JP7034785B2 - Polishing equipment - Google Patents

Description

The present invention relates to a polishing device for polishing a wafer.

In the field of semiconductor manufacturing, a polishing device for polishing a wafer in order to remove a clutch remaining on a semiconductor wafer (hereinafter referred to as "wafer") such as a silicon wafer is known.

The polishing device described in Patent Document 1 is a polishing device in which a polishing pad is seated on a wafer during polishing processing, and the upper surface of the wafer is polished by pressing the polishing pad against the wafer while rotating the wafer and the polishing pad. In such a polishing device, a thickness measuring means for measuring the thickness of the wafer is arranged on the rotation axis of the polishing head outside the polishing device, and the slurry is supplied to the upper surface of the wafer through the cavity in the center of the polishing head. The thickness measuring means measures the thickness of the wafer through the cavity in a non-contact manner.

Japanese Unexamined Patent Publication No. 2015-134383

However, in the polishing apparatus described in Patent Document 1, when the wafer height changes for each wafer, the distance from the thickness measuring means to the upper surface of the wafer is suitable for measuring the distance from the thickness measuring means when the optical thickness measuring means is used. It was necessary to manually perform the complicated work of adjusting the polishing pad to match the appropriate distance and seating the polishing pad on the wafer.

Therefore, a technical problem to be solved arises in order to smoothly set the polishing device, and an object of the present invention is to solve this problem.

In order to achieve the above object, the polishing apparatus according to the present invention is a polishing apparatus for a wafer, and includes a polishing pad for polishing the upper surface of the wafer and an accommodating portion opening to the polishing surface of the polishing pad. The polishing head is provided, and an optical thickness measuring means for measuring the thickness of the wafer through the opening in a non-contact manner and the polishing head are mounted. A feed mechanism that is integrally connected to the thickness measuring means and raises and lowers the polishing head and the thickness measuring means, and a control device that controls the feed amount of the feed mechanism are provided. In the feed mechanism, the polishing head is the wafer. The polishing head is separated when the polishing head is lowered until it is seated on the surface, and the sensor head is lowered to a measurement position separated from the upper surface of the wafer by a predetermined distance.

According to this configuration, when the polishing head is seated on the wafer while the feed mechanism is descending the sensor head to the measurement position, the polishing head is separated from the feed mechanism, so that the work of seating the polishing head on the wafer is omitted and the sensor is used. Since the head is smoothly lowered to a measurement position suitable for measurement, the setting of the polishing device can be smoothly performed.

Further, in the polishing device according to the present invention, the control device corrects the reference feed amount for lowering the sensor head from the initial position to the measured position according to the height of the wafer before polishing measured in advance. Is preferable.

According to this configuration, since the measurement position of the sensor head can be adjusted according to the height of the wafer, a predetermined distance from the sensor head to the upper surface of the wafer can be maintained regardless of the height of the wafer. The thickness of the wafer can be measured with high accuracy.

In the present invention, when the polishing head is seated on the wafer while the feeding mechanism is lowering the sensor head to the measurement position, the polishing head is separated from the feeding mechanism, so that the work of seating the polishing head on the wafer is omitted and the sensor head is mounted. Since the polishing device is smoothly lowered to a measurement position suitable for measurement, the polishing device can be set smoothly.

The vertical sectional view schematically showing the polishing apparatus which concerns on one Embodiment of this invention. The vertical sectional view schematically showing the main part of a polishing head. The schematic diagram which shows the positional relationship of a polishing pad and a wafer. The schematic diagram which shows the setting procedure of the polishing apparatus before processing.

An embodiment of the present invention will be described with reference to the drawings. In the following, when the number, numerical value, quantity, range, etc. of the components are referred to, the number is limited to the specific number unless it is explicitly stated or the principle is clearly limited to the specific number. It is not a thing, and it may be more than or less than a specific number.

In addition, when referring to the shape and positional relationship of components, etc., unless otherwise specified or when it is considered that it is not clearly the case in principle, those that are substantially similar to or similar to the shape, etc. are used. include.

In addition, the drawings may be exaggerated by enlarging the characteristic parts in order to make the features easy to understand, and the dimensional ratios and the like of the components are not always the same as the actual ones. Further, in the cross-sectional view, hatching of some components may be omitted in order to make the cross-sectional structure of the components easy to understand.

FIG. 1 is a vertical sectional view schematically showing a polishing apparatus 1 according to an embodiment of the present invention. FIG. 2 is a vertical sectional view schematically showing a main part of the polishing head 10. The polishing device 1 polishes the upper surface of the wafer W adsorbed and held by the wafer chuck 2 to remove the damaged layer including microcracks generated during the grinding process.

The wafer chuck 2 is rotatably provided around the rotation axis a1 passing through the center of the wafer chuck 2. An adsorbent (not shown) made of a porous material such as alumina is embedded in the upper surface of the wafer chuck 2. The wafer chuck 2 includes a pipeline (not shown) that extends through the interior to the surface. The pipeline is connected to a vacuum source, compressed air source or water supply source via a rotary joint (not shown). When the vacuum source is activated, the wafer W placed on the wafer chuck 2 is attracted and held by the wafer chuck 2. Further, when the compressed air source or the water supply source is activated, the adsorption between the wafer W and the wafer chuck 2 is released.

A plurality of wafer chucks 2 are arranged on an index table (not shown). The wafer chucks 2 are arranged on a concentric circumference centered on the rotation axis of the index table at predetermined intervals. As a result, when the polishing device 1 and the grinding device for grinding the upper surface of the wafer W are used in combination, the index table is rotated to transport the ground wafer W to the polishing device 1, thereby continuously transferring the wafer W. Can be processed.

The wafer W is adsorbed and held by the wafer chuck 2 in a state of being mounted on a support substrate such as a bag grind tape, a glass substrate, or a silicon substrate. In particular, as the wafer W becomes thinner and has a larger diameter, a support substrate is often used.

The polishing device 1 includes a polishing head 10 provided above the wafer chuck 2. A polishing pad 30 is horizontally attached to the lower end of the spindle 20 of the polishing head 10.

The spindle 20 is a bearing interposed between the motor 21, the hollow cylindrical rotating portion 22 connected to the motor 21, the fixing portion 23 accommodating the rotating portion 22, and the rotating portion 22 and the fixing portion 23. 24 and. The rotating portion 22 is rotated about the rotation shaft a2 by the motor 21.

The polishing pad 30 is integrated with the rotating portion 22, and rotates with the rotation of the rotating portion 22. In the polishing pad 30, the polishing surface 31 of the polishing pad 30 is pressed downward by a pressure cylinder (not shown). In this way, the upper surface of the wafer W is polished by the polishing pad 30 being pressed downward by the pressure cylinder while rotating. The amount of polishing by the polishing pad 30 is set to, for example, 2 μm from the upper surface of the wafer W.

The polishing pad 30 is formed with a supply hole 32 that opens in the polishing surface 31. The supply holes 32 are provided in three rows from the inside to the outside in the radial direction of the polishing head 10. Eight supply holes 32 are provided in each row. The supply holes 32 in each row are arranged on concentric circles centered on the rotation axis a2 of the polishing head 10 at a predetermined distance from each other.

The polishing device 1 includes a feeding mechanism 40. The feed mechanism 40 is a known ball screw slider mechanism including a motor 41, a ball screw 42, and a slider 43. The ball screw 42 is rotated by the motor 41, and the slider 43 moves up and down in the vertical direction according to the rotation direction of the ball screw 42. The slider 43 supports the supported portion 25 projecting from the outer periphery of the fixed portion 23 so as to be placed on the supported portion 25.

The cavity 26 in the rotating portion 22 is provided with a spiral pipe 50 through which the slurry flows. The upper end of the pipe 50 is connected to the external slurry supply source 52 via the rotary joint 51. The lower end of the pipe 50 is connected to the supply hole 32 as shown by the broken line in FIG. The slurry supplied to the upper surface of the wafer W is diffused over the entire surface of the wafer W by the centrifugal force accompanying the rotation of the wafer W.

At the center of the polishing head 10, an accommodating portion 12 that opens in the center of the polishing surface 31 is formed. Specifically, the accommodating portion 12 is formed from the lower part of the cavity 26 to the lower end of the polishing pad 30.

A translucent window 14 is attached to the opening 13 of the accommodating portion 12. The translucent window 14 is adhered so as to close the accommodating portion 12. As a result, the slurry supplied to the upper surface of the wafer W is prevented from entering the accommodating portion 12.

The polishing device 1 includes a thickness measuring means 60 for measuring the thickness of the wafer W in a non-contact manner during the polishing process. As the thickness measuring means 60, for example, a spectroscopic interference type film thickness measuring device is preferable. The spectral interferometry type film thickness measuring instrument is resistant to disturbances such as vibration and can measure the thickness of the wafer W with high accuracy. Hereinafter, a case where a spectral interferometry type film thickness measuring device is adopted as the thickness measuring means 60 will be described as an example.

The thickness measuring means 60 includes a sensor head 61 arranged in the accommodating portion 12. The sensor head 61 is connected to the slider 43 via the bracket 62. The sensor head 61 irradiates light toward the wafer W through the opening 13, and receives the reflected light that the light reflected on the upper surface and the lower surface of the wafer W interferes with. The reflected light received by the sensor head 61 is separated by a spectroscope (not shown), and a control device 70 described later calculates an optical path difference between the light reflected on the upper surface of the wafer W and the light reflected on the lower surface of the wafer W. The thickness of the wafer W is calculated based on this optical path difference.

The measurement point on the wafer W on which the sensor head 61 measures the thickness is set so as to substantially coincide with the rotation axis a2 of the polishing head 10 (including within a range that can be regarded as optically matching) when viewed from a plane. That is, the optical path of the light emitted by the sensor head 61 and the optical path of the light reflected from the wafer W are set to the path connecting the sensor head 61 and the measurement point on the wafer W. Needless to say, the measurement point of the sensor head 61 is not limited to the case where it substantially coincides with the rotation axis a2 of the polishing head 10 when viewed from a plane.

It is preferable to provide a dry air supply means 3 for supplying dry air between the translucent window 14 and the sensor head 61. As a result, the humidity inside the accommodating portion 12 is maintained constant by the dry air, so that the thickness of the wafer W is accurately measured even when the temperature of the slurry is raised by the frictional heat generated during the polishing process. be able to.

Further, it is preferable to provide a moving means 4 for moving the polishing device 1 in the horizontal direction. As a result, the thickness profile of the entire wafer W can be measured by using the polishing device 1 without preparing an independent device for measuring the thickness of the wafer, so that the throughput can be improved.

The operation of the polishing device 1 is controlled by the control device 70. The control device 70 controls each of the components constituting the polishing device 1. The control device 70 is composed of, for example, a CPU, a memory, and the like. The function of the control device 70 may be realized by controlling using software, or may be realized by operating using hardware.

Next, the arrangement relationship between the polishing pad 30 and the wafer W will be described with reference to FIG. FIG. 3 is a schematic view of the polishing pad 30 and the wafer W as viewed from below. The polishing pad 30 is formed to have a diameter larger than that of the wafer W. The diameters of the polishing pad 30 and the wafer W are set to, for example, 450 mm and 300 mm, respectively.

Further, the rotation directions of the polishing pad 30 and the wafer W are the same, and the outer periphery of the polishing pad 30 and the outer periphery of the wafer W overlap at one point. As a result, the velocity vectors in the wafer W plane match. Further, the polishing pad 30 can uniformly polish the entire surface of the wafer W by constantly covering the entire surface of the wafer W during processing.

As shown in FIG. 3, when the polishing pad 30 is arranged so as to cover the wafer W, the slurry is supplied to the upper surface of the wafer W from the outside of the polishing device 1 and the thickness of the wafer W is measured during the polishing process. However, in the polishing apparatus 1, while the slurry is supplied to the upper surface of the wafer W through the supply hole 32, the thickness measuring means 60 housed in the polishing head 10 is connected to the wafer W through the opening 13. The thickness can be measured non-contact.

Next, the setting procedure of the polishing apparatus 1 before processing will be described with reference to FIG. FIG. 4A is a diagram showing a state before the polishing head 10 is seated on the wafer W. FIG. 4B is a diagram showing a state in which the polishing head 10 is seated on the wafer W. FIG. 4C is a diagram showing a state in which the sensor head 61 is lowered.

First, the height of the wafer W before polishing, which is adsorbed and held by the wafer chuck 2, is measured. This is because when the polishing apparatus 1 continuously processes the wafer W, the thickness is not constant between different support substrates, and the height of the wafer W mounted on the support substrate tends to vary. This is because the optical thickness measuring means 70 may not be able to measure due to the deviation from the measuring range due to the variation in the height of the wafer W. A known contact type or non-contact type measuring instrument is used for measuring the height of the wafer W. If the height of the wafer W is known, that value may be used.

Next, the control device 70 corrects the reference feed amount stored in advance based on the height measurement value of the wafer W before polishing. The reference feed amount is the amount of descent from the initial position of the sensor head 61 to the measurement position of the sensor head 61 separated by a predetermined distance (for example, 80 mm) from the upper surface of the wafer W at the reference height. The reference height is the height of the wafer W which is a virtually determined reference. Further, the distance between the sensor head 61 and the upper surface of the wafer W at the measurement position is set within a range suitable for measurement. For example, when the measured height of the wafer W before polishing is larger than the reference height of the wafer W by a deviation Δt, the control device 70 calculates a correction feed amount obtained by subtracting the deviation Δt from the reference feed amount.

Next, as shown in FIG. 4A, when the control device 70 starts rotating the motor 41 according to the corrected feed amount, the ball screw 42 rotates and the slider 43 starts to descend. As shown in FIG. 4B, when the slider 43 is lowered until the polishing head 10 is seated on the wafer W, the supported portion 25 is separated from the slider 43. On the other hand, the sensor head 61 is integrated with the slider 43 via the bracket 62, and further descends together with the slider 43.

Then, as shown in FIG. 4C, when the control device 70 rotates the motor 41 by the rotation speed corresponding to the corrected feed amount, the sensor head 61 is positioned at the measured value. Therefore, the sensor head 61 can measure the thickness of the wafer W at the measurement position during the polishing process.

In this way, in the polishing apparatus 1 according to the present embodiment, when the polishing pad 30 is seated on the wafer W while the feed mechanism 40 is lowering the sensor head 61 to the measurement position, the polishing head 10 is separated from the slider 43. Since the work of seating the polishing head 10 on the wafer W is omitted and the sensor head 61 is smoothly lowered to a measurement position suitable for measurement, the polishing device 1 can be set smoothly.

Further, the present invention can be modified in various ways other than the above as long as it does not deviate from the spirit of the present invention, and it is natural that the present invention extends to the modified ones.

1 ・ ・ ・ Polishing device 2 ・ ・ ・ Wafer chuck 3 ・ ・ ・ Dry air supply means 4 ・ ・ ・ Transportation means 10 ・ ・ ・ Polishing head 12 ・ ・ ・ Accommodating part 13 ・ ・ ・ Opening 14 ・ ・ ・ Translucent window 20 ・ ・ ・ Spindle 21 ・ ・ ・ Motor 22 ・ ・ ・ Rotating part 23 ・ ・ ・ Fixed part 24 ・ ・ ・ Bearing 25 ・ ・ ・ Supported part 26 ・ ・ ・ Cavity 30 ・ ・ ・ Polishing pad 31 ・ ・ ・ Polishing Surface 32 ・ ・ ・ Supply hole 40 ・ ・ ・ Feed mechanism 41 ・ ・ ・ Motor 42 ・ ・ ・ Ball screw 43 ・ ・ ・ Slider 50 ・ ・ ・ Piping 51 ・ ・ ・ Rotary joint 52 ・ ・ ・ Slurry supply source 60 ・ ・ ・Thickness measuring means 61 ・ ・ ・ Sensor head 62 ・ ・ ・ Bracket 70 ・ ・ ・ Control device W ・ ・ ・ Wafer a1 ・ ・ ・ Rotating shaft a2 (of wafer chuck) ・ ・ ・ Rotating shaft (of polishing head)

Claims (2)

Wafer polishing equipment
A polishing head provided with a polishing pad for polishing the upper surface of the wafer and an accommodating portion opened in the polishing surface of the polishing pad.
An optical thickness measuring means provided with a sensor head provided in the accommodating portion and measuring the thickness of the wafer through the opening in a non-contact manner.
A feed mechanism that mounts the polishing head, is integrally connected to the thickness measuring means, and raises and lowers the polishing head and the thickness measuring means.
A control device that controls the feed amount of the feed mechanism, and
Equipped with
The feeding mechanism is a polishing apparatus characterized in that when the polishing head is lowered until it is seated on the wafer, the polishing head is separated and the sensor head is lowered to a measurement position separated from the upper surface of the wafer by a predetermined distance. The control device according to claim 1, wherein the control device corrects a reference feed amount for lowering the sensor head from the initial position to the measurement position according to the height of the wafer before polishing measured in advance. Polishing equipment.

Images