A method for removing unreacted nickel platinum alloy from self-aligned silicide

Abstract

The present application relates to the technical field of semiconductor manufacturing, in particular to a method for removing unreacted nickel platinum alloy in self-aligned silicide, comprising the following steps: a) providing a wafer with a metal layer on the surface; the metal layer comprises nickel platinum alloy; b) forming a porous titanium dioxide layer on the surface of the metal layer; c) removing the metal layer at room temperature by using a photocatalytic reaction; d) removing the porous titanium dioxide layer by using a hydrogen peroxide complexation reaction; e) sequentially performing impurity removal, water washing and drying on the surface of the wafer to obtain self-aligned silicide. Compared with the prior art, the method for removing unreacted nickel platinum alloy in self-aligned silicide provided by the present application realizes overall good interaction by using specific process steps and conditions, can remove unreacted nickel platinum alloy in self-aligned silicide at room temperature, avoids the influence of high-temperature wet process on the thermal stability of nickel silicide compound, and does not lose nickel silicide, thereby improving the process stability of self-aligned silicide, and further improving the product yield.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and more specifically, to a method for removing unreacted nickel-platinum alloy from self-aligned silicides. Background Technology

[0002] Self-aligned silicide (SASil) is a key process in semiconductor manufacturing, primarily used to reduce the resistance of the source, drain, and gate structures, thereby improving device performance and operating speed. This process involves depositing a nickel-platinum thin film on the exposed silicon surface of the source and drain electrodes. After a rapid thermal annealing reaction to form nickel silicide, unreacted nickel-platinum alloy is removed using a wet etching process. Finally, a second rapid thermal annealing step forms a low-resistivity metallic silicide, NiSi. (See [link to documentation]). Figure 1 As shown.

[0003] Currently, existing technologies typically use single-piece wet etching equipment combined with high-temperature sulfuric acid-hydrogen peroxide solution or aqua regia solution to remove unreacted nickel-platinum alloys. (See also...) Figure 2 As shown. When etching nickel-platinum using high-temperature sulfuric acid and hydrogen peroxide solution, the reaction temperature needs to reach above 200℃, placing high demands on equipment hardware. Furthermore, nickel silicides have poor thermal stability. The high-temperature sulfuric acid and hydrogen peroxide reaction is exothermic, resulting in an actual wafer temperature exceeding 220℃, which affects the performance of nickel silicides after the first rapid thermal annealing. In addition, the high-temperature sulfuric acid and hydrogen peroxide solution has a significant temperature difference with the ambient temperature. Therefore, during wet etching, the wafer surface temperature tends to decrease from the center to the edge, which is detrimental to the uniformity of wet etching (see...). Figure 3 As shown); while aqua regia can easily damage nickel silicides (see...). Figure 4 (As shown). Summary of the Invention

[0004] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides a method for removing unreacted nickel-platinum alloy from self-aligned silicides, which can remove unreacted nickel-platinum alloy from self-aligned silicides at room temperature, avoiding the impact of high-temperature wet processing on the thermal stability of nickel-silicon compounds, and without losing the nickel silicide.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0006] According to one aspect of the present invention, a method for removing unreacted nickel-platinum alloy from self-aligned silicides is provided, comprising the following steps:

[0007] a) Provide a wafer with a metal layer on its surface; said metal layer comprising a nickel-platinum alloy;

[0008] b) A porous titanium dioxide layer is formed on the surface of the metal layer;

[0009] c) Remove the metal layer at room temperature using a photocatalytic reaction;

[0010] d) The porous titanium dioxide layer was removed by a hydrogen peroxide complexation reaction;

[0011] e) The wafer surface is sequentially cleaned, washed with water, and dried to obtain a self-aligned silicide.

[0012] In some of these embodiments, in step a), the thickness of the metal layer is 150 nm to 200 nm.

[0013] In some of these embodiments, step b) involves forming the porous titanium dioxide layer via atomic deposition.

[0014] In some embodiments, the deposition temperature of the atomic deposition method is 350°C to 450°C.

[0015] In some of these embodiments, in step b), the thickness of the porous titanium dioxide layer is 50 nm to 100 nm.

[0016] In some of these embodiments, in step b), the pore size of the porous titanium dioxide layer is 5 nm to 10 nm.

[0017] In some embodiments, step c), the process of removing the metal layer at room temperature using a photocatalytic reaction specifically includes:

[0018] An organic phase system of acetonitrile and dichloromethane was used to dissolve the metal layer under light conditions at a temperature of 15°C to 35°C.

[0019] In some embodiments, the flow ratio of acetonitrile to dichloromethane in the organic phase system of acetonitrile and dichloromethane is 1:(0.5~2).

[0020] In some embodiments, the illumination conditions specifically include: 400mW / cm² 2 ~600mW / cm 2 Xenon lamp illumination.

[0021] In some embodiments, step d) specifically includes the process of removing the porous titanium dioxide layer using a hydrogen peroxide complexation reaction:

[0022] The porous titanium dioxide layer was dissolved using a mixed solution of dilute sulfuric acid and hydrogen peroxide at 50℃~80℃.

[0023] In some embodiments, the concentration of the dilute sulfuric acid is 0.5M to 1.5M.

[0024] In some of these embodiments, the concentration of the hydrogen peroxide is 20wt% to 40wt%.

[0025] In some embodiments, the mass ratio of dilute sulfuric acid to hydrogen peroxide in the mixed solution of dilute sulfuric acid and hydrogen peroxide is 1:(1~4).

[0026] In some of these implementations, step e) specifically includes the following impurity removal process:

[0027] The wafer was treated with a hydrochloric acid-hydrogen peroxide solution at 15℃~35℃; the mass ratio of HCl, H2O2 and H2O in the hydrochloric acid-hydrogen peroxide solution was 1:(0.5~1.5):(5~10).

[0028] This invention provides a method for removing unreacted nickel-platinum alloy from self-aligned silicides, comprising the following steps: a) providing a wafer with a metal layer on its surface; the metal layer comprising a nickel-platinum alloy; b) forming a porous titanium dioxide layer on the surface of the metal layer; c) removing the metal layer at room temperature using a photocatalytic reaction; d) removing the porous titanium dioxide layer using a hydrogen peroxide complexation reaction; e) sequentially removing impurities, washing with water, and drying the wafer surface to obtain the self-aligned silicide. Compared with the prior art, the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided by this invention employs specific process steps and conditions to achieve better overall interaction, enabling the removal of unreacted nickel-platinum alloy from self-aligned silicides at room temperature, avoiding the impact of high-temperature wet processing on the thermal stability of nickel-silicon compounds, and without losing nickel silicide, thereby improving the process stability of self-aligned silicides and thus improving product yield.

[0029] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0030] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0031] Figure 1 This is a flowchart of a self-aligned silicide process in the prior art.

[0032] Figure 2 This is a schematic diagram of a prior art method for removing unreacted nickel-platinum alloy from self-aligned silicides.

[0033] Figure 3 This is a schematic diagram illustrating how existing technologies use high-temperature sulfuric acid and hydrogen peroxide to cause the surface temperature of a wafer to decrease from the center to the edge.

[0034] Figure 4This is a schematic diagram illustrating the damage caused to nickel silicides by the use of aqua regia in existing technologies.

[0035] Figure 5 This is a schematic diagram illustrating the photocatalytic principle used in the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided by the present invention.

[0036] Figure 6 The image shows the effect of the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided in Example 1.

[0037] Figure 7 The effect of the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided in Comparative Example 1 is shown in the figure.

[0038] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0039] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0040] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0041] In the description of this application, "same chemical composition" should be interpreted broadly, that is, the main components of the two have the same chemical composition, or the two have substantially the same chemical composition, but may have errors or impurities within the acceptable range that can be understood by those skilled in the art.

[0042] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0043] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0044] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0045] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0046] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0047] Currently, to address the technical challenge of removing unreacted nickel-platinum alloys from self-aligned silicides, existing technologies typically employ single-wafer wet etching equipment combined with high-temperature sulfuric acid-hydrogen peroxide solution or aqua regia solution. However, high-temperature sulfuric acid-hydrogen peroxide etching requires a reaction temperature exceeding 200°C, placing high demands on the equipment hardware. Furthermore, nickel silicides exhibit poor thermal stability, and the exothermic reaction of high-temperature sulfuric acid-hydrogen peroxide results in an actual wafer temperature exceeding 220°C, negatively impacting the performance of nickel silicides after the first rapid thermal annealing. Additionally, the significant temperature difference between high-temperature sulfuric acid-hydrogen peroxide and ambient temperature causes the wafer surface temperature to decrease from the center to the edges during wet etching, hindering uniformity. Aqua regia, on the other hand, can easily damage nickel silicides.

[0048] Based on this, the inventors of this invention have conducted in-depth research on the mechanism of removing unreacted nickel-platinum alloy from self-aligned silicides. Based on extensive experiments and combined with experimental data, they have innovatively proposed a method for removing unreacted nickel-platinum alloy from self-aligned silicides. This method can remove unreacted nickel-platinum alloy from self-aligned silicides at room temperature, avoiding the impact of high-temperature wet processing on the thermal stability of nickel-silicon compounds, and without losing the nickel silicide, thus solving the problems existing in the prior art. Specifically, this invention adopts the following technical solution:

[0049] According to one aspect of the present invention, a method for removing unreacted nickel-platinum alloy from self-aligned silicides is provided, comprising the following steps:

[0050] a) Provide a wafer with a metal layer on its surface; said metal layer comprising a nickel-platinum alloy;

[0051] b) A porous titanium dioxide layer is formed on the surface of the metal layer;

[0052] c) Remove the metal layer at room temperature using a photocatalytic reaction;

[0053] d) The porous titanium dioxide layer was removed by a hydrogen peroxide complexation reaction;

[0054] e) The wafer surface is sequentially cleaned, washed with water, and dried to obtain a self-aligned silicide.

[0055] This invention first provides a wafer with a metal layer on its surface. This invention does not impose any particular restriction on the source of the wafer with the metal layer; commercially available products or self-made products well-known to those skilled in the art can be used. In a preferred embodiment of this invention, the wafer is an initial semiconductor structure well-known to those skilled in the art for self-aligned silicide processes, with a metal layer on its surface. This invention does not impose any particular restriction on the formation method of this metal layer; physical vapor deposition, chemical vapor deposition, or atomic layer epitaxy processes well-known to those skilled in the art can all be used.

[0056] In a specific embodiment of the present invention, the metal layer comprises a nickel-platinum alloy; therefore, the metal layer can also be referred to as a nickel-platinum thin film. In this invention, the thickness of the metal layer is preferably 150 nm to 200 nm, specifically 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, or any value between these two. It should be noted that the use of a metal layer of suitable thickness in this invention facilitates the subsequent formation of a porous titanium dioxide layer and simultaneously meets the requirements for achieving the desired self-aligned silicide effect.

[0057] Furthermore, the present invention forms a porous titanium dioxide layer on the surface of the metal layer.

[0058] In a specific embodiment of the present invention, the method for forming the porous titanium dioxide layer preferably includes atomic deposition. In a preferred embodiment of the present invention, the deposition temperature of the atomic deposition method is preferably 350℃~450℃, specifically 350℃, 400℃, 450℃, or any value between the above two. It should be noted that the present invention uses the above-mentioned suitable deposition temperature to ensure that a porous titanium dioxide layer meeting the expected requirements is deposited on the surface of the metal layer.

[0059] In a specific embodiment of the present invention, the thickness of the porous titanium dioxide layer is preferably 50 nm to 100 nm, specifically 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value between the above two. It should be noted that the use of a porous titanium dioxide layer of the above-mentioned suitable thickness in the present invention can achieve a good covering effect, thereby better exerting its photocatalytic effect, and also facilitating subsequent removal, thus avoiding any adverse effects on the self-aligned silicide.

[0060] In a specific embodiment of the present invention, the pore size of the porous titanium dioxide layer is preferably 5nm to 10nm, specifically 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, or any value between the above two. It should be noted that the present invention uses the above-mentioned suitable pore size to ensure that the reagents used in the photocatalytic reaction can fully contact the metal layer, thereby facilitating the photocatalytic reaction.

[0061] After the porous titanium dioxide layer is formed, the present invention uses a photocatalytic reaction to remove the metal layer at room temperature.

[0062] In a specific embodiment of the present invention, the process of removing the metal layer at room temperature using a photocatalytic reaction preferably includes:

[0063] An organic phase system of acetonitrile and dichloromethane was used to dissolve the metal layer under light conditions at a temperature of 15°C to 35°C.

[0064] In a specific embodiment of the present invention, the preferred flow ratio of acetonitrile to dichloromethane in the organic phase system of acetonitrile and dichloromethane is 1:(0.5~2), specifically 1:0.5, 1:1, 1:2, or any ratio between the two mentioned above. The present invention does not impose any special restrictions on the source of the acetonitrile and dichloromethane; commercially available products well-known to those skilled in the art can be used. The organic phase system of acetonitrile and dichloromethane can be prepared using techniques well-known to those skilled in the art, such as mixing acetonitrile and dichloromethane to obtain the corresponding organic phase system; the present invention does not impose any special restrictions on this. It should be noted that the use of the above-mentioned suitable components and ratios in the organic phase system ensures the smooth progress of the photocatalytic reaction and achieves the effect of completely removing the metal layer at room temperature. In actual operation, the flow ratio is specifically a volumetric flow ratio, and the present invention does not impose any special restrictions on this.

[0065] In a specific embodiment of the present invention, the preferred illumination conditions include: 400 mW / cm². 2 ~600mW / cm 2 Xenon lamp illumination, specifically: 400mW / cm² 2 500mW / cm 2 600mW / cm2 Or, a value between any two of the above. The inventors of this invention have found through experiments that if the light intensity is too low, the photocatalytic reaction cannot proceed smoothly, while if the light intensity is too high, the photocatalytic reaction cannot guarantee a good removal effect on nickel-platinum alloys. Based on this, this invention selects suitable light conditions within the above range to achieve the expected photocatalytic reaction effect and realize the complete removal of unreacted nickel-platinum alloys from self-aligned silicides.

[0066] This invention utilizes the aforementioned photocatalytic reaction to achieve complete removal of unreacted nickel-platinum alloy from self-aligned silicides at room temperature. A schematic diagram of the photocatalytic principle is shown below. Figure 5 As shown: The photocatalytic dissolution of free radicals first involves the photoexcitation of a semiconductor (TiO2) under suitable light conditions, generating photo-generated electrons and holes. Then, the photo-generated electrons reduce oxygen to superoxide radical anions (•O). 2- Holes oxidize acetonitrile (CH2Cl2) and dichloromethane (CH3CN) into cyano radicals (•CN) and chlorine radicals (•Cl), respectively. The resulting free radicals work together to cause PGMs to... 0 Oxidation to PGMs x+ It should be noted that PGMs represents platinum group metals, including: Ru, Rh, Pd, Os, Ir, and Pt; PGMs 0 That is, platinum group metals, PGMs x+ This indicates the valence state of the platinum group metal ions.

[0067] After removing the metal layer, the present invention uses a hydrogen peroxide complexation reaction to remove the porous titanium dioxide layer.

[0068] In a specific embodiment of the present invention, the process of removing the porous titanium dioxide layer by hydrogen peroxide complexation reaction preferably includes:

[0069] The porous titanium dioxide layer was dissolved using a mixed solution of dilute sulfuric acid and hydrogen peroxide at 50℃~80℃.

[0070] In a specific embodiment of the present invention, the mass ratio of dilute sulfuric acid to hydrogen peroxide in the mixed solution is preferably 1:(1~4), specifically 1:1, 1:2, 1:3, 1:4, or any ratio between the two mentioned above; wherein, the concentration of the dilute sulfuric acid is preferably 0.5M~1.5M, specifically 0.5M, 1M, 1.5M, or any value between the two mentioned above; the concentration of the hydrogen peroxide is preferably 20wt%~40wt%, specifically 20wt%, 30wt%, 40wt%, or any value between the two mentioned above. The present invention does not impose any special restrictions on the source of the dilute sulfuric acid and hydrogen peroxide, and commercially available products well known to those skilled in the art can be used; the mixed solution of dilute sulfuric acid and hydrogen peroxide can be prepared using techniques well known to those skilled in the art, and the present invention does not impose any special restrictions on this. It should be noted that the present invention uses a mixed solution with the above-mentioned suitable components and proportions, which can ensure the smooth progress of the hydrogen peroxide complexation reaction, achieve the complete removal of the porous titanium dioxide layer, and avoid its residue from adversely affecting the performance of the self-aligned silicide.

[0071] After removing the porous titanium dioxide layer, the present invention sequentially removes impurities, washes with water, and dries the wafer surface to obtain a self-aligned silicide.

[0072] In this invention, the purpose of the impurity removal is to remove residual metal ions on the wafer surface.

[0073] In a specific embodiment of the present invention, the impurity removal process preferably includes:

[0074] The wafer was treated with a hydrochloric acid-hydrogen peroxide solution at 15℃~35℃. Therefore, the impurity removal process can also be performed at room temperature.

[0075] In a specific embodiment of the present invention, the preferred mass ratio of HCl, H2O2, and H2O in the hydrochloric acid-hydrogen peroxide solution is 1:(0.5~1.5):(5~10), specifically 1:1:5, 1:1:6, 1:1:7, 1:1:8, 1:1:9, 1:1:10, or any ratio between the above two. The present invention uses the above-mentioned suitable hydrochloric acid-hydrogen peroxide solution to ensure optimal impurity removal while avoiding adverse effects on self-aligned silicides. The present invention does not impose any special restrictions on the source of the hydrochloric acid-hydrogen peroxide solution; commercially available products or homemade products well-known to those skilled in the art can be used.

[0076] In a specific embodiment of the present invention, the water washing adopts the deionized water washing technique known to those skilled in the art, and the drying adopts the conventional drying method known to those skilled in the art. The present invention has no special restrictions on this. After completing the above steps, the unreacted nickel-platinum alloy in the self-aligned silicide is removed, and a self-aligned silicide that meets the expected requirements is obtained.

[0077] This invention provides a method for removing unreacted nickel-platinum alloy from self-aligned silicides, comprising the following steps: a) providing a wafer with a metal layer on its surface; the metal layer comprising a nickel-platinum alloy; b) forming a porous titanium dioxide layer on the surface of the metal layer; c) removing the metal layer at room temperature using a photocatalytic reaction; d) removing the porous titanium dioxide layer using a hydrogen peroxide complexation reaction; e) sequentially removing impurities, washing with water, and drying the wafer surface to obtain the self-aligned silicide. Compared with the prior art, the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided by this invention employs specific process steps and conditions to achieve better overall interaction, enabling the removal of unreacted nickel-platinum alloy from self-aligned silicides at room temperature, avoiding the impact of high-temperature wet processing on the thermal stability of nickel-silicon compounds, and without losing nickel silicide, thereby improving the process stability of self-aligned silicides and thus improving product yield.

[0078] The present application will be described in detail below with reference to the accompanying drawings and embodiments. However, the implementation and protection of the present invention are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0079] Example 1

[0080] (1) A wafer with a nickel-platinum thin film deposited on its surface is provided, the nickel-platinum thin film having a thickness of 180 nm.

[0081] (2) A porous photocatalytic material TiO2 is deposited on the surface of the above wafer at 400°C using atomic deposition method. The deposition thickness is 75 nm and the pore size of the porous photocatalytic material TiO2 is 8 nm.

[0082] (3) Removal of unreacted nickel-platinum thin films using photocatalysis: An organic phase system of acetonitrile and dichloromethane with a flow ratio of 1:1 was prepared, and the reaction was carried out at 500 mW / cm 2 The wafers were treated at 25°C under xenon lamp irradiation to dissolve the nickel-platinum alloy.

[0083] (4) Then, the porous photocatalytic material TiO2 is removed by hydrogen peroxide complexation. Specifically, the wafer is treated at 65°C with a mixed solution of 1M dilute sulfuric acid and 30wt% hydrogen peroxide at a mass ratio of 1:2 to remove TiO2.

[0084] (5) Then, the wafer was treated with hydrochloric acid hydrogen peroxide solution (HCl, H2O2, H2O in a mass ratio of 1:1:8) at 25°C to remove residual metal ions on the wafer surface.

[0085] (6) Finally, the above wafers are washed with deionized water and dried in sequence to complete the method of removing unreacted nickel-platinum alloy from the self-aligned silicide and obtain the self-aligned silicide.

[0086] Testing showed that the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided in Example 1 of this invention can completely remove the unreacted nickel-platinum alloy; more importantly, it causes minimal damage to the nickel silicide, within 2.7 nm. (See [reference needed]). Figure 6 The SEM image is shown.

[0087] Comparative Example 1

[0088] (1) A wafer with a nickel-platinum thin film deposited on its surface is provided, the nickel-platinum thin film having a thickness of 180 nm.

[0089] (2) Use a high-temperature SPM system to remove unreacted nickel-platinum thin films: Prepare a sulfuric acid and hydrogen peroxide SPM system with a flow ratio of 4:1, and treat the above wafers at 170°C with H2SO4 to dissolve the nickel-platinum alloy.

[0090] (3) Then, the above wafers were treated with an ammonia-hydrogen peroxide solution (NH4OH, H2O2, H2O in a flow ratio of 1:2:50) at 25°C to remove the residual particulate matter on the wafer surface.

[0091] (4) Finally, the above wafers are washed with deionized water and dried in sequence to complete the method of removing unreacted nickel-platinum alloy from the self-aligned silicide and obtain the self-aligned silicide.

[0092] Testing showed that the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided in Comparative Example 1, while capable of completely removing the unreacted nickel-platinum alloy, caused significant damage to the nickel silicides, exceeding 5 nm. (See [reference needed]). Figure 7 The SEM image is shown.

[0093] Example 2

[0094] (1) A wafer with a nickel-platinum thin film deposited on its surface is provided, the nickel-platinum thin film having a thickness of 150 nm.

[0095] (2) A porous photocatalytic material TiO2 is deposited on the surface of the above wafer at 350°C using atomic deposition method. The deposition thickness is 50 nm and the pore size of the porous photocatalytic material TiO2 is 5 nm.

[0096] (3) Removal of unreacted nickel-platinum thin films using photocatalysis: An organic phase system of acetonitrile and dichloromethane with a flow ratio of 1:1 was prepared, and the reaction was carried out at 400 mW / cm². 2 The wafers were treated at 25°C under xenon lamp irradiation to dissolve the nickel-platinum alloy.

[0097] (4) Then, the porous photocatalytic material TiO2 is removed by hydrogen peroxide complexation. Specifically, the wafer is treated at 50°C with a mixed solution of 1M dilute sulfuric acid and 30wt% hydrogen peroxide at a mass ratio of 1:4 to remove TiO2.

[0098] (5) Then, the wafer was treated with hydrochloric acid hydrogen peroxide solution (HCl, H2O2, H2O in a mass ratio of 1:1:10) at 25°C to remove residual metal ions on the wafer surface.

[0099] (6) Finally, the above wafers are washed with deionized water and dried in sequence to complete the method of removing unreacted nickel-platinum alloy from the self-aligned silicide and obtain the self-aligned silicide.

[0100] Tests have shown that the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided in Embodiment 2 of this invention can completely remove unreacted nickel-platinum alloy; more importantly, it causes minimal damage to nickel silicides, within 3 nm.

[0101] Example 3

[0102] (1) A wafer with a nickel-platinum thin film deposited on its surface is provided, the nickel-platinum thin film having a thickness of 200 nm.

[0103] (2) A porous photocatalytic material TiO2 is deposited on the surface of the above wafer at 450°C using atomic deposition method. The deposition thickness is 100 nm and the pore size of the porous photocatalytic material TiO2 is 10 nm.

[0104] (3) Removal of unreacted nickel-platinum thin films using photocatalysis: An organic phase system of acetonitrile and dichloromethane with a flow ratio of 1:1 was prepared, and the reaction was carried out at 600 mW / cm². 2 The wafers were treated at 25°C under xenon lamp irradiation to dissolve the nickel-platinum alloy.

[0105] (4) Then, the porous photocatalytic material TiO2 is removed by hydrogen peroxide complexation. Specifically, the wafer is treated at 80°C with a mixed solution of 1M dilute sulfuric acid and 30wt% hydrogen peroxide in a mass ratio of 1:1 to remove TiO2.

[0106] (5) Then, the wafer was treated with hydrochloric acid hydrogen peroxide solution (HCl, H2O2, H2O in a mass ratio of 1:1:5) at 25°C to remove residual metal ions on the wafer surface.

[0107] (6) Finally, the above wafers are washed with deionized water and dried in sequence to complete the method of removing unreacted nickel-platinum alloy from the self-aligned silicide and obtain the self-aligned silicide.

[0108] Tests have shown that the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided in Embodiment 3 of this invention can completely remove the unreacted nickel-platinum alloy; more importantly, it causes minimal damage to nickel silicides, within 2.8 nm.

[0109] Comparative Example 2

[0110] The method for removing unreacted nickel-platinum alloy from self-aligned silicides provided in Example 1 is different in that acetonitrile is used as the organic phase system.

[0111] Tests showed that the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided in Comparative Example 2 could not completely remove the unreacted nickel-platinum alloy.

[0112] Comparative Example 3

[0113] The method for removing unreacted nickel-platinum alloy from self-aligned silicides provided in Example 1 is different in that dichloromethane is used as the organic phase system.

[0114] Tests showed that the method for removing unreacted nickel-platinum alloy from self-aligned silicides provided in Comparative Example 3 could not completely remove the unreacted nickel-platinum alloy.

[0115] In summary, this invention provides a method for removing unreacted nickel-platinum alloy from self-aligned silicides. This method can remove unreacted nickel-platinum alloy from self-aligned silicides at room temperature (25°C in the examples), avoiding the impact of high-temperature wet processing on the thermal stability of nickel-silicon compounds, and without losing nickel silicides. This improves the stability of the self-aligned silicide process and thus increases product yield.

[0116] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0117] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0118] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for removing unreacted nickel-platinum alloy from self-aligned silicides, characterized in that, Includes the following steps: a) Provide a wafer with a metal layer on its surface; said metal layer comprising a nickel-platinum alloy; b) A porous titanium dioxide layer is formed on the surface of the metal layer; c) Remove the metal layer at room temperature using a photocatalytic reaction; The process of removing the metal layer at room temperature using a photocatalytic reaction specifically includes: An organic phase system of acetonitrile and dichloromethane was used to dissolve the metal layer under light conditions at 15℃~35℃. d) Removing the porous titanium dioxide layer using a hydrogen peroxide complexation reaction; the process of removing the porous titanium dioxide layer using a hydrogen peroxide complexation reaction specifically includes: The porous titanium dioxide layer was dissolved using a mixed solution of dilute sulfuric acid and hydrogen peroxide at 50℃~80℃. e) The wafer surface is sequentially cleaned, washed with water, and dried to obtain a self-aligned silicide.

2. The method for removing unreacted nickel-platinum alloy from self-aligned silicides according to claim 1, characterized in that, In step a), the thickness of the metal layer is 150nm~200nm.

3. The method for removing unreacted nickel-platinum alloy from self-aligned silicides according to claim 1, characterized in that, In step b), the method of forming the porous titanium dioxide layer includes atomic deposition.

4. The method for removing unreacted nickel-platinum alloy from self-aligned silicides according to claim 3, characterized in that, The deposition temperature for the atomic deposition method is 350℃~450℃.

5. The method for removing unreacted nickel-platinum alloy from self-aligned silicides according to claim 1, characterized in that, In step b), the thickness of the porous titanium dioxide layer is 50 nm to 100 nm; and / or, The porous titanium dioxide layer has a pore size of 5nm to 10nm.

6. The method for removing unreacted nickel-platinum alloy from self-aligned silicides according to claim 1, characterized in that, In the organic phase system of acetonitrile and dichloromethane, the flow ratio of acetonitrile to dichloromethane is 1:(0.5~2); and / or, The specific lighting conditions include: 400mW / cm² 2 ~600mW / cm 2 Xenon lamp illumination.

7. The method for removing unreacted nickel-platinum alloy from self-aligned silicides according to claim 1, characterized in that, The concentration of the dilute sulfuric acid is 0.5M to 1.5M; and / or, The concentration of the hydrogen peroxide is 20wt%~40wt%; and / or, The mass ratio of dilute sulfuric acid to hydrogen peroxide in the mixed solution of dilute sulfuric acid and hydrogen peroxide is 1:(1~4).

8. The method for removing unreacted nickel-platinum alloy from self-aligned silicides according to claim 1, characterized in that, In step e), the impurity removal process specifically includes: The wafer was treated with a hydrochloric acid-hydrogen peroxide solution at 15℃~35℃; the mass ratio of HCl, H2O2 and H2O in the hydrochloric acid-hydrogen peroxide solution was 1:(0.5~1.5):(5~10).

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