阅读说明：本技术 化学机械研磨过程中稳定铜研磨速率的方法 (Method for stabilizing copper grinding speed in chemical mechanical grinding process ) 是由 王凯 孙延松 严钧华 王春伟 于 2019-11-26 设计创作，主要内容包括：本发明公开了一种化学机械研磨过程中稳定铜研磨速率的方法,包括：利用电化学镀铜清洗液对研磨垫进行冲洗；对研磨垫进行整理和超纯水冲洗；对晶圆进行铜研磨；晶圆研磨结束后,利用电化学镀铜清洗液对研磨垫进行冲洗,对研磨垫进行整理和超纯水冲洗。本发明在铜研磨之前使用电化学镀铜清洗液对研磨垫进行预冲洗,而且在铜研磨完成后再次使用电化学镀铜清洗液对研磨垫进行冲洗,这样可以提高研磨垫上研磨副产物的去除率,有效地保证研磨垫的持续清洁度,有效地降低铜研磨速率发生异常波动的几率,使铜研磨制程的工艺能力指数稳定度显著提高。(The invention discloses a method for stabilizing copper grinding rate in a chemical mechanical grinding process, which comprises the following steps: washing the grinding pad by using an electrochemical copper plating cleaning solution; finishing and rinsing the grinding pad with ultrapure water; carrying out copper grinding on the wafer; after the wafer is ground, the grinding pad is washed by using the electrochemical copper plating cleaning solution, and the grinding pad is cleaned and washed by ultrapure water. The method uses the electrochemical copper plating cleaning solution to pre-flush the grinding pad before copper grinding, and uses the electrochemical copper plating cleaning solution to flush the grinding pad after copper grinding is finished, so that the removal rate of grinding byproducts on the grinding pad can be improved, the continuous cleanliness of the grinding pad is effectively ensured, the probability of abnormal fluctuation of the copper grinding rate is effectively reduced, and the process capability index stability of the copper grinding process is obviously improved.)

1. A method for stabilizing the polishing rate of copper in the chemical mechanical polishing process is characterized by comprising the following steps:

step 1, washing a grinding pad by using an electrochemical copper plating cleaning solution;

step 2, carrying out copper grinding on the wafer;

and 3, after the wafer is polished, washing the polishing pad by using the electrochemical copper plating cleaning solution.

2. The method of claim 1, wherein between step 1 and step 2, the polishing pad is conditioned and rinsed with ultra-pure water.

3. The method of claim 1, wherein after step 3, the polishing pad is conditioned and rinsed with ultra-pure water.

4. The method of claim 1, wherein the rinsing step 1 is performed with an electrochemical copper plating cleaning solution with a flow rate of 80-100 mL/min.

5. The method of claim 4, wherein the rinsing is performed with an electrochemical copper plating cleaning solution flow rate of 90 mL/min.

6. The method of claim 4, wherein the rinsing time is 5 s-25 s.

7. The method of claim 6, wherein the rinsing time is 8 s.

8. The method as claimed in claim 1, wherein the rinsing step 3 is performed by using an electrochemical copper plating cleaning solution with a flow rate of 200 mL/min.

9. The method of claim 8, wherein the rinsing time in step 3 is 5-25 s.

10. The method of claim 9, wherein the rinsing time is 16 s.

Technical Field

The invention relates to a process control technology of microelectronic and semiconductor integrated circuits, in particular to a method for stabilizing copper grinding speed in a chemical mechanical grinding process.

Background

As device dimensions continue to shrink, lithographic exposure resolution relatively increases, and with the reduction in exposure depth of field, tolerance for topography of the wafer surface becomes more stringent. The chemical mechanical polishing method is a technology capable of providing global planarization of very large scale integrated circuit process, and its unique anisotropic polishing property can be used for planarization of wafer surface contour, and can also be applied to the manufacture of vertical and horizontal metal wire connection, the manufacture of element shallow groove isolation and advanced element in front-stage process, the planarization of micro electro mechanical system and the manufacture of flat panel display, etc. by means of metal polishing.

The conventional chemical mechanical polishing apparatus basically comprises a polishing table (PolishingTable) for polishing the chip and a Carrier head (Carrier) for carrying the chip to be polished. Wherein the Polishing head holds the back side of the chip and then presses the front side of the chip against a Polishing table on which a layer of Polishing Pad (Polishing Pad) is laid. When performing chemical mechanical polishing, the polishing table rotates along a fixed direction, and the motion direction of the polishing head is, for example, linear movement or rotation along a fixed direction and the same angular velocity as the polishing table, and during the polishing, a polishing Slurry (Slurry) is added to polish the surface of the chip.

In the era of ultra-large scale integrated circuits (VLSI) developing to less than 0.13 μm, the time delay caused by impedance and the like needs to be overcome effectively to increase the execution speed of the chip, so that materials with low dielectric constant and metallic copper are mostly adopted as the interconnect structure.

In the traditional method, a polishing pad is finished by a polishing pad finisher (Dresser) and washed by ultrapure water (DIW), but in the cleaning process, the removal rate of by-products generated by chemical mechanical polishing is unstable, so that the copper polishing rate of a monitoring item (Offline) of a machine table and a monitoring item (Inline) of an engineering sheet or a product is easy to change suddenly, and the safety and the stability of a copper polishing process are insufficient. Therefore, there is a need for an enhanced method for removing the copper polishing by-products, so as to maintain the cleanliness of the polishing pad and stabilize the copper polishing rate of the cmp apparatus.

Disclosure of Invention

The invention aims to provide a method for stabilizing the copper grinding rate in the chemical mechanical grinding process, which can solve the problem that the copper grinding rate is suddenly changed due to unstable removal rate of byproducts in the cleaning process of the conventional chemical mechanical grinding process.

In order to solve the above technical problems, the method for stabilizing the polishing rate of copper in the chemical mechanical polishing process provided by the invention comprises the following steps:

step 1, washing a grinding pad by using an electrochemical copper plating cleaning solution;

step 2, carrying out copper grinding on the wafer;

and 3, after the wafer is polished, washing the polishing pad by using the electrochemical copper plating cleaning solution.

Preferably, between step 1 and step 2, the polishing pad is conditioned and rinsed with ultra-pure water.

Preferably, after step 3, the polishing pad is conditioned and rinsed with ultra-pure water.

Preferably, in step 1, the electrochemical copper plating cleaning solution with a flow rate of 80mL/min to 100mL/min is used for washing.

Preferably, the rinsing is performed with an electrochemical copper plating rinse solution at a flow rate of 90 mL/min.

Further, the rinsing time is 5 to 25 seconds.

Preferably, the rinsing time is 8 s.

Preferably, in step 3, the electrochemical copper plating cleaning solution with the flow rate of 200mL/min is used for washing.

Further, in step 3, the washing time is 5 to 25 seconds.

Preferably, the rinsing time is 16 s.

Compared with the prior art, the method has the advantages that the polishing pad is pre-washed by the electrochemical copper plating cleaning solution before copper polishing, and the polishing pad is washed by the electrochemical copper plating cleaning solution after copper polishing is finished, so that the removal rate of polishing by-products on the polishing pad can be improved, the continuous cleanliness of the polishing pad is effectively ensured, the probability of abnormal fluctuation of the copper polishing rate is effectively reduced, and the process capability index (Cpk) stability of the copper polishing process is obviously improved.

Drawings

FIG. 1 is a flowchart of a method according to a first embodiment of the present invention;

FIG. 2 is a flowchart of a method according to a second embodiment of the present invention;

FIG. 3 is a topographical map of the monitoring project (Offline) copper removal rate of the machine itself over the life cycle of a retaining Ring (Retainer Ring);

FIG. 4 is a graph comparing the process capability index of the conventional method and the copper polishing process of the present invention.

Detailed Description

Other advantages and effects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown in the accompanying drawings, wherein the specific embodiments are by way of illustration. In the following description, specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced or applied in different embodiments, and the details may be based on different viewpoints and applications, and may be widely spread and replaced by those skilled in the art without departing from the spirit of the present invention.