JPH10315124A - Polishing method and polishing apparatus - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a means capable of detecting a polishing efficiency and a polishing amount on the spot by CMP of an LSI wafer. A sliding resistance acting between a surface of a polishing pad and a semiconductor substrate is detected. Further sliding resistance 8
By measuring the relationship between the polishing efficiency and the polishing efficiency in advance, the in-situ detection of the polishing efficiency was made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polishing apparatus and a polishing method.

[0002]

2. Description of the Related Art In a process of forming a high-density semiconductor integrated circuit device, an LS is formed by forming a pattern of an insulating film or a metal film.
I wafer surface has complicated irregularities. L with this unevenness
If pattern formation is continued on the surface of the SI wafer, high resolution semiconductors such as insufficient resolution in pattern transfer due to lack of depth of focus in the lithography process and loss of metal wiring film at uneven steps In some cases, this was an obstacle to the production of integrated circuits. In order to solve this problem, a CMP method is employed in which the surface of the LSI wafer is slid while being pressed against a polishing platen to which a polishing pad is attached, and the unevenness is flattened by polishing.

Conventionally, the polishing amount in the CMP method is controlled by measuring the polishing amount per unit time, that is, the polishing efficiency in advance, and dividing the desired polishing amount by the measured polishing efficiency. I was going to decide on the time. However, even if the polishing conditions such as the polishing rate and the polishing load are kept constant, the polishing efficiency fluctuates greatly because the polishing pad surface is worn with the progress of polishing. For this reason, in the conventional CMP method, it is necessary to measure the polishing efficiency with a dummy substrate every predetermined number of times of polishing and to correct the polishing time.
Also, the polishing pad whose surface has been worn needs to be dressed using a diamond whetstone etc. for repair,
Each time, measurement and calibration of polishing efficiency are performed. As described above, the conventional control of the polishing amount is extremely complicated, and there has been a demand for technical development for avoiding this.

[0004]

SUMMARY OF THE INVENTION The present invention provides a means for in-situ detection of polishing efficiency by detecting a sliding resistance between a polishing pad surface and a semiconductor substrate surface.

[0005]

The sliding resistance acting between the polishing pad surface and the semiconductor substrate is detected. Further, by measuring the relationship between the sliding resistance and the polishing efficiency in advance, the in-situ detection of the polishing efficiency was made possible.

In the polishing of an LSI wafer, the total work W given to the wafer is obtained by integrating the sliding resistance between the wafer and the polishing pad by the sliding distance. The sliding resistance is F, and the sliding distance is x.
Then, it is represented by (W = ∫F (x) dx). The work required to remove the wafer surface is a part of the total work W, and the remaining work changes into frictional heat due to sliding. Therefore,
In the range where the ratio of the work used for removing the wafer surface in the total work is almost constant, the total work and the removal amount of the wafer surface, that is, the polishing amount are proportional, and the proportional coefficient is k and the polishing amount is v.
Then (v = k∫F (x) dx). Here, since the sliding distance x is a time integral of the polishing rate u (x = ∫u (t) dt), this is expressed as (v =
k∫F (x) dx) and taking the time derivative of both sides gives (dv / dt =
kF (t) u (t)) is obtained. If the polishing rate (u (t)) is constant regardless of time, the sliding resistance F and the time differential of the polishing amount
(dv / dt), that is, the polishing efficiency is proportional.
In practice, it is considered that the sliding resistance and the polishing efficiency are not necessarily proportional to the influence of the polishing conditions, but the relationship between the sliding resistance and the polishing efficiency under any polishing conditions is measured in advance, and this is used. Thus, the polishing efficiency (dv / dt) can be grasped from the sliding resistance F during polishing.

[0007]

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

FIG. 1 is a schematic diagram of a sliding resistance detecting method according to the present invention. When the polishing load 2 is applied to polish the wafer 6, the sliding resistance 8 generated between the polishing pad 5 and the wafer 6 is determined by a chuck.
7, is converted into a sliding resistance signal 9 by the load converter 1 via the main shaft 3 and the bearing 4. Since the direction of the sliding resistance during polishing varies depending on the position of the wafer on the polishing pad radius, the load converter 1 measures a two-component force orthogonal to a plane perpendicular to the main axis, and determines the resultant force of the two components as the sliding resistance. Signal 9 is assumed.

FIG. 2 is a block diagram of a polishing apparatus according to the present invention. During the polishing, the sliding resistance signal 9 from the load converter 1 is A / D converted by the A / D converter 20 and then input to the personal computer 18, and reference data of the sliding resistance and the polishing efficiency measured in advance. From 21 is converted to polishing efficiency by the method described below. The polishing amount is calculated by integrating the polishing efficiency with the polishing time. The calculated polishing amount is displayed on the display 19, and when the desired polishing amount is reached, a stop signal is sent to the platen drive motor controller 17 to automatically stop the platen drive motor 11. Further, monitoring of the polishing efficiency during polishing is performed as needed, and when the polishing efficiency falls below a predetermined value, a signal for switching the air flow path switching valve 14 is sent from the personal computer 18 to compress the compressed air from the air compressor 15 into the air cylinder. 12 and has a function of performing dressing by pressing a diamond grindstone 16 against a polishing pad 5 attached to a polishing platen 10. The pressing pressure can be adjusted to an arbitrary value by the pressure regulator 13, and the diamond grindstone can be rotated at an arbitrary rotation speed by a motor (not shown). A polishing sample was prepared by spin-coating liquid glass on the surface of a Si wafer having a diameter of 150 mm, and then performing a heat treatment to form a Si oxide film having a thickness of about 2 μm.

FIG. 3 shows polishing of an Si wafer by supplying an aqueous solution having a SiO ₂ abrasive concentration of 3% at a rate of 100 ml / min onto a polishing platen having a compression elastic modulus of 100 MPa and a foamed polyurethane having a thickness of 1 mm adhered to the surface. And the change in the sliding resistance and polishing efficiency with the number of polished wafers in the case of performing the above. At this time, the pressure for pressing the Si wafer against the polishing platen is 500 g / cm ² , and the sliding speed of the polishing platen at the center position of the Si wafer is 300 mm / s. The Si wafer was rotated at 20 r / min. It can be seen from the figure that as the number of polished wafers increases, both the sliding resistance and the polishing efficiency decrease. The polishing efficiency was measured by measuring the thickness of the Si oxide film on the Si wafer before polishing using a thin spectrometer Nanospec4100 manufactured by Nanometrix (USA), and again after polishing.
The thickness of the Si oxide film was measured, and the difference in film thickness before and after polishing was divided by the polishing time.

FIG. 4 shows the correlation between the sliding resistance and the polishing efficiency from the results of FIG. From this data, the polishing efficiency is approximated as a sliding resistance polynomial, the polishing efficiency is calculated in real time using a personal computer from the sliding resistance detected on the spot, and the polishing efficiency is integrated over time on a personal computer. Calculate the polishing amount.

Using the above results, 25 wafers were continuously polished with a polishing amount of 1 μm as a target, without dressing the polishing pad. Each wafer was polished when the polishing amount indicated on the display became 1 μm after the start of polishing. As a result, the polishing amount is about ± 0.15μ
It was confirmed that the variation in the polishing amount was suppressed to about ± 0.03 μm in the polishing processing using the present polishing apparatus, while the variation in m was caused (see FIG. 5).

Next, a sequence for automatically dressing the polishing pad when the polishing efficiency falls below a predetermined value was executed, and a comparison was made with the conventional method. In the conventional method, the polishing efficiency was actually measured by a dummy wafer every time 10 Si wafers were polished, and the polishing time was corrected and the polishing pad was dressed when the polishing efficiency was lower than a predetermined value. The target value of the polishing amount is 1 μm, and the wafer 10
0 sheets were continuously polished. As a result, it was confirmed that the variation in the polishing amount was about ± 0.15 μm in the conventional polishing method, whereas the variation in the polishing amount was suppressed to about ± 0.03 μm in the present invention (see FIG. 6). . In addition, the required time for polishing 100 Si wafers at this time was about 1400 minutes in the polishing processing using the conventional method, whereas the polishing processing using the present polishing apparatus was one third of that time. 500mi
n, indicating an improvement in wafer manufacturing efficiency.

[0014]

The greatest effect obtained by the present invention is CMP.
The problem is that the polishing amount, which is a problem, can be more easily controlled than before. An additional effect is that the management can be automated, and the manufacturing process can be greatly simplified.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a sliding resistance detection method.

FIG. 2 is a block diagram of a polishing apparatus.

FIG. 3 is a characteristic diagram showing the correlation between the number of polished wafers, sliding resistance, and polishing efficiency.

FIG. 4 is a characteristic diagram showing a correlation between sliding resistance and polishing efficiency.

FIG. 5 is an explanatory diagram of a comparison between the present invention and a conventional method regarding a change in a polishing amount according to the number of polished wafers.

FIG. 6 is an explanatory diagram of a comparison between the present invention and a conventional method regarding a change in a polishing amount according to the number of polished wafers.

[Explanation of symbols]

1 ... Load converter, 2 ... Polishing load, 3 ... Spindle, 4 ... Bearing,
5 polishing pad, 6 wafer, 7 chuck, 8 sliding resistance, 9 sliding resistance signal.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Nobuo Kayaba 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd. Production Technology Laboratory (72) Inventor Takashi Nishiguchi 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd. Production Technology Laboratory

Claims (5)

[Claims] 1. A semiconductor substrate on which a fine circuit pattern is formed is pressed against a polishing pad attached to a polishing platen via a pressure head, and the unevenness caused by the formation of the fine circuit pattern is polished flat. A polishing apparatus having a function of detecting a sliding resistance generated between the surface of the semiconductor substrate and the polishing pad. 2. The polishing method according to claim 1, wherein the progress of polishing is monitored from the change in the sliding resistance and the polishing time. 3. A polishing apparatus incorporating the polishing method according to claim 2 in an operation sequence. 4. The polishing method according to claim 1, wherein the polishing pad surface is repaired by determining a worn state of the polishing pad surface from the sliding resistance. 5. A polishing apparatus incorporating the polishing method according to claim 4 in an operation sequence.