JP2009164445A - Etching processing method and method of manufacturing silicon carbide semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform etching of a desired amount of etching with superior reproducibility by monitoring the amount of etching, while performing the etching processing of a SiC substrate. <P>SOLUTION: The etching processing method includes (a) a step of performing etching processing of the surface of a SiC substrate 2, both surfaces of which have been mirror-polished with reactive plasma, and at the same time, irradiating the surface or the backside of the SiC substrate 2 with a laser light 14. Then, the method is also provided with (b) a step of detecting the light intensity of the laser light 14, reflected from both the surface and the backside of the SiC substrate 2, calculating an amount of etching, based on an interference waveform indicated by the detected light intensity, and stopping the etching processing in the step (a), when the amount of etching reaches a desired amount of etching. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an etching processing method and a method for manufacturing a silicon carbide (SiC) semiconductor device, and more particularly to an etching processing method and manufacturing of an insulated gate field effect transistor (MOSFET) for high breakdown voltage and high power using a SiC substrate. It is about the method.

  MOSFETs using silicon (Si) are widely used as power devices, but it has become difficult to further increase the breakdown voltage and increase the current of the devices due to the physical properties of Si. Therefore, SiC, which is one of wide band gap semiconductors, has attracted attention as a new substrate material that can replace Si. SiC not only has a dielectric breakdown strength that is an order of magnitude higher than that of Si and has an excellent breakdown voltage, but also has a low on-resistance and a low-loss power device. Thermal conductivity is about 3 times larger than Si, and it is suitable as a substrate material for high-power power devices.

  Patent Document 1 discloses a MOSFET structure using a SiC substrate and a manufacturing process thereof. This Patent Document 1 describes an etching process using reactive plasma. In the etching method described in Patent Document 2, an etch rate of a film to be etched on a SiC substrate is obtained in advance, and a film thickness to be etched and an etching time are calculated from the etch rate. That is, the etching process is performed by determining the processing time for the calculated time.

  However, in plasma etching, numerous internal parameters (density and energy of electrons and ions in plasma, density of neutral active species, and density of impurities (impurities released from the mask material and reaction vessel wall)) are complicated. The etching reaction proceeds while being entangled with each other. In particular, the reaction product deposited on the reaction vessel wall is re-emitted to the plasma during etching, and this is re-incident on the SiC substrate surface, thereby greatly affecting the etching reaction. Since the amount of reaction product deposited on the reaction vessel wall increases with the processing of the SiC substrate, the etch rate is not unchanged and varies with each processing of the SiC substrate.

  When the etching target film is completely removed using such plasma etching, if the etching rate is smaller than the assumed etching rate, the etching amount is reduced and the etching target film is completely removed. There may not be. On the other hand, if the etch rate is higher than the expected etch rate, the etching amount increases and the underlying film of the film to be etched may be etched deeply, resulting in a low device manufacturing yield. Become. In order to prevent this, an end point detection method and an etching amount monitoring method have been proposed as follows.

As the former end point detection method, a method of monitoring the emission intensity of atoms contained in the etching target film and detecting the etching end point from the change in the emission intensity when the etching target film is completely removed is often used. . However, when the film to be etched and the underlying film are almost the same material, it is difficult to detect the end point of etching because the emission intensity hardly changes. In particular, the difference between these films is only the atomic species (Al, N) doped in the SiC film and the doping amount, and the density of these atomic species is at most about 10 ⁻³ compared to Si and C atoms. In the case where only this exists, it is extremely difficult to detect the end point of etching.

  As a method for monitoring the latter etching amount, a method using optical interference of laser light is known. Laser light is incident on the surface of the substrate, the reflected light is detected by a photodetector, and the light intensity is measured. Specifically, when the refractive index of the film to be etched and the refractive index of the underlying film are significantly different, a so-called optical interface exists, and a part of the light incident on the inside of the film is reflected by the optical interface. Then, the reflected light from the etched film surface interferes with the reflected light from the optical interface. The etching amount is calculated based on repetition of the intensity of light in the interference waveform, and the etching process is stopped when the etching amount reaches a desired etching amount.

JP-A-10-308510 JP 2007-208076 A

  However, in the method using the optical interference of the laser light, the difference between the film to be etched and the base film is different from the atomic species and the doping amount in the SiC film as in the method for detecting the change in emission intensity. When there is only a difference, there is no difference in the refractive index between these films. Therefore, there is no optical interface that reflects the laser beam on the back surface of the silicon carbide substrate, and as a result, only the reflected light from the surface of the silicon carbide substrate is detected, and the interference waveform cannot be observed. .

  The present invention has been made in order to solve the above-described problems, and by performing etching processing of a film to be etched while monitoring the etching amount, etching can be performed with a desired etching amount with high reproducibility. The purpose is to do.

  The etching processing method according to the present invention includes the step of (a) etching the surface of a silicon carbide substrate whose both surfaces are mirror-polished with a reactive plasma, and injecting laser light on the surface or the back surface of the silicon carbide substrate. Prepare. And (b) detecting the light intensity of the laser beam reflected from each of the front and back surfaces of the silicon carbide substrate, calculating the etching amount based on the interference waveform indicated by the detected light intensity, and the etching amount is desired A step of stopping the etching process in the step (a) when the amount of etching reaches the predetermined amount.

  According to the etching processing method of the present invention, the light intensity of the reflected light of the laser beam can be observed. Therefore, the etching amount can be monitored while etching the silicon carbide substrate, for example, the channel epilayer. it can. Thereby, it is possible to perform etching with a desired etching amount with high reproducibility.

<Embodiment 1>
In the present embodiment, MOSFET 50 shown in FIG. 1 is formed using the method for manufacturing a silicon carbide semiconductor device according to the present invention. This MOSFET 50 includes an n − type epi (epitaxial) layer 52, a p type base region 53, an n + type source region 54, an n − type channel epi layer 55, a gate insulating film 56, a gate electrode 57, and an interlayer. An insulating film 58, a source electrode 59, and a drain electrode 60 are provided.

This MOSFET 50 is a type of MOSFET in which an n − type channel epi layer 55 is arranged on the surface. First, an n + type SiC substrate 51 that is a silicon carbide substrate is prepared. The impurity density of the n + -type SiC substrate 51 is, for example, 5 × 10 ¹⁸ cm ⁻³ . Then, MOSFET 50 which is a transistor is formed on n + type SiC substrate 51. In order to form this MOSFET 50, an n − type epi layer 52 is deposited on the entire surface of the n + type SiC substrate 51. The impurity density of the n − type epi layer 52 is, for example, 1 × 10 ¹⁶ cm ⁻³ .

  A mask pattern is formed on the surface layer portion of the n − -type epi layer 52, and the p-type base region 53 is formed by ion implantation using, for example, aluminum (Al). Then, a mask pattern is formed on the surface layer portion of the p-type base region 53, and the n + -type source region 54 is further formed by ion implantation with nitrogen (N), for example. Here, it is assumed that the depth of the p-type base region 53 and the depth of the n + -type source region 54 are, for example, about 800 nm and about 300 nm.

Next, an n − type channel epi layer 55 is grown on the entire surface of the n − type epi layer 52, the p type base region 53, and the n + type source region 54. In this way, the n − type channel epi layer 55 which is the channel epi layer of the MOSFET 50 is formed on the entire surface of the n + type SiC substrate 51. Here, the film thickness of the n − type channel epitaxial layer 55 is, for example, about 500 nm, and the impurity density is, for example, 2 × 10 ¹⁶ cm ⁻³ .

  In the present embodiment, n + type SiC substrate 51, n − type epi layer 52, and n − type channel epi layer 55 are all made of silicon carbide. Therefore, hereinafter, in the present embodiment, a silicon carbide substrate made of these is described as SiC substrate 2. In addition, the surface of the n − type channel epitaxial layer 55 that is later etched with reactive plasma may be described as the surface of the SiC substrate 2, and the surface of the n + type SiC substrate 51 on the opposite side is referred to as the back surface of the SiC substrate 2. May be described. Further, etching the n − type channel epitaxial layer 55 may be described as etching the SiC substrate 2.

  Next, both front and back surfaces of SiC substrate 2 which is a silicon carbide substrate on which n − type channel epi layer 55 is formed are mirror-polished. That is, the surface of the n − type channel epi layer 55 and the surface of the n + type SiC substrate 51 on the opposite side are mirror-polished. Thereafter, an etching mask made of a photoresist or a silicon oxide film is formed. After the mask pattern is formed, a part of the unnecessary n − type channel epitaxial layer 55 is etched by an etching method using reactive plasma described later. By this process, a part of the unnecessary n− type channel epi layer 55 is completely removed so that a part of the p type base region 53 and the n + type source region 54 is exposed.

  Thereafter, an insulating film and a polycrystalline silicon film are deposited, and a gate insulating film 56 and a gate electrode 57 made of polycrystalline silicon (poly-Si) are formed using a mask pattern. Subsequently, an interlayer insulating film 58 is deposited to cover the gate insulating film 56 and the gate electrode 57, and a part of the interlayer insulating film 58 and the gate insulating film 56 is opened using a mask pattern, and the p-type base region 53 and A part of the n + type source region 54 is exposed. Finally, a metal film is deposited on the exposed surfaces of the p-type base region 53 and the n + -type source region 54 and the back surface of the SiC substrate 2 to form the source electrode 59 and the drain electrode 60.

  Of the above-described steps, when the n − -type channel epi layer 55 is completely removed by the etching process using reactive plasma, an etching amount (over-etch amount) larger than the film thickness is required. For example, when the film thickness of the n − type channel epitaxial layer 55 is 500 nm, the etching amount needs to be in the range of 500 nm or more and 550 nm or less.

  However, the etch rate varies with processing of the SiC substrate 2. Therefore, when the etch rate is lower than the assumed etch rate, the n − type channel epi layer 55 may not be completely removed. On the other hand, when the etch rate is higher than the expected etch rate, the p-type base region 53 and the n + -type source region 54 are thinned, and as a result, the on-resistance may be increased. Manufacturing yield is low. In particular, when the n + type source region 54 is only about 300 nm deep from the surface, it is necessary to suppress the etching amount as much as possible. Thus, in the etching of the n − type channel epi layer 55, it is important to precisely control the etching amount. The etching processing method according to the present embodiment aims to make it possible to monitor the etching amount while etching the n − type channel epi layer 55.

  FIG. 2 is a diagram showing a configuration of an apparatus used in the etching method according to the present embodiment. As shown in FIG. 2, the apparatus used for this etching process mainly includes a vacuum vessel 1, an RF (Radio Frequency) power supply 4, a laser light generator 8, and a photodetector 11. The vacuum vessel 1 has a quartz window 6, and the coil 5 disposed in the vicinity of the quartz window 6 is electrically connected to the RF power source 4. In this figure, a sectional view of one coil is shown.

  In the vacuum container 1, the SiC substrate 2 is disposed in contact with the back surface of the SiC substrate 2 and the surface of the substrate stage 3. The back surface of SiC substrate 2 here is the surface of n + type SiC substrate 51 on the opposite side to n − type channel epitaxial layer 55 in the present embodiment. Then, the surface of the SiC substrate 2 whose both surfaces are mirror-polished is etched with the reactive plasma 7 and the laser beam 14 is incident on the surface of the SiC substrate 2. The surface of SiC substrate 2 here is the surface of n − type channel epilayer 55 in the present embodiment.

While the vacuum vessel 1 is evacuated, a fluorine-based gas such as CF ₄ + O ₂ , SF ₆ , or NF ₃ is supplied. In this state, for example, when a high frequency current having a frequency of 13.56 MHz is supplied from the RF power source 4 to the coil 5, the above-described gas plasma 7 is generated in the vacuum chamber 1 by the high frequency electromagnetic field radiated from the coil 5. . Neutral active species and ions that are particles of the plasma 7 thus generated enter the surface of the SiC substrate 2 that is not covered by the etching mask, that is, the surface of the n − type channel epilayer 55. These particles react with Si atoms and C atoms on the surface of the n-type channel epilayer 55, and the gas generated by the reaction is exhausted from the vacuum vessel 1, whereby the n-type channel epilayer 55 is etched. The

  A laser beam generator 8 is installed outside the vacuum vessel 1. In the present embodiment, it is assumed that the laser beam 14 generated by the laser beam generator 8 is He—Ne, wavelength 633 nm, and power 1 mW. The laser beam 14 generated by the laser beam generator 8 is subjected to on / off modulation at a certain frequency by the optical chopper 9 and then introduced into the vacuum chamber 1 through the mirror 10 and the quartz window 6. Then, the laser beam 14 is incident on the surface of the SiC substrate 2 substantially perpendicularly.

  FIG. 3 is a diagram showing a state when the laser beam 14 is incident on the surface of the SiC substrate 2. The principle of monitoring in the etching method according to the present embodiment will be described with reference to FIG. As shown in FIG. 3, a light absorption layer 15 that is a light absorption portion is formed on the surface of the substrate stage 3, and the SiC substrate 2 is placed on the light absorption layer 15. The laser beam 14 is applied to the n − type channel epi layer 55 on which no etching mask is formed. In the present embodiment, it is assumed that the p-type base region 53 and the n + -type source region 54 are not formed under the n− type channel epi layer 55 irradiated with the laser beam 14.

  The vicinity of the surface of the n − type channel epitaxial layer 55 is almost vacuum. Since the refractive index of the n− type channel epi layer 55 and the refractive index of vacuum are greatly different, an optical interface exists. The surface of the n − type channel epi layer 55 is mirror-polished. Therefore, as shown in FIG. 3, a part of the laser beam 14 is reflected by the surface of the n − type channel epi layer 55, and the rest is transmitted through the n − type channel epi layer 55.

  The laser beam 14 transmitted through the n − type channel epi layer 55 reaches the underlying n − type epi layer 52. Here, since the refractive index hardly changes between the n − type channel epi layer 55 and the n − type epi layer 52, the laser light 14 is transmitted through the n − type epi layer 52 without being reflected, and finally. Is reached to the back surface of the SiC substrate 2, that is, the surface of the n + -type SiC substrate 51.

  There is a slight gap between the n + -type SiC substrate 51 and the light absorption layer 15, and the gap is almost vacuum. Since the refractive index of the n + type SiC substrate 51 and the refractive index of vacuum are greatly different, an optical interface exists. The back surface of SiC substrate 2, that is, the surface of n + type SiC substrate 51 is mirror-polished. Therefore, as shown in FIG. 3, the laser beam 14 is specularly reflected not only on the surface of the SiC substrate 2 but also on the back surface. The reflected laser light 14 is transmitted toward the surface of the SiC substrate 2 and emitted from the surface of the SiC substrate 2. Laser light 14 emitted from the back surface of SiC substrate 2 (the surface of n + -type SiC substrate 51) is absorbed by light absorption layer 15 without being reflected by the surface of substrate stage 3.

  As shown in FIG. 2, the laser light 14 reflected from both the front and back surfaces of the SiC substrate 2 enters the photodetector 11 installed outside the vacuum vessel 1 through the quartz window 6. The photodetector 11 is installed on the surface side of the SiC substrate 2. The light intensity of the laser beam 14 reflected from both the front and back surfaces of the SiC substrate 2 is detected on the surface side of the SiC substrate 2. Thus, in the present embodiment, the laser light 14 is incident on the surface of the SiC substrate 2 and the light intensity of the reflected light is detected from the surface side of the SiC substrate 2. For the photodetector 11, for example, a silicon photodiode is used.

  The output of the photodetector 11 is amplified by a lock-in amplifier 12 using the on / off frequency of the optical chopper 9 as a reference signal, and a noise component is removed by a low-frequency filter inside the lock-in amplifier 12. The output of the lock-in amplifier 12, that is, the light intensity of the laser light 14 reflected from both the front and back surfaces of the SiC substrate 2 is displayed on the display unit 13 together with the processing time.

  The intensity of the reflected light displayed on the display unit 13 interferes according to the phase difference between the laser light 14 reflected on the surface of the SiC substrate 2 and the laser light 14 reflected on the back surface of the SiC substrate 2, so-called Interference waveform. The phase difference changes according to the etching amount of the n − type channel epi layer 55. Therefore, the light intensity of the interference waveform displayed on the display unit 13 changes with the etching processing time.

  When the incidence of the laser beam 14 is perpendicular to the surface of the SiC substrate 2, the n − type channel epilayer 55 is etched by λ / (2n) during one period of the interference waveform. . Here, λ is the wavelength of the laser beam 14, and n is the refractive index of the n − type channel epilayer 55. Thus, the etching amount of the n − type channel epi layer 55 can be monitored by calculating the etching amount based on the period of the interference waveform detected by the photodetector 11. When the calculated etching amount reaches a desired etching amount, the etching process is stopped. In this embodiment, it is assumed that the desired etching amount is obtained by adding the overetching amount to the target etching amount.

  As described above, in the etching processing method according to the present embodiment, the light intensity of the laser light 14 reflected from both the front and back surfaces of the SiC substrate 2 is detected, and the etching amount is determined based on the interference waveform indicated by the detected light intensity. When the calculated etching amount reaches a desired etching amount, the above-described etching process is stopped.

  According to the etching method according to the present embodiment as described above, both the front and back surfaces of SiC substrate 2 are mirror-polished, so that laser beam 14 can be reflected on both the front and back surfaces of SiC substrate 2. As a result, the light intensity of the laser light 14 reflected from the front and back surfaces of the SiC substrate 2 can be detected, so that the etching amount can be monitored while the n − type channel epilayer 55 is being etched. . Since the etching process is stopped when the etching amount reaches a desired etching amount, the etching can be performed with a desired etching amount with good reproducibility.

  Actually, in order to compare the conventional etching processing method based on time determination and the etching processing method according to the present embodiment, an SiC substrate on which an n − type channel epi layer 55 (film thickness: 500 nm) is formed by each method. Eight pieces of 2 were continuously etched. A level difference measurement was performed after the treatment. As a result, in the conventional etching method, the SiC etching amount of the n − type channel epi layer 55 varied in the range of 452 nm to 578 nm. On the other hand, in the etching method of the present embodiment, when etching was performed while monitoring the etching amount of the n − type channel epi layer 55, the etching amount was in the range of 510 nm to 523 nm. Thus, according to the etching method according to the present embodiment, it was possible to perform etching with a desired etching amount with good reproducibility.

  In the present embodiment, laser light 14 emitted from the back surface of SiC substrate 2 is absorbed by light absorption layer 15 formed on the surface of substrate stage 3. Thereby, since only the laser beam 14 necessary for the measurement of the etching amount can be reflected, the etching amount can be accurately measured. In the present embodiment, the light absorption layer 15 is formed on the surface of the substrate stage 3, but the present invention is not limited to this. For example, an infinite number of fine irregularities may be formed on the surface of the substrate stage 3, and the incident laser light 14 may be irregularly reflected. Alternatively, a hole through which the laser beam 14 passes may be provided inside the substrate stage 3 so that the laser beam 14 does not return from the substrate stage 3 to the surface side of the SiC substrate 2.

  In the present embodiment, the wavelength of the laser beam 14 is 633 nm. Thereby, the laser beam 14 can pass through the SiC substrate 2. The wavelength of laser beam 14 is not limited to 633 nm, and the same effect as described above can be obtained as long as it is 370 nm or more and 440 nm or less or 480 nm or more that can pass through SiC substrate 2. In the present embodiment, a general He—Ne laser is used as the laser beam 14 from the laser beam generator 8. However, other laser light sources such as an Ar ion laser and a diode laser may be used. .

<Embodiment 2>
In the first embodiment, as shown in FIG. 2, the laser beam 14 is incident on the inside of the vacuum vessel 1 through the quartz window 6 provided in the vacuum vessel 1, and the n − type channel epi layer 55 is formed. The surface of SiC substrate 2 was irradiated with laser light 14. The laser beams 14 reflected from both the front and back surfaces of the SiC substrate 2 enter the photodetector 11 installed outside the vacuum vessel 1 through the quartz window 6 again. Thus, the laser beam 14 was incident on the surface of the SiC substrate 2 and the light intensity of the laser beam 14 reflected from the surface side of the SiC substrate 2 was detected.

  In such an etching method, the quartz window 6 is constantly exposed to reactive plasma 7 (including fluorine atoms and ions) that etches the surface of the SiC substrate 2. Therefore, as the etching process is repeated, the surface inside the vacuum vessel 1 of the quartz window 6 is gradually etched by the reactive plasma 7, and the laser light 14 incident on the quartz window 6 is scattered due to the increase in surface roughness. . Further, a reaction product generated by etching the SiC substrate 2 adheres to the inner surface of the quartz window 6 in the vacuum vessel 1. If the etching process is repeated due to these reasons, the reflected laser beam 14 is not incident on the photodetector 11, and the light intensity of the laser beam 14 detected by the photodetector 11 is greatly reduced. Therefore, the etching amount is monitored. It becomes difficult.

  An object of the present embodiment is to solve this problem. An etching method of the semiconductor device manufacturing method according to the present embodiment will be described with reference to FIGS. In the etching method according to the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the components not newly described are the same as those in the first embodiment. To do.

  FIG. 4 is a diagram showing a configuration of an apparatus used in the etching method according to the present embodiment. As shown in FIG. 4, a small quartz window 16 is provided on the back side of the substrate stage 3 on which the SiC substrate 2 is installed for vacuum sealing and for introducing the laser beam 14. In addition, a small space in which the laser beam 14 travels is provided inside the substrate stage 3 so that the laser beam 14 incident on the quartz window 16 from the mirror 10 can reach the back surface of the SiC substrate 2 without being blocked. Yes. In the etching method according to the present embodiment, the surface of SiC substrate 2 whose both surfaces are mirror-polished is etched with reactive plasma 7 and laser light 14 is incident on the back surface of SiC substrate 2.

  FIG. 5 is a diagram showing a state when the laser beam 14 is incident on the back surface of the SiC substrate 2. The principle of monitoring in the etching method according to the present embodiment will be described with reference to FIG. In the present embodiment, as in the first embodiment, an optical interface exists on the front surface and the back surface of SiC substrate 2, and no optical interface exists inside SiC substrate 2. The both surfaces of the SiC substrate 2 are mirror-polished. In the present embodiment, the roughness of the surface of the n − type channel epi layer 55 is maintained during the etching process. In this case, as shown in FIG. 5, a part of the laser beam 14 is reflected on the back surface of the SiC substrate 2, that is, on the surface of the n + type SiC substrate 51, and the rest passes through the n + type SiC substrate 51. The remaining laser light 14 that has been transmitted is reflected also on the surface of the SiC substrate 2, that is, on the surface of the n − -type channel epilayer 55.

  As shown in FIG. 5, the laser light 14 reflected from both the front and back surfaces of the SiC substrate 2 enters the photodetector 11 installed outside the vacuum vessel 1 through the quartz window 6. The photodetector 11 is installed on the back side of the SiC substrate 2. Therefore, in the present embodiment, the light intensity of laser light 14 reflected from both the front and back surfaces of SiC substrate 2 is detected on the back surface side of SiC substrate 2. Thus, unlike Embodiment 1, in the etching method according to the present embodiment, laser light 14 is incident on the back surface of SiC substrate 2 and is reflected from the back surface side of SiC substrate 2. Detect intensity.

  In the etching processing method according to the present embodiment, the same process as in the first embodiment is performed after the light intensity is detected. That is, the light intensity of the laser light 14 reflected from each of the front and back surfaces of the SiC substrate 2 is detected, the etching amount is calculated based on the interference waveform indicated by the detected light intensity, and the etching amount is a desired etching amount. When this happens, the etching process described above is stopped.

  According to the manufacturing method of the semiconductor device according to the present embodiment as described above, the quartz window 16 for introducing the laser beam 14 is disposed on the back surface opposite to the surface of the SiC substrate 2 to be etched, thereby generating the plasma 7. Do not touch directly. Since the surface of the quartz window 16 is not etched and the reaction product does not adhere to the surface of the quartz window 16, the light intensity of the laser light 14 does not decrease even if the etching process is repeated. Etching could be monitored over time.

3 is a cross-sectional view showing a MOSFET formed by the method for manufacturing a semiconductor device according to the first embodiment. FIG. It is a figure which shows the structure of the apparatus used for the etching processing method which concerns on Embodiment 1. FIG. It is a figure explaining the principle of monitoring of the etching processing method which concerns on Embodiment 1. FIG. It is a figure which shows the structure of the apparatus used for the etching processing method which concerns on Embodiment 2. FIG. It is a figure explaining the principle of monitoring of the etching processing method which concerns on Embodiment 2. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Vacuum container, 2 SiC substrate, 3 Substrate stage, 4 RF power supply, 5 Coil, 6,16 Quartz window, 7 Plasma, 8 Laser light generator, 9 Optical chopper, 10 Mirror, 11 Photo detector, 12 Lock-in amplifier , 13 Display unit, 14 Laser light, 15 Light absorption layer, 51 n + type SiC substrate, 52 n− type epi layer, 53 p type base region, 54 n + type source region, 55 n− type channel epi layer, 56 Gate insulation Film, 57 gate electrode, 58 interlayer insulating film, 59 source electrode, 60 drain electrode.

Claims (5)

(A) a step of etching the surface of the silicon carbide substrate whose front and back surfaces are mirror-polished with reactive plasma, and injecting laser light on the surface or the back surface of the silicon carbide substrate;
(B) The light intensity of the laser beam reflected from each of the front and back surfaces of the silicon carbide substrate is detected, the etching amount is calculated based on the interference waveform indicated by the detected light intensity, and the etching amount is a desired etching amount. A step of stopping the etching process of the step (a) when the amount is reached,
Etching method. (C) before the step (a), further comprising the step of placing the silicon carbide substrate in contact with the back surface of the silicon carbide substrate and the surface of the substrate stage;
A light absorbing portion is formed on the surface of the substrate stage.
The etching method according to claim 1. The step (b)
In the step (a), when the laser beam is incident on the surface of the silicon carbide substrate, the silicon carbide substrate is incident when the laser beam is incident on the back surface of the silicon carbide substrate from the surface side of the silicon carbide substrate. A step of detecting the light intensity of the reflected laser light from the back side of
The etching method according to claim 1. The wavelength of the laser light is 370 nm or more and 440 nm or less, or 480 nm or more.
The etching processing method according to claim 1. (A) preparing a silicon carbide substrate;
(B) forming a transistor on the silicon carbide substrate,
The step (B)
(B-1) forming a channel epilayer of the transistor;
(B-2) a step of mirror polishing both front and back surfaces of the silicon carbide substrate on which the channel epi layer is formed;
(B-3) After the step (B-2), the step of etching the channel epilayer by the etching method according to any one of claims 1 to 4 is provided.
A method for manufacturing a silicon carbide semiconductor device.

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