Chemical-mechanical polishing solution

Abstract

The present invention provides a chemical-mechanical polishing solution for backside copper reveal process of through silicon vias. The polishing solution comprises abrasive particles, an organic acid, an organic amine, an azole compound, a non-ionic surfactant, and an oxidizing agent. The chemical-mechanical polishing solution of the present invention can maintain a relatively high monocrystalline silicon removal rate and an adjustable copper removal rate, and can also effectively reduce copper contamination on a polished silicon surface.

Description

A chemical mechanical polishing fluid Technical Field

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

[0002] With the development of semiconductor technology and the miniaturization of electronic components, Moore's Law has faced challenges from physics and materials science. 2.5D and 3D advanced packaging technologies offer new directions for continuing Moore's Law. One of the key technologies in advanced packaging is the fabrication of Through Silicon Vias (TSVs). TSVs enable low-power, high-bandwidth communication between chips through vertical interconnects, making high-density integration and miniaturization of devices possible.

[0003] To achieve vertical interconnects between different chips, the wafer thickness needs to be thinned to expose the copper pillars of the TSV (Through-Side Via). In the widely used Backside Via Reveal (BVR) process, the backside of the wafer is first thinned to a certain distance from the TSV copper pillars using mechanical grinding. Then, silicon is selectively removed using wet or dry etching to expose the bottom copper pillars. A layer of SiN is then deposited, and finally, CMP (Chemical Mechanical Polishing) is used to remove the SiN / Oxide from the copper pillar surface, exposing the copper vias. This process requires precise control over the total thickness variation (TTV) of the TSV copper pillars. If the height difference is too large during fabrication, some copper pillars may not be fully exposed, leading to device failure.

[0004] In another TSV (Through-the-Video) backside via planarization (BFR) process, the backside thickness of the wafer is first thinned to a certain distance from the TSV copper pillars using a grinding wheel. Then, a silicon-copper chemical mechanical polishing (CMP) slurry is used to remove the silicon layer until the copper pillars are exposed. Compared to BVR (Browser-Visor-Reveal), the BFR method reduces etching steps, is faster, more efficient, and less affected by TTV. However, because the copper pillars and the silicon wafer surface are exposed simultaneously during polishing, copper ions migrate rapidly in the silicon atomic lattice and easily remain on the silicon surface after polishing, forming contamination. This increases the conductivity of the insulating layer, thus affecting device performance. Therefore, the BFR process requires a CMP slurry that protects the silicon surface and reduces copper ion contamination. Patents CN102533117A and CN03834306A describe a polishing slurry for TSVs with a high silicon polishing rate. However, this invention does not address the protection of the silicon wafer surface after polishing or the control of copper ion contamination on the silicon surface. Summary of the Invention

[0005] To overcome the above-mentioned technical defects, the present invention provides a method that can maintain a high single-crystal silicon removal rate, an adjustable copper removal rate, and effectively reduce copper ion contamination on the silicon surface.

[0006] Specifically, the present invention provides a chemical mechanical polishing fluid, comprising: abrasive particles, organic acid, organic amine, nitrile compound, nonionic surfactant and oxidant.

[0007] Furthermore, the organic acid is preferably glycine, alanine, arginine, serine, iminodiacetic acid, aminotriacetic acid, ethylenediaminetetraacetic acid, citric acid, or malonic acid.

[0008] Furthermore, the organic amine is preferably ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, N,N'-dimethylethylenediamine, diethylenetriamine, or triethylenetetramine.

[0009] Furthermore, the organic acid content is 0.1%-3% by mass.

[0010] Furthermore, the organic amine has a mass percentage content of 0.01%-0.2%.

[0011] Furthermore, the nonionic surfactant is selected from polymers containing repeating ethylene oxide units, preferably polyethylene oxide, alkylphenol ethoxylates, fatty alcohol ethoxylates, or fatty acid ethoxylates. The nonionic surfactant has the following molecular structure: R-[C2H4O] n -H, where n is 90 to 5000, and R is a hydroxyl, alkoxy, or alkyl group. When R is an alkoxy or alkyl group, R has 10 to 18 carbon atoms.

[0012] Furthermore, the nonionic surfactant includes, but is not limited to, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, dodecylphenol polyoxyethylene ether, cashew nut phenol polyoxyethylene ether, lauryl alcohol polyoxyethylene ether, cetyl alcohol polyoxyethylene ether, myristyl alcohol polyoxyethylene ether, isotretinoin polyoxyethylene ether, polyoxyethylene ether laurate, polyoxyethylene ether stearate, and polyoxyethylene ether oleate. Preferably, the nonionic surfactant is selected from one or more of nonylphenol polyoxyethylene ether, isotretinoin polyoxyethylene ether, polyoxyethylene ether stearate, and polyoxyethylene ether oleate.

[0013] Furthermore, the nonionic surfactant has a mass percentage of 0.001%-0.1%.

[0014] Furthermore, the azole compound is preferably selected from one or more of benzotriazole, methylbenzotriazole, carboxybenzotriazole, 2,2'-[[(methyl-1H-benzotriazole-1-yl)methyl]imino]diethanol, 1,2,4-triazole, tetrazolium, 5-methyl-1H-tetrazolium, 5-amino-1H-tetrazolium, and 5-phenyl-1H-tetrazolium.

[0015] Furthermore, the mass percentage content of the azole compound is 0.01%-0.5%.

[0016] Furthermore, the abrasive particles are silicon dioxide. The mass percentage concentration of the abrasive particles is 5%-20%. The particle size of the abrasive particles is 50-200 nm.

[0017] Furthermore, the oxidant is hydrogen peroxide; the mass percentage concentration of the oxidant is 0.05%-2.0%.

[0018] Furthermore, the pH of the chemical mechanical polishing slurry is 9.0-12.0.

[0019] The polishing solution of the present invention may also contain pH adjusters, bactericides and other additives commonly used in the art.

[0020] The polishing solution of the present invention can be concentrated and prepared by means of components other than oxidant. Before use, it can be diluted with deionized water and oxidant can be added to the concentration range of the present invention.

[0021] The present invention also discloses a method for using the chemical mechanical polishing slurry described above in any of the above-described methods for exposing copper on the back side of a TSV through-silicon via.

[0022] Compared with existing technologies, the above technical solution has the following advantages:

[0023] 1. The chemical mechanical polishing slurry of the present invention has a high silicon removal rate for monocrystalline silicon and an adjustable copper removal rate.

[0024] 2. The chemical mechanical polishing slurry of the present invention can effectively reduce copper ion contamination on the silicon surface after polishing. Attached Figure Description

[0025] Figure 1 shows the AFM scanning results of polished TSV wafers in some comparative examples and embodiments; where Figures (A)-(G) are comparative examples 1, 3, and 4 and embodiments 1, 2, 6, and 11, respectively. Detailed Implementation

[0026] The advantages of the present invention will be further illustrated below with reference to specific embodiments.

[0027] It should be understood that all contents mentioned in this invention refer to mass percentages.

[0028] Table 1 shows comparative examples 1-4 and examples 1-12 of the chemical mechanical polishing slurry of the present invention. According to the formulations given in the table, all components except the oxidant are mixed thoroughly in sequence. The pH is adjusted to the desired value using a pH adjuster (such as KOH or HNO3). The oxidant is added and mixed thoroughly before use. The polishing slurry of the present invention can also be pre-prepared as a concentrated sample, diluted with deionized water at a certain ratio, and then the oxidant is added before use.

[0029] The reagents and raw materials used in this invention are all commercially available.

[0030] Table 1. Composition and content of Comparative Examples 1-4 and Examples 1-12 of the present invention

[0031] The polishing slurries of the embodiments and comparative examples of this invention were used to polish blank electroplated copper wafers and silicon wafers under the following conditions: a 12” Reflexion LK polishing machine, an IC1000 (Dupont) polishing pad, a polishing pressure of 3.0 psi, a polishing disc and polishing head rotation speed of 93 / 87 rpm, a polishing slurry flow rate of 300 mL / min, and a polishing time of 1 minute. The thickness of the copper wafer was measured using a four-point probe metal thin film measuring instrument, and the thickness of the silicon wafer was measured using a reflective film thickness gauge (SR-Mapping).

[0032] The polishing slurries of the embodiments and comparative examples of the present invention were used to perform back-side polishing on wafers containing TSV patterns under the following conditions to characterize the degree of copper ion contamination on the silicon wafer surface after TSV back-side copper exposure polishing. The TSV patterned wafers had already undergone back-side thinning to expose the copper pillars.

[0033] The specific polishing conditions were as follows: a 12” Reflexion LK polishing machine, a polishing disc and polishing head rotation speed of 93 / 87 rpm, and a polishing slurry flow rate of 300 mL / min. On polishing disc 3, an H800 (Fujibo) polishing pad was used, with a polishing pressure of 1.5 psi. The TSV polishing slurry invented in this patent was used to polish the back side of the TSV wafer for 1 minute. The patterned wafer after polishing was then cleaned with an acidic cleaning solution. An atomic force microscope (AFM) was used to scan the silicon surface within a 50 μm × 50 μm area around the copper pillars to qualitatively characterize the degree of copper ion contamination on the silicon surface after polishing.

[0034] Table 2 shows the effects of Comparative Examples 1-4 and Examples 1-12.

[0035] Table 2. Results of Comparative Examples 1-4 and Examples 1-12 of the present invention

[0036] Figure 1 shows the AFM scan results of TSV wafers polished with the polishing slurry used in the comparative examples and embodiments.

[0037] As can be seen from Comparative Examples 1 and 4 and Examples 1-3, 4-6 and 8-12 in Table 2, by adding the organic acids and organic amines recommended in this invention and adjusting the amount of organic acids and organic amines added, the TSV polishing slurry formulation disclosed in this invention can have an adjustable copper polishing rate.

[0038] As can be seen from Comparative Examples 1-4 and Examples 1-12 in Table 2, the TSV polishing slurry formulation disclosed in this invention has a high polishing rate for single-crystal silicon.

[0039] As can be seen from the AFM scanning results of the polished TSV wafer surface in Comparative Examples 1, 3, 4 and Examples 1, 2, 6, 11 and Figure 1, by adding a nonionic surfactant, an organic acid and an organic amine recommended in this invention, the TSV polishing slurry formulation combination disclosed in this invention can effectively reduce the residual copper by-products on the silicon surface after polishing the back-side through-silicon vias to expose copper, reduce copper ion contamination of the silicon wafer, and improve the electrical performance of the device.

[0040] 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, characterized in that, include: Abrasive particles, organic acids, organic amines, nitrazole compounds, nonionic surfactants, and oxidants.

2. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The organic acid is selected from glycine, alanine, arginine, serine, iminodiacetic acid, aminotriacetic acid, ethylenediaminetetraacetic acid, citric acid, or malonic acid.

3. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The organic amine is selected from ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, diethylenetriamine, or triethylenetetramine.

4. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The organic acid content is 0.1%-3% by mass.

5. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The organic amine has a mass percentage content of 0.01%-0.2%.

6. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The nonionic surfactant is a polymer containing repeating ethylene oxide units. The nonionic surfactant has the following molecular structure: R-[C2H4O] n -H, n is 90–5000; R is hydroxyl, alkoxy, or alkyl acyl.

7. The chemical mechanical polishing slurry as described in claim 6, characterized in that, When R is an alkoxy or alkanoyl group, R has 10 to 18 carbon atoms.

8. The chemical mechanical polishing slurry as described in claim 6, characterized in that, The nonionic surfactants mentioned are polyethylene oxide, alkylphenol ethoxylates, fatty alcohol ethoxylates, and fatty acid ethoxylates.

9. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The nonionic surfactant is selected from one or more of nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, dodecylphenol polyoxyethylene ether, cashew phenol polyoxyethylene ether, lauryl alcohol polyoxyethylene ether, cetyl alcohol polyoxyethylene ether, myristyl alcohol polyoxyethylene ether, isotridecyl alcohol polyoxyethylene ether, polyoxyethylene ether laurate, polyoxyethylene ether stearate, and polyoxyethylene ether oleate.

10. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The nonionic surfactant is present in a mass percentage of 0.001%-0.1%.

11. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The azole compounds are selected from one or more of benzotriazole, methylbenzotriazole, carboxybenzotriazole, 2,2'-[[(methyl-1H-benzotriazole-1-yl)methyl]imino]diethanol, 1,2,4-triazole, tetrazolium, 5-methyl-1H-tetrazolium, 5-amino-1H-tetrazolium, and 5-phenyl-1H-tetrazolium.

12. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The mass percentage content of the nitrazole compound is 0.01%-0.5%.

13. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The abrasive particles are silicon dioxide abrasive particles.

14. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The mass percentage concentration of the grinding particles is 5%-20%.

15. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The average particle size of the grinding particles is 50-200 nm.

16. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The oxidant is hydrogen peroxide.

17. The chemical mechanical polishing slurry as described in claim 1, characterized in that, The oxidant has a mass percentage content of 0.05%-2.0%.

18. The chemical mechanical polishing slurry according to any one of claims 1-17, characterized in that, The pH value of the chemical mechanical polishing fluid is 9.0-12.0.

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