JPH11142318A - Particle monitoring sensor head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle monitoring sensor head capable of being used in all of vacuum apparatuses. SOLUTION: A laser diode 1 and a microlens 2 are provided as a laser beam emitting part, and an optical filter 4 and a detector 3 are provided as a light receiving part. A measuring container 10A is coupled with the internal space of a vacuum apparatus to irradiate particles in the vacuum apparatus with laser beam. Lights scattered by respective particles pass through the optical filter 4 to be incident on the detector 3. At this time, a shield plate 5 or a honeycomb structure is arranged so as to prevent that plasma beam is directly incident on the measuring container 10A. By this constitution, the arrival of unnecessary direct beam can be prevented and the measuring accuracy of particles is enhanced even under a plasma condition having a spectrum near to the wavelength of the laser diode 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particle monitor sensor head capable of directly and in real time measuring submicron-order particles floating in a vacuum apparatus.

[0002]

2. Description of the Related Art In recent years, attention has been paid to the influence of submicron-order particles floating in a vacuum apparatus such as sputtering, plasma CVD, low pressure CVD, dry etcher, and resist asher. These particles affect the yield in semiconductor manufacturing, and the particle measurement technology is an important element of the semiconductor manufacturing technology.

[0003] A conventional particle measuring method will be described below. As a first measurement method, there is one that adopts the following procedure. That is, using a wafer dedicated to particle measurement,
Particles attached to the surface in advance are measured by a surface inspection device using a laser beam or the like. On the other hand, the wafer is processed in a vacuum apparatus under conditions dedicated to particle measurement, and the wafer is measured by the same inspection apparatus. Next, the particle density is determined from the difference between these particles. In this method, the particle measurement cycle is performed after the cumulative number of wafers (product wafers) serving as products reaches a predetermined value or every time the semiconductor manufacturing apparatus is maintained.

[0004] As a second measuring method, there has been a method in which a product wafer is processed, a few wafers are extracted from the processed wafer, and particles on the surface are measured by a dedicated inspection device to measure particles.

In the case of the first measurement method, the dedicated wafer used for the measurement has a surface structure and state different from those of the product wafer, and the processing conditions are often different from those actually used for the product wafer. For this reason, the state in the apparatus at the time of measurement can be grasped to some extent, but the state when processing a product wafer is not clear.

In the case of the second measuring method, although the actual state of the product wafer can be known, it is difficult to grasp the information of all the product wafers. In addition, in order to confirm after processing a wafer, when a measurement result is obtained, several lots of product wafers are often processed. Therefore, this method has a disadvantage that the feedback to the result is delayed.

Therefore, in recent years, an apparatus capable of directly measuring particles in a vacuum apparatus by using a laser beam has been used. FIG. 8 shows a schematic diagram of such a conventional sensor head for particle monitoring. In the figure, a laser emitting unit 11 and a light receiving unit 12 are provided on a sensor head for particle monitoring with a measuring container 10 interposed therebetween.
The laser emission unit 11 is a light source that emits a laser beam toward the measurement container 10 having a measurement space. Light receiving section 12
Is a portion which is installed at a position shifted from the optical axis of the laser beam and receives scattered light scattered by particles existing in the measurement container 10.

[0008] The sensor head is directly mounted on a vacuum device, and the laser beam oscillated from the laser light emitting unit 11 is irradiated to particles jumping into the measurement container 10 of the sensor head. Then, the scattered light generated upon hitting the particles is received by the light receiving unit 12, and the size and the number of the particles are analyzed based on the intensity of the scattered light.

[0009]

However, in the conventional sensor head for particle monitoring, in the case of an apparatus using plasma such as dry etcher or plasma CVD, plasma light (plasma light) is generated in the measurement space of the measurement container 10. It jumps in and enters the detector of the light receiving unit 12. For this reason, there is a disadvantage that the scattered light due to the original particles cannot be distinguished from the direct input light, and the number of particles cannot be accurately counted.

Conventionally, one set of laser diodes of one wavelength band is used as the laser diode of the laser emitting section 11. On the other hand, the plasma light in the apparatus may have a strong emission spectrum near the wavelength band of the laser beam. In this case, there has been a problem that the counted number of particles becomes larger than the actual number or disappears and becomes zero.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and can be used in almost all of the reaction chambers and processing chambers of a vacuum apparatus, and is capable of measuring the state of particles in real time. It is an object to provide a sensor head.

[0012]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present application provides a measurement container having a particle measurement space, a measurement container attached to the measurement container, A particle monitoring sensor, comprising: a laser emitting unit that emits a laser beam; and a light receiving unit that is attached to the measurement container and detects scattered light generated when particles cross the laser beam in the measurement space. It is characterized in that a shielding means for preventing light incident on the space from being incident on the light receiving section is provided.

According to a second aspect of the present invention, in the particle monitor sensor head according to the first aspect, the shielding means is a thin plate-shaped member having a plane perpendicular to an optical axis of a laser beam of the laser emitting section. It is characterized by having.

According to a third aspect of the present invention, in the particle monitor sensor head according to the first aspect, the shielding means includes a divided portion formed with a plurality of tubes perpendicular to an optical axis of a laser beam of the laser emitting section. It is characterized by being a tubular body.

According to a fourth aspect of the present invention, in the particle monitor sensor head according to the first aspect, the laser emitting section includes a laser diode for outputting a laser beam;
And a lens that focuses the laser light.

According to a fifth aspect of the present invention, in the particle monitor sensor head according to the first aspect, the light receiving portion is provided outside a central axis of the laser beam, and has a same wavelength as a wavelength of the laser beam. And a detector for detecting the amount of light passing through the optical filter.

According to a sixth aspect of the present invention, there is provided a measurement container having a particle measurement space, and a first laser beam having a center wavelength λ1 attached to the measurement container and having a center wavelength λ1 in a first direction. A first laser light-emitting unit for emitting light to the measurement container, a first light-receiving unit attached to the measurement container, for detecting scattered light generated when particles cross the first laser beam in the measurement space, and the measurement container A second laser light-emitting unit that is attached to the measurement space and emits a second laser beam having a center wavelength λ2 different from the wavelength λ1 to the measurement space in a second direction different from the first direction; A second light receiving unit attached to the measurement container and detecting scattered light generated when particles traverse the second laser beam in the measurement space. It is intended to.

The invention according to claim 7 of the present application is the particle monitor sensor head according to claim 6, wherein the first
The first laser emitting section outputs the laser light of the wavelength λ1.
And a first lens that focuses the laser light of the first laser diode. The second laser emitting unit outputs a laser light having a wavelength of λ2. And a second lens for focusing the laser light of the second laser diode.

The invention according to claim 8 of the present application is the particle monitor sensor head according to claim 6, wherein
A first optical filter that is provided outside the central axis of the laser beam of wavelength λ1 and transmits light of wavelength λ1, and a first detector that detects the amount of light that has passed through the first optical filter. The second light receiving unit is provided outside the center axis of the laser beam having the wavelength λ2,
And a second detector that detects the amount of light that has passed through the second optical filter.

[0020]

(Embodiment 1) A particle monitor sensor head according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of a particle monitor sensor head according to the present embodiment, and FIG. 2 is a schematic cross-sectional view when the particle monitor sensor head is attached to a vacuum device. In FIG. 1, a sensor head for particle monitoring includes a measuring container 10 for receiving particles to be measured.
A, a laser emitting unit 11A that emits a laser beam toward a measurement space of the measurement container 10A, and a light receiving unit 12 that detects scattered light scattered by particles of the measurement container 10A.
A is included.

The laser emitting section 11A has a laser diode 1 and a microlens 2 for focusing laser light from the diode. The light receiving unit 12A has an optical filter 4 that allows only scattered light of a specific wavelength to pass, and a detector 3 that detects the amount of scattered light that has passed through the optical filter 4. Further, the shielding plate 5 which is a feature of the present embodiment is provided in the measuring container 10A as shielding means. FIG. 3 is a perspective view showing a structure of the sensor head for particle monitoring, and black circles in the figure show particles.

The measurement principle of the particle monitor sensor head having such a structure will be described. First, the measurement container 10A is attached to a part of the vacuum device, and is shielded so as to be at a position that straddles the measurement space of the measurement container 10A and the inside of the vacuum device as shown in FIG. Attach plate 5. At this time, positioning is performed so that the shielding plate 5 does not block the laser beam. The laser light oscillated from the laser diode 1 is condensed into a beam by a microlens 2 on the extension thereof.

When particles enter the measuring container 10A, the particles cross the laser beam. At this time, when the laser beam hits the particles, the hit portion is scattered. Further, since the optical filter 4 is attached around the irradiation position in the direction of the laser beam, only the scattered light passing through the optical filter is detected by the detector 3. Therefore, light other than the oscillated laser beam is blocked. From the intensity of the scattered light measured as described above, the number of particles is classified by size.

Since the particle monitor sensor head is directly connected to a vacuum device as shown in FIG. 2, in a dry etcher using plasma or plasma CVD, plasma light is directly transmitted to the measuring vessel 10 without the shielding plate 5.
There is a possibility of getting into A. In particular, when the wavelength of the laser beam and the wavelength of the plasma light are almost the same, if the entered plasma light passes through the optical filter 4 and irradiates the detector 3, it is erroneously recognized as a particle.

In this embodiment, since the shielding plate 5 is provided at the center of the measuring container 10A, as shown by an arrow P in FIG.
Even if plasma light arrives from the plasma source, the detector 3
Does not enter the plasma light. It is preferable that the width of the shielding plate 5 is 1.5 to 2 times the width of the detector 3 in order to effectively shield the plasma light.

In the present embodiment, the shielding plate 5 is
A, but the shielding plate 5 is attached to the measurement container 10A depending on the installation position of the sensor head for particle monitoring.
It is also possible to attach it around. Further, since the shielding means introduces only the scattered light into the light receiving portion, the shielding means may cover the inner periphery of the measurement container 10A and may be a cylindrical body made of a thin plate.

(Embodiment 2) Next, a particle monitor sensor head according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 4A is a front view showing the structure of the particle monitor sensor head according to the present embodiment, and FIG. 4B is a sectional view. In these drawings, the description of the same parts as in the first embodiment will be omitted.

In the case of the first embodiment, only one shield plate 5 is attached, and the structure is very simple. However, since a part of the shielding plate 5 protrudes into the vacuum device, the process of the vacuum device may be hindered. Therefore, in the present embodiment, a honeycomb structure 6 as shown in FIG. 4A is attached to the measurement container 10B as a shielding means. FIG.
As shown in (b), the laser emitting unit 11B and the light receiving unit 12
Assuming that the direction connecting B is the x-axis and the direction perpendicular to the x-axis is the y-axis, in this structure, a number of thin tubes parallel to the y-axis are arranged in parallel.
The same effect as that obtained by installing the device in a location can be obtained. Further, since it is not necessary to make the honeycomb structure 6 as long as one shield plate, and this honeycomb structure 6 does not protrude into the vacuum device, there is no obstacle when using the vacuum device.

The shielding means does not need to be limited to the honeycomb structure, but is formed by forming a plurality of tubes perpendicular to the optical axis of the laser beam of the laser emitting section 11B in order to introduce only the scattered light into the light receiving section 12B. It may be. In the present embodiment, these shielding means are referred to as divided tubular bodies. The particle monitor sensor head having such a structure can be attached to any vacuum device.

As described above, the measuring container 1 of the sensor head
By attaching the shielding plate 5 or the honeycomb structure 6 to 0A or 0B, it is possible to prevent direct incidence of plasma light on the detector 3.

(Embodiment 3) A particle monitor sensor head according to Embodiment 3 of the present invention will be described with reference to the drawings. In the above embodiment, the provision of the shielding plate 5 or the honeycomb structure 6 has a disadvantage that the cross-sectional area of the measurement container 10 is slightly reduced. FIG.
(A) is a front view showing the structure of the particle monitor sensor head in the present embodiment, and (b) is a sectional view. In these drawings, the description of the same parts as in the first embodiment will be omitted.

Here, for one measurement container 10C,
Two sets of sensor heads that are orthogonal to each other are provided. When the upper side of the vacuum device is in the + z-axis direction, the first sensor head directs the first laser beam having the wavelength λ1 in the x-axis direction, and has a first laser emitting unit 11C in the + x direction.
The first light receiving section 12C is provided in the −x direction. The second sensor head directs a second laser beam having a wavelength λ2 different from the wavelength λ1 in the z-axis direction. The second laser head 11D is provided in the + z direction, and the second laser beam is emitted in the −z direction.
Is provided.

When particles are actually measured by a dry etcher using a conventional sensor head for particle monitoring, measurement may not be possible at all depending on the type of gas used for etching and high-frequency power. FIG. 5 shows particle data obtained by changing the type of gas. When discharging with nitrogen, oxygen, and argon gas, particles are counted by nitrogen, but particles are hardly counted by oxygen and argon gas.

The following can be considered as the cause. That is, with oxygen or argon gas, 78
It has a strong emission spectrum near 0 nm. This coincides with the wavelength band of the laser used for the particle monitor. Therefore, when a gas that emits light in this wavelength band is used, a laser light emitting portion having an emission band near 780 nm cannot be used.

Therefore, in the present embodiment, particles can be monitored even under the condition using such a gas. As shown in FIG. 5, a conventional laser having a wavelength of around 780 nm is used for a pair of laser emitting units 11D, and an optical filter corresponding to the laser is provided for a light receiving unit 12D. A laser near 1000 nm is used for the other set of laser emitting units 11C, and the light receiving unit 12C is used.
C is provided with an optical filter corresponding to the laser wavelength.

With the above structure, 780n
Under the process conditions where there is no strong light emission near m, the measurement of particles becomes possible by using the laser light emitting unit 11D and the light receiving unit 12D. Further, under the process conditions having strong light emission near 780 nm, measurement of particles becomes possible by using the laser light emitting unit 11C and the light receiving unit 12C.

Here, if only a laser of 1000 nm is used, the wavelength is too long, so that the probability of colliding with particles is reduced, and the intensity of scattered light generated by colliding with particles is also reduced. For this reason, the measurement sensitivity decreases. Therefore, when the 780 nm laser can be used sufficiently, the measurement is performed simultaneously on the long wave side, and the difference is corrected. As a result, even when only a long wavelength laser is used, measurement can be performed with the same measurement sensitivity as when using a 780 nm laser.

In selecting the laser, the wavelength of the laser beam can be selected before the laser is actually used because it can be assumed in advance depending on the type of gas to be used. FIG. 7 shows particle data obtained in the present embodiment. It can be seen that particles can be detected under process conditions using oxygen or argon gas, which could not be measured conventionally, by changing the wavelength of the laser.

Further, a two-channel system is provided in which two types of laser diodes for oscillating laser light are mounted on the same laser light-emitting portion, and a detector incorporating two types of optical filters corresponding to the wavelength band of the laser light is provided. ,
Particles can be reliably detected even under process conditions such as all kinds of gases and high-frequency power.

Also, as shown in FIG. 5, by installing a pair so as to be orthogonal to each other, if both lasers can be used due to process conditions, the optical filter is replaced to detect particles with both detectors. .
This improves the detection sensitivity not only for forward scattering but also for side scattering. And the minimum detection limit can be further improved.

As described above, by using the sensor head alone or by combining the sensor heads,
It can be used for all dry etcher sputtering and plasma CVD. This makes it easier to measure particles generated during the process. By using such a sensor head for particle monitoring, abnormalities and troubles of equipment and processes can be directly grasped in real time and quick feedback is possible.

[0042]

According to the first to fifth aspects of the present invention, by providing the measuring container with the shielding means, it is possible to prevent light other than the light scattered by the particles from directly entering the light receiving portion. For this reason, even if the spectrum of the plasma light includes light having the same wavelength component as that of the laser light emitting unit, particles in the vacuum apparatus can be accurately measured in real time.

According to the sixth to eighth aspects of the present invention, since two sets of the laser emitting section and the light receiving section are provided with the measuring container interposed therebetween,
Even if the plasma light spectrum contains light having the same wavelength component as that of one of the laser light emitting units, the scattered light is detected by using the laser beam of the other laser light emitting unit.
Particles in a vacuum device can be measured in real time and more accurately.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a particle monitor sensor head according to Embodiment 1 of the present invention.

FIG. 2 is a cross-sectional view showing a state where the particle monitor sensor head according to Embodiment 1 is attached to a vacuum device.

FIG. 3 is an explanatory diagram illustrating a detection principle of a sensor head for particle monitoring.

4A and 4B are a front view and a cross-sectional view illustrating a configuration of a particle monitor sensor head according to Embodiment 2 of the present invention.

5A and 5B are a side view and a cross-sectional view illustrating a configuration of a particle monitoring sensor head according to Embodiment 3 of the present invention.

FIG. 6 is a graph showing the count number of particles when measured by a conventional particle monitor sensor head.

FIG. 7 is a graph showing the number of particles measured when measured by the particle monitoring sensor head according to the third embodiment.

FIG. 8 is a top view and a sectional view showing the structure of a conventional sensor head for particle monitoring.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser diode 2 Micro lens 3 Detector 4 Optical filter 5 Shield plate 6 Honeycomb structure 10A, 10B, 10C Measurement container 11A, 11B, 11C, 11D Laser light emitting part 12A, 12B, 12C, 12D Light receiving part

Claims (8)

[Claims] 1. A measurement container having a measurement space for particles, a laser emitting unit attached to the measurement container and emitting a laser beam to the measurement space, and a particle attached to the measurement container and attached to the measurement space. A light-receiving unit for detecting scattered light generated when the light beam crosses the laser beam, wherein a shielding unit for preventing light incident on the measurement space from being incident on the light-receiving unit is provided. A sensor head for particle monitoring, comprising: 2. The particle monitor sensor head according to claim 1, wherein said shielding means is a thin plate-shaped member having a plane perpendicular to an optical axis of a laser beam of said laser light emitting section. 3. The particle monitor sensor head according to claim 1, wherein said shielding means is a divided tubular body formed with a plurality of tubes perpendicular to an optical axis of a laser beam of said laser emitting section. . 4. The particle monitor sensor head according to claim 1, wherein the laser light emitting unit includes a laser diode that outputs a laser beam, and a lens that focuses the laser beam. 5. An optical filter provided outside the center axis of the laser beam, the optical filter passing light having the same wavelength as the wavelength of the laser beam, and a detector for detecting the amount of light passing through the optical filter. 2. The sensor head according to claim 1, wherein the sensor head comprises: 6. A measurement container having a particle measurement space, and a first laser emission mounted on the measurement container and emitting a first laser beam having a center wavelength λ1 to the measurement space in a first direction. And a first light receiving unit attached to the measurement container and detecting scattered light generated when particles traverse the first laser beam in the measurement space, attached to the measurement container, and attached to the measurement space. On the other hand, a second laser emitting section that emits a second laser beam having a center wavelength λ2 different from the wavelength λ1 in a second direction different from the first direction; A second light receiving unit for detecting scattered light generated when the particles cross the second laser beam in space. The sensor head. 7. The first laser emitting section includes: a first laser diode that outputs a laser beam having a wavelength λ1; and a first laser diode that focuses the laser beam of the first laser diode.
A second laser diode that outputs a laser beam having a wavelength of λ2, and a second laser diode that focuses the laser beam of the second laser diode.
7. The sensor head for particle monitoring according to claim 6, comprising: 8. The first light receiving section is provided outside a central axis of a laser beam having a wavelength of λ1, and has a wavelength of λ1.
A first optical filter that transmits the first light, and a first optical filter that detects the amount of light that has passed through the first optical filter.
Wherein the second light receiving portion is provided outside the central axis of the laser beam having the wavelength λ2, and the second light receiving portion has the wavelength λ.
A second optical filter that transmits the second light, and a second optical filter that detects the amount of light that has passed through the second optical filter.
7. The sensor head for particle monitoring according to claim 6, comprising: