A deep groove etching method for silicon

Abstract

The present invention discloses a deep groove etching method for silicon, and relates to the field of semiconductor technology. The present invention comprises the following steps: S1: preheating; S2: adjusting external factors; S3: deposition; S4: etching; S5: sidewall improvement, and then forming a second protective layer on the sidewall of the etching interface by a second deposition gas, which adheres to the surface of the first protective layer; S6: performing S3, S4, and S5 in an alternating cycle until the etching reaches a predetermined depth, and in the alternating cycle process, the mixing amount of each component of the first deposition gas and the second deposition gas is dynamically adjusted with the change of the etching depth; S7: ending the etching. The method of the present invention can be applied to the etching of ultra-high aspect ratio groove structures. By decomposing an etching cycle into three sub-processes of deposition, etching, and sidewall improvement, double sidewall deposition can greatly improve the morphology of the sidewall, solving the problems of low processing efficiency and unsatisfactory sidewall morphology of the existing deep groove etching method.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a deep groove etching method for silicon. Background Art

[0002] In recent years, with the development of microelectronics technology, MEMS has been highly valued by governments and scientists in developed countries. As the key to realizing MEMS, deep silicon etching technology has received more and more attention. With MEMS devices and MEMS systems being more and more widely used in the fields of automobiles and consumer electronics, and the broad prospects of TSV through-hole etching technology in the future packaging field, dry plasma deep silicon etching process has gradually become one of the mainstream processes in the field of MEMS processing and TSV technology.

[0003] At present, the Bosch process is mainly used for deep silicon etching. Specifically, the process of deep silicon etching using the Bosch process is a process in which etching steps and deposition steps are alternately cycled, wherein the deposition step is used to deposit a layer of polymer on the sidewall of the trench as a protective layer to protect the sidewall from corrosion. However, the existing deep trench etching method still has the following disadvantages in actual use:

[0004] 1. The existing deep trench etching method has insufficient etching accuracy, low etching rate and sidewall morphology needs to be improved;

[0005] 2. The contact between the deposited layer and the silicon material in the existing deep trench etching method is not tight enough, and the quality of the etched deep trench is poor.

[0006] Therefore, the existing deep trench etching method cannot meet the needs in actual use, so there is an urgent need for improved technology in the market to solve the above problems. Summary of the invention

[0007] The purpose of the present invention is to provide a deep trench etching method for silicon. The method of the present invention can be applied to the etching of ultra-high aspect ratio trench structures. By decomposing an etching cycle into three sub-processes of deposition, etching and sidewall improvement, double sidewall deposition can greatly improve the morphology of the sidewall, thereby solving the problems of low processing efficiency and less than ideal sidewall morphology of existing deep trench etching methods.

[0008] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0009] The present invention is a method for deep trench etching of silicon, comprising the following steps:

[0010] S1: Preheating: preheating the silicon material, the first deposition gas, the second deposition gas, and the etching gas to 25-30°C;

[0011] S2: Adjust external factors, control the external etching environment temperature to 25-30°C, and the external environment humidity to 40%-70%;

[0012] S3: Deposition, generating a first protective layer by using a first deposition gas to protect the etching sidewall;

[0013] S4: etching, etching the bottom and sidewalls of the etching by etching gas;

[0014] S5: improving the sidewall, providing a second deposition gas, and cavitating the second deposition gas through an ultrasonic device, and then forming a second protective layer on the sidewall of the etching interface through the second deposition gas, which adheres to the surface of the first protective layer;

[0015] S6: performing S3, S4, and S5 alternately and cyclically until the etching reaches a predetermined depth, and in the alternating cycle process, the mixing amount of each component of the first deposition gas and the second deposition gas is dynamically adjusted as the etching depth changes;

[0016] S7: End etching.

[0017] Furthermore, the first deposition gas is set to SiF 4 and O 2 mixture.

[0018] Furthermore, the second deposition gas is set to C 4 F 8 and O 2 mixture.

[0019] Furthermore, the etching gas is set to SF 6 .

[0020] Furthermore, the flow rate of the first deposition gas is 300 sccm-350 sccm, the upper RF power is 1200W-1400W, the lower RF power is 0W, the process gas pressure is 80mT-120mT, the deposition temperature is 15°C-20°C, and the deposition time is 4s.

[0021] Furthermore, the flow rate of the etching gas is 300sccm~500sccm, the upper RF power is 1800W~2200W, the lower RF power is 30W~60W, the lower RF frequency is 1000Hz, the lower RF duty cycle is 30%, the process gas pressure is 50mT~80mT, the etching temperature is 15℃~20℃, and the etching time is 3s.

[0022] Furthermore, the flow rate of the second deposition gas is 100 sccm-150 sccm, the upper RF power is 600W-800W, the lower RF power is 0W, the process gas pressure is 40mT-80mT, the deposition temperature is 15°C-20°C, and the deposition time is 1s.

[0023] Furthermore, in the side wall improvement step, the power of the ultrasonic equipment is set to 2.5KW and the frequency is set to 35KHZ.

[0024] Furthermore, during the S6 alternating cycle execution, the first deposition gas dynamically adjusts the SiF 4 With O 2 The ratio is 3:7, and the SiF 4 With O 2 The ratio of SiF in the Nth deposition step is 5:5. 4 With O 2 The ratio changes dynamically and evenly.

[0025] Furthermore, during the S6 alternating cycle, the second deposition gas dynamically adjusts the C of the first sidewall improvement step. 4 F 8 With O 2 The ratio is 4:6, and the C of the last sidewall improvement step 4 F 8 With O 2 The ratio of C is 7:3, and the C of the Nth sidewall improvement step 4 F 8 With O 2 The ratio changes dynamically and evenly.

[0026] The present invention has the following beneficial effects:

[0027] 1. The method of the present invention can be applied to the etching of ultra-high aspect ratio trench structures. The present invention decomposes an etching cycle into three sub-processes of deposition, etching and sidewall improvement. Double sidewall deposition can greatly improve the morphology of the sidewall. In the process of sidewall improvement, ultrasonic equipment is used to cavitate the second deposition gas to increase the activity of the second deposition gas, making it more dispersed and enhancing the vertical bombardment capability of plasma, thereby improving the deposition of the deep groove sidewall and achieving better deposition uniformity.

[0028] 2. The present invention preheats the silicon material and the first deposition gas, the second deposition gas, and the etching gas, improves external environmental factors, and optimizes process parameters, thereby greatly increasing the etching rate and improving the etching morphology. The ratio of the reaction gas changes dynamically based on the change in the depth value, so that the reaction gas can fully contact the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0030] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0032] Embodiment 1

[0033] See also Figure 1 As shown, the present invention is a deep trench etching method for silicon, comprising the following steps:

[0034] S1: Preheating: preheat the silicon material and the first deposition gas, the second deposition gas, and the etching gas to 25°C. The first deposition gas is set to SiF 4 and O 2 The second deposition gas is set to C 4 F 8 and O 2 The etching gas is set to SF 6 ;

[0035] S2: Adjust external factors, control the external etching environment temperature to 25°C, and the external environment humidity to 40%;

[0036] S3: Deposition, generating a first protective layer by a first deposition gas to protect the etching sidewall, the flow rate of the first deposition gas is 300 sccm, the upper RF power is 1200 W, the lower RF power is 0 W, the process gas pressure is 80 mT, the deposition temperature is 15 ° C, and the deposition time is 4 s;

[0037] S4: Etching: etching the bottom and sidewalls of the etching by etching gas, the flow rate of the etching gas is 300 sccm, the upper RF power is 1800 W, the lower RF power is 30 W, the lower RF frequency is 1000 Hz, the lower RF duty cycle is 30%, the process gas pressure is 50 mT, the etching temperature is 15 ° C, and the etching time is 3 s;

[0038] S5: Improve the sidewall, provide a second deposition gas, and perform cavitation on the second deposition gas through an ultrasonic device, the power of the ultrasonic device is set to 2.5KW, the frequency is set to 35KHZ, and then the second deposition gas is used to form a second protective layer on the sidewall of the etching interface, attached to the surface of the first protective layer, the flow rate of the second deposition gas is 100sccm, the upper RF power is 600W, the lower RF power is 0W, the process gas pressure is 40mT, the deposition temperature is 15°C, and the deposition time is 1s;

[0039] S6: S3, S4, and S5 are performed alternately and cyclically until the etching reaches a predetermined depth. In the alternating cycle, the mixing amount of each component of the first deposition gas and the second deposition gas is dynamically adjusted as the etching depth changes. The SiF 4 With O 2 The ratio is 3:7, and the SiF 4 With O 2 The ratio of SiF in the Nth deposition step is 5:5. 4 With O 2 The ratio of the second deposition gas is dynamically and uniformly changed, and the C of the first sidewall improvement step is dynamically adjusted. 4 F 8 With O 2 The ratio is 4:6, and the C of the last sidewall improvement step 4 F 8 With O 2 The ratio of C is 7:3, and the C of the Nth sidewall improvement step 4 F 8 With O 2 The ratio of changes dynamically and evenly. Specifically, the deep groove to be etched needs to be etched in five stages. The SiF 4 With O 2 The ratio is 3:7, and the second deposition step of SiF 4 With O 2 The ratio of SiF in the third deposition step is 3.5:6.5. 4 With O 2 The ratio is 4:6, and the SiF 4 With O 2 The ratio is 4.5:5.5, and the SiF 4 With O 2 The ratio is 5:5, and the C of the first sidewall improvement step 4 F 8 With O 2 The ratio is 4:6, and the C of the second sidewall improvement step 4 F 8 With O 2The ratio is 4.75:5.25, and the C of the third sidewall improvement step 4 F 8 With O 2 The ratio is 5.5:4.5, and the C of the fourth sidewall improvement step 4 F 8 With O 2 The ratio is 6.25:3.75, and the C of the last sidewall improvement step 4 F 8 With O 2 The ratio is 7:3;

[0040] S7: End etching.

[0041] Embodiment 2

[0042] See also Figure 1 As shown, the present invention is a deep trench etching method for silicon, comprising the following steps:

[0043] S1: Preheating: preheat the silicon material and the first deposition gas, the second deposition gas, and the etching gas to 30°C. The first deposition gas is set to SiF 4 and O 2 The second deposition gas is set to C 4 F 8 and O 2 The etching gas is set to SF 6 ;

[0044] S2: Adjust external factors, control the external etching environment temperature to 30°C and the external environment humidity to 70%;

[0045] S3: Deposition, generating a first protective layer by a first deposition gas to protect the etching sidewall, the flow rate of the first deposition gas is 350 sccm, the upper RF power is 1400 W, the lower RF power is 0 W, the process gas pressure is 120 mT, the deposition temperature is 20° C., and the deposition time is 4 s;

[0046] S4: Etching: etching the bottom and sidewalls of the etching by etching gas, the flow rate of the etching gas is 500 sccm, the upper RF power is 2200 W, the lower RF power is 60 W, the lower RF frequency is 1000 Hz, the lower RF duty cycle is 30%, the process gas pressure is 80 mT, the etching temperature is 20°C, and the etching time is 3 s;

[0047] S5: Improve the sidewall, provide a second deposition gas, and perform cavitation on the second deposition gas through an ultrasonic device, the power of the ultrasonic device is set to 2.5KW, the frequency is set to 35KHZ, and then the second deposition gas is used to form a second protective layer on the sidewall of the etching interface, attached to the surface of the first protective layer, the flow rate of the second deposition gas is 150sccm, the upper RF power is 800W, the lower RF power is 0W, the process gas pressure is 80mT, the deposition temperature is 20°C, and the deposition time is 1s;

[0048] S6: S3, S4, and S5 are performed alternately and cyclically until the etching reaches a predetermined depth. In the alternating cycle, the mixing amount of each component of the first deposition gas and the second deposition gas is dynamically adjusted as the etching depth changes. The SiF 4 With O 2 The ratio is 3:7, and the SiF 4 With O 2 The ratio of SiF in the Nth deposition step is 5:5. 4 With O 2 The ratio of the second deposition gas is dynamically and uniformly changed, and the C of the first sidewall improvement step is dynamically adjusted. 4 F 8 With O 2 The ratio is 4:6, and the C of the last sidewall improvement step 4 F 8 With O 2 The ratio of C is 7:3, and the C of the Nth sidewall improvement step 4 F 8 With O 2 The proportion of changes dynamically and evenly;

[0049] S7: End etching.

[0050] Embodiment 3

[0051] See also Figure 1 As shown, the present invention is a deep trench etching method for silicon, comprising the following steps:

[0052] S1: Preheating: preheat the silicon material and the first deposition gas, the second deposition gas, and the etching gas to 23°C. The first deposition gas is set to SiF 4 and O 2 The second deposition gas is set to C 4 F 8 and O 2 The etching gas is set to SF 6 ;

[0053] S2: Adjust external factors, control the external etching environment temperature to 23°C, and the external environment humidity to 60%;

[0054] S3: Deposition, generating a first protective layer by a first deposition gas to protect the etching sidewall, the flow rate of the first deposition gas is 330 sccm, the upper RF power is 1300 W, the lower RF power is 0 W, the process gas pressure is 100 mT, the deposition temperature is 18 ° C, and the deposition time is 4 s;

[0055] S4: Etching: etching the bottom and sidewalls of the etching by etching gas, the flow rate of the etching gas is 400 sccm, the upper RF power is 2000 W, the lower RF power is 50 W, the lower RF frequency is 1000 Hz, the lower RF duty cycle is 30%, the process gas pressure is 60 mT, the etching temperature is 18 ° C, and the etching time is 3 s;

[0056] S5: Improve the sidewall, provide a second deposition gas, and perform cavitation on the second deposition gas through an ultrasonic device, the power of the ultrasonic device is set to 2.5KW, the frequency is set to 35KHZ, and then the second deposition gas is used to form a second protective layer on the sidewall of the etching interface, attached to the surface of the first protective layer, the flow rate of the second deposition gas is 130sccm, the upper RF power is 700W, the lower RF power is 0W, the process gas pressure is 60mT, the deposition temperature is 17°C, and the deposition time is 1s;

[0057] S6: S3, S4, and S5 are performed alternately and cyclically until the etching reaches a predetermined depth. In the alternating cycle, the mixing amount of each component of the first deposition gas and the second deposition gas is dynamically adjusted as the etching depth changes. The SiF 4 With O 2 The ratio is 3:7, and the SiF 4 With O 2 The ratio of SiF in the Nth deposition step is 5:5. 4 With O 2 The ratio of the second deposition gas is dynamically and uniformly changed, and the C of the first sidewall improvement step is dynamically adjusted. 4 F 8 With O 2 The ratio is 4:6, and the C of the last sidewall improvement step 4 F 8 With O 2 The ratio of C is 7:3, and the C of the Nth sidewall improvement step 4 F 8 With O 2 The proportion of changes dynamically and evenly;

[0058] S7: End etching.

[0059] The above are only preferred embodiments of the present invention and do not limit the present invention. Any modification to the technical solutions recorded in the aforementioned embodiments, any equivalent replacement of some of the technical features therein, and any modification, equivalent replacement, and improvement made are all within the protection scope of the present invention.

Claims

1. A method for deep trench etching of silicon, characterized in that: The following steps are involved: S1: Preheating: preheating the silicon material, the first deposition gas, the second deposition gas, and the etching gas to 25-30°C; S2: Adjust external factors, control the external etching environment temperature to 25-30°C, and the external environment humidity to 40%-70%; S3: Deposition, generating a first protective layer by using a first deposition gas to protect the etching sidewall; S4: etching, etching the bottom and sidewalls of the etching by etching gas; S5: improving the sidewall, providing a second deposition gas, and cavitating the second deposition gas through an ultrasonic device, and then forming a second protective layer on the sidewall of the etching interface through the second deposition gas, which adheres to the surface of the first protective layer; S6: performing S3, S4, and S5 alternately and cyclically until the etching reaches a predetermined depth, and in the alternating cycle process, the mixing amount of each component of the first deposition gas and the second deposition gas is dynamically adjusted as the etching depth changes; S7: End etching.

2. A method for deep trench etching of silicon according to claim 1, characterized in that: The first deposition gas is set to be a mixture of SiF4 and O2.

3. A method for deep trench etching of silicon according to claim 1, characterized in that: The second deposition gas is set to be a mixture of C4F8 and O2.

4. A method for deep trench etching of silicon according to claim 1, characterized in that: The etching gas is set to be SF6.

5. The method for deep trench etching of silicon according to claim 1, characterized in that: The flow rate of the first deposition gas is 300 sccm-350 sccm, the upper RF power is 1200W-1400W, the lower RF power is 0W, the process gas pressure is 80mT-120mT, the deposition temperature is 15°C-20°C, and the deposition time is 4s.

6. A method for deep trench etching of silicon according to claim 1, characterized in that: The flow rate of the etching gas is 300sccm~500sccm, the upper RF power is 1800W~2200W, the lower RF power is 30W~60W, the lower RF frequency is 1000Hz, the lower RF duty cycle is 30%, the process gas pressure is 50mT~80mT, the etching temperature is 15℃~20℃, and the etching time is 3s.

7. A method for deep trench etching of silicon according to claim 1, characterized in that: The flow rate of the second deposition gas is 100 sccm-150 sccm, the upper RF power is 600W-800W, the lower RF power is 0W, the process gas pressure is 40mT-80mT, the deposition temperature is 15°C-20°C, and the deposition time is 1s.

8. The method for deep trench etching of silicon according to claim 1, characterized in that: In the side wall improvement step, the power of the ultrasonic equipment is set to 2.5KW and the frequency is set to 35KHZ.

9. A method for deep trench etching of silicon according to claim 2, characterized in that: During the S6 alternating cycle, the first deposition gas dynamically adjusts the ratio of SiF4 to O2 in the first deposition step to 3:7, the ratio of SiF4 to O2 in the last deposition step to 5:5, and the ratio of SiF4 to O2 in the Nth deposition step changes dynamically and evenly.

10. The method for deep trench etching of silicon according to claim 3, characterized in that: During the alternating cycle of S6, the ratio of C4F8 to O2 in the first sidewall improvement step dynamically adjusted by the second deposition gas is 4:6, the ratio of C4F8 to O2 in the last sidewall improvement step is 7:3, and the ratio of C4F8 to O2 in the Nth sidewall improvement step is dynamically and evenly changed.

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