JP2001068440A - Polishing pad and polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately and automatically measure dress efficiency of a polishing pad in a polishing process for efficient polishing by, related to a polishing pad for polishing the surface of a work, providing a metal thin film layer between arbitrary layers of a multi-layer structure in the thickness direction. SOLUTION: A metal thin film 6, a position sensor 7 for a polishing pad surface, a position sensor 8 for a metal thin film, a signal.storage calculation part 9, and a display device 10 are provided between layers of a polishing pad 1 with a multi-layer structure which is pasted to a polish surface plate. Related to a calculation method for dress efficiency, a position d1 of the polishing pad surface at a time t1 as well as a position d2 of a metal thin film are measured, and its difference d2-d1 is calculated by the signal storage calculation part 10, which is stored as a thickness d3 of a -th layer 11 of polishing pad. d3 is measured likewise at a time t2 when an arbitrary time has passed since t1, for calculation. The difference of the acquired d3 is divided by the time difference between times t1 and t2 to provide a dress efficiency dv.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing method for a surface of a workpiece, and more particularly to a polishing method and a polishing apparatus suitable for flattening a surface of a semiconductor circuit substrate in a semiconductor manufacturing process.

[0002]

2. Description of the Related Art Conventionally, in a process of planarizing a semiconductor substrate surface using CMP (Chemical Mechanical Polishing), the surface of a polishing pad is deteriorated by repeating polishing, and the stability of polishing efficiency and the substrate surface are reduced. It has been empirically known that the processing characteristics such as the uniformity of the polishing amount in the substrate and the frequency of occurrence of polishing scratches on the substrate surface are deteriorated. For this reason, the deteriorated polishing pad surface is appropriately dressed (conspicuous) with a dresser such as a diamond grindstone to recover polishing characteristics. At this time, it is important to manage and maintain a sufficient amount of dressing ability to suppress the progress of deterioration of the polishing pad surface. Dressing efficiency (abrasion amount of the polishing pad per unit time) is generally used as an index of the dressing ability. The surface of the polishing pad to which the polishing pad is attached is used as a reference surface, and the height of the polishing pad surface before and after dressing is used as an index. The dress efficiency is calculated by dividing the difference by the dressing time. In this case, in general, since the shaving amount of the polishing pad in the polishing pad surface is not uniform in the surface, measurement is performed at a plurality of points in the polishing pad surface,
It is necessary to obtain an average value and perform evaluation.

[0003]

However, the above-described measuring operation is complicated and the polishing operation is interrupted by the operator, so that there is a problem that the productivity is significantly reduced. Also, C
In MP, a two-layer structure using a material with a high elastic modulus for the polished surface and a material with a low elastic modulus for the lower layer in order to balance the uniformity of the polishing amount within the substrate surface and the ability to remove unevenness on the substrate surface Is generally used. For this reason, when the wafer polishing is repeated, the lower layer of the polishing pad having a low elastic modulus is compressed and deformed, and when the thickness of the polishing pad is measured, the amount of compressive deformation of the lower layer of the polishing pad is included in the measured value. There is a problem that a measurement error increases.

As a method of monitoring the consumption of the polishing pad, Japanese Patent Application Laid-Open No. 10-100062 discloses a method of using a polishing pad having a multilayer structure in which the color is changed in the thickness direction of the polishing pad or measuring the displacement of the polishing pad surface. Have been. However, the former is an excellent method for easily knowing the time of replacement of the polishing pad, but the point that a plurality of color changing layers must be provided in order to monitor the dressing efficiency, and when the dressing efficiency is quantified. However, there is a problem that the configuration is complicated, for example, the color needs to be identified by some method. The latter poses a problem of measurement error due to deformation of the lower layer in the polishing pad having the two-layer structure as described above.

An object of the present invention is to provide a polishing pad and a polishing apparatus capable of accurately and automatically measuring the dress efficiency of a polishing pad in a polishing process, and to improve the efficiency of the polishing process.

[0006]

In order to solve the above-mentioned problems, the present invention provides a polishing pad for polishing a surface of a workpiece, comprising a multilayer structure in a thickness direction and a metal thin film layer between any layers. The present invention provides a polishing pad comprising:

A polishing apparatus for polishing a surface of a workpiece by giving a relative movement between the polishing pad and the workpiece, wherein the polishing apparatus holds the polishing pad and the workpiece, respectively.
A polishing pad comprising: a driving means for applying the relative motion to the polishing pad and the workpiece; a multilayer structure in a thickness direction; and a metal thin film layer between any layers. Measuring means for measuring the position of the polishing pad surface in the thickness direction of the pad, measuring means for measuring the position of the metal thin film in the thickness direction of the polishing pad, and measuring the difference between the position of the polishing pad surface and the position of the metal thin film. Means for quantifying and storing the polishing pad thickness based on the position of the metal thin film, time measuring means, and quantifying the change in the polishing pad thickness based on the time measured by the time measuring means. And a polishing apparatus.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic view of a polishing apparatus used in this embodiment.

The present polishing apparatus rotates a polishing platen 2 to which a polishing pad 1 is attached, and slides a workpiece 4 held by a workpiece holder 3 at an arbitrary polishing pressure while pressing the workpiece 4 against the polishing pad 1. A slurry (not shown) is supplied between the workpiece 4 and the polishing pad 1 to perform polishing. The dressing of the polishing pad 1 can be performed using the dresser 5 at an arbitrary timing. In addition to the well-known basic configuration as a polishing apparatus as described above, a metal thin film 6, a position sensor 7 on the polishing pad surface, and a metal thin film between the layers of the polishing pad 1 having a multi-layer structure attached to a polishing platen. A position sensor 8, a signal storage / operation unit 9, and a display 10 are provided.

Next, a method of calculating the dressing efficiency will be described with reference to FIG. The position d ₁ (t ₁ ) of the polishing pad surface at time t ₁ is measured, and the position d ₂ (t ₁ ) of the metal thin film is measured, and the difference d ₂ (t ₁ ) −d ₁ (t ₁ ) is stored in a signal. The calculation is performed by the unit 10 and this is stored as the thickness d ₃ (t ₁ ) of the first layer 11 of the polishing pad. Further, d ₃ (t ₂ ) is similarly measured and calculated at time t ₂ when an arbitrary time has elapsed from t ₁ . By dividing the obtained difference between d ₃ (t ₁ ) and d ₃ (t ₂ ) by the time difference between times t ₁ and t ₂ , dress efficiency d _v = (d ₃ (t ₁ ) −d ₃ (t) _{2)) ÷ (t 2 -} t 1)
Is obtained.

As described above, in the present invention, the thickness d ₃ of the first layer 11 of the polishing pad to be dressed is measured using the metal thin film 6 provided immediately below the first layer of the polishing pad as a reference plane. The measurement error due to the compression deformation of the pad second layer 12 can be eliminated. Similarly, since there is no measurement error such as surface deviation of the polishing table, the thickness d ₃ (t) of the first polishing pad layer 11 can be measured while rotating the polishing table. For this reason, the polishing platen is rotated while the polishing apparatus is in operation, and the position measurement sensors 7 and 8 are scanned over the radius of the polishing platen as appropriate.
Definitive any of a plurality of points of the polishing pad in the surface d ₃ (t) is measured, calculated Dress efficiency d _v at each point may be averaged.

FIG. 3 shows the thickness d ₃ of the first layer 11 of the polishing pad.
₃ shows the correlation between the thickness d ₃ of the first polishing pad layer 11 measured according to the present invention and the actual thickness d ₃ of the first polishing pad layer 11 for several types of polishing pads different from each other.

The thickness d ₃ of the polishing pad first layer 11 was measured as follows.

A position measuring sensor is fixed at a position with a radius of 150 mm (a position where the center of the wafer rubs) with respect to the center of rotation of the surface platen. Continuously obtain the thickness data of the polishing pad first layer for 20 points on the polishing pad at equal intervals,
The average of the obtained 20 points was defined as the thickness d _{3 of the} polishing pad first layer 11. After the measurement, the actual thickness d ₃ of the first polishing pad layer 11 was measured by a micrometer after peeling off the first polishing pad layer 11.

The basic measurement conditions were as follows.

(1) Rotation speed of polishing table 2: 3.14r
ad / s (2) Position measurement sensor 7: Fluid micrometer (working fluid: pure water) (3) Position measurement sensor 8: Eddy current displacement meter (4) Polishing pad first layer 11: Foamed polyurethane (thickness 1) 0.2 mm to 0.8 mm (5 types), compression modulus of 100 Mpa) (5) Polishing pad second layer 12: foamed polyurethane (thickness: 1.2 mm, compression modulus of 1 Mpa) (6) Metal thin film 6: aluminum foil ( (Thickness: 5 μm) In order to reduce the amount of displacement of the measurement position, the position measurement sensors 7 and 8 are arranged coaxially as shown in FIG.

FIG. 3 shows that the thickness d ₃ of the first layer 11 of the polishing pad can be measured while the polishing platen according to the present invention is rotated. Therefore, the thickness d of the polishing pad first layer 11 in the dressed polishing pad
₃ is measured with a time difference, and it can be seen that dress efficiency can be measured. The measurement repeatability is ± 2μ
m.

As described above, by employing the present polishing apparatus in the flattening polishing step in the semiconductor manufacturing process, the dressing efficiency can be accurately measured in the operating state of the polishing apparatus.
Conventionally, the time and labor required for measuring the dressing efficiency of the polishing pad can be reduced, and the productivity can be improved.

In the present embodiment, the semiconductor circuit board is polished, but the same effect can be achieved by polishing other workpieces.

Hereinafter, a conventional measuring method (hereinafter referred to as a conventional method) for an embodiment of polishing using the polishing apparatus shown in FIG.
This will be described in comparison with the embodiment. The basic polishing conditions, polishing pad, position measurement sensor, etc. were as follows.

(1) Slurry 5: SiO ₂ abrasive content 3%
(2) Slurry supply amount: 200 ml / min (3) Polishing pressure: 350 g / cm ² (4) Rotation speed of polishing platen 2: 188 rad / min (5) Rotation angular speed of workpiece 4: 188 rad / min ( 6) Work 4: Si wafer with Si oxide film (approximately 2 μm) (diameter 125 mm) (7) Polishing time: 3 min Dress efficiency was measured by the measurement method described in the section of the embodiment of the present invention. Every polishing (30 min interval)
The difference in the thickness d ₃ of the polishing pad first layer 11 was divided by 30 minutes to obtain the dressing efficiency. The measurement was performed at the time of polishing pad cleaning at the end of wafer polishing in the wafer polishing sequence. Therefore, there is no increase in the time of one wafer polishing cycle due to the measurement.

In the conventional method, a through hole having a diameter of 1.5 mm is made at 20 points on the polishing pad slightly shifted on the same circumference as the data measurement point of the present invention, and each point is measured with a depth gauge. The average of the values obtained by dividing the obtained polishing pad shaving amount by 30 minutes was defined as the dressing efficiency.

FIG. 4 is a graph showing the correlation between the dressing efficiency and the number of polished wafers according to the present invention and the conventional method.

FIG. 4 shows that the dressing efficiency is stably measured in the present invention, while the polishing pad abrasion amount is reduced to about 30 minutes (about 90 min) from the start of wafer polishing in the conventional method. The amount of compressive deformation of the two layers 12 is added and measured, and shows a dress efficiency higher than the actual dress efficiency. Further, it can be seen that the dressing efficiency measured after the amount of compressive deformation of the polishing pad second layer 12 is not stable after that also fluctuates in an unstable manner. From the above, it was confirmed that the dressing efficiency of the polishing pad can be accurately measured in the operating state of the polishing apparatus according to the present invention.

The work time required to polish 100 Si wafers at this time was about 500 min in the conventional method, but 400 min in the present invention. Was reduced by 20%. That is, the effect of improving the efficiency of the polishing process was confirmed.

Further, the present invention is not limited to the above-described embodiment, and it is also possible to take a configuration in which the dress efficiency and the dressing speed of the dresser 5 are automatically controlled by using the measured dress efficiency as an input to keep the dress efficiency constant. .

[0028]

According to the present invention, the dressing efficiency of the polishing pad can be accurately and simply measured in the polishing process, and the efficiency of the polishing process can be improved.

[Brief description of the drawings]

FIG. 1 is a view showing a dressing efficiency measuring method of a polishing pad according to an embodiment of the present invention.

FIG. 2 is a diagram showing a basic configuration of a polishing apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing a correlation between a thickness d ₃ of a first layer 11 of a polishing pad and a measurement value according to the present invention.

FIG. 4 is a diagram showing a correlation between dress efficiency and the number of polished wafers according to the present invention and a conventional method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Polishing pad, 2 ... Polishing table, 3 ... Workpiece holder, 4
... workpiece, 5 ... dresser, 6 ... metal thin film, 7 ... position sensor, 8 ... position sensor, 9 ... signal calculation unit, 10 ... display,
11: polishing pad first layer, 12: polishing pad second layer.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Takashi Nishiguchi 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi, Ltd. Production Engineering Research Laboratory F-term (reference) 3C058 AA07 AA09 AA19 AC02 BA02 BA07 BB09 CB03 DA17

Claims (2)

[Claims] 1. A polishing pad for polishing a surface of a workpiece, comprising a multilayer structure in a thickness direction and a metal thin film layer between any layers. 2. A polishing apparatus for polishing a surface of a workpiece by giving a relative motion between the polishing pad and the workpiece, wherein the polishing pad holds the polishing pad and the workpiece, respectively. A driving means for giving the relative movement to a workpiece, a multilayer structure in a thickness direction, a polishing pad provided with a metal thin film layer between any layers, and a polishing pad surface in a thickness direction of the polishing pad. Position measuring means, means for measuring the position of the metal thin film in the thickness direction of the polishing pad, and a polishing pad based on the position of the metal thin film from a difference between the position of the polishing pad surface and the position of the metal thin film. Means for quantifying and storing the thickness, time measuring means, and means for quantifying a change in the polishing pad thickness based on the time measured by the time measuring means. Polishing equipment.