Novel furnace tube LPCVD (low pressure chemical vapor deposition) film forming mode for improving uniformity

Abstract

The invention provides a novel furnace tube LPCVD (Low Pressure Chemical Vapor Deposition) film forming mode for improving uniformity, which comprises the following steps: S1, placing a silicon wafer in a vertical cylindrical tray, and placing the vertical cylindrical tray in a deposition chamber of LPCVD equipment; s2, dichlorosilane (DCS) and ammonia gas (NH3) are introduced into the deposition chamber to serve as precursor gas; s3, heating the deposition chamber to 750 DEG C, and keeping the temperature for 5 minutes to start the growth of the SiN film; and S4, reducing the temperature of the deposition chamber from 750 DEG C to 720 DEG C at a rate of 5 DEG C per minute so as to ensure that the temperature of the edge of the silicon wafer is reduced faster than that of the central region. According to the novel furnace tube LPCVD film forming mode for improving the uniformity, circulation of high-temperature deposition, rapid cooling and slow heating is repeatedly carried out in the deposition process, so that the deposition rate of the edge and the center area of a silicon wafer is effectively balanced, the uniformity of the thickness of a thin film is remarkably improved, and the uniformity of the thin film is improved. And the problem of non-uniform thickness in the traditional method is solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a new LPCVD film forming method with furnace tubes for improving uniformity. Background Art

[0002] In the semiconductor manufacturing process, the thickness uniformity of the film is critical to device performance and production yield. Low-pressure chemical vapor deposition (LPCVD) is a commonly used method for depositing silicon nitride (SiN) films, usually using dichlorosilane (DCS) and ammonia (NH3) as precursor gases. However, in the traditional LPCVD process, when a vertical cylindrical tray is used to place silicon wafers, the edge of the silicon wafer is often hotter than the center area (ΔT of an 8-inch furnace tube is about 1°C), and the gas concentration is also greater, resulting in a significantly higher deposition rate of the SiN film at the edge than in the center, causing uneven film thickness.

[0003] In the prior art, there are some methods that attempt to improve film uniformity by controlling temperature gradients or optimizing gas flow. For example, a patent document discloses a method for improving film uniformity by optimizing gas flow at a constant temperature; another patent document proposes a method for dynamically adjusting the deposition temperature using a multi-point temperature monitoring system. However, these methods are still difficult to completely eliminate the thickness difference between the edge and the center in practical applications, especially in the deposition process of large-size silicon wafers (8 / 12 inches), which reduces uniformity.

[0004] Therefore, it is necessary to provide a new LPCVD film forming method with furnace tubes that improves uniformity to solve the above technical problems. Summary of the invention

[0005] The present invention provides a new LPCVD film forming method with furnace tubes for improving uniformity, which solves the problem that it is difficult to completely eliminate the thickness difference between the edge and the center, thereby reducing the uniformity.

[0006] In order to solve the above technical problems, the present invention provides a novel LPCVD film forming method with furnace tubes for improving uniformity, comprising the following steps:

[0007] S1. Place the silicon wafer in a vertical cylindrical tray and place it in the deposition chamber of the LPCVD equipment;

[0008] S2, introducing dichlorosilane (DCS) and ammonia (NH3) as precursor gases into the deposition chamber;

[0009] S3, heating the deposition chamber temperature to 750° C. and maintaining the temperature for 5 minutes to start the growth of the SiN film;

[0010] S4, reducing the deposition chamber temperature from 750°C to 720°C at a rate of 5°C per minute to ensure that the temperature at the edge of the silicon wafer drops faster than that in the center area;

[0011] S5. Raise the deposition chamber temperature from 720°C to 750°C at a rate of 1°C per minute to ensure a gradual rise in temperature and avoid adverse effects of temperature fluctuations on film uniformity.

[0012] S6. Steps S3 to S5 form a cycle, and are repeated for more than 10 cycles to complete the deposition of the SiN film.

[0013] Preferably, the 10 or more cycles are used to ensure that the deposition rate of the entire SiN film deposition process can fully balance the deposition rate of the edge and center regions.

[0014] Preferably, the vertical cylindrical tray configuration helps to achieve a temperature difference between the edge and center areas of the silicon wafer during cyclic temperature control, thereby promoting an improvement in the uniformity of film thickness.

[0015] Preferably, a vertical cylindrical pallet is required in step S1, and the vertical cylindrical pallet includes a tray body, and positioning columns are fixedly installed inside the three sides of the tray body, a positioning groove is opened on the top of the positioning column, a support rod is fixedly installed on the bottom of the positioning column, and a positioning rod is fixedly installed on the bottom of the support rod.

[0016] Preferably, a groove is formed on the top of the disk body, and a positioning hole is formed on the side of the positioning rod.

[0017] Preferably, the inner thread of the side surface of the positioning column is connected with a positioning piece, and the positioning piece is arranged on the top of the disk body.

[0018] Preferably, a replacement disk is provided on the inner side surface of the groove, and the outer side surface of the replacement disk is in contact with the inner side surface of the groove.

[0019] Preferably, a placement slot is provided on the top of the replacement tray.

[0020] Preferably, a clamping groove is provided at the bottom of the inner side surface of the groove, and a clamping block is fixedly mounted at the bottom of the replacement plate.

[0021] Preferably, the engaging block is engaged with the inner side surface of the engaging groove, and acts on the replacement limit on the inner side surface of the groove.

[0022] Compared with the related art, the novel LPCVD film forming method of furnace tube with improved uniformity provided by the present invention has the following beneficial effects:

[0023] The present invention provides a new LPCVD film-forming method with furnace tubes for improving uniformity. By repeatedly performing cycles of high-temperature deposition, rapid cooling and slow heating during the deposition process, the deposition rates at the edge and center areas of a silicon wafer are effectively balanced, thereby significantly improving the uniformity of the film thickness and overcoming the problem of uneven thickness in traditional methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the overall structure of the chamber of the LPCVD deposition device (α8SEi) provided by the present invention;

[0025] Figure 2 The temperature distribution curve of the edge and center area of ​​the silicon wafer when constant temperature deposition is adopted provided by the present invention;

[0026] Figure 3 The temperature dynamic change curve of the edge and center area of ​​the silicon wafer after adopting the cyclic temperature control method provided by the present invention;

[0027] Figure 4 The thickness distribution of SiN film at the edge and center of silicon wafer before and after the method of the present invention is adopted;

[0028] Figure 5 A simulated temperature drop curve diagram provided by the present invention;

[0029] Figure 6 A schematic structural diagram of a first embodiment of a vertical cylindrical tray for a novel LPCVD film forming method with improved uniformity provided by the present invention;

[0030] Figure 7 for Figure 5 The schematic diagram of the disc structure shown;

[0031] Figure 8 for Figure 7 The schematic diagram of the top view of the positioning column shown;

[0032] Fig. 9 A schematic structural diagram of a second embodiment of a vertical cylindrical tray for a novel LPCVD film forming method with improved uniformity provided by the present invention;

[0033] Fig.10 for Fig. 9 The schematic diagram of the side structure of the replacement disk shown;

[0034] Fig.11 for Fig. 9 Schematic diagram of the disc structure from top view.

[0035] Numbers in the figure: 1, disk body, 11, groove, 2, positioning column, 21, positioning groove, 22, positioning piece, 3, support rod, 4, positioning rod, 41, positioning hole, 5, snap-in groove, 51, snap-in block, 52, replacement disk, 53, placement groove. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings and implementation modes.

[0037] First embodiment

[0038] Please refer to Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 ,in, Figure 1 A schematic diagram of the overall structure of the chamber of the LPCVD deposition device (α8SEi) provided by the present invention; Figure 2 The temperature distribution curve of the edge and center area of ​​the silicon wafer when constant temperature deposition is adopted provided by the present invention; Figure 3 The temperature dynamic change curve of the edge and center area of ​​the silicon wafer after adopting the cyclic temperature control method provided by the present invention; Figure 4 The thickness distribution of SiN film at the edge and center of silicon wafer before and after the method of the present invention is adopted; Figure 5 A simulated temperature drop curve diagram provided by the present invention; Figure 6 A schematic structural diagram of a first embodiment of a vertical cylindrical tray for a novel LPCVD film forming method with improved uniformity provided by the present invention; Figure 7 for Figure 5 The schematic diagram of the disc structure shown; Figure 8 for Figure 7 A novel LPCVD film forming method with furnace tubes for improving uniformity comprises the following steps:

[0039] S1. Place the silicon wafer in a vertical cylindrical tray and place it in the deposition chamber of the LPCVD equipment;

[0040] S2, introducing dichlorosilane (DCS) and ammonia (NH3) as precursor gases into the deposition chamber;

[0041] S3, heating the deposition chamber temperature to 750° C. and maintaining the temperature for 5 minutes to start the growth of the SiN film;

[0042] S4, reducing the deposition chamber temperature from 750°C to 720°C at a rate of 5°C per minute to ensure that the temperature at the edge of the silicon wafer drops faster than that in the center area;

[0043] S5. Raise the deposition chamber temperature from 720°C to 750°C at a rate of 1°C per minute to ensure a gradual rise in temperature and avoid adverse effects of temperature fluctuations on film uniformity.

[0044] S6. Steps S3 to S5 form a cycle, and are repeated for more than 10 cycles to complete the deposition of the SiN film.

[0045] The above 10 cycles ensure that the deposition rate of the entire SiN film deposition process can fully balance the deposition rate of the edge and the center regions.

[0046] The vertical cylindrical tray configuration helps to achieve temperature differences between the edge and center areas of the silicon wafer during cyclic temperature control, thereby promoting improved uniformity of film thickness.

[0047] Deposition device settings:

[0048] like Figure 1 Using a standard vertical cylindrical tray, multiple silicon wafers are evenly placed in the deposition chamber of the α8SEi LPCVD equipment;

[0049] The deposition chamber is equipped with a precise temperature control system, the M560 controller, which can achieve the required temperature regulation rate;

[0050] Dichlorosilane (DCS) and ammonia (NH3) were introduced as precursor gases to ensure uniform gas flow;

[0051] Cyclic deposition procedure:

[0052] Initial deposition stage: The deposition chamber temperature is heated to 750°C and maintained at this temperature for 5 minutes to start the deposition of SiN film;

[0053] Temperature control stage:

[0054] Cooling process: reduce the temperature from 750°C to 720°C at a rate of 5°C per minute for 6 minutes;

[0055] Heating process: Raise the temperature from 720°C to 750°C at a rate of 1°C per minute for 30 minutes;

[0056] Cycle repetition: The above deposition, cooling and heating processes form a complete cycle and are repeated more than 10 times to complete the entire SiN film deposition process;

[0057] Process parameter optimization:

[0058] Deposition time and temperature control rate: According to the specific equipment characteristics and silicon wafer size (the invention patent corresponds to an 8-inch silicon substrate wafer), the deposition time of each cycle is optimized (the patent verification conditions are 5 minutes deposition, cooling rate 5℃ / min and heating rate 1℃ / min) to achieve the best film uniformity;

[0059] Gas flow and pressure control: Ensure that the flow of DCS (0.16slm / min) and NH3 (1.6slm / min) gases and the pressure in the deposition chamber remain stable (pressure control 30Pa) throughout the deposition process to avoid uneven deposition due to gas concentration fluctuations;

[0060] Deposition results:

[0061] By implementing the above-mentioned cyclic temperature control method, the thickness difference between the edge and center areas of the deposited SiN film is significantly reduced (edge ​​thick-center thick skew: 30A-->15A), achieving highly uniform film deposition.

[0062] Significantly improve thickness uniformity: Through cyclic temperature control, the deposition rate at the edge and center of the silicon wafer is balanced (Δ15A), significantly reducing the edge and center differences in film thickness, and achieving higher thickness uniformity. Specifically, in each cycle, the high temperature stage of 750°C promotes the rapid deposition of SiN film on the entire silicon wafer surface (15A / min), and the subsequent cooling process to 720°C causes the edge of the silicon wafer to drop faster than the center due to higher thermal conductivity and larger surface area (0.5°C skew). This dynamic change in temperature gradient effectively regulates the deposition rate at the edge and center, reducing the deposition rate at the edge and maintaining a higher deposition rate in the center, thereby achieving self-balance in thickness;

[0063] Enhanced device performance and yield: Uniform SiN film thickness helps ensure the stability of the electrical and physical properties of semiconductor devices. For example, a uniform dielectric layer can reduce electric field concentration, reduce device leakage current, and improve device reliability. In addition, improved thickness uniformity also reduces process deviations caused by film non-uniformity in subsequent process steps, improving overall production yield and product consistency;

[0064] Optimized cyclic deposition program: By setting the deposition at 750°C, cooling rate of 5°C per minute to 720°C, and heating rate of 1°C per minute to 750°C, and repeating the cycle program for more than 10 times, it is ensured that the dynamic change of temperature during the entire deposition process can fully adjust the deposition rate distribution of the film. This optimized cycle program not only improves the uniformity of film thickness, but also shortens the deposition time and improves production efficiency;

[0065] Calculation: The high temperature object is silicon, the initial temperature is 750 degrees Celsius, the cooling airflow is 720 degrees Celsius, and the convection heat transfer coefficient is 20;

[0066] Material properties: Specific heat capacity of silicon (c): about 700 J / (kg·K); Mass of silicon (m): assumed to be 0.1 kg; Cooling surface area (A): assumed to be 0.05 m2;

[0067] Cooling model: Using Newton's law of cooling:

[0068] dTdt=-hAmc(TT∞)\frac{dT}{dt}

[0069] =-\frac{hA}{mc}(T-T_{\infty})dtdT

[0070] =-mchA(TT∞)

[0071] The solution is:

[0072] T(t)=T∞+(T0-T∞)e-hAmctT(t)

[0073] =T_{\infty}+(T_0-T_{\infty})\cdot e^{-\frac{hA}{mc}t}T(t)

[0074] =T∞+(T0-T∞)e-mchAt;

[0075] Parameter substitution: Convection heat transfer coefficient (h) = 20W / (m2·K)

[0076] Initial temperature (T0) = 750°C

[0077] Ambient temperature (T∞) = 720°C

[0078] Calculate the time constant (τ):

[0079] τ=mchA=0.1×70020×0.05=70 seconds\tau=\frac{mc}{hA}=\frac{0.1\times700}{20\times 0.05}=70\text{seconds}τ=hAmc=20×0.050.1×700=70 seconds

[0080] Temperature change formula:

[0081] T(t)=720+30e-t70T(t)=720+30\cdot e^{-\frac{t}{70}}T(t)=720+30e-70t

[0083] The following is the temperature change over time data calculated based on the above formula:

[0084]

[0085]

[0086] We keep the previous assumptions unchanged and only change the convective heat transfer coefficient h:

[0087]

[0088] According to the above calculation model, combined with the actual initial temperature center egde temperature difference, draw the simulated temperature cooling curve as shown in the attached figure Figure 5 ;

[0089] Reduce subsequent process problems: Improved thickness uniformity not only optimizes the performance of the film itself, but also reduces problems caused by uneven film in subsequent process steps. For example, in the photolithography and etching steps, uniform SiN film helps to achieve more accurate pattern transfer and etching control, reduces defect rate and process deviation, and improves the stability and consistency of the overall process;

[0090] Energy saving and environmental protection: By optimizing the deposition temperature cycle, the present invention not only achieves high uniformity, but also effectively controls the energy consumption during the deposition process. The more reasonable temperature control strategy reduces unnecessary high temperature residence time, reduces overall energy consumption, and has certain energy-saving and environmental protection advantages.

[0091] A vertical cylindrical pallet is required in step S1, and the vertical cylindrical pallet includes a tray body 1, and positioning columns 2 are fixedly installed inside the three sides of the tray body 1. A positioning groove 21 is opened on the top of the positioning column 2, and a support rod 3 is fixedly installed at the bottom of the positioning column 2. A positioning rod 4 is fixedly installed at the bottom of the support rod 3.

[0092] The top of the plate body 1 is provided with a groove 11 , and the side of the positioning rod 4 is provided with a positioning hole 41 .

[0093] The inner thread of the side surface of the positioning column 2 is connected with a positioning member 22 , and the positioning member 22 is arranged on the top of the disk body 1 .

[0094] When in use, the user can place the silicon wafer on the inner side of the groove 11, and then select the appropriate number of disks 1 according to the number of silicon wafers, and arrange the disks 1 up and down, so that the positioning rod 4 at the bottom of the top disk 1 is inserted into the inner side of the positioning groove 21 of the bottom disk 1, and then rotate the positioning member 22 so that one end of the positioning member 22 abuts against the inner side of the positioning hole 41, thereby connecting the upper and lower disks 1. In this way, the disks 1 can be reasonably installed according to the number of silicon wafers, thereby increasing adaptability.

[0095] Compared with the related art, the novel LPCVD film forming method of furnace tube with improved uniformity provided by the present invention has the following beneficial effects:

[0096] By repeatedly performing cycles of high-temperature deposition, rapid cooling, and slow heating during the deposition process, the deposition rates at the edge and center of the silicon wafer are effectively balanced, significantly improving the uniformity of the film thickness and overcoming the uneven thickness problem existing in traditional methods.

[0097] Second embodiment

[0098] Please refer to Fig. 9 , Fig.10 and Fig.11 Based on the first embodiment of the present application, which provides a new furnace tube LPCVD film forming method with improved uniformity, the second embodiment of the present application provides another new furnace tube LPCVD film forming method with improved uniformity. The second embodiment is only a preferred method of the first embodiment, and the implementation of the second embodiment will not affect the independent implementation of the first embodiment.

[0099] Specifically, the difference of the new LPCVD film-forming method with furnace tube for improving uniformity provided in the second embodiment of the present application is that, in the new LPCVD film-forming method with furnace tube for improving uniformity, a replacement disk 52 is provided on the inner side surface of the groove 11, and the outer side surface of the replacement disk 52 is attached to the inner side surface of the groove 11.

[0100] A placement slot 53 is formed on the top of the replacement tray 52 .

[0101] A clamping groove 5 is formed at the bottom of the inner side of the groove 11 , and a clamping block 51 is fixedly mounted at the bottom of the replacement plate 52 .

[0102] The clamping block 51 is clamped on the inner side surface of the clamping groove 5 , and acts on the displacement 52 to be limited on the inner side surface of the groove 11 .

[0103] The working principle of a novel LPCVD film forming method with improved uniformity provided by the present invention is as follows:

[0104] When in use, when silicon wafers of different sizes need to be placed, the user can replace the corresponding replacement tray 52 so that the silicon wafer can be placed just on the inner side of the placement groove 53, thereby placing the silicon wafer. After that, the user puts the replacement tray 52 with the silicon wafer into the inner side of the groove 11, so that the clamping block 51 and the clamping groove 5 are clamped, and then the replacement tray 52 is limited.

[0105] Compared with the related art, the novel LPCVD film forming method of furnace tube with improved uniformity provided by the present invention has the following beneficial effects:

[0106] By means of the cooperation of structures such as the snap-in slot 5, the snap-in block 51, the replacement disk 52 and the placement slot 53, when in use, a suitable replacement disk 52 can be selected according to the size of the silicon wafer, and then the replacement disk 52 and the disk body 1 are installed by snapping together through the snap-in block 51 and the snap-in slot 5. In this way, silicon wafers of different sizes can be limited, thereby increasing adaptability.

[0107] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A novel LPCVD film forming method with furnace tubes for improving uniformity, characterized in that: The following steps are involved: S1. Place the silicon wafer in a vertical cylindrical tray and place it in the deposition chamber of the LPCVD equipment; S2, introducing dichlorosilane (DCS) and ammonia (NH3) as precursor gases into the deposition chamber; S3, heating the deposition chamber temperature to 750° C. and maintaining the temperature for 5 minutes to start the growth of the SiN film; S4, reducing the deposition chamber temperature from 750°C to 720°C at a rate of 5°C per minute to ensure that the temperature at the edge of the silicon wafer drops faster than that in the center area; S5. Raise the deposition chamber temperature from 720°C to 750°C at a rate of 1°C per minute to ensure a gradual rise in temperature and avoid adverse effects of temperature fluctuations on film uniformity. S6. Steps S3 to S5 form a cycle, and are repeated for more than 10 cycles to complete the deposition of the SiN film.

2. A novel LPCVD film forming method with furnace tube for improving uniformity according to claim 1, characterized in that: The above 10 cycles ensure that the deposition rate of the entire SiN film deposition process can fully balance the deposition rate of the edge and the center regions.

3. The novel LPCVD film forming method with furnace tube for improving uniformity according to claim 1, characterized in that: The vertical cylindrical tray configuration helps to achieve temperature differences between the edge and center areas of the silicon wafer during cyclic temperature control, thereby promoting improved uniformity of film thickness.

4. The novel LPCVD film forming method with furnace tube for improving uniformity according to claim 1, characterized in that: In step S1, a vertical cylindrical pallet is required, and the vertical cylindrical pallet includes a pallet body, and positioning columns are fixedly installed inside the three sides of the pallet body, a positioning groove is opened on the top of the positioning column, a support rod is fixedly installed on the bottom of the positioning column, and a positioning rod is fixedly installed on the bottom of the support rod.

5. The novel LPCVD film forming method with furnace tube for improving uniformity according to claim 4, characterized in that: A groove is formed on the top of the disk body, and a positioning hole is formed on the side of the positioning rod.

6. A novel LPCVD film forming method with furnace tube for improving uniformity according to claim 5, characterized in that: The inner thread of the side surface of the positioning column is connected with a positioning piece, and the positioning piece is arranged on the top of the disk body.

7. A novel LPCVD film forming method with furnace tube for improving uniformity according to claim 6, characterized in that: A replacement disc is arranged on the inner side surface of the groove, and the outer side surface of the replacement disc is fitted to the inner side surface of the groove.

8. The novel LPCVD film forming method with furnace tube for improving uniformity according to claim 7, characterized in that: The top of the replacement tray is provided with a placement slot.

9. A novel LPCVD film forming method with furnace tube for improving uniformity according to claim 8, characterized in that: A clamping groove is provided at the bottom of the inner side surface of the groove, and a clamping block is fixedly installed at the bottom of the replacement disk.

10. A novel LPCVD film forming method with furnace tube for improving uniformity according to claim 9, characterized in that: The clamping block is clamped on the inner side surface of the clamping groove, and acts on the replacement limit on the inner side surface of the groove.

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