JP2000326217A - Polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing device capable of smoothly transferring a polished workpiece to a next stage of work. SOLUTION: This device is provided with a polishing table 10 having a polishing surface 16a; a substrate holding member 34 for holding a substrate W; a pressing mechanism 12 for pressing a polished surface of the substrate W against the polishing surface 16a; and a circularly moving mechanism for circularly moving the substrate W and the polishing surface in relative relation. The circularly moving mechanism is provided with an overhang controlling means for controlling respective stopping positions of the substrate holding member 34 and the polishing table 10 so that the polished surface of the substrate W can be in a certain overhang state with respect to the polishing surface 16a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus for polishing a polishing object such as a semiconductor wafer in a flat and mirror-like manner.

[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 having a line width of 0.5 μm or less, the allowable depth of focus becomes shallow, so that the image plane of the stepper needs to be flat. Therefore, it is necessary to planarize the surface of the semiconductor wafer, and chemical mechanical polishing (CMP) is employed as one of the planarization methods.

FIG. 6 is a diagram showing a main part of an example of a conventional polishing apparatus for performing CMP. This includes a rotating turntable (polishing table) 102 having a polishing cloth 100 adhered to the upper surface, a top ring 104 for holding a substrate W such as a semiconductor wafer which is a polishing target so as to be rotatable and pressable, and a polishing cloth 100. A polishing liquid supply nozzle 106 for supplying the polishing liquid Q is provided. The top ring 104 is connected to a drive shaft 108, and the drive shaft 108 is supported by a top ring head (not shown) via an air cylinder so as to be vertically movable.

The top ring 104 has an elastic mat 110 made of polyurethane or the like on its lower surface, and holds the substrate W via the elastic mat 110.
A cylindrical guide ring 112 is attached to the outer peripheral edge of the top ring 104 so that its lower end surface projects from the holding surface of the top ring 104, and a recess for holding a substrate W to be polished inside the cylindrical guide ring 112. To form a substrate W
Are not detached from the top ring 104 during polishing.

In the polishing apparatus having such a configuration, the substrate W is held under the elastic mat 110 on the lower surface of the top ring 104, and the substrate W is pressed against the polishing cloth 100 on the turntable 102 by the top ring 104. By rotating the turntable 102 and the top ring 104, the polishing pad 100 and the substrate W are relatively moved to perform polishing. From the abrasive liquid supply nozzle 106, an abrasive liquid Q in which abrasive grains composed of fine particles are suspended in an alkaline solution, for example, is supplied onto the polishing surface of the polishing cloth 100, and a chemical polishing action by alkali and a mechanical polishing by abrasive grains are performed. The substrate W is polished by a combined action with the action.

At the end of polishing, since the polishing liquid Q is contained between the substrate W and the polishing cloth 100, if these are to be separated in a direction perpendicular to the surface, the surface tension acting between the substrate W and the polishing surface , A great deal of force is needed to counteract the problem, and the substrate W may be detached from the top ring 104. Therefore, after the rotation of the polishing table 102 is stopped or during the rotation, the arm holding the top ring 104 is swung so that the top ring 104 is moved so as to crawl on the polishing surface while rotating. Then, after a part of the substrate W held by the top ring 104 is moved in parallel to an overhang position protruding from the polishing surface, the top ring 104 is raised to separate the substrate W from the polishing surface. As a result, the substrate W is separated from the polishing surface, and a decrease in transport accuracy and an unstable operation due to surface tension generated between the substrate W and the polishing surface are prevented.

In the above-described polishing apparatus, polishing is performed by the rotating polishing table 102, and there is no displacement at the center of rotation, and polishing is not performed.
Therefore, in order to perform polishing at an off-center, the size of the polishing table 102 should be at least two times the diameter of the substrate.
It is set to have a diameter twice or more. For this reason, the polishing table occupies a large area, the polishing apparatus itself becomes large, and the equipment cost also increases. This disadvantage becomes more remarkable as the size of the substrate increases.

Therefore, it is conceivable to employ a polishing apparatus in which the polishing table performs a circular translational motion (scrolling motion) along a circular orbit in place of or in combination with the above polishing apparatus. In this case, since the polished surface takes the same motion at any point, the size may be substantially the same as the size of the substrate to be polished if the diameter of the scroll operation is small.

In the conventional method as described above, the polishing pad is easily deformed during polishing because of its elasticity. When the wiring density on the substrate W is low, the insulating layer is polished in a concave shape. Therefore, there is a problem that undulations occur on the substrate surface after processing, or that it takes time to eliminate steps on the substrate surface. For this reason, for example, using a grindstone processed into a plate shape by combining abrasive grains such as silica with a binder, this is stuck on a polishing table, and the top ring 10
There has been proposed a method of performing polishing by pressing and sliding the semiconductor wafer W held by the semiconductor wafer W. As a result, the polishing is performed while the binder collapses or dissolves to generate abrasive grains as the whetstone and the wafer slide.

According to such a polishing method, since the grindstone is harder than the polishing cloth, the problem of undulation on the substrate surface after processing is eliminated. In addition, since a slurry-like abrasive liquid containing a large amount of abrasive grains is not used, there is an advantage that the treatment is unnecessary, the operating cost is reduced, and the environment is easily maintained.

[0011]

In the conventional rotating polishing table, the center of the table itself does not move. Therefore, if the arm holding the top ring is swung by a certain angle, the substrate is fixed with respect to the polishing table. Overhang condition. However, in a polishing table that performs a circular translational motion along a circle as described above, the stop position of the polishing table at the end of polishing is not constant. Therefore, even if the top ring is moved to the overhang position, the contact area between the substrate and the polished surface is not constant, and the distance between the substrate and the polished surface is increased when the top ring is lifted to separate the substrate from the polished surface. In this case, there is a problem that the transfer of the substrate becomes impossible, the substrate falls off or cracks, and a scratch is generated due to the inclination of the top ring. The same applies to a polishing apparatus of a type in which the polishing table circulates and moves.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a polishing apparatus capable of smoothly transporting a polishing object after polishing to the next process.

[0013]

According to the present invention, a polishing table having a polishing surface, a substrate holding member for holding a substrate, and a surface to be polished of the substrate are pressed against the polishing surface. A pressing mechanism, and a circulating movement mechanism that circulates and moves the substrate and the polishing surface relatively, wherein the circulating movement mechanism is configured such that the surface to be polished of the substrate is in a certain overhang state with respect to the polishing surface. An overhang control means for controlling a stop position of the substrate holding member and the polishing table is provided.

Thus, when the substrate after polishing is separated from the polished surface, the surface tension generated between the substrate and the polished surface is always kept constant, the substrate is smoothly transported, and an extra load is applied to the substrate. It can be done without. Here, the overhang state refers to a state in which the polished surface of the substrate is displaced from the polished surface of the polishing table, that is, a state in which the substrate protrudes. The constant overhang state means that such an overhang amount (overhang amount) is constant. As for the amount of overhang, the larger the contact area, the smaller the contact area and the lower the surface tension, so the separation becomes easier, but the posture of the substrate holding member becomes unstable when the center of the substrate holding member approaches the edge of the polished surface. Therefore, about 50% is preferable, and the center of the substrate holding member should not exceed the edge of the polished surface at the maximum.

According to a second aspect of the present invention, the overhang control means is configured to stop the polishing table at a predetermined fixed position. It is. If the polishing table is stopped at a predetermined fixed position, the substrate holding member always moves to the same position, whereby a certain overhang state can be achieved.

According to a third aspect of the present invention, the overhang control means detects a stop position of the polishing table and controls the position of the substrate holding member in accordance with the stop position. The polishing apparatus according to claim 1, wherein

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 5 show a polishing apparatus according to one embodiment of the present invention. As shown in FIG. Placed on the other end,
A load / unload unit 4 for mounting the substrate storage cassettes 4a and 4b is provided. Between the polishing section 2 and the load / unload unit 4, a transport section 6 having two transport robots 6a and 6b, and washing machines 8a and 8b and a reversing machine 8c are arranged.

The polishing section 2 is provided with a polishing table 10 and a top ring device 12 and a dressing device 14 at positions sandwiching the polishing table 10.
A pusher 15 that mediates transfer of the substrate W to and from the transfer robot 6b is provided on the side of 0. A disc-shaped grindstone 16 as a polishing member is fixed to the upper surface of the polishing table 10, and a flat polished surface 16 a is formed on the surface of the grindstone 16. Below the polishing table 10, a drive motor 18 constituted by, for example, a controllable servomotor is arranged. In particular, in the case of finish polishing, a polishing cloth may be used instead of a grindstone as a conventional polishing member.

The drive pin 20a is provided with an axis O ₂ vertically to the upper end of the driving shaft 20 to the direction extending eccentric by eccentricity "e" to the axis O ₁ of the drive shaft 20 position of the drive motor 18 ing. On the other hand, a concave portion 10a is formed in the center of the back surface of the polishing table 10, and the bearing 2 is provided inside the concave portion 10a.
The drive pin 20a is accommodated through the drive pin 20. Although not shown, the support mechanism of the polishing table 10 is provided with a mechanism for preventing the polishing table 10 from rotating around the drive pins 20a.

As a result, the rotation of the drive shaft 20 accompanying the drive of the drive motor 18 causes the drive pin 20a to move the eccentric amount.
Draw a circular orbit with a radius of e ", and the polishing table 10
Without rotating, a circular translational motion (scrolling motion), which is a revolving motion with the eccentricity "e" as a radius, is performed.

An encoder 24 is mounted on the drive motor 18, and the polishing table 1 is provided below the polishing table 10.
An origin sensor 26 for detecting the zero origin position is arranged. Then, signals from the encoder 24 and the origin sensor 26 are input to the control device 28, and a control signal is output from the control device 28 to the drive motor 18, whereby the stop position of the polishing table 10 is controlled. I have.

The top ring device 12 is provided with a support shaft 32 inserted through the inside of the cover 30.
While holding the substrate W at the lower end of the substrate W, the substrate W is
A substantially disk-shaped top ring 34 that is pressed with a predetermined force toward “a” is attached. A motor, a swing arm, and a vertically movable cylinder (not shown) are disposed inside the cover 30, and a base end of the swing arm is connected to an upper end of a rotatable column 36 extending vertically.
A support shaft 32 is supported at the free end of the swing arm so as to be vertically movable and rotatable.

As a result, the swing arm swings in the horizontal direction together with the cover 30 by the rotation of the support column 36, and the support shaft 32 is driven by the driving of the motor and the operation of the vertical movement cylinder.
And the top ring 34 are integrally rotated and moved up and down.

Next, the operation of the polishing apparatus having such a configuration will be described with reference to FIGS. First, the substrate W placed on the pusher 15 is sucked and held by the top ring 34, and the top ring 3 is moved via the swing arm.
4 is moved to a position where the axis of the support shaft 32 above the polishing table 10 coincides with the axis O ₁ of the drive shaft 20. The polishing table 10 makes a circular translational movement that draws a circular locus by driving of the drive motor 18. In this state, FIG.
As shown in FIG. 5, the substrate W is lowered while being rotated, and is pressed toward the polishing surface 16a of the polishing table 10, so that the substrate W
Polish.

After the polishing is completed, the polishing table 10 is stopped at a fixed position, that is, the position where the axis O ₂ of the drive pin 20 a comes in a predetermined direction with respect to the axis O ₁ of the drive shaft 20. Drive motor 18 so as to stop at
Control. This is performed, for example, as follows. That is, the position when the origin of the polishing table 10 passes through the origin sensor 26 is stored in the control device 28 in advance. Then, the number of pulses of the encoder 24 from the origin to the stop position is set in advance, and the drive motor 18 is stopped when the number of pulses output from the encoder 24 after passing through the origin reaches a set value.

Next, as shown in FIG. 5B, the swing arm is swung by a predetermined angle while rotating the top ring 34, and the top ring 34 The surface to be polished is translated while sliding on the polishing surface 16a, and is stopped at a predetermined overhang position shown in FIG. 5C. The method of stopping the swing arm at a predetermined position is basically the same as that described above.

The amount of overhang at this overhang position (the ratio of the area of the surface to be polished of the substrate W protruding outward from the surface of the polished surface 16a) is a diagram when FIG. 5C is viewed from below. As shown in FIG. 5 (d), about 20 to 5
It is about 0%, and the position of the center of the substrate W is on the polished surface 16a. As described above, in this embodiment, the stop position of the polishing table 10 is always constant,
Since the swing distance of the top ring 34 is constant, the overhang position is always constant. Therefore, the sensor can be provided to detect the stop position of the polishing table each time, and the overhang amount can be made constant without going through a complicated process of determining the swing amount of the top ring based on the detected position.

Then, as shown in FIG. 5 (e), the substrate W is lifted while rotating the top ring 34 to separate the substrate W from the polishing surface 16a. At this time, since the amount of overhang is constant, the surface tension generated between the substrate W and the polishing surface 16a is constant, so that a stable detaching operation can be always performed. Thereafter, the rotation of the top ring 34 is stopped, the swing arm is swung, the top ring 34 is moved above the pusher 15, and the substrate W after polishing is conveyed onto the pusher 15.

In this embodiment, an example is shown in which the separation position between the substrate and the polishing table is fixed and the overhang amount is fixed, but the polishing table stop position at the end of polishing is set. Without detecting the stop position, the top ring is moved to the overhang position so that the contact area between the substrate and the polishing surface is constant according to the stop position of the polishing table. May be controlled.

In the above description, the position control between the substrate held by the top ring and the polishing table has been described. However, similar control is performed on the dresser (dressing tool) and the polishing table in the dressing apparatus. Is also good. Thereby, it is possible to prevent an accident such as the dresser coming off smoothly from the polishing table and the grindstone or the polishing cloth coming off the polishing table.

[0031]

As described above, according to the present invention,
By making the amount of overhang on the polished surface of the substrate constant when the substrate is removed from the polishing table, the operation of transporting the object to be polished after polishing can be performed smoothly, and unnecessary force is applied to the substrate and the apparatus. Or the occurrence of an accident due to the above.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing a main part of the polishing apparatus according to the embodiment of the present invention.

FIG. 3 is a plan view of the polishing table of FIG. 2;

FIG. 4 is a sectional view of the polishing apparatus of FIG. 2;

FIG. 5 is a perspective view for explaining the operation of the polishing apparatus of FIG. 2;

FIG. 6 is a sectional view of a conventional polishing table.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Polishing table 12 Top ring device 15 Pusher 16 Grinding stone 16a Polishing surface 18 Drive motor 20 Drive shaft 20a Drive pin 22 Bearing 24 Encoder 26 Origin sensor 28 Control device 34 Top ring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuji Togawa 11-1, Haneda Asahimachi, Ota-ku, Tokyo Inside the Ebara Corporation (72) Inventor Nobuyuki Takada 11-1, Haneda Asahi-cho, Ota-ku, Tokyo EBARA F term (reference) 3C058 AA06 AA11 AA16 AB06 BA07 BB02 BB08 BB09 BC02 CB03 CB04 DA17

Claims (3)

[Claims] A polishing table having a polishing surface; a substrate holding member for holding a substrate; a pressing mechanism for pressing a polished surface of the substrate against the polishing surface; A circulating movement mechanism for circulating the substrate, wherein the circulating movement mechanism stops the substrate holding member and the polishing table so that the polished surface of the substrate is in a constant overhang state with respect to the polished surface. A polishing apparatus, comprising overhang control means for controlling a position. 2. The polishing apparatus according to claim 1, wherein the overhang control means is configured to stop the polishing table at a predetermined fixed position. 3. The apparatus according to claim 1, wherein said overhang control means detects a stop position of said polishing table, and controls a position of said substrate holding member in accordance with said stop position. Item 2. A polishing apparatus according to Item 1.