Doped amorphous boron nitride films and methods for stabilizing amorphous boron nitride films
By doping amorphous boron nitride film with dopants such as K, Ba, Sr, Rb, Sc, Na, In or La, the problem of crystallization of amorphous boron nitride film when the thickness increases is solved, and the ultra-low dielectric constant and mechanical stability is improved, and it is suitable for low k dielectrics in modern semiconductor devices.
Patent Information
- Application Number
- CN202510143665.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-10-10
- Filing Date
- 2025-02-10
- Publication Date
- 2025-08-19
AI Technical Summary
In the prior art, amorphous boron nitride films are prone to crystallization when the growth thickness increases, resulting in an increase in the dielectric constant, unable to effectively maintain ultra-low dielectric characteristics, and there is a risk of mechanical instability and ion diffusion.
The amorphous boron nitride film was doped with dopants such as K, Ba, Sr, Rb, Sc, Na, In or La, and the dopant with stable amorphous phase and unstable crystal phase were screened through DFT calculations, and the doped amorphous boron nitride film was prepared by sputtering, CVD and other methods.
It realizes the maintenance of ultra-low dielectric constant in thicker film layers, improves mechanical stability, reduces the possibility of dielectric breakdown and ion diffusion, and is suitable for low-k dielectrics in modern semiconductor devices.
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Figure CN120511259A_ABST
Abstract
Description
Technical Field
[0001] Materials according to embodiments relate to doped amorphous boron nitride films, and other embodiments relate to methods for stabilizing amorphous boron nitride films. Background Art
[0002] Advances in modern semiconductor devices have been driven by process and material improvements that enable greater transistor density. However, resistance-capacitance (RC) delays are a key issue for increasing transistor density and reducing metal interconnect size. Therefore, new materials with lower resistance and capacitance are needed to offset the negative impact of increased RC delay on chip performance. Ultra-low dielectric materials offer a way to overcome these obstacles, as they prevent quantum tunneling.
[0003] The IEEE International Roadmap for Devices and Systems (IRDS) for Low-k Dielectrics in Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) is published in Figure 1 As shown in Figure 2, low-k dielectrics in copper interconnects Figure 2 and the IRDS roadmap for low-k dielectrics in interconnects is shown in Figure 3 Shown in. Figure 1 where Rsd is the resistance per micron of MOSFET width. Specifically, according to the note in the IRDS roadmap [5], Rsd is the total parasitic series resistance (source plus drain) per micron of MOSFET width; these values include all components (such as accumulation layers, diffusion resistance, sheet resistance, and contacts) and assume a 5% improvement per node cycle (2 or 3 years).
[0004] Current state-of-the-art materials include porous SiCOH (p-SiCOH). The pores lower the dielectric constant, but do so at the expense of reduced structural stability and increased likelihood of dielectric breakdown and ion diffusion through the dielectric.
[0005] The current state-of-the-art technology involves introducing fluorine or CH3 into SiO2 (collectively referred to as SiCOH) to achieve relatively low dielectric constants, i.e., κ = 4 for SiO2, κ = 3.7 for SiOF, and κ = 2.4 to 2.8 for SiCOH. Figure 4 As shown in , p-SiCOH further reduces the dielectric constant relative to SiCOH by introducing pores (k = 1). However, this is based on Figure 5 This comes at the expense of reduced structural stability as shown in , and an increased likelihood of dielectric breakdown and ion diffusion through the dielectric.
[0006] Amorphous boron nitride (aBN) is a promising candidate for achieving ultra-low dielectric constants. Specifically, amorphous boron nitride (aBN) is a promising new low-k dielectric material for future devices that has been synthesized with dielectric constants of 2 or less (exceeding the IRDS roadmap target). However, lowering the dielectric constant is not easy; in fact, the dielectric constant of aBN increases as the film grows thicker, likely due to increased crystallinity as the film becomes thicker.
[0007] Therefore, there is a need for ultra-low dielectric constant materials that overcome the above problems.
[0008] The information disclosed in this background section was known to the inventors before the disclosure of this application or was technical information acquired during the process of making this disclosure. Therefore, it may contain information that does not form prior art known to the public. Summary of the Invention
[0009] In the present disclosure, candidate dopants are discovered that prevent amorphous BN from crystallizing. Thus, when the film is grown thicker than a critical width (e.g., thicker than 3 nm in some embodiments, or thicker than 5 nm in other embodiments, or thicker than 10 nm in yet other embodiments), the candidate dopants keep the dielectric constant of the structure ultra-low.
[0010] In particular, K, Ba, Sr, Rb, Sc, Na, In, and La are candidate dopants for stabilizing the amorphous phase and destabilizing the crystalline phase.
[0011] The materials in this disclosure are newly discovered dopants for amorphous BN that stabilize the amorphous phase and destabilize the crystalline phase. Thus, thick films of ultra-low dielectric constant materials can be synthesized according to this disclosure.
[0012] Advantages of the present disclosure include the ability to synthesize ultra-low dielectric constant materials according to the present disclosure by doping amorphous BN, which can be used as a diffusion barrier to resist electromigration from interconnects in next-generation semiconductors. The dielectric constant of aBN is comparable to that of p-SiCOH, but aBN lacks pores and thus does not suffer from the drawbacks associated with pores. Therefore, by doping aBN to prevent crystallization, it can replace p-SiCOH as a low-k dielectric with greater mechanical stability, reduced dielectric breakdown potential, and no ion diffusion through the aBN.
[0013] A first embodiment of the present disclosure provides a doped amorphous boron nitride film, comprising amorphous boron nitride and a dopant, wherein the dopant comprises K, Ba, Sr, Rb, Sc, Na, In, or La.
[0014] A second embodiment of the present disclosure provides the doped amorphous boron nitride film of the first embodiment, wherein the dopant comprises K.
[0015] A third embodiment of the present disclosure provides the doped amorphous boron nitride film of the first embodiment, wherein the dopant includes Ba.
[0016] A fourth embodiment of the present disclosure provides the doped amorphous boron nitride film of the first embodiment, wherein the dopant includes Sr.
[0017] A fifth embodiment of the present disclosure provides the doped amorphous boron nitride film of the first embodiment, wherein the dopant includes Rb.
[0018] A sixth embodiment of the present disclosure provides the doped amorphous boron nitride film of the first embodiment, wherein the dopant includes Sc.
[0019] A seventh embodiment of the present disclosure provides the doped amorphous boron nitride film of the first embodiment, wherein the dopant includes Na.
[0020] An eighth embodiment of the present disclosure provides the doped amorphous boron nitride film of the first embodiment, wherein the dopant includes In.
[0021] A ninth embodiment of the present disclosure provides the doped amorphous boron nitride film of the first embodiment, wherein the dopant includes La.
[0022] A tenth embodiment of the present disclosure provides the doped amorphous boron nitride film of the first embodiment, wherein the doped amorphous boron nitride film has (i) a stable configuration as measured by energy above the convex hull (defined as less than 100 meV per atom above the convex hull), (ii) a lower energy above the convex hull in the amorphous phase than in the crystalline phase, and (iii) a dielectric constant of 4 or less. Another embodiment provides the doped amorphous boron nitride film of the tenth embodiment, wherein the dielectric constant is 2 or less.
[0023] An eleventh embodiment of the present disclosure provides a doped amorphous boron nitride film of the first embodiment, wherein the doped amorphous boron nitride film has (i) a metastable configuration as measured by energy above the convex hull (defined as less than 250 meV per atom above the convex hull), (ii) a lower energy above the convex hull in the amorphous phase than in the crystalline phase, and (iii) a dielectric constant of 4 or less. Another embodiment provides the doped amorphous boron nitride film of the eleventh embodiment, wherein the dielectric constant is 2 or less.
[0024] A twelfth embodiment of the present disclosure provides a method for stabilizing an amorphous boron nitride film, the method comprising doping the amorphous boron nitride film with a dopant comprising K, Ba, Sr, Rb, Sc, Na, In, or La.
[0025] A thirteenth embodiment of the present disclosure provides the method for stabilizing an amorphous boron nitride film of the twelfth embodiment, wherein the dopant includes K.
[0026] A fourteenth embodiment of the present disclosure provides the method for stabilizing an amorphous boron nitride film of the twelfth embodiment, wherein the dopant includes Ba.
[0027] A fifteenth embodiment of the present disclosure provides the method for stabilizing an amorphous boron nitride film of the twelfth embodiment, wherein the dopant includes Sr.
[0028] A sixteenth embodiment of the present disclosure provides the method for stabilizing an amorphous boron nitride film of the twelfth embodiment, wherein the dopant includes Rb.
[0029] A seventeenth embodiment of the present disclosure provides the method for stabilizing an amorphous boron nitride film of the twelfth embodiment, wherein the dopant includes Sc.
[0030] An eighteenth embodiment of the present disclosure provides the method for stabilizing an amorphous boron nitride film of the twelfth embodiment, wherein the dopant includes Na.
[0031] A nineteenth embodiment of the present disclosure provides the method for stabilizing an amorphous boron nitride film of the twelfth embodiment, wherein the dopant includes In.
[0032] A twentieth embodiment of the present disclosure provides the method for stabilizing an amorphous boron nitride film of the twelfth embodiment, wherein the dopant includes La. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The patent or application file contains at least one drawing executed in color.
[0034] Example embodiments of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings.
[0035] Figure 1 An IRDS roadmap for low-k dielectrics in MOSFETs is shown.
[0036] Figure 2 Shown is a low-k dielectric in a copper interconnect.
[0037] Figure 3 Shown is the IRDS roadmap for low-k dielectrics in interconnects.
[0038] Figure 4Shown is p-SiCOH in which pores have been introduced into the SiCOH.
[0039] Figure 5 is a graph showing mechanical instability with increasing porosity.
[0040] Figure 6 is a flow chart illustrating a screening procedure for finding candidate dopants for stabilizing amorphous boron nitride while destabilizing the crystalline phase.
[0041] Figure 7A is a diagram of the doped hBN structure, Figure 7B is a diagram of the doped cBN structure, and Figure 7C is a diagram of the doped aBN structure.
[0042] Figure 8 is through relative E hull A graphical representation of the candidate list with the results of the filter calculations.
[0043] Figure 9 is a graphical representation of the dielectric constant calculation results for the candidate list.
[0044] Figure 10 An exemplary embodiment of amorphous BN doped with potassium and the energy above the convex hull and the dielectric constant resulting from doping with different concentrations of potassium are shown. DETAILED DESCRIPTION
[0045] In this disclosure, we discovered candidate dopants that stabilize amorphous boron nitride (BN) and destabilize the crystalline phase. Thus, the candidate dopants enable the BN structure to maintain an ultra-low dielectric constant when the film is grown thicker than a critical width.
[0046] To find candidate dopants, use Figure 6 The screening procedure is shown in and discussed below.
[0047] Screen open databases for all possible elements that can form stable structures with boron, nitrides, or boron nitride.
[0048] All toxic materials and high-cost elements were removed, and then 24 candidates were selected.
[0049] The atomic structures of hexagonal BN (hBN), cubic BN (cBN), and three types of amorphous BN (aBN) were generated using first-principles density functional theory (DFT).
[0050] All five structures were doped with 24 candidate elements with doping ratios ranging from 1% to 2% and DFT calculations were performed to obtain the energy and electronic structures. 7A to 7C As shown in Figure 7A is a diagram of the doped hBN structure, Figure 7B is a diagram of the doped cBN structure, and Figure 7C is a diagram of the doped aBN structure.
[0051] Specific dopants that change the overall electronic structure to metallic (ie, energy band gap (Eg) = 0 eV) are excluded.
[0052] Calculate the energy above the convex hull (E hull ), and select E hull <0.1eV to find dopable elements.
[0053] The E is compared between aBN and hBN using the following equation (1): hull :
[0054] And six candidate dopants were screened out: K, Rb, Sr, Zr, Ba and La.
[0055] Then the dielectric constant change κ caused by doping was calculated. Finally, five candidate dopants were screened: K, Rb, Sr, Ba and La.
[0056] Specifically, by relative E hull The results of the calculation for the candidate list are filtered in Figure 8 Shown in. Figure 8 The top of the figure shows the E of 24 dopants. hull The red dashed line represents 100MeV. Figure 8 The bottom of the figure shows the calculation of E between aBN and hBN using Equation (1). hull The difference, blue negative values indicate stabilization of the amorphous phase, and the arrows show the final candidate dopants.
[0057] Further, the dielectric constant calculation results and the final candidate list are in Figure 9 As shown in Figure 9 The top of the graph shows the average dielectric constant of doped aBN, and the red dashed line represents the average dielectric constant of aBN. Figure 9 At the bottom of the figure, the dielectric constant difference between the doped aBN and the original aBN is shown, and 8 candidate dopants were finally selected: K, Ba, Sr, Rb, Sc, Na, In and La.
[0058] The doped amorphous boron nitride films disclosed herein can be produced by techniques known in the art, such as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and atomic layer deposition (ALD). For example, the films can be produced by inductively coupled PECVD using borazine precursor molecules at 50°C to 550°C for 10 to 40 minutes. The doped amorphous boron nitride films disclosed herein can be used as low-k dielectrics in modern semiconductor devices, such as in copper interconnects for MOSFETs. Doping stabilizes the amorphous phase of boron nitride and destabilizes the crystalline phase, allowing the formation of thicker amorphous boron nitride films with a low dielectric constant.
[0059] Example Embodiments will now be illustrated by the following examples, which do not limit the present disclosure in any way.
[0060] Figure 10 An exemplary embodiment of the present disclosure is shown in FIG. Figure 10 In the right part, the potassium dopant in a-BN is located in the sp 2 between the coordination spheres, thus reducing the crystallinity and increasing the entropy of the system. Figure 10 In the middle part of , doping with different concentrations of K does not lead to very large convex hull energy, indicating that doped amorphous structures can be synthesized. Figure 10 In the left part, doping with varying concentrations of K does not result in a large dielectric constant.
[0061] The foregoing is an illustration of exemplary embodiments and should not be construed as limiting the present disclosure. Although a few exemplary embodiments have been described, those skilled in the art will readily appreciate that many modifications may be made to the above-described embodiments without materially departing from the present disclosure.
Claims
1. A doped amorphous boron nitride film comprising: Amorphous boron nitride and a dopant, wherein the dopant comprises K, Ba, Sr, Rb, Sc, Na, In or La.
2. The doped amorphous boron nitride film according to claim 1, wherein The dopant includes K.
3. The doped amorphous boron nitride film according to claim 1, wherein The dopant includes Ba.
4. The doped amorphous boron nitride film according to claim 1, wherein The dopant includes Sr.
5. The doped amorphous boron nitride film according to claim 1, wherein The dopant includes Rb.
6. The doped amorphous boron nitride film according to claim 1, wherein The dopant includes Sc.
7. The doped amorphous boron nitride film according to claim 1, wherein The dopant includes Na.
8. The doped amorphous boron nitride film according to claim 1, wherein The dopant includes In.
9. The doped amorphous boron nitride film according to claim 1, wherein The dopant includes La.
10. The doped amorphous boron nitride film according to claim 1, wherein The doped amorphous boron nitride film has (i) a stable configuration as measured by the energy above the convex hull, (ii) a lower energy above the convex hull in the amorphous phase than in the crystalline phase, and (iii) a dielectric constant of 4 or less.
11. The doped amorphous boron nitride film according to claim 1, wherein The doped amorphous boron nitride film has (i) a metastable configuration as measured by an energy above the convex hull, (ii) a lower energy above the convex hull in the amorphous phase than in the crystalline phase, and (iii) a dielectric constant of 4 or less.
12. A method for stabilizing an amorphous boron nitride film, comprising: The amorphous boron nitride film is doped with a dopant including K, Ba, Sr, Rb, Sc, Na, In, or La.
13. The method according to claim 12, wherein: The dopant includes K.
14. The method according to claim 12, wherein: The dopant includes Ba.
15. The method according to claim 12, wherein: The dopant includes Sr.
16. The method according to claim 12, wherein The dopant includes Rb.
17. The method according to claim 12, wherein: The dopant includes Sc.
18. The method according to claim 12, wherein: The dopant includes Na.
19. The method according to claim 12, wherein: The dopant includes In.
20. The method according to claim 12, wherein The dopant includes La.