1. A chemical mechanical polishing method is characterized by comprising the following steps:

providing a grinding pad and a wafer to be ground;

carrying out first grinding on the wafer to be ground on the grinding pad;

removing the wafer after the first grinding from the surface of the grinding pad;

cleaning the grinding pad to remove the residues of the first grinding;

and carrying out secondary grinding on the wafer after the primary grinding on the cleaned grinding pad.

2. The chemical mechanical polishing method of claim 1, further comprising a polishing head, wherein the wafer to be polished is loaded on the polishing head.

3. The chemical mechanical polishing method of claim 2, wherein the first polishing step comprises: and driving the grinding head, wherein the grinding head drives the wafer to be ground to grind on the grinding pad, and in the grinding process, adding a first grinding fluid to the grinding pad.

4. The chemical mechanical polishing method of claim 2, further comprising: the method for adding the first grinding liquid to the grinding pad comprises the following steps: and conveying the first grinding fluid to the grinding pad through the drainage groove.

5. The chemical mechanical polishing method of claim 3, wherein the first polishing slurry comprises a chemical polishing slurry; the chemical grinding fluid comprises hydrogen peroxide and grinding particles, and the flow rate of the first grinding fluid is 200 ml/min to 400 ml/min.

6. The chemical mechanical polishing method of claim 3, wherein the residue of the first polishing comprises the first polishing slurry.

7. The chemical mechanical polishing method of claim 1, further comprising, after cleaning the polishing pad to remove the residue of the first polishing, before performing the second polishing: detecting the residue of the first grinding on the grinding pad.

8. The chemical mechanical polishing method of claim 2, wherein in the first polishing, the pressure between the polishing head and the polishing pad is 1 psi-2 psi, the rotation speed of the polishing head is 30 rpm-100 rpm, and the motion time of the polishing head is 50 seconds-200 seconds.

9. The chemical mechanical polishing method of claim 1, wherein the step of cleaning the polishing pad comprises cleaning the polishing pad with pure water at a flow rate of 300 ml/min to 500 ml/min for a cleaning time of 5 seconds to 15 seconds.

10. The chemical mechanical polishing method of claim 2, wherein the second polishing step comprises: and driving the grinding head, wherein the grinding head drives the wafer subjected to the first grinding to grind on the cleaned grinding pad, and in the grinding process, adding a second grinding fluid to the cleaned grinding pad.

11. The chemical mechanical polishing method of claim 10, wherein the second polishing slurry comprises water, and the flow rate of the second polishing slurry is 200 ml/min to 400 ml/min.

12. The chemical mechanical polishing method of claim 2, wherein in the second polishing, the pressure between the polishing head and the polishing pad is 0psi to 1psi, the rotation speed of the polishing head is 30rpm to 80rpm, and the motion time of the polishing head is 5 seconds to 15 seconds.

Background

In semiconductor technology, various circuit device structures are processed and manufactured on a wafer, so that the wafer becomes an IC product with specific electrical functions. For computer products, the quality of the wafer affects the performance of the entire computer.

At present, in the manufacturing process of semiconductor products, wafers are the basic semi-finished products of the current integrated circuits, and the quality of the wafer processing directly influences the quality of the semiconductor finished products. In the wafer processing process, the wafer surface needs to be polished to remove mark residues or edge residues on the wafer surface.

Chemical Mechanical Polishing (CMP) process is an important surface planarization technique. The chemical mechanical polishing process integrates the advantages of chemical polishing and mechanical polishing, can ensure the removal efficiency of the residues on the surface of the wafer, and simultaneously obtains a perfect surface of the wafer with high surface flatness.

How to remove mark residues or edge residues on the surface of a wafer based on a chemical mechanical polishing method without leaving defects on the wafer so as to ensure the flatness of the surface of the wafer and the removal efficiency of the residues on the surface of the wafer is a problem which needs to be solved urgently at present.

Disclosure of Invention

The invention provides a chemical mechanical polishing method, which avoids mark residue or edge residue on the surface of a wafer after chemical mechanical polishing so as to ensure the cleanliness and the flatness of the surface of the wafer.

In order to solve the above problems, the present invention provides a chemical mechanical polishing method, comprising: providing a grinding pad and a wafer to be ground; carrying out first grinding on the wafer to be ground on the grinding pad; removing the wafer after the first grinding from the surface of the grinding pad; cleaning the grinding pad to remove the residues of the first grinding; and carrying out secondary grinding on the wafer after the primary grinding on the cleaned grinding pad.

Optionally, the polishing apparatus further comprises a polishing head, and the wafer to be polished is loaded on the polishing head.

Optionally, the first grinding method includes: and driving the grinding head, wherein the grinding head drives the wafer to be ground to grind on the grinding pad, and in the grinding process, adding a first grinding fluid to the grinding pad.

Optionally, the method further includes: the method for adding the first grinding liquid to the grinding pad comprises the following steps: and conveying the first grinding fluid to the grinding pad through the drainage groove.

Optionally, the first polishing solution comprises a chemical polishing solution; the chemical grinding fluid comprises hydrogen peroxide and grinding particles, and the flow rate of the first grinding fluid is 200 ml/min to 400 ml/min.

Optionally, the residue of the first grinding comprises the first grinding fluid.

Optionally, after the polishing pad is cleaned to remove the residue of the first polishing, before the second polishing, the method further includes: detecting the residue of the first grinding on the grinding pad.

Optionally, in the first polishing, the pressure between the polishing head and the polishing pad is 1psi to 2psi, the rotation speed of the polishing head is 30rpm to 100rpm, and the movement time of the polishing head is 50 seconds to 200 seconds.

Optionally, in the step of cleaning the polishing pad, a cleaning solution used for cleaning the polishing pad is pure water, a flow rate of the cleaning solution is 300 ml/min to 500 ml/min, and a cleaning time is 5 seconds to 15 seconds.

Optionally, the second grinding method includes: and driving the grinding head, wherein the grinding head drives the wafer subjected to the first grinding to grind on the cleaned grinding pad, and in the grinding process, adding a second grinding fluid to the cleaned grinding pad.

Optionally, the second grinding fluid includes water, and the flow rate of the second grinding fluid is 200 ml/min to 400 ml/min.

Optionally, in the second polishing, the pressure between the polishing head and the polishing pad is 0psi to 1psi, the rotation speed of the polishing head is 30rpm to 80rpm, and the movement time of the polishing head is 5 seconds to 15 seconds.

Compared with the prior art, the technical scheme of the invention has the following advantages:

after a wafer to be ground is ground on a grinding pad for the first time, the wafer after the first grinding is moved out of the surface of the grinding pad, the grinding pad is cleaned, residues of the first grinding are removed, and then the wafer after the first grinding is ground on the cleaned grinding pad for the second time. The grinding method removes the residues left on the grinding pad during the first grinding, ensures that no residues left on the grinding pad during the second grinding are left, avoids the damage of the residues left on the grinding pad during the first grinding to the surface of the wafer during the second grinding, and improves the grinding quality of the wafer.

Drawings

Fig. 1-3 are process diagrams of chemical mechanical polishing according to an embodiment.

Fig. 4 to 8 are process diagrams of chemical mechanical polishing according to an embodiment of the present invention.

Detailed Description

When there is mark residue or edge residue on the wafer surface, in order to remove the residue on the wafer surface and ensure the planarization of the wafer surface, a chemical mechanical polishing method is usually used to remove the residue on the wafer surface. The common method is to polish the wafer surface with a chemical polishing slurry for the first time, and then polish the wafer surface with water as the polishing slurry for the second time, thereby reducing the particle defects on the wafer.

The specific chemical mechanical polishing method comprises the following steps:

referring to fig. 1, a polishing apparatus 1 is provided having a polishing pad 2, a polishing head 3, and drainage channels 4 thereon.

The polishing pad 2 follows the polishing apparatus 1 to move counterclockwise.

The grinding head 3 performs a grinding motion along a path according to the direction of the bidirectional arrow, a wafer to be ground is loaded on the grinding head 3, and the wafer to be ground is chemically and mechanically ground on the grinding pad 2 under the driving of the grinding head 3.

The drainage grooves 4 introduce the polishing liquid 41 into the polishing pad 2 near the polishing head 3.

The specific chemical mechanical polishing process comprises the following steps:

referring to fig. 1, first grinding:

the grinding head 3 carries the wafer to be ground to carry out the first grinding motion in the range between the two-way arrows;

in the first polishing process, the drainage grooves 4 continuously introduce a first polishing liquid 41, i.e. a chemical polishing liquid, onto the polishing pad 2 near the polishing head 3, and after a period of polishing, the first polishing is completed;

referring to fig. 2 and 3, wherein fig. 2 is a top view of fig. 3 and fig. 3 is a front view of fig. 2 with the grinding bit removed; and (3) second grinding:

the drainage grooves 4 continuously introduce a second polishing solution 42, i.e. water, onto the polishing pad 2 near the polishing head 3;

the polishing head 3 carries the wafer 31 to be polished to perform a second polishing motion within the range of the polishing pad 2, and after a period of time, the second polishing is completed, thus completing the chemical mechanical polishing of the wafer.

The inventor finds that, in the method of reducing Particle defects (Particle defects) on the surface of a wafer after polishing by using a second polishing, i.e. water polishing, after the first polishing, i.e. chemical liquid polishing, when water directly contacts the polishing pad 2 and the wafer to be polished, referring to fig. 3, the polishing pad 2 has a lot of residual chemical polishing liquid 41, when the chemical polishing liquid encounters water 42, the concentration and pH of the chemical polishing liquid change instantaneously, so that chemical corrosion is generated on the surface of the wafer to be polished, and when the wafer to be polished rubs on the polishing pad 2, the surface of the wafer to be polished is easily corroded, thereby reducing the quality of the surface of the wafer after polishing.

The inventor researches and discovers that after a wafer to be ground is ground for the first time, the wafer after the first grinding is moved out of the surface of a grinding pad, the grinding pad is cleaned, residues after the first grinding on the grinding pad are removed, and then the wafer after the first grinding is ground for the second time on the cleaned grinding pad, so that the residues left by the first grinding cannot exist in the process of the second grinding, the damage to the wafer to be ground in the process of the second grinding by the residues after the first grinding is avoided, the quality of the surface of the ground wafer is improved, the damage to the surface of the wafer is reduced, and the production efficiency is improved.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Fig. 4 to 8 are process diagrams of chemical mechanical polishing according to an embodiment of the present invention.

Referring first to fig. 4 and 5, a polishing apparatus 100 is provided, wherein the polishing apparatus 100 has a polishing pad 200, a polishing head 300, and a drainage groove 400.

Fig. 4 is a plan view of fig. 5, and fig. 5 is a front view of fig. 4 with the polishing head removed.

In this embodiment, the polishing head 300 is loaded with a wafer 301 to be polished.

In this embodiment, with continued reference to fig. 4, the first grinding method includes: the polishing head 300 is driven, the polishing head 300 drives the wafer to be polished to polish on the polishing pad 200, and during the polishing process, the first polishing solution 401 is delivered to the polishing pad 200 through the drainage groove 400.

In this embodiment, the polishing path S1 adopted by the polishing head 300 in the first polishing process is described.

In this embodiment, the first polishing slurry 401 includes a chemical polishing slurry; the chemical grinding fluid 401 comprises hydrogen peroxide and grinding particles, and the flow rate of the first grinding fluid is 200 ml/min to 400 ml/min.

In this embodiment, the first polishing liquid 401 is a chemical polishing liquid, and aims to remove the residue of the marker or the residue of the impurity on the surface of the wafer to be polished by using the dual functions of chemistry and machinery in the polishing process, so that the polished wafer can meet the use requirement.

In this embodiment, in the first polishing, the pressure between the polishing head and the polishing pad is 1psi to 2psi, the rotation speed of the polishing head is 30rpm to 100rpm, and the movement time of the polishing head is 50 seconds to 200 seconds.

Referring to fig. 6, the wafer after the first polishing is removed from the surface of the polishing pad 200, and the polishing pad 200 is cleaned to remove the residue of the first polishing.

In this embodiment, the polishing head 300 is driven to move the wafer after the first polishing out of the surface of the polishing pad 200, so as to clean the surface of the polishing pad 200 after the first polishing.

In this embodiment, the purpose of removing the wafer after the first polishing from the polishing pad 200 is to separate the surface of the wafer after the first polishing from the surface of the polishing pad 200, so that the surface of the wafer after the first polishing is not damaged when the polishing pad 200 is cleaned later.

After the wafer after the first polishing is moved out of the polishing pad 200, the polishing pad 200 is cleaned to remove the residue of the first polishing.

In this embodiment, in the step of cleaning the polishing pad 200, the cleaning liquid used for cleaning the polishing pad is pure water, the flow rate of the cleaning liquid is 300 ml/min to 500 ml/min, and the cleaning time is 5 seconds to 15 seconds.

When the cleaning time is less than 5 seconds, the residue of the first polishing on the polishing pad 200 cannot be completely removed because the cleaning time is too short; when the washing time is more than 15 seconds, the washing time is too long, resulting in a reduction in production efficiency.

When the flow rate of the cleaning liquid 500 is less than 300 ml/min, the flow rate of the cleaning liquid 500 is too small to remove the first-time polishing residue on the polishing pad 200; when the flow rate of the cleaning solution 500 is greater than 500 ml/min, the impact force on the polishing pad 200 is too large due to too large flow rate of the cleaning solution 500, which affects the subsequent second polishing.

In this embodiment, the first polishing residue includes the first polishing slurry.

In this embodiment, after the first polished wafer is moved out of the surface of the polishing pad 200, the polishing pad 200 is cleaned, so that on one hand, the residues of the first polishing on the polishing pad 200 can be removed completely, and a good polishing environment is provided for the second polishing; on the other hand, the wafer after the first polishing is moved out of the surface of the polishing pad 200, so that when the polishing pad 200 is cleaned, when the residue after the first polishing meets the cleaning solution, the concentration and the pH of the residue after the first polishing change instantaneously, and a chemical corrosion effect on the surface of the wafer after the first polishing cannot be generated, so that the surface quality of the wafer after the polishing can be improved, and the damage to the surface of the wafer can be reduced.

Referring to fig. 7 and 8, the wafer after the first polishing is polished for the second time on the cleaned polishing pad.

Fig. 7 is a plan view of fig. 8, and fig. 8 is a front view of fig. 7 with the polishing head removed.

In this embodiment, after cleaning the polishing pad 200 to remove the residue of the first polishing, before performing the second polishing, the method further includes: the residue of the first polishing on the polishing pad 200 is detected.

In this embodiment, the method for detecting the residue after the first grinding includes: chemical composition detection, and charge detection of the wafer surface.

In this embodiment, the wafer 301 to be polished is polished for the first time to form a wafer 302.

In this embodiment, the second grinding method includes: and driving the polishing head 300, wherein the polishing head 300 drives the wafer after the first polishing to polish on the cleaned polishing pad, and in the polishing process, adding a second polishing solution to the cleaned polishing pad.

In this embodiment, the second slurry 402 includes water, and the flow rate of the second slurry 402 is 200 ml/min to 400 ml/min.

When the flow rate of the second polishing slurry 402 is less than 200 ml/min, the flow rate of the second polishing slurry 402 is too small to have enough polishing slurry, so that the particle defects left on the surface of the wafer after the first polishing cannot be removed during the polishing process; when the flow rate of the second polishing liquid 402 is greater than 400 ml/min, the flow rate of the second polishing liquid 402 is too high, and compared with the active metal, the active metal surface is easily oxidized, which affects the quality of the second polishing.

In this embodiment, in the second polishing, the pressure between the polishing head and the polishing pad is 0psi to 1psi, the rotation speed of the polishing head is 30rpm to 80rpm, and the movement time of the polishing head is 5 seconds to 15 seconds.

In this embodiment, in the first polishing, the rotation speed of the polishing head 300 is different from the rotation speed of the polishing head 300 in the second polishing, because the purpose of the two polishing processes is different, the purpose of the first polishing is to thin the wafer to be polished and remove traces on the surface of the wafer to be polished, and the purpose of the second polishing is to remove particle defects left on the surface of the wafer after the first polishing, so that the wafer after the two times of polishing can meet the use condition.

In this embodiment, referring to fig. 8, after the polishing pad is cleaned, when the wafer 302 after the first polishing is subjected to the second polishing on the polishing pad, only the second polishing liquid 402 is present between the wafer 302 after the first polishing and the polishing pad 200, and the first polishing liquid 401 is not remained, after the wafer 301 to be polished is subjected to the second polishing, the particle defects and corrosion defects on the surface are greatly reduced, the surface quality of the finally obtained wafer is greatly improved, and the wafer has a good application prospect.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.