KR20150005672A - Methods and apparatus for active substrate precession during chemical mechanical polishing - Google Patents

Abstract

In some aspects, a chemical mechanical polishing (CMP) apparatus is provided that includes a polishing head, wherein the polishing head comprises: (a) a rotatable spindle; (b) a rotatable spindle connected to the rotatable spindle, And (c) a retaining ring rotatably connected to the spindle, the retaining ring surrounding the substrate being pushed towards the polishing pad during polishing to limit lateral movement of the substrate relative to the polishing head. The CMP apparatus also includes a drive mechanism coupled to the retaining ring and adapted to drive the retaining ring at a different rotational speed than the spindle during polishing. Numerous other aspects are provided.

Description

≪ Desc / Clms Page number 1 > METHODS AND APPARATUS FOR ACTIVE SUBSTRATE PRECISION DURING CHEMICAL MECHANICAL POLISHING BACKGROUND OF THE INVENTION [0001]

<Related application>

This application claims priority from U.S. Patent Application No. 13 / 459,075 (Attorney Docket No. 17268), filed April 27, 2012, entitled " METHODS AND APPARATUS FOR ACTIVE SUBSTRATE PRECISION DURING CHEMICAL MECHANICAL POLISHING & , The entire contents of which are hereby incorporated by reference for all purposes.

<Technical Field>

The present invention relates to semiconductor device processing, and more particularly to active substrate precession during chemical mechanical polishing.

During the fabrication of semiconductor devices, multiple layers of material are deposited, patterned, and etched to form electronic circuitry and / or electrical connections on the substrate. In many cases, the top surface of the substrate may be planarized between processing steps. Such planarization is typically performed using an etch-back step or chemical mechanical polishing (CMP).

During CMP, the substrate is placed face down on the polishing pad and pressed against the polishing pad through the polishing head in the presence of slurry and rotated against the polishing pad. The slurry may contain abrasive particles, and / or chemicals that help to remove material from the substrate. The polishing continues until sufficient material is removed to form a flat surface on the substrate.

In order to ensure a uniform layer thickness for the devices formed on the substrate, it is important to maintain uniformity across the substrate during CMP. However, it is difficult to maintain thickness uniformity over the entire surface of the substrate. Especially for larger diameter substrates. Therefore, there is a need for a method and apparatus for improving uniformity during chemical mechanical polishing, especially for large substrate sizes.

In some aspects, a chemical mechanical polishing (CMP) apparatus is provided that includes a polishing head, the polishing head comprising: (a) a rotatable spindle; (b) a membrane coupled to the rotatable spindle and adapted to press the substrate against the polishing pad during polishing of the substrate; And (c) a retaining ring rotatably connected to the spindle and configured to surround the substrate being pressed toward the polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head. The CMP apparatus also includes a drive mechanism coupled to the retaining ring and adapted to drive the retaining ring at a different rate of rotation than the spindle during polishing.

In some aspects, there is provided a chemical mechanical polishing apparatus comprising a polishing head, the polishing head comprising: (a) a rotatable spindle; (b) a membrane coupled to the rotatable spindle and adapted to press the substrate against the polishing pad during polishing of the substrate; (c) a retaining ring connected to the spindle and adapted to limit the lateral movement of the substrate relative to the polishing head, surrounding the substrate being pressed towards the polishing pad during polishing; And (d) has at least one rotation mechanism coupled to the retaining ring, adapted to contact the substrate during polishing, and adapted to allow the substrate to rotate at a different speed than the spindle during polishing.

In some aspects, there is provided a method of polishing a substrate, the method comprising pressing a substrate toward a polishing pad using a polishing head, the polishing head comprising: (a) a rotatable spindle; (b) a membrane coupled to the rotatable spindle and adapted to press the substrate against the polishing pad during polishing of the substrate; And (c) a retaining ring rotatably connected to the spindle and configured to surround the substrate being pressed toward the polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head. The method includes rotating the spindle and the membrane of the polishing head at a first rotational speed during polishing; And rotating the retaining ring of the polishing head at a second rotational speed during polishing, to cause the substrate to rotate relative to the membrane of the polishing head.

In some aspects, a method of polishing a substrate is provided, the method comprising pressing a substrate against a polishing pad using a polishing head, the polishing head comprising: (a) a rotatable spindle; (b) a membrane coupled to the rotatable spindle and adapted to press the substrate against the polishing pad during polishing of the substrate; (c) a retaining ring connected to the spindle and adapted to limit the lateral movement of the substrate relative to the polishing head, surrounding the substrate being pressed towards the polishing pad during polishing; And (d) has at least one rotation mechanism coupled to the retaining ring, adapted to contact the substrate during polishing, and adapted to allow the substrate to rotate at a different speed than the spindle during polishing. The method includes rotating the spindle and the membrane of the polishing head at a first rotational speed during polishing; And rotating the at least one rotating mechanism connected to the retaining ring of the polishing head at a second rotational speed during polishing, to cause the substrate to rotate relative to the membrane of the polishing head.

Numerous other aspects are provided. Other features and aspects of the present invention will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings.

1 is a schematic diagram illustrating a side view of an exemplary chemical mechanical planarization system for polishing a substrate in accordance with embodiments.
2A-2B are top schematic views of a substrate and a retaining ring during polishing according to embodiments of the present invention.
Figure 3 is a schematic side view of a first embodiment of an exemplary polishing system provided in accordance with the present invention.
4A is a schematic side view of a second embodiment of an exemplary polishing system provided in accordance with the present invention.
Figures 4b-4c are schematic top views of exemplary embodiments of the polishing system of Figure 4a according to the present invention.

The present invention provides a method and system for uniformly performing chemical mechanical polishing of large substrates (e.g., semiconductor wafers, solar cells or glass substrates used in a liquid crystal display (LCD), or any other similar bottom and / The present invention provides a method and an apparatus for improving performance.

As mentioned, during CMP, the substrate is turned upside down on the polishing pad, pressed against the polishing pad through the polishing head, and rotated about the polishing pad. A slurry containing abrasive particles and / or chemicals may be supplied to the polishing pad to assist removal of material from the substrate as the substrate is pressed against the polishing pad and rotated relative to the polishing pad. In this way, the top surface of the substrate can be planarized.

Figure 1 illustrates a side view of an exemplary chemical mechanical planarization (CMP) system 100 for polishing a substrate in accordance with the present invention. The system 100 includes a load cup assembly 102 for receiving a substrate to be polished (not shown in FIG. 1) and for holding the substrate in place such that the polishing head 104 is lifted. The polishing head 104 is supported by an arm 106 that is operable to move the head 104 between the polishing pad 108 on the rotating platen 110 and the load cup assembly 102. In operation, the polishing head 104 lifts the substrate from the load cup assembly 102 and transports it to the polishing pad 108. When the polishing pad 108 is rotated on the platen 110, the head 104 pushes the substrate toward the polishing pad 108 while rotating the substrate. For example, the expandable membrane 111 in the polishing head 104 may contact the substrate and push the substrate toward the polishing pad 108. [ It should be noted that, in the illustrated embodiment, the diameter of the polishing pad 108 is greater than twice the diameter of the substrate. Other platens, polishing pads, and / or substrate sizes may be used.

2A-2B, in order to keep the substrate 202 in place under the polishing head 104, the polishing head 104 surrounds the substrate 202 during polishing and moves its lateral movement (Not shown). The substrate 202 has a diameter D ₁ that is slightly less than the diameter D ₂ of the retaining ring 204 (which forms a gap 206 between the substrate 202 and the retaining ring 204, 2b is exaggerated). In some embodiments, the gap 206 may be about 0.01 inches, but other gap sizes may be used.

The rotation of the polishing pad 108 during polishing creates a force to push the substrate 202 toward the retaining ring 204 as shown in Figure 2b (Not aligned with the center of rotation of retaining ring 204 and retaining ring 204). As mentioned, the polishing head 104 is rotated during polishing, which causes the retaining ring 204 to rotate similarly. This rotation of the retaining ring 204 causes the substrate 202 to rotate (pre-session) in a manner similar to a gear wheel due to misalignment of the rotational centers of the substrate 202 and the retaining ring 204 . (The membrane 111 of the polishing head 104 used to press the substrate 202 toward the polishing pad 108 typically has a low coefficient of friction so that the substrate 202 is exposed to the surface of the polishing head 104 during polishing It is possible to rotate about the membrane.)

Due to the alignment and / or tolerance within the polishing head 104, the polishing head 104 has a non-concentric pressure profile (not shown) when pressing the substrate 202 toward the polishing pad 108 Can be generated. Such a non-concentric pressure profile may create a non-concentric and / or asymmetric polishing profile on the substrate 202 and is therefore undesirable. However, the rotation (pre-session) of the substrate 202 relative to the polishing head 104 during polishing as described above can alleviate the effect of the non-concentric pressure profile produced by the polishing head 104. [ For example, for a 300 mm substrate, a discrepancy between the diameter of the retaining ring 204 and the substrate 202 typically allows the substrate 202 to pre-session about 180 degrees with respect to the polishing head 104 during polishing Is sufficiently large. This is generally sufficient to reduce and / or mask any asymmetric polishing profile that would have resulted from the non-concentric pressure profile of the polishing head if it were not present. However, any asymmetric polishing profile is undesirable. Also, for larger substrate sizes, such as 450 mm substrates, the asymmetric polishing profile can be more pronounced. For example, the amount of pre-session of the substrate relative to the retaining ring 204 is proportional to the gap between the substrate and the retaining ring divided by the diameter of the substrate.

(D ₂ -D ₁ ) / D ₁ = (gap 206) / D ₁

Thus, if the gap 206 remains relatively constant as the substrate size increases, the amount of pre-session of the substrate 202 during polishing is reduced. This reduced pre-session may be insufficient to mask the asymmetric polishing profile resulting from the non-concentric polishing head pressure profile.

According to embodiments of the present invention, a polishing head / retaining ring configuration is used that allows active control over the amount of substrate pre-session during polishing. Such "active precession" allows the substrate to pre-session sufficiently to reduce and / or minimize the asymmetric polishing profile resulting from the non-concentric polishing head pressure profile. This is advantageous for substrates of any size (e.g., 200 mm, 300 mm, 450 mm, or other sizes of semiconductor wafers, or any other substrate type or size).

Figure 3 is a schematic side view of a first embodiment of an exemplary polishing system 300 provided in accordance with the present invention. 3, the polishing system 300 includes a polishing head 104 connected to a controller 302. The polishing head 300 includes a polishing head 104, The controller 302 may be a computer, a microcontroller, a programmable logic controller, or any other suitable controller.

The polishing head 104 includes a center spindle 304 rotatably connected to the retaining ring 204 via one or more bearing assemblies 306. The membrane 308 is connected to the center spindle 304 and can contact the substrate 202 and push the substrate 202 toward the polishing pad 108. The membrane 308 expands to push the substrate 202 toward the polishing pad 108. For example, the membrane 308 may be a liquid or gas filled bladder. In some embodiments, the portion of the membrane 308 that contacts the substrate 202 may be a low friction material, such as polytetrafluoroethylene (PTFE) or similar materials.

The spindle 304 is connected to the first drive mechanism 310 and the retaining ring 204 is connected to the second drive mechanism 312 such that the spindle 304 and the retaining ring 204 are rotated at different rotational speeds Lt; / RTI &gt; In some embodiments, a single drive mechanism may be used with appropriate gearing and / or belts to allow the spindle 304 and retaining ring 204 to rotate at different speeds. Any suitable drive mechanisms, such as one or more motors, may be utilized. The controller 302 may include computer program code for directing the rotation of the spindle 304 and / or the retaining ring 204 during polishing as described further below.

The bearing assembly 306 may be configured to hold the retaining ring 204 concentrically with the membrane 308 and may include any suitable bearing such as a ball bearing, a roller bearing, a slide bearing, a track bearing, a contactless bearing, Assemblies. The components of the bearing assembly 306, such as balls and races, may be chemically (e.g., chemically) immersed in the polishing system 300 in order to avoid creating or rapidly deteriorating particles that can contaminate the substrate being polished. And may be formed of a material compatible with the chemical used during mechanical polishing. For example, the bearing assembly 306 may be formed of a suitable polymeric material. Alternatively or additionally, the bearing assembly 306 may be shielded, sealed, or otherwise isolated from the polishing chemistry.

The substrate 202 is positioned on the polishing pad 108 and pressed against the polishing pad 108 by the polishing head 104 (through the expansion of the membrane 308). The retaining ring 204 surrounds the substrate 202 within the polishing head 104 and also contacts the polishing pad 108. It should be noted that a suitable polishing slurry (not shown) may be applied to the polishing pad 108 prior to and / or during polishing of the substrate 202.

The controller 310 causes the drive 310 to rotate the spindle 304 and the membrane 308 as indicated by arrow 314 and the drive 312 rotates the spindle 304 and the membrane 308 as indicated by the arrow 316, Thereby rotating the inner ring 204. The polishing pad 108 is also rotated using the same or another drive mechanism under the control of the controller 302 or other controller (not shown). The rotation of the polishing pad 108 causes the substrate 202 to slide in contact with the retaining ring 204 as indicated by arrow 318. [

In some embodiments, the retaining ring 204 is rotated at a higher speed than the spindle 304. In other embodiments, the retaining ring 204 is rotated at a slower speed than the spindle 304. In either case, the retaining ring 204 and spindle 304 are rotated at different speeds, whereby the substrate 302 is actively pre-sessioned to the membrane 308 (e.g., (202) is completely rotated under the membrane (308) during polishing).

In one or more embodiments, the spindle 304 may be rotated at a rate of about 10 to about 150 RPM (rotations per minute), and the retaining ring 204 may be rotated at a rate of about 5 to about 300 RPM Can be rotated. For example, in some embodiments, the retaining ring 204 may be rotated about one-half the rotational speed of the spindle 304, and in other embodiments, the retaining ring 204 may be rotated about the spindle 304 Of the rotational speed of the rotor. For spindle 304 and / or retaining ring 204, other rotational speeds may be used. The retaining ring 204 may be rotated during the entire time that the spindle 304 is rotated, or a portion thereof, and / or may remain stationary at least once during polishing. Also, in some embodiments, the retaining ring 204 may switch the direction of rotation during polishing.

The polishing of the substrate 202 continues until a desired amount of material is removed from the substrate 202. Because the retaining ring 204 rotates at a different speed than the spindle 204, the substrate 202 is actively pre-sessioned with the membrane 308 and a non-concentric or otherwise asymmetric polishing head pressure profile is applied during polishing (E. G., Produces a more uniform polishing). This is advantageous for substrates of any size (e.g., 200 mm, 300 mm, 450 mm, or other sizes of semiconductor wafers, or any other substrate type or size).

4A is a schematic side view of a second embodiment of an exemplary polishing system 400 provided in accordance with the present invention. The polishing system 400 of FIG. 4A is similar to the polishing system 300 of FIG. 4a, the retaining ring 204 remains stationary during polishing, as indicated by the coupling 402, and the substrate 202 is held against the membrane 308 during polishing One or more rollers 404 are used to rotate. 4B is a schematic top view of a polishing system 400 showing two rollers 404a and 404b. It will be appreciated that a different number of rollers (e.g., three, four, five, etc.) may be used.

The rollers 404a and 404b may be formed of any suitable material such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyethylene terephthalate, or the like. Exemplary diameters for the rollers 404a-b may range from about 0.5 to about 2 inches. In some embodiments, the rollers 404a-b may be spaced about one to five inches apart. For the rollers, other materials, sizes and / or spacings may be used.

The controller 312 causes the drive 310 to rotate the spindle 304 and the membrane 308 as indicated by the arrow 314 and the drive 312 rotates the spindle 304 and membrane 308 as indicated by the arrow 414, 404a and 404b. In some embodiments, a single drive mechanism may be used to rotate the spindle 304, the roller 404a and / or the roller 404b through the use of suitable belts, gears, or the like; A separate drive mechanism may be used as shown in FIG. 4A. The polishing pad 108 is also rotated using the same or another drive mechanism under the control of the controller 302 or other controller (not shown). The rotation of the polishing pad 108 causes the substrate 202 to slide in contact with the rollers 404a and 404b as indicated by arrow 418. [ This area may be referred to as the trailing edge of the retaining ring 204 and the opposite side may be referred to as the leading edge of the retaining ring 204. [

In some embodiments, the rollers 404a and 404b are rotated at a higher speed than the spindle 304. [ In other embodiments, the rollers 404a and 404b are rotated at a slower speed than the spindle 304. In either case, the rollers 404a-b and spindle 304 are rotated at different speeds, whereby the substrate 302 is actively pre-sessioned with respect to the membrane 308 (e.g., The substrate 202 is completely rotated under the membrane 308 during polishing).

In one or more embodiments, the spindle 304 may be rotated at a speed of from about 10 to about 150 RPM, and the rollers 404a-b may be rotated at a speed of from about 30 to about 3600 (depending on the diameter of the rollers) 0.0 &gt; RPM. &Lt; / RTI &gt; For example, in some embodiments, the rollers 404a-b may be rotated so that the substrate 202 rotates at about half the rotational speed of the spindle 304, and in other embodiments, B 404a-b may be rotated so that the substrate 202 rotates about twice the rotational speed of the spindle 304. For spindle 304 and / or rollers 404a-b, different rotational speeds may be used. The rollers 404a-b may be rotated during the entire time that the spindle 304 is rotated, or a portion thereof, and / or may remain stationary at least once during polishing. Also, in some embodiments, the rollers 404a-b may switch the direction of rotation during polishing.

The polishing of the substrate 202 continues until a desired amount of material is removed from the substrate 202. The rollers 404a-b rotate at a different speed than the spindle 204 so that the substrate 202 is actively pre-sessioned with the membrane 308 and any non-concentric or other asymmetric polishing head pressure profile Is averaged during the polishing (e.g., produces a more uniform polishing). This is advantageous for substrates of any size (e.g., 200 mm, 300 mm, 450 mm, or other sizes of semiconductor wafers, or any other substrate type or size).

In general, the retaining ring 204 may be formed of any suitable material, such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyethylene terephthalate, or the like. In embodiments in which the rollers 404 are used as in Figures 4A-4C, the retaining ring 204 may be modified to improve substrate edge polish behavior. For example, the features used to allow the slurry to enter the polishing head 104 may vary depending on the application. In some embodiments, it may be desirable to allow the slurry to build up during polishing, and thus the retention of the retaining ring 204 against the trailing edge of the retaining ring 204 (near the rollers 404a-b) Additional slurry grooves may be provided along the leading edge of the slurry grooves 204. Likewise, in some embodiments, it may be desirable to have less slurry accumulate during polishing, and thus it may be desirable to maintain the retaining ring (in the vicinity of the rollers 404a-b), as compared to following the leading edge of the retaining ring 204 More slurry grooves may be provided along the trailing edge of the slurry 204. Similarly, different forces can be applied along the trailing edge of the retaining ring 204, relative to the leading edge of the retaining ring 204, to better control the pad rebound during polishing. Likewise, the retaining ring 204 may have different geometric shapes (e.g., widths) along the trailing edge and the leading edge of the retaining ring 204.

Although the retaining ring 204 is shown as being a single ring section, the retaining ring 204 includes a plurality of ring sections as shown by the ring sections 204a and 204b of Figure 4c. You can understand that you can do it. More than two ring sections may be used as the inner or outer ring sections. 4D is a schematic view of a portion of the retaining ring 204 having a larger and / or more slurry grooves 420a along the leading edge of the retaining ring 204 than the slurry grooves 420b along the trailing edge of the retaining ring 204, And an inning ring 204. FIG. If desired, such a configuration can be inverted. 4E shows a wider retaining ring 204 in that it follows the leading edge of the retaining ring 204 rather than along the trailing edge of the retaining ring 204. If desired, such a configuration can be inverted.

Thus, while the present invention has been disclosed with respect to exemplary embodiments thereof, it is to be understood that other embodiments may be included within the scope of the present invention as defined by the following claims.

Claims (15)

As a chemical mechanical polishing apparatus,
A polishing head, comprising:
A rotatable spindle,
A membrane coupled to the rotatable spindle and adapted to press the substrate against the polishing pad during polishing of the substrate,
A retaining ring rotatably connected to the spindle and configured to surround a substrate being pressed toward the polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head,
&Lt; / RTI &gt; And
A drive mechanism coupled to the retaining ring and adapted to drive the retaining ring at a different rotational speed than the spindle during polishing,
And a chemical mechanical polishing apparatus. The apparatus of claim 1, further comprising a controller adapted to cause the drive mechanism to rotate the retaining ring at a different rotational speed than the spindle during polishing. 3. The chemical mechanical polishing apparatus of claim 2, wherein the controller is configured to cause the drive mechanism to rotate the retaining ring at about twice the rotational speed of the spindle during polishing. 3. The apparatus of claim 2, wherein the controller is configured to cause the drive mechanism to rotate the retaining ring about a half speed of rotation of the spindle during polishing. A method of polishing a substrate,
Pressing the substrate toward the polishing pad using a polishing head,
Rotatable spindle,
A membrane coupled to the rotatable spindle and adapted to press the substrate toward the polishing pad during polishing of the substrate,
A retaining ring coupled to the spindle and configured to surround a substrate being pressed toward the polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head,
-;
Rotating the spindle of the polishing head and the membrane at a first rotational speed during polishing; And
Rotating the retaining ring of the polishing head at a second rotational speed during polishing to cause the substrate to rotate relative to the membrane of the polishing head
&Lt; / RTI &gt; 6. The method of claim 5, wherein the first rate is less than the second rate. 6. The method of claim 5, wherein the first rate is greater than the second rate. A chemical mechanical polishing apparatus comprising:
Comprising a polishing head,
The polishing head includes:
Rotatable spindle,
A membrane coupled to the rotatable spindle and configured to press the substrate against the polishing pad during polishing of the substrate,
A retaining ring rotatably connected to the spindle and configured to surround a substrate being pressed toward the polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head,
At least one rotation mechanism coupled to the retaining ring and adapted to contact the substrate during polishing and to allow the substrate to rotate at a different speed than the spindle during polishing,
Wherein the chemical mechanical polishing apparatus comprises: 9. The chemical mechanical polishing apparatus of claim 8, wherein the at least one rotation mechanism comprises at least one roller rotatably connected to a trailing edge of the retaining ring. 9. The apparatus of claim 8, wherein the retaining ring is stationary during polishing. 9. The chemical mechanical polishing apparatus of claim 8, wherein the retaining ring comprises a plurality of retaining ring sections. 9. The method of claim 8, wherein the retaining ring has a number of slurry grooves along a leading edge of the retaining ring, different from a slurry groove along a trailing edge of the retaining ring. Chemical mechanical polishing apparatus. 9. The chemical mechanical polishing apparatus of claim 8, wherein the retaining ring has a width along the leading edge of the retaining ring, the width being different from the width along the trailing edge of the retaining ring. A method of polishing a substrate,
Pressing the substrate toward the polishing pad using a polishing head,
Rotatable spindle,
A membrane coupled to the rotatable spindle and configured to press the substrate against the polishing pad during polishing of the substrate,
A retaining ring connected to the spindle and configured to surround a substrate being pressed toward the polishing pad during polishing and to limit lateral movement of the substrate relative to the polishing head,
At least one rotating mechanism coupled to the retaining ring and adapted to contact the substrate during polishing and to allow the substrate to rotate at a different speed than the spindle during polishing,
-;
Rotating the spindle of the polishing head and the membrane at a first rotational speed during polishing; And
Rotating the at least one rotating mechanism coupled to the retaining ring of the polishing head to a second rotational speed during polishing to cause the substrate to rotate relative to the membrane of the polishing head
/ RTI &gt; 15. The method of claim 14, wherein the at least one rotating mechanism comprises at least one roller rotatably connected to a trailing edge of the retaining ring.

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