Wafer cleaning solution and semiconductor structure forming method

Abstract

A wafer cleaning solution and a method for forming a semiconductor structure wherein the wafer cleaning solution comprises a mixed solution of an oxidizing agent, a cationic surfactant and water, and the wafer cleaning solution is used for removing a hard mask layer formed by a carbon-doped tungsten material after an etching process and enhancing the dispersibility of carbon in the solution, thereby reducing the adhesion of carbon on the surface of a wafer and improving the quality of the wafer. And the dissolution of carbon is promoted, so that the cleanliness of the wafer surface is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a wafer cleaning liquid and a semiconductor structure forming method. Background Art

[0002] In advanced processes, tungsten doped Carbon (WdC) is a new type of metal hard mask material. Its advantage is that its smaller grain size can achieve lower pattern roughness and higher etching selectivity when transferring patterns in the etching process.

[0003] After the etching process, the hard mask material needs to be removed by a wet etching process. However, the existing wet etching process may lead to poor device performance or fail to meet the requirements of the current semiconductor process for wafer surface cleanliness. The existing wet etching process needs to be further improved. Summary of the invention

[0004] The technical problem solved by the invention is to provide a wafer cleaning liquid to improve the cleanliness of the wafer surface.

[0005] In order to solve the above technical problems, the technical solution of the present invention provides a wafer cleaning solution, including: a mixture of an oxidant, a cationic surfactant and water.

[0006] Optionally, in the cleaning solution, the molar percentage content of the oxidant ranges from 10% to 25%, and the molar percentage content of the cationic dispersant ranges from 0.1% to 3%.

[0007] Optionally, the cleaning solution also includes: an organic amine compound.

[0008] Optionally, in the cleaning solution, the molar percentage content of the organic amine compound ranges from 0.5% to 5%.

[0009] Optionally, the organic amine compound includes a mixture of one or more of methylamine, ethylamine, triethylamine, triethanolamine, isobutylamine, tert-butylamine, tributylamine, dipropylamine, dimethylamine, diethylene glycolamine, monoethanolamine, methyldiethanolamine, diisopropylamine, diisobutylamine, aniline, pentamethyldiethylenetriamine, acetoacetamide, ammonium carbamate, ammonium pyrrolidine dithiocarbamate, N-methylacetoacetamide and tetramethylammonium thiobenzoate.

[0010] Optionally, the oxidant includes a mixture of one or more of hydrogen peroxide, urea peroxide, peroxodisulfuric acid, ammonium persulfate, peroxymonosulfuric acid, pyrosulfuric acid and ozone.

[0011] Optionally, the cationic surfactant includes a mixture of one or more of hexadecyltrimethylammonium bromide, hexadecyldimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyldimethylamine oxide, didecyldimethylammonium bromide, dodecyldimethylammonium chloride, N-hexadecylpropylenediamine diammonium chloride and didecyldimethylammonium chloride.

[0012] Correspondingly, the technical solution of the present invention also provides a method for forming a semiconductor structure, comprising: providing a layer to be etched, wherein the layer to be etched is located on the surface of a wafer; forming a hard mask layer on the layer to be etched, wherein the hard mask layer exposes a portion of the layer to be etched; using the hard mask layer as a mask, etching the layer to be etched to form a graphic layer; after forming the graphic layer, using any of the wafer cleaning solutions described above to clean the surface of the wafer to remove the hard mask layer.

[0013] Optionally, the material of the hard mask layer includes carbon-doped tungsten.

[0014] Optionally, an adhesion layer is provided between the layer to be etched and the hard mask layer; and the wafer cleaning solution is also used to remove the adhesion layer.

[0015] Optionally, the material of the adhesion layer includes tungsten nitride.

[0016] Optionally, the cleaning solution has an operating temperature range of 25°C to 70°C.

[0017] Optionally, the method for forming the hard mask layer includes: forming a mask material layer on the surface of the layer to be etched; forming a patterned photoresist layer on the surface of the mask material layer; and etching the mask material layer using the photoresist layer as a mask to form the hard mask layer.

[0018] Optionally, before the cleaning process, the photoresist layer is also removed.

[0019] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0020] The wafer cleaning liquid provided by the technical solution of the present invention is used to remove a hard mask layer formed by a carbon-doped tungsten material after an etching process, wherein an oxidant is used to dissolve tungsten. In the aqueous solution after the removal of tungsten, since the remaining carbon surface in the carbon-doped tungsten material is prone to hanging -OH bonds, negatively charged active groups are generated on the carbon surface. The cations in the cationic surfactant in the wafer cleaning liquid and the negative charges on the carbon surface are tightly adsorbed to form a double layer, thereby enhancing the dispersion of carbon in the solution, thereby reducing the adhesion of carbon on the wafer surface, promoting the dissolution of carbon, and thus improving the cleanliness of the wafer surface.

[0021] Furthermore, the cleaning solution also includes: an organic amine compound. The cleaning solution is also used to remove etching byproducts on the wafer surface after dry etching, further improving the cleanliness of the wafer surface.

[0022] The method for forming a semiconductor structure provided by the technical solution of the present invention is beneficial to reducing the pattern roughness of the transferred pattern when the carbon-doped tungsten material is used as the hard mask layer, thereby obtaining a higher etching selectivity. After the pattern layer is formed, the wafer surface is cleaned with a wafer cleaning solution to remove the hard mask layer, wherein an oxidant is used to dissolve tungsten. In the aqueous solution after the tungsten is removed, since the remaining carbon surface in the carbon-doped tungsten material is prone to hanging -OH bonds, negatively charged active groups are generated on the carbon surface. The cations in the cationic surfactant in the wafer cleaning solution and the negative charges on the carbon surface are tightly adsorbed to form a double electric layer, thereby enhancing the dispersion of carbon in the solution, thereby reducing the adhesion of carbon on the wafer surface, promoting the dissolution of carbon, and thus improving the cleanliness of the wafer surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of a wet etching method;

[0024] Figures 2 to 3 It is a structural schematic diagram of each step of the method for forming a semiconductor structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] It should be noted that the terms “surface” and “on” in this specification are used to describe relative positional relationships in space and are not limited to direct contact.

[0026] As described in the background art, the existing wet etching method needs to be further improved. Now, a wet etching method is described and analyzed.

[0027] In the existing process, SPM cleaning solution (a mixture of sulfuric acid, hydrogen peroxide and deionized water) is often used to remove the carbon-doped tungsten hard mask material. However, the high temperature environment of the SPM cleaning solution can easily have an adverse effect on the performance of the device.

[0028] Figure 1 It is a structural schematic diagram of a wet etching method.

[0029] Please refer to Figure 1, as shown in the figure, a semiconductor structure is obtained after a mask layer 105 formed of a carbon-doped tungsten material is used as a mask to etch a dielectric layer 104 to form a contact hole 106, comprising: a substrate, the substrate comprising a base 100 and a fin 101 located on the base 100; a gate 102 spanning the fin 101; a source-drain layer 103 located in the fin 101 on both sides of the gate 102; a dielectric layer 104 located on the surface of the substrate and the gate 102; a mask layer 105 located on the dielectric layer 104; and a contact hole 106 located in the dielectric layer 104, wherein the contact hole 106 exposes the source-drain layer 103.

[0030] After forming the semiconductor structure, the mask layer 105 can be effectively removed by using SPM cleaning solution (a mixture of sulfuric acid, hydrogen peroxide and deionized water) to obtain a clean wafer surface. However, as the size of semiconductors continues to shrink, the thickness of the dielectric layer 104 becomes thinner and thinner. The high temperature environment of the SPM cleaning solution can easily cause the deformation of the dielectric layer 104, resulting in an SPM cleaning solution channel (such as a channel between the outside of the dielectric layer 104 and the gate 102) Figure 1 As shown by the arrow, the gate 102 is corroded, thereby affecting the performance of the device.

[0031] In order to overcome the above problems, a possible alternative is to replace the SPM cleaning solution with a solution containing hydrogen peroxide, such as SC1 cleaning solution (a mixture of ammonia, hydrogen peroxide and water) or SC2 cleaning solution (a mixture of hydrochloric acid, hydrogen peroxide and water). However, since hydrogen peroxide can only dissolve tungsten but not carbon, during the cleaning process, after the tungsten is dissolved, the carbon continues to adhere to the wafer surface, resulting in excessive impurities remaining on the wafer surface, which cannot meet the current semiconductor process requirements for wafer surface cleanliness.

[0032] In order to solve the above problems, the present invention provides a wafer cleaning liquid and a semiconductor structure formation method, wherein the wafer cleaning liquid is used to remove a hard mask layer formed by a carbon-doped tungsten material after an etching process, wherein an oxidant is used to dissolve tungsten, and in the aqueous solution after the removal of tungsten, since the remaining carbon surface in the carbon-doped tungsten material is prone to hanging -OH bonds, negatively charged active groups are generated on the carbon surface, and the cations in the cationic surfactant in the wafer cleaning liquid and the negative charges on the carbon surface are tightly adsorbed to form a double layer, thereby enhancing the dispersion of carbon in the solution, thereby reducing the adhesion of carbon on the wafer surface, promoting the dissolution of carbon, and thus improving the cleanliness of the wafer surface.

[0033] In order to make the above-mentioned objects, features and beneficial effects of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0034] Figures 2 to 3It is a structural schematic diagram of each step of the method for forming a semiconductor structure according to an embodiment of the present invention.

[0035] Please refer to Figure 2 , providing a layer to be etched (not shown in the figure), wherein the layer to be etched is located on the surface of a wafer 200; forming a hard mask layer 201 on the layer to be etched, wherein the hard mask layer 201 exposes a portion of the layer to be etched; using the hard mask layer 201 as a mask, etching the layer to be etched to form a graphic layer 202.

[0036] In this embodiment, the material of the layer to be etched is silicon oxide. In other embodiments, the layer to be etched can also be other materials, such as silicon, silicon nitride, silicon oxynitride and other materials commonly used in semiconductor processes.

[0037] In this embodiment, the material of the hard mask layer 201 includes carbon-doped tungsten. Using carbon-doped tungsten as the hard mask layer is beneficial to reducing the pattern roughness of the transfer pattern and obtaining higher etching selectivity and size uniformity.

[0038] In this embodiment, an adhesion layer 203 is further provided between the layer to be etched and the hard mask layer 201. The adhesion layer 203 is used to improve the adhesion between the hard mask layer 201 and the layer to be etched.

[0039] In this embodiment, the material of the adhesion layer 203 includes tungsten nitride.

[0040] In this embodiment, the method for forming the hard mask layer 201 includes: forming a mask material layer (not shown in the figure) on the surface of the layer to be etched; forming a patterned photoresist layer (not shown in the figure) on the surface of the mask material layer; using the photoresist layer as a mask, etching the mask material layer to form the hard mask layer 201.

[0041] In this embodiment, the photoresist layer is also removed before the cleaning process.

[0042] In this embodiment, the process of removing the photoresist layer includes an ashing process.

[0043] After etching the layer to be etched, etching byproducts A are usually attached to the surface of the pattern layer 202. The etching byproducts A include silicon-containing polymers. In this embodiment, when the surface of the wafer 200 is subsequently cleaned, the wafer cleaning solution is also used to remove the etching byproducts A, further improving the cleanliness of the wafer surface.

[0044] In this embodiment, the process of etching the layer to be etched includes a dry etching process; the etching gas of the dry etching process includes CF4 gas. The etching byproduct A includes polymers of carbon, silicon, fluorine and the like.

[0045] Please refer to Figure 3 After forming the pattern layer 202, a wafer cleaning solution 204 is used to clean the surface of the wafer 200 to remove the hard mask layer 201, wherein the wafer cleaning solution 204 includes a mixture of an oxidant, a cationic surfactant and water.

[0046] In the above method, an oxidant is used to dissolve tungsten. In the aqueous solution 205 after removing tungsten, since the remaining carbon surface in the carbon-doped tungsten material is prone to hanging -OH bonds, negatively charged active groups are generated on the carbon surface. The cations in the cationic surfactant in the wafer cleaning solution and the negative charges on the carbon surface are tightly adsorbed to form a double layer 206, which increases the dispersion of carbon in the solution, thereby reducing the adhesion of carbon on the wafer surface, promoting the dissolution of carbon, and thus improving the cleanliness of the wafer surface.

[0047] The oxidant includes a mixture of one or more of hydrogen peroxide, urea peroxide, peroxodisulfuric acid, ammonium persulfate, peroxymonosulfuric acid, pyrosulfuric acid and ozone. In this embodiment, the oxidant is hydrogen peroxide (H2O2).

[0048] In this embodiment, the reaction formula for removing tungsten by using hydrogen peroxide includes:

[0049] W+2H2O2→WO2+2H2O

[0050] WO2+H2O2→H2WO4

[0051] 3H2WO4+2H2O2→H2W3O 12 +4H2O

[0052] The cationic surfactant includes a mixture of one or more of hexadecyltrimethylammonium bromide, hexadecyldimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyldimethylamine oxide, didecyldimethylammonium bromide, dodecyldimethylammonium chloride, N-hexadecylpropylenediamine diammonium chloride and didecyldimethylammonium chloride. In this embodiment, the cationic surfactant is hexadecyltrimethylammonium bromide.

[0053] In this embodiment, in the cleaning solution, the molar percentage content of the oxidant ranges from 10% to 25%, and the molar percentage content of the cationic dispersant ranges from 0.1% to 3%.

[0054] In this embodiment, the operating temperature range of the cleaning solution is 25°C to 70°C.

[0055] In this embodiment, the wafer cleaning solution is also used to remove the adhesion layer 203 .

[0056] In this embodiment, since the dispersibility of carbon in the solution is enhanced, during the cleaning process, the adhesion of carbon to the adhesion layer 203 is reduced, which is beneficial to improving the removal ability of the adhesion layer 203.

[0057] In this embodiment, the cleaning solution further comprises: an organic amine compound. The organic amine compound is used to remove etching byproducts of silicon-containing polymers. Specifically, the organic amine compound is used to remove the etching byproduct A.

[0058] In this embodiment, in the cleaning solution, the molar percentage content of the organic amine compound ranges from 0.5% to 5%.

[0059] In this embodiment, the organic amine compound includes a mixture of one or more of methylamine, ethylamine, triethylamine, triethanolamine, isobutylamine, tert-butylamine, tributylamine, dipropylamine, dimethylamine, diethylene glycolamine, monoethanolamine, methyldiethanolamine, diisopropylamine, diisobutylamine, aniline, pentamethyldiethylenetriamine, acetoacetamide, ammonium carbamate, ammonium pyrrolidine dithiocarbamate, N-methylacetoacetamide and tetramethylammonium thiobenzoate. In this embodiment, the organic amine compound is methylamine.

[0060] Accordingly, the embodiment of the present invention also provides a wafer cleaning solution used in the semiconductor structure forming method, please continue to refer to Figure 3 The wafer cleaning solution 204 includes a mixture of an oxidant, a cationic surfactant and water.

[0061] The wafer cleaning solution 204 is used to remove the hard mask layer 201 formed by the carbon-doped tungsten material after the etching process, wherein the oxidant is used to dissolve tungsten. In the aqueous solution after the removal of tungsten, since the remaining carbon surface in the carbon-doped tungsten material is prone to hanging -OH bonds, negatively charged active groups are generated on the carbon surface. The cations in the cationic surfactant in the wafer cleaning solution and the negative charges on the carbon surface are tightly adsorbed to form a double layer 206, which enhances the dispersion of carbon in the solution, thereby reducing the adhesion of carbon on the wafer surface, promoting the dissolution of carbon, and thus improving the cleanliness of the wafer surface.

[0062] In this embodiment, in the cleaning solution, the molar percentage content of the oxidant ranges from 10% to 25%, and the molar percentage content of the cationic dispersant ranges from 0.1% to 3%.

[0063] In this embodiment, the cleaning solution further comprises: an organic amine compound. The cleaning solution is also used to remove etching byproducts A on the surface of the wafer after dry etching, thereby further improving the cleanliness of the wafer surface.

[0064] In this embodiment, in the cleaning solution, the molar percentage content of the organic amine compound ranges from 0.5% to 5%.

[0065] In this embodiment, the organic amine compound includes a mixture of one or more of methylamine, ethylamine, triethylamine, triethanolamine, isobutylamine, tert-butylamine, tributylamine, dipropylamine, dimethylamine, diethylene glycolamine, monoethanolamine, methyldiethanolamine, diisopropylamine, diisobutylamine, aniline, pentamethyldiethylenetriamine, acetoacetamide, ammonium carbamate, ammonium pyrrolidine dithiocarbamate, N-methylacetoacetamide and tetramethylammonium thiobenzoate.

[0066] In this embodiment, the oxidant includes a mixture of one or more of hydrogen peroxide, urea peroxide, peroxodisulfuric acid, ammonium persulfate, peroxymonosulfuric acid, pyrosulfuric acid and ozone.

[0067] In this embodiment, the cationic surfactant includes a mixture of one or more of hexadecyltrimethylammonium bromide, hexadecyldimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyldimethylamine oxide, didecyldimethylammonium bromide, dodecyldimethylammonium chloride, N-hexadecylpropylenediamine diammonium chloride and didecyldimethylammonium chloride.

[0068] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A wafer cleaning solution, characterized in that: include: A mixture of oxidant, cationic surfactant and water.

2. The wafer cleaning solution according to claim 1, characterized in that: In the cleaning solution, the molar percentage content of the oxidant ranges from 10% to 25%, and the molar percentage content of the cationic dispersant ranges from 0.1% to 3%.

3. The wafer cleaning solution as claimed in claim 2, characterized in that: The cleaning solution also includes: an organic amine compound.

4. The wafer cleaning solution as claimed in claim 3, characterized in that: In the cleaning solution, the molar percentage content of the organic amine compound ranges from 0.5% to 5%.

5. The wafer cleaning solution as claimed in claim 4, characterized in that: The organic amine compound includes a mixture of one or more of methylamine, ethylamine, triethylamine, triethanolamine, isobutylamine, tert-butylamine, tributylamine, dipropylamine, dimethylamine, diethylene glycolamine, monoethanolamine, methyldiethanolamine, diisopropylamine, diisobutylamine, aniline, pentamethyldiethylenetriamine, acetoacetamide, ammonium carbamate, ammonium pyrrolidine dithiocarbamate, N-methylacetoacetamide and tetramethylammonium thiobenzoate.

6. The wafer cleaning solution according to claim 1, characterized in that: The oxidizing agent includes one or a mixture of more than one of hydrogen peroxide, urea peroxide, peroxodisulfuric acid, ammonium persulfate, peroxymonosulfuric acid, pyrosulfuric acid and ozone.

7. The wafer cleaning solution according to claim 1, characterized in that: The cationic surfactant includes a mixture of one or more of hexadecyltrimethylammonium bromide, hexadecyldimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyldimethylamine oxide, didecyldimethylammonium bromide, dodecyldimethylammonium chloride, N-hexadecylpropylenediamine diammonium chloride and didecyldimethylammonium chloride.

8. A method for forming a semiconductor structure, characterized in that: include: Providing a layer to be etched, wherein the layer to be etched is located on the surface of the wafer; forming a hard mask layer on the layer to be etched, wherein the hard mask layer exposes a portion of the layer to be etched; Using the hard mask layer as a mask, etching the layer to be etched to form a pattern layer; After forming the pattern layer, the wafer surface is cleaned using the wafer cleaning solution as described in any one of claims 1 to 7 to remove the hard mask layer.

9. The method for forming a semiconductor structure according to claim 8, wherein: The material of the hard mask layer includes carbon-doped tungsten.

10. The method for forming a semiconductor structure according to claim 8, wherein: An adhesion layer is also provided between the layer to be etched and the hard mask layer; and the wafer cleaning liquid is also used to remove the adhesion layer.

11. The method for forming a semiconductor structure according to claim 10, wherein: The material of the adhesion layer includes tungsten nitride.

12. The method for forming a semiconductor structure according to claim 8, wherein: The use temperature range of the cleaning solution is 25°C to 70°C.

13. The method for forming a semiconductor structure according to claim 8, wherein: The method for forming the hard mask layer comprises: forming a mask material layer on the surface of the layer to be etched; forming a patterned photoresist layer on the surface of the mask material layer; and etching the mask material layer using the photoresist layer as a mask to form the hard mask layer.

14. The method for forming a semiconductor structure according to claim 13, wherein: Before the cleaning process, the photoresist layer is also removed.

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