CN102408836A - A kind of nano-polishing liquid for chemical mechanical planarization of titanium oxide thin film and its application - Google Patents

Abstract

A nanometer polishing solution for chemical mechanical planarization of a titanium oxide film is formed by mixing a nanometer abrasive, a pH regulator, a surfactant, a defoaming agent, a bactericide, an auxiliary cleaning agent and a solvent, wherein the nanometer abrasive is cerium oxide or silicon dioxide, the pH regulator is a composite pH regulator formed by an inorganic pH regulator and an organic pH regulator, the surfactant is silane polyethylene glycol ether, polyethylene glycol ether or dodecyl glycol ether, the defoaming agent is polydimethylsilane, the bactericide is isomeric thiazolinone, the auxiliary cleaning agent is isopropanol, and the solvent is deionized water; the nano polishing solution is used for preparing a resistive random access memory based on a titanium oxide film material. The invention has the advantages that: stable and controllable polishing rate, less surface damage of the film, easy cleaning, no environmental pollution and long storage time. The polishing solution is used for carrying out chemical mechanical planarization on the titanium oxide thin film material of the resistive random access memory to prepare the resistive random access memory, and the method is simple and easy to implement and is completely compatible with the integrated circuit process.

Description

A kind of nano-polishing liquid for chemical mechanical planarization of titanium oxide thin film and its application

technical field

The invention relates to the technical field of microelectronic auxiliary materials and processing techniques, in particular to a nano-polishing liquid for chemical mechanical planarization of titanium oxide films and its application.

Background technique

With the rapid development of microelectronic technology and computer technology, the demand for large-capacity non-volatile memory is becoming more and more urgent. However, due to the high operating voltage, complex circuit structure, and the fact that the floating gate structure cannot be infinitely thinned, the further application of the flash memory in various fields is severely restricted. Especially when the process node enters 45nm, because the integration density cannot be further increased, the demand for new types of memory to replace the flash memory becomes more urgent. Therefore, various non-volatile memories based on new theories and new materials have emerged, and the resistive memory (also called resistive memory) developed by using the current-induced resistance transition effect is one of them. Resistive Random Access Memory (RRAM) is a new type of non-volatile memory, which has low operating voltage, fast read and write speed, strong durability for repeated operations, high storage density, long data retention time, and low power consumption. , low cost, compatible with CMOS technology and other characteristics, known as the most powerful competitor of the next generation of non-volatile memory. The key material of the resistive memory is the recordable transition metal oxide thin film material, among which the titanium oxide material with resistive properties has attracted much attention from all walks of life. Seoul National University in South Korea (Appl. Phys. Lett. 95, 093508, 2009), Sun Yat-sen University of China (Appl. Phys. Lett. 93, 043502, 2008), Tokyo University of Japan (Appl. Phys. Lett. 92, 043510, 2008), Asia University (Thin Solid Films 516, 2008, 8693–8696), HP Laboratories and others are conducting research on the resistive properties of titanium oxide and related technologies for the manufacture of resistive memory devices. It can be seen that resistive memory devices based on titanium oxide will have a good application prospect in the field of resistive memory devices. However, various existing methods of growing titanium oxide, such as: sputtering, pulsed laser deposition, low-pressure chemical vapor deposition, electron beam evaporation, atomic layer deposition, sol-gel, etc., have large surface roughness. And the surface contains pinhole defects, which will seriously affect the growth of subsequent thin films, thereby seriously affecting the performance of the entire resistive switch device. Especially when the process node enters 40nm, the large roughness of the grown titanium oxide surface restricts the realization of high-precision lithography, which seriously restricts the manufacture and application of titanium oxide thin films and related devices. Therefore, the growth of titanium oxide film must be planarized to reduce its surface roughness before it can be applied to the actual device manufacturing. In addition, the key technology for manufacturing resistive variable memory based on titanium oxide thin film material is how to form a damascene structure of resistive variable material, and then form a memory cell. Combined with the wide application of chemical mechanical planarization in the field of device interconnection, how to make titanium oxide-based resistive memory through chemical mechanical planarization of titanium oxide has become a current research hotspot, and the work on chemical mechanical planarization of titanium oxide has also become a topic in this field. one of the focuses of attention.

At present, Chemical Mechanical Planarization (CMP), as the only technology that can achieve global planarization, has become an indispensable process in VLSI process, and is widely used in deep submicron In the multilayer copper interconnection system. The International Technology Roadmap for Semiconductors (ITRS) proposed in 2007 that the research on chemical mechanical planarization of new materials used in non-volatile memories is extremely needed, and the formation of deep trench structures and redundant Material removal requires chemical mechanical planarization to complete.

In order to continuously increase the storage density and reduce the voltage and power consumption during resistive switching, it is required that the feature size in the resistive memory device unit be reduced to the nanometer level. In view of the technology below 0.25 micron in the semiconductor process, the surface of the material must be globally planarized by chemical mechanical planarization, so that the general photolithography exposure process can be used for sub-micron size processing. Secondly, through chemical mechanical planarization, the flatness of the film can be improved, the contact area between the interfaces can be increased, and the current density captured by the interface between the electrode and the resistive film can be reduced, thereby improving the electrical characteristics and fatigue resistance of the resistive film material. At the same time, the defects are reduced, and the reliability of the device is enhanced. Moreover, in order to make the manufacturing process of the resistive memory device compatible with the CMOS process so as to minimize the manufacturing cost, it is necessary to study the key process of chemical mechanical planarization of the resistive switch material. The cell structure of RRAM devices involves the formation of nanostructures, including the formation of nanopores, nanofilling and chemical-mechanical planarization of redundant materials. In order to form the filling structure, the device unit can only be formed by filling the resistive material and chemical mechanical planarization. After reviewing domestic and foreign patents and literature, there is no report on the chemical mechanical polishing of titanium oxide resistive material. Since the composition of the polishing liquid has a great influence on the practicability of polishing and the quality of the polished surface, the study of the composition of the polishing liquid not only determines the quality of polishing, but also determines the efficiency of polishing. It can be predicted that the development of chemical mechanical planarization of titanium oxide thin films for resistive memory materials will provide the possibility for further high-performance and low-cost development of resistive memory devices.

Since deep submicron IC process materials must be globally planarized, the research on chemical mechanical planarization of resistive memory thin film materials will become the bottleneck technology for the development of next-generation higher-performance resistive memory. High-resolution lithography exposure can be performed to form nano-scale feature sizes, which makes memory materials require lower voltage, lower power consumption, smaller volume, higher storage density, and lower cost when resistively changing. Therefore, the research on RRAM resistive switching thin film materials not only has great scientific significance, but also has potential huge commercial value.

Contents of the invention

The purpose of the present invention is to provide a nano-polishing liquid for chemical mechanical planarization of titanium oxide thin films and its application in view of the above-mentioned technical analysis and problems. The global planarization of variable thin film materials meets the requirements of preparing high-performance resistive variable memory, and has a good application prospect.

Technical scheme of the present invention:

A nano-polishing liquid for chemical-mechanical planarization of titanium oxide films, composed of nano-abrasives, pH regulators, surfactants, defoamers, bactericides, cleaning aids and solvents, the weight percentage of each component Yes: the nano-abrasive is 1.0-30.0wt%, the pH regulator is added so that the pH of the nano-polishing solution is 3-12, the surfactant is 0.01-1.0wt%, the defoamer is 20-200ppm, and the bactericide is 10-50ppm, 0.01-0.1wt% cleaning aid, and solvent as the balance.

The nano-abrasive is a mixture of one or two of cerium oxide and silicon dioxide in any proportion, wherein the cerium oxide is its water dispersion, and the silicon dioxide is a colloidal solution; the average particle diameter of the nano-abrasive is less than 200nm.

The pH regulator is a composite pH regulator consisting of an inorganic pH regulator and an organic pH regulator, wherein the inorganic pH regulator is KOH, HNO ₃ or H ₂ SO ₄ , and the organic pH regulator is tetramethyl hydroxide Ammonium, tetraethylammonium hydroxide, hydroxylamine, acetic acid, sulfonic acid and citric acid or a mixture of any two; the ratio of inorganic pH regulator to organic pH regulator is 1:1-8.

The surfactant is one of silane polyglycol ether, polyglycol ether and lauryl glycol ether or a mixture of two in any proportion.

The defoamer is polydimethylsilane.

The fungicide is isomeric thiazolinone.

The auxiliary cleaning agent is isopropanol.

The solvent is deionized water.

An application of the nano-polishing liquid for chemical-mechanical planarization of titanium oxide thin films, for the preparation of resistive memory based on titanium oxide thin film materials, the steps are as follows:

1) Deposit the bottom electrode on the substrate Si/SiO ₂ , deposit the SiO ₂ dielectric layer on the bottom electrode, open and etch the SiO ₂ dielectric layer, and then deposit the resistive material titanium oxide resistive thin film material to fill and cover all array holes;

2) through chemical mechanical planarization, using the nano-polishing liquid to remove and planarize the redundant titanium oxide resistive thin film material layer;

3) After depositing the upper electrode and wiring, a resistive variable memory based on nickel oxide thin film material can be made.

Technical analysis of the present invention:

The main function of the abrasive is mechanical friction during CMP. The pH regulator is mainly to adjust the pH value of the polishing solution, so that the polishing solution is stable and helps to carry out CMP; select a compound acid or alkali as the pH regulator, inorganic alkali KOH or inorganic acid _HNO3 can enhance the chemical action of the polishing solution, The organic base or organic acid can well keep the pH value of the solution stable and ensure the consistent and stable chemical action, thereby realizing the stability of the polishing rate. The role of the surfactant is to make the abrasive in the polishing liquid highly stable. During the CMP process, it is preferentially adsorbed on the surface of the material, and the chemical corrosion effect is reduced. Because the friction force of the concave is small, the polishing rate of the convex is higher than that of the concave, which plays a role To improve the polishing convex-concave selectivity, enhance the high-low selectivity ratio, reduce the surface tension and reduce the surface damage. The addition of surfactants in the polishing liquid usually leads to the generation of foam, which is not controlled by the production process. A low-foaming or non-foaming polishing liquid can be achieved by adding a small amount of defoaming agent, which is easy to operate and use. The polishing liquid contains a lot of organic matter, long-term storage is easy to form mold, resulting in the deterioration of the polishing liquid, so a small amount of fungicide is added to the polishing liquid. The addition of auxiliary cleaning agent helps to reduce the adsorption of particles and reduce the cleaning cost in the later stage.

The invention has the advantages of stable and controllable polishing rate, less damage on the coated film surface, easy cleaning, no environmental pollution and long storage time. By using the nano-polishing liquid provided by the invention, the global planarization of the resistive material titanium oxide resistive film material can be realized, and the surface roughness RMS (5 μm×5 μm) after polishing is less than 1.0 nm, which meets the requirements for preparing high-performance RRAM. The resistive variable memory is prepared by chemically mechanically planarizing the resistive variable titanium oxide thin film material with the polishing liquid, and the method is simple and easy, and is fully compatible with the integrated circuit technology.

Description of drawings

Figure 1 is a schematic diagram of the structure of a titanium oxide polished sample deposited on _SiO2 with array holes.

Figure 2 is a schematic diagram of the structure of the excess part of the resistive material titanium oxide after CMP.

FIG. 3 is a schematic diagram of the structure of the resistive variable memory.

Figure 4 is an AFM image of the titanium oxide film before polishing.

Figure 5 is an AFM image of the titanium oxide film after polishing.

Detailed ways

Further illustrate substantive characteristics and remarkable progress of the present invention by following examples. However, the present invention is by no means limited to the examples.

Example 1:

A nano-polishing liquid for chemical-mechanical planarization of titanium oxide films is composed of nano-abrasives, pH regulators, surfactants, defoamers, bactericides, cleaning aids and solvents.

Preparation of nano-polishing liquid: the polishing liquid contains 20wt% silica colloid of 10~30nm; 0.2wt% lauryl glycol ether; 50ppm polydimethylsilane; 10ppm isomeric thiazolinone; isopropanol 0.03wt%; KOH and tetramethylammonium hydroxide (volume ratio of 1:1) are the pH regulator, the pH is 8, and the rest is deionized water. When preparing, mix the above raw materials, use a magnetic stirrer to stir evenly, and then directly experiment on the machine.

Realization of polishing process: 6EC nSpire polishing machine from Strasbaugh in the United States is used, the polishing pad is Rohm&Haas IC1000, the rotational speed of the polishing head is 35rpm, the rotational speed of the polishing disc is 40rpm, the flow rate of the polishing liquid is 100ml/min, and the downforce is 2psi.

The polished sample is prepared as follows: 1) deposit a bottom electrode W layer with a thickness of 100 nm on the substrate Si/SiO ₂ ; 2) deposit a dielectric layer SiO ₂ with a thickness of 200 nm on the bottom electrode W layer; 3) process SiO by photolithography _2- layer etching to form 1000nm array holes; 4) Deposit titanium oxide resistive thin film material on SiO ₂ with array holes to fill and cover all array holes. Figure 1 is a schematic diagram of the structure of the polished sample.

Polishing effect test: use a Dektak 150 profiler to measure the thickness difference of the resistive material titanium oxide film before and after polishing, divide it by the polishing time to get the polishing rate, use Agilent's atomic force microscope (AFM) to measure the resistive material before and after polishing Surface morphology and roughness of TiO thin films. Fig. 4 is an AFM image of the titanium oxide film before polishing, and Fig. 5 is an AFM image of the titanium oxide film after polishing.

Polishing effect: the polishing rate of resistive material titanium oxide is 52nm/min, the polishing rate of SiO ₂ is 12nm/min, the surface roughness RMS (5μm×5μm) before polishing is 8.7nm, and the surface roughness RMS (5μm×5μm) after polishing is 0.9 nm, the TiO ₂ /SiO ₂ selection ratio is 4.3:1. Fig. 2 is a schematic diagram of the structure after CMP of the redundant part of the resistive switch material titanium oxide.

Example 2:

A nano-polishing liquid for chemical-mechanical planarization of titanium oxide films is composed of nano-abrasives, pH regulators, surfactants, defoamers, bactericides, cleaning aids and solvents.

Preparation of nano-polishing liquid: the polishing liquid contains 5wt% of 10~30nm silica colloid, 4wt% of 40nm cerium oxide; 0.1wt% of polyglycol ether, 0.1wt% of dodecyl glycol ether; Methylsilane 50ppm; isomeric thiazolinone 10ppm; isopropanol 0.03wt%; KOH and hydroxylamine (volume ratio 1:3) are pH regulators, pH is 9.01, and the rest is deionized water. When preparing, mix the above raw materials, use a magnetic stirrer to stir evenly, and then directly experiment on the machine.

The polishing process, polishing sample preparation and polishing effect test are the same as in Example 1.

Polishing effect: the polishing rate of resistive material titanium oxide is 124nm/min, the polishing rate of SiO ₂ is 12.3nm/min, the surface roughness RMS (5μm×5μm) before polishing is 12.4nm, and the surface roughness RMS (5μm×5μm) after polishing is 0.63nm, TiO ₂ /SiO ₂ selection ratio is 10:1.

Example 3:

A nano-polishing liquid for chemical-mechanical planarization of titanium oxide films is composed of nano-abrasives, pH regulators, surfactants, defoamers, bactericides, cleaning aids and solvents.

Preparation of nano-polishing liquid: the polishing liquid contains 10~30nm silica colloid 5wt%, 80nm cerium oxide 2wt%; polyglycol ether 0.3wt%; polydimethylsilane 50ppm; isothiazolinone 10ppm ; Isopropanol 0.03wt%; H ₂ SO ₄ and acetic acid (volume ratio 1:3) are the pH regulator, the pH is 6.02, and the rest is deionized water. When preparing, mix the above raw materials, use a magnetic stirrer to stir evenly, and then directly experiment on the machine.

The polishing process, polishing sample preparation and polishing effect test are the same as in Example 1.

Polishing effect: the polishing rate of resistive material titanium oxide is 149.8nm/min, the polishing rate of SiO ₂ is 7nm/min, the surface roughness RMS (5μm×5μm) before polishing is 13.7nm, and the surface roughness RMS (5μm×5μm) after polishing is 0.45nm, the TiO ₂ /SiO ₂ selection ratio is 21.4:1.

Example 4:

A nano-polishing liquid for chemical-mechanical planarization of titanium oxide films is composed of nano-abrasives, pH regulators, surfactants, defoamers, bactericides, cleaning aids and solvents.

Preparation of nano-polishing liquid: the polishing liquid contains 80nm cerium oxide 5wt%; silane polyglycol ether 0.5wt%; polydimethylsilane 50ppm; isothiazolinone 10ppm; isopropanol _0.03wt %; SO ₄ and sulfonic acid (volume ratio 1:2) are pH adjusters, the pH is 5.01, and the rest is deionized water. When preparing, mix the above raw materials, use a magnetic stirrer to stir evenly, and then directly experiment on the machine.

The polishing process, polishing sample preparation and polishing effect test are the same as in Example 1.

Polishing effect: the polishing rate of resistive material titanium oxide is 196nm/min, the polishing rate of SiO ₂ is 5nm/min, the surface roughness RMS before polishing is 9.8nm, and the surface roughness RMS (5μm×5μm) after polishing is 0.78nm, TiO ₂ / The _SiO2 selectivity ratio is 39.2:1.

Example 5:

A preparation of a resistive variable memory based on nickel oxide thin film material, the steps are as follows:

1) Deposit a 100nm thick bottom electrode W on the flat and smooth Si/ _SiO2 substrate, deposit a 200nm thick _SiO2 dielectric layer on the bottom electrode, and use the reactive ion etching process to open the _SiO2 dielectric layer. etch, and then deposit the resistive material titanium oxide resistive thin film material on the sunken bottom array with holes carved, so that it fills and covers all the array holes;

2) Carrying out chemical mechanical planarization on the sample of the deposited resistive material titanium oxide thin film, using the nano-polishing solution provided by the present invention to remove and planarize the redundant titanium oxide resistive thin film material layer;

3) Deposit a layer of 100nm upper electrode W on the surface of the sample after polishing.

FIG. 3 is a schematic diagram of the resistive memory structure.

By adopting the nano-polishing liquid provided by the invention, the global planarization of the titanium oxide resistive switch thin film material can be realized, and the surface roughness RMS (5 μm×5 μm) after polishing is less than 1.0 nm, which meets the requirements for preparing high-performance RRAM. The resistive variable memory is prepared by chemically mechanically planarizing the resistive variable titanium oxide thin film material with the polishing liquid, and the method is simple and easy, and is fully compatible with the integrated circuit technology.

Claims (9)

1. A nano-polishing liquid for chemical-mechanical planarization of titanium oxide thin films, characterized in that: it is composed of nano-abrasives, pH regulators, surfactants, defoamers, bactericides, cleaning aids and solvents, The weight percentage of each component is: nano-abrasive is 1.0-30.0wt%, the amount of pH regulator is to make the nano-polishing liquid pH value is 3-12, surfactant is 0.01-1.0wt%, defoaming agent is 20 -200ppm, 10-50ppm fungicide, 0.01-0.1wt% cleaning aid, and solvent as the balance. 2. according to claim 1, be used for the nano-polishing liquid of chemical mechanical planarization of titanium oxide thin film, it is characterized in that: described nano-abrasive is the mixture of one or two arbitrary ratios in cerium oxide and silicon dioxide, Wherein the cerium oxide is its water dispersion, and the silicon dioxide is a colloidal solution; the average particle size of the nano grinding material is less than 200nm. 3. according to claim 1, be used for the nano-polishing liquid of chemical mechanical planarization of titanium oxide film, it is characterized in that: described pH adjuster is the compound pH adjuster that is made up of inorganic pH adjuster and organic pH adjuster, wherein The inorganic pH regulator is KOH, HNO ₃ or H ₂ SO ₄ , and the organic pH regulator is one or more of tetramethylammonium hydroxide, tetraethylammonium hydroxide, hydroxylamine, acetic acid, sulfonic acid and citric acid Two mixtures in any ratio; the ratio of inorganic pH regulator and organic pH regulator is 1:1-8. 4. according to claim 1, be used for the nano-polishing liquid of chemical mechanical planarization of titanium oxide film, it is characterized in that: described surfactant is silane polyglycol ether, polyglycol ether and lauryl glycol One or two mixtures of ethers in any proportion. 5 . The nano-polishing liquid for chemical mechanical planarization of titanium oxide thin films according to claim 1 , wherein the defoaming agent is polydimethylsilane. 6 . The nano-polishing liquid for chemical mechanical planarization of titanium oxide thin films according to claim 1 , wherein the fungicide is iso-thiazolinone. 6 . 7. The nano-polishing liquid for chemical-mechanical planarization of titanium oxide thin films according to claim 1, wherein the cleaning aid is isopropanol. 8 . The nano-polishing liquid for chemical mechanical planarization of titanium oxide thin films according to claim 1 , wherein the solvent is deionized water. 9. An application of a nano-polishing liquid for titanium oxide thin film chemical mechanical planarization as claimed in claim 1, characterized in that it is used for the preparation of the resistive memory based on titanium oxide thin film material, and the steps are as follows: 1) Deposit the bottom electrode on the substrate Si/SiO ₂ , deposit the SiO ₂ dielectric layer on the bottom electrode, open and etch the SiO ₂ dielectric layer, and then deposit the resistive material titanium oxide resistive thin film material to fill and cover all array holes; 2) through chemical mechanical planarization, using the nano-polishing liquid to remove and planarize the redundant titanium oxide resistive thin film material layer; 3) After depositing the upper electrode and wiring, a resistive variable memory based on nickel oxide thin film material can be made.

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