CMP polisher substrate removal control mechanism and method

ABSTRACT

A slurry removal control mechanism for a CMP polisher is provided. After slurry dispense has been terminated, a high pressure fluid spray removes the slurry from the polishing pad, while the plated causes the pad to rotate at a high rpm rate, thus clearing the slurry from contact with the wafer. Additionally, there is provided a slurry dispense bar including high pressure spray nozzles for providing a high pressure spray upon slurry dispense termination.

INFORMATION

DETAILED DESCRIPTION OF THE INVENTION

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of the inventions, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the inventions is thereby intended, such alterations and further modifications of the principles of the inventions as illustrated therein being contemplated as would normally occur to one skilled in the art to which the inventions relate.

Referring now to FIGS. 3 and 4, there is shown one embodiment of the slurry dispense bar with high pressure spray of the present inventions. Slurry dispense bar includes a slurry dispense tubes and and a high pressure spray tube . If desired one of slurry dispense tubes and could be used to dispense deionized water, or other fluids. The bar additionally includes a spray guard located over the high pressure spray tube , which prevents excessive splashing of the high pressure liquid spray. In the present embodiment the slurry dispense tubes are located on the body of the high pressure spray tube above the splash guard . Nozzles are exemplary of the delivery holes in high pressure spray portion from which the high pressure liquid is sprayed. Hole size for the slurry dispense holes and the high pressure fluid holes can be adjusted, as desired. In one particular embodiment of the present inventions, the high pressure fluid holes have a diameter of ¼ inch.

The slurry dispense bar is supported from the arm . In one embodiment of the present inventions, the arm is mounted to a clip which engages the bar . Alternatively, the arm may be connected to the bar in other ways, such as by direct bolting, welding or forming or machining with the bar. In the embodiment including clip , the arm is hingedly connected to the clip via a ferrule and bolt combination . Similarly, in the present embodiment, the arm is hingedly connected to a mounting bracket , via the ferrule and bolt combination . The bracket may be mounted to the CMP machine. Arm is hinged at hinge bolts and so that slurry dispense bar can be positioned as desired.

A high pressure fluid tube brings a high pressure fluid into the high pressure spray portion of the slurry dispense bar . Low pressure slurry and/or deionized water are brought into the slurry dispense bar by tubes and , respectively.

Referring now to FIG. 5 there is a schematic diagram of the high pressure spray portion of the slurry dispense bar with high pressure spray. A solenoid controls the table rinse using the high pressure fluid, which in one embodiment shown in FIG. 5 is deionized water. A compressed dry air source controls the activation of the solenoid based on programmed logic in the CMP machine. When activated, solenoid opens a valve connecting high pressure fluid tube to high pressure fluid tube . A regulator regulates the pressure on the fluid tube and is adjusted based on feedback. A pressure gauge monitors the pressure of the fluid in tube from between 0 and 20 PSI. In a preferred embodiment of the present inventions the high pressure spray is between 10 and 20 PSI. In a more preferred embodiment of the present inventions, the high pressure spray is about 14 PSI. The pressure gauge may additionally provide the information to the regulator to keep the fluid pressure regulated. The high pressure tube is connected to the dispense bar high pressure spray tube ( of FIG. 4) including high pressure nozzles.

Referring now to FIGS. 6A and 6B, there will be described a method for using a slurry bar with high-pressure spray. Referring to FIG. 6A, wafers are inversely mounted on the carrier arms . The slurry is dispensed onto the pad through a slurry dispense tune on the spray bar . The wafer carriers bias the wafers against the pad . During this time both the pad and the wafer carriers are rotating, with the pad rotating between 30-60 RPM.

Referring now to FIG. 6B, slurry dispense is terminated by turning off a pump, which will stop the flow of slurry on to the pad. After the slurry dispense process is terminated, the wafer substrate is still exposed to the slurry and pad. At this time the solenoid ( of FIG. 5) is activated and a high pressure fluid is sprayed onto the pad via the high pressure spray portion of the slurry dispense bar , while the wafer is still in contact with the slurry on the pad. In the present embodiment, the fluid is deionized water, however other fluids may be used, such as solvent, low pH or high pH chemicals and/or mixtures of those chemicals and or deionized water. During the high pressure spray, in the present embodiment of the invention, the pad is rotated at a high speed of RPMs, such as between 60-200 RPMs. More preferably, the pad rotates between 90 and 120 RPMs. Additionally, in one particular embodiment the high-pressure fluid is at 14 PSI. However it can be seen that the removal rate of the slurry, and thus of the substrate, can be adjusted by adjusting the pressure of the high-pressure fluid. By using high-pressure water flowing through the nozzles on the spray bar, onto the surface of the pad while rotating at a high RPM, the removal rate of the substrate will be enhanced. Additionally the quick removal of the residue chemical from the pad surface will increase the removal of particles and defects left on the surface of the pad during the CMP process. The high-pressure fluid will quickly remove the residue and/or stagnate slurry from the pad. The quick removal of the chemical from the pad results in an increase in controllability of the chemical or slurry reacting with the substrate. This improvement in uniformity of the removal rate will enhance the controllability of the CMP process, which will result in an improvement in device reliability and wafer die yields. Another benefit from the removal control mechanism of the present invention is a reduction in microdefects in the substrate, which results in an improvement in wafer die yield. In the above-described embodiment, the high-pressure stream of fluid removes the residue slurry from the surface of the pad within one to three seconds. The volume and pressure of chemical to be sprayed on the pad will have an effect on the time to remove the residue slurry from the pad.

Referring now to FIG. 7, there is shown a polish rate standard deviation for tungsten wafers showing the experimental results before and after the use of the spray bar of the present inventions. As shown, it was found that the polish rate standard deviation before the spray bar was 8.2% versus 6.1% after the spray bar was installed.

Additionally, referring now to FIG. 8, there is shown the prior art removal method defect density as compared to the high-pressure spray bar defect density. As shown, experimentally use of the slurry dispense bar with high-pressure spray of the present inventions provides for a 15.15% average reduction in defect density.

While the inventions have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that a changes and modifications that come within the spirit of the invention are desired to be protected.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

Prior art FIG. 1A shows a partial perspective view of a prior art CMP machine.

Prior art FIG. 1B shows a partial enlarged view of the slurry and water tubes of the prior art CMP machine of FIG. 1A taken on the dotted line.

FIG. 2 shows a partial side view of a wafer held over a portion of the rotating pad with a slurry therebetween.

FIG. 3 shows a top view of a slurry dispense bar with high pressure spray in accordance with one embodiment of the present inventions.

FIG. 4 shows a perspective view of the slurry dispense bar with high pressure spray of FIG. .

FIG. 5 shows a schematic diagram of the high pressure spray portion of the slurry dispense bar with high pressure spray in accordance with one embodiment of the present inventions.

FIG. 6A shows a partial perspective view of a CMP machine including the slurry dispense bar with high pressure spray in accordance with one embodiment of the present invention.

FIG. 6B shows a partial perspective view of a CMP machine including the slurry dispense bar with high pressure spray in accordance with one embodiment of the present invention.

FIG. 7 shows a graph of standard deviation in polish rate before and after the installation of a slurry dispense bar with high pressure spray in accordance with one embodiment of the present invention.

FIG. 8 is a bar showing the defect density results of the standard slurry tube method and the slurry dispense bar with high pressure spray method in accordance with one embodiment of the present inventions.

CLAIMS

1. A method for clearing slurry from a polishing pad in a CMP process, comprising: placing a wafer substrate in contact with a polishing pad; rotating said polishing pad; providing a slurry dispense bar including a high pressure spray portion and a slurry dispense portion located over the polishing pad; dispensing slurry from said slurry dispense bar on said polishing pad while said pad is rotating with said wafer substrate in contact with said pad; terminating slurry dispense; and while said wafer substrate is on the pad, spraying a high pressure fluid to remove slurry from between said water substrate and said pad with said high pressure spray portion of said slurry dispense bar.

2. The method of claim 1, wherein said high pressure spray includes water and is between 10 and 20 PSI.

3. The method of claim 2, wherein said high pressure spray is about 14 PSI.

4. The method of claim 1, including: rotating said pad at a high speed during said spraying step.

5. The method of claim 4, wherein said high speed is between 90 and 120 RPMs.

6. The method of claim 1, wherein said slurry dispense bar includes a splash guard located above said high pressure spray portion.

7. The method or claim 6, wherein said slurry dispense portion is located above said splash guard.

8. The method of claim 7, including a second slurry dispense portion located above said splash guard.

9. A method for clearing slurry from a polishing pad in a CMP process, comprising: placing a wafer substrate in contact with a polishing pad; rotating said polishing pad at a first speed; dipensing slurry onto said polishing pad while said pad it rotating with said wafer substrates in contact with said pad; terminating slurry dispense; while said wafer substrate is on the pad, spraying a high pressure fluid around said wafer substrate to remove slurry from between said wafer substrate and said pad using said high pressure spray portion of said slurry dispense bar; and rotating said pad at a second speed during said spraying step.

10. The method of claim 9, wherein said high pressure spray is between 10 and 20 PSI.

11. The method of claim 10, wherein said second speed is between 60 and 200 RPMs.

12. The method of claim 10, wherein said second speed is between 90 and 120 RPMs.

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