Dielectric layer and preparation method thereof
By depositing BPSG and USG films of different concentrations in stages, the precipitation of boron and phosphorus was controlled, solving the problems of film inhomogeneity and device stability during BPSG film deposition, and achieving high quality of dielectric layer and high performance of semiconductor device.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-03-27
AI Technical Summary
In the prior art, the precipitation of boron and phosphorus during the deposition of BPSG film affects the stability and performance of the device. At the same time, it is difficult to ensure the flatness and uniformity of the film, resulting in a decline in the manufacturing quality and performance of the device.
By using staged deposition of boron phosphosilicate glass (BPSG) films and undoped silicate glass (USG) films with different concentrations, and by controlling the flow rates of boron source, phosphorus source and oxidant as well as the deposition time, a dielectric layer is formed layer by layer to block the precipitation of boron and phosphorus and improve the flatness and uniformity of the film.
It significantly reduces the precipitation rate of boron and phosphorus, enhances the stability and reliability of the process, improves the surface quality and uniformity of the film, avoids device short circuits and performance degradation, and ensures stable operation and high performance of the device over a long period of time.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of semiconductor technology, in particular to a dielectric layer and a preparation method thereof. BACKGROUND
[0002] In the field of semiconductor manufacturing, the deposition of dielectric layers is one of the key steps in building multi-layer interconnection structures, mainly used to isolate different metal layers to prevent current leakage, while providing a transmission path for electrical signals between metal layers. Traditional high-temperature chemical vapor deposition (CVD) technology is used to deposit silicon dioxide (SiO2) or doped silicon dioxide (such as BPSG) films to meet this demand. However, high-temperature CVD processes have significant limitations, especially when silicon carbide (SiC) devices are involved, the required temperature far exceeds the tolerance limit of the metallization layer (such as aluminum), which easily leads to device failure. In addition, pure SiO2 films often exhibit porous and uneven characteristics during deposition, which not only increases the complexity of the photolithography process, but also may cause short circuits between metal layers, affecting device performance.
[0003] Borophosphosilicate glass (BPSG), as a SiO2 material doped with boron and phosphorus, improves the flowability and uniformity of the film by reducing the melting point, and is therefore widely used in CMOS semiconductor processes. BPSG can be reflowed at a relatively low temperature (800℃~900℃), and the surface tension promotes its automatic filling of trenches, forming a smooth and flat surface, providing a good substrate for subsequent photolithography and metal interconnection steps.
[0004] In the prior art, the deposition of BPSG film usually adopts one-step deposition method, that is, under a single process condition, by controlling the flow rates of boron source, phosphorus source and silicon source, and the ratio of oxidizing agent, the required concentration of BPSG film is deposited at one time. However, this deposition method is difficult to accurately control the concentration of boron and phosphorus, and during the deposition and reflow heat treatment of BPSG, the precipitated boron and phosphorus are easy to react with water molecules in the air to form boric acid and phosphoric acid, resulting in the loss of dielectric layer structure, further affecting the stability and performance of the device during metal filling. Especially in the reflow heat treatment, the precipitation and diffusion of phosphorus in the BPSG layer will cause changes in internal stress of the film, which may cause the film to warp, crack or peel off, the film thickness is not uniform, and even voids appear. These problems will significantly affect the manufacturing quality and performance of semiconductor devices.
[0005] Therefore, after depositing the BPSG film, how to prevent the precipitation of boron and phosphorus, while optimizing the flatness and uniformity of the film, to improve the stability and performance of the device, is a technical problem to be solved in the field of semiconductor manufacturing. SUMMARY
[0006] This application provides a dielectric layer and its preparation method to solve the problems in related technologies where the precipitation of boron and phosphorus affects the stability and performance of devices during the deposition of BPSG films, and it is difficult to ensure the flatness and uniformity of the film.
[0007] According to one aspect of this application, a method for preparing a dielectric layer is provided, comprising the following steps:
[0008] A first preparatory layer is formed by deposition using a first process condition and a first gaseous raw material, wherein the components of the first gaseous raw material include a silicon source, a boron source, a phosphorus source, and an oxidant;
[0009] A second preparatory layer is deposited on the first preparatory layer using a second process condition and a second gas feedstock. The components of the second gas feedstock include a silicon source, a boron source, a phosphorus source, and an oxidant. The flow rate of the boron source in the first process condition is greater than the flow rate of the boron source in the second process condition, the flow rate of the phosphorus source in the first process condition is greater than the flow rate of the phosphorus source in the second process condition, the flow rate of the silicon source in the first process condition is equal to the flow rate of the silicon source in the second process condition, and the flow rate of the oxidant in the first process condition is equal to the flow rate of the oxidant in the second process condition.
[0010] A third preparatory layer is formed by depositing a third gas raw material on the second preparatory layer. The components of the third gas raw material are a silicon source and an oxidant. The first preparatory layer, the second preparatory layer and the third preparatory layer constitute the dielectric layer.
[0011] Optionally, the deposition time of the first preparatory layer is T1, and T1 satisfies: T1=(D×X)×T01 / D1; where D is the preset thickness value of the dielectric layer, D1 is the actual thickness value of the film layer deposited under the first process conditions, T01 is the reference deposition time of the film layer deposited under the first process conditions, and X is the first preset percentage, which is 80%~90%.
[0012] Optionally, in the first process conditions, the flow rate of the silicon source is 800~1000 mg / m³. 3 The flow rate of the boron source is 300~400 mg / m³. 3 The flow rate of the phosphorus source is 60~80 mg / m³. 3 .
[0013] Optionally, the deposition time of the second preparatory layer is T2, which satisfies: T2=(D×Y)×T02 / D2; where D is the preset thickness value of the dielectric layer, D2 is the actual thickness value of the film layer deposited under the second process conditions, T02 is the reference deposition time of the film layer deposited under the second process conditions, and Y is the second preset percentage, which is 5%~15%.
[0014] Optionally, the flow rate of the boron source in the second process condition is 50%-60% of the flow rate of the boron source in the first process condition; the flow rate of the phosphorus source in the second process condition is 50%-60% of the flow rate of the phosphorus source in the first process condition.
[0015] Optionally, using the third process conditions and the third gas feedstock, the third preparatory layer is deposited on the second preparatory layer to form the third preparatory layer. The deposition time of the third preparatory layer is T3, and T3 satisfies: T3=(D×Z)×T03 / D3; where D is the preset thickness value of the dielectric layer, D3 is the actual thickness value of the film layer deposited under the third process conditions, T03 is the reference deposition time of the film layer deposited under the third process conditions, and Z is the third preset percentage, which is 5%~10%.
[0016] Optionally, the third preparatory layer is deposited on the second preparatory layer using the third process conditions and the third gas feedstock, wherein the flow rate of the silicon source in the third process conditions is equal to the flow rate of the silicon source in the first process conditions.
[0017] Optionally, before forming the first preparatory layer, the preparation method further includes: placing the wafer in a chamber, and continuously introducing an auxiliary gas containing oxygen for a duration of more than 30 seconds, provided that the chamber pressure meets a preset range.
[0018] According to another aspect of this application, a dielectric layer is provided, prepared by the aforementioned preparation method, the dielectric layer comprising a first preparatory layer, a second preparatory layer, and a third preparatory layer stacked sequentially, wherein: the boron content concentration of the first preparatory layer is greater than the boron content concentration of the second preparatory layer; and the phosphorus content concentration of the first preparatory layer is greater than the phosphorus content concentration of the second preparatory layer.
[0019] Optionally, the boron content concentration of the first preparatory layer ranges from 5 to 6 wt%, and the phosphorus content concentration of the first preparatory layer ranges from 6 to 7 wt%; the boron content concentration of the second preparatory layer ranges from 3 to 4 wt%, and the phosphorus content concentration of the first preparatory layer ranges from 4 to 5 wt%.
[0020] This application utilizes a phased deposition method to deposit boron and phosphorus precipitation using boron-phosphorus silicate glass (BPSG) films and undoped silicate glass (USG) films of varying concentrations. Through progressive deposition under different process conditions in three stages, each layer effectively blocks boron and phosphorus precipitation in the next layer, with the blocking effect increasing sequentially. This significantly reduces the precipitation rate of boron and phosphorus, enhancing process stability and reliability, and improving the surface quality and uniformity of the film. It also prevents device short circuits and performance degradation, ensuring stable operation and high performance over extended periods. Furthermore, the third preparatory layer, the USG film, further improves surface flatness and acts as a doping barrier, reducing the risk of impurity diffusion and electrochemical corrosion, thus providing a foundation for subsequent metallization and other processes. Experiments demonstrate that the method described in this application can significantly improve the quality of the dielectric layer, thereby enhancing the overall performance and manufacturing yield of semiconductor devices. Attached Figure Description
[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:
[0022] Figure 1 This is a schematic flowchart of a method for preparing a dielectric layer according to an embodiment of this application;
[0023] Figure 2 This is a schematic cross-sectional view of a dielectric layer according to an embodiment of this application;
[0024] Figure 3 This is a schematic diagram comparing the U% before and after process optimization in Comparative Example 1 and Example 1;
[0025] Figure 4 This is a schematic diagram comparing B% before and after process optimization in Comparative Example 1 and Example 1;
[0026] Figure 5 This is a schematic diagram comparing the P% before and after process optimization in Comparative Example 1 and Example 1.
[0027] The above figures include the following reference numerals:
[0028] 10. First preparatory layer; 20. Second preparatory layer; 30. Third preparatory layer; 40. Wafer; 50. Silicon dioxide layer; 60. Metal layer. Detailed Implementation
[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.
[0030] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.
[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0032] As described in the background section, BPSG (boron- and phosphorus-doped silicon dioxide) can achieve automatic surface planarization through reflow heat treatment at lower temperatures, overcoming the limitations of pure SiO2. However, BPSG is prone to boron and phosphorus precipitation after deposition, which reacts with water molecules in the air to form boric acid and phosphoric acid, leading to defects in the dielectric layer structure and affecting the manufacturing quality and performance stability of semiconductor devices. Therefore, providing a method for preparing a dielectric layer that can effectively control boron and phosphorus precipitation while improving the flatness and uniformity of the thin film has become a pressing technical problem in the semiconductor manufacturing field. To solve the above technical problem, embodiments of this application provide a dielectric layer and its preparation method.
[0033] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
[0034] According to one embodiment of this application, a method for preparing a dielectric layer is provided, such as... Figure 1 As shown, it includes the following steps:
[0035] S1, using the first process conditions and the first gas raw material, a first preparatory layer is deposited to form a first preparatory layer. The components in the first gas raw material include a silicon source, a boron source, a phosphorus source, and an oxidant.
[0036] S2, using the second process conditions and the second gas feedstock, a second preparatory layer is deposited on the first preparatory layer to form a second preparatory layer. The components in the second gas feedstock include a silicon source, a boron source, a phosphorus source, and an oxidant. In the first process conditions, the flow rate of the boron source is greater than that in the second process conditions. In the first process conditions, the flow rate of the phosphorus source is greater than that in the second process conditions. In the first process conditions, the flow rate of the silicon source is equal to that in the second process conditions. In the first process conditions, the flow rate of the oxidant is equal to that in the second process conditions.
[0037] S3 uses a third gas raw material to deposit a third preparatory layer on the second preparatory layer. The components of the third gas raw material are silicon source and oxidant. The first preparatory layer, the second preparatory layer and the third preparatory layer constitute a dielectric layer.
[0038] In this embodiment, by depositing boron phosphosilicate glass (BPSG) films and undoped silicate glass (USG) films of different concentrations in stages, the precipitation of boron (B) and phosphorus (P) is effectively controlled. Specifically:
[0039] In this process, using the first process conditions and the first gaseous feedstock, a first preparative layer is deposited. The gaseous feedstock includes a silicon source, a boron source, a phosphorus source, and an oxidant. At this stage, a relatively high proportion of boron, phosphorus, silicon, and oxidant is present. Through this high-concentration BPSG deposition, the basic framework of the dielectric layer is initially constructed. Due to the high boron and phosphorus content, they rapidly form a stable BPSG network structure in the initial stage. This not only provides excellent electrical insulation properties but also, due to the high concentration, prevents further deposition of boron and phosphorus in subsequent stages.
[0040] Next, a second preparatory layer is deposited on the first preparatory layer using the second process conditions and the second gas feedstock. Although it still contains silicon source, boron source, phosphorus source and oxidant, the flow rates of boron source and phosphorus source are reduced, while the flow rates of silicon source and oxidant remain unchanged. This results in a reduction of boron and phosphorus content in the second preparatory layer compared to the first preparatory layer, forming a lower concentration BPSG film. Due to the relatively increased proportion of silicon source and oxidant, this film inhibits the precipitation of boron and phosphorus from the high-concentration BPSG film below. It also reduces the internal stress changes of the film layer caused by B and P diffusion during reflow treatment, thereby avoiding film warping, cracking or peeling, and enhancing the overall process stability.
[0041] Finally, using a third gas feedstock containing only silicon source and oxidant, a third preparatory layer, namely the USG film, is deposited on the second preparatory layer. As the topmost layer, the USG film contains no dopants, therefore the integrity and performance of the dielectric layer will not be affected by boron (B) and phosphorus (P) precipitation. The USG layer not only further improves the flatness of the dielectric layer, ensuring the accuracy of subsequent process steps (such as photolithography and metal deposition), but also acts as a doping barrier layer, effectively preventing dopant elements from propagating upwards from the underlying BPSG layer. This reduces the contact between subsequent metal layers and other materials, lowers the risk of impurity diffusion and electrochemical corrosion, and further enhances the stability and reliability of the entire process.
[0042] Through progressive deposition under different process conditions in the three stages described above, each layer effectively blocks the deposition of boron and phosphorus in the next layer, with the blocking effect increasing sequentially. This not only significantly reduces the deposition rate of B and P, enhancing the stability and reliability of the process, but also improves the surface quality and uniformity of the film, avoiding short circuits and performance degradation in the device, and ensuring stable operation and high performance of the device over a long period. Experiments demonstrate that the method of this application can significantly improve the quality of the dielectric layer, thereby enhancing the overall performance and manufacturing yield of semiconductor devices.
[0043] In some alternative embodiments, prior to the step of forming the first preparatory layer, the preparation method further includes: placing the wafer in a chamber, and continuously introducing an auxiliary gas containing oxygen for a duration of more than 30 seconds, provided that the chamber pressure meets a preset range.
[0044] In the above optional implementation, when the cavity pressure reaches the set pressure (i.e. the preset range mentioned above), a pretreatment step (STABLE step) is added to ensure that the overall temperature of the wafer is close to the cavity temperature, reduce moisture residue, and provide a uniform substrate for subsequent deposition.
[0045] Specifically, after the CVD chamber reaches the set chamber pressure, the conventional BPSG process introduces O3 for reaction. During this process, uneven heating of the wafer surface can cause variations in the surface deposition rate, resulting in an uneven wafer surface and affecting film uniformity. Furthermore, residual moisture on the wafer surface may reduce film adhesion. In this embodiment, the STABLE step is performed before forming the first preparatory layer. Its purpose is to bring the overall wafer temperature closer to the chamber's set temperature, ensuring uniform heating of the wafer surface and effectively removing residual moisture, reducing film quality fluctuations caused by temperature differences and moisture residue. This pretreatment process prepares the wafer for subsequent film deposition by providing thermal balance and cleaning, reducing surface deposition rate differences, improving film flatness during deposition, enhancing film adhesion and surface flatness, and ultimately improving the uniformity and stability of the entire dielectric layer.
[0046] For example, the wafer is placed in the chamber, and when the chamber pressure stabilizes at a set value of 220 ± 0.1 Torr, oxygen is continuously introduced to remove moisture from the wafer surface. The time is set to T = 30 seconds. <T<40s。
[0047] In step S1 above, a first preparatory layer is deposited using the first process conditions and the first gas feedstock, i.e., a high-concentration BPSG film is deposited. Taking the silicon source, boron source, phosphorus source, and oxidant in the first gas feedstock as tetraethyl orthosilicate (TEOS), triethyl borate (TEB), triethyl phosphate (TEPO), and ozone (O3) as an example, compared with the one-time BPSG deposition, this process deposits a film thickness that accounts for 80% to 90% of the total film thickness, preferably 85%. Assuming the amount of BPSG deposited before process optimization is D, then the modulus of the deposited BPSG after optimization is D × 85%; the boron content concentration range is C. B1 =5~6wt%, phosphorus concentration range in C P1 =6~7wt%. TEOS, TEB, and TEPO react with ozone to form the stable compound BPSG, as shown in the following reaction equation:
[0048] Si(OC2H5)4+2O3→SiO2+4CH3CHO+2H2O;
[0049] 2B(OC2H5)3+2O3→B2O3+6CH3CHO+3H2O;
[0050] 2PO(OC2H5)3+2O3→P2O5+6CH3CHO+3H2O.
[0051] In this embodiment of the application, the deposition time of the first preparatory layer is T1, which can satisfy: T1=(D×X)×T01 / D1; where D is the preset thickness value of the dielectric layer, D1 is the actual thickness value of the deposited film layer under the first process conditions, T01 is the reference deposition time of the deposited film layer under the first process conditions, and X is the first preset percentage, which is 80%~90%.
[0052] The deposition duration T1 of the above first preparatory layer (i.e., the reaction time of the high-concentration BPSG film) can be determined according to the actual experimental results. The experimental scheme is as follows: Assume that the deposited BPSG thickness is D×85%. Deposit the BPSG film on a wafer using a PECVD machine, measure the film thickness value of BPSG as D1, react the wafer under the above reaction conditions for a period of time T01 (30s < T1 < 60s), and based on this, determine the reaction time T1 of the above reaction conditions. Therefore, the calculation formula is obtained: T1 = (D×85%)×T01 / D1.
[0053] Specifically, the first preparatory layer is prepared using a plasma-enhanced chemical vapor deposition (PECVD) device. By regulating the deposition duration T1 of the above first preparatory layer, it is ensured that the thickness of this layer accounts for 80% - 90% of the preset thickness D of the entire dielectric layer. The specific ratio is determined by the first preset percentage X. By extending the deposition time, the gas reaction on the wafer surface under the PECVD machine becomes more uniform, thereby reducing the precipitation risk caused by excessive boron and phosphorus contents, and enhancing the structural stability and electrical property consistency of the dielectric layer. By controlling the deposition process of the first preparatory layer, not only the accurate deposition of the high-concentration BPSG film is achieved, but also a solid foundation is established for the subsequent deposition of the low-concentration BPSG film and the USG film.
[0054] In some optional embodiments, under the first process conditions, the flow rate of the silicon source is 800 - 1000mg / m 3 , the flow rate of the boron source is 300 - 400mg / m 3 , and the flow rate of the phosphorus source is 60 - 80mg / m 3 .
[0055] In the above optional embodiments, the setting of the first process conditions, especially controlling the flow rate of the silicon source at 800 - 1000mg / m 3 , the flow rate of the boron source at 300 - 400mg / m 3 , and the flow rate of the phosphorus source at 60 - 80mg / m 3 , this specific parameter configuration can optimize the deposition process of the BPSG film, form a high-concentration BPSG thin film, so as to provide good electrical insulation performance and stress release ability. Due to the relatively high concentrations of boron and phosphorus, this thin film can flow and fill the trenches better during the subsequent reflow process, forming a flatter surface. At the same time, the high concentrations of boron and phosphorus will increase the internal stress of the thin film to a certain extent, and can be balanced by the subsequent deposition of the low-concentration BPSG film and the USG film.
[0056] For example, step S1 above includes: after the TABLE step is completed, reaction gases TEOS, TEB, TEPO and O3 are introduced into the chamber, and when the chamber pressure is stabilized at a set value P1, deposition begins, with the time set to T2, and the TEOS gas flow rate is 800~1000 mg / m³. 3 The TEB gas flow rate is 300~400 mg / m³. 3 The TEPO gas flow rate is 60~80 mg / m³. 3 The chamber pressure is set to 220±0.1 Torr, and the chamber temperature is 400~500℃.
[0057] In step S2 above, a second preparatory layer is formed on the first preparatory layer using the second process conditions and the second gas feedstock. This involves depositing a low-concentration BPSG film. Compared to step S1, the same gases are used, but the flow rates of TEB and TEPO are halved. Taking the gases used in step S1 as an example, with the flow rates of TEOS and O3 remaining constant, the TEB and TEPO in the chamber react more fully with O3 compared to step 2, effectively reducing the content of unreacted TEB and TEPO in the chamber. However, due to the reduced flow rates of TEB and TEPO, the content of B and P in the deposited BPSG film also decreases. The increased SiO2 content in the deposited low-concentration BPSG film provides some resistance to the precipitation of boron and phosphorus from the high-concentration BPSG film deposited in step S1. Compared to a one-time BPSG deposition, this process deposits a film thickness that accounts for 5%-15% of the total film thickness, preferably 10%. Assuming the amount of BPSG deposited before process optimization is D, then the amount of low-concentration BPSG film deposited after optimization is D × 10%, and the boron concentration range is C. B2 =3~4wt%, phosphorus concentration range is C P2 =4~5wt%, used for stress relief during reflow, increasing the reflow effect and improving the compactness of the membrane. TEOS, TEB, TEPO react with ozone to form the stable compound BPSG, and the reaction equation is as follows:
[0058] Si(OC2H5)4+2O3→SiO2+4CH3CHO+2H2O;
[0059] 2B(OC2H5)3+2O3→B2O3+6CH3CHO+3H2O;
[0060] 2PO(OC2H5)3+2O3→P2O5+6CH3CHO+3H2O.
[0061] In the embodiment of the present application, the deposition duration of the second preliminary layer is T2, and T2 satisfies: T2 = (D × Y) × T02 / D2; where D is the preset thickness value of the dielectric layer, D2 is the actual thickness value of the deposited film layer under the second process conditions, T02 is the reference deposition duration of the deposited film layer under the second process conditions, Y is the second preset percentage, and the second preset percentage is 5% - 15%.
[0062] The deposition duration T2 of the above-mentioned second preliminary layer (i.e., the reaction time of the low-concentration BPSG film) needs to be determined according to the actual experimental results. The experimental scheme is as follows: Assume that the deposited BPSG thickness is D × 10%. Use a PECVD machine to deposit a BPSG film on a wafer, measure the film thickness value of BPSG as D2, and react the wafer under the above reaction conditions for a period of time T02 (30s < T < 60s). Taking this as a reference, determine the reaction time T2 of the above reaction conditions. Therefore, the calculation formula is obtained: T2 = (D × Y) × T02 / D2.
[0063] Specifically, after forming the first preliminary layer, continue to use a plasma-enhanced chemical vapor deposition (PECVD) device to deposit and form a second preliminary layer on the first preliminary layer. By adjusting the deposition duration T2 of the above-mentioned second preliminary layer, it is ensured that the ratio of the actual thickness value D2 of the deposited film layer to the preset thickness value D of the dielectric layer conforms to the second preset percentage Y, that is, within the range of 5% - 15%. This setting is based on the reference deposition duration T02 of the deposited film layer under the second process conditions. By calculating T2 = (D × Y) × T02 / D2, precise control of the deposition process is achieved, ensuring the deposition thickness of the low-concentration BPSG film, and effectively blocking the precipitation of boron and phosphorus in the high-concentration BPSG film. By adopting the above implementation method, not only the uniformity of the film layer is improved, the surface roughness is reduced, but also the stability and reliability of the device are significantly enhanced, thereby preventing problems such as short circuits in the metal layer.
[0064] In some optional implementation manners, the flow rate of the boron source in the second process conditions is 50% - 60% of the flow rate of the boron source in the first process conditions; the flow rate of the phosphorus source in the second process conditions is 50% - 60% of the flow rate of the phosphorus source in the first process conditions.
[0065] In the above optional implementation manner, the flow rate of the boron source in the second process conditions is set to 50% - 60% of the flow rate of the boron source in the first process conditions. Similarly, the flow rate of the phosphorus source is also set to 50% - 60% of the flow rate of the phosphorus source in the first process conditions. By reducing the flow rates of the boron source and the phosphorus source, the concentrations of B and P in the deposited second preliminary layer are reduced, which effectively limits the diffusion of doping elements in the BPSG layer, especially provides better control for the precipitation problems of boron and phosphorus, enhances the stability of the film layer, and reduces the risk of device short circuits in subsequent processes.
[0066] Specifically, a first preparatory layer containing a high-concentration BPSG film is first deposited using first process conditions and a first gas feedstock. Then, a second preparatory layer is deposited on the first preparatory layer using second process conditions and a second gas feedstock. During this process, the flow rates of the silicon source and oxidant remain constant, while the flow rates of the boron source and phosphorus source are halved, resulting in a low-concentration BPSG film. This low-concentration BPSG film in the second preparatory layer acts as an intermediate buffer, mitigating the precipitation of dopant elements from the high-concentration BPSG film in the first preparatory layer, further enhancing the structural stability and electrical performance of the entire dielectric layer. Through this optimized gradient deposition method, the embodiments of this application solve problems such as uneven film thickness and large surface roughness caused by internal stress changes in the film during traditional deposition processes, significantly improving the quality of the dielectric layer and the reliability of the device. By controlling the flow rate of the reactive gas, precise control of the dopant elements in the BPSG film is achieved, avoiding the formation of boric acid and phosphoric acid, and the resulting structural defects in the dielectric layer and degradation of device performance. This not only improves the uniformity and surface quality of the film but also effectively prevents impurity diffusion, reduces the risk of short circuits during metal filling, and effectively improves the manufacturing quality and reliability of semiconductor devices.
[0067] For example, step S2 above includes: after step S1 (depositing a high-concentration BPSG membrane) is completed, the flow rates of the reactive gases TEOS, TEB, and O3 into the chamber remain unchanged, while the flow rate of TEPO is reduced. When the chamber pressure is stabilized at the set value P1, deposition begins, with the time set to T3, and the TEOS gas flow rate is 800~1000 mg / m³. 3 The TEB gas flow rate is 300~400 mg / m³. 3 ×(50%~60%), TEPO gas flow rate is 60~80 mg / m³ 3 ×(50%~60%), the chamber pressure is set to 220±0.1Torr, and the chamber temperature is 400-500℃.
[0068] In step S3 above, a third gas feedstock is used to deposit a third preparatory layer on the second preparatory layer, i.e., a pure USG film is deposited. Compared with the one-time BPSG deposition, this process results in a film thickness that accounts for 5%-10% of the total film thickness, preferably 5%. Assuming the amount of BPSG deposited before process optimization is D, then the modulus of the deposited USG after optimization is D×5%. Taking TEOS and O3 as the third gas feedstock as an example, TEOS reacts with O3 to form the stable compound USG. The reaction equation is as follows:
[0069] Si(OC2H5)4+2O3→SiO2+4CH3CHO+2H2O.
[0070] Due to the slow deposition rate of USG by TEOS and O3, the uniformity of USG deposited by TEOS and O2 under high-temperature radio frequency is better. USG helps with surface planarization, improves the roughness of the BPSG surface, and provides a better foundation for subsequent process steps. In addition, the USG layer can act as a doping barrier layer to prevent the diffusion of doping elements (such as boron and phosphorus) in the BPSG layer. Moreover, the USG layer can prevent the direct contact between the BPSG layer and subsequent metals or other materials, thereby reducing the risk of impurity diffusion and electrochemical corrosion.
[0071] In the embodiment of the present application, a third preparation layer is deposited on the second preparation layer by using a third process condition and a third gas raw material. The deposition duration of the third preparation layer is T3, and T3 satisfies: T3 = (D × Z) × T03 / D3; where D is the preset thickness value of the dielectric layer, D3 is the actual thickness value of the deposited film layer under the third process condition, T03 is the reference deposition duration of the deposited film layer under the third process condition, and Z is the third preset percentage, and the third preset percentage is 5% - 10%.
[0072] The deposition duration T3 of the above-mentioned third preparation layer (i.e., the reaction time of the pure USG film), the reaction time needs to be determined according to the actual experimental results. The experimental plan is as follows: Assume the thickness of the deposited USG is D × 5%. Use a PECVD machine to deposit a USG film on a wafer, measure the film thickness value of the USG as D3, and react the wafer under the above reaction conditions for a period of time T03 (30s < T < 60s). Based on this, determine the reaction time T3 of the above reaction conditions, and obtain the calculation formula: T3 = (D × 5%) × T03 / D3.
[0073] Specifically, after forming the second preparation layer, continue to use a plasma-enhanced chemical vapor deposition (PECVD) device, and use a third process condition and a third gas raw material to deposit a third preparation layer on the second preparation layer. By adjusting the deposition duration T3 of the above-mentioned third preparation layer, ensure that the actual thickness D3 of the deposited film layer meets the third preset percentage Z of the preset thickness D of the dielectric layer, that is, 5% - 10%. By adjusting the flow rates of TEOS and O3, promote the formation of the USG layer. The USG layer not only helps with surface planarization and reduces the roughness of the BPSG surface, but also acts as a doping barrier layer to effectively inhibit the diffusion of doping elements (such as boron and phosphorus) in the BPSG layer, prevent the direct contact between the BPSG layer and the subsequent metal layer, and reduce the risk of impurity diffusion and electrochemical corrosion.
[0074] In some optional embodiments, a third preparation layer is deposited on the second preparation layer by using a third process condition and a third gas raw material, and the flow rate of the silicon source in the third process condition is equal to the flow rate of the silicon source in the first process condition.
[0075] In the above optional embodiments, the deposition of the third preparatory layer is performed based on the second preparatory layer. The same silicon source flow rate as the first preparatory layer is used, but boron and phosphorus sources are not employed; only silicon and an oxidant are used as the reaction gases. By first depositing a high-concentration BPSG film (first preparatory layer), then a low-concentration BPSG film (second preparatory layer), and finally a pure USG film (third preparatory layer), the progressively decreasing doping concentration effectively suppresses the precipitation of boron and phosphorus. In particular, the deposition of the USG film not only further strengthens the barrier function against boron and phosphorus precipitation but also utilizes the excellent surface smoothing properties of the USG film generated by the reaction of TEOS and O3, significantly reducing the surface roughness of the BPSG film. This provides a flatter interface for subsequent metallization and other processes, avoiding focusing difficulties and the risk of short circuits between metal layers.
[0076] For example, step S3 above includes: after step S2 (depositing a low-concentration BPSG membrane) is completed, the flow of TEB and TEPO gases into the chamber is stopped, while TEOS and O3 are continued to flow in. The chamber pressure remains stable at the set value of 220±0.1 Torr. USG deposition begins, with the time set to T6, and the TEOS gas flow rate is 800~1000 mg / m³. 3 The chamber pressure is set to 220±0.1 Torr, and the chamber temperature is 400-500℃.
[0077] In summary, the embodiments of this application first deposit a first preparatory layer and a second preparatory layer containing high and low concentrations of BPSG using first and second process conditions, respectively. Then, a third preparatory layer, i.e., a USG layer, without doped elements, is deposited. The entire process flow aims to improve the overall performance of the dielectric layer by controlling the gas flow rate and deposition time at each stage. First, a high-concentration BPSG film is deposited in the first preparatory layer to provide sufficient electrical isolation and signal transmission capabilities. Next, a low-concentration BPSG film is deposited in the second preparatory layer to reduce boron and phosphorus precipitation while maintaining electrical performance, alleviating internal stress in the film, and preventing warping, cracking, and peeling. Finally, a pure USG film is deposited in the third preparatory layer as a top capping layer, further improving the flatness of the film surface, enhancing the barrier effect against doped elements, and ensuring the reliability of subsequent metal layer filling. Through this series of progressive deposition strategies, the uniformity and stability of the dielectric layer are effectively improved, the risk of device short circuits caused by boron and phosphorus precipitation is reduced, and the stress distribution of the film is optimized, significantly improving the manufacturing yield and performance consistency of semiconductor devices.
[0078] According to an embodiment of this application, a dielectric layer is also provided, which is obtained by the preparation method of the dielectric layer in the above embodiments, such as... Figure 2As shown, the dielectric layer includes a first preparatory layer 10, a second preparatory layer 20 and a third preparatory layer 30 stacked in sequence, wherein: the boron content concentration of the first preparatory layer 10 is greater than the boron content concentration of the second preparatory layer 20; and the phosphorus content concentration of the first preparatory layer 10 is greater than the phosphorus content concentration of the second preparatory layer 20.
[0079] In this embodiment, the dielectric layer includes a first preparatory layer 10, a second preparatory layer 20, and a third preparatory layer 30 sequentially stacked. The boron concentration of the first preparatory layer 10 is greater than that of the second preparatory layer 20, and the phosphorus concentration of the first preparatory layer 10 is also greater than that of the second preparatory layer 20. The first preparatory layer 10 is a high-concentration BPSG film. Its high boron and phosphorus content allows for rapid formation of a dense structure during initial deposition, effectively isolating moisture that may be present in subsequent processes and reducing the formation of boric acid and phosphoric acid, thereby preventing the loss of dielectric layer structure and the risk of short circuits during metal filling. The second preparatory layer 20 is a low-concentration BPSG film. Its reduced boron and phosphorus content helps to reduce changes in internal stress during reflow heat treatment, reducing the risk of film warping, cracking, or peeling. It also helps to improve the thickness uniformity of the film, avoid void formation, and ensure the stability of device performance. The combined use of the first preparatory layer 10 and the second preparatory layer 20 can significantly improve the problem of boron and phosphorus precipitation during the deposition process of the BPSG film, enhance process stability, and optimize the flatness of the film, laying a solid foundation for subsequent metal interconnects and other process steps. Furthermore, the third preparatory layer 30 is a pure USG film that does not contain boron and phosphorus. It can act as a doping barrier layer to effectively prevent the diffusion of dopants in the BPSG layer, while preventing the BPSG layer from directly contacting metals or other materials, reducing the risk of impurity diffusion and electrochemical corrosion, and further improving the reliability and service life of the device.
[0080] In some alternative embodiments, the boron content concentration of the first preparatory layer 10 ranges from 5 to 6 wt%, and the phosphorus content concentration of the first preparatory layer 10 ranges from 6 to 7 wt%; the boron content concentration of the second preparatory layer 20 ranges from 3 to 4 wt%, and the phosphorus content concentration of the first preparatory layer 10 ranges from 4 to 5 wt%.
[0081] In the above optional embodiments, the boron concentration of the first preparatory layer 10 is set to 5-6 wt%, and the phosphorus concentration is set to 6-7 wt%. This high concentration configuration enables the first preparatory layer 10 to effectively transport charge carriers while providing the necessary chemical stability to ensure that the performance of the dielectric layer is not affected under high-temperature conditions. The second preparatory layer 20, which is subsequently deposited, has a boron concentration of 3-4 wt% and a phosphorus concentration of 4-5 wt%. By reducing the concentration of boron and phosphorus in the second preparatory layer 20, the risk of boron and phosphorus precipitation in subsequent processes is reduced, forming a more stable interface that acts as a barrier against impurity diffusion during the upper layer deposition process.
[0082] In the embodiments of this application, such as Figure 2 As shown, the dielectric layer also includes a wafer 40, a silicon dioxide layer 50, and a metal layer 60. The silicon dioxide layer 50 is located between the wafer 40 and the first preparatory layer 10, and the metal layer 60 is located on the side of the third preparatory layer 30 away from the wafer 40. That is, the dielectric layer includes a wafer 40, a silicon dioxide layer 50, a second preparatory layer 20, a third preparatory layer 30, and a metal layer 60 stacked sequentially from bottom to top.
[0083] The dielectric layer and its preparation method in this application will be further described below with reference to specific embodiments and comparative examples.
[0084] Example 1
[0085] The method for preparing the dielectric layer provided in this embodiment includes the following stages:
[0086] STABLE phase:
[0087] After the CVD chamber reaches the set pressure, the STABLE step is implemented, which reduces the gas flow rate and extends the time to reach the set pressure, so that the overall temperature of the wafer is closer to the chamber temperature.
[0088] Specific parameters:
[0089] Chamber pressure: stable at 220±0.1 Torr.
[0090] Oxygen flow rate: Continuously supplied to remove moisture from the wafer surface.
[0091] Temperature: Maintain at 450℃.
[0092] Time: Between 35 seconds.
[0093] High-concentration BPSG film deposition stage:
[0094] After the STABLE stage is completed, TEOS, TEB, TEPO and O3 gases are introduced to deposit a BPSG membrane containing high concentrations of boron and phosphorus.
[0095] Specific parameters:
[0096] TEOS gas flow rate: 900 mg / m³ 3 .
[0097] TEB gas flow rate: 350 mg / m³ 3 .
[0098] TEPO gas flow rate: 70 mg / m³ 3 .
[0099] Chamber pressure: stable at 220±0.1 Torr.
[0100] Cavity temperature: 450℃.
[0101] Time: Adjusted according to actual film thickness requirements.
[0102] Deposition of low-concentration BPSG membrane stage:
[0103] After high-concentration BPSG membrane deposition, while keeping the TEOS and O3 gas flow rates constant, the TEB and TEPO flow rates were halved to deposit a BPSG membrane containing lower concentrations of boron and phosphorus.
[0104] Specific parameters:
[0105] TEOS gas flow rate: 900 mg / m³ 3 .
[0106] TEB gas flow rate: reduced to the original 350 mg / m³ 3 55%.
[0107] TEPO gas flow rate: reduced to the original 70 mg / m³ 3 55%.
[0108] Chamber pressure: 220±0.1 Torr.
[0109] Cavity temperature: 450℃.
[0110] Time: Adjusted according to actual film thickness requirements.
[0111] The stage of depositing a pure USG membrane:
[0112] After low-concentration BPSG film deposition, TEB and TEPO gas introduction is stopped, and only TEOS and O3 gas are maintained to deposit an undoped USG film, which is used as the upper planarization layer and doping barrier layer.
[0113] Specific parameters:
[0114] TEOS gas flow rate: 900 mg / m³ 3 .
[0115] O3 gas flow rate: Maintain an appropriate level to promote the reaction.
[0116] Chamber pressure: 220±0.1 Torr.
[0117] Cavity temperature: 450℃.
[0118] Time: Adjusted according to actual film thickness requirements, usually shorter than the deposition time of BPSG film.
[0119] Example 2
[0120] The method for preparing the dielectric layer provided in this embodiment differs from that in Embodiment 1 in that:
[0121] High-concentration BPSG film deposition stage:
[0122] The flow rate of the silicon source is 800 mg / m³. 3 The flow rate of the boron source is 300 mg / m³. 3 The phosphorus source flow rate is 60 mg / m³. 3 .
[0123] Example 3
[0124] The method for preparing the dielectric layer provided in this embodiment differs from that in Embodiment 1 in that:
[0125] High-concentration BPSG film deposition stage:
[0126] The flow rate of the silicon source is 1000 mg / m³. 3 The flow rate of the boron source was 400 mg / m³. 3 The phosphorus source flow rate is 80 mg / m³. 3 .
[0127] Example 4
[0128] The method for preparing the dielectric layer provided in this embodiment differs from that in Embodiment 1 in that:
[0129] Deposition of low-concentration BPSG membrane stage:
[0130] TEB gas flow rate: reduced to the original 350 mg / m³ 3 50%;
[0131] TEPO gas flow rate: reduced to the original 70 mg / m³ 3 50%.
[0132] Example 5
[0133] The method for preparing the dielectric layer provided in this embodiment differs from that in Embodiment 1 in that:
[0134] Deposition of low-concentration BPSG membrane stage:
[0135] TEB gas flow rate: reduced to the original 350 mg / m³ 3 60%;
[0136] TEPO gas flow rate: reduced to the original 70 mg / m³ 3 60%.
[0137] Example 6
[0138] The method for preparing the dielectric layer provided in this embodiment differs from that in Embodiment 1 in that:
[0139] High-concentration BPSG film deposition stage:
[0140] The flow rate of the silicon source is 700 mg / m³. 3 The flow rate of the boron source was 200 mg / m³. 3 The phosphorus source flow rate is 50 mg / m³. 3 .
[0141] Example 7
[0142] The method for preparing the dielectric layer provided in this embodiment differs from that in Embodiment 1 in that:
[0143] Deposition of low-concentration BPSG membrane stage:
[0144] TEB gas flow rate: reduced to the original 350 mg / m³ 3 40%;
[0145] TEPO gas flow rate: reduced to the original 70 mg / m³ 3 40%.
[0146] Example 8
[0147] The method for preparing the dielectric layer provided in this embodiment differs from that in Embodiment 1 in that:
[0148] High-concentration BPSG film deposition stage: chamber temperature: 400℃.
[0149] Deposition of low-concentration BPSG film stage: chamber temperature: 400℃.
[0150] Example 9
[0151] The method for preparing the dielectric layer provided in this embodiment differs from that in Embodiment 1 in that:
[0152] High-concentration BPSG film deposition stage: chamber temperature: 500℃.
[0153] Deposition of low-concentration BPSG film stage: chamber temperature: 500℃.
[0154] Comparative Example 1
[0155] The method for preparing the dielectric layer provided in this comparative example includes only one deposition stage:
[0156] TEOS, TEB, TEPO and O3 gases were introduced to deposit a BPSG membrane.
[0157] Specific parameters:
[0158] TEOS gas flow rate: 900 mg / m³ 3 .
[0159] TEB gas flow rate: 350 mg / m³ 3 .
[0160] TEPO gas flow rate: 70 mg / m³ 3 .
[0161] Chamber pressure: stable at 220±0.1 Torr.
[0162] Cavity temperature: 450℃.
[0163] Time: Adjusted according to actual film thickness requirements.
[0164] The uniformity measurement data of wafers during CVD chamber operations for 30 consecutive days in Example 1 (after process optimization) and Comparative Example 1 (before process optimization), as well as the uniformity (U), boron (B), and phosphorus (P) content after 2 hours of film formation, were monitored. The monitoring results are as follows: Figures 3 to 5 And as shown in Table 1, Figures 3 to 5 The horizontal axis represents the number of days, and the vertical axis represents the percentage.
[0165] Table 1
[0166]
[0167] Table 2 shows the uniformity measurement data of wafers in Examples 2 to 9 (after process optimization) and Comparative Example 1 (before process optimization) during CVD chamber operation on day 30, as well as the monitoring results of uniformity (U), boron (B), and phosphorus (P) content 2 hours after film formation.
[0168] Table 2
[0169]
[0170] According to monitoring data over 30 days, compared with Comparative Example 1 before process optimization, Examples 1 to 9 after process optimization significantly improved the uniformity of the wafers in the CVD chamber and effectively controlled the fluctuation of B and P content 2 hours after film deposition, demonstrating the significant effect of this application in improving film uniformity and suppressing the diffusion of dopant elements.
[0171] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.
[0172] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.
Claims
1. A method for preparing a dielectric layer, characterized in that, Includes the following steps: A first preparatory layer is formed by deposition using a first process condition and a first gaseous raw material, wherein the components of the first gaseous raw material include a silicon source, a boron source, a phosphorus source, and an oxidant; A second preparatory layer is deposited on the first preparatory layer using a second process condition and a second gas feedstock. The components of the second gas feedstock include a silicon source, a boron source, a phosphorus source, and an oxidant. The flow rate of the boron source in the first process condition is greater than the flow rate of the boron source in the second process condition, the flow rate of the phosphorus source in the first process condition is greater than the flow rate of the phosphorus source in the second process condition, the flow rate of the silicon source in the first process condition is equal to the flow rate of the silicon source in the second process condition, and the flow rate of the oxidant in the first process condition is equal to the flow rate of the oxidant in the second process condition. A third preparatory layer is formed by depositing a third gas raw material on the second preparatory layer. The components of the third gas raw material are a silicon source and an oxidant. The first preparatory layer, the second preparatory layer and the third preparatory layer constitute the dielectric layer.
2. The preparation method according to claim 1, characterized in that, The deposition time of the first preparatory layer is T1, and T1 satisfies: T1 = (D × X) × T01 / D1; Wherein, D is the preset thickness value of the dielectric layer, D1 is the actual thickness value of the film layer deposited under the first process conditions, T01 is the reference deposition time for depositing the film layer under the first process conditions, and X is the first preset percentage, which is 80%~90%.
3. The preparation method according to claim 1, characterized in that, In the first process conditions, the flow rate of the silicon source is 800~1000 mg / m³. 3 The flow rate of the boron source is 300~400 mg / m³. 3 The flow rate of the phosphorus source is 60~80 mg / m³. 3 .
4. The preparation method according to claim 1, characterized in that, The deposition time of the second preparatory layer is T2, and T2 satisfies: T2 = (D × Y) × T02 / D2; Wherein, D is the preset thickness value of the dielectric layer, D2 is the actual thickness value of the film layer deposited under the second process conditions, T02 is the reference deposition time for depositing the film layer under the second process conditions, and Y is the second preset percentage, which is 5%~15%.
5. The preparation method according to claim 1, characterized in that, The flow rate of the boron source in the second process condition is 50%-60% of the flow rate of the boron source in the first process condition; The flow rate of the phosphorus source in the second process condition is 50%-60% of the flow rate of the phosphorus source in the first process condition.
6. The preparation method according to claim 1, characterized in that, Using the third process conditions and the third gas feedstock, the third preparatory layer is deposited on the second preparatory layer to form the third preparatory layer. The deposition time of the third preparatory layer is T3, and T3 satisfies: T3 = (D × Z) × T03 / D3; Wherein, D is the preset thickness value of the dielectric layer, D3 is the actual thickness value of the film layer deposited under the third process conditions, T03 is the reference deposition time for depositing the film layer under the third process conditions, and Z is the third preset percentage, which is 5%~10%.
7. The preparation method according to claim 1, characterized in that, Using the third process conditions and the third gas feedstock, the third preparatory layer is deposited on the second preparatory layer to form the third preparatory layer, wherein the flow rate of the silicon source in the third process conditions is equal to the flow rate of the silicon source in the first process conditions.
8. The preparation method according to any one of claims 1 to 7, characterized in that, Prior to the step of forming the first preparatory layer, the preparation method further includes: The wafer is placed in the chamber, and while the chamber pressure meets a preset range, an auxiliary gas containing oxygen is continuously introduced for a duration of more than 30 seconds.
9. A dielectric layer, characterized in that, The dielectric layer is prepared by the preparation method according to any one of claims 1 to 8, wherein the dielectric layer comprises a first preparatory layer, a second preparatory layer, and a third preparatory layer stacked in sequence, wherein: The boron concentration in the first preparatory layer is greater than that in the second preparatory layer; The phosphorus concentration of the first preparatory layer is greater than that of the second preparatory layer.
10. The dielectric layer according to claim 9, characterized in that, The boron content concentration of the first preparative layer ranges from 5 to 6 wt%, and the phosphorus content concentration of the first preparative layer ranges from 6 to 7 wt%. The boron content concentration of the second preparative layer ranges from 3 to 4 wt%, and the phosphorus content concentration of the first preparative layer ranges from 4 to 5 wt%.