A composition for polishing a ruthenium-based barrier layer of copper interconnects

Abstract

The application provides a composition for polishing a ruthenium-based barrier layer of a copper interconnection, comprising, based on the total mass of the composition being 100 wt%, 0.1-5 wt% of a silicon dioxide abrasive, 0.01-2 wt% of hydrogen peroxide, 0.01-3 wt% of a compound, 0.1-0.3 wt% of potassium ferrocyanide, 0.01-0.3 wt% of 5-methylthio-1H-tetrazole, ammonia water and the balance of deionized water, and the pH value of the composition is 9.0. By introducing 5-methylthio-1H-tetrazole as a copper inhibitor and introducing potassium ferrocyanide and ethylenediamine as a ruthenium removal promoting component in the polishing system, the application can improve the removal rate of ruthenium while inhibiting the excessive removal of copper and galvanic corrosion, thereby achieving the copper protection and ruthenium removal, realizing the planarization treatment of the wafer, and improving the dish-shaped pit and etch pit morphology.

Description

Technical Field

[0001] This invention relates to the field of semiconductor polishing technology, and in particular to a composition for polishing ruthenium-based barrier layers for copper interconnects. Background Technology

[0002] Chemical mechanical planarization (CMP) is a critical process step in integrated circuit manufacturing, significantly impacting wafer surface planarization effectiveness, subsequent process accuracy, and device yield. In advanced copper interconnect processes, ruthenium is widely used as a barrier layer material in copper interconnect structures due to its low resistivity, high thermal stability, good adhesion to copper, and direct electroplating capability.

[0003] In the CMP process of ruthenium-based barrier layers in copper interconnects, ruthenium is an inert metal and its removal rate is typically low; while copper is a more reactive metal and is more easily removed during polishing. Simultaneously, the potential difference between ruthenium and copper easily induces galvanic corrosion during polishing, further exacerbating the morphology of dish-shaped pits and etching pits, making it difficult to achieve the desired planarization effect.

[0004] Typical polishing slurry systems often focus on increasing the ruthenium removal rate or inhibiting copper corrosion, but they cannot simultaneously achieve effective ruthenium removal, copper inhibition, and adjustment of the Ru / Cu removal rate selectivity ratio. Therefore, it is difficult to achieve targeted planarization treatment based on different wafer initial morphologies.

[0005] On the other hand, some polishing fluid systems have a large number of additives, making the system complex and lacking in stability, which is not conducive to practical process applications. Therefore, a composition for polishing ruthenium-based barrier layers for copper interconnects is proposed. Summary of the Invention

[0006] In view of this, the present invention provides a composition for polishing ruthenium-based barrier layers for copper interconnects, providing at least one beneficial alternative to the technical problems existing in the prior art.

[0007] The first aspect of this invention provides a composition for polishing ruthenium-based barrier layers in copper interconnects. The composition, based on a total mass of 100 wt%, comprises 0.1-5 wt% silica abrasive, 0.01-2 wt% hydrogen peroxide, 0.01-3 wt% a compound, 0.1-0.3 wt% potassium ferrocyanide, 0.01-0.3 wt% 5-methylthio-1H-tetrazole, ammonia, and the balance deionized water; the pH of the composition is 9.0. The silica abrasive in the composition provides mechanical removal, the hydrogen peroxide oxidizes the wafer surface, the compound and potassium ferrocyanide promote ruthenium removal, and the 5-methylthio-1H-tetrazole protects the copper surface, thereby achieving synergistic regulation of copper removal inhibition and ruthenium removal promotion within the same polishing system.

[0008] Furthermore, the particle size of the silica abrasive is 30-100 nm. Using silica abrasive within this particle size range is beneficial for balancing polishing removal capacity and surface quality, and improving the planarization effect during the barrier layer polishing stage.

[0009] Furthermore, the compound is selected from one or more of monoethanolamine, diethanolamine, tetrahydroxyethylethylenediamine, ethylenediamine, triethanolamine, diethylene glycolamine, monoisopropanolamine, N-methyldiethanolamine, dimethylethanolamine, and diethylethanolamine; and can be used as a complexing agent for ruthenium metal.

[0010] Furthermore, the compound is ethylenediamine; when ethylenediamine is used in combination with hydrogen peroxide, potassium ferrocyanide and 5-methylthio-1H-tetrazole, it can form a relatively stable alkaline polishing system, which is beneficial for controlling the removal rate during the barrier layer polishing stage.

[0011] Furthermore, the content of the silica abrasive is 5 wt%, and the content of the hydrogen peroxide is 0.15 wt%.

[0012] Furthermore, the content of the ethylenediamine is 0.12 wt%.

[0013] Further, the content of potassium ferrocyanide is 0.20 wt%, and the content of 5-methylthio-1H-tetrazole is 0.20 wt%. Under the above ratio conditions, 5-methylthio-1H-tetrazole showed better inhibition of copper, while potassium ferrocyanide had a more significant promoting effect on ruthenium, which is conducive to obtaining a better Ru / Cu removal rate selectivity ratio and better repair effect of dish pits and corrosion pits.

[0014] A second aspect of this invention provides a chemical mechanical polishing (CMP) method for a ruthenium-based barrier layer with copper interconnects. The method employs the composition described in any one of the preceding claims to perform CMP on a wafer to be polished, wherein the wafer to be polished includes a copper-coated silicon substrate wafer and a ruthenium-coated silicon substrate wafer. Further, the CMP process parameters are: operating pressure of 1-2 psi, wafer rotation speed of 70-90 rpm, polishing disc rotation speed of 80-100 rpm, composition flow rate of 200-400 mL / min, and polishing time of 60 s. These process parameters, combined with the composition, can form a relatively stable material removal process during the barrier layer polishing stage.

[0015] Furthermore, in the chemical mechanical polishing method, the Ru / Cu removal rate selectivity ratio is controlled by adjusting the content ratio of 5-methylthio-1H-tetrazole to potassium ferrocyanide in the composition, so as to improve the morphology of dish pits and etch pits on the surface of the wafer to be polished.

[0016] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: I. This invention introduces 5-methylthio-1H-tetrazole as a copper inhibitor and potassium ferrocyanide as a ruthenium removal promoter into the polishing system. This can improve the ruthenium removal rate while inhibiting excessive copper removal and galvanic corrosion, thereby achieving both copper protection and ruthenium removal, realizing wafer planarization, and improving the morphology of dish pits and etch pits.

[0017] Second, by adjusting the ratio of 5-methylthio-1H-tetrazole to potassium ferrocyanide, this invention can regulate the Ru / Cu removal rate selectivity, thereby achieving targeted planarization treatment based on different initial wafer morphologies and improving the morphology of dish pits and etching pits. At the same time, this invention uses a single copper inhibitor and a single inorganic promoter to construct a polishing system, which has relatively simple components, a clear mechanism, and a simple preparation process, and has good practical application value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating the preparation and polishing application of the composition of the present invention. Figure 2 This is a structural diagram of the MTT structure and a diagram illustrating the mechanism for suppressing Cu in this invention. Detailed Implementation

[0020] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0021] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] like Figure 1 As shown, the composition for chemical mechanical polishing of ruthenium-based barrier layers for copper interconnects provided by the present invention comprises, by weight percentage, 0.1-5 wt% abrasive, 0.01-2 wt% oxidant, 0.01-3 wt% compound, 0.1-0.3 wt% inorganic compound, 0.01-0.3 wt% azole compound and its derivatives, ammonia as a pH adjuster, and the balance being deionized water, with a pH value of 9.0. The abrasive is preferably silicon dioxide with a particle size of 30-100 nm, the oxidant is preferably hydrogen peroxide, the compound is preferably ethylenediamine, the inorganic compound is preferably potassium ferrocyanide, and the azole compound and its derivatives are preferably 5-methylthio-1H-tetraazole.

[0023] When the composition of this invention is used for CMP polishing of ruthenium-based barrier layers in copper interconnects, silica abrasive provides mechanical removal, hydrogen peroxide provides oxidation, and ethylenediamine helps maintain the stability of the alkaline polishing system. 5-Methylthio-1H-tetrazole forms a protective film on the copper surface to inhibit excessively rapid copper removal and galvanic corrosion during polishing. Potassium ferrocyanide promotes the oxidation reaction on the ruthenium surface, increasing the ruthenium removal rate. By adjusting the ratio of 5-methylthio-1H-tetrazole to potassium ferrocyanide, the Ru / Cu removal rate selectivity can be controlled, thereby achieving differentiated planarization treatment for different initial wafer morphologies and improving dishing and erosion morphologies.

[0024] In this embodiment, the composition can be formulated as follows: Weigh out the silica abrasive, hydrogen peroxide, compound, inorganic compound, azole compound and its derivatives according to the predetermined mass percentage, add them to deionized water and mix evenly. Then adjust the pH of the system to 9.0 using nitric acid and ammonia, and add the remaining deionized water to obtain the composition to be used.

[0025] In this embodiment, CMP polishing employs the following process window: the composition is added to the CMP polishing machine, the working pressure is controlled at 1-2 psi, the wafer rotation speed is controlled at 70-90 rpm, the polishing disc rotation speed is controlled at 80-100 rpm, the composition flow rate is controlled at 200-400 mL / min, and the polishing time is 60 s. When the above process parameters are combined with the composition of this invention, a relatively stable removal process can be formed in the barrier layer polishing stage, and the effects of different additive ratios on Cu removal, Ru removal, and morphology repair can be well reflected.

[0026] Example 1 This embodiment is used to verify the effect of changes in 5-methylthio-1H-tetrazole (MTT) content on copper removal rate, ruthenium removal rate, and dishing and erosion remediation effects.

[0027] In this embodiment, the CMP polishing process parameters are: working pressure 1-2 psi, wafer rotation speed 70-90 rpm, polishing disc rotation speed 80-100 rpm, composition flow rate 200-400 mL / min, and polishing time 60 s. The composition contains 5 wt% silica and 50 nm abrasive particles; 0.15 wt% hydrogen peroxide; 0.12 wt% ethylenediamine; 0.20 wt% potassium ferrocyanide; and 5-methylthio-1H-tetrazazole at different weight percentage concentrations. The remainder is deionized water, and the pH is adjusted to 9.0 using nitric acid and ammonia.

[0028] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that 5-methylthio-1H-tetrazazole is not added, that is, the content of 5-methylthio-1H-tetrazazole is 0 wt%. The other raw material components, proportions and polishing equipment conditions are the same as those in Example 1.

[0029] Table 1: Effect of MTT concentration variation on Cu / Ru polishing rate and morphology restoration.

[0030]

[0031] Table 1 shows that without the addition of MTT, Cu exhibits the highest polishing rate, reaching 2329 Å / min, while Ru's polishing rate remains at 539 Å / min, resulting in a Ru / Cu rate selectivity ratio of only 0.23. The Dishing and Erosion repair values ​​are only 156 Å and 89 Å, respectively, indicating that a significant amount of copper is removed during polishing, making it difficult to effectively balance barrier layer removal and surface morphology repair. As the MTT concentration gradually increases, the Cu polishing rate decreases significantly, while the Ru polishing rate remains relatively stable within the range of 538-557 Å / min, suggesting that MTT primarily acts on the copper surface and has almost no significant inhibitory effect on ruthenium removal.

[0032] When the MTT concentration was increased to 0.20 wt%, the Cu polishing rate decreased to 459 Å / min, while the Ru polishing rate was 542 Å / min. The Ru / Cu rate selectivity ratio increased to 1.18, and the Dishing repair value reached 470 Å, while the Erosion repair value reached 280 Å, indicating that the polishing system achieved a good balance between suppressing copper and retaining and removing ruthenium. Further increasing the MTT concentration to 0.25 wt% and 0.30 wt% did not significantly decrease the Cu polishing rate, and the Ru / Cu rate selectivity ratio remained around 1.17, indicating that the morphology repair effect entered a plateau region. Therefore, it can be considered that when the MTT concentration reached approximately 0.20 wt%, the suppression effect on copper had essentially reached an effective level.

[0033] The S and N atoms in 5-methylthio-1H-tetrazole can form S-Cu and N-Cu bonds with the copper surface, respectively. Through a combination of electrostatic and chemisorption, a relatively stable protective film is constructed on the copper surface, making it less susceptible to further oxidation by hydrogen peroxide and facilitating rapid removal under mechanical action. Since ruthenium is an inert metal, its surface oxide is relatively dense and stable, and it hardly reacts effectively with MTT. Therefore, increasing the MTT concentration has little effect on the Ru removal rate. Figure 2 As shown.

[0034] Example 2 This embodiment is used to verify the effect of changes in potassium ferrocyanide concentration on ruthenium removal rate, copper removal rate, and the remediation effects of dishing and erosion.

[0035] In this embodiment, the composition contains 5 wt% silica and 50 nm abrasive particles; 0.15 wt% hydrogen peroxide; 0.12 wt% ethylenediamine; a fixed 0.20 wt% 5-methylthio-1H-tetrazazole; potassium ferrocyanide at different weight percentage concentrations; and the remainder is deionized water, with the pH adjusted to 9.0 using nitric acid and ammonia. The CMP polishing equipment and process parameters used are the same as in Example 1.

[0036] Comparative Example 2 Based on the data in Example 2 and Table 2, Comparative Example 2 should be understood as follows: except for the absence of potassium ferrocyanide (i.e., the potassium ferrocyanide content is 0 wt%), the other raw material components, proportions, and equipment conditions are the same as in Example 2.

[0037] Table 2: Effects of potassium ferrocyanide concentration variation on polishing rate and morphology restoration of Cu / Ru

[0038] Table 2 shows that, under the condition of a fixed MTT content of 0.20 wt%, when the potassium ferrocyanide content is 0 wt%, the Cu polishing rate is 453 Å / min, while the Ru polishing rate is only 28 Å / min, the Ru / Cu rate selectivity ratio is only 0.06, and the Dishing and Erosion repair values ​​are only 89 Å and 23 Å, respectively. This indicates that without the promoting effect of potassium ferrocyanide on the oxidation reaction of ruthenium surface, it is difficult to achieve effective removal of ruthenium by relying solely on hydrogen peroxide.

[0039] As the concentration of potassium ferrocyanide gradually increased from 0.10 wt% to 0.30 wt%, the Ru polishing rate increased from 186 Å / min to 544 Å / min, while the Cu polishing rate remained within a narrow range of 440-467 Å / min. This indicates that the addition of potassium ferrocyanide mainly promoted Ru removal with little impact on the Cu removal rate. Particularly in the 0.20-0.30 wt% range, the Ru / Cu rate selectivity ratio remained stable between 1.18 and 1.19, and both the Dishing and Erosion repair values ​​significantly increased, indicating that this concentration range can achieve a good match between copper inhibition and Ru promotion.

[0040] Potassium ferrocyanide can catalyze the decomposition of hydrogen peroxide to generate strong oxidizing hydroxyl radicals, thereby enhancing the oxidation of Ru surface and forming a looser, more porous, and easier-to-remove oxide layer on Ru surface, thus improving Ru polishing rate.

[0041] Potassium ferrocyanide can be a key promoter for controlling the Ru / Cu rate selectivity ratio in this invention due to its oxidation-promoting effect.

[0042] Example 3 This embodiment is used to verify the effect of the basic polishing system on Cu removal, Ru removal and morphology repair without the addition of MTT and potassium ferrocyanide, so as to illustrate the necessity of the two key additives in this invention.

[0043] In this embodiment, the composition contains 5 wt% silica and 50 nm abrasive particles; 0.15 wt% hydrogen peroxide; 0.12 wt% ethylenediamine; no 5-methylthio-1H-tetrazazole or potassium ferrocyanide is added; the remainder is deionized water, and the pH is adjusted to 9.0 using nitric acid and ammonia.

[0044] Table 3: Polishing rate and morphology restoration data of Cu / Ru without the addition of MTT and potassium ferrocyanide

[0045] Table 3 shows that without the addition of MTT and potassium ferrocyanide, the polishing rate of Cu is as high as 2325 Å / min, while the polishing rate of Ru is only 30 Å / min, and the Ru / Cu rate selectivity ratio is only 0.01. At the same time, the Dishing repair value is only 40 Å, and the Erosion repair value is only 8 Å. These results clearly demonstrate that the basic system consisting of silica, hydrogen peroxide, and ethylenediamine alone cannot simultaneously achieve effective protection of copper, efficient removal of ruthenium, and significant improvement of surface morphology.

[0046] Combining Table 3 with Tables 1 and 2, it can be seen that the addition of MTT significantly inhibits Cu removal, while the addition of potassium ferrocyanide enhances Ru removal. The combination of the two can not only increase the Ru / Cu rate selectivity ratio to over 1, but also improve the Dishing and Erosion repair values, thus providing more targeted process control space for planarization of wafers with different initial morphologies.

[0047] In the polishing system of this invention, 5-methylthio-1H-tetrazole mainly acts on the copper surface, forming a relatively stable protective layer and reducing the corrosion and removal rate of copper during polishing. Potassium ferrocyanide mainly acts on the oxidation reaction process of ruthenium, promoting the formation of an oxide layer on the ruthenium surface that is more easily removed mechanically, thereby increasing the polishing removal rate of ruthenium. Because the two components have distinct functions in terms of their target and mode of action, this invention can simultaneously protect copper and remove ruthenium within the same polishing system, allowing the polishing solution to no longer be limited to a single control direction but possess the ability to synergistically regulate the removal behavior of both materials.

[0048] As shown in Table 1, with other components remaining constant, the copper polishing rate decreased significantly with increasing 5-methylthio-1H-tetrazole concentration, while the ruthenium polishing rate remained relatively stable. This indicates that this component has a significant inhibitory effect on copper and a relatively small impact on ruthenium removal. When the 5-methylthio-1H-tetrazole concentration reached 0.20 wt%, the Ru / Cu removal rate was relatively high, and the dishing and erosion repair effects were good, indicating that effective control of copper removal behavior can be achieved at this concentration while also maintaining a good planarization effect.

[0049] Table 2 shows that, while maintaining a constant 5-methylthio-1H-tetrazole content, the ruthenium polishing rate significantly increased with increasing potassium ferrocyanide concentration, while the copper polishing rate showed little change. This indicates that potassium ferrocyanide significantly promotes ruthenium removal while having a limited effect on copper removal. When the potassium ferrocyanide concentration is around 0.20 wt%, the Ru / Cu removal rate is relatively high, and the dishing and erosion repair effects are superior, indicating that this component can effectively enhance the ruthenium removal capability during the barrier layer polishing stage.

[0050] Table 3 further shows that, without the addition of 5-methylthio-1H-tetrazole and potassium ferrocyanide, the copper removal rate in the basic polishing system is high, while the ruthenium removal rate is low, the Ru / Cu removal rate selectivity is significantly low, and the dishing and erosion repair values ​​are both small. These results indicate that relying solely on the abrasive, oxidant, and alkaline conditioning system is insufficient to simultaneously achieve effective copper protection, efficient ruthenium removal, and significant improvement in surface morphology. The copper-inhibiting component and ruthenium-promoting component used in this invention play a crucial role in achieving Ru / Cu removal rate selectivity control and surface planarization treatment.

[0051] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A composition for chemical mechanical polishing of ruthenium-based barrier layers in copper interconnects, characterized in that, Based on a total mass of 100 wt%, the composition comprises: 0.1-5wt% silica abrasive; 0.01-2 wt% hydrogen peroxide; 0.01-3 wt% of compounds; 0.1-0.3 wt% potassium ferrocyanide; 0.01-0.3 wt% of 5-methylthio-1H-tetrazole; Ammonia solution and the remainder deionized water; The pH value of the composition is 9.0; The compound is selected from one or more of monoethanolamine, diethanolamine, tetrahydroxyethylethylenediamine, ethylenediamine, triethanolamine, diethylene glycolamine, monoisopropanolamine, N-methyldiethanolamine, dimethylethanolamine, and diethylethanolamine.

2. The composition for chemical mechanical polishing of a ruthenium-based barrier layer for copper interconnects according to claim 1, characterized in that: The particle size of the silica abrasive is 30-100 nm.

3. The composition for chemical mechanical polishing of a ruthenium-based barrier layer for copper interconnects according to claim 1, characterized in that: The compound is ethylenediamine.

4. The composition for chemical mechanical polishing of a ruthenium-based barrier layer for copper interconnects according to claim 1, characterized in that: The content of the silica abrasive is 5 wt%, and the content of the hydrogen peroxide is 0.15 wt%.

5. The composition for chemical mechanical polishing of a ruthenium-based barrier layer for copper interconnects according to claim 3, characterized in that: The content of the ethylenediamine is 0.12 wt%.

6. The composition for chemical mechanical polishing of a ruthenium-based barrier layer for copper interconnects according to claim 1, characterized in that: The content of potassium ferrocyanide is 0.20 wt%, and the content of 5-methylthio-1H-tetrazole is 0.20 wt%.

7. A chemical mechanical polishing method for a ruthenium-based barrier layer for copper interconnects, characterized in that: The composition for chemical mechanical polishing of copper interconnect ruthenium-based barrier layer according to any one of claims 1-6 is used to perform chemical mechanical polishing on a wafer to be polished, wherein the wafer to be polished includes a copper-coated silicon substrate wafer and a ruthenium-coated silicon substrate wafer.

8. The chemical mechanical polishing method according to claim 7, characterized in that: The process parameters for the chemical mechanical polishing are as follows: working pressure of 1-2 psi, wafer rotation speed of 70-90 rpm, polishing disc rotation speed of 80-100 rpm, composition flow rate of 200-400 mL / min, and polishing time of 60 s.

9. The chemical mechanical polishing method according to claim 8, characterized in that: By adjusting the ratio of 5-methylthio-1H-tetrazole to potassium ferrocyanide in the composition, the Ru / Cu removal rate selectivity ratio is controlled to improve the morphology of dish-shaped pits and etch pits on the surface of the wafer to be polished.

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