Method for preparing low dielectric constant porous thin film and semiconductor device
By forming small pores in the dielectric film, the problems of easy water absorption and damage of the dielectric film are solved, and a dielectric film with low dielectric constant and strong mechanical properties is realized, thereby improving the performance of the device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHONGQING XINLIAN MICROELECTRONICS CO LTD
- Filing Date
- 2026-02-06
- Publication Date
- 2026-06-05
AI Technical Summary
Existing low dielectric constant dielectric films are prone to water absorption and damage during subsequent processes, leading to an increase in dielectric constant and a decrease in mechanical properties, which affects device performance.
Small pores are formed in the dielectric film by ultraviolet irradiation. The Si-O-Si bonds and CC/C=C bonds are broken by ultraviolet irradiation of the first and second wavelengths, respectively, forming small and dense pores. The film is then planarized by chemical mechanical polishing.
This achieves low dielectric constant, strong adhesion, and stress dispersion of the dielectric film, reduces water absorption, and avoids RC delay phenomenon and damage to the film from subsequent processes.
Smart Images
Figure CN122161350A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a method for preparing a porous thin film with low dielectric constant and a semiconductor device thereof. Background Technology
[0002] Dielectric thin films are deposited in different interconnect layers to achieve insulation between interconnect structures. The dielectric constant (k) of dielectric thin films in semiconductor manufacturing continues to decrease as devices shrink. To further reduce feature sizes, minimizing integration disruption to low-dielectric-constant (low-k) films is crucial. As integrated circuit density increases and the number of conductor interconnects grows, the resistive-capacitive (RC) delay caused by metal interconnects becomes significant, necessitating a reduction in dielectric constant to decrease parasitic capacitance. Low-dielectric-constant (low-k) porous thin film materials are typically used as the insulating medium between different circuit layers.
[0003] While existing low-k dielectric films possess a lower dielectric constant, they also exhibit significant porosity, resulting in a sparse and porous structure that readily absorbs water, causing the dielectric constant to rise again. Furthermore, the large porosity degrades the mechanical properties of the dielectric film during subsequent processing, making it susceptible to damage during polishing processes.
[0004] It should be noted that the information disclosed in the background section of this invention is intended only to enhance the understanding of the general background of this invention, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing a porous thin film with a low dielectric constant and a semiconductor device, so as to solve the problem that the dielectric constant of the dielectric film is high and it is easily damaged.
[0006] To solve the above-mentioned technical problems, the present invention provides a method for preparing a low dielectric constant porous thin film, comprising:
[0007] A semiconductor substrate is provided, and a dielectric thin film is formed on the semiconductor substrate. The substrate for forming the dielectric thin film includes a silicon substrate and a pore-forming agent.
[0008] The semiconductor substrate on which the dielectric film is formed is irradiated with ultraviolet light of a first wavelength λ1 and a second wavelength λ2 for a set time to cure it, so as to form pores in the dielectric film, wherein the value of λ1 is greater than the value of λ2.
[0009] Preferably, the pore-forming agent includes at least one of α-terpinene and diethylene glycol monobutyl ether.
[0010] Preferably, the silicon substrate comprises a silicon oxide containing carbon and hydrogen.
[0011] Preferably, the semiconductor substrate on which the dielectric thin film is formed is irradiated with a first wavelength to break a portion of the Si-O-Si bond network in the carbon and hydrogen silicon oxide to form Si-OH functional groups, and the semiconductor substrate on which the dielectric thin film is formed is irradiated with a second wavelength to break the C-C bonds and C=C bonds in the pore-forming agent to form CxHy gas, where x and y are both positive integers.
[0012] Preferably, the value of λ1 is 254 nm, and the range of λ2 is 190 < λ2 ≤ 220.
[0013] Preferably, the value of λ1 is 254 nm, and the second wavelength range is 200 ≤ λ2 ≤ 220.
[0014] Preferably, the temperature range of the process chamber during the formation of the dielectric film is 300℃≤t≤400℃.
[0015] Preferably, the method further includes:
[0016] The surface of the cured dielectric film is planarized, wherein the planarization includes chemical mechanical polishing.
[0017] Preferably, the diameter of the pores is in the range of 4 Å to 6 Å.
[0018] Based on the same inventive concept, the present invention also provides a semiconductor device, comprising:
[0019] Low dielectric constant porous films are prepared using the preparation method described above.
[0020] Compared with the prior art, the method for preparing low dielectric constant porous films of the present invention has the following advantages:
[0021] This invention cures a semiconductor substrate with a dielectric thin film by irradiating it with ultraviolet light of a first wavelength and a second wavelength. The first wavelength of ultraviolet light is used to irradiate the dielectric film to insert additional carbon into the dielectric film, thereby reducing the dielectric constant of the dielectric film. The second wavelength of ultraviolet light is used to irradiate the dielectric film to decompose the pore-forming agent into small molecules that overflow, thereby forming small and dense pores in the dielectric film. This gives the dielectric film strong load-bearing capacity, strong adhesion, stress dispersion, and reduced water absorption effect, thereby avoiding RC delay phenomenon in the device and preventing damage to the dielectric film by subsequent processes.
[0022] The semiconductor device provided by this invention and the method for preparing low dielectric constant porous thin films provided by this invention belong to the same inventive concept. Therefore, the semiconductor device provided by this invention has at least all the advantages of the method for preparing low dielectric constant porous thin films provided by this invention, avoiding RC delay phenomenon and improving device performance. Attached Figure Description
[0023] Figure 1 This is a schematic diagram illustrating the principle of forming the first pore in a dielectric thin film;
[0024] Figure 2 This is a schematic diagram of the formation of the first pore in a dielectric thin film;
[0025] Figure 3 Is adopted Figure 1 A schematic diagram illustrating the principle by which the dielectric film formed absorbs water;
[0026] Figure 4 This is a schematic diagram showing the increase in dielectric constant after absorption by the dielectric thin film;
[0027] Figure 5 This is a flowchart of a method for preparing a low dielectric constant porous thin film according to an embodiment of the present invention;
[0028] Figure 6 This is a schematic diagram illustrating the principle of forming a second pore in one embodiment of the present invention;
[0029] Figure 7 This is a schematic diagram of the second pore formed in one embodiment of the present invention;
[0030] In the picture,
[0031] 10 - First pore; 20 - Dielectric layer;
[0032] 100 - Second pore; 200 - Dielectric film. Detailed Implementation
[0033] To make the objectives, advantages, and features of the present invention clearer, the following further elaborates in detail on the preparation method of the low dielectric constant porous film and the semiconductor device proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. It should be noted that the accompanying drawings are in extremely simplified forms and use non-precise scales, only for the purpose of facilitating and clearly assisting in explaining the objectives of the embodiments of the present invention. It should be understood that the drawings in the specification do not necessarily show the specific structure of the present invention in proportion, and the illustrative features used to explain certain principles of the present invention in the drawings of the specification will also adopt a slightly simplified drawing method. The specific design features of the present invention disclosed herein, such as specific dimensions, directions, positions, and shapes, will be partially determined by the specific application and usage environment. Also, in the following described embodiments, sometimes the same reference numerals are used commonly between different drawings to represent the same part or parts with the same functions, and the repeated description thereof is omitted. In this specification, similar reference numerals and letters are used to represent similar items. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.
[0034] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.
[0035] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.
[0036] Refer Figures 1 to 4As shown, BD (Black Diamond) refers to a low-k dielectric material, a specific organic-inorganic mixture dielectric material used as an interconnect insulating layer in chip manufacturing. In preparing the low-k dielectric layer 20, introducing pores into the silicon substrate and additionally introducing carbon can reduce the dielectric constant of the dielectric layer 20. For example, using diethoxymethylsilane (DEMS) and α-terpinene (ATRP) as substrates, first pores 10 are formed in the dielectric layer 20 under ultraviolet (UV) irradiation. (See reference...) Figure 1 As shown, Figure 1 This diagram illustrates the breaking of CH and C=C bonds in α-terpinene at a UV wavelength of 245 nm. In other words, when the dielectric layer 20 is irradiated with UV light at 245 nm, the energy is insufficient to break the C=C bonds, resulting in incomplete decomposition of α-terpinene and its release as large molecules, thus forming... Figure 2 The first pore 10 is shown in the diagram. For Figure 2 The first pore 10 shown, after being tested by the detection equipment, has a diameter of 9 Å to 12 Å. (See reference...) Figure 3 and Figure 4 As shown, because a first aperture 10 is formed in the dielectric layer 20, the dielectric constant of the dielectric layer 20 can be reduced. The dielectric constant of the formed dielectric layer 20, as measured by the testing equipment, is 2.3. Although the dielectric constant of the dielectric layer 20 is low, for a dielectric layer 20 with the first aperture 10 formed... Figure 3 As shown, the dielectric layer 20, with its sparse and porous structure, readily absorbs water. After planarization using chemical mechanical polishing (CMP) to form the first pore 10, the dielectric constant of the dielectric layer 20 increases again, reaching 3.1. Therefore, when the dielectric layer 20 is irradiated with UV light at a wavelength of 245 nm, the relatively large diameter of the first pore 10 results in weak load-bearing capacity, weak adhesion, stress concentration, and easy water absorption.
[0037] The core idea of this invention is to provide a method for preparing a low dielectric constant porous film. While reducing the dielectric constant of the dielectric film, it can also reduce the diameter of the pores, thereby enabling the dielectric film to have strong load-bearing capacity, strong adhesion, stress dispersion, and reduced water absorption effect.
[0038] To achieve the above-mentioned goal, this invention provides a method for preparing a low dielectric constant porous thin film, as described above. Figures 5 to 7 This invention discloses a specific embodiment of a method for preparing a low dielectric constant porous thin film. The method for preparing the low dielectric constant porous thin film includes the following steps S1 and S2.
[0039] Step S1: Provide a semiconductor substrate and form a dielectric thin film on the semiconductor substrate. The substrate for forming the dielectric thin film includes a silicon substrate and a pore-forming agent.
[0040] Specifically, refer to Figure 5 and Figure 7 As shown, the semiconductor substrate (not shown) is the transistor after the front-end process. In the back-end process of the transistor (fabricating the metal interconnect structure), for example, an insulating layer is first deposited on the transistor to isolate the contact holes formed in the transistor. Alternatively, an insulating layer is formed between the first metal layer and the second metal layer to isolate them. To reduce the RC delay caused by the metal interconnect lines in the metal interconnect structure, a material with a low dielectric constant is used as the insulating layer (i.e., Figure 7 The dielectric film 200 in the middle is used to reduce parasitic capacitance.
[0041] The substrate forming the dielectric thin film 200 includes a silicon substrate and a porogen. The silicon substrate includes a carbon- and hydrogen-containing silicon oxide. The carbon- and hydrogen-containing silicon oxide includes diethoxymethylsilane (DEMS), trimethylmethoxysilane (TMMS), etc. The porogen includes at least one of α-terpinene (ATRP) and diethylene glycol monobutyl ether. The following explanation uses commonly used DEMS and ATRP as examples.
[0042] The molecular structure of DEMS is as follows:
[0043] It contains a Si-O-Si bond network.
[0044] The molecular structural formula of ATRP is as follows:
[0045] abbreviated as It contains C-C bonds, C=C bonds, and CH bonds.
[0046] A semiconductor substrate is placed in a process chamber, and DEMS and ATRP are introduced into the chamber. A dielectric thin film 200 is formed by deposition within a temperature range of 300℃≤t≤400℃. It should be noted that the specific process for forming the dielectric thin film 200 on the semiconductor substrate using DEMS and ATRP as substrates is familiar to those skilled in the art and will not be described in detail here.
[0047] Step S2: The semiconductor substrate on which the dielectric film is formed is irradiated with ultraviolet light of a first wavelength λ1 and a second wavelength λ2 for a set time to cure, so as to form pores in the dielectric film, wherein the value of λ1 is greater than the value of λ2.
[0048] Specifically, refer to Figures 5 to 7 As shown, the semiconductor substrate on which the dielectric thin film 200 is formed is removed from the process chamber and subjected to a curing process. During the curing process, the semiconductor substrate is simultaneously irradiated with two different wavelengths of UV light. The two wavelengths include a first wavelength λ1 and a second wavelength λ2.
[0049] The semiconductor substrate on which the dielectric thin film is formed is irradiated with a first wavelength λ1 to break a portion of the Si-O-Si bond network in the carbon-hydrogen silicon oxide, forming Si-OH bonds. The value of λ1 is 254 nm. As can be seen from the molecular structure of DEMS, it contains a Si-O-Si bond network. The breakage of a portion of the Si-O-Si bond network in DEMS to form Si-OH bonds allows additional carbon to be inserted into the dielectric thin film 200, thereby reducing the dielectric constant of the dielectric thin film 200. By controlling the irradiation time of the dielectric thin film 200 with the first wavelength λ1, the number of Si-O-Si network breaks can be controlled, thus controlling the dielectric constant of the dielectric thin film 200. For example, irradiating the dielectric thin film 200 with the first wavelength λ1 can reduce the dielectric constant of the dielectric thin film 200 to 2.3. Simultaneously, irradiating the dielectric thin film 200 with the first wavelength λ1 can also break the CC and CH bonds in ATRP. However, the energy of ultraviolet light at this wavelength is insufficient to break C=C bonds; it can only open the first layer of the C=C bond. Therefore, ATRP leaks out in the form of a large molecule, forming... Figure 2 The large-diameter first pore 10 shown has a diameter of 9 Å to 12 Å.
[0050] The range of λ2 is 190nm < λ2 ≤ 220nm. When λ2 is 190nm, it damages the Si-O bonds and the dielectric film 200, therefore λ2 avoids 190nm. Furthermore, to avoid damage to the dielectric film 200, the range of the second wavelength λ2 is preferably 200nm ≤ λ2 ≤ 220nm.
[0051] from Figure 6 As can be seen, when the semiconductor substrate on which the dielectric thin film 200 is formed is irradiated with a second wavelength, the C=C bonds and C=C bonds in the pore-forming agent are broken to form CxHy gas, where x and y are both positive integers. The CxHy gas can include CH4, C2H6, CH2, etc., all of which are small molecule gases. Because the pore-forming agent decomposes into small molecule gases that escape from the dielectric thin film 200, a gaseous environment is formed, such as... Figure 7 The second pore 100 is shown. The diameter of the second pore ranges from 4 Å to 6 Å. From Figure 7It can be seen that the dielectric film 200 formed by the method disclosed in this application has small diameter and dense second pores 100, which enables the dielectric film 200 to have strong load-bearing capacity, strong adhesion, stress dispersion, and reduced water absorption effect.
[0052] It should be noted that the porosity of the dielectric film 200 can be controlled by adjusting the duration of ultraviolet irradiation with the second wavelength, according to actual design requirements. Therefore, the irradiation time of the dielectric film 200 with ultraviolet light is set according to actual needs and no specific requirements are specified here.
[0053] The method also includes:
[0054] The surface of the cured dielectric film is planarized, including chemical mechanical polishing (CMP). Because the dielectric film 200 has strong load-bearing capacity, strong adhesion, stress dispersion, and low water absorption, CMP planarization of its surface prevents a further increase in the dielectric constant of the dielectric film 200 and avoids damage to the dielectric film 200, thus preventing RC delay in the device.
[0055] To achieve the above-mentioned idea, this embodiment also discloses a semiconductor device, including:
[0056] Low dielectric constant porous films are prepared using the preparation method described above.
[0057] The semiconductor device disclosed in this embodiment and the method for preparing low dielectric constant porous thin films provided in this embodiment belong to the same inventive concept. Therefore, the semiconductor device provided in this embodiment has at least all the advantages of the method for preparing low dielectric constant porous thin films provided in this invention, avoiding RC delay phenomenon and improving device performance.
[0058] In summary, the above embodiments have provided a detailed description of the preparation method of low dielectric constant porous thin films and different configurations of semiconductor devices. Of course, the above description is only a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. The present invention includes but is not limited to the configurations listed in the above embodiments. Those skilled in the art can draw inferences from the above embodiments. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.
Claims
1. A method for preparing a porous thin film with low dielectric constant, characterized in that, include: A semiconductor substrate is provided, and a dielectric thin film is formed on the semiconductor substrate. The substrate for forming the dielectric thin film includes a silicon substrate and a pore-forming agent. The semiconductor substrate on which the dielectric film is formed is irradiated with ultraviolet light of a first wavelength λ1 and a second wavelength λ2 for a set time to cure it, so as to form pores in the dielectric film, wherein the value of λ1 is greater than the value of λ2.
2. The method for preparing a low dielectric constant porous thin film according to claim 1, characterized in that, The pore-forming agent includes at least one of α-terpinene and diethylene glycol monobutyl ether.
3. The method for preparing a low dielectric constant porous thin film according to claim 1, characterized in that, The silicon substrate comprises silicon oxide containing carbon and hydrogen.
4. The method for preparing a low dielectric constant porous thin film according to claim 3, characterized in that, The semiconductor substrate on which the dielectric thin film is formed is irradiated with a first wavelength to break a portion of the Si-O-Si bond network in the carbon and hydrogen silicon oxide to form Si-OH functional groups. The semiconductor substrate on which the dielectric thin film is formed is irradiated with a second wavelength to break the C-C bonds and C=C bonds in the pore-forming agent to form CxHy gas, where x and y are both positive integers.
5. The method for preparing a low dielectric constant porous thin film according to claim 4, characterized in that, The value of λ1 is 254 nm, and the range of λ2 is 190 < λ2 ≤ 220.
6. The method for preparing a low dielectric constant porous thin film according to claim 4, characterized in that, The value of λ1 is 254 nm, and the second wavelength range is 200 ≤ λ2 ≤ 220.
7. The method for preparing a low dielectric constant porous thin film according to claim 1, characterized in that, During the formation of the dielectric thin film, the temperature range of the process chamber is 300℃≤t≤400℃.
8. The method for preparing a low dielectric constant porous thin film according to claim 1, characterized in that, The method also includes: The surface of the cured dielectric film is planarized, wherein the planarization includes chemical mechanical polishing.
9. The method for preparing a low dielectric constant porous thin film according to claim 1, characterized in that, The diameter of the pores ranges from 4 Å to 6 Å.
10. A semiconductor device, characterized in that, include: Low dielectric constant porous thin film prepared by the preparation method according to any one of claims 1-9.