Polishing condition control apparatus and polishing condition control method of CMP apparatus

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a polishing condition control apparatus and a polishing condition control method of a CMP apparatus, and particularly, it relates to a polishing condition control apparatus and a polishing condition control method of a CMP apparatus for optimizing the polishing condition of a wafer from the measurements result of the remaining film thickness of the wafer.

2. Description of the Related Art

Conventionally, in polishing a wafer by this kind of CMP apparatus, a platen is rotated by a motor driven, and an abrasive is supplied onto an polishing pad stuck to the platen, and the wafer is pushed to the polishing pad while rotating the wafer held by a carrier of the polishing head, and thereby films to be polished including the oxide film, the metal film and the like formed on the wafer surface are polished.

In the CMP processing, the thickness of remaining film of the wafer surface (hereinafter, referred to as remaining film thickness) is measured by use of a remaining film thickness measuring apparatus, and the wafer is polished so as for the remaining film thickness to become the target value. In this case, the remaining film thickness is measured by the vertical direction displacement of the polishing pad. In addition, there are known a method in which the CMP processing is performed by a simple feedback control of the remaining film thickness measurement, and another method in which the state of the wafer polishing is monitored by a monitor, and the polishing state of the wafers to be polished afterward on the basis of the monitor result is forecasted and polishing is performed (refer to, for example, Patent Documents 1 to 3).

[Patent Document 1] Japanese Patent No. 308285

[Patent Document 2] Japanese Patent No. 3311864

[Patent Document 3] Japanese Patent Application Laid-Open Publication No. 2005-518654

In the conventional CMP apparatus, in the case where the remaining film thickness of the wafer is measured and polishing is performed, since the vertical direction displacement of the polishing pad is measured as a remaining film thickness, it is difficult to obtain a highly precise measurement result. Further, in the case where the CMP processing is performed by the simple feedback control of the remaining film thickness measurement, it is not possible to obtain a high remaining film thickness measurement result stably, and consequently, the method does not cope with ultrafine and highly integrated wafers sufficiently.

On the other hand, in the case where the state of the wafer polishing is monitored by a monitor, and the polishing state of the wafers to be polished afterward is forecasted, the polishing conditions differ with the respective modules of the apparatus, that is, respective rotating axes (hereinafter referred to as polishing axes), and respective platens, and as a result, the film thickness of wafers after the polishing process is apt to be uneven among the modules.

As mentioned, according to the conventional art, it is difficult to precisely measure the remaining film thickness of the wafers, and since unevenness in the remaining film thickness occurs among the modules, excessive polishing and insufficient polishing easily take place, and polishing efficiency of the wafer declines. Defects occur in wafers after the polishing, and the yield decreases. Furthermore, expendable supplies such as abrasives are wasted more than necessary, and accordingly the running cost of the expendable supplies increases, and these have been problems in the conventional art.

SUMMARY OF THE INVENTION

Therefore, there has been a technological subject to eliminate the unevenness of the remaining film thickness of the wafers, and increase the polishing efficiency, reduce the running cost and enhance the yield, and accordingly, the object of the present invention is to solve the problems.

The present invention has been made to achieve the object, and according to a first aspect of the present invention, there is provided a polishing condition control apparatus of the CMP apparatus that polishes the film to be polished formed on the wafer surface, and the polishing condition control apparatus includes, a polishing recipe preparing means that prepares polishing conditions so that the polishing conditions such as polishing speed, polishing pressure, and an abrasive and the like for the wafer become optimal, a remaining film thickness forecasting means that forecasts the remaining film thickness of the wafer to be polished under the polishing conditions after polishing, a remaining film thickness measuring apparatus that measures the remaining film thickness of the wafer after the polishing, and a computer that controls the measurement results of the remaining film thickness and the polishing conditions, and further the computer includes a calculating unit that calculate the difference between the measured value of the remaining film thickness and the forecasted value thereof, and a polishing condition correcting/changing unit that corrects/changes the polishing conditions so that the calculated difference becomes minimal, and thereby, the correction/change of the polishing conditions is carried out in real time.

According to this structure, the polishing conditions are prepared by the polishing recipe preparing means so that the polishing conditions such as polishing speed, polishing pressure, abrasives and the like become optimal, further, the remaining film thickness of the wafer polished under the optimal polishing conditions after the polishing is forecasted by the remaining film thickness forecasting means.

And, after wafer is polished under the optimal polishing conditions, the remaining film thickness of the wafer surface by the remaining film thickness measuring apparatus. In the next time and after that, the difference between the measured value of the remaining film thickness and the forecasted value thereof is calculated by the calculating unit of the computer, and the polishing conditions are corrected/changed by the polishing condition correcting/changing unit in real time so that the calculated difference becomes minimal. Thus, wafers are always polished under the optimal polishing conditions, and the remaining film thickness of the wafers are processed into the target value.

According to a second aspect of the present invention, there is provided a polishing condition control apparatus of a CMP apparatus according to the first aspect of the invention, wherein the polishing recipe preparing means prepares the optimal polishing conditions for each polishing step of the wafer, each polishing shaft of the CMP apparatus, each platen, or each combination of the polishing shaft and the platen.

According to this structure, the optimal polishing conditions are prepared for each polishing step of the wafer, each polishing shaft corresponding to a rotating shaft of the polishing head, each platen, or each combination of the polishing shaft and the platen. Therefore, the wafers are polished under the optimal polishing conditions according to each individual polishing step, polishing shaft, or platen.

According to a third aspect of the present invention, there is provided a polishing condition control apparatus of a CMP apparatus according to the first or second aspect of the invention, wherein the polishing recipe preparing means prepares the optimal polishing conditions on the basis of data of an approximate expression prepared from past polishing history and a polishing model that the CMP apparatus itself stores beforehand.

According to this structure, since the optimal polishing condition is prepared on the basis of the data of the approximate expression prepared from past polishing history, and the polishing model that the CMP apparatus itself stores beforehand, the polishing conditions that reflect the data of the past polishing history and the polishing model peculiar to the apparatus are prepared. The polishing model is a model showing the relations between of polishing parameters such as the polishing pressure and the polishing time and the like and the polishing quantity that are made into fixed quantities and numerical values.

According to a fourth aspect of the present invention, there is provided a polishing condition control apparatus of a CMP apparatus according to the first aspect of the invention, wherein the remaining film thickness forecasting means forecasts the remaining film thickness of the wafer on the basis of the approximate expression prepared from past polishing history.

According to this structure, the remaining film thickness of the wafer is forecasted on the basis of the approximate expression prepared from the past polishing history, and accordingly, the data of the polishing history is reflected to the forecasted value of remaining film thickness of the wafer.

According to a fifth aspect of the present invention, there is provided a polishing condition control apparatus of a CMP apparatus according to the first aspect of the invention, wherein the computer has a monitoring unit that displays the difference between the measured value of the polishing time and the forecasted value thereof, and, polishing states of the wafers and the like.

According to this structure, since the difference between the measured value of the polishing time and the forecasted value thereof, and polishing states of the wafers and the like are monitored by the monitoring unit, changing data and polishing condition are grasped in real time.

According to a sixth aspect of the present invention, there is provided a polishing condition control apparatus of a CMP apparatus according to the first or fifth aspect of the invention, wherein the computer includes a polishing state judging unit that outputs an attention signal, an alarm signal and/or a polishing stop signal, when the calculated difference exceeds a predetermined value.

According to this structure, when the calculated difference exceeds the specified value, the attention signal, the alarm signal and/or the polishing stop signal are output. Accordingly, when the polishing state gets erroneous, the effect to that is automatically notified, and at an emergency, the polishing process is stopped immediately.

According to a seventh aspect of the present invention, there is provided a polishing condition control apparatus of a CMP apparatus according to the first aspect of the invention, wherein the polishing condition correcting/changing unit corrects/changes the polishing conditions for each polishing step of the wafer, each polishing shaft of the CMP apparatus, each platen, or each combination of the polishing shaft and the platen.

According to this structure, the correction/change of the polishing conditions is performed independently for each polishing step, each polishing shaft, each platen, or each combination of the polishing shaft and the platen. Therefore, the polishing conditions are corrected/changed to the optimal polishing conditions for each polishing step, and further, the optimal polishing conditions are corrected/changed in the same manner among the polishing shafts, the platens, or, the combinations of the polishing shaft and the platen.

According to an eighth aspect of the present invention, there is provided a polishing condition control method of a CMP apparatus that polishes a film to be polished formed on the wafer surface, and the polishing condition control method includes, a polishing recipe preparing step of preparing polishing conditions so that the polishing conditions such as polishing speed, polishing pressure, and an abrasive and the like for the wafer become optimal, a remaining film thickness forecasting step of forecasting the remaining film thickness of the wafer to be polished under the polishing conditions after polishing, a remaining film thickness measuring step of measuring the remaining film thickness of the wafer after the polishing, and a calculating step of calculating the difference between the measured value of the remaining film thickness and the forecasted value thereof, and a polishing condition correcting/changing step of correcting/changing the polishing conditions so that the calculated difference becomes minimal, and thereby, the correction/change of the polishing conditions is carried out in real time.

According to this method, the polishing conditions are so prepared that the polishing conditions such as polishing speed, polishing pressure, abrasives and the like become optimal, further, the remaining film thickness of the wafer to be polished under the optimal polishing conditions after polishing is forecasted. And, after the wafer is polished under the optimal polishing conditions, the remaining film thickness of the wafer surface is measured. In the next time and after that, the difference between the measured value of the remaining film thickness and the forecasted value thereof is calculated, subsequently, the polishing conditions are corrected/changed in real time so that the difference becomes minimal. Thus, wafers are always processed under the optimal polishing conditions, and the remaining film thickness of the wafers is processed smoothly into the target film thickness.

According to the first aspect of the present invention, the polishing conditions such as the polishing speed (polishing time), and the flow quantity of abrasives and the like can be always maintained optimally, and accordingly, it is possible to eliminate the unevenness in the remaining film thickness of the wafers by eliminating the excessive polishing and insufficient polishing, and improve the polishing efficiency, and reduce running costs (wastes of abrasives and the like). In addition, since the occurrence of defective products can be prevented, and the yield can be improved.

According to the second aspect of the present invention, the optimal polishing conditions can be prepared according to individual polishing step, polishing shaft or platen, and accordingly, in addition to the effect of the first aspect, it is possible to polish the remaining film thickness of the wafers into the target value more efficiently.

According to the third aspect of the present invention, since it is possible to obtain the polishing conditions that reflect the data of the past polishing history and the polishing model peculiar to the apparatus, in addition to the effect of the first or second aspect, it is possible to polish the remaining film thickness of the wafer into the target value more precisely.

According to the fourth aspect of the present invention, since the remaining film thickness of the wafer is forecasted on the basis of the data of the past polishing history, and accordingly, in addition to the effect of the first aspect, it has a merit to increase the reliability of the forecasted value of the remaining film thickness.

According to the fifth aspect of the present invention, since it is possible to grasp the changing result data and polishing states in real time, in addition to the effect of the first aspect, it is possible to check whether the polishing process of the wafers goes well.

According to the sixth aspect of the present invention, since when the polishing state gets erroneous, the effect to that is automatically notified, and at an emergency, the polishing process is stopped immediately, in addition to the effect of the first or fifth aspect, it is possible to prevent the wafer from being polished and processed in an erroneous state.

According to the seventh aspect of the present invention, since the optimal polishing conditions can be corrected/changed independently for each polishing step, each polishing shaft, each platen, or each combination of the polishing shaft and the platen, in addition to the effect of the first aspect, it is possible to eliminate the unevenness of the remaining film thickness of wafers among the polishing steps, the polishing shafts and/or the platens more efficiently.

According to the eighth aspect of the present invention, the polishing conditions such as the polishing speed (polishing time), and the flow quantity of abrasives and the like are always maintained, and accordingly, it is possible to improve the polishing precision of the remaining film thickness of the wafers, and the unevenness of the film thickness of the wafers can be eliminated, and further the high running costs (the wastes of abrasives) can be reduced. Furthermore, since the occurrence of defective products can be reduced, it is possible to improve the yield of the wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a polishing condition control apparatus of a CMP apparatus according to an embodiment of the present invention;

FIG. 2 is a perspective view showing a polishing unit according to an embodiment;

FIG. 3 is a flow chart for explaining the procedure of a polishing condition control according to an embodiment;

FIG. 4 are graphs showing the relation between the number of already polished sheets and the remaining film quantity, and 4A is a graph for explaining the permissible range of the remaining film quantity, and 4B is a graph for explaining the real polishing time and the forecasted time; and

FIG. 5 are graphs for explaining the characteristics of a polishing model according to an embodiment, and 5A is a graph for explaining a case where the remaining film quantity increases with time with the polishing pressure as its parameter, and 5B is a graph for explaining a case where the remaining film quantity decreases with time with the polishing pressure as its parameter, and 5C is a graph showing the relation between the remaining film quantity and the polishing time when the polishing speed changes.

DESCRIPTION OF PREFERRED EMBODIMENTS

In order to achieve the object to eliminate the unevenness of the remaining film thickness of the wafers, and, increase the polishing efficiency, reduce the running cost and enhance the yield, the present invention is embodied by that in a CMP apparatus that polishes a film to be polished formed on the wafer surface, a polishing recipe preparing means that prepares polishing conditions so that the polishing conditions such as polishing speed, polishing pressure, and an abrasive and the like for the wafer become optimal, a remaining film thickness forecasting means that forecasts the remaining film thickness of the wafer to be polished under the polishing conditions after polishing, a remaining film thickness measuring apparatus that measures the remaining film thickness of the wafer after the polishing, and a computer that controls the measurement results of the remaining film thickness and the polishing conditions, are arranged, and further, the computer includes a calculating unit that calculate the difference between the measured value of the remaining film thickness and the forecasted value thereof, and a polishing condition correcting/changing unit that corrects/changes the polishing conditions so that the calculated difference becomes minimal, and thereby, the correction/change of the polishing conditions is carried out in real time.

Hereinafter, an embodiment according to the present invention is explained with reference to FIG. 1 through FIG. 5. The present embodiment is structured so that the optimal polishing conditions are prepared, and the remaining film thickness of the wafers is forecasted, and the wafers are processes by CMP, and thereafter, the remaining film thickness of the wafers after polished is measured for each module, and the difference between the measured value of the remaining film thickness and the forecasted value thereof are compared and thereby the difference thereof is obtained, and the polishing conditions are corrected/changed in real time as much as possible so that the difference becomes minimal.

The data of the polishing history including the polishing time and the polishing quantity and the like acquired by the polishing process of wafers are controlled for each polishing shaft and/or each platen, and the data is used in preparing the polishing conditions. The forecasted value of the remaining film thickness may be calculated on the basis of the approximate expression prepared from the past polishing history data. Furthermore, the whole or part of the plural polishing conditions, detection results and polishing states may always be monitored optionally and selectively by the monitoring unit.

As shown in FIG. 1, a CMP apparatus 1 is structured of a remaining film thickness measuring apparatus 2, a polishing recipe preparing means 3, a remaining film thickness forecasting means 4, a polishing unit 5 and a computer 6 and the like. The remaining film thickness measuring apparatus 2 measures the remaining film thickness of the wafers after the polishing. And, the polishing recipe preparing means 3 prepares the polishing conditions so that the polishing conditions such as the polishing speed, the polishing pressure, and abrasives and the like become optimal.

The polishing recipe preparing means 3 refers to the past polishing history for each polishing step, or, each polishing shaft, each platen, or each combination of the polishing shaft and the platen, and thereby prepares the optimal polishing conditions.

Further, the polishing recipe preparing means 3 may prepare the optimal polishing conditions on the basis of one or both of the data on the basis of the approximate expression prepared from the past abrasion history, and the data of the polishing model which the CMP apparatus 1 has stored beforehand.

For example, FIG. 5A is a graph of a polishing model showing the relations between the polishing time and the polishing quantity at each polishing pressure that are made into fixed quantities and numerical values. FIG. 5B is a graph of a polishing model showing the relations between the polishing time and the polishing quantity at each polishing pressure that are made into fixed quantities and numerical values, on the basis of FIG. 5A, in the case where the film thickness before polishing is 280 nm. By these polishing models, the forecasted polishing quantity is calculated.

In this case, the latest data of the polishing history may be weighted and used.

The remaining film thickness forecasting means 4 forecasts the remaining film thickness of the wafer after the polishing to be polished under the polishing conditions. It can forecast the remaining film thickness of the wafer on the basis of the approximate expression prepared from the past polishing history. Meanwhile, the function of the remaining film thickness forecasting means 4 may also be performed by the polishing recipe preparing means 3.

In addition, the polishing unit 5 is the main body unit of a CMP apparatus that polishes wafers, and as shown in FIG. 2, it is structured so as to rotate a rotating shaft 8A of a platen 8 by a motor 7, and supply an abrasive (not illustrated) onto a polishing pad 9 attached to the platen 8, and drive to rotate a polishing shaft 10A of a polishing head 10 and rotate a wafer held on the polishing head 10, and push the wafer onto the polishing pad 9, and thereby polish the film to be polished of the wafer surface.

The computer 6 performs the control of the polishing condition on the basis of the measurement result of the remaining film thickness. This computer 6 includes a calculating unit 11, a memory unit 12, a polishing condition correcting/changing unit 13, a monitoring unit 14, a polishing state judging unit 15 and an apparatus control unit 16 and the like. The calculating unit 11 calculates the difference between the measured value of the remaining film thickness and the forecasted value thereof. In addition, the memory unit 12 memorizes the data of control state of the polishing conditions and others on the basis of the measurement result of the remaining film thickness.

Further, the polishing condition correcting/changing unit 13 corrects/changes the polishing conditions so that, when the calculated difference is a specified value or, the difference becomes minimal. In more addition, the monitor unit 14 displays difference between the measured value of the remaining film thickness and the forecasted value thereof, as well as the polishing state of the wafer. In addition, the polishing state judging unit 15 outputs an attention signal, an alarm signal and/or a polishing stop signal, when the calculated difference is the specified value or. Furthermore, the apparatus control unit 16 has a function to control the actions of respective portions of the CMP apparatus mainly on the basis of various kinds of order signals and the like.

The polishing condition control method according to the present embodiment makes the control on the basis of the measurement result of the remaining film thickness of the wafers and the forecast result before the polishing. The forecast result is the value set by obtaining an appropriate polishing time of the wafers.

In addition, when the polishing end point detection (not illustrated) is employed, in addition to the measurement result and the forecast result before polishing, the control of the end point detection result is also carried out. Meanwhile, the detection principle of the polishing end point detection means is not limited in particular, and, for example, a method to detect the torque fluctuation of the drive motor of the polishing head 10 or the platen 8, or a method to optically detect the remaining film thickness, and a method to use an eddy current and the like may be employed.

The polishing condition control apparatus 11 measure films to be polished including the metal film, oxide film and the like formed on the wafer surface after polishing for each module, that is, for each polishing shaft 10A, each platen 8, or, each combination of the polishing shaft 10A and the platen 8, and compares the measured value with the forecasted value, and corrects/changes the polishing conditions in real time as much as possible so that the difference becomes minimal.

As the polishing conditions, there are, for example, the polishing time, the polishing pressures (wafer pressure, zone pressure), the polishing speed (rotation speed of the platen 8 or the polishing shaft 10A), the polishing temperature of the wafer (the temperature of the polishing head, the temperature of the platen 8), the air flow quantity in the polishing head 10, and the kinds, components and flow quantity of abrasives, the like.

In the evaluation of the results of the measured remaining film thickness, a modulus difference or a deviation (a deviation of the remaining film thickness to the average remaining film thickness) between the measured value and the forecasted value is adopted, and the evaluation is carried out for each polishing step, or each polishing shaft 10A, each platen 8, or each combination of the polishing shaft 10A and the platen 8.

Hereinafter, an example of the procedure of the polishing condition control according to the present embodiment is explained in detail with reference to the flow chart in FIG. 3. First, the optimal polishing conditions are prepared by the polishing condition preparing unit (step S1). In this case, in consideration of useful information pieces about the polishing conditions to be obtained from wafer processing factories and bar code leaders, the polishing conditions are prepared for each polishing step.

In the preparation of the optimal polishing conditions, the polishing conditions are determined on the basis of a calculating expression. In this case, by many polishing history information, an approximate expression of the relations between the polishing conditions such as the polishing time, the polishing quantity, and on the basis of the result calculated by inserting concrete data into this approximate expression, the optimal polishing conditions to the wafers (objectives to be polished) W at the next time and after that are determined and adopted. FIG. 4A is a graph showing the relation between the number of already polished wafers and the remaining film quantity. In the figure, on the basis of this increase-decrease rate of the remaining film quantity to the latest i-th (i being an integer n of 1 or higher) wafer, the inclination in the graph, that is, the degree of changes of the remaining film quantity to the number of the already polished wafers is obtained. Then, on the basis of the degree of changes of the remaining film quantity, the remaining film quantity of the next (i+1)-th wafer is obtained, and the obtained remaining film quantity is assigned to the approximate expression, and the optimal polishing conditions are determined and adopted.

FIG. 4B is a graph showing the relations between the number of already polished wafers and the remaining film quantity. On the basis of the degree of the change of this remaining film quantity, an approximate expression using a multinomial expression approximation curve is prepared, and the remaining film quantity of the next (i+1)-th wafer is obtained, and the obtained remaining film quantity is assigned to the EDP time, and the forecasted value is obtained by extrapolation. On the basis of the forecasted value, the remaining film quantity of the (i+1)-th wafer is obtained, and the obtained remaining film quantity is assigned to the approximate expression, and thereby, the optimal polishing conditions are determined and adopted.

The remaining film thickness after the polishing of the wafer polished under the polishing conditions at the next time and after that is forecasted by the remaining film thickness forecasting means 4 (step S2). The forecast of this remaining film thickness is completed before the remaining film thickness of the wafer is measured by the remaining film thickness measuring apparatus at step S4. Then, at step S3, the CMP processing is started. The polishing data acquired by the CMP processing is controlled for each polishing shaft 10A and/or each platen 8, or each polishing step.

As the polishing data, the data of the polishing time, the remaining film quantity of each polishing process type, the EPD time, the use time and the number of used pieces of expendable supplies of the polishing pad 9 and the polishing head 10, and the temperature of the polishing pad 9, the temperature of the polishing head 10 and the like are included. These polishing data are memorized and controlled in the memory unit 12 as the past polishing history, and are used as useful data pieces when the optimal polishing recipes are prepared (step S4).

For example, among the polishing data, the polishing time, the remaining film quantity of each polishing process type, and the EPD time are controlled for each polishing step (for each polishing process type), and for each platen 8. In addition, the use time and the number of used pieces of expendable supplies such as abrasives and the like are controlled for each polishing shaft 10A and/or each platen 8. Further, the use time or the number of used pieces of the polishing pad 9, and the dressers is controlled for each platen 8, and the use time or the number of used pieces of the retainers for wafers and the polishing head 10 is controlled for each polishing shaft 10A. In the present embodiment, the polishing temperature of the wafer is also controlled for each polishing shaft 10A and/or each platen 8. For example, the temperature of the polishing pad 9 is controlled for each platen 8, and the temperature of the polishing head 10 is controlled for each polishing shaft 10A.

Thereafter, the remaining film thickness of the wafer is measured by the remaining film thickness measuring apparatus at step S5. In this case, a metal film remaining film thickness measuring apparatus or an oxide film remaining film thickness measuring apparatus is employed according to the kind of the film to be polished, and the measurement principle of the remaining film thickness measuring apparatus may be any of an optical method, an electric capacity method, an X-rays method, an eddy current method and the like.

At the next time and after that, the progress states of the CMP processing, that is, the change states of the wafer polished surface and the polishing temperature and the like are displayed in real time on the monitor unit 6 and are confirmed. In the present embodiment, a confirmation screen is divided into three ways and confirmed. In the confirmation screen 1, the result of calculating the difference between the forecasted value of the remaining film thickness and the measured value thereof by the calculating unit 11 is confirmed.

Further, in the confirmation screen 2, the use time and the number of sheets used for polishing of the expendable supplies such as abrasives, polishing pads and the like are monitored for each apparatus (for each polishing shaft 10A or each platen 8), and it is confirmed whether the use time and the number of sheets used for polishing are away from specified values preset for the each apparatus.

Furthermore, in the confirmation screen 3, the polishing temperature of the wafer measured by the temperature sensor, that is, the temperature of the polishing pad or the temperature of the polishing head are monitored, and it is confirmed whether the measuring temperature are away from specified values preset for the apparatus.

At the next time and after that, on the basis of the gap value between the result value and the forecasted value, and the unevenness of the result value, it is evaluated and judged whether the polishing is normal or abnormal (step S7). This evaluation is judged for each polishing step, and each polishing shaft 10A and/or each platen 8 by the polishing state judging unit 15. In the present embodiment, this judgment is evaluated into three states of “Normal state”, “Attention state” and “Warning state”.

That is, according to whether the gap value between the result value and the measured value, or the unevenness value of result values is larger than the predetermined permissible value or a warning value, the evaluation is made into three stages, and, a signal corresponding to the evaluation is output to the outside or the respective units of the apparatus. For example, in the case where the value is below the permissible value, it is judged as a “Normal state”, and the polishing process of the wafers at the next time and after that is continued as it is.

In addition, in the case where the value is the permissible value, and below the warming value, it is judged as an “Attention state”, and an attention signal (alarm) is given for attention to the operator. Furthermore, in the case where the value is the warning value, it is judged as a “Warning state”, and a warning signal (alarm) is given for attention to the operator, and also a polishing stop signal is output and the polishing process is stopped immediately. In addition, in the case when the gap value between the result value and the forecasted value exceeds the predetermined range, the approximate expressions and the like are changed. Further, the evaluation may be made by a combination of the evaluation methods of the “Attention state” and “Warning state”.

As explained, according to the present embodiment, the polishing conditions such as the polishing speed, the polishing pressure, the abrasives, and the like for the wafers are prepared by the polishing recipe preparing means 3 so as to become optimal, and the polishing conditions are corrected/changed in real time by the polishing condition correcting/changing unit 13 so that the difference between the measured value of the remaining film thickness of the wafers after polishing and the forecasted value thereof becomes minimal.

For example, as shown in FIG. 5C, in the case when the polishing speed is low by 30%, the target remaining film quantity is calculated at step 10. In addition, after the approximate expression is obtained when the polishing speed is low by 30%, at steps 11 and 12, the polishing time is expanded until the target polishing speed is obtained while the polishing speed is low by 30%.

Meanwhile, since the film thickness measurement of the wafers W is carried out after the wafers W are washed, the polishing conditions after the correction/change is not always reflected to the wafer W that is polished after the first wafer W that is measured, and they may be reflected to the second wafer W and wafer after that to be polished.

Therefore, since the polishing conditions such as the polishing speed, the polishing time, the flow quantity of abrasives and the like can be always maintained optimally, the remaining film thickness of the wafers is polished precisely into the target value, and accordingly, it is possible to eliminate the unevenness of the remaining film thickness of the wafers, and improve the polishing efficiency. In addition, the use time of the expendable supplies such as the polishing pads 9, the polishing heads 10, abrasives and the like is shortened to a necessary minimum, and consequently, the running cost is reduced by reducing the waste of expendable supplies. Furthermore, the occurrence of defective products is decreased, and consequently, it is possible to enhance the yield substantially.

Further, the past polishing histories are referred to for each polishing step of the wafers, or, each polishing shaft 10A or, each platen 8, or, each combination of the polishing shaft 10A and the platen 8, and thereby the optimal polishing conditions are prepared. And consequently, it is possible to polish the wafers under the optimal polishing conditions individually set for each polishing step, each polishing shaft 10A or each platen 8, and accordingly it is possible to polish the remaining film thickness of the wafers into the target value further more efficiently.

Furthermore, in the case when the data of the latest polishing history of high information value is weighted, since wafers can be polished under the polishing conditions in which importance is put on the latest raw data, the polishing efficiency of the wafers improves further more.

Moreover, in the preparation of the polishing conditions, the approximate expression prepared from the past polishing history, and the data of the polishing model that the apparatus itself already stores are used, the wafers can be polished under the polishing conditions reflecting the data of the past polishing history and the polishing model peculiar to the apparatus, and consequently, it is possible to polish the remaining film thickness of the wafers efficiently and precisely.

Still further, since the remaining film thickness of the wafers is forecasted on the basis of the approximate expression prepared from the past polishing history, it is possible to obtain a highly reliable forecasted value.

Furthermore, since the difference between the measured value of the polishing time and the forecasted value thereof, and the polishing states of the wafers can be monitored and grasped on the screen of the monitoring unit 14 in real time, it is possible to easily confirm the polishing states of the wafers during the polishing, and always maintain the polishing conditions according to the specifications of the wafers and the polishing environment.

Moreover, when the calculated difference value is of the permissible value or the attention signal is automatically output from the polishing state judging unit 15, and, when the calculated difference value is of the warning value or the warning signal and the polishing stop signal are automatically output, and accordingly, even an erroneous polishing state occurs, such a state can be coped with immediately and appropriately.

In the present embodiment, the correction/change of the polishing conditions are carried out independently for each polishing step of the wafers, each polishing shaft 10A, each platen 8, or each combination of the polishing shaft 10A and the platen 8. Accordingly, it is possible to obtain the optimal polishing conditions according to each polishing step, and to obtain the optimal polishing conditions according to each polishing shaft 10A, each platen 8, or each combination of the polishing shaft 10A and the platen 8. And consequently, it is possible to eliminate the unevenness of the remaining film thickness of the wafers among plural polishing steps, polishing shafts 10A and/or platens 8.

The present invention can be variously modified within the scope of the present invention, and it goes without saying that the present invention comes to the modified structure.

DESCRIPTION OF REFERENCE NUMERALS

1 CMP apparatus

2 Remaining film thickness measuring apparatus

3 Polishing recipe preparing means

4 Remaining film thickness forecasting means

5 Polishing unit

6 Computer (control means)

8 Platen

10 Polishing head

11 Calculating unit

12 Memory unit

13 Polishing condition correcting/changing unit

14 Monitoring unit

15 Polishing state judging unit

Polishing condition control apparatus and polishing condition control method of CMP apparatus

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