Selective etching solution for titanium nitride and molybdenum

Abstract

The application provides a selective etching solution of titanium nitride and molybdenum, which comprises 0.05-0.1% of a fluorine ion source, 0.15-0.35% of an acid, 0.1-0.3% of a fluorine ion stabilizer, 0.01-0.02% of an oxidizing agent, 0.1-0.3% of a complexing agent, 0.12-0.16% of a silicon etching inhibitor, and the rest is deionized water. The etching solution can guarantee that the selectivity ratio of titanium nitride and molybdenum is in the range of 20-60, and has a good lifetime (Lifetime>12h) for a low etching rate of Poly etching solution.

Description

Technical Field

[0001] This invention belongs to the field of electronic chemicals and relates to an etching solution, particularly a selective etching solution for titanium nitride and molybdenum. Background Technology

[0002] Titanium nitride (TiN) and molybdenum (Mo) are key metal layer materials in semiconductor devices, and their selective etching technology directly affects device performance and process stability. Current etching solution systems need to balance high etching rates, selectivity, and process compatibility.

[0003] The current etching solution market is dominated by selective etching solutions using titanium nitride (TiN) and tungsten (W), primarily because both are widely used as metal layer / electrode materials in semiconductor manufacturing, and the related etching technologies are relatively mature. In contrast, etching solutions using TiN and molybdenum (Mo) are less common.

[0004] Molybdenum exhibits significant advantages over tungsten in the semiconductor field. Its lower resistivity (approximately 5.2 μΩ·cm) effectively reduces signal transmission delay and improves overall chip energy efficiency. Furthermore, atomic layer deposition (ALD) technology for molybdenum enables high-precision, uniform filling of nanoscale trenches, fully meeting the stringent requirements of advanced processes for material morphology. Molybdenum has a similar coefficient of thermal expansion to silicon (approximately 4.8 × 10⁻⁶). -6 The presence of molybdenum at ℃ significantly reduces thermal stress-induced material deformation, thereby improving device reliability. Simultaneously, molybdenum's excellent oxidation resistance makes it less prone to oxide formation during high-temperature processes, ensuring long-term device stability. More importantly, molybdenum exhibits good plasticity at low temperatures, enabling the fabrication of thin foils or filaments with complex structures, providing a material foundation for precision semiconductor manufacturing.

[0005] As semiconductor devices continue to evolve towards smaller sizes and higher integration, developing specialized etching solutions capable of selectively etching titanium nitride (TiN) and molybdenum (Mo) has become a key technological requirement for constructing precise TiN / Mo composite structures and overcoming device performance bottlenecks. Therefore, developing an etching solution capable of selectively etching titanium nitride (TiN) and molybdenum (Mo) is of great significance for promoting the development of semiconductor technology.

[0006] This invention provides a selective etching solution composition of titanium nitride (TiN) and molybdenum (Mo) and its method of use, the selectivity of which can reach [missing information]. The etching solution has a long lifespan and can effectively meet customers' requirements to completely etch the TiN film while retaining a certain thickness of Mo film, without damaging the electrical properties of the substrate. Summary of the Invention

[0007] This invention aims to provide a selective etching solution formulation for titanium nitride and molybdenum, wherein the selective ratio of titanium nitride to molybdenum is... Furthermore, it has a low etching rate for Poly and the etching solution has a good lifespan.

[0008] The technical solution of this invention comprises, by mass percentage, 0.05%-0.1% of a fluoride ion source, 0.15%-0.35% of an acid, 0.1%-0.3% of a fluoride ion stabilizer, 0.01%-0.02% of an oxidant, 0.1%-0.3% of a complexing agent, and 0.12%-0.16% of a silicon etching inhibitor, with the remainder being deionized water. The mass percentages refer to the percentage of each component of the etching solution relative to the total mass of the raw materials.

[0009] Furthermore, the fluoride ions can be derived from one or more of the following: hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, fluorosilicic acid, fluoroboric acid, etc.

[0010] Furthermore, the fluoride ion source primarily serves to provide the F required for the reaction. - Etching of titanium nitride and molybdenum.

[0011] Furthermore, the acid is one or a combination of methanesulfonic acid, p-toluenesulfonic acid, sulfuric acid, and benzenesulfonic acid, and its main function is to provide the acidic environment required for the reaction, and it has the effect of reacting with F. - Combined, SO2F is generated. - This inhibits the effect of Poly etching.

[0012] Furthermore, the fluoride ion stabilizer can be one or a combination of boric acid, Tween, polyvinyl alcohol, polyacryl alcohol, ethylenediaminetetraacetic acid, etc., mainly to prevent fluoride ions from oxidizing. - Other reactions occur, which play a role in slowing down the release and prolonging the life of the etching solution.

[0013] Furthermore, the oxidant is one or a combination of periodic acid, hydrogen peroxide, nitric acid, etc., which plays a role in oxidizing titanium nitride and molybdenum, thereby promoting the reaction.

[0014] Furthermore, the complexing agent can be one or a combination of several of the following: phytic acid, polyaspartic acid, polyglutamic acid, triethylenetetraminehexaacetic acid, trans-1,2-cyclohexanediaminetetraacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, etc., which can complex molybdenum and thus slow down the molybdenum etching rate.

[0015] Furthermore, the silicon etching inhibitor is a composition of inorganic silica sol and silane, wherein the silane is one or more of 3-aminopropyltriethoxysilane, glycidoxypropyltrimethoxysilane, methacryloyloxypropyltrimethoxysilane, vinyltrimethoxysilane, ureopropyltriethoxysilane, etc. The synergistic effect of inorganic silica sol and silane inhibits the etching of Poly.

[0016] Furthermore, the preferred operating temperature range for the etching solution is 47°C-53°C, and more preferably 50°C.

[0017] Furthermore, the etching rate ratio of titanium nitride to molybdenum in the etching solution is in the range of 20-60.

[0018] Furthermore, this etching solution exhibits a low etching rate for Poly, less than [a certain value].

[0019] Furthermore, the etching solution has a good lifespan, with a relatively stable etching rate and a decay of less than 5% within 12 hours.

[0020] The present invention has the following beneficial effects:

[0021] In this invention, a fluoride ion source is added to provide the F required for the reaction. - Etching of titanium nitride and molybdenum.

[0022] In this invention, a sulfur-containing, water-soluble organic or inorganic strong acid is added to provide the acidic environment required for the reaction, and it has the properties of reacting with F. - Combined, SO2F is generated. - This inhibits the effect of Poly etching.

[0023] In this invention, a fluoride ion stabilizer is added to prevent F - Other reactions occur, resulting in a sustained release and giving the solution a longer lifespan.

[0024] In this invention, an oxidizing agent is added to oxidize titanium nitride and molybdenum, thereby promoting the reaction.

[0025] The addition of a complexing agent in this invention can complex molybdenum, thereby slowing down the molybdenum etching rate.

[0026] In this invention, a composition of inorganic silica sol and silane is added as a mixed inhibitor. The synergistic effect of the two inhibits the etching of Poly. Detailed Implementation

[0027] The abbreviations used in the examples and below are as follows: PAA - polyacrylic acid; PASP - polyaspartic acid; TTHA - triethylenetetraminehexaacetic acid; CDTA - trans-1,2-cyclohexanediaminetetraacetic acid; A - silica sol; B - 3-aminopropyltriethoxysilane (CAS: 919-30-2); C - glycidoxypropyltrimethoxysilane (CAS: 2530-83-8); D - methacryloxypropyltrimethoxysilane (CAS: 2530-85-0); E - vinyltrimethoxysilane (CAS: 2768-02-7); TiN - titanium nitride; Mo - molybdenum; DHF - low concentration hydrofluoric acid; ER - etching rate.

[0028] A selective etching solution for titanium nitride and molybdenum, comprising, by mass percentage: 0.05%-0.1% fluoride ion source, 0.15%-0.35% acid, 0.1%-0.3% fluoride ion stabilizer, 0.01%-0.02% oxidant, 0.1%-0.3% complexing agent, 0.12%-0.16% silicon etching inhibitor, with the remainder being deionized water.

[0029] 1. Solution preparation

[0030] Prepare 100g of etching solution according to the above formula, place it in a 100ml round-bottom three-hole flask, add a stir bar to the flask, set the temperature of the electric heating pot to 50℃ and the stirring rate to 500r / min, and etch TiN / Mo / Poly when the solution temperature reaches and stabilizes at 50±0.5℃.

[0031] 2. Etching process

[0032] TiN: Silicon substrate, thickness approximately [missing information].

[0033] Mo: Silicon substrate, approximately [thickness missing]

[0034] Poly: Silicon substrate, approximately 23nm thick.

[0035] (1) Calculation of TiN and Mo etching rates

[0036] Before etching, TiN and Mo were cut into 1.5*1cm slices, and lines were drawn on the slices to divide them into 1*1cm and 0.5*1cm sections (without cutting them completely off). The initial thickness of the 1*1cm section was measured twice using a four-point probe, and the arithmetic mean was taken. The slices were then immersed in the etching solution and etched for 5 minutes each, rinsed thoroughly with water, and dried with nitrogen. The thickness of the slices after etching was measured twice using a four-point probe, and the arithmetic mean was taken. The etching rates of TiN and Mo were calculated.

[0037] (2) Poly etching rate calculation

[0038] Before etching, Poly was cut into 2*1cm slices. To avoid the influence of the oxide layer on the surface of the sample on the experimental results, the sample was soaked in 200:1 DHF for 1 minute, rinsed with clean water, and then dried with nitrogen. The initial thickness of the sample was measured using an ellipsometer, and the arithmetic mean was taken twice. The sample was then immersed in the etching solution for 30 minutes, rinsed with clean water, and dried with nitrogen. The thickness of the sample after etching was measured using an ellipsometer, and the arithmetic mean was taken twice. The etching rate of Poly was calculated.

[0039] (3) Test method for the effect of temperature on etching rate and selectivity

[0040] Based on Example 1, the experimental process of Comparative Examples 11-14 was completed by adjusting the temperature. The experimental process was the same as described above.

[0041] (4) Etching solution life test method

[0042] For Examples 1, 11-14, and Comparative Example 5, lifetime experiments were conducted to determine the etching lifetime within 12 hours. The experimental procedures were the same as described above.

[0043] Table 1. Component content of examples and comparative examples

[0044]

[0045]

[0046]

[0047]

[0048] Table 2. Etching rates and selectivity of the examples and comparative examples.

[0049]

[0050]

[0051] The experimental results in Table 2 show that the etching solution formulations of all the above embodiments are as follows. Example: Etching rate selectivity ratio of TiN and Mo in etching solution

[0052] By comparing and analyzing the experimental results in Table 2, it can be seen from Examples 1, 2, and 3 that as the F in the solution... - With increasing concentration, the etching rate of both TiN and Mo increases.

[0053] As can be seen from Examples 1, 4-7 and Comparative Examples 2-3, the stronger the acidity, the stronger the etching rate of both TiN and Mo, but the effect on the selectivity is not significant. After adding a sulfur-containing water-soluble organic or inorganic strong acid, the etching rate of Poly decreases, and the selectivity of TiN and Mo increases.

[0054] As can be seen from the examples and comparative examples, the etching rate of both TiN and Mo increases with the increase of oxidant content. Without the addition of oxidant, TiN and Mo are basically not etched, and there is also basically no etching effect on Poly.

[0055] Analysis of Comparative Example 7 and the Example shows that the addition of the chelating agent mainly plays a role in inhibiting Mo etching.

[0056] Analysis of Comparative Examples 8-10 and the Examples shows that the addition of silicon etching inhibitor can suppress poly etching. When either of them works alone, the poly etching rate is relatively fast. When they work synergistically, they have a better inhibition effect.

[0057] Etching was performed according to the method of Example 1, with only the etching temperature adjusted. The etching results are shown in Table 3.

[0058] Table 3. Etching rates and selectivity of the examples and comparative examples at different temperatures.

[0059]

[0060] As shown in the comparative examples in Table 3, the etching rates of both TiN and Mo increase with increasing temperature. Their selectivity initially increases and then decreases, reaching its maximum of 55.63 at 50℃. Therefore, selecting an appropriate etching temperature can improve the selectivity of the etching solution.

[0061] Table 4. Etching rate of titanium nitride after 12 hours of continuous heating.

[0062]

[0063] As can be seen from the data in Table 4, Example 1 exhibits good etching lifetime within 11-14 and 12 hours, with a decay rate of <5%, while Comparative Example 5, which did not add a fluoride ion stabilizer, shows a more severe lifetime decay. Comparative Examples 7 and 8 indicate that the fluoride ion stabilizer is the main factor affecting the TiN etching lifetime, while the complexing agent and silicon etching inhibitor have virtually no impact on the TiN etching lifetime.

[0064] In summary, the fluoride ion source has the ability to provide the F required for the reaction. - The etching effect on titanium nitride and molybdenum, the acid provides the acidic environment required for the reaction, and has a similar effect to F. - Combined, SO2F is generated. - This inhibits the etching effect of Poly, and the fluoride ion stabilizer can prevent F... - Other reactions occur, providing a slow-release effect. The oxidant oxidizes TiN and Mo, thereby promoting the reaction. The complexing agent complexes Mo, thus inhibiting Mo etching. The silicon etching inhibitor acts synergistically with the inorganic silica sol and silane, inhibiting the etching of Poly. The etching solution, with the above combination, achieves a suitable selectivity and good etching lifetime.

[0065] Based on the features described above, any changes in proportions and equivalent substitutions or recombinations of raw materials are within the scope of protection of this invention.

Claims

1. A selective etching liquid for titanium nitride and molybdenum, characterized by, By mass percentage, it includes 0.05%-0.1% fluoride ion source, 0.15%-0.35% acid, 0.1%-0.3% fluoride ion stabilizer, 0.01%-0.02% oxidant, 0.1%-0.3% complexing agent, 0.12%-0.16% silicon etching inhibitor, and the remainder is deionized water. The fluoride ion source is a combination of one or more fluorine-containing compounds such as hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, fluorosilicic acid, and fluoroboric acid. The acid is one or a combination of several of methanesulfonic acid, p-toluenesulfonic acid, sulfuric acid, or benzenesulfonic acid, and the fluoride ion stabilizer is one or a combination of several of boric acid, Tween, polyvinyl alcohol, polyacryl alcohol, or ethylenediaminetetraacetic acid. The oxidizing agent is one or a combination of periodic acid, hydrogen peroxide or nitric acid; The complexing agent is selected from one or a combination of several of phytic acid, polyaspartic acid, polyglutamic acid, triethylenetetraminehexaacetic acid, trans-1,2-cyclohexanediaminetetraacetic acid, or ethylene glycol diethyl ether diaminetetraacetic acid. The silicon etching inhibitor is a composition of inorganic silica sol and silane, wherein the silane is one or more of 3-aminopropyltriethoxysilane, glycidoxypropyltrimethoxysilane, methacryloyloxypropyltrimethoxysilane, vinyltrimethoxysilane or ureopropyltriethoxysilane.

2. The selective etching liquid of titanium nitride and molybdenum according to claim 1, characterized by: The etching solution can be used in a temperature range of 47℃-53℃.

3. The selective etching solution for titanium nitride and molybdenum according to claim 1, characterized in that: The etching solution is designed for use at a temperature of 50°C.

4. The selective etching solution for titanium nitride and molybdenum according to claim 1, characterized in that: The etching rate ratio of titanium nitride to molybdenum in the etching solution is in the range of 20-60.

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