JP2885836B2 - X-ray exposure equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an exposure apparatus using synchrotron radiation.

[Prior Art] As the miniaturization of integrated circuits advances, the line width of a pattern transferred by exposure also becomes smaller, and the line width control of a resist becomes stricter. As is well known, the line width of the resist greatly changes with the change of the exposure amount. Therefore, it is important to control the actual exposure amount so as to exactly match the desired exposure amount. As a method of strictly controlling the exposure amount, JP-A-57-101839 and JP-A-59-1987
As disclosed in Japanese Patent No. 26, there is a method in which a detector is installed near a mask to measure the intensity of exposure light during exposure, and a jitter is closed when a desired exposure amount is reached.

[Problems to be Solved by the Invention] However, in X-ray exposure using synchrotron radiation (hereinafter, referred to as “SOR”), which has attracted attention in recent years, it is difficult to use the conventional technique as it is. This is because, in the conventional apparatus, the region where the intensity of the exposure light was uniform was relatively wide, so that there was no significant difference from the intensity in the exposure region even at the intensity measurement position around the mask.
This is because, in the exposure method according to the above, since the area where the intensity of the SOR as the exposure light is uniform is narrow, the X-ray intensity differs between the measurement position and the exposure area.

Therefore, a method of detecting the exposure intensity, in which the X-ray detector is extended to the exposure area when the exposure is not performed, the X-ray intensity is measured, and the detector is retracted so as not to block the X-ray during the exposure, is considered. However, when the X-ray intensity changes every moment as in SOR, there is a possibility that an X-ray intensity difference occurs between the measurement time and the exposure time, resulting in a new error.

SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray exposure apparatus capable of performing exposure control by recognizing X-ray intensity with high accuracy even in the case of using SOR, in view of the above-described problems in the conventional type. .

[Means for Solving the Problems] In order to achieve the above object, an X-ray exposure apparatus using synchrotron radiation according to the present invention comprises: a current amount measuring unit for measuring a current amount of orbital electrons of a SOR ring; X-ray intensity measurement means for measuring the intensity of X-rays corresponding to the exposure area, and capable of retracting outside the exposure area during exposure, and the current amount measurement means after electron injection for generating synchrotron radiation and before exposure. And the amount of orbital electron current and X
Means for measuring the line intensity and controlling the exposure time based on the measurement result before the exposure and the measurement result of the current amount measuring means at the time of the exposure.

[Operation] In this configuration, the SOR exposure is started after low-energy electrons are injected from the injector into the SOR ring and accelerated to reach a predetermined energy. The number collides with the residual gas molecules and the like existing inside, and the number thereof gradually decreases, and accordingly, the intensity of the emitted light decreases. Therefore, prior to the start of the exposure, the current amount of the orbital electrons and the X-ray intensity are simultaneously measured. When the X-ray intensity decay during exposure is small, the X-ray intensity is proportional to the amount of orbital electron current unless the accelerating voltage is changed. Based on the above, the exposure time is determined by assuming that the X-ray intensity is constant during the exposure time, and the exposure is performed. If the X-ray intensity decay during exposure cannot be ignored, after measuring the current amount of the orbital electrons and the X-ray intensity simultaneously, measure the current amount of the orbital electrons at regular intervals from the start of exposure and integrate the exposure amount, When the integrated value reaches a predetermined value, the exposure ends. When the amount of current of the orbital electrons or the emitted X-rays becomes lower than a certain intensity, the electrons are cut off and the exposure is interrupted. Then, the electrons are incident again and the exposure is started.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram showing a configuration of an X-ray exposure apparatus according to one embodiment of the present invention. This X-ray exposure apparatus is based on a fixed mirror method. In the figure, 1 is a SOR ring,
Reference numeral 3 denotes an X-ray mirror, 5 denotes an X-ray transmission window such as Be, 6 denotes a movable X-ray detector, 7 denotes a shutter, 8 denotes an X-ray mask, and 9 denotes a wafer coated with a photosensitive material. 2 indicates an X-ray, and 4 indicates an X-ray enlarged by the X-ray mirror 3. Also, 10 is an electron injector, 11 is a signal processing unit, 12 is an X-ray detector drive unit, 13 is a shutter drive unit, 14 is an X-ray detector control unit, 15 is a shutter control unit, 16 is a CPU unit, 17 Is an ammeter for measuring the amount of current of orbital electrons, 18 is a signal processing unit, and 19 is a communication path.

Here, the ammeter 17 used for measuring the current value of the orbital current may be a DC current transfer (DC current transfer) or any other ammeter with little disturbance to orbital electrons. The ammeter 17 is provided in the SOR ring. For example, when the ammeter 17 is a DC current transformer, it is provided in a SOR ring so that orbital electrons pass through a coil in the current transformer.

Generally, the SOR exposure is started after low energy electrons are injected from the injector 10 into the SOR ring 1 and accelerated to reach a predetermined energy. However, the injected electrons collide with the residual gas molecules and the like existing in the orbit of the SOR ring 1 and the number thereof gradually decreases, and the radiation light intensity decreases accordingly. Therefore, when the orbital electrons or the emitted X-rays fall below a certain intensity, the electrons are cut off and the exposure is interrupted.
Then, after that, electrons are incident again and exposure is started.

Next, the operation of the X-ray exposure apparatus of FIG. 1 will be described. First, in a state where the shutter 7 is closed (dotted line in FIG. 1), electrons are supplied from the injector 10 to the SOR ring 1 and accelerated to generate emitted light. Thereafter, an instruction for measuring the exposure intensity is issued from the CPU unit 16 to measure the X-ray intensity. This is because the X-ray detector 6 is moved into the exposure area by the X-ray detector drive unit 12 via the X-ray detector control unit 14 (dotted line in FIG. 1), and the X-ray intensity in the exposure area is reduced. Measure. In this case, the X-ray detector 6 may have an integrated structure with the wafer stage, and may move at the time of measurement using a drive unit (not shown) of the wafer stage. In this case, a dedicated driving unit is not required, and the apparatus can be simplified.
In this case, the shutter is in an opened state, and the wafer has not been transferred or has been retracted to the non-irradiation position. After the measurement is completed, the shutter is closed, and the wafer is transferred or moved under the mask. Return to the description of the previous embodiment.

Next, at the same time as the measurement by the X-ray detector, the current amount of the orbital electrons is measured by the ammeter 17, and the measured current value is sent to the CPU unit 16 via the signal processing unit 18. The X-ray output of the detector 6 and a current meter 17 at this time, respectively and I _x Oyo i _0.

The measured X-ray intensity is sent to the CPU unit 16 via the signal processing unit 11, and then the X-ray detector 6 is retracted outside the exposure area.

Next, the CPU unit 16 calculates the X-ray intensity I _e (t) during exposure based on the measured X-ray intensity. Then, the exposure time T is calculated and set from the set exposure amount D, and the positions of the X-ray mask 8 and the wafer 9 are aligned. The exposure time T can be calculated by T = D / ( _Ie · α) if the X-ray intensity attenuation during exposure is small. Here, α is the X of the X-ray mask 8
It is a line transmittance. Thereafter, an exposure command is issued from the CPU unit 16 to the shutter control unit 15, whereby the shutter 7 is opened by the shutter drive unit 13 and exposure is started. After the exposure starts, when the exposure time T has been reached, the shutter 7 is closed.

The X-ray intensity emitted from the orbital electrons has a proportional relationship with the current amount of the orbital electrons unless the acceleration voltage changes.
Therefore, the output i (t) and obtained by simultaneous measurement I _x ammeter 17 at time t, I _e with i _o is determined by the following equation.

For example, the set exposure amount D is set to 50 mJ / cm ^2, and the simultaneous measurement after electron injection is performed by the X-ray intensity detector 6 and the ammeter 17 respectively.
An output of 15 mW / cm ² and 100 mA was obtained, and the exposure time t _e
Assuming that the output of the ammeter 17 is 50 mA at
Line strength is determined by the formula When the transmittance α of the mask is 0.5, the exposure time T is 4 seconds according to the equation.

If the X-ray intensity decay during exposure cannot be ignored,
The X-ray intensity is measured in real time using
_The exposure amount can be controlled by _e (t).

For example, after the electron injection, the outputs I _x and i _o of the X-ray intensity detector 6 and the ammeter 17 are measured at the same time. Then, the output i of the ammeter 17 from time t ₁ to open the shutter 7 at every predetermined time Δt
Measure (t) and use CPU unit 16 And calculate the total exposure Is calculated. Then, the integrated exposure amount D _P (t) is equal to the set exposure amount.
Close the shutter 7 reaches the D _e.

Next, this operation will be described in detail with reference to the flowchart of FIG. After completing the initialization process (step 21) of each peripheral, the CPU unit 16 that controls the exposure enters a normal operation. That is, the exposure start command is given via the communication path 19 and is transmitted by setting one of the service request flags. The CPU unit 16 constantly checks whether or not this service request flag is set (step 22), and if any one of these flags is set, identifies the request (step 23). The process starts based on the flag. For example, if the flag indicates a start processing start request (exposure start), the value of the previous integrated exposure amount , Start the interrupt timer, open the shutter, set the end processing request flag, and clear its own request flag (start processing request flag) (step
twenty four). The started timer interrupts the CPU at certain time intervals, and the CPU reads the output i (t) of the ammeter 17 in the interrupt processing routine, The processing carried out by going in addition to the ΣI _Ex (steps 25, 26).

When the end processing request flag is set, the CPU enters the end processing sequence. Here, it is determined whether .SIGMA.I _EX (accumulated exposure amount) reaches a desired exposure amount D _e (step 27), the flow returns to step 22 if not reached. If so, the timer interrupt is turned off, the shutter 7 is closed, and its own request flag (end processing request flag) is cleared (step 28).

[Effects of the Invention] As described above, according to the present invention, after electron injection, X
Since the measurement of the line intensity is performed only once, it is possible to cope with the subsequent attenuation of the X-ray intensity, so that efficient and highly accurate exposure can be performed. Further, by measuring the current amount of the orbital electrons sequentially, the X-ray intensity can be known in real time, and it is possible to cope with a rapid change in the X-ray intensity.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration of an X-ray exposure apparatus according to one embodiment of the present invention, and FIG. 2 is a flowchart for explaining an operation example of the apparatus of FIG. 1: SOR ring, 2: X-ray, 3: X-ray mirror, 4: Enlarged X-ray, 5: Be window, 6: Movable X-ray detector, 7: Shutter, 8: X-ray mask, 9 : Wafer coated with photosensitive material, 10: electron injector, 11: signal processor, 12: X-ray detector driver, 13: shutter driver, 14: X-ray detector controller, 15: shutter controller, 16: CPU unit, 17: ammeter, 18: signal processing unit, 19: communication path.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 21/30 531A (72) Inventor Kunitaka Ozawa 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Shigeru Terashima 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shunichi Uzawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-64-26182 (JP, A) JP-A-64-17427 (JP, A) JP-A-64-35300 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G21K 5/00-5 / 10 H05H 13/04 G01T 1/00-1/40 H01L 21/30

Claims (1)

(57) [Claims] 1. An X-ray exposure apparatus using synchrotron radiation, comprising: a current amount measuring means for measuring a current amount of orbital electrons of a SOR ring; and an X-ray intensity corresponding to an exposure area. X-ray intensity measuring means capable of retreating outside the exposure region; and after electron injection for generation of synchrotron radiation, before the exposure, the current amount of orbital electrons and X are measured by the current amount measuring means and the X-ray intensity measuring means. An X-ray exposure apparatus, comprising: means for measuring a line intensity and controlling an exposure time based on a measurement result before the exposure and a measurement result of a current amount measuring means at the time of exposure.