JPH0769135B2 - Gap measuring device between X-ray mask and substrate to be exposed and gap measuring method - Google Patents

Description

The present invention relates to a gap measuring device and a gap measuring method between an X-ray mask and a substrate to be exposed.

(Prior Art) To transfer a pattern of a semiconductor integrated circuit or the like to a photosensitive resin coated on a substrate to be exposed such as a Si wafer by using X-ray, X
An X-ray mask in which a pattern shape is formed by an X-ray absorber containing a heavy metal such as gold, tungsten, tantalum, or molybdenum as a main component on a thin film of SiN, BN, SiC or the like which transmits rays well is used. In this way, the X-ray mask is placed in close proximity to a substrate to be exposed such as a Si wafer coated with a photosensitizer, and X-rays are radiated through the X-ray mask, so that the pattern on the X-ray mask is exposed. Is transcribed to.

At this time, the gap between the X-ray mask and the substrate to be exposed is about several μm.
It is a fine gap of about 100 μm. The pattern transfer accuracy depends on the amount of X-rays diffracted to the back side of the X-ray absorber.
The narrower the gap, the better. However, if the X-ray mask and the substrate to be exposed come into contact with each other, the fragile X-ray mask will be damaged. Therefore, whether the X-ray mask and the substrate to be exposed can be accurately and quickly set to an appropriate gap. Greatly influences the performance of the exposure apparatus.

Conventionally, to set the gap between the X-ray mask and the substrate to be exposed, Journal of Vacuum Science TechnologyB3 (6), N
ov / Dec 1985 Pages 1581 to 1585 A step−and−repeatx
−ray exposure system for 0.5μm pattern replicatio
As disclosed in n, the marks on the X-ray mask and the substrate to be exposed are simultaneously magnified and observed by the bifocal objective lens, and the X-ray mask and the substrate to be exposed are the two focal points of the bifocal objective lens. X to match each focus
The line mask and the substrate to be exposed are set.

Further, as disclosed in Japanese Patent Application No. 59-254242, in a gap control method using a diffraction grating and an alignment control method using the same, a diffraction grating is attached to an X-ray mask or a substrate to be exposed, A method of setting the gap between the X-ray mask and the substrate to be exposed by measuring the gap by utilizing the fact that the intensity and phase of the diffracted light change depending on the gap between the X-ray mask and the substrate to be exposed is used. ing.

(Problems to be Solved by the Invention) However, in the method using the bifocal objective lens described above,
The distance between the two focal points specific to the objective lens does not change, and the gap between the X-ray mask and the substrate to be exposed can only be set to a predetermined gap corresponding to the distance between the two focal points. Also,
When the X-ray mask and the substrate to be exposed are at positions deviated from the focal points of the objective lens, it is not possible to know where the X-ray mask and the substrate to be exposed are and how much their relative gap is. .

On the other hand, a method in which a diffraction grating is inserted in the X-ray mask and the gap between the X-ray mask and the substrate to be exposed is measured is such that the intensity signal or phase signal of the diffracted light causes the gap between the X-ray mask and the substrate to be exposed. The gap between the X-ray mask and the substrate to be exposed is measured by some other means and is preset within the gap range corresponding to one period of the intensity signal or phase signal of the diffracted light. You need to do it.

Further, since the intensity signal and the phase signal of the diffracted light change sinusoidally within the one period, there are gaps that are easy to detect and gaps that are difficult to detect. By changing the pitch of the diffraction grating used, it is possible to arbitrarily select a gap that is easy to detect, but since the direction in which the diffracted light exits also changes, the position of the diffracted light receiver must be made variable. Create difficult challenges.

With such a conventional technique, it is impossible to immediately measure freely and monitor an arbitrary gap between the X-ray mask and the substrate to be exposed.

When transferring patterns by X-ray exposure, transfer accuracy and X
From the balance with the establishment of damage to the X-ray mask, both the X-ray mask and the exposed substrate come into contact with each other according to the unevenness and warpage of the X-ray mask and the exposed substrate within the range in which the necessary fineness of the pattern is obtained. It is desirable to leave only the gaps that are not separated.
However, as described above, in the conventional apparatus, it is impossible to measure the gap between the X-ray mask and the substrate to be exposed immediately and arbitrarily at all times. Therefore, it is extremely difficult to freely set the gap to an arbitrary gap. It was difficult.

Further, in the conventional apparatus shown above, it is necessary to previously provide a gap setting mark for observation or diffraction light acquisition on both or one of the X-ray mask and the substrate to be exposed,
If the mark for setting the gap was not entered, the gap between the X-ray mask and the substrate to be exposed could not be set. For this reason, an extra man-hour is required to make the gap setting mark in advance before the exposure.

Further, since the detection for setting the gap is performed by an optical means, the gap between the photosensitive resin applied to the substrate to be exposed and the film thickness of the transparent thin film which may be present on the substrate to be exposed may be different. There is also a drawback that the detection is easily affected and the optimum film thickness for forming a fine pattern by exposure cannot be freely selected.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a means for placing an X-ray mask and a substrate to be exposed in close proximity to each other, and an X-ray on the X-ray transparent thin film of the X-ray mask. A first sensor (hereinafter, referred to as a first capacitance-type gamp sensor) that detects the magnitude of the capacitance between the radiation absorber and the X-ray mask, and A second sensor (hereinafter, referred to as a second capacitance gap sensor) that detects the magnitude of the electrostatic capacitance with the surface position of the substrate to be exposed and measures the distance to the substrate to be exposed. The gap between the X-ray mask and the substrate to be exposed is determined from the distance measured by the gap measuring device and the first and second capacitance type gap sensors. The gist is a gap measuring method characterized in that the measurement is performed.

(Operation) According to the present invention, the first and second capacitance type gap sensors are applied on the exposed substrate without providing any marks on the X-ray mask and the exposed substrate. The absolute value of the gap between the X-ray mask and the exposed substrate can be patterned by X-ray exposure without being affected by the film thickness of the photosensitive resin or the transparent thin film existing on the exposed substrate. Immediate measurement is possible with the accuracy required when performing.

(Example) An example of the present invention will be described. Needless to say, the embodiment is merely an example, and various modifications and improvements can be made without departing from the spirit of the present invention.

FIG. 1 is a configuration diagram of an embodiment of the present invention, 1 is an X-ray mask, 2 is an X-ray transparent thin film, 3 is an X-ray absorber, 4 is a first capacitance type gap sensor, Reference numeral 5 is a second capacitance type gap sensor, 6 is a substrate to be exposed, 7 is a window portion having an X-ray transparent thin film, 8 is a window portion having an X-ray absorber on the X-ray transparent thin film, 9 is an X-ray absorber pattern for exposure,
Reference numeral 10 is a window portion in which an X-ray transmissive thin film on which an X-ray absorber pattern for exposure is placed.

A change in capacitance between the conductive object to be measured and the sensor head is detected in a portion of the X-ray mask 1 on the non-conductive X-ray transparent thin film 2 where the X-ray absorber 3 does not exist. The first capacitance type gap sensor 4 for measuring the relative gap of the object to be measured with respect to the sensor head is installed, and the X-ray transparent thin film 2 of the X-ray mask 1 (on the front surface or the back surface of the X-ray transparent thin film 2) is installed. ) X
A second electrostatic capacitance type gap sensor 5 different from the first electrostatic capacitance type gap sensor 4 is provided in a portion where the line absorber 3 is present.
Set up. These gap sensors are attached to the X-ray mask side using a support tool. As the capacitance type gap sensor, specifically, Non-Contact, Capacitive Displacement Transduce manufactured by US LION PRECISION
r PX type, Photonics, capacitance type displacement sensor, probe TMP type, US ADE, MICROSENSE, etc. can be used.

Each of the capacitance gap sensors described above can measure even an insulator such as quartz as long as a conductive film of several hundred liters or more is attached to the surface of the measurement target. Of course, it goes without saying that the electrically conductive object may be the object.
Further, an object generally called a semiconductor such as silicon, germanium, gallium arsenide, etc. can be regarded as a conductor and can be measured.

The X-ray absorber 3 is mainly composed of a heavy metal such as gold, tungsten, tantalum or molybdenum, and the exposed substrate 6 is also a semiconductor such as silicon, germanium or gallium arsenide. When the first and second capacitance type gap sensors 4 and 5 are installed in this state and the X-ray mask and the substrate to be exposed are brought close to each other, the first capacitance type gap sensor 4 is non-conductive. X-ray transparent thin film 2
To detect the position of the surface of the conductive substrate 6 to be exposed through
The second capacitance type gap sensor 5 detects the position of the X-ray absorber 3 existing on the front surface or the back surface of the non-conductive X-ray transparent thin film 2.

Neither of the first and second electrostatic capacitance type gap sensors 4 and 5 requires any mark for detecting the gap with the object.

FIG. 4 is a diagram for explaining the gap measured by the first and second capacitance type gap sensors 4 and 5.

The first capacitance type gap sensor 4 measures the distance d ₁ between the front end surface of the first capacitance gap sensor 4 and the exposed substrate 6.

The second capacitance gap sensor 5 measures the distance d ₂ between the tip surface of the second capacitance gap sensor 5 and the X-ray absorber 3 on the X-ray mask 1.

According to the present invention, the X-ray mask 1 to be measured and the exposed substrate 6
The gap d between and is obtained from d = d ₁ −d ₂ .

The non-conductive X-ray transparent thin film 2 is generally a very thin film of about 1 to 3 μm in order to secure X-ray transmittance.
The detection value of the electrostatic capacitance type gap sensor 4 is hardly affected by the influence. Since the capacitance type gap sensor is designed to measure the tip of the sensor and the object to be measured at a distance of 100 μm to 1 mm or more, the air between the tip of the capacitance type gap sensor and the object to be measured is measured. This is because the capacitance is determined by the thickness of the medium, such as helium and vacuum space. When the non-conductive X-ray transmissive thin film 2 is thick, for example, about 10 μm or more, the thickness and dielectric constant of the non-conductive X-ray transmissive thin film 2 are taken into consideration, The measured value should be corrected.

A photosensitive resin having sensitivity to X-rays is applied to the surface of the substrate 6 to be exposed, and the photosensitizer is generally non-conductive. Also,
In some cases, a non-conductive film such as SiO ₂ , Si ₃ N ₄ or phosphosilicate glass may be present. However, the existence of these thin films is similar to that of the above-mentioned non-conductive X-ray transparent thin film 2, and has almost no effect.

Further, the gap measurement is not affected by the photosensitive resin applied on the substrate 6 to be exposed and the film thickness of the transparent thin film on the surface of the substrate 6 to be exposed unlike the conventional apparatus.

If the substrate 6 to be exposed is a semiconductor whose conductivity is extremely poor, the measured value of the first capacitance type gap sensor 4 is
This is slightly different from the case of using a good conductor including the target. In such a case, the first capacitance type gap sensor 4 may be calibrated according to the material of the substrate 6 to be exposed and the thin film existing on the surface thereof.

On the other hand, even if the X-ray mask 1 and the substrate 6 to be exposed are close to each other and the substrate 6 to be exposed is behind the X-ray absorber 3, the detection value of the second capacitance type gap sensor 5 has an influence. Do not receive Also, when the X-ray absorber is present on the back side of the X-ray transparent thin film 2, that is, on the opposite side of the X-ray transparent thin film 2 from the second capacitance type gap sensor 5, as shown in FIG. Similar to the case of the first capacitance type gap sensor 4, the X-ray transmissive thin film 2 has almost no influence, and the measured value may be slightly corrected in the worst case.

When the X-ray absorber 3 for detecting the position of the X-ray mask 1 is on the opposite side of the gap sensor 4 of the X-ray transmissive thin film 2 as described above, the d ₁ and d ₂ are measured. Since the influence of the X-ray transmissive thin film 2 is equally applied,
Even if d ₁ and d ₂ are used without correcting the influence of the X-ray transparent thin film 2, the correct gap d can be obtained.

As described above, the first capacitance type gap sensor 4 detects the position of the surface of the conductive substrate 6 to be exposed through the non-conductive X-ray transparent thin film 2 to obtain the second capacitance. Since the gap sensor 5 detects the position of the X-ray absorber 3 existing on the front surface or the back surface of the non-conductive X-ray transmissive thin film 2, the first capacitance gap sensor 4 and the second electrostatic gap sensor 4 can be detected. By comparing the gap measurement values with the capacitive gap sensor 5 and taking the difference, the close gap between the X-ray mask 1 and the substrate 6 to be exposed can be accurately measured.

Non-Contact, Capacitive D manufactured by LION PRECISION, USA
As a result of an experiment using the isplacement Transducer PX-305H5M type, the positions of the X-ray absorber 3 of the X-ray mask 1 and the surface of the exposed substrate 6 can be measured with a resolution of 0.02 μm, and the reproducibility and stability over time are stable. It was found that the proximity gap between the X-ray mask 1 and the substrate 6 to be exposed can be measured with an accuracy of ± 0.2 μm even in consideration of the characteristics.

X-ray mask 1 required for pattern formation by X-ray exposure
The accuracy of the measurement of the close gap between the substrate and the exposed substrate 6 is 0.5-2 μm.
Therefore, the present invention enables sufficient measurement. The measuring range of the sensor is ± 130 μm, but if an appropriate sensor having a narrower measuring range is selected, more accurate measurement is possible.

Each of the first capacitance type gap sensor 4 and the second capacitance type gap sensor 5 is attached three by three, and the proximity gap between the X-ray mask and the substrate to be exposed is measured at three points. If a mechanism (not shown) for adjusting the gap and the tilt angle is attached to at least one of the side of the X-ray mask 1 and the substrate 6 to be exposed, the proximity gap between the X-ray mask 1 and the substrate 6 to be exposed is measured including the parallelism. can do.

In this case, in FIG. 1, the window portion 7 or the X-ray transmissive portion in which the non-conductive X-ray transmissive thin film 2 exists corresponding to the positions of the first and second capacitance type gap sensors 4 and 5. The window 8 having the X-ray absorber 3 on the thin film 2 is provided around the window 10 having the X-ray transparent thin film 2 on which the X-ray absorber pattern 9 for exposure is placed. The entire area where the first and second capacitance type gap sensors 4 and 5 are present may be used as the window.

2 and 3 show examples of arrangement of the capacitance type gap sensor. 2 and 3 show that the X-ray mask 1 and the substrate 6 to be exposed are in close proximity to each other from the X-ray mask side.
And the state where the second capacitance type gap sensors 4 and 5 are arranged, the first and second capacitance type gap sensors 4,
5, the substrate 6 to be exposed, and the X-ray mask 1 are overlaid and drawn.
In the figure, 11 is a thin film window and 12 is the outer edge of the X-ray mask.

FIG. 2 shows the first capacitance type gap sensor 4 and the second capacitance type gap sensor 5 arranged concentrically alternately around the X-ray absorber pattern 9 for exposure. Yes, FIG. 3 shows an X-ray absorber pattern 9 for exposing.
A first capacitance type gap sensor 4 and a second capacitance type gap sensor 5 are radially arranged around the. In the case of FIG. 3, it goes without saying that either the first capacitance type gap sensor 4 or the second capacitance type gap sensor 5 may come inside.

Even when a window is provided for each capacitance type gap sensor as shown in FIG. 1, the first capacitance type gap sensor is arranged around the X-ray absorber pattern for exposure similar to that of FIG. 4 and the second capacitance type gap sensor 5 are arranged concentrically alternately, or the first capacitance type gap sensor is arranged around the X-ray absorber pattern for exposure similar to FIG. The sensor 4 and the second capacitance type gap sensor 5 can be arranged radially.

Taking either concentric or radial arrangement,
Arranging the X-ray absorber pattern to be exposed at the center of the X-ray mask 1 facilitates the algorithm for parallelizing the X-ray mask 1 and the substrate 6 to be exposed and setting the gap.

Of course, when the gap and tilt angle adjusting mechanism on the X-ray mask 1 side or the substrate 6 side to be exposed can be automatically controlled and moved toward a target value using a computer or the like based on the gap measurement value thus measured. , The X-ray mask 1 and the exposed substrate 6 can be easily parallelized and the gap can be set even if the first and second capacitance type gap sensors 4 and 5 are not arranged in such a regular arrangement but are arranged arbitrarily. be able to.

As for how to open the windows, it is shown that each of the capacitance type gap sensors is opened individually (Fig. 1) and one large window is opened (Figs. 2 and 3). It will be apparent that the capacitive gap sensor may be arbitrarily opened depending on the arrangement.

The required number of capacitance type gap sensors is X-ray mask 1.
And the substrate 6 to be exposed are set in parallel by some other means in advance and only the average gap between the X-ray mask 1 and the substrate 6 to be exposed is measured, the first capacitance type gap sensor The number of each of the fourth capacitive gap sensor 5 and the second capacitance type gap sensor 5 may be one, and in order to better measure the average value of the gap in consideration of the unevenness of the X-ray mask 1 and the exposed substrate 6, It is also possible to use four or more of each of the electrostatic capacity type gap sensor 4 and the second electrostatic capacity type gap sensor 5.

(Effect of the Invention) As described above, according to the present invention, the positions of the surfaces of both the X-ray mask and the substrate to be exposed can be detected accurately at all times. Can be monitored. Therefore, if the gap adjusting mechanism is provided on at least one side of the X-ray mask and the substrate to be exposed, the X-ray mask and the substrate to be exposed can be set to an arbitrary gap.

If the gap between the X-ray mask and the substrate to be exposed is measured at three or more points and an adjustment mechanism for the gap and the inclination angle is provided on at least one side of the X-ray mask and the substrate to be exposed, the parallelism including the parallelism can be obtained. The gap between the line mask and the substrate to be exposed can be set.

The gap can be set arbitrarily within the measurement range of the capacitance type gap sensor, and the gap can be freely selected according to the fineness of the pattern, the warp of the X-ray mask or the exposed substrate, etc. be able to. If the capacitance type gap sensor is selected according to the measurement accuracy of the gap and the required measurement range, it is possible to set the gap with high accuracy and set the gap in a wide range.

In addition, taking advantage of the fact that the gap between the X-ray mask and the substrate to be exposed can be constantly monitored, when the exposure time is long, etc.
The gap can be controlled so that the gap between the X-ray mask and the substrate to be exposed does not drift.

Furthermore, according to the present invention, in measuring the gap between the X-ray mask and the exposed substrate, it is not necessary to provide any mark for measuring the gap between the X-ray mask and the exposed substrate. For this reason,
It is not necessary to form a gap measurement mark before exposure, which was required in the past, and the number of preparation steps for exposure can be significantly reduced.

Since the measurement is not affected by the thickness of the transparent thin film existing on the surface of the substrate to be exposed or the photosensitive resin to be applied, it is possible to freely select the film thickness.

The present invention relates to an X-ray source such as an electron beam excitation type X-ray source and a plasma X-ray source.
It can be used not only for an X-ray exposure apparatus that uses a radiation source, but also for an exposure apparatus that uses synchrotron radiation.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a plan view of another embodiment of the present invention, and FIG. 3 is a plan view of another embodiment of the present invention. FIG. 4 is a diagram for explaining measurement by the first and second capacitance type gap sensors. 1 ... X-ray mask 2 ... X-ray transmissive thin film 3 ... X-ray absorber 4 ... First capacitance type gap sensor 5 ... Second capacitance type gap sensor 6 ... Exposure Substrate 7 ... Window portion where X-ray transparent thin film exists 8 ... Window portion where X-ray absorber exists on X-ray transparent thin film 9 ... X-ray absorber pattern for exposure 10 ... Exposure Window on which the X-ray transparent thin film on which the X-ray absorber pattern is present is located ..... Boundary of the thin film window .............. Outer edge of the X-ray mask.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01L 21/027

Claims (2)

[Claims] 1. An electrostatic discharge between an X-ray mask having a structure in which an X-ray absorber is arranged on an X-ray transmissive thin film, and a means for placing the substrate to be exposed in close proximity, and the X-ray absorber. A first for measuring the distance to the X-ray mask by detecting the amount of capacitance;
And a second sensor that detects the magnitude of the electrostatic capacitance between the sensor and the surface position of the substrate to be exposed to measure the distance to the substrate to be exposed. A gap measuring device between the X-ray mask and the substrate to be exposed. 2. A first region in which a conductive X-ray absorber is arranged on a non-conductive X-ray transparent thin film of an X-ray mask, and a second region in which a conductive X-ray absorber is not arranged. Is formed, the X-ray mask and the substrate to be exposed are arranged close to each other, and a capacitance between the first region of the X-ray mask and the first sensor is measured by the first sensor. The size of
A distance between a line mask and the first sensor is measured, and a second sensor passes between the surface of the exposed substrate and the second sensor through the second region of the X-ray mask. The magnitude of the capacitance is detected to measure the distance between the surface of the substrate to be exposed and the second sensor, and the distance measured by the first and second sensors is used as the X-ray mask. A method for measuring a gap between an X-ray mask and a substrate to be exposed, characterized in that a gap between the substrate and the surface to be exposed is measured.