Chemical mechanical polishing solution and method of use

Abstract

The present application provides a chemical mechanical polishing liquid and a method for using the same. The chemical mechanical polishing liquid contains cerium oxide abrasive particles, hydroxylamine and its derivatives, and a pH adjuster, wherein the surface of the cerium oxide abrasive particles is positively charged. The chemical mechanical polishing liquid of the present application can reduce the polishing rate of the polishing liquid as the height of the pattern step on the wafer decreases, thereby achieving the function of automatic stop. The use conditions are relatively mild, and the chemical mechanical polishing liquid can be used in large-scale production, can be applied to pattern wafers with different patterns, and has a wide application prospect in the field.

Description

Technical Field

[0001] This invention relates to the field of chemical mechanical polishing, and more particularly to a chemical mechanical polishing slurry. Background Technology

[0002] Currently, chemical mechanical polishing (CMP) has become the most effective and mature planarization technology in the fabrication of micro and nano devices. In the fabrication of micro and nano devices, interlayer dielectric (ILD) technology, with its outstanding isolation performance, flat surface morphology, and good locking performance, has become the mainstream isolation technology in recent years. CMP planarizes the stepped oxide layer during ILD structure formation, and its main parameters characterizing its polishing performance are polishing rate and planarization efficiency. Increasing the polishing rate of dielectric materials is generally achieved by using cerium oxide as polishing particles; however, if the polishing rate is too high, it often leads to over-polishing, i.e., a high trench loss on the patterned silicon wafer, resulting in low planarization efficiency. In existing technologies, CMP processes generally use polishing slurries with an automatic stop function. This type of polishing slurry can maintain a high polishing rate at high step heights, and the polishing rate decreases as the step height decreases, thus achieving the automatic stop function. Once the polishing slurry has this function, then there is no need to design the dielectric layer to be too thick, nor is it necessary to invest in the detection equipment at the polishing endpoint. This can reduce the loss of low points in the silicon wafer trench and improve the efficiency of the planarization process.

[0003] Currently, several patents have been filed related to automatic-stop polishing slurries. For example, US Patent 7,696,095 discloses an auto-stop cerium oxide polishing slurry with polyvinylamine as an additive. However, this slurry has a solid content of 2% or higher and is subject to high polishing pressure, making it unsuitable for large-scale production. US Patent 2017,001,4969A1 discloses an automatic-stop polishing slurry with low solid content containing salicylic acid, but salicylic acid has low solubility and requires other additives to increase it. US Patent 2019,018,5716A1 discloses a molecule containing the RC(=O)-NH-OH structure as an automatic-stop additive, but this polishing slurry can only be used under alkaline conditions and is not suitable for acidic polishing slurries. US Patent 2018,024,4956A1 discloses maltol, benzoic acid, and hydroxybenzoic acid as automatic-stop additives, but the application conditions for this polishing slurry are also unsuitable, and its repeatability is low, making it unsuitable for large-scale production.

[0004] Therefore, there is an urgent need in the field for a polishing slurry that is suitable for acidic conditions, easy to prepare, and suitable for large-scale production, with an automatic stop effect, which can effectively improve the efficiency of the planarization process. Summary of the Invention

[0005] In order to overcome the above-mentioned technical defects, the present invention aims to provide a chemical mechanical polishing fluid, specifically containing: cerium oxide abrasive particles, hydroxylamine and its derivatives, and a pH adjuster.

[0006] Preferably, the content of the cerium oxide grinding particles is 0.1%-0.5% by mass.

[0007] Preferably, the content of the cerium oxide grinding particles is 0.3% by mass.

[0008] Preferably, the particle size of the cerium oxide grinding particles is 45-75 nm.

[0009] Preferably, the concentration of the hydroxylamine and its derivatives is 50 ppm to 2000 ppm by mass.

[0010] Preferably, the hydroxylamine and its derivatives have the following structural formula:

[0011] Wherein, R1 and R2 are H or other functional groups, and the functional groups contain C, H, N, and O elements.

[0012] Preferably, the hydroxylamine and its derivatives are selected from one or more of hydroxylamine, N-methylhydroxylamine, N,N-diethylhydroxylamine, benzohydroxyxamic acid and ethyl acetylhydroxyxamic acid.

[0013] Preferably, the pH value of the chemical polishing solution is 3.0 to 6.0.

[0014] Preferably, the pH value of the chemical polishing solution is 4.0 to 4.5.

[0015] In another aspect, the present invention provides a method for using a chemical mechanical polishing slurry, wherein the chemical mechanical polishing slurry described above is applied to achieve automatic stopping of the polishing process.

[0016] When polishing patterned wafers using the polishing slurry of this invention, the polishing rate of the slurry decreases as the height of the pattern step decreases, thereby achieving an automatic stop function. The polishing slurry of this invention uses additives with high solubility, operates under relatively mild conditions, can be used in large-scale production, and is applicable to image wafers with different patterns, thus having broad application prospects in the field. Detailed Implementation

[0017] The advantages of the present invention will be further illustrated below with reference to specific embodiments.

[0018] Polishing solutions for Examples 1-2 and Comparative Examples 1-3 were prepared according to the components and their contents listed in Table 1. Benzoic acid and potassium hydroxide were used as pH adjusters to adjust the pH value of the polishing solutions to the desired value. The particle size of the cerium oxide abrasive particles used was measured using the BET surface area method.

[0019] Table 1. Components and content of polishing solutions in Examples 1-3 and Comparative Examples 1-3

[0020]

[0021]

[0022] TEOS blank wafers and patterned wafers were tested using polishing slurries from Examples 1-2 and Comparative Examples 1-3, respectively. Specific polishing conditions were as follows: a Mirra polishing machine was used, with the following parameters: IC1010 polishing pad, Platten and Carrier rotation speeds of 93 rpm and 87 rpm, pressures of 3 psi and 5 psi, polishing slurry flow rate of 150 mL / min, and polishing time of 60 seconds. The silicon oxide (TEOS wafer) thickness was measured using a NanoSpec thickness measurement system (NanoSpec 6100-300, Shanghai Nanospec Technology Corporation). Starting 3 mm from the wafer edge, 49 points were measured at equal intervals along the diameter line. The polishing rate was the average of these 49 points. The step height of the patterned wafer was measured using a high-resolution profilometer, and the silicon oxide thickness was measured using NanoSpec. Patterned structures are generally described using linewidth / groove width, in μm. The patterned wafer used in this application has a 70 μm / 30 μm pattern, i.e., 70 μm linewidth and 30 μm groove width. The test results are shown in Table 2.

[0023] Table 2. Test results of polishing slurries in Examples 1-2 and Comparative Examples 1-3

[0024]

[0025]

[0026] Table 2 data shows that the polishing slurry in the comparative examples does not have an automatic stop function. Specifically, in Comparative Example 1, the polishing rate ratio of the blank sheet to the highest point of the pattern (AA / BLK) is 1, meaning that the polishing rate of the Comparative Example 1 polishing slurry is independent of the step height and polishing pressure. Furthermore, at a polishing pressure of 5 psi, the step height to lowest point of the step (AA / TA) ratio of the Comparative Example 1 polishing slurry is as high as 97, indicating that the polishing rate of the Comparative Example 1 polishing slurry is closely related to the relative height of the step height and the lowest point of the step. This is because when the step is high, the polishing pad deformation is insufficient to reach the lowest point, equivalent to no pressure at the lowest point. When the step is low, the polishing pad deformation is sufficient to reach the lowest point, resulting in polishing pressure at the lowest point and an increased polishing rate. This is essentially the basic principle of planarization. When the cerium oxide surface carries a negative charge, such as in Comparative Examples 2 and 3, the polishing rate of the blank sheet is very low, below 100 A / min. However, when polishing patterned wafers, if the step height is higher than 6000 Å, the polishing rate is only 396 Å / min and 84 Å / min, which is far from meeting the requirements of actual production. Therefore, the cerium oxide particles used in the polishing slurry also affect the polishing rate.

[0027] The polishing slurries in Examples 1 and 2 exhibit very low polishing rates on blank wafers (BLK), both below 300 A / min. However, when used for polishing the high points of pattern steps, the step height significantly impacts the polishing rate. When the step height exceeds 5000 A, the polishing rate at the high points can reach 12-14 times that of the blank wafer. As the step height decreases, the polishing rate at the high points also decreases until it approaches the polishing rate of the blank wafer. At this point, the polishing rate at the low points of the step also approaches that of the blank wafer, thus achieving an automatic stop function.

[0028] The polishing slurry in this invention not only effectively achieves automatic stop functionality but is also applicable to patterned wafers of different shapes. Polishing tests were conducted on blank TEOS wafers and patterned wafers using the polishing slurry of Example 2. Specific polishing conditions were as follows: a Mirra polishing machine was used, with the following parameters: IC1010 polishing pad, Platten and Carrier speeds of 93 rpm and 87 rpm respectively, pressure of 3 psi, polishing slurry flow rate of 150 mL / min, and polishing time of 60 seconds. The silicon oxide (TEOS wafer) film thickness was measured using a NanoSpec film thickness measurement system (NanoSpec6100-300, Shanghai Nanospec Technology Corporation). Starting 3 mm from the wafer edge, 49 points were measured at equal intervals along the diameter line. The polishing rate was the average of these 49 points. The step height of the patterned wafer was measured using a high-resolution profilometer, and the silicon oxide thickness was measured using NanoSpec. The patterned wafer used had a pattern structure of 40 μm / 240 μm, i.e., 40 μm linewidth and 240 μm groove width. The test results are shown in Table 3.

[0029] Table 3. Test results of polishing slurry in Example 2

[0030]

[0031] As shown in Table 3, the polishing slurry in Example 2 still exhibits excellent automatic stopping performance on patterned wafers with a pattern structure of 40µm / 240µm. When the step height of the patterned wafer is greater than... At that time, the polishing rate at the highest point of the step is greater than The polishing rate is reduced to 4 μm / min. As the step height decreases, the polishing rate at the high point approaches that at the low point, and thus gradually approaches the polishing rate of the blank wafer, achieving self-stopping. This prevents the polishing slurry from over-polishing and removing excessive material. Therefore, the polishing slurry in this invention can automatically stop polishing on wafers with different patterns and designs.

[0032] Benzyl hydroxamic acid was used as an additive with an automatic stop function, and 4-hydroxybenzoic acid was used as a pH buffer. Both contained 0.3 wt% cerium oxide. The polishing solutions of Examples 3 to 9 were prepared, and the pH value of the polishing solutions was adjusted to 4.0 using potassium hydroxide as a pH adjuster. The polishing rate of the polishing solutions at 3 psi was measured according to the above measurement method. The specific components of the polishing solutions of Examples 3 to 9 and the measured polishing rates are shown in Table 5.

[0033] Table 4. Components and polishing rates of the polishing slurries in Examples 4 to 10

[0034]

[0035] As can be seen from the data in Table 4, when the content of benzoic acid is 600-800 ppm and the content of 4-hydroxybenzoic acid fluctuates from 100 ppm to 800 ppm, the polishing rate of the polishing solution does not fluctuate significantly.

[0036] Polishing solutions of Examples 10 to 17 were prepared according to the components and their contents in Table 5, and the pH value of the polishing solution was adjusted to the required value using potassium hydroxide as a pH adjuster.

[0037] Table 5. Components and content of polishing fluids in Examples 10-17

[0038]

[0039] The polishing rates of the polishing slurries in Examples 10 to 12 were tested: Following the above test methods and conditions, the polishing rates of the blank TEOS and the step heights of the polishing slurries in Examples 10 to 12 were tested respectively. and the height of the steps is lower than The polishing speed at the location was measured, and the data are shown in Table 6. Similarly, using cerium oxide abrasive particles with a particle size of 60 nm, polishing slurries of Examples 13 to 17 and Comparative Example 4 were prepared according to the components and contents shown in Table 4, and the polishing rate of the polishing slurries of Examples 13 to 17 was tested: according to the above test methods and test conditions, the polishing rate of the polishing slurries of Examples 13 to 17 and Comparative Example 4 was tested at pressures of 2 psi, 3 psi and 4 psi, respectively, and the data are shown in Table 7.

[0040] Table 6. Polishing rates of the polishing slurries in Examples 10-12

[0041]

[0042]

[0043] Table 7. Components, contents, and polishing rates of polishing solutions in Examples 13-17 and Comparative Example 4

[0044]

[0045] As shown in Tables 6 and 7, in this invention, various chemical substances containing hydroxylamine functional groups are added to the polishing slurry. The polishing rate of the slurry is related to the step height on the patterned wafer; the higher the step height, the higher the polishing rate, thus enabling an automatic stop function. Furthermore, when the pressure is high, the polishing rate of the slurry in this invention is much lower than that of the slurry without hydroxylamine and its derivatives (Comparative Example 4), indicating that hydroxylamine and its derivatives can meet the requirement of automatic stop.

[0046] In summary, the polishing slurry of this invention incorporates hydroxylamine and its derivatives as additives, enabling effective control of the polishing rate within a specific pH range. This allows for automatic stopping during the polishing of patterned wafers. Furthermore, the polishing slurry of this invention is suitable for wafers with different patterns and has broad application prospects in the field.

[0047] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A chemical mechanical polishing slurry, comprising cerium oxide abrasive particles, hydroxylamine and its derivatives, and a pH adjuster; The cerium oxide abrasive particles have a positive charge on their surface; the pH adjuster is hydroxybenzoic acid; The hydroxylamine and its derivatives are selected from one or more of hydroxylamine, N-methylhydroxylamine, and N,N-diethylhydroxylamine; the pH value of the chemical mechanical polishing solution is 3.0 to 6.

0.

2. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The content of the cerium oxide grinding particles is 0.1%-0.5% by mass.

3. The chemical mechanical polishing slurry as described in claim 2, characterized in that, The content of the cerium oxide grinding particles is 0.3% by mass.

4. The chemical mechanical polishing slurry according to claim 1, wherein the cerium oxide abrasive particles have a particle size of 45-75 nm.

5. The chemical mechanical polishing slurry according to claim 1, wherein the concentration of hydroxylamine and its derivatives is 50 ppm to 2000 ppm by mass.

6. The chemical mechanical polishing slurry according to claim 1, wherein the pH value of the chemical mechanical polishing slurry is 4.0 to 4.

5.

7. A method of using a chemical mechanical polishing slurry, characterized in that, The chemical mechanical polishing slurry according to any one of claims 1-6 is used to achieve automatic stopping of the polishing slurry during the polishing process.

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