CN102229105A - Chemically mechanical polishing method - Google Patents

Abstract

The invention discloses a chemical mechanical polishing method. The chemical mechanical polishing method comprises: A) clamping a wafer by a polishing head to perform chemical mechanical polishing on the wafer on a polishing pad; B) in the step A) Conditioning the polishing pad with a conditioner before, after, or simultaneously with, wherein the conditioning continues at least until the end of the chemical mechanical polishing. The chemical mechanical polishing method according to the embodiment of the present invention can greatly improve the uniformity of the polished thickness of the wafer surface.

Description

chemical mechanical polishing

technical field

The invention relates to the field of integrated circuits, in particular to a chemical mechanical polishing method.

Background technique

In the manufacturing process of integrated circuits, as the feature size shrinks and the number of metal interconnection layers increases, the requirements for the flatness of the wafer surface are getting higher and higher. Currently, chemical mechanical polishing is the most effective global planarization technique. Chemical mechanical polishing is to hold the wafer by the rotating polishing head and press it on the rotating polishing pad with a certain pressure. The polishing liquid composed of abrasive grains and chemical solution flows between the wafer and the polishing pad. The surface is planarized by a combination of chemical and mechanical action. In the actual chemical mechanical polishing process, the problem of uneven surface thickness of the polished wafer is more significant, and the uneven surface thickness of the wafer greatly affects the good rate of the product.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art.

After in-depth research by the inventors, it was found that due to the repeated use of the polishing pad during the chemical mechanical polishing process, the polishing residue on the polishing pad continued to increase, making the local polishing thickness of the wafer less than the predetermined standard value, resulting in the polishing of the wafer surface. Uneven thickness.

Therefore, an object of the present invention is to provide a chemical mechanical polishing method that can greatly improve the uniformity of the polished thickness of the wafer surface.

In order to achieve the above object, a chemical mechanical polishing method is proposed according to an embodiment of the present invention, and the chemical mechanical polishing method includes: A) clamping a wafer by a polishing head to perform chemical mechanical polishing on the wafer on a polishing pad; and B) using a dresser to condition the polishing pad before, after or simultaneously with the step A), wherein the conditioning continues at least until the end of the chemical mechanical polishing.

According to the chemical mechanical polishing method of the embodiment of the present invention, the polishing residue on the polishing pad can be removed in time by using the dresser to dress the polishing pad during the chemical mechanical polishing process of the wafer, In this way, the polished thickness of the entire wafer surface reaches a predetermined standard value. Therefore, the chemical mechanical polishing method according to the embodiment of the present invention can greatly improve the uniformity of the polished thickness of the wafer surface.

In addition, the chemical mechanical polishing method according to the embodiment of the present invention may have the following additional technical features:

According to an embodiment of the present invention, the chemical mechanical polishing is performed simultaneously with the trimming. In this way, the polishing residue on the polishing pad can be removed in time during the entire chemical mechanical polishing process, thereby further improving the uniformity of the polishing thickness of the wafer surface.

According to an embodiment of the present invention, the trimming starts simultaneously with the chemical mechanical polishing, and the chemical mechanical polishing ends before the trimming. In this way, the polishing residue on the polishing pad can be further removed, so as to prepare for the next chemical mechanical polishing.

According to an embodiment of the present invention, after the chemical mechanical polishing is finished, the trimming continues for 10 seconds.

According to an embodiment of the present invention, the dressing pressure of the dressing head is 0.5-5psi, the rotating speed is 30-150rpm, and the oscillation frequency is 5-30 times/minute, so that the polishing residue on the polishing pad can be removed more effectively .

According to an embodiment of the present invention, the dressing pressure of the dressing head is 0.5-2psi, the rotating speed is 60-120rpm, and the swing frequency is 8-16 times/minute, so that the polishing residue on the polishing pad can be further effectively removed .

According to an embodiment of the present invention, the chemical mechanical polishing method further includes: C) rinsing the polishing pad with water before the chemical mechanical polishing starts, and performing the chemical mechanical polishing after the rinsing is completed, Or rinse the polishing pad with water after the chemical mechanical polishing. This can more effectively remove the polishing residue on the polishing pad.

According to an embodiment of the present invention, the polishing pad is rinsed with water with a pressure greater than 10 psi, and the flow rate of the water is greater than 2 liters/minute. This can further effectively remove the polishing residue on the polishing pad.

According to an embodiment of the present invention, the polishing pad is rinsed with water at a pressure of 10-30 psi, and the flow rate of the water is 2-6 liters/minute. This can further effectively remove the polishing residue on the polishing pad.

According to an embodiment of the present invention, after the chemical mechanical polishing is finished, the rinsing is started and the trimming is continued for 10 seconds at the same time, the trimming and the rinsing are ended at the same time, wherein water with a pressure of 20 psi is used The flushing, and the flow rate of the water is 4 liters/minute.

Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

1 is a schematic diagram of chemical mechanical polishing of a wafer using a chemical mechanical polishing method according to an embodiment of the present invention;

Fig. 2 is a comparison diagram of polishing results between a chemical mechanical polishing method according to an embodiment of the present invention and an existing chemical mechanical polishing method;

3 is a flow chart of a chemical mechanical polishing method according to one embodiment of the present invention; and

FIG. 4 is a flowchart of a chemical mechanical polishing method according to another embodiment of the present invention.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

In describing the present invention, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientation or positional relationship indicated by "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than Nothing indicating or implying that a referenced device or element must have a particular orientation, be constructed, and operate in a particular orientation should therefore not be construed as limiting the invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and should not be understood as indicating or implying relative importance.

In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be mechanical connection or electrical connection, or two The internal communication of each element may be directly connected or indirectly connected through an intermediary. Those skilled in the art can understand the specific meanings of the above terms according to specific situations.

After in-depth research by the inventors, it was found that due to the repeated use of the polishing pad during the chemical mechanical polishing process, the polishing residue on the polishing pad continued to increase, making the local polishing thickness of the wafer less than the predetermined standard value, resulting in the polishing of the wafer surface. Uneven thickness.

A chemical mechanical polishing method according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 3 . As shown in FIGS. 1 and 3 , the chemical mechanical polishing method according to the embodiment of the present invention includes: A) Utilizing a polishing head 100 to hold a wafer so as to perform chemical polishing on the wafer on a polishing pad (not shown in the figure). mechanical polishing; and B) using a dresser 400 to condition the polishing pad before, after or simultaneously with step A), wherein the conditioning continues at least until the end of the chemical mechanical polishing.

According to the chemical mechanical polishing method of the embodiment of the present invention, the polishing residue on the polishing pad can be removed in time by using the dresser 400 to dress the polishing pad during the chemical mechanical polishing process of the wafer, so that This makes the polishing thickness of the entire wafer surface reach a predetermined standard value. Therefore, the chemical mechanical polishing method according to the embodiment of the present invention can greatly improve the uniformity of the polished thickness of the wafer surface.

Those skilled in the art can understand that, according to the chemical mechanical polishing method of the embodiment of the present invention, the polishing head 100, the polishing pad (the polishing pad is arranged on the polishing disc 200), the polishing liquid delivery arm 300, the dressing The device 400, polishing liquid, etc. may be known, and the polishing pad may be conditioned by known conditioning methods, so no detailed description will be given here.

In some embodiments of the present invention, the chemical mechanical polishing and the trimming can be performed simultaneously. In other words, the chemical mechanical polishing and the conditioning can start at the same time and can end at the same time. In this way, the polishing residue on the polishing pad can be removed in time during the entire chemical mechanical polishing process, thereby further improving the uniformity of the polishing thickness of the wafer surface.

In some examples of the invention, the trimming and the chemical mechanical polishing can be started simultaneously, and the chemical mechanical polishing can be ended before the trimming. Continuing to dress the polishing pad after the chemical mechanical polishing is finished can further remove the polishing residue on the polishing pad, so as to be ready for the next chemical mechanical polishing. In a specific example of the present invention, after the chemical mechanical polishing is finished, the trimming may continue for 10 seconds.

Those skilled in the art can understand that the polishing pad is dressed by using the dressing head 410 of the dresser 400 . Specifically, the trimming pressure of the trimming head 410 can be 0.5-5 psi (pounds per square inch), the rotation speed (autorotation) of the trimming head 410 can be 30-150 rpm, and the swing frequency of the trimming head 410 can be 5-30 times/min. This can more effectively remove the polishing residue on the polishing pad. Advantageously, the trimming pressure of the trimming head 410 can be 0.5-2 psi, the rotation speed of the trimming head 410 can be 60-120 rpm, and the swing frequency of the trimming head 410 can be 8-16 times/minute. Further advantageously, the trimming pressure of the trimming head 410 may be 1.0 psi, the rotational speed of the trimming head 410 may be 90 rpm, and the swing frequency of the trimming head 410 may be 12 times/min.

As shown in FIG. 4, in one embodiment of the present invention, the chemical mechanical polishing method may further include: C) before the chemical mechanical polishing starts, the polishing pad may be rinsed with water and the The chemical mechanical polishing is performed after the rinsing, or the polishing pad can be rinsed with water after the chemical mechanical polishing, so that the polishing residue on the polishing pad can be removed more effectively. Advantageously, the polishing pad can be rinsed with water at a pressure greater than 10 psi, and the flow rate of the water can be greater than 2 liters/minute. Further advantageously, the polishing pad can be rinsed with water at a pressure of 10-30 psi, and the flow rate of the water can be 2-6 liters/minute.

In a specific example of the present invention, after the chemical mechanical polishing is finished, the rinsing can be started and the trimming can be continued for 10 seconds at the same time, the trimming and the rinsing can be ended at the same time, wherein pressure can be used to The flushing is performed with 20 psi of water, and the flow rate of the water may be 4 liters/minute. In other words, the trimming can be continued for 10 seconds after the chemical mechanical polishing is finished, and the rinsing can be started immediately.

Existing methods can be used to measure the removal rate and non-uniformity of the polished thickness of the wafer surface. For example, 49 measurement points are selected on the wafer, and the film thickness measuring instrument is used to measure the thickness difference of these 49 measurement points before and after chemical mechanical polishing. Calculate the mean and standard deviation of the thickness difference of these 49 measurement points, where:

The removal rate of the polished thickness of the wafer surface=the average value of the thickness difference of 49 measurement points/chemical mechanical polishing time;

The non-uniformity of the polished thickness of the wafer surface=(the standard deviation of the thickness differences of the 49 measurement points/the average value of the thickness differences of the 49 measurement points)×100%.

FIG. 2 shows the removal rate and non-uniformity of the polished thickness of the wafer surface after chemical mechanical polishing of the wafer by using the chemical mechanical polishing method according to the embodiment of the present invention and the existing chemical mechanical polishing method. It can be seen from FIG. 2 that after the wafer is chemically mechanically polished using the existing chemical mechanical polishing method, the removal rate of the polished thickness of the wafer surface is 5689A/min (A/min), and the non-uniformity is 7.94%. After the wafer is chemically mechanically polished using the chemical mechanical polishing method according to the embodiment of the present invention, the removal rate of the polished thickness of the wafer surface is 5816A/min, and the non-uniformity is 6.49%.

Therefore, the chemical mechanical polishing method according to the embodiment of the present invention can greatly improve the removal rate of the polished thickness of the wafer surface and can greatly reduce the non-uniformity of the polished thickness of the wafer surface, that is, the uniformity of the polished thickness of the wafer surface can be greatly improved. sex.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications, substitutions and modifications can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.

Claims (10)

1. a cmp method is characterized in that, comprising:

A) utilize rubbing head clamping wafer on polishing pad, described wafer is carried out chemically mechanical polishing; With

B) in described steps A) before the beginning, utilize trimmer that described polishing pad is repaired afterwards or simultaneously, wherein said finishing continues to described chemically mechanical polishing at least and finishes.

2. cmp method according to claim 1 is characterized in that, described chemically mechanical polishing and described finishing are carried out synchronously.

3. cmp method according to claim 1 is characterized in that, described finishing and described chemically mechanical polishing begin simultaneously, and described chemically mechanical polishing finishes prior to described finishing.

4. cmp method according to claim 3 is characterized in that, after described chemically mechanical polishing finished, described finishing was proceeded 10 seconds.

5. according to each described cmp method among the claim 1-4, it is characterized in that the finishing pressure of described finishing head is that 0.5-5psi, rotating speed are that 30-150rpm, hunting frequency are 5-30 time/minute.

6. cmp method according to claim 5 is characterized in that, the finishing pressure of described finishing head is that 0.5-2psi, rotating speed are that 60-120rpm, hunting frequency are 8-16 time/minute.

7. cmp method according to claim 1 is characterized in that, also comprises:

C) before described chemically mechanical polishing begins, utilize water that described polishing pad is washed and described flushing is carried out described chemically mechanical polishing after finishing again, or after described chemically mechanical polishing finishes, utilize water that described polishing pad is washed.

8. cmp method according to claim 7 is characterized in that, utilize pressure greater than the water of 10psi described polishing pad to be washed, and the flow of described water is greater than 2 liters/minute.

9. cmp method according to claim 8 is characterized in that, utilizes pressure for the water of 10-30psi described polishing pad to be washed, and the flow of described water be the 2-6 liter/minute.

10. cmp method according to claim 7, it is characterized in that, after described chemically mechanical polishing finishes, begin to carry out described flushing and proceed described finishing 10 seconds simultaneously, described finishing and described flushing finish simultaneously, wherein utilize pressure to carry out described flushing, and the flow of described water is 4 liters/minute for the water of 20psi.

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