JP2008103517A - Method of controlling semiconductor manufacturing process and polishing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manage the cutting rate of a conditioner precisely and easily and to manage the use limit (life) of the conditioner viewed from the cutting rate of a polishing pad. <P>SOLUTION: The polishing apparatus has an optical displacement meter for measuring the unevenness (groove depth) of the polishing pad, and therefore the cutting rate of the conditioner used for toothing the polishing pad can be managed precisely and easily. By feeding back conditioner load calculated from the output data of the displacement meter to a polishing recipe, the cutting rate can be maintained stably independently of the accumulated use time of the conditioner. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polishing technique, and in particular, a polishing apparatus and a conditioner cutting that can manage the cutting rate of a conditioner with high accuracy and ease, and can manage the conditioner use limit (life) as viewed from the cutting rate of the polishing pad. The present invention relates to a rate control method, a conditioner load control method, and a semiconductor manufacturing process control method.

  Reduction in process variation with respect to a CMP (Chemical Mechanical Polishing) process is strongly desired as semiconductor elements become finer. In the prior art, since the process condition value is set as a fixed value, it is impossible to construct a process considering individual performance differences such as consumable members.

  A typical recipe structure in a conventional CMP apparatus is shown in FIG. As shown in FIG. 8, in the conventional recipe structure, various process condition values have a structure using fixed values. The conditioner condition used for sharpening on the polishing pad is similarly set as a fixed value. As described above, in the CMP process, various process condition values have a structure using fixed values, but since a process that takes into consideration the performance solid difference for each conditioner has not been constructed, the current conditioner management method is: In general, a standard value is determined based on data obtained at the time of introduction evaluation, and a management standard is set. The management method of the polishing pad is the same.

  In addition, please refer to the following patent document 1 as a prior art relevant to this invention.

JP-A-2004-25413

  That is, in the prior art, (1) the cutting rate of the conditioner cannot be controlled, and (2) the use limit (life) of the conditioner viewed from the cutting rate is not managed, resulting in individual performance differences of the conditioner. Process stability degradation is a well-known matter.

  In addition, since the difference in the solid performance of the conditioner is not taken into consideration at all, an unstable process is induced, and the consumable member replacement cycle is accelerated, leading to an increase in process cost.

  In the above-described prior art, a large margin is actually set for the load condition of the conditioner and the use limit (life) standard of the conditioner. As a result, due to the difference in the solid performance of the conditioner, if the process is performed with an excessive conditioner load, an excessive cutting rate results, and the use limit (life) of the conditioner and the polishing pad is shortened. Therefore, the replacement cycle of the consumable member is accelerated and the process cost is increased.

  In the opposite case, the process may be carried out with insufficient conditioner load, resulting in an inadequate cutting rate, which may induce an unstable process and create a large number of defective products. is there. From this, it can be said that condition management load management (cutting rate management) is very important to realize process stabilization, and it is necessary to construct a process that takes into account the condition of performance condition of the conditioner (precision control). . In general, it is well known that among the consumable members constituting the CMP process, the difference in the solid performance of the conditioner varies greatly. In order to realize stabilization of the CMP process, it is important to control the variation of the consumable member by some method.

  Accordingly, an object of the present invention is to attach an optical displacement system that can monitor the unevenness (groove depth) of the polishing pad, so that the cutting rate of the conditioner can be managed with high accuracy and ease. The present invention provides a conditioner cutting rate control method, a conditioner pressure control method, and a polishing apparatus for a polishing pad capable of managing a conditioner use limit (life) as viewed from the rate.

  Another object of the present invention is to maintain a stable cutting rate independent of the cumulative usage time of the conditioner by constructing a system that can feed back the conditioner load to the polishing recipe from the output data of the displacement meter. A conditioner cutting rate control method for a polishing pad that can realize a stable process construction that takes into account the difference in solid performance of the members, and that can effectively use the consumable members by performing precise management of the consumable members The present invention provides a conditioner pressure control method and a polishing apparatus.

  The polishing apparatus according to the first aspect of the present invention holds the polishing pad (2) attached to the rotating surface plate (6) and the wafer (4), and the wafer (4) on the polishing pad (2). A wafer holding head (3) that rotates while pressing, a slurry supply part (1) arranged in the radial direction of the polishing pad (2), and a conditioner (5) used for sharpening the polishing pad (2). Displacement arm portion (7) having a plurality of optical displacement meters for measuring the groove depth of polishing pad (2) arranged in the radial direction of polishing pad (2), and electrically connected to the optical displacement meter And a computer (8). The computer (8) calculates a cutting rate before and after wafer polishing from a groove depth before and after wafer polishing measured by the optical displacement meter, and based on the cutting rate before and after wafer polishing. Then, the conditioner load condition value of the next polishing wafer is calculated, and the conditioner load condition value is fed back to the polishing recipe.

  A method for controlling a semiconductor manufacturing process according to a second aspect of the present invention includes a first step of measuring a groove depth of a polishing pad with an optical displacement meter, and a reference value in which the first measured value is predetermined. A second step for determining whether or not the above is satisfied, and a third step for giving a polishing pad replacement instruction when the first measurement value obtained in the first step is less than a predetermined reference value. And when the first measurement value is equal to or greater than the reference value, the process proceeds to test conditioning, and a fourth step of measuring the groove depth of the polishing pad with an optical displacement meter, and the first measurement value, A conditioner cutting rate obtained by dividing the difference between the second measurement values obtained in the fourth step by a predetermined time is calculated, and it is determined whether or not the cutting rate is within a predetermined reference value range. To do the fifth A step of giving a conditioner replacement instruction when the cutting rate is outside the range of the reference value, and a conditioner load corresponding to the cutting rate when the cutting rate is within the range of the reference value Obtained in the seventh step, the eighth step of starting the wafer polishing process after adjusting the conditioner load, and measuring the groove depth of the polishing pad with an optical displacement meter, and the seventh step. An eighth step for determining whether or not the third measured value is equal to or greater than a predetermined reference value; and an instruction to replace the polishing pad when the third measured value is less than a predetermined reference value And a difference obtained by dividing a difference between the third measurement value and the second measurement value by a predetermined time when the third measurement value is equal to or greater than the reference value. Calculating a Ishona cutting rate, having an eleventh step of which the cutting rate is determined if it is within range of a predetermined reference value. The fifth to eleventh steps are repeated until the polishing pad replacement instruction or the conditioner replacement instruction is issued.

  The first effect of the present invention is that an optical displacement meter is attached and a conditioner load can be fed back to the polishing recipe from the output data of the displacement meter, so that the cutting rate of the conditioner can be adjusted with high accuracy and simplicity. It becomes possible to manage.

  The second effect of the present invention is that an optical displacement meter is attached, and a stable cutting that does not depend on the cumulative use time of the conditioner is achieved by constructing a system that can feed back the conditioner load to the polishing recipe from the output data of the displacement meter. It is possible to maintain the rate.

  The third effect of the present invention is that, as described above, the cutting rate can be managed with high accuracy and simplicity, so that it is possible to manage the conditioner use limit (life) as viewed from the cutting rate of the polishing pad.

  The fourth effect of the present invention is that a stable process construction considering the solid performance difference of members can be realized by attaching an optical displacement meter.

  On the other hand, in the case of a system that changes the conditioner time based on the results of the contact displacement meter and the cutting rate result disclosed in Patent Document 1 as the prior art document, data of wear due to the wear of the needle tip for monitoring the displacement is obtained. There is concern about accuracy deterioration and metal contamination of the wafer due to the metallic member of the needle tip. Further, there is a problem that T / P is lowered by changing the conditioner time. However, by applying the present invention, it is possible to solve all of the disadvantages of the contact displacement meter and problems such as T / P reduction due to the change of the conditioner time.

  1A and 1B are a top view and a side view showing an embodiment of a polishing apparatus according to the present invention. FIG. 2 is a view showing the structure of a recipe serving as a basis for calculating the conditioner load condition of the next polished wafer. As shown in FIGS. 1A and 1B, the polishing apparatus according to the present invention holds the polishing pad 2 attached to the rotating surface plate 6 and the wafer 4 and presses the wafer 4 against the polishing pad 2. A wafer holding head 3 that rotates, a slurry supply unit 1 arranged in the radial direction of the polishing pad 2, a conditioner 5 used for sharpening the polishing pad 2, and a conditioner cutting rate arranged in the radial direction of the polishing pad 2. It has a displacement meter arm portion 7 to be measured. A first optical displacement meter 7a, a second optical displacement meter 7b,... N-th (n is an integer of 3 or more) optical displacement meters 7c are attached to the displacement meter arm section 7. . The displacement meter arm unit 7 is connected to a computer 8 for calculating the cutting rate and feeding back the conditioner load from the cutting rate to the polishing recipe. As shown in FIG. 2, the computer 8 stores the cutting rate before wafer polishing and the cutting rate after polishing measured by the optical displacement meter in the computer, and calculates the conditioner load condition of the next polished wafer. . The value is fed back to the polishing recipe.

  Next, a control method according to the present invention will be described. The present invention is characterized in that a stable process can be realized by constructing a system attached with an optical displacement meter and feeding back the cutting rate of the conditioner to the polishing pad to the polishing recipe. FIG. 3 is a graph showing the transition of the cutting rate of each conditioner when the process is performed according to the conventional technique and when the process is performed using the control method of the present invention. It is the graph which showed the polishing rate in-plane uniformity transition. The horizontal axis of FIGS. 3 and 4 is the cumulative usage time of the conditioner, and the time is plotted. In the present embodiment, the standard value of the conditioner load is set to 9 lbf, and five optical displacement meters are attached. The type of slurry is silica-based slurry, and IC1000 system is used for the polishing pad.

  In the prior art, a reduction in the cutting rate is seen from an early stage together with the cumulative usage time of the conditioner. Further, as the cutting rate is lowered, the polishing rate is lowered and the uniformity of the polishing rate in the surface is also seen. On the other hand, when the control method of the present invention is used, it can be easily understood that a stable cutting rate is realized with respect to the cumulative usage time of the conditioner. It can also be seen that by realizing a stable cutting rate, the polishing rate and the in-plane uniformity of the polishing rate are also stable. Furthermore, in this control method, the conditioner load is varied while monitoring the cutting rate of the conditioner, so that it can be seen that the life of the member is extended as compared with the prior art.

  In the present invention, process control is performed in a flowchart as shown in FIG. First, prior to polishing, a polishing recipe is read (step S101), and polishing pad groove depth measurement (dpre) is performed (step S102). Next, it is determined whether or not the measured polishing pad groove depth is equal to or greater than a predetermined reference value (A) (step S103). Here, steps S101 and S102 are defined as routine i.

  As a result of the measurement of the groove depth of the polishing pad, when the first measurement value measured in step S102 is less than the predetermined reference value (A) (No in step S103), the calculator 8 replaces the polishing pad. An instruction is given to a CPU (not shown) of the CMP apparatus, the polishing operation is stopped as a determination NG, and the polishing pad replacement operation is performed. If the first measurement value measured in step S102 is equal to or greater than a predetermined reference value (A) (Yes in step S103), the determination is OK and the process proceeds to the test conditioning step (step S105). Then, the polishing pad groove depth is measured (dpost), and the second measurement value is calculated (step S106). Here, steps S105 and S106 are defined as routine ii.

  A difference between the first measurement value and the second measurement value obtained in step S106 is divided by a predetermined time to calculate a conditioner cutting rate, and the cutting rate is within a predetermined reference value range. It is determined whether or not there is (step S107). Here, the calculation / determination of the conditioner cutting rate is performed using Formula 1a or Formula 1b in FIG. When the calculation results of Formula 1a and Formula 1b do not satisfy the determination conditions of Formula 2a and Formula 2b of FIG. 6 (No in Step S107), the polishing operation is stopped (Step S107), and the conditioner is performed according to the flow of FIG. Exchange work is performed (step S108). When the determinations of Formula 2a and Formula 2b in FIG. 6 are satisfied (Yes in Step S107), the load of the conditioner is corrected using Formula 3a and Formula 3b in FIG. 6 and load adjustment (DF) is performed. (Step S109), the wafer polishing process is started (Step S110). Here, the processing flow of steps S107, S109, and S110 is referred to as routine iii.

  After the wafer polishing process is started, the groove depth of the polishing pad is measured (dpont) with the optical displacement meter in the same manner as described above (step S111) to obtain a third measured value, and this third measured value Is greater than or equal to a predetermined reference value (step S112). If the third measurement value is less than the predetermined reference value (A) (No in step S112), a polishing operation stop command is sent and a polishing pad replacement instruction is given (step S104).

  When the third measurement value is equal to or greater than the reference value (Yes in step S112), a conditioner cutting rate obtained by dividing the difference between the third measurement value and the second measurement value by a predetermined time is calculated. Then, it is determined whether or not the cutting rate is within a predetermined reference value range (step S107). Thereafter, the processes of steps S107 and S109 to S112 are repeated until a polishing pad replacement instruction or a conditioner replacement instruction is issued. Here, the processing flow of steps S107 and S109 to S112 is referred to as routine iv.

  In step S109, the condition in which the relationship between the cutting rate and the conditioner load is described in advance in the computer is stored in a table, and an appropriate conditioner load can be determined by referring to the table. FIG. 7 is a graph showing the relationship between the conditioner load to be determined and the cutting rate. For example, arbitrary upper limit values and lower limit values may be set in the memory of the cutting rate on the vertical axis, and when the slope of the graph changes within the range, load correction that restores the slope may be performed. .

  After the polishing operation is started (step S110), the routine iv is repeatedly performed, the wafer polishing process is continued, and the polishing operation is finally finished. If the determination in step S112 is NG, polishing pad replacement work and conditioner replacement work are performed as necessary.

  Further, each of the above-described embodiments is merely an example of a preferred embodiment of the present invention, and the present invention can be implemented with various modifications without departing from the gist thereof. For example, the routine i and the routine ii in FIG. 5 may be executed, and after performing the determination in step S107, the load adjustment is not performed and the processing steps after step S110 may be executed.

  INDUSTRIAL APPLICABILITY According to the present invention, in the CMP process of the semiconductor manufacturing process, it can be applied to the case where the performance difference between consumable members constituting the CMP process is monitored by some method and the result is fed back to the polishing recipe to construct the process. It is.

(A) is the top view which showed one Embodiment of the grinding | polishing apparatus based on this invention, (b) is a side view. It is the figure which showed the structure of the grinding | polishing recipe which stored various conditions used for the semiconductor manufacturing process control method which concerns on this invention. It is the graph which showed the cutting rate transition of each conditioner when the process was implemented by the prior art and when the process was implemented using the control method of the present invention. 5 is a graph showing a change in polishing rate and a change in uniformity in the polishing rate surface. It is the flowchart which showed each step of the semiconductor manufacturing process control method which concerns on this invention. It is the figure which showed the determination formula used at the determination process step in the semiconductor manufacturing process control method concerning this invention. It is a graph which shows the relationship between the conditioner load to determine and a cutting rate. It is the figure which showed the typical recipe structure in the conventional CMP apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slurry supply part 2 Polishing pad 3 Wafer holding head 4 Wafer 5 Conditioner 6 Surface plate 7 Displacement meter arm part 7a, 7b, 7c Optical displacement meter 8 Calculator

Claims (6)

A polishing pad affixed to a rotating surface plate and a conditioner used for sharpening the polishing pad, supplying a slurry between the polishing pad and the wafer, and applying the load to the polishing pad and the wafer; In a polishing apparatus for polishing the wafer by relatively moving
A displacement meter arm portion disposed in a radial direction of the polishing pad and provided with an optical displacement meter for measuring a groove depth of the polishing pad;
A cutting rate before wafer polishing and a cutting rate after polishing are calculated from the groove depth before and after wafer polishing measured by the optical displacement meter, and a conditioner for the next polishing wafer is calculated based on the cutting rate before and after wafer polishing. A polishing apparatus comprising: a calculator that calculates a load condition value and feeds back the conditioner load condition value to a polishing recipe.   The polishing apparatus according to claim 1, wherein n (n is an integer of 2 or more) optical displacement meters are attached to the displacement meter arm portion. A first step of measuring a groove depth at n (n is an integer of 2 or more) of the polishing pad with an optical displacement meter;
A second step of giving a polishing pad replacement instruction when the first measurement value obtained in the first step is less than a predetermined reference value;
When the first measurement value is equal to or greater than the reference value, the process proceeds to test conditioning, and a third step of measuring the groove depth of the polishing pad with an optical displacement meter;
A conditioner cutting rate obtained by dividing the difference between the first measured value and the second measured value obtained in the third step by a predetermined time is calculated, and the cutting rate is within a predetermined reference value range. A fourth step of determining whether or not
When the cutting rate is outside the range of the reference value, a conditioner replacement instruction is given, and when the cutting rate is within the range of the reference value, a fifth step of starting a polishing process is provided. Conditioner cutting rate control method. First and second measured values are calculated by measuring the groove depth at n (n is an integer of 2 or more) locations of the polishing pad at predetermined time intervals, and the calculated first and second calculated values are calculated. A first step of calculating a conditioner cutting rate based on the difference between the measured values;
A conditioner load control method comprising: a second step of correcting and adjusting a suitable conditioner load corresponding to a predetermined upper limit value and lower limit value range of the calculated cutting rate. A first step of measuring the groove depth of the polishing pad with an optical displacement meter;
A second step of determining whether the first measurement value is greater than or equal to a predetermined reference value;
A third step of giving a polishing pad replacement instruction when the first measurement value obtained in the first step is less than a predetermined reference value;
If the first measurement value is greater than or equal to the reference value, the process proceeds to test conditioning, and a fourth step of measuring the groove depth of the polishing pad with an optical displacement meter;
A conditioner cutting rate obtained by dividing the difference between the first measured value and the second measured value obtained in the fourth step by a predetermined time is calculated, and the cutting rate is within a predetermined reference value range. A fifth step of determining whether or not
A sixth step of giving a conditioner replacement instruction if the cutting rate is outside the range of the reference value;
A seventh step of adjusting the conditioner load corresponding to the cutting rate when the cutting rate is within the range of the reference value;
After adjusting the conditioner load, the eighth step of starting the wafer polishing process and measuring the groove depth of the polishing pad with an optical displacement meter;
An eighth step of determining whether or not the third measurement value obtained in the seventh step is greater than or equal to a predetermined reference value;
A tenth step of giving a polishing pad replacement instruction when the third measurement value is less than a predetermined reference value;
When the third measurement value is equal to or greater than the reference value, a conditioner cutting rate obtained by dividing the difference between the third measurement value and the second measurement value by a predetermined time is calculated, and the cutting rate is calculated in advance. An eleventh step for determining whether or not the value is within a predetermined reference value range;
Thereafter, the fifth to eleventh steps are repeated until the polishing pad replacement instruction or the conditioner replacement instruction is issued.   The first to third measurement values are values obtained by measuring the groove depth at n (n is an integer of 2 or more) of the polishing pad at an interval of the predetermined time, 6. The adjustment of the conditioner load is performed by correcting the conditioner load to a suitable conditioner load corresponding to a predetermined upper limit value and lower limit value of the calculated cutting rate. Method for controlling the semiconductor manufacturing process.

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