solution of hydrofluoric acid is also commonly used.
- a mixed water solution of hydrofluoric acid and ozone water or a mixed water solution of hydrofluoric acid and hydrogen peroxide is also used.
- a wafer cleaning method is roughly divided into the following two types.
- One is a method of immersing a plurality of wafers in a processing tank filled with a chemical solution. This is so-called a batch cleaning method.
- the other is a method of supplying a chemical solution to the surfaces of a plurality of wafers by rotating one by one. This is so-called a single wafer cleaning method.
- the end of rinsing (the rinsing time) is generally determined based on the density of a specified ion included in the chemical solution existing in the liquid in the processing tank. Concretely, measure the ion density of a chemical solution by monitoring the resistivity or the reciprocal number thereof, conductivity of the solution flowed out from the processing tank during the final rinse step. When the measured ion density of a chemical solution is equal to or less than the value indicating that the chemical solution adhered to a wafer is sufficiently eliminated, the final rinse step is regarded completed.
- the value indicating that the chemical solution adhered to a wafer is sufficiently eliminated is generally determined by experiments.
- the technique using the resistivity end point, as well as the method of deciding the rise time is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-1138.
- a wafer cleaning method comprising: supplying a cleaning water to a wafer cleaned with a chemical solution; measuring the resistivity of a solution including the chemical solution and cleaning water, and differentiating the measured value with respect to time; and cleaning the wafer continuously with the cleaning water until the time differential value of the resistivity becomes equal to or less than a preset value and is held at that values for preset time.
- a wafer cleaning method comprising: supplying a cleaning water to a wafer cleaned with a chemical solution; measuring the conductivity of a solution including the chemical solution and cleaning water, and differentiating the measured value with respect to time; and cleaning the wafer continuously with the cleaning water until the time differential value of the conductivity becomes equal to or more than a preset value and is held at that values for preset time.
- a wafer cleaning equipment comprising: a cleaning tank which contains a wafer cleaned with a chemical solution; a cleaning water supplying unit which supplies the cleaning tank with a cleaning water to clean the wafer; an electric characteristic measuring unit which measure the resistivity of a solution including the cleaning water and the chemical solution used for cleaning the wafer; an arithmetic unit which differentiates with respect to time the resistivity of the solution measured with the electric characteristic measuring unit; and a control unit which operates the cleaning water supplying unit and supplies the cleaning water to the cleaning tank, until the time differential value of the resistivity calculated by the arithmetic unit becomes equal to or less than a preset value and is held at that value for preset time.
- a wafer cleaning equipment comprising: a cleaning tank which contains a wafer cleaned with a chemical solution; a cleaning water supplying unit which supplies the cleaning tank with a cleaning water to clean the wafer; an electric characteristic measuring unit which measures the conductivity of a solution including the cleaning water and the chemical solution used for cleaning the wafer; an arithmetic unit which differentiates with respect to time the conductivity of the solution measured with the electric characteristic measuring unit; and a control unit which operates the cleaning water supplying unit and supplies the cleaning water to the cleaning tank, until the time differential value of the conductivity calculated by the arithmetic unit becomes equal to or more than a preset value and is held at that value for preset time.
- FIG. 1 is a flowchart showing a wafer cleaning method according to a first embodiment
- FIG. 2 is a simplified block diagram showing a wafer cleaning equipment according to a first embodiment
- FIG. 3 is a graph showing the relationship between the time of cleaning the wafer according to a first embodiment and the time differential values of the resistivity for each kind of cleaning chemical solutions and the number of wafers to be cleaned;
- FIG. 4 is a simplified block diagram showing a wafer cleaning equipment according to a second embodiment
- FIGS. 5A and 5B are sectional views showing a simplified wafer cleaning equipment according to a prior art
- FIG. 6 is a graph showing the relationship between the time of cleaning a wafer and the resistivity according to a prior art.
- FIG. 7 is a graph showing the relationship between the time of cleaning a wafer and the resistivity according to a prior art for each kind of cleaning chemical solutions and the number of wafers to be cleaned.
- a method of measuring the resistivity of a common conventional solution uses two types of cleaning equipments 101 and 102 shown in FIG. 5A and FIG. 5B .
- a resistivity measuring cell (a resistivity meter) 106 which monitors the resistivity of the solution 105 , is provided in proximity to an upper opening 104 a of a tank 104 containing a wafer 103 .
- the resistivity measuring cell 106 measures the resistivity of the solution 105 overflowed from the upper opening 104 a.
- a port 108 is provided at the middle of the tank 107 to extract the solution 105 from the tank 107
- the resistivity measuring cell 106 is provided at the port 108 .
- the resistivity measuring cell 106 measures the resistivity of the sampling solution 105 extracted from the tank 107 through the port 108 .
- FIG. 6 shows an example of the changes with time of the resistivity of the solution 105 measured by the method shown in FIG. 5A .
- measure the changes with time of the resistivity at least once and obtain the data as shown in FIG. 6 .
- the chemical solution in the tank 104 is regarded as almost completely replaced by pure water.
- the final rising time is set to 10 minutes.
- the resistivity of the solution 105 is substantially stabilized at approximately 16 M ⁇ cm about 2 minutes after stop of rising.
- the chemical solution in the tank 104 is regarded as almost completely replaced by pure water and the chemical solution adhered to the wafer 103 is regarded sufficiently eliminated.
- the rinsing time is usually set with sufficient allowance as described above.
- the rinsing time has been reduced by decreasing the pure water volume in cleaning a wafer, or by reducing the time required by cleaning a wafer.
- the rinsing is finished at the point when the resistivity reaches a preset value.
- the resistivity of the solution 105 rises equal to or more than 16 M ⁇ cm
- the wafer rinsing is regarded as finished. Therefore, in this case, the end of rinsing is set at the point when the resistivity of the solution 105 reaches the point A indicated by the solid arrow mark in FIG. 6 .
- This embodiment has been made to solve the above problems. It is an object of the embodiment to provide a wafer cleaning method and equipment which can clean a wafer to the proper clean state while increasing the cleaning efficiency regardless of the number of wafers to be cleaned, and the kinds and density of chemical solution. It is another object of the embodiment is to provide a wafer which is completely cleaned to the proper clean state with no chemical solution remained, and a semiconductor device which is provided with such a clean wafer and improved in the performance, quality, reliability and yield.
- the first embodiment of the invention will be explained in details with reference to FIG. 1 - FIG. 3 .
- FIG. 1 is a flowchart showing a wafer cleaning method according to this embodiment.
- FIG. 2 is a simplified block diagram showing a wafer cleaning (equipment according to this embodiment.
- FIG. 3 is a graph showing the relationship between the rinsing (cleaning) time of the wafer according to this embodiment and the time differential value of the resistivity for each kind of cleaning chemical solution and the number of wafers.
- This embodiment defines the end time of the final rinsing after cleaning a wafer with a chemical solution, to reduce the volume of cleaning water and net rinsing time (Row Process Time: RPT) in the wafer cleaning process, and cleans a wafer to the proper clean state.
- RPT Low Process Time
- the pure water resistivity (conductivity) of the solution including the cleaning water is continuously monitored during the final rinsing in order to define the end of final wafer rinsing.
- the obtained resistivity data is differentiated to obtain the change in the inclination with time.
- the end point of rinsing is determined based on the inclination change with time and the continued final rinsing time.
- the method reduces the cleaning water volume and RPT in this way, and cleans a wafer to the proper clean state. Detailed explanation will be given below.
- the cleaning equipment 1 has a cleaning tank 3 which contains one or more wafers 2 cleaned with a chemical solution.
- the cleaning tank 3 may be either a processing tank dedicated to rinsing the wafer 2 with adhesion of a cleaning chemical solution, or a processing tank provided with a device to switch the solution supplied to the wafer 2 from a chemical solution to cleaning water after the wafer 2 is cleaned with a chemical solution.
- the bottom of the cleaning tank 3 is connected to a water supply pipe 4 which supplies a cleaning water used for rinsing the wafer 2 to the inside of the cleaning tank 3 .
- a cleaning water supply valve 5 is provided as a cleaning water supply device to supply a cleaning water to the inside of the cleaning tank 3 .
- ultra-pure water is used as a cleaning water. Therefore, the cleaning water supply valve can also be called an ultra-pure water supply valve 5 .
- the cleaning tank 3 has an opening 3 a at the top.
- the chemical solution adhered to the wafer 2 and the solution 6 including the pure water supplied to the inside of the cleaning tank 3 overflow from the inside to outside of the cleaning tank through the opening 3 a.
- a drain port 7 Provided near the opening 3 a of the cleaning tank 3 is a drain port 7 to drain the solution 6 to the outside of the cleaning tank 3 after once receiving the solution 6 overflowed from the inside of the cleaning tank 3 .
- An electric character measuring unit 8 which measures the resistivity or conductivity of the solution 6 is provided contacting the solution 6 in the drain port 7 .
- the resistivity and conductivity are reciprocal to each other. Therefore, measurement of at least one of the resistivity and conductivity of the solution 6 corresponds to measurement of the other.
- the resistivity of the solution 6 is to be measured with the electric characteristic measuring unit 8 . Therefore, in this embodiment, a resistivity meter (resistivity measuring cell) 8 is used as an electric characteristic measuring unit.
- the resistivity measuring cell 8 measures, as the resistivity of the solution 6 , the resistivity of the overflowed water 6 a drained from the inside to outside of the cleaning tank 3 through the opening 3 a at the top of the cleaning tank 3 .
- the resistivity of the solution 6 measured with the resistivity measuring cell 8 is sent to a resistivity measuring circuit 9 as an electric signal.
- the resistivity measuring circuit 9 measures the resistivity of the solution 6 that is measured with the resistivity measuring cell 8 , based on the electric signal output from the resistivity measuring cell 8 .
- the resistivity of the solution 6 measured with the resistivity measuring circuit 9 is sent from the resistivity measuring circuit 9 to an A/D converter 10 as an electric signal.
- the resistivity measuring circuit 9 is set to output the measured resistivity of the solution 6 as an analog signal.
- An arithmetic control circuit 11 is set to receive a digital signal. Therefore, in this embodiment, the A/D converter 10 is set to convert an analog signal output from the resistivity measuring circuit 9 to a digital signal, and send this digital signal to the arithmetic control circuit 11 .
- the resistivity of the solution 6 converted from analog to a digital signal with the A/D converter 10 is sent to the arithmetic control unit 11 .
- the arithmetic control unit 11 obtains the resistivity of the solution 6 measured with the resistivity measuring circuit 9 at every preset time, holds it for preset time, differentiates the obtained measured value with respect to time, and controls open/close of the ultra-pure water supply valve 5 .
- the arithmetic control unit 11 consists of an arithmetic unit (arithmetic section, arithmetic circuit) which differentiates with respect to time the resistivity of the solution 6 measured with the resistivity measuring cell 8 , and a control unit (control section, control circuit) which is integrated with the arithmetic unit, and supplies a cleaning water to the cleaning tank 3 by operating the ultra-pure water supply valve 5 until the differential value calculated by the arithmetic unit becomes equal to or less than a preset value and is held at that value for preset time.
- arithmetic unit arithmetic section, arithmetic circuit
- the cleaning tank 3 , water supply pipe 4 and ultra-pure water supply valve 5 constitute a cleaning system 12 of the cleaning equipment 1 .
- the resistivity measuring cell 8 , resistivity measuring circuit 9 , A/D converter 10 and arithmetic control unit 11 constitute a measuring system 13 of the cleaning equipment 1 .
- the wafer cleaning method of this embodiment is concretely a cleaning method in the final wafer rinsing process, which eliminates stains such as chemical solution adhered to the wafer 2 cleaned with a chemical solution, and clean the wafer 2 to the proper clean state.
- the wafer cleaning method of this embodiment measures the resistivity of the chemical solution used for cleaning the wafer 2 and the solution 6 including the cleaning water used for rinsing the wafer 2 cleaned with the chemical solution, and differentiates the measured value with respect to time.
- the wafer 2 is continuously rinsed until the differentiated value becomes equal to or less than a preset value and held at that value for preset time.
- the wafer 2 is rinsed by using the wafer cleaning equipment 1 . Detailed explanation will be given below.
- the ultra-pure water supply valve 5 by sending a valve control signal to open the ultra-pure water supply valve 5 from the arithmetic control unit 11 to the ultra-pure water supply valve 5 .
- the ultra-pure water is supplied to the inside of the cleaning tank 3 , and the wafer 2 is begun to be cleaned with ultra-pure water (rinsed with ultra-pure water).
- the resistivity measuring cell 8 starts measuring the resistivity of the solution 6 (overflowed water 6 a) drained from the cleaning tank 3 .
- the resistivity measuring circuit 9 measures continuously the value (detected value) measured with the resistivity measuring cell 8 .
- the A/D converter 10 converts continuously the resistivity value outputted as an analog signal (analog value) from the resistivity measuring circuit 9 , into a digital signal (digital value).
- the A/D converter 10 outputs the digital signal to the arithmetic control unit 11 .
- the arithmetic control unit 11 receives the digital signal output from the A/D converter 10 , and performs a predetermined processing based on the digital signal.
- the predetermined processing performed by the arithmetic control unit 11 is indicated by a dashed line in FIG. 1 . Detailed explanation will be given below.
- the arithmetic control unit 11 calculates the inclination (change rate), or the differential value of the resistivity with respect to the holding time, based on the held number of resistivity values and the holding time.
- the differential value can be calculated after smoothing the resistivity values, if necessary.
- the differential value of the resistivity corresponds to the inclination of the resistivity at a predetermined time. Thus, it is also permitted to obtain the inclination by smoothing real time the predetermined number of held resistivity data before holding the resistivity data held for obtaining the differential value.
- a method and degree of smoothing is not specified as long as noises in the cleaning system 12 and measuring system 13 of the cleaning equipment 1 are taken into account.
- a weighted average (a weighted smoothing), a weighted mean, or Savizky-Golay method is permitted.
- the arithmetic control unit 11 determines by the arithmetic control unit 11 whether the differential value obtained by the arithmetic control unit 11 is equal to or less than a preset value and held at that value for preset time.
- the stains such as a chemical solution adhered to the wafer 2 is regarded as completely eliminated, and the wafer 2 is regarded as cleaned to the proper clean state.
- the arithmetic control unit 11 is set to determine whether the differential value is equal to or less than 0.05 M ⁇ cm/sec and held at that value for equal to or more than 5 seconds after passing the maximum value.
- the wafer 2 When the differential value is equal to or less than 0.05 M ⁇ cm/sec and held at that value for equal to or more than 5 seconds after passing the maximum value, the wafer 2 is regarded as cleaned to the proper clean state, and rinsing the wafer 2 with ultra-pure water is finished.
- the above differential value measuring condition is set to an appropriate value according to the cleanness demanded for the wafer 2 .
- the value of the condition is previously obtained by experiments.
- the ideal timing to finish the rinsing with ultra-pure water is a point when the differential value of the resistivity reaches 0.00 M ⁇ cm/sec, or the inclination of the resistivity with respect to time becomes zero.
- noises electric signal noises
- the differential value of the resistivity can not practically reach 0.00 M ⁇ cm/sec.
- the wafer 2 can be cleaned to the proper clean state regardless of the number of wafers and the kinds and density of chemical solution used for cleaning. Therefore, it is set in this embodiment that if the differential value of the resistivity is held equal to or less than 0.05 M ⁇ cm/sec for at least 5 seconds after passing the maximum value, the rinsing the wafer 2 with ultra-pure water is finished.
- the arithmetic control unit 11 determines that the differential value is not held equal to or less than 0.05 M ⁇ cm/sec for equal to or more than 5 seconds after passing the maximum value, rinsing the wafer 2 with ultra-pure water is continued and the arithmetic control unit 11 holds the resistivity data and repeats differentiation of the resistivity based on that data, until the differential value meets that condition. If the data is held repeatedly and the data is held for a long time, the number of held data is increased and the load to the arithmetic control unit 11 is increased. To avoid this, it is permitted to set to abandon the data after the preset time passes.
- the arithmetic control unit 11 determines that the differential value is held equal to or less than 0.05 M ⁇ cm/sec for equal to or more than 5 seconds after passing the maximum, the arithmetic control unit 11 sends a valve control signal which closes the ultra-pure water supply valve 5 to the ultra-pure water supply valve 5 , and closes the ultra-pure water supply valve 5 .
- the arithmetic control unit 11 sends a valve control signal which closes the ultra-pure water supply valve 5 to the ultra-pure water supply valve 5 , and closes the ultra-pure water supply valve 5 .
- FIG. 3 is a graph showing that the resistivity data is obtained at every second and held for a second in the cleaning method of one example of this embodiment, and the differential value of the resistivity with respect to the changes with time is calculated based on the held data.
- differentiation is performed by obtaining the resistivity data at about every second and holding it for a second, but the data holding time, differential value calculating interval and differential value holding time are not limited to about 1 second. They may be the time sufficiently short against the net time (RPT) required by the rinsing of the wafer 2 with ultra-pure water.
- RPT net time
- HF200/lwf in FIG. 3 indicates the ultra-pure water rinsing (final rinsing) of one wafer 2 that is cleaned by using the chemical solution composed of pure water and water solution of 50% hydrofluoric acid, and diluted to have an about 1:200 volume ratio of the water solution of 50% hydrofluoric acid to pure water.
- the solid line in the graph of FIG. 3 indicates the changes of the time differential value of the resistivity with respect to the ultra-pure water rinsing time in HF200/lwf.
- HF500/lwf indicates the ultra-pure water rinsing of one wafer 2 that is cleaned by using the chemical solution composed of pure water and water solution of 50% hydrofluoric acid, and diluted to have an about 1:500 volume ratio of the water solution of 50% hydrofluoric acid to pure water.
- the dashed line in the graph of FIG. 3 indicates the changes in the time differential value of the resistivity with respect to the ultra-pure water rinsing time in HF500/lwf.
- HF200/44wf indicates the ultra-pure water rinsing of 44 wafers 2 that are cleaned by using the chemical solution composed of pure water and water solution of 50% hydrofluoric acid, and diluted to have an about 1:200 volume ratio of the water solution of 50% hydrofluoric acid to pure water.
- the chain line in the graph of FIG. 3 indicates the changes in the time differential value of the resistivity with respect to the ultra-pure water rinsing time in HF200/44wf.
- HF500/44wf indicates the ultra-pure water rinsing of 44 wafers 2 that are cleaned by using the chemical solution composed of pure water and water solution of 50% hydrofluoric acid, and diluted to have an about 1:500 volume ratio of the water solution of 50% hydrofluoric acid to pure water.
- the chain double-dashed line in the graph of FIG. 3 indicates the changes in the time differential value of the resistivity with respect to the ultra-pure water rinsing time in HF500/44wf.
- the differential value (inclination) of resistivity generally shows a curve projecting upward, descending after once rising regardless of the number of wafers 2 and the kinds and density of the cleaning chemical solution. Even if the rinsing time is extended under each of the four conditions, and the differential value 0 of resistivity is not held various due to noise components. Among the four conditions, the peak (maximum) position of differential value and sweep time are largely different. According to the graph of FIG. 3 , the differential value of resistivity can take the same value at different points except the peak. FIG. 3 indicates that the resistivity greatly changes until the differential value reaches its peak. While the resistivity is so changing, the chemical solution is substituted by ultra-pure water.
- the differential value of resistivity at which the wafer 2 is regarded as cleaned to the proper clean state may be set to an appropriate value according to the cleanness demanded for the wafer 2 as long as it has once reached the peak. As the above differential value is set smaller, the cleanness of wafer 2 is increased, but the time required to finish the ultra-pure water rinsing becomes long. If the rinsing time with ultra-pure water is long, the row process time (RPT) of rinsing with ultra-pure water becomes long, decreasing the productivity, and increasing the production cost with the increased volume of ultra-pure water.
- RPT row process time
- the part where the differential value sweeps indicates the state that the maximum and minimum differential values are repeated due to the various noise components. If the value that the wafer 2 is regarded as cleaned to the proper clean state is set small to the state that the differential value sweeps as shown in FIG. 3 , it becomes very difficult to hold the value for equal to or more than 5 seconds even if the value is equal to or less than 0.05 M ⁇ cm/sec. Further, it may become impossible to prolong the wafer 2 cleaning time, and finish rinsing the wafer 2 with ultra-pure water. Therefore, it is necessary to set the differential value of resistivity at white the wafer 2 is regarded as cleaned to the proper clean state to the value that the wafer 2 cleaning time becomes the shortest within the range satisfying the cleanness demanded for the wafer 2 .
- the wafer 2 when the differential value of resistivity is held equal to or less than 0.05 M ⁇ cm/sec for equal to or more than 5 seconds after passing the maximum value for all the four kinds, the wafer 2 is regarded as cleaned to the proper clean state, and the rinsing of the wafer 2 is finished.
- the final rinsing of the wafer 2 can be finished in substantially the same state, even if the resistivity of the solution 6 in the cleaning tank 3 is different for the processing conditions in cleaning with a chemical solution.
- stains such as chemical solution adhered to the wafer 2 can be sufficiently eliminated and the wafer 2 can be cleaned to substantially the same clean state in various conditions, regardless of the number of wafers 2 to be cleaned, the kinds and density of cleaning chemical solution, or the resistivity of the solution 6 in the cleaning tank 3 .
- the wafer 2 can be cleaned to the proper clean state and the final rinsing can be finished within about 7 to 8 minutes for all of the four kinds of cleaning solution.
- FIG. 7 is a graph showing the relationship between the wafer rinsing time (cleaning time) and resistivity according to a prior art, with respect to the kinds of cleaning chemical solution and the number of wafers to be cleaned.
- the graph of FIG. 7 indicates the resistivity measured by the wafer cleaning method and the cleaning equipment 101 according to the prior art shown in FIG. 5A , under the four conditions of HF200/lwf, HF500/lwf, HF200/44wf and HF500/44wf, as in the embodiment described above.
- the 7 indicates the changes in the resistivity with respect to the ultra-pure water rinsing time in HF200/lwf, or the resistivity recovery time.
- the dashed line in the graph of FIG. 7 indicates the changes in the resistivity with respect to the ultra-pure water rinsing time in HF500/lwf, or the resistivity recovery time.
- the chain line in the graph of FIG. 7 indicates the changes in the resistivity with respect to the ultra-pure water rinsing time in HF200/44wf, or the resistivity recovery time.
- the chain double-dashed line in the graph of FIG. 7 indicates the changes in the resistivity with respect to the ultra-pure water rinsing time in HF500/44wf, or the resistivity recovery time.
- whether a wafer is cleaned to the proper clean state is determined by whether the resistivity of solution reaches a preset value.
- a wafer is regarded as cleaned to the proper clean state.
- the ultra-pure water rinsing time is different according to the density of chemical solution (hydrofluoric acid). The resistivity of the solution reaches 16 M ⁇ cm in both conditions.
- the end time of final wafer rinsing can be determined (confirmed) also in the above setting.
- the ultra-pure water rinsing time is different according to the density of chemical solution, and the resistivity of the solution does not reach 16 M ⁇ cm. Therefore, in HF200/lwf and HF500/lwf, the end time of final wafer rinsing can not be determined (confirmed) in the above setting.
- the resistivity of the solution at which a wafer is regarded as cleaned to the proper clean state is set to 13 M ⁇ , for example, so as to determine the end time of final wafer rinsing even in HF200/lwf and HF500/lwf. Then, the final wafer rinsing can be finished when the resistivity of the solution reaches 13 M ⁇ cm I HF200/lwf and HF500/lwf. However, in HF200/44wf and HF500/44wf, when the resistivity of the solution reaches 13 M ⁇ cm, the ion contained in the chemical solution remains in the solution in the cleaning tank.
- the wafer rinsing time is set long including a sufficient allowance considering variations of the rinsing time due to the cleaning conditions, so as to clean a wafer to the sufficiently cleaned state, regardless of the various conditions such as the number of wafers, the kinds and density of cleaning chemical solution, and the resistivity of the solution in the cleaning tank.
- the rinsing time is generally set to about 10 minutes.
- the wafer 2 can be cleaned to the proper clan state in 7-8 minutes in all of the four conditions, and the final rinsing can be finished.
- the prior art can reduce the rinsing time by about 200 seconds by applying this embodiment to the cleaning tank that requires about 600 seconds (10 minutes) for rinsing a wafer.
- the flow rate per unit time of ultra-pure water supplied to the cleaning tank is set to about 20L/min, the ultra-pure water can be decreased by about 67 liters.
- the rinsing time is about 70 seconds different between HF200/lwf with the longest rinsing time and HF500/44wf with the shortest rinsing time in the above example.
- the rinsing time can be decreased by about 70 seconds in HF500/44wf compared with HF200/lwf.
- the flow rate per unit time of ultra-pure water supplied to the cleaning tank 3 is set to about 20L/min, the ultra-pure water can be decreased by about 23 liters.
- the rinsing time is set to about 600 seconds for both HF200/lef and HF500/44wf, as described above. Therefore, in the prior art, about 70 seconds of rinsing time and about 23 liters of ultra-pure water are wasted in HF500/44wf.
- the resistivity recovery time in the final rinsing of the wafer 2 is easy to be influenced by the number of wafers 2 , and the kinds and density of chemical solution.
- the resistivity recovery time is not even. Therefore, in the prior art, the wafer rinsing time is determined considering the longest rinsing time. Contrarily, in this embodiment, even if the wafer 2 cleaning condition is different, the wafer 2 can be cleaned to the same state while controlling a waste of ultra-pure water, and the wafer rinsing can be finished. Namely, according to this embodiment, the wafer 2 can be cleaned to substantially the same proper clean state regardless of the wafer 2 cleaning conditions. Compared with the prior art, this embodiment cal also improve the wafer 2 cleaning efficiency by decreasing the volume of ultra-pure water and reducing the row process time (RPT) of the wafer 2 .
- RPT row process time
- this embodiment uses the time differential value of resistivity. This corresponds to using the replacement of chemical solution by ultra-pure water. Therefore, this is difficult to be influenced by a final resistivity value attained by the resistivity of the solution 6 in the cleaning tank 3 when the wafer 2 is cleaned with ultra-pure water. Namely, this embodiment is little influenced by the final resistivity difference caused by the different number of wafers 2 to be cleaned, and the lowered final resistivity caused by deterioration of the measuring accuracy of a resistivity meter.
- the rinsing of wafer 2 is finished at the point when the time differential values of the resistivity of the chemical solution used for cleaning the wafer 2 and the solution 6 including the cleaning water used for rinsing the cleaned wafer 2 are equal to or less than preset values, and held at that values for preset time. This makes it possible to clean the wafer 2 to the proper clean state while improving the wafer 2 cleaning efficiency, regardless of the number of wafers 2 to be cleaned and the kinds and density of the chemical solution used for cleaning.
- the wafer 2 according to this embodiment has been rinsed by the wafer cleaning method or the wafer cleaning equipment 1 according to this embodiment. Therefore, the wafer 2 of this embodiment has been cleaned to the proper clean state with stains of chemical solution removed sufficiently. Further, the wafer 2 of this embodiment provides high yield (production efficiency), and reduces the production cost.
- the semiconductor device according to this embodiment has the wafer 2 according to this embodiment. Therefore, the semiconductor device of this embodiment is improved in the performance, quality, reliability and yield. Further, the semiconductor device of this embodiment provides high production efficiency, and reduces the production cost.
- FIG. 4 is a simplified block diagram showing a wafer cleaning equipment according to this embodiment.
- the same reference numerals are given to the same components as in the first embodiment, and a detailed explanation will be omitted.
- a resistivity meter resistivity measuring cell
- a take-out port (solution extraction port) 23 is provided to take out the solution 6 from the cleaning tank 22 without exposing to the air.
- a resistivity meter (resistivity measuring cell) 8 is provided contacting the solution 6 b taken out from the cleaning tank 3 through the solution extraction port 23 . Namely, in this embodiment, the resistivity measuring cell 8 is set to measure the resistivity of the solution 6 b without contacting the air.
- the wafer cleaning method, wafer, and semiconductor device according to this embodiment are the same as those of the first embodiment, and explanation will be omitted.
- the second embodiment can provide the same effects as the first embodiment.
- the resistivity measuring cell 8 measures the resistivity of the solution 6 b without contacting the air. Therefore, the measured value is difficult to be influenced by the carbonic acid gas or the like in the air dissolved in the solution 6 through an upper opening 22 a of the cleaning tank 22 as a result of so-called air involving. Namely, the measured value of the resistivity in this embodiment is difficult to be influenced by the noises occurred in a cleaning system 24 of the cleaning equipment 21 comprising the cleaning tank 22 , water supply pipe 4 , and ultra-pure water supply valve 5 .
- this embodiment can measure the resistivity of the solution 6 with a high accuracy, and clean the wafer 2 to more clean state. Namely, stains such as chemical solution adhered to the wafer 2 of this embodiment are sufficiently eliminated, and the wafer 2 is cleaned to more proper clean state. Further, though not shown, the semiconductor device of this embodiment is improved in the performance, quality, reliability and yield.
- the cleaning method and equipment according to the present invention are not limited to the first and second embodiments.
- the invention may be embodied in other specific forms without departing from its spirit or essential characteristics modifications.
- the configurations and processes of the embodiments may be partially modified, or combined appropriately.
- the A/D converter 10 is provided between the resistivity measuring circuit 9 and arithmetic control circuit 11 in the first and second embodiments, but the A/D converter 10 is not always necessary. If the resistivity measuring circuit 9 and arithmetic control circuit 11 are set to process the same form analog or digital signal, the A/D converter 10 is unnecessary.
- the arithmetic section (arithmetic circuit) and control section (control circuit) of the arithmetic control unit 11 are constructed as one body, but they may not necessarily be one body.
- the arithmetic section and control section of the arithmetic control unit 11 may be configured as separate independent units.
- the resistivity measuring cell 8 is not necessary provided near the upper opening 3 a of the cleaning tank 3 or at the middle of the cleaning tank 2 . If the solution extracted to the resistivity cell 8 is not replaced from a chemical solution to pure water before the atmosphere solution of wafer 2 , the resistivity measuring cell 8 may be provided near the bottom of the cleaning tanks 3 and 22 . In this setting, the measured value of the resistivity of the solution 6 is more difficult to be influenced by the noises occurred in the cleaning systems 12 and 24 caused by the carbonic acid gas dissolved in the solution 6 .
- the cleaning tanks 3 and 22 may be either a so-called batch type capable of cleaning a plurality of wafers 2 at one time, or a single wafer type for cleaning the wafer 2 one by one.
- the cleaning systems 12 and 24 there is carbonic acid gas such as carbon dioxide in the air dissolved in the solution 6 .
- the carbonic acid gas dissolved in the solution 6 affects largely the resistivity even if the dissolved amount is very small.
- the amount of the carbonic acid gas dissolved in the solution 6 is changed by the speed of supplying ultra-pure water to the cleaning tanks 3 and 22 , the speed of draining the solution 6 from the cleaning tanks 3 and 22 , or the changes in the air contact area of the solution 6 by the surface fluctuation of the solution 6 .
- the change rate of the dissolved amount of carbonic acid gas is largely influenced by the shapes of the cleaning tanks 3 and 22 , the sizes of the upper openings 3 a and 22 a, or the installation method and position of the resistivity measuring cell 8 . Therefore, the method of smoothing the resistivity values to eliminate the noises in the cleaning systems 12 and 24 is not limited to the weighted average (the weighted smoothing), a weighted mean, or the Savizky-Golay method. Any method suitable for the noises in the cleaning systems 12 and 24 may be used.
- the differential value of resistivity that the wafer 2 is regarded as cleaned to the proper clean state Is not necessarily limited to 0.05 M ⁇ m/sec. Any value equal to or less than 0.05 M ⁇ cm/sec is usable as a differential value of resistivity that the wafer 2 is regarded as cleaned to the proper clean state.
- the conditions that the wafer 2 is regarded as cleaned to the proper clean state that the differential value of resistivity is equal to or less than 0.05 M ⁇ cm/sec after passing the maximum value and held at that value for equal to or more than 5 seconds but the conditions are not necessarily limited to them.
- the conditions that the wafer 2 is regarded as cleaned to the proper clean state may be determined to appropriate values according to the number of wafers 2 to be cleaned, the sizes of the processing tanks 3 and 22 , the shapes of the openings 3 a and 22 a, or the kinds and density of the chemical solution used for the cleaning with a chemical solution, and other various conditions.
- ultra-pure water as a cleaning water is supplied to the cleaning tanks 2 and 22 from the bottom, but the setting is not limited to this.
- Ultra-pure water may be supplied from the middle of the cleaning tanks 3 and 22 . If the ultra-pure water is exposed to the air when it is supplied to the cleaning tanks 3 and 22 through the upper openings 3 a and 22 a, for example, air involving occurs and the carbonic acid gas or the like in the air is dissolved in the ultra-pure water. The carbonic acid gas or the like dissolved in the ultra-pure water causes a noise component in the cleaning systems 12 and 24 when measuring the resistivity and conductivity of the solution 6 , and the measuring accuracy is lowered.
- the possibility of dissolving carbonic acid gas or the like in the ultra-pure water will be eliminated to almost zero.
- the noise components in the cleaning systems 12 and 24 can be controlled and the accuracy of measuring the resistivity and conductivity of the solution 6 can be improved. Further, the wafer 2 can be cleaned to more clean state while improving the cleaning efficiency.
- the cleaning tank 3 is either a processing tank dedicated to rinsing the wafer 2 with adhesion of a cleaning chemical solution, or a processing tank provided with a device to switch the solution supplied to the wafer 2 from a chemical solution to cleaning water after the wafer 2 is cleaned with a chemical solution.
- the cleaning tanks 3 and 22 as a processing tank dedicated to rinsing, the volume of chemical solution to be eliminated by a cleaning water can be decreased.
- the wafer 2 cleaning efficiency can be improved furthermore.
- the resistivity of the solution 6 is measured by using the resistivity measuring cell 8 , but the measurement is not limited to this. It is allowed to measure the conductivity of the solution 6 instead of the resistivity.
- a conductivity meter may be used instead of the resistivity measuring cell 8 (a resistivity meter) as an electric characteristic measuring unit. Cleaning of the wafer 2 with the cleaning water may be continued until reaching the condition that the time differential value of the conductivity of the solution 6 becomes larger than a preset value and is held at that value for preset time.
- the cleaning of the wafer 2 with the cleaning water may be continued until the time differential value of the conductivity of the solution becomes equal to or more than ⁇ 20 ⁇ S/cm ⁇ sec after passing the minimum value and is held at that value for equal to or more than 5 seconds.
- the time differential value of the conductivity of the solution including the chemical solution used for cleaning a wafer and the cleaning water used for cleaning a wafer are substantially zero at the start of measurement, regardless of the number of wafers to be cleaned and the kinds and density of the chemical solution used for the cleaning.
- the time differential value of the conductivity descends as the measurement time elapses and reaches the peak at preset time. Thereafter, the time differential value of the conductivity ascends as the measurement time elapses and becomes substantially zero. Namely, the value obtained by differentiating the conductivity with respect to time traces a curve projecting downward, regardless of the number of wafers to be cleaned and the kinds and density of the chemical solution used for the cleaning.
- the features of the time differential value of the conductivity Namely, continue cleaning a wafer until the time differential value of the conductivity of cleaning solution becomes larger than a preset value determined based on the experiment data at which a wafer can be cleaned to the proper clean state, and is held at that value for preset time.
- the wafer cleaning with a cleaning water can be finished immediately after a wafer is cleaned to the proper clean state.
- the cleaning water volume used for cleaning a wafer can be decreased, and a wafer can be cleaned to the proper clean state while reducing the wafer cleaning time, regardless of the number of wafers to be cleaned and the kinds and density of the cleaning solution used for the cleaning.
- the time differential value of the conductivity of the solution is not necessarily limited to ⁇ 20 ⁇ S/cm ⁇ sec. Any values equal to or more than ⁇ 20 ⁇ S/cm ⁇ sec may be used as the differential value of the conductivity at which the wafer 2 is regarded as cleaned to the proper clean state.
- the conditions that the wafer 2 is regarded as cleaned to the proper clean state are also not necessarily limited to that the differential value of the conductivity is equal to or more than ⁇ 20 ⁇ S/cm ⁇ sec after passing the minimum value, and is held at that value for equal to or more than 5 seconds.
- the conditions that the wafer 2 is regarded as cleaned to the proper clean state may be determined to an appropriate value according to the number of wafers 2 to be cleaned, the size of the processing tanks 3 and 22 , the shapes of the openings 3 a and 22 a, the kinds and density of the chemical solution used for the cleaning, and other various conditions.
Abstract
Description
- This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-314513, filed Sep. 5, 2003, the entire contents of which are incorporated herein by reference.
- 1. Field of the Invention
- The present invention relates to a wafer cleaning process. More particularly, the invention relates to a wafer cleaning method and equipment in a final wafer cleaning process using cleaning water after cleaning chemical a wafer with a chemical solution.
- 2. Description of the Related Art
- Variety of measures are taken to protect a wafer against contamination during a semiconductor manufacturing process and other unexpected contamination for improving the characteristics and yield of semiconductor elements provided on a wafer. Generally, a wafer is cleaned with a chemical solution. Common chemical solutions used for cleaning a wafer include a mixed water solution of hydrochloric acid and hydrogen peroxide, a mixed water solution of ammonia and hydrogen peroxide, and a mixed solution of dense sulfuric acid and hydrogen peroxide. A water solution of hydrofluoric acid is also commonly used. Recently, a mixed water solution of hydrofluoric acid and ozone water or a mixed water solution of hydrofluoric acid and hydrogen peroxide is also used.
- A wafer cleaning method is roughly divided into the following two types. One is a method of immersing a plurality of wafers in a processing tank filled with a chemical solution. This is so-called a batch cleaning method. The other is a method of supplying a chemical solution to the surfaces of a plurality of wafers by rotating one by one. This is so-called a single wafer cleaning method.
- After the chemical cleaning, eliminate the chemical solution adhered to a wafer by using ultra-pure water, and dry a wafer. Then, go to the next semiconductor manufacturing process. If it is difficult to eliminate the impurities adhered to a wafer with one kind of chemical solution, use two or more kinds of chemical solutions and continue cleaning a wafer using each chemical solution. Insert a rinse step using ultra-pure water into the wafer cleaning process using chemical solutions. At the end of the cleaning process, eliminate sufficiently the chemical solution adhered to a wafer by final rinse with ultra-pure water, and dry a wafer. This final rise with ultra-pure water aims at eliminating sufficiently the chemical solution adhered to a wafer.
- However, it is impossible to know directly the end of the rinsing at which the chemical solution adhered to a wafer is sufficiently eliminated. In the batch cleaning method, the end of rinsing (the rinsing time) is generally determined based on the density of a specified ion included in the chemical solution existing in the liquid in the processing tank. Concretely, measure the ion density of a chemical solution by monitoring the resistivity or the reciprocal number thereof, conductivity of the solution flowed out from the processing tank during the final rinse step. When the measured ion density of a chemical solution is equal to or less than the value indicating that the chemical solution adhered to a wafer is sufficiently eliminated, the final rinse step is regarded completed. The value indicating that the chemical solution adhered to a wafer is sufficiently eliminated is generally determined by experiments. Though, unlike the wafer cleaning method, as a method of controlling the resistivity in an equipment of refining ultra-pure water used for cleaning a wafer, the technique using the resistivity end point, as well as the method of deciding the rise time, is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-1138.
- According to an aspect of the invention, there is provided a wafer cleaning method comprising: supplying a cleaning water to a wafer cleaned with a chemical solution; measuring the resistivity of a solution including the chemical solution and cleaning water, and differentiating the measured value with respect to time; and cleaning the wafer continuously with the cleaning water until the time differential value of the resistivity becomes equal to or less than a preset value and is held at that values for preset time.
- According to another aspect of the invention, there is provided a wafer cleaning method comprising: supplying a cleaning water to a wafer cleaned with a chemical solution; measuring the conductivity of a solution including the chemical solution and cleaning water, and differentiating the measured value with respect to time; and cleaning the wafer continuously with the cleaning water until the time differential value of the conductivity becomes equal to or more than a preset value and is held at that values for preset time.
- According to another aspect of the invention, there is provided a wafer cleaning equipment comprising: a cleaning tank which contains a wafer cleaned with a chemical solution; a cleaning water supplying unit which supplies the cleaning tank with a cleaning water to clean the wafer; an electric characteristic measuring unit which measure the resistivity of a solution including the cleaning water and the chemical solution used for cleaning the wafer; an arithmetic unit which differentiates with respect to time the resistivity of the solution measured with the electric characteristic measuring unit; and a control unit which operates the cleaning water supplying unit and supplies the cleaning water to the cleaning tank, until the time differential value of the resistivity calculated by the arithmetic unit becomes equal to or less than a preset value and is held at that value for preset time.
- According to still another aspect of the invention, there is provided a wafer cleaning equipment comprising: a cleaning tank which contains a wafer cleaned with a chemical solution; a cleaning water supplying unit which supplies the cleaning tank with a cleaning water to clean the wafer; an electric characteristic measuring unit which measures the conductivity of a solution including the cleaning water and the chemical solution used for cleaning the wafer; an arithmetic unit which differentiates with respect to time the conductivity of the solution measured with the electric characteristic measuring unit; and a control unit which operates the cleaning water supplying unit and supplies the cleaning water to the cleaning tank, until the time differential value of the conductivity calculated by the arithmetic unit becomes equal to or more than a preset value and is held at that value for preset time.
-
FIG. 1 is a flowchart showing a wafer cleaning method according to a first embodiment; -
FIG. 2 is a simplified block diagram showing a wafer cleaning equipment according to a first embodiment; -
FIG. 3 is a graph showing the relationship between the time of cleaning the wafer according to a first embodiment and the time differential values of the resistivity for each kind of cleaning chemical solutions and the number of wafers to be cleaned; -
FIG. 4 is a simplified block diagram showing a wafer cleaning equipment according to a second embodiment; -
FIGS. 5A and 5B are sectional views showing a simplified wafer cleaning equipment according to a prior art; -
FIG. 6 is a graph showing the relationship between the time of cleaning a wafer and the resistivity according to a prior art; and -
FIG. 7 is a graph showing the relationship between the time of cleaning a wafer and the resistivity according to a prior art for each kind of cleaning chemical solutions and the number of wafers to be cleaned. - Hereinafter the present invention will be explained in detail according to embodiments shown in the accompanying drawings.
- (1st. Embodiment)
- Before explaining the embodiment, description will be given on a method of measuring the resistivity of a common solution according to a prior as an example comparative to the embodiment, with reference to
FIG. 5A -FIG. 7 . - A method of measuring the resistivity of a common conventional solution uses two types of
cleaning equipments FIG. 5A andFIG. 5B . In the method using thecleaning equipment 101 shown inFIG. 5A , a resistivity measuring cell (a resistivity meter) 106, which monitors the resistivity of thesolution 105, is provided in proximity to anupper opening 104a of atank 104 containing awafer 103. Theresistivity measuring cell 106 measures the resistivity of thesolution 105 overflowed from theupper opening 104a. In the method using thecleaning equipment 102 shown inFIG. 5B , aport 108 is provided at the middle of thetank 107 to extract thesolution 105 from thetank 107, and theresistivity measuring cell 106 is provided at theport 108. Theresistivity measuring cell 106 measures the resistivity of thesampling solution 105 extracted from thetank 107 through theport 108. As thetanks wafer 103 with adhesion of a chemical solution, or a processing tank with a mechanism to replace pure water for the solution supplied to the tank, after thewafer 103 is cleaned with a chemical solution in the tank. -
FIG. 6 shows an example of the changes with time of the resistivity of thesolution 105 measured by the method shown inFIG. 5A . Usually, measure the changes with time of the resistivity at least once and obtain the data as shown inFIG. 6 . If the resistivity rises and becomes stable at a certain value, the chemical solution in thetank 104 is regarded as almost completely replaced by pure water. In the example shown inFIG. 6 , the final rising time is set to 10 minutes. In this case, the resistivity of thesolution 105 is substantially stabilized at approximately 16 MΩcm about 2 minutes after stop of rising. Namely, the chemical solution in thetank 104 is regarded as almost completely replaced by pure water and the chemical solution adhered to thewafer 103 is regarded sufficiently eliminated. The rinsing time is usually set with sufficient allowance as described above. - In recent years, however, semiconductor devices have been marketed at a low price, and mass production of semiconductor devices with reduced costs has been demanded. Thus, the rinsing time has been reduced by decreasing the pure water volume in cleaning a wafer, or by reducing the time required by cleaning a wafer. For example, in the above-mentioned cleaning method of determining the final wafer rinsing time by measuring the resistivity of solution, the rinsing is finished at the point when the resistivity reaches a preset value. In
FIG. 6 , when the resistivity of thesolution 105 rises equal to or more than 16 MΩcm, the wafer rinsing is regarded as finished. Therefore, in this case, the end of rinsing is set at the point when the resistivity of thesolution 105 reaches the point A indicated by the solid arrow mark inFIG. 6 . - In the wafer cleaning method of finishing the rinsing at the point when the resistivity of solution reaches a preset value, there are problems that the rinsing time varies with the kinds and density of solution or the number of wafers to be processed, and the resistivity does not reach a preset value. Thus, it has been practically difficult to use a wafer cleaning equipment which is incorporated with a system adopting the above cleaning method. Particularly, in the method (equipment) shown in
FIG. 5A , so-called air involving occurs, and carbonic acid gas, etc. in the air is easily dissolved in thesolution 105 overflowed from theupper opening 104a of thetank 104. If carbonic acid gas such as carbon dioxide is dissolved in thesolution 105, a noise occurs in the cleaning system of thecleaning equipment 101, and the resistivity of thesolution 105 is lowered. In addition, in the method (equipment 101) shown inFIG. 5A , the area of thesolution 105 contacting the air varies (the surface fluctuates) and the dissolved amount of the carbonic acid gas in thesolution 105 varies easily, the noise in the cleaning system is easy to change. - In the conventional wafer cleaning methods, it is difficult to measure stably and accurately whether the resistivity (conductivity) of solution reaches a preset value. Namely, it is difficult to determine stably and accurately whether a chemical solution or stains adhered to a wafer is completely eliminated and a wafer is cleaned to the proper clean state. It is further difficult to improve the efficiency of cleaning a wafer by decreasing the volume of pure water used for cleaning a wafer, or reducing the cleaning time. If semiconductor elements are mounted on a wafer contaminated by the chemical solution not completely eliminated, the characteristics and yield of the semiconductor elements will be lowered. Namely, a semiconductor device using a contaminated wafer will have low performance, quality, reliability and yield. Such a semiconductor device will also have low production efficiency, and increase production costs.
- This embodiment has been made to solve the above problems. It is an object of the embodiment to provide a wafer cleaning method and equipment which can clean a wafer to the proper clean state while increasing the cleaning efficiency regardless of the number of wafers to be cleaned, and the kinds and density of chemical solution. It is another object of the embodiment is to provide a wafer which is completely cleaned to the proper clean state with no chemical solution remained, and a semiconductor device which is provided with such a clean wafer and improved in the performance, quality, reliability and yield. Hereinafter the first embodiment of the invention will be explained in details with reference to
FIG. 1 -FIG. 3 . -
FIG. 1 is a flowchart showing a wafer cleaning method according to this embodiment.FIG. 2 is a simplified block diagram showing a wafer cleaning (equipment according to this embodiment.FIG. 3 is a graph showing the relationship between the rinsing (cleaning) time of the wafer according to this embodiment and the time differential value of the resistivity for each kind of cleaning chemical solution and the number of wafers. - This embodiment defines the end time of the final rinsing after cleaning a wafer with a chemical solution, to reduce the volume of cleaning water and net rinsing time (Row Process Time: RPT) in the wafer cleaning process, and cleans a wafer to the proper clean state. Concretely, the pure water resistivity (conductivity) of the solution including the cleaning water is continuously monitored during the final rinsing in order to define the end of final wafer rinsing. The obtained resistivity data is differentiated to obtain the change in the inclination with time. Then, the end point of rinsing is determined based on the inclination change with time and the continued final rinsing time. The method reduces the cleaning water volume and RPT in this way, and cleans a wafer to the proper clean state. Detailed explanation will be given below.
- First, explanation will be given on a
wafer cleaning equipment 1 according to this embodiment with reference toFIG. 2 . Thecleaning equipment 1 has acleaning tank 3 which contains one ormore wafers 2 cleaned with a chemical solution. Thecleaning tank 3 may be either a processing tank dedicated to rinsing thewafer 2 with adhesion of a cleaning chemical solution, or a processing tank provided with a device to switch the solution supplied to thewafer 2 from a chemical solution to cleaning water after thewafer 2 is cleaned with a chemical solution. The bottom of thecleaning tank 3 is connected to awater supply pipe 4 which supplies a cleaning water used for rinsing thewafer 2 to the inside of thecleaning tank 3. At the middle of thewater supply pipe 4, a cleaningwater supply valve 5 is provided as a cleaning water supply device to supply a cleaning water to the inside of thecleaning tank 3. In this embodiment, ultra-pure water is used as a cleaning water. Therefore, the cleaning water supply valve can also be called an ultra-purewater supply valve 5. - The
cleaning tank 3 has anopening 3a at the top. The chemical solution adhered to thewafer 2 and thesolution 6 including the pure water supplied to the inside of thecleaning tank 3 overflow from the inside to outside of the cleaning tank through theopening 3a. Provided near theopening 3a of thecleaning tank 3 is adrain port 7 to drain thesolution 6 to the outside of thecleaning tank 3 after once receiving thesolution 6 overflowed from the inside of thecleaning tank 3. An electriccharacter measuring unit 8 which measures the resistivity or conductivity of thesolution 6 is provided contacting thesolution 6 in thedrain port 7. - The resistivity and conductivity are reciprocal to each other. Therefore, measurement of at least one of the resistivity and conductivity of the
solution 6 corresponds to measurement of the other. In this embodiment, the resistivity of thesolution 6 is to be measured with the electriccharacteristic measuring unit 8. Therefore, in this embodiment, a resistivity meter (resistivity measuring cell) 8 is used as an electric characteristic measuring unit. Theresistivity measuring cell 8 measures, as the resistivity of thesolution 6, the resistivity of the overflowedwater 6a drained from the inside to outside of thecleaning tank 3 through theopening 3a at the top of thecleaning tank 3. - The resistivity of the
solution 6 measured with theresistivity measuring cell 8 is sent to aresistivity measuring circuit 9 as an electric signal. Theresistivity measuring circuit 9 measures the resistivity of thesolution 6 that is measured with theresistivity measuring cell 8, based on the electric signal output from theresistivity measuring cell 8. - The resistivity of the
solution 6 measured with theresistivity measuring circuit 9 is sent from theresistivity measuring circuit 9 to an A/D converter 10 as an electric signal. In this embodiment, theresistivity measuring circuit 9 is set to output the measured resistivity of thesolution 6 as an analog signal. Anarithmetic control circuit 11 is set to receive a digital signal. Therefore, in this embodiment, the A/D converter 10 is set to convert an analog signal output from theresistivity measuring circuit 9 to a digital signal, and send this digital signal to thearithmetic control circuit 11. - The resistivity of the
solution 6 converted from analog to a digital signal with the A/D converter 10 is sent to thearithmetic control unit 11. Thearithmetic control unit 11 obtains the resistivity of thesolution 6 measured with theresistivity measuring circuit 9 at every preset time, holds it for preset time, differentiates the obtained measured value with respect to time, and controls open/close of the ultra-purewater supply valve 5. In this embodiment, thearithmetic control unit 11 consists of an arithmetic unit (arithmetic section, arithmetic circuit) which differentiates with respect to time the resistivity of thesolution 6 measured with theresistivity measuring cell 8, and a control unit (control section, control circuit) which is integrated with the arithmetic unit, and supplies a cleaning water to thecleaning tank 3 by operating the ultra-purewater supply valve 5 until the differential value calculated by the arithmetic unit becomes equal to or less than a preset value and is held at that value for preset time. - The
cleaning tank 3,water supply pipe 4 and ultra-purewater supply valve 5 constitute acleaning system 12 of thecleaning equipment 1. Theresistivity measuring cell 8,resistivity measuring circuit 9, A/D converter 10 andarithmetic control unit 11 constitute a measuringsystem 13 of thecleaning equipment 1. - Next, explanation will be given on a wafer cleaning method according to this embodiment with reference to
FIG. 1 . The wafer cleaning method of this embodiment is concretely a cleaning method in the final wafer rinsing process, which eliminates stains such as chemical solution adhered to thewafer 2 cleaned with a chemical solution, and clean thewafer 2 to the proper clean state. The wafer cleaning method of this embodiment measures the resistivity of the chemical solution used for cleaning thewafer 2 and thesolution 6 including the cleaning water used for rinsing thewafer 2 cleaned with the chemical solution, and differentiates the measured value with respect to time. Thewafer 2 is continuously rinsed until the differentiated value becomes equal to or less than a preset value and held at that value for preset time. In the wafer cleaning method of this embodiment, thewafer 2 is rinsed by using thewafer cleaning equipment 1. Detailed explanation will be given below. - First, put one or
more wafers 2 in thecleaning tank 3 in the stat that the wafer is cleaned but the cleaning solution is not completely eliminated. Next, open the ultra-purewater supply valve 5 by sending a valve control signal to open the ultra-purewater supply valve 5 from thearithmetic control unit 11 to the ultra-purewater supply valve 5. The ultra-pure water is supplied to the inside of thecleaning tank 3, and thewafer 2 is begun to be cleaned with ultra-pure water (rinsed with ultra-pure water). At the same time, theresistivity measuring cell 8 starts measuring the resistivity of the solution 6 (overflowedwater 6a) drained from thecleaning tank 3. Theresistivity measuring circuit 9 measures continuously the value (detected value) measured with theresistivity measuring cell 8. The A/D converter 10 converts continuously the resistivity value outputted as an analog signal (analog value) from theresistivity measuring circuit 9, into a digital signal (digital value). The A/D converter 10 outputs the digital signal to thearithmetic control unit 11. - The
arithmetic control unit 11 receives the digital signal output from the A/D converter 10, and performs a predetermined processing based on the digital signal. The predetermined processing performed by thearithmetic control unit 11 is indicated by a dashed line inFIG. 1 . Detailed explanation will be given below. - First, hold the resistivity value inputted as a digital signal to the
arithmetic control unit 11 at every preset time for preset time predetermined by thearithmetic control unit 11. Next, thearithmetic control unit 11 calculates the inclination (change rate), or the differential value of the resistivity with respect to the holding time, based on the held number of resistivity values and the holding time. The differential value can be calculated after smoothing the resistivity values, if necessary. The differential value of the resistivity corresponds to the inclination of the resistivity at a predetermined time. Thus, it is also permitted to obtain the inclination by smoothing real time the predetermined number of held resistivity data before holding the resistivity data held for obtaining the differential value. A method and degree of smoothing is not specified as long as noises in thecleaning system 12 and measuringsystem 13 of thecleaning equipment 1 are taken into account. A weighted average (a weighted smoothing), a weighted mean, or Savizky-Golay method is permitted. - Next, determine by the
arithmetic control unit 11 whether the differential value obtained by thearithmetic control unit 11 is equal to or less than a preset value and held at that value for preset time. When the differential value is equal to or less than the preset value and held at that value for the preset time, the stains such as a chemical solution adhered to thewafer 2 is regarded as completely eliminated, and thewafer 2 is regarded as cleaned to the proper clean state. In this embodiment, thearithmetic control unit 11 is set to determine whether the differential value is equal to or less than 0.05 MΩcm/sec and held at that value for equal to or more than 5 seconds after passing the maximum value. When the differential value is equal to or less than 0.05 MΩcm/sec and held at that value for equal to or more than 5 seconds after passing the maximum value, thewafer 2 is regarded as cleaned to the proper clean state, and rinsing thewafer 2 with ultra-pure water is finished. - The above differential value measuring condition is set to an appropriate value according to the cleanness demanded for the
wafer 2. The value of the condition is previously obtained by experiments. The ideal timing to finish the rinsing with ultra-pure water is a point when the differential value of the resistivity reaches 0.00 MΩcm/sec, or the inclination of the resistivity with respect to time becomes zero. However, noises (electric signal noises) occur in thecleaning system 12 and measuringsystem 13 of thecleaning equipment 1, and the differential value of the resistivity can not practically reach 0.00 MΩcm/sec. According to the experience and experiments done by the inventors, it is seen that when the differential value of the resistivity is held equal to or less than 0.05 MΩcm/sec for at least 5 seconds after passing the maximum value, thewafer 2 can be cleaned to the proper clean state regardless of the number of wafers and the kinds and density of chemical solution used for cleaning. Therefore, it is set in this embodiment that if the differential value of the resistivity is held equal to or less than 0.05 MΩcm/sec for at least 5 seconds after passing the maximum value, the rinsing thewafer 2 with ultra-pure water is finished. - If the
arithmetic control unit 11 determines that the differential value is not held equal to or less than 0.05 MΩcm/sec for equal to or more than 5 seconds after passing the maximum value, rinsing thewafer 2 with ultra-pure water is continued and thearithmetic control unit 11 holds the resistivity data and repeats differentiation of the resistivity based on that data, until the differential value meets that condition. If the data is held repeatedly and the data is held for a long time, the number of held data is increased and the load to thearithmetic control unit 11 is increased. To avoid this, it is permitted to set to abandon the data after the preset time passes. - If the
arithmetic control unit 11 determines that the differential value is held equal to or less than 0.05 MΩcm/sec for equal to or more than 5 seconds after passing the maximum, thearithmetic control unit 11 sends a valve control signal which closes the ultra-purewater supply valve 5 to the ultra-purewater supply valve 5, and closes the ultra-purewater supply valve 5. By this action, supply of ultra-pure water to thecleaning tank 3 is stopped, and the ultra-pure water rinsing of thewafer 2 is finished. After the end of ultra-pure water rinsing of thewafer 2, take out thewafer 2 from thecleaning tank 3, and dry the wafer. This completes the final wafer rinsing process. -
FIG. 3 is a graph showing that the resistivity data is obtained at every second and held for a second in the cleaning method of one example of this embodiment, and the differential value of the resistivity with respect to the changes with time is calculated based on the held data. In this example, differentiation is performed by obtaining the resistivity data at about every second and holding it for a second, but the data holding time, differential value calculating interval and differential value holding time are not limited to about 1 second. They may be the time sufficiently short against the net time (RPT) required by the rinsing of thewafer 2 with ultra-pure water. - HF200/lwf in
FIG. 3 indicates the ultra-pure water rinsing (final rinsing) of onewafer 2 that is cleaned by using the chemical solution composed of pure water and water solution of 50% hydrofluoric acid, and diluted to have an about 1:200 volume ratio of the water solution of 50% hydrofluoric acid to pure water. The solid line in the graph ofFIG. 3 indicates the changes of the time differential value of the resistivity with respect to the ultra-pure water rinsing time in HF200/lwf. HF500/lwf indicates the ultra-pure water rinsing of onewafer 2 that is cleaned by using the chemical solution composed of pure water and water solution of 50% hydrofluoric acid, and diluted to have an about 1:500 volume ratio of the water solution of 50% hydrofluoric acid to pure water. The dashed line in the graph ofFIG. 3 indicates the changes in the time differential value of the resistivity with respect to the ultra-pure water rinsing time in HF500/lwf. HF200/44wf indicates the ultra-pure water rinsing of 44wafers 2 that are cleaned by using the chemical solution composed of pure water and water solution of 50% hydrofluoric acid, and diluted to have an about 1:200 volume ratio of the water solution of 50% hydrofluoric acid to pure water. The chain line in the graph ofFIG. 3 indicates the changes in the time differential value of the resistivity with respect to the ultra-pure water rinsing time in HF200/44wf. HF500/44wf indicates the ultra-pure water rinsing of 44wafers 2 that are cleaned by using the chemical solution composed of pure water and water solution of 50% hydrofluoric acid, and diluted to have an about 1:500 volume ratio of the water solution of 50% hydrofluoric acid to pure water. The chain double-dashed line in the graph ofFIG. 3 indicates the changes in the time differential value of the resistivity with respect to the ultra-pure water rinsing time in HF500/44wf. - As seen from the graph of
FIG. 3 , the differential value (inclination) of resistivity generally shows a curve projecting upward, descending after once rising regardless of the number ofwafers 2 and the kinds and density of the cleaning chemical solution. Even if the rinsing time is extended under each of the four conditions, and thedifferential value 0 of resistivity is not held various due to noise components. Among the four conditions, the peak (maximum) position of differential value and sweep time are largely different. According to the graph ofFIG. 3 , the differential value of resistivity can take the same value at different points except the peak.FIG. 3 indicates that the resistivity greatly changes until the differential value reaches its peak. While the resistivity is so changing, the chemical solution is substituted by ultra-pure water. In view of this, it is obviously necessary to keep cleaning thewafer 2 until the differential value reaches the peak in the graph ofFIG. 3 . Therefore, when the differential value of resistivity reaches a preset value after once reaching the peak, thewafer 2 is regarded as cleaned to the proper clean state. - The differential value of resistivity at which the
wafer 2 is regarded as cleaned to the proper clean state may be set to an appropriate value according to the cleanness demanded for thewafer 2 as long as it has once reached the peak. As the above differential value is set smaller, the cleanness ofwafer 2 is increased, but the time required to finish the ultra-pure water rinsing becomes long. If the rinsing time with ultra-pure water is long, the row process time (RPT) of rinsing with ultra-pure water becomes long, decreasing the productivity, and increasing the production cost with the increased volume of ultra-pure water. - According to the graph of
FIG. 3 , it is seen that the part where the differential value sweeps indicates the state that the maximum and minimum differential values are repeated due to the various noise components. If the value that thewafer 2 is regarded as cleaned to the proper clean state is set small to the state that the differential value sweeps as shown inFIG. 3 , it becomes very difficult to hold the value for equal to or more than 5 seconds even if the value is equal to or less than 0.05 MΩcm/sec. Further, it may become impossible to prolong thewafer 2 cleaning time, and finish rinsing thewafer 2 with ultra-pure water. Therefore, it is necessary to set the differential value of resistivity at white thewafer 2 is regarded as cleaned to the proper clean state to the value that thewafer 2 cleaning time becomes the shortest within the range satisfying the cleanness demanded for thewafer 2. - Because of the above reason, in the embodiment shown in
FIG. 3 , when the differential value of resistivity is held equal to or less than 0.05 MΩcm/sec for equal to or more than 5 seconds after passing the maximum value for all the four kinds, thewafer 2 is regarded as cleaned to the proper clean state, and the rinsing of thewafer 2 is finished. By this method, the final rinsing of thewafer 2 can be finished in substantially the same state, even if the resistivity of thesolution 6 in thecleaning tank 3 is different for the processing conditions in cleaning with a chemical solution. Namely, stains such as chemical solution adhered to thewafer 2 can be sufficiently eliminated and thewafer 2 can be cleaned to substantially the same clean state in various conditions, regardless of the number ofwafers 2 to be cleaned, the kinds and density of cleaning chemical solution, or the resistivity of thesolution 6 in thecleaning tank 3. As shown inFIG. 3 , in this embodiment, thewafer 2 can be cleaned to the proper clean state and the final rinsing can be finished within about 7 to 8 minutes for all of the four kinds of cleaning solution. - Next, a brief explanation will be given on an example comparative to the above embodiment with reference to
FIG. 7 .FIG. 7 is a graph showing the relationship between the wafer rinsing time (cleaning time) and resistivity according to a prior art, with respect to the kinds of cleaning chemical solution and the number of wafers to be cleaned. Concretely, the graph ofFIG. 7 indicates the resistivity measured by the wafer cleaning method and thecleaning equipment 101 according to the prior art shown inFIG. 5A , under the four conditions of HF200/lwf, HF500/lwf, HF200/44wf and HF500/44wf, as in the embodiment described above. The solid line in the graph ofFIG. 7 indicates the changes in the resistivity with respect to the ultra-pure water rinsing time in HF200/lwf, or the resistivity recovery time. The dashed line in the graph ofFIG. 7 indicates the changes in the resistivity with respect to the ultra-pure water rinsing time in HF500/lwf, or the resistivity recovery time. The chain line in the graph ofFIG. 7 indicates the changes in the resistivity with respect to the ultra-pure water rinsing time in HF200/44wf, or the resistivity recovery time. The chain double-dashed line in the graph ofFIG. 7 indicates the changes in the resistivity with respect to the ultra-pure water rinsing time in HF500/44wf, or the resistivity recovery time. - According to the prior art, whether a wafer is cleaned to the proper clean state is determined by whether the resistivity of solution reaches a preset value. In this comparative example, when the resistivity of solution reaches 16 MΩcm, a wafer is regarded as cleaned to the proper clean state. Among the four conditions, in HF200/44wf and HF500/44wf for rinsing 44 wafers, the ultra-pure water rinsing time is different according to the density of chemical solution (hydrofluoric acid). The resistivity of the solution reaches 16 MΩcm in both conditions. Therefore, in HF200/44wf and HF500/44wf, the end time of final wafer rinsing can be determined (confirmed) also in the above setting. Contrarily, in HF200/lwf and HF500/lwf for rinsing 1 wafer, the ultra-pure water rinsing time is different according to the density of chemical solution, and the resistivity of the solution does not reach 16 MΩcm. Therefore, in HF200/lwf and HF500/lwf, the end time of final wafer rinsing can not be determined (confirmed) in the above setting.
- The resistivity of the solution at which a wafer is regarded as cleaned to the proper clean state is set to 13 MΩ, for example, so as to determine the end time of final wafer rinsing even in HF200/lwf and HF500/lwf. Then, the final wafer rinsing can be finished when the resistivity of the solution reaches 13 MΩcm I HF200/lwf and HF500/lwf. However, in HF200/44wf and HF500/44wf, when the resistivity of the solution reaches 13 MΩcm, the ion contained in the chemical solution remains in the solution in the cleaning tank. Namely, in HF200/44wf and HF500/44wf, if the resistivity of the solution at which a wafer is regarded as cleaned to the proper clean state is set to 13 MΩcm, the final rinsing will be finished before a wafer is sufficiently rinsed.
- Therefore, in the prior art, the wafer rinsing time is set long including a sufficient allowance considering variations of the rinsing time due to the cleaning conditions, so as to clean a wafer to the sufficiently cleaned state, regardless of the various conditions such as the number of wafers, the kinds and density of cleaning chemical solution, and the resistivity of the solution in the cleaning tank. For example, in the comparative example shown in
FIG. 7 , the rinsing time is generally set to about 10 minutes. On the contrary, in the above-mentioned embodiment, as seen fromFIG. 3 , thewafer 2 can be cleaned to the proper clan state in 7-8 minutes in all of the four conditions, and the final rinsing can be finished. - For example, under the condition of HF500/44wf, the prior art can reduce the rinsing time by about 200 seconds by applying this embodiment to the cleaning tank that requires about 600 seconds (10 minutes) for rinsing a wafer. In this case, if the flow rate per unit time of ultra-pure water supplied to the cleaning tank is set to about 20L/min, the ultra-pure water can be decreased by about 67 liters. The rinsing time is about 70 seconds different between HF200/lwf with the longest rinsing time and HF500/44wf with the shortest rinsing time in the above example. Namely, according to this embodiment, the rinsing time can be decreased by about 70 seconds in HF500/44wf compared with HF200/lwf. In this case, if the flow rate per unit time of ultra-pure water supplied to the
cleaning tank 3 is set to about 20L/min, the ultra-pure water can be decreased by about 23 liters. On the contrary, in the prior art, the rinsing time is set to about 600 seconds for both HF200/lef and HF500/44wf, as described above. Therefore, in the prior art, about 70 seconds of rinsing time and about 23 liters of ultra-pure water are wasted in HF500/44wf. - The resistivity recovery time in the final rinsing of the
wafer 2 is easy to be influenced by the number ofwafers 2, and the kinds and density of chemical solution. The resistivity recovery time is not even. Therefore, in the prior art, the wafer rinsing time is determined considering the longest rinsing time. Contrarily, in this embodiment, even if thewafer 2 cleaning condition is different, thewafer 2 can be cleaned to the same state while controlling a waste of ultra-pure water, and the wafer rinsing can be finished. Namely, according to this embodiment, thewafer 2 can be cleaned to substantially the same proper clean state regardless of thewafer 2 cleaning conditions. Compared with the prior art, this embodiment cal also improve thewafer 2 cleaning efficiency by decreasing the volume of ultra-pure water and reducing the row process time (RPT) of thewafer 2. - Further, this embodiment uses the time differential value of resistivity. This corresponds to using the replacement of chemical solution by ultra-pure water. Therefore, this is difficult to be influenced by a final resistivity value attained by the resistivity of the
solution 6 in thecleaning tank 3 when thewafer 2 is cleaned with ultra-pure water. Namely, this embodiment is little influenced by the final resistivity difference caused by the different number ofwafers 2 to be cleaned, and the lowered final resistivity caused by deterioration of the measuring accuracy of a resistivity meter. - According to the first embodiment, the rinsing of
wafer 2 is finished at the point when the time differential values of the resistivity of the chemical solution used for cleaning thewafer 2 and thesolution 6 including the cleaning water used for rinsing the cleanedwafer 2 are equal to or less than preset values, and held at that values for preset time. This makes it possible to clean thewafer 2 to the proper clean state while improving thewafer 2 cleaning efficiency, regardless of the number ofwafers 2 to be cleaned and the kinds and density of the chemical solution used for cleaning. - The
wafer 2 according to this embodiment has been rinsed by the wafer cleaning method or thewafer cleaning equipment 1 according to this embodiment. Therefore, thewafer 2 of this embodiment has been cleaned to the proper clean state with stains of chemical solution removed sufficiently. Further, thewafer 2 of this embodiment provides high yield (production efficiency), and reduces the production cost. - In addition, thought not shown, the semiconductor device according to this embodiment has the
wafer 2 according to this embodiment. Therefore, the semiconductor device of this embodiment is improved in the performance, quality, reliability and yield. Further, the semiconductor device of this embodiment provides high production efficiency, and reduces the production cost. - (2nd. Embodiment)
- Now, explanation will be given on a second embodiment of the present invention with reference to
FIG. 4 .FIG. 4 is a simplified block diagram showing a wafer cleaning equipment according to this embodiment. The same reference numerals are given to the same components as in the first embodiment, and a detailed explanation will be omitted. - Unlike the wafer cleaning equipment according to the first embodiment, in the wafer cleaning equipment according to this embodiment, a resistivity meter (resistivity measuring cell) is provided near the middle part of a cleaning tank. Concrete explanation will be given below.
- As shown in
FIG. 4 , in the middle part of acleaning tank 22 of awafer cleaning equipment 21 according to this embodiment, a take-out port (solution extraction port) 23 is provided to take out thesolution 6 from thecleaning tank 22 without exposing to the air. A resistivity meter (resistivity measuring cell) 8 is provided contacting thesolution 6b taken out from thecleaning tank 3 through thesolution extraction port 23. Namely, in this embodiment, theresistivity measuring cell 8 is set to measure the resistivity of thesolution 6b without contacting the air. - The wafer cleaning method, wafer, and semiconductor device according to this embodiment are the same as those of the first embodiment, and explanation will be omitted.
- The second embodiment can provide the same effects as the first embodiment. In this embodiment, the
resistivity measuring cell 8 measures the resistivity of thesolution 6b without contacting the air. Therefore, the measured value is difficult to be influenced by the carbonic acid gas or the like in the air dissolved in thesolution 6 through anupper opening 22a of thecleaning tank 22 as a result of so-called air involving. Namely, the measured value of the resistivity in this embodiment is difficult to be influenced by the noises occurred in acleaning system 24 of thecleaning equipment 21 comprising thecleaning tank 22,water supply pipe 4, and ultra-purewater supply valve 5. Particularly, the measured value is difficult to be influenced by the changes in the noises in thecleaning system 24 caused by the changes in the air contacting area of thesolution 6 as a result of the surface fluctuation of thesolution 6. Therefore, this embodiment can measure the resistivity of thesolution 6 with a high accuracy, and clean thewafer 2 to more clean state. Namely, stains such as chemical solution adhered to thewafer 2 of this embodiment are sufficiently eliminated, and thewafer 2 is cleaned to more proper clean state. Further, though not shown, the semiconductor device of this embodiment is improved in the performance, quality, reliability and yield. - The cleaning method and equipment according to the present invention are not limited to the first and second embodiments. The invention may be embodied in other specific forms without departing from its spirit or essential characteristics modifications. The configurations and processes of the embodiments may be partially modified, or combined appropriately.
- For example, the A/
D converter 10 is provided between theresistivity measuring circuit 9 andarithmetic control circuit 11 in the first and second embodiments, but the A/D converter 10 is not always necessary. If theresistivity measuring circuit 9 andarithmetic control circuit 11 are set to process the same form analog or digital signal, the A/D converter 10 is unnecessary. - The arithmetic section (arithmetic circuit) and control section (control circuit) of the
arithmetic control unit 11 are constructed as one body, but they may not necessarily be one body. The arithmetic section and control section of thearithmetic control unit 11 may be configured as separate independent units. - The
resistivity measuring cell 8 is not necessary provided near theupper opening 3a of thecleaning tank 3 or at the middle of thecleaning tank 2. If the solution extracted to theresistivity cell 8 is not replaced from a chemical solution to pure water before the atmosphere solution ofwafer 2, theresistivity measuring cell 8 may be provided near the bottom of thecleaning tanks solution 6 is more difficult to be influenced by the noises occurred in thecleaning systems solution 6. - The
cleaning tanks wafers 2 at one time, or a single wafer type for cleaning thewafer 2 one by one. - As a representative noise in the
cleaning systems solution 6. The carbonic acid gas dissolved in thesolution 6 affects largely the resistivity even if the dissolved amount is very small. The amount of the carbonic acid gas dissolved in thesolution 6 is changed by the speed of supplying ultra-pure water to thecleaning tanks solution 6 from thecleaning tanks solution 6 by the surface fluctuation of thesolution 6. The change rate of the dissolved amount of carbonic acid gas is largely influenced by the shapes of thecleaning tanks upper openings resistivity measuring cell 8. Therefore, the method of smoothing the resistivity values to eliminate the noises in thecleaning systems cleaning systems - Actually, the noise components cannot be completely eliminated only by smoothing the resistivity values. Thus, the differential value of resistivity that the
wafer 2 is regarded as cleaned to the proper clean state Is not necessarily limited to 0.05 MΩm/sec. Any value equal to or less than 0.05 MΩcm/sec is usable as a differential value of resistivity that thewafer 2 is regarded as cleaned to the proper clean state. - In the first and second embodiments, the conditions that the
wafer 2 is regarded as cleaned to the proper clean state that the differential value of resistivity is equal to or less than 0.05 MΩcm/sec after passing the maximum value and held at that value for equal to or more than 5 seconds, but the conditions are not necessarily limited to them. The conditions that thewafer 2 is regarded as cleaned to the proper clean state may be determined to appropriate values according to the number ofwafers 2 to be cleaned, the sizes of theprocessing tanks openings - In the first and second embodiment, ultra-pure water as a cleaning water is supplied to the
cleaning tanks cleaning tanks cleaning tanks upper openings cleaning systems solution 6, and the measuring accuracy is lowered. Contrarily, if ultra-pure water is supplied directly to thecleaning tanks cleaning systems solution 6 can be improved. Further, thewafer 2 can be cleaned to more clean state while improving the cleaning efficiency. - In the first and second embodiments, the
cleaning tank 3 is either a processing tank dedicated to rinsing thewafer 2 with adhesion of a cleaning chemical solution, or a processing tank provided with a device to switch the solution supplied to thewafer 2 from a chemical solution to cleaning water after thewafer 2 is cleaned with a chemical solution. By using thecleaning tanks cleaning tanks wafer 2 cleaning efficiency can be improved furthermore. - In the first and second embodiments, the resistivity of the
solution 6 is measured by using theresistivity measuring cell 8, but the measurement is not limited to this. It is allowed to measure the conductivity of thesolution 6 instead of the resistivity. In this case, a conductivity meter may be used instead of the resistivity measuring cell 8 (a resistivity meter) as an electric characteristic measuring unit. Cleaning of thewafer 2 with the cleaning water may be continued until reaching the condition that the time differential value of the conductivity of thesolution 6 becomes larger than a preset value and is held at that value for preset time. - Concretely, the cleaning of the
wafer 2 with the cleaning water may be continued until the time differential value of the conductivity of the solution becomes equal to or more than −20 μS/cm·sec after passing the minimum value and is held at that value for equal to or more than 5 seconds. - Generally, the time differential value of the conductivity of the solution including the chemical solution used for cleaning a wafer and the cleaning water used for cleaning a wafer are substantially zero at the start of measurement, regardless of the number of wafers to be cleaned and the kinds and density of the chemical solution used for the cleaning. The time differential value of the conductivity descends as the measurement time elapses and reaches the peak at preset time. Thereafter, the time differential value of the conductivity ascends as the measurement time elapses and becomes substantially zero. Namely, the value obtained by differentiating the conductivity with respect to time traces a curve projecting downward, regardless of the number of wafers to be cleaned and the kinds and density of the chemical solution used for the cleaning.
- When using the time differential value of the conductivity of solution to determine the wafer cleaning time, use the features of the time differential value of the conductivity. Namely, continue cleaning a wafer until the time differential value of the conductivity of cleaning solution becomes larger than a preset value determined based on the experiment data at which a wafer can be cleaned to the proper clean state, and is held at that value for preset time. Thus, the wafer cleaning with a cleaning water can be finished immediately after a wafer is cleaned to the proper clean state. As a result, the cleaning water volume used for cleaning a wafer can be decreased, and a wafer can be cleaned to the proper clean state while reducing the wafer cleaning time, regardless of the number of wafers to be cleaned and the kinds and density of the cleaning solution used for the cleaning.
- Like the time differential value of the resistivity of the cleaning solution, the time differential value of the conductivity of the solution is not necessarily limited to −20 μS/cm·sec. Any values equal to or more than −20 μS/cm·sec may be used as the differential value of the conductivity at which the
wafer 2 is regarded as cleaned to the proper clean state. The conditions that thewafer 2 is regarded as cleaned to the proper clean state are also not necessarily limited to that the differential value of the conductivity is equal to or more than −20 μS/cm·sec after passing the minimum value, and is held at that value for equal to or more than 5 seconds. The conditions that thewafer 2 is regarded as cleaned to the proper clean state may be determined to an appropriate value according to the number ofwafers 2 to be cleaned, the size of theprocessing tanks openings - Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
Claims (16)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/081,460 US20080202559A1 (en) | 2003-09-05 | 2008-04-16 | Wafer cleaning method and equipment |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2003-314513 | 2003-09-05 | ||
JP2003314513A JP4330959B2 (en) | 2003-09-05 | 2003-09-05 | Semiconductor substrate cleaning method and cleaning apparatus, semiconductor substrate, and semiconductor device |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/081,460 Division US20080202559A1 (en) | 2003-09-05 | 2008-04-16 | Wafer cleaning method and equipment |
Publications (1)
Publication Number | Publication Date |
---|---|
US20050081886A1 true US20050081886A1 (en) | 2005-04-21 |
Family
ID=34415088
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/932,006 Abandoned US20050081886A1 (en) | 2003-09-05 | 2004-09-02 | Wafer cleaning method and equipment |
US12/081,460 Abandoned US20080202559A1 (en) | 2003-09-05 | 2008-04-16 | Wafer cleaning method and equipment |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/081,460 Abandoned US20080202559A1 (en) | 2003-09-05 | 2008-04-16 | Wafer cleaning method and equipment |
Country Status (5)
Country | Link |
---|---|
US (2) | US20050081886A1 (en) |
JP (1) | JP4330959B2 (en) |
KR (1) | KR100575171B1 (en) |
CN (1) | CN1311520C (en) |
TW (1) | TWI249766B (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060043073A1 (en) * | 2004-08-24 | 2006-03-02 | Dainippon Screen Mfg. Co., Ltd. | Substrate treating method and apparatus |
US20080295862A1 (en) * | 2007-05-28 | 2008-12-04 | Hayato Iwamoto | Method of and apparatus for cleaning substrate |
US20100059180A1 (en) * | 2006-01-30 | 2010-03-11 | Kabushiki Kaisha Toshiba | Method of manufacturing semiconductor device and cleaning apparatus |
US20100078043A1 (en) * | 2008-09-30 | 2010-04-01 | Masaki Kitabata | Cleaning device and cleaning method |
EP2381017A4 (en) * | 2008-12-26 | 2015-05-20 | Mitsubishi Materials Corp | Method for washing polycrystalline silicon, washing device, and method for producing polycrystalline silicon |
US20170098558A1 (en) * | 2015-10-06 | 2017-04-06 | United Microelectronics Corp. | Acid replenishing system and method for acid tank |
WO2023137815A1 (en) * | 2022-01-19 | 2023-07-27 | 上海晶盟硅材料有限公司 | Epitaxial wafer resistance value measurement pretreatment method |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN101582372B (en) * | 2008-05-12 | 2012-11-07 | 盛美半导体设备(上海)有限公司 | Device or method for preparing solution for processing single-chip semiconductor |
CN104722239A (en) * | 2008-05-19 | 2015-06-24 | 恩特格里公司 | Gasification method and device for making bubble free solutions of gas in liquid |
US7838425B2 (en) * | 2008-06-16 | 2010-11-23 | Kabushiki Kaisha Toshiba | Method of treating surface of semiconductor substrate |
CN102468126B (en) * | 2010-11-05 | 2013-10-23 | 无锡华润上华半导体有限公司 | Wafer cleaning method |
JP2013038260A (en) * | 2011-08-09 | 2013-02-21 | Fujifilm Corp | Manufacturing method of photoelectric conversion element |
CN109108032A (en) * | 2018-06-25 | 2019-01-01 | 上海华力微电子有限公司 | A kind of unproductive method for cleaning wafer |
CN111715606A (en) * | 2020-03-30 | 2020-09-29 | 横店集团东磁股份有限公司 | Full-automatic graphite boat cleaning device and cleaning method thereof |
CN113644009B (en) * | 2021-07-15 | 2023-11-07 | 长江存储科技有限责任公司 | Cleaning liquid generating method and device and cleaning system control method and device |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5275957A (en) * | 1984-01-10 | 1994-01-04 | Anatel Corporation | Instrument and method for measurement of the organic carbon content of water |
JPH0192475A (en) * | 1987-09-30 | 1989-04-11 | Takemoto Oil & Fat Co Ltd | Oil composition for treating synthetic fiber |
US5518933A (en) * | 1989-03-10 | 1996-05-21 | Unitika Ltd. | Method of analyzing washings for free acids and ions |
JPH05296959A (en) * | 1992-04-23 | 1993-11-12 | Fuji Electric Co Ltd | Pure water specific resistance measuring device of wafer washing bath |
JP3209489B2 (en) * | 1995-06-23 | 2001-09-17 | オルガノ株式会社 | End point detection method for ion exchange type pure water production equipment |
AU8777598A (en) * | 1997-08-11 | 1999-03-01 | Motorola, Inc. | Apparatus and method for processing an object |
JP2001058277A (en) * | 1999-06-17 | 2001-03-06 | Nadex Co Ltd | Resistance welding equipment with enhanced accuracy of detection of timewise fluctuation of work resistance and method therefor |
JP2001029903A (en) * | 1999-07-22 | 2001-02-06 | Matsushita Electronics Industry Corp | Method and apparatus for cleaning |
JP4046486B2 (en) * | 2001-06-13 | 2008-02-13 | Necエレクトロニクス株式会社 | Cleaning water and wafer cleaning method |
JP5092367B2 (en) * | 2006-01-13 | 2012-12-05 | 旭硝子株式会社 | Process for producing fluorinated elastic copolymer and crosslinked fluororubber |
-
2003
- 2003-09-05 JP JP2003314513A patent/JP4330959B2/en not_active Expired - Fee Related
-
2004
- 2004-09-02 US US10/932,006 patent/US20050081886A1/en not_active Abandoned
- 2004-09-03 KR KR1020040070146A patent/KR100575171B1/en not_active IP Right Cessation
- 2004-09-03 TW TW093126724A patent/TWI249766B/en not_active IP Right Cessation
- 2004-09-03 CN CNB2004100832983A patent/CN1311520C/en not_active Expired - Fee Related
-
2008
- 2008-04-16 US US12/081,460 patent/US20080202559A1/en not_active Abandoned
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20060043073A1 (en) * | 2004-08-24 | 2006-03-02 | Dainippon Screen Mfg. Co., Ltd. | Substrate treating method and apparatus |
US20100059180A1 (en) * | 2006-01-30 | 2010-03-11 | Kabushiki Kaisha Toshiba | Method of manufacturing semiconductor device and cleaning apparatus |
US7850818B2 (en) * | 2006-01-30 | 2010-12-14 | Kabushiki Kaisha Toshiba | Method of manufacturing semiconductor device and cleaning apparatus |
US20080295862A1 (en) * | 2007-05-28 | 2008-12-04 | Hayato Iwamoto | Method of and apparatus for cleaning substrate |
US8038798B2 (en) * | 2007-05-28 | 2011-10-18 | Sony Corporation | Method of and apparatus for cleaning substrate |
US20100078043A1 (en) * | 2008-09-30 | 2010-04-01 | Masaki Kitabata | Cleaning device and cleaning method |
EP2381017A4 (en) * | 2008-12-26 | 2015-05-20 | Mitsubishi Materials Corp | Method for washing polycrystalline silicon, washing device, and method for producing polycrystalline silicon |
US9238876B2 (en) | 2008-12-26 | 2016-01-19 | Mitsubishi Materials Corporation | Method of washing polycrystalline silicon, apparatus for washing polycrystalline silicon, and method of producing polycrystalline silicon |
US20170098558A1 (en) * | 2015-10-06 | 2017-04-06 | United Microelectronics Corp. | Acid replenishing system and method for acid tank |
WO2023137815A1 (en) * | 2022-01-19 | 2023-07-27 | 上海晶盟硅材料有限公司 | Epitaxial wafer resistance value measurement pretreatment method |
Also Published As
Publication number | Publication date |
---|---|
CN1591779A (en) | 2005-03-09 |
KR100575171B1 (en) | 2006-05-02 |
TWI249766B (en) | 2006-02-21 |
CN1311520C (en) | 2007-04-18 |
KR20050024610A (en) | 2005-03-10 |
JP4330959B2 (en) | 2009-09-16 |
TW200515471A (en) | 2005-05-01 |
US20080202559A1 (en) | 2008-08-28 |
JP2005085892A (en) | 2005-03-31 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US20080202559A1 (en) | Wafer cleaning method and equipment | |
US10658203B2 (en) | Substrate processing apparatus and processing cup cleaning method | |
US8038798B2 (en) | Method of and apparatus for cleaning substrate | |
US20200243349A1 (en) | Semiconductor processing apparatus and method | |
US11839839B2 (en) | Apparatus and system for filtrating liquid | |
US6875287B2 (en) | Water reclamation rate in semiconductor fabrication wet benches | |
US10618004B2 (en) | Abatement device | |
JP3133049U (en) | Semiconductor wafer cleaning equipment | |
US6348289B1 (en) | System and method for controlling polysilicon feature critical dimension during processing | |
JP2006222293A (en) | Method and apparatus for cleaning semiconductor wafer | |
US20100078043A1 (en) | Cleaning device and cleaning method | |
KR101078145B1 (en) | Apparatus and method for drying substrate | |
JP3459719B2 (en) | Silicon wafer processing equipment | |
KR101516905B1 (en) | Dissolved nitrogen concentration monitoring method, substrate cleaning method, and substrate cleaning apparatus | |
JP2001267286A (en) | Management method of etching solution and wet etching system | |
JPH10172947A (en) | Single tank-type cleaning method and device therefor | |
KR200234232Y1 (en) | Wafer cleaning device | |
JP3891776B2 (en) | Substrate processing equipment | |
JP2001028356A (en) | Cleaning apparatus | |
JP3169004B2 (en) | Semiconductor wafer wet processing equipment | |
KR20070010824A (en) | Method for etching a wafer | |
KR20220110054A (en) | Substrate processing device and substrate processing method | |
JP5549274B2 (en) | Water quality evaluation method and apparatus | |
JP2006222292A (en) | Process and apparatus for processing semiconductor wafer | |
CN114914165A (en) | Method for monitoring wafer etching solution replacement period |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: SEIKO EPSON CORPORATION, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MIYAZAKI, KUNIHIRO;HIGUCHI, TAKASHI;NAKAJIMA, TOSHIKI;AND OTHERS;REEL/FRAME:016102/0483;SIGNING DATES FROM 20040917 TO 20041108 Owner name: DAINIPPON SCREEN MFG. CO., LTD., JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MIYAZAKI, KUNIHIRO;HIGUCHI, TAKASHI;NAKAJIMA, TOSHIKI;AND OTHERS;REEL/FRAME:016102/0483;SIGNING DATES FROM 20040917 TO 20041108 Owner name: KABUSHIKI KAISHA TOSHIBA, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MIYAZAKI, KUNIHIRO;HIGUCHI, TAKASHI;NAKAJIMA, TOSHIKI;AND OTHERS;REEL/FRAME:016102/0483;SIGNING DATES FROM 20040917 TO 20041108 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |