JP2002355748A - Chemical-mechanical polishing method and chemical- mechanical polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce scratches formed on a polished object without excessively shortening the service life of a polishing pad in chemical-mechanical polishing(CMP). SOLUTION: In a method of performing CMP to the surface of the polished object 4 using a polishing pad 3 while dressing by pressing a dresser 21 to the polishing pad 3, data of the grinding quantity per unit time of the polishing pad 3 in CMP, and the number of scratches formed on the polished objects by CMP are collected in advance to obtain the optimum grinding quantity per unit time of the polishing pad 3 to reduce the scratches. Dressing conditions are adjusted so that the grinding quantity per unit time of the polishing pad 3 in CMP takes the previously obtained optimum value of the grinding quantity per unit time of the polishing pad 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor wafer, L
The present invention relates to a chemical mechanical polishing (CMP) method useful for polishing a thin plate-like object to be polished such as a glass plate for a CD, and an apparatus used for performing the method.

[0002]

2. Description of the Related Art CMP is used as a flattening technique for a semiconductor wafer in a semiconductor device manufacturing process or a glass plate in an LCD panel manufacturing process.

FIG. 7 is a schematic sectional view of a conventional CMP apparatus 1. This apparatus comprises a surface plate 2 having a rotating mechanism, a surface plate 2
A polishing pad 3 fixed thereon with a double-sided tape or the like, and a polishing head 5 for holding a workpiece 4 such as a semiconductor wafer are provided. On the holding surface of the polishing object 5 of the polishing head 5, an adsorption film 6 is provided as an adsorption holding material and a buffer material.
On the outer peripheral portion of the polishing head 5, the workpiece 4 is
A retainer ring 7 is provided so as not to come off.

[0006] In the vicinity of the polishing head 5, an abrasive supply line 10 for supplying a slurry-like abrasive 9 onto the polishing pad 3.
Is provided.

At the time of polishing, while the polishing agent 9 is supplied to the polishing pad 3 from the polishing agent supply line 10, the platen 2 is rotated while the polishing head 5 holding the workpiece 4 is rotated while rotating the platen 2. After the object to be polished 4 comes in contact with the polishing pad 3, the object to be polished 4 is further pressed against the polishing pad 3 to perform polishing.

[0008] As shown in FIG. 8, the polishing pad 3 is sharpened so as to have an innumerable pointed protrusion 11 having a height h of about 1 to 2 mm. Enters the concave portion of the gap between the pointed convex portions 11,
The abrasive grains 12 and the pointed projections 11 appropriately press and polish the polished surface of the workpiece 4 to be polished.

When the pointed projections 11 of the polishing pad 3 are worn away by polishing, and the polishing surface of the polishing pad 3 is flattened, the area of the polishing pad 3 in contact with the workpiece 4 is increased.
It is difficult to press the protrusions 2 and the sharp projections 11 against the workpiece 4 with an intended force. Further, the polishing debris of the polishing pad 3 is clogged in the concave portion between the protruding portions 11, and the polishing debris accumulated in the concave portion between the protruding portions 11 scratches (scratches) the polishing surface of the workpiece 4. Cause.

Therefore, the CMP apparatus 1 is provided with a dresser unit 20 for performing dressing (that is, a process of shaving the polished surface of the worn polishing pad 3 and correcting its surface condition).
Is provided. The dressing is performed by polishing the dresser unit 20 at the time of polishing or separately from the polishing.
This is performed by pressing against the polishing pad 3 while rotating in the same manner as described above.

The dresser unit 20 includes a dresser 2
1 and its supporting portion 22. The dresser 21 includes, for example, a metal base 24 mounted on a SUS plate 23 as shown in FIG.
It is composed of diamond particles 25 concentrically fixed thereon by Ni vapor deposition.

[0010]

However, in the conventional CMP method, dressing is generally insufficient in many cases, so that the polishing surface of the workpiece 4 is likely to be scratched. When scratches occur on a semiconductor wafer due to CMP, problems such as destruction of a gate electrode and dielectric breakdown of an insulating film formed on the scratch are caused, and the yield of semiconductor devices is significantly reduced.

On the other hand, it is conceivable that the dressing is performed excessively, but if the dressing is performed excessively,
Since the life of the polishing pad 3 is shortened, the cost of CMP is high.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems by reducing scratches and preventing the polishing pad from having an excessively short life when performing CMP.

[0013]

According to the present invention, there is provided a method of performing CMP while performing dressing, wherein (i) abrasion of the polishing pad is caused exclusively by dressing, and (ii)
The amount of grinding of the polishing pad per unit time by dressing and the number of scratches generated on the object to be polished have a close relationship, (iii) Therefore, the amount of grinding of the polishing pad per unit time and the object to be polished in advance Accumulation of data on the number of scratches generated in the polishing pad is accumulated, and based on the data, the optimum grinding amount per unit time of the polishing pad to reduce the number of scratches generated is determined. When the chemical mechanical polishing is performed by adjusting the dressing conditions so that the polishing object can be significantly reduced scratches generated on the object to be polished, (iv) In particular, as a method of adjusting the dressing conditions in this case, a polishing pad It has been found that it is effective to adjust the pressure of the dresser against the pressure.

That is, the present invention relates to a method for chemically and mechanically polishing a surface of an object to be polished using a polishing pad while performing dressing for pressing a dresser against the polishing pad. Collect data on the amount of grinding per unit time of the pad and the number of scratches generated on the workpiece by chemical mechanical polishing to determine the optimal amount of grinding of the polishing pad per unit time to reduce scratches. In the chemical mechanical polishing, the grinding amount per unit time of the polishing pad is adjusted, and dressing conditions are adjusted so as to take an optimal value of the grinding amount per unit time of the polishing pad previously determined. To provide a chemical mechanical polishing method.

Further, as an apparatus for performing the CMP method, a polishing pad, a surface plate for fixing the polishing pad, a polishing head for holding the object to be polished and pressing the object to be polished against the polishing pad, and a dressing for the polishing pad. In a CMP apparatus provided with a dresser, a polishing pad shape measuring means, and a polishing amount per unit time of the polishing pad calculated from a change in the shape of the polishing pad obtained by the polishing pad shape measuring means are fixed. A pressure adjusting means for adjusting the pressing force of the dresser against the polishing pad.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. In each drawing, the same reference numerals represent the same or equivalent components.

FIG. 1 is an overall configuration diagram of an embodiment of a CMP apparatus according to the present invention. The CMP apparatus 1A generally includes a polishing unit 100, a dresser unit 20 for performing dressing in the polishing unit 100, a pad shape measuring unit 200 for measuring a shape of a polishing pad in the polishing unit 100, cleaning of an object to be polished after CMP, Cleaning unit 300 for drying, HF, N used in cleaning unit 300
A chemical supply unit 400 for supplying a cleaning chemical such as H ₃ ,
It comprises a polishing unit 100, a cleaning unit 300, and a transfer unit 600 for unloading the object to be polished into the cassette 500.

The polishing unit 100 holds a surface plate 2 having a rotating mechanism, a polishing pad 3 fixed on the surface plate 2 with a double-sided tape or the like, and an object to be polished such as a semiconductor wafer, similarly to a conventional CMP apparatus. The polishing head 5 is provided. The polishing head 5 rotates about a shaft 5a and is vertically movable. Near the polishing head 5, an abrasive supply unit 70 is provided.
An abrasive supply line 10 that supplies a slurry-like abrasive supplied from 0 onto the polishing pad 3 is provided.

In the CMP apparatus 1A, as the polishing pad 3, a known polishing pad having a myriad of sharp projections 11 as shown in FIG. 8 can be used.

As shown in FIG. 2, the dresser unit 2
Numeral 0 designates a structure in which a rotatable dresser 21 shown in FIG. 9 is attached to a support portion 22 which is movable in the radial direction of the polishing pad 3.
Is provided with a pressure adjusting mechanism for adjusting the pressing force with respect to.

The pad shape measuring unit 200
This is one of the characteristic configurations of the MP device 1A. The pad shape measuring unit 200 is configured by attaching a dial gauge 201 as a pad shape measuring means to the support portion 22 of the dresser unit 20. The shape of the polishing pad 3 is measured when the surface plate 2 is at rest. As this measuring method, for example, first, the support 22 is attached to the polishing pad 3.
The radial gauge 201 is moved in the radial direction to move the dial gauge 201 over the center of the polishing pad 3, and about ten points sequentially moved radially from the center toward the outer periphery of the polishing pad 3 at predetermined intervals are set as measurement points. The measurement is performed by measuring the position of the surface of the polishing pad 3 as needed, and calculating the average of each measurement point as needed.

FIG. 3 is a process chart in the case where the method of the present invention is carried out using the CMP apparatus 1A. First,
The dressing pressing force when CMP is performed while dressing with a predetermined pressing force using the CMP apparatus 1A, the grinding amount of the polishing pad per unit time at that time, and a predetermined size generated on the workpiece. The relationship between the number of scratches and the number of scratches is determined by various CMP conditions (type of polishing pad, type of dresser, rotation speed of dresser, pressing force of dresser, rotation speed of platen, pressing force of polishing head, polishing head The number of rotations, the film type of the object to be polished, etc.) are collected, and under the CMP conditions, the optimal amount of grinding of the polishing pad per unit time to be reduced is obtained in advance. As the optimum grinding amount, for example, a single layer of urethane foam is used as a polishing pad, and other CMP conditions are set to a dresser load of 6
lbf (26.7N), dresser rotation speed 87rpm, polishing head load 5lbf (22.3N), polishing head rotation speed 93rpm, surface plate rotation speed 90rpm, it can be 45-55μm / hr, and polishing pad In the case where a stud pad in which the surface layer is made of urethane foam and a flexible pad is laminated on the base is used, and other CMP conditions are the same as described above, the speed can be set to 30 to 35 μm / hr.

Next, using the pad shape measuring unit 200, a pad shape measurement for examining the film thickness of the polishing pad 3, the height of the protruding portions formed on the surface of the polishing pad 3, and the distribution of the protruding portions is performed. Do.

Next, a dummy wafer is mounted on the polishing head 5, and a CMP process is performed while dressing with a predetermined pressing force (preliminary process). Thereafter, the pad shape is measured again.

From the measurement of the pad shape before and after the preliminary processing, the grinding amount per unit time of the polishing pad 3 in the preliminary processing is obtained, and the value is used to optimize the previously obtained polishing amount of the polishing pad 3 per unit time. It is determined whether the value matches the value. If the value deviates from the optimum value, the pressing force of the dresser unit 20 against the polishing pad 3 is appropriately adjusted, and the preliminary processing is performed again. Thus, the pressing force of the dresser unit 20 is adjusted until the grinding amount of the polishing pad 3 per unit time matches the optimum value. The amount of grinding of the polishing pad 3 depends exclusively on the dressing conditions.
It is not necessary to attach a dummy wafer to the polishing head 5 in the preliminary processing because it hardly depends on the presence or absence of the object to be polished on the polishing surface. The finish is affected by the polishing temperature.
In order to match the temperature of the P treatment, in the preliminary treatment,
Preferably, a dummy wafer is used.

In this method, the adjustment of the pressing force of the dresser unit 20 is performed as one of the adjustment methods of the dressing conditions for making the grinding amount of the polishing pad 3 per unit time coincide with the optimum value. However, as a method of adjusting the dressing conditions, the swing width and the swing speed of the dresser unit 20 that swings in the radial direction of the polishing pad 3 may be adjusted. 5. The rotation speed, pressing force, etc. of each of the dresser units 20 may be adjusted.

In the pad shape measurement, when it is found that the variation in the film thickness of the polishing pad 3 or the height of the sharp protrusion in the radial direction of the polishing pad 3 exceeds a predetermined range (for example, within 10 μm), In order to make them uniform, the swing speed of the dresser unit 20 may be made different for each predetermined area in the radial direction of the polishing pad 3 when adjusting the dressing conditions.

After the dressing conditions are adjusted as described above, the original polishing object is subjected to CMP while dressing (main body processing). In this main body processing, CMP is performed on a predetermined number of objects to be polished (for example, semiconductor wafers 25 to 50).
Sheet).

The number of scratches on the polished surface of the object to be polished in this manner is measured, and the relationship between the measured number of scratches and the amount of grinding of the polishing pad per unit time in the main processing is described above. It is preferable to accumulate the data as one of data on the relationship between the amount of grinding of the polishing pad per unit time and the number of scratches generated on the workpiece.

After the predetermined number of main body processes have been performed, the preliminary processing and the shape measurement of the polishing pad 3 before and after the preliminary processing are performed in the same manner as described above, and the amount of grinding of the polishing pad per unit time is determined. The dressing condition is adjusted so that the value becomes the optimum value, and then the main processing is restarted.

When the CMP is performed as described above, the grinding amount per unit time of the polishing pad to be polished by the dressing is adjusted to an optimum value which does not cause scratches on the workpiece by adjusting the pressing force of the dresser unit against the polishing pad. Therefore, generation of scratches on the object to be polished can be significantly reduced, and dressing is not excessively performed, so that the life of the polishing pad can be extended. The end of the life of the polishing pad can also be monitored by measuring the pad shape.

In contrast to the aspect of the present invention in which the pressing force of the dresser unit is adjusted every time a predetermined number of main body processes are performed, the conventional CMP method changes the once set pressing force of the dresser unit during the main body processing. Nothing has been done. However, as the height of the tip of the polishing pad decreases due to wear, the optimum pressure of the dresser changes. For this reason, readjusting the pressing force of the dresser unit every time a predetermined number of main processes are performed as in the present embodiment is effective in reducing scratches.

The present invention can take various aspects. For example, instead of the pad shape measurement unit 200 described above, as shown in FIG.
The polishing pad 3 may be attached to an independent stand 202 outside the surface plate 2 so as to be movable in the radial direction of the polishing pad 3.

As the pad shape measuring means, as shown in FIG. 5, a laser type or optical type linear displacement meter 203 is mounted just above the surface plate 2 in place of the dial gauge 201, and the pad shape is measured. Polishing pad 3 as measuring means
Polishing pad 3 at a time without moving in the radial direction of
May be made to be able to measure the thickness in the radial direction, the height of the pointed projection, and the like.

Further, the pressure adjusting mechanism provided in the dresser unit 20 and the pad shape measuring unit 200 are connected to an arithmetic and control unit such as a personal computer, and the arithmetic and control unit uses the pressure control mechanism based on the measurement data obtained by the pad shape measuring unit 200. The grinding amount per unit time of the polishing pad is automatically calculated, the grinding amount is compared with a predetermined set value, and the pressing force of the dresser against the polishing pad is adjusted so that the grinding amount takes a predetermined setting value. The adjustment may be made automatically.

As the dresser unit, in addition to the type in which the dresser swings in the radial direction with respect to the polishing pad, the dresser has a sufficient size with respect to the radius of the polishing pad, and A type that can be attached without swinging may be used.

[0037]

EXAMPLE A CMP was performed on a semiconductor wafer using the CMP apparatus shown in FIG. In this case, as a polishing pad,
A urethane foam having a diameter of 20 inches (50.8 cm) was used, and the rotation speed of the platen was 95 rpm. A diamond dresser having a diameter of 4 inches (10.2 cm) was used while rotating at 93 rpm while oscillating in the radial direction of the polishing pad. Model number ID-C112P manufactured by Mitutoyo Corporation was used as a dial gauge. As a polishing agent, use a silica-based slurry (Cabot, SS-25)
It was fed at 150 ml / min.

In the CMP under these conditions, data on the relationship between the amount of grinding of the polishing pad per unit time and the number of scratches on the object to be polished was collected, and the optimum value of the amount of grinding was determined in advance to be 30 to 35 μm / hr. , And the optimal pressing force of the dresser is 5.5 to 6.5 lbf (2
4.5-28.9N). Therefore, the pressure of the dresser is set to 6 lbf (26.7 N), and 800 semiconductor wafers (# 1 to # 800) are sequentially subjected to the CMP processing as the main body processing.
0.2 μm in width or length generated on each subsequent semiconductor wafer
The number of scratches was measured. FIG. 6 shows the results. 6 during the CMP processing of 800 semiconductor wafers.
The polishing pad was changed four times as shown in FIG.

For comparison, the pressing force of the dresser was 4 lbf
(17.8N) in the same way except that
00 semiconductor wafers (# 1 to # 800) are sequentially CMPed
Was performed, and the number of scratches having a width or length of 0.2 μm or more generated on each semiconductor wafer after the CMP was measured. FIG. 6 shows the results.

FIG. 6 shows that the number of scratches can be significantly reduced by adjusting the pressure of the dresser and performing CMP so that the grinding amount of the polishing pad per unit time becomes an optimum value.

[0041]

According to the present invention, when performing CMP, scratches generated on the object to be polished can be significantly reduced without excessively shortening the life of the polishing pad.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a CMP apparatus according to an embodiment.

FIG. 2 is a side view of a dresser unit to which a pad shape measuring unit is attached.

FIG. 3 is a process chart of a CMP method according to an embodiment.

FIG. 4 is a view showing C to which a pad shape measuring unit is attached.
It is a side view near the dresser unit of MP apparatus.

FIG. 5 is a side view of the vicinity of a dresser unit of a CMP apparatus to which a laser or optical linear displacement meter is attached.

FIG. 6 is a relationship diagram between the number of processed objects to be polished and the number of scratches in the main body processing.

FIG. 7 is a schematic sectional view of a conventional CMP apparatus.

FIG. 8 is an explanatory sectional view of a polishing pad.

FIG. 9 is a schematic view of a dresser ((a) plan view, (b)
FIG.

[Explanation of symbols]

1A: CMP apparatus of the embodiment, 2: surface plate, 3: polishing pad, 4: polishing object, 5: polishing head, 9: abrasive, 10: abrasive supply line, 11: pointed projection,
12: abrasive grains, 20: dresser unit, 21: dresser

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichi Daiichi 6-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference) 3C047 AA01 AA08 3C058 AA09 AA12 AA19 AC02 BA01 BA02 BA05 BA07 BA09 BB06 CA01 CB02 CB06 DA12 DA17

Claims (4)

[Claims] 1. A method for chemically and mechanically polishing a surface of an object to be polished using a polishing pad while performing dressing by pressing a dresser on the polishing pad, wherein a unit time of the polishing pad in the chemical and mechanical polishing is determined in advance. Data on the number of scratches per unit and the number of scratches generated on the object to be polished by chemical and mechanical polishing are collected to determine the optimal amount of grinding per unit time of the polishing pad to reduce scratches. Dressing conditions are adjusted so that the grinding amount per unit time of the polishing pad in the mechanical polishing takes an optimum value of the grinding amount per unit time of the polishing pad previously determined. Polishing method. 2. The chemical mechanical polishing method according to claim 1, wherein the dressing is performed by adjusting the pressing force of the dresser against the polishing pad so that the amount of grinding per unit time of the polishing pad takes an optimum value. 3. Preliminary processing for performing chemical mechanical polishing while dressing a dummy wafer as an object to be polished, and grinding the polishing pad per unit time in the preliminary processing based on measurement of the shape of the polishing pad before and after the preliminary processing. 2. The chemical mechanical polishing method according to claim 1, wherein the amount is determined, and the dressing conditions are adjusted so that the amount of grinding takes an optimum value of the amount of grinding per unit time of the polishing pad previously determined. 4. A polishing pad, a platen for fixing the polishing pad, a polishing head for holding the object to be polished and pressing the object to be polished against the polishing pad, and a chemical mechanical polishing comprising a dresser for dressing the polishing pad. In the apparatus, the polishing pad shape measuring means, and the polishing pad grinding unit per unit time calculated from the polishing pad shape change obtained by the polishing pad shape measuring means, takes a predetermined value, with respect to the polishing pad A chemical mechanical polishing apparatus, comprising: pressure adjusting means for adjusting the pressing force of the dresser.