DE10345398B3 - Hard mask for anisotropic etching has through openings with greater cross-section in first mask region than in second, transition region arranged between first and second mask regions with continuously reducing opening cross-section - Google Patents

Abstract

The hard mask (4) has a first mask region (6) arranged on a substrate surface (2) via a rear surface of the mask, at least one second mask region (5) with one side on the first mask region and the other forming a front surface of the mask, a number of through openings (7,8) with greater cross-section in the first mask region than in the second and a transition region (10) arranged between the first and second mask regions with continuously reducing opening cross-section. Independent claims are also included for the following: (A) a method of manufacturing a hard mask (B) and a method of anisotropic etching of structures in a substrate.

Description

The The invention relates to a hard mask for masking a substrate with a hard mask. The invention further relates to a method for producing such a hard mask and a method for anisotropic etching of Structures in the substrate using a hard mask.

at the production of highly integrated and highly integrated Circuits it is generally the goal, the highest possible number of components on a given surface of the semiconductor substrate. Especially in the production of memory chips can be shortened by shortening lengths of the conductor tracks higher Clock frequency and thus a faster device are provided. The generation of smaller structures today becomes essentially realized by optimized photolithography. While currently produced integrated circuits with minimal resolution structure widths in the range from 110 nm to 140 nm, it is the goal at future Technologies structure widths in the range of 70 nm to 90 nm to realize. With this reduction of the structure width is also an increase in the aspect ratio in particular associated with vertical semiconductor devices, since the Contact holes, trenches for memory cells and the like then very much compared to the lateral dimensions are deeply trained. Under aspect ratio is the ratio of to understand the depth of a structure to its diameter.

at The manufacturing of semiconductor devices often occurs Requirement that in a structuring step can be carried out by etching must, at the areas of the semiconductor material to be removed at least partially formed by a silicon oxide or silicon nitride. An example of this is the production of semiconductor memory cells, which are a trench capacitor and a selection transistor. Considering the lateral Dimensions of the corresponding wells of the trench capacitor, the current technologies in the order of 100 nm to 200 nm, the said process provides for the creation of the trench highest Requirements for positional accuracy, dimensional accuracy and edge steepness of the etching process to be used, since the flank of the to be etched Deepening none possible or at least a very small lateral Abnormal position may have.

Especially at the called small structure widths and thus a high aspect ratio the dry chemical etching from contact holes and trenches very expensive. For these reasons will be for dry chemical etching of very high aspect ratio structures, typically hard masks uses.

In the simplest embodiment, only a single hard mask layer is used here, which is structured, for example, directly with the aid of a resist mask. The etching of semiconductor substrates having a very high aspect ratio or structuring of materials which are difficult to etch, however, is no longer possible or only unsatisfactory with such a monolayer hard mask. Therefore, for such applications increasingly two- or multi-layer hard masks are provided in order to etch structures with very high aspect ratios while maintaining the required dimensional accuracy and edge steepness still can. Methods for producing such two- or multi-layer hardmasks are described, for example, in US Pat DE 199 58 904 C2 and in the DE 199 58 905 C1 described.

A essential boundary condition in the production and use of such Two- or multi-layer hard masks is now that for that too generating profile of a Kontaktlo ches or digging a hard mask must be produced, which is a true to size and therefore CD-faithful Figure (DC = critical dimension) of the structures to be etched. This means, when using such a hard mask must be etched with the contact holes and Trench structures even with very deep structures and therefore very high aspect ratios a high edge steepness, dimensional stability and have positional accuracy. So far, for this purpose in essential cylindrical holes or vertical flanks for used the mask profile of the hard mask.

Also when using such hard masks with substantially cylindrical Recesses but gives the problem that not arbitrarily deep structures etched with the required edge steepness and dimensional stability can. Cause for it is the so-called ARDE effect (ARDE = aspect ratio dependence etch rate), which is a progress of an anisotropic dry chemical etching with increasing depth of structures obstructed. With increasing aspect ratio or with increasing texture depth, this ARDE effect can no longer neglected become. In the aforementioned future 70 nm to 90 nm technologies, therefore, it is using conventional Single or multi-layer hard masks with vertical profile flanks increasingly problematic, the required edge steepnesses of too corrosive To comply with structures.

JP 03-43736 A describes a hard mask which has a total of three mask areas. The hard mask serves to mask a semiconductor substrate. Furthermore, there are Ausneh provided in the hard mask, which pass through each of the mask areas, wherein the cross-section of the recesses decreases stepwise in the direction of the semiconductor substrate.

Similar hard masks are also described in WO 02/073668 A2, the US 6,177,331 B1 and US 2002/0061625 A1.

Of the The present invention is therefore based on the object structures with a very high aspect ratio better and as possible produce faster.

According to the invention this Task by a hard mask with the features of the claim 1, a method for producing such a hard mask with the Features of claim 8 and a method for anisotropic etching of Structures in the substrate using a hard mask according to the invention solved with the features of claim 15.

The The idea underlying the present invention is that divide the hardmask into two areas, an upper area, in the etching particles for etching the structures are coupled into the hard mask, and at least an area below that is directly to be etched Substrate is connected. The for etching the structures have required recesses in the hard mask in the upper and lower mask area, however, not the same cross section on. The lower portion of the hard mask, which is connected to the substrate is, has recesses whose cross-section on the target size to be etched Structure is held so that one CD-faithful picture of the to be etched Structure guaranteed is. The upper area of the hard mask, however, has a higher capture cross section on, that is the cross section of the recesses in the upper area is opposite to the Recesses in the lower area significantly enlarged.

By an optimal adaptation of the profile in the hard mask according to the invention can produce structures with a very high aspect ratio. additionally let yourself also the etching process speed up hard. Optionally, only by means of a Hardmask according to the invention a propulsion at very large aspect ratios realize. Due to the special shape or choice of dimensions is a CD-faithful image without deforming the one to be etched Structure possible.

The underlying idea underlying the present invention is that the etching rate of the structures to be etched is proportional to the number of ions (I _n ) or to the number of fast neutral radicals (N _n ), which per unit time to a surface of the structure to be etched arrives. In this case, the ion density (i _n ) or the radical density (n _n ) is determined by the plasma density provided by the etching reactor. The plasma density depends in particular on the pressure, the power and the magnetic field in the etching reactor. The etching rate is thus essentially, with otherwise constant outer plasma parameters, only dependent on the opening cross-section A _{n of} a hole in the hard mask. This results in the following relationship for the number of ions I _n and the number of radicals N _n as a function of the opening cross-section A _n : I n ~ A n · i n N n ~ A n n · n

The The present invention is based knowledge now in that through an enlargement of the effective diameter of a recess in the hard mask in the area the incident ions or radicals and the associated larger capture cross-section the etching rate in Ideally increased by the factor C = A1 / A2. Here A1 denotes the Cross section of a recess in the hard mask in the region of surface and A2 the cross-section of the recess in the region of the to be etched Structure.

By the different cross sections of a recess in the hard mask according to the invention thus become, so to speak funnel-shaped recesses provided in the region of the funnel opening a very high capture cross section for the etching radicals or ions. In this way, a corresponding to the area ratios C = A1 / A2 increased Number of radicals or ions are recovered. This higher number The ions or radicals are due to the funnel shape of the recesses in the hard mask on the structure to be etched directed. It will be a higher Ionic density in the range of to be etched Structure generated.

The Hardmask according to the invention is particularly suitable for structuring and for etching very deep holes with a relatively small cross section, which thus have a very high aspect ratio. Due to the higher etching rate can be at same process time depending on the etching media and too corrosive Structures - about Etch 10% to 25% deeper structures.

It is essential that a transition between the upper region and the lower region of the hard mask is not formed stepwise, but is formed as continuously as possible similar to a funnel shape. Particularly advantageous angle in the transition region between the top and bottom of the hard mask are at 60 ° to 90 °, optimally at 70 ° to 80 °. Due to the funnel shape of the holes, however, almost all reactive ions or radicals reach the surface to be etched in the substrate due to reflections on the walls.

The Layer thicknesses of the upper region and the lower region of Hard mask must so chosen be that one optionally occurring within the recess of the hard mask Push at the Wall of the hard mask with medium ion energy or momentum still happens inside the hard mask. That way, one might become in the upper part of the to be etched Structure occurring deformation of the etched profile in the etched Material avoided.

By the profile shape according to the invention the hard mask is advantageously also a significant Reduction of the so-called choking problem. Choking is the effect the one with the deposit of etched Material related to the sidewall of an etched hole stands. The choking is thus an undesirable constriction an etched hole (Bottleneck effect), what a further etching progress reduced. This is a reduction of the effective cross section the one to be etched Structure in the region of the capture cross-section and thus another increase of the aspect ratio associated. When using the hard mask according to the invention, the deposition not even at the narrowest point of the structure to be etched, because by purely physical Wechselwir effects with radiated Ions and radicals the hole is kept free. This reduction the choking effect can be advantageously without the aid of appropriate chemical additive etching gases realize.

The Hardmask according to the invention is particularly advantageous for the generation of storage capacities, in a very deep hole in a crystalline silicon substrate etched must become. As material for The hard mask can be used here, for example, silicon dioxide. In another application, the hard mask may also be used to etch vias small technology nodes are used. As material for the hard mask For example, polysilicon and / or carbon may be used here become. About that In addition, the hard mask of the invention also for the production of holes in the oxide for a so-called stack capacitor can be used. As a hard mask can Here, for example, polysilicon or a carbon-containing Layer or a mixture thereof can be used.

advantageous Embodiments and developments of the invention are the subject the further subclaims and the description with reference to the drawing.

The Invention will be described below with reference to the schematic figures The drawings specified embodiments explained in more detail. It shows attended:

1 a schematic cross-sectional view of a semiconductor substrate to be structured with thereon arranged hardmask;

2 a plan view of the surface of the hard mask 1 ;

3 several schematic sections, by which the inventive method for producing a according to 1 designed hard mask is explained in more detail.

In all figures of the drawing are the same or functionally identical elements and characteristics - if nothing else is stated - with the same reference numerals have been provided.

1 shows a schematic cross-sectional view of a semiconductor substrate to be structured with thereon arranged hardmask.

In 1 is with reference numerals 1 denotes a substrate. Although applicable in principle to a wide variety of substrate structures, the present invention will be described below with reference to a semiconductor substrate. In the present exemplary embodiment, the semiconductor substrate is a silicon semiconductor body, but an arbitrary semiconductor body, for example silicon carbide (SiC), gallium arsenide (GaAs), or the like may be provided here. The semiconductor substrate 1 has a first surface 2 , for example, the substrate front, and a second surface 3 , for example, the substrate back, on.

On the side of the substrate front 2 should deep holes or trenches in the semiconductor substrate 1 be introduced. For the purpose of structuring and masking the substrate front 2 is a hard mask 4 provided directly on the substrate front 2 is applied and which is connected to this. The hard mask 4 consists in the present embodiment of at least two different areas 5 . 6 , an upper mask area 5 and a lower mask area 6 , The lower mask area 6 has a layer thickness h1 and the upper mask area 5 has a layer thickness h2. The lower mask area 6 is directly on the substrate front 2 applied and thus is in contact with the semiconductor substrate 1 , The upper mask area 5 adjoins the lower mask area 6 at.

The hard mask 4 also contains recesses 7 . 8th , which cross the hard mask 4 go through and which thus a front side 9 the hard mask 4 with a back, to the substrate front 2 adjacent side of the hard mask 4 connect.

2 shows a plan view of the surface of the hard mask 4 out 1 , The recesses 7 . 8th In the present example, they have a round cross-section, but here also any other cross-sectional shape can be provided. Inside the recesses 8th are the recesses 7 shown in dashed lines. According to the invention, the cross section of the recesses 7 . 8th not constant as a function of depth. Rather, the recesses rejuvenate 7 . 8th from the mask front 9 to the substrate front 2 out. In the area of the mask front 9 have the recesses 8th in the case of round recesses, a diameter d1 which is greater than the diameter d2 in the region of the substrate front side 2 , The recesses 8th show in the area of the surface 9 Thus, a cross section A1 = π (d1 / 2) ² , while the recesses 7 have a cross-sectional area A2 = π (d2 / 2) ² . The cross-sectional area A1 is a measure of the in the recesses 8th coupled reactive ions or radicals. The cross-sectional area A2, however, determines the cross-section of the structure to be etched. The ratio C = A1 / A2 thus denotes the percentage of reactive ions or radicals, the one compared to a cylindrical shape of the recesses 7 . 8th ensures a higher number of reactive ions or radicals.

In the upper mask area 5 is also a transition area 10 intended. In the transition area 10 takes the diameter d1 or the cross-sectional area of the recesses 8th advantageously continuously from until the recesses 8th at the interface 11 between upper mask area 5 and lower mask area 6 have the diameter d2. The recesses 7 . 8th in the upper and lower mask area 5 . 6 thus, as it were, have the shape of a funnel.

Advantageously, should be in the transition area 10 a steepest possible angle α may be provided. The inclination angle α of the trench walls 12 in the transition area 10 should be at least 60 °, optimally in the range between 70 ° and 80 °, with an inclination angle α of 90 ° one to the surface 9 vertical recess 7 . 8th designated. By choosing the steepest possible inclination angle α of the trench wall 12 in the transition area 10 will ensure that over the surface 9 in the recesses 8th penetrating ions or radicals not undesirable or only to a small extent in the trench wall 12 penetration. Rather, they are distracted and virtually into the recesses 7 "Channeled". In this way it is ensured that almost all over the surface 9 coupled ions or radicals via the recesses 8th in the recesses 7 in the lower mask area 6 reach. It thus advantageously results in a funnel effect in which (almost) all over the mask surface 9 trapped ions or etching radicals also to the substrate surface to be etched 2 can reach the production of deep trenches or holes.

3 shows several schematic partial sections, on the basis of which the inventive method for producing a according to 1 designed hard mask is explained in more detail.

3A shows a semiconductor substrate 1 , on its substrate front 2 a layer 20 is applied. In this layer 20 should accordingly 1 configured, funnel-shaped recesses 7 . 8th etched, which later forms part of the hard mask 4 should be. As material for as a hard mask 4 provided layer 20 If silicon dioxide (SiO ₂ ) is provided in the present exemplary embodiment, any other material, such as, for example, silicon nitride (Si ₃ N ₄ ), silicon oxynitride, etc., may also be provided here. The layer thickness of the layer to be etched 20 and thus the depth of the recesses in the layer to be etched 20 , which is to form the hard mask later, is typically in the range between 100 nm to 300 nm.

On the surface 21 the layer 20 is an auxiliary layer 22, for example a carbon-containing layer 22 , applied. On the surface 23 the auxiliary layer 22 is a further auxiliary layer, for example made of SiO _n , arranged. The auxiliary layer 22 serves to structure the layer to be etched 20 whereas the second auxiliary layer 24 again for structuring the auxiliary layer 22 is provided. The thicknesses of the first and second auxiliary layers 22 . 24 are selected depending on the choice of their materials suitable and are for example in the range of a few nanometers for the auxiliary layer 24 ,

In 3A is on the surface of the second auxiliary layer 24 Furthermore, an already exposed and developed lacquer layer 25 applied.

In the next step ( 3B ) are made using the varnish layer 25 structures 26 into the auxiliary layers 22 . 24 etched by an anisotropic etching process. It can also be provided that for each of the layers 22 . 24 a separate etching process is provided. In this etching process be using the structure of the paint layer 25 corresponding structures 26 For example, holes or trenches, perpendicular to the layers 22 . 24 etched. The etching parameters, in particular the temperature, the etching rate, the number of etching ions or radicals, the etching pressure, etc., are chosen so that the highest possible dimensional stability and edge steepness of the structures to be etched 26 after the etching process is guaranteed.

The second auxiliary layer gives the first auxiliary layer 22 when etching the structures 26 a higher stability, that is in particular the surface of the first auxiliary layer 22 is better protected here. Such a second auxiliary layer 24 is therefore advantageous because when etching deep structures 26 the paint mask 25 is removed very quickly by the etching ions or etching radicals and thus can no longer be used for masking and structuring. The function of this paint mask 25 is then through the second auxiliary layer 24 , which is compared to the first auxiliary layer very hard and thus formed largely etch resistant, taken. Of course, such a second auxiliary layer is only required if the structures to be etched 26 should be so deep that the paint layer 25 is no longer sufficient for structuring.

Subsequently, the remaining remnants of the lacquer layer 25 and the second auxiliary layer 24 from the surface 23 the first auxiliary layer are removed or removed ( 3C ). The first auxiliary layer 22 or the structures introduced therein 26 serve as a mask for etching structures 27 in the hardmask layer 20 and thus for the production of the hard mask 4 , In this case, in a first etching step on the structures 26 in the first auxiliary layer 22 vertical structures 27 in the layer to be etched 20 etched to a first depth t1. In the layer to be etched 20 become holes or ditches 27 etched, the dimensionally stable to the structures 26 are arranged and which have a depth t1, relative to the surface 21 , exhibit. As etching media for etching the structures 27 in the layer 20 For example, argon or oxygen can be used. The etching of the carbon layer 22 and the underlying silicon dioxide layer 20 In addition, it is also advantageously possible to carry out etching mediums containing chlorine or fluorine. For example, the etching media used may be Cl ₂ , BCl ₃ , SiCl ₄ , CCl ₄ , CHCl ₃ , CF ₄ , CHF ₃ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₈ or SF ₆ .

at Use of argon or oxygen as the etching medium can be, for example a so-called dual-frequency etching reactor be used. In a particularly advantageous embodiment the depth t1 is controlled by means of interferometric end point measurement. In this way, it is possible to set a specific depth t1 in a targeted manner become.

In the next step ( 3D ) become the structures 26 in the carbon layer 22 on widened so that they have a larger diameter d2. This can be done, for example, by an isotropic etching of the layer 22 respectively. It is essential here that a selective etching directed only at the carbon of the material of the layer 22 takes place, so that by this etching the underlying layer 20 as well as their structures 27 are not affected. For example, the lateral extension of the structures 26 be made by an O ₂ etchant. It is essential here that the etching parameters of this etching process, in particular the etching time, the etching rate, etc., are controlled very precisely, by a specific diameter d2 of the structures 26 to create. The exact control of these etch parameters defines the angle of inclination α. Here, the use of a decoupled so-called dual-frequency system is advantageous. After extension of the diameter of the structures 26 these have a diameter d2 which is greater than the diameter d1 of the corresponding underlying structures 27 in the layer 20 ,

Due to the different diameters d1, d2 now creates a step 28 on the surface 21 between the two layers 20 . 22 ,

In the next etching step ( 3E ) is made using the layer 22 with the advanced structures 26 as a mask in a second etching step, the etching of the layer 20 or the structures 27 continued. In this case, the same etching parameters, and in particular the same etching chemistry, as for the etching of the trenches and holes 27 be used. The etching process then ends when the layer to be etched is 20 completely etched through, that is, when the structures 27 completely through the layer 27 go through. This can in turn be controlled by an interferometric end point detection, for example.

During anisotropic etching, the recesses form 27 virtually the mask for the etching through the layer to be etched 20 that is the recesses 27 are etched while maintaining the diameter d1 until the entire layer 20 etched through. Because etching ions or etching radicals not only in the area 27 but due to the larger diameter d2 also on the step-shaped areas 28 These areas are correspondingly further etched down, in which case, due to the anisotropic etching, the carbon layer 22 acts as an etching mask. This will be the upper areas of the recesses 27 also laterally expanded, wherein the transition from the laterally enlarged recesses 27 to the recesses with the diameter d1 with increasing etching a flowing, that is as continuous as possible transition between the upper mask area and un terem mask area 5 . 6 is produced. This flowing transition later forms the transitional area 10 the hard mask.

Following the through-etching of the layer 20 becomes the carbon layer 22 replaced. Using the textured layer 20 as a hard mask can now be the underlying semiconductor substrate 1 as described in detail above, be suitably structured. The advantage here is in particular that the funnel-shaped recesses 7 . 8th inside the hard mask 20 have a higher capture cross section of etch radicals or etching ions, whereby a higher etching rate in the region of the surface to be etched of the substrate front side 2 is realized.

Although the present invention above based on a preferred embodiment has been described in detail, it is not limited thereto, but Modifiable in a variety of ways.

So the invention is not necessarily on silicon dioxide as Material for the hardmask limited, but lets himself according to the respective application with any materials realize that are suitable for structuring and masking, for example, silicon nitride. Also needs to mask and generate The hard mask does not necessarily have a two-layer mask as well a resist mask can be used. Conceivable here would be the use only a mask layer.

It It goes without saying that the described circular structures the hard mask have been given by way of example only, without the invention to limit it. The invention is based on any cross sections and profile shapes of Recesses applicable, for example, oval, triangular, quadrangular, hexagonal or arbitrary or strip-shaped recesses.

Also be the described production process for the preparation of Hard mask and the etching materials, etching media and etching process merely exemplified and may be within the scope of the invention suitably changed or modified.

in the present embodiment were funnel-shaped Structures described in the hard mask. Of course, these can could also be designed differently, for example, could linear continuous, concave or convex transition of the diameter of the Recesses may be provided in the hard mask. However, this is process technology extraordinarily hard to realize, so that one Funnel shape of the recesses, as described above with reference to an advantageous embodiment was described, for process-technical reasons alone is preferable.

1

Semiconductor substrate

2

first Surface, Front substrate

3

second Surface, Substrate back

4

hard mask

5

upper mask area

6

lower mask area

7

recesses in the lower mask area

8th

recesses in the upper mask area

9

Surface of the hard mask

10

Transition area

11

Interface between the mask areas

12

grave wall

20

to be etched (hardmask) layer

21

Surface of the Hard mask layer

22

first Auxiliary layer, carbon layer

23

Surface of the first auxiliary layer

24

second auxiliary layer, SiO _n layer

25

resist mask

26

Structures / recesses in the auxiliary layers

27

Structures / recesses in the hardmask layer

28

step

d1 d2

Diameter, distance

h1, h2

layer thicknesses the mask areas

t1

depth

Claims (16)

Hard mask ( 4 ) for masking a substrate with a hard mask ( 4 ), with a first mask area ( 6 ), which extends over a back surface of the hard mask ( 4 ) on a surface ( 2 ) of the substrate ( 1 ), with at least one second mask area ( 5 ), one side of which on the first mask area ( 6 ) and the other side has a front surface ( 9 ) of the hard mask ( 4 ), with a variety of through the hard mask ( 4 ) continuous recesses ( 7 . 8th ), wherein the recesses ( 8th ) in the second mask area ( 5 ) have a larger cross-section (A1) than the recesses ( 7 ) in the first mask area ( 6 ), and with a transitional area ( 10 ) located between the first mask area ( 6 ) and the second mask area ( 5 ) is arranged and in which a cross section (A1, A2) of the recesses ( 7 . 8th ) decreased continuously. Hard mask according to claim 1, characterized in that the continuous recesses ( 7 . 8th ) are funnel-shaped. Hard mask according to claim 2, characterized in that the trench walls ( 12 ) of the recesses ( 7 . 8th ) in the transition area ( 10 ) have an inclination angle (α) in the range of 60 ° to less than 90 °, in particular in the range between 70 ° to 80 °. Hard mask according to one of the preceding claims, characterized in that the recesses ( 7 . 8th ) have a round cross-sectional area and the recesses ( 7 ) in the first mask area ( 6 ) have a smaller diameter (d2) than the recesses ( 8th ) in the second mask area ( 5 ). Hard mask according to one of the preceding claims, characterized in that the hard mask ( 4 ) Comprises silicon dioxide and / or silicon nitride and / or a silicon dioxide or silicon nitride-containing material. Hard mask according to one of the preceding claims, characterized in that the hard mask ( 4 ) Has polysilicon and / or carbon and / or a polysilicon or carbon-containing material. Hard mask according to one of the preceding claims, characterized characterized in that Hard mask has a thickness in the range of 100 nm to 300 nm. Method for producing a hard mask ( 4 ), in particular a hard mask ( 4 ) according to any one of the preceding claims, comprising the steps of: (a) a hardmask layer ( 20 ), on the front of the mask ( 21 ) at least one auxiliary layer ( 22 . 24 ). is arranged is provided; (b) the at least one auxiliary layer ( 22 . 24 ). is patterned using photolithography and anisotropic etch processes such that in the auxiliary layer (FIG. 22 . 24 ). first recesses ( 26 ) are produced with a first cross-section (A1) that is from a surface ( 23 ) of the auxiliary layer ( 22 . 24 ) to the front of the mask ( 21 ) go through; (c) using the first recesses ( 26 ) as a mask become second recesses ( 27 ) with a second cross section (A1) in the hard mask layer ( 20 ) is anisotropically etched to a first depth (t1); (d) the first recesses ( 26 ) are laterally expanded by selective etching to a second predetermined cross-section (A2); (e) using the first flared recesses ( 26 ) as a mask, the second recesses ( 27 ) etched anisotropically until the second recesses ( 27 ) through the hardmask layer ( 20 ) are formed throughout. Method according to claim 8, characterized in that that the first depth (t1) measured by interferometric endpoint detection becomes. Method according to one of claims 8 or 9, characterized in that the hard mask layer ( 20 ) before the structuring of the auxiliary layers ( 22 . 24 . 25 ) as well as before the structuring of the hardmask layer ( 20 ) on a substrate ( 1 ), in particular on a semiconductor substrate ( 1 ) is applied. Method according to one of claims 8 to 10, characterized in that at least two auxiliary layers ( 22 . 24 ), wherein a first auxiliary layer ( 22 ) on the front of the mask ( 21 ) of the hardmask layer ( 20 ) is applied and the second auxiliary layer ( 24 ) for protecting a surface ( 23 ) of the first auxiliary layer ( 22 ) is applied to this. Method according to one of claims 8 to 11, characterized in that for structuring the at least one auxiliary layer ( 22 . 24 ) a paint layer ( 25 ) on a free surface of at least one of the auxiliary layers ( 22 . 24 ) is applied. Method according to one of claims 8 to 12, characterized in that after the passage through the second recesses ( 27 ) through the hardmask layer ( 20 ) the remains of the mask on the front ( 21 ) remaining auxiliary layers ( 22 . 24 . 25 ) be replaced. Method according to one of claims 8 to 13, characterized in that as the first auxiliary layer ( 22 ) a carbon-containing material and as a second auxiliary layer ( 24 ) a silicon-containing material, in particular polysilicon or SiO _n , is provided. Process for the anisotropic etching of structures in the substrate using a hard mask ( 4 ) according to one of claims 1 to 7, with the following method steps: (A) providing a substrate, in particular a semiconductor substrate ( 1 ), with on its substrate front side ( 2 ) arranged hard mask ( 4 ); (B) Anisotropic etching of the structures in the substrate front side ( 2 ) using the recesses ( 7 . 8th ) surrounding areas of the hard mask ( 4 ) until a predetermined depth of the structures is reached; (C) Removing the hard mask ( 4 ) from the substrate front side ( 2 ). Process according to Claim 15, characterized in that the depth of the substrate ( 1 ) etched structures by interferometric endpoint detection is measured.