Method for forming a semiconductor structure

Abstract

The present invention provides a method for forming a semiconductor structure, comprising: providing a substrate, the substrate including a silicon region and a non-silicon region; forming a metal material layer, the metal material layer including cobalt; performing a first annealing process to form a metal silicide in the silicon region of the metal material layer; performing a wet etching process, using a mixed solution of ammonia water and hydrogen peroxide to remove unreacted cobalt, and turning on an ultrasonic device before the substrate enters the mixed solution of ammonia water and hydrogen peroxide, so as to prevent cobalt oxide crystals in the mixed solution from precipitating and adhering to the surface of the substrate by using the ultrasonic waves emitted by the ultrasonic device. In the present invention, the ultrasonic device of the mixed solution is turned on in advance, and the ultrasonic waves emitted by the ultrasonic device make the energy of the mixed solution itself greater, improving the solubility of the mixed solution in cobalt oxide to form an environment that is not conducive to the precipitation of cobalt oxide crystals, thereby avoiding the problem that cobalt oxide crystals precipitate and adhere to the surface of the substrate when the substrate enters the mixed solution.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly relates to a method for forming a semiconductor structure. Background Art

[0002] In the semiconductor manufacturing process, it is widely used to form cobalt silicide (metal silicide) by using cobalt and silicon in the substrate to reduce the contact resistance.

[0003] The formation process of the cobalt silicide can be, for example: depositing cobalt on the surface of the substrate, then performing an annealing process and a wet etching process. The annealing process is used to form cobalt silicide from cobalt and silicon, and the wet etching process is used to remove the unreacted cobalt, so as to form self-aligned metal silicide on the surface of the substrate.

[0004] However, cobalt oxide particles (crystals) are often found to remain on the surface of the substrate after the above wet etching process, seriously affecting the product yield. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for forming a semiconductor structure, which is used to solve the problem of cobalt oxide crystal residue on the surface of the substrate after the wet etching process.

[0006] To solve the above technical problems, the present invention provides a method for forming a semiconductor structure, including: providing a substrate, where the substrate includes a silicon region and a non-silicon region; forming a metal material layer on the substrate, the metal material layer covering the silicon region and the non-silicon region, and the material of the metal material layer includes cobalt; performing a first annealing process to form a metal silicide in the silicon region of the metal material layer, the metal silicide including cobalt silicide; placing the substrate in a first liquid medicine tank to perform a wet etching process, and the etching solution used in the wet etching process includes a mixed solution of ammonia water and hydrogen peroxide, so as to remove the metal material layer in the non-silicon region and retain the metal silicide; wherein, a megasonic device is turned on before the substrate enters the mixed solution of ammonia water and hydrogen peroxide, and megasonic waves are used to prevent cobalt oxide crystals in the mixed solution of ammonia water and hydrogen peroxide from crystallizing out and adhering to the surface of the substrate during the wet etching process.

[0007] Optionally, the metal material layer includes one or more of cobalt, cobalt-nickel, and cobalt-titanium alloy.

[0008] Optionally, the ratio of ammonia water to hydrogen peroxide in the mixed solution of ammonia water and hydrogen peroxide is 1:1 to 1:0.25.

[0009] Optionally, the wet etching process includes placing the substrate in a second liquid medicine tank to remove organic impurities on the surface of the substrate before the substrate enters the first liquid medicine tank, and the second liquid medicine tank includes a mixed solution of sulfuric acid and hydrogen peroxide.

[0010] Optionally, the wet etching process further includes, after the substrate enters the first chemical solution tank, placing the substrate in a third chemical solution tank to remove partial metal silicide on the surface of the substrate, wherein the third chemical solution tank contains a mixed solution of phosphoric acid, nitric acid, and acetic acid.

[0011] Optionally, the power of the megasonic device is 500 watts to 5000 watts, and the frequency of the megasonic device is 800 kHz to 2000 kHz.

[0012] Optionally, the megasonic device is turned on 10 seconds to 60 seconds before the substrate enters the mixed solution of ammonia water and hydrogen peroxide.

[0013] Optionally, the first annealing process is rapid thermal annealing, the annealing temperature of the rapid thermal annealing is 300°C to 650°C, and the annealing time of the rapid thermal annealing is 10 seconds to 60 seconds.

[0014] Optionally, after performing the wet etching process, the method further includes: performing a second annealing process on the substrate, and the annealing temperature of the second annealing process is higher than that of the first annealing process.

[0015] Optionally, the annealing temperature of the second annealing process is 400°C to 800°C, and the annealing time of the second annealing process is 2 seconds to 60 seconds.

[0016] In summary, the method for forming a semiconductor structure provided by the present invention: before the substrate enters the mixed solution of ammonia water and hydrogen peroxide, the megasonic device of the mixed solution of ammonia water and hydrogen peroxide is turned on in advance, and the megasonic wave emitted by the megasonic device makes the energy of the mixed solution itself greater, improving the solubility of cobalt oxide in the mixed solution to form an environment that is not conducive to the crystallization and precipitation of cobalt oxide, so as to reduce or prevent the problem that when the substrate just enters the mixed solution and when the substrate performs the wet etching process in the mixed solution, cobalt oxide in the mixed solution crystallizes and adheres to the surface of the substrate, thereby solving the problem of residual cobalt oxide crystals on the surface of the substrate after the wet etching process. Description of the Drawings

[0017] Those of ordinary skill in the art should understand that the provided drawings are used to better understand the present invention and do not constitute any limitation to the scope of the present invention.

[0018] Figure 1 is a flowchart of the method for forming a semiconductor structure provided by an embodiment of the present application;

[0019] Figures 2a to 2d is a schematic structural diagram corresponding to the corresponding steps of the method for forming a semiconductor structure provided by an embodiment of the present application.

[0020] In the drawings:

[0021] 10 - Substrate; 11 - Isolation structure; 12 - Sidewall structure; 13 - Gate structure; 14 - Source / drain structure;

[0022] 20 - Metal material layer; 30 - Metal silicide. Detailed implementation manners

[0023] Through experiments by the inventor, it is found that cobalt oxide is formed after etching cobalt with a mixed solution of ammonia water and hydrogen peroxide. Cobalt oxide is slightly soluble in the mixed solution of ammonia water and hydrogen peroxide and remains in the liquid medicine tank. When the subsequent substrate just enters the liquid medicine tank, cobalt oxide in the mixed solution of ammonia water and hydrogen peroxide crystallizes out and adheres to the surface of the substrate to form cobalt oxide crystals. Moreover, the formed cobalt oxide crystals are difficult to be etched away (dissolved) in the mixed solution of ammonia water and hydrogen peroxide by using megasonic waves even when the megasonic device is turned on subsequently.

[0024] Based on the above research, the present invention provides a method for forming a semiconductor structure. Before the substrate enters the mixed solution of ammonia water and hydrogen peroxide, the megasonic device of the mixed solution of ammonia water and hydrogen peroxide is turned on in advance. The megasonic waves emitted by the megasonic device make the energy of the mixed solution itself greater, improve the solubility of the mixed solution to cobalt oxide, so as to form an environment that is not conducive to the crystallization and precipitation of cobalt oxide, thereby reducing or preventing the problem that when the substrate just enters the mixed solution and when the substrate performs a wet etching process in the mixed solution, cobalt oxide in the mixed solution crystallizes and adheres to the surface of the substrate, and thus solving the problem of the residue of cobalt oxide crystals on the surface of the substrate after the wet etching process.

[0025] To make the objectives, advantages and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are all in very simplified forms and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the objectives of the embodiments of the present invention. In addition, the structures shown in the accompanying drawings are often part of the actual structures. In particular, the accompanying drawings need to show different emphases and sometimes different scales are used.

[0026] As used in the present invention, the singular forms "a", "an" and "the" include plural objects. The term "or" is generally used in the sense of including "and / or". The term "several" is generally used in the sense of including "at least one". The term "at least two" is generally used in the sense of including "two or more". In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third" may explicitly or implicitly include one or at least two of such features, unless the content clearly indicates otherwise.

[0027] Figure 1 Flow chart of the method for forming a semiconductor structure provided by an embodiment of the present application.

[0028] As Figure 1 shown, the method for forming a semiconductor structure provided by this embodiment includes:

[0029] S01: Provide a substrate, the substrate including a silicon region and a non-silicon region;

[0030] S02: Form a metal material layer on the substrate, the metal material layer covering the silicon region and the non-silicon region, and the material of the metal material layer including cobalt;

[0031] S03: Perform a first annealing process to form a metal silicide in the silicon region, the metal silicide including cobalt silicide;

[0032] S04: Place the substrate in a first chemical solution tank to perform a wet etching process, the etching solution used in the wet etching process including a mixed solution of ammonia water and hydrogen peroxide, to remove the metal material layer in the non-silicon region and retain the metal silicide; wherein, turn on an ultrasonic device before the substrate enters the mixed solution of ammonia water and hydrogen peroxide, and use ultrasonic waves to prevent cobalt oxide crystals in the mixed solution of ammonia water and hydrogen peroxide from crystallizing and depositing on the surface of the substrate during the wet etching process.

[0033] Figures 2a to 2d is a schematic structural diagram corresponding to the corresponding steps of the method for forming a semiconductor structure provided by an embodiment of the present application. Next, the method for forming a semiconductor structure will be described in detail with reference to Figures 2a to 2d below.

[0034] First, please refer to Figure 2a , perform step S01 to provide a substrate 10, the substrate 10 including a silicon region and a non-silicon region.

[0035] Among them, the substrate 10 can be any suitable silicon substrate material well known to those skilled in the art, for example, at least one of the materials mentioned below: silicon, silicon germanide, silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanide on insulator (S-SiGeOI), etc. In this embodiment, the material of the substrate 10 is silicon as an example for illustration.

[0036] The substrate 10 includes a silicon region and a non-silicon region. The surface of the silicon region is exposed silicon (single-crystalline silicon, polycrystalline silicon or amorphous silicon), which can be a source / drain structure 14 and / or a gate structure 13 (polycrystalline silicon gate), and the surface of the non-silicon region is a dielectric layer, such as a silicon oxide layer or a silicon nitride layer, and can correspond to, for example, an isolation structure 11 or a sidewall structure 12.

[0037] Next, please refer to Figure 2b and perform step S02 to form a metal material layer 20 on the substrate 10. The metal material layer 20 covers the substrate 10, and the material of the metal material layer 20 includes cobalt.

[0038] The material of the metal material layer 20 can be cobalt or an alloy of cobalt, such as a cobalt-nickel alloy or a cobalt-titanium alloy. Of course, the metal material layer 20 can also be a stack of at least two metals. For example, a cobalt layer is first formed, and then a titanium layer or a nickel layer is formed on the cobalt layer. In this embodiment, the material of the metal material layer 20 is cobalt and can be formed, for example, by a sputtering process; the metal material layer 20 conformally covers the surface of the substrate 10, including the silicon region and the non-silicon region of the substrate 10.

[0039] Next, please refer to Figure 2c and perform step S03 to perform a first annealing process to cause the metal material layer 20 to react in the silicon region to form a metal silicide 30, and the metal silicide 30 includes cobalt silicide.

[0040] The first annealing process can be a rapid thermal annealing process to reduce the influence of high temperature on other structures (such as the source / drain structure 14 and the gate structure 13). Specifically, the annealing temperature of the first annealing process can be 300°C to 650°C, and the annealing time is 10 seconds to 60 seconds, so that cobalt in the metal material layer 20 reacts with silicon to form cobalt silicide (such as CoSi with relatively high resistance). Of course, if the metal material layer 20 is an alloy of cobalt and other metal materials, the annealing time and annealing temperature of the first annealing process also need to take into account the formation conditions of silicides of other metal materials. At the same time, the metal material layer 20 in the non-silicon region on the substrate 10 remains without reacting with the dielectric layer in the above first annealing process.

[0041] It should be noted that the first annealing process is an oxygen-free environment to prevent the metal material layer 20 from being oxidized at high temperature, and the process gas in the first annealing process can include argon or nitrogen. Of course, it is not difficult to understand that it is also possible that there is still (remaining) a part of the un-silicided (unreacted) metal material layer 20 on the top of the silicon region.

[0042] In some other embodiments, the annealing temperature of the first annealing process can be relatively higher than 300°C to 650°C or the annealing time can be relatively longer than 10 seconds to 60 seconds, so that cobalt in the metal material layer 20 directly forms cobalt silicide with lower resistance (such as CoSi2).

[0043] Next, please refer to Figure 2d, perform step S04, place the substrate 10 in the first chemical solution tank to perform a wet etching process. The etching solution used in the wet etching process includes a mixed solution of ammonia water and hydrogen peroxide, so as to remove the metal material layer 20 in the non-silicon region and retain the metal silicide 30. Among them, turn on the megasonic device before the substrate 10 enters the mixed solution of ammonia water and hydrogen peroxide, and use megasonic waves to prevent cobalt oxide crystals in the mixed solution of ammonia water and hydrogen peroxide from precipitating and adhering to the surface of the substrate 10 during the wet etching process.

[0044] Among them, the wet etching process may include multiple etching steps and multiple cleaning steps. Each etching step can perform wet etching using different etching solutions (in different chemical solution tanks) to improve the etching effect. Specific etching steps may include, for example:

[0045] S041: Use a mixed solution of sulfuric acid and hydrogen peroxide to remove organic impurities on the substrate 10;

[0046] S042: Use a mixed solution of ammonia water and hydrogen peroxide to remove the remaining metal material layer 20;

[0047] S043: Use a mixed solution of phosphoric acid, nitric acid and acetic acid to remove a part of the thickness of the metal silicide 30;

[0048] S044: Perform a drying process on the substrate 10.

[0049] Among them, after step S041, step S042 and step S043, perform a quick dump rinse (QDR) on the substrate 10 using deionized water (DI) to remove the residual chemical solution of the previous etching step, so as to improve the service life of the chemical solution in the chemical solution tank.

[0050] In step S041, the substrate 10 can be placed in the second chemical solution tank to remove organic impurities on the surface of the substrate 10. The second chemical solution tank is provided with a mixed solution of sulfuric acid and hydrogen peroxide. The mixed solution of sulfuric acid and hydrogen peroxide (also known as SPM or SC-3) has strong oxidation ability and can remove organic substances on the surface of the substrate 10. Among them, the volume ratio of sulfuric acid to hydrogen peroxide can be, for example, 1:3 to 2:7, and the temperature of the mixed solution of sulfuric acid and hydrogen peroxide can be, for example, 120°C to 150°C, so as to use high temperature to improve the removal effect of organic substances on the surface of the substrate 10.

[0051] In step S042, the substrate 10 can be placed in the first chemical solution tank to remove the remaining metal material layer 20 on the substrate 10. The etching solution in the first chemical solution tank includes a mixed solution of ammonia water and hydrogen peroxide. The mixed solution of ammonia water and hydrogen peroxide (also known as APM or SC-1) can react the metal material layer 20 with hydrogen peroxide for etching and removal. Among them, the ratio of ammonia water to hydrogen peroxide in the mixed solution of ammonia water and hydrogen peroxide can be 1:1 to 1:0.25. Cobalt in the metal material layer 20 reacts with hydrogen peroxide to form cobalt oxide (CoO). Cobalt oxide is insoluble in water and slightly soluble in the APM solution. Most of the cobalt oxide formed by etching is filtered out by the circulating filtration system of the chemical solution tank (Tank), and a small part of cobalt oxide remains dissolved in the APM solution.

[0052] It should be specifically noted that in this embodiment, before the substrate 10 enters the APM solution, the megasonic device of the chemical solution tank is turned on in advance (the megasonic device is turned on until the substrate 10 leaves the first chemical solution tank). The megasonic waves emitted by the megasonic device make the energy (surface energy) of the APM solution itself greater, improve the solubility of cobalt oxide in the APM solution, and at the same time form an environment that is more unfavorable for the crystallization and precipitation of cobalt oxide in the APM solution, thereby avoiding the problem that cobalt oxide in the APM solution crystallizes and precipitates and adheres to the surface of the substrate 10 when the substrate 10 enters the APM solution. It should be understood that the above-mentioned effect of improving solubility can only be manifested after the megasonic waves last for a certain period of time, and it is mainly to prevent the crystallization and precipitation of cobalt oxide dissolved in the APM solution. Compared with turning on the megasonic device when the substrate 10 enters the APM solution or after the substrate 10 enters the APM solution, cobalt oxide crystallizes and precipitates and adheres to the surface of the substrate 10 before the above-mentioned effect of being unfavorable for cobalt oxide crystallization is manifested, and the crystallized and precipitated cobalt oxide is difficult to be dissolved again by the megasonic waves. In a preferred embodiment, the megasonic device can be turned on 10 seconds to 60 seconds before the substrate 10 enters the APM solution. The frequency of the megasonic waves emitted by the megasonic device is 800 kHz to 2000 kHz, and the megasonic power of the megasonic device is 500 W to 5000 W.

[0053] After the substrate 10 is removed from the APM solution, the megasonic device of the APM solution can be turned off to facilitate the crystallization and precipitation of cobalt oxide in the APM solution, and the cobalt oxide is filtered out by the circulating filtration system of the first chemical solution tank, thereby being beneficial to extending the service life of the chemical solution. Of course, according to the actual situation, the megasonic device of the APM solution can also be turned off after etching multiple substrates continuously to achieve the above filtration.

[0054] In step S043, the substrate 10 can be placed in the third chemical solution tank to remove the residual metal material layer 20 and a part of the thickness of the metal silicide 30 on the substrate 10. The etching solution in the third chemical solution tank includes a mixed solution of phosphoric acid, nitric acid, and acetic acid. The mixed solution of phosphoric acid, nitric acid, and acetic acid (also known as M2) has a certain etching ability for both metals and metal silicides. By controlling the etching time, a part of the thickness (top layer part) of the metal silicide 30 can be removed, and the metal silicide 30 with a lower resistivity located in its bottom layer part can be retained.

[0055] In step S044, for example, an IPA (isopropyl alcohol) slow pull-up drying system can be used to dry the substrate 10 that has undergone step S043 and fast drain rinsing.

[0056] Then, a second annealing process can also be performed on the substrate 10. The annealing temperature of the second annealing process can be 400°C to 800°C, and the annealing time is 2 seconds to 60 seconds, so that the high-resistance cobalt silicide (CoSi) is transformed into low-resistance cobalt silicide (CoSi2), thereby realizing the formation of cobalt silicide in the silicon region, that is, the formation of a semiconductor structure. The process gas of the second annealing process can include hydrogen in addition to nitrogen or argon to facilitate the oxygen-free atmosphere of the annealing process.

[0057] In summary, the method for forming a semiconductor structure provided by the present invention: Before the substrate enters the mixed solution of ammonia water and hydrogen peroxide, the megasonic device of the mixed solution of ammonia water and hydrogen peroxide is turned on in advance. The megasonic waves emitted by the megasonic device make the energy of the mixed solution itself greater, improve the solubility of the mixed solution in cobalt oxide, and form an environment that is not conducive to the crystallization and precipitation of cobalt oxide, so as to reduce or prevent the problem that the substrate is crystallized by cobalt oxide in the mixed solution and adheres to the surface of the substrate when the substrate first enters the mixed solution and during the wet etching process of the substrate in the mixed solution, thereby solving the problem of the residual cobalt oxide crystals on the surface of the substrate after the wet etching process.

[0058] The above description is only a description of the preferred embodiments of the present invention, and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method for forming a semiconductor structure, characterized in that, Comprising: Providing a substrate, on which there are a silicon region and a non-silicon region; Forming a metal material layer on the substrate, the metal material layer covering the silicon region and the non-silicon region, and the material of the metal material layer includes cobalt; Performing a first annealing process to form a metal silicide in the silicon region, the metal silicide including cobalt silicide; Placing the substrate in a first chemical solution tank to perform a wet etching process, and the etching solution used in the wet etching process includes a mixed solution of ammonia water and hydrogen peroxide, so as to remove the metal material layer in the non-silicon region and retain the metal silicide; Wherein, a megasonic device is turned on before the substrate enters the mixed solution of ammonia water and hydrogen peroxide, and megasonic waves are utilized during the wet etching process to prevent cobalt oxide crystals in the mixed solution of ammonia water and hydrogen peroxide from crystallizing and depositing on the surface of the substrate; the power of the megasonic device is 500 watts to 5000 watts, the frequency of the megasonic device is 800 kHz to 2000 kHz, and the megasonic device is turned on 10 seconds to 60 seconds before the substrate enters the mixed solution of ammonia water and hydrogen peroxide.

2. The method for forming a semiconductor structure according to claim 1, wherein, The metal material layer includes one or more of cobalt, cobalt-nickel, and cobalt-titanium alloy.

3. The method for forming a semiconductor structure according to claim 1, wherein The ratio of ammonia water to hydrogen peroxide in the mixed solution of ammonia water and hydrogen peroxide is 1:1 to 1:0.

25.

4. The method for forming a semiconductor structure according to claim 3, wherein, The wet etching process includes placing the substrate in a second chemical solution tank to remove organic impurities on the surface of the substrate before the substrate enters the first chemical solution tank, and the second chemical solution tank includes a mixed solution of sulfuric acid and hydrogen peroxide.

5. The method for forming a semiconductor structure according to claim 4, wherein, The wet etching process further includes placing the substrate in a third chemical solution tank to remove part of the metal silicide on the surface of the substrate after the substrate enters the first chemical solution tank, and the third chemical solution tank includes a mixed solution of phosphoric acid, nitric acid, and acetic acid.

6. The method for forming a semiconductor structure according to claim 1, wherein, The first annealing process is rapid thermal annealing, the annealing temperature of the rapid thermal annealing is 300 °C to 650 °C, and the annealing time of the rapid thermal annealing is 10 seconds to 60 seconds.

7. The method for forming a semiconductor structure according to claim 6, wherein, After performing the wet etching process, it further includes: Performing a second annealing process on the substrate, and the annealing temperature of the second annealing process is higher than that of the first annealing process.

8. The method for forming a semiconductor structure according to claim 7, wherein The annealing temperature of the second annealing process is 400 °C to 800 °C, and the annealing time of the second annealing process is 2 seconds to 60 seconds.

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