JP2851620B2 - Control method of thin film polishing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control technique for a thin film polishing apparatus, and more particularly to a technique effective when applied to a field requiring high polishing accuracy.

[Conventional technology]

For example, in the case of a magnetic disk used as a storage medium in an information processing system or the like, information such as surface roughness and film thickness of a magnetic thin film deposited on the surface is used for recording / recording information.
It is known that it greatly affects the reproduction performance. For this reason, the magnetic thin film is precisely polished to a predetermined thickness before use.

By the way, such a magnetic disk polishing technique is known, for example, from Japanese Patent Application Laid-Open No. 57-104806.

The outline is that the change in the thickness of the magnetic thin film during polishing is monitored by a non-contact type film thickness measuring device, and the polishing is terminated when the target film thickness is reached. The purpose is to prevent the thickness from being affected by variations in the thickness before processing.

[Problems to be solved by the invention]

By the way, in the precision polishing described above, it is common to perform the work while wetting an object to be polished with a grinding fluid, and unevenness, wavyness, and machining of the magnetic disk caused by the grinding fluid occur during the processing. Correction of the error of the measured value of the film thickness due to accumulation of residue and contamination on the magnetic disk surface is indispensable for realizing high-precision polishing. No specific means are presented.

That is, according to the study of the present inventors, for example, a large error such as uneven wetness and waving of the grinding fluid is 5 times, accumulation of the residue is 10 times, and dirt is about 5 times with respect to the required dispersion of the film thickness. It has been found to be a factor.

Therefore, an object of the present invention is to provide a control technique of a thin film polishing apparatus that can improve the accuracy of polishing by correcting a measured value of a film thickness during polishing.

Another object of the present invention is to provide a control technique of a thin film polishing apparatus capable of controlling a required time for polishing processing to a predetermined value.

The above and other objects and novel features of the present invention are as follows.
It will be apparent from the description of this specification and the accompanying drawings.

[Means for solving the problem]

The outline of a representative invention among the inventions disclosed in the present application will be briefly described as follows.

That is, a polishing head for polishing a thin film deposited on a substrate while pouring a grinding fluid, a film thickness measuring unit for measuring the film thickness of the thin film as needed, and a change in the film thickness measured by the film thickness measuring unit. A method for controlling a thin film polishing apparatus, comprising: a control unit for controlling an operation of a polishing head unit based on the amount of fluorescent X-rays from the thin film to measure the thickness of the thin film and to detect the presence of a grinding fluid. By grasping at least one of the first and second influence amounts on the measured value of the film thickness due to the presence or absence of each and the residue generated during the polishing process, the measured value of the film thickness during the process is corrected. It was done.

[Action]

According to the above-described means, it is possible to reliably eliminate an error that is involved in measuring the thickness of a thin film during polishing due to, for example, a grinding fluid or a residue. As a result, it is possible to precisely control the polishing amount of the thin film, and the precision in the polishing process is improved.

Also, by controlling the pressing force of the polishing head against the substrate during processing to control the true film thickness reduction amount per unit time, the polishing to the target film thickness is completed within the target processing time. By doing so, it is possible to control the required time in the polishing operation of each substrate to a predetermined value without being affected by, for example, a reduction in the polishing capability due to wear of the polishing head.

〔Example〕

FIG. 1 is a flowchart showing an example of a control operation in a method for controlling a thin film polishing apparatus according to one embodiment of the present invention, and FIG. 2 is a thin film polishing apparatus used in the method for controlling a thin film polishing apparatus according to this embodiment. FIG. 3 is a block diagram showing an example of the configuration of the main part, and FIGS. 3 and 4 are diagrams illustrating an example of the operation of the control method of the thin film polishing apparatus according to the present embodiment.

First, as shown in FIG. 2, the thin film polishing apparatus according to the present embodiment comprises a spindle 2 for rotating a magnetic disk 1 (substrate) having a predetermined magnetic thin film or the like adhered to both surfaces thereof, and a grinding belt (not shown). A polishing head unit 5 including a roller 3 to be bridged and a processing load adjuster 4 for driving the roller 3 in a direction perpendicular to the surface of the magnetic disk 1, and a grinding belt (not shown) stretched around the roller 3 The magnetic thin film adhered to the surface of the magnetic disk 1 is polished by pressing the rotating magnetic disk 1 with a desired load while rotating.

In the vicinity of the magnetic disk 1, a grinding liquid nozzle 7 for pouring a polishing liquid 6 having a predetermined composition onto the surface of the magnetic disk 1 from above the roller 3 is arranged. It is configured such that residues such as polishing dust generated from the surface are removed.

At the position on the same side of the magnetic disk 1 that is aligned with the polishing head unit 5 via the spindle 2, for example, the amount of fluorescent X-rays from iron contained in the magnetic thin film deposited on the surface of the magnetic disk 1 is detected. Accordingly, a film thickness measuring device 8 for measuring the thickness of the magnetic thin film in a non-contact manner is provided, and a change in the thickness of the magnetic thin film during polishing can be measured at any time.

A control operation unit 9 is provided between the film thickness measuring device 8 and the polishing head unit 5, and the control operation unit 9 is based on information on the thickness of the magnetic thin film obtained from the film thickness measuring device 8. Thus, the operation of the polishing head unit 5 is controlled.

Although not shown, a polishing head 5, a grinding fluid nozzle 7, a film thickness measuring device 8 and the like are also arranged on the back side of the magnetic disk 1 via the magnetic disk 1 so as to be symmetrical with the front side. The polishing of the magnetic thin films deposited on both surfaces of the magnetic disk 1 is performed simultaneously under the control of the control arithmetic unit 9.

In this case, the control operation unit 9 includes a grinding fluid effect evaluation unit 10.
, A measured film thickness calculation unit 11, a residue effect evaluation unit 12, and a determination unit
13 and a load control unit 14 are provided.
The actual amount of decrease in film thickness is calculated by performing a predetermined correction on the measurement value obtained from the above, and the polishing process is terminated when the thickness of the magnetic thin film on the magnetic disk 1 reaches a predetermined value. It performs various control operations.

That is, the grinding fluid impact evaluation unit 10, a thickness X ₁ before the process of the average obtained from a plurality of measured values of the grinding fluid 6 a dry state is not supplied to the magnetic disk 1, while pouring a grinding liquid 6 Yuku is brought closer to the roller 3 on the magnetic disk 1, the unprocessed W = X ₂ from unprocessed thickness X ₂ Metropolitan obtained from a plurality of measurement values obtained in the so-called landing operation of -X ₁ · · · (1) To determine the first influence amount W due to the presence or absence of the supply of the grinding fluid 6, and further calculate the moving average using the value of W obtained in the processing up to n times ago by the following formula, and The influence amount W ' j: Subscript indicating the order of processing k _j : Load average count Further, from this W ', the grinding fluid 6 is present on the surface of the magnetic disk 1 by the following equation: X ₂ ' = X ₁ + W '(3) This is to grasp the film thickness X ₂ ′ in the landing before processing.

Further, the measured film thickness calculating section 11 obtains the current approximate value X _mi of the film thickness that is changing during processing by the following equation by the least square method.

Here, X _k : the past k-th measured value k: a subscript indicating the order of measurement i: the number of measurements The residue influence evaluation unit 12 calculates the current approximate value of the film thickness.
From the X _mi and the film thickness X ₂ ′ at the landing, q _i ′ = X ₂ ′ −X _mi (5) The current apparent machining amount q _i ′ is obtained from the following equation. 'by the correlation function f in the second influencing variables r _i according to the residue at that time, r _i = f (q _i' the wanted amount of machining apparent q _i) ··· (6) film due to the presence of residues The second influence quantity r _i on the thickness measurement
Ask for.

According to the study of the present inventors, it has been found that the correlation function f is a linear function.

Then, 'the Tocharian formula _{(7), q i = r} i + q i' the second influencing variables r _i and an apparent processing amount q _i ··· (7) to calculate the true working volume q _i, by subtracting the film thickness X ₁ before the process of the average obtained from a plurality of measurements of the true amount of machining q _i a dry state that is measured in the absence of the influence of the grinding fluid 6, X _Pi = X ₁₋ q _i (8) The true film thickness X _Pi at that time is calculated.

The determination unit 13 determines whether or not the average value of the true film thicknesses X _pia and X _{pib on} each of the A and B surfaces of the magnetic disk 1 is equal to or _smaller than a target film thickness. The control operation for stopping the polishing operation is performed.

Further, the load control unit 14, from said determining unit 13 target processing time TO _t set in advance from one machining time 15 and the outside of the magnetic disk 1 during processing resulting from the side of, for example, the following formula indicated by PI (proportional-integral) processing load P _t command the processing load regulator polishing head 5 by a control that is appropriately increased or decreased, and performs control so as to complete the grinding in a target machining time is there.

_{P t = k I · TD t} + k P (TD t -TD t-1) TD t = TO t -TM t ··· (9) However, k _P: proportional gain k _I: integral gain TM _t: control time Incidentally, the integral gain k _I is obtained by the relationship between the processing time and the processing amount in the predetermined processing time is set to about 1/2 in the case of the present embodiment.

Further, the proportional gain k _P is determined so as to compensate for the delay of the integral gain, in the case of the embodiment is set to about 1/3.

Moreover, processing time 15 performs proportional correction in accordance with the thickness X ₁ before processing.

 Hereinafter, the operation of the present embodiment will be described.

First, the magnetic disk 1 to be polished is mounted on the spindle 2 and the film thickness is measured a plurality of times by the film thickness measuring device 8 while rotating without supplying the grinding fluid 6, and the average value is supplied to the grinding fluid 6. the thickness X ₁ before the magnetic thin film.
(Step 101) Next, while pouring the grinding liquid 6, a landing operation for bringing the roller 3 of the polishing head unit 5 close to the surface of the magnetic disk 1 is started, and the film thickness is set in a state where the magnetic disk 1 is wet with the grinding liquid 6. and multiple measurements and the average value X ₂ (step 10
2), further to grasp the first influence quantity W with respect to the film thickness measurement by the presence of the grinding fluid 6 from the difference between X ₂ and X _1. (Step
103) Here, the distribution of W in each magnetic disk 1 (1
σ) can be obtained relatively stably as about 0.005 μm, but in a large number of processing steps, unusual measured values also occur sporadically depending on the state of the grinding fluid 6 and the like. And minimize the effects of errors. (Step 104) Then, the smoothed first influence amount W ′ and the X ₁
And the film thickness before processing taking into account the effect of the grinding fluid 6.
X ₂ ′ is calculated. (Step 105) Next, a grinding belt (not shown) stretched around the roller 3 by a desired load is pressed against the surface of the rotating magnetic disk 1 to start polishing, and the processing is performed at predetermined time intervals. The film thickness is measured, and an approximate value X _mi is sequentially calculated from the measured value before that by the least square method. (Step 10
6) Further, the apparent processing amount q _i ′ is calculated by subtracting the approximate value X _{mi of the} film thickness measured at that time from the film thickness X ₂ ′ before processing taking into account the effect of the grinding fluid 6 (step 107). ), further, the processing amount q _i 'of this apparent, the correlation function f that has been determined by an experiment or the like in advance, calculates a second influencing variables r _i due to the presence of residues such as polishing debris generated during processing (step 108), calculates a true working volume q _i from the machining amount q _i 'of the second influencing variables r _i and apparent (step 109),
The true processing amount q _i from the film thickness X ₁ before processing which is not affected by the grinding fluid 6
Is subtracted to calculate the true thickness _Xpi of the thin film adhered to the magnetic disk 1 at that time during the processing. (Step 110) Then, the average value of the true film thicknesses X _pia and X _{pib on} each of the A and B surfaces of the magnetic disk 1 is compared with the target film thickness (Step 111), and the true film thickness X _pia and X _If the average value of _pib is larger than the target film thickness, polishing is continued while repeating steps 106 to ₁₁₀ , and the average value of the true film thicknesses X _pia and X _pib becomes equal to or smaller than the target film thickness. At this point, the polishing is completed.

Further, in this embodiment, steps 106 to 1 are performed during the processing.
When the calculation of 10 is performed, the amount of calculation in step 106 is particularly large. This is because the terms from k = 1 to i−1 are calculated within the idle time of the calculation unit immediately after the calculation of the previous measurement value X _mi. To do it.

Shows the processing of the measurement values in this sequence of course is a third view, as shown in the figure, individual measurements X _k
There also varies greatly affected by residues of polishing debris generated during the grinding liquid 6 and processing, without receiving their effects, can be precisely polished to a predetermined target thickness X _p.

On the other hand, the load control unit 14 during processing, control and control time TM _t obtained by the operation, a preset target time T
O _t based on such increasing the processing load P _t by PI control, for example, as shown in FIG. 4, the processing load P _t is polished number of magnetic disk 1, i.e., with increasing polishing operation times However, the required processing time for polishing one magnetic disk 1 is not affected by the polishing ability and the like that deteriorates with an increase in the amount of polishing work, and the predetermined target time TO _t
Converges gradually.

As described above, according to this embodiment, error factors such as the resin such as the grinding fluid 6 supplied to the surface of the magnetic disk 1 during processing and the polishing debris generated during processing adhere to the surface of the magnetic disk 1. Can be accurately corrected by the film thickness measuring device 8 during the polishing process, and the magnetic disk 1 after the polishing process of the magnetic disk 1 controlled based on the measured value can be accurately corrected. The thickness of the magnetic thin film can be precisely set to a desired value.

Further, by the PI control based on the processing load P _t during polishing, etc. elapsed time of the actual processing and target machining time, thereby completing the polishing work of the individual magnetic disk 1 within a predetermined set time Can be.

Further, in step 106 for obtaining X _mi requiring a relatively large amount of calculation, the terms from k = 1 to i−1 are calculated within the idle time of the calculation unit immediately after the calculation of the previous measured value X _mi , By causing the calculation operation for each measurement value to be performed in parallel, there is no inconvenience that the control operation of the control calculation unit 9 is delayed from the actual polishing operation and the control becomes impossible.

Although the invention made by the inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments, and it is needless to say that various changes can be made without departing from the gist of the invention. Nor.

〔The invention's effect〕

The effect obtained by the representative one of the inventions disclosed in the present application will be briefly described as follows.

That is, a polishing head for polishing a thin film deposited on a substrate while pouring a grinding fluid, a film thickness measuring unit for measuring the film thickness of the thin film as needed, and the film thickness measured by the film thickness measuring unit. A control unit for controlling the operation of the polishing head unit based on the change of the thin film polishing apparatus, wherein the thickness of the thin film is measured by detecting the amount of fluorescent X-rays from the thin film, By grasping at least one of the first and second amounts of influence on the measured value of the film thickness due to the presence or absence of the grinding fluid and the residue generated during the polishing process, the film thickness of the film during the process is determined. Since the measured value is corrected, an error in measuring the thickness of the thin film during polishing can be reliably eliminated.

This makes it possible to precisely control the polishing amount of the thin film based on the accurately measured film thickness, thereby improving the accuracy of the polishing process.

Also, by controlling the pressing force of the polishing head against the substrate during processing to control the true film thickness reduction amount per unit time, the polishing to the target film thickness is completed within the target processing time. By doing so, it is possible to control the required time for the polishing process to a predetermined value without being affected by, for example, a decrease in the polishing ability due to wear of the polishing head.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an example of a control operation in a method for controlling a thin film polishing apparatus according to one embodiment of the present invention. FIG. 2 is a thin film used in a method for controlling a thin film polishing apparatus according to one embodiment of the present invention. FIG. 3 is a block diagram illustrating an example of a configuration of a main part of the polishing apparatus. FIG. 3 is a diagram illustrating an example of an operation of a method of controlling a thin film polishing apparatus according to an embodiment of the present invention. FIG. It is a diagram explaining an example of an operation of the control method of the thin film polishing apparatus according to the embodiment. 1 ... magnetic disk (substrate), 2 ... spindle, 3 ...
... roller, 4 ... working load adjuster, 5 ... polishing head unit, 6 ... grinding fluid, 7 ... grinding fluid nozzle, 8 ... film thickness measuring device, 9 ... control computing unit, 10 ... grinding Liquid Impact Assessment Department, 11
... Measurement film thickness calculation unit, 12 ... Residue effect evaluation unit, 13 ... Judgment unit, 14 ... Load control unit, 15 ... Processing time.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsugu Kanno 2880 Kozuhara, Odawara-shi, Kanagawa Prefecture Inside Odawara Plant, Hitachi, Ltd. 72) Inventor Ryo Otsuka 2-6-2 Otemachi, Chiyoda-ku, Tokyo Inside Hitachi Electronics Engineering Co., Ltd. (56) References JP-A-57-104806 (JP, A) JP-A-56-22904 (JP, A) JP-A-61-230855 (JP, A) JP-A-61-213611 (JP, A) JP-B-51-2157 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) B24B 49/02-49/04 G01B 11/06

Claims (6)

(57) [Claims] 1. A polishing head section for polishing a thin film deposited on a substrate while pouring a grinding liquid, a film thickness measuring section for measuring the film thickness of the thin film as needed, and a film thickness measured by the film thickness measuring section. A control unit for controlling the operation of the polishing head unit based on the change in the film thickness, the method comprising: detecting the amount of fluorescent X-rays from the thin film to determine the thickness of the thin film. By measuring at least one of the first and second amounts of influence on the measured value of the film thickness due to the presence or absence of the grinding fluid and the residues generated during the polishing process. Wherein the measurement value of the film thickness is corrected. 2. A first average measured value of the film thickness in a dry state before pouring the grinding fluid, and a landing operation before processing for bringing the polishing head portion close to the substrate while pouring the grinding fluid. Wherein the first influence amount on the measured value of the film thickness due to the presence or absence of the grinding fluid is grasped from the difference from the second average measured value of the film thickness. Item 3. A method for controlling a thin film polishing apparatus according to Item 1. 3. A first film thickness reduction amount obtained as a difference between the film thickness before processing corrected by the first influence amount and a film thickness during processing measured at an arbitrary time during processing. The second influence amount is calculated based on the measured value of the film thickness due to the residue adhering to the substrate during processing, and a true value is obtained as the sum of the second influence amount and the first film thickness decrease amount. 2. The thin film according to claim 1, wherein a true film thickness at that time is obtained from a difference between the first average measured value and the true film thickness decrease amount. A method for controlling a polishing apparatus. 4. A process in which the true thickness reduction per unit time is controlled by changing the pressing force of the polishing head against the substrate during the processing, so that the target film thickness is reached within the target processing time. 2. The method according to claim 1, wherein the polishing is completed. 5. The processing film thickness measured at an arbitrary time during processing is calculated by a least squares method based on data including a plurality of measurement values at different times before the processing. The method for controlling a thin film polishing apparatus according to claim 1. 6. In the least square method calculation for each measured value, the calculation of the term including the measured value before the measured value is performed during the idle time of the calculator after the end of the least square method calculation for the previous measured value. 6. The method for controlling a thin film polishing apparatus according to claim 5, wherein the control is performed.