JP2004001227A - Device and method for polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for polishing which can sense a membrane thickness of a polishing surface in real time with a semiconductor wafer attached to a top ring, without shifting the top ring outside a turntable. <P>SOLUTION: The polishing device contains the turntable 1 and the top ring 3 holding the semiconductor wafer 2, pressing the semiconductor wafer 2 held by the top ring 3 onto the top surface of the turntable 1 to polish the polishing surface of the semiconductor wafer 2. Within the turntable 1, a plurality of membrane thickness sensing means detecting the membrane thickness of a polishing surface are located, which consecutively provide the membrane thickness sensing of the polishing surface. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a polishing apparatus and method, particularly when polishing an object to be polished such as a semiconductor wafer, without exposing a polished surface of the object to be polished while the object to be polished is mounted on a top ring. The present invention relates to a polishing apparatus and a polishing method capable of continuously detecting the film thickness in real time.

、 In recent years, as the degree of integration of semiconductor devices has increased, circuit wiring has become finer, and the distance between wirings has become smaller. In particular, in the case of optical lithography of 0.5 μm or less, since the depth of focus becomes shallow, a flatness of the image formation surface of the stepper is required. Therefore, it is necessary to flatten the surface of the semiconductor wafer. As one of the flattening methods, the surface of the semiconductor wafer is polished by a polishing apparatus.

This type of polishing apparatus is provided with a turntable and a top ring which face each other and rotate independently, the top ring applies a constant pressure to the turntable, and a semiconductor wafer is interposed between the turntable and the top ring. The surface of the semiconductor wafer is polished flat and mirror-finished.

A problem when polishing a semiconductor wafer using the above polishing apparatus is to determine whether the polished surface of the semiconductor wafer is polished to a desired flatness or thickness. For example, it is often desirable to form a vapor deposited layer on a semiconductor wafer, form various integrated circuit elements thereon, and remove the thickness of the oxide material. In removing or planarizing this oxide material, it is desirable to remove the oxide to the top of various integrated circuit devices without removing any portion of the device.

Traditionally, this planarization process has been performed by controlling the rotation speed of the turntable and top ring, the pressure applied to the top ring turntable, the chemical slurry, and the time of the planarization process. The thickness, flatness, and the like of the polished surface of the semiconductor wafer were confirmed by mechanically removing the semiconductor wafer from the polishing apparatus and physically measuring the semiconductor wafer by a method known in the art.

Here, when the wafer does not conform to the specifications, the wafer is returned to the polishing apparatus, and the second flattening and polishing step is performed. That is, in order to detect the film thickness of the polished surface, it is necessary to repeat the work of removing the semiconductor wafer from the polishing apparatus and setting the semiconductor wafer again in the polishing apparatus when polishing is insufficient, and the time required for this work is required. And labor was a problem.

To solve this problem, a method has been proposed in which the top ring is shifted out of the turntable during polishing while the semiconductor wafer is mounted on the top ring, and the film thickness is detected in a state where the surface to be polished is exposed. According to this method, the above-described problem of time and labor is largely solved.However, in order to detect the film thickness, a step of temporarily moving the top ring out of the turntable is required. There are problems such as the inability to detect the film thickness in real time and the increase in polishing time.

The present invention has been made in view of the above circumstances, and has a polishing apparatus and method capable of detecting the thickness of a surface to be polished in real time without displacing the top ring out of a turntable while the semiconductor wafer is mounted on the top ring. The purpose is to provide.

In order to achieve the above-described object, one embodiment of the polishing apparatus of the present invention includes a turntable and a top ring for holding an object to be polished, wherein the object to be polished held by the top ring is attached to the turntable. A polishing apparatus for pressing the upper surface of the object to polish the surface to be polished of the object to be polished, wherein a plurality of film thickness detecting means for detecting the film thickness of the surface to be polished are arranged in the turntable, The plurality of film thickness detecting means continuously detects the film thickness of the surface to be polished.

The polishing apparatus further includes a polishing cloth attached to an upper surface of the turntable and polishing the surface to be polished, wherein the polishing cloth has at least one polishing cloth corresponding to a position of a film thickness detecting means in the turntable. It is characterized by having an opening.
The plurality of film thickness detecting means may simultaneously detect the film thickness of the surface to be polished.
At least one of the plurality of film thickness detecting means is an optical film thickness detecting means.

In one embodiment of the polishing method of the present invention, in a polishing apparatus having a turntable and a top ring, an object to be polished held by the top ring is pressed against a polishing surface of the turntable, and the object to be polished is polished. A polishing method for polishing a polished surface, wherein the film thickness of the polished surface is detected by a plurality of film thickness detecting means, and the intensity obtained from the plurality of film thickness detecting means is calculated by an arithmetic unit, The film thickness is detected from the sum of the calculated intensities.

The operating condition of the polishing apparatus is controlled based on the film thickness detected from the sum of the calculated intensities.
The plurality of film thickness detecting means simultaneously detects the film thickness of the surface to be polished.
The plurality of film thickness detecting means continuously detects the film thickness of the surface to be polished.
A polishing speed is calculated from a difference between the added value and a previously stored initial value, and a polishing operation condition is controlled based on the polishing speed.

Another embodiment of the polishing apparatus of the present invention has a turntable and a holder for holding the object to be polished, and presses the object to be polished held by the holder against the upper surface of the turntable to form the polishing object. A polishing apparatus for polishing a surface to be polished of an object to be polished, wherein the turntable has a polishing cloth attached to an upper surface of the turntable, wherein the polishing cloth is provided with a sealing material in a part thereof, The material is characterized by having a low polishing ability.

It is characterized by having a film thickness detecting means for measuring the film thickness of the surface to be polished.
The film thickness detecting means is provided in the turntable.
The polishing pad has an opening corresponding to a position where the plurality of film thickness detecting means are arranged.
The film thickness detecting means has a light projecting portion and a light receiving portion, and the sealing material is provided at a portion where the light projecting portion and the light receiving portion are arranged.

Another aspect of the polishing method of the present invention is that, in a polishing apparatus having a turntable and a top ring, an object to be polished held by the top ring is pressed against a polishing surface of the turntable, and A polishing method for polishing a surface to be polished, wherein a change in film thickness with time at a plurality of points at different radial positions of the surface to be polished is detected by a film thickness detecting means, and a polishing profile of the surface to be polished is measured behind the surface to be polished. The polishing is controlled during polishing using pressure from

Another aspect of the polishing method of the present invention is that, in a polishing apparatus having a turntable and a top ring, an object to be polished held by the top ring is pressed against a polishing surface of the turntable, and A polishing method for polishing a surface to be polished, characterized in that a change in film thickness with time at a specific point on the surface to be polished is detected by a film thickness detecting means, and polishing conditions are controlled during polishing.

A preferred embodiment of the polishing apparatus of the present invention includes a turntable having a top ring and a polishing cloth opposed to each other and independently rotating, and a plate-shaped object to be polished is interposed between the turntable and the top ring. In a polishing apparatus for pressing the object to be polished with a predetermined force and polishing the surface of the object to be polished, light is projected onto the surface to be polished of the object to be polished on a track of a top ring on the turntable. An object to be polished film thickness detecting means provided with a sensor comprising a light projecting portion that emits light and a light receiving portion that receives light reflected by the surface to be polished is provided, and the object to be polished is mounted on the top ring. Without exposing the object to be polished, the thickness of the object to be polished can be continuously detected in real time from the reflected light received by the light receiving section.

The thickness of the object to be polished may be detected from a change in the intensity of the reflected light of the light received by the light receiving section.

The polishing object film thickness detecting means is configured by arranging a plurality of sensors each including a light projecting unit and a light receiving unit in a radial direction on a turntable, and simultaneously measuring the film thickness of the entire surface of the object to be polished in real time. It may be detectable.

The object-to-be-polished film thickness detecting means may be provided with a polishing cloth having an extremely low polishing ability or a material having no polishing ability in a region including the sensor, which is surrounded by the arc of the center and the outer periphery of the turntable. .

The polished object film thickness detecting means includes an amplifier for amplifying a light reception signal received by the light receiver, an analog filter for removing noise from the light reception signal amplified by the amplifier, and a light receiver for removing the noise. An A / D converter for converting a signal into a digital signal; calculating an absolute value of a difference between the digitalized light receiving signal and an initial value; and comparing the absolute value of the difference with a predetermined threshold value It may be made up of an arithmetic unit that performs the calculation.

The present invention adopts the above configuration, during polishing, projects light from the light projecting portion to the polishing surface, receives light reflected by the object to be polished by the light receiving portion, and receives light reflected by the light receiving portion. The thickness of the object to be polished can be automatically detected in real time and continuously from the light. Therefore, unlike the related art, it is not necessary to remove the object to be polished from the top ring every time the thickness of the object to be polished is detected, and it is not necessary to shift the top ring to outside the turntable during polishing.

According to the present invention, during polishing, light is projected from the light projecting portion to the polished surface of the object to be polished, light reflected on the surface to be polished is received by the light receiving portion, and light is reflected from the reflected light received by the light receiving portion. The film thickness of the polished object can be automatically detected in real time and continuously. Therefore, unlike the related art, it is not necessary to remove the object to be polished from the top ring every time the thickness of the object to be polished is detected, and it is not necessary to shift the top ring to outside the turntable during polishing.

Hereinafter, embodiments of a polishing apparatus according to the present invention will be described with reference to the drawings. In this embodiment, a semiconductor wafer will be described as an example of the object to be polished.
FIG. 1 is a longitudinal sectional view showing the overall configuration of the polishing apparatus of the present invention. As shown in FIG. 1, the polishing apparatus includes a turntable 1 and a top ring 3 that holds the semiconductor wafer 2 and presses the semiconductor wafer 2 against the turntable 1. The turntable 1 is connected to a motor (not shown), and is rotatable around its axis as indicated by an arrow. A polishing cloth 4 is stuck on the upper surface of the turntable 1.

The top ring 3 is connected to a motor (not shown) and to a lifting cylinder (not shown). As a result, the top ring 3 can move up and down as shown by an arrow and can rotate around its axis, so that the semiconductor wafer 2 can be pressed against the polishing cloth 4 with an arbitrary pressure. ing. A guide ring 6 for preventing the semiconductor wafer 2 from coming off is provided on a lower outer peripheral portion of the top ring 3.
A polishing abrasive liquid nozzle 5 is provided above the turntable 1, and the polishing abrasive liquid Q is supplied onto the polishing cloth 4 attached to the turntable 1 by the polishing abrasive liquid nozzle 5. I have.

In the polishing apparatus having the above structure, the semiconductor wafer 2 is held on the lower surface of the top ring 3, and the semiconductor wafer 2 is pressed against the polishing cloth 4 on the upper surface of the rotating turntable 1 by a lifting cylinder. On the other hand, by flowing the polishing abrasive liquid Q from the polishing abrasive liquid nozzle 5, the polishing abrasive liquid Q is held on the polishing cloth 4, and the polishing is performed between the polishing surface (lower surface) of the semiconductor wafer 2 and the polishing cloth 4. Polishing is performed in the presence of the polishing liquid Q.

FIG. 2 is a diagram showing details of a main part of the polishing apparatus of the present invention. On the semiconductor wafer 2, an oxide film made of SiO ₂ is formed on the surface of the substrate. The polishing apparatus includes a film thickness detecting means for measuring the thickness of the oxide film during polishing. The top ring 3 takes a position such that the entire surface to be polished of the semiconductor wafer 2 is covered with the upper surface of the turntable 1, that is, the polishing cloth 4, until the polishing is completed. The detection means detects the thickness of the oxide film on the surface to be polished during polishing in real time and continuously.

As shown in FIG. 2, the film thickness detecting means includes a sensor S including a light projecting unit 7 for projecting light on the surface to be polished of the semiconductor wafer 2 and a light receiving unit 8 for receiving light reflected on the surface to be polished. It comprises a unit 9, an analog filter 10, an A / D converter 11, an operation unit 12, and a control unit 13. The sensor S including the light projecting unit 7 and the light receiving unit 8 is arranged on the track of the top ring 3 on the turntable 1 and is provided inside the turntable 1 below the polishing pad 4. The light projecting unit 7 and the light receiving unit 8 of the sensor S include a single or a plurality of light projecting elements and light receiving elements, respectively, and irradiate light to the polished surface of the semiconductor wafer 2 from each of the light projecting elements. Is received by the light receiving element. Further, the polishing pad 4 is provided with a hole so as to allow the light of the sensor S to pass therethrough.

In addition, if the light projecting unit 7 and the light receiving unit 8 of the sensor S are arranged on a track located at the center of the semiconductor wafer 2, only one set is required. Detection is possible. However, in this case, since a slight time lag occurs in the detection time, when detection at the same time is required, a plurality of sets of the light projecting unit 7 and the light receiving unit 8 are required.

(4) The reflected light received by the light receiving unit 8 is converted into an electric signal proportional to each intensity, amplified by the amplification unit 9 at a fixed magnification, and passed through the analog filter 10 to remove noise. Next, each electric signal is sent to the A / D converter 11, the analog signal is converted into a digital signal, and is sampled as a signal at a constant interval.

Next, each digital signal is input to the arithmetic unit 12, and the arithmetic unit 12 calculates the intensity of each signal, and adds each intensity to obtain an added value. The film thickness of the polished surface of the semiconductor wafer 2 is calculated from the added value. The addition value is compared with an initial value (an addition value of the reflected light intensity before the start of polishing, that is, an initial addition value) stored in advance, and the polishing speed is calculated from the absolute value of the difference between the addition value and the initial value. Is calculated. The operating conditions of the polishing apparatus are calculated based on the film thickness and polishing rate of the entire surface to be polished, and the calculation result is sent to the control unit 13 to control the operating conditions of the polishing apparatus, and To improve the flatness of the polished surface. Further, the flatness of the polished surface can be known by comparing the film thickness measured at each point on the polished surface of the semiconductor wafer.

(4) By measuring the film thickness at a specific point on the semiconductor wafer with respect to the passage of time, it is possible to capture a change in polishing rate with time during polishing. Using this information, it is possible to control the polishing conditions (pressure, number of revolutions, etc.) to achieve a constant polishing rate, to determine and predict the life of the polishing cloth, and to determine appropriate dressing conditions. It becomes possible. Further, by using the time change of the film thickness at a plurality of measurement points having different radial positions on the semiconductor wafer, the polishing profile of the wafer can be controlled during polishing by using a backside pressure or the like.

Further, the polishing apparatus can be controlled so that the polishing operation is finished when the detected film thickness substantially matches the predetermined film thickness.
Further, the polishing apparatus can be controlled so as to end the polishing operation when the detected flatness substantially matches the predetermined flatness.

FIG. 3 shows a case where the sensor S including the light projecting unit 7 and the light receiving unit 8 is embedded and arranged in the turntable 1. FIG. 3A is a plan view, and FIG. 3B is a partial sectional view. By arranging the light projecting unit 7 and the light receiving unit 8 on the track 14 at the center of the semiconductor wafer 2, it is possible to detect the film thickness of the entire surface to be polished with only one set. However, in this case, since the film thickness is detected while moving on the wafer surface within a certain time, a slight time lag occurs at the detection time of each film thickness. Therefore, when detection at the same time is necessary, it is necessary to arrange a plurality of sensors S including the light projecting unit 7 and the light receiving unit 8.

4A and 4B are diagrams showing a case where a plurality of sensors S are arranged in the radial direction of the turntable. FIG. 4A is a plan view, and FIG. 4B is a partial sectional view. The plurality of sensors S are arranged at predetermined intervals in the radial direction. In this case, all the sensors S are located in the trajectory of the semiconductor wafer 2.
When the light emitting unit 7 and the light receiving unit 8 are embedded in the turntable 1, the polishing cloth 4 does not exist in that area. This results in unevenness in strength. In order to correct this, as shown in FIGS. 3 and 4, a hatched portion of the polishing pad 4 (including a portion where the light emitting portion 7 and the light receiving portion 8 are arranged) (surrounded by the center O of the turntable and the arc of the outer periphery). In the region A), a polishing cloth having an extremely low polishing ability or a material having no polishing ability (such as a seal tape) is provided.

The thickness of the oxide film can be measured by the following method. That is, the light incident on the semiconductor wafer from the light projecting part enters the oxide film and is reflected on the upper and lower surfaces of the film. The reflected lights reflected on the upper and lower surfaces of this film interfere with each other to generate an interference color. The thickness of the oxide film can be measured by measuring the interference color with the light receiving unit.
In the embodiments, the film formed on the surface of the semiconductor wafer has been described using an oxide film as an example, but the type of the film is not limited to the oxide film.

It is a longitudinal section showing the schematic structure of the polish device concerning the present invention. It is a longitudinal section showing the important section composition of the polish device concerning the present invention. FIG. 3 is a diagram showing an arrangement relationship between a light projecting unit and a light receiving unit of a sensor in the polishing apparatus according to the present invention. FIG. 6 is a diagram illustrating another example of the positional relationship between the light projecting unit and the light receiving unit of the sensor in the polishing apparatus according to the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Turntable 2 Semiconductor wafer 3 Top ring 4 Polishing cloth 5 Polishing liquid nozzle 6 Guide ring S Sensor 7 Light emitting part 8 Light receiving part 9 Amplifying part 10 Analog filter 11 A / D conversion part 12 Operation part 13 Control part

Claims (16)

Turntable,
And a top ring for holding the object to be polished,
A polishing apparatus for pressing the object to be polished held by the top ring against the upper surface of the turntable to polish the surface to be polished of the object to be polished,
A plurality of film thickness detecting means for detecting the film thickness of the surface to be polished is arranged in the turntable,
The polishing apparatus according to claim 1, wherein the plurality of film thickness detecting means continuously detect the film thickness of the surface to be polished. The polishing apparatus further includes a polishing cloth attached to the upper surface of the turntable, and polishing the surface to be polished,
2. The polishing apparatus according to claim 1, wherein the polishing cloth has at least one opening corresponding to a position of the film thickness detecting means in the turntable. 3. The polishing apparatus according to claim 1, wherein the plurality of film thickness detecting means simultaneously detect the film thickness of the surface to be polished. The polishing apparatus according to any one of claims 1 to 3, wherein at least one of the plurality of film thickness detecting means is an optical film thickness detecting means. In a polishing machine with a turntable and a top ring,
The object to be polished held by the top ring is pressed against the polishing surface of the turntable,
A polishing method for polishing a surface to be polished of the object to be polished,
The film thickness of the polished surface is detected by a plurality of film thickness detecting means,
A polishing method, comprising: calculating intensities obtained from the plurality of film thickness detecting means in a calculation unit; and detecting a film thickness from an added value of the calculated intensities. 6. The polishing method according to claim 5, wherein operating conditions of the polishing apparatus are controlled based on the film thickness detected from the calculated sum of the intensities. 6. The polishing method according to claim 5, wherein the plurality of film thickness detecting means simultaneously detect the film thickness of the polished surface. 6. The polishing method according to claim 5, wherein the plurality of film thickness detecting means continuously detect the film thickness of the polished surface. 9. A polishing speed is calculated from a difference between the added value and an initial value stored in advance, and a polishing operation condition is controlled based on the polishing speed. 3. The polishing method according to 1. Polishing, having a turntable and a holder for holding the object to be polished, pressing the object to be polished held by the holder against the upper surface of the turntable to polish the surface to be polished of the object to be polished A device,
The polishing apparatus, wherein the turntable has a polishing cloth attached to an upper surface of the turntable, and the polishing cloth is partially provided with a sealing material, and the sealing material is a material having a low polishing ability. . 11. The polishing apparatus according to claim 10, further comprising a film thickness detecting means for measuring a film thickness of the surface to be polished. The polishing apparatus according to claim 11, wherein the film thickness detecting means is provided in the turntable. 12. The polishing apparatus according to claim 11, wherein the polishing cloth has an opening corresponding to a position where the plurality of film thickness detecting means are arranged. 14. The method according to claim 13, wherein the film thickness detecting means has a light projecting portion and a light receiving portion, and the sealing material is provided at a portion where the light projecting portion and the light receiving portion are arranged. Polishing equipment. In a polishing machine with a turntable and a top ring,
The object to be polished held by the top ring is pressed against the polishing surface of the turntable,
A polishing method for polishing a surface to be polished of the object to be polished,
The film thickness detecting means detects a time-dependent change in film thickness at a plurality of points at different radial positions of the polished surface,
A polishing method, wherein a polishing profile of the surface to be polished is controlled during polishing by using a pressure from behind the surface to be polished. In a polishing machine with a turntable and a top ring,
The object to be polished held by the top ring is pressed against the polishing surface of the turntable,
A polishing method for polishing a surface to be polished of the object to be polished,
A change in film thickness with time at a specific point on the surface to be polished is detected by a film thickness detecting means,
A polishing method, wherein polishing conditions are controlled during polishing.

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