Chemical mechanical polishing solution and application thereof

Abstract

The invention provides a chemical mechanical polishing solution. The chemical mechanical polishing solution comprises cerium oxide grinding particles with the surface potential being lower than-30 mV and piperazine. After the technical scheme is adopted, the chemical mechanical polishing solution can remarkably improve the polishing rate of Si, meanwhile, TEOS can also achieve high polishing rate, for example, the polishing rate reaches or is larger than # imgabs0 #, and TEOS: Si polishing selectivity can be adjusted to be 1: 1.

Description

Technical Field

[0001] The present invention relates to the field of chemical polishing, and particularly to a chemical mechanical polishing liquid and its use. Background Art

[0002] With the rise of SoIC (System on Integrated Chips), the requirements for CMP polishing liquid are to have similar but higher polishing rates on silicon oxide (TEOS) and silicon (Si) substrates, that is, the polishing rates of TEOS and Si are 1:1, and the polishing rates of both are as high as possible, for example, higher than Or higher than Common polishing liquids for polishing TEOS on the market include cerium oxide polishing liquid and silicon oxide polishing liquid.

[0003] Generally, the TEOS polishing rate of cerium oxide polishing liquid is much higher than that of silicon oxide polishing liquid. The TEOS polishing rate of silicon oxide polishing liquid can reach Above, but it is difficult to reach Above; on the other hand, the silicon oxide chemical mechanical polishing liquid can reach a very high Si polishing rate, for example Above, even Above (US8017524 B2), but it is difficult to adjust the TEOS:Si polishing selectivity to 1:1. Summary of the Invention

[0004] In order to overcome the above technical defects, the present invention provides a chemical mechanical polishing liquid, which includes cerium oxide abrasive particles with a negative Zeta potential (< -30 mV) and piperazine. Under alkaline conditions (pH value of 9 - 12), piperazine can effectively improve the polishing rate of Si. In addition, it can also adjust the polishing selectivity ratio of TEOS and Si to be close to 1:1, and the polishing rates of both can reach Above, close to

[0005] Specifically, the present invention discloses a chemical mechanical polishing liquid, including piperazine and cerium oxide particles with a surface potential lower than -30 mV; the particle size range of the cerium oxide abrasive particles is 20 - 500 nm; the mass percentage concentration of piperazine is 10 ppm - 3000 ppm.

[0006] Preferably, the cerium oxide particles include sol-type and calcined-type cerium oxide.

[0007] Preferably, the concentration of the cerium oxide particles is 0.1 wt% - 1.0 wt%.

[0008] Preferably, the particle size of the cerium oxide particles is 150 - 220 nm.

[0009] Preferably, the mass percentage concentration of piperazine is 100 ppm to 1500 ppm.

[0010] Preferably, the chemical mechanical polishing liquid further comprises a pH regulator selected from KOH or HAc.

[0011] Preferably, the pH value of the chemical mechanical polishing liquid is 9 - 12.

[0012] On the other hand, the present invention provides a use of a chemical mechanical polishing liquid, wherein the chemical mechanical polishing liquid as described above is used to adjust the polishing selectivity of TEOS:Si to 1:1.

[0013] After adopting the above technical solution, compared with the prior art, it has the following beneficial effects:

[0014] 1. High polishing rates can be achieved for both TEOS and Si, for example, reaching or greater than

[0015] 2. At the same time, the polishing selectivity of TEOS:Si is adjusted to 1:1. Specific Embodiments

[0016] The advantages of the present invention are further elaborated below in conjunction with specific embodiments.

[0017] Here, the exemplary embodiments will be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0018] The method for detecting the polishing rate of the chemical mechanical polishing liquid in the comparative examples and embodiments of the present invention:

[0019] The TEOS and Si blank wafers were polished and tested using a Mirra polishing machine. The corresponding polishing conditions included: an IC1010 polishing pad, with the Platten and Carrier rotation speeds being 93 rpm and 87 rpm respectively, a pressure of 3 psi, and a polishing fluid flow rate of 150 mL / min. The TEOS film thickness was measured using a NanoSpec film thickness measurement system (NanoSpec6100 - 300, Shanghai Nanospec Technology Corporation). For the blank wafer film thickness, starting from 3 mm from the wafer edge, 49 points were measured at equal intervals on the diameter line. The polishing rate was the average of the 49 points. The removal amount of Si was obtained by the weighing method. The Si wafers were weighed using an analytical balance with a precision of 0.0002 g before and after polishing. The total weight loss was divided by the wafer area and the Si density to calculate the average removed thickness, and then divided by the polishing time to calculate the polishing rate.

[0020] The measurement method for the Zeta potential on the surface of cerium oxide particles is as follows:

[0021] The surface charge of cerium oxide particles is characterized by the Zeta potential. The cerium oxide polishing fluid was diluted to a cerium oxide particle concentration of 0.2%, and then placed in a quartz cuvette. The Zeta potential was measured using Malvern instruments.

[0022] Effect Example 1:

[0023] To prove that piperazine can effectively improve the polishing rate of the polishing fluid on silicon (Si), a series of amino - containing molecules were tested in a polishing fluid containing 0.5 wt% sol - type cerium oxide particles (referred to as type - 1). The type - 1 cerium oxide particles are negatively charged particles (Zeta potential less than - 30 mV) with a particle size of approximately 150 nm.

[0024] According to the ratios of the components in Table 1, the components were dissolved in deionized water, the pH was adjusted to 12 with KOH, and the mass percentage was made up to 100% with deionized water to obtain the chemical mechanical polishing fluids of Comparative Examples 1 - 6 and Example 1 of the present invention. The polishing rates of Si and TEOS measured according to the above - mentioned test methods are shown in Table 1.

[0025] Table 1 Components and contents of the chemical mechanical polishing fluids of Comparative Examples 1 - 6 and Example 1, and polishing performance

[0026]

[0027] According to the data in Table 1, at a pH value of 12, the silicon removal rate of Comparative Example 1 containing only cerium oxide particles was Taking this as the standard, the Si polishing rates of Comparative Examples 2-5 with methylguanamine, triethanolamine, salicylhydrazide, and carbohydrazide added respectively all decreased by more than 20%; 1,2,4-triazole had almost no effect on the Si polishing rate. Contrary to the above compounds, adding piperazine could increase the Si polishing rate by 20%. In summary, when the surface of cerium oxide particles is negatively charged, under the condition of high pH value (12), the addition of piperazine can effectively improve the polishing rate of the polishing liquid on Si. This may be due to the fact that under chemical mechanical action, the addition of piperazine promotes the breakage of Si-Si bonds. In addition, after adding piperazine, due to the significant increase in the Si polishing rate, the removal rate ratio of TEOS to Si can be adjusted to 1:1.

[0028] Effect Example 2:

[0029] In order to study the effect of piperazine concentration on the Si polishing rate, based on Comparative Example 1, cerium oxide polishing liquids containing different concentrations of piperazine were prepared. As shown in Table 2, according to the formulations in Table 2, each component was dissolved in deionized water, the pH was adjusted to 12 with KOH, and the mass percentage was made up to 100% with deionized water to obtain the chemical mechanical polishing liquids of Comparative Example 1 and Examples 1-4 of the present invention. The corresponding polishing data are shown in Table 2.

[0030] Table 2 Components, contents, and polishing performance of the chemical mechanical polishing liquids of Examples 1-6 and Comparative Example 1

[0031]

[0032]

[0033] The components and contents of Comparative Example 1 and Example 1 are the same as those in Table 1, and there are slight fluctuations in the polishing rate, which are within the normal range. The results in Table 2 show that within the range of 10 ppm to 3000 ppm of piperazine concentration, the polishing rate of the polishing liquid on Si can be improved, and the Si polishing rate reaches the maximum value at a concentration of 3000 ppm. Compared with Comparative Example 1 without piperazine added, the polishing liquids of Examples 3-6 have at least a 20% increase in the Si polishing rate.

[0034] Effect Example 3

[0035] To further examine the pH range required for piperazine to increase the Si polishing rate, piperazine was added to the dispersion liquid containing negatively charged cerium oxide particles. The concentration of piperazine was 0.1 wt%, and the pH value of the polishing liquid was adjusted to 11, 9, and 5 respectively using potassium hydroxide or acetic acid, and the mass percentage was made up to 100% with water. The components, contents, and polishing performance of the chemical mechanical polishing liquids of Examples 5-6 and Comparative Examples 7-10 are shown in Table 3.

[0036] Table 3. Components, contents and polishing performance of chemical mechanical polishing fluids in Examples 7-8 and Comparative Examples 7-10

[0037] Among them, Comparative Example 7 contains type-2 sol-type cerium oxide particles, which are the same as type-1 cerium oxide particles. Its Zeta potential is negative (< -30 mV), and the particle size is about 150 nm. The difference is that the dispersions used for the two are different. On the basis of Comparative Example 7, Example 4 added 1000 ppm of piperazine. Comparative Example 8 is based on Comparative Example 7, with the pH adjusted down to 9. Example-5 is based on Comparative Example-8 and further added 1000 ppm of piperazine. If the pH is further lowered in the type-2 cerium oxide system, the stability of the cerium oxide colloidal particles will be destroyed, and particle agglomeration and precipitation will occur.. Therefore, to prevent particle precipitation, Comparative Example-9 uses calcined cerium oxide particles (type-3), with a zeta potential of negative (< -30 mV) and a particle size of about 220 nm, which can be stable at a pH value of 5. Comparative Example 10 added 1000 ppm of piperazine on the basis of Comparative Example 9. Based on the test data in Table 3, it can be seen that within the alkaline range, such as when the pH value is 9 and 11, the addition of piperazine can improve the polishing rate of the polishing fluid for Si. However, when the pH is adjusted to 5, the promoting effect of piperazine on the Si polishing rate disappears. In summary, piperazine can improve the polishing rate of Si within the pH range of 9-12.

[0038] Effect Example Four

[0039] Further verify the effect of piperazine on the Si rate in cerium oxide dispersions with different concentrations. According to the component ratios in Table 4, each component was dissolved in deionized water, the pH was adjusted to 12 with KOH, and the mass percentage was made up to 100% with deionized water to obtain the chemical mechanical polishing fluids of the comparative examples and examples. The polishing data measured according to the above test method are shown in Table 4.

[0040] Table 4 Components, contents and polishing test results of Comparative Examples 1, 11-12 and Examples 1, 9-10

[0041]

[0042] Based on the results in Table 4, it can be seen that when the cerium oxide concentration is 0.1%, Comparative Example 11 has almost no polishing rate for Si, while after adding piperazine, the polishing rate of Si is significantly improved. Similarly, in the polishing fluids with cerium oxide concentrations of 0.5% and 1%, adding 1000 ppm of piperazine can significantly improve the polishing rate of Si.

[0043] Effect Example Five

[0044] To further verify the influence of the surface charge of cerium oxide particles, the polishing performance of a polishing liquid using positively charged cerium oxide (type-4 cerium oxide particles, Zeta potential > 30 mV) was detected. According to the ratios in Table 5, each component was dissolved in deionized water, and the pH was adjusted to 5 with HAc (since positively charged cerium oxide particles are prone to agglomeration and precipitation under alkaline pH conditions, the pH was set to 5 to stabilize the particles), and the mass percentage was made up to 100% with deionized water to obtain the chemical mechanical polishing liquids of Comparative Examples 13 and 14 of the present invention. The corresponding polishing data are shown in Table 5.

[0045] Table 5. Components and contents, and polishing performance of the chemical mechanical polishing liquids of Comparative Examples 13-14

[0046]

[0047] As can be seen from the data shown in Table 4, whether piperazine was added or not, the polishing rate of the polishing liquid for Si was very low, approaching the measurement limit of silicon weight loss. Therefore, in the polishing liquid containing positively charged cerium oxide particles, the addition of piperazine could not improve the polishing rate of Si.

[0048] Effect Example Six

[0049] To further verify the influence of the particle size of cerium oxide particles, the polishing performance of polishing liquids using cerium oxide with different particle sizes was detected. According to the ratios of each group in Table 6, each component was dissolved in deionized water, the pH was adjusted to 12 with KOH, and the mass percentage was made up to 100% with deionized water to obtain the chemical mechanical polishing liquids of the comparative examples and examples. The polishing data measured according to the above test method are shown in Table 6.

[0050] Table 6. Component contents, polishing performance, and particle size of Comparative Examples 1, 15-16, and Examples 1, 11-12

[0051]

[0052] Among them, type-5 is sol-type cerium oxide particles with a negative zeta potential (< -30 mV) and a particle size of about 20 nm, and type-6 is calcined cerium oxide particles with a negative zeta potential (< -30 mV) and a particle size of about 500 nm. According to the data in Table 6, for cerium oxide particles, when the particle size distribution is in the range of 20 - 500 nm, piperazine has an improving effect on the polishing rate of Si.

[0053] It should be noted that the embodiments of the present invention have better implementability and do not impose any form of limitation on the present invention. Any person skilled in the art may use the technical content disclosed above to modify or transform it into equivalent effective embodiments. However, as long as it does not depart from the technical solution of the present invention, any modification, equivalent change or modification made to the above embodiments based on the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A chemical mechanical polishing liquid, characterized in that, including: cerium oxide abrasive particles with a surface potential lower than -30 mV and piperazine; the particle size range of the cerium oxide abrasive particles is 20 - 500 nm; the mass percentage concentration of piperazine is 10 ppm - 3000 ppm.

2. The chemical mechanical polishing liquid according to claim 1, wherein The cerium oxide abrasive particles include sol-type and calcined cerium oxide particles.

3. The chemical mechanical polishing liquid according to claim 1, wherein The concentration of the cerium oxide particles is 0.1 wt% - 1.0 wt%.

4. The chemical mechanical polishing liquid according to claim 1, characterized in that, The particle size range of the cerium oxide particles is 20 - 500 nm.

5. The chemical mechanical polishing liquid according to claim 1, characterized in that, the mass percentage concentration of the piperazine is 10 ppm - 3000 ppm.

6. The chemical mechanical polishing liquid according to claim 1, wherein The polishing liquid includes a pH regulator.

7. The chemical mechanical polishing composition according to claim 6, wherein The pH regulator is KOH or HAc.

8. The chemical mechanical polishing liquid according to claim 1, characterized in that, the pH value of the chemical mechanical polishing liquid is 9 - 12.

9. Use of a chemical mechanical polishing liquid, using the chemical mechanical polishing liquid according to any one of claims 1 - 8 to adjust the polishing selectivity of TEOS:Si to 1:1.

Images