DE102004041921B4 - Phase shift mask and method for its manufacture - Google Patents

Abstract

A phase shift mask for projecting a pattern (1) formed on the mask from features to a substrate, comprising:
A mask substrate (58) formed from a transparent material, which has a flat surface in the region of a first portion (4) of the pattern (1) and partially to a predetermined depth in the region of a second portion (6) of the pattern (1) in the surface of the mask substrate (58) sunken further surface (58 '), wherein the first portion (4) of the pattern (1) and the second portion (6) of the pattern (1) arranged non-overlapping in different areas on the mask and the second portion (6) of the pattern (1) comprises a densely packed line-column pattern;
- the first portion (4) of the pattern (1) representing first structural elements (50, 53, 54, 55), which are formed as raised ridges of a semi-transparent, phase-shifting material on the planar surface of the transparent mask substrate (58);
- the second part (6) of the sample ...

Description

The The invention relates to a phase shift mask for the projection of a the mask formed by structural elements on a substrate. The invention further relates to methods for producing the phase shift mask.

integrated Circuits are made by photolithographic projection of Patterns formed on photomasks on semiconductor wafers produced. For Each layer is usually a mask with the circuit level corresponding pattern used.

highly integrated Circuits, such as dynamic or non-volatile memory as well as logic devices, are currently being manufactured with circuit elements, whose width extends down to 70 nm. In the example of the memory modules this applies, for example, to the very dense and periodically arranged patterns of narrow word or bit lines and, where appropriate, the corresponding contacts or trenches.

there It can often happen that the corresponding highly integrated Structure pattern in a circuit plane with the structural elements electrically subsequent Peripheral area are arranged together. Structural elements, for example Tracks, such peripheral areas are usually relaxed Requirements for the structure width. On the for the formation of the circuit level Accordingly, photomasks to be used together are dense, often periodic arrangements of structural elements as well as isolated or semi-insulated, larger sized Structural elements arranged together in a pattern.

US 5,302,477 A discloses a phase shift mask having a pattern of contact holes that has raised features above a surface of a transparent material, and wherein light beams passing through the transparent material undergo a phase shift. The respective proportions of the sample have a uniform packing density; In particular, the mask has no densely packed line-column patterns. A phase shift mask with a line-column pattern is off US 6,593,039 B1 known.

DE 197 09 470 A1 discloses a method of forming a pattern on a phase shift mask. A method of forming an alternating phase shift mask is described in Wong, Alfred Kwok Kit: Resolution Enhancement Techniques in Optical Lithography, Bellingham, Washington: SPIE Press, 2001, Chapter 5.2, pp. 121-122, ISBN: 0-8194-3995-9 disclosed.

It it is known that in the lithographic projection structural elements, their width each near the resolution limit of the relevant exposure device is different because of the optical imaging characteristics larger sized, transfer non-periodic structure elements into the image plane become. This is partly because of the limited numerical Aperture of the exposure device, on the other hand, s.den individual exposure settings in the device. In the presence of lens aberrations, for example due to of lens defects, can the different imaging effects intensify, which in particular Linewidth variations or positional accuracy errors in the Structural pattern shares can be visible.

An approach is in the DE 103 59 991 A1 described. The basic idea is to form semitransparent and trench-like, web-like, absorber-free structural elements on a photomask formed in phase mask technique. The trench or web-like structural elements are formed in CPL technology as a trench or mesa structure. In a layout, in particular dense, but possibly also semi-isolated and isolated, but in any case preferably particularly thin, pattern portions are selected in order to produce them in CPL technique on the photomask. In contrast, isolated, broader sample portions are formed in semitone-phase masking techniques as semitransparent structural elements. The respective process windows are comparatively large in their own right and are also adapted to each other. This greatly increases the common process window.

at this approach However, it is necessary that the structural elements manufactured in mesa technique in a big one Area on an etched surface of the substrate must be formed. A mask of this type is very difficult in the required Accuracy, since the formation of the etched surface precise etching step is required without phase errors occur.

It It is therefore an object of the present invention to provide a phase mask, which can be easily manufactured, as well as a method to provide the phase mask.

• – ein aus einem transparenten Material gebildetes Maskensub strat, das im Bereich eines ersten Anteils des Musters eine ebene Oberfläche und im Bereich eines zweiten Anteils des Musters teilweise eine bis zu einer vorherbestimmten Tiefe in die Oberfläche des Maskensubstrates eingesenkte weitere Oberfläche aufweist, wobei der erste Anteil des Musters und der zweite Anteil des Musters nicht überlappend in verschiedenen Bereichen auf der Maske angeordnet sind und der zweite Anteil des Musters ein dicht gepacktes Linien-Spalten-Muster umfasst;
• – den ersten Anteil des Musters repräsentierende erste Strukturelemente, die als erhabene Stege aus einem semitransparenten, phasenschiebenden Material auf der ebenen Oberfläche des transparenten Maskensubstrates gebildet sind;
• – den zweiten Anteil des Musters repräsentierende zweite Strukturelemente, die als erhabene Stege mit Stegkanten mit der vorherbestimmten Tiefe auf der weiteren Oberfläche aus dem transparenten Material gebildet sind und jeweils eine Breite besitzen, welche geringer oder gleich einem vorbestimmten Grenzwert ist, wobei innerhalb der erhabenen Stege der ersten Strukturelemente und innerhalb der erhabenen Stege der zweiten Strukturelemente das Maskensubstrat durchdringende Lichtstrahlen jeweils einen Phasensprung von 160° bis 200° gegenüber einem das Maskensubstrat auf der ebenen Oberfläche außerhalb der Stege durchdringenden Lichtstrahl erfahren; und
• – eine einen Phasensprung hervorrufende Grenzlinie zwischen der ebenen Oberfläche und der weiteren Oberfläche, wobei der kleinste Abstand der Grenzlinie zu einem zweiten Strukturelement wenigstens dem doppelten Abstand der Stegkanten eines zweiten Strukturelements entspricht.

The object is achieved by a phase mask for the projection of a pattern of structural elements formed on the mask onto a substrate, preferably a semiconductor wafer, comprising:

• A mask substrate formed of a transparent material, which has a flat surface in the region of a first portion of the pattern, and in the region of a first portion of the pattern The second portion of the pattern partially has a further surface sunk into the surface of the mask substrate to a predetermined depth, wherein the first portion of the pattern and the second portion of the pattern are non-overlappingly disposed in different areas on the mask and the second portion of the pattern Pattern comprises a densely packed line-column pattern;
• First structural elements representing the first portion of the pattern, which are formed as raised webs of a semitransparent, phase-shifting material on the planar surface of the transparent mask substrate;
• Second structural elements representing the second portion of the pattern, which are formed as raised ridges with ridge edges of the predetermined depth on the further surface of the transparent material and each have a width which is less than or equal to a predetermined limit, wherein within the raised ridges the first structure elements and light beams penetrating the mask substrate within the raised webs of the second structural elements each experience a phase jump of 160 ° to 200 ° with respect to a light beam penetrating the mask substrate on the flat surface outside the webs; and
• A phase-edge-causing boundary line between the planar surface and the further surface, the smallest distance of the boundary line to a second structural element corresponding to at least twice the spacing of the web edges of a second structural element.

The Pattern of the phase mask according to the invention therefore comprises first portions which are in halftone phase mask technique are formed, as well as second parts, which are manufactured in CPL technology. Preferably, those according to the CPL technique formed closely adjacent web walls as structural elements in those areas of a circuit layout formed on the photomask, in which dense arrangements of fine structural elements required are, if necessary, also for isolated ones or semi-isolated fine structures. Structures of greater width are preferably in Halbtonphasenmaskentechnik or as opaque structures formed.

In a preferred embodiment borders through trenches formed structural elements at least partially directly as RIM structures to the first structural elements.

The first structural elements can improved in their imaging behavior by RIM structural elements which have a steeper intensity profile at the edges of the provide respective structural elements. For example, the RIM structure elements in a separate etching step be formed. It is also possible to use RIM structures directly adjacent to the semitransparent or opaque first features or form therein, wherein the etching of the RIM structures in common with the formation of the etched surface of the mask substrate without additional Extra work done can be.

According to this The procedure is structures below a certain limit assigned to the closely adjacent webs formed in CPL technology. Based on a comparison of the dimensions of the structural elements of Pattern with that of each of the resolving power in a projection determining Parameters dependent Limit value easily reach an assignment.

In a further preferred embodiment possess the semitransparent, phase-shifting material or first structural elements formed by opaque material, respectively a width which is greater than is the predetermined limit.

According to this The procedure is structures above a certain limit semitransparent structures formed in halftone phase masking technique or the opaque formed in COG technology (COG = chrome on glass) Structures assigned. Based on a comparison of the dimensions of Structural elements of the pattern with that of the respective resolution A limit value dependent on a projection-determining parameter can be determined easily achieve an assignment.

In a further preferred embodiment are the first structural elements and / or the second structural elements surrounded by auxiliary structures that in the case of a projection of the pattern do not map.

According to this Approach auxiliary structures are provided, which is in the art often is used to determine the imaging behavior in the case of a lithographic To improve projection. The invention is simple for these types of masks used, which creates a variety of applications.

The Task is also performed by method of forming a pattern on the Phase shift mask according to the sibling claims 7, 8 and 9 solved.

According to these procedures, a hybrid mask is created in a simple manner, which in a first portion by a halftone phase mask and in a second portion by a CPL mask is formed.

The Invention should be closer explained are based on an embodiment with the help of a drawing. Show:

1 in a plan view, a pattern of structural elements to be formed on a semiconductor wafer;

2 in a plan view of an embodiment of a phase shift mask to form the in 1 shown pattern on the semiconductor wafer according to the invention;

3 in a plan view of a section of the phase shift mask after 2 and a simulated resist pattern in the photolithographic projection;

4A to 4D in schematic cross-sectional views of the resulting in the application of a conventional method components of a conventional phase shift mask; and

5A to 5D in schematic cross-sectional views of the resulting in the application of the method according to the invention components of a phase shift mask according to the invention

1 shows a simplified representation of a section of a circuit layout or a pattern to be formed on a semiconductor wafer 1 containing both dense and periodically arranged structural elements 14 as well as isolated or semi-isolated arranged structural elements 10 . 12 . 16 . 18 having.

The structural element 10 For example, corresponds to a contact hole, which by irradiation of a corresponding opening in an opaque or semi-transparent layer 8th on the mask into a photosensitive layer on the wafer (positive resist), followed by development and transfer to an underlying layer in an etching step.

The structural element 12 For example, a semi-isolated gap may also be transferred by irradiating the corresponding aperture on the mask into a photosensitive layer on the wafer. For example, semi-isolated gaps occur in the manufacture of dynamic random access memory (DRAM) in the area of the peripheral electronics driving the memory cells.

The isolated structural element 16 and the also isolated, but larger dimensions having structural element 18 are common patterns encountered in the manufacture of integrated circuits.

In 1 are also the dense and periodically arranged structural elements 14 shown, for example, in the area of the cell array of a DRAN device in the production of trenches or active areas defining areas occur.

Overall, the pattern includes 5 a first share 4 containing the semi-isolated, isolated or wider structural elements 10 . 12 . 16 . 18 represents, and a second share 6 holding the tightly packed structural elements 14 represents.

aim The invention is to provide a phase shift mask, the is suitable, the structural elements shown in only one projection step transferred to a semiconductor wafer to be able to.

in the The following is the phase shift mask according to the invention in one embodiment, in more detail explained. Subsequently Several methods are shown for the production of the phase shift mask are suitable.

The for the simultaneous projection of the first share 4 and the second share 6 of the pattern 5 According to the invention suitable phase shift mask is in 2 shown.

The phase shift mask comprises a fully transparent mask substrate 58 that is in the range of the first share 4 of the pattern 1 has a substantially planar surface. As a fully transparent mask substrate 58 For example, quartz is used. In general, all materials known to the person skilled in the art are suitable whose transmission is sufficiently high at the wavelength intended for the exposure.

In a first embodiment, these are the first portion 4 of the pattern 1 representing the first structural elements 50 . 53 . 54 . 55 as raised webs of an opaque material on the planar surface of the transparent mask substrate 58 educated. The opaque material includes, for example, chromium or a so-called black chrome provided with an antireflecting layer. Other materials known to those skilled in the art are of course also possible.

The pattern comprises on a fully transparent mask substrate 58 or on its level surface, a number of first structural elements formed within the opaque layer 50 . 53 . 54 . 55 , Through openings within the opaque structural element 50 become light areas of the first share 4 of the pattern 1 which defines the on the Wafer to be formed via hole opening 10 or semi-isolated column 12 (see. 1 ) in case of exposure.

The dashed lines indicate the result to be achieved on the wafer for the contact hole opening to be formed on the wafer 10 and the semi-insulated gap 12 at. Supporting the optical imaging properties are SRAF auxiliary structures formed as gaps 51 provided (SRAF = subresolution assist feature, auxiliary structure feature below the resolution limit). The selection of shape, dimensions or distances of these auxiliary structures, which in the case of a projection itself do not generate any structures and improve the imaging behavior of the adjacent structures, are familiar to the person skilled in the art, as already mentioned at the outset.

Dark structures in a bright environment are created by opaque structural elements 54 educated. To support the imaging properties of a dense field of narrow structure elements to be described below in this exemplary embodiment, further opaque auxiliary structure elements are provided 53 intended. They also support the optical imaging properties of a semi-isolated structural element 55 whose process window is to be adapted to that of the periodically arranged field of narrow structural elements which is likewise to be imaged.

In the area of the second share 6 of the pattern 1 The mask substrate partially penetrates to a predetermined depth into the surface of the mask substrate 58 etched further surface 58 ' on. The second part 6 the pattern representing second structural elements 52 are as raised webs on the further surface 58 ' formed from the transparent material. The raised webs of the second structural elements 52 have closely adjacent web edges.

The structural elements 52 are in the in 2 shown example formed as webs of the etched to the predetermined depth mask substrate surface 58 ' are surrounded. The surface of the webs corresponds to the original, unetched surface of the mask substrate 58 , so that the height of the structural elements 52 corresponds to the predetermined depth.

Depending on the exposure wavelength and the optical properties of the mask substrate material, the predetermined depth of the etched substrate is 58 ' selected so that a corresponding incident light beam within the trenches phase shift of about 180 ° compared to a light beam, which is the adjacent surface of the mask substrate 58 permeates, experiences. Destructive interference is thereby achieved at the web edges.

The web edges therefore form as lines with a certain width in the resist on the wafer, wherein the structural elements 52 themselves have a width such that the lines formed in the resist on the wafer in the case of projection merge together as an image of the opposite web edges.

Condition for this cancellation is the neighborhood of two ridge edges below the resolution limit of the imaging system, wherein between the ridge edges in the region of the structural elements unetched mask substrate 58 is present.

Within the raised webs of the second structural elements 52 each of the mask substrate penetrating light beams undergoes a phase jump of about 180 ° with respect to a mask substrate on the flat surface 58 outside the webs penetrating light beam. The resulting difference in the phase jump must be set to approximately 20 ° in order to produce the desired interference effects. A phase jump in the range of 160 ° to 200 ° is usually sufficient.

In a second embodiment, for their discussion also on 2 are the first share 4 of the pattern 1 representing the first structural elements 50 . 53 . 54 . 55 as raised webs not of an opaque but of a semi-transparent, phase-shifting material on the flat surface of the transparent mask substrate 58 educated. The semitransparent, phase shifting material includes, for example, molybdenum silicide. Other materials known to those skilled in the art are of course also possible.

On the flat surface of the fully transparent mask substrate 58 are a number of first structural elements formed within the semitransparent layer 50 . 53 . 54 . 55 arranged. Through openings within the extended semitransparent structural element 50 become light areas of the first share 4 of the pattern 1 defines the contact hole opening to be formed on the wafer 10 or semi-isolated column 12 (see. 1 ) in case of exposure. Supporting the optical imaging properties are SRAF auxiliary structures formed as gaps 51 intended.

Dark structures in the bright environment are replaced by semitransparent structural elements 54 educated. To support the imaging properties of a density to be described below into which sem embodiment of periodic field of narrow structure elements are further semitransparent auxiliary structure elements 53 intended. They support the optical imaging properties of a semi-isolated structural element 55 whose process window to that of the likewise to be imaged periodically arranged structural elements 52 to adapt.

The thickness of the semitransparent layer is preferably such that within the raised ridges of the first structural elements 50 . 53 . 54 . 55 incident light with a phase shift of 180 ° with an uncertainty of at most 20 ° with respect to a surrounding mask substrate 58 penetrating light beam is applied.

The in the range of the second share 6 of the pattern 1 formed second structural elements 52 are unchanged from the first embodiment.

As in 2 can be seen, occurs in both embodiments on the photomask a phase-edge causing borderline 60 between the flat surface 58 and the other surface 58 on. Without appropriate measures, as described below, this boundary would 60 cause a narrow line in the case of exposure of the semiconductor wafer.

In 3 The result of a simulation corresponding to the projection of a periodic arrangement of second features onto a resist layer is shown. For the simulation, the Solid-C simulation program from Sigma-C was used. This simulation program is able to take into account certain exposure conditions of a simulated projection apparatus and from an aerial image calculated at the location of the resist layer, taking into account specific properties of the resist layer, such as e.g. B. Sensitivity or refractive index, a resist pattern 64 to calculate.

At the in 3 In the simulation shown, an exposure wavelength of 193 nm was chosen with a numerical aperture of 0.80. The resolution capability, ie the smallest structure to be imaged, amounts to approximately 70 nm on the semiconductor wafer. Based on the scale of the semiconductor wafer, this results in a limit value, wherein structures on the semiconductor wafer that are smaller than or equal to this limit value are the second component 6 of the pattern 1 be assigned to. For the width of the raised webs of the second structural elements 52 A value of about 48 nm was chosen based on the wafer scale to achieve the above-described fusing of the ridge edges. For the mask substrate 58 Quartz was assumed. The predetermined depth of the etched surface is about 172 nm to achieve the phase jump of about 180 °.

As the simulation has shown, the distance is 62 the horizontal borderline 60 to one end of the line-shaped second structural elements 52 critical for the picture. If the distance of the boundary line is chosen to be too small, a resist structure results 64 in which the ends of the second structural elements 52 would be associated with resist bridges, ie would not be resolved individually. As in 3 is shown, then, when the distance 62 the borderline 60 at least twice the distance between the web edges of the second structural elements 52 corresponds to each of the second structural elements 52 individually resolved. In the present case, this results in a value of 200 nm for the distance 62 , In 3 In particular, no resist bridges are to be recognized that would not enable a functioning circuit. The distance of the vertical lines 60 to the second structural elements 52 is less critical, here is sufficient as shown in the present case, a distance as between second structural elements 52 itself. In general, the distance must be at least twice the width of a bridge 52 be.

The specified value for the distance 62 the borderline 60 can be transferred to other exposure wavelengths or smallest dimensions in a simple manner known to those skilled in the art.

The following is based on the 4A to 4D a conventional method of manufacturing a conventional phase shift mask is described. The 4A to 4D are cross-sectional views along the in 2 drawn dashed line AB.

First, the pattern is provided 1 with the first share 4 which has semi-isolated or isolated structures, and the second part 6 which has the densely packed structures.

The starting point of the method is a mask blank 100 , as in 4A shown. The mask blank 100 , also called mask blank, comprises a mask substrate and an absorber layer applied on a surface of the mask substrate 102 , For the mask substrate 58 For example, quartz is used. The absorber layer 102 is applied, for example, as a chromium layer on the mask substrate. The absorber layer 102 can also reflect partially or completely. It is important that the transmission of light in the area of this absorber layer 102 is reduced.

Subsequently, for example, by spin coating a photosensitive first resist layer on the absorber layer 102 applied.

The actual mask production takes place by a first mask lithography step with an etching of the mask-lithographically structured first resist layer, around a first resist pattern 104 to form, so that from the first share 4 bright areas to be formed and of the second part 6 bright areas to be formed in the first resist pattern 104 be opened.

In an etching step, the first resist pattern becomes 104 in the absorber layer 102 transfer.

To the removal of the resist is carried out a new application of a second Resist layer.

Subsequently, the second resist layer is formed to form a second resist pattern 108 structured in a mask-lithographically manner. The second resist structure 108 covers those in the range of the first share 4 formed openings in the absorber layer 102 off, as in 4B is shown.

By etching the mask substrate in the region of the second portion 6 using the patterned absorber layer and the second resist pattern 108 as etching masks becomes an etched surface 58 ' to a predetermined depth 106 educated. This is in 4C shown. The depth 106 is, as already explained above, chosen so that the mask substrate on the flat surface 58 penetrating light beam a phase jump of about 180 ° relative to the etched surface 58 ' penetrating light beam experiences. Subsequently, the absorber layer is in the region of the etched surface 58 ' removed, preferably by conventional wet or dry etching.

After removing the second resist pattern 108 are the opaque webs of the first structural elements 54 exposed. The finished mask is in cross-section in FIG 4D shown.

The following is based on the 5A to 5D an inventive method for producing a phase shift mask according to the invention described. The 5A to 5D are again cross-sectional views along the in 2 drawn dashed line AB.

First, the pattern is provided 1 with the first share 4 which has semi-isolated or isolated structures, and the second part 6 which has the densely packed structures.

The starting point of the method is in turn a mask blank, as in 5A shown. The mask blank, also called mask blank, comprises the mask substrate 58 a phase-shifting semitransparent layer deposited on a surface of the mask substrate 110 and one on a surface of the semi-transparent, phase-shifting layer 110 applied absorber layer 102 , For the mask substrate 58 For example, quartz is used. The absorber layer 102 is, for example, as a chromium layer on the mask substrate 58 applied. It can replace the absorber layer 102 any other hardmask may be used because it is removed in the further process steps so that it no longer exists on the final mask.

Subsequently, for example, by spin coating a photosensitive first resist layer on the absorber layer 102 applied.

Thereafter, the mask-lithographic patterning of the first resist layer takes place around a first resist pattern 104 to form, so that from the first share 4 bright areas to be formed and of the second part 6 bright areas to be formed in the first resist pattern 104 be opened.

In an etching step, the first resist pattern becomes 104 in the absorber layer 102 transfer. Subsequent to the semitransparent layer 110 To structure, two process control are conceivable. In the first possibility anisotropic etching is continued to the layer 110 to structure. Subsequently, the removal of the resist pattern 104 , In the second option, first, the remaining first resist pattern 104 removed the etching process for the semitransparent layer 110 not to disturb, and if necessary, an inspection and repair of the structured absorber layer 102 and then further etched.

Then done reapplying a second resist layer.

By mask lithographic patterning of the second resist layer, a second resist pattern is formed 108 formed in the area of the first share 4 formed openings in the absorber layer 102 covers. The result is in 5B shown.

Thereafter, an etching of the mask substrate in the region of the second portion takes place 6 using the bright region of the second resist pattern 108 exposed structured absorber layer and the second resist pattern 108 as an etching mask to form the etched surface 58 ' to a predetermined depth 106 where the depth 106 is chosen so that the mask substrate 58 on the plane surface penetrating light beam, a phase jump of about 180 ° relative to the etched surface 58 ' piercing Beam experiences. The result after these process steps is in 5C shown.

After the etching remains in the range of the first portion 4 of the pattern the second resist pattern 108 with a smaller layer thickness. The layer thickness of the second resist structure 108 for example, is only half as high as before the etching. Depending on whether subsequent steps with this reduced layer thickness of the second resist pattern 108 can be performed reliably, several variants of the method are possible for the further process control.

In a first variant is then in the area 6 the absorber layer remaining after the etching 102 and the semitransparent phase shift layer 110 removed, and then the resist layer 108 removed, as a result, as in 5D shown.

In a second variant, after the etching of the etched surface 58 ' the remaining resist structure 108 removed, then the absorber layer 102 removed a large area, then for the third time with a resist layer and a third resist pattern comparable to the second resist pattern 108 generated, possibly with slight excess, around the semitransparent phase-shifting layer 110 in the second area 6 to remove.

In a third variant, after the etching of the etched surface 58 ' the remaining resist structure 108 removed, then varnished with a resist layer for the third time and a third resist pattern comparable to the second resist pattern 108 produced, possibly with slight excess, to the absorber layer 102 and the semitransparent phase shift layer 110 in the area 6 to remove. After removal of the third resist pattern, the absorber layer then becomes 102 also in the area 4 away.

Both methods (and their variants) can be used together with the etched surface 58 ' so-called RIM structures or Phasenassist structures directly to the semitransparent structural elements 50 . 54 . 55 be formed adjacent or therein. By the common etching with the etched surface 58 ' in the formation of the second structural elements 52 No additional effort is required.

In the previously described methods or phase shift masks, the first structural elements were the first portion 4 of the pattern 1 correspond, formed as a homogeneous semitransparent or opaque layer. According to the invention, however, it is also provided that the first structural elements 50 . 53 . 54 . 55 have a strip-shaped substructure. This strip-shaped substructure is known in the art as a zebra structure and leads to a further improvement in the conformity of the process window with respect to the first portions 4 and the second shares 6 of the pattern.

applications the phase shift mask according to the invention In the case of dynamic memory modules, the layers relate to the Formation of active areas in the memory cell field, which in difference be formed to the periphery in CPL technology. The application will Here particularly advantageous because the memory cell array and the Peripheral area formed in this plane as separate areas are.

Another example relates to the lowermost metallization level (bit lines), which are again implemented in CPL technology in the area of the memory cell array, wherein the paths running from the cell field into the support or peripheral area on the mask form a transition of a web-like second structural element 52 to a raised, semi-transparent or opaque structural element 54 require.

In the field of application of logic circuits are often isolated or semi-insulated, but very thin strip conductors before. Here is not selected according to the periodicity, but only after the structure width, the very thin conductor tracks as web-like second structural elements 52 are formed while the rest are carried out as semitransparent or opaque structural elements.

From design data of a layout, an assignment to the first part or the second part can be easily made for these examples 6 of the pattern. In this case, for example, data structures are generated which are transmitted to mask writers. These data structures are generated for example with a layout program and in the context of the 4 and 5 used explained method.

1

template

4

first proportion of

6

second proportion of

8-18

structural elements in the circuit layout

50, 53, 54, 55

semitransparent or opaque structural elements

52

web-like structural elements

51

SRAF auxiliary structures

58

fully transparent mask substrate

58 '

etched mask substrate

60

boundary line

62

distance

64

simulated resist structure

100

mask blank

102

absorber layer

104

first resist structure

106

depth

108

second resist structure

110

semitransparent layer

Claims (14)

Phase shift mask for the projection of a pattern formed on the mask ( 1 ) of structural elements on a substrate, comprising: a mask substrate formed from a transparent material ( 58 ), which is in the range of a first share ( 4 ) of the pattern ( 1 ) a flat surface and in the region of a second portion ( 6 ) of the pattern ( 1 ) partially to a predetermined depth into the surface of the mask substrate ( 58 ) sunken further surface ( 58 ' ), the first portion ( 4 ) of the pattern ( 1 ) and the second share ( 6 ) of the pattern ( 1 ) are arranged non-overlapping in different areas on the mask and the second portion ( 6 ) of the pattern ( 1 ) comprises a densely packed line-column pattern; - the first share ( 4 ) of the pattern ( 1 ) representing first structural elements ( 50 . 53 . 54 . 55 ) formed as raised webs of a semi-transparent, phase-shifting material on the planar surface of the transparent mask substrate ( 58 ) are formed; - the second share ( 6 ) of the pattern representing second structural elements ( 52 ), which are designed as raised webs with web edges of the predetermined depth on the further surface ( 58 ' ) are formed from the transparent material and each have a width which is less than or equal to a predetermined limit, wherein within the raised webs of the first structural elements ( 50 . 53 . 54 . 55 ) and within the raised webs of the second structural elements ( 52 ) light beams penetrating the mask substrate each have a phase jump of 160 ° to 200 ° with respect to a mask substrate on the flat surface ( 58 ) experience penetrating light beam outside the webs; and - a boundary line between the flat surface (FIG. 58 ) and the further surface ( 58 ' ), wherein the smallest distance of the boundary line to a second structural element ( 52 ) At least twice the distance of the web edges of a second structural element ( 52 ) corresponds. Phase-shift mask according to claim 1, wherein the structural elements formed by trenches at least partially directly as RIM structures to the first structural elements ( 50 . 53 . 54 . 55 ). Phase-shift mask according to one of the preceding claims, in which the first structural elements formed by semitransparent, phase-shifting material ( 50 . 53 . 54 . 55 ) each have a width which is greater than the predetermined limit value. Phase-shift mask according to one of the preceding claims, in which - the pattern ( 1 ) represents a circuit level of a memory device having a cell array; - the first share ( 4 ) comprises all structural elements arranged outside the cell field in the support or peripheral area; and - the second part ( 6 ) comprises all the structural elements arranged within the cell array. Phase-shift mask according to one of Claims 1 to 4, in which the first structural elements formed by semitransparent, phase-shifting material ( 50 . 53 . 54 . 55 ) Comprise molybdenum silicide. Phase-shift mask according to one of Claims 1 to 5, in which the first structural elements ( 50 . 53 . 54 . 55 ) and / or the second structural elements ( 52 ) of auxiliary structures ( 51 ) are surrounded, which do not map in the case of a projection of the pattern. A method for forming a pattern on the phase shift mask comprising the steps in the order given: - providing the pattern with a first portion ( 4 ), which has semi-isolated or isolated structures, and a second fraction ( 6 ) having densely packed structures; - providing a mask blank ( 100 ), with a mask substrate, one on a surface of the mask substrate ( 58 ) applied semitransparent, phase-shifting layer ( 110 ) and an absorber layer applied to a surface of the semitransparent, phase-shifting layer ( 102 ); - Applying a radiation-sensitive first resist layer on the absorber layer; Masking lithographic patterning of the first resist layer to form a first resist pattern such that from the first portion (FIG. 4 ) to be formed and the second portion ( 6 ) to be formed in the first resist structure ( 104 ) are opened; Transferring the first resist structure ( 104 ) in the absorber layer ( 102 ) and into the underlying semitransparent phase-shifting layer ( 110 ); Removing the resist and reapplying a second resist layer; Mask lithographic patterning of the second resist layer to form a second resist pattern ( 108 ) in the area of the first share ( 4 ) covers openings in the absorber layer; Etching the mask substrate ( 58 ) in the range of the second share ( 6 ) using the patterned absorber layer and the second resist pattern as etch masks to form the etched surface ( 58 ' ) to a predetermined depth, wherein the depth is selected so that the mask substrate on the flat surface ( 58 ) penetrating light beam a phase jump of 160 ° to 200 ° relative to the etched surface ( 58 ' ) undergoes penetrating light beam; - etching the absorber layer ( 102 ) and the semitransparent phase-shifting layer ( 110 ) in the area of the etched surface 58 '; Removing the second resist structure ( 108 ); and - removing the absorber layer ( 102 ) to expose the semi-transparent, raised webs ( 54 ) of the first structural elements. A method of forming a pattern on the phase shift mask comprising the steps in the order given: providing the pattern with a first portion having semi-isolated or isolated structures and a second portion having densely packed structures; Providing a mask blank with a mask substrate, a semitransparent, phase-shifting layer applied to a surface of the mask substrate, and an absorber layer applied to a surface of the semitransparent, phase-shifting layer; - Applying a radiation-sensitive first resist layer on the absorber layer; Masking lithographic patterning of the first resist layer to form a first resist pattern such that from the first portion (FIG. 4 ) to be formed and the second portion ( 6 ) are to be opened in the first resist pattern to be formed bright areas; Transferring the first resist structure into the absorber layer and into the underlying semitransparent phase-shifting layer; Removing the resist and reapplying a second resist layer; Masking lithographic patterning of the second resist layer to form a second resist pattern similar to that in the region of the first portion ( 4 ) covers openings in the absorber layer; Etching the mask substrate in the region of the second portion ( 6 ) using the patterned absorber layer and the second resist pattern as etch masks to form the etched surface ( 58 ' ) to a predetermined depth, wherein the depth is selected so that the mask substrate on the flat surface ( 58 ) penetrating light beam a phase jump of 160 ° to 200 ° relative to the etched surface ( 58 ' ) undergoes penetrating light beam; Removing the second resist pattern; - Entire surface removal of the absorber layer; - reapplying a third resist layer; Masking lithographic patterning of the third resist layer to form a third resist pattern covering the region of the first portion ( 4 ) covers; - etching the semitransparent phase-shifting layer in the region of the second portion exposed by the third resist pattern; and - removing the residues of the third resist. A method of forming a pattern on the phase shift mask comprising the steps in the order given: providing the pattern with a first portion having semi-isolated or isolated structures and a second portion having densely packed structures; Providing a mask blank with a mask substrate, a semitransparent, phase-shifting layer applied to a surface of the mask substrate, and an absorber layer applied to a surface of the semitransparent, phase-shifting layer; - Applying a radiation-sensitive first resist layer on the absorber layer; Masking lithographic patterning of the first resist layer to form a first resist pattern such that from the first portion (FIG. 4 ) to be formed and the second portion ( 6 ) are to be opened in the first resist pattern to be formed bright areas; - transferring the first resist structure into the absorber layer and into the underlying semitransparent phase-shifting layer; Removing the resist and reapplying a second resist layer; Masking lithographic patterning of the second resist layer to form a second resist pattern similar to that in the region of the first portion ( 4 ) covers openings in the absorber layer; Etching the mask substrate in the region of the second portion ( 6 ) using the patterned absorber layer and the second resist pattern as etch masks to form the etched surface ( 58 ' ) to a predetermined depth, wherein the depth is selected so that the mask substrate on the flat surface ( 58 ) penetrating light beam a phase jump of 160 ° to 200 ° relative to the etched surface ( 58 ' ) undergoes penetrating light beam; Removing the second resist pattern; - reapplying a third resist layer; Mask lithographic patterning of the third resist layer to form a third resist pattern, which is similar to that in the region of the first part ( 4 ) covers openings in the absorber layer; Etching the absorber layer and the semitransparent phase-shifting layer in the region of the openings of the third resist structure; Removing the residues of the third resist; and - removal of the remainder of the absorber over the entire surface layer. Method according to one of claims 7 to 9, wherein in the case the etching steps the etching each anisotropic becomes. Method according to one of claims 7 to 10, wherein the step the provision of the mask blank comprises that the absorber layer is provided as a chromium layer. The method of claim 7 to 11, wherein the step the provision of the mask blank comprises the semitransparent phase-shifting layer of molybdenum silicide is provided. Method according to one of claims 7 to 12, wherein the step the provision of the mask blank comprises that the mask substrate is provided from silicon dioxide. Use of data structures that are suitable in a mask writer writing the mask structures according to a the method according to any one of claims 7 to 9 to enable.