CN110534424B - Etching method of SiC substrate - Google Patents
Etching method of SiC substrate Download PDFInfo
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- CN110534424B CN110534424B CN201810857556.0A CN201810857556A CN110534424B CN 110534424 B CN110534424 B CN 110534424B CN 201810857556 A CN201810857556 A CN 201810857556A CN 110534424 B CN110534424 B CN 110534424B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/3065—Plasma etching; Reactive-ion etching
- H01L21/30655—Plasma etching; Reactive-ion etching comprising alternated and repeated etching and passivation steps, e.g. Bosch process
Abstract
An etching method of a SiC substrate, wherein etching is performed in a reaction chamber, and the etching method alternately performs an etching step and a byproduct discharging step; in the etching step, etching the SiC substrate arranged in the reaction chamber; in the byproduct discharge step, the reaction byproduct in the reaction chamber is discharged. The etching method can reduce the possibility of deposition of reaction byproducts on the side wall of the reaction chamber and the surface of the dielectric window, greatly prolong the cleaning and maintenance period of the equipment, and reduce the maintenance difficulty and workload of the equipment.
Description
Technical Field
The invention relates to the technical field of semiconductor manufacturing, in particular to an etching method of a SiC substrate.
Background
With the continuous progress of communication technology, the application of GaN-based HEMT microwave power devices is gradually increased. A schematic structural view of a GaN-based HEMT device is shown in fig. 1, which is a device structure in which a GaN-based AlGaN/GaN layer, for example, is grown on a SiC substrate to produce a GaN-based device. The manufacturing process of the GaN-based HEMT microwave power device comprises a front process and a back process, wherein the front process mainly forms a core function part of the device, the back process mainly comprises the steps of etching a through hole 2 on a SiC substrate 3 and connecting a metal lead with the GaN device on the front, the obtained GaN-based HEMT microwave power device comprises deposited metal 4, the SiC substrate 3 and an AlGaN/GaN layer 5 as shown in figure 1, the through hole 2 penetrates through each layer, and a source electrode gasket 1 is arranged on the AlGaN/GaN layer 5.
In the back surface process of the GaN-based HEMT microwave power device, SiC through hole etching is a very critical step. In order to realize large-depth SiC through hole etching, metal Ni is generally selected as a general etching mask.
The Ni material used as the mask is gradually lost in the etching process, Ni cannot form volatile gaseous byproducts with etching reaction gas, the volatile gaseous byproducts exist in the reaction chamber in the form of solid particles, a part of the solid particles move along with plasma and gas flow and are pumped away by a vacuum pump body, and most of the remaining solid particles are attached to the inner wall of the reaction chamber and the surface of a dielectric window. These solid by-products gradually accumulate and, when accumulated to a certain extent, fall off in the form of particles on the wafer surface due to unstable adhesion thereof or bombardment by plasma. If the particles fall into the SiC etched through hole, the particles become a micro-mask to block the normal etching, and a bamboo shoot-shaped defect is formed, so that the device fails.
The etching rate of SiC is generally in the range of 0.3-1.5 μm/min, and the thickness of the SiC substrate is generally 50-100 μm, so that the whole etching time is as long as several hours, and a large amount of Ni byproducts are accumulated in the process. In the normal production process, production needs to be stopped when etching several to more than ten pieces, by-products in the reaction chamber are cleaned and maintained, otherwise, the product yield is influenced, and the production maintenance difficulty and workload are greatly increased.
Disclosure of Invention
The invention aims to provide an etching method of a SiC substrate, which is used for reducing the deposition of reaction byproducts in a reaction chamber.
The invention provides an etching method of a SiC substrate, wherein the etching is carried out in a reaction chamber, and the etching method alternately carries out an etching step and a byproduct discharging step;
in the etching step, etching the SiC substrate arranged in the reaction chamber;
in the byproduct discharging step, the reaction byproduct in the reaction chamber is discharged.
Preferably, the difference between the reaction chamber pressure P1 adopted in the etching step and the reaction chamber pressure P2 adopted in the byproduct discharging step is not greater than a first threshold, the difference between the upper electrode rf power W1 adopted in the etching step and the upper electrode rf power W2 adopted in the byproduct discharging step is not greater than a second threshold, and the difference between the total gas flow Q1 adopted in the etching step and the total gas flow Q2 adopted in the byproduct discharging step is not greater than a third threshold.
Preferably, none of the first threshold, the second threshold, and the third threshold is greater than 5%.
Preferably, the radio frequency power of the lower electrode adopted in the byproduct discharging step is 0-200W.
Preferably, the ratio of the duration T2 of the byproduct discharging step to the duration T1 of the etching step is 5% to 15%.
Preferably, the duration T1 of the etching step is 10-600 s, and the duration T2 of the byproduct discharging step is 1-60 s.
Preferably, the byproduct discharging step uses a reaction chamber pressure P2 of 2 to 100 mT.
Preferably, the byproduct discharging step adopts an upper electrode radio frequency power W2 of 300-3000W.
Preferably, the total gas flow rate Q2 used in the byproduct discharging step is 100-1000 sccm.
Preferably, the process gas used in the byproduct discharging step includes at least one of argon, helium, oxygen, and nitrogen.
The method has the advantages that the etching step and the byproduct discharging step are alternately executed, the SiC substrate is etched in the etching step, and the byproduct is discharged out of the reaction chamber in the byproduct discharging step, so that the possibility of deposition of the reaction byproduct on the side wall of the reaction chamber and the surface of the dielectric window is reduced to the maximum extent, the cleaning and maintenance period of the equipment can be greatly prolonged, and the maintenance difficulty and the workload of the equipment are reduced.
The method of the present invention has other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts.
FIG. 1 shows a schematic structural view of a GaN-based HEMT device;
fig. 2 shows a flowchart of an etching method of a SiC substrate according to an exemplary embodiment of the present invention.
Description of reference numerals:
1-source pad, 2-via, 3-SiC substrate, 4-deposited metal, 5-AlGaN/GaN layer.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The embodiment of the invention provides an etching method of a SiC substrate, wherein the etching is carried out in a reaction chamber, the etching method alternately carries out an etching step and a byproduct discharging step, and the SiC substrate arranged in the reaction chamber is etched in the etching step; in the byproduct discharging step, the reaction byproduct in the reaction chamber is discharged.
The etching method alternately executes the etching step and the byproduct discharging step, wherein the SiC substrate is etched in the etching step, and the byproduct generated in the etching step is discharged out of the reaction chamber along with the action of the airflow in the byproduct discharging step, so that the reaction byproduct is prevented from being deposited on the side wall of the reaction chamber and the surface of the medium window, the cleaning and maintenance period of the equipment can be prolonged, and the maintenance difficulty and the workload of the equipment are reduced.
In one example, the difference between the reaction chamber pressure P1 used in the etching step and the reaction chamber pressure P2 used in the byproduct removal step is not greater than a first threshold, the difference between the upper electrode rf power (excitation power) W1 used in the etching step and the upper electrode rf power W2 used in the byproduct removal step is not greater than a second threshold, and the difference between the total gas flow rate Q1 used in the etching step and the total gas flow rate Q2 used in the byproduct removal step is not greater than a third threshold.
For a plasma apparatus, when the plasma is in a steady state, minute particles are more easily maintained inside the plasma without falling off; when the plasma is in an unstable state, such as at the moment of glow starting or glow extinguishing, these tiny particles will fall off due to the action of gas flow or gravity, and in the unstable state of the plasma, due to the larger voltage of the sheath, the bombardment effect on the sidewall of the reaction chamber and the surface of the dielectric window will be enhanced. Therefore, the reaction chamber pressure, the upper electrode RF power and the total gas flow rate are kept close to or the same in the etching step and the byproduct discharging step, so that the plasma will be in a stable ignition state in the byproduct discharging step, and the byproducts generated in the etching step will be maintained in the plasma and discharged out of the reaction chamber along with the gas flow. Thereby reducing the possibility of the deposition of reaction by-products on the side wall of the reaction chamber and the surface of the medium window to the utmost extent.
Preferably, the first threshold, the second threshold and the third threshold are all no greater than 5% so that the plasma continues to be in a stable ignition state in the byproduct discharge step. More preferably, the etching step and the byproduct removal step use the same reaction chamber pressure, upper electrode RF power, and total gas flow.
In one example, the byproduct discharging step uses a lower electrode RF power of 0-200W. Generally speaking, the higher the radio frequency power of the lower electrode is, the better the byproduct discharge effect is, but the mask on the surface of the SiC substrate can be bombarded, so that the selectivity ratio is reduced, and therefore, the radio frequency power of the lower electrode is not more than 200W in general.
In one example, the ratio of the duration of the byproduct removal step T2 to the duration of the etch step T1 is 5% to 15%. The duration of the byproduct discharge step is 5% -15% of the duration of the etching step, and the byproducts generated in the etching step can be basically discharged. Preferably, this ratio is 10%.
In one example, the duration of the etching step is 1-7200 s, preferably 10-600 s; the duration of the byproduct discharge step is 1 to 300s, preferably 1 to 60 s. The duration of the etching step can be determined according to the factors such as the SiC etching area, the requirement on the etching rate and the like, wherein the larger the SiC etching area is, the more byproducts are generated, and correspondingly, the duration of the etching step is shorter, and if the requirement on the etching rate is high, the duration of the etching step is properly prolonged, and the duration of the byproduct discharging step is shortened.
In one example, the byproduct removal step employs a reaction chamber pressure P2 of 2-500mT, preferably 2-100 mT; in one example, the byproduct discharging step uses 20-5000W of upper electrode RF power W2, preferably 300-3000W; the total gas flow Q2 used in the byproduct discharge step is 100-1000 sccm. Accordingly, the chamber pressure P1, the upper electrode rf power W1, and the total gas flow Q1 of the etch step are close to the chamber pressure P2, the upper electrode rf power W2, and the total gas flow Q2, respectively.
In one example, the byproduct removal step uses a gas that does not chemically react with SiC, and may include at least one of argon, helium, oxygen, and nitrogen. Several gases are freely selectable, and it is preferable to keep the total gas flow constant in the etching step and the byproduct discharging step. Preferably, the total gas flow rate used in the byproduct discharging step is 10-5000 sccm, preferably 100-1000 sccm.
In one example, the etching step uses process gases including sulfur hexafluoride, oxygen, and argon to obtain a desired etch profile.
Examples
Fig. 2 shows a flowchart of an etching method of a SiC substrate according to an exemplary embodiment of the present invention. The etching method of the SiC substrate alternately executes an etching step and a byproduct discharging step, and in the etching step, the SiC substrate arranged in the reaction chamber is etched; in the byproduct discharging step, the reaction byproducts in the reaction chamber are discharged, and the processes of the etching step and the byproduct discharging step are as follows:
etching: 10mT/SRF 1600W/BRF 700W/100SF6+30O2+20Ar/10s, i.e. the pressure of the reaction chamber is 10mT, the RF power of the upper electrode is 1600W, the RF power of the lower electrode is 700W, the flow of the process gas is sulfur hexafluoride (SF)6)100sccm of oxygen (O)2)30sccm of argon (Ar) gas of 20sccm for 10 s;
a byproduct discharge step: 10mT/SRF 1600W/BRF 0W/150Ar/1s, i.e. the pressure of the reaction chamber is 10mT, the RF power of the upper electrode is 1600W, the RF power of the lower electrode is 0W, the flow rate of the process gas is 150sccm of argon (Ar), and the duration is 1 s.
In fig. 2, three cycles of the etching step and the complex product discharge step are shown, and the number of cycles is optional in the actual process.
The SiC substrate etching method alternately executes an etching step and a byproduct discharging step for a plurality of times, wherein in the etching step, the SiC substrate is etched, in the byproduct discharging step, because the pressure of a reaction chamber, the radio-frequency power of an upper electrode and the total gas flow are the same as those in the etching step, a plasma is continuously in a stable bright starting state, and reaction byproducts generated in the etching step are maintained in the plasma and are discharged out of the reaction chamber along with the action of gas flow. When the time of the etching step and the byproduct discharging step is short enough, the byproducts generated in one etching step are also very few, and can be discharged in the next byproduct discharging step, thereby minimizing the possibility of deposition on the side wall of the reaction chamber and the surface of the dielectric window.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (8)
1. A method for etching a SiC substrate, the etching being performed in a reaction chamber, characterized in that the etching method alternately performs an etching step and a byproduct discharging step;
in the etching step, etching the SiC substrate arranged in the reaction chamber;
discharging the reaction byproduct in the reaction chamber in the byproduct discharging step;
the difference between the reaction chamber pressure P1 adopted in the etching step and the reaction chamber pressure P2 adopted in the byproduct discharging step is not larger than a first threshold, the difference between the upper electrode radio-frequency power W1 adopted in the etching step and the upper electrode radio-frequency power W2 adopted in the byproduct discharging step is not larger than a second threshold, and the difference between the total gas flow Q1 adopted in the etching step and the total gas flow Q2 adopted in the byproduct discharging step is not larger than a third threshold, so that the reaction chamber pressure, the upper electrode radio-frequency power and the total gas flow in the etching step and the byproduct discharging step are kept to be similar or identical.
2. The method for etching the SiC substrate according to claim 1, wherein the radio frequency power of the lower electrode used in the byproduct discharging step is 0 to 200W.
3. The method of etching the SiC substrate according to claim 1, wherein a ratio of a duration T2 of the byproduct discharging step to a duration T1 of the etching step is 5% to 15%.
4. The method of etching the SiC substrate according to claim 3, wherein the duration T1 of the etching step is 10 to 600s, and the duration T2 of the by-product discharging step is 1 to 60 s.
5. The method of etching the SiC substrate according to claim 1, wherein the reaction chamber pressure P2 used in the byproduct discharging step is 2 to 100 mT.
6. The method for etching the SiC substrate according to claim 1, wherein the byproduct discharge step uses an upper electrode RF power W2 of 300-3000W.
7. The method of etching the SiC substrate according to claim 1, wherein the by-product discharging step uses a total gas flow rate Q2 of 100 to 1000 sccm.
8. The method of etching the SiC substrate according to claim 1, wherein the process gas used in the byproduct discharging step includes at least one of argon, helium, oxygen, and nitrogen.
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| CN111952168B (en) * | 2020-08-18 | 2022-11-25 | 上海华力微电子有限公司 | Etching process switching method |
| CN116092922B (en) * | 2023-02-02 | 2024-01-23 | 江苏昕感科技有限责任公司 | Silicon carbide wafer groove etching method |
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