DE102004044765A1 - Device for lithographic exposure of photosensitive layer has system provided with pressure modulator which changes gas pressure in path of rays resulting in change of gas density so that position of focal plane is varied - Google Patents

Abstract

The device has a radiation source (1), a mask (8), a focusing unit (3) and a photosensitive layer (7) on a semiconducting wafer (9). The radiation source sends radiation in the prescribed path (5). A system (10,11,12) has a pressure modulator (13) in the path of rays. The modulator changes the gas pressure which changes the gas density resulting in the alteration of the focal plane (6) of the radiation. An independent claim is also included for the method of lithographic exposure of a photosensitive layer.

Description

The The invention relates to a device for lithographic exposure a radiation-sensitive layer according to claim 1 and a Process for the lithographic exposure of a radiation-sensitive Layer according to claim 9th

background the invention

lithographic Exposure method and apparatus for lithographic exposure go to shorter and shorter Wavelengths over. It become wavelengths, for example used in the range of 193 nm. Due to the short wavelengths are the focal areas occurring in lithographic exposure, in which focuses on the structures mapped using masks become smaller and smaller. this leads to to that increased Requirements for focusing the layer to be exposed in the focal plane are placed. However, uneven layers may be involved already lead to exposure errors.

Out US patent application 2002/0048288 A1 is a lithographic exposure method for integrated Circuits are known in which a laser for generating the light radiation is used, the radiation spectrum can be changed. The ones from Laser radiated radiation is transmitted via deflection and focusing units and an imaging mask and a lens on a radiation-sensitive Layer passed. The while Radiation emitted by a laser pulse is changed in wavelength, so that a radiation spectrum with at least two different wavelength is obtained. Because of during of an exposure process acting beams with two different wavelength is a smearing of the depth of focus and thus an increase in the Focusbereiches achieved in which the radiation-sensitive layer precise can be exposed. The described method requires a complex and very elaborate Control of the laser used.

The The object of the invention is a simplified device for lithographic exposure of a radiation-sensitive layer to provide a greater depth of focus.

Farther the object of the invention is to provide a method for lithographic Exposing a radiation-sensitive layer to provide in which by simple technical means an enlargement of the Focus depth is achieved.

The Objects of the invention are achieved by the device according to claim 1 and by the method according to claim 9 solved.

Further advantageous embodiments of the invention are in the dependent claims specified.

The The invention relates to a device for lithographic exposure a radiation-sensitive layer of a carrier, in particular a semiconductor wafer, with a radiation source, with an imaging mask, with a Focusing unit and with a holder for the carrier. The radiation source generates a radiation in an optical path through the imaging mask and the focusing unit is guided to a holder. The focusing unit bundles the Radiation in a focal plane, wherein a feed system is provided with the gas can be introduced into the beam path is. The feeding system has a pressure modulator with which the gas pressure at least in a part of the beam path for changing the position of the focal plane the radiation changeable is.

The Device has the advantage that by the change the gas pressure in the beam path of the refractive index is changed and so that the position of the focal plane is changeable. In this way can be a focal plane adjustment regardless of a control of the Radiation source can be made. This is another parameter for setting the focal plane available.

The The invention further relates to a device in which the delivery system gas nozzles which has the gas at a specified pressure in the beam path blow. By using gas nozzles is a fast and precise adjustment of the Gas pressure in the beam path possible. By using gas nozzles, the nearby the beam path are arranged, is a dynamic setting the focal plane with a low gas consumption possible.

Furthermore, the invention relates to a lithographic exposure apparatus having a first positioning mask for the imaging mask and a second positioning system for the holder. The device is designed in such a way that the radiation-sensitive layer can be exposed in successive exposure processes in different areas. In addition, the pressure modulator is designed in such a way that the pressure of the gas in the beam path is variable during an exposure process in a predetermined pressure range. In this way, the focal plane of the radiation during an exposure process of the radiation-sensitive layer in a fixed range ver changes, so that a larger focal plane area is obtained for the exposure process. This also unevenness of the radiation-sensitive layer can be compensated solely by the increased focal plane area, without the need for a multiple exposure or a change in the position of the photosensitive layer during the exposure process.

Farther the invention relates to a device for lithographic exposure, which has a pressure modulator formed in the manner is that the gas pressure during an exposure process starting from an initial value increases a set value can be and is lowered back to baseline. By This design of the pressure modulator, it is possible to set a specified pressure range while to exit an exposure process. This can be the area of Focus plane can be set within specified limits.

The The invention relates to a device for lithographic exposure with a pressure modulator, which is designed in such a way that the gas pressure in the beam path can be changed between 1 and 50 mbar is. Dependent on from the embodiment used the pressure modulator is designed in such a way that the gas pressure in the beam path between 1 and 5 mbar during an exposure process can be varied.

The The invention further relates to a device for lithographic Exposure at the gas nozzles are arranged between the light source and the focusing unit. The arrangement of the gas nozzles and the focusing unit has less adverse effects of the beam path.

In a further embodiment can they gas nozzles also between the focusing unit and the holder of the radiation-sensitive Layer can be arranged.

The The invention relates to a device for lithographic exposure a radiation-sensitive layer having a pressure chamber, wherein the pressure chamber at least partially disposed in the beam path is and the pressure in the pressure chamber via the pressure modulator adjustable is. By using a pressure chamber can be a precise and fast Setting the desired Focus depth can be achieved.

The The invention also relates to a method for lithographic exposure a radiation-sensitive layer, in particular a semiconductor wafer, with a radiation source, with an imaging mask, with a Focusing unit, wherein from the radiation source radiation in a beam path through the imaging mask and the focusing unit directed to the radiation-sensitive layer and in a focal plane is focused. In addition, a pressure system is provided, with the gas introduced into the beam path becomes. The printing system has a pressure modulator that at least the gas pressure in a part of the beam path during an exposure process changed the position of the focal plane of the radiation during the exposure process to vary.

aid the described method, it is possible, the focal plane during the lithographic exposure process using a gas pressure change set in the beam path. This gives another parameter with which the position of the focal plane is adjustable.

figure description

The The invention will be explained in more detail with reference to the following figures. Show it:

1 a schematic structure of an apparatus for photolithographic exposure of a radiation-sensitive layer, and

2 a partial section of a device for lithographic exposure with gas nozzles.

Full description

1 shows a schematic representation of an apparatus for lithographic exposure of a radiation-sensitive layer. The device has a radiation source 1 , an image mask layout 2 , a focusing unit 3 and a layer support unit 4 on. The radiation source 1 has a radiation transmitter 21 , Deflection mirror 22 and a slot 23 on. The focusing unit 3 includes in particular a lens with which the radiation is focused in the focal plane.

The radiation source 1 generates electromagnetic radiation that is transmitted through a beam path 5 through the imaging mask assembly 2 , the focusing unit 3 in a focal plane 6 on a photosensitive layer 7 the layer carrier unit 4 is focused. In the picture mask arrangement 2 is an illustration mask 8th arranged with an imaging pattern in the focal plane 6 is reproduced. The photosensitive layer 7 is on a carrier 9 arranged. The photosensitive layer consists, for example, of a photoresist which is converted by the exposure process into soluble and insoluble areas. In a follow-up process, the soluble areas with a corresponding developer solution from the carrier 9 from washed. In this way, a structuring of the photosensitive layer 7 achieved, which is used as a structured layer for subsequent processes, such as deposition processes or etching processes.

For a precise image of the imaging pattern of the imaging mask 8th it is necessary that the photosensitive layer 7 in the focal plane area of the focal plane 6 is arranged.

The focal plane is the wavelength used by the radiation source 1 generated radiation and the focusing unit 3 established.

For an enlargement of the focal plane area, ie the area in which a precise mapping of the imaging pattern of the imaging mask 8th on the photosensitive layer 7 is reached, the gas pressure in the beam path 5 the radiation varies during an exposure process. For this purpose, a variety of means may be provided. In the embodiment of the 1 is a pressure chamber 10 in the beam path 5 arranged, via a pressure line 11 with a printing system 12 connected is. The printing system 11 has a pressure modulator 13 on, with that of the printing system 12 delivered gas pressure is adjustable. The pressure chamber 10 is for example cylindrical and parallel to the axis of the beam path 5 arranged. An upper and a lower end surface of the pressure chamber 10 are for the radiation of the radiation source 1 permeable.

The pressure modulator 13 of the printing system 12 is via a control line 14 with a control unit 15 connected. The control unit 15 is also available with a first positioning drive 16 via a second control line 17 in connection. The first positioning drive 16 holds the picture mask 8th and is configured to be the imaging mask 8th to move in an XY plane perpendicular to the beam path 5 is arranged. The first positioning drive 16 moves the picture mask 8th according to the control by the control unit 15 ,

The control unit 15 is also via a third control line 18 with a second positioning drive 19 connected. The second positioning drive 19 carries a holder 20 on which the carrier 9 with the photosensitive layer 7 is attached. The second positioning drive 19 is formed in the manner to the holder 20 in the XY plane, perpendicular to the beam path 5 is arranged to move. The second positioning drive 19 moves the holder 20 and with it the carrier 9 with the photosensitive layer 7 depending on the control by the control unit 15 ,

In an exposure process of the photosensitive layer 7 is through the control unit 15 the pressure modulator 13 driven in the way that the printing system 12 the gas pressure in the pressure chamber 10 changed in a desired pressure range. Depending on the embodiment used, the gas pressure is increased during an exposure process from an initial pressure to a maximum pressure and then returned to the initial pressure. In a further embodiment, the gas pressure is lowered during an exposure process, starting from an initial pressure to a minimum pressure and then increased again to the initial pressure. By changing the gas pressure in the pressure chamber 10 the refractive index is changed so that the focal plane 6 in the height position, ie in the Z direction, parallel to the axis of the beam path 5 is arranged, moves. By the temporal shift of the focal plane 6 During an exposure process, an enlargement of the focal plane area is achieved, within which an image of the imaging pattern of the imaging mask 8th in the photosensitive layer 7 is reached.

As a carrier 9 For example, any type of carrier can be used, wherein the photolithographic method is particularly suitable for patterning photoresist layers on a semiconductor wafer, in particular a silicon wafer.

2 shows in a schematic representation of another embodiment of the apparatus for photolithographic exposure of a radiation-sensitive layer, wherein in 2 only sections of the arrangement are shown. The parts of the arrangement, not shown, correspond to the arrangement of 1 , In contrast to the device according to 1 are in place of a pressure chamber 10 gas nozzles 24 side of the beam path 5 arranged. The gas nozzles 24 are over pressure lines 11 with the printing system 12 connected. The gas nozzles 24 can be between the focusing unit 3 and the photosensitive layer 7 and / or between the focusing unit 3 and the picture mask 8th be arranged. The arrangement is in a housing 25 introduced, the suction 26 that has a suction system 27 are connected. The suction system 27 is via a fourth control line 28 with the control unit 15 in connection. The control unit 15 controls through the pressure modulator 13 from the printing system 12 over the gas nozzles 24 in the beam path 5 discharged gas quantity, ie the gas flow. In addition, in an advantageous embodiment of the device, the possibility of the gas pressure in the housing 25 to lower the setting of the suction power. The suction system 27 is in the suction power through the third control line from the control unit 15 driven.

The control unit 15 has stored control programs stored in a program memory 29 are stored. In the stored programs it is determined with which control power the control unit 15 the pressure modulator 13 must control that at a fixed wavelength of the radiation of the radiation source 1 a change in the position of the focal plane 6 along the Z-axis in a desired range is achieved. In particular, the programs store temporal print modulations which are used for defined exposure processes. In addition, it is also determined in the programs, with which control power the control unit 15 the pressure modulator and / or the suction system 27 at a desired change in the position of the focal plane 6 must drive.

The corresponding parameters for the control programs have been determined experimentally.

The described device and the method described are suitable in particular for the exposure of photosensitive layers of a semiconductor wafer, on which, for example, DRAM circuits are produced. The described apparatus for lithographic exposure of the radiation-sensitive Layer of a carrier is preferably part of a scanning wafer stepper, wherein the imaging mask parallel to the wafer, i. the carrier is moved. The picture mask is usually moved faster than the wafer. usual Speed relationships are in the range of 1: 4. In addition, in the figure, exposure slots used on the wafer with a thickness d. Is now the mask speed v is the quadruple value of the wafer speed vw, it follows a modulation frequency for the change the gas density of at least the value f = (4 vw) / (2 · d). Becomes uses a laser with a laser pulse frequency FL as the radiation source, Thus, the maximum modulation frequency of the gas density through the half laser frequency FL limited.

In a preferred embodiment the gas pressure becomes according to a sine and / or a cosine course changed.

investigations on a ZEISS system with a 1100 lens have shown that the Focus plane at a pressure change with a distance s of 0.023 μm per millibar pressure change shifts. The wafer movement speed vw, for example, corresponds 0.3 mm per second. The slot width is approximately 10 mm. From these data results a minimum modulation frequency for the pressure of 60 Hz and a pressure amplitude of 4.35 mbar to one shift the focal plane during an exposure process of ± 100 nm to achieve. These However, data is only an example and limiting not the scope of the device or the described Process. Dependent on From the application, the person skilled in the relevant parameters for adjustment to determine the pressure.

1

radiation source

2

Figure mask arrangement

3

focusing

4

Substrate unit

5

beam path

6

focal plane

7

layer

8th

Figure mask

9

carrier

10

pressure chamber

11

pressure line

12

printing system

13

pressure modulator

14

control line

15

control unit

16

first positioning

17

second control line

18

third control line

19

second positioning

20

holder

21

beam transmitter

22

deflecting

23

slot

24

gas nozzle

25

casing

26

suction

27

suction

28

fourth control line

29

program memory

Claims (9)

Apparatus for the lithographic exposure of a radiation-sensitive layer ( 7 ) of a carrier ( 9 ), in particular a semiconductor wafer, with a radiation source ( 1 ), with an imaging mask ( 8th ), with a focusing unit ( 3 ) and with a holder ( 20 ) for the wearer ( 9 ), the radiation source ( 1 ) a radiation in a beam path ( 5 ) through the imaging mask ( 8th ) and the focusing unit ( 3 ) to the holder ( 20 ), the focusing unit ( 3 ) the radiation in a focal plane ( 6 ), characterized in that a delivery system ( 10 . 11 . 12 ; 24 ) is provided, with the gas in the beam path ( 5 ) is feasible that the feeding system ( 10 . 11 . 12 ; 24 ) a pressure modulator ( 13 ), with which the gas pressure at least in one part ( 10 ) of the beam path ( 5 ) for changing the position of the focal plane ( 6 ) of the radiation is variable. Apparatus according to claim 1, characterized in that the feed system gas nozzles ( 24 ), which the gas with a fixed Pressure in the beam path ( 5 ) to lead. Device according to one of claims 1 or 2, characterized in that the device comprises a first positioning drive ( 16 ) for the image mask ( 8th ) and a second positioning drive ( 17 ) for the holder ( 20 ), that the radiation-sensitive layer ( 7 ) is exposed in successive exposures in different areas that the pressure modulator ( 13 ) is adapted to vary the pressure during an exposure process in a predetermined pressure range, so that the focal plane ( 6 ) of the radiation during an exposure process in a predetermined range moves. Device according to one of claims 1 to 3, characterized in that the pressure modulator ( 13 ) is adapted to increase the gas pressure during an exposure process from an initial value to a predetermined value and to lower it back to the initial value. Device according to one of claims 1 to 4, characterized in that the pressure modulator ( 13 ) is adapted to vary the pressure between 1 and 50 mbar, preferably between 1 and 5 mbar. Device according to one of claims 2 to 5, characterized in that the gas nozzles ( 24 ) between the radiation source ( 1 ) and the focusing unit ( 3 ) are arranged. Device according to one of claims 1 to 6, characterized in that the gas nozzles ( 24 ) between the focusing unit ( 3 ) and the holder ( 20 ) are arranged. Device according to one of claims 1 and 3 to 5, characterized in that in the beam path ( 5 ) a pressure chamber ( 10 ) and that the delivery system ( 11 . 12 . 13 ) to the pressure chamber ( 10 ) connected. Process for the lithographic exposure of a radiation-sensitive Layer, in particular a semiconductor wafer, with a radiation source, with an imaging mask, with a focusing unit, wherein of the Radiation source radiation in a beam path through the imaging mask and the focusing unit is sent to the radiation-sensitive layer and focused in a focal plane, wherein a printing system is provided is, is guided with the gas in the beam path, characterized in that the printing system has a pressure modulator that the pressure modulator the gas pressure at least in a part of the beam path during a Exposure process changed to the position of the focal plane of the radiation during the exposure process to vary.