JPH09148281A - Polishing apparatus and polishing method - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide a polishing apparatus and a polishing method for surely detecting the end point of polishing for stable planarization. SOLUTION: A polishing pad 2 formed on a surface plate 1 which can move in a plane, a means for supplying a polishing liquid 5 onto the polishing pad 2, and a polishing pad 2 supplied with the polishing liquid 5 are brought into contact with each other to polish. Polishing apparatus having a carrier 4 for holding a substrate for performing heat treatment, a radiant thermometer 6 for measuring the temperature of the surface of the polishing pad 2, and a temperature change detector 7 for detecting a change in temperature measured by the radiant thermometer 6. .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus and a polishing method represented by, for example, chemical mechanical polishing (CMP), which is used for flattening a substrate surface in, for example, a manufacturing process of a silicon semiconductor device.

[0002]

2. Description of the Related Art In order to improve the performance of silicon semiconductor devices, it is indispensable to miniaturize the elements and increase the number of layers. However, as the miniaturization progresses, the depth of focus in the photolithography process becomes shallower. Therefore, in order to form a finer pattern in multiple layers, it is necessary to reduce the step difference that occurs during the manufacturing process.

In recent years, a polishing technique has been introduced into the silicon semiconductor process as means for reducing (flattening) the step.

Therefore, hereinafter, an example of a conventional polishing apparatus and polishing method in the above-mentioned polishing technique will be described with CMP as an example, with reference to the drawings.

FIG. 3 is a schematic view of a conventional polishing apparatus used for flattening. In FIG. 3, reference numeral 31 is a rotatable flat platen, and 32 is a polishing pad, which is attached onto the platen 31. Reference numeral 33 denotes a substrate, which is supported by a carrier 34 and is pressed against the polishing pad 32 on the surface plate 31 while rotating. Further, 35 is a polishing liquid containing abrasive grains (fine particles for polishing), which is quantitatively dropped on the polishing pad 32, and the polishing pad 32 and the substrate 3 are rotated by the rotation of the platen 31.
It is supplied between 3 and. Reference numerals 38 and 39 denote a platen rotary motor and a carrier rotary motor, respectively.

In the polishing apparatus constructed as above,
By pressing the substrate 33 while rotating the polishing pad 32 to which the polishing liquid 35 is supplied, the surface of the substrate 33 is polished and the surface of the semiconductor device is planarized. Explaining the above-described planarization mechanism, when the surface of the substrate 33 has irregularities, the convex portion has a high contact pressure with the polishing pad 32 and thus the polishing rate is high, and the concave portion has a contact pressure with the polishing pad 32. Since it is low, it is hardly polished. Therefore, the irregularities on the surface of the substrate 33 are alleviated and the surface of the substrate becomes flat.

The above-mentioned polishing technique is, for example, "19
January 1994 Monthly Semiconductor Wo
"rld" pages 58-59 and "Solid Sta"
technology "July. 1992 / Japanese version This is introduced on pages 32-37.

In the following, there will be explained the problems when the above polishing technique is used for manufacturing a semiconductor device.

Generally, in the planarization by polishing in the manufacturing process of a semiconductor device, in consideration of mass production, the polishing amount for each semiconductor device (wafer) is kept constant, and the residual film thickness (or base film thickness) between each wafer is kept. Must be polished so that

Therefore, in order to make the remaining film thickness (or the base film thickness) between the wafers constant as described above, it is possible to fix the polishing time constant. It is very difficult to keep the amount of polishing constant, because it slightly changes depending on the surface state (small roughness) and the state of the polishing liquid (pH, temperature, etc.).

Further, even if the polishing conditions are such that the polishing rate is always constant, the contact area with the polishing pad 32 is different when the convex area of the step difference caused by the underlying pattern on the surface of the substrate 33 is different. Therefore, the contact pressure at the convex portion is different. Therefore, the difference in pressure becomes the difference in polishing rate, and the time for polishing and flattening the convex portion varies depending on the convex portion area. As a result, when the unevenness amount of the substrate is different, a constant (predetermined) time The polishing causes a difference in the remaining film thickness.

The above problems will be described below with reference to FIG. In FIG. 4, (a) shows the shape of the insulating film in the case where the pattern that causes unevenness in the insulating film to be polished is dense, and FIG. 4 (b) shows the shape of the insulating film to be polished. It shows the shape of the insulating film when the pattern that causes unevenness is rough. And
In FIG. 4, 41 is a base substrate, 42 is an insulating film, and 43
Is a wiring pattern formed on the insulating film 42, and 44 is an insulating film formed on the wiring pattern 43 and having irregularities to be polished.

The insulating film 44 as shown in FIG.
In the shape of (1), since the wiring pattern is dense, the unevenness of the unevenness is small, and the area of the first contact with the polishing pad when polishing is large. On the other hand, in the shape of the insulating film 44 as shown in FIG. 4B, since the wiring pattern is rough, the unevenness of the unevenness is large, and the area of the first contact at the time of polishing is small. Therefore,
When the insulating film shown in FIGS. 4A and 4B is polished for the same time, the film shown in FIG. 4B is polished faster than that shown in FIG. 4A and 4B, polishing progresses to a portion indicated by a broken line, one is polished until the wiring pattern 43 is exposed, and the other is stopped before the wiring pattern 43 is exposed. Become.

As a method for solving these problems, detection of the end point during polishing is considered to be the most effective.

As a conventional technique of the above-mentioned end point detecting method, the torque (current) of the surface plate rotating motor 38 (or the carrier rotating motor 39) for rotating the surface plate 31 (or the carrier 34) is generally detected. Is.

This end point detecting method utilizes the fact that the contact resistance (resistance during polishing) between the substrate 33 and the polishing pad 32 is different when the surface condition of the substrate 33 such as the presence or absence of unevenness or the material is different. If the contact resistance changes during polishing,
Since the surface plate 31 (or the carrier 34) is rotating at a constant speed, the surface plate 31 (or the carrier 34)
Paying attention to the change in the torque (current) of the motor 38 (or 39) for rotating the motor, the end point is determined by detecting the change in the torque.

[0017]

However, the above-described structure for determining the end point has the following problems, which will be described with reference to FIG.

That is, in polishing the insulating film as shown in FIG. 5A, the purpose is to polish until the wiring pattern 53 is exposed (in the case of FIG. 5B).
In this case, since the quality of the film to be polished changes when the wiring pattern is exposed, the torque of the motor changes within a detectable range, so that the end point can be detected.

On the other hand, as in the flattening of the interlayer insulating film in the multi-layer wiring process of the silicon semiconductor device, polishing of a single layer film having irregularities (that is, the wiring pattern 53 is exposed as shown in FIG. 5C). If you want to finish polishing before, and the film quality does not change during polishing), the polishing end point must be determined when the surface irregularities are alleviated, but the film quality does not change during polishing. Moreover, the change in contact resistance due to the disappearance of the unevenness is slight. Therefore, even if the torque of the motor is monitored, the change cannot be detected accurately (actually, since about 1990, it has been used for flattening an interlayer insulating film in a multilayer wiring process of a semiconductor device). In polishing, even if the unevenness of the substrate surface changes due to polishing, the change in motor torque is so small that it cannot be detected, so the above-mentioned detection method is not used).

Furthermore, since the change in contact resistance is fundamentally minimal and the surface plate 1 (or the carrier 5) is rotated in the state where there is contact resistance, the amount of torque fluctuation due to the change in contact resistance is , The amount of fluctuation cannot be detected because it is extremely small with respect to the entire torque. In addition, in the above-mentioned part, it was pointed out that it is difficult to detect the end point in the case of polishing a single-layer film having irregularities such as flattening of the interlayer insulating film, but when polishing is performed up to the part where the film quality changes. However, it is difficult to detect the contact resistance as torque.

To solve this problem, if a motor with a small torque is used, the amount of torque fluctuation will be relatively large, and it will be possible to detect the end point.

However, in an apparatus for mass-producing semiconductors, in order to be able to cope with an abnormal situation (such as when a torque more than expected is applied), it is usually larger than the torque required for actual polishing. It is not desirable to use a motor with a small torque because a device with a permissible amount is used so that it can cope with the torque.

Therefore, in polishing for flattening a single-layer film having irregularities as described above, it is fundamentally limited in detection accuracy to detect a torque fluctuation and determine an end point.

Further, the contact resistance is greatly influenced by the surface condition of the polishing pad, and the torque may not change depending on the condition of the polishing pad.

[0025]

In order to solve the above problems, the polishing apparatus and the polishing method of the present invention have the following means.

According to a first aspect of the present invention, there is provided a polishing apparatus having a polishing pad formed on a platen capable of plane movement, a means for supplying a polishing liquid onto the polishing pad, and a polishing pad supplied with the polishing liquid. And a substrate holding means for holding the substrate to be polished, a temperature measuring means for measuring the temperature of the surface of the polishing pad, and a temperature change detecting means for detecting a change in the temperature measured by the temperature measuring means. With this configuration, the mechanism for measuring the temperature of the polishing pad surface and detecting the change in the temperature can accurately detect the change in the polishing state.

The polishing apparatus according to a second aspect of the present invention is characterized in that the polishing apparatus according to the first aspect further measures the temperature in a non-contact manner. With this configuration, the polishing pad is affected. It is possible to measure the temperature of the pad surface without giving, and it is also possible to detect the end point with high accuracy.

The polishing apparatus according to a third aspect of the present invention is the polishing apparatus according to the first aspect, wherein the temperature measuring means is provided at a position near the surface of the polishing pad on the movement side of the surface plate with respect to the substrate. It is characterized in that it is installed so as to measure the temperature.With this configuration, the means for measuring the temperature is installed at a position where the temperature of the polishing pad surface immediately after contacting the substrate can be measured. Therefore, it becomes possible to sensitively detect a contact resistance (friction) or a heat change caused by a chemical reaction during polishing of the substrate, and further, it becomes possible to detect an end point with high accuracy.

The polishing apparatus according to claim 4 is different from the polishing apparatus according to claim 1 in that the temperature change detecting means further comprises:
Based on the temperature data measured by the temperature measuring means, the temperature change per unit time based on the movement cycle of the surface plate or the substrate holding mechanism is detected, and this configuration enables the constant cycle. The averaging mechanism eliminates fluctuations in the measured temperature due to the motion cycle, oscillation, and cycle of the surface plate and carrier, facilitating detection of minute changes in temperature, and providing accurate end point detection. It will be possible.

In the polishing method according to the fifth aspect of the present invention, the rigid platen provided with the polishing pad is moved in a plane and the polishing liquid is flowed over the polishing pad to press the substrate against the polishing pad to polish the substrate. A method for measuring the temperature of a polishing pad surface and a polishing liquid during polishing of a substrate, and detecting the end point of polishing by detecting a change in the temperature of the polishing pad surface and the polishing liquid. If the surface roughness or film quality of the substrate changes during polishing of the substrate, the contact resistance with the polishing pad will change, and the amount of mechanical polishing or chemical reaction by the polishing liquid will also change, resulting in a heating value during polishing. Since the temperature of the polishing pad changes due to the change, the temperature of the polishing pad surface is measured during polishing, and the end point of polishing can be detected by detecting the temperature change.

The polishing method according to claim 6 is the polishing method according to claim 5, wherein the object to be polished is a single layer and the unevenness of the single layer is flattened. With this configuration, it is possible to detect a change in the polishing state, which could not be detected in the past.

The polishing method according to claim 7 is characterized in that the temperature is measured in a non-contact manner in addition to the polishing method according to claim 5 or 6, and with this configuration, the polishing pad The temperature of the pad surface can be measured without affecting the temperature, and the end point can be detected with high accuracy.

In addition to the polishing method according to claim 5 or 6, the polishing method according to claim 8 is characterized in that the temperature measuring means is provided in the vicinity of the surface of the polishing pad on the movement side of the surface plate with respect to the substrate. It is characterized in that it is installed so as to measure the temperature of the position.With this configuration, the means for measuring the temperature is installed at a position where the temperature of the polishing pad surface immediately after contacting the substrate can be measured. As a result, it becomes possible to sensitively detect a change in contact resistance (friction) or heat generated by a chemical reaction during polishing of the substrate, and further, it becomes possible to detect an end point with high accuracy.

The polishing method according to claim 9 is different from the polishing method according to claim 5 or 6 in that the temperature change detecting means determines the temperature based on the temperature data measured by the temperature measuring means. It is characterized by detecting the temperature change per unit time based on the movement cycle of the board and substrate holding mechanism.With this configuration, the movement cycle and swing of the surface plate and the carrier are adjusted by the averaging mechanism at a fixed cycle. It is possible to eliminate fluctuations in the measured temperature due to movements, cycles, etc., facilitate detection of minute changes in temperature, and further enable accurate end point detection.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION A polishing apparatus and a polishing method according to embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment of the Invention) FIG. 1 is a schematic view of a polishing apparatus according to the first embodiment of the present invention.

In FIG. 1, 1 is a platen made of a flat rigid body that can be rotated as one of the plane motions, and 2 is a polishing pad, which is attached on the platen 1. Next, 3 is a substrate, which is supported by a carrier 4 and pressed against the polishing pad 2 on the surface plate 1 while rotating. Further, 5 is a polishing liquid containing abrasive grains, which is quantitatively dropped on the polishing pad 2 and supplied between the polishing pad 2 and the substrate 3 by the rotation of the surface plate 1. 6 is a radiant heat thermometer for measuring the temperature of the surface of the polishing pad 2, and 7 is a temperature change detector for detecting the temperature change of the surface of the polishing pad 2 measured by the radiant heat thermometer 6. Further, 8 and 9 are a platen rotary motor and a carrier rotary motor, respectively.

As described above, according to the embodiment of the present invention, as a method for detecting the end point, the temperature of the polishing pad surface is measured instead of observing the change in the torque of the motor. In recent years, even minute temperature changes can be detected, so that the end point of polishing can be accurately determined by detecting the temperature changes.

In the embodiment of the present invention, the radiation heat thermometer 6 is used to measure the temperature of the surface of the polishing pad 2.
Since the temperature can be measured in a non-contact manner, the temperature measurement does not affect the polishing, and thus more accurate measurement can be made possible, but other methods can be used as long as they can detect the temperature. Needless to say, it doesn't matter.

In the polishing state shown in FIG. 1, the surface plate 1 is shown to rotate counterclockwise, and the radiant heat thermometer 6 is installed near the counterclockwise side of the carrier 4,
Further, the radiant heat thermometer 6 is installed at substantially the same position as the radial position of the carrier 4 on the surface plate 1. With this configuration, the amount of heat generated when the substrate 3 is polished (= the temperature of the polishing pad) can be measured before being radiated (cooled) to the atmosphere or the surface plate, and the temperature change of the polishing pad can be measured. It is possible to measure more accurately. In the above description, the radiant heat thermometer 6 is installed to detect the temperature of the polishing pad, but when detecting the temperature by radiation, for example, the temperature of the polishing liquid is also detected. However, since the heat generated by the contact resistance during polishing is also transferred to the polishing liquid, the same effect can be obtained even if the temperature of the polishing liquid is detected.

Here, in general, when polishing is performed using the apparatus shown in FIG. 1, the carrier 4 swings on the surface plate 1 in the radial direction. Therefore, when the position of the radiant heat thermometer 6 is fixed, in some cases, just beside the carrier 4 (that is, on the circle having the same radius as the semiconductor wafer being polished).
Will measure the temperature of the
Since the temperature at a position apart from (that is, not on a circle having the same radius as the semiconductor wafer being polished) is measured, the measured temperature varies. Therefore, if the temperature change measuring device 7 is configured to detect the temperature change after being averaged by the rotation period of the surface plate 1 or the carrier 4 or the swinging period of the carrier 4, the measured temperature change amount is smaller than the periodically changing measurement temperature. It is possible to detect various temperature changes.

(Embodiment of the Second Invention) Referring to the drawings, a polishing method in a second embodiment of the present invention using the polishing apparatus having the apparatus configuration described in the above-mentioned embodiment of the first invention will be described. However, it will be described below.

The surface of the polishing pad 2 on the surface plate 1 is quantitatively dropped on the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface of the surface 1. The surface of the substrate 3 is polished. At this time, carrier 4
The temperature of the surface of the polishing pad 2 is measured by the radiant heat thermometer 6 installed in the vicinity of and the change in the surface temperature of the polishing pad 2 is examined.

FIG. 2 is a schematic diagram for explaining a temperature change on the surface of the polishing pad 2 from the start of polishing. In FIG. 2, the horizontal axis is the elapsed time from the start of polishing, and the vertical axis is the temperature of the surface of the polishing pad 2.

In FIG. 2, first, in the region 1, when the polishing is started, frictional heat or reaction heat (heat generated by mechanical polishing or chemical polishing) due to the contact between the substrate 3 and the polishing pad 2 causes the surface of the polishing pad 2 to disappear. The temperature is rising.

Next, in the area 2, the heat generated by frictional heat or reaction heat, the cooling by the quantitative supply of the polishing liquid 5 and the heat radiation to the surface plate 1 and the atmosphere are balanced, and the surface temperature of the polishing pad 2 is Stabilizes at t1.

Next, in the region 3, the surface condition of the substrate 3 changes as the surface of the substrate 3 is polished. For example, when the surface becomes flat and smooth, frictional heat and reaction heat decrease. Then, the temperature of the surface of the polishing pad 2 decreases. It should be noted that the manner of lowering depends on the uniformity of polishing and the material. The above example describes the case where unevenness disappears when a single layer such as an insulating film is polished and a temperature change occurs when it is flattened.However, the endpoint detection can be performed only in this case. Not just not,
By polishing, it is also possible to detect a temperature change that occurs when the wiring pattern is exposed and the material in contact with the polishing pad changes.

Finally, in the region 4, the surface of the substrate 3 is completely changed, and the temperature of the surface of the polishing pad 2 becomes stable again at t2. This area 4 is a so-called over-polished area.

As described above, the temperature change on the surface of the polishing pad 2 is detected, the change in the state of the surface of the substrate 3 is detected by the temperature change in the region 3, and the end point of the polishing is determined to determine the polishing rate. Even if there is a variation in the value, stable polishing can be performed that enables accurate end point detection without controlling the polishing according to the polishing time. The polishing method according to the present embodiment is particularly effective when polishing a single material such as polishing an insulating film having irregularities so that the irregularities disappear.

Here, in the above-described polishing method, the radiation heat thermometer 6 is used to measure the temperature of the polishing pad 2 in a non-contact manner. Therefore, the temperature measurement does not affect the polishing state, and more accurate measurement can be performed. .

Further, when measuring the surface of the polishing pad 2, it is difficult to detect the amount of change due to cooling or heat radiation, so it is desirable to measure the surface of the polishing pad 2 immediately after contact with the substrate 3.

Further, the temperature change amount Δ due to the change of the surface condition Δ
Since t is at most 0.1 to 1 ° C, by averaging it periodically, variations in the measurement temperature due to rotation and rocking of the surface plate 1 and carrier 4, and differences in measurement points (formed on the polishing pad It is possible to improve the detection sensitivity of the temperature change by reducing the influence of the difference between the flatness of the groove or hole) and the noise of the measurement system.

In the first and second embodiments described above, the radiant thermometer was used to measure the temperature of the surface of the polishing pad 2, but this can be achieved by using other temperature measuring means.
The effects of the present invention can be obtained.

In the first and second embodiments described above, the structure of the polishing apparatus and the polishing method are explained using the single-wafer polishing apparatus. This is an apparatus for polishing a plurality of substrates at the same time. Even in the case of using, the effect of the present invention can be obtained similarly.

Furthermore, in the temperature change in the second embodiment, the explanation has been made such that the temperature of the surface of the polishing pad 2 is lowered in the region 3, but this is due to the combination of the material of the surface and the material of the base and the polishing conditions. Depending on the situation, it may rise. However, even when the temperature rises, the end point determination can be performed as in the above-mentioned means.

[0056]

As described above, according to the present invention, since the end point is detected by the change in the temperature of the polishing pad when the state of the substrate surface is changed during polishing, unevenness can be obtained even when polishing a single film or the like. It is possible to determine the end point of the polishing by the temperature change when it disappears.

Therefore, even if the polishing conditions that cause variations in the polishing rate are used, a certain amount of polishing can be performed and accurate and stable flattening can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a polishing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a temperature change on a polishing pad surface in the embodiment of the present invention.

FIG. 3 is a schematic view of a conventional polishing apparatus.

FIG. 4 is a sectional process view showing polishing of an insulating film using a conventional polishing apparatus.

FIG. 5 is a sectional process diagram showing polishing of an insulating film using a conventional polishing apparatus.

[Explanation of symbols]

 1 surface plate 2 polishing pad 3 substrate 4 carrier 5 polishing liquid 6 radiant heat thermometer 7 temperature change detector 8 surface plate rotation motor 9 carrier rotation motor 31 surface plate 32 polishing pad 33 substrate 34 carrier 35 polishing liquid 38 surface plate rotation motor 39 Carrier Rotation Motor 41 Substrate 42 Insulating Film 43 Wiring Pattern 44 Insulating Film 51 Substrate 52 Insulating Film 53 Wiring Pattern 54 Insulating Film

Claims (9)

[Claims] 1. A polishing pad formed on a surface plate capable of plane movement, and means for supplying a polishing liquid onto the polishing pad,
Substrate holding means for holding a substrate to be polished by bringing it into contact with the polishing pad supplied with the polishing liquid, temperature measuring means for measuring the temperature of the polishing pad surface, and temperature measuring means for measuring the temperature of the polishing pad. A polishing apparatus having a temperature change detecting means for detecting a change. 2. The polishing apparatus according to claim 1, wherein the temperature measuring means is a means for measuring the temperature in a non-contact manner. 3. The temperature measuring means is installed so as to measure the temperature at a position in the vicinity of the surface of the polishing pad on the movement direction side of the surface plate with respect to the substrate. Polishing equipment. 4. The temperature change detection means detects a temperature change per unit time based on the movement period of the surface plate and the substrate holding mechanism based on the temperature data measured by the temperature measurement means. The polishing apparatus according to claim 1. 5. A polishing method for polishing a substrate by pressing a substrate against the polishing pad while supplying a polishing liquid onto the polishing pad while the platen on which the polishing pad is installed is moved in a plane. A polishing method, wherein the temperature of the surface of the polishing pad is measured during polishing of the substrate, and the end point of polishing is detected by detecting changes in the temperatures of the surface of the polishing pad and the polishing liquid. 6. The polishing method according to claim 5, wherein unevenness of the single material layer formed on the substrate is eliminated by polishing so as to be planarized. 7. The polishing method according to claim 5, wherein the temperature of the polishing pad is measured in a non-contact manner. 8. The polishing method according to claim 5, wherein the temperature of the surface of the polishing pad is measured at a position close to the substrate on the surface of the polishing pad on the movement direction side of the surface plate. 9. The temperature change on the surface of the polishing pad is detected by detecting the temperature change per unit time based on the temperature measurement data on the surface of the polishing pad based on the motion cycle of the surface plate and the substrate holding mechanism. The polishing method according to claim 5 or 6, characterized in that.