Chemical mechanical polishing method and method for manufacturing semiconductor device

Abstract

The application provides a chemical mechanical polishing method and a semiconductor device manufacturing method, the chemical mechanical polishing method comprising: using a polishing liquid and a corrosion inhibitor to perform main polishing on a metal layer on a substrate to remove a first set thickness of the metal layer; using the polishing liquid and the corrosion inhibitor to perform secondary polishing on the metal layer to remove a second set thickness of the metal layer, so that the thickness of the metal layer is reduced to a target thickness, and the second set thickness is smaller than the first set thickness; the polishing rate in the secondary polishing stage is smaller than the polishing rate in the main polishing stage; and the corrosion inhibitor concentration in the secondary polishing stage is greater than the corrosion inhibitor concentration in the main polishing stage, so as to form a protective film on the surface of the metal layer in the secondary polishing stage. The technical scheme of the application can improve the corrosion effect while maintaining high polishing efficiency.

Description

Technical Field

[0001] This invention relates to the field of semiconductor integrated circuit manufacturing, and in particular to a chemical mechanical polishing method and a method for manufacturing semiconductor devices. Background Technology

[0002] During the grinding process, grinding fluids and chemical cleaning solutions can easily corrode the metal itself, which has always been a major challenge in chemical mechanical grinding, especially for relatively reactive metals like aluminum (containing 0.5% copper). Adding corrosion inhibitors during grinding can mitigate the corrosion effect to some extent; however, high concentrations of these inhibitors severely impact the grinding rate, while low concentrations are ineffective at inhibiting corrosion, making a balance difficult. Furthermore, during post-grinding cleaning, both chemical cleaning solutions and deionized water continue to corrode the aluminum surface. Removing grinding fluid residue and grinding particles requires sufficient cleaning time, which, like the corrosion effect, presents a balancing risk.

[0003] Therefore, how to improve the corrosion effect while maintaining high grinding efficiency is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a chemical mechanical polishing method and a method for manufacturing semiconductor devices, which can improve the corrosion effect while maintaining high polishing efficiency.

[0005] To achieve the above objectives, the present invention provides a chemical mechanical grinding method, comprising:

[0006] The metal layer on the substrate is subjected to primary polishing using polishing slurry and corrosion inhibitor to remove the metal layer of a first predetermined thickness;

[0007] The metal layer is subjected to secondary polishing using the polishing slurry and the corrosion inhibitor to remove the metal layer of a second predetermined thickness, thereby reducing the thickness of the metal layer to a target thickness, wherein the second predetermined thickness is less than the first predetermined thickness; the polishing rate of the secondary polishing stage is less than the polishing rate of the primary polishing stage; and the concentration of the corrosion inhibitor in the secondary polishing stage is greater than the concentration of the corrosion inhibitor in the primary polishing stage, so as to form a protective film on the surface of the metal layer in the secondary polishing stage.

[0008] Optionally, the substrate is electrically connected to the metal layer, and a negative voltage is applied to the substrate during the main polishing stage.

[0009] Optionally, a negative voltage is applied to the substrate throughout the main grinding stage, and the applied negative voltage gradually increases as grinding proceeds.

[0010] Optionally, during the main grinding stage, when the difference between the remaining thickness of the metal layer and the target thickness is less than 0.5 times the sum of the first set thickness and the second set thickness, a negative voltage is applied to the substrate.

[0011] Optionally, the difference between the remaining thickness of the metal layer and the target thickness is 50 nm to 80 nm.

[0012] Optionally, the power source that applies the negative voltage includes a constant voltage power source or a pulse power source.

[0013] Optionally, the second set thickness is 20nm to 50nm.

[0014] Optionally, the material of the metal layer includes aluminum-copper alloy, aluminum-silicon alloy, copper, aluminum, or tungsten.

[0015] Optionally, the corrosion inhibitor includes benzotriazole, benzotriazole, methylbenzotriazole, or triethanolamine.

[0016] Optionally, the chemical mechanical grinding method further includes:

[0017] The metal layer is cleaned with a cleaning solution.

[0018] Optionally, the cleaning solution includes deionized water, ammonia, hydrofluoric acid, sulfuric acid, or hydrochloric acid.

[0019] The present invention also provides a method for manufacturing a semiconductor device, comprising:

[0020] A substrate is provided on which a metal layer is formed;

[0021] The metal layer is ground using the aforementioned chemical mechanical polishing method.

[0022] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0023] 1. The chemical mechanical polishing method of the present invention involves primary polishing of a metal layer on a substrate using a polishing slurry and a corrosion inhibitor to remove a metal layer of a first predetermined thickness; secondary polishing of the metal layer using the polishing slurry and the corrosion inhibitor to remove a metal layer of a second predetermined thickness, thereby reducing the thickness of the metal layer to a target thickness, wherein the second predetermined thickness is less than the first predetermined thickness; the polishing rate in the secondary polishing stage is less than the polishing rate in the primary polishing stage; and the concentration of the corrosion inhibitor in the secondary polishing stage is greater than the concentration of the corrosion inhibitor in the primary polishing stage, so as to form a protective film on the surface of the metal layer in the secondary polishing stage, thereby improving the corrosion effect while maintaining high polishing efficiency.

[0024] 2. The semiconductor device manufacturing method of the present invention, by employing the aforementioned chemical mechanical polishing method to polish the metal layer on the substrate, improves the corrosion effect while maintaining high polishing efficiency. Attached Figure Description

[0025] Figure 1 This is a flowchart of a chemical mechanical grinding method according to an embodiment of the present invention;

[0026] Figures 2a-2c yes Figure 1 A schematic diagram of the device used in the chemical mechanical polishing method is shown.

[0027] Among them, the appendix Figures 1 to 2c The annotations in the attached figures are explained as follows:

[0028] 11-Substrate; 12-Insulating dielectric layer; 121-Metal interconnect structure; 13-Metal layer. Detailed Implementation

[0029] To make the objectives, advantages, and features of the present invention clearer, the chemical mechanical polishing method and the semiconductor device manufacturing method proposed in this invention will be further described in detail below with reference to the accompanying drawings. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0030] An embodiment of the present invention provides a chemical mechanical grinding method, see reference. Figure 1 , Figure 1 This is a flowchart of a chemical mechanical polishing method according to an embodiment of the present invention, the chemical mechanical polishing method comprising:

[0031] Step S1: Use polishing slurry and corrosion inhibitor to perform main polishing on the metal layer on the substrate to remove the metal layer of the first set thickness;

[0032] Step S2: The metal layer is subjected to secondary grinding using the grinding slurry and the corrosion inhibitor to remove the metal layer of a second predetermined thickness, thereby reducing the thickness of the metal layer to a target thickness, wherein the second predetermined thickness is less than the first predetermined thickness; the grinding rate of the secondary grinding stage is less than the grinding rate of the main grinding stage; the concentration of the corrosion inhibitor in the secondary grinding stage is greater than the concentration of the corrosion inhibitor in the main grinding stage, so as to form a protective film on the surface of the metal layer in the secondary grinding stage.

[0033] See below. Figures 2a-2c The chemical mechanical grinding method provided in this embodiment will be described in more detail.

[0034] Following step S1, as follows Figure 2a and Figure 2bAs shown, the metal layer 13 on the substrate is subjected to primary polishing using polishing slurry and corrosion inhibitor to remove the metal layer 13 of a first predetermined thickness.

[0035] The substrate may include a substrate 11 and an insulating dielectric layer 12 formed on the substrate 11. A metal interconnect structure 121 may be formed in the insulating dielectric layer 12. A metal layer 13 is formed on the insulating dielectric layer 12 and is electrically connected to the substrate 11 through the metal interconnect structure 121.

[0036] The substrate may contain device structures such as transistors and capacitors (not shown), and the device structures may be electrically connected to the metal layer 13 through the metal interconnect structure 121.

[0037] The material of the metal layer 13 may include an elemental metal or an alloy; the alloy may include an alloy of metals, or an alloy of metal and semiconductor. For example, it may include aluminum-copper alloys, aluminum-silicon alloys, copper, aluminum, or tungsten, but is not limited thereto.

[0038] Following step S2, as Figure 2b and Figure 2c As shown, the metal layer 13 is subjected to secondary grinding using the grinding slurry and the corrosion inhibitor to remove the metal layer 13 of a second predetermined thickness, thereby reducing the thickness of the metal layer 13 to a target thickness, wherein the second predetermined thickness is less than the first predetermined thickness; the grinding rate of the secondary grinding stage is less than the grinding rate of the main grinding stage; the concentration of the corrosion inhibitor in the secondary grinding stage is greater than the concentration of the corrosion inhibitor in the main grinding stage, so as to form a protective film (not shown) on the surface of the metal layer 13 in the secondary grinding stage.

[0039] like Figures 2a-2c As shown, the first set thickness is h1-h2, and the second set thickness is h2; when the second grinding is completed, the grinding is carried out to the target line L1, at which point the remaining thickness of the metal layer 13 is the target thickness.

[0040] Preferably, the second set thickness h2 is 20nm to 50nm.

[0041] During the primary and secondary grinding stages, the grinding slurry corrodes the surface of the metal layer 13. Specifically, when the metal layer 13 is made of a single metallic element, the grinding slurry reacts with the element in a redox reaction, causing the element to oxidize and lose electrons. When the metal layer 13 is made of an alloy, the grinding slurry reacts with the alloy in a galvanic cell reaction. The more reactive metal in the alloy is oxidized and loses electrons, and the oxidation rate of the more reactive metal is faster than that of the single metallic element; that is, the galvanic cell reaction accelerates the corrosion of the metal layer 13. For example, when the metal layer 13 is made of an aluminum-copper alloy, the more reactive aluminum in the aluminum-copper alloy is rapidly oxidized and loses electrons.

[0042] Furthermore, during the primary and secondary grinding stages, the corrosion inhibitor reacts with the more reactive metal in the elemental metal or alloy to form a complex. This complex acts as a protective film, protecting the metal layer 13 and preventing corrosion from the grinding fluid. Therefore, if the concentration of the corrosion inhibitor is too high, the protective film will form faster and be thicker, severely affecting the grinding rate. Conversely, if the concentration of the corrosion inhibitor is too low, the protective film will form more slowly and be thinner, failing to inhibit corrosion.

[0043] In this invention, by setting the second set thickness to be less than the first set thickness, the grinding rate of the secondary grinding stage to be less than the grinding rate of the main grinding stage, and the corrosion inhibitor concentration of the secondary grinding stage to be greater than the corrosion inhibitor concentration of the main grinding stage, that is, by setting the main grinding stage to grind until the remaining thickness of the metal layer 13 is close to the target thickness, using a high grinding rate and a low concentration of the corrosion inhibitor, the corrosion of the metal layer 13 is reduced to a certain extent in the main grinding stage without significantly affecting the grinding rate, achieving the most efficient grinding to quickly grind away the metal layer 13 of the first set thickness, so that the remaining thickness of the metal layer 13 quickly approaches the target thickness; and by setting the secondary grinding stage to grind away only a very thin metal layer 13, using a low grinding rate and a high concentration of the corrosion inhibitor, the corrosion of the surface of the metal layer 13 can be significantly suppressed in the secondary grinding stage, and the minor corrosion pits generated in the main grinding stage are mainly slowly smoothed out in the secondary grinding stage, and a complex is formed on the surface of the metal layer 13 as a protective film to prevent corrosion of the surface of the metal layer 13 during subsequent cleaning. Furthermore, due to the low grinding rate in the secondary grinding stage, the grinding can be precisely stopped at the target line L1.

[0044] Therefore, by combining the primary grinding with the secondary grinding, the surface smoothness of the metal layer 13 after grinding can be maintained while maintaining high grinding efficiency, thus improving the corrosion effect on the metal layer 13.

[0045] Preferably, a negative voltage (or potential) is applied to the substrate during the main grinding stage. Specifically, a negative voltage can be applied to the side of the substrate 11 away from the metal layer 13, causing negative charges to be transferred through the metal interconnect structure 121 to the surface of the metal layer 13 (e.g., ...). Figure 2a (As shown).

[0046] The principle of corrosion of the metal layer 13 is that the metal layer 13 is oxidized and loses electrons, that is, the metal layer 13 discharges. By applying a negative voltage to the substrate, negative charges can be transferred to the surface of the metal layer 13. When the metal layer 13 needs to discharge, the negative charges transferred to the surface of the metal layer 13 can be released, so that the metal layer 13 itself does not need to discharge, thereby protecting the metal layer 13 and preventing the polishing fluid from causing significant corrosion to the metal layer 13.

[0047] In one embodiment, a negative voltage (or potential) is applied to the substrate throughout the main grinding stage, and the applied negative voltage gradually increases as grinding progresses. That is, the negative voltage applied in the early stage of the main grinding stage is small, and the negative voltage applied in the later stage of the main grinding stage is large. This is to prevent excessive protection of the metal layer 13 in the early stage of the main grinding stage, which would reduce the grinding rate, and to enable the grinding rate to be reduced in the later stage of the main grinding stage while enhancing the anti-corrosion effect. This allows for rapid grinding of the metal layer 13 in the main grinding stage while reducing corrosion damage on the remaining surface of the metal layer 13 when the main grinding is completed. Alternatively, in another embodiment, in the main grinding stage, when the difference between the remaining thickness of the metal layer 13 and the target thickness is less than 0.5 times the sum of the first set thickness and the second set thickness, a negative voltage (or potential) is applied to the substrate. That is, no negative voltage is applied to the substrate in the early stage of the main grinding stage, and the negative voltage is applied to the substrate in the later stage of the main grinding stage. This allows the metal layer 13 to be ground at a very high rate in the early stage of the main grinding stage, and the grinding rate to be reduced and the corrosion resistance to be enhanced in the later stage of the main grinding stage. In this way, the metal layer 13 can be ground quickly in the main grinding stage, while reducing the corrosion damage that occurs on the surface of the remaining metal layer 13 when the main grinding is completed. During the application of the negative voltage to the substrate, the magnitude of the negative voltage can remain constant; or, the applied negative voltage can be gradually increased as grinding progresses.

[0048] The reason for applying a negative voltage to the substrate at a specific thickness in the later stage of the main grinding process is to provide a better start for the entire secondary grinding process. The probability of pitting corrosion (due to the electrochemical corrosion caused by the uniform presence of copper in aluminum) of the metal layer 13 consumed during the grinding process is extremely small. Furthermore, the pitting corrosion that existed before can also be consumed by the grinding process of applying the negative voltage, thus acting as a buffer layer. Therefore, the surface is smoother, providing a smoother foundation for the secondary grinding process.

[0049] The secondary grinding process involves a higher concentration of corrosion inhibitors, which are more suitable for controlling uniform corrosion. Based on the protection provided earlier, the grinding will begin from a smoother surface.

[0050] Meanwhile, prolonged changes to the substrate voltage also increase the risk of impacting the electrical performance of devices on the wafer. Therefore, by only setting a negative voltage at the position where the thickness is "0.5 times" during the main grinding process, the possibility of impact on the devices can be greatly reduced.

[0051] Preferably, when the difference between the remaining thickness of the metal layer 13 and the target thickness is 50 nm to 80 nm, a negative voltage is applied to the substrate.

[0052] Power supplies that apply negative voltage include constant voltage power supplies or pulse power supplies.

[0053] The constant voltage power supply provides stable protection that can be continuously applied during the grinding process. However, because this process reduces the loss of electrons from metal layer 13, it also continuously slows down the reaction process. This may be more conducive to precise control of the final grinding stop position (because the slower the speed, the easier it is to stop precisely). But it may sacrifice the overall reaction speed.

[0054] The potential provided by the pulse power supply appears intermittently at a specific frequency. It supplies and shuts off the potential (or voltage) by a pre-set frequency (such as the duty cycle). The magnitude of the pulse potential and the duty cycle can jointly affect the protection of the metal layer 13 during the grinding process.

[0055] The potential provided by the pulse power supply is given by the following formula:

[0056] E avg =E on ×D+E off ×(1-D) (1)

[0057] Among them, E avg It is the average potential of a single pulse cycle. E onD is the potential provided by the pulse power supply when it is in the "on" state during a single cycle. D is the duty cycle, which refers to the ratio of the time the signal is in an active state to the total time of the cycle. E is the voltage. off It is the potential in the "off" state, if E off If it is 0, then the above formula (1) will be simplified.

[0058] When polishing and protecting the metal layer 13, using a pulsed potential can yield better results. For example, when "on" (i.e., a potential is provided), protection can be provided to the surface of the metal layer 13, while when "off" (i.e., no potential is provided), no protection is provided. When no protection is provided, the accumulation of byproducts in the electrolyte can be reduced, such as the accumulation of hydrogen bubbles (hydrogen bubbles often occur during the chemical mechanical polishing of the metal layer, and their accumulation on the polished surface may lead to uneven surface polishing), thereby making the surface polishing of the metal layer 13 more uniform.

[0059] At the same time, the E supplied by the power supply can be utilized by adjusting the duty cycle. on Without changing the underlying structure, this provides different protection requirements when grinding to different thicknesses. During this period, E on Maintaining the current level might be more beneficial for the stability of the electrical performance of devices across the entire wafer. The duty cycle D can be gradually increased throughout the grinding process; that is, less potential can be provided earlier to accelerate the grinding speed, while as the target thickness approaches, it can be adjusted to be more "on" to increase protection and slow down the process. Slowing down the grinding speed also allows for more precise stopping of the main grinding process, further enhancing protection.

[0060] It should be noted that the applied negative voltage should not exceed the device's breakdown voltage.

[0061] The corrosion inhibitors include, but are not limited to, benzotriazole, benzotriazole, methylbenzotriazole, or triethanolamine.

[0062] After the first grinding is completed, the chemical mechanical polishing method further includes cleaning the metal layer 13 with a cleaning solution to remove residual polishing solution and ground particles from the surface of the metal layer 13.

[0063] Because a protective film is formed on the surface of the metal layer 13 during the grinding process, the surface of the metal layer 13 can be prevented from being corroded by the residual grinding fluid and the cleaning fluid during the cleaning process, thus allowing sufficient time to completely remove the residual grinding fluid and the ground particles.

[0064] The cleaning solution includes, but is not limited to, deionized water, ammonia, hydrofluoric acid, sulfuric acid, or hydrochloric acid.

[0065] In summary, the chemical mechanical polishing method provided by this invention includes: primary polishing of a metal layer on a substrate using an polishing slurry and a corrosion inhibitor to remove the metal layer of a first predetermined thickness; secondary polishing of the metal layer using the polishing slurry and the corrosion inhibitor to remove the metal layer of a second predetermined thickness, thereby reducing the thickness of the metal layer to a target thickness, wherein the second predetermined thickness is less than the first predetermined thickness; the polishing rate in the secondary polishing stage is less than the polishing rate in the primary polishing stage; and the concentration of the corrosion inhibitor in the secondary polishing stage is greater than the concentration of the corrosion inhibitor in the primary polishing stage, so as to form a protective film on the surface of the metal layer in the secondary polishing stage. This chemical mechanical polishing method of the present invention improves the corrosion effect while maintaining high polishing efficiency.

[0066] An embodiment of the present invention provides a method for manufacturing a semiconductor device, comprising:

[0067] First, a substrate is provided on which a metal layer is formed.

[0068] The substrate may include a substrate and an insulating dielectric layer formed on the substrate. A metal interconnect structure may be formed in the insulating dielectric layer. A metal layer is formed on the insulating dielectric layer and is electrically connected to the substrate through the metal interconnect structure.

[0069] The substrate may contain device structures such as transistors and capacitors (not shown), and these device structures can be electrically connected to the metal layer through the metal interconnect structure.

[0070] Then, the metal layer is ground using the aforementioned chemical mechanical polishing method.

[0071] The chemical mechanical grinding method is described above and will not be repeated here.

[0072] By using the aforementioned chemical mechanical polishing method to polish the metal layer, the corrosion effect can be improved while maintaining high polishing efficiency.

[0073] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A chemical mechanical grinding method, characterized in that, include: The metal layer on the substrate is subjected to primary polishing using polishing slurry and corrosion inhibitor to remove the metal layer of a first predetermined thickness; The metal layer is subjected to secondary polishing using the polishing slurry and the corrosion inhibitor to remove the metal layer of a second predetermined thickness, thereby reducing the thickness of the metal layer to a target thickness, wherein the second predetermined thickness is less than the first predetermined thickness. The grinding rate in the secondary grinding stage is lower than the grinding rate in the main grinding stage; the concentration of the corrosion inhibitor in the secondary grinding stage is higher than the concentration of the corrosion inhibitor in the main grinding stage, so as to form a protective film on the surface of the metal layer in the secondary grinding stage, wherein the protective film is a complex formed by the reaction of the corrosion inhibitor and the metal layer. The metal layer on which the protective film is formed is cleaned using a cleaning solution; The substrate is electrically connected to the metal layer; a negative voltage is applied to the substrate throughout the main grinding stage, and the applied negative voltage gradually increases as grinding progresses; or, during the main grinding stage, when the difference between the remaining thickness of the metal layer and the target thickness is less than 0.5 times the sum of the first set thickness and the second set thickness, a negative voltage is applied to the substrate.

2. The chemical mechanical grinding method as described in claim 1, characterized in that, The difference between the remaining thickness of the metal layer and the target thickness is 50nm~80nm.

3. The chemical mechanical grinding method as described in claim 1, characterized in that, Power supplies that apply negative voltage include constant voltage power supplies or pulse power supplies.

4. The chemical mechanical grinding method as described in claim 1, characterized in that, The second set thickness is 20nm~50nm.

5. The chemical mechanical grinding method as described in claim 1, characterized in that, The metal layer may be made of aluminum-copper alloy, aluminum-silicon alloy, copper, aluminum, or tungsten.

6. The chemical mechanical grinding method as described in claim 1, characterized in that, The corrosion inhibitors include benzotriazole, benzotriazole, methylbenzotriazole, or triethanolamine.

7. The chemical mechanical grinding method as described in claim 1, characterized in that, The cleaning solution includes deionized water, ammonia, hydrofluoric acid, sulfuric acid, or hydrochloric acid.

8. A method for manufacturing a semiconductor device, characterized in that, include: A substrate is provided on which a metal layer is formed; The metal layer is ground using the chemical mechanical polishing method as described in any one of claims 1 to 7.

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