JPH0743311A - Surface inspection device and aligner with the device - Google Patents

Abstract

PURPOSE:To make detection sensitivilty nearly constant at every point on the surface to be inspected. CONSTITUTION:A light which is emitted from a laser 3 and shows Gaussian sectional intensity distribution is converted into a parallel light through a lens 4, and the parallel light is then separated by a optical separator 20 into two lights, that is, a reflected light directed upward and a transmissive light going straight toward the separator 21. The reflected light is further reflected by a corner cube 22 and is made incident to the separator 21 so as to overlap the transmissive light partially, then the reflected light and transmissive light are combined together, so that a light flux in which its sectional intensity distribution is made nearly constant can be formed. Furthermore, the light flux is made incident to the surface of reticle 1 in a direction almost parallel thereto, and the scattering lights from foreign matters 11 adhering on the surface of the reticle 1 are received by a refractive-index distribution type micro-lens array 12, then the pictures of the foreign matters 11 are projected on a one- dimensional image sensor 13 by the array 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface condition inspection apparatus, and in particular, a circuit pattern used for manufacturing semiconductor devices such as IG and LSI, CCDs, liquid crystal panels, magnetic heads and other devices. A surface state inspection device for accurately detecting the presence or absence of foreign matter and its position on the surface of a pellicle film for preventing the foreign matter from adhering to the surface of a substrate such as a reticle or a photomask or / and to a substrate mounted on the substrate, and The present invention relates to an exposure apparatus including an apparatus.

[0002]

2. Description of the Related Art Generally, in an IC or LSI manufacturing process, a circuit pattern formed on a substrate such as a reticle or photomask is transferred onto a resist-coated wafer by an exposure device (stepper or mask aligner). is doing.

At the time of this transfer, if a foreign substance such as a pattern defect or dust is present on the surface of the substrate, the foreign substance is also transferred onto the wafer at the same time, which reduces the yield of IC or LSI manufacturing.

In particular, when a reticle is used and a circuit pattern is repeatedly printed on a large number of shot areas on the wafer by the step-and-repeat method, if there is one harmful foreign substance on the reticle, this foreign substance will be present on the entire surface of the wafer. It is burned, which greatly reduces the yield of IC and LSI manufacturing.

Therefore, it is indispensable to detect the presence of foreign matter on the substrate in the process of manufacturing ICs and LSIs. Generally, there is an inspection method utilizing the property that foreign matter isotropically scatters light. It is used.

For example, a parallel light beam is irradiated onto the surface to be inspected obliquely from above, and scattered light from the foreign matter is made incident on a one-dimensional image sensor (sensor array) by a gradient index microlens array to bond the foreign matter. The surface to be inspected is inspected by imaging.

[0007]

When the laser beam from the semiconductor laser is obliquely incident on the surface to be inspected, the intensity distribution in the cross section of the laser beam is a Gaussian distribution. As shown, the light intensity distribution 50 of the linear inspection region formed on the surface to be inspected also has a Gaussian distribution.

At this time, when the surface to be inspected has a setting error in the Z direction by ΔZ, as shown in FIG. 5 (B), the light intensity distribution 50 of the linear inspection area formed on the surface to be inspected. Shifts in the Y direction.

Therefore, conventionally, the detection sensitivity for foreign matter in the inspection area has varied.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a surface state inspection apparatus capable of making the detection sensitivity on the surface to be inspected constant, and an exposure apparatus including the apparatus. The purpose is to do.

In order to achieve this object, the surface condition inspection apparatus of the present invention illuminates the surface to be inspected with a beam having a nonuniform cross-sectional intensity distribution, and detects scattered light generated on the surface to be inspected. The apparatus for inspecting the surface state of the surface to be inspected has means for making the cross-sectional intensity distribution of the beam substantially uniform.

In order to achieve this object, another surface condition inspection apparatus of the present invention is designed to form a parallel beam having a non-uniform cross-sectional intensity distribution on a surface to be inspected to form a substantially linear illumination area. An apparatus for inspecting the surface state of the surface to be inspected by obliquely incident on the surface to be inspected and detecting scattered light generated on the surface to be inspected, has means for making the cross-sectional intensity distribution of the parallel beam substantially uniform. is doing.

In one aspect of the surface condition inspection apparatus, the parallel beam is directed from a direction substantially parallel to the surface to be inspected so as to form a substantially linear illumination area on the surface to be inspected. Is made incident on. This substantially parallel direction means that the incident angle of the parallel beam on the surface to be inspected is
Including those of 0.5 ° to 6.5 °.

The cross-sectional intensity equalizing means divides the parallel beam into two light beams and recombines the two light beams so that when the cross-sectional intensity distributions of the two light beams are combined, the distributions become substantially uniform. Consisting of.

In a preferred aspect of the present invention, the cross-section intensity equalizing means supplies two light beams having a uniform cross-sectional intensity distribution, and the two light beams are directed to the corresponding surfaces to be inspected.

The surface condition inspection apparatus of the present invention is an IC, LS
It is used by being incorporated in an exposure apparatus for manufacturing various devices such as semiconductor devices such as I, CCDs, liquid crystal panels, magnetic heads, etc., or used alone.

By using the surface condition inspection apparatus of the present invention to inspect for a foreign substance on the reticle for manufacturing the device or on the pellicle for protecting the reticle from the foreign substance, the foreign substance is not overlooked. The yield in manufacturing the device is improved.

[0018]

1 is a schematic view showing an embodiment of the present invention, FIG. 1 (A) is a view showing an optical system, and FIG. 1 (B) is a view showing an appearance.

Since the laser light emitted from the semiconductor laser 3 has a divergence angle, it is converted into a parallel light flux by the collimator lens 4 and directed to the intensity distribution uniformizing device (20 to 22) which is a feature of the present invention. .

The laser light composed of parallel light beams is divided into two light beams having the same light intensity by the beam splitter 20, the transmitted light B is incident on the beam splitter 21, and the reflected light A is reflected twice by the corner cube 22 to form a beam. It is incident on the splitter 21. Since the corner cube 22 is set to be shifted by a predetermined amount L / 2 in the X direction, the beam splitter 21 synthesizes the light fluxes A and B and then the beam splitter 2
The light beams Aa and Ba emitted from 1 in the X direction are parallel light beams, and the distance between the centers of the two light beams is separated by L.

Since the beam splitter 21 is a half mirror, the light beams Ab and Bb whose center-to-center distance is L are emitted in the Z direction from the beam splitter 21, and the combined light beams Aa + Ba and Ab + Bb are emitted in two directions in the light beam 6a. , 6b
As the inspection light fluxes on the blank surface 1a and the lower pellicle surface of the reticle 1, respectively.

The blank surface inspection light beam 6a has a substantially uniform cross-sectional intensity distribution, and is obliquely incident on the blank surface 1a at a predetermined angle θ by the mirror 7. The cross-sectional intensity distribution of the lower pellicle surface inspection light beam 6b is substantially uniform, and is obliquely incident on the lower pellicle surface 1b at a predetermined angle θ by the mirrors 8 and 9. As a result, the linear illumination area 10 formed by the laser beam extending in the Y direction is formed on each surface to be inspected. The intensity of unevenness in each linear illumination area is small.

For simplification of description, the present embodiment will be described by taking the inspection of the blank surface 1a, which is the back surface of the reticle 1, as an example.

When the foreign matter 11 exists on the illumination area 10, scattered light is generated from the foreign matter 11. The scattered light is imaged on the line sensor 13 by the imaging lens 12 for receiving scattered light arranged along the illumination area 10. In this embodiment, an array lens such as a gradient index lens array is used as the scattered light receiving lens, but an imaging lens such as a normal camera lens or a Fourier transform lens may be used.

Further, as shown in FIG. 1B, the entire optical system 14 is relatively scanned with respect to the reticle 1 in the X direction intersecting (orthogonal to) the illumination area 10 so that the reticle 1 is scanned. The entire surface is inspected.

Details of the intensity distribution uniformizing device 5 are shown in FIGS.
This will be described with reference to FIG.

FIG. 2 is a sectional view of the intensity distribution equalizing device 5. In FIG. 2, the parallel light beam C emitted from the collimator lens 4 has a Gaussian distribution in which the intensity distribution of the light beam cross section is Ic.

The parallel light beam C is once split by the beam splitter 20 into two light beams A and B having the same intensity. The transmitted light beam B is the beam splitter 21 as it is.
Head straight toward and the reflected light flux A is the corner cube 22.
Is reflected twice, the optical path is turned back, and is directed to the beam splitter 21. The two light fluxes A and B are recombined by the beam splitter 21, but since the corner cube 22 is set by shifting by a predetermined amount L / 2 in the X direction, the light fluxes A and B are set by the beam splitter 21.
The light fluxes Aa and Ba and the light fluxes Ab and Bb emitted from the beam splitter 21 after being combined are parallel light fluxes, and the distance between the centers of the light fluxes is L.

FIG. 3 is an explanatory view showing a light flux after the light flux Aa and the light flux Ba are combined.

By parallel shifting the distance between the centers of the two light fluxes Aa and Ba by L, the Gaussian distributions of the two light fluxes are shifted and overlapped, and as shown in FIG. 3, a setting error ΔZ in the Z direction of the surface 10 to be inspected. It is possible to obtain a light flux having a substantially uniform intensity distribution within the range of the light flux diameter S required for the inspection. Here, the luminous flux diameter S required for inspection is a setting error ΔZ in the Z direction between the inspection area Y ′ on the reticle 1 and the reticle 1,
It is related to the incident angle θ of the inspection light beam 6a with respect to the reticle 1, and is obtained from the following equation.

[0031]

[Outer 1]

Further, the intensity distributions Ia and Ib due to the superposition of the beams shown in FIG. 3 (Ib is the intensity distribution of the light beam 6b)
Is related to the shift amount L of the light flux and the intensity distribution Ic of the parallel light flux from the collimator lens 4 (the light flux diameter is ω at the 1 / e ² value of the central intensity), and can be calculated by the following equation. Z'is a radial coordinate axis of the light beam.

[0033]

[Outside 2]

By optimizing L and ω in the above equation (3), the a intensity unevenness ΔI is ± 1.5% within the luminous flux diameter S required for inspection, in consideration of the positional variation in the direction of the reticle 1. It can be suppressed to the following level.

In the configuration of the present invention, the corner cube 22
Is moved in the X direction in FIG. 2, the center-to-center distance L of the two light beams can be set arbitrarily, so that the corner cube 22
It is possible to make adjustments to obtain a uniform cross-sectional intensity distribution, regardless of the diameter of the light beam incident on.

When the incident light beam C is linearly polarized light, the transmittance and reflectance of the multilayer film on the half mirror surface of the beam splitter 20 and the half mirror surface of the beam splitter 21 can be set by the polarization direction of the incident light beam C. The polarization state of the light beam whose intensity distribution has been made uniform is preserved in the same state as the polarization state of the incident light beam C.

The above is the beam splitters 20 and 21.
Although the description has been made on the assumption that the division ratio of 1 is completely 1: 1, in reality, the division ratio will not be 1: 1 due to factors such as manufacturing errors. In this case, as shown in FIG. 2, the light amount adjusting member 23 such as an ND filter is inserted in the optical path of the beam A, and the intensity difference between the two beams is adjusted so as to be almost zero. The shape of the beam profile after may be controlled.

Since the laser light has a good coherence, there is a possibility that the laser light interferes with each other in this embodiment, but in FIG. 2, the difference in the optical path length between the light beam A and the light beam B is determined by the coherence distance of the laser 3. With the above settings, the influence of the interference of the two light beams disappears.

As described above, according to this embodiment, an arbitrary cross-sectional strength distribution can be formed, and a uniform strength distribution can be formed on the surface to be inspected as shown in FIG. B)
As shown in FIG. 7, by making the intensity distribution in the necessary irradiation area including the error in the Z direction of the surface to be inspected uniform, even if the intensity distribution of the illumination light is shifted due to Z variation of the surface to be inspected, a uniform signal can be obtained. Since the level is obtained, it is not necessary to strictly control the position of the inspection surface in the Z direction.

FIG. 6 shows another embodiment of the present invention. The first light splitter used in the above-described embodiment is for amplitude-dividing the incident light beam, but in this embodiment, the total reflection mirror surface 30 is first
The same effect as that of the above-described embodiment is obtained by using the method of dividing the incident light flux into two from the center of the beam by using it as a light splitter (wavefront division). The other structure of this embodiment is the same as that of the previous embodiment.

In particular, in this embodiment, since the first light splitting means is the wavefront splitting means, the central intensity of the light beam B is kept at the original intensity. Since the first dividing means in the above embodiment is an amplitude dividing means, the central intensity of the light beam B is ½ of the original intensity.
Becomes Since the means for synthesizing the light fluxes A and B is an amplitude dividing means in both embodiments, finally, the beam center intensity after uniforming the intensity distribution in this embodiment is 2 compared to that in the above embodiment. Double strength is obtained.

The foreign matter inspection device described above is an IC or LSI.
Etc. are incorporated in an exposure apparatus used for manufacturing a semiconductor device such as a CCD, a liquid crystal panel, a magnetic head, or the like, or used alone.

Further, the cross-sectional strength distribution uniforming device may take a form other than that disclosed herein.

FIG. 7 is a block diagram showing a surface condition inspection apparatus according to another embodiment of the present invention. In this embodiment, the entire inspection apparatus is incorporated in a semiconductor printing apparatus.

Reference numeral 1101 is a far-ultraviolet light source such as an excimer laser, 1102 is an illumination system unit, and the reticle 108 is uniformly distributed over the entire area to be inspected from above and at a predetermined NA (aperture). It has the function of illuminating with (number).

Reference numeral 1109 denotes a reticle pattern on the wafer 11.
It is an ultra-high resolution lens system (or mirror system) for transferring onto the wafer 10, and at the time of printing, the wafer moving stage 11
Exposure is performed by shifting each shot according to the step feed of 11. Reference numeral 1110 is an alignment optical system for aligning the reticle with the wafer prior to exposure, and has at least one reticle observation microscope system.

1114 is a reticle changer,
It is a unit that stores a plurality of reticles and makes them stand by.
Reference numeral 1113 is a foreign matter inspection unit, which includes all the configuration conditions of the above embodiment. In this unit, the reticle is pulled out from the changer and the exposure position (E and P in the figure)
The reticle is inspected for foreign matter before being set to.

The controller 1118 controls the sequence of the alignment operation and the step feed of the wafer, which are the basic operations of the stepper.

Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described. FIG. 7 shows a flow of manufacturing a semiconductor device (semiconductor chip such as IC or LSI, liquid crystal panel, CCD or the like). Step 1
In (Circuit design), a circuit of a semiconductor device is designed.
In step 2 (mask manufacturing), a mask having the designed circuit pattern is manufactured. On the other hand, in step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process,
An actual circuit is formed on the wafer by the lithography technique using the mask and the wafer prepared above. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip by using the wafer manufactured in step 4, such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), and the like. including. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 7).

FIG. 8 shows a detailed flow of the wafer process. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), electrodes are formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted in the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the exposure apparatus described above
The circuit pattern of the mask after the inspection is printed and exposed on the wafer by the foreign substance inspection apparatus. In step 17 (development), the exposed wafer is developed. Step 18 (Etching)
Then, parts other than the developed resist image are scraped off. In step 19 (resist stripping), the resist that is no longer needed after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

By using the manufacturing method of this embodiment, a highly integrated device can be manufactured.

[0052]

As described above, according to the present invention, the detection sensitivity of foreign matters and the like in the inspection region of the surface to be inspected can be made substantially uniform.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the intensity distribution uniformizing device of FIG.

3 is an explanatory diagram showing a cross-sectional intensity distribution of a light beam obtained from the intensity distribution uniformizing device of FIG.

FIG. 4 is an explanatory diagram for explaining an effect obtained by the device of FIG.

FIG. 5 is an explanatory diagram showing an influence of a position variation of the surface to be inspected in the Z direction on the intensity distribution of the inspection region.

FIG. 6 is a schematic view showing another embodiment of the present invention.

FIG. 7 is a diagram showing an exposure apparatus of the present invention.

FIG. 8 is a diagram showing a manufacturing flow of a semiconductor device.

FIG. 9 is a diagram showing the wafer process of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 reticle 2 pellicle 3 semiconductor laser 4 collimator lens 5 intensity distribution uniforming device 6 inspection light beam 7, 8, 9 mirror 10 illumination area 11 foreign matter 12 imaging lens (array lens) 13 line sensor 14 entire optical system 20, 21 Beam splitter 22 corner cube

Claims (9)

[Claims] 1. An apparatus for inspecting a surface state of an inspected surface by illuminating the inspected surface with a beam having a nonuniform cross-sectional intensity distribution and detecting scattered light generated on the inspected surface, A surface condition inspection apparatus having means for making the cross-sectional strength distribution substantially uniform. 2. A parallel beam having a non-uniform cross-sectional intensity distribution,
Apparatus for inspecting the surface condition of the surface to be inspected by obliquely incident on the surface to be inspected so as to form a substantially linear illumination area on the surface to be inspected and detecting scattered light generated on the surface to be inspected. The surface condition inspection apparatus according to claim 1, further comprising means for making the cross-sectional intensity distribution of the parallel beam substantially uniform. 3. The beam is made incident on the surface to be inspected from a direction substantially parallel to the surface to be inspected so as to form a substantially linear illumination area on the surface to be inspected. The surface condition inspection apparatus according to claim 1. 4. The surface condition inspection apparatus according to claim 3, wherein an incident angle of the beam on the surface to be inspected is set to 0.5 ° to 6.5 °. 5. The surface condition inspection apparatus according to claim 3, further comprising a semiconductor laser for forming the beam and a collimator lens. 6. The means for homogenizing the cross-section intensity divides the beam into two light fluxes, and recombines the two light fluxes so that when the cross-sectional intensity distributions of the two light fluxes are combined, the distributions become substantially uniform. It has, Claim 1 or 2 characterized by having.
Surface condition inspection device. 7. The surface condition inspection apparatus according to claim 4, wherein the cross-sectional intensity equalizing means supplies two light beams having a uniform cross-sectional intensity distribution, each of which is directed to a corresponding surface to be inspected. . 8. The surface condition inspection apparatus according to claim 1, further comprising means for moving the beam with respect to the surface to be inspected. 9. An exposure apparatus, which detects foreign matter on a reticle using the apparatus according to claim 1.