JP2000097912A - Surface analyzing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an apparatus for analyzing surface by laser-induced temperature rise desorption which can start measuring in a short time after a sample is set and is compact in total constitution. SOLUTION: A laser 7 and a mass spectrograph 5 constituting the surface- analyzing apparatus which utilizes an induced temperature rise desorption of adhering substances by the laser 7 radiating a laser light toward a sample 2 are arranged in series and set so that the laser light is radiated through an ion source 8 to the sample 2. At the same time, a means for differentially exhausting the mass spectrograph 5 to a sample chamber 1 is set. Since the mass spectrograph 5 is differentially exhausted with respect to the sample chamber 1, the sample 2 can be exchanged in a state while the mass spectrograph 5 is kept in high vacuum. Since not a high degree of vacuum is required for the sample chamber 1, it is enough to rough the sample chamber 1 for several minutes after the sample 2 is exchanged and open a gate valve 4 set between the sample chamber 1 and a mass spectrographic chamber 3 after the roughing. Accordingly, various kinds of samples 2 can be measured in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface analyzer, and more particularly, to a downsized surface analyzer by laser-induced thermal desorption for analyzing a substance attached to a surface in a semiconductor device manufacturing process or the like. Arrangement structure, and
The present invention relates to a surface analyzer characterized by a configuration for reducing a waiting time for evacuation after sample setting.

[0002]

2. Description of the Related Art In recent years, the miniaturization of semiconductor devices such as IGFETs (insulated gate field effect transistors) has been unavoidable. In the manufacturing process of such semiconductor devices, deposits adhering to the wafer surface, for example, corrosion ( The analysis of deposits such as Cl (chlorine) which causes corrosion is indispensable for improving the stability and the production yield of the semiconductor device manufacturing process.

Conventionally, such an analysis of the deposits on the wafer surface has been carried out using a device requiring an ultra-high vacuum atmosphere such as a thermal desorption method using substrate heating or an X-ray photoelectron spectroscopy. Therefore, it is necessary to take out a sample to be analyzed from the production line and perform analysis using a dedicated analyzer. Therefore, it took several hours and much effort to identify the cause of the manufacturing process from which the deposit on the wafer surface originated.

In recent years, in order to analyze such attached matter on the wafer surface locally, in a short time and with high sensitivity, the wafer is heated by laser induction to detach the attached matter. Has been developed by laser thermal desorption which can identify the deposits by analyzing with a mass spectrometer. Here, referring to FIG. The surface analyzer will be described.

FIG. 6 is a schematic configuration diagram of a conventional surface analyzer. This surface analyzer includes a sample chamber 31 for storing a sample 32 to be analyzed and a mass for storing a mass analyzer. The sample chamber 31 includes a plurality of ports 34 serving as ports for observation or for taking in / out of a sample or a processing material gas.
One of the ports is used as an exhaust port 33, and the sample chamber 31 is connected through the exhaust port 33.
Is connected to a turbo-molecular pump and is evacuated to a degree of vacuum of 10 ^-4 Torr or more. In this specification, “10
^-4 Torr or higher vacuum ”is 10 ^-6 T
It means a degree of vacuum higher than 10 ^-4 Torr such as orr.

On the other hand, in the mass spectrometry chamber 35, a quadrupole type mass comprising an ion source 36 for ionizing a substance 41 desorbed from the sample 32 by electron impact, a quadrupole 37, and an ion detector 38 is provided. An analyzer is provided, and a laser light source 39 such as a YAG laser is
Is arranged.

[0007] The analysis principle of this surface analyzer will be briefly described. The surface of a sample 32 is locally heated by a laser beam 40 emitted from a laser light source 39, and the substance attached to the surface of the sample 32 is heated. A part of the desorbed substance 41 is scattered in the direction of the mass spectrometry chamber 35, is ionized in the ion source 36, and is simultaneously ionized by the applied bias. Is taken into the quadrupole 37, and only the substance type having a mass number corresponding to a predetermined applied bias to the quadrupole 37 is detected by the ion detection unit 38. That is, by changing the bias applied to the quadrupole 37, the analysis is performed with only the target species having a specific mass number as the target.

As a surface analyzer using such laser irradiation, a surface analyzer having another configuration has been proposed. For example, a sample is irradiated with an ultraviolet laser beam to remove substances adhering to the sample surface. It is proposed to directly ionize and perform mass spectrometry on the ionized substance (if necessary, see Japanese Unexamined Patent Publication No.
290732). In this proposal, the laser beam is irradiated from the direction of the mass analyzer.

[0009]

However, in a conventional surface analyzer using a laser beam, it is necessary to maintain the mass analyzer in a high vacuum state in order to measure the desorbed species with high sensitivity. Therefore, every time the sample is exchanged, it is necessary to evacuate the entire sample chamber system including the mass spectrometry chamber for several hours, and there is still a problem that much time is required for measurement.

In the above-described surface analysis apparatus using laser-induced thermal desorption shown in FIG. 6, it is important to align the laser light source, the sample, and the mass spectrometer. However, this alignment is not easy. As shown in the figure, a port for attaching the mass spectrometer and a port for irradiating the laser beam, that is, an irradiation window are required separately, so that the space in front of the sample is occupied at a considerable ratio, which is convenient. There is a problem that it is not an analyzer that can be used.

Therefore, an object of the present invention is to provide a surface analysis apparatus by laser-induced thermal desorption that can start measurement in a short time after setting a sample and has a compact overall configuration.

[0012]

FIG. 1 is an explanatory view of the principle configuration of the present invention. Referring to FIG. 1, means for solving the problems in the present invention will be described. See FIG. 1. (1) The present invention relates to a surface analyzer using laser-induced thermal desorption of attached matter by irradiating a sample 2 with a laser beam, in which a laser 7 and a mass analyzer 5 are arranged in series. A laser beam is set to be irradiated on the sample 2 through the ion source 8, and a means for differentially exhausting the mass spectrometer 5 to the sample chamber 1 is provided.

As described above, since the mass spectrometer 5 is differentially evacuated to the sample chamber 1, the sample 2 can be exchanged while the mass spectrometer 5 is maintained at a high vacuum. Room 1
Since the degree of vacuum does not require a very high vacuum, the sample chamber 1 after exchanging the sample 2 only needs to be roughed for a few minutes, and after roughing, the space between the sample chamber 1 and the mass spectrometry chamber 3 is obtained. It is only necessary to open the provided gate valve 4, and therefore,
Various samples 2 can be measured in a short time. In this case, the “ion source 8” means a portion that ionizes the desorbed species by electron impact.

Further, since the laser 7 and the mass analyzer 5 are arranged in series and the laser beam is irradiated on the sample 2 through the ion source 8, it is provided in the sample chamber 1 for the measurement system. Since only one of the ports is occupied, the overall configuration of the analyzer can be made compact, and
Since the optical axis of the laser beam and the mass spectrometer 5 are previously arranged coaxially in series, accurate alignment is not required.

(2) In the present invention, in the above (1), the mass analyzer 5 is a quadrupole mass analyzer, and the longitudinal direction of the quadrupole 6 is orthogonal to the irradiation direction of the laser beam. It is characterized by being arranged so that it may be.

As described above, by using a quadrupole mass spectrometer as the mass spectrometer 5, the presence or absence of a desorbed species having a specific mass number can be measured in a short time.
The quadrupole 6 may be arranged so that its longitudinal direction is orthogonal to the direction of laser light irradiation. In this case, the length of the device in the direction along the optical axis of the laser light should be reduced. Can be.

(3) In the present invention, in the above (1), the mass analyzer 5 is a quadrupole mass analyzer, and the longitudinal direction of the quadrupole 6 is parallel to the irradiation direction of the laser beam. And the laser beam is applied to the sample 2 through a quadrupole mass spectrometer.

As described above, when a quadrupole mass analyzer is used as the mass analyzer 5, the quadrupole 6 is arranged so that its longitudinal direction is parallel to the laser beam irradiation direction. In this case, all the longitudinal directions are along the optical axis of the laser beam, so that the area occupied by the space near the port can be reduced.

In this case, since the ion source 8 can be separated from the mass analyzer 5 and can be brought closer to the surface of the sample 2, the solid angle with respect to the sample 2 to be analyzed can be increased. Thereby, the detached species can be captured with higher sensitivity.

(4) In the present invention, in the above (1), the mass analyzer 5 is a time-of-flight mass analyzer, and the longitudinal direction of the flight tube is parallel to the irradiation direction of the laser beam. And the sample 2 is irradiated with the laser beam through the flight tube.

As described above, a time-of-flight mass spectrometer may be used as the mass spectrometer 5. In this case,
Compared to the case where a quadrupole mass spectrometer is used, the configuration of the entire apparatus becomes simpler, and desorbed species having different mass numbers can be simultaneously measured. In this case as well, it becomes possible to separate the ion source 8 from the mass spectrometer 5 and bring it closer to the surface of the sample 2.

(5) The present invention is characterized in that, in any one of the above (1) to (4), the laser 7 is provided with means for changing the wavelength.

As described above, by making the wavelength of the laser 7 variable using, for example, a second harmonic generation device or the like,
It is possible to separate and analyze the deposits attached to the surfaces of different materials in the sample 2.

(6) Further, the present invention is characterized in that in any one of the above (1) to (5), a scanning reflector for scanning a laser beam is provided.

As described above, the distribution of the deposits on the surface of the sample 2 can be measured by scanning the surface of the sample 2 with the laser beam irradiated on the sample 2 by the scanning reflecting mirror.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, referring to FIG. 2 to FIG. 5, a surface analysis apparatus by laser-induced thermal desorption according to each embodiment of the present invention will be described. Next, a first embodiment of the present invention will be described. FIG. 2 is a schematic configuration diagram of a surface analyzer by laser-induced thermal desorption according to the first embodiment of the present invention. This surface analyzer has a sample chamber 11 containing a sample 12 and a sample chamber 11. , A mass spectrometry chamber 15 accommodating a quadrupole mass spectrometer 18, the sample chamber 11 and the mass spectrometry chamber 15 are connected via a gate valve 16, and the mass spectrometry chamber 15 Beak isolation valve 17 with small orifice
A laser light source 22 made of a YAG laser is provided through a window at a port provided at the other end of the mass spectrometry chamber 15. As the laser light source 22, any of a pulse laser and a continuous wave laser may be used.

This quadrupole mass analyzer 18 is an ion source 1 that ionizes and accelerates desorbed species by electron impact.
9. Detection of the quadrupole 20 to which a predetermined electric field corresponding to the mass number of the desorbed species to be measured is applied to the ionized desorbed species, and the presence or absence of the set mass number of the desorbed species. And a multi-channel plate-type ion detector 21.

In the first embodiment,
The quadrupole mass analyzer 18 is arranged so that the longitudinal direction of the quadrupole 20 is orthogonal to the irradiation direction of the laser light indicated by the arrow in the figure, and the laser light from the laser light source 22 passes through the ion source 19. Thus, the sample 12 is irradiated. An ion source 1 for ionizing desorbed species by electron impact
9 has the same configuration as a hot cathode using a filament, a grid, and the like, and does not hinder the transmission of laser light.

The sample chamber 11 is provided with an exhaust port 13, and the sample chamber 11 is evacuated to a degree of vacuum of 10 ⁻³ Torr or more by a turbo-molecular pump connected through the exhaust port 13. A plurality of ports 14 are provided in the sample chamber 11, and a mass spectrometry chamber 15 is attached using one of these ports.

The mass spectrometry chamber 15 is kept in a higher vacuum state than the sample chamber 11 by separately evacuating by a turbo molecular pump, and the quadrupole mass spectrometer 18
The gas itself is separately evacuated by an ion pump to maintain an ultra-high vacuum of 10 ⁻⁷ Torr or more.

As described above, since the sample chamber 11, and the quadrupole mass spectrometer 18 and the mass spectrometry chamber 15 are set to be independently evacuated, differential exhaust can be performed. When the sample 12 is replaced, the gate valve 16 is closed, the sample 12 is replaced while the quadrupole mass spectrometer 18 and the mass spectrometry chamber 15 are kept in a high vacuum, and the sample 12 is set. The sample chamber 11 is evacuated for several minutes to 10 ^-3 To
The degree of vacuum may be set to rr or more, for example, 10 ^-4 Torr. After the evacuation, the measurement can be started by opening the gate valve 16.

That is, the sample chamber 1 after setting the sample 12
The degree of vacuum of 1 is such that the mean free path of the desorbed species is smaller than the distance between the sample 12 and the small hole at the tip of the beak-shaped isolation valve 17 so that the desorbed species is not scattered by other gas molecules. It is sufficient if the degree of vacuum is so large that the sample 12
Although it depends on the distance to the small hole at the tip of the beak-shaped isolation valve 17, the degree of vacuum of 10 ^-3 Torr or more, for example, 1
Since the pressure may be set to about 0 ^-4 Torr, the time from the replacement of the sample 12 to the start of the measurement may be about several minutes, and the waiting time for evacuation can be greatly reduced as compared with the related art.

When measuring, the laser light source 22
Source 19 and beak-shaped isolation valve 1
7, the surface of the sample 12 is irradiated through the small hole at the tip of the sample 7, and the surface of the sample 12 is heated by the irradiation.
The desorbed species is introduced into the quadrupole mass spectrometer 18 through the small hole at the tip of the beak-shaped isolation valve 17 without being scattered by other gas molecules, ionized by the ion source 19 and then quadrupole 20
Is detected by the ion detection unit 21 via.

In the first embodiment,
Since the quadrupole mass spectrometer 18 is used as the mass spectrometer, the presence or absence of a desorbed species having a specific mass number can be measured in a short time. Since the light source 22 and the light source 22 are arranged in series along the irradiation direction of the laser light indicated by the arrow in the drawing, one port may be used for the measurement system, and the occupation ratio of the space in front of the sample is reduced. Further, since the longitudinal direction of the quadrupole 20 constituting the quadrupole mass analyzer 18 is arranged so as to be orthogonal to the irradiation direction of the laser beam, the measurement system along the laser optical axis , The overall configuration of the device can be made compact.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic configuration diagram of a surface analyzer by laser-induced thermal desorption according to the second embodiment of the present invention. The surface analyzer of the first embodiment described above includes: The arrangement state of the quadrupole mass analyzer 18 and the ion detector 21
And other configurations are only slightly different, so that the description of the exhaust system and the like is omitted. This surface analyzer comprises a sample chamber 11 containing a sample 12 and a mass spectrometry chamber 15 containing a quadrupole mass analyzer 18. The sample chamber 11 and the mass spectrometer 15 are connected via a gate valve 16. The mass spectrometry chamber 15 is connected to the sample chamber 11 by a beak-shaped isolation valve 17 having a small hole at the end, and a port is provided at the other end of the mass spectrometry chamber 15. A laser light source 22 composed of a YAG laser is provided through the light source.

In this case, the quadrupole mass analyzer 18 is arranged so that the longitudinal direction of the quadrupole 20 is parallel to the irradiation direction of the laser beam, and accordingly, the ion detection unit 21 is also provided with the laser beam. Is provided at the center of the multi-channel plate, and the laser light from the laser light source 22 passes through the small hole 23, the quadrupole 20, and the ion source 19 provided in the ion detector 21. The sample 12 passes through and irradiates the sample 12.

In the second embodiment,
Since the ion source 19 is separated from the quadrupole mass analyzer 18 and disposed in the space between the gate valve 16 and the beak-shaped isolation valve 17, the distance between the ion source 19 and the sample 12 can be reduced. So that sample 12, and thus,
Since the solid angle of the ion source 19 with respect to the desorbed species is increased, the desorbed species desorbed from the sample 12 can be captured with higher sensitivity.

In the second embodiment,
Since the quadrupole mass spectrometer 18 is arranged so that the longitudinal direction of the quadrupole 20 is parallel to the irradiation direction of the laser beam, the occupancy ratio of the space near the port is determined according to the first embodiment. It can be smaller than the form. However, the length of the device configuration of the measurement system in the direction along the optical axis of the laser light becomes longer.

In the above description of the second embodiment, the ion source 19 is separated from the quadrupole mass analyzer 18 and arranged in the space between the gate valve 16 and the beak-shaped isolation valve 17. However, it is not essential, and may be provided close to the quadrupole 20 as in the first embodiment.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic configuration diagram of a surface analysis apparatus using laser-induced thermal desorption according to a third embodiment of the present invention, and shows a scanning for scanning a laser beam along the surface of a sample 12. Mirror 2
Since the configuration is the same as that of the surface analyzer of the above-described first embodiment except that 4 is provided, the description of the exhaust system and the like is omitted. This surface analyzer is a sample chamber 1 containing a sample 12.
1 and a mass spectrometer 15 containing a quadrupole mass analyzer 18
The sample chamber 11 and the mass spectrometry chamber 15 are connected via a gate valve 16. The mass spectrometry chamber 15 is connected to the sample chamber 1 by a beak-shaped isolation valve 17 having a small hole at the end.
1, a scanning mirror 24 is provided in the space on the other end side of the mass spectrometry chamber 15, and the laser light source 2
2 is arranged so that its optical axis is substantially orthogonal to the direction of laser beam irradiation.

In this case, the laser beam from the laser light source 22 is deflected by approximately 90 ° by the scanning mirror 24 and the scanning mirror 24 is rotated within a predetermined angle range, thereby scanning the laser beam on the surface of the sample 12. That is, by scanning with a laser beam, it becomes possible to measure the distribution of the deposits on the surface of the sample 12 on the sample surface.

Further, in the third embodiment,
The quadrupole 20 constituting the quadrupole mass analyzer 18 is arranged so that the longitudinal direction is orthogonal to the laser light irradiation direction, and the longitudinal direction of the laser light source 22 is also orthogonal to the laser light irradiation direction. The length of the device configuration of the measurement system along the laser beam irradiation direction can be further reduced.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic configuration diagram of a surface analyzer by laser-induced thermal desorption according to a fourth embodiment of the present invention, except that a time-of-flight mass analyzer 25 is used as a mass analyzer. Are the same as those in the above-described second embodiment, so that the description will be simplified. This surface analyzer comprises a sample chamber 11 containing a sample 12 and a mass spectrometer chamber 15 containing a time-of-flight quality analyzer 25. Connected to the mass spectrometer 15
Is separated from the sample chamber 11 by a beak-shaped isolation valve 17 having a small hole at the tip. A laser light source 22 composed of a YAG laser is provided through a window at a port provided at the other end of the mass spectrometry chamber 15. Is provided.

The time-of-flight mass spectrometer 25 is composed of a flight tube 26 and a multi-channel plate type ion detector 21 disposed inside. In this case, a laser beam passes through the center of the multi-channel plate. A small hole 23 is provided. Note that the ion source 19 is provided with the time-of-flight mass spectrometer 2 in the same manner as in the second embodiment.
5 and is disposed in the space between the gate valve 16 and the beak-shaped isolation valve 17, but in the vicinity of the tip of the flight tube 26 constituting the mass analyzer as in the first embodiment. They may be arranged.

In the fourth embodiment, since the time-of-flight mass analyzer 25 is used as the mass analyzer, the apparatus configuration is simpler than that of the quadrupole mass analyzer, and In this case, it is necessary to use pulsed laser light as the laser light, but it becomes possible to simultaneously measure desorbed species having different mass numbers.

Next, a modified example common to the first to fourth embodiments will be described. In the description of the first to fourth embodiments, laser light of a single wavelength is used. However, the wavelength may be variable.
By combining a second harmonic generator with a YAG laser, or by arranging a YAG laser and a green-light argon laser in parallel and using a prism mirror to make the optical axes of the two close to each other in parallel, an infrared ray near 1 μm can be obtained. And 50
Irradiation with visible light near 0 nm can be performed.

As described above, when the wavelength of the laser beam is made variable, the wavelength band to be absorbed differs depending on the material of the substrate. For example, when light of about 500 nm is used, the silicon layer is absorbed, so that the silicon surface is heated. by deposits adhered to the silicon surface leaving Suruga, since hardly absorbed in the SiO ₂ film deposits adhering to the SiO ₂ film surface is not desorbed, thus, different in the surface of the sample 12 material The deposits on the top can be selectively measured.

The embodiments of the present invention have been described above. However, the present invention is not limited to the configuration described in the embodiments, and various modifications are possible. In the description of the mode, the sample chamber and the mass spectrometry chamber are evacuated with a turbo molecular pump, and the mass analyzer is evacuated with an ion pump, but may be evacuated with a molecular turbo pump of the mass analyzer. Further, any vacuum pump may be used as long as a predetermined exhaust capacity and a predetermined ultimate vacuum degree can be obtained.

[0049]

According to the present invention, the sample chamber accommodating the sample and the mass spectrometer chamber accommodating the mass spectrometer are independently evacuated, and the mass spectrometer chamber is differentially evacuated to the sample chamber. Therefore, when exchanging the sample, the sample is exchanged with only the sample chamber at normal pressure, and after the sample exchange, measurement can be started only by roughing the sample chamber for several minutes, which is necessary for measurement. Since the total time can be greatly reduced, and the laser light source and the mass spectrometer are arranged in series, the overall configuration of the apparatus can be made compact. Since the analysis can be easily performed, it greatly contributes to the improvement of the stability and the manufacturing yield of the semiconductor device manufacturing process in which the miniaturization is advanced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is a schematic configuration diagram of a surface analyzer according to the first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a surface analyzer according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a surface analyzer according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram of a surface analyzer according to a fourth embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a conventional surface analyzer.

[Explanation of symbols]

 Reference Signs List 1 sample chamber 2 sample 3 mass spectrometry chamber 4 gate valve 5 mass spectrometer 6 quadrupole 7 laser 8 ion source 11 sample chamber 12 sample 13 exhaust port 14 port 15 mass spectrometry chamber 16 gate valve 17 beak isolation valve 18 four Quadrupole mass spectrometer 19 Ion source 20 Quadrupole 21 Ion detector 22 Laser light source 23 Small hole 24 Scanning mirror 25 Time-of-flight mass spectrometer 26 Flight tube 31 Sample chamber 32 Sample 33 Exhaust port 34 Port 35 Mass spectrometer 36 Ion source 37 Quadrupole 38 Ion detector 39 Laser light source 40 Laser light 41 Desorbed substance

Claims (6)

[Claims] 1. A surface analysis apparatus utilizing laser-induced thermal desorption of a substance adhering to a sample by irradiating the sample with a laser beam, wherein a laser and a mass analyzer are arranged in series, and the laser beam is applied to the sample through an ion source. A surface analyzer comprising: means for irradiating, and means for differentially evacuating the mass analyzer to a sample chamber. 2. The mass spectrometer according to claim 1, wherein the mass spectrometer is a quadrupole mass spectrometer, and a longitudinal direction of the quadrupole is arranged to be orthogonal to an irradiation direction of the laser beam. Item 4. The surface analyzer according to Item 1. 3. The mass spectrometer is a quadrupole mass spectrometer, and is arranged so that a longitudinal direction of the quadrupole is parallel to an irradiation direction of the laser light. The surface analyzer according to claim 1, wherein the sample is irradiated through a quadrupole mass spectrometer. 4. The mass spectrometer is a time-of-flight mass spectrometer, and is arranged such that a longitudinal direction of the flight tube is parallel to an irradiation direction of the laser beam, and the laser beam passes through the flight tube. The surface analyzer according to claim 1, wherein the surface analyzer is irradiated with the sample. 5. The surface analyzer according to claim 1, wherein the laser has a means for changing a wavelength. 6. The surface analyzer according to claim 1, further comprising a scanning mirror for scanning the laser beam.