JP2011154958A - In-vacuum processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an in-vacuum processing device or charged particle beam device that reduces the size of a vacuum sample room, without requiring an elongated reflector, while miniaturizing a top table and reducing the mass of the top table. <P>SOLUTION: A stage is structured so that a pair of an interferometer and a reflector, both of which being used to measure length, are both made movable, and move in a direction parallel to a moving axis among a plurality of moving axes of the stage which crosses a direction, in which a length is measured by the pair of the interferometer and the reflector with the pair of the interferometer and the reflector kept mutually facing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an in-vacuum processing apparatus, in particular, a scanning electron microscope for observing a sample, and a charged particle beam apparatus for performing ion beam processing.

  In recent years, the degree of integration of semiconductor products has been increasingly demanded, and the circuit pattern has been further refined. In order to manufacture and inspect a fine pattern, it is necessary to accurately move the wafer to a desired position. As a means for confirming whether the wafer has moved to a desired position, a laser length measuring instrument is generally employed.

  The laser length measuring device separates two orthogonally deflected laser beams irradiated from the laser head in the interferometer, reflects one of them as a reference beam in the interferometer, and the other as a measuring beam. After being reflected by the reflecting mirror as the object to be measured, it is again taken into the interferometer and overlapped with the reference light to generate interference light. The interference light is converted into an electrical signal by a photodetector (hereinafter referred to as a receiver) and converted into position information by a laser substrate. Since the interference light changes due to a relative change between the reflecting mirror and the interferometer, the position is managed by adding / subtracting the change with a counter in the laser substrate.

  An inspection apparatus that uses a laser length measuring instrument is a scanning electron microscope (hereinafter referred to as a length measuring SEM) that irradiates a charged particle beam to measure the dimensional accuracy of a circuit pattern on the wafer, and irradiates the charged particle beam on the wafer. And a scanning electron microscope (hereinafter referred to as a review SEM) for evaluating the defect of the circuit pattern or the attached foreign matter.

  In recent years, review SEM has become more multifunctional, and in addition to the original observation mechanism of foreign particles using charged particle beams, a foreign substance detection / observation mechanism using an optical microscope, a wafer charging state measurement mechanism using a surface potential meter, etc. have been added. It is coming. The top table that moves the wafer serving as the sample needs to move within a range in which a distance corresponding to the wafer diameter can be secured around these mechanisms. That is, the range of movement of the stage (stage stroke) tends to widen due to the increase in functionality. In addition, in order to reduce the cost of mass production, the introduction of a Φ450 mm wafer has been studied in place of the Φ300 mm wafer that has been the mainstream until now, and further increase in the stage stroke is required.

  As the stage stroke increases, the sample chamber becomes larger and the cost increases. Further, since the stage moving time also increases, the throughput of the semiconductor product decreases, and the cost also increases. In order to reduce the stage moving time, it is necessary to increase the stage moving speed and acceleration. For this purpose, the mass of the top table on which the sample is placed must be reduced as much as possible.

  FIG. 11 is a diagram showing a conventional example of a review SEM apparatus equipped with an optical microscope. The laser beam from the laser head 40 is separated by the beam splitter 41, enters the interferometers 23X and 23Y, is reflected by the bar mirror 22 serving as a reflector, and enters the interferometers 23X and 23Y again. When the top table moves in this state, interference light due to the Doppler effect is generated. The interference light is detected by the receiver 42 and converted into an electrical signal by the laser unit 75, thereby managing the position of the top table 21A. As shown in FIG. 11, generally, since the long and heavy bar mirror 22 is installed on the top table 21A, the top table 21A becomes heavy. Further, the top table 21A is substantially enlarged by the bar mirror, and thereby the sample chamber 2 including the moving range of the top table 21A is also enlarged.

  Patent Document 1 proposes a structure in which a light interferometer is arranged instead of removing the heavy bar mirror from the top table, and conversely, the bar mirror is fixedly arranged on the base in the sample chamber. Thereby, the weight of the top table can be reduced, and the effect of suppressing the stage characteristic deterioration factor such as vibration can be obtained while increasing the acceleration. Further, since the top table can be downsized, the sample chamber can be downsized.

JP-A-4-351905

  However, in the stage disclosed in Patent Document 1, the bar mirror itself is also arranged in the vacuum sample chamber, and it is necessary to ensure a length equivalent to the movement stroke of the top table. Therefore, although it is effective in terms of downsizing the top table, it is not so effective in reducing the size of the vacuum sample chamber itself.

  The present invention has been made in view of such a situation, and achieves downsizing of the top table and weight reduction of the top table, and does not require a long reflector such as a bar mirror. An object of the present invention is to realize an in-vacuum processing apparatus capable of downsizing the vacuum sample chamber.

  The stage disposed in the in-vacuum processing apparatus has a moving axis corresponding to the moving direction. For example, in the case of an XY stage, the X-axis and the Y-axis are two movement axes that are orthogonal to each other, and the top table on which various structures such as a sample stage and a sample fixing device are placed is along each of the two movement axes. Can be moved. In the case of the XY stage, in principle, the stage can be moved to an arbitrary position in the XY plane direction as long as the two movement axes intersect.

  The problem with the prior art is due to the fact that one or both of the interferometer and the reflector that reflects light to the interferometer are fixed. For example, the stage having the structure disclosed in Patent Document 1 has a configuration in which a pair of interferometers and reflectors are arranged in a direction along the movement axis in the X direction or the Y direction. The stage is configured to be able to move in a direction that intersects one moving axis, but the reflector is fixed. Therefore, the reflector needs to have a length corresponding to the moving stroke with respect to the intersecting direction.

  Therefore, the present invention configures a stage so that both a pair of interferometers and reflectors used for length measurement are movable, and among the plurality of moving axes of the stage, the interferometer and the reflection are performed. A position relationship in which the interferometer and reflector pair face each other along a movement axis (or a direction parallel to the movement axis) intersecting with a direction (or a direction parallel to the direction) formed by the pair of bodies. The above-described problem is solved by configuring the stage so that the stage can be moved while being maintained.

  According to the present invention, an in-vacuum processing apparatus or a charged particle beam apparatus capable of reducing the size of the vacuum sample chamber while realizing a reduction in the size of the top table and a reduction in the weight of the top table is realized. In the charged particle beam apparatus, the vacuum sample chamber occupies a considerable portion of the apparatus volume, so that the charged particle beam apparatus with a small installation space can be realized by downsizing the vacuum sample chamber. As a result, the time required for evacuation is small, the charged particle optical column and the vacuum sample chamber can be maintained at a high vacuum, and a charged particle beam apparatus with little sample contamination and discharge can be realized.

Explanatory drawing which shows the review SEM of this invention The top view which shows the stage of this invention, and a laser length measuring device structure The side view which shows the stage of this invention, and a laser length measuring device structure The top view which shows each dimension of the stage of this invention, and a laser length measuring device The top view which shows the stage of this invention, and a laser length measuring device structure The side view which shows the stage of this invention, and a laser length measuring device structure Sectional view showing the method of fixing the bar mirror to the sample chamber Plan view showing deviation between SEM center and interferometer measurement axis when moving stage The top view which shows the stage of this invention, and a laser length measuring device structure The top view which shows the stage of this invention, and a laser length measuring device structure Plan view showing conventional stage and laser length measuring instrument configuration Plan view showing conventional stage and laser length measuring instrument configuration

  The present invention relates to an in-vacuum processing apparatus, in particular, a scanning electron microscope for observing a sample, and a charged particle beam apparatus for performing ion beam processing.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be noted that this embodiment is merely an example for realizing the present invention, and does not limit the technical scope of the present invention. In each drawing, the same reference numerals are assigned to common components.

  In this embodiment, a charged particle beam device such as a review SEM will be described as an example of the in-vacuum processing device. However, the present invention is not limited to the review SEM, and the same effect can be obtained if the device uses a laser length measuring device in a vacuum. Can be expected.

<First Embodiment>
First, a first embodiment of the present invention will be described with reference to FIGS.

(Review SEM system configuration)
FIG. 1 is a schematic configuration diagram of a review SEM of the present embodiment. A mount 4 for removing vibrations from the floor is attached to the gantry 6 installed on the floor, and the mount 4 supports the sample chamber 2. The sample chamber 2 is provided with an optical column 1 that generates and controls an electron beam, and a load lock 3 that includes a transport robot 31 that transports the sample. The sample chamber 2 is always evacuated by a vacuum pump 5, and the optical column 1 is also kept at a high vacuum level by a vacuum pump (not shown). On the other hand, the atmosphere side gate valve 33 that isolates from the atmosphere and the vacuum side gate valve 32 that isolates from the sample chamber 2 are attached to the load lock 3.

  An electrostatic chuck 24 that electrostatically attracts the wafer 10 and an interferometer 23 and a reflecting mirror 26 for grasping a relative distance change of the stage 21 by laser length measurement are attached to the stage 21. The position management of the stage 21 is performed by a position control unit 71 that generates position information of the stage and a stage control unit 72 that performs stage driving. The stage control unit 72 performs feedback control so that there is no deviation between the current position information and the target coordinates. As feedback control, control performed by simple position feedback alone, PID control for improving response speed and positioning accuracy by adding stage speed information and stage position deviation integration information, and the like can be considered.

  The optical column 1 includes an electron lens 13 for converging the electron beam 12 generated by the electron gun 11, an electron lens 16, a deflector 14 for deflecting the electron beam to a desired trajectory, reflected electrons generated from the sample 10 by irradiation of the electron beam, Alternatively, a detector 15 for detecting secondary electrons is attached. An image of the wafer 10 is generated by the image control unit 73 based on the control information of the deflector 14 and the obtained information from the detector 15 and displayed on the monitor 74.

  Above the sample chamber 2, an optical Z sensor 25 for detecting the height of the sample is mounted, and the height of the wafer can be monitored at all times. The signal obtained from the Z sensor 25 is a position control unit. After being converted in position 71, it is transmitted to the column controller. With this signal, the column control unit changes the optical conditions of the electron lens and performs processing so that the focus does not shift even if the height of the sample changes.

  The above-described stage position information is also transmitted to the column control unit 70 that controls the optical column 1 and corrects the deflection control signal of the electron beam generated by the deflector 14. The deflector 14 is divided into a position deflector 14A that positions the deflection center of the electron beam at the wafer position, and a scanning deflector 14B that scans the charged particle beam in the target field at a high speed for imaging. Each of the devices is controlled by the deflection control unit 17. For example, if the current position of the stage deviates from the target coordinates within the deflection range (for example, within 10 μm), the deviation is transmitted from the position control unit 71 to the column control unit 70, and the deviation command value in a state without deviation is deviated. Add minutes as a correction amount. By the above series of operations, the wafer can be positioned so as to be accurately at the center of the image.

(Configuration and operation of laser length measuring device)
Next, the configuration and operation of the laser length measuring device according to the present embodiment will be described in detail with reference to FIGS.

  FIG. 2 is a plan view showing the configuration of the stage and the laser length measuring device of the present embodiment, and FIG. 3 is a side view showing the configuration of the stage and the laser length measuring device of the present embodiment.

  In the present embodiment, an X reflecting mirror 26X and a Y reflecting mirror 26Y are mounted on the top table 21A, and an X interferometer 23X and a Y interferometer 23Y are mounted on the X slider 21X and the Y slider 21Y, respectively. It is characterized by. Details will be described below.

  The X interferometer 23X and the Y interferometer 23Y are attached to one end of the X slider 21X and the Y slider 21Y via an X attachment base 57X and a Y attachment base (not shown). The X slider 21X and the Y slider 21Y can move in the X direction or the Y direction along the movement axis in the X direction and the movement axis in the Y direction, respectively. This movement axis may be virtual or may be some physical shaft member used for slider movement. Therefore, the X interferometer 23X moves in the Y direction together with the X slider 21X, and the Y interferometer 23Y moves in the X direction together with the Y slider 21Y.

  The X slider 21X is attached to the Y guide 28Y by Y attachment spacers 29Y connected to both ends, and is guided in the Y direction by the Y guide 28Y. Here, the guidance means an operation that allows movement only in a specific direction and does not move in other directions. On the other hand, the Y slider 21Y is attached to the X guide 28X by X attachment spacers 29X connected to both ends, and is guided in the X direction by the X guide 28X. As described above, the X interferometer 23X and the Y interferometer 23Y are attached to one end of the X slider 21X or the Y slider 21Y. Accordingly, if the X slider 21X or the Y slider 21Y moves in the Y direction or the X direction along the Y guide 28Y or the X guide 28X, respectively, the X interferometer 23X or the Y interferometer 23Y also becomes the Y guide 28Y or the X guide. It moves in the Y direction or the X direction along 28X. It is clear from the figure that the movement axis of the X guide 28X or Y guide 28Y is parallel to the movement axis of the X slider 21X or Y slider 21Y.

  Furthermore, the top table 21A is connected to an X slider guide 27X on the X slider 21X, and the top table 21A is connected to a Y slider guide 27Y on the Y slider 21Y by a connection base 21B and a connection column 21C. Therefore, the top table 21A can also move in the XY horizontal plane along the movement axis of the X slider 21X or the movement axis of the Y slider 21Y.

  An optical path when the above configuration is employed will be described. First, in FIG. 2, the laser light emitted from the laser head 40 passes through the transmission window 56 and is introduced into the sample chamber 2. Thereafter, the beam is split into two paths by the beam splitter 41 and introduced into the X interferometer 23X and the Y interferometer 23Y, respectively. The laser light introduced into the X interferometer 23X and the Y interferometer 23Y is reflected by the X reflecting mirror 26X and the Y reflecting mirror 26Y mounted on the top table 21A, and is again introduced into the X interferometer 23X and the Y interferometer 23Y. The The laser beams interfered by the X interferometer 23X and the Y interferometer 23Y are bent by the mirror 49, pass through the transmission window 56, and enter the receiver 42. Here, after the interference light is converted into an electric signal, it is transmitted to the laser unit 75 and converted into position information. In this embodiment, since a double-pass method is assumed, two laser beams are described between the interferometer and the reflector. However, the reflector is changed to a corner cube, and the interferometer is used for a single pass. By changing to, it is possible to operate as a single-pass laser length measurement system without any problem.

  As shown in FIG. 2, the X interferometer 23X and the X reflecting mirror 26X and the Y interferometer 23Y and the Y reflecting mirror 26Y each constitute an optical path, and each of these optical paths is an X slider 21X. And Y slider 21Y. As described above, the reflector is mounted on the top table, and the interferometer is fixed to one end of the X slider 21X or the Y slider 21Y. The X slider 21X or the Y slider 21Y can move along the Y guide 28Y or the X guide 28X, respectively.

  By adopting such a configuration, the pair of X and Y interferometers and reflectors can be moved along the movement axis of the slider or guide while maintaining the positional relationship facing each other. . Therefore, no matter how the top table moves, the optical path does not deviate from between the interferometer and the reflector. Therefore, the long bar mirror that has been required in the past is unnecessary, the size of the vacuum sample chamber can be reduced, and a length measurement function that is not different from the conventional one can be realized. That is, when the top table 21A moves in the X direction, the interference light is detected by the X reflecting mirror 26X and the X interferometer 23X. When moving in the Y direction, interference light is detected by the Y reflecting mirror 26Y and the Y interferometer 23Y. The interference light is converted into an electric signal, and the position of the stage 21 is managed.

  In addition, in the vacuum processing apparatus described above, the light reflecting means is provided on the top table side, and the interferometer is provided on the slider end side. Therefore, it is not necessary to arrange optical components such as a reflecting mirror and a beam splitter on the top table, and the top table can be downsized and the top table mass can be reduced. Thereby, a sample chamber can be reduced in size and cost can be reduced. In addition, the stage moving time can be reduced and the throughput of the semiconductor product can be improved.

  In this embodiment, in order to place importance on downsizing the top table, a configuration is shown in which a reflector is installed on the top table and an interferometer is installed on the slider. However, an interferometer is installed on the top table and a reflector is installed on the slider. Needless to say, the stage can be managed even if it is installed.

  In the case of a configuration in which an interferometer is installed on the top table and a reflecting mirror is installed on the slider, the size of the top table cannot be expected to be smaller than that of Patent Document 1. However, unlike Patent Document 1, there is no need to install a bar mirror on the wall of the sample chamber, so that even if the outer periphery of the sample chamber 2 expands or contracts due to thermal expansion, there is no effect on the reflecting mirror installed on the slider. Therefore, the influence on the positioning accuracy due to thermal expansion can be reduced, and excellent dynamic characteristics can be obtained.

<Comparison between the prior art and this embodiment>
The effect of the in-vacuum processing apparatus of this embodiment is verified by comparing the prior art with the first embodiment.

(Conventional sample room size and top table mass)
Here, the sample chamber size and the top table mass in the case of a review SEM apparatus (FIG. 11) having an optical microscope mechanism in which a bar mirror is installed on the top table, which is a conventional technique, are calculated.

  First, in order to calculate the sample chamber size, the length required for the bar mirror is obtained. In the case of having an optical microscope (hereinafter referred to as OM) in addition to the review SEM apparatus, the stage needs to move the entire Φ300 mm wafer with respect to the center position of both mechanisms (dotted line portion in FIG. 11). When the offset amount (Xof, Yof) between the SEM center 60 and the OM center 61 as shown in FIG. 12 is provided, the length Lb necessary for the bar mirror can be expressed as follows.

Lb = wafer diameter + offset amount between SEM center and OM center + laser beam diameter + laser beam axis distance = 300 + 150 + 6 + 12.7 = 468.7 mm

In addition, Lb was calculated using the following numerical values.
Wafer diameter: Φ300mm
SEM center and OM center offset (Xof, Yof): 150mm
Laser beam diameter: 6mm
Laser optical axis distance (double-pass optical axis distance to the bar mirror): 12.7 mm

  Actually, the region that guarantees the reflective surface accuracy of the bar mirror is about 1 to 2 mm inside the bar mirror outer shape, so the length Lb of the bar mirror is at least 470 mm or more.

  If the length of the bar mirror is obtained, the internal dimensions of the sample chamber can be expressed as follows.

Lx (Ly) = Bar mirror length (Lb) + Stage stroke
= 470mm + 450mm = 920mm

In addition, Lx (Ly) was calculated using the following numerical values.
Lb: 470 mm
Stage stroke: wafer diameter + SEM center and OM center offset = 450 mm

  In practice, a gap is required between the bar mirror and the sample chamber wall. Therefore, the sample chamber size is about 930 mm.

  Next, the bar mirror mass added to the top table mass is calculated. Assuming that the bar mirror shape is Φ30 mm × 470 mm and the material is general quartz glass, it becomes about 0.9 kg per one. Therefore, about 1.8 kg is added to the top table mass.

(Sample chamber size and top table mass of Patent Document 1)
Here, the dimensions of the sample chamber and the top table mass in the case of a review SEM apparatus (Patent Document 1) having an optical microscope mechanism in which an interferometer is installed on the top table are calculated.

  First, in order to calculate the sample chamber size, the top table size is obtained. Since the interferometer can usually be configured with a size of about 80 mm, if the interferometer mounting space required for the top table is 80 mm, the top table size (Ltx, Lty) can be expressed as follows.

Ltx (Lty) = wafer diameter + interferometer mounting space
= 300mm + 80mm = 380mm

  If the top table size is obtained, the sample chamber size can be expressed as follows.

Lx (Ly) = top table size (Ltx, Lty) + stage stroke + bar mirror mounting space (Lbt)
= 380mm + 450mm + 50mm = 880mm

  Actually, since a gap is required between the interferometer and the bar mirror, and the top table and the sample chamber, the size of the sample chamber is about 890 mm.

  Next, the interferometer mass added to the top table mass is calculated. Since one interferometer is about 0.3 kg, about 0.6 kg is added to the top table mass.

(Sample chamber size and top table mass in this embodiment)
Finally, the dimensions of the sample chamber and the top table mass in the case of a review SEM apparatus having an optical microscope mechanism in which a reflecting mirror is installed on the top table are calculated.

  First, in order to calculate the sample chamber size, the top table size is obtained. The length of the reflector required for reflection of the double path installed on the top table can be expressed as follows.

Optical axis distance 12.7 mm + laser beam diameter 6 mm + tolerance 5 mm = 23.6 mm
That is, in a normal double-pass optical system, about 30 mm is sufficient. Therefore, the thickness suitable for the length of the reflecting mirror is sufficient to be about 5 mm in consideration of processing and maintaining rigidity of the mirror alone. If the space required for mounting the reflector is 20 mm in consideration of the angle adjustment mechanism and the like, the top table size (Ltx, Lty) can be expressed as follows.

Ltx (Lty) = wafer diameter + reflection mirror mounting space
= 300mm + 20mm = 320mm

  If the top table size is obtained, the sample chamber size can be expressed as shown in FIG.

Lx (Ly) = top table size (Ltx / Lty) + stage stroke + interferometer size (Lit)
= 320mm + 450mm + 80mm = 850mm

  Actually, since a gap is required between the interferometer, the top table, and the sample chamber, the size of the sample chamber is about 860 mm.

  Next, the mirror mass added to the top table mass is calculated. Assuming that the reflector shape is Φ30 mm × 5 mm and the material is general quartz glass, it will be about 0.01 kg per piece. Therefore, about 0.02 kg is added to the top table mass.

(Effects of this embodiment compared with the prior art)
The effect of this embodiment compared with the prior art will be verified. First, the sample chamber size according to the present embodiment can be reduced to 930 mm−860 mm = 70 mm compared to the conventional technique shown in FIG. 11 and 890 mm−860 mm = 30 mm compared to Patent Document 1. Become.

  Next, the top table mass is 1.8 kg−0.02 kg = 1.78 kg lighter than the prior art shown in FIG. 11, and 0.6 kg−0.02 kg = 0. A weight reduction of 58 kg can be realized.

  As described above, according to the in-vacuum processing apparatus of the present embodiment, it is possible to improve the stage moving speed and acceleration by realizing miniaturization and weight reduction of the top table. Thereby, the stage moving time can be reduced and the throughput of the semiconductor product can be improved. In addition, the influence on stage vibration and positioning accuracy can be reduced, and excellent dynamic characteristics can be obtained.

<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIGS. In the first embodiment, the reference mirror is used as the reference light by using the reflecting mirror installed on the top table as a reference mirror and making the reference light enter the reference mirror. Here, a description will be given of a configuration in which a bar mirror attached to the upper part of the sample chamber wall near the column is used as a reference mirror.

(Configuration of laser length measuring device)
The interferometer used in the present embodiment is a type in which a reflecting mirror is arranged in addition to the interferometer to serve as a reference mirror, and the reference light is incident on the reference mirror to be used as reference light. That is, it is not the type (FIG. 11) in which the reference light is made incident on a reference mirror that is configured as an interferometer. The interferometer used in this embodiment is generally commercially available from laser length measuring instrument manufacturers and is used by many users.

  In this embodiment, reference mirrors are arranged as an X bar mirror 22X and a Y bar mirror 22Y. Each bar mirror is attached to the upper part of the vacuum inner wall located in the vicinity of the optical column 1 in the sample chamber 2 by a bar mirror mounting base 51, and is used as reference light by making reference light incident on the bar mirror.

  As described above, by mounting a bar mirror as a reference mirror in the vicinity of the optical column 1, even if a temperature difference between the optical column 1 and the outer peripheral wall of the sample chamber 2 occurs due to a temperature gradient, Can be measured. Moreover, even if the outer periphery of the sample chamber 2 expands and contracts due to thermal expansion, it is possible to reduce the influence such as distortion of the bar mirror.

  Further, since the bar mirror for generating the reference light is fixed to the upper part of the vacuum inner wall (wall surface of the ceiling plate) of the sample chamber 2, the X slider 21X and the Y slider 21Y on which the interferometer is mounted have a moving direction and Even if distortion occurs in the orthogonal direction, no measurement error occurs. At the same time, even when the movement of the interferometer is restricted, that is, when the guide rigidity of the X guide 28X and the Y guide 28Y is small and the distortion is large, the position measurement error of the interferometer is not included in the measurement error. Therefore, the influence on stage vibration and positioning accuracy can be reduced, and excellent dynamic characteristics can be obtained.

  Next, the fixing method of the bar mirror of this embodiment is demonstrated. FIG. 7 is a cross-sectional view showing a method of fixing the bar mirror 22X to the sample chamber. The bar mirror 22X is arranged on a mirror base 51 attached to the inner wall of the sample chamber 2, and is pressed against the adjusting screw 53 by a spring force generated by the pressing spring 55 and the pressing pin 54 so as not to move. The perpendicularity of the X-axis and Y-axis bar mirrors can be adjusted by the adjusting screw 53. The Y bar mirror 22Y has the same configuration.

<Third Embodiment>
Next, a third embodiment of the present invention will be described with reference to FIGS. In the first embodiment, the length measurement axes in the X direction and the Y direction are one axis at a time. Here, in order to measure yawing by adding another measuring axis in the X direction, 23X2 is attached to the X slider 21X in addition to the X1 interferometer 23X1.

(Configuration of laser length measuring device)
FIG. 8 shows the amount of deviation (ΔX, ΔY) between the SEM center 60 and the interferometer when the stage is moved in the first embodiment. Usually, most of the positioning errors caused by the stage attitude accuracy can be eliminated by measuring the measurement error using the reference wafer in advance and correcting it according to the actual stage movement coordinates as a correction value. However, some non-reproduction (variation) occurs due to factors such as the stage guide and table rigidity, resulting in positioning errors.

  Abbe errors ΔDx and ΔDy that occur when yawing non-reproduction is Δθ can be expressed as follows.

ΔDx ≒ ΔY ・ Δθ
ΔDy ≒ ΔX ・ Δθ

Taking the outer periphery of a Φ300 mm wafer as an example, assuming that Δθ = 5 μrad,
ΔDx ≒ 150mm ・ 5μrad = 750nm
It becomes. There is no problem if the apparatus can tolerate the positioning error, but in this embodiment, a review SEM in which positioning accuracy is improved when the error cannot be tolerated will be described.

  FIG. 9 is a plan view showing the configuration of the stage and the laser length measuring device of this embodiment.

  The stage position in the X direction is measured by the X1 interferometer 23X1, and the yawing is measured by the difference between the X1 interferometer 23X1 and the X2 interferometer 23X2. The difference from the first embodiment is that the mirror 49, the transmission window 56, and the receiver 42 are each increased to three axes due to the three-axis measurement, and the X reflector 26X is long enough to support the yawing axis. That's it.

  Here, the length LXyaw required for the X reflecting mirror 26X can be expressed as follows.

LXyaw = optical axis distance 12.7 mm + laser beam diameter 6 mm + tolerance 5 mm + (yaw measurement optical axis and X distance measurement optical axis distance 26 mm)
= 49.6mm

  Since the general outer shape of the wafer is Φ200 mm or Φ300 mm, the size of the top table for holding them needs to be at least the same size. In addition to this, conventionally, it is common to install a bar mirror with a length longer than the size of the top table or two interferometers with a certain width and size on the top table. .

  As can be seen from the above calculation, in the present embodiment, the X reflecting mirror 26X can be configured to be much shorter, thinner, and smaller than the outer shape of the top table. That is, the top table on which the X reflecting mirror 26X is mounted can be made small.

  With such a configuration, the size of the sample chamber can be reduced, and the apparatus cost and footprint can be reduced.

  Further, since yawing of the top table 21A can always be measured, position correction can be performed based on the stage position and the amount of non-reproducing yawing.

  Each measurement coordinate (Xn, Ym), positioning error (ΔXn, ΔYm) and yawing (θn) at that time when measured with a reference wafer in advance are stored as a set (for example, as a table) and actually positioned. The following correction amounts can be manipulated by the coordinates (X1 ′, Y1 ′) of time and yawing (θ1 ′).

ΔX1 ′ = ΔX1 + X1 ′ · (θ1−θ1 ′)
ΔY1 ′ = ΔY1 + Y1 ′ · (θ1−θ1 ′)

  In the present embodiment, the case where the top table has a simple table format has been described. However, the same effect can be obtained by a method of linearly complementing coordinates between tables, a curved surface correction equation using a polynomial, or the like. Regardless of which method is employed, the positioning accuracy can be dramatically improved as compared with the first embodiment, so that it is possible to sufficiently cope with an apparatus that has a relatively high positioning accuracy requirement. In addition, the laser beam axis distance from the observation point (the intersection of the SEM center and the wafer) is farthest away, focusing on yawing where the Abbe error is increased, and a length measurement axis is added. It can also be applied to rolling, and a certain improvement effect can be obtained also for these.

<Fourth Embodiment>
Next, a fourth embodiment of the present invention will be described with reference to FIG. Here, instead of the mirror 49 in the sample chamber used in the first to third embodiments, laser light is introduced into the interferometer by an optical fiber.

(Configuration and operation of laser length measuring device)
The spectroscopic unit 43 that divides the laser light emitted from the laser head 40 into two paths includes a beam splitter 41, a mirror 49, a condensing lens 43A, and an optical fiber connection 43B. In the present embodiment, the light is split into two axes, but even with a larger number of axes, the same configuration can be used.

  An optical fiber 48 is connected to the spectroscopic unit 43 and is connected to the atmosphere side of the irradiation side feedthrough 44 provided in the sample chamber 2. Thereafter, the optical fiber is connected again from the vacuum side of the irradiation side feedthrough 44, routed to the X mounting base 57 </ b> X and the Y mounting base 57 </ b> Y, and connected to the irradiation unit 46.

  The irradiation unit 46 can be formed by a collimating lens (not shown) and an optical fiber connecting part. However, a dual frequency laser as shown in Patent Document 1 is introduced by a separate optical fiber, and 2 in the irradiation unit by a polarization splitter. It is also possible to irradiate the interferometer after synthesis as a frequency laser.

  The X interferometer 23X and the Y interferometer 23Y are arranged so as to coincide with the axial center of the wafer 10, the positional relationship between the irradiation unit 46 and each interferometer is aligned, and the interferometer is simply connected by connecting the fibers. An appropriate incident angle and position can be secured.

  The light receiving pickup 47 that receives the laser light incident on and reflected by the X reflecting mirror 26X and the Y reflecting mirror 26Y disposed on the top table 21A is connected to the vacuum side of the light receiving side feedthrough by an optical fiber. The light receiving pickup has a condensing lens (not shown) mounted at the entrance, and has a function of introducing laser light into the optical fiber. Thereafter, the optical fiber 48 is connected again from the atmosphere side of the irradiation side feedthrough 44, connected to the receiver 42, converted into an electrical signal, transmitted to the laser unit 75, and converted into position information.

  In the present embodiment, the illumination unit, the light receiving pickup, and the interferometer are shown separately, but these can also be configured as a single unit, and by using such an integrated configuration, compactness is achieved. And improved ease of installation. Here, for the optical fiber on the vacuum side, the coating is preferably made of a low outgas material such as tetrafluoroethylene resin in order to reduce contamination by the emitted gas. Further, when the vacuum degassing is performed at a temperature at which the optical fiber is not damaged (for example, 80 ° C.), the amount of emitted gas can be further reduced. Also, the optical fiber feed-through is divided into the irradiation side and the light-receiving side. However, depending on the device layout, the optical fiber for irradiation and the optical fiber for light reception may be divided for each length measurement axis. good. Alternatively, a single feedthrough that can connect all the optical fibers for irradiation and the optical fibers for light reception may be used.

  Conventionally, even if an optical fiber is introduced into an interferometer on a top table as in Patent Document 1, it is necessary to route the optical fiber to a top table that moves in a two-dimensional plane, which complicates the optical path. Further, when the length of the optical fiber is increased, the amount of released gas generated by the volatilization of the resin used to coat the optical fiber also increases, and the effect on the degree of vacuum of the in-vacuum processing apparatus becomes a problem.

  However, in the present embodiment, with the above configuration, it is possible to mount an optical fiber movable in a vacuum with a short length without being routed to the top table. Thereby, since the quantity of resin used for coating | covering an optical fiber can be decreased, the emitted gas generation amount can be reduced.

  In addition, since the optical fiber of the present embodiment only needs to be movable in one direction, either the X direction or the Y direction, it is easy to route. Thereby, damage to the optical fiber such as bending and rubbing can be reduced.

<Summary>
In the present embodiment, the bar mirror or interferometer that has been conventionally installed on the top table 21A is removed, and the X reflecting mirror 26X and the Y reflecting mirror 26Y are installed on the top table 21A. The X interferometer 23X and the Y interferometer 23Y are installed on the X slider 21X and the Y slider 21Y.

  With such a configuration, the top table can be reduced in size and weight, and the stage moving speed and acceleration can be improved. Thereby, the stage moving time can be reduced and the throughput of the semiconductor product can be improved. In addition, the influence on stage vibration and positioning accuracy can be reduced, and excellent dynamic characteristics can be obtained.

  In this embodiment, a bar mirror is attached as a reference mirror to the upper part of the sample chamber wall near the column.

  With such a configuration, the stage position can be measured at a temperature in the vicinity of the column even if a temperature difference from the optical column 1 occurs on the outer peripheral wall of the sample chamber 2 due to a temperature gradient. In other words, even if the outer periphery of the sample chamber 2 expands or contracts due to thermal expansion, it is possible to reduce the influence of distortion and the like of the bar mirror.

  Further, even when the X slider 21X and the Y slider 21Y on which the interferometer is mounted are distorted in the direction orthogonal to the moving direction, or when the guide rigidity of the X guide 28X and the Y guide 28Y is small and the distortion is large, Interferometer position variation is not included in the measurement error. Therefore, the influence on stage vibration and positioning accuracy can be reduced, and excellent dynamic characteristics can be obtained.

  In this embodiment, in addition to the X1 interferometer 23X1, 23X2 is attached to the X slider 21X.

  With such a configuration, while the top table on which the X reflecting mirror 26X is mounted can be made small, another measuring axis in the X direction can be added and yawing measurement can be performed. As a result, the size of the sample chamber can be reduced, and the apparatus cost and footprint can be reduced. Further, since yawing of the top table can always be measured, position correction can be performed based on the stage position and the amount of non-reproducing yawing.

  In the present embodiment, laser light is introduced into the interferometer attached to the slider using an optical fiber.

  With such a configuration, the optical fiber can be mounted with a short length without being routed to the top table. Thereby, since the quantity of resin used for coating | covering an optical fiber can be decreased, the emitted gas generation amount can be reduced. In addition, since the optical fiber of the present embodiment only needs to be movable in one direction, either the X direction or the Y direction, it is easy to route. Thereby, damage to the optical fiber such as bending and rubbing can be reduced.

  In this case, if the coating of the optical fiber is tetrafluoroethylene resin, the generation amount of the released gas can be further reduced.

DESCRIPTION OF SYMBOLS 1 ... Column, 2 ... Sample chamber, 3 ... Load lock, 4 ... Mount, 5 ... Vacuum pump, 6 ... Mount, 7 ... Interferometer container, 10 ... Wafer, 11 ... electron gun, 12 ... electron beam, 13 ... electron lens, 14 ... deflector, 14A ... position deflector, 14B ... scanning deflector, 15 ... -Detector, 16 ... Electron lens, 17 ... Deflection control unit, 21 ... Stage, 21A ... Top table, 21B ... Connection base, 21C ... Connection column, 21X ... X slider, 21Y ... Y slider, 22 ... bar mirror, 22X ... X bar mirror, 22Y ... Y bar mirror, 23 ... interferometer, 23X ... X interferometer, 23X1 ... X1 Interferometer, 23X2 ... X2 interferometer, 23Y ... Y interferometer, 24 ... Electrostatic chuck, 25 ... Z sensor, 26 ... reflecting mirror, 26X ... X reflecting mirror, 26Y ... Y reflecting mirror, 27X ... X slider guide, 27Y ... Y slider guide, 28X ... X guide, 28Y ... Y guide, 29X ... X mounting spacer, 29Y ... Y mounting spacer, 31 ... Transport robot, 32 ... Vacuum side gate valve, 33 ... Atmosphere side gate valve, 40 ... laser head, 41 ... beam splitter, 42 ... receiver, 43 ... spectral unit, 43A ... condensing lens, 43B ... optical fiber connector, 44 ... irradiation side feedthrough, 45 ... light reception side feedthrough, 46 ... irradiation unit, 47 ... light receiving pickup, 48 ... optical fiber, 49 ... mirror, 51 ... mirror , 52 ... Screw receiver, 53 ... Adjustment screw, 54 ... Pressing pin, 55 ... Push spring, 56 ... Transmission window, 57X ... X mounting base, 57Y ... Y mounting 60, SEM center, 61 ... OM center, 70 ... column controller, 71 ... position controller, 72 ... stage controller, 73 ... image controller, 74. ..Monitor, 75 ... Laser unit

Claims (7)

A vacuum processing apparatus having a vacuum sample chamber and a sample stage stored in the vacuum sample chamber,
A top table provided on the sample stage and arranged to be movable along a first movement axis and a second movement axis intersecting each other;
A pair of light reflecting means and a first interferometer, one of which is disposed on the top table and the other of which is disposed away from the top table;
Means for introducing light to the first interferometer;
A receiver for detecting the output light of the first interferometer,
The pair of light reflecting means and the first interferometer are arranged in parallel to the first movement axis, and the pair of light reflecting means and the first interferometer have a positional relationship facing each other. An in-vacuum processing apparatus that is movable along the second movement axis while being maintained. In the vacuum processing apparatus of Claim 1,
The pair of light reflecting means and the first interferometer are provided with at least one in a direction parallel to the first movement axis and at least one in a direction parallel to the second movement axis. In-vacuum processing equipment. In the vacuum processing apparatus of Claim 1,
A second interferometer disposed at a position facing the light reflecting means;
An in-vacuum processing apparatus, wherein a set of the light reflecting means, the first interferometer and the second interferometer is movable in an axial direction parallel to the second movement axis. In the vacuum processing apparatus of Claim 1,
An optical fiber for introducing and deriving the light to and from the interferometer;
An in-vacuum processing apparatus comprising a feedthrough for introducing the optical fiber from the atmosphere into a vacuum. In the vacuum processing apparatus of Claim 4,
The in-vacuum processing apparatus, wherein the optical fiber includes a coating containing tetrafluoroethylene resin. In the vacuum processing apparatus of Claim 1,
Having a bar mirror attached to the ceiling wall of the vacuum sample chamber;
An in-vacuum processing apparatus, wherein a longitudinal direction of the bar mirror is parallel to the second moving axis. In a vacuum processing apparatus for measuring the position of a top table that moves in an XY horizontal plane with a laser beam in a vacuum chamber,
An X-axis slider attached to the top table and sliding the top table in the Y-axis direction;
A Y-axis slider attached to the top table and sliding the top table in the X-axis direction;
A stage controller that drives the X-axis slider and the Y-axis slider to move the top table to a desired position;
An X interferometer attached to the X-axis slider, translating the Y-axis in conjunction with the X-axis slider, receiving the laser beam and generating interference light;
A Y interferometer that is attached to the Y-axis slider, translates the X-axis in conjunction with the Y-axis slider, receives the laser light, and generates interference light;
An X reflector that is installed on the top table and is located on the same Y axis as the X interferometer and reflects the interference light;
A Y reflecting mirror that is installed on the top table and is located on the same X axis as the Y interferometer and reflects the interference light;
An in-vacuum processing apparatus comprising:

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