CN104164660B - A kind of low-k dielectric constant porous SiOCNH thin film and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of ultra-large-scale integrated circuit manufacturing, in particular to a low dielectric constant porous SiOCNH film and a preparation method thereof. The invention adopts PECVD technology, uses MTES and LIMO as liquid sources, and after being vaporized, helium gas is loaded into the cavity and mixed with ammonia gas. By controlling the substrate temperature, radio frequency power, working pressure in the reaction chamber, and reaction Inorganic-organic composite thin films were deposited according to the source ratio and other process parameters, and then the organic components were removed by thermal annealing treatment, and finally a low dielectric constant porous SiOCNH thin film was obtained. The dielectric constant of the film is 2.38± ^0.06-2.58 ±0.05; the leakage current density reaches the order of 10-9-10-8 A/ ^cm2 under the electric field strength of ^1MV /cm; the Young's modulus is 35.41-36.31 GPa, The hardness is 1.88-2.48 GPa. Because the nitrogen element is doped in the film, the low dielectric constant material film not only has good electrical properties, but also has excellent mechanical properties.

Description

A kind of low dielectric constant porous SiOCNH film and preparation method thereof

technical field

The invention belongs to the technical field of VLSI manufacturing, and in particular relates to a low dielectric constant porous SiOCNH film and a preparation method thereof.

Background technique

With the rapid development of VLSI, its feature size has also decreased rapidly, and the resistance-capacitance (RC) delay effect caused by the back-end interconnection of integrated circuits has become increasingly severe, seriously restricting the improvement of chip performance. . In order to reduce the RC delay effect, using low dielectric constant (k) materials to replace the traditional interconnect dielectric SiO ₂ (k≈4.0) is an effective way to improve chip performance [1]. In order to obtain dielectric materials with lower k values, in addition to introducing less polar Si-C bonds, Si-F bonds, and CC bonds into the dielectric [2,3], another more effective method is to introduce Nanoscale pores are introduced into the material. This is due to the k value of 1 for air. As the porosity in the film increases, the value of k decreases relatively quickly [4]. However, if a low-k material film with a porous structure is to be used in an integrated circuit, its thermal stability, hydrophobicity, and electrical properties must also be considered, especially to have sufficient mechanical strength to meet the requirements of the downstream process of the integrated circuit. CMP process requirements [5,6].

Currently, spin-coating technology and plasma-enhanced chemical vapor deposition (PECVD) technology are two main methods for preparing low-k material thin films. PECVD technology is widely used in industry due to its advantages of low growth temperature, fast deposition rate and good stress controllability. In addition, by using PECVD technology, adding a pore-forming agent into the organic liquid source, and removing the pore-forming agent through thermal annealing, a low-k material film with a porous structure can be obtained, but its mechanical and electrical properties also face the risk of degradation. Therefore, it is of great practical significance to find a low-k material with excellent mechanical properties and its preparation process.

In order to improve the mechanical properties of the porous film at a lower k value, the present invention uses organic liquid sources tri-ethoxymethylsilane (MTES), dipentene (LIMO) and ammonia (NH ₃ ) as reaction Raw materials, low dielectric constant porous SiOCNH films were prepared by PECVD technology and post-annealing method. By introducing nitrogen, the mechanical properties of the porous film are also effectively improved while keeping the k value low.

references

[1]International Technology Roadmap for Semiconductors 2011,www.itrs.net.

[2]S. J. Ding. Chem. Vap. Deposition. 2001, 7, 4.

[3]P. F. Wang. et al. Appl. Phys. A. 2001, 72, 721.

[4]T. Jiang. et al. J. Mater. Chem. C. 2014, 2, 6502.

[5] E. P. Guyer. et al. J. Mater. Res. 2006, 21, 882.

[6]A. Grill. et al. J. Appl. Phys. 2008, 103, 054104.

Contents of the invention

The object of the present invention is to provide a low dielectric constant SiOCNH film material with excellent mechanical properties and good electrical properties and a preparation method thereof.

The preparation method of the porous low dielectric constant film material provided by the present invention adopts PECVD technology, uses NH ₃ gas, dipentene (LIMO) and tri-ethoxymethylsilane (MTES) vapor as reaction sources, and deposits inorganic -Organic composite film, and obtain low-k porous SiOCNH film through high-temperature thermal annealing; the specific steps are as follows:

(1) At room temperature, put the wafer substrate on the tray in the reaction chamber of the plasma-enhanced chemical vapor deposition (PECVD) equipment, and then evacuate the reaction chamber so that the vacuum degree of the chamber reaches 0.02~0.03 torr ; Then, the substrate temperature is heated to 150~300 ℃;

(2) Through the control of the liquid flow meter (LFM), set the flow rates of tri-ethoxymethylsilane (MTES) and dipentene (LIMO) to 1-2 g/min and 1.5-3 g/min, respectively. min, and pass into the vaporizer; the vaporized MTES and LIMO steam are loaded into the reaction chamber through He gas along different gas paths. 2000~8000 sccm;

(3) The other reaction gas NH ₃ is controlled by a mass flow meter (MFC) and directly enters the reaction chamber with a flow rate of 100~1000 sccm;

(4) NH ₃ , He carrier gas, vaporized MTES and LIMO are mixed in the reaction chamber. When the pressure in the reaction chamber reaches the set value of 3~7 torr, stabilize for 1~2 minutes, and then turn on the radio frequency Power supply, the frequency is 13.56MHz, the radio frequency power is 100~800W, and the inorganic-organic composite thin film is deposited;

(5) Place the obtained inorganic-organic composite film in a tube furnace, a box furnace or other cavities for thermal annealing. The annealing temperature is 300-500 °C, the annealing time is 1-5 hours, the annealing atmosphere can be argon, helium or nitrogen, etc., and the pressure is 0.1-800 torr. During the annealing process, some organic components were thermally decomposed, and finally a low-k porous SiOCNH film was obtained.

In the present invention, the thickness of the film is controlled by PECVD deposition time. The doping amount of porogen LIMO can adjust the k value of the film within a certain range.

In the present invention, the thin film contains NH, Si-O, and Si-CH ₃ components, and is referred to as SiOCNH thin film for short. The film has a low dielectric constant, with a k value of 2.38±0.06~2.58±0.05; the leakage current density is on the order of 10 ^-9 ~10 ^-8 A/cm ² at an electric field strength of 1MV/cm; Young's modulus The hardness is 35.41~36.31 GPa, the hardness is 1.88~2.48 GPa, and the mechanical properties are outstanding.

The present invention has the following advantages:

(1) The film provided by the present invention has excellent uniformity, and the preparation process is simple and controllable, and is suitable for large-scale batch production in industry;

(2) The low-k thin film material prepared by the present invention has excellent mechanical properties, Young's modulus is 35.41 ~ 36.31GPa, hardness is 1.88 ~ 2.48 GPa, compared with other low k thin film materials, it is in an obvious position in terms of mechanical properties leading position;

(3) The porous SiOCNH film obtained by the present invention has excellent mechanical properties and also good insulation properties, and the leakage current density is on the order of 10 ^-9 ~10 ^-8 A/cm ² under the electric field strength of 1MV/cm.

Description of drawings

Figure 1 is a Fourier Transform Infrared Spectrum (FTIR) diagram of a film obtained by PECVD after thermal annealing.

Fig. 2 is a transmission electron microscope (TEM) photo of the section of the film after thermal annealing treatment.

detailed description

1. Put the wafer substrate into the chamber at room temperature, and evacuate the reaction chamber at the same time, so that the vacuum degree of the chamber reaches 0.02~0.03 torr. Then the substrate temperature is raised to 150~300°C. After the temperature rises to 150~300 °C, He gas is introduced into the cavity to preheat the gas pipeline to prevent the incompletely vaporized liquid source from condensing on the tube wall.

2. Through the control of LFM, set the flow rates of tri-ethoxymethylsilane (MTES) and dipentene (LIMO) to 1~2g/min and 1.5~3g/min respectively, and pass them into the vaporizer to vaporize The final MTES and LIMO steam are respectively loaded into the reaction chamber by He gas along different gas paths. The flow rate of He gas for transporting MTES steam is 1000-6000 sccm, and the flow rate of He gas for transporting LIMO steam is 2000-8000 sccm.

3. The reaction gas NH ₃ is controlled by a mass flow meter (MFC) and directly enters the reaction chamber with a flow rate of 100 ~ 1000 sccm.

4. In the reaction chamber, NH ₃ , He carrier gas and vaporized MTES and LIMO are mixed. When the pressure in the reaction chamber reaches the set value of 3~7 torr, stabilize for 1~2 minutes, and then turn on RF power supply (frequency 13.56MHz), RF power 100~800W. After deposition for 1-10 min, the inorganic-organic composite film was obtained.

5. Place the inorganic-organic composite film in a tube furnace, box furnace or other cavity for thermal annealing. The annealing temperature is 300-500 °C, the annealing time is 1-5 hours, and the annealing atmosphere can be argon , helium, nitrogen, etc., the pressure is 0.1~800 torr. During the annealing process, part of the organic components were thermally decomposed, and a porous SiOCNH film was finally obtained.

In order to measure the electrical properties of the above-mentioned porous SiOCNH thin film, the porous SiOCNH thin film was prepared according to the above process with a low-resistance silicon wafer (resistivity 0.001-0.01Ω·cm) as the substrate, using a mask plate and electron beam evaporation technology, in A circular aluminum electrode with a thickness of 300nm and a diameter of 400-420μm is grown on the surface of the SiOCNH film for electrical testing. At the same time, after removing the natural oxide layer on the back of the silicon wafer, an aluminum film is grown to form a test structure of aluminum/SiOCNH film/silicon/aluminum. In order to further improve the reliability of the test structure, the above test structure was annealed in nitrogen-hydrogen mixed gas (N ₂ /H ₂ ) for 1 hour, and the annealing temperature was 200° C. Then, the dielectric constant is extracted by measuring the capacitance-voltage characteristics of the structure, and a reliable average k value is obtained by multi-point measurement. In addition, the leakage current density was obtained by measurement of the current-voltage characteristics of the structure. The mechanical properties and chemical composition of the films were measured by nanoindentation and Fourier transform infrared spectroscopy (FTIR), respectively.

Accompanying drawing 1 is the FTIR picture of inorganic-organic composite film after annealing. The absorption peaks around 800cm ^-1 and 1050cm ^-1 correspond to the Si-O structure of the film, and the absorption peak around 1590cm ^-1 corresponds to the NH structure, which indicates that the N element in the NH ₃ gas has been successfully incorporated into the silicon oxide film. The incorporation of elements helps to improve the mechanical properties of materials. The absorption peak near 1270cm ^-1 comes from the stretching vibration of Si-CH ₃ , which indicates that the film contains a certain amount of CH ₃ groups, and its incorporation helps to reduce the k value of the film. The peak at 2890cm ^-1 corresponds to the CH _x structure in the film. Although there is some porogen left after annealing, the CH _x peak area is much smaller than the Si-O peak area. Accompanying drawing 2 is the transmission electron microscope (TEM) picture of SiOCNH thin film, can obviously see that this thin film contains a large amount of nanopores, this shows that after thermal annealing treatment, pore-forming agent is removed in a large amount, thereby forms porous structure, and this is exactly It is the main reason for the decrease of film k value.

Attached Table 1 lists the electrical and mechanical performance test results of the films prepared under different flow ratios of MTES and NH ₃ . It can be seen from the table that the dielectric constant of the film is 2.38±0.06 ~ 2.58±0.05. The leakage current density is in the order of 10 ^-9 ~10 ^-8 A/cm ² under the electric field intensity of 1MV/cm, showing very good insulation performance. It can be seen from the table that the Young's modulus of the two films ranges from 35.41 to 36.31 GPa, and the hardness ranges from 1.88 to 2.48 GPa, both of which exhibit excellent mechanical properties.

Attached Table 1 Thin Film Electrical and Mechanical Properties Test Results SHAPE\* MERGEFORMAT

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Claims (2)

1. A method for preparing a low dielectric constant porous SiOCNH thin film, characterized in that: using PECVD technology, with _NH3 gas, LIMO and MTES steam as reaction source, depositing inorganic-organic composite thin film, and then through high temperature thermal annealing Obtain low dielectric constant porous SiOCNH film; Concrete steps are as follows: (1) At room temperature, put the wafer substrate on the tray in the reaction chamber of the PECVD equipment, and then evacuate the reaction chamber so that the vacuum degree of the chamber reaches 0.02~0.03 torr; then, heat the substrate temperature to 150～300℃; (2) Through the control of the liquid flow meter, the MTES and LIMO are passed into the vaporizer at the flow rate of 1-2 g/min and 1.5-3 g/min respectively; the vaporized MTES and LIMO steam pass He gas along different gas The flow rate of the carrier gas for transporting MTES steam is 1000~6000 sccm, and the flow rate of carrier gas for transporting LIMO steam is 2000~8000 sccm; here, LIMO is dipentene and MTES is tri-ethoxy Methylsilane; (3) The other reaction gas NH ₃ directly enters the reaction chamber through mass flow meter control, and its flow rate is 100-1000 sccm; (4) NH ₃ , He carrier gas, vaporized MTES and LIMO are mixed in the reaction chamber. When the pressure in the reaction chamber reaches the set value of 3-7 torr, stabilize for 1-2 minutes, and then turn on the radio frequency Power supply, the frequency is 13.56MHz, the radio frequency power is 100-800W, and the inorganic-organic composite thin film is deposited; (5) Place the obtained inorganic-organic composite film in a tube furnace, box furnace or other cavity for thermal annealing; the annealing temperature is 300-500 °C, the annealing time is 1-5 hours, and the annealing atmosphere is argon Gas, helium or nitrogen, the pressure is 0.1~800 torr, and finally a low dielectric constant porous SiOCNH film is obtained. 2. a kind of low dielectric constant porous SiOCNH film is prepared by the preparation method described in claim 1, contains NH, Si-O, Si-CH ₃ compositions in the described film; Its dielectric constant k value is 2.38 ± 0.06～ 2.58±0.05; the leakage current density is in the order of 10 ^-9 ~ 10 ^-8 A/cm ² under the electric field strength of 1MV/cm; the Young's modulus is 35.41 ~ 36.31 GPa, and the hardness is 1.88 ~ 2.48 GPa.