JP3250282B2 - Wafer surface inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting foreign particles attached to the surface of a wafer, and more particularly to an apparatus for inspecting a plurality of wafers simultaneously on one wafer stage. It is possible. To a device that

[0002]

2. Description of the Related Art Along with the high integration of semiconductor devices, pattern line widths have been miniaturized, and in a 4 megabit DRAM, the pattern line width has reached a sub-micron region, and further has reached a half-micron region to a quarter micron region. On the other hand, the number of steps on the wafer surface is increasing with the increase in the number and complexity of circuit patterns, and a technique for accurately detecting particles on the wafer is required.

Conventionally, various types of wafer surface inspection apparatuses have been proposed, but the basic principle is that laser light emitted from a laser light source such as a He-Ne laser or a semiconductor laser is applied to the wafer surface. Irradiation, the scattered light is collected on a photomultiplier tube, and the particle size, number, distribution, etc. of the particles are analyzed based on the scattering intensity at this time.

[0004] Wafer surface inspection devices are roughly classified into two types, a raster type and a spiral type, according to the scanning method of laser light. The raster system is a system in which the laser beam is scanned in a zigzag manner on the wafer surface by moving the wafer stage in the Y direction while synchronizing with the high-speed reciprocating motion of the galvanomirror of the optical system in the X direction. The scattered light caused by the particles is focused on the photomultiplier via the focusing lens.

On the other hand, in the spiral method, a laser stage is rotated at a constant linear velocity and at the same time is moved in the radial direction of the wafer, thereby scanning the laser light spirally from the center of the wafer to the outer periphery. It is. The scattered light is collected on the photomultiplier via an integrating sphere or the like.

[0006]

The conventional wafer surface inspection apparatus is a single wafer type apparatus for inspecting wafers one by one. For example, it takes about 60 seconds to inspect one 5-inch diameter wafer even with the current highest level equipment. However, in a semiconductor device manufacturing line, each time various processes are completed, a wafer is required. Since the inspection is performed at any time, the inspection time or the waiting time greatly limits the throughput. In order to mitigate this decrease in throughput, several wafer surface inspection devices are usually installed in one line of the production line, but this increases the equipment budget and the occupied floor area in the clean room. It is a cause to cause.

Further, there is a problem that occurrence of cross contamination cannot be completely prevented in a single-wafer apparatus. This is because wafers with different contamination levels after various processes are inspected on a common wafer stage, and particles generated in one process adhere to the back surface of another wafer using the wafer stage as a medium, causing contamination. Is diffused. However, it is impractical to provide the same number of wafer inspection devices as the types of processes in view of budget and occupied floor space.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wafer surface inspection apparatus which is excellent in throughput and economy and does not cause cross contamination.

[0009]

SUMMARY OF THE INVENTION A wafer surface inspection apparatus according to the present invention has been proposed in order to achieve the above-mentioned object, and has a polygonal column shape capable of mounting a wafer on each side wall surface. A driving stage for rotating the wafer stage around a rotation axis parallel to the main surface of the wafer; and a driving unit for scanning the main surface of the wafer with laser light while scanning the laser beam. An inspection optical system for detecting scattered light caused by foreign matter on the surface, wherein a trajectory of the beam spot of the laser light within one cycle of the rotational movement of the wafer stage is formed over a plurality of wafers. That's what I did.

The driving means used here is for moving the wafer stage in a direction orthogonal to the trajectory of the beam spot while synchronizing with the rotational movement.

In the apparatus according to the present invention, further, the inspection optical system may make the position of the beam spot on the main surface of the wafer orthogonal to the trajectory while synchronizing with the rotational movement of the wafer stage. A shift mechanism for shifting in the direction.

[0012]

According to the present invention, a batch processing method for processing several wafers at a time is adopted. The present invention is provided with a wafer stage on which a plurality of wafers can be placed at one time. I have. In this apparatus, a plurality of wafers are scanned in one cycle of a rotating motion performed by a wafer stage. According to such a method, the starting and stopping of the means for driving the wafer stage are performed before the start of the surface inspection and the wafer stage.
The inspection need only be performed when all the wafers on the stage have been inspected, and the movement speed during that period can be kept high. Therefore, it is possible to greatly improve the throughput.

[0013] The plurality of wafers are wafers having a polygonal prism shape.
The trajectory of the beam spot on the wafer is placed on a straight line by mounting the wafer stage on each side wall surface and rotating the wafer stage around a rotation axis parallel to the main surface of the wafer by the driving means. State.

By using a shift mechanism in the inspection optical system, the position of the beam spot on the main surface of the wafer can be shifted in a direction orthogonal to the trajectory.
This shift operation is also synchronized with the rotational movement of the wafer stage.

When a wafer is inspected using the wafer surface inspection apparatus according to the present invention, inspection information on the surfaces of a plurality of wafers can be obtained at a time. In this case, a plurality of wafers need to be distinguished from each other during the inspection process.
This can be realized by, for example, detecting a change in the reflectance between the wafer surface and the stage surface and forming a program capable of sequentially specifying the position of each wafer in synchronization with the detection signal.

In the present invention, since a plurality of wafers can be inspected collectively, cross contamination can be minimized. In other words, it is sufficient to specify in advance that only a wafer carried out from the same process is always set at a specific wafer set position on the wafer stage. As a result, there is no possibility that particles generated in another process adhere to the back surface of another wafer using the wafer stage as a medium, and as a result, contamination is diffused.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

Prior to the embodiment of the present invention, a specific example prior to the present invention will be described.

In this prior example, it is possible to simultaneously inspect the surface of eight wafers while rotating a disk-shaped wafer stage. An outline of this configuration will be described with reference to FIG.

This wafer surface inspection apparatus 100 is shown in FIG.
As shown in FIG. 1A, a disc-shaped wafer stage 1, a motor 3 connected via a rotating shaft 2 for rotating the wafer stage 1 at a high speed in the direction of an arrow W, and an inspection optical system are main components. Element. On the wafer stage 1,
A configuration is provided in which eight wafers 50 can be set at positions A to H obtained by dividing the circumference into eight equal parts by using a clamp, an electrostatic chuck mechanism, or the like (not shown).

The inspection optical system basically includes a laser light source 4,
A collimator lens 5 for enlarging and shaping the beam shape of the laser light emitted from the laser light source 4;
A scanning mirror 6 for shifting the trajectory of the spot on the wafer 50, a condensing lens 7 for condensing the scattered light of the laser beam irradiated on the wafer 50 by the particles,
It comprises a photomultiplier tube 8 for detecting this weak scattered light. The scanning mirror 6 can be tilted in the direction of the arrow Y, whereby the trajectory l ₁ of the laser spot can be sequentially shifted on the wafer 50 in the Y direction.

In the following description, this "Y direction" is defined as a direction perpendicular to the orientation flat portion. On the other hand, the X direction is a direction perpendicular to the Y direction, that is, a direction parallel to the orientation flat portion.

A signal processing system (not shown) is further connected to the subsequent stage of the inspection optical system, and after an output signal of the photomultiplier tube 8 is amplified by a preamplifier, various signal processing is performed based on the detection signal. Thus, particle mapping, drive control of the wafer stage 1, scanning control of laser light, and the like are performed.

In this wafer surface inspection apparatus 100,
The scanning by the laser beam is performed, for example, in the radial direction from the center side of the wafer stage 1. In this case, while the wafer stage 1 makes one round, position A → position B →
... The top of each wafer 50 is scanned in the order of position H. When the rotation of the wafer stage 1 enters the second rotation, the scanning mirror 6 is slightly tilted in the Y direction, and scanning is performed in the direction of the orientation flat portion in the same manner as in the third and fourth rotations. to continue. That is, while maintaining the high speed rotation state of the wafer stage 1 is shifted toward the turn outer peripheral side loci l ₁ of the beam spot by the operation of the scanning mirror 6. However, this high-speed rotation requires the wafer stage 1 to keep the inspection sensitivity constant.
Is performed at a constant linear velocity, that is, the rotational speed is reduced as the scanning portion moves toward the outer peripheral side.

In such an apparatus, the trajectory l ₁ of the beam spot on each wafer 50 is substantially arc-shaped as shown in FIG. Here, "substantially" is denied because the inclination of the scanning mirror 6 is equal to that of the wafer stage 1.
This is because it may not be strictly arcuate depending on whether the rotation is performed stepwise or continuously in synchronization with one rotation. That is, when a gradual and constitute a part of each other loci l ₁ between the adjacent concentric circles, forming loci l ₁ if it is continuously throughout eight wafers 50 are spirally Because it is done.

With the use of the wafer surface inspection apparatus 100, the inspection time per wafer 50 can be greatly reduced as compared with the conventional case. Also, by specifying the type of the wafer 50 set in each of the positions A to H in advance,
Cross contamination can be prevented.
For example, at position A, a wafer after an Al film is formed by sputtering, at position B, a wafer after depositing an interlayer insulating film, at position C, a wafer after etching a polycide film, and so on. If the relationship between the position and the process is fixed, the wafer 50 having different types of particles or different particle levels can be used.
The risk of cross contamination between them is extremely low.

The occupied floor area of the apparatus 100 is even smaller than that of eight conventional single-wafer apparatuses. Therefore, the throughput can be greatly improved without sacrificing any economic efficiency.

The above-described wafer surface inspection apparatus uses a beam
The shift of the spot trajectory l ₁ may be achieved by the horizontal feed mechanism of the wafer stage 1. An outline of the configuration of this device will be described with reference to FIG.
Note that reference numerals in FIG. 2 are partially common to those in FIG. 1, and description of common parts is omitted.

The wafer surface inspection apparatus 101
The stage 1 has a disk shape as in the first embodiment and can set eight wafers 50 at the positions A to H. The motor 3 for driving the stage is further integrated with a motor holding member 9. ing. The motor holding member 9 can horizontally move the wafer stage 1 in the direction of arrow P by being engaged with a screw shaft 10 coaxially connected to a horizontal feed motor 11.

In the wafer surface inspection apparatus 101, even if the scanning mirror 6 of the inspection optical system remains fixed, the horizontal position of the wafer stage 1 changes the relative position between the wafer 50 and the beam irradiation site. A trajectory l ₁ of the beam spot similar to the above is formed.

Next, a specific embodiment of the wafer surface inspection apparatus according to the present invention will be described with reference to FIG.

Embodiment 1 A wafer surface inspection apparatus 102 according to the present invention simultaneously inspects the surface of eight wafers set on the side walls of a wafer while rotating an octagonal column-shaped wafer stage. It is possible to do. Note that reference numerals in FIG. 3 are partially common to those in FIG. 1, and detailed description of common portions is omitted.

The wafer surface inspection apparatus 102 according to the present invention
As shown in FIG. 3 (a), an octagonal prism wafer
The main components are a stage 21, a motor 23 connected via a rotating shaft 22 for rotating the wafer stage 21 in the direction of arrow Q at a high speed, and an inspection optical system. At positions a to h corresponding to the eight sidewall surfaces 21 a of the wafer stage 21, a total of eight wafers 50 can be set one by one using a clamp, an electrostatic chuck mechanism, or the like (not shown). It is configured.

In this wafer surface inspection apparatus 102,
The scanning by the laser beam is performed, for example, from the orientation flat side of the wafer 50 toward the top and from the left side to the right side in the drawing. In this case, while the wafer stage 21 makes one rotation, the left end of each wafer 50 is scanned in the order of position a → position b →... → position h. When the rotation of the wafer stage 21 enters the second rotation, the scanning mirror 6 is slightly tilted in the X direction, and scanning is continued in the rightmost direction in the same manner as in the third and fourth rotations.

[0035] In the wafer surface inspection apparatus 102, since the principal surface of the rotary shaft 22 and the wafer 50 of the wafer stage 21 are parallel, as shown in FIG. 3 (b), the trajectory of the beam spot l ₂ Are straight lines substantially perpendicular to the orientation flat and parallel to each other. Here, “substantially” is refused because the wafer stage 2
This is because it is assumed that the tilting operation of the scanning mirror 6 synchronized with the one rotational movement is performed not only stepwise but also continuously. In this case, the rotation of the wafer stage 21 may be a constant speed rotation, and no control such as a constant linear velocity is required. However, since the incident angle of the laser beam on the wafer 50 changes every moment depending on the rotation angle of the wafer stage 21, it is necessary to incorporate a control mechanism for keeping the angle constant in the optical system.

Embodiment 2 In this embodiment, as a modification of Embodiment 1, a wafer surface inspection capable of simultaneously performing a surface inspection of eight wafers while rotating an octagonal column-shaped wafer stage in the horizontal direction. The device was configured. An outline of this configuration will be described with reference to FIG. This wafer surface inspection apparatus 103 is configured as shown in FIG.
As shown in (a), an octagonal pillar-shaped wafer stage 31 and a motor 3 connected via a rotating shaft 32 to rotate the wafer stage 31 in the direction of arrow R at high speed.
3 and the inspection optical system are main components. Position a corresponding to eight side wall surfaces 31a of wafer stage 31
The position h is configured such that a total of eight wafers 50 can be set one by one.

The trajectory l3 of the beam spot on the wafer 50 when the wafer surface inspection apparatus 103 is used.
4B run from left to right in the drawing of the wafer 50 and are sequentially arranged from the top toward the orientation flat portion, as shown in FIG. 4B, for example. In this case, the wafer stage 31 may be rotated at a constant speed. However, as in the first embodiment, a control mechanism for keeping the incident angle of the laser beam on the wafer 50 constant should be incorporated in the optical system. is necessary.

[0038]

As described above, the wafer surface inspection apparatus according to the present invention is capable of simultaneously inspecting a plurality of wafers on one wafer stage, thereby greatly improving the throughput. Further, the device budget, the occupied floor area, and the size can be significantly reduced as compared with the case where a plurality of devices are provided. Furthermore, by designating the wafer setting position on the wafer stage for each process, it is possible to effectively suppress cross contamination.

The present invention makes it possible to greatly improve economic efficiency, throughput, yield, and the like, for example, in the field of manufacturing semiconductor devices.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration example of a wafer surface inspection apparatus prior to the present invention, which has a disk-shaped wafer stage, and (a) is a schematic perspective view showing a main part of the apparatus. (B) is a plan view showing the trajectory of the beam spot on the wafer.

FIG. 2 is a schematic perspective view showing another configuration example of a wafer surface inspection apparatus having a disk-shaped wafer stage.

FIG. 3 shows a wafer surface inspection apparatus according to the present invention, and is a view showing a configuration example of a wafer surface inspection apparatus having an octagonal column-shaped wafer stage, and (a) shows a main part of the apparatus. Schematic perspective view, (b) beam on wafer
It is a top view showing the locus | trajectory of a spot.

4A and 4B are diagrams showing another configuration example of a wafer surface inspection apparatus having an octagonal column-shaped wafer stage, wherein FIG. 4A is a schematic perspective view showing a main part of the apparatus, and FIG. It is a top view showing the locus | trajectory of a spot.

[Description of Signs] 21, 31 Wafer stage, 22, 32 Rotation axis, 23, 33 Motor, 4 Laser light source, 6
Scanning mirror, 8 photomultiplier tube, 21a, 31a
Side wall (of wafer stage), 50 wafers, 1
02,103 Wafer surface inspection device, l ₂ , l ₃
Trajectory (of beam spot)

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-179242 (JP, A) JP-A-4-330751 (JP, A) JP-A-4-206940 (JP, A) JP-A-61- 59851 (JP, A) JP-A-2-101583 (JP, A) JP-A-4-152545 (JP, A) JP-A-1-129145 (JP, A) JP-A-4-59818 (JP, U)

Claims (3)

(57) [Claims] (1) A polygonal column is formed on each side wall surface.
A wafer stage on which a wafer can be placed, and the wafer around a rotation axis parallel to a main surface of the wafer.
Drive means for rotating the wafer stage; and an inspection optical system for detecting scattered light caused by foreign matter on the main surface while scanning laser light on the main surface of the wafer, the wafer stage comprising: A trajectory of the beam spot of the laser beam within one cycle of the rotational movement of the wafer surface inspection apparatus formed on a plurality of wafers. 2. The driving means further synchronizes the wafer stage with the beam stage while synchronizing with the rotational movement.
2. The wafer surface inspection apparatus according to claim 1, wherein the wafer surface inspection apparatus is moved in a direction orthogonal to a locus of the spot. 3. A shift mechanism for shifting a position of the beam spot on a main surface of the wafer in a direction orthogonal to the trajectory while synchronizing with the rotational movement of the wafer stage. Claim 1 comprising
2. A wafer surface inspection apparatus according to claim 1.