Polishing solution for reducing surface defects of copper interconnection barrier layer and preparation method of polishing solution

Abstract

The invention provides a polishing solution for reducing surface defects of a copper interconnection barrier layer and a preparation method of the polishing solution. The polishing solution comprises the following components: a silicon dioxide abrasive, an inhibitor, a surfactant, a complexing agent, a bactericide, a pH regulator and the balance of a solvent, the surfactant is composed of polyethylene glycol and hydroxyethyl cellulose in a mass ratio of (1.5-2.5): 1. Through mutual cooperation of the silicon dioxide abrasive, the inhibitor, the surfactant, the complexing agent and the sterilizing agent, polyethylene glycol and hydroxyethyl cellulose in a specific proportion are adopted as the surfactant, and the requirements for the polishing rate and the selection ratio of various materials in the polishing process can be met; and moreover, the defects of dish-shaped recesses and corrosion pits after copper polishing can be effectively corrected and controlled, and the yield and the yield of chips can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical mechanical polishing, and relates to a polishing liquid for reducing surface defects of a copper interconnection barrier layer and a preparation method thereof. Background Art

[0002] With the development of microelectronics technology, the integration of large-scale integrated circuit chips has reached billions of components, and the feature size has entered the nanometer level, which requires hundreds of processes in the microelectronics process, especially multi-layer wiring, substrate, and dielectric must undergo chemical mechanical planarization (CMP). The material of large-scale integrated wiring is changing from traditional Al to Cu. Compared with Al, Cu wiring has the advantages of low resistivity, high resistance to electromigration, and short RC delay time, which enables Cu wiring to replace Al as the interconnect metal in semiconductor manufacturing.

[0003] However, there is currently no effective plasma etching or wet etching technology for copper materials to fully form copper interconnects in integrated circuits. Therefore, it is currently the only key process technology that can achieve global and local planarization. Generally, the chemical mechanical polishing of copper wiring is divided into three steps, which are performed on three polishing discs respectively: the first step uses a higher down force to remove a large amount of copper on the substrate surface at a fast and efficient removal rate and leave a certain thickness of copper; the second step uses a lower down force to remove a small amount of remaining metal copper at a lower removal rate and stop on the barrier layer; the third step uses a barrier layer polishing liquid to remove the barrier layer, part of the dielectric layer and a small amount of metal copper, thereby achieving planarization. However, in order to effectively remove the metal copper, in the second step of polishing, in order to effectively remove the residual copper on the surface of the copper interconnect, a certain period of over-polishing is usually performed during the CMP process, but dishing pits and etch pits will be generated and deepened during the over-polishing process. Therefore, the final barrier layer CMP needs to have a certain copper and dielectric removal rate selection ratio to achieve effective correction of dishing depressions and etch pits.

[0004] However, after polishing, the existing polishing liquid has a low defect correction ability and a high surface contaminant index, and the defects of dishing and pitting cannot be effectively corrected; at the same time, the existing polishing liquid has problems such as poor stability and metal ion contamination. Summary of the invention

[0005] The object of the present invention is to provide a polishing liquid for reducing surface defects of copper interconnect barrier layer and a preparation method thereof, wherein the polishing liquid can meet the requirements of polishing rate and selectivity ratio for various materials during the polishing process, and can effectively correct and control the defects of dishing and etch pits after copper polishing.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a polishing liquid for reducing surface defects of a copper interconnect barrier layer, the polishing liquid comprising the following components: a silicon dioxide abrasive, an inhibitor, a surfactant, a complexing agent, a bactericide, a pH regulator, and the balance being a solvent;

[0008] The surfactant is composed of polyethylene glycol and hydroxyethyl cellulose in a mass ratio of (1.5-2.5):1.

[0009] The polishing liquid provided by the present invention can meet the requirements of polishing rate and selectivity of various materials in the polishing process through the mutual coordination of silicon dioxide abrasive, inhibitor, surfactant, complexing agent and bactericide, and the use of polyethylene glycol and hydroxyethyl cellulose in a specific ratio as surfactants, and can effectively correct and control the defects of dishing and pitting after copper polishing.

[0010] It is worth noting that the polishing liquid using the specific surfactant of the present invention has a small contact angle on the copper surface and increased wettability, so it can be fully spread on the copper surface, and the fluidity is improved during the polishing process, thereby reducing mechanical friction and reducing scratch defects on the Cu surface; secondly, the surfactant molecules are wrapped around the abrasive particles, increasing the repulsive force between the abrasive particles, thereby effectively avoiding the agglomerates formed by adsorption between the particles, thereby reducing scratches caused by particle agglomeration and SiO2 agglomerate contamination and other defects. In addition, the specific compound surfactant provided by the present invention has excellent dispersibility and wettability, which can not only obtain better surface quality after CMP, but also improve the stability of the polishing liquid.

[0011] As a preferred technical solution of the present invention, the mass percentage of the silica abrasive is 0.1-30%, for example, it can be 1%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25% or 28%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0012] Preferably, the total content of metal ions contained in the silica abrasive is ≤100 ppm, for example, it can be 90 ppm, 80 ppm, 70 ppm, 60 ppm, 50 ppm, 40 ppm or 30 ppm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] In the present invention, the total content of metal ions contained in the silica abrasive does not include the content of potassium ions in the silica abrasive.

[0014] Preferably, the average particle size of the silica abrasive is 75-90 nm, for example, 77 nm, 78 nm, 80 nm, 82 nm, 85 nm, 86 nm or 88 nm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] In the present invention, by controlling the average particle size range of the silicon dioxide abrasive, not only the scratches and scratches on the material surface during the polishing process are avoided, the requirements for polishing flatness are met, but also a higher polishing efficiency is ensured.

[0016] Preferably, the silica abrasive is a spherical structure.

[0017] As a preferred technical solution of the present invention, the mass percentage of the inhibitor is 0.1-10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] Preferably, the inhibitor comprises a nitrogen-containing azole compound.

[0019] Preferably, the nitrogen-containing azole compound includes benzotriazole.

[0020] As a preferred technical solution of the present invention, the mass percentage of the surfactant is 0.1-5%, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0021] It is worth noting that the present invention controls the addition amount range of the surfactant, thereby significantly reducing the defects on the product surface while ensuring the polishing rate, thereby improving the product yield.

[0022] Preferably, the relative molecular mass of the polyethylene glycol is 200-600, for example, 200, 400 or 600, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] As a preferred technical solution of the present invention, the mass percentage of the complexing agent is 0.1-5%, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] Preferably, the complexing agent comprises potassium citrate.

[0025] Preferably, the mass percentage of the fungicide is 0.1-5%, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4% or 4.5%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the bactericide comprises Kathon and / or BIT-20.

[0027] As a preferred technical solution of the present invention, the pH regulator includes any one of ammonia water, potassium hydroxide or nitric acid, or a combination of at least two of them.

[0028] Preferably, the pH value of the polishing liquid adjusted by the pH adjuster is 10-11, for example, it can be 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8 or 10.9, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Preferably, the solvent comprises water.

[0030] In a second aspect, the present invention provides a method for preparing the polishing liquid as described in the first aspect, the preparation method comprising the following steps:

[0031] (1) mixing a solvent, a surfactant, a complexing agent and an inhibitor, and performing a first stirring to obtain a first mixed solution;

[0032] (2) mixing the silica abrasive and the first mixed solution obtained in step (1), performing a second stirring, and then adding a pH adjuster thereto, adjusting the pH, and performing a third stirring to obtain a second mixed solution;

[0033] (3) Mixing the bactericide and the second mixed solution obtained in step (2), performing a fourth stirring, and then performing double-stage filtration and canning in sequence to obtain the polishing liquid.

[0034] In the present invention, the mixing method in step (1) is: adding polyethylene glycol, hydroxyethyl cellulose and inhibitor into water.

[0035] The preparation method provided by the invention is simple to operate, short in time, and suitable for large-scale industrial production.

[0036] As a preferred technical solution of the present invention, the rotation speeds of the first stirring, the second stirring, the third stirring and the fourth stirring are all 180-220 r / min, for example, 185 r / min, 190 r / min, 195 r / min, 200 r / min, 205 r / min, 210 r / min or 215 r / min, etc., but are not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0037] As a preferred technical solution of the present invention, the second stirring time in step (2) is 50-70 min, for example, it can be 52 min, 55 min, 58 min, 60 min, 62 min, 65 min, 66 min or 68 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Preferably, the third stirring time in step (2) is 20-40 min, for example, it can be 22 min, 25 min, 28 min, 30 min, 32 min, 35 min, 36 min or 38 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] As a preferred technical solution of the present invention, the fourth stirring time in step (3) is 50-70 min, for example, it can be 52 min, 55 min, 58 min, 60 min, 62 min, 65 min, 66 min or 68 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the double-stage filtration in step (3) includes a first filtration and a second filtration performed sequentially.

[0041] Preferably, the accuracy of the first filtration is 0.9-1.1 μm, for example, it can be 0.92 μm, 0.95 μm, 0.96 μm, 0.98 μm, 1 μm, 1.02 μm, 1.05 μm, 1.06 μm or 1.08 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, the accuracy of the second filtration is 0.4-0.6μm, for example, it can be 0.42μm, 0.45μm, 0.46μm, 0.48μm, 0.5μm, 0.52μm, 0.55μm, 0.58μm or 0.59μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In the present invention, before the polishing operation is performed, an oxidant with a mass percentage of 0.1-2% needs to be added to the polishing liquid, that is, 0.1-2g of the oxidant is added to 100g of the polishing liquid; the oxidant includes hydrogen peroxide.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The polishing liquid provided by the present invention can meet the requirements of polishing rate and selectivity for various materials during the polishing process through the mutual coordination of silica abrasive, inhibitor, surfactant, complexing agent and bactericide, combined with the use of polyethylene glycol and hydroxyethyl cellulose in a specific ratio as surfactants, and can effectively correct and control the defects of dishing and pitting after copper polishing, which is beneficial to improving the finished product rate and yield of chips;

[0046] (2) The polishing liquid provided by the present invention is composed of silica abrasive, inhibitor, surfactant, bactericide and water, and is low in price, simple in composition and excellent in stability; the preparation method is simple to operate, short in time, and suitable for large-scale industrial production. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0048] In the following examples and comparative examples, the total content of metal ions (excluding potassium ions) contained in the silicon dioxide abrasive is ≤100ppm; the silicon dioxide abrasives are all spherical. According to the pH value of the polishing liquid, select the corresponding ammonia water, potassium hydroxide or nitric acid to adjust to the required pH value. Before using the polishing liquid, add an oxidant (hydrogen peroxide with a mass percentage of 1%, prepared and used immediately) and mix well.

[0049] Example 1

[0050] This embodiment provides a polishing liquid for reducing surface defects of a copper interconnect barrier layer and a preparation method thereof, wherein the polishing liquid comprises the following components: a silicon dioxide abrasive, an inhibitor, a surfactant, a complexing agent, a bactericide, a pH regulator, and the balance is water;

[0051] The average particle size of the silicon dioxide abrasive is 80 nm, and its mass percentage is 20%;

[0052] The inhibitor is benzotriazole, and its mass percentage is 5%;

[0053] The surfactant is composed of polyethylene glycol 400 and hydroxyethyl cellulose in a mass ratio of 2:1, and the mass percentage thereof is 3%;

[0054] The complexing agent is potassium citrate, and its mass percentage is 3%;

[0055] The bactericide is kason, and its mass percentage is 3%;

[0056] The pH value of the polishing liquid adjusted by the pH adjuster is 10.2;

[0057] The preparation method comprises the following steps:

[0058] (1) adding polyethylene glycol 400, hydroxyethyl cellulose, a complexing agent and an inhibitor to water in sequence, and performing a first stirring at a speed of 200 r / min to obtain a first mixed solution;

[0059] (2) mixing the silica abrasive and the first mixed solution obtained in step (1), performing a second stirring at a speed of 200 r / min for 60 min, and then adding a pH adjuster thereto to adjust the pH value of the solution to 10.2, and then performing a third stirring at a speed of 200 r / min for 30 min to obtain a second mixed solution;

[0060] (3) Mixing the bactericide and the second mixed solution obtained in step (2), performing a fourth stirring at a rotation speed of 200 r / min for 60 min, and then performing a first filtration with a precision of 1 μm, a second filtration with a precision of 0.5 μm and canning in sequence to obtain the polishing liquid.

[0061] Examples 2-9 and Comparative Examples 1-4

[0062] The mass percentage of each component of the polishing liquid, the average particle size range of the silicon dioxide abrasive, the specific composition of the surfactant and other parameters were changed as shown in Table 1. Other conditions were the same as in Example 1.

[0063] Table 1

[0064]

[0065]

[0066] To verify the use effect of the polishing liquid of the present invention, a polishing experiment was carried out using the polishing liquid obtained in the above embodiments and comparative examples. The specific polishing conditions are as follows: the polishing pad is a Fujibo pad; the polishing pressure is 1.5 psi; the rotation speeds of the polishing head and the polishing disk are 86 r / min and 74 r / min respectively, the polishing liquid flow rate is 300 mL / min, and the polishing time is 75 s.

[0067] The test method for dishing and dielectric layer erosion is as follows: Use a step profiler to measure in the order of dielectric layer-copper line dishing-dielectric layer. The results are shown in Table 2.

[0068] Table 2

[0069]

[0070]

[0071] From Table 2, we can see that:

[0072] (1) The polishing liquid provided by the present invention can meet the requirements of polishing rate and selectivity for various materials during the polishing process through the mutual coordination of silica abrasive, inhibitor, surfactant and bactericide, combined with the use of polyethylene glycol and hydroxyethyl cellulose in a specific ratio as surfactants, and can effectively correct and control the defects of dishing and pitting after copper polishing, and at the same time has a lower surface contaminant index;

[0073] (2) It can be seen from the comparison between Example 1 and Examples 4-5 that if the average particle size of the silica abrasive is too low, the surface energy of the SiO2 particles tends to become smaller and agglomeration occurs due to the increase in the number of particles, and the correction ability of the dish-shaped depression and the etch pit is low; if the average particle size of the silica abrasive is too high, the friction between the abrasive and the metal increases, resulting in an increase in the dish-shaped depression and the etch pit;

[0074] (3) By comparing Example 1 with Examples 6-8, it can be seen that when the content of silica abrasive is too high, the abrasive particles are easy to agglomerate, resulting in a low ability to correct dishing and pitting; when the content of surfactant or inhibitor is too high, the contact area between the polishing liquid and the copper surface becomes small, resulting in a low ability to correct dishing and pitting;

[0075] (4) From the comparison between Example 1 and Example 9, it can be seen that when the relative molecular mass of polyethylene glycol is too large, the contact angle increases significantly, the spreading ability of the polishing liquid on the wafer surface is weakened, and the contact between the polishing liquid and copper is reduced, resulting in a lower correction ability of dishing and etch pits;

[0076] (5) From the comparison between Example 1 and Comparative Examples 1-2, it can be seen that the mass ratio of polyethylene glycol to hydroxyethyl cellulose will affect the surface defects of the product after polishing; if the proportion of polyethylene glycol is too low, the contact angle is significantly increased, the spreading ability of the polishing liquid on the wafer surface is weakened, and the contact between the polishing liquid and copper is reduced, resulting in a lower ability to correct dishing and pits; if the proportion of polyethylene glycol is too high, the contact angle is significantly reduced, the spreading ability of the polishing liquid on the wafer surface is enhanced, and the contact between the polishing liquid and copper is increased, resulting in a larger dishing after polishing;

[0077] (6) From the comparison between Example 1 and Comparative Examples 3-4, it can be seen that when the surfactant is not selected from the combination of polyethylene glycol and hydroxyethyl cellulose, its dispersibility and wettability are poor, resulting in poor surface quality after CMP.

[0078] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0079] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0080] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0081] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A polishing liquid for reducing surface defects of a copper interconnect barrier layer, characterized in that: The polishing liquid comprises the following components: silicon dioxide abrasive, inhibitor, surfactant, complexing agent, bactericide, pH regulator, and the balance is solvent; The surfactant is composed of polyethylene glycol and hydroxyethyl cellulose in a mass ratio of (1.5-2.5):

1.

2. The polishing liquid according to claim 1, characterized in that The mass percentage of the silicon dioxide abrasive is 0.1-30%; Preferably, the total content of metal ions contained in the silica abrasive is ≤100 ppm; Preferably, the average particle size of the silica abrasive is 75-90 nm; Preferably, the silica abrasive is a spherical structure.

3. The polishing liquid according to claim 1 or 2, characterized in that: The mass percentage of the inhibitor is 0.1-10%; Preferably, the inhibitor comprises a nitrogen-containing azole compound; Preferably, the nitrogen-containing azole compound includes benzotriazole.

4. The polishing liquid according to any one of claims 1 to 3, characterized in that: The mass percentage of the surfactant is 0.1-5%; Preferably, the relative molecular mass of the polyethylene glycol is 200-600.

5. The polishing liquid according to any one of claims 1 to 4, characterized in that: The mass percentage of the complexing agent is 0.1-5%; Preferably, the complexing agent comprises potassium citrate; Preferably, the mass percentage of the bactericide is 0.1-5%; Preferably, the bactericide comprises Kathon and / or BIT-20.

6. The polishing liquid according to any one of claims 1 to 5, characterized in that: The pH regulator includes any one of ammonia water, potassium hydroxide or nitric acid, or a combination of at least two of them; Preferably, the pH value of the polishing liquid is adjusted by the pH adjuster to 10-11; Preferably, the solvent comprises water.

7. A method for preparing a polishing liquid according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: (1) mixing a solvent, a surfactant, a complexing agent and an inhibitor, and performing a first stirring to obtain a first mixed solution; (2) mixing the silica abrasive and the first mixed solution obtained in step (1), performing a second stirring, and then adding a pH adjuster thereto, adjusting the pH, and performing a third stirring to obtain a second mixed solution; (3) Mixing the bactericide and the second mixed solution obtained in step (2), performing a fourth stirring, and then performing double-stage filtration and canning in sequence to obtain the polishing liquid.

8. The preparation method according to claim 7, characterized in that: The rotation speeds of the first stirring, the second stirring, the third stirring and the fourth stirring are all 180-220 r / min.

9. The preparation method according to claim 7 or 8, characterized in that: Step (2) the second stirring time is 50-70 min; Preferably, the third stirring time in step (2) is 20-40 min.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The fourth stirring time in step (3) is 50-70 minutes; Preferably, the double-stage filtration in step (3) comprises a first filtration and a second filtration performed sequentially; Preferably, the precision of the first filtration is 0.9-1.1 μm; Preferably, the second filtration has an accuracy of 0.4-0.6 μm.

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