Method and apparatus for lithography in semiconductor fabrication

A reticle holding tool is provided. The reticle holding tool includes a housing including a top housing member and a lateral housing member. The lateral housing member extends from the top housing member and terminates at a lower edge. The reticle holding tool further includes a reticle chuck. The reticle chuck is positioned in the housing and configured to secure a reticle. The reticle holding tool also includes a gas delivery assembly. The gas delivery assembly is positioned within the housing and configured to supply gas into the housing.

BACKGROUND

A lithography exposure process forms a patterned photoresist layer for various patterning processes, such as etching or ion implantation. In a typical lithography process, a photosensitive layer (resist) is applied to a surface of a semiconductor substrate, and an image of features defining parts of the semiconductor device is provided on the layer by exposing the layer to a pattern of high-brightness light. As semiconductor processes evolve to provide for smaller critical dimensions, and devices become smaller and increase in complexity, including the number of layers, a way of accurately patterning the features is needed in order to improve the quality, reliability, and yield of the devices.

Although numerous improvements to the methods of performing a lithography exposure process have been invented, they have not been entirely satisfactory in all respects. Consequently, it would be desirable to provide a solution to improve the lithographic system so as to increase the production yield of the semiconductor wafers.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter provided. Specific examples of solutions and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

The advanced lithography process, method, and materials described in the current disclosure can be used in many applications, including fabrication of fin-type field effect transistors (FinFETs). For example, the advanced lithography process of the present disclosure is well suited to produce relatively closely-spaced features of FinFETs. In addition, spacers used in forming fins of FinFETs can be processed according to the current disclosure.

FIG. 1is a schematic and diagrammatic view of a lithography system10, in accordance with some embodiments. The lithography system10is configured to use a high-brightness light7to expose a photoresist layer coated on the semiconductor wafer2. The lithography system10may be generically referred to as a scanner that is operable to perform lithography exposure process with respective high-brightness light source and exposure mode.

In some embodiments, the lithography system10includes a number of vacuum vessels, such as first vacuum vessel11and second vacuum vessel12, a wafer stage13, and an exposure tool14. The elements of the lithography system10can be added to or omitted, and the invention should not be limited by the embodiment.

The first vacuum vessel11and the second vacuum vessel12preserve respective vacuum environments at ultra-high vacuum pressures. The vacuum pressure in the first vacuum vessel11may be lower than the second vacuum vessel12. For example, the vacuum pressure in the first vacuum vessel11may be about 1.5*10−2mB to about 2.8*10−2mB, and the vacuum pressure in the second vacuum vessel12may be about 8*10−2mB.

The wafer stage13is configured for supporting the semiconductor wafer2during the lithography exposing process. In some embodiments, the wafer stage13is positioned in the second vacuum vessel12and moveable between a leveling position and an exposure position in the second vacuum vessel12by a driving member, such as linear motor (not shown in figures). A radial and rotational movement of the wafer stage13can be coordinated or combined in order to transfer, and deliver the semiconductor wafer2.

The exposure tool14is configured to apply a high-brightness light beam including a pattern in the beam's cross-section onto the surface of the semiconductor wafer2so as to print desired patterns over a photoresist layer coated on the semiconductor wafer2. The exposure tool14is positioned over the wafer stage13when the wafer stage13is positioned in the exposure position.

In some embodiments, the exposure tool14includes a high-brightness light source15, an illuminator16, a projection optics module (or projection optics box (POB))17, a number of pumping members18, a reticle19, and a reticle holding tool20. In some embodiments, all elements of the exposure tool14are positioned in the first vacuum vessel11. In some other embodiments, partial elements of the exposure tool14are positioned in the first vacuum vessel11. The technical features of the exposure tool14, according to some embodiments, are described below.

The high-brightness light source15is configured to generate radiation having a wavelength ranging between about 1 nm and about 100 nm. In one particular example, the high-brightness light source15generates an extreme ultraviolet (EUV) light with a wavelength centered at about 13.5 nm. Accordingly, the high-brightness light source15is also referred to as EUV light source. However, it should be appreciated that the high-brightness light source15should not be limited to emitting EUV light. The high-brightness light source15can be utilized to perform any high-intensity photon emission from excited target material. For example, the high-brightness light source15may include a high-brightness light source, such as an ultraviolet (UV) source or a deep ultra-violet (DUV) source.

In some embodiments, the illuminator16includes a chamber160. The chamber160is positioned in the first vacuum vessel11and has a number of orifices161for exhausting gas inside the chamber160. In addition, the chamber160includes a light entry passage162and a light emitting passage163for allowing the light generated from the high-brightness light source15to enter and leave the chamber160.

In some embodiments, the illuminator16further includes a gas inlet164located in the chamber160. The gas inlet164is configured for discharging gas, such as H2, N2or XCDA into the chamber160. Due to the gas being supplied into the chamber160from the gas inlet164, the vacuum pressure in the chamber160may be higher than the vacuum pressure in the first vacuum vessel11(i.e., the space outside of the chamber160). In some embodiments, the vacuum pressure in the first vacuum vessel11may be about 1.5*10−2mB to about 2.8*10−2mB, and the vacuum pressure in the chamber160may be about 3.3*10−2mB.

In some embodiments, the illuminator16also includes various refractive optical components165,166and167. The refractive optical components165,166and167may be a lens system having multiple lenses (zone plates) or alternatively reflective optics (for EUV lithography system), such as a single mirror or a mirror system having multiple mirrors in order to direct light from the high-brightness light source15onto the reticle holding tool20, particularly to a reticle19secured on the reticle holding tool20. In the present embodiment where the high-brightness light source15generates light in the EUV wavelength range, reflective optics is employed.

The projection optics module (or projection optics box (POB))17is configured for imaging the pattern of the reticle19on to the semiconductor wafer2secured on the wafer stage13. In some embodiments, the POB17includes a chamber170. The chamber170is positioned in the first vacuum vessel11and has a number of orifices171for exhausting gas inside the chamber170. In addition, the chamber170includes a light entry passage172and a light emitting passage173for allowing the light generated from the high-brightness light source15to enter and leave the chamber170.

In some embodiments, the POB17further includes a gas inlet174located in the chamber170. The gas inlet174is configured for discharging gas, such as H2, N2or XCDA into the chamber170. Due to gas being supplied into the chamber170from the gas inlet174, the vacuum pressure in the chamber170may be higher than the vacuum pressure in the first vacuum vessel11(i.e., the space outside of the chamber170). In some embodiments, the vacuum pressure in the first vacuum vessel11may be about 1.5*10−2mB to about 2.8*10−2mB, and the vacuum pressure in the chamber170may be about 3.8*10−2mB.

In some embodiments, the POB17also includes various refractive optical components175,176and177, such as refractive optics (such as for a UV lithography system) or alternatively reflective optics (such as for an EUV lithography system) in various embodiments. The light directed from the reticle19, carrying the image of the pattern defined on the mask, is collected by the POB17. The illuminator16and the POB17are collectively referred to as an optical module of the exposure tool14.

In some embodiments, the exposure tool14further includes a number of actuators (not shown in the figures) connected to the illuminator16and the POB17to adjust the position of optic elements of the illuminator16and the POB17. The actuators are electrically connected to the controlling apparatus (not shown in figures). In addition, the actuator is controlled to drive the movement of the optic elements of the illuminator16and the POB17according the signals issued by the controlling apparatus. As a result, the focal length of the high-brightness light scanned over the semiconductor wafer2can be adjusted.

The pumping members18are configured to create a vacuum in the first vacuum vessel11and the second vacuum vessel12. The pumping members18may include a number of vacuum pumps with different ultimate pressure connected in series so as to improve the pumping speed of the first vacuum vessel11and the second vacuum vessel12.

For example, the pumping member18includes a primary pump connected in series to a secondary pump. The primary pump is used to lower pressure from one pressure state (typically atmospheric pressure) to a lower pressure state, and after which the secondary pump is used to evacuate the process chamber down to high-vacuum levels needed for processing. The primary pump may be a skimmer pump, a diaphragm pump, a rotary vane pump, or a scroll pump. The secondary pump may be a high-vacuum molecular pump, or a rotary pump. The gas exhausted from the pumping member18may be discharged into a gas handling system (not shown) of a FAB via a gas conduit (not shown in figure).

FIG. 2shows a cross-sectional view of the reticle holding tool20, in accordance with some embodiments. In some embodiments, the reticle holding tool20includes a lateral housing member212, a lower housing member214, a stage22, a reticle chuck23, and a gas delivery assembly24. The elements of the reticle holding tool20can be added to or omitted, and the invention should not be limited by the embodiment.

The stage22is configured to support the reticle chuck23and control the movement of the reticle chuck23. In some embodiments, the stage22is positioned on a top panel110of the first vacuum vessel11. The top panel110and the light emitting passage173may be located at two opposite sides of the first vacuum vessel11, as shown inFIG. 1. In some embodiments, the stage22includes one or more actuators and guiding members to drive a movement of the reticle chuck23in one or multiple directions. For example, as shown inFIG. 2, the stage22includes an actuator221and a guiding member222connected to the actuators221. The actuator221may be a step motor and the guiding member222may include a linear guideway.

In some embodiments, the reticle chuck23is an electrostatic chuck (e-chuck) to secure the reticle19by an electrostatic force. In some embodiments, the reticle chuck23is connected to the guiding member222. When the actuator221is operated, the guiding member222is driven to move to control a movement of the reticle chuck23forth and back in a direction that is parallel to a predetermined plane PP as indicated byFIG. 2.

In some embodiments, an area of the bottom surface231of the reticle chuck23which is covered by the reticle19during the lithography exposure process is referred to as an effective area. In some embodiments, partial area of the bottom surface231is covered by the reticle19during the lithography exposing process. In some other embodiments, the entire area of the bottom surface231is covered by the reticle19during the lithography exposing process.

In some embodiments, the lateral housing member212has a ring shape and extends away from the top panel110and terminates at a predetermined plane PP with a lower edge213. The predetermined plane PP may be parallel to the horizontal direction and located away from the top panel110. A distance d2between the top panel110and the predetermined plane PP is greater than a distance d1from the top panel110to the effective surface of the reticle chuck23. That is, the effective surface is located between the predetermined plane PP and the top panel110.

In some embodiments, the extending direction of the lateral housing member212is perpendicular to the top panel110. In some other embodiments, the extending direction of the lateral housing member212is askew with the top panel110. An included angle between the inner wall of the lateral housing member212and the top panel110is an obtuse angle. Namely, the width of the lateral housing member212gradually decreases in a direction away from the top panel110.

The lower housing member214has a ring shape and is connected to the lower edge213of the lateral housing member212. In some embodiments, the lower housing member214extends on the predetermined plane PP. In some other embodiments, the lower housing member214extends away from the lower edge213and terminates at its inner edge2142to form an opening215. In some other non-illustrated embodiments, the lower housing member214is inclined relative to the predetermined plane PP, and a distance formed between the lower housing member214and the top panel110may gradually increases in a direction away from the lower edge213to the inner edge2142. In some embodiments, the lower housing member214is omitted. The lower housing member214may be replaced by a blade of reticle mask (REMA) which defines an area of an exposure field.

In some embodiments, the inner edge2142of the lower housing member214defines an opening215. The opening215may have a rectangular shape, a circular shape, an elliptical shape, a polygonal shape, an irregular shape, or combinations thereof. In some embodiments, the width of the opening215is sufficiently large to allow the entry or exit of the high-brightness light from the high-brightness light source15and to allow the reticle19to be replaced.

In some embodiments, during the lithography exposure process, the reticle chuck23is movable between two boundary lines B1and B2. The width of the opening215is greater than the distance between the two boundary lines B1and B2. That is, in a direction that is perpendicular to the effective surface of the reticle chuck23(or the top panel110of the first vacuum vessel11), the projection of the lower housing member214is located outside of the effective surface of the reticle chuck23.

FIG. 3shows a bottom view of the reticle holding tool20and a reticle handling robot8, in accordance with some embodiments. In some embodiments, there is a recess216formed on the bottom surface of the lower housing member214. The recess216extends from the outer edge2141to the inner edge2142. The recess216has a shape that is compatible with the shape of the reticle handling robot8which is used to move the reticle19to and from the reticle chuck23.

The recess216allows an upward movement of the reticle handling robot8relative to the reticle chuck23. In some embodiments, to load the reticle19on the reticle chuck23, the reticle chuck23is lowered down by the stage22to approach the opening215. In addition, the reticle handling robot8is moved below the opening215, and then is move upward to put the reticle19on the reticle chuck23. After the upward movement of the reticle handling robot8, a portion of the reticle handling robot8is received in the recess216. In some other embodiments, the recess216is omitted, the distance d2(FIG. 2) of the lateral housing member212is configured so that the reticle19puts on the reticle chuck23by the reticle handling robot8while the reticle19is lowered by the stage22.

Referring back toFIG. 2, in some embodiments, a portion of the top panel110which is surrounded by the lateral housing member212is referred to as a top housing member211. In addition, the top housing member211, the lateral housing member212and the lower housing member214are collectively referred to as a housing21. The interior of the housing21is shielded from the exterior of the housing21(i.e., the interior of the first vacuum vessel11) by the top housing member211, the lateral housing member212and the lower housing member214. The opening215allows a gas to flow between the interior of the housing21and the exterior of the housing21.

The gas delivery assembly24is configured for supplying one or more gases into the housing21. In some embodiments, the gas delivery assembly24includes a number of gas inlets, such as two first gas inlets241and a second gas inlet242, and a gas outlet243.

In some embodiments, the two first gas inlets241are positioned in the interior of the housing21. The two first gas inlets241are configured so that the gas from the first gas inlets241flowing toward the opening215located on the predetermined plane PP as indicated byFIG. 5.

For example, as shown inFIG. 2, the two first gas inlets241are positioned at two opposite sides of the stage22and connected to the top housing member211. The two first gas inlets241face the predetermined plane PP, so that the gas from the two first gas inlets241flows to the predetermined plane PP and leaves the interior of the housing21via the opening215. The first gas inlets241may be connected to a gas source (not shown in figures) via conduits (not shown in figures) formed in the first vacuum vessel11. The gas supplied from the gas source may include H2, N2or XCDA. The two first gas inlets241may include a nozzle which fixed on the top housing member211. Alternatively, the two first gas inlets241may be slits which penetrate the top housing member211.

However, it should be appreciated that many variations and modifications can be made to embodiments of the disclosure. In some other embodiments, the two first gas inlets241are connected to the lateral housing member212and positioned toward the stage22or the lower housing member214. The two first gas inlets241may be connected to the gas source via a conduit formed in the lateral housing member212. In some other embodiments, there is only one first gas inlet241positioned in the housing21. The first gas inlet241may partially or entirely surround the stage22. It should be appreciated that the number of the first gas inlets241should not be limited to the embodiment shown inFIG. 2and can be varied according to demands. In some other embodiments, the first gas inlets241are omitted.

In some embodiments, the second gas inlet242is positioned in the interior of the housing21. The second gas inlet242is configured so that gas from the second gas inlet242can flow in a direction that is substantially parallel to the effective surface of the reticle chuck23as indicated by arrows shown inFIG. 5.

For example, as shown inFIG. 2, the second gas inlet242is positioned adjacent to the stage22and connected to the top housing member211. The second gas inlet242faces toward the reticle chuck23, such that the gas from the second gas inlet242flows to the reticle chuck23and passes through the bottom surface231of the reticle chuck23.

The second gas inlet242may be connected to a gas source (not shown in figures) via conduits (not shown in figures) formed in the top housing member211. The gas supplied from the gas source may include H2, N2or XCDA. The second gas inlet242may include a nozzle which is fixed on the top housing member211.

In some embodiments, the gas outlet243is positioned in the interior of the housing21. The second gas inlet242and the gas outlet243are configured such that the gas from the second gas inlet242passes through the bottom surface231of the reticle chuck23and is evacuated via the gas outlet243as indicated arrows shown inFIG. 5.

For example, as shown inFIG. 2, the second gas inlet242and the gas outlet243are positioned at two sides of the reticle chuck23and connected to the top housing member211or the reticle chuck23. The height d3of the second gas inlet242and the gas outlet243extending from the top housing member211may be the same. In addition, the opening of the second gas inlet242and the gas outlet243may face each other directly. Namely, the opening of the second gas inlet242and the gas outlet243are both located at a target plane TP which is parallel to the top housing member211and/or the predetermined plane PP. As a result, the gas from the second gas inlet242is sucked away by the gas outlet243after passing through the reticle chuck23. The gas outlet243may be connected to a vacuum source via a conduit formed in the top housing member211. In some embodiments, the gas outlet243is omitted. The gas from the second gas inlet242is supplied into the housing and leaves the interior of the housing via the opening215.

FIG. 4is a flow chart illustrating a method S10for performing a lithography exposure process on the semiconductor wafer2, in accordance with some embodiments. For illustration, the flow chart ofFIG. 4will be described along with the schematic views shown inFIGS. 3 and 5-6. Some of the stages described can be replaced or eliminated for different embodiments.

The method S10includes operation S11, in which a first vacuum pressure is generated in a vacuum vessel, such as the first vacuum vessel11and second vacuum vessel12. In some embodiments, the pumping members18are used to evacuate the first vacuum vessel11and the second vacuum vessel12down to high-vacuum levels needed for processing. In some embodiments, the vacuum pressure in the first vacuum vessel11may be about 1.5*10−2mB to about 2.8*10−2mB, and the vacuum pressure in the second vacuum vessel12may be about 8*10−2mB.

The method S10also includes operation S12, in which the reticle19is placed into the housing21located in the vacuum vessel. In some embodiments, the reticle19is transferred by a robotic arm8(FIG. 3) to a position below the reticle chuck23. Before the reticle19aligns with the reticle chuck23, the reticle chuck23may be lowered down in advance. Afterwards, the robotic arm8is lifted and inserted into the recess216to create a contact between the reticle19and the reticle chuck23. Once the reticle19is in contact with the reticle chuck23, the reticle19may be affixed to the reticle chuck23by an electrostatic force generated by the reticle chuck23.

In the present embodiment, the reticle19is a reflective mask. One exemplary structure of the reticle19includes a substrate made of a suitable material, such as a low thermal expansion material (LTEM) or fused quartz. In various examples, the LTEM includes TiO2doped SiO2, or another suitable material with low thermal expansion. The reticle19includes reflective multiple layers (ML) deposited on the substrate. The ML includes a plurality of film pairs, such as molybdenum-silicon (Mo/Si) film pairs (e.g., a layer of molybdenum above or below a layer of silicon in each film pair). Alternatively, the ML may include molybdenum-beryllium (Mo/Be) film pairs, or other suitable materials that are configurable to highly reflect the EUV light.

The reticle19may further include a capping layer, such as ruthenium (Ru), disposed on the ML for protection. The reticle19may also include an absorption layer, such as a tantalum boron nitride (TaBN) layer, deposited over the ML. The absorption layer is patterned to define a layer of an integrated circuit (IC). Alternatively, another reflective layer may be deposited over the ML and is patterned to define a layer of an integrated circuit, thereby forming an EUV phase shift mask.

The method S10also includes operation S13, in which gas is supplied into the housing21and the first vacuum vessels11via one or more gas inlets. In some embodiments, as shown inFIG. 5, a flow of the gas f1is supplied into the housing21via the first inlets241. After the flow of the gas f1has left the first gas inlets241, a portion of the flow of the gas f1leaves the housing21via the opening215directly. In addition, a portion of the flow of the gas f1is blocked by the top housing member211, the lateral housing member212and the lower housing member214and stays in the interior of the housing21for a while. As a result, a second vacuum pressure that is higher than the first vacuum pressure is established in the interior of the housing21.

In some embodiments, as shown inFIG. 5, the difference between the first vacuum pressure and the second vacuum pressure leads the first flow of gas f1to stably flow outside of the housing21via the opening215so that particles9located outside of the housing21are blocked from entering the housing21. Therefore, contamination of the reticle19and the reticle chuck23can be mitigated or avoided.

In some embodiments, as shown inFIG. 5, a second flow of gas f2is supplied into the housing21via the second gas inlet242, and at least a portion of the second flow of gas f2is evacuated via the gas outlet243. As a result, the second flow of gas f2flows through the reticle chuck23and reticle19. The second flow of gas f2serves as an air curtain between the reticle19and the opening215and prevents the particle9from attaching the reticle19. Moreover, the reticle19and the reticle chuck23are cooled by the second flow of gas f2and kept at an acceptable temperature. Therefore, deformation of the reticle19due to high temperatures can be prevented.

In some embodiments, in addition to the gas supplied from the gas inlets241and242, the gas inlets164and174located in the chambers160and170are used to supply gas into the chambers160and170as shown inFIG. 6. Additionally, with the operation of the pumping members18, the gas supplied from the gas inlets241,242,164and174are evacuated as along directions indicated by the arrows shown inFIG. 6.

The method S10also includes operation S14, in which a lithography exposure process is performed on the semiconductor wafer2in the lithography system10. In operation S14, the high-brightness light7generated by the high-brightness light source15is illuminated on the reticle19(by the illuminator16), and is further projected on the resist layer coated on the semiconductor wafer2(by the POB17), thereby forming a latent image on the resist layer. In some embodiments, the lithography exposure process is implemented in a scan mode.

The method S10may further include other operations, such as an operation to perform a fabrication process on the semiconductor wafer2through the openings of the resist pattern. In one example, the fabrication process includes an etch process performed on the semiconductor wafer2using the resist pattern as an etch mask. In another example, the fabrication process includes an ion implantation process performed on the semiconductor wafer2using the resist pattern as an implantation mask.

FIG. 7shows a cross-sectional view of the reticle holding tool20a, in accordance with some embodiments. In the embodiments shown inFIG. 7, elements that are similar to those shown inFIGS. 1-3are provided with the same reference numbers, and the features thereof are not reiterated in the interests of brevity. Differences between the reticle holding tool20aand the reticle holding tool20include the housing21being replaced by the housing21aand the gas delivery assembly24being replaced by the gas delivery assembly24a.

The housing21aincludes a top housing member211a, a lateral housing member212aand a lower housing member214a. The top housing member211ais connected to the reticle chuck23. In some embodiments, the top housing member211ahas a ring shape and surrounds the reticle chuck23. The lateral housing member212ais connected to the outer edge of the top housing member211aand extends from the top housing member211ato the predetermined plane PP. A distance d4between the top panel110and the predetermined plane PP is greater than a distance d3from the top panel110to the effective surface of the retinal chuck23. That is, the effective surface is located between the predetermined plane PP and the top panel110.

The lower housing member214ahas a ring shape and is connected to the lower edge213aof the lateral housing member212a. In some embodiments, the lower housing member214aextends on the predetermined plane PP. In some other embodiments, the lower housing member214aextends away from the lower edge213aand terminates at its inner edge2142ato form an opening215a. In some other non-illustrated embodiments, the lower housing member214ais inclined relative to the predetermined plane PP, and a distance formed between the lower housing member214aand the top panel110may gradually increases in a direction away from the lower edge213to the inner edge2142. The distance between the lower housing member214aand the top panel110gradually increases. In some embodiments, the lower housing member214ais omitted.

In some embodiments, the inner edge2142aof the lower housing member214adefines an opening215a. The opening215amay have a rectangular shape, a circular shape, an elliptical shape, a polygonal shape, an irregular shape, or a combination thereof. In some embodiments, the width of the opening215ais sufficiently large to allow the entry or exit of the high-brightness light from the high-brightness light source and to allow the reticle to be replaced. In some embodiments, in a direction that is perpendicular to the effective surface of the reticle chuck23(or the top panel110of the first vacuum vessel11), the projection of the lower housing member214ais located outside of the effective surface of the reticle chuck23.

The gas delivery assembly24ais configured for supplying one or more gases into the housing21a. In some embodiments, the gas delivery assembly24aincludes a number of gas inlets, such as two first gas inlets241aand a second gas inlet242a, and a gas outlet243a.

In some embodiments, the two first gas inlets241aare positioned in the interior of the housing21a. The two first gas inlets241aare configured such that the gas from the first gas inlets241aflowing toward the opening215alocated on the predetermined plane PP.

For example, the two first gas inlets241aare positioned at two opposite sides of the reticle chuck23and connected to the top housing member211a. The two first gas inlets241aface the predetermined plane PP, such that the gas from the two first gas inlets241aflow to the predetermined plane PP and leaves the interior of the housing21avia the opening215a. The first gas inlets241amay be connected to a gas source (not shown in figures) via conduits (not shown in figures) formed in the top housing member211a. The gas supplied from the gas source may include H2, N2or XCDA. The two first gas inlets241amay include a nozzle which fixed on the top housing member211a. Alternatively, the two first gas inlets241amay be slits which penetrate the top housing member211a.

In some embodiments, the second gas outlet242ais positioned in the interior of the housing21a. The second gas inlet242ais configured such that a gas from the second gas inlet flows in a direction that is substantially parallel to the effective surface of the reticle chuck23.

For example, the second gas inlet242ais positioned adjacent to the reticle chuck23and connected to the top housing member211a. The second gas inlet242afaces toward the reticle chuck23, such that the gas from the second gas inlet242aflows to the reticle chuck23and passes through the bottom surface231of the reticle chuck23.

The second gas inlet242amay be connected to a gas source (not shown in figures) via conduits (not shown in figures) formed in the top housing member211a. The gas supplied from the gas source may include H2, N2or XCDA. The second gas inlet242amay include a nozzle which is fixed on the top housing member211a.

In some embodiments, the gas outlet243ais positioned in the interior of the housing21a. The second gas inlet242aand the gas outlet243aare configured such that the gas from the second gas inlet242apasses through the reticle chuck23and is evacuated via the gas outlet243a.

For example, as shown inFIG. 7, the second gas inlet242aand the gas outlet243aare positioned at two sides of the reticle chuck23and connected to the top housing member211aor the reticle chuck23. The height of the second gas inlet242aand the gas outlet243aextending from the top housing member211amay be the same. In addition, the opening of the second gas inlet242aand the gas outlet243amay face each other directly. Namely, the opening of the second gas inlet242aand the gas outlet243aare both located at a target plane TP which is parallel to the top housing member211aand/or the predetermined plane PP. As a result, the gas from the second gas inlet242ais sucked away by the gas outlet243aafter passing through the reticle chuck23. The gas outlet243amay be connected to a vacuum source via a conduit formed in the top housing member211aor the reticle chuck23. In some embodiments, the gas outlet243ais omitted.

The method of using the reticle holding tool20ato perform a lithography exposure process may be similar to the method S10described above. However, while the reticle chuck23is moved by the stage22during the lithography exposing process, the housing21ais moved along with the reticle chuck23. Since the interior of the housing21ahas smaller volume, the second vacuum pressure can be created sooner in operation S13of method S10.

Embodiments of a method and system for performing a lithography exposure process generating a flow of gas around the reticle chuck which is used to secure a reticle. The flow of gas prevents the reticle from being contaminated. As a result, the processing quality and the production yield are improved. In addition, since the life span of the reticle is prolonged, the manufacturing cost is reduced.

In accordance with some embodiments, a reticle holding tool is provided. The reticle holding tool includes a housing including a top housing member and a lateral housing member. The lateral housing member extends from the top housing member and terminates at a lower edge which is located on a predetermined plane. The reticle holding tool further includes a reticle chuck. The reticle chuck is positioned in the housing and has an effective surface configured to secure a reticle. The effective surface is located between the predetermined plane and the top housing member. The reticle holding tool also includes a gas delivery assembly. The gas delivery assembly is positioned within the housing and configured to supply gas into the housing.

In accordance with some embodiments, a lithographic system is provided. The lithographic system includes a vacuum vessel having a first vacuum pressure. The lithographic system further includes a housing positioned in the vacuum vessel and having a second vacuum pressure that is higher than the first vacuum pressure. The housing has an opening allowing an interior of the housing to communicate to the vacuum vessel. The lithographic system also includes a reticle chuck positioned in the housing. The reticle chuck has an effective surface for holding a reticle. The effective surface faces the opening. In addition, the lithographic system includes an exposure tool configured to generate high-brightness light toward the reticle. The lithographic system further includes a wafer stage configured to support a semiconductor wafer so as to allow the semiconductor wafer to receive the high-brightness light from the reticle.

In accordance with some embodiments, a method for performing a lithography exposing process is provided. The method includes generating a first vacuum pressure in a vacuum vessel. The method further includes placing a reticle into a housing located in the vacuum vessel. The housing communicates with the vacuum vessel via an opening, and a front surface of the reticle faces the opening. The method also includes applying a first flow of gas into the housing to create a second vacuum pressure which is higher than the first vacuum pressure in the housing. In addition, the method includes directing a high-brightness light to a semiconductor wafer via the front surface of the reticle.