JP2003059869A - Chemical-mechanical polishing apparatus and method employing cylindrical roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve superior planarization of semiconductor wafers having various surface profiles. SOLUTION: This CMP(chemical-mechanical polishing) apparatus has a wafer carrier (303) for carrying a wafer (301) whose polished surface is exposed and a polishing roller (304), which is cylindrical, has a polishing pad stuck to its surface and composed of a plurality of portions having different polishing characteristics, and is brought into line contact with the polished surface. The polishing roller carries out polishing, while it undergoes two rotating motions with the center axis of the cylinder and an axis perpendicular to the polished surface, which divides the longitudinal length of the cylinder into two and is perpendicular to the center axis as two rotation axes of the two rotating motions; and at the same time, undergoes translation motion. A polishing pressure applied to the polished surface by the roller, the two rotating motions, and the translation are controlled by a built-in controller.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to chemical mechanical polishing (CMP) of semiconductor wafer surfaces, and more particularly to achieving a desired film thickness profile on the wafer surface after polishing. Chemical mechanical polishing systems and methods.

[0002]

2. Description of the Related Art A semiconductor device is manufactured by forming a circuit on a semiconductor substrate using metal wiring.
Specifically, the metal wiring is formed by connecting a plurality of elements discretely present in the device to each other to form an integrated circuit, and is insulated from other layers by using an interlayer insulating film. For electrical connection between layers, a contact hole is formed through the insulating film, and an electrical connection is provided through the contact hole. Recently, as the density of integrated circuits has increased due to technological advances, it has been required to further increase the number of layers of wirings and elements laminated on a semiconductor substrate.

When metal wiring is formed on a substrate, its surface is generally rough. However, when forming multiple layers, in order to accurately form contact holes and metal films, improve the device yield, and maintain the reliability of the final integrated circuit, each layer including the interlayer insulating film and wiring is Is very important.

A chemical mechanical polishing method (CMP) is widely used at present as a process for this planarization.
Is. An example thereof is an oxide film CMP which is a step of flattening an interlayer insulating film of an oxide film (SiO ₂ ). In an apparatus for performing CMP, a semiconductor wafer is held between a wafer carrier and a polishing cloth (pad), and the carrier and the polishing table are rotated at predetermined rotational speeds so that the semiconductor wafer and the polishing pad are separated from each other. Is applied with polishing pressure. At this time, a polishing liquid (slurry) in which solid abrasive grains (silica particles, alumina particles, cerium oxide, etc.) are dispersed in an alkaline solution is dropped onto a pad stuck on the polishing table to impregnate it. By performing the polishing, mechanical polishing by the abrasive grains and chemical softening of the wafer surface by the alkaline solution simultaneously proceed on the wafer surface, and the wafer surface is flattened. In the slurry, the dispersion and agglomeration state of the abrasive grains are controlled according to the abrasive grains and the material to be polished, and further, the components are chemically adjusted to optimize the chemical effect of polishing. . Due to the combined chemical and mechanical effects of this polishing, excellent planarization of the polishing surface is achieved.

FIG. 1 shows a typical device configuration for performing CMP. Wafer 101 includes wafer carrier 102 and polishing pad 104 on polishing table 103.
It is fixed at a constant pressure 106 between and. In such a structure, the actual polishing is performed while supplying the slurry 105 while the polishing table 103 and the wafer carrier 102 are being supplied.
It is done by rotating both and. In CMP, (1) polishing rate, (2) polishing pressure and (3) polishing table and wafer
Between the three values of relative velocity with the carrier,
It is known that the relationship "the polishing rate is proportional to the product of the polishing pressure and the relative speed" is established. This relationship is called Preston's Equation.

[0006]

Recently, a multi-zone control type wafer carrier has begun to be provided in a CMP apparatus. One of the multi-zone control methods is to apply a different air pressure to the back surface of the wafer (the surface opposite to the polishing surface) depending on the position (zone) of the wafer to generate a relatively different polishing pressure. , Means control such that the polishing rate changes for each position on the wafer. In a conventional polishing apparatus in which the polishing pressure is uniform over the entire wafer, the film thickness profile from the center of the wafer to the edge is similar to the film thickness profile of the film before polishing even after polishing is completed. However, it may not always be possible to achieve the desired flattening of the film thickness profile. On the other hand, in a multi-zone control type carrier capable of providing a plurality of pressures, the polishing rate is increased by applying a larger polishing pressure to a region to be polished more than to a region not to be polished (from Preston's formula. Leading to a better planarization of the film thickness profile than with a single pressure wafer carrier.

A problem with the conventional CMP is a phenomenon called rebound in which a convex portion is formed in the peripheral region near the edge of the wafer surface after polishing. FIG. 2A shows the principle of rebound. Further, FIG. 2B shows a rebound situation. The rebound phenomenon is caused by elastic deformation of the wafer due to vertical polishing pressure applied from the polishing pad to the surface of the wafer while the circumferential portion of the wafer is fixed horizontally by the wafer carrier. To do. If the rebound phenomenon occurs, the flattening of the wafer is not naturally achieved in that region, so the wafer region in which the rebound occurs cannot be used, leading to a reduction in yield.

Since the conventional polishing method uses a large-diameter polishing pad and a wafer carrier, a stable high-revolution polishing process has not been put into practical use. In addition, a high polishing pressure process is adopted to ensure a certain device throughput. Due to this combination of high pressure and low speed, the polishing pad is severely deformed, the relative speed of the polishing pad and the carrier is also lowered, and excellent flatness on wiring is not obtained.
(In general, the flatness on the device is proportional to the relative velocity, but inversely proportional to the polishing pressure.) In a typical CMP apparatus, as shown in FIG. It is usual to carry out polishing by pressing a wafer carrier holding a wafer from above with a vacuum chuck or the like against a circular rotary table on which is mounted. As a polishing device with a completely different structure from this, a wafer carrier that holds the wafer is provided below the device,
It has also been proposed so far that a polishing pad is placed on the surface and polishing is performed using a cylindrical roller that is in contact with a wafer carrier by a narrow linear region.
For example, JP-A-2-269552 and JP-A-7-6616.
No. 0, JP-A-2000-218518 and the like disclose a CMP apparatus having such a configuration.

In the CMP apparatus and method according to the present invention, polishing is performed in such a manner that different polishing rates are produced depending on the area of the wafer, as in the above-described multi-zone control type polishing. However, instead of changing the polishing rate by changing the polishing pressure, the polishing rate is controlled by the cylindrical polishing pad capable of high rotation with the small diameter opening and the conditioning method thereof according to the present invention. Therefore, a multi-zone control type CM using a cylindrical roller
It is an object of the present invention to implement P and solve the problems that existed in conventional CMP.

[0010]

According to one embodiment of the present invention, there is provided an apparatus for performing chemical mechanical polishing of a semiconductor wafer, comprising: (1) exposing a semiconductor wafer to be polished with its surface to be polished exposed. A wafer carrier that holds the
(2) A polishing roller having a cylindrical shape and having a polishing pad adhered on a surface thereof, wherein the polishing pad is composed of a plurality of strip-shaped portions having different polishing characteristics along a long axis direction of the cylinder, A polishing roller that contacts the surface to be polished of the semiconductor wafer via a line segment having a length in the long axis direction of the cylinder;
A chemical mechanical polishing apparatus including (3) slurry supply means and (4) controller is provided. In this apparatus, the polishing roller has two axes: a central axis of the cylinder and a longitudinal axis of the cylinder, which is divided into two and is perpendicular to the surface to be polished and orthogonal to the central axis. Two rotations are performed as a rotation axis, and at the same time, a translational movement is performed over the entire surface to be polished, and polishing is performed while the slurry supplying means supplies the slurry to the contact portion with the surface to be polished. The polishing pressure applied from the roller to the surface to be polished, the two rotational movements, and the translational movement are controlled by the controller according to the intended polishing.

According to another embodiment of the present invention, there is provided a method of performing chemical mechanical polishing of a semiconductor wafer.
The method can also be provided in the form of a computer program stored in a computer-readable storage medium or transmitted via a communication medium. In this method, (1) the wafer carrier is
A step of holding a semiconductor wafer to be polished in a state where a surface to be polished is exposed; and (2) a polishing roller having a cylindrical shape and having a polishing pad attached on the surface thereof. Is a polishing roller composed of a plurality of strip-shaped portions having different polishing characteristics along the long axis direction of the cylinder, and a surface to be polished of the semiconductor wafer and a line segment of the length of the cylinder in the long axis direction. Contacting step, (3)
In the polishing roller, two central axes of the cylinder and a longitudinal axis of the cylinder are divided into two, and an axis perpendicular to the central axis and perpendicular to the surface to be polished is two rotation axes. A step of performing a rotational movement and, at the same time, a translational movement over the entire surface to be polished, and performing polishing while supplying slurry to the contact portion with the surface to be polished. The polishing pressure applied to, the two rotational movements, and the translational movement are controlled by the controller according to the intended polishing.

[0012]

DETAILED DESCRIPTION OF THE INVENTION FIGS. 3 and 4 schematically illustrate a polishing system according to the present invention. 3 is a cross-sectional view of the cylindrical roller in the direction along the long axis, and FIG.
It is sectional drawing of the direction orthogonal to a long axis.

As shown in FIG. 3, the wafer 301 to be polished is placed on a wafer carrier 303. The device side (surface to be polished) faces upward, and the backing film 302 is provided on the opposite side, and is held via the wafer carrier 303 and a vacuum hole provided in the backing film 302. The roller is, for example, a hollow metal rod. This rod is equipped with multiple slurry holes,
Slurry is supplied to the pad surface through the holes. It should be noted that the slurry may be supplied from an external source instead of being supplied through the pad, depending on the actual conditions of polishing. This external source is shown in the figure as a tube 306 external to the roller pad device. For example, JP-A-7-66160 and JP-A-2000-2185 cited above.
No. 18, the slurry is not dropped from above the polishing surface, but is supplied to the polishing surface through holes provided on the roller surface, so that the slurry is evenly distributed over the entire wafer. It is described that it is possible to avoid that the hydroplane phenomenon occurs and the polishing does not proceed. However, the supply mode of the slurry is not a characteristic part of the present invention, and since such contents are widely known to those skilled in the art, further details will be omitted.

Incidentally, in FIG. 3 and FIG.
Although the carrier is shown at the bottom and the polishing roller at the top, this is merely an example, and the positional relationship shown is not critical to the apparatus and method according to the present invention. Therefore, rotate 90 degrees or 180
It is also possible to rotate it once and turn it upside down. However, if the top and bottom are turned upside down, it may be necessary to give some consideration to the slurry supply mode. Unlike conventional polishing, where the surfaces are in contact with each other, it may require some technique to properly supply the slurry to the straight portion where polishing occurs.

The polishing pad 304 attached to the surface of the cylindrical roller may be a single polishing pad, or may be a stack formed of two layers having different materials and compressibility.
This pad or pad stack is deposited on a roller to form a polishing pad. A roller having a polishing pad affixed to its surface is located above the wafer carrier and descends and rotates to perform CMP of the wafer. It is important that the longitudinal length of the cylindrical roller does not exceed the diameter of the wafer. The characteristic of the length of the roller is to move the roller two-dimensionally over the surface of the wafer, so that a polishing pad having different polishing characteristics depending on the position of the roller can be pressed to different regions of the wafer. Is. Further, in order to reduce the above-mentioned rebound phenomenon, it is important that the roller does not stick out from the wafer edge, and even if it sticks out, it takes only a short time.

A film having a pad conditioning abrasive adhered to a pad conditioning cover is stuck on the roller. This film is divided into a plurality of strip-shaped portions that are parallel to each other along the major axis direction, and each portion has different abrasive particles and density, and therefore has different polishing characteristics. These multiple parts are shown in FIG.
Shown as dressers n, n + 1, n + 2, n + 3. Of course, it may be divided into more than four parts shown in FIG. 3, or may be divided into less than three parts, for example. The polishing characteristics at each portion can be set by the user according to the purpose of polishing so that the desired film thickness profile can be obtained.

When polishing is ordered, the wafer carrier 3
03 starts rotating at a speed set by the user. At this time, the straight line A- which is the center of the wafer carrier
A (FIG. 3) is the axis of rotation. The roller 304 having the polishing pad attached to its surface rotates around the center line BB (FIG. 3) of the cylinder as a rotation axis while applying the polishing pressure set by the user downward to the surface of the wafer to perform polishing. Run. The wafer surface and the roller come into contact with each other via a line segment corresponding to the length of the roller. While the roller is in contact with the wafer through the line segment, the roller performs a translational motion in the X-axis direction and the Y-axis direction over the entire surface of the wafer to polish the entire surface of the wafer to achieve flatness. Performs two rotational movements. The two rotational movements are rotation about the central axis BB of the roller in the horizontal direction and rotation about the vertical axis AA of the center of the roller pad device. The rotation speed and the linear speed can all be set by the user according to the purpose of polishing. The rotary shafts are all shown in FIGS. 3 and 4.

When the wafer is polished, portions n, n
Conditioner strips with different particle sizes and densities at +1, n + 2, and n + 3 condition the pad surface. Due to the different properties of the conditioning material in different parts of the roller pad 304, the pad surface has different polishing properties, and thus the polishing rate is different from part to part. By using such a method, the polishing rate on the wafer surface can be adjusted according to the thickness profile of the wafer before polishing, and it becomes possible to generate a desired thickness profile after polishing.

As described above, the roller 304, which is in charge of polishing, makes two rotations and, at the same time, makes a two-dimensional translational motion over the entire wafer surface. These complicated movements of the roller 304 are controlled by a controller (not shown) incorporated in the polishing apparatus of the present invention. In conventional CMP, the number of control parameters related to polishing was very small. However, in the polishing apparatus according to the present invention, since the roller itself to which the pad having a plurality of different polishing characteristics is attached makes a complicated motion,
The number of control parameters has increased dramatically. If the number of control parameters is increased, it is possible to deal with various polishing required at present and in the future.

The adjustment of conditioning in the polishing method according to the present invention will be additionally described. The combination of conditioning abrasive grains, density, etc. is experimentally determined according to the film thickness profile in the wafer surface. If the various conditions (various habits such as thick, thin, almost flat wafer center) used in the device used to form (deposit) the insulating film are understood, an experiment using conditioning abrasive grains and density as a factor Determines the polishing conditioning process. If the deposition device is unstable at this time, many kinds of conditioning strips must be prepared.

[0021]

The rebound phenomenon can be alleviated by using the polishing method according to the present invention. The reason is as follows.
It is impossible to avoid rebounds entirely by polishing the wafer edge. In particular, in the conventional polishing technique, the polishing pad is larger than the wafer (including the carrier), so it protrudes from the wafer edge, and the protruding pad part remains deformed while the wafer
Since the edges were polished, the rebound occurred remarkably. In contrast, in the polishing according to the present invention, by appropriately controlling the movement of the roller pad in the X-axis and Y-axis directions, the pad does not stick out from the edge of the wafer or the sticking time can be shortened. Therefore, rebound can be reduced.

Further, according to the polishing method of the present invention, the polishing time can be shortened. The reason is as follows. First, according to the above Preston equation, the cutting amount is proportional to the product of the pressure and the relative speed. Since the roller pad according to the present invention is smaller than the conventional polishing pad, it can be adjusted to high rotation. Therefore, the relative speed becomes high, the amount of cutting per unit time increases even if the pressure is the same, and the polishing time can be shortened.

A significant feature of the present invention is the combination of a roller pad with two axes of rotation and a pad treatment using multiple types of conditioning abrasives to achieve the flatness and thickness profile desired by the user. It is a point that can be achieved. As the number of layers formed on the wafer substrate increases, the surface profile of the surface to be polished before polishing may become more and more diverse. Therefore, it is necessary to provide different polishing rates for each region of the wafer in order to realize the planarization on the basis of such various profiles.

In such a case, when the polishing apparatus and method according to the present invention is used, it is possible to provide a wide variety of polishing rates by performing polishing while appropriately controlling many parameters, and thus it is complicated. The surface to be polished having a surface profile can be appropriately dealt with. The apparatus and method according to the present invention can also polish only the region of the wafer that needs to be polished, so that excessive polishing does not occur and the cost of consumables such as slurry can be minimized. Is.

Further, according to the apparatus and method of the present invention, excellent planarization on wiring can be obtained by high relative speed polishing,
The DOF margin in photolithography can be expanded, the flatness of the stacked metal can be improved, and excessive etching can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a general CMP apparatus according to the prior art.

FIG. 2 is an example of a rebound phenomenon occurring at an edge portion of a wafer.

FIG. 3 is a sectional view of a polishing apparatus according to the present invention.

FIG. 4 is a sectional view of the polishing apparatus according to the present invention from another direction.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor 邱 楷 文             10 Kitahara, Tsukuba City, Ibaraki Prefecture             Rusui Logic Japan Semico             In the doctor (72) Inventor Masakazu Okada             10 Kitahara, Tsukuba City, Ibaraki Prefecture             Rusui Logic Japan Semico             In the doctor (72) Inventor Masao Onodera             10 Kitahara, Tsukuba City, Ibaraki Prefecture             Rusui Logic Japan Semico             In the doctor (72) Inventor Takuya Nagamine             10 Kitahara, Tsukuba City, Ibaraki Prefecture             Rusui Logic Japan Semico             In the doctor (72) Inventor Yuko Kitade             10 Kitahara, Tsukuba City, Ibaraki Prefecture             Rusui Logic Japan Semico             In the doctor F-term (reference) 3C047 AA34 FF08                 3C058 AA09 AA11 AA14 AA19 BB02                       BB06 CB03 DA12 DA17

Claims (4)

[Claims] 1. An apparatus for performing chemical mechanical polishing of a semiconductor wafer, comprising: a wafer carrier for holding a semiconductor wafer to be polished with its surface to be polished exposed; and a cylindrical shape. A polishing roller having a polishing pad adhered on a surface thereof, wherein the polishing pad is composed of a plurality of strip-shaped portions having different polishing characteristics along the long axis direction of the cylinder, and the polishing surface of the semiconductor wafer and The polishing roller comprises: a polishing roller that contacts via a line segment having a length in the long axis direction of the cylinder; a slurry supply unit; and a controller, wherein the polishing roller has a center axis of the cylinder and a long axis direction of the cylinder. 2 is divided into two parts, and two rotations are performed with two axes that are perpendicular to the surface to be polished and that is perpendicular to the surface to be polished. At the same time, translational movement is performed over the entire surface to be polished. , Said slurry The polishing is performed while the slurry is supplied from the means to the contact portion with the surface to be polished, and the polishing pressure applied from the roller to the surface to be polished, the two rotational movements, and the translational movement are: A chemical mechanical polishing apparatus controlled by the controller according to a target polishing. 2. A method for chemical mechanical polishing of a semiconductor wafer, the method comprising: a wafer carrier holding a semiconductor wafer to be polished with its surface to be polished exposed; and a cylindrical shape. A polishing roller having a polishing pad adhered to the surface thereof, wherein the polishing pad comprises a plurality of strip-shaped portions having different polishing characteristics along the long axis direction of the cylinder, Contacting the surface to be polished of the semiconductor wafer with a line segment having a length in the long axis direction of the cylinder, and dividing the center axis of the cylinder and the length in the long axis direction of the cylinder into two parts to the polishing roller. Then, two rotational movements are performed with two axes, which are orthogonal to the central axis and perpendicular to the surface to be polished, as two rotation axes, and at the same time, a translational movement is made over the entire surface to be polished. Touch the contact part of In the step of performing polishing while receiving a supply of slurry, the polishing pressure applied from the roller to the surface to be polished, the two rotary motions, and the translational motion are, depending on the target polishing, A chemical mechanical polishing method comprising the steps of: being controlled by the controller. 3. A computer-readable storage medium in which a computer program configured by each step for realizing the method according to claim 2 is stored. 4. A computer program comprising each step for realizing the method according to claim 2.