JP5973850B2 - Cleaning end point detection method - Google Patents

Description

  The present invention relates to a cleaning end point detection method capable of suppressing damage to members constituting a film forming apparatus by improving the accuracy of cleaning end point detection by a simple method.

  A film forming apparatus (for example, a CVD apparatus or an epitaxial apparatus) is an apparatus for growing a thin film on a predetermined substrate. In such a film forming apparatus, when a thin film is formed, a part other than the substrate (specifically, a gas introduction part for introducing a raw material gas to be a thin film precursor into the thin film growth chamber, a substrate seat part, and an inner surface of the chamber In addition, a solid substance containing a thin film precursor as a component is deposited on an exhaust line including a vacuum pump for discharging the gas introduced into the chamber out of the system.

  When the solid matter (hereinafter referred to as “deposit”) adheres to the substrate, it becomes an impurity in the film, lowers the yield, causes malfunction of various drive valves necessary for the progress of the process, and It may cause malfunction of the vacuum pump.

Therefore, conventionally, a reactive gas phase fluid is introduced into the system at a certain frequency, and the reactive gas phase fluid and the deposit are reacted to generate a product, thereby removing the deposit. (In other words, in-situ dry cleaning) is performed.
In-situ dry cleaning has been widely applied to silicon-based thin film growth apparatuses.

  As another conventional cleaning method, there is an ex-situ dry cleaning in which a member constituting the film forming apparatus to which the deposit is attached is taken out and the deposit is removed by a dry cleaning apparatus. .

  In dry cleaning used in the in-situ method and the ex-situ method, a cleaning gas (fluorine-based gas) that is highly reactive mainly using atomic fluorine is used. For this reason, when dry cleaning is performed for a long time, there is a problem that a member constituting the film forming apparatus reacts with the cleaning gas and is damaged.

  Therefore, in order to suppress damage to the members constituting the film forming apparatus during cleaning, the time point at which deposits are removed is accurately detected (in other words, the cleaning end point is accurately detected), and the cleaning time is reduced. It is important to keep it as short as possible.

  Patent Document 1 discloses a first step of applying a power to an electrode inside a CVD process chamber and introducing a cleaning gas into the CVD process chamber to start a cleaning process inside the CVD process chamber; The cleaning process started by the step is continued, and the exhaust line connected to the CVD process chamber is closer to the second end of the exhaust line (the end connected to the exhaust means) than the variable valve. The change in pressure measured by the first pressure detecting means connected to the exhaust line and detecting the pressure in the exhaust line is monitored, and the change in pressure detected by the first pressure detecting means is monitored to end the cleaning. Is monitored by one or more control means to detect the end point of cleaning when the predetermined pressure change is detected. A second step and a cleaning method for CVD process chamber with a control means for detecting is disclosed.

  Patent Document 2 discloses a step of exciting a reaction gas using plasma in a reaction chamber to deposit a desired film, and introducing a cleaning gas excited in a remote plasma excitation chamber into the reaction chamber to introduce a non-plasma excitation atmosphere. In the method of manufacturing a semiconductor integrated circuit device, which repeatedly repeats the step of remote plasma cleaning the reaction chamber in step 1, a local plasma is generated in the vacuum chamber for exhausting the reaction chamber or the reaction chamber by a capacitively coupled plasma excitation system. A method for detecting the end point of remote plasma cleaning by monitoring the electrical characteristics of the plasma is disclosed.

Japanese Patent No. 3768575 JP 2009-38102 A

By the way, the amount of change per unit time of the pressure change in the exhaust line decreases near the end point of cleaning.
Accordingly, when the cleaning end point detection method described in Patent Document 1 is used, it is difficult to accurately detect the end point of cleaning, and as a result, it is necessary to lengthen the cleaning time. For this reason, there has been a problem that a member constituting the film forming apparatus is damaged by the cleaning gas.

  In the cleaning end point detection method described in Patent Document 2, it is possible to accurately detect the end point of cleaning, but it is necessary to generate local plasma in the reaction chamber or the vacuum system for exhausting the reaction chamber. It was difficult to detect the cleaning end point by a simple method.

  When the cleaning end point detection method described in Patent Document 2 is used, the gas discharged from the reaction chamber during cleaning is extremely high, such as fluorine gas, silicon tetrafluoride in which deposits and atomic fluorine react, and the like. Since a fluid having reactivity is mainly contained, there is a possibility that the plasma source is deteriorated.

  Therefore, an object of the present invention is to provide a cleaning end point detection method capable of suppressing damage to members constituting the film forming apparatus by improving the accuracy of the cleaning end point detection by a simple method.

To solve the above problems, the invention according to claim 1, a cleaning end point detection method for detecting the end point of the cleaning deposits adhering to the members constituting the film formation apparatus, Ji is a vacuum Yanba And the step of starting the cleaning by starting the supply of a fluorine-based gas that is a cleaning gas, and the pressure measuring step of continuously measuring the pressure of the exhaust gas discharged from the chamber during the cleaning And during the cleaning, the absorbance of the fluorine gas contained in the fluorine-containing gas obtained by irradiating the exhaust gas with atmospheric pressure as the atmospheric pressure and irradiating the exhaust gas with atmospheric pressure is measured. Based on the measurement process and continuously measured absorbance of the fluorine gas, the concentration of the fluorine gas contained in the exhaust gas is continuously measured. An end point detecting step of detecting the end point of the cleaning based on the pressure of the exhaust gas and the concentration of the fluorine gas, and a step of stopping the supply of the fluorine-based gas after detecting the end point of the cleaning, , only containing, in the end point detection step, falls to a second threshold pressure of the exhaust gas is smaller than the first threshold value, and the variation of the concentration of the fluorine gas in the predetermined time is within a predetermined range A cleaning end point detection method is provided , wherein the cleaning end point is detected .

According to a second aspect of the present invention, there is provided a cleaning end point detection method for detecting an end point of cleaning of deposits adhering to a member constituting a film forming apparatus, wherein a cleaning gas is contained in a vacuum chamber. A process of starting the cleaning by starting the supply of a certain fluorine-based gas; a pressure measuring process of continuously measuring the pressure of the exhaust gas discharged from the chamber during the cleaning; and during the cleaning. An absorbance measurement step of continuously measuring the absorbance of fluorine gas contained in the fluorine-based gas obtained by irradiating the exhaust gas at atmospheric pressure with light, wherein the pressure of the exhaust gas is atmospheric pressure; Continuously acquiring the concentration of the fluorine gas contained in the exhaust gas based on the absorbance of the fluorine gas measured in the step, An end point detecting step of detecting an end point of the cleaning based on a gas pressure and a concentration of the fluorine gas, and a step of stopping the supply of the fluorine-based gas after detecting the end point of the cleaning, In the absorbance measurement step, there is provided a cleaning end point detection method characterized by continuously measuring ultraviolet absorbance in a wavelength band of 280 to 290 nm as the absorbance by irradiating the exhaust gas with ultraviolet rays .

According to a third aspect of the present invention, there is provided a cleaning end point detection method for detecting an end point of cleaning of deposits adhering to a member constituting the film forming apparatus, wherein the cleaning gas is contained in a vacuum chamber. A process of starting the cleaning by starting the supply of a certain fluorine-based gas; a pressure measuring process of continuously measuring the pressure of the exhaust gas discharged from the chamber during the cleaning; and during the cleaning. An absorbance measurement step of continuously measuring the absorbance of fluorine gas contained in the fluorine-based gas obtained by irradiating the exhaust gas at atmospheric pressure with light, wherein the pressure of the exhaust gas is atmospheric pressure; Continuously acquiring the concentration of the fluorine gas contained in the exhaust gas based on the absorbance of the fluorine gas measured in the step, An end point detecting step of detecting an end point of the cleaning based on a gas pressure and a concentration of the fluorine gas, and a step of stopping the supply of the fluorine-based gas after detecting the end point of the cleaning, In the end point detection step, when the pressure of the exhaust gas is smaller than the first threshold value and the variation in the concentration of the fluorine gas within a predetermined time falls within the second threshold value set in a predetermined range, the cleaning process is performed. An end point is detected, and in the absorbance measurement step, a cleaning end point detection method is provided , wherein the absorbance in the wavelength band of 280 to 290 nm is continuously measured by irradiating the exhaust gas with ultraviolet rays. Is done.

  According to the cleaning end point detection method of the present invention, two pieces of information on the pressure of the exhaust gas and the concentration of the fluorine gas (in other words, the concentration of the product generated by the reaction between the deposit and fluorine contained in the cleaning gas, and By detecting the end point of cleaning based on the concentration of fluorine gas that does not contribute to cleaning, the accuracy of detection of the end point of cleaning can be improved by a simple method.

  In addition, since the accuracy of detection of the end point of cleaning can be improved, the cleaning time can be shortened as compared with the conventional case, so that deposits adhere and damage to members constituting the film forming apparatus can be suppressed. it can.

  That is, according to the cleaning end point detection method of the present invention, the accuracy of the cleaning end point detection can be improved by a simple method, and damage to the members constituting the film forming apparatus due to the cleaning gas can be suppressed.

It is a figure which shows schematic structure of the film-forming apparatus used when enforcing the cleaning end point detection method concerning embodiment of this invention. It is a figure which shows the relationship between progress of cleaning time, the pressure of waste gas, and the density | concentration of fluorine gas. It is a figure which shows schematic structure of the film-forming apparatus used when performing an experiment example. The concentration of C ₂ F ₆ during cleaning, the concentration of product (SiF _4), is a graph showing pressure of the exhaust gas, the concentration of fluorine gas, the emission intensity of fluorine radicals, and the transition of the pressure of a concentration / exhaust of the fluorine gas .

  Embodiments to which the present invention is applied will be described below in detail with reference to the drawings. Note that the drawings used in the following description are for explaining the configuration of the embodiment of the present invention, and the size, thickness, dimensions, and the like of each part shown in the drawings are different from the dimensional relationship of an actual film forming apparatus. There is a case.

(Embodiment)
FIG. 1 is a diagram showing a schematic configuration of a film forming apparatus used when carrying out a cleaning end point detection method according to an embodiment of the present invention.

  Here, before describing the cleaning end point detection method according to the present embodiment, the configuration of the film forming apparatus 10 used when performing the cleaning end point detection method of the present embodiment will be described.

Referring to FIG. 1, a film forming apparatus 10 includes a cleaning end point detection device, and includes a chamber 11, a susceptor 12, a film forming gas supply source 14, a cleaning gas supply source 15, and a film forming gas supply line 17. The cleaning gas supply line 18, the exhaust gas line 22, the pressure measuring device 24, the first dry pump 25, the abatement device 29, the first branch line 31, and the ultraviolet absorbance measuring device 33 (ultraviolet absorption type F ₂ concentration measuring device), a second branch line 34, a needle valve 36, a second dry pump 37, and a control device 41.
The cleaning end point detection device includes a pressure measuring device 24, an ultraviolet absorbance measuring device 33, and a control device 41.

  The chamber 11 is a reaction chamber in which film formation processing and cleaning processing are performed. The chamber 11 has an upper wall 11A and a lower wall 11B that are arranged to face each other. Deposits adhere to the inner surface 11a of the chamber 11 by performing a film forming process. The chamber 11 is one of members constituting the film forming apparatus 10. During the film forming process and during cleaning, the chamber 11 is evacuated.

The material of the chamber 11 is preferably a material having resistance to a fluorine-based gas (specifically, fluorine gas) used as a cleaning gas. Specifically, for example, C ₂ F ₆ , C ₃ F ₈ , or NF ₃ can be used as the material of the chamber 11.

The susceptor 12 is accommodated in the chamber 11. The susceptor 12 is disposed on the lower wall 11B of the chamber 11. The susceptor 12 has a substrate placement surface 12a on which a substrate (for example, a semiconductor substrate (specifically, a single crystal silicon substrate)) on which a thin film is formed is placed.
Deposits adhere to the portions of the susceptor 12 other than the substrate mounting surface 12a on which a substrate (not shown) is mounted by performing a film forming process. The susceptor 12 is one of members constituting the film forming apparatus 10.

As a material of the susceptor 12, a material having resistance to a fluorine-based gas (specifically, fluorine gas) used as a cleaning gas is preferable. Specifically, for example, C ₂ F ₆ , C ₃ F ₈ , or NF ₃ can be used as the material of the susceptor 12.

The film forming gas supply source 14 is connected to one end of the film forming gas supply line 17. The film forming gas supply source 14 supplies the film forming gas into the chamber 11 through the film forming gas supply line 17.
The cleaning gas supply source 15 is connected to one end of the cleaning gas supply line 18. The cleaning gas supply source 15 supplies the cleaning gas into the chamber 11 through the cleaning gas supply line 18.

  The film forming gas supply line 17 has one end connected to the film forming gas supply source 14 and the other end connected to the upper wall 11 </ b> A of the chamber 11. The other end of the film forming gas supply line 17 passes through the upper wall 11 </ b> A of the chamber 11. The film forming gas supply line 17 is a line for supplying a film forming gas into the chamber 11.

  The cleaning gas supply line 18 has one end connected to the cleaning gas supply source 15 and the other end connected to the upper wall 11 </ b> A of the chamber 11. The other end of the cleaning gas supply line 18 passes through the upper wall 11 </ b> A of the chamber 11. The cleaning gas supply line 18 is a line for supplying the cleaning gas into the chamber 11.

  One end of the exhaust gas line 22 is connected to the lower wall 11 </ b> B of the chamber 11, and the other end is connected to the abatement device 29 via the first dry pump 25. One end of the exhaust gas line 22 passes through the lower wall 11B of the chamber 11.

The exhaust gas line 22 is disposed between the first portion 22-1 disposed between the lower wall 11B of the chamber 11 and the first dry pump 25, and between the first dry pump 25 and the detoxifying device 29. Second portion 22-2.
The exhaust gas line 22 is a line for exhausting gas existing in the chamber 11 (exhaust gas containing fluorine gas) to the outside of the chamber 11.

  The pressure measuring device 24 is connected to the exhaust gas line 22 in a state where the pressure of the exhaust gas (including fluorine gas) flowing through the first portion 22-1 of the exhaust gas line 22 can be measured. The pressure measuring device 24 is electrically connected to the control device 41.

  The pressure measuring device 24 continuously measures the pressure of the exhaust gas exhausted from the vacuum chamber 11 to the first portion 22-1 of the exhaust gas line 22 during cleaning using a fluorine-based gas as the cleaning gas. Measure (in other words, measure the pressure of the exhaust gas from the start to the end of the cleaning process).

Further, the pressure measuring device 24 transmits data regarding the pressure of the exhaust gas measured during cleaning to the control device 41 in real time.
As the pressure measuring instrument 24, for example, a commercially available pressure sensor, pressure-voltage conversion sensor, pressure-current conversion sensor, or the like can be used.

The first dry pump 25 is provided between the first part 22-1 and the second part 22-2. The first dry pump 25 is connected to the first and second portions 22-1 and 22-2. The first dry pump 25 is a pump for exhausting the gas in the chamber 11 through the first portion 22-1.
Further, the first dry pump 25 exhausts exhaust gas (including fluorine gas) at atmospheric pressure to the second portion 22-2 of the exhaust gas line 22.

  The abatement device 29 is connected to the other end of the exhaust gas line 22. The detoxifying device 29 performs the detoxifying process so that the exhaust gas transported by the second portion 22-2 of the exhaust gas line 22 is equal to or less than a safe value (TLV value) for the human body.

  The first branch line 31 branches from the second portion 22-2 located on the first dry pump 25 side. The first branch line 31 is connected to the lower end side of the gas cell 45 constituting the ultraviolet absorbance measuring device 33. During the cleaning, the first branch line 31 supplies the gas cell 45 with the exhaust gas (including the fluorine gas) set to the atmospheric pressure.

The ultraviolet absorbance measuring device 33 includes a gas cell 45, a first window material 46, a second window material 47, an ultraviolet light source 51, and an ultraviolet detector 52.
The gas cell 45 is a straight pipe, from which an exhaust gas (including fluorine gas) at atmospheric pressure is introduced, and an exhaust gas (including fluorine gas) from which the ultraviolet absorbance of the fluorine gas is measured is derived. And a lead-out port.

The inlet of the gas cell 45 is arranged on the lower end side of the gas cell 45. The inlet of the gas cell 45 is connected to the end of the first branch line 31.
The outlet of the gas cell 45 is disposed at the upper end of the gas cell 45. The outlet of the gas cell 45 is connected to the end of the second branch line 34.

As a material of the gas cell 45, a material having excellent corrosion resistance against fluorine gas contained in the cleaning gas may be used. For example, sapphire or calcium fluoride can be used as the material of the gas cell 45 that satisfies this condition.
The diameter of the gas cell 45 can be 5-15 mm, for example. Moreover, the length of the gas cell 45 can be suitably selected within the range of 5-100 cm, for example.

  The first window member 46 is disposed at one end of the gas cell 45 located in the vicinity of the ultraviolet light source 51. The second window member 47 is disposed at the other end of the gas cell 45 located in the vicinity of the ultraviolet detector 52. The first and second window members 46 and 47 hermetically seal the gas cell 45.

The distance between the first and second window members 46 and 47 can be selected as appropriate. When the distance between the first and second window members 46 and 47 is 50 cm, it is possible to measure the F ₂ concentration up to 20%. Further, when the distance between the first and second window members 46 and 47 is 10 cm, it is possible to measure the F ₂ concentration up to 100%.
Therefore, most conditions can be met by setting the distance between the first and second window members 46 and 47 to about 10 cm.
As the material of the first and second window members 46 and 47, a material that easily transmits ultraviolet rays having a wavelength of 300 nm or less may be used. For example, quartz, sapphire, and fluorite can be used as the material of the first and second window members 46 and 47 that satisfy this condition.

The ultraviolet light source 51 is provided at the upper end of the gas cell 45 so as to face the first window member 46. The ultraviolet light source 51 is a light source for irradiating the exhaust gas (including fluorine gas) introduced into the gas cell 45 and having an atmospheric pressure during cleaning with ultraviolet light.
As the ultraviolet light source 51, a deuterium lamp can be used. As the deuterium lamp, for example, a D2 lamp L2D2 manufactured by Hamamatsu Photonics can be used.

The ultraviolet detector 52 is provided at the lower end of the gas cell 45 so as to face the second window member 47. The ultraviolet detector 52 is electrically connected to the control device 41.
The ultraviolet detector 52 continuously measures the ultraviolet absorbance of fluorine gas contained in a fluorine-based gas (cleaning gas) obtained by irradiating the exhaust gas at atmospheric pressure with ultraviolet rays during cleaning, and the measurement result. (Data relating to the ultraviolet absorbance of fluorine gas) is transmitted to the control device 41 in real time.

  As the ultraviolet detector 52, for example, an ultraviolet detector with a monochromator can be used. As an ultraviolet detector with a monochromator, for example, RM300 manufactured by Horiba, Ltd. can be used.

  In the case where the ultraviolet absorbance in the wavelength band of 280 to 290 nm (in other words, the absorption wavelength band of fluorine gas) cannot be detected using the ultraviolet detector 52, the first and second window members 46 and 47 are not detected. Alternatively, an absorbance necessary for detection of the end point of cleaning may be obtained by providing an ultraviolet cut filter, a band pass filter, or the like and detecting the entire wavelength of 300 nm or less.

The second branch line 34 branches from a second portion 22-2 (a part of the exhaust gas line 22) located between the branch position of the first branch line 31 and the abatement apparatus 29. The end of the second branch line 34 is connected to the upper part of the gas cell 45 located below the position where the first window material 46 is disposed.
The second branch line 34 is a line for returning the exhaust gas used for measuring the ultraviolet absorbance of the fluorine gas to the exhaust gas line 22 (second portion 22-2).

The needle valve 36 is provided in the second branch line 34. The needle valve 36 is a valve for making the flow rate of the exhaust gas flowing through the gas cell 45 substantially constant.
The second dry pump 37 is provided in the second branch line 34 located between the branch position of the second branch line 34 and the position where the needle valve 36 is disposed. The second dry pump 37 is a pump for introducing exhaust gas to the first branch line 31, the gas cell 45, and the second branch line 34.

  The control device 41 is electrically connected to the film forming gas supply source 14, the cleaning gas supply source 15, the pressure measuring device 24, the first dry pump 25, the second dry pump 37, and the ultraviolet detector 52. . The control device 41 performs overall control of the film forming apparatus 10.

  The control device 41 includes a storage unit 53 and a calculation and end point detection unit 54. The storage unit 53 includes a recipe relating to the film forming process, a recipe relating to the cleaning process, a first threshold A relating to the pressure of exhaust gas during cleaning, a second threshold B relating to the concentration of fluorine gas during cleaning, and an overcleaning time ( Data such as the time for which the cleaning process is continued after the end point of cleaning is detected is stored in advance.

  The first and second threshold values A and B are threshold values used when detecting the end point of cleaning. As the first threshold A, for example, a specific numerical value (for example, 600 × 10 mTorr) can be used. As the second threshold value B, for example, a threshold value (threshold value having a width) in a predetermined range (for example, 3500 to 4000 ppm) can be used.

That is, in the cleaning end point detection method of the present embodiment, the cleaning end point is detected based on two threshold values (first and second threshold values A and B).
Specifically, in the cleaning end point detection method of the present embodiment, the concentration of the fluorine gas varies during a predetermined time (for example, about 60 seconds) while the exhaust gas pressure is smaller than the first threshold value A. When it falls within the second threshold B, the end point of cleaning (cleaning completed) is detected.

The calculation and end point detection unit 54 determines whether or not the pressure of the exhaust gas continuously transmitted from the pressure measuring device 24 during the cleaning has become smaller than the first threshold A.
When the measured exhaust gas pressure is equal to or higher than the first threshold value A, the calculation and end point detection unit 54 determines that the cleaning process has not been completed.

The calculation and end point detection unit 54 continuously calculates the concentration of fluorine gas contained in the exhaust gas during cleaning by calculation based on the UV absorbance data continuously transmitted from the UV detector 51 during cleaning.
When the calculated fluorine gas concentration does not fall within the second threshold value B for a predetermined time (for example, about 60 seconds), the calculation and end point detection unit 54 performs cleaning. It is determined that the process has not been completed.

In addition, the calculation and end point detection unit 54 determines the concentration of the fluorine gas during cleaning for a predetermined time (for example, about 60 seconds) while the measured exhaust gas pressure is smaller than the first threshold A. When the fluctuation is within the range of the second threshold B, the end point of cleaning is detected.
The control device 41 stops the fluorine-based gas supplied from the cleaning gas supply source 15 when the calculation and end point detection unit 54 detects the end point of the cleaning, and then the overcleaning process is completed. Thereby, the cleaning process is completed.

  Next, the cleaning end point detection method of the present embodiment using the film forming apparatus 10 shown in FIG. 1 will be described with reference to FIG. In the present embodiment, in-situ cleaning will be described as an example of the cleaning method.

First, after the supply of the deposition gas is stopped and the inside of the chamber 11 is purged, the substrate (not shown) placed in the chamber 11 and having a thin film formed thereon is carried out of the chamber 11.
At this stage, deposits (not shown) adhere to the surfaces of members (specifically, for example, the chamber 11 and the susceptor 12) constituting the film forming apparatus 10.

Next, supply of a fluorine-based gas (for example, C ₂ F ₆ , C ₃ F ₈ , NF _3, etc.) that is a cleaning gas into the chamber 11 in a vacuum state (for example, a pressure of 0.01 Torr or less) is started. Thus, a cleaning process for removing the deposit is started.

Next, during cleaning (from the start of cleaning until the end of cleaning is detected), the pressure measuring device 24 continuously measures the pressure of exhaust gas (including fluorine gas) discharged from the chamber 11 ( Pressure measurement step).
Data on the measured exhaust gas pressure is transmitted to the control device 41 in real time.

  Simultaneously with the measurement of the exhaust gas pressure, during the cleaning (from the start of cleaning until the end of detection of the cleaning is completed), the ultraviolet light absorbance measuring device 33 irradiates the exhaust gas that has flowed through the gas cell 45 and is at atmospheric pressure with light. Then, the absorbance of the fluorine gas contained in the fluorine-based gas obtained is measured continuously (absorbance measurement step).

Specifically, in the absorbance measurement step, the UV absorbance in the wavelength band of 280 to 290 nm (fluorine gas absorption wavelength band) is continuously measured as the absorbance by irradiating the exhaust gas with ultraviolet rays.
Data on the ultraviolet absorbance of the fluorine gas continuously measured is transmitted to the control device 41 in real time.
The calculation and end point detection unit 54 constituting the control device 41 continuously acquires the concentration of the fluorine gas contained in the exhaust gas based on the continuously measured data relating to the ultraviolet absorbance of the fluorine gas.

FIG. 2 is a graph showing the relationship between the passage of cleaning time, the pressure of the exhaust gas, and the fluorine gas concentration.
Here, with reference to FIG. 2, the relationship between the passage of the cleaning time, the pressure of the exhaust gas, and the fluorine gas concentration will be described.
Referring to FIG. 2, the pressure of the exhaust gas increases with the start of the cleaning process of the deposit (for example, SiO ₂ film), and then gradually decreases to maintain a low numerical value.

As shown in FIG. 4 to be described later, the pressure of the exhaust gas during cleaning is generated by a reaction between fluorine (F) contained in the fluorine-based gas (cleaning gas) and silicon (Si) contained in the deposit. It is influenced by the product (in this case, SiF ₄ ) and shows a transition similar to the concentration of the product (SiF ₄ ).
Therefore, the pressure of the exhaust gas, the product (SiF ₄₎ is often generated (in other words, the cleaning process is performed actively) increases, product cleaning process is generated by progressive (SiF ₄ ) Decreases (in other words, the cleaning process approaches the end).

Since there are many deposits in the first half of the cleaning process, the deposits (for example, SiO ₂ film) and fluorine are likely to react, and in the second half of the cleaning process, the deposits that react with fluorine are reduced.
Therefore, as shown in FIG. 4 to be described later, the concentration of the fluorine gas increases with the lapse of time of the cleaning process, and when the removal of the deposit is completed, the fluorine gas contained in the fluorine-based gas supplied into the chamber 11 However, most fluorine gas is exhausted without contributing to the removal of deposits.

  Further, as shown in FIG. 4 described later, the concentration of the fluorine gas contained in the exhaust gas during cleaning shows a transition similar to the waveform of the emission intensity of fluorine radicals. Therefore, by continuously acquiring the concentration of the fluorine gas contained in the exhaust gas during cleaning, the end point of cleaning can be detected using a simple method without generating fluorine radicals.

  In the calculation and end point detection unit 54, the measured exhaust gas pressure is smaller than the first threshold value A, and the variation in the concentration of the fluorine gas within a predetermined time (for example, 60 seconds) is within a predetermined range (for example, 3500). When the value falls within the second threshold B set to ˜4000 ppm, the cleaning end point is detected (end point detection step), and overcleaning is performed for a predetermined time after the cleaning end point is detected. Thereafter, the supply of the fluorine-based gas into the chamber 11 is stopped.

  That is, in the present embodiment, the end point of cleaning is detected based on the continuously measured exhaust gas pressure, the continuously acquired fluorine gas concentration, the first threshold A, and the second threshold B. To do.

  In the cleaning end point detection method of the present embodiment, the process of starting the cleaning by starting the supply of the fluorine-based gas, which is a cleaning gas, into the vacuumed chamber 11 and the inside of the chamber 11 during the cleaning. Included in the fluorine-containing gas obtained by continuously measuring the pressure of the exhaust gas discharged and the pressure of the exhaust gas at atmospheric pressure during cleaning and irradiating the exhaust gas at atmospheric pressure with ultraviolet light An absorbance measurement step for continuously measuring the absorbance of the fluorine gas, a step of continuously obtaining the concentration of the fluorine gas contained in the exhaust gas based on the continuously measured absorbance of the fluorine gas, a pressure of the exhaust gas, fluorine An end point detecting step for detecting an end point of cleaning based on the gas concentration, the first threshold value A, and the second threshold value B; After detecting the end point of the grayed, and a step of stopping the supply of the fluorine-based gas.

Thus, by continuously measuring the pressure of the exhaust gas during cleaning, it is possible to infer from the pressure of the exhaust gas the increase or decrease in the concentration of the product generated by the reaction between the fluorine gas and the deposit. .
When the pressure of the exhaust gas is high, there are many deposits, and the reaction between the deposits and fluorine is promoted, so that the concentration of the produced product increases. Thereafter, when the pressure of the exhaust gas is lowered, the deposit that reacts with fluorine is reduced due to the progress of the removal of the deposit, so that the concentration of the produced product is reduced.

Further, by continuously acquiring the concentration of fluorine gas contained in the exhaust gas during cleaning, it is possible to recognize the concentration of fluorine gas that has not contributed to cleaning among the fluorine gas supplied into the chamber 11. Become.
As a result, it is understood that when a considerably smaller amount of fluorine gas than the amount supplied into the chamber 11 is exhausted, the fluorine gas reacts with the deposit to remove the deposit.
Further, when the difference in the concentration change of the fluorine gas becomes small, the deposit is removed and the cleaning process comes to an end, so that most of the fluorine gas supplied into the chamber 11 is discharged.

  That is, according to the cleaning end point detection method of the present embodiment, two pieces of information of the exhaust gas pressure and the concentration of fluorine gas (in other words, the concentration of the product and the amount of fluorine gas not contributing to cleaning) and Since the cleaning end point is detected based on the first and second threshold values A and B, the cleaning end point detection accuracy can be improved by a simple method without generating fluorine radicals. .

  In addition, since the accuracy of detection of the end point of cleaning can be improved, the cleaning time can be shortened as compared with the conventional case, so that deposits adhere and damage to the members constituting the film forming apparatus 10 is suppressed. Can do.

  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.

  For example, as shown in FIG. 2, a value obtained by dividing the concentration of fluorine gas by the pressure of exhaust gas (= fluorine gas concentration / exhaust gas pressure) is obtained by calculation, and the transition of this value is monitored, as shown in FIG. In addition, a point (point C shown in FIG. 2) where the slope of the graph of the value changes greatly may be detected, and a point when a predetermined time has elapsed from this point may be set as the end point of cleaning.

  In this embodiment, in-situ cleaning has been described as an example of the cleaning method. However, the cleaning end point detection method of this embodiment includes remote cleaning and ex-situ cleaning using a film forming apparatus. The present invention can also be applied to ex situ cleaning using a processing apparatus, and when applied to these, effects similar to the cleaning end point detection method of the present embodiment can be obtained.

(Experimental example)
FIG. 3 is a diagram showing a schematic configuration of a film forming apparatus used in performing the experimental example.
First, the configuration of the film forming apparatus 60 used when performing the experimental example will be described with reference to FIG.
In addition to the configuration of the film forming apparatus 10 shown in FIG. 1, the film forming apparatus 60 further measures a plasma emission spectrometer 55 (OES), a Fourier transform infrared spectrometer 56 (FT-IR), and a discharge sustaining voltage. The configuration was the same as the film forming apparatus 10 except that a Vpp monitor 58 and a Vdc monitor 59 for measuring plasma potential were provided.
As the Vpp monitor 58, a high-pressure probe (P6015a) manufactured by Sony Tektronix was used. As the Vdc monitor 59, a voltage measuring device manufactured by Arios was used.
By providing the Vpp monitor 58 and the Vdc monitor 59, it is possible to confirm the plasma state confirmation at the time of cleaning, so that the accuracy of the cleaning end point detection can be improved.
As the film forming apparatus main body constituting the film forming apparatus 60, Precision 5000, which is plasma CVD manufactured by Applied Materials, was used.

  As the pressure measuring device 24, a general-purpose absolute pressure transducer (622B) manufactured by MKS, which is a pressure sensor, was used. A general-purpose absolute pressure transducer (622B) manufactured by MKS was used to measure the pressure of exhaust gas during cleaning.

The ultraviolet absorbance measuring device 33 has the following configuration. As the gas cell 45, an SUS cell (tubular member) having an optical path length of 700 mm was used. As the first and second window members 46 and 47, a window member made of CaF ₂ was used. As the ultraviolet light source 51, a Hamamatsu Photonics D2 lamp (L2D2) was used. As the ultraviolet detector 52, RM300 (C7460) manufactured by HORIBA, Ltd. was used.
The ultraviolet absorbance measuring device 33 configured as described above was used for measuring the ultraviolet absorbance of fluorine contained in the exhaust gas during cleaning.

  The plasma emission spectrometer 55 was connected to the chamber 11 in a state where the emission intensity of fluorine radicals existing in the chamber 11 could be measured. As the plasma emission spectrometer 55, a plasma monitor C7460 manufactured by Hamamatsu Photonics was used. Further, the spectral intensity of 703 nm, which is the emission wavelength of the fluorine radical, was measured using a plasma monitor C7460 manufactured by Hamamatsu Photonics.

The Fourier transform infrared spectrometer 56 was connected to the second branch line 34 in a state where the amount of product (in this case, SiF ₄ ) contained in the exhaust gas flowing through the second branch line 34 was measurable.
As the Fourier transform infrared spectrometer 56, FG120A (electronically cooled MCT detector) manufactured by Horiba Ltd. was used. The analysis conditions using FG120A manufactured by HORIBA, Ltd. were a resolution of 2 cm ⁻¹ , a total number of times when collecting a background spectrum was 128 times, and a total number of times when collecting a sample spectrum was 4 times (about 2 sec). . The standard spectrum used for data analysis was a reference spectrum built in FG120A manufactured by Horiba.
The reference spectrum here means a spectrum for comparison reference measured using a standard gas.

  The calculation and end point detection unit 54 is composed of NR1000 manufactured by Keyence Corporation and a data processing device (for example, a computer).

  Further, 600 × 10 mTorr was used as the first threshold A for detecting the end point of cleaning, and a numerical value in the range of 3500 to 4000 was used as the second threshold B. Further, the end point of cleaning was detected when it was within the range of the second threshold B for 60 seconds (predetermined time).

Before performing the deposit cleaning process (in-situ chamber cleaning process), a plasma TEOS film was formed on the single crystal silicon substrate using the film forming apparatus 60.
Further, the deposit cleaning process was performed after the pre-coating and the film forming process were completed.
In the film formation process, a plasma TEOS film having a thickness of 820 nm was formed on a single crystal silicon substrate. The pre-coating conditions were the same as the film forming process, and the time treatment for forming a 100 nm-thick plasma TEOS film was performed.

Cleaning of deposits adhering to the members constituting the film forming apparatus 60 was performed in two steps (first and second steps).
The first step is a step of cleaning the shower head, the peripheral part of the susceptor 12 and the peripheral part of the electrode, which are objects to be cleaned.
The second step is a step of cleaning the inner wall surface of the chamber 11 that is the object to be cleaned and the exhaust pipe on the downstream side. In the second step, unlike the first step, the plasma is spread by changing the pressure, and the object to be cleaned is cleaned.

In the first step, the pressure in the chamber 11 was 4 Torr. In the second step, the pressure in the chamber 11 was set to 2 Torr so that the pressure in the chamber was lower than that in the first step.
The first step was performed from the start of cleaning to the end of cleaning. In the first step, deposits mainly attached to the periphery of the electrode were removed. The second step was performed from the start of cleaning to the end of cleaning. In the second step, deposits mainly adhered to the inner surface of the chamber 11 were removed.

In the first and second steps, a mixed gas in which hexafluoroethane and oxygen are mixed is used as the cleaning gas (fluorine-based gas).
In the first and second steps, a mixed gas (cleaning gas) obtained by mixing 600 cc of O ₂ (oxygen) and 450 cc of C ₂ F ₆ (hexafluoroethane) was used. That is, in the first and second step, the mixing ratio of each gas _{O 2: C 2 F 6 =} 1: set to 0.75.

The NR1000 manufactured by Keyence Co., Ltd. has 0 to 10 V data on the pressure of the exhaust gas measured by the pressure measuring device 24 (pressure signal) and data on the ultraviolet absorbance of the fluorine gas measured by the ultraviolet absorbance measuring device 33 (ultraviolet absorbance signal). Input as analog data.
The data processor calculated the concentration of fluorine gas by calculation based on the ultraviolet absorbance of fluorine gas based on data transmitted from NR1000 manufactured by Keyence Corporation.

C ₂ F ₆ concentration, product (SiF ₄ ) concentration, exhaust gas pressure, fluorine gas concentration, fluorine radical emission intensity, fluorine gas concentration / exhaust gas pressure at the time of cleaning obtained in this experiment The transition is shown in FIG.
FIG. 4 shows changes in C ₂ F ₆ concentration, product (SiF ₄ ) concentration, exhaust gas pressure, fluorine gas concentration, fluorine radical emission intensity, and fluorine gas concentration / exhaust gas pressure during cleaning. It is a graph to show. In FIG. 4, the result of only the first step is illustrated.
The concentration of C ₂ F ₆ was measured using a Fourier transform infrared spectrometer 56 (FT-IR). From the start of cleaning to the end of cleaning, the C ₂ F ₆ concentration has hardly changed.

Referring to FIG. 4, the transition of the pressure of the exhaust gas during cleaning shows a behavior similar to the transition of the concentration of the product (SiF ₄ ).
Specifically, when the cleaning process is started (first step is started), the pressure of the exhaust gas and the concentration of the product (SiF ₄ ) increase, and then gradually decrease and stabilize at a low value. .
That is, by measuring the pressure of the exhaust gas during cleaning, the concentration of the product (SiF ₄ ) can be estimated by a simple method without using the Fourier transform infrared spectrometer 56.

In the period when the pressure of the exhaust gas and the concentration of the product (SiF ₄ ) increase, the reaction between the fluorine contained in the cleaning gas and the silicon contained in the deposit becomes active, and a lot of product (SiF ₄ ) is produced. The concentration of the product (SiF ₄ ) increases.
Thereafter, as the removal of the deposit proceeds, the amount of the deposit that reacts with fluorine decreases, and the product is less likely to be generated, so the concentration of the product (SiF ₄ ) decreases.

Referring to FIG. 4, the transition of the concentration of fluorine gas contained in the exhaust gas during cleaning shows a behavior similar to the transition of the emission intensity of fluorine radicals in the chamber 11.
Specifically, when the cleaning process is started (first step is started), the concentration of fluorine gas and the emission intensity of fluorine radicals increase at a relatively steep angle first, and then increase at a moderate angle. After that, the fluctuation almost disappeared and became a substantially constant value.
That is, by measuring the concentration of fluorine gas contained in the exhaust gas during cleaning, the concentration of fluorine radicals can be estimated by a simple method without using the plasma emission spectrometer 55.

During the period in which the concentration of fluorine gas and the emission intensity of fluorine radicals increase, the reaction between fluorine contained in the cleaning gas and silicon contained in the deposit becomes active, and a large amount of product (SiF ₄ ) is produced. It is considered that a large amount of fluorine gas contained in the gas contributed to the production of the product (SiF ₄ ).
Thereafter, as the product (SiF ₄ ) is generated and the removal of the deposit proceeds, the fluorine gas contributing to the generation of the product (SiF ₄ ) decreases. Therefore, most of the fluorine gas introduced into the chamber 11 is exhaust gas. It is estimated that it was included.

In the present experimental example, the exhaust gas pressure becomes smaller than the first threshold A (600 × 10 mTorr) after 40 seconds from the start of cleaning, and thereafter shows a value less than the first threshold (600 × 10 mTorr). It was.
In addition, the concentration of fluorine gas contained in the exhaust gas was detected after 40 seconds from the start of cleaning, because the variation in the concentration of fluorine gas was within the second threshold B for 20 seconds. (The end point is detected after 60 seconds from the start of cleaning).

  After detecting the end point of cleaning, overcleaning is performed for about 10 seconds, and then it is confirmed whether the deposit is removed. The deposit is removed cleanly while suppressing damage to the members of the film forming apparatus 60. It has been confirmed that.

  As shown in FIG. 4, a value obtained by dividing the concentration of fluorine gas by the pressure of exhaust gas (= fluorine gas concentration / exhaust gas pressure) is obtained by calculation, the transition of this value is monitored, and the slope of the graph of the value is A point that changes greatly (point C shown in FIG. 4) is detected, and when a predetermined time has elapsed from this time, the end point of cleaning is performed. Thereafter, overcleaning is performed for about 10 seconds, and then the deposit is removed. As a result, it was confirmed that the deposits were removed cleanly while suppressing damage to the members of the film forming apparatus 60.

  In this experimental example, the case where the cleaning process is divided into two steps is described as an example. However, when the cleaning step is performed in one step (in other words, the cleaning process is performed only under the conditions of the first step). The same results were obtained.

  The present invention can be applied to a cleaning end point detection method capable of suppressing damage to members constituting the film forming apparatus by improving the accuracy of cleaning end point detection.

  DESCRIPTION OF SYMBOLS 10,60 ... Film-forming apparatus, 11 ... Chamber, 11a ... Inner surface, 11A ... Upper wall, 11B ... Lower wall, 12 ... Susceptor, 12a ... Substrate mounting surface, 14 ... Film-forming gas supply source, 15 ... Cleaning gas supply Source: 17 ... Film forming gas supply line, 18 ... Cleaning gas supply line, 22 ... Exhaust gas line, 22-1 ... First part, 22-2 ... Second part, 24 ... Pressure measuring instrument, 25 ... First Dry pump, 29 ... abatement device, 31 ... first branch line, 33 ... UV absorbance measuring device, 34 ... second branch line, 36 ... needle valve, 37 ... second dry pump, 41 ... control device, 45 ... Gas cell, 46 ... First window material, 47 ... Second window material, 51 ... Ultraviolet light source, 52 ... Ultraviolet detector, 53 ... Storage unit, 54 ... Calculation and end point detection unit, 55 ... Plasma emission spectrometer 56 ... Fourier transform infrared Optical device, 58 ... Vpp monitor, 59 ... Vdc monitor

Claims (3)

A cleaning end point detection method for detecting an end point of cleaning of deposits adhering to a member constituting a film forming apparatus,
In Ji Yanba which is a vacuum, by starting supply of fluorine gas is a cleaning gas, a step of initiating the cleaning,
A pressure measuring step for continuously measuring the pressure of the exhaust gas discharged from the chamber during the cleaning;
An absorbance measurement step of continuously measuring the absorbance of fluorine gas contained in the fluorine-containing gas obtained by irradiating the exhaust gas at atmospheric pressure with light during the cleaning. When,
Continuously acquiring the concentration of the fluorine gas contained in the exhaust gas based on the absorbance of the fluorine gas continuously measured;
An end point detection step of detecting an end point of the cleaning based on the pressure of the exhaust gas and the concentration of the fluorine gas;
After detecting the end point of the cleaning, stopping the supply of the fluorine-based gas;
Only including,
In the end point detection step, when the pressure of the exhaust gas is smaller than a first threshold value and the variation in the concentration of the fluorine gas within a predetermined time falls within a second threshold value within a predetermined range, the cleaning is performed. A method for detecting a cleaning end point, wherein the end point of the cleaning is detected. A cleaning end point detection method for detecting an end point of cleaning of deposits adhering to a member constituting a film forming apparatus,
  Starting the cleaning by starting the supply of a fluorine-based gas that is a cleaning gas into the vacuum chamber; and
  A pressure measuring step for continuously measuring the pressure of the exhaust gas discharged from the chamber during the cleaning;
  An absorbance measurement step of continuously measuring the absorbance of fluorine gas contained in the fluorine-containing gas obtained by irradiating the exhaust gas at atmospheric pressure with light during the cleaning. When,
  Continuously acquiring the concentration of the fluorine gas contained in the exhaust gas based on the absorbance of the fluorine gas continuously measured;
  An end point detection step of detecting an end point of the cleaning based on the pressure of the exhaust gas and the concentration of the fluorine gas;
  After detecting the end point of the cleaning, stopping the supply of the fluorine-based gas;
  Including
  In the absorbance measuring step, the cleaning end point detection method is characterized by continuously measuring ultraviolet absorbance in a wavelength band of 280 to 290 nm as the absorbance by irradiating the exhaust gas with ultraviolet rays. A cleaning end point detection method for detecting an end point of cleaning of deposits adhering to a member constituting a film forming apparatus,
  Starting the cleaning by starting the supply of a fluorine-based gas that is a cleaning gas into the vacuum chamber; and
  A pressure measuring step for continuously measuring the pressure of the exhaust gas discharged from the chamber during the cleaning;
  An absorbance measurement step of continuously measuring the absorbance of fluorine gas contained in the fluorine-containing gas obtained by irradiating the exhaust gas at atmospheric pressure with light during the cleaning. When,
  Continuously acquiring the concentration of the fluorine gas contained in the exhaust gas based on the absorbance of the fluorine gas continuously measured;
  An end point detection step of detecting an end point of the cleaning based on the pressure of the exhaust gas and the concentration of the fluorine gas;
  After detecting the end point of the cleaning, stopping the supply of the fluorine-based gas;
  Including
  In the end point detection step, when the pressure of the exhaust gas is smaller than a first threshold value and the variation in the concentration of the fluorine gas within a predetermined time falls within a second threshold value within a predetermined range, the cleaning is performed. Detects the end point of
  In the absorbance measuring step, the cleaning end point detection method is characterized by continuously measuring ultraviolet absorbance in a wavelength band of 280 to 290 nm as the absorbance by irradiating the exhaust gas with ultraviolet rays.

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