JP2010092633A - Method for measuring gas component in vacuum chamber, and vacuum device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a method for accurately measuring gas components in a vacuum chamber capable of high evacuation; and a vacuum device. <P>SOLUTION: In the method for measuring gas component of the device provided with a gas component measuring device to measure the gas components in the vacuum chamber, upon measuring gas components, the speed of evacuation in the vacuum chamber is lowered. That is, after creating an environment in which residual gas is not easily exhausted, analysis of the gas components is carried out. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vacuum apparatus used in a charged particle beam apparatus or the like, and more particularly to a method and apparatus for measuring a gas in a vacuum apparatus.

  A charged particle beam apparatus that scans an electron beam on a sample and measures and observes the size and shape of a pattern or a contact hole formed on the sample from the obtained secondary electron or reflected electron image is a semiconductor element. As miniaturization progresses, the role becomes more important.

  On the other hand, when observation is performed using an electron microscope, contaminants adhere to the portion of the sample irradiated with the electron beam. For example, as explained in Non-Patent Document 1, the cause of sample contamination is due to adsorption of hydrocarbon molecules adhering to the sample and hydrocarbons in the residual gas in the apparatus to the sample. Can be considered. In any case, it is said that the adsorbed gas is solidified by receiving electron beam energy, and a true surface image cannot be captured by the attached matter. Particularly in the case of a semiconductor inspection apparatus, it is a serious problem because it is intended for dimension measurement and appearance inspection.

  Further, as described in Non-Patent Document 2, DOP (dioctyl phthalate), a molecular chemical pollutant that releases components contained in members used inside the apparatus or enters the apparatus from a clean room atmosphere. It has also been pointed out that DBP (dibutyl phthalate), siloxane, and the like adhere to the sample and cause semiconductor performance deterioration. In addition, a gas component brought into the sample itself may cause a problem with another sample.

  Furthermore, recently, as disclosed in Patent Document 1, a fluorine-based compound adheres to a semiconductor wafer that has undergone measurement and inspection processes in a semiconductor charged particle beam apparatus, and in the resist coating process, Bubbles may be generated. There is a possibility that a problem arises that the resist is thinly formed by the bubbles, and pits are formed in the base in the subsequent dry etching process.

  Patent Documents 1 and 2 explain how to measure various gas components as described above using a mass spectrometer or the like.

JP 2007-141741 A JP 2007-149571 A Specimen Protection in the Electron Microscope (HEYWOOD J A, Pract Metallogr 19 (1982) 465) New version of silicon wafer surface cleaning technology (Satoshi Hattori, Realize Inc. (2000) 37)

  Patent Documents 1 and 2 describe a method for detecting a gas component remaining in a vacuum chamber, but it is an invention that the gas component cannot be sufficiently detected depending on the exhaust speed of the vacuum exhaust system. It became clear by their experiment. In particular, when the exhaust speed is high, the detectable gas component decreases. On the other hand, in order to keep the degree of vacuum in the vacuum chamber above a certain level, an exhaust speed higher than a predetermined value is required.

  Hereinafter, a gas measuring method and a vacuum apparatus for measuring a gas component in a vacuum chamber capable of high vacuum evacuation with high accuracy will be described.

  As an aspect for achieving the above object, in a gas component measurement method for a device having a measurement device for measuring a gas component in the vacuum chamber in the vacuum chamber, the vacuum exhaust rate of the vacuum chamber is lowered during the measurement of the gas component. A gas component measuring method and apparatus are proposed. That is, the gas component analysis is performed after creating an environment in which it is difficult to exhaust the residual gas.

  According to the above configuration, it is possible to improve the gas analysis accuracy by lowering the exhaust speed when measuring the gas component.

According to the experiment conducted by the inventors, a silicon gas-releasing member and a clean silicon wafer were placed in a vacuum container and evacuated, and the wafer exposed to the silicon gas was subjected to GC-MS (Gas Chromatography-Mass Spectrometry). As a result, the adhesion of gas mainly containing silicon having mass numbers 73 (Si (CH ₃ ) ₃ ) and 146 (Si ₂ (CH ₃ ) ₆ ) was detected. However, when a member for releasing a silicon-based gas was similarly put into the apparatus with another vacuum apparatus (pumping speed 300 L / s), the residual gas in the vacuum exhaust was measured up to a mass number of 200 with a mass spectrometer. Although the gas with mass number of 73 could be detected, the gas with mass number of 146 could not be measured. Further, when the gas released from the same member was measured with a mass evacuator with another vacuum evacuation device (evacuation speed: 48 L / s) However, a gas having a mass number of 146 was detected.

  In this way, in residual gas measurement with a mass spectrometer, it becomes clear that detection is possible depending on the pumping speed of the vacuum pumping system, and it can be seen that the presence or absence of a problem may be misjudged depending on the device configuration. It was. Control of the exhaust speed and measurement of residual gas can be realized in the experimental apparatus by using means such as vacuum pumps having different exhaust speeds or installing an orifice in the vacuum pump suction port.

  In the following, a method for measuring the residual gas with a mass spectrometer with high sensitivity, and a charged particle beam apparatus having a function for accurately monitoring the state of the apparatus will be described.

  As an example of the charged particle beam device, a mass spectrometer is attached to a vacuum chamber to be measured via a variable valve that can arbitrarily set the opening, and the mass spectrometer is usually measured with the valve opening fully opened. An apparatus equipped with a mechanism for maintaining the same vacuum atmosphere will be described. When performing gas analysis, the valve opening is reduced, and the vacuum exhaust conductance of the space from the valve to the mass spectrometer side is reduced to form an environment in which residual gas is not easily exhausted. A high sensitivity measurement can be achieved by performing a gas analysis of this space.

  Such a residual gas measuring method can be automatically performed at the time or time interval before and after the sample measurement of the charged particle beam apparatus or arbitrarily set, and the state of the apparatus is monitored. Further, by performing measurement at an arbitrary timing before and after the apparatus maintenance work, it is possible to maintain and manage the apparatus performance.

  Hereinafter, an apparatus provided with a measuring apparatus for detecting residual gas will be described with reference to the drawings.

  FIG. 1 shows an example of the present invention in which a variable valve 3 is installed between a vacuum chamber 1 and a vacuum exhaust device 2. A mounting tube 5 equipped with a mass spectrometer 4 for measuring residual gas is attached to a vacuum chamber. The attachment tube 5 may be any size that can accommodate the mass spectrometer 4. Normally, the variable valve 3 is evacuated with the valve fully opened. However, when the residual gas is measured by the mass spectrometer 4, the residual gas in the vacuum chamber 1 is exhausted by reducing the opening of the variable valve 3. Make it difficult. The molecular density of the residual gas in the vacuum chamber 1 is increased, and high sensitivity for residual gas measurement can be achieved.

  Also, when the vacuum pump is continuously evacuated at a predetermined pumping speed, temporarily reducing the pumping speed creates an environment in which residual gas is difficult to be exhausted. Perform analysis. The mass spectrometer 4 and the variable valve 3 provide a certain space or more and detect gas remaining in the space. As one aspect of the present embodiment, it is conceivable to create the space by making the wall surface on the mounting side of the variable valve 3 in the vacuum chamber 1 different from the mounting side wall surface of the mass spectrometer 4. Moreover, quantitative gas analysis can be performed by setting the exhaust speed to a predetermined value.

  In the example of FIG. 1, the vacuum chamber 1 is, for example, a sample chamber of a scanning electron microscope, and a sample stage for moving the sample is provided in the vacuum chamber 1. The opening of the variable valve is controlled by a control device (not shown).

  FIG. 4 is a diagram for explaining an example in which a mass spectrometer for residual gas detection is attached to a scanning electron microscope which is an embodiment of the charged particle beam apparatus. In the example of FIG. 4, an example in which the variable valve 3 is installed on the mass spectrometer 4 side is described, but this aspect will be described later. In this embodiment, an example in which a variable valve is installed on the vacuum exhaust device side will be mainly described.

  FIG. 4 shows an example in which the attachment tube 5 having the mass spectrometer 4 is attached to the sample chamber 8 via the variable valve 3. The charged particle beam apparatus includes an electron gun chamber 6, a condenser lens chamber 7, and a sample chamber 8, and an intermediate chamber 9 is provided between the condenser lens chamber 7 and the sample chamber 8. A sample exhaust chamber 10 is adjacent to the sample chamber 8, and a sample exchange chamber 11 is installed at the top.

  The electron gun chamber 6 has an electron gun 12, an extraction electrode 13, an acceleration electrode 14, and a fixed aperture 15. The condenser lens chamber 7 has a condenser lens 16. The intermediate chamber 9 has a deflection coil 17, an objective lens 18, and an objective lens. A diaphragm 19 is installed. Vacuum pumps 24 and 25 are evacuated in the electron gun chamber 6 and a vacuum pump 26 is evacuated in the condenser lens chamber 7 so that a stable electron beam 29 is obtained.

  The sample chamber 8 is evacuated by the vacuum pump 27, and the intermediate chamber 9 is connected to the sample chamber 8 via the exhaust bypass 32 and is evacuated by the vacuum pump 27. The preliminary exhaust chamber 10 is exhausted by a vacuum pump 28. The sample 21 is first introduced into the sample exchange chamber 11, placed on the sample holder 20 in the preliminary exhaust chamber 10 through the gate valve 23, and the sample 21 is sampled together with the sample holder 20 by opening the gate valve 22. Move to chamber 8 and set to measurement position. A reflected electron / secondary electron detector 31 for detecting secondary electrons or reflected electrons 30 from the surface of the sample 21 when the electron beam 29 is irradiated is attached to the intermediate chamber 9. An image is created.

  As described above, the interior of the charged particle beam apparatus is composed of many parts, and has a complicated structure including parts such as a movable mechanism and signal wiring. The parts installed inside the equipment are thoroughly cleaned and cleaned so that they do not adversely affect the vacuum or sample. However, due to some trouble, gas from parts that are insufficiently cleaned or cleaned, or gas release due to abnormalities in moving parts, etc. can be considered.

  In such a case, the state of the vacuum inside the apparatus must be measured quickly using a mass spectrometer, and the abnormal state must be grasped and dealt with.

  In FIG. 4, a gas detection measuring device is applied to the sample chamber 8. However, if the measurement device is replaced with the electron gun chamber 6, the condenser lens chamber 7, the intermediate chamber 9, the preliminary exhaust chamber 10, and the sample replacement chamber 11, Residual gas in the room can be measured and the condition can be monitored.

  An example in which a residual gas measuring device is attached to the preliminary exhaust chamber will be described below. In a semiconductor measurement / inspection apparatus, there is a preliminary exhaust chamber (hereinafter also referred to as a load lock chamber) for pre-exhausting the atmosphere around the sample introduced into a vacuum chamber (sample chamber) for measuring and inspecting the sample. Often provided. If the above-described measuring device is attached to the preliminary exhaust chamber and the gas analysis is performed, the gas analysis can be performed in the normal measurement and inspection process.

  The load lock chamber is for making the atmosphere around the sample into a vacuum state before introducing the sample into the sample chamber. By providing such an exhaust chamber, the sample chamber can be broken without breaking the vacuum in the sample chamber. Samples can be brought into and out of the chamber. In other words, since the load lock chamber is a chamber that is evacuated each time a sample is introduced, a mass spectrometer is attached to the exhaust system of the load lock chamber, so that the normal load lock chamber exhaust process can be performed. It becomes possible to carry out gas analysis.

  With the configuration described above, it is possible to monitor degassing from the sample in particular. For example, when performing residual gas measurement during evacuation performed each time a sample is loaded, if a residual gas of a predetermined value or more is detected when a specific sample is introduced, it indicates that the presence of the sample. It can be determined that the residual gas is caused by the above. Further, in the present embodiment, the exhaust time increases as compared with the case where the measurement is performed by reducing the opening of the variable valve and performing the residual gas measurement. Therefore, not every sample, but every predetermined unit (for example, every number of semiconductor device units), every wafer cassette of a semiconductor wafer, every manufacturing lot of a semiconductor device, every predetermined time, every predetermined number of days, every kind of semiconductor device Alternatively, the residual gas measurement can be performed without delaying the exhaust time by configuring the residual gas measurement every semiconductor device manufacturing process or the like.

  Furthermore, even when a gas component is attached to the sample, when the amount is very small, not only the measurement of each sample but also the transition of the measurement result may be recorded. . By recording the transition of the gas measurement results, for example, a small amount of gas components adhering to the sample gradually adheres to the load lock chamber, and as a result, a large amount of gas is detected. It is possible to identify the cause of whether a large amount of gas components adhere to the result.

  By grasping such a transition, it is possible to properly set the maintenance timing of the apparatus, and it is possible to eliminate the unexpected immobility time of the apparatus. More specifically, as shown in FIG. 8, it is possible to identify the cause of residual gas generation by creating a graph with the horizontal axis as a predetermined unit of the sample and the vertical axis as the gas measurement value. . FIG. 8 illustrates an example in which the horizontal axis indicates the sample cassette and the vertical axis indicates the gas measurement value. In the example of FIG. 8, the amount of gas B increases rapidly in the cassette 5, and in the cassette 6, the amount of gas B has almost returned to the original value, so that the gas B becomes a sample contained in the cassette 6. It can be estimated that there is a cause. Also, the unit of the horizontal axis can be switched, or multiple units are displayed in a superimposed manner, so whether there is a gas generation factor in the single sample, whether there is residual gas in one cassette, or a certain semiconductor process itself It becomes easy to specify the cause, such as whether there is a gas adhesion factor.

  In the example of FIG. 8, a graph is used as the display format of the gas measurement value. However, the present invention is not limited to this, and may be expressed in, for example, a table format as long as the transition of the measurement value can be understood. . This also applies to the embodiments described later.

  The vacuum chamber 1, the vacuum evacuation device 2, the variable valve 3, the mass spectrometer 4 and the like in FIG. 1 perform predetermined operations by signals supplied from a control device (not shown) and are further transmitted from these components. The signal is stored in a storage medium in the control device, and the measurement value is displayed as described above. A scanning electron microscope, which is one application example of the vacuum chamber of FIG. 1, is connected to a display device for displaying a scanned image, and the measurement value can be displayed on the display device.

  The control device supplies the variable valve 3 with a signal for performing opening / closing control of the variable valve when performing gas measurement. As described above, when the variable valve 3 is throttled, the exhaust time is delayed as compared with the case where the variable valve 3 is not throttled. Therefore, control by the control device for the variable valve is performed so that the variable valve is selectively throttled and exhausted only when gas measurement is performed. The control device can also manage data as follows.

  FIG. 9 is a diagram for explaining an example in which a length measurement value obtained by a scanning electron microscope (SEM) and a transition of a gas measurement amount are superimposed and displayed. Among SEMs, an apparatus called CD-SEM (Critical Dimension-SEM) detects electrons emitted from a sample based on scanning of the electron beam with respect to the sample, and measures a pattern dimension based on the electrons. The pattern dimension is measured, for example, by forming a line profile indicating a change in luminance from an image formed based on detected electrons and measuring the length between the peaks of the line profile.

  As described above, since the residual gas may be solidified when it is irradiated with the electron beam, the pattern dimension value may change depending on the solidified substance. In other words, the dimensional measurement value of the apparatus is correct, but the dimensional value for properly evaluating the semiconductor process is a value with an error. Furthermore, it is difficult to determine whether such a dimensional value change is due to residual gas adhesion or due to process variation that is the original measurement target.

  As illustrated in FIG. 9, if the transition of the gas measurement value and the change in the measurement value are displayed in a superimposed manner, it is possible to determine whether or not the dimension value has changed due to gas adhesion. At first glance, even though the dimensional value seems to change only slowly, it is increased to link with the gas increase amount by comparing with the gas measurement value, or linked with the change of gas measurement value. It is possible to estimate that the variation of the pattern is not caused by the variation of the process or the like but is changed depending on the adhered gas when the pattern variation is caused. In the present embodiment, since the gas measurement is performed in the same vacuum atmosphere as the apparatus that performs the pattern measurement, the relationship with the pattern dimension measurement value can be accurately grasped. In the example of FIG. 9, the vertical axis of the graph is the ratio between the pattern measurement result by CD-SEM and the value (the ideal dimension of the pattern) derived from the design data of the pattern. For example, an actual measurement value may be used.

  Further, by monitoring the transition of the measured gas value as shown in FIGS. 8 and 9, the gas component gradually accumulates, so that maintenance of the apparatus is required in the future, or a sample with a large amount of degassing is required. The difference can be judged whether it was just introduced. In this case, for example, if a message indicating that maintenance is required is issued when the change in the measured gas value with respect to the displacement amount in a predetermined unit exceeds a predetermined value, the manager of the apparatus can receive the message at an appropriate time. It is possible to plan to perform maintenance.

  The control device described above performs pattern dimension measurement, gas measurement, and data management thereof based on a program that executes data management as described above. The gas measurement value may be a statistical value for each predetermined unit or a representative value.

  The display examples in FIGS. 8 and 9 are intended for the load lock chamber, but can naturally be applied to other vacuum chambers.

  FIG. 10 is a flowchart for explaining the operation process of each component in the load lock chamber to which the mass spectrometer is connected. Unlike the sample chamber, the load lock chamber is a chamber that is once opened to the atmosphere, so it is not always necessary to control the exhaust speed with a variable valve. However, a richer gas component is more accurate depending on the situation. Can be expected. Therefore, in the flowchart of FIG. 10, as in the case of the gas component measurement for the sample chamber, a method for detecting the gas component by reducing the exhaust speed will be described as an example.

  First, the gate valve on the atmosphere side of the load lock chamber is opened ((1)). Next, the sample is loaded ((2)), and the opened gate valve is closed ((3)). Next, it is determined whether or not to perform gas measurement ((4)). Necessity of execution of gas measurement is set in advance by a recipe or the like registered in a control device or the like, and in this step, necessity of gas measurement is determined based on the setting. Next, when gas measurement is not required, the variable valve is fully opened ((6)) and then evacuated by a vacuum pump ((8)). On the other hand, when carrying out gas measurement, a predetermined amount of the variable valve is opened ((5)), and then evacuation by a vacuum pump is started ((7)).

  In terms of shortening the evacuation time, it is desirable to perform evacuation after fully opening the variable valve (or increasing the opening relative to the time of gas measurement). By reducing the vacuum exhaust conductance of the side space, the opening degree is limited in order to form an environment in which it is difficult to be temporarily exhausted (the valve is closed compared to the case where gas measurement is not performed). According to such control, it is possible to measure the residual gas or the like with high accuracy and without significantly reducing the time for evacuation.

  After starting evacuation, gas analysis is performed by the mass spectrometer 4 ((9)). After the preliminary exhaust is completed, the gate valve on the sample chamber side is opened ((10)), and the sample is carried out ((11)).

  Charged particle beam equipment has a function to capture and record measured values obtained by the above-mentioned residual gas measurement method in a charged particle beam device, display them on an operation screen, etc., and issue an alarm when an arbitrarily set threshold value is exceeded. The state of the apparatus can be monitored by automatically performing the measurement operation before and after the sample measurement or at an arbitrarily set time or time interval. Further, if measurement is performed at an arbitrary timing before and after the apparatus maintenance work, it can be used for maintenance and management of the apparatus performance.

  Although the example in which the variable valve 3 is disposed between the space to be evacuated and the evacuation device has been described so far, in this configuration, the evacuation speed of the evacuation device is equivalent to the amount of the variable valve installed. Decreases. Therefore, a configuration example for suppressing the decrease will be described below.

  FIG. 2 is a diagram for explaining an example in which the variable valve is disposed between the vacuum chamber 1 and the mass spectrometer 4. The vacuum chamber 1 is evacuated by the evacuation device 2.

  A mounting tube 5 having a mass spectrometer 4 for measuring residual gas is attached to the vacuum chamber 1 via a variable valve 3 whose opening degree can be controlled. In such an apparatus configuration, when the variable valve 3 is fully opened and the evacuation apparatus 2 performs evacuation, the inside of the vacuum chamber 1 and the attachment pipe 5 is almost the same vacuum atmosphere.

  The gas remaining in the space of the mounting tube 5 to which the vacuum chamber 1 and the mass spectrometer 4 are attached is the gas released from its inner wall and the original atmospheric component gas remaining without being exhausted. Measurement can be performed by the analyzer 4. If there is a part built in the vacuum chamber 1, the gas released by this part can also be measured by the mass spectrometer 4.

  According to the configuration example shown in FIG. 2, when performing measurement using the mass spectrometer 4, the residual gas in the attachment tube 5 to which the mass spectrometer 4 is attached is exhausted by reducing the opening of the variable valve 3. Make it harder. As a result, the molecular density of the residual gas in the mounting tube 5 is increased, and it is possible to achieve high sensitivity of residual gas measurement by the mass spectrometer 4.

  A display example of the gas measurement value obtained as described above will be described with reference to FIG. According to the display example illustrated in FIG. 3, it is possible to monitor and manage the state of residual gas in the apparatus. The display part of the display screen may be a display device provided in the operation / control device of the mass spectrometer or a display device provided in the entire operation panel of the vacuum system to be attached.

FIG. 3 illustrates a display example of measured values acquired by the apparatus configuration shown in FIG. A horizontal axis arranges the gas of the mass number measured with the mass spectrometer. FIG. 3 shows three kinds of gas A, gas B, and gas C arbitrarily determined, and the vertical axis represents the value of each gas and is a bar graph. A threshold value can be arbitrarily set for each gas, and an alarm is generated when the threshold value is exceeded. The type of gas can be arbitrarily set, and the sum of a plurality of gases can be handled as one gas. For example, the gas A is a hydrocarbon gas [(CH ₄ : mass number 16) + (C ₂ H ₆ : mass number 30) +...]], And the gas B is a fluorine gas [(CF: mass number 31) + (CF ₃ : Mass number 69+...

  FIG. 5 shows a configuration example in which a vacuum gauge and a mass spectrometer are used together. In the configuration example illustrated in FIG. 5, in addition to the configuration illustrated in FIG. 2, an upstream vacuum gauge 33 and a downstream vacuum gauge 34 are provided on the mass spectrometer 4 side and the vacuum chamber 1 side of the variable valve 3, respectively. This makes it possible to quantify the gas amount. If the values indicated by the two vacuum gauges are calibrated, the discharge gas amount Q passing through the variable valve 3 can be calculated by the equation (1) based on the conductance obtained from the opening degree of the variable valve 3.

Q = (P ₁ −P ₂ ) × C (1)
(However, Q: amount of released gas, P ₁ : upstream pressure, P ₂ : downstream pressure, C: conductance)
The downstream vacuum gauge 34 in FIG. 5 can be replaced with a vacuum gauge that measures the pressure in the vacuum chamber 1.

  The device has a function to automatically record and display the amount of released gas obtained in this way, and the state of residual gas in the device can be quantified by issuing an alarm when the threshold value is exceeded as shown in the second embodiment. Can be monitored and managed automatically.

  Although not shown, a mass spectrometer is separately added on the downstream side of the variable valve 3, and the value measured by calibrating the absolute value together with the mass spectrometer 4 is converted into pressure, and the equation (1) If it is applied, it becomes possible to obtain | require the quantity which the gas of each mass number passes through the variable valve 3. FIG.

For example, when attention is paid to siloxane, the silicon-based gas is represented by mass numbers 73 and 146, and expressed as P _Si = (pressure of mass number 73) + (pressure of mass number 146), the upstream side is P1 _Si and the downstream side. side of the silicon-based gas passing through the P2 _Si Tosureba variable valve 3 may be Q _Si = quantification and _{(P1 Si -P2 Si) × C} (Pa · m 3 / s). Further, if Q _Si is divided by the Boltzmann constant k and the absolute temperature T, it can be converted into a gas molecular weight per unit time. n _Si (pieces / sec) = Q _Si / k · T Displaying in this way makes it easier for the user who manufactures the semiconductor device to monitor the apparatus state.

  FIG. 6 shows a configuration example in which a gas trap and a mass spectrometer are used together. The present embodiment aims to further increase the sensitivity of residual gas analysis. For this purpose, as shown in FIG. 6, a gas trap 35 that adsorbs and captures residual gas is added between the variable valve 3 and the mass spectrometer 4.

  The gas trap 35 is provided with a cooling means to enable gas adsorption. As the cooling means, a pipe through which a refrigerant passes may be provided, or the gas trap surface may be cooled by heat conduction. Alternatively, there is a method using a Peltier element. In this embodiment, after starting evacuation with the variable valve 3 fully opened, the gas trap 35 is operated to adsorb the residual gas. When measuring the residual gas with the mass spectrometer 4, the variable valve 3 is throttled, and then the cooling of the gas trap 35 is stopped. Since the temperature of the gas trap 35 that has stopped cooling rises, the adsorbed gas is desorbed. For this reason, it is possible to measure the residual gas with higher sensitivity than the method shown in the second embodiment.

  The gas trap 35 may be a gas trap having a function for forcibly desorbing the adsorbed gas. Heating is a method for desorption, and it is simple to provide a heater as a means. is there. In this method, assuming that the gas passing through the variable valve 3 is all released by the gas trap 35, the amount of released gas per unit area of the gas trap 35 from the area of the adsorption surface of the gas trap 35 and the equation (1). The released gas velocity can be calculated by equation (2).

q = (P ₁ −P ₂ ) × C / A (2)
(However, q: discharge gas velocity, P ₁ : upstream pressure, P ₂ : downstream pressure, C: conductance, A: gas adsorption area of gas trap)
As for the release gas velocity, as described in Example 3, if a vacuum gauge that measures the total pressure is used, the release gas velocity of all the gases is obtained, and if the result measured by the mass spectrometer is used, The outgassing rate can be indicated. A device with higher sensitivity can be obtained by providing a function for automatically recording and displaying the value obtained in this way, and generating an alarm when a threshold value is exceeded as described in the second embodiment. Can be monitored.

  Further, as a means for increasing the adsorption amount of the gas trap 35, there is a method using activated carbon as an adsorbent. A powdery adsorbent may be applied to the gas adsorption surface, or a plate-like adsorbent may be applied to the adsorption surface. In this case, the adsorption area of the gas trap may be calculated from the geometrical dimensions of the shape, and the actual surface area of the porous activated carbon may be taken into account.

  FIG. 7 shows a probe portion of the analyzer, taking a quadrupole mass spectrometer as an example. The probe of the mass spectrometer is composed of a quadrupole 36 and an ion source 37, and is generally attached using the attachment tube 5 or the like so that the probe does not protrude into the vacuum chamber. In the combination of the mass spectrometer 4 and the variable valve 3 shown in (Embodiment 2), the variable valve 3 is attached using the attachment pipe 5 that is arranged so that the quadrupole 36 and the ion source 37 do not touch the valve valve. The inner wall of the attachment pipe 5 may be a surface for adsorbing residual gas, or the attachment pipe 5 having a function of adsorbing residual gas may be used. Further, irregularity may be formed on the inner wall of the attachment tube 5 to increase the adsorption area.

  Hereinafter, other application examples of gas measurement will be described. The gas released from the sample is measured by comparing the residual gas before and after the sample measurement or by measuring the residual gas measurement during the sample measurement. For example, in a charged particle beam device for semiconductors, the gas emitted from the wafer to be measured is measured, the value of the gas released from the wafer that has undergone the same manufacturing process is recorded and the deviation from the average value is calculated, and the amount of deviation If the apparatus has a function of issuing an alarm when the value deviates from an arbitrarily set allowable value, it is possible to know the abnormality of the wafer from the viewpoint of the released gas, and to find defects in other processes.

  As described above, by reducing the evacuation conductance in the mass spectrometer, an environment in which the residual gas is difficult to be exhausted is formed, and highly sensitive residual gas measurement can be performed. Furthermore, it is possible to provide a charged particle beam apparatus having a function of accurately monitoring the apparatus state by performing highly sensitive analysis.

The figure explaining an example of the vacuum device which installed the variable valve between the vacuum chamber and the vacuum exhaust apparatus. The figure explaining an example of the vacuum device which installed the variable valve between the vacuum chamber and the gas component measuring apparatus. The figure explaining the example of a display of a gas measurement result. The schematic block diagram of a scanning electron microscope. The figure explaining an example of the vacuum device which installed the vacuum gauge before and behind the variable valve. The figure explaining an example of the vacuum device which installed the gas trap between the variable valve and the gas component measurement apparatus. The figure explaining the example which made the attachment pipe inner surface of a quadrupole mass spectrometer the gas trap. The figure explaining the example of a display which shows transition of the gas measurement value with respect to the change of a predetermined sample unit. The figure explaining the example of a display which shows transition of the gas measurement value and pattern dimension with respect to the change of a predetermined sample unit. The flowchart explaining the flow of a process in the case of implementing gas measurement in a load lock chamber.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Vacuum exhaust apparatus 3 Variable valve 4 Mass spectrometer 5 Attachment tube 6 Electron gun chamber 7 Condenser lens chamber 8 Sample chamber 9 Intermediate chamber 10 Preliminary exhaust chamber 11 Sample exchange chamber 12 Electron gun 13 Extraction electrode 14 Acceleration electrode 15 Fixation Diaphragm 16 Condenser lens 17 Deflection coil 18 Objective lens 19 Objective lens iris 20 Sample holder 21 Sample 22, 23 Gate valve 24-28 Vacuum pump 29 Electron beam 30 Secondary electron or reflected electron 31 Reflected electron / secondary electron detector 32 Exhaust Bypass 33 Upstream vacuum gauge 34 Downstream vacuum gauge 35 Gas trap 36 Quadrupole 37 Ion source section

Claims (9)

In a vacuum apparatus comprising a vacuum chamber and a vacuum exhaust device connected to the vacuum chamber and exhausting the vacuum chamber at a predetermined exhaust speed,
A gas component measuring device that measures the gas component in the vacuum chamber; and a control device that controls the exhaust time of the vacuum exhaust device, the control device, when the gas component measurement by the gas component measuring device is performed, A vacuum apparatus characterized by lowering an exhaust speed by the vacuum exhaust apparatus. In claim 1,
A variable valve is provided between the vacuum chamber and the vacuum exhaust device, and the control device compares the opening of the variable valve with the predetermined exhaust speed when measuring the gas component. The vacuum device is characterized by being controlled so as to be squeezed. In claim 1,
A variable valve is provided between the vacuum chamber and the gas component measuring device, and the control device determines the opening of the variable valve when the gas component is measured at the predetermined exhaust velocity. A vacuum apparatus characterized by controlling to squeeze in comparison. In claim 3,
A first vacuum gauge connected between or between the vacuum chamber and the variable valve; and a second vacuum gauge connected between the variable valve and the gas component measuring device. The control device calculates a gas amount based on a pressure difference between the first and second vacuum gauges. In claim 3,
A vacuum apparatus, wherein a gas trap is connected between the variable valve and the gas component measuring device. In claim 1,
The control device generates a signal to that effect when a measured value by the gas component measuring device exceeds a predetermined value. In a charged particle beam apparatus comprising a charged particle source and a sample chamber surrounding a sample irradiated with charged particles emitted from the charged particle source,
A gas component measuring device for detecting a gas component in a vacuum space surrounding the sample is provided, and a display device for displaying a transition of a measurement result by the gas component measuring device with respect to a change in a predetermined unit of the sample. A charged particle beam device. In claim 7,
A charged particle beam apparatus characterized by displaying information on a measured value of a pattern on the sample obtained by irradiating the sample with a charged particle beam along with the transition of the measurement result. In a gas component measurement method for measuring a gas component in a vacuum chamber to which a vacuum exhaust device that performs vacuum exhaust at a predetermined exhaust speed is connected,
A gas component measuring method, wherein when the gas component in the vacuum chamber is measured by a gas component measuring device, the exhaust speed is lowered from the predetermined speed.

Images