KR20000039842A - Circuit for sensing misalignment of focus in stepper - Google Patents

Abstract

PURPOSE: A circuit is provided to sense a misalignment of focus in a stepper and thereby to prevent inferiority of a semiconductor device. CONSTITUTION: A stepper which is a kind of an exposure equipment is for transcribing an image of a reticle into circuit pattern of a wafer placed on a wafer stage. In a sensing circuit(10), a first input terminal(11) receives a shutter driving pulse signal, and a second input terminal(12) receives a stage driving pulse signal. When the wafer is subjected to an exposure process, the shutter driving pulse signal is high and the stage driving pulse signal is low. Further, when the wafer stage is moved to align the wafer, the shutter signal is low and the stage signal is high. Accordingly, such normal pulse signals become a low signal via an AND gate(15). However, if the wafer stage is vibrated while the shutter is opened, a certain high signal is generated in the low stage driving pulse signal. Therefore, two pulse signals are all in high level, and an output signal of the AND gate(15) is also in high level, so that a display part(16) indicates a poor operation.

Description

Defocus sensing circuit for stepper of alignment exposure device

The present invention relates to a defocus detection circuit of an alignment exposure apparatus, and more particularly, to detect a vibration of a wafer stage on which a wafer is placed when an image of a reticle is exposed on a wafer in an alignment exposure apparatus, thereby preventing the light from focusing. A focus shake detection circuit for preventing.

An alignment exposure apparatus (stepper) is an apparatus for transferring an image of a reticle onto a wafer using a light source having a constant wavelength in order to form a circuit pattern on a semiconductor device on a wafer in a semiconductor manufacturing process. The alignment exposure apparatus repeatedly moves the image of the reticle reduced by, for example, about 5: 1 by the optical system to produce a checkered image on the wafer. The wafer is exposed while being placed on a wafer stage. The wafer stage on which the wafer is placed serves to sequentially expose the wafer by repeatedly moving on the x-y coordinates by the reduced reticle image.

When the shutter is opened, the light generated by the light source exposes an image of the reticle onto the wafer. At this time, the wafer stage should be stopped while the reticle and the wafer are aligned, and the wafer may be shaken during exposure by vibration generated when the wafer stage moves so that the wafer is sequentially exposed. If the wafer is shaken during exposure, light is out of focus and the resolution of the circuit pattern formed on the wafer is reduced, resulting in defects in the semiconductor device.

Accordingly, an object of the present invention is to detect whether the wafer stage vibrates at the moment the shutter is opened to prevent defects in the semiconductor device.

1 is a circuit diagram illustrating a focus shake detection circuit according to an exemplary embodiment of the present invention;

2 is a waveform diagram showing a case where a pulse signal for driving the shutter and the wafer stage normally occurs;

3 is a waveform diagram illustrating a case where an abnormally generated pulse signal for driving a shutter and a wafer stage is generated.

Description of the main parts of the drawing

10; Focus shake detection circuits 11 and 12; Input terminal

13, 14; Transistor 15; Logical gate

16; Display

In order to achieve the above object, the present invention divides an open state and a closed state into different signals so that a first input unit to which a shutter driving pulse signal is input, and a moving state and a stopped state of the wafer stage are different signals. An output for outputting a predetermined signal only when a second input unit for inputting a stage driving pulse signal separately and a shutter driving pulse signal indicating a shutter open state and a wafer stage driving signal indicating a state in which the wafer stage moves are simultaneously input; It provides a focus shake detection circuit comprising a portion.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram illustrating a focus shake detection circuit according to an exemplary embodiment of the present invention. FIG. 2 is a waveform diagram illustrating a case in which a pulse signal for driving a shutter and a wafer stage is normally generated. FIG. 3 is a shutter and a wafer stage. This is a waveform diagram showing a case where an abnormally generated pulse signal for driving of.

Referring to FIGS. 1 to 3, the focus shake detection circuit 10 may include a first input unit 11 including a shutter driving pulse signal and a first transistor 13 and a stage driving pulse signal. And a second input unit including a second input terminal 12 and a second transistor 14, an AND gate 15, and a display unit 16. The first transistor 13 and the second transistor 14 are connected to the power supply Vcc, the input terminals 11 and 12, and the AND gate 15.

A shutter drive pulse signal indicating an operating state of a shutter (not shown) of the alignment exposure apparatus is input to the first input terminal 11. The shutter drive pulse signal is input high when the shutter is opened and low when the shutter is closed. A stage driving pulse signal indicating an operating state of a wafer stage (not shown) is input to the second input terminal 12. The stage driving pulse signal is input low when the wafer stage is stopped and high when moving.

Therefore, the shutter drive pulse signal is high when the wafer is exposed, the stage drive pulse signal is low, and the shutter drive pulse signal is low and the stage drive pulse signal is high when the wafer stage moves to align the reticle with the wafer. It is input to the 1st input terminal 11 and the 2nd input terminal 12. FIG. In this way, when the normal pulse signal is input to the first input terminal 11 and the second input terminal 12, the low-state signal is outputted by the AND gate 15 to continue the exposure process.

However, if the wafer stage vibrates while the shutter is open, the signal A in the high state appears in the stage driving pulse signal in the low state. As described above, when the stage driving pulse signal becomes high when the shutter driving pulse signal is high, the high gate signal is output by the AND gate 15 to detect that an exposure failure occurs.

When an exposure failure occurs, the display unit 16 may display it so that an operator may recognize it, or the operation of the wafer stage may be stopped by a control device (not shown). The display unit 16, such as a liquid crystal display, decodes the high and low binary signals output from the AND gate 15, displays them numerically, and generates a failure in the case of a failure. You can check the location.

As described above, according to the present invention, when a defect due to the focus shake occurs, the occurrence of the defect can be reduced by finding the detected position and confirming the generated position.

Claims (3)

A first input unit configured to input a shutter driving pulse signal by dividing an open state and a closed state into different signals; A second input unit configured to divide the moving state and the stopped state of the wafer stage into different signals and input a stage driving pulse signal; And an output unit for outputting a predetermined signal only when the shutter driving pulse signal representing the open state of the shutter and the wafer stage driving signal representing the state of moving the wafer stage are simultaneously input. Circuit. The focus shake detection circuit of claim 1, wherein the output unit is an AND gate. The focus shake detection circuit of claim 1, wherein the focus shake detection circuit further comprises a display unit for displaying the signal output from the output unit.