CN111376169A

CN111376169A - Method for cleaning polished wafer

Info

Publication number: CN111376169A
Application number: CN201811627102.0A
Authority: CN
Inventors: 李守田; 尹先升; 贾长征
Original assignee: Anji Microelectronics Technology Shanghai Co ltd
Current assignee: Anji Microelectronics Technology Shanghai Co ltd; Anji Microelectronics Shanghai Co Ltd
Priority date: 2018-12-28
Filing date: 2018-12-28
Publication date: 2020-07-07

Abstract

The invention provides a chemical mechanical polishing and cleaning method, which is characterized by comprising the following steps: (1) continuously polishing the polished wafer by using a first cleaning solution; (2) and (3) washing the polished and cleaned wafer in the step (1) at least once by using a second cleaning solution. The polishing and cleaning method is used, and residual cerium oxide particles on the surface of the wafer can be effectively removed for the wafer polished by cerium oxide, so that the particle defects on the surface of the wafer are reduced, and the cleaning effect is greatly improved; meanwhile, the using amount of the cleaning liquid is reduced, and deionized water is used as the cleaning liquid, so that the cleaning cost is greatly reduced.

Description

Method for cleaning polished wafer

Technical Field

The invention relates to the technical field of semiconductor wafer manufacturing, in particular to a method for cleaning a polished wafer.

Background

Currently, cerium-based Chemical Mechanical Polishing (CMP) slurry has been widely used for selective or non-selective CMP polishing of integrated circuits, including selective or non-selective polishing, for removing silicon-based dielectric materials, such as silicon oxide, silicon nitride, or polysilicon (also referred to as oxide silicon, nitride silicon, and polysilicon). The cerium oxide abrasive has a strong affinity for silicon-based materials such as silicon dioxide, and thus is easily adsorbed on the surface of a wafer with silicon dioxide.

The CMP polishing process typically includes two steps, polishing and cleaning, wherein one of the purposes of cleaning is to remove abrasive particles from the wafer surface to reduce particulate defects during wafer fabrication. Generally, particles on the surface of the wafer are removed by using a specific cleaning solution composition under a set cleaning method.

It has now been found that the use of a positively charged acidic ceria polishing solution has a good polishing effect on silicon oxide wafers. However, a certain amount of cerium oxide particles are adsorbed on the surface of the silicon oxide wafer polished by the polishing solution, and the silicon oxide wafer is difficult to effectively remove by the existing cleaning solution and cleaning method, so that the wafer surface has large particle defects, and the subsequent production is influenced.

Disclosure of Invention

In order to solve the above problems, the present invention provides a method for cleaning a polished wafer, wherein a specific first cleaning solution is used, a chemical mechanical polishing method is adopted, and a wafer polished by a cerium oxide polishing solution is polished and cleaned, and a rinsing process is matched, so that particle defects on the surface of the wafer are reduced.

Specifically, the invention provides a method for cleaning a polished wafer, which is characterized by comprising the following steps:

(1) continuously polishing the polished wafer by using the first cleaning solution for a preset time;

(2) and (3) washing the polished and cleaned wafer in the step (1) at least once by using a second cleaning solution.

Preferably, the first cleaning solution comprises TMAH and/or ethanolamine.

Preferably, the second cleaning solution is deionized water or TMAH.

Preferably, the mass percentage concentration of the first cleaning liquid is 5%.

Preferably, the mass percentage concentration of the second cleaning liquid is 5%.

Preferably, the polishing conditions in step (1) are a polishing pressure of 3psi, a rotational speed of the polishing table of 93rpm, a rotational speed of the polishing head of 87rpm, and a flow rate of the polishing solution of 300 ml/min.

Compared with the prior art, the invention has the advantages that:

1) by using the method of polishing and washing, residual cerium oxide particles on the surface of the wafer can be effectively removed for the wafer polished by cerium oxide, so that the particle defects on the surface of the wafer are reduced, and the cleaning effect is greatly improved;

2) the using amount of the cleaning liquid is reduced, so that the cleaning cost is greatly reduced.

Drawings

FIG. 1 is a schematic illustration of particle defects on a wafer surface after cleaning the wafer using the method of comparative example 1;

FIG. 2 is a schematic diagram illustrating particle defects on the wafer surface after cleaning the wafer by the method of example 7.

Detailed Description

The advantages of the present invention are further illustrated by the following specific examples, but the scope of the present invention is not limited to the following examples.

Table 1 lists the cleaning methods employed in comparative examples 1-17 and examples 1-7, and the included components of the first cleaning solution or the second cleaning solution used in each method. The cleaning object is PETEOS blank wafer. Wherein, the polishing and cleaning conditions are as follows: the polishing pad was a Dow IC1010, Disk was 3M company A165, polishing pressure was 3psi, platen speed was 93rpm, polishing head speed was 87rpm, slurry flow rate was 300ml/min, and polishing time was 60 seconds. The washing conditions were: the flow rate of the cleaning solution was 1400ml/min, and the cleaning time was 30 seconds.

In order to reduce the disturbance factor, in the following embodiments, the washing brush is still opened without using the washing liquid.

HPR stands for high pressure flush.

TABLE 1 comparative examples 1-17 and examples 1-7

After the cleaning was completed, the wafer surfaces cleaned in comparative examples 1 to 17 and examples 1 to 7 were tested for particle defects using a wafer surface particle defect tester KLA-color's SP 2. The specific results are shown in Table 2.

TABLE 2 results of testing for particle defects on the surfaces of wafers after cleaning comparative examples 1-17 and examples 1-7

Cleaning method	Number of defect particles on wafer surface
		Comparative example 1	64,356
Comparative example 2	66,123
		Comparative example 3	64,313
Comparative example 4	64,447
		Comparative example 5	66,230
Comparative example 6	65,753
		Comparative example 7	68,104
Comparative example 8	68,261
		Comparative example 9	67,063
Comparative example 10	67,623
		Comparative example 11	66,188
Comparative example 12	7,866
		Comparative example 13	7,005
Comparative example 14	44,134
		Comparative example 15	1,454
Comparative example 16	1,084
		Comparative example 17	4,110
Example 1	313
		Example 2	548
Example 3	282
		Example 4	390
Example 5	367
		Example 6	670
Example 7	271

As can be seen from table 2, the cleaning method according to the embodiment of the present invention greatly reduces the particle defects on the wafer surface as compared to the comparative example. In the cleaning results of the comparative examples, the number of defect particles on the wafer surface was 1000 or more and the maximum number was 68261 (comparative example 8), whereas in the cleaning results of the examples of the present invention, the number of defect particles on the wafer surface was 700 or less and the minimum number was 271. The cleaning method provided by the embodiment of the invention can obviously reduce the particle defects on the surface of the wafer.

In addition, whether a polishing cleaning step is used or not has a great influence on the number of defect particles on the surface of the wafer after cleaning. As can be seen from comparative examples 1 to 11, the number of defect particles was higher than 60000 without using the polish cleaning step, regardless of the cleaning liquid selected; in contrast, in comparative examples 12 to 17, the number of defect particles on the wafer surface was greatly reduced after the polishing cleaning step was used, and the number of defect particles was 45000 or less. This shows that the use of a polishing cleaning step can greatly reduce the particle defects on the wafer surface; comparative examples 12, 13, 15, 16 and 17 were further washed after polishing and cleaning, and the number of defect particles on the wafer surface was further reduced to less than 10000 compared with comparative example 14 in which only one polishing and cleaning step was performed.

It can be seen from examples 1 to 7 of the present invention that performing two rinsing steps can achieve a better effect of reducing the particle defects on the wafer surface than performing one rinsing step under the same conditions. It is generally considered that, with the aid of more cleaning steps, more excellent clear results are obtained, but as can be seen from the cleaning results of comparative example 13, the use of HPR leads to an increase in the number of particles on the wafer surface in the cleaning results under otherwise identical conditions, and it is seen that the HPR function is not good for reducing particle defects on the wafer surface.

In addition, refer to fig. 1 and 2, which are comparative graphs of the cleaning effect of comparative example 1 and example 7 of the present invention. As can be seen from the figure, by using the cleaning method of the embodiment 7 of the present invention, compared with the comparative example 1, the defect particles on the wafer surface are greatly reduced, the particle defects on the wafer surface are effectively improved, and the requirements of the subsequent production process are met.

In summary, the best cleaning method in the present invention is: and performing a polishing and cleaning step by using tetramethylammonium hydroxide as a first cleaning solution, and performing a rinsing step by using deionized water as a second cleaning solution. The rinsing step is repeated at least twice.

It should be noted that the contents in the present invention are all the contents by mass percentage unless otherwise specified.

It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are given by way of illustration only, since the invention is not limited to the specific embodiments described above. Any equivalent modifications and substitutions to those skilled in the art are also within the scope of the present invention. Accordingly, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be covered by the present invention.

Claims

1. A method for cleaning a polished wafer is characterized by comprising the following steps:

(1) continuously polishing the polished wafer by using the first cleaning solution;

2. The method of claim 1,

the first cleaning solution comprises TMAH and/or ethanolamine.

3. The method of claim 1,

the second cleaning solution is deionized water or TMAH.

4. The method of claim 1,

the mass percentage concentration of the first cleaning liquid is 5%.

5. The method of claim 1,

the mass percentage concentration of the second cleaning liquid is 5%.

6. The method of claim 1,

the polishing conditions in the step (1) are that the polishing pressure is 3psi, the rotating speed of the polishing table is 93rpm, the rotating speed of the polishing head is 87rpm, and the flow rate of the polishing solution is 300 ml/min.