DE102004004597A1 - Method for measuring a structure formed on semiconductor wafer e.g. for manufacture of integrated circuits, involves use of raster electron microscope with electron beam source and detector - Google Patents

Abstract

A method for measuring a semiconductor wafer structure involves initially preparing a semiconductor wafer with a structure comprising several equally spaced protuberances between which are formed gaps on the front face of the wafer, preparing a raster electron microscope with electron beam source and detector, preparing a substrate holder for accommodating the semiconductor wafer, irradiating the front face of the wafer in a measurement window, detecting the electrons scattered on the structure in the measuring window to obtain an intensity profile of the electrons, tilting the electron beam in second direction, irradiating the front face of the semiconductor wafer with the electron beam, detecting the scattered electrons in the detector to determine a second intensity profile of the scattered electrons and then determining the position of the gaps from the difference of the two intensity profiles. An independent claim is given for an arrangement for measuring a structure with a raster electron microscope and a semiconductor wafer.

Description

The The invention relates to a method for measuring a structure a semiconductor wafer with a scanning electron microscope. The invention concerns about it In addition, an arrangement for measuring a structure with a scanning electron microscope and a semiconductor wafer.

to Integrated circuit fabrication is commonly done on semiconductor wafers provided with different electrical properties layers applied and each lithographically structured. A lithographic Structuring step may consist of a photosensitive Apply Resist, this with a desired structure for the relevant Level to illuminate and develop, and then the thus resulting resist mask in the underlying layer in an etching step transferred to.

With the ever increasing integration densities of integrated circuits increase also the requirements for dimensional accuracy of a on the semiconductor substrate to be projected structure. Especially if already pre-levels in underlying layers, eg. In a lithographic projection step have to ever stricter tolerance limits with respect to mutual alignment the structure currently being projected onto the substrate relative to the structures of the aforementioned preliminary levels are taken into account to the functioning to ensure the circuit.

The progressive miniaturization in semiconductor technology also the production of increasingly powerful electronic components. So can For example, dynamic random access memory (DRAM) is nowadays being manufactured which contain a plurality of memory cells. Memory cells of DRAMs usually become arranged in the form of a matrix on a semiconductor wafer. The memory cells usually consist of one storage capacitor and one each Selection transistor. In a read or write operation is the Storage capacitor with an electrical charge, which is a respective Data value responds via the Loading or discharging selection transistor. For this purpose, the selection selection transistor addressed with the aid of a bit line and a word line.

in the The ever-decreasing pattern resolution has become more and more important during the training the memory cells established a structure in which the inner and outer capacitor electrode of the storage capacitor can be arranged in a deep trench. The inner capacitor electrode forms the storage node of the memory cell and becomes common by filling up the deep trench made with a conductive filler. at this known as a so-called trench capacitor construction is by means of a conductive bridge a connection of the inner capacitor electrode to the selection transistor generated. The selection transistor is often a planar transistor between the deep trenches the memory cell array formed.

density Line-column patterns, such as those in the field of manufacture of dynamic random access memories (DRAM) are formed, have, for example, line widths of 70, 90 or 110 nm. For the lithographic projection step of such a circuit pattern becomes common a wafer scanner or wafer stapler used.

at advanced technologies with high structural resolution, for example at the 90nm or 70nm process line, assign the range to the select transistor is assigned, and the area of the deep trenches often the same dimensions. While The production of a memory cell array are often those for the photolithographic Projection characteristic parameters, such. B. the Exposure Do you sis, the sharpness setting or the illumination mode of the projection apparatus, very accurate controlled to a high dimensional accuracy Projection of a pattern of deep trenches on a surface of Reach substrate. To the number of memory cells on one To increase DRAM, the pattern of the trenches, or in general of line-column patterns, will be minimal Dimensions executed. For monitoring the manufacturing quality these are called critical dimensions (CD) designated structures regularly, for example with a scanning electron microscope, controlled.

at In a scanning electron microscope, those from an electron source emitted electrons scattered from the surface of the semiconductor wafer be detected in a detector. This gives you one different intensity profile, depending on whether the electrons are on a plane or a textured one surface be scattered. Generally, parts of surfaces that produce each an equal angle to the incident electron beam have a nearly identical intensity profile in the detector. Usually the evaluation of the intensity profiles thus obtained takes place with the help of a pattern recognition device, that of the detector to disposal Asked intensity profile after searches and misses known structures. This fully automatic Surveying is usually with a computer, such as a microprocessor performed.

One problem that has received little attention in this context is that in the case of a memory cell array, its line-column pattern have the same dimensions, an automatic assignment of trenches and columns is very difficult to perform. In particular, the area of the bottom of the columns and the area of the flat tops outside the columns have almost the same intensity signal, since these areas each have the same angle to the electron beam source. In order to distinguish the signals from areas inside and outside the columns, the semiconductor wafer must be aligned very precisely relative to the electron beam. This causes a measuring window of the electron microscope to lie in a precisely defined area and has no displacement relative to the gaps. However, in advanced manufacturing processes, such as pattern resolutions less than 100 nm, this is difficult.

It It is therefore an object of the invention to overcome the above-mentioned problems and to provide a method and an arrangement to provide a reliable one Measuring a periodic structure on a semiconductor wafer enable.

• – Bereitstellen eines Halbleiterwafers mit einer Struktur, umfassend mehrere äquidistant beabstandete Vorsprünge, zwischen denen Spalten auf der Vorderseite des Halbleiterwafers ausgebildet sind, wobei die Spalten, die alle eine im wesentlichen gleiche Breite aufweisen, im wesentlichen parallel zueinander in einem jeweiligen Abstand ausgeführt sind, der im wesentlichen gleich der Breite der Spalten ist;
• – Bereitstellen eines Rasterelektronenmikroskops, das eine Elektronenstrahlquelle und einen Detektor umfasst;
• – Bereitstellen eines Substrathalters, der geeignet ist, den Halbleiterwafer aufzunehmen, und der geeignet ist, den Halbleiterwafer im Rasterelektronenmikroskop relativ zur Elektronenstrahlquelle auszurichten;
• – Ablegen des Halbleiterwafers auf dem Substrathalter;
• – Bestrahlen der Vorderseite des Halbleiterwafers in einem Messfenster mit einem Elektronenstrahl aus einer ersten Richtung;
• – Detektieren der an der Struktur im Messfenster gestreuten Elektronen mit dem Detektor, um ein erstes Intensitätsprofil der gestreuten Elektronen als erstes Messergebnis zu bestimmen;
• – Kippen des Elektronenstrahls in eine zweite Richtung, die mit der ersten Richtung einen Kippwinkel einschließt;
• – Bestrahlen der Vorderseite des Halbleiterwafers mit der Struktur mit dem Elektronenstrahl aus der zweiten Richtung;
• – Detektieren der gestreuten Elektronen im Detektor, um ein zweites Intensitätsprofil der gestreuten Elektronen als zweites Messergebnis zu bestimmen; und
• – Bestimmen der Kanten der Spalten aus dem Unterschied des erstes Intensitätsprofils und des zweiten Intensitätsprofils.

This object is achieved by a method for measuring a periodic structure on a semiconductor wafer with a scanning electron microscope, which comprises the following steps:

• Providing a semiconductor wafer having a structure comprising a plurality of equidistant spaced protrusions between which gaps are formed on the front side of the semiconductor wafer, the gaps all having a substantially equal width being substantially parallel to each other at a respective pitch; is substantially equal to the width of the columns;
• Providing a scanning electron microscope comprising an electron beam source and a detector;
• - Providing a substrate holder, which is adapted to receive the semiconductor wafer, and which is adapted to align the semiconductor wafer in the scanning electron microscope relative to the electron beam source;
• - depositing the semiconductor wafer on the substrate holder;
• - irradiating the front side of the semiconductor wafer in a measuring window with an electron beam from a first direction;
• Detecting the electrons scattered on the structure in the measuring window with the detector in order to determine a first intensity profile of the scattered electrons as a first measurement result;
• Tilting the electron beam in a second direction including a tilt angle with the first direction;
• - irradiating the front side of the semiconductor wafer with the structure with the electron beam from the second direction;
• Detecting the scattered electrons in the detector to determine a second intensity profile of the scattered electrons as the second measurement result; and
• Determining the edges of the columns from the difference of the first intensity profile and the second intensity profile.

By the inventive method result in two measurement results, with the first measurement result Irradiate with an electron beam from a first direction and the second measurement result by irradiation with an electron beam is achieved from a second direction. The first direction and close the second direction a tilt angle, which causes the edges of the line-column pattern are at different angles from be hit by the electron beam. This results in different intensity profiles between the first and the second measurement result, so that from the Difference of both intensity gradients the location of the edges of the line-column pattern has been deduced can be. This results in an ambiguity-free measurement of the edges of the column pattern.

According to one preferred embodiment the step of tilting the electron beam is performed by the substrate holder relative to the electron beam by the tilt angle is tilted.

According to this Procedure can be in a simple way, an electron beam of a first and a generate second direction, since scanning electron microscopes often a have tiltable electron beam.

According to one another preferred embodiment For example, the step of tilting the electron beam is performed by the electron beam source relative to the substrate holder by the tilt angle is tilted.

According to this Course of action the irradiation with an electron beam from a first Direction and from a second direction in a simple way Achieve that substrate holder with a simple tilting mechanism is provided. A structure modified in this way can be almost with all commercially available Scanning electron microscopes are combined.

According to another preferred embodiment, the step of tilting the electron beam is carried out so that the tilt angle Weni ger than 2 °.

According to this Proceeding will be the direction of incidence of the substrate on the Semiconductor wafer striking electron beam only slightly changed. In order to are not modifications, for example in electron beam optics, the depth of field the image of the electron beam on the top of the semiconductor wafer can influence, necessary.

According to one another preferred embodiment For example, the step of tilting the electron beam is performed so that the tilt angle about 0.5 °.

According to this Procedure ensures that only small shifts of the electron beam in the second direction must be performed. Thereby have to no adjustment sequences of the electron beam source to the substrate holder executed after tilting In particular, it can be ensured that the measurement window the first and second measurements match.

According to one preferred embodiment the first direction perpendicular to the front side of the semiconductor wafer selected.

A Irradiation with an electron beam perpendicular to the surface of the executed to be irradiated object is is a common one Arrangement with a scanning electron microscope. Thus can be the inventive method perform in a simple manner.

According to one another preferred embodiment The step of providing the semiconductor wafer comprises Providing one arranged on the front side of the semiconductor wafer Memory cell array with trenches for trench capacitors and contact holes, wherein the memory cell array in the region of the trench capacitors and / or contact hole planes forming the structure with columns.

According to this Course of action the procedure for apply dynamic random access memory trench capacitors commonly used in advanced manufacturing processes be used, the equidistant are spaced.

According to one another preferred embodiment the columns are provided with a width of less than 110 nm.

According to this Course of action the method applies to memory cell arrays whose structure resolution is so low is that a positioning of the substrate holder in one Measuring window only with very large Difficulties are feasible.

According to one another preferred embodiment For example, the columns are provided with a width of about 70 nm.

According to this Course of action The process is based on state-of-the-art production processes of memory cell arrays apply.

• – Zurückkippen des Elektronenstrahls um den Kippwinkel;
• – Verschieben des Halbleiterwafers auf dem Substrathalter, um den Halbleiterwafer in einem weiteren Messfenster auszurichten;
• – Bestrahlen der Oberfläche des Halbleiterwafers in dem anderen Messfenster mit dem Elektronenstrahl aus der ersten Richtung;
• – Detektieren der Spalten im weiteren Messfenster gestreuten Elektronen mit dem Detektor, um ein drittes Intensitätsprofil der gestreuten Elektronen als drittes Messergebnis zu bestimmen; und
• – Bestimmen der Abmessungen der Struktur anhand des dritten Intensitätsprofils.

According to another preferred embodiment, following the step of determining the edges of the columns, the following steps are performed:

• - tilt back the electron beam by the tilt angle;
• - Moving the semiconductor wafer on the substrate holder to align the semiconductor wafer in another measuring window;
• - irradiating the surface of the semiconductor wafer in the other measurement window with the electron beam from the first direction;
• - Detecting the columns scattered in the further measurement window scattered electrons with the detector to determine a third intensity profile of the scattered electrons as the third measurement result; and
• - Determining the dimensions of the structure based on the third intensity profile.

According to this The procedure becomes the first measurement result and the second measurement result used the semiconductor wafer in another measurement window align. This additional measurement window can be chosen that it is due to the inaccuracy of position when moving the semiconductor wafer originally on the substrate holder corresponds to the targeted measurement window. Measuring the dimensions The structure with the columns is based on the third intensity profile. This can be particularly advantageous in automatic pattern recognition be used, since the automatic pattern recognition often of assumes a predetermined reference pattern within the measuring window must be arranged.

• – einen Halbleiterwafer mit einer Struktur umfassend mehrere äquidistant beabstandete Spalten, die auf der Vorderseite des Halbleiterwafers ausgebildet sind, wobei die Spalten, die alle eine im wesentlichen gleiche Breite aufweisen, im wesentlichen parallel zueinander in einem jeweiligen Abstand ausgeführt sind, der im wesentlichen gleich der Breite der Spalten ist;
• – ein Substrathalter auf dem der Halbleiterwafer abgelegt ist, wobei der Substrathalter geeignet ist, den Halbleiterwafer aufzunehmen und den Halbleiterwafer in einem Rasterelektronenmikroskop relativ zu einem Elektronenstrahl;
• – ein Rasterelektronenmikroskop, das Mittel zum Bestrahlen der Vorderseite des Halbleiterwafers in einem Messfenster mit dem Elektronenstrahl und Mittel zum Detektieren der an der Struktur in dem Messfenster gestreuten Elektronen umfasst; und
• – Mittel zum Kippen des Elektronenstrahls.

The object is also achieved by an arrangement for measuring a periodic structure with a scanning electron microscope and a semiconductor wafer, comprising:

• A semiconductor wafer having a structure comprising a plurality of equidistantly spaced columns formed on the front side of the semiconductor wafer, the columns all having a substantially equal width being substantially parallel to each other at a respective pitch substantially equal to that of FIG Width of the columns is;
• A substrate holder is deposited on which the semiconductor wafer, wherein the substrate holder is adapted to receive the semiconductor wafer and the half conductor wafer in a scanning electron microscope relative to an electron beam;
• A scanning electron microscope comprising means for irradiating the front side of the semiconductor wafer in a measuring window with the electron beam and means for detecting the electrons scattered on the structure in the measuring window; and
• - Means for tilting the electron beam.

preferred Further developments of the invention are specified in the subclaims.

The The invention will now be described with reference to the accompanying drawings. In show the drawing:

1 a flow chart of the steps of the method according to the invention;

2 schematically a periodic structure with columns on a semiconductor wafer in a side view;

3 schematically in a cross-sectional view the parts required for carrying out the method according to the invention comprising a scanning electron microscope and a semiconductor wafer;

4 schematically a diagram of a first intensity profile;

5 schematically in a further cross-sectional view of the parts required for carrying out the method according to the invention parts comprising a scanning electron microscope and a semiconductor wafer;

6 schematically in a further cross-sectional view of the parts required for carrying out the method according to the invention parts comprising a scanning electron microscope and a semiconductor wafer;

7 schematically a diagram of a second intensity profile; and

8th further steps of the method according to the invention with reference to a flow chart.

The method for measuring a periodic structure on a semiconductor wafer with a scanning electron microscope according to the invention will be described below with reference to a flow chart, which is shown in FIG 1 is illustrated explained. The determination of dimensions of a structure on a semiconductor wafer is an important aspect in quality control in order to be able to monitor the individual process steps of the semiconductor fabrication. These measurements are also referred to in the art as CD-SEM (critical dimension scanning electron microscopy, critical dimension scanning electron microscopy).

Starting point of the method according to the invention is a semiconductor wafer with a periodic structure, as in 2 and a scanning electron microscope and a substrate holder adapted to receive the semiconductor wafer. This construction is in 3 shown.

The semiconductor wafer 5 has a structure on the front 10 on. An example of this structure 10 is in 2 shown. The structure 10 includes several equidistant spaced columns 12 formed on the front side of the semiconductor wafer. The columns all have a substantially equal width 14 on and are substantially parallel to each other at a respective distance 16 executed. The distance 16 is substantially equal to the width 14 the columns 12 , This results in the periodic structure 10 with equidistant spaced columns 12 ,

An embodiment of this structure 10 For example, one is on the front of the semiconductor wafer 5 arranged memory cell array of a dynamic random access memory (DRAM). The memory cell array of a DRAM has at the beginning of the manufacturing process on the front trenches, which are used for the formation of trench capacitors. In the area between the trenches, selection transistors are formed in later process steps. Advanced DRAM manufacturing technologies include trenches with a width 14 provided, for example, 110 nm or 70 nm. The distance 16 is also 110 nm or 70 nm, so that the memory cell array in the region of the trench capacitors, the periodic structure 10 with columns 12 forms.

Likewise, memory cell arrays of DRAMs have contact holes, which are provided, for example, for connecting the selection transistor to an overlying metal line. The memory cell array thus forms the structure as a further example in the area of the contact hole levels 10 with columns 12 ,

The scanning electron microscope 20 includes an electron beam source 22 and a detector 24 , as in 3 shown. The electron beam source 22 is usually with a focusing device 25 provided one from the electron beam source 22 emitted electron beam bundles with example by means of electromagnets. The detector 24 includes an electron sensitive measuring device. Scanning electron microscopes and their components are well known in the art, so that a detailed explanation is omitted here can.

The substrate holder 26 is suitable for the semiconductor wafer 5 and the semiconductor wafer 5 in a scanning electron microscope 20 relative to the electron beam source 22 align. This results in a structure, as in 3 shown. The electron beam source 22 is above the substrate holder 26 attached and the detector 24 laterally from the substrate holder so that one from the electron beam source 22 emitted electron beam on top of the substrate holder 26 is focused without the detector 24 to be disturbed.

In a first step 100 becomes a semiconductor wafer 5 provided. The semiconductor wafer has a periodic structure on the front as related to 2 was discussed.

In the next step 102 becomes a scanning electron microscope 20 provided. The scanning electron microscope 20 includes, as in 3 shown an electron beam source 22 and a detector 24 ,

In the next step 104 becomes a substrate holder 26 provided on the following in the next step 106 the semiconductor wafer 5 on the substrate holder 26 is filed. The front of the structure 10 is located after the deposition of the semiconductor wafer on the electron beam source 22 facing side. The substrate holder 26 Allows the alignment of the semiconductor wafer 5 by the semiconductor wafer 5 is positioned relative to an electron beam by shifting.

Subsequently, in the next step 108 of the method, irradiating the front side of the semiconductor wafer 5 in a measurement window with an electron beam 28 from a first direction. The measuring window is determined both by the focusing of the electron beam and by the adjustment or alignment of the semiconductor wafer 5 determined relative to the electron beam. Usually, Scanning Electron Microscopes have only a limited scanning range, which is covered by the measuring window. The first direction is chosen in this example so that the electron beam strikes perpendicular to the front of the semiconductor wafer.

After that, in the next step 110 the process of the structure 10 electrons scattered in the measuring window 36 with the detector 24 detected. This will produce a first intensity profile 30 the scattered electrons 36 determined as the first measurement result.

In 4 is schematically the intensity profile 30 shown the location of the structure 10 with dashed lines to the interpretation of the intensity profile 30 to facilitate. In the area of the soil 40 the columns 12 and on the flat top 42 of the semiconductor wafer outside the columns 12 has the intensity profile 30 almost the same value. It is thus not possible to distinguish these two areas by means of an automatic evaluation program. In the area of the edges of the columns 12 has the intensity profile 30 to the area of the soil higher values, which, as in 4 shown as local maxima 38 in the intensity profile 30 can be seen.

Determining the dimension of the structure would be very difficult on the basis of this measurement result for a periodic structure. In particular, as mentioned above, a slight misalignment of the substrate holder results 26 to a displacement of the measuring window, whereby at very fine structural dimensions, a misallocation of the areas 40 the columns and the areas 42 the flat surfaces outside the columns 12 is possible. This would cause wrong values to be determined for the CD-SEM and thus the manufacturing process to be incorrectly characterized.

In the next step 112 The electron beam is tilted in a second direction. The second direction forms a tilt angle with the first direction 32 , The tilt angle is set in the range less than about 2 °, for example, the tilt angle is about 0.5 °.

The tilting of the electron beam can be done in several ways. For one, it is possible to use the substrate holder 26 relative to the electron beam about the tilt angle 32 to tilt, as in 5 is shown. On the other hand, it is also conceivable, the electron beam source 22 around the tilt angle 32 tilt relative to the substrate holder. This is in 6 shown.

Regardless of how the tilting of the electron beam is performed, however, it is important that the measurement window is not displaced. For this purpose, it is necessary that the imaginary pivot is located on the top of the semiconductor wafer. Otherwise, the tilting would also lead to a shift of the measuring window. Commercial scanning electron microscopes often have a possibility of electron beam source 22 to tilt. However, if this is not provided, a tiltable substrate holder will provide an equivalent alternative.

In the next step 114 is an irradiation of the front side of the semiconductor wafer 5 performed with the structure with the electron beam from the second direction.

Below is the next step 116 which are scattered on the surface of the semiconductor wafer ten electrons 36 in the detector 24 detected. The second measurement result is a second intensity profile 34 the scattered electrons 36 certainly.

In 7 is schematically the second intensity profile 34 shown, again below the now tilted structure 10 with the tilt angle 34 is drawn. In the area of the bottom of the columns 12 and on the planar top of the semiconductor wafer has the intensity profile 30 again the same value. In the area of the edges of the columns 12 has the intensity profile 34 turn on local maxima. However, these are for opposite edges of a column 12 different high. An edge that faces the electron beam as a result of the tilting has a different value of the local intensity maximum 38 ' on, as that edge, which lies by the tilting "in the shadow" of the electron beam and thus hardly any more of electrons is irradiated. The value of the local intensity maximum 38 '' points in 7 a lower value.

In the next step 116 the position of the columns is the difference of the first intensity profile 30 and the second intensity profile 34 certainly. Due to the different maxima 38 ' and 38 '' in the second intensity profile 34 the position of the columns is now known and there is an assignment of the almost identical values in the first intensity profile 30 to the area 40 the bottom of the columns 12 and to the area 42 the planar top of the semiconductor wafer outside the columns 12 , The determination of the dimensions of the structure 10 takes place with a known position of the columns 12 , so that a misallocation is excluded.

As mentioned above, the measurement window for determining the first intensity profile 30 characterized in that the semiconductor wafer by means of the substrate holder 26 and the focusing device 25 is aligned relative to the electron beam in a measuring position. The error in registration is often greater than the width of the columns when aligning the semiconductor wafer 12 , This is particularly important in the measurement of memory cell arrays with very fine structural resolution of less than 110 nm, If the measuring position for determining the first intensity profile 30 is selected in a region near the edge of the memory cell array, can be based on the known circuit layout, an association between the area of the bottom of the columns 12 and the area of the planar upper side of the semiconductor wafer. For this purpose, all the columns would have to lie to the edge of the memory cell array in the measurement window to the intensity maxima of the first intensity profile 30 to be able to count. This approach would be cumbersome and time consuming.

The method according to the invention allows a simple determination of the dimensions of the columns 12 , The method is particularly advantageous if the measuring position for determining the first intensity profile is selected in a region less close to the edge of the memory cell array.

In a further embodiment of the method, after step 118 for determining the position of the columns 12 still carry out further steps, which are described below. This method is particularly suitable for automated determination of the critical dimensions of structures.

The measurement window for determining the first intensity profile 30 and the second intensity profile 34 must be present in the present case only with a reduced accuracy and is only used for coarse adjustment of the semiconductor wafer.

First, as in 8th is shown in a further step 120 a tilt back of the electron beam by the tilt angle 32 , as described above, by tilting the substrate holder 26 or tilting the electron beam source 22 ,

By moving the semiconductor wafer 5 on the substrate holder 26 will be in the next step 122 the semiconductor wafer 5 aligned in another measurement window. The further measuring window is chosen so that, using the now known position of the columns 12 a match of the further measurement window is achieved with a reference pattern. The reference pattern is usually in an evaluation unit, which receives the measurement results from the detector 24 receives, filed.

The following is in the step 124 the front side of the semiconductor wafer 5 in the further measuring window with the electron beam 28 irradiated from the first direction.

Subsequently, in the step 126 the scattered electrons in the further measuring window with the detector 24 detected. As the third measurement result, a third intensity profile of the scattered electrons is determined. This measurement result now has a match with the reference pattern and can subsequently in step 128 for determining the dimensions of the structure 10 be used on the basis of the third intensity profile.

That in connection with the 8th described method is suitable both for use with scanning electron microscopes from different manufacturers as well as with similar scanning electron microscopes, each a different calibration of their components (such as substrate holder and focusing) or different Have Liche Justiergenauigkeiten. In a high-volume manufacturing process, as is customary for the production of DRAMs, for example, the reference patterns and the position of the measurement windows are stored centrally on the semiconductor wafer and distributed to the scanning electron microscopes via data lines.

By the method according to 8th Initially, only a coarse positioning of the structure relative to the electron beam is required, the actual determination of the critical dimensions takes place only after using the method steps 100 to 118 the location of the columns was determined. As a result, a large number of identical or different CD-SEM measuring stations can be provided in a high-volume manufacturing process, which are centrally controlled with measuring tasks, without taking into account individual characteristics of the measuring stations.

5

Semiconductor wafer

10

structure

12

column

14

width the column

16

distance the column

18

Side wall

20

scanning Electron Microscope

22

electron beam source

24

detector

25

focusing

26

substrate holder

28

electron beam

30

first intensity profile

32

tilt angle

34

second intensity profile

36

scattered electrons

38

38 ', 38 "intensity maximum

40

Area of the soil

42

Area the flat top

100

to 128 process steps

Claims (23)

Method for measuring a structure on a semiconductor wafer with a scanning electron microscope, comprising the following steps: - providing a semiconductor wafer ( 5 ) with a structure ( 10 ) comprising a plurality of equidistantly spaced protrusions between which gaps ( 12 ) are formed on the front side of the semiconductor wafer, the columns ( 12 ), all of a substantially equal width ( 14 ) substantially parallel to each other at a respective distance ( 16 ) are made substantially equal to the width ( 14 ) of the columns ( 12 ); Providing a scanning electron microscope ( 20 ), which is an electron beam source ( 22 ) and a detector ( 24 ); Providing a substrate holder ( 26 ), which is suitable for the semiconductor wafer ( 5 ), and which is suitable for the semiconductor wafer ( 5 ) in the scanning electron microscope relative to the electron beam source ( 22 ) to align; Depositing the semiconductor wafer on the substrate holder ( 26 ); Irradiating the front side of the semiconductor wafer ( 5 ) in a measuring window with an electron beam ( 28 ) from a first direction; - Detecting the on the structure ( 10 ) in the measuring window scattered electrons with the detector ( 24 ) to obtain a first intensity profile ( 30 ) of the scattered electrons to be determined as a first measurement result; Tilting the electron beam in a second direction, which with the first direction has a tilt angle ( 32 ) includes; - irradiating the front side of the semiconductor wafer with the structure with the electron beam from the second direction; Detecting the scattered electrons in the detector to obtain a second intensity profile ( 34 ) of the scattered electrons to be determined as a second measurement result; and determining the position of the columns from the difference of the first intensity profile ( 30 ) and the second intensity profile ( 34 ). The method of claim 1, wherein the step of Tipping the electron beam is performed by the substrate holder tilted relative to the electron beam by the tilt angle. The method of claim 1, wherein the step of Tipping the electron beam is performed by the electron beam source tilted relative to the substrate holder by the tilt angle. Method according to one of claims 1 to 3, wherein the step the tilting of the electron beam is performed so that the tilt angle less than 2 °. The method of claim 4, wherein the step of Tipping the electron beam is carried out so that the tilt angle approximately 0.5 °. Method according to one of claims 1 to 5, wherein the first Direction is selected perpendicular to the front of the semiconductor wafer. Method according to one of claims 1 to 6, wherein the step of providing the semiconductor wafer ( 5 ) with the structure ( 10 ) comprises: providing on the front side of the semiconductor wafer ( 5 ) arranged memory cell array with trenches for trench capacitors and contact holes, wherein the memory cell array in the region of Trench capacitors and / or contact holes the structure ( 10 ) with columns ( 12 ). The method of claim 7, wherein the columns are of width ( 14 ) of less than 110 nm are provided. The method of claim 8, wherein the columns are of width ( 14 ) of about 70 nm are provided. Method according to one of claims 7 to 9, wherein the measuring window for determining the first intensity profile ( 30 ) is determined by the fact that the semiconductor wafer by means of the substrate holder ( 26 ) is aligned relative to the electron beam in a measuring position, wherein the error in the positional accuracy when aligning the semiconductor wafer is greater than the width of the columns ( 12 ). The method of claim 10, wherein the measuring position for determining the first intensity profile in a region is selected near the edge of the memory cell array. The method of claim 10, wherein the measuring position for determining the first intensity profile in a region is selected less near the edge of the memory cell array. Method according to one of claims 1 to 12, wherein after the step of determining the edges of the columns ( 12 ) the following steps are carried out: tilting back the electron beam by the tilt angle; Shifting the semiconductor wafer ( 5 ) on the substrate holder ( 26 ) to the semiconductor wafer ( 5 ) in another measuring window; Irradiating the surface of the semiconductor wafer ( 5 ) in the further measuring window with the electron beam ( 28 ) from the first direction; - Detecting the columns ( 10 ) in the further measuring window scattered electrons with the detector ( 24 ) to obtain a third intensity profile ( 30 ) of the scattered electrons to be determined as a third measurement result; and determining the dimensions of the structure ( 10 ) based on the third intensity profile. Arrangement for measuring a structure with a scanning electron microscope and a semiconductor wafer, comprising: a semiconductor wafer ( 5 ) with a structure ( 10 ) comprising a plurality of equidistantly spaced protrusions between which gaps ( 12 ) are formed on the front side of the semiconductor wafer, the columns ( 12 ), all of a substantially equal width ( 14 ) substantially parallel to each other at a respective distance ( 16 ) are made substantially equal to the width ( 14 ) of the columns ( 12 ); A substrate holder ( 26 ) is deposited on the semiconductor wafer, wherein the substrate holder is adapted to the semiconductor wafer ( 5 ) and the semiconductor wafer ( 5 ) relative to an electron beam; A scanning electron microscope ( 20 ) comprising an electron beam source for irradiating the front side of the semiconductor wafer ( 5 ) in a measuring window with the electron beam ( 28 ) and a detector for detecting the at the structure ( 10 ) comprises electrons scattered in the measurement window; and means for tilting the electron beam to tilt the electron beam in a first direction and in a second direction, the first direction and the second direction including a tilt angle. Arrangement according to claim 14, wherein the means for Tipping the electron beam is suitable, the substrate holder relative to tilt the electron beam by the tilt angle. Arrangement according to claim 14, wherein the means for Tipping the electron beam is suitable, the electron beam source relative to the substrate holder to tilt by the tilt angle. Arrangement according to one of claims 14 to 16, wherein the Tilt angle is less than 2 °. Arrangement according to claim 17, wherein the tilt angle approximately 0.5 °. Arrangement according to one of claims 14 to 18, in which the first direction provided perpendicular to the front side of the semiconductor wafer is. Arrangement according to one of Claims 14 to 19, in which the semiconductor wafer ( 5 ) one on top of the semiconductor wafer ( 5 ) arranged memory cell array with trenches for trench capacitors and contact holes, wherein the memory cell array in the region of the trench capacitors and / or contact holes, the columns of the structure ( 10 ) having. Arrangement according to claim 20, wherein the columns are of width ( 14 ) of less than 110 nm are provided. Arrangement according to Claim 21, in which the columns are of a width ( 14 ) of about 70 nm are provided. Arrangement according to one of claims 14 to 22, wherein the detector for detecting the scattered electrons is arranged laterally of the substrate holder, so that the electron beam, the path between the electron beam source and the Subst Rathalter passed unhindered.