KR20000074978A - Method and apparatus capable of variably controlling width of slit sensors for automatically focusing and leveling a wafer - Google Patents

Abstract

PURPOSE: A method for variably controlling disposition intervals of slit sensors is provided to precisely perform a focusing and a labeling regarding an exposure region of a wafer, by using five slit sensors in extracting labeling data. CONSTITUTION: Light generated at a light source(100) is changed to a focused light beam. The focused light beam passes through a slit array(120) wherein a plurality of slits are formed as a matrix format, the slits being penetrated by light, and is irradiated to a wafer substrate. The light beam reflected on the wafer substrate is detected to focus the wafer substrate and perform a labeling. The light beam passing through the slit array and reflected on the wafer substrate is zooming-controlled to vary disposition intervals of the slits.

Description

METHOD AND APPARATUS CAPABLE OF VARIABLY CONTROLLING WIDTH OF SLIT SENSORS FOR AUTOMATICALLY FOCUSING AND LEVELING A WAFER}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic process for the manufacture of semiconductor devices, and more particularly to an improvement in focusing and leveling of a wafer upon exposure of the semiconductor wafer.

In the photo process associated with the manufacture of semiconductor circuit elements, the process of transferring the circuit pattern contained in the reticle to the semiconductor wafer is called an exposure process. During exposure, the focusing state of the exposure beam projected onto the photosensitive liquid on the wafer has a great influence on the accuracy of the processing in processing very fine structures on the wafer. In order to accurately transfer the pattern of the reticle onto the wafer, the one-shot area on the wafer is exposed, and then focusing and leveling control on the one-shot area is performed to expose the next one-shot area.

FIG. 1 shows a simplified configuration of an automatic focusing and leveling device for a wafer employed in a conventional scanner type exposure system, and FIG. 2 shows a conventional configuration employed in the device of FIG. 1 as a focusing and leveling sensor. The structure of the slit array 25 is shown.

Referring to Figs. 1 and 2, the principle of operation of the automatic focusing and leveling device will be described. When the light source 10, which is different from the exposure light and does not expose the photoresist on the wafer 35, emits light, the emitted light is removed. It is focused by one focusing lens 15 and is transmitted to the slit plate 20 via the opening plate 17. The slit plate 20 is provided with a slit array 25 in which a plurality of slits 27 are formed in a matrix array form. The light beam passing through each slit 27 is incident through the first objective lens 30 to any one-shot region 40 of the exposure surface of the wafer 35 and is reflected again. The reflected light is subsequently changed in path by the reflective mirror 55 via the second objective lens 50 on the light receiving side, focused by the second focusing lens 60, and then projected onto the detector 65. The detector 65 senses only the light beams projected at a predetermined number of predetermined positions among the projected light beams, and extracts information necessary for focusing and leveling from the amount of light and the deviation of the light incident path. From the extracted information, a correction amount for accurate focusing and leveling of the one-shot region of the current period is calculated and provided to the actuators 40a, 40b, and 40b of the wafer stage 37, and the actuators are based on the transferred correction amount. By moving the stage 37 three-dimensionally, accurate focusing and leveling are realized.

In such a conventional automatic focusing and leveling device, a plurality of slits 27 are arranged in a fixed position in the form of a matrix array in the slit array 25 used as a focusing and leveling sensor. Specifically, for example, in the case of a Nikon scanner, the slit array 25 is composed of a prescan slit sensor located in the top row and the bottom row and three rows of exposed slit sensors in the middle as shown in FIG. The total number of slits is 45 and the size of each slit is 0.19mm x 2mm.

In the case of the conventional slit array 25, the left and right intervals between the slits 27 are 2.9 mm and 4 mm, respectively, as shown. In addition, in the conventional scanner, although the multi-point automatic focusing method is used, not all of the light beams passing through the slit array 25 are used in the detector 65, but a predetermined number, up to 9 slits in the case of a Nikon scanner Can be used, but in practice only the light beam passing through the eight slits is utilized. The user can choose which slit to use. That is, only three prescan slit sensors may be selected when designating each slit sensor, and five exposed slit sensors may be selected only in a row of the selected prescan slit sensor.

In the conventional slit array 25, for example, when there is no slit sensor at a suitable position of the one-shot area of the device or when considering the arrangement interval between the slit sensors, a portion of the slit sensor is scribe-line of the wafer. It may be over. In this case, we have no choice but to select the slit sensor in the lane position.

As can be seen from the above example, since the position of the slit sensor 27 is fixed in the conventional slit array 25 of FIG. 2, it cannot flexibly cope with various element sizes. In addition, since only the slit sensor can be used, it is difficult to obtain reliable focusing and leveling data from the light beam automatically sensed by the detector 65 when the size of the slit array 25 does not exactly match the size of the one shot region. There is a difficult problem.

On the other hand, as shown in FIG. 3, the leveling for any one-shot area 40 is controlled using the average value of three data obtained using three prescan slit sensors. The leveling method using the three-point detection may be a structure in which the one-shot region 40 of the wafer has a linear step, or the one-shot region 40 is a structure in which the step is positively symmetrical with respect to the center even if the one-shot region 40 has a non-linear step. Reliability can be acknowledged at this time, but if the one-shot area 40 has asymmetric steps left and right, it is difficult to secure accurate leveling data.

In order to solve the above-mentioned problems of the prior art, the present invention can obtain more accurate focusing and leveling data for an exposure area of a wafer by controlling the placement interval of the slit sensors variably and using five slit sensors for leveling data extraction. It is an object of the present invention to provide a method and apparatus.

1 is a view for explaining a simplified configuration and operating principle of a conventional wafer automatic focusing and leveling device.

2 shows a configuration of a conventional slit array used as a focusing and leveling sensor.

3 is a view for explaining a wafer leveling operation using a conventional three-point detection method.

FIG. 4 is a diagram illustrating a simplified configuration and operation principle of an automatic focusing and leveling device of a wafer capable of variably adjusting an arrangement interval of slits of a slit array.

5 shows a configuration of a slit array according to an embodiment of the present invention.

6 is a view for explaining a wafer leveling operation using a five-point detection method according to the present invention.

<Description of the symbols for the main parts of the drawings>

100: light source 105: first focusing lens

110: opening plate 120: slit array

122: slit 125: first zoom optical system

130: wafer 135: one-shot area

137: wafer stage 140a, 140b, 140c: actuator

150: second zoom optical system 155: reflective mirror

160: second focusing lens 165: detector

Wafer autofocus and leveling method according to the present invention,

The light generated from the light source is changed into a focused light beam, and the plurality of transmissive slits are transmitted through the focused light beam through the slit array formed in the form of a matrix array to be incident on the wafer substrate, and the light beam reflected by the wafer substrate is detected. In focusing and leveling the wafer substrate,

Zooming control (zooming control) of the light beam passed through the slit array and the light beam reflected by the wafer substrate to vary the interval of placement of the slits.

In particular, the light beams that have passed through the slit array are zoomed out to reduce the spacing of the slits. In addition, zoom-in control of the light beam reflected by the wafer substrate is performed to restore the reduced arrangement interval of the slits to the original arrangement interval.

On the other hand, the wafer auto focus and leveling apparatus according to the present invention,

An incident side focusing lens for focusing light generated from the light source;

A slit array formed in a matrix array form at a position where a plurality of transmissive slits are fixed to transmit the focused light beam through the slits;

An incident-side zoom optical system for inputting the light beam passing through the slit array to the wafer substrate by varying the arrangement interval of the slits through zooming control;

A light-receiving side zoom optical system for restoring the variable placement intervals of the slits by the incident-side zoom optical system through a zooming control of the light beam reflected from the wafer substrate;

A light receiving-side focusing lens for focusing the reflected light beam passing through the reflection-side zoom optical system; And

And detection means for extracting data for adjusting the focus and level of the wafer substrate from the reflected light transmitted through the light receiving side focusing lens.

According to the present invention, when the size of the slit array and the size of the one-shot region on the wafer do not match, the incident light is zoomed out at an appropriate zoom ratio to reduce the image of the snail array to match the one-shot region and the wafer. The reflected light from the back is again zoomed in by applying the zoom ratio in reverse to restore the original spacing of the slits. Through this zooming control, it is possible to variably adjust the placement interval of the slits.

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

4 shows a simplified configuration of an automatic focusing and leveling device of a wafer according to an embodiment of the present invention. The apparatus uses the light source 100, the first focusing lens 105, the aperture plate 110, and the slit array 120 on the light transmitting side on the left side with respect to the semiconductor wafer 130 seated on the wafer stage 137. The slit plate 110 and the first zoom optical system 125 are sequentially provided. In addition, a second zoom optical system 150, a reflection mirror 155, a second focusing lens 160, and a detector 165 are sequentially provided on the light receiving side on the right side of the wafer 130. In addition, actuators 140a, 140b, 140c for three-dimensionally adjusting the position of the wafer stage 137 are provided to the wafer stage 137.

As can be seen from FIG. 4, the configuration of the embodiment of the present invention differs from that of the apparatus of FIG. 1 in that the first and second objective lenses 30 and 50 are connected to the first and second zoom optical systems 125 and 150. ).

Zooming control continuously enlarges or reduces an image on the screen by using a zoom lens that moves a part of the optical system in the optical axis direction to continuously change the focal length. In other words, zooming in or out of an image until the screen is full (zoom-in), or vice versa, can zoom in on a portion of the current image. Say. The reduction or enlargement ratio of an image is called a zoom ratio, which is defined as the ratio of the maximum focal length (magnification) and the minimum focal length (image reduction).

When such zoom optical systems 125 and 150 are provided before and after the wafer 135 on the path of the light beam, although the positions of the plurality of slits formed in the slit array 120 are fixed, the positions of the slits are variably moved. The same effect can be achieved. This will be described in detail as follows.

The configuration of the slit array 120 according to the embodiment of the present invention is shown in Figure 5, the slit array 25 is a prescan slit sensor located in the top row and the bottom row as shown, and three rows of exposed slit sensors in the middle. It is composed. The total number of slit sensors 122 formed in the slit array 120 is 35, and the size of each slit is 0.19mm x 2mm as in the prior art. The total number of slit sensors 122 is 10 reduced compared to the prior art. Reducing the number of the slit sensors 122 is because the position of the slit can be variably controlled by the zoom control, so that it is not necessary to have a large number of slit sensors as in the prior art. In addition, the distance between each slit sensor is also conventionally set to 2.9mm, but narrowly disposed to 2.3mm. By narrowing the arrangement interval of the slit sensors in this manner and combining zooming control, as shown in FIG. 6, the region of the slit array 120 corresponding to the one shot region 135 of the wafer 130 is narrowed ( 124 or a wide area 124 ′ may be elastically selected.

The light generated by the light source 100 is projected onto the slit array 120 of the slit plate 115 through the first focusing lens 105 and the opening plate 110 to pass the wafer 130 through the first zoom optical system 125. Investigate. Here, when the zooming control is not performed on the light beam incident on the wafer 130, the light beam projected to the one shot region 135 through the first zoom optical system 125 leaves the one shot region 135 on the wafer 130. Assume a case where a state is not matched with a so-called one-shot region 135 that spans a scribe line or does not fully examine the one-shot region 135. Specifically, when the narrow area 124 of the slit array 120 does not irradiate all of the one shot area 135, the first zoom optical system 125 zooms out the light beam passing through the slit array 120, thereby making the one shot area. The portion of the slit array 120 formed at 135 is enlarged from the narrow region 124 to the wide region 124 '. Also, for example, when the light beam passing through the slit sensor # 29 spans the outer boundary of the one-shot region 135, that is, the scribe line, the slit array 120 is controlled through the first zoom optical system 125 as described above. The image is enlarged so that a large area 124 'of the image) is formed in the one shot area 135. FIG.

When the zoom-out control of the incident light is performed as described above, the zoom-in control is performed on the reflected light by applying the same zoom ratio in reverse by using the second zoom optical system 150. The enlarged image is reduced again by the zoom-in control so that the light beam restored to its original size is provided to the detector 165 via the reflection mirror 165 and the second focusing lens 160. The zoom ratio applied in the zooming control is appropriately determined according to the size of the one-shot region 135 and the size of the slit array 120.

On the other hand, only three of the prescan slit sensors arranged in the top row and the bottom row of the slit array 120 can be used in the prior art, as shown in FIG. Apply the way you do. To this end, it may be appropriately controlled to select five light receiving sensors (not shown) disposed in the detector 165 corresponding to each slit sensor. By adopting the five-point detection method as described above, even if the one-shot area 135 has a structure having a stepped or curved surface with asymmetrical left and right, more accurate leveling data can be extracted. That is, when leveling data is obtained from three slit sensors as in the prior art, the leveling or focusing data may show a slight difference depending on the position of the slit sensor in the left-right asymmetrical or curved one-shot region. By increasing it as above and taking the average of the whole, you can get more reliable data. However, in case of unavoidable, elasticity is given by allowing three slit sensors to be taken as in the prior art.

As described above, since the arrangement interval of the slit sensors can be changed, it is possible to flexibly cope with various devices having various sizes, so that it is not necessary to replace the sludge array or the like for each device. In addition, since the data used for focusing and leveling can be secured more reliably, it can greatly contribute to improving the reliability and productivity of the exposure process.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the present invention without departing from the spirit and scope of the invention described in the claims below. I can understand that you can.

Claims (3)

The light generated from the light source is changed into a focused light beam, and the plurality of transmissive slits are transmitted through the focused light beam through the slit array formed in the form of a matrix array to be incident on the wafer substrate, and the light beam reflected by the wafer substrate is detected. In the wafer auto focusing and leveling method of focusing and leveling the wafer substrate, And zooming control of the light beam passing through the slit array and the light beam reflected by the wafer substrate to vary the placement interval of the slits. The optical beam of claim 1, wherein the light beam passing through the slit array is zoomed out to reduce an interval of arrangement of the slits, and zoom-in control of the light beam reflected by the wafer substrate is performed. Thereby restoring the reduced spacing of the slits to the original spacing. An incident side focusing lens for focusing light generated from the light source; A slit array formed in a matrix array form at a position where a plurality of transmissive slits are fixed to transmit the focused light beam through the slits; An incident-side zoom optical system for inputting the light beam passing through the slit array to the wafer substrate by varying the arrangement interval of the slits through zooming control; A light-receiving side zoom optical system for restoring the variable placement intervals of the slits by the incident-side zoom optical system through a zooming control of the light beam reflected from the wafer substrate; A light receiving-side focusing lens for focusing the reflected light beam passing through the reflection-side zoom optical system; And And detection means for extracting data for adjusting the focus and level of the wafer substrate from the reflected light transmitted through the light receiving-side focusing lens.