JP2003059876A - Device and method for detecting object and polishing the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and method for detecting an object which can correspond various materials, have large degrees of freedom in installation and make an accurate detection, and a polishing device provided with such a detection device. SOLUTION: There are provided a light-emitting part 62, having a light- emitting axis A1 inclined to an object; a light-receiving part 63 having a light- receiving axis A2 positioned on a side opposite to a regular reflection axis A3 , corresponding to the light-emitting axis A1 ; and a detection part 64 for detecting presence of a wafer W, by changing the amount of light received in the light-receiving part 63.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detector and a detection method for an object, and more particularly to a wafer ejection detector and a detection method for detecting a wafer ejected from a top ring, and a polishing apparatus equipped with such a detector. It is a thing.

[0002]

2. Description of the Related Art 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 with a line width of 0.5 μm or less, the depth of focus becomes shallow, so that the flatness of the image plane of the stepper is required. Chemical mechanical polishing (CMP) is one of means for flattening the surface of such a semiconductor wafer.
There is known a polishing apparatus for performing the above.

In this type of polishing apparatus, a polishing table having a polishing surface formed by adhering a polishing cloth (polishing pad) to the upper surface thereof, and a substrate such as a semiconductor wafer to be polished which is a surface to be polished on the polishing table. It has a top ring that holds it toward you. When a semiconductor wafer is polished using such a polishing apparatus, the polishing table and the top ring are respectively rotated, and a polishing liquid (slurry) is supplied from a polishing liquid supply nozzle installed above the polishing table. At the same time, the semiconductor wafer is pressed against the polishing cloth of the polishing table with a constant pressure by the top ring. As the polishing liquid supplied from the polishing liquid supply nozzle, for example, an abrasive in which abrasive grains made of fine particles such as silica are suspended in an alkaline solution is used, and a chemical polishing action by an alkali and a mechanical polishing action by the abrasive grains are combined. The semiconductor wafer is polished flat and mirror-like by the action of chemical / mechanical polishing.

In such a polishing apparatus, when the wafer is normally delivered to the top ring, the wafer rarely jumps out of the top ring during polishing. However, when the wafer is not delivered normally and the wafer rides on the guide ring of the top ring, a phenomenon occurs in which the wafer pops out of the top ring during polishing.

When the wafer jumps out of the top ring, the wafer rotates with the polishing table and collides with the top ring to damage the wafer itself, or the guide ring of the top ring constituting the polishing apparatus and the polishing on the polishing table. There is a risk of damaging the cloth, backing material, dressing member, and the like. In order to cope with such a phenomenon, a wafer pop-out detector including an optical sensor or the like is attached to a polishing device to detect the pop-up of the wafer from the top ring.

When an optical sensor is used to detect the jumping out of a wafer, an optical sensor arranged in the vicinity of the top ring emits light from directly above the polishing cloth, receives the specularly reflected light, and measures the amount of light. To do. Since the glossiness of the polishing cloth (the amount of specularly reflected light) and the glossiness of the wafer surface (the amount of specularly reflected light) are different, foreign matter (wafer) is detected on the polishing cloth by detecting the change in the received light amount. Whether or not there is detected.

[0007]

Recently, as semiconductor devices have been highly integrated, various materials have been used for semiconductor wafers. Although the property with respect to light differs depending on the material, recently, a material that cannot detect specularly reflected light by the above-mentioned optical sensor is being used for the semiconductor wafer. When such a material is used, the presence of the wafer cannot be detected by the above-described method of measuring the amount of specularly reflected light, so that the jumping out of the wafer cannot be detected. Therefore, there is a demand for the development of a detector that can detect popping out of a wafer using such a material.

Further, since the conventional wafer pop-out detector described above needs to be arranged near the top ring,
There is a low degree of freedom in the installation of the wafer pop-out detector, and there is a possibility that the slurry or the like used for polishing may hit the detector and prevent accurate detection.

The present invention has been made in view of the above-mentioned problems of the prior art, and can deal with various materials, has a high degree of freedom in installation, and can be accurately detected. An object of the present invention is to provide a detector, a detection method, and a polishing apparatus including the detector.

[0010]

In order to solve the problems in the prior art, the first aspect of the present invention is
A light projecting portion having a light projecting axis inclined with respect to the object, a light receiving section having a light receiving axis located on the opposite side of the specular reflection optical axis corresponding to the light projecting axis, and a light receiving amount of the light receiving section. A detector for an object, comprising: a detector that detects the presence of the object by a change.

A second aspect of the present invention comprises a polishing table having a polishing surface, a top ring for holding an object to be polished and pressing the polishing surface, and the detector described above.
The polishing apparatus is characterized in that the detector detects the protrusion of the object to be polished from the top ring.

A third aspect of the present invention is characterized in that light is projected from a position inclined with respect to the object, and the presence of the object is detected by a change in the amount of diffusely reflected light generated by the light projection. It is a method of detecting a target object.

According to the object detector of the present invention, it is possible to incline the projection axis of the projection section and detect the presence of the object based on the change in the quantity of diffusely reflected light caused by the projection. it can. Further, according to the polishing apparatus equipped with such a detector, it is possible to effectively detect that the wafer has jumped out of the top ring, and for a wafer using a material that could not be conventionally detected. Even then, it is possible to detect the pop-out. Also, since the projection axis is tilted, it is not necessary to place the detector near the top ring, so the degree of freedom in installing the detector is increased, and at the same time the slurry used for polishing is applied to the detector. Without this, accurate detection is possible.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a polishing apparatus according to the present invention will be described in detail with reference to FIGS. 1 is a schematic plan view showing an overall configuration of a polishing apparatus according to an embodiment of the present invention, FIG. 2 is a partial plan view of FIG. 1, and FIG. 3 is a sectional view taken along line III-III of FIG.

The polishing apparatus holds a polishing table 11 having a polishing cloth 10 adhered on the upper surface thereof and a semiconductor wafer W, which is an object to be polished, by vacuum suction, and presses this against the polishing table 11 to polish the top ring. A housing 40 is provided with a dresser 20 and a dresser 30 for dressing the polishing cloth 10 on the polishing table 11.

A pusher 51 for transferring the semiconductor wafer W between the robot arm 50 and the top ring 20 is installed in the housing 40. The pusher 51 has a function of receiving an unpolished wafer from the robot arm 50 and delivering it to the top ring 20, and receiving a polished wafer from the top ring 20 and delivering it to the robot arm 50. In addition, the pusher 51 has
A cleaning mechanism (not shown) for cleaning the robot arm 50 and the top ring 20 is provided.

The polishing table 11 is arranged at a substantially central portion of the housing 40, and a cover 12 is provided on the outer periphery of the polishing table 11 to prevent slurry of polishing liquid and polishing particles from scattering to the outside of the polishing table 11. Is installed.
As shown in FIG. 3, the surface of the polishing pad 10 of the polishing table 11 constitutes a polishing surface that is in sliding contact with the semiconductor wafer W that is the object to be polished. The polishing table 11 has a table shaft 13
The polishing table 11 is connected to a motor (not shown) disposed thereunder via a shaft, and is configured to be rotatable about its table shaft 13 as shown by an arrow A in FIGS. ing.

A polishing liquid supply nozzle 14 is arranged above the polishing table 11, and the polishing liquid supply nozzle 1 is provided.
4 is fixed to the tip of the nozzle arm 15. By the swing of the nozzle arm 15, the polishing liquid supply nozzle 14
Is rotatable about the rotation center O in the direction indicated by the arrow B in FIG. Therefore, the polishing liquid supply nozzle 14
Can be moved from a polishing liquid supply position on the upper surface of the polishing table 11 shown by a solid line to a standby position outside the polishing table 11 shown by a chain double-dashed line.

The polishing liquid supply nozzle 14 has a nozzle arm 1
A polishing liquid supply pipe (not shown) arranged in the inside of 5 is connected, and the polishing liquid is supplied from the polishing liquid supply pipe to the polishing liquid supply nozzle 14. As a result, the polishing liquid used for polishing becomes the polishing liquid supply nozzle 1.
4 is supplied onto the polishing cloth 10 of the polishing table 11.

The top ring 20, as shown in FIG.
It is connected to the lower end of a top ring shaft 22 that hangs from the free end of the top ring arm 21. The swing of the top ring arm 21 allows the top ring 20 to rotate about the rotation center P in the direction indicated by the arrow C in FIG. Therefore, the top ring 20 can be moved between the polishing position on the upper surface of the polishing table 11 shown by the solid line and the wafer delivery position 52 on the pusher 51 shown by the two-dot chain line. Further, the top ring shaft 22 is connected to a motor and an elevating cylinder (not shown) provided inside the top ring arm 21, so that the top ring 20 can move up and down as shown by arrows D and E and the top ring 20 can be moved up and down. It is rotatable around the ring shaft 22.

The semiconductor wafer W to be polished is adsorbed and held on the lower end surface of the top ring 20 by vacuum or the like. Therefore, the top ring 20 is capable of pressing the semiconductor wafer W held on the lower surface thereof against the polishing cloth 10 with an arbitrary pressure while rotating on its own axis.

The dresser 30 is used to regenerate and sharpen the deteriorated surface of the polishing cloth 10 by polishing, and is arranged on the opposite side of the top ring 20 from the center of the polishing table 11. Like the top ring 20, the dresser 30 is connected to the lower end of a dresser shaft (not shown) that hangs from the free end of the dresser arm 31. By swinging the dresser arm 31,
The dresser 30 is capable of turning around the rotation center Q in the direction indicated by the arrow F in FIG. Therefore, the dresser 30 can move between the dresser standby position 32 outside the polishing table 11 shown by the solid line and the position shown by the two-dot chain line on the upper surface of the polishing table 11. Further, the dresser shaft is connected to a motor (not shown) and an elevating cylinder provided inside the dresser arm 31, whereby the dresser 30 can be elevated and rotated around the dresser shaft. At the dresser standby position 32, the dresser 3
A dresser cleaning mechanism (not shown) for cleaning 0 is provided.

On the lower surface of the dresser 30, a dressing member for slidingly contacting the polishing cloth 10 and dressing the polishing cloth 10 is attached. The dresser 30 presses the dressing member against the polishing cloth 10 with an arbitrary pressure and rotates to rotate (semiconductor wafer is
The deformation of the surface of the polishing pad 10 which is caused by polishing by abutting against the () is corrected (or sharpened).

On the downstream side of the polishing table 11 in the rotation direction,
A wafer sensor (wafer detector) 60 for detecting the protrusion of the semiconductor wafer W from the top ring 20 is arranged. The wafer sensor 60 is supported by a sensor support arm 61 near the side of the top ring 20.

FIG. 4 is a schematic diagram showing the wafer sensor 60 shown in FIG. As shown in FIG. 4, the wafer sensor 60
Is a light projecting portion 62 for projecting light onto the polishing cloth 10 or the wafer, a light receiving portion 63 arranged below the light projecting portion 62, and a light receiving portion 63.
Detector 64 for detecting the presence of a wafer based on the amount of received light
Are provided in the casing 65. Wafer sensor 60
The light used in, for example, the emission wavelength 670n
m, a JIS class 2 visible light laser can be used, and as such a wafer sensor 60, for example, OMRON F3C-AL14 or the like can be used.

FIG. 5 is a schematic diagram showing a state when light is projected onto the polishing cloth 10, and FIG. 6 is a schematic diagram showing a state when light is projected onto the wafer. As shown in FIG. 4 to FIG.
The projection axis A _{1 of} is inclined with respect to the object (polishing cloth 10 or wafer W). Further, the light receiving axis A of the light receiving unit 63
₂ is located on the opposite side of the specular reflection optical axis A ₃ corresponding to the projection axis A ₁ . Although the reflected light includes regular reflection light and irregular reflection light, the light receiving unit 63 is configured to receive irregular reflection light generated by the light projection from the light projecting unit 62.

In general, the polishing cloth 10 has a low glossiness and the surface of the wafer W has a high glossiness. Therefore, the polishing cloth 10 has a small proportion of regular reflection and a large proportion of irregular reflection (FIG. 5), whereas the wafer W has a large proportion of regular reflection and a small proportion of irregular reflection (FIG. 6). The present invention is
Using this principle, the protrusion of the wafer W from the top ring 20 is detected. That is, as described above, the light receiving section 63 receives the irregularly reflected light generated by the light projected from the light projecting section 62, but when the light from the light projecting section 62 hits the polishing cloth 10 ( The amount of irregularly reflected light received by the light receiving unit 63 differs between FIG. 5) and the case where the light from the light projecting unit 62 strikes the wafer W (FIG. 6). In the present embodiment, in the detection unit 64, when the light receiving unit 63 receives a predetermined amount of irregularly reflected light, it is determined that the wafer W is in a normal state without popping out, and the light receiving unit 63 detects the predetermined amount. It is determined that the wafer W has jumped out of the top ring 20 when the irregularly reflected light is no longer received.

Here, in FIG. 4, the angle formed by the regular reflection optical axis A ₃ corresponding to the projection axis A ₁ and the light receiving axis A ₂ is defined as a sensor inclination angle α. In other words, α = 2θ + β, where θ is an angle formed by a vertical line with respect to the surface of the object (polishing cloth or wafer) and the projection axis A _1, and β is an angle formed by the projection axis A ₁ and the light receiving axis A _2. Define. In the present embodiment, an example in which the angle β formed by the light projecting axis A ₁ and the light receiving axis A ₂ is 10 ° will be described. However, depending on the type of thin film formed on the surface of the polishing cloth or the wafer,
Β can be appropriately set to an optimal value so that the wafer can be optimally detected when an abnormality occurs.

FIG. 7 is a graph showing the result of verifying the detection limit of the polishing cloth or the wafer in the wafer sensor 60. In FIG. 7, the horizontal axis represents the distance L (see FIG. 4) between the object (polishing cloth or wafer) and the wafer sensor 60. The vertical axis is the object (polishing cloth or wafer)
Shows the maximum sensor tilt angle α (see FIG. 4) that can detect the object, that is, the detection limit angle. At a sensor tilt angle larger than this detection limit angle, the amount of light received by the light receiving unit becomes too small to detect an object. It means that you cannot do it. Therefore, in the dry state,
This means that the polishing cloth and the wafer can be distinguished in the shaded area shown in FIG. 7, and it is possible to detect that the wafer has jumped out of the top ring in this area. The point R in FIG. 7 is considered to be the optimum point.

Thus, according to the present invention, the light projecting portion 62
The projection axis A ₁ of the wafer is tilted, and the projection of the wafer from the top ring is detected based on the change in the amount of diffusely reflected light generated by the projection. Therefore, it is effective that the wafer is projected from the top ring. It has become possible to detect pop-out even on a wafer using a material that could not be detected in the past.

Next, the operation of polishing a semiconductor wafer using the polishing apparatus having such a structure will be described. First, the unpolished wafer carried by the robot arm 50 is passed to the pusher 51. At the wafer transfer position 52 of the pusher 51, the top ring 20 receives the unpolished wafer W so as to fit in the guide ring, and sucks the wafer on its lower surface by vacuum suction. And the top ring arm 21
Is rotated in the direction of arrow C, and the surface to be polished of the wafer W is brought into contact with the upper surface of the polishing pad 10 at a predetermined polishing position on the polishing table 11 for polishing. The surface to be polished of the wafer W is polished by rotating the polishing table 11 in the direction of arrow A and rotating the top ring 20 in the direction of arrow E. At the time of this polishing, the polishing liquid is supplied from the polishing liquid supply nozzle 14.

When the polishing is completed, the top ring 20 turns in the direction of arrow C and the pusher 51 transfers the wafer W to the pusher. The robot arm 50 receives the polished wafer W from the pusher and transfers it to the next step.

Here, the unpolished wafer W is pushed by the pusher 5
1 is transferred to the top ring 20, the wafer W is guided by the guide ring 20a (see FIG. 8) if the transfer is normally performed.
(See) will be housed inside. Therefore, even when the polishing operation is started and the frictional force generated by the relative movement of the polishing cloth and the wafer W and the surface tension of the polishing liquid act on the wafer W to cause the wafer W to jump out of the top ring 20, this guide is used. It is blocked by the ring 20a and does not jump out of the top ring 20.

However, from the pusher to the top ring 2
When the delivery of the wafer W to 0 is not normally performed,
As shown in, the phenomenon that the wafer W rides on the guide ring 20a of the top ring 20 occurs.
When the wafer W is brought into contact with the upper surface of the polishing pad 10 in this state to perform polishing, the frictional force generated by the relative movement of the polishing pad and the wafer W and the surface tension of the polishing liquid act on the wafer W as described above. As a result, the wafer W easily pops out of the top ring 20.

When the wafer W jumps out of the top ring 20, the wafer W rotates together with the polishing table 11, and when the polishing table 11 makes one rotation, the wafer W collides with the top ring 20. Due to the impact of this collision, the wafer W itself may be damaged, and the components of the top ring 20 such as the guide ring 20a and the backing material (film having elasticity attached to the lower surface of the top ring) may be damaged or damaged. Further, the wafer W is ejected by the impact of the collision with the top ring 20 and collides with the components of the apparatus, which may damage the wafer W itself or damage to the polishing cloth 10, the dresser 30, and other equipment and members that configure the polishing apparatus. May invite.

In the present embodiment, when a part of the wafer W jumps to the outside of the top ring 20, the wafer sensor 60 immediately detects it as described above and stops the rotation of the polishing table 11 and the top ring 20. . Further, the top ring 20 may be lifted by an elevating mechanism such as an air cylinder (not shown) provided in the top ring arm 21. As a result, the polishing process is stopped before the protruding wafer W collides with the top ring 20 after the polishing table 11 makes one rotation, and the wafer W itself is prevented from being damaged or the constituent devices or members are damaged. be able to.

In this way, the top ring 20 of the wafer W is
The wafer sensor 60 detects the protrusion of the wafer W, and the rotation of the polishing table 11 and the rotation of the top ring 20 are immediately stopped by this detection signal, thereby damaging the wafer W itself due to the protrusion of the wafer, the guide ring of the top ring 20, and the polishing table. There is no possibility of damaging the components such as the polishing cloth 10 on the back surface 11, the backing material and the dressing member and the members.

In the above-described embodiment, an example in which the light projecting portion 62 is arranged on the upper side and the light receiving portion 63 is arranged on the lower side in the casing 65 of the wafer sensor 60 has been described, but the light projecting portion 62 is arranged on the lower side. The part 63 can also be arranged on the upper side.

Further, in the above-described embodiment, an example in which the polishing surface is constituted by a polishing cloth has been described, but the present invention is not limited to this. For example, fine abrasive grains (comprising CeO ₂ etc.) made of resin or the like may be used. The upper surface of the fixed abrasive plate hardened with a binder may be used as a polishing surface. Further, a belt-shaped polishing pad, a polishing tape, or the like can be used as the polishing surface.

Although one embodiment of the present invention has been described so far, it goes without saying that the present invention is not limited to the above-mentioned embodiment and may be implemented in various different forms within the scope of the technical idea thereof.

[0041]

As described above, according to the object detector of the present invention, the object axis is tilted, and the object is detected based on the change in the quantity of irregularly reflected light caused by the light projection. The presence of can be detected. Further, according to the polishing apparatus equipped with such a detector, it is possible to effectively detect that the wafer has jumped out of the top ring, and for a wafer using a material that could not be conventionally detected. Even then, it is possible to detect the pop-out. Also, since the projection axis is tilted, it is not always necessary to place the detector near the top ring, so the degree of freedom in installing the detector is increased, and at the same time, the slurry used for polishing may affect the detector. Without this, accurate detection is possible.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an overall configuration of a polishing device according to an embodiment of the present invention.

FIG. 2 is a partial plan view of FIG.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a schematic diagram showing a wafer sensor according to an embodiment of the present invention.

5 is a schematic view showing a state in which light is projected on a polishing cloth using the wafer sensor shown in FIG.

FIG. 6 is a schematic view showing a state in which light is projected onto a wafer using the wafer sensor shown in FIG.

7 is a graph showing a result of verifying a detection limit of a polishing cloth or a wafer in the wafer sensor shown in FIG.

FIG. 8 is a schematic view showing a state where the semiconductor wafer is not normally mounted on the top ring.

[Explanation of symbols]

10 polishing cloth 11 polishing table 12 covers 13 table axis 14 Polishing liquid supply nozzle 15 nozzle arm 20 top ring 20a guide ring 21 Top Ring Arm 22 Top ring shaft 30 dresser 31 Dresser Arm 32 Dresser standby position 40 casing 50 robot arm 51 pusher 52 Wafer delivery position 60 wafer sensor 61 Sensor support arm 62 Projector 63 Light receiving part 64 detector 65 casing

Claims (3)

[Claims] 1. A light projecting portion having a light projecting axis inclined with respect to an object, a light receiving section having a light receiving axis located on the opposite side of a specular reflection optical axis corresponding to the light projecting axis, and the light receiving section. A detector for a target object, comprising: a detection unit that detects the presence of the target object based on a change in the amount of light received by the unit. 2. A polishing table having a polishing surface, a top ring for holding a polishing object and pressing it against the polishing surface, and the detector according to claim 1, wherein the polishing object is provided by the detector. A polishing device for detecting a protrusion from the top ring. 3. A method of detecting a target object, which comprises projecting light from a position inclined with respect to the target object and detecting the presence of the target object by a change in the amount of diffusely reflected light generated by the projection.