CN211193454U

CN211193454U - Chemical mechanical polishing retaining ring and chemical mechanical polishing bearing head

Info

Publication number: CN211193454U
Application number: CN201921656271.7U
Authority: CN
Inventors: 赵德文; 刘远航; 孟松林
Original assignee: Tsinghua University; Huahaiqingke Co Ltd
Current assignee: Tsinghua University; Huahaiqingke Co Ltd
Priority date: 2019-09-30
Filing date: 2019-09-30
Publication date: 2020-08-07
Anticipated expiration: 2029-09-30

Abstract

A chemical mechanical polishing retainer ring and a chemical mechanical polishing carrier head include an annular body composed of an upper portion and a lower portion, the upper portion being made of metal, the lower portion being made of plastic and having grooves for passage of a polishing liquid, the upper portion and the lower portion being integrated by a bonding layer containing a wave-absorbing material to prevent the retainer ring from reflecting electromagnetic waves or generating eddy currents.

Description

Chemical mechanical polishing retaining ring and chemical mechanical polishing bearing head

Technical Field

The utility model belongs to the technical field of the chemical mechanical polishing, especially, relate to a chemical mechanical polishing retaining ring and chemical mechanical polishing bear head.

Background

Chemical mechanical polishing is a mainstream substrate polishing method in the field of chip manufacturing. The polishing method generally attracts and holds the substrate at the lower part of the carrier head, one surface of the substrate with a deposition layer abuts against the rotating polishing pad, and the carrier head rotates in the same direction with the polishing pad under the driving of the driving part and gives a downward load to the substrate; meanwhile, the polishing solution is supplied to the upper surface of the polishing pad and distributed between the substrate and the polishing pad, so that the substrate is polished globally under the combined action of chemistry and machinery.

The carrier head is an important component of the chemical mechanical polishing apparatus, and the operation performance of the carrier head is directly related to the chemical mechanical polishing effect of the substrate. US20130065495a1 discloses a carrier head comprising a carrier tray and a flexible membrane detachably arranged at the lower part of the carrier tray; the carrier tray includes a first portion and a second portion, the first portion being movably disposed concentrically within an upper recess of the second portion such that the first portion and the second portion are movable relative to each other in a direction perpendicular to a bottom surface of the carrier tray. The flexible membrane is arranged below the second part, so that a plurality of air cavities are formed between the second part and the flexible membrane, and the pressure profile of the substrate can be adjusted by adjusting the pressure of each independent air cavity. In the prior art, external air enters the channel inside the first part through the air holes on the upper surface of the first part and flows out from the air holes on the side wall of the first part, and then is conveyed to the air holes on the upper surface of the second part which are respectively communicated with the independent air cavities through the air pipes.

The lower portion of the carrier head is provided with a retaining ring, which plays an important role in the chemical mechanical polishing of the substrate. On the one hand, it can prevent the substrate from slipping or flying off the bottom of the carrier head during polishing; on the other hand, the bottom of the retaining ring is provided with a groove which can provide a fluid channel for renewing the polishing liquid between the substrate and the polishing pad; moreover, the retaining ring is pressed against the polishing pad to participate in the adjustment of the edge pressure of the substrate, which is beneficial to realizing the global planarization of the substrate and improving the uniformity of the planarization.

In the chemical mechanical polishing process, in order to adjust the material removal rate in real time, the thickness of the material layer to be removed needs to be measured on line, and when the material to be removed is metal, the eddy current film thickness measuring method is more applicable. The existing eddy current film thickness measuring device generates an alternating electromagnetic field signal through a signal generator, so that an eddy current is formed in a metal film of a substrate, and detects an inductance change signal caused by the eddy current in the metal film through a sensor, thereby determining the thickness of the metal film.

The detection accuracy requirement of the chemical mechanical polishing end point detection is improved along with the continuous reduction of the size of the characteristic structure, and because metal parts or metal materials are contained in the components such as the retaining ring of the traditional chemical mechanical polishing bearing head, and the like, eddy current can also be generated in the metal parts in the eddy current film thickness measurement, so that the signals which are acquired by the sensor and generated by the metal characteristic structure can be interfered, and the accuracy of the end point detection is influenced. It is therefore desirable to be able to ensure that the metal structure of the carrier head interferes as little as possible with the measurement signals when measuring the thickness of the metal structure features of the substrate to determine chemical mechanical polishing emphasis.

SUMMERY OF THE UTILITY MODEL

The utility model provides a chemical mechanical polishing retaining ring and chemical mechanical polishing bear head aims at solving one of above-mentioned technical problem to a certain extent, and its technical scheme is as follows:

a chemical mechanical polishing retainer ring includes an annular body composed of an upper portion and a lower portion, the upper portion being made of a metal material, the lower portion being made of a plastic material and having grooves for passage of a polishing liquid, the upper portion and the lower portion being integrated by a bonding layer containing a wave-absorbing material to prevent the retainer ring from reflecting electromagnetic waves or generating eddy currents;

in the above scheme, the wave-absorbing material is a magnetic medium type wave-absorbing material, a dielectric medium type wave-absorbing material and/or a resistance type wave-absorbing material;

further, the wave-absorbing material is ferrite micro powder and/or graphene micro powder plated with nickel-phosphorus alloy.

Further, the wave-absorbing material accounts for 2-20% of the total weight of the bonding layer;

in the above solution, the lower surface of the upper part has a reinforced joint part, and the reinforced joint part can be an annular protrusion, an annular groove, a radial protrusion or a radial groove;

further, the cross section of the reinforced combining part can be rectangular, trapezoidal, triangular, conical or semicircular;

further, the height of the reinforced combination part is 0.1mm to 2 mm.

Further, the lower surface of the upper portion of the retainer ring has a roughened structure by laser processing, sand blasting, shot blasting, grinding, and/or cutting;

further, the lower surface has a roughness Ra of 0.8 to 6.3.

Furthermore, the utility model also provides a chemical mechanical polishing bears the head, should bear the head and include that any kind of above-mentioned basis the utility model discloses a retaining ring.

Compared with the prior art, the embodiment of the utility model beneficial effect who exists includes: the interference of the eddy current generated by the retaining ring to the electromagnetic wave during the measurement of the thickness of the eddy current metal film is reduced, and the detection precision is improved.

Drawings

The advantages of the invention will become clearer and more easily understood from the detailed description given with reference to the following drawings, which are given purely by way of illustration and do not limit the scope of protection of the invention, wherein:

FIG. 1 illustrates, without limitation, a schematic of a typical chemical mechanical polishing cell configuration;

FIG. 2 is a schematic diagram illustrating, without limitation, the structure of a chemical mechanical polishing carrier head in accordance with the present invention;

FIG. 3 is a schematic diagram illustrating, without limitation, the structure of a retaining ring of a chemical mechanical polishing carrier head in accordance with the present invention;

FIG. 4 illustrates, without limitation, the effect of a metal portion of a retaining ring of a chemical mechanical polishing carrier head on a chemical mechanical polishing endpoint detection signal;

FIG. 5 is an enlarged, non-limiting illustration of one configuration of an attachment layer for a retaining ring of a chemical mechanical polishing carrier head in accordance with the present invention;

FIG. 6 illustrates, without limitation, a bonding layer of a CMP retaining ring having a spacer structure in accordance with the present invention;

FIG. 7 illustrates, without limitation, a structure in which a portion of the upper metal structure of the CMP retaining ring is coated with a metallic wave-absorbing coating in accordance with the present invention;

FIG. 8 illustrates, without limitation, a chemical mechanical polishing retaining ring in accordance with the present invention in which the entire surface of the metal structure of the variation of the retaining ring is coated with a wave absorbing coating;

fig. 9A and 9B show a comparison of the characteristic structure thicknesses of the substrates measured by the eddy current measuring device and the four-probe device when the retaining ring containing no wave-absorbing material and containing a wave-absorbing material is used, respectively.

Detailed Description

The technical solution of the present invention will be described in detail with reference to the following embodiments and accompanying drawings. The embodiments described herein are specific embodiments of the present invention and are provided to illustrate the concepts of the present invention; the description is intended to be illustrative and exemplary and should not be taken to limit the scope of the invention. In addition to the embodiments described herein, those skilled in the art will be able to employ other technical solutions which are obvious based on the disclosure of the claims and the specification thereof, and these technical solutions include technical solutions which make any obvious replacement or modification of the embodiments described herein. In order to explain the technical solution of the present invention, the following description is made by using specific examples.

Fig. 1 is a schematic perspective view of the basic structural configuration of a polishing unit 2A, the polishing unit 2A including a polishing disk 10, a polishing pad 20, a substrate carrier device 30, a dressing device 40, and a polishing liquid supply device 50; the polishing pad 20 is arranged on the upper surface of the polishing disk 10 and rotates along the axis Ax1 synchronously therewith; a horizontally movable substrate carrier 30 disposed above the polishing pad 20, and coupled to a lower surface of a carrier head to which a substrate W to be polished is sucked; the dressing device 40 comprises a dressing arm 41 and a dressing head 42, wherein the dressing arm 41 drives the rotating dressing head 42 to swing so as to dress the surface of the polishing pad 20 to an optimal state suitable for polishing; the polishing liquid supply device 50 spreads the polishing liquid over the upper surface of the polishing pad 20; when performing the chemical mechanical polishing operation, the substrate carrier 30 presses the surface to be polished of the substrate W against the upper surface of the polishing pad 20, and the polishing liquid is distributed between the polishing pad 20 and the substrate W, so as to complete the removal of the substrate material under the chemical and mechanical actions. The substrate carrier 30 includes a carrier head 31 and an Upper Pneumatic Assembly 32 (UPA), the carrier head 31 being coupled to the Upper Pneumatic Assembly 32 by a connection Assembly (not shown).

Fig. 2 is a schematic diagram of an external structure of a carrier head 31 of the substrate carrier device 30, and a flexible film 314 for attracting and/or loading a substrate W and a retaining ring 312 which is coaxially arranged with the flexible film and located outside the circumference of the flexible film for retaining and limiting the substrate W from sliding out of the carrier head 31 are arranged at the bottom of the carrier head 31, wherein a certain gap is formed between the outer circumference wall of the flexible film 314 and the inner circumference wall of the retaining ring 312. Fig. 3 illustrates the structure of the cmp retaining ring according to the present invention in isolation, and as can be seen in fig. 2 and 3, the retaining ring 312 includes an upper portion 3121, a lower portion 3123, and an intermediate bonding layer.

FIG. 4 is a partial cross-sectional view of a carrier head 31 having a retaining ring 312, the carrier head 31 including a carrier platter 313, a flexible membrane 314, an annular platen 315, and a retaining ring 312, the retaining ring 312 generally having a metal skeleton or metal frame structure; the eddy current inspection device 203 embedded between the polishing disk 10 and the polishing pad 20 emits electromagnetic waves toward the substrate W to measure the thickness of the substrate surface structure feature layer to capture the polishing endpoint, and the metal skeleton or metal structure of the retaining ring 312 generates eddy currents and electromagnetic wave reflections to affect the signal measurement accuracy of the eddy current inspection device 203, especially to significantly affect the polishing endpoint detection near the edge of the substrate W, for this reason, the wave-absorbing material is added to the bonding layer 3122 of the retaining ring 312 in this embodiment to reduce the effect of the metal part of the retaining ring on the electromagnetic wave measurement.

FIG. 5 is an enlarged partial view of the retaining ring portion of FIG. 4, wherein the annular body of the retaining ring 312 includes annular upper and

lower portions

3121 and 3123, the upper portion 3121 may be made of a metal material such as stainless steel, titanium alloy, or aluminum alloy, and the lower portion 3123 may be made of a hard engineering plastic such as PPS, PEEK, polycarbonate, polyurethane, or PET; the upper portion 3121 and the lower portion 3123 are coaxially integrated by the bonding layer 3122, and the thickness of the bonding layer 3122 may be uniform. In some embodiments, since the retaining ring 312 is subjected to a shearing force during a chemical mechanical polishing operation to cause the upper portion 3121 to be partially or completely separated from the lower portion 3123, in order to increase the bonding strength of the upper and lower portions of the retaining ring 312, the lower surface of the upper portion 3121 may be provided with a reinforced bonding portion (not shown) for reinforcing bonding, which may be at least one of an annular protrusion, an annular groove, a radial protrusion, and a radial groove, and the lower surface of the upper portion 3121 of the retaining ring 312 or the surface of the reinforced bonding portion may be roughened to increase the bonding strength thereof with the bonding layer 3122, thereby increasing the bonding strength of the upper portion 3121 and the lower portion 3123; further, the roughness Ra of the bottom surface of the upper portion 3121 may be controlled to between 0.8 and 6.3, preferably 1.6 or 3.2 (corresponding to 7 and 6 surface finishes, respectively), by sanding, laser surface treatment, shot blasting, sand blasting and/or plasma spraying, etc., it being noted that excessive roughening may lead to extended tack-down time of the bonding layer and/or the bottom surface of the upper portion 3121 may not be sufficiently wetted by the adhesive forming the bonding layer 3122, thereby reducing the bonding strength.

Similarly, reference may also be made to the treatment of the upper surface of the lower portion 3123 to increase the bonding strength by using the above method, in which case, the cross section of the annular protrusion, the annular groove, the radial protrusion, and the radial groove may be rectangular, trapezoidal, triangular, tapered, semicircular, and/or any other regular or irregular shape, and the height and/or depth of the annular protrusion, the annular groove, the radial protrusion, and the radial groove is 0.1mm to 2mm, preferably 0.3mm to 1mm, where the "height" and the "depth" refer to the distance between the lowest point and the highest point of the protrusion or groove.

As shown in fig. 6, in some embodiments, the bonding layer 3122 is provided with a spacer structure 3124, and the bonding layer 3122 may be formed by curing an adhesive such as epoxy resin, during which the distance between the upper portion 3121 and the lower portion 3123 of the retaining ring may be maintained at a certain value due to the spacer structure 3124, thereby ensuring that the bonding layer 3122 has a uniform thickness. Further, the spacer structure 3124 also has wave absorbing properties, and preferably wave absorbing properties close to the unit wave absorbing properties of the bonding layer 3122, for example the spacer structure 3124 may be made of a carbon fiber skeleton, such as a graphene micro-coating with a nickel-phosphorus alloy plated surface, and the spacer structure 3124 has a thickness of between 0.2mm and 2mm, preferably 0.3 to 1 mm. The spacer 3124 may be formed in any structure such as a ring structure, a block structure, and the like, which can support to form the bonding layer 3122 having a certain thickness and have the same wave-absorbing property as the bonding layer 3122. It should be noted that although the weight ratio of the wave-absorbing material may vary depending on the thickness of the bonding layer 3122 and may vary depending on the specific process requirements, in general, the wave-absorbing material may comprise 2 to 20%, preferably 6 to 18%, of the total mass of the bonding layer 3122.

In some embodiments of the present invention, the bonding layer 3122 contains at least one of a magnetic medium type wave-absorbing material, a dielectric type wave-absorbing material, and a resistance type wave-absorbing material. Preferably, ferrite micro powder and/or graphene micro powder plated with nickel-phosphorus alloy are/is adopted as the wave-absorbing material in the bonding layer 3122. As shown in fig. 7, in some embodiments of the present invention, the wave-absorbing plating layer 3121A is provided on the bottom surface and the side surface of the upper portion 3121 of the retaining ring, or the wave-absorbing plating layer 3121A may be formed only on the inner side surface and the bottom surface of the retaining ring 312. Preferably, a nickel-phosphorus-graphene plating layer can be used as the wave-absorbing plating layer 3121A, and the plating layer has not only excellent electromagnetic wave absorption performance, but also strong corrosion resistance, wear resistance and hardness.

As shown in fig. 8, it is another embodiment of the retaining ring of the present invention, wherein the retaining ring 312 is composed of a ring-shaped metal inner core 3125 and a coating layer 3127, wherein the inner core 3125 is made of a metal material such as stainless steel, titanium alloy or aluminum alloy, and the coating layer 3127 is made of a hard engineering plastic such as PPS, PEEK, polycarbonate, polyurethane, or PET. In some embodiments, the surface of the inner core 3125 is coated with a wave-absorbing coating 3125A; preferably, a nickel-phosphorus-graphene coating can be adopted as the wave-absorbing coating 3125A. Alternatively, the surface of the inner core 3125 may be coated with a non-metal coating having a wave-absorbing function or formed with a non-metal wave-absorbing structure by means of thermal injection molding, and in order to combine and fasten the non-metal wave-absorbing structure with the inner core 3125, a reinforced combination portion similar to the above-mentioned one for reinforcing combination may be disposed on the surface of the inner core 3125A, and then a sacrificial plastic structure for chemical mechanical polishing may be formed outside the non-metal wave-absorbing structure, and the sacrificial plastic structure may be lost along with the chemical mechanical polishing operation. The reinforced combination part can also be at least one of an annular protrusion, an annular groove, a radial protrusion and a radial groove; further, the surface roughness Ra of the inner core 3125A may be controlled to between 0.8 and 6.3, preferably 1.6 or 3.2 (corresponding to 7-grade and 6-grade surface finishes, respectively), by sanding, laser surface treatment blasting, plasma spraying and/or shot blasting, to account for the phenomenon that excessive roughening may lead to an extended tack-free time of the bonding layer and/or the bottom surface may not be sufficiently wetted by the adhesive, thereby reducing the bonding strength; the cross section of the annular protrusion, the annular groove, the radial protrusion and the radial groove can be rectangular, trapezoidal, triangular, conical, semicircular and/or any other regular or irregular shape, and the height and/or depth of the annular protrusion, the annular groove, the radial protrusion and the radial groove is 0.1-5 mm, preferably 1.5-3 mm.

Further, the wave-absorbing material can be divided into the following steps according to the process:

1. coating (plating) layer type: the powder mixed with the binder is solidified on the surface of the workpiece, or a coating is formed on the surface of the workpiece, so that the service life is long;

2. the structure type is as follows: meanwhile, the wave absorbing material has the dual functions of bearing and absorbing waves and can be formed into various complex shapes;

3. sticking sheet type: the universality is good, and the use is easy;

the structure of the retaining ring and the environment of use determine the difficulty of application of the patch type, considering only the first two forms.

Further, the wave-absorbing material is prepared according to a loss mechanism:

1. conductive loss type

2. Dielectric loss type

3. Magnetic loss type

The ferrite wave-absorbing material has the characteristics of the two materials 2 and 3; in the low frequency band, the loss of electromagnetic waves is mainly caused by the loss of hysteresis effect, eddy effect and magnetic after effect; in the high frequency band, the loss of the ferrite to the electromagnetic wave mainly comes from natural resonance loss, domain wall resonance loss and dielectric loss, and has the following advantages: the ferrite wave-absorbing material is wide in absorption frequency band, high in absorption rate, low in cost, simple in preparation process and thin in matching thickness, so that the ferrite wave-absorbing material is preferably considered.

On the other hand, ferrite wave-absorbing materials have the following disadvantages: high density, poor corrosion resistance and can not be used as a coating. In order to prevent the wafer from being polluted by the debris, the retaining ring also has certain requirements on the surface hardness and the wear resistance of the component. The carbon fiber material can be used as a structural member and applied to various parts; the nickel-phosphorus-graphene coating has excellent wave-absorbing performance, strong wear resistance, corrosion resistance and hardness, and is better combined with a matrix.

In order to verify the improvement effect of the retaining ring 312 of the bonding layer 3122 containing the wave-absorbing material on the thickness measurement accuracy of the metal film, the retaining ring without the wave-absorbing material in the prior art and the retaining ring with the wave-absorbing material in the utility model are respectively adopted to carry out a contrast experiment, the experimental result is shown in fig. 9A and 9B, in fig. 9A, when the solid line is used for carrying out 300mm substrate chemical mechanical polishing on a bearing head which is provided with the environment-friendly bearing head without the wave-absorbing material of the bonding layer 3122, the film thickness appearance obtained by carrying out online measurement on the metal film thickness of the substrate by adopting an eddy current method, and the dotted line is the result of carrying out offline film thickness measurement on the same; because the off-line measurement is not interfered by chemical mechanical polishing equipment, the result is more accurate and more reliable than the on-line measurement and can be used as a reference value. It can be seen that at the ± 150mm edge, the measurement error is significant.

For comparison, in fig. 9B, the solid line is the film thickness profile obtained by online measurement of the metal film thickness of the substrate by the eddy current method when the carrier head with the bonding layer 3122 containing the wave-absorbing material is used for chemical mechanical polishing of a 300mm substrate, and the dotted line is the result of offline film thickness measurement of the same substrate by the four-probe method. It can be seen that the measurement error of the edge portion of the substrate is significantly reduced compared to the prior art.

In the above embodiments, the description of each embodiment has a respective emphasis, and the embodiments may be combined arbitrarily, and a new embodiment formed by combining the embodiments is also within the scope of the present application. For parts which are not described or illustrated in a certain embodiment, reference may be made to the description of other embodiments.

The above-mentioned embodiments are only used for illustrating the technical solution of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.

Claims

1. A chemical mechanical polishing retainer ring, comprising an annular body composed of an upper portion and a lower portion, the upper portion being made of a metal material, the lower portion being made of a plastic material and having grooves for passage of a polishing liquid, the upper portion and the lower portion being integrated by a bonding layer containing a wave-absorbing material to prevent the retainer ring from reflecting electromagnetic waves or generating eddy currents.

2. The retaining ring of claim 1, wherein the absorbing material is a magnetic medium type absorbing material, a dielectric type absorbing material, or a resistive type absorbing material.

3. The retaining ring of claim 2, wherein the wave absorbing material is ferrite micro powder or graphene micro powder plated with a nickel-phosphorus alloy.

4. The retaining ring of any one of claims 1-3, wherein the lower surface of the upper portion has a reinforced engagement portion that may be an annular protrusion, an annular groove, a radial protrusion, or a radial groove.

5. The retaining ring of claim 4, wherein the reinforced joint is rectangular, trapezoidal, triangular, tapered, or semi-circular in cross-section.

6. The retaining ring of claim 4, wherein the reinforced bond has a height of 0.1mm to 2 mm.

7. The retainer ring according to claim 1, wherein a lower surface of the upper portion of the retainer ring has a roughened structure by laser processing, sand blasting, shot blasting, grinding, and/or cutting.

8. The retaining ring of claim 7, wherein the lower surface has a roughness Ra of 0.8 to 6.3.

9. A chemical mechanical polishing carrier head comprising the retaining ring of any of claims 1-8.