JPH06260394A - Exposure method and system for semiconductor substrate - Google Patents

Abstract

PURPOSE:To enable the prevention of the occurrence of portions having poor resolution due to the existence of foreign objects on the rear of a wafer and on the surface of a wafer chuck immediately before mounting the wafer on the chuck for wafer exposure. CONSTITUTION:Immediately before mounting a wafer 6 on a wafer chuck 7 by a wafer handling mechanism 9, the existence of foreign objects on the rear of the wafer 6 and on the surface of the wafer chuck 7 is detected by a foreign object detection means 10. A CPU 12 compares the value of the degree of flatness of the wafer 6 expected from the detected value stored in a memory means 11 with the preset value of the depth of focus of an optical system to determine which is larger or smaller. If no foreign object is detected, and if the degree of flatness is within the depth of focus, the wafer 6 is mounted on the wafer chuck 7 to start the exposure. If the expected degree of flatness is larger than the depth of focus, the wafer 6 is not mounted on the wafer chuck 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate exposure method and exposure apparatus for exposing a pattern on a semiconductor substrate such as a wafer in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art Conventionally, in this type of exposure, for example, projection exposure of a wafer, an exposure mask is illuminated by light from a light source, and a pattern image of the illuminated mask is irradiated by an optical system such as a projection lens. Alternatively, the film is exposed by projecting it onto a photoresist on various thin films already formed on the wafer.

At the time of this exposure, in order to resolve a fine pattern with high accuracy, the focus of the optical system of the exposure apparatus is accurately aligned on the wafer (the optimum height in the photoresist film), and the exposure is performed. It is necessary to ensure that the target surface is within the depth of focus of the optical system.

By the way, the depth of focus of an optical system is predetermined depending on the characteristics of the optical system. However, in conventional exposure, the flatness of the wafer is not controlled before the exposure, and the flatness of the wafer is determined by the optical system. It was exposed as it was, assuming it was within the depth of focus of.

[0005]

However, as shown in FIG. 6, when the wafer 6 is held on the wafer chuck 7 which is a wafer holding member of the exposure apparatus, the wafer 6 is held on the back surface of the wafer 6 or the front surface of the wafer chuck 7. For example, when the foreign matter 19 is attached, the corresponding portion of the wafer 6 becomes convex and the flatness is locally deteriorated, and the deformation amount Δt may be larger than the depth of focus of the optical system. It should be noted that although shown in an exaggerated manner in the figure, this flatness becomes a problem on the order of μ.

In this case, as described above, in the conventional exposure, since the flatness of the wafer 6 is not controlled before the exposure, the exposure is performed as it is, so that the wafer 6 is locally defocused and unclear. Image defects occur. As a result, there is a problem in that the reliability in quality is significantly reduced and the yield is significantly deteriorated.

Therefore, according to the present invention, in the state immediately before mounting the semiconductor substrate on the holding member, occurrence of a defective resolution portion due to the presence or absence of foreign matter on the back surface of the semiconductor substrate and the surface of the holding member is prevented in advance. An object of the present invention is to provide a semiconductor substrate exposure method and an exposure apparatus that can perform the exposure.

[0008]

In order to achieve the above-mentioned object, the present invention provides a method for exposing a semiconductor substrate, wherein the semiconductor substrate is held on a holding member and the semiconductor substrate is exposed by an optical system. Immediately before mounting the semiconductor substrate on the holding member, the presence or absence of foreign matter on the back surface of the semiconductor substrate and the surface of the holding member is detected, and only when the foreign matter is not detected, the semiconductor substrate is placed on the holding member. It is mounted and the semiconductor substrate is exposed.

Further, the present invention provides a semiconductor substrate exposure method in which a semiconductor substrate is held on a holding member and the semiconductor substrate is exposed by an optical system, immediately before mounting the semiconductor substrate on the holding member. In, the presence or absence of foreign matter on the back surface of the semiconductor substrate and the surface of the holding member is detected, and when the foreign matter is detected, the flatness of the semiconductor substrate expected from the detected value and the preset optical system Determining the size by comparing with the depth of focus, when the foreign matter is not detected and when the flatness is within the depth of focus, the semiconductor substrate is mounted on the holding member, and the semiconductor substrate is exposed. is there.

Further, according to the present invention, in a semiconductor substrate exposure apparatus in which a semiconductor substrate is held on a holding member and the optical system exposes the semiconductor substrate, the semiconductor substrate is placed on the holding member by means of a substrate attaching / detaching means. Immediately before mounting on the semiconductor substrate, foreign matter detection means for detecting the presence or absence of foreign matter on the back surface of the semiconductor substrate and the front surface of the holding member is provided.

Further, according to the present invention, in a semiconductor substrate exposure apparatus in which a semiconductor substrate is held on a holding member and the optical system exposes the semiconductor substrate, the semiconductor substrate is placed on the holding member by a substrate attaching / detaching means. Immediately before mounting on the back surface of the semiconductor substrate and the front surface of the holding member, a foreign matter detecting means for detecting the presence or absence of the foreign matter, and when the foreign matter is detected by the foreign matter detecting means, it is expected from the detection value thereof. It is provided with a comparison / determination means for comparing the flatness of the semiconductor substrate with a preset depth of focus of the optical system to determine the magnitude thereof.

[0012]

According to the present invention configured as described above, the semiconductor substrate is mounted on the holding member only when no foreign matter is detected on the back surface of the semiconductor substrate and the front surface of the holding member. When exposing a semiconductor substrate, the occurrence of a defective resolution due to local defocus on the semiconductor substrate is prevented in advance, and good exposure is always performed.

When a foreign substance is detected, the flatness of the semiconductor substrate expected from the detected value is compared with the depth of focus of the optical system to determine whether the foreign substance is large or small. Since it is accurately grasped, even if a foreign substance is detected, it is possible to perform exposure in a range in which there is no influence due to the size of the foreign substance or the like.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a reduction projection exposure method for a wafer and a reduction projection exposure apparatus will be described below with reference to FIGS.

FIG. 1 is a schematic configuration diagram of the apparatus, and FIG. 2 is a schematic configuration diagram of a main part showing a foreign matter detecting means of the apparatus.

First, as shown in FIG. 1, this reduction projection exposure apparatus comprises a light source 1 and an illumination lens group 2 as an apparatus main body.
A reticle mount 4 holding a reticle (enlarged mask) 3, a reduction projection lens group 5, a wafer chuck 7 holding a wafer 6, and an XY supporting the wafer chuck 7.
And stage 8. Further, in this apparatus, the wafer chuck 7 and the XY stage 8 are reciprocally movable between an exposure position shown by a solid line and an inspection position shown by a virtual line, and the wafer 6 is mounted on the wafer chuck 7 ( A wafer handling mechanism 9 for loading and unloading is provided.

Further, this apparatus has a foreign matter detecting means 10 for detecting the presence or absence of foreign matter on the back surface of the wafer 6 and the front surface of the wafer chuck 7, and a storage section 11 for storing the detection result by the foreign matter detecting means 10. A comparison determination unit that compares the value of the flatness of the wafer 6 expected from the stored detection result with the value of the depth of focus of the optical system to determine the magnitude thereof is provided. This comparison / determination unit can be configured by the CPU 12, for example. The value of the flatness of the wafer 6 is preliminarily obtained by a test based on the size of foreign matter and stored in the storage unit 11, and the value of the depth of focus of the optical system is based on the characteristics of the reduction projection lens group 5 and the like. Is set in advance. In addition, an alarm 13 including a warning sound and a warning lamp display is provided, and the alarm 13 is a CP.
The operation is controlled by U12.

Incidentally, the apparatus is additionally provided with an exposure control section for activating the light source 1 of the apparatus body, the XY stage 8 and the like, a handling control section for activating the wafer handling mechanism 9, etc., but these are individually configured. Even above CPU
You may comprise by 12. In this embodiment, CPU1
2 will be described as having the functions of the above control units.

As shown in FIG. 2, the foreign matter detecting means 10 includes a laser light source 14 for generating a laser beam for inspecting a foreign matter, a beam splitter 15, a reflecting mirror 16 rotatable by a rotary shaft 18, and a foreign matter. The photoelectric conversion element 17 detects the scattered light reflected by 19.

In the foreign matter detecting means 10, first, immediately before the wafer 6 is loaded onto the wafer chuck 7 by the wafer handling mechanism 9, the laser light oscillated from the laser light source 14 is beam splitter 15.
Then, the back surface of the wafer 6 at the inspection position is irradiated horizontally through the reflection mirror 16. In this irradiation, the reflection mirror 16 is rotated by the rotating shaft 18 or the wafer 6 is horizontally moved by the wafer handling mechanism 9 to scan the entire back surface of the wafer 6 with laser light. Similarly, for the surface of the wafer chuck 7 at the inspection position, the above irradiation is performed while rotating the reflection mirror 16 or moving the XY stage 8.

As a result, if the foreign matter 19 adheres to the back surface of the wafer 6 or the front surface of the wafer chuck 7 or both, the foreign matter 19 scatters the laser light. The foreign material 19 is detected by detecting the scattered light through the reflection mirror 16 and the beam splitter 15 by the photoelectric conversion element 17. Then, in FIG. 1, the value of the detected signal strength is stored in the storage unit 11. Storage unit 11
Since the flatness of the wafer 6 obtained in advance is stored in the CPU, the CPU 12 causes the flatness value of the wafer 6 expected from the value of the detection signal intensity stored in the storage unit 11 and the preset focus. The depth value is compared to determine the flatness with respect to the depth of focus. Then, the CPU 12 controls the loading of the wafer 6 by the wafer handling mechanism 9, the light emission of the light source 1 of the apparatus main body, the exposure operation by the movement of the XY stage 8, the operation of the alarm 13 and the like based on the comparison and determination result.

Next, FIG. 3 is a schematic configuration diagram of a main part showing another example of the foreign matter detecting means of the apparatus. This foreign matter detecting means 10
In the above, the concave reflection mirror 21 that reflects the scattered light reflected by the foreign matter 19 again is used, and the scattered light reflected by the reflective mirror 21 is detected by the photoelectric conversion element 17. The reflection mirror 21 is used for the wafer 6 at the inspection position.
Are provided at positions facing the back surface of the wafer chuck 7 and the front surface of the wafer chuck 7, and even if the foreign material 19 adheres to any position on the back surface of the wafer 6 or the front surface of the wafer chuck 7, the scattered light by the foreign material 19 is generated. It is formed so that it is incident on the concave surface and the light reflected by the concave surface is incident on the photoelectric conversion element 17. According to this example, the scattered light due to the foreign matter 19 can be detected more reliably.

In the foreign matter detecting means 10 shown in FIGS. 2 and 3, since the laser light is irradiated from the direction in which the wafer 6 and the wafer chuck 7 are connected in series, the wafer 6 and the wafer chuck 7 are inspected at the same time. In this case, the wafer handling mechanism 9 raises the wafer 6 slightly to irradiate the surface of the wafer chuck 7 with laser light, and then lowers the wafer 6 to irradiate the back surface of the wafer 6 with laser light. The presence or absence of foreign matter 19 on the front surface of the wafer and the back surface of the wafer 6 can be individually detected. Further, by irradiating the laser light from the parallel direction of the wafer 6 and the wafer chuck 7, the front surface of the wafer chuck 7 and the back surface of the wafer 6 can be individually inspected according to the scanning direction of the laser light.

4 and 5 are flow charts for explaining a series of operations of the apparatus. A series of operations of the apparatus configured as described above will be described according to FIGS. 4 and 5 together with FIGS.

First, in step S1, the wafer handling mechanism 9 transfers the wafer 6 to the inspection position. At this time, the wafer chuck 7 is also moved to the inspection position.

Next, in step S2, the presence or absence of the foreign matter 19 is inspected by the foreign matter detecting means 10 over the entire back surface of the wafer 6 and the front surface of the wafer chuck 7.

Next, when the foreign matter 19 is not detected in step S3, the process proceeds to step S4 and the wafer handling mechanism 9 holds the wafer 6 by the wafer chuck 7.
The wafer chuck 7 is loaded on the upper side and moved to the exposure position.

Then, in step S5, the reticle 3 and the wafer 6 are aligned in the apparatus main body,
Exposure is started in step S6.

That is, the reticle 3 is uniformly illuminated by the light from the light source 1 through the illumination lens group 2, and the reticle 3 is illuminated.
Pattern image of the wafer 6 by the reduction projection lens group 5.
(Or various thin films already formed on the wafer 6)
The image is reduced and projected on the photoresist above. XY stage 8
The wafer 6 is successively moved in the X and Y directions by means of repeated reduction projection, and the entire surface of the wafer 6 is exposed by this step and repeat.

Then, in step S7, the wafer 6
It is determined whether or not the exposure of the entire surface of the wafer has been completed. If it is not completed, the above alignment and exposure are repeated. If completed, the wafer 6 is unloaded from the wafer chuck 7 by the wafer handling mechanism 9 in step S8. To load.

Then, in step S9, it is determined whether or not the lot processing of the same type of wafer 6 is completed. If completed, a series of operations is ended, and if not completed, the wafer chuck 7 is moved to the inspection position. And step S1
Then, the wafer handling mechanism 9 transfers the next wafer 6 to the inspection position, and the above-mentioned foreign matter inspection is started.

On the other hand, in step S3, the foreign matter 1
When 9 is detected, in step S10, the CPU
12 compares the value of the flatness of the wafer 6 based on the value of the detected signal intensity stored in the storage unit 11 with the value of the depth of focus;
The degree of flatness with respect to the depth of focus is determined.

As a result of this comparison and determination, the wafer 6 expected
If it is determined that the flatness is within the depth of focus (flatness ≦ depth of focus), the process proceeds to step S4, and the wafer 6 is loaded on the wafer chuck 7 described above.

On the other hand, when it is determined that the expected flatness of the wafer 6 is larger than the depth of focus (flatness> depth of focus) as a result of the comparison determination in step S10,
The wafer 6 is not loaded onto the wafer chuck 7, and the alarm 13 is activated in step S11.

If the foreign matter 19 is detected only from the back surface of the wafer 6 according to the detection state of the foreign matter 19 described above, the process proceeds to step S12 of FIG.
Is discharged from the inspection position, the process returns to step S1 of FIG. 4, and the next wafer 6 is transferred to the inspection position. Further, when the foreign matter 19 is detected from the back surface of the wafer 6 and the front surface of the wafer chuck 7, the process proceeds to step S12 of FIG. 5B to eject the wafer 6 from the inspection position and step S13.
After removing the foreign matter 19 on the surface of the wafer chuck 7, the process returns to step S1 in FIG. 4 to transfer the next wafer 6 to the inspection position. Further, when the foreign matter 19 is detected only from the surface of the wafer chuck 7, the process proceeds to step S13 in FIG. 5C to remove the foreign matter on the surface of the wafer chuck 7, and then returns to step S2 in FIG. Inspection of the foreign material 19 is started.

The above series of operations is repeated until the lot processing is completed.

In this way, the wafer 6 is attached to the wafer chuck 7
The upper loading is performed when the foreign matter 19 is not detected on the back surface of the wafer 6 and the front surface of the wafer chuck 7, and when the flatness of the wafer 6 expected from the detected foreign matter 19 is within the focal depth of the optical system. In this case, when the wafer 6 is exposed, it is possible to prevent occurrence of a defective resolution portion due to local defocus on the wafer 6, and always perform good exposure. it can.

If the expected flatness is larger than the depth of focus, the wafer 6 is ejected from the inspection position and the next wafer 6 is transferred to the inspection position. The subsequent series of operations can be automatically performed.

Further, by activating the alarm 13 when the expected flatness is larger than the depth of focus, an abnormal flatness is immediately warned, and based on this, the wafer 6 ejected from the inspection position is detected. The wafer chuck 7 at the inspection position may be inspected or washed.

In this embodiment, the foreign matter detecting means 1
When the movement of the wafer handling mechanism 9 and the XY stage 8 is used when detecting the foreign matter on the wafer 6 and the wafer chuck 7 with the laser light of 0, the laser light scanning mechanism is unnecessary and the structure can be simplified. Further, the wafer 6
When the laser beam is irradiated from the direction perpendicular to the wafer chuck 7 and the value of the detection signal intensity is stored in the storage unit 11, the irradiation position on the wafer 6 and the wafer chuck 7 and the value of the detection signal intensity are associated with each other. By doing so, it is possible to easily determine the location where the foreign matter is attached.

The embodiments of the present invention have been described above.
The present invention is not limited to the above embodiments, and various effective modifications and applications are possible based on the technical idea of the present invention. For example, in the embodiment, the flatness of the semiconductor substrate expected from the foreign matter detected on the semiconductor substrate and the holding member and the depth of focus of the optical system are compared to determine the size thereof. The comparison determination may be made only by detecting the presence / absence of foreign matter on the semiconductor substrate and the holding member. Further, although the holding member is movable between the exposure position and the inspection position in the embodiment, the holding member may be inspected at the exposure position. Although the embodiment described the reduction projection exposure method and apparatus for a wafer, the present invention exposes various patterns to various semiconductor substrates.
For example, it can be applied to various exposure methods and apparatuses such as EB drawing and X-ray exposure.

[0042]

As described above, according to the present invention,
Immediately before mounting the semiconductor substrate on the holding member, the presence or absence of foreign matter on the back surface of the semiconductor substrate and the surface of the holding member is detected to prevent the occurrence of a defective resolution portion due to local defocus on the semiconductor substrate. It can be prevented in advance. Therefore, it is possible to significantly improve the reliability in terms of quality and the yield.

In particular, according to the present invention, when there is a risk of useless exposure that causes a defective resolution portion, the mounting of the semiconductor substrate on the holding member, which is the preceding step, is not performed. As a result, the processing rate of the exposure apparatus can be significantly improved and the working time can be significantly shortened by reducing the reproduction rate.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus in an embodiment in which the present invention is applied to a wafer reduced projection exposure method and apparatus.

FIG. 2 is a schematic configuration diagram of a main part showing a foreign matter detection unit of the apparatus of the above-described embodiment.

FIG. 3 is a schematic configuration diagram of a main part showing another example of the foreign matter detecting means of the apparatus of the above-described embodiment.

FIG. 4 is a flowchart for explaining a series of operations in the above embodiment.

FIG. 5 is a flowchart for explaining a series of operations in the above embodiment.

FIG. 6 is a schematic view of a main part showing deformation of a wafer when a foreign substance adheres to the back surface of the wafer or the surface of the wafer chuck in the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 illumination lens group 3 reticle 4 reticle mount 5 reduction projection lens group 6 wafer 7 wafer chuck 8 XY stage 9 wafer handling mechanism 10 foreign matter detection means 11 storage unit 12 CPU 13 alarm 14 laser light source 15 beam splitter 16 reflection mirror 17 photoelectric Conversion element 19 Foreign matter 21 Concave reflection mirror

Claims (6)

[Claims] 1. A method of exposing a semiconductor substrate, wherein a semiconductor substrate is held on a holding member and the semiconductor substrate is exposed by an optical system, wherein the semiconductor substrate is mounted on the holding member immediately before the semiconductor substrate is mounted on the holding member. A semiconductor substrate characterized by detecting the presence or absence of foreign matter on the back surface of the substrate and the front surface of the holding member, mounting the semiconductor substrate on the holding member only when no foreign matter is detected, and exposing the semiconductor substrate. Exposure method. 2. A semiconductor substrate exposure method in which a semiconductor substrate is held on a holding member and the semiconductor substrate is exposed by an optical system, wherein the semiconductor substrate is mounted on the holding member immediately before the mounting of the semiconductor substrate. The presence or absence of foreign matter on the back surface of the substrate and the front surface of the holding member is detected, and when the foreign matter is detected, the flatness of the semiconductor substrate expected from the detected value and the depth of focus of the optical system set in advance are set. Compare and judge the size,
An exposure method for a semiconductor substrate, comprising mounting the semiconductor substrate on the holding member and exposing the semiconductor substrate when no foreign matter is detected and when the flatness is within the depth of focus. 3. An exposure apparatus for a semiconductor substrate, which holds a semiconductor substrate on a holding member and exposes the semiconductor substrate by an optical system, immediately before mounting the semiconductor substrate on the holding member by a substrate attaching / detaching means. An exposure apparatus for a semiconductor substrate, further comprising foreign matter detection means for detecting the presence or absence of a foreign matter on the back surface of the semiconductor substrate and the front surface of the holding member. 4. The semiconductor substrate is mounted on the holding member by the substrate attaching / detaching means only when the foreign matter is not detected by the foreign matter detecting means, and the exposing means of the apparatus main body is operated to expose the semiconductor substrate. 4. The exposure apparatus for a semiconductor substrate according to claim 3, wherein the exposure apparatus is a semiconductor substrate exposure apparatus. 5. A semiconductor substrate exposure apparatus in which a semiconductor substrate is held on a holding member and the semiconductor substrate is exposed by an optical system, immediately before mounting the semiconductor substrate on the holding member by a substrate attaching / detaching means. In addition, foreign matter detection means for detecting the presence or absence of foreign matter on the back surface of the semiconductor substrate and the front surface of the holding member, and when the foreign matter is detected by the foreign matter detection means, the flatness of the semiconductor substrate expected from the detected value An exposure apparatus for a semiconductor substrate, comprising: a comparison determination unit that compares the degree of focus with a preset depth of focus of the optical system to determine the magnitude thereof. 6. The semiconductor substrate is mounted on the holding member by the substrate attaching / detaching means when no foreign matter is detected by the foreign matter detecting means and when the flatness is determined to be within the depth of focus by the comparing / determining means. The semiconductor substrate exposure apparatus according to claim 5, wherein the exposure means of the apparatus main body is operated to expose the semiconductor substrate.