KR20140003830A

KR20140003830A - Membrane of carrier head in chemical mechanical polishing apparatus

Info

Publication number: KR20140003830A
Application number: KR1020120070720A
Authority: KR
Inventors: 손준호; 황지영
Original assignee: 주식회사 케이씨텍
Priority date: 2012-06-29
Filing date: 2012-06-29
Publication date: 2014-01-10

Abstract

The present invention relates to a carrier head of a chemical mechanical polishing device and a membrane used for the same. A lower surface of the membrane touched to a wafer is formed into a flat surface, wherein a chemical mechanical polishing process is applied to the wafer. An upper surface which is based on elastic material and is not touched to the wafer is provided to be slantly formed from the center to the outer direction, thereby maintaining a state of attaching the membrane and the wafer. The present invention is provided to maintain a state of adsorbing the wafer and the membrane without slip by applying force, which pressurizes the membrane by air pressure of a chamber positioned in the upper part of the membrane, to pressurize the wafer symmetrically based on the center of the wafer, thereby providing the carrier head of the chemical mechanical polishing device and the membrane used for the same capable of performing chemical mechanical polishing with accurate flatness.

Description

Membrane for carrier head of chemical mechanical polishing device {MEMBRANE OF CARRIER HEAD IN CHEMICAL MECHANICAL POLISHING APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier head of a chemical mechanical polishing apparatus and a membrane used therein. More specifically, the present invention relates to a carrier head of a chemical mechanical polishing apparatus. It relates to a carrier head and a membrane used therein that can suppress the occurrence of asymmetrical polishing with different polishing degrees at points located at a distance.

The chemical mechanical polishing (CMP) apparatus is a device for performing a wide-area planarization that removes a height difference between a cell region and a peripheral circuit region due to unevenness of a wafer surface generated by repeatedly performing masking, etching, To improve the surface roughness of the wafer due to contact / wiring film separation and highly integrated elements, and the like.

In such a CMP apparatus, the carrier head presses the wafer in a state in which the polished surface of the wafer faces the polishing pad before and after the polishing step to perform the polishing process, and at the same time, when the polishing process is finished, the wafer is directly or indirectly Vacuum-adsorbed and held, and then moved to the next step.

1 is a schematic diagram of a conventional carrier head 1. As shown in Fig. 1, the carrier head 1 includes a main body portion 40, a base 20 rotatably mounted with respect to the main body portion 40, and a retainer mounted on the circumference of the base 20. An end 10a is fixed between the ring 30 and the base 20 and the retainer ring 30, and is composed of an elastic membrane 10 that contacts the wafer W. The chamber C is formed between the base 20 and the membrane 10 made of an elastic material, and the pressure P 'inside the chamber C is controlled as shown in FIG. 2, thereby during the chemical mechanical polishing process. While the pressure P 'of the chamber C is controlled at a constant pressure, the wafer W is rotated in a pressurized state between the membrane 10 and the polishing pad (not shown).

Since the membrane 10 of the conventional carrier head 1 has a uniform thickness of the portion in contact with the wafer W as shown in FIG. 2, the pressure in the chamber C is uniformly applied to the entire membrane 10. It appears that the wafer W is pressed more effectively.

However, since the actual membrane 10 is an elastic material and the bottom surface of the wafer W that does not contact the membrane 10 is in contact with a rotating polishing pad (not shown), the CMP process is performed. Since the force in the revolution direction due to the rotation of the polishing pad and the rotation direction as it is rotated while being pressed by the membrane 10 of the carrier head 1 are simultaneously received, the surface of the wafer W is periodically subjected to pressure distribution. Will fluctuate. Furthermore, the surface tension of the wafer W acts on the surface of the wafer W by the slurry applied for the chemical polishing process, so that the wafer W is easily warped by an external force.

Accordingly, the wafer W, which is subjected to the chemical mechanical polishing process while being pressed by the membrane 10 having a constant thickness, has two points X1, which are separated by the same radius R2 from the center O as shown in FIG. 3. The degree of polishing in X2) was uneven, which caused a problem of polishing in an asymmetrical polishing state. As a result, an error occurs in the planarization process of the elaborate polishing process of the wafer W, which causes a problem of limiting the fabrication of finer and more precise semiconductor devices.

SUMMARY OF THE INVENTION The present invention has been made under the foregoing technical background, and the present invention provides a membrane of a carrier head and the same, which allows the wafer to be polished while being pressed by the membrane of the carrier head to be uniformly polished to the same radius during the chemical mechanical polishing process. It is an object to provide one carrier head.

Through this, the present invention is to be able to perform chemical mechanical polishing with a more precise flatness on the wafer, it is an object to enable high integration of the semiconductor device.

In order to achieve the above object, the present invention provides a membrane of a carrier head for a chemical mechanical polishing apparatus, wherein the membrane has a bottom surface in contact with a wafer for performing a chemical mechanical polishing process, and is formed with a flat surface, and does not contact with the wafer. The upper surface provides a membrane of the carrier head, which is formed to be inclined radially outward from the center and formed of an elastic material.

Through this, as the bottom surface of the membrane is formed into a flat surface, the membrane and the wafer can be kept in close contact with each other, and at the same time, as the upper surface of the membrane is formed to be inclined radially outward from the center, the chamber located above the membrane. The force to pressurize the membrane by the air pressure of the symmetrical with respect to the center acts to be able to pressurize the wafer.

Therefore, the wafer pressurized by the membrane of the chemical mechanical polishing apparatus formed as described above is subjected to the force in the revolving direction due to the rotation of the polishing pad during the CMP process, the force in the rotating direction due to the rotation of the membrane, and the surface tension of the slurry. Despite the force caused by the membrane, the membrane is held between the membrane and the wafer by pneumatically acting symmetrically while maintaining close contact with the membrane. Thus, during the CMP process, the slip between the wafer and the membrane located at the bottom of the membrane The occurrence is suppressed to the maximum, leading to the coincidence of the rotation of the membrane and the wafer so that the wafer can be uniformly polished over the entire surface.

As a result, the membrane having a uniform thickness used in the conventional chemical mechanical polishing apparatus is forced to generate a wafer and slip, which is pressurized by the force of various components acting during the CMP process, resulting in an asymmetric polishing phenomenon. The elastic membrane used in the carrier head of the chemical mechanical polishing apparatus according to the present invention has a bottom surface formed into a flat surface and an upper surface formed symmetrically inclined with respect to the center so as to securely hold the wafer and rotate together without slipping. Therefore, it has been experimentally confirmed that the same radius of polishing is reliably performed at the same radius, thereby solving the conventional asymmetric polishing phenomenon.

The elastic membrane formed as described above does not hold the wafer reliably when the bottom surface is not formed as a flat surface, thereby causing a problem of large slip phenomenon. In addition, according to one embodiment of the present invention, the elastic membrane may be formed in a shape that becomes thinner as it approaches the radius from the center, but according to the best embodiment of the present invention, the membrane located at the bottom of the membrane is reliably held. In order to minimize the slip phenomenon between the wafer and the wafer to reliably eliminate the conventional asymmetric polishing phenomenon, the membrane should be formed on the top surface of the membrane in such a manner that the thickness becomes thicker as it approaches the radius outward from the center.

This allows the forces acting on the wafer through the elastic membrane to have radially outward components, so that the wafers can reliably settle in a fixed position on the elastic membrane even if the forces in the orbiting and rotating directions and the surface tension of the slurry act on the wafer. By rotating together with the membrane, it is possible to prevent CMP polishing at different polishing amounts for the same radial position.

In this case, the inclined surface formed on the upper surface of the elastic membrane may be formed as a straight inclined surface that increases gradually from the center toward the outer radius, or may be formed as a curved inclined surface that gradually increases toward the outer radius from the center. Then, the inclination of the inclined surface is formed from 2 ° to 20 °.

On the other hand, the membrane may be used to form a pressure chamber in which a plurality of flips are formed and partitioned along the radial direction from the center to control the pressure independently of each other. In this way, even if controlled by different chambers by different chambers in the radial direction, the bottom surface of the elastic membrane is flat and the inclined surface becomes higher as the upper surface approaches the radius outward from the center. The slip phenomenon between can be suppressed.

In addition, the membrane may have an opening formed at a central portion thereof as a passage for applying suction pressure directly to the wafer.

According to another aspect of the present invention, A base rotatably driven with respect to the main body; An elastic membrane fixed to the base, the pressure chamber being formed between the base and configured to press downwardly the wafer located at the bottom during the chemical mechanical polishing process by pressure control of the pressure chamber; A retainer ring installed to be supported by any one of the main body and the base and surrounding the outer periphery of the membrane; The present invention also provides a carrier head of a chemical mechanical polishing apparatus comprising:

According to the present invention, the membrane has a bottom surface in contact with a wafer performing a chemical mechanical polishing process is formed into a flat surface, the top surface not in contact with the wafer is formed to be inclined radially outward from the center, formed of an elastic material, The membrane and the wafer can be kept in close contact with each other, and the force that pressurizes the membrane by the air pressure of the chamber located above the membrane acts to be inclined symmetrically with respect to the center to press the wafer so that the wafer is adsorbed without slipping onto the membrane. By maintaining the state, there is provided a carrier head of a chemical mechanical device and a membrane used therein, which enables chemical mechanical polishing to be performed with more precise flatness.

That is, the present invention, despite the force in the revolving direction due to the rotation of the polishing pad during the CMP process, the rotational direction due to the rotation of the membrane, the force due to the surface tension of the slurry, etc., in the radially outward direction during the CMP process Since the membrane and the wafer rotate integrally while pneumatic pressure keeps the wafer in close contact with the membrane, an advantageous effect can be obtained in which the wafer can be constantly polished over the entire surface.

Therefore, the present invention enables the CMP process to be performed more precisely with the same polishing amount with respect to the same radius of the wafer by using the carrier head with the membrane formed as described above, thereby obtaining the advantage of achieving high integration of semiconductor devices. Lose.

1 is a schematic cross-sectional view of a conventional carrier head
FIG. 2 is a half sectional view showing the configuration of the elastic membrane of FIG.
FIG. 3 shows the bottom surface of the wafer polished by FIG.
4 is a schematic cross-sectional view of a carrier head according to the first embodiment of the present invention.
FIG. 5A is a half sectional view showing the configuration of the elastic membrane of FIG.
FIG. 5B is a half sectional view showing another configuration of the present invention applicable to the elastic membrane of FIG.
6 is a schematic cross-sectional view of a carrier head according to a second embodiment of the present invention.
FIG. 7 is a half sectional view showing the configuration of the elastic membrane of FIG. 6. FIG.

Hereinafter, a carrier head 100 for a chemical mechanical polishing apparatus having an elastic membrane 110 according to a first embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions are designated by the same or similar reference numerals and the description thereof will be omitted for the sake of clarity of the present invention.

As shown in FIG. 4, the carrier head 100 including the membrane 110 according to the first embodiment of the present invention is rotatably mounted with respect to the main body 140 and the main body 140. The end 10a is fixed between the base 120, the retainer ring 130 mounted on the circumference of the base 120, and the base 120 and the retainer ring 130 to contact the wafer W. It is composed of a membrane 110 of an elastic material.

In the embodiment shown in the figure has a configuration in which the end 110a of the membrane 110 is fixed between the base 120 and the retaining ring 130 as an example, the present invention is the membrane 110 only in the base 120 End 110a of the configuration is fixed.

As shown in FIG. 5, the membrane 110 is formed as an inclined surface in which the upper surface 110s gradually increases as the radially outward direction approaches the center of rotation, and the lower surface 110b closely contacting the wafer W is flat. It is formed of cotton. Thus, the thickness of the membrane 110 is thinnest at the center and thicker as it goes out of the radius. As a result, the thickness at the center portion and the thickness at the edge portion have a step indicated by reference numeral d. The membrane 110 is molded to have elasticity with a material such as silicone, rubber, and the like, and contracts or expands according to the pressure change of the chamber C between the membrane 110 and the base 120. Through this, the membrane 110 presses the wafer W downward during the CMP process, and moves to a state in which the negative pressure is applied to the wafer W when the CMP process is completed.

The top surface 110s of the membrane 110 may be formed as a straight inclined surface from the center portion to the edge portion as shown in FIG. 5A, and may be formed as a curved inclined surface 110s ′ as shown in FIG. 5B. Can be. In addition, although not shown in the drawings, the upper surface 110s of the membrane 110 may be formed as an inclined surface only in a portion of a region in the radial direction from the center portion to the edge portion. At this time, the inclined surface is formed to 2 to 20 degrees, preferably 7 to 15 degrees. If the inclination of the inclined surface is lower than this, the force component in the radially outward direction applied to the wafer by the pressure of the chamber C is lowered, so that the effect of holding the wafer W is insignificant. If the inclination of the inclined surface is higher than this, the membrane 110 The thickness of the film becomes thicker, so that the control sensitivity of pressing the wafer W according to the pressure of the chamber C decreases.

In the elastic membrane 110 according to the first embodiment of the present invention configured as described above, the bottom surface 110b is formed as a flat surface to maintain a close contact with the wafer W, and the top surface 110s is edged from the center. There is a region in which an inclined surface is formed to become thicker and thicker toward the negative portion, and a force of radially outward components is applied to the wafer W by the pressure of the chamber C on the membrane 110. It firmly holds between the wafers W, so that the slip of the membrane 110 and the wafers W during the rotation of the wafer W and the surface tension of the slurry acts on the wafers W during the CMP process. ) Is suppressed, so that an advantageous effect of performing the CMP process with the same amount of polishing at the same radial position (X1, X2) can be obtained.

Hereinafter, a carrier head 200 for a chemical mechanical polishing apparatus equipped with a membrane 210 according to a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. However, in describing the second embodiment of the present invention, the same or similar reference numerals are assigned to the same or similar functions and configurations as the above-described first embodiment, and the description thereof will be directed to the gist of the second embodiment of the present invention. It will be omitted for clarity.

As shown in FIG. 5, the carrier head 200 having the membrane 210 according to the second embodiment of the present invention rotates together with the main body 240 and the main body 240 that are rotatably installed. The base 220, the retainer ring 230 mounted to the edge portion of the main body 240, and the opening is formed in the center portion, the center portion and the edge portion is fixed to the base 220 to contact the wafer (W) It is configured to include an elastic membrane (210).

As shown in FIG. 7, the membrane 210 has a central end 210a fixed to the base 220 such that an opening 77 is formed at the center of rotation, and an outer edge of the edge portion of the membrane 210 is formed of the base 220 and the retainer. It is fixed to the ring 230, respectively. The membrane 210 is formed with flips 211 and 212 coupled to the extension part 222 of the base 220 on the upper surface 210s to form a first chamber (A) along a radial direction about an opening 77 at the center thereof. C1) is divided into a second chamber C2, a third chamber C3, a fourth chamber C4, and a fifth chamber C5 to control the pressure independently. Accordingly, the pressure for pressurizing the wafer W varies for each of the chambers C1, ..., C5.

In this case, the thickness d2 of the edge portion is thicker than the thickness d1 of the central portion of the membrane 210, and the bottom surface contacting the wafer W is formed as a flat surface. 210s) is formed as an inclined surface that gradually increases from the center portion to the edge portion. In addition, the membrane 210 is molded to have elasticity with a material such as silicone or rubber, and contracts or expands according to the pressure change of the chambers C1,..., C5 between the membrane 210 and the base 220. . Accordingly, the force P2 for pressing the membrane 210 by the pneumatic pressure of each of the chambers C1, ..., C5 includes a component facing radially outward as shown in FIG. The wafer W can be rotated together without slipping while reliably placing the wafer W on the bottom surface of the membrane 210.

FIG. 7 illustrates a configuration in which the upper surface 210s is formed as an inclined surface over the entire section reaching the edge portion from the center of the membrane 210, but may be formed as an inclined surface only in some chambers C1,..., C5. . In addition, the inclination of the inclined surface is formed from 5 degrees to 15 degrees.

In the elastic membrane 210 according to the second embodiment of the present invention configured as described above, the bottom surface is also formed into a flat surface and maintains the state in close contact with the wafer W, while the top surface 110s is thick from the center toward the edge portion. Slope is formed so that the thickness of the thin film becomes thicker, and the force of the radially outward component is applied to the wafer W by the pressure of the chamber C on the membrane 110, thereby between the membrane 110 and the wafer W. It serves to hold firmly. Therefore, even if the surface tension of the rotating, revolving, and slurry acting on the wafer W during the CMP process is applied, the membrane 110 and the wafer W are polished without slipping while maintaining a consistent state of adhesion. An advantage of solving the asymmetrical polishing problem of is obtained.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Modified, modified, or improved.

100, 200: carrier head 110, 210: membrane
120, 220: base 130, 230: retainer ring
140, 240: main body W: wafer

Claims

In the membrane of the carrier head for chemical mechanical polishing apparatus,
The membrane is a bottom surface in contact with the wafer performing a chemical mechanical polishing process is formed into a flat surface, the top surface that is not in contact with the wafer is formed including an area inclined radially outward from the center, it is formed of an elastic material Membrane of carrier head.

The method of claim 1,
Wherein the inclined region is formed over the entire top surface of the membrane.

The method of claim 1,
Wherein the membrane is thicker and thicker as it approaches radially outward from the center.

The method of claim 3,
The upper surface of the membrane is a membrane of the carrier head formed in a straight inclined surface toward the radial outward from the center.

5. The method of claim 4,
The inclined surface has a slope of 2 ° to 20 °.

The method of claim 3,
The upper surface of the membrane is a membrane of the carrier head formed in a curved inclined surface outward from the center radius.

The method of claim 3,
The membrane of the carrier head, characterized in that the membrane is formed with a plurality of flips, partitioned radially from the center to control the pressure independently of each other.

The method of claim 3,
The membrane of the carrier head, characterized in that the opening is formed in the center portion that is a passage for applying the suction pressure directly to the wafer.

A body;
A base rotatably driven with respect to the main body;
Any one of claims 1 to 8 fixed in the base, wherein a pressure chamber is formed between the base to press downward the wafer located at the bottom during the chemical mechanical polishing process by pressure control of the pressure chamber. A membrane according to claim;
A retainer ring installed to be supported by any one of the main body and the base and surrounding the outer periphery of the membrane;
The carrier head of the chemical mechanical polishing apparatus comprising: