JP5643679B2 - Method for removing silicon carbide - Google Patents

Description

  The present invention relates to a silicon carbide removing device and a silicon carbide removing method.

  Silicon carbide composed of silicon and carbon is used in various fields as an important ceramic material. In particular, it is expected to be used as a basic material for electronic parts for automobiles, for example, because it has characteristics as a semiconductor, can be manufactured with low power consumption, and operates at a high temperature.

In the silicon carbide forming apparatus used when forming the silicon carbide, silicon carbide is deposited on the inner wall of a processing vessel (reaction vessel) which is one of the members of the silicon carbide forming device after the silicon carbide is formed. The silicon carbide may be a source of particles.
For this reason, a method of removing silicon carbide (deposited layer) deposited on the inner wall of the processing container by periodic gas cleaning has been proposed.

Patent Document 1 discloses that silicon carbide adhering to the inner wall of a processing container of a silicon carbide forming apparatus is removed by chlorine trifluoride gas.
Patent Document 2 discloses removing carbon contained in silicon carbide as carbon dioxide or carbon monoxide using an oxygen-containing gas as a method for selectively removing the carbon.
Patent Documents 3 and 4 disclose a method for cleaning a film forming apparatus using remote plasma.

  On the other hand, as a method for detecting the end point of cleaning, there is a method using a light emission monitor. For example, Patent Document 5 discloses that the ratio D / I between the radical emission intensity D that decreases as cleaning progresses and the radical emission intensity I that increases increases, and the end point is detected from the change over time. ing.

  As another method for detecting the end point of cleaning, Patent Document 6 includes a method for measuring the thickness of a deposited layer.

JP 2005-129724 A JP 2009-117399 A JP 2002-280376 A Japanese Patent No. 3693798 JP 2006-86325 A Special table 2008-536306 gazette

  However, although the method described in Patent Document 1 can efficiently remove silicon (silicon component) contained in silicon carbide, there is a problem that carbon (carbon component) remains.

Further, even if silicon carbide is removed by combining the methods described in Patent Documents 1 and 2, it is difficult to remove silicon and carbon contained in silicon carbide in the same manner.
Further, in the methods described in Patent Documents 1 and 2, it is not possible to determine whether or not silicon carbide has been removed (in other words, there is no end point detection system). When performing, there was a possibility that the processing container might be damaged.

  In the case of a silicon carbide forming apparatus, since the film is formed at a high temperature of about 1500 ° C., most of the apparatus members are made of a high heat resistant material such as silicon carbide or carbon. Therefore, in a silicon carbide forming apparatus, for example, when a member to which silicon carbide is attached is cleaned using the remote plasma described in Patent Documents 3 and 4, there is a possibility that a member to which silicon carbide is not attached is damaged. there were.

  Further, in the methods described in Patent Documents 5 and 6, it is difficult to separately detect silicon and carbon contained in silicon carbide, which is unsuitable as a method for detecting the end point of silicon carbide.

  Therefore, an object of the present invention is to provide a silicon carbide removing device and a silicon carbide removing method capable of accurately removing a carbon component and a silicon component contained in silicon carbide deposited on a member of the silicon carbide forming device. .

In order to solve the above-described problem, according to the first aspect of the present invention, there is provided a silicon carbide removal method for removing silicon carbide adhering to a member of a silicon carbide forming apparatus, wherein the silicon carbide formation is performed by adhering the silicon carbide. A first step of removing silicon contained in the silicon carbide by supplying a fluorine-containing gas into plasma into a processing chamber that accommodates members of the apparatus, and plasma in the processing chamber. A second step of removing carbon contained in the silicon carbide by supplying an oxygen-containing gas, and alternately performing the first step and the second step, Of the exhaust gas in the chamber, the time variation of the concentration of silicon tetrafluoride was measured, and after the concentration of silicon tetrafluoride reached the maximum value, the concentration of silicon tetrafluoride was continuously measured for 5 to 10 measurement time intervals. After the negative change, the first step is terminated, and the time change of the carbon dioxide concentration in the exhaust gas in the processing chamber is measured, and after the carbon dioxide concentration reaches the maximum value A method for removing silicon carbide is provided in which the second step is terminated when the concentration of carbon dioxide continuously changes negatively in a 5 to 10 measurement time interval .

Further, according to the invention of claim 2, when the concentration of the silicon tetrafluoride or the concentration of the carbon dioxide is equal to or lower than a preset threshold value, the processing of the first and second steps is performed. The method for removing silicon carbide according to claim 1, wherein the method is stopped .

According to the invention of claim 3, the concentration of the silicon tetrafluoride and the concentration of carbon dioxide are measured by a non-dispersive infrared analyzer. 2. The method for removing silicon carbide according to 2, is provided.

According to a fourth aspect of the present invention, the first and second steps are performed by heating a member of the silicon carbide forming device to which the silicon carbide is adhered. Item 4. A method for removing silicon carbide according to any one of Items 3 is provided.

  According to the silicon carbide removing device of the present invention, a processing chamber that houses a member of a silicon carbide forming device to which silicon carbide is adhered, a fluorine-containing gas supply means that supplies a fluorine-containing gas, and an oxygen-containing gas that supplies an oxygen-containing gas A gas supply means, a fluorine-containing gas supply means, and an oxygen-containing gas supply means are connected to cause the fluorine-containing gas and / or the oxygen-containing gas to become plasma, and the plasma-containing fluorine-containing gas and plasma-ized oxygen-containing gas. Plasma generating means for supplying the gas into the processing chamber, so that silicon contained in silicon carbide is removed by the plasma-containing fluorine-containing gas, and carbon contained in silicon carbide is removed by the plasma-ized oxygen-containing gas. Therefore, carbon and silicon contained in silicon carbide can be accurately removed.

  In addition, in the silicon carbide removing device, which is a separate device from the silicon carbide forming device, it is possible to clean only the members of the silicon carbide forming device to which silicon carbide has adhered. Among them, it is possible to prevent a member to which silicon carbide is not attached from being damaged by the cleaning.

  Further, by having an exhaust gas analysis means for analyzing the exhaust gas in the processing chamber, and a control means for controlling the fluorine-containing gas supply means, the oxygen-containing gas supply means, and the plasma generation means based on the analysis result of the exhaust gas analysis means. Since it is possible to detect whether or not the removal of silicon carbide has been completed, damage to the members of the silicon carbide forming apparatus due to the removal of silicon carbide can be suppressed.

  In addition, according to the method for removing silicon carbide of the present invention, plasma-containing fluorine-containing gas is supplied into a processing chamber that houses a member of a silicon carbide forming apparatus to which silicon carbide is adhered, so that silicon carbide is contained in silicon carbide. And a second step of removing carbon contained in silicon carbide by supplying plasma-containing oxygen-containing gas into the processing chamber. By alternately performing the step and the second step, carbon and silicon contained in silicon carbide can be accurately removed.

It is a figure which shows schematic structure of the silicon carbide removal apparatus which concerns on embodiment of this invention. It is a figure which shows schematic structure of the silicon carbide removal apparatus which concerns on the modification of embodiment of this invention. It is a figure which shows typically the mode of removal of the silicon carbide which concerns on embodiment of this invention. It is a figure which shows typically the mode of removal of silicon carbide only by fluorine-containing gas. It is a figure which shows the flowchart for demonstrating the removal method of the silicon carbide of this Embodiment. It is a figure which shows the time-dependent change of the density | concentration of the silicon tetrafluoride in a waste gas, and the density | concentration of a carbon dioxide when performing a 1st and 2nd step alternately.

  Embodiments to which the present invention is applied will be described below in detail with reference to the drawings. The drawings used in the following description are for explaining the configuration of the embodiment of the present invention, and the size, thickness, dimensions, etc. of each part shown in the figure are the dimensional relations of an actual silicon carbide removing apparatus. May be different.

(Embodiment)
FIG. 1 is a diagram showing a schematic configuration of a silicon carbide removing apparatus according to an embodiment of the present invention.
Referring to FIG. 1, a silicon carbide removing apparatus 10 of the present embodiment includes a processing chamber 11, a heating means (not shown), a fluorine-containing gas supply means 13, an oxygen-containing gas supply means 14, and plasma generation. Means 15, vacuum pump 16, gas pipe 17, exhaust gas analysis means 19, and control means 21 are provided. Silicon carbide removing apparatus 10 is an apparatus different from the silicon carbide forming apparatus that forms silicon carbide.

Processing chamber 11 accommodates a member of a silicon carbide forming device (hereinafter referred to as “member A of silicon carbide forming device”) to which silicon carbide (not shown) (hereinafter referred to as “silicon carbide B”) adheres.
By supplying the plasma-containing fluorine-containing gas and / or oxygen-containing gas into the processing chamber 11 so as to come into contact with the silicon carbide attached to the member A of the silicon carbide forming device, the member of the silicon carbide forming device is provided. Silicon carbide B adhering to A is removed.

 Therefore, the processing chamber 11 is made of a material that is sufficiently resistant to the fluorine-containing gas. As the member A of the silicon carbide forming apparatus, for example, a processing container of the silicon carbide forming apparatus can be cited as an example.

The heating means (not shown) is a heater (for example, a heater) for heating the member A of the silicon carbide forming apparatus housed in the processing chamber 11.
Since silicon carbide is chemically very stable, simply removing it from contact with a plasma-containing fluorine-containing gas and / or oxygen-containing gas is not sufficient.
Therefore, by providing a heating means (not shown) for heating the member A of the silicon carbide forming apparatus, the reaction between the plasma-containing fluorine-containing gas and / or oxygen-containing gas and silicon carbide B can be promoted.

As heating temperature of member A of a silicon carbide forming device, 300 ° C or more is preferred. It is not preferable to heat member A of the silicon carbide forming apparatus at an excessively high temperature, because member A of the silicon carbide forming apparatus changes heat.
Further, heating the member A of the silicon carbide forming apparatus at a very high temperature is not preferable because the processing chamber 11 reacts with the fluorine-containing gas and / or the oxygen-containing gas (cleaning gas).

The fluorine-containing gas supply means 13 is connected to the plasma generation means 15. The fluorine-containing gas supply unit 13 supplies a fluorine-containing gas to the plasma generation unit 15. The fluorine-containing gas removes silicon (silicon component) contained in silicon carbide.
Examples of the fluorine-containing gas include fluorine (F ₂ -GWP: 0), hydrogen fluoride (HF-GWP: 0), hydrofluorocarbon (CxHyFz (x, y, z are integers of 1 or more), for example, CH ₃ F— Among GWP-97), one containing at least one can be used.

Examples of the fluorine-containing gas include fluorocarbon (CF ₄ -GWP: 7,390, C ₂ F ₆ -GWP: 12,200), sulfur hexafluoride (SF ₆ -GWP: 22,800), and three fluorine. Nitrogenide (NF ₃ -GWP: 17,200), chlorine trifluoride (ClF ₃ -GWP: 0), carbonyl difluoride (COF ₂ -GWP: 1), etc. can also be used.
However, since these gases have a large global warming potential (GWP), they are not so preferable from the viewpoint of global warming. A low environmental load gas such as F ₂ or HF having a small GWP value is preferred.

The oxygen-containing gas supply unit 14 is connected to the plasma generation unit 15. The oxygen-containing gas supply unit 14 supplies an oxygen-containing gas to the plasma generation unit 15.
The oxygen-containing gas supply means 14 is connected to the plasma generating means 15 in a state where only the oxygen-containing gas or an oxygen-containing gas mixed with the fluorine-containing gas supplied from the fluorine-containing gas supply means 13 can be supplied. Yes. The oxygen-containing gas is a gas that removes carbon (carbon component) contained in silicon carbide.

The oxygen-containing gas includes at least one of oxygen (O ₂ ), ozone (O ₃ ), nitrogen oxide (NxOy (x and y are integers of 1 or more)), and water vapor (H ₂ O). Gas can be used.

  The plasma generating means 15 is connected to the fluorine-containing gas supply means 13 and the oxygen-containing gas supply means 14 and is supplied with fluorine-containing gas and / or oxygen-containing gas. The plasma generating means 15 converts the fluorine-containing gas and / or oxygen-containing gas into plasma and supplies the plasma-containing fluorine-containing gas and / or oxygen-containing gas into the processing chamber 11.

  In addition, in order to efficiently convert the fluorine-containing gas and / or oxygen-containing gas, which is a cleaning gas, into plasma, an inert gas such as Ar, He, or Ne is added as a discharge gas to the fluorine-containing gas and / or oxygen-containing gas. May be.

  The vacuum pump 16 is connected to the processing chamber 11 and the gas pipe 17. The vacuum pump 16 exhausts the gas in the processing chamber 11 and causes the gas pipe 17 to lead the exhaust gas. The gas pipe 17 is connected to the vacuum pump 16 and the exhaust gas analysis means 19.

  The exhaust gas analysis means 19 is connected to the gas pipe 17. The exhaust gas analysis means 19 is a gas analyzer that measures the concentration of silicon tetrafluoride and the concentration of carbon dioxide contained in the exhaust gas. The exhaust gas analyzing means 19 is connected to the control means 21 and transmits the measured concentration of silicon tetrafluoride and / or carbon dioxide to the control means 21.

As the exhaust gas analyzing means 19, for example, a non-dispersive infrared analyzer may be used. Thus, by using a non-dispersive infrared analyzer as the exhaust gas analyzing means 19, the concentrations of silicon tetrafluoride and carbon dioxide can be measured easily and at low cost.
For example, an analyzer such as a Fourier transform infrared spectrometer, an ultraviolet absorber, a mass spectrometer, or a gas chromatograph may be used as the exhaust gas analysis means 19.

  The control means 21 is electrically connected to a heating means (not shown), a fluorine-containing gas supply means 13, an oxygen-containing gas supply means 14, a plasma generation means 15, and an exhaust gas analysis means 19.

Control means 21 performs overall control of silicon carbide removing apparatus 10. For example, the control means 21 is based on the concentration of silicon tetrafluoride and the concentration of carbon dioxide transmitted from the exhaust gas analysis means 19, plasma generation means 15, heating means (not shown), fluorine-containing gas supply means 13, And the oxygen-containing gas supply means 14 is controlled.
The control means 21 has a storage unit and a calculation unit not shown. The storage unit stores a silicon tetrafluoride concentration threshold value or a carbon dioxide concentration threshold value inputted in advance.

  In addition, in the calculation unit (not shown), the silicon tetrafluoride concentration threshold value input in advance or the carbon dioxide concentration threshold value and the silicon tetrafluoride generated in the first and second steps described later are used. A comparison is made with the concentration or the concentration of carbon dioxide, and when the concentration falls below the threshold value, the processing chamber 11, heating means (not shown), so as to stop the processing of the first and second steps, Control of the fluorine-containing gas supply means 13 and the oxygen-containing gas supply means 14 is performed.

  According to the silicon carbide removing device of the present embodiment, the processing chamber 11 that houses the member A of the silicon carbide forming device to which the silicon carbide B is adhered, the fluorine-containing gas supply means 13 that supplies the fluorine-containing gas, and the oxygen-containing material The oxygen-containing gas supply means 14 for supplying the gas, the fluorine-containing gas supply means 13 and the oxygen-containing gas supply means 14 are connected to cause the fluorine-containing gas and / or the oxygen-containing gas to be converted into plasma and to be converted into plasma. Plasma generating means 15 for supplying a gas and / or an oxygen-containing gas into the processing chamber 11, thereby removing silicon contained in silicon carbide B with the plasma-containing fluorine-containing gas, and converting the plasma into oxygen Since the carbon contained in the silicon carbide B can be removed by the contained gas, the carbon and silicon contained in the silicon carbide are refined. Well it can be removed.

  Further, in silicon carbide removing device 10 which is a device different from the silicon carbide forming device, it is possible to clean only member A of the silicon carbide forming device to which silicon carbide B adheres. Of these members, it is possible to prevent a member to which silicon carbide is not attached from being damaged by the cleaning.

  Further, the exhaust gas analyzing means 19 for analyzing the exhaust gas in the processing chamber 11 and the control means for controlling the fluorine-containing gas supply means 13, the oxygen-containing gas supply means 14, and the plasma generating means 15 based on the analysis result of the exhaust gas analysis means 19. 21, the carbon and silicon contained in the silicon carbide B can be removed while monitoring whether or not the silicon carbide B remains in the member A of the silicon carbide forming device. It is possible to suppress silicon carbide B from remaining on member A of the silicon carbide forming apparatus.

  FIG. 2 is a diagram showing a schematic configuration of a silicon carbide removing device according to a modification of the embodiment of the present invention. In FIG. 2, the same components as those of silicon carbide removing apparatus 10 of the present embodiment shown in FIG.

Referring to FIG. 2, silicon carbide removing apparatus 25 according to a modification of the present embodiment is the same except that plasma generating means 15 provided in silicon carbide removing apparatus 10 of the present embodiment is provided in processing chamber 11. The configuration is the same as that of the silicon carbide removing device 10.
Silicon carbide removal device 25 according to the modification of the present embodiment having such a configuration can obtain the same effects as silicon carbide removal device 10 of the present embodiment.

FIG. 3 is a diagram schematically showing the removal of silicon carbide according to the embodiment of the present invention, and FIG. 4 is a diagram schematically showing the removal of silicon carbide using only the fluorine-containing gas. .
In the present invention, the removal of silicon carbide B is divided into silicon contained in silicon carbide B and carbon contained in silicon carbide B. As shown in FIG. 3, the silicon component contained in silicon carbide B is selectively removed by the fluorine-containing gas, and the carbon component contained in silicon carbide B is selectively removed by the oxygen-containing gas.

Here, for example, as shown in FIG. 4, when silicon carbide B is removed only with a fluorine-containing gas, only silicon is removed, carbon remains, and silicon cannot be removed uniformly. .
Therefore, in the present invention, silicon carbide B is removed by switching between a fluorine-containing gas and an oxygen-containing gas under certain conditions.

FIG. 5 is a flowchart for illustrating the silicon carbide removal method of the present embodiment.
Next, with reference to FIG. 1 and FIG. 5, the silicon carbide removal method of the present embodiment will be described.
First, in STEP1, the member A of the silicon carbide forming apparatus to which the silicon carbide B is adhered is accommodated in the processing chamber 11 of the silicon carbide removing apparatus 10 shown in FIG. Thereafter, the process continues to STEP2.

  Next, in STEP 2, a first step of selectively removing silicon contained in silicon carbide B by supplying plasma-containing fluorine-containing gas to member A of the silicon carbide forming apparatus to which silicon carbide B is adhered. To do. At this time, silicon contained in silicon carbide B reacts with the fluorine-containing gas to form silicon tetrafluoride, which is desorbed and removed.

In the first step, the time change of the concentration of silicon tetrafluoride, which is the exhaust gas discharged from the processing chamber 11, is measured by the exhaust gas analysis means 19, and after the concentration of silicon tetrafluoride reaches the maximum value, 5 The process is terminated when the concentration of silicon tetrafluoride is negatively changed continuously in 10 to 10 measurement time intervals. Thereafter, the process continues to STEP3.
The reason why the concentration of silicon tetrafluoride is gradually decreased is that the reaction on the surface of silicon carbide B is reduced and the reaction is hindered by an increase in carbon.

  Next, in STEP 3, a second step of selectively removing carbon contained in silicon carbide B by supplying plasma-containing oxygen-containing gas to member A of the silicon carbide forming apparatus to which silicon carbide B is adhered. To do. At this time, carbon contained in the silicon carbide B reacts with the oxygen-containing gas to become carbon dioxide, which is desorbed and removed.

  In the second step, the time change of the concentration of carbon dioxide discharged from the processing chamber 11 is measured by the exhaust gas analysis means 19, and it is 5 to 10 measurement time intervals from the time when the concentration of carbon dioxide becomes the maximum value. The process is terminated when the carbon dioxide concentration continuously changes negatively. The process then continues to STEP4.

The reason why the concentration of carbon dioxide gradually decreases is that the carbon on the surface of silicon carbide B decreases and the reaction increases because silicon increases.
Further, as the concentration of silicon tetrafluoride and the concentration of carbon dioxide, values obtained by adding arithmetic processing such as moving average may be used. Thereby, it becomes possible to grasp the behavior change of the stable density | concentration.

Next, in STEP 4, it is determined whether or not the concentration of silicon tetrafluoride discharged from the processing chamber 11 has become equal to or lower than a preset threshold after the processing of the first and second steps.
In STEP 4, when it is determined that the concentration of silicon tetrafluoride is equal to or lower than a preset threshold value (determined as Yes), the process illustrated in FIG. 5 ends. In STEP 4, when the negative determination (determination of No) that the concentration of silicon tetrafluoride is not lower than the preset threshold value is made, the process returns to STEP 2, and the process of the first and second steps ( Steps 2 and 3 are performed), and the process proceeds to STEP 4 again.

  That is, in STEP 4, the first and second steps are repeatedly performed until an affirmative determination is made, thereby repeatedly removing silicon contained in silicon carbide B and removing carbon contained in silicon carbide B. In other words, the silicon carbide B adhering to the member A of the silicon carbide forming apparatus is removed by repeating the first and second steps.

By the way, when the removal of silicon carbide B approaches the end, the concentration of silicon tetrafluoride generated in the first step and the concentration of carbon dioxide generated in the second step gradually decrease.
Therefore, as described in STEP 4 above, when the concentration of silicon tetrafluoride is equal to or lower than a preset threshold value, the processing of the first and second steps is terminated, whereby the member A of the silicon carbide forming apparatus is completed. The silicon carbide B adhering to the member A of the silicon carbide forming apparatus can be accurately removed without damaging the substrate.

Further, as the above-mentioned threshold value of the concentration of silicon tetrafluoride (a preset threshold value), for example, the concentration of silicon tetrafluoride is higher than the maximum value of the concentration of silicon tetrafluoride detected in the first step. A value of 1/10 or less can be used.
Further, the threshold value of the silicon tetrafluoride concentration is determined in advance by the relationship between the silicon carbide amount of a certain amount and the removal processing speed (the maximum value of the silicon tetrafluoride concentration in the first step, the first and second values). It can be arbitrarily set according to the amount of silicon carbide in the initial stage and the target silicon carbide removal processing amount after grasping the relationship between the concentration of silicon tetrafluoride when the steps are repeated.

  Further, the threshold value of the concentration of silicon tetrafluoride is stored in advance in the control means 21 (specifically, a storage unit (not shown)) shown in FIG. A comparison is made between the concentration of silicon tetrafluoride detected by 19 and the threshold value of the concentration of silicon tetrafluoride. Based on this result, the control means 21 performs processing chamber 11, fluorine-containing gas supply means 13, oxygen The contained gas supply means 14 and the plasma generation means 15 are controlled.

  In FIG. 5, the case where it is determined whether or not the concentration of silicon tetrafluoride is equal to or lower than the threshold value in STEP 4 is described as an example. It may be determined whether or not. In this case, it is possible to obtain the same effect as in STEP 4 in which it is determined whether or not the concentration of silicon tetrafluoride is equal to or lower than the threshold value.

Further, as the exhaust gas analyzing means 19 for measuring the concentrations of silicon tetrafluoride and carbon dioxide, a non-dispersive infrared analyzer may be used.
In this way, by using a non-dispersive infrared analyzer as the exhaust gas analyzing means 19 for measuring the concentrations of silicon tetrafluoride and carbon dioxide, the time required for collecting one data is several seconds longer if it is short. Since it takes several tens of seconds, it is possible to efficiently remove silicon carbide B by providing a response time of 10 measurement time intervals when the data collection time is short and 5 measurement intervals when the data collection time is long. Can be performed.

In the present embodiment, the components generated from silicon carbide B are specified as silicon tetrafluoride and carbon dioxide. However, one of the components is silicon tetrafluoride and carbon dioxide. Because it occupies most.
Another reason is that the removal reaction conditions for mainly generating silicon tetrafluoride and carbon dioxide are such that the concentration of the fluorine-containing gas component is low and the heating temperature can be set low. This is because good removal performance can be obtained by removing the silicon carbide B with the silicon carbide removing device 10 of the embodiment.

  However, for example, when a considerable amount of carbon tetrafluoride is generated by the reaction between silicon carbide B and a fluorine-containing gas, carbon tetrafluoride is added to carbon dioxide as carbon derived from silicon carbide, and endpoint detection is performed. By adjusting the detection control mechanism, it is possible to obtain a silicon carbide removing device with higher performance and to remove silicon carbide B with higher accuracy.

  According to the silicon carbide removal method of the present embodiment, carbonized carbon is supplied by supplying the plasma-containing fluorine-containing gas into the processing chamber 11 that houses the member A of the silicon carbide forming apparatus to which the silicon carbide B is adhered. A first step of removing silicon contained in silicon B; a second step of removing carbon contained in silicon carbide B by supplying plasma-containing oxygen-containing gas into processing chamber 11; By alternately performing the steps, carbon and silicon contained in the silicon carbide B can be accurately removed.

When silicon carbide B is removed using silicon carbide removing apparatus 25 according to the modification of the present embodiment described above, the same method as the silicon carbide removing method of the present embodiment described in FIG. Silicon carbide B can be removed by this method.
Further, silicon carbide removing devices 10 and 25 shown in FIGS. 1 and 2 may be applied to a silicon carbide forming device (not shown).

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to such specific embodiments, and within the scope of the present invention described in the claims, Various modifications and changes are possible.

( Test Example 1)
A silicon carbide removal test was performed using the silicon carbide removal apparatus 10 shown in FIG. Specifically, a silicon carbide substrate (length 10 mm × width 10 mm × thickness 0.75 mm) was placed in the processing chamber 11, and the silicon carbide substrate was heated and held at a temperature of 400 ° C.

  In the first step, a gas obtained by adding argon (500 sccm) to fluorine (100 sccm) was used as a cleaning gas (fluorine-containing gas). In the first step, the high frequency applied power was 1000 W (2.56 GHz), the pressure in the processing chamber 11 was 2 torr, and the processing time was 3 minutes.

  In the second step, a gas obtained by adding fluorine (100 sccm) and argon (100 sccm) to oxygen (700 sccm) was used as a cleaning gas (oxygen-containing gas). In the second step, the high frequency applied power was 1000 W (2.56 GHz), the pressure in the processing chamber 11 was 1 torr, and the processing time was 3 minutes.

  Each of the first and second steps is performed once, and the concentration of silicon tetrafluoride and carbon dioxide in each process of the first and second steps, and the amount of change in film thickness after the completion of each step. (Actual measurement value), film thickness change amount after each step (measured value calculated from exhaust gas concentration), film thickness change ratio (actual film thickness change value / calculated film thickness change value), , Got.

Table 1 shows the result of the first step of Test Example 1. Table 2 shows the result of the second step of Test Example 1. Note that a laser microscope was used to actually measure the amount of change in film thickness.

(Reference Example 1)
Instead of the silicon carbide substrate used in Test Example 1, using a silicon substrate (vertical 10 mm × width 10 mm × thickness 0.75 mm) and a carbon substrate (length 10 mm × width 10 mm × thickness 0.75 mm), The same experiment as in Test Example 1 was performed to acquire data.
Table 1 shows data obtained when the first step of Reference Example 1 (silicon substrate and carbon substrate) was performed. Table 2 shows data obtained when the second step of Reference Example 1 (silicon substrate and carbon substrate) was performed.

(About the results of Table 1 and Table 2)
Referring to Table 1 and Table 2, silicon (Si) is largely removed by the fluorine-containing gas (cleaning gas) used in the first step, and carbon (C) is oxygen used in the second step. It was confirmed that a large amount of the contained gas (cleaning gas) was removed.

Further, referring to Tables 1 and 2, silicon carbide (SiC) was removed in both the first and second steps, but the film thickness estimated from the exhaust gas concentration was not reached.
In the case of the first step, this is not only silicon on the surface of the silicon carbide substrate but also silicon (inside) silicon than the surface of the silicon carbide substrate, which reacts with silicon tetrafluoride and desorbs. It is presumed that the carbon on the surface of silicon carbide remains as it is without desorption.

  Actually, for example, when the atomic ratio of silicon and carbon after the first step is measured by X-ray fluorescence analysis on the surface, middle, and back surface of the silicon carbide substrate, the surface is (Si: C = 40.7). : 59.3), the middle was (Si: C = 37.0: 63.0), and the back surface was (Si: C = 48.6: 51.4). From this, it was confirmed that although the silicon desorption had reached the inside, carbon remained in the surface layer. This is considered to be the reason why the film thickness is increased.

( Test Example 2)
From the results of Test Example 1 and Reference Example 1 described above, in order to efficiently remove silicon carbide, the first step for removing silicon and the second step for removing carbon are combined. It was confirmed that it was necessary.

Therefore, in Test Example 2, the first step and the second step are alternately performed twice using the conditions described in Test Example 1, and the first and second steps are in the process. While measuring the density | concentration of silicon tetrafluoride and the density | concentration of a carbon dioxide, the variation | change_quantity of the film thickness after the 1st and 2nd step completion | finish was calculated | required. The results are shown in Table 3.

(Reference Example 2)
As Reference Example 2, only the first step (same conditions as in Test Example 1) was performed four times using a silicon carbide substrate, and the concentrations of silicon tetrafluoride and carbon dioxide in the process of the first step were determined. While measuring, the amount of change in film thickness after the first step was completed four times was determined. The results are shown in Table 4.

Further, only the second step is performed four times using the silicon carbide substrate, and the concentration of silicon tetrafluoride and the concentration of carbon dioxide in the process of the second step (same conditions as in Test Example 1) are measured. The amount of change in film thickness after the second step was completed four times was determined. The results are shown in Table 5.

(About the results of Tables 3 to 5)
Referring to Tables 3 to 5, it was confirmed that silicon carbide can be removed most frequently when the first step and the second step are alternately combined.
Further, when the atomic ratio of silicon and carbon existing on the surface, middle, and back surface of the silicon carbide substrate after the above removal treatment was measured, the surface was (Si: C = 48.1: 51.9), and the middle was (Si: C = 48.5: 51.5) and the back surface was (Si: C = 49.6: 50.4). From this result, it was confirmed that carbon and silicon contained in silicon carbide could be removed with high accuracy.

( Test Example 3)
The first step (same conditions as in Test Example 1) and the second step (same conditions as in Test Example 1) are alternately performed, and 90% or more of the members in which about 75 μm of silicon carbide in exhaust gas is deposited (thickness of silicon carbide) And the concentration of silicon tetrafluoride and the concentration of carbon dioxide contained in the exhaust gas were measured. The result is shown in FIG.

FIG. 6 is a diagram showing temporal changes in the concentration of silicon tetrafluoride and the concentration of carbon dioxide in the exhaust gas when the first and second steps are alternately performed.
As the threshold value here, a value that the exhaust gas concentration of carbon dioxide obtained in another evaluation was 10 ppm or less was adopted. This threshold value is a value determined from the behavior of the concentration of carbon dioxide when a member having a silicon carbide film thickness of about 10 μm is removed in the second step.

As shown in FIG. 6, the process is normally performed until the third time of the first step, and in the third time of the second step, the maximum value 58 ppm of the carbon dioxide concentration in this step is detected and then the threshold value (carbon dioxide After reaching a concentration of 10 ppm or less, the treatment was terminated.
After the treatment, the actual film thickness of silicon carbide was measured and found to be 7.1 μm. Further, when the atomic ratio of silicon to carbon in the silicon carbide on the outermost surface was measured by fluorescent X-ray analysis, the surface was (Si: C = 47.9: 52.1), and silicon carbide was removed with high precision. I was able to confirm that it was possible.

  The present invention is applicable to a silicon carbide removing device and a silicon carbide removing method capable of accurately removing a carbon component and a silicon component contained in silicon carbide.

  DESCRIPTION OF SYMBOLS 10,25 ... Silicon carbide removal apparatus, 11 ... Processing chamber, 13 ... Fluorine containing gas supply means, 14 ... Oxygen containing gas supply means, 15 ... Plasma generation means, 16 ... Vacuum pump, 17 ... Gas pipe, 19 ... Exhaust gas analysis Means, 21 ... control means

Claims (4)

A silicon carbide removing method for removing silicon carbide adhering to a member of a silicon carbide forming device,
A first step of removing silicon contained in the silicon carbide by supplying a plasma-containing fluorine-containing gas into a processing chamber containing a member of the silicon carbide forming apparatus to which the silicon carbide has adhered;
A second step of removing carbon contained in the silicon carbide by supplying a plasma-containing oxygen-containing gas into the processing chamber;
Said first step, alternating rows that have a said second step,
Of the exhaust gas in the processing chamber, the time change of the concentration of silicon tetrafluoride is measured, and after the concentration of the silicon tetrafluoride reaches the maximum value, the tetrafluoride is continuously generated for 5 to 10 measurement time intervals. When the silicon concentration is negatively changed, the first step is terminated,
Of the exhaust gas in the processing chamber, the time change of the carbon dioxide concentration is measured, and after the carbon dioxide concentration reaches the maximum value, the carbon dioxide concentration is negative continuously for 5 to 10 measurement time intervals. The method of removing silicon carbide , wherein the second step is terminated at the stage of change . The concentration of the silicon tetrafluoride, or the concentration of the carbon dioxide is, at the stage of equal to or less than a threshold value set in advance, to claim 1, characterized in that the stop processing of the first and second step The method for removing silicon carbide as described. The method for removing silicon carbide according to claim 1 or 2, wherein the concentration of the silicon tetrafluoride and the concentration of the carbon dioxide are measured by a non-dispersive infrared analyzer. Said first and second step, the silicon carbide according to any one of claims 1 to 3, characterized in that conducted by heating the member of the silicon carbide forming apparatus wherein the silicon carbide is adhered Removal method.

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