DE102018220889B4 - Method for repairing a connection in a projection exposure system for semiconductor lithography - Google Patents

Abstract

Method for repairing a connection (30) between a first (31) and a second component (32) with a connection element (38) in a projection exposure system (1) for semiconductor lithography, wherein in one of the two components (31), (32) a receptacle (34) is formed for the connecting element (38), comprising the following method steps: a) detection of a defect in the connection (30), b) removal of the connecting element (38), c) definition of a replacement connecting element (41), d) connecting of the replacement connecting element (41) with the receptacle (34), the method being suitable for use in a clean room, the receptacle (34) at least one upper area (36) for receiving the connecting element (38) and a lower area (37) for receiving the replacement connecting element (41), and wherein the upper region (36) of the receptacle (34) is designed with a larger thread (35) than the lower region (37) of the receptacle (34).

Description

The invention relates to a method for repairing a connection, in particular a screw connection in a projection exposure system for semiconductor lithography.

Screw connections play an important role in the field of projection exposure systems for semiconductor lithography, particularly in EUV projection exposure systems. The projection exposure systems are installed in a clean room and the projection exposure systems are operated in a vacuum, which is why it is important to take into account the special conditions of vacuum technology. The cleanliness requirement in a vacuum prohibits the use of conventional lubricants, such as greases or oils, in particular silicone oils, on screw connections, which can lead to so-called seizing of the screws without further measures. To prevent this, the screws are coated, for example gold-plated, or made from special alloys such as Nitronic®, which, thanks to their material composition, minimize the tendency for cold welding and seizure.

In addition, only cleaned components may be installed in the assembly area in clean rooms, such as those that are common in the manufacture of lenses and lighting systems for semiconductor technology. Despite the use of gold-coated and / or screws made of Nitronic®, seizure and thus failure of the connection can occur, especially with small threads, i.e. smaller than / equal to M4. Such threads, especially if they are made in a component made of stainless steel, such as X2 or X5, cannot be repaired, i.e. recut, without the use of oil.

Therefore, in such cases, the assembly typically has to be dismantled into its individual parts, whereupon the defective component has to be replaced or removed for rework. This can lead to a complex dismantling and a new assembly with sometimes complex calibration of the components involved.

The object of the present invention is to provide a method which solves the disadvantages of the prior art described above.

This object is achieved by a method with the features of the independent claim. The subclaims relate to advantageous developments and variants of the invention.

1. a) Detektion eines Defektes der Verbindung,
2. b) Entfernen des Verbindungselementes,
3. c) Definition eines Ersatzverbindungselementes,
4. d) Verbinden des Ersatzverbindungselementes mit der Aufnahme.

In a method according to the invention for repairing a connection between a first and a second component with a connecting element in a projection exposure system for semiconductor lithography, a receptacle for the connecting element is formed in one of the two components. The method is suitable for use in the clean room and includes in particular the following method steps:

1. a) detection of a defect in the connection,
2. b) removing the connecting element,
3. c) Definition of a replacement connecting element,
4. d) connecting the replacement connecting element to the receptacle.

Processes are suitable for use in the clean room if none of the process steps violates the applicable requirements regarding cleanliness and contamination. The requirements include avoiding lubricants that can be carried over, such as lubricants containing oil, and work that causes particles, such as grinding. In particular, a requirement can contain a ban on cleaning components in the clean room, so that all process steps that require cleaning of the component cannot be carried out in the clean room. With the method according to the invention, only large particles (chips) are generated, which can also be removed in the clean room. In this way, dismantling and time-consuming cleaning of individual parts can be prevented. Furthermore, recutting a defective threaded hole can be avoided with the method according to the invention. Recutting would be almost impossible with the auxiliaries and lubricants permitted in the clean room, the tap would break off. This would make the component unusable.

In particular, the method can also be suitable for vacuum. This further restricts the use of lubricants, for example any outgassing materials must be avoided.

In a variant of the invention, the connection can be designed as a screw connection and the receptacle can be designed as a threaded hole.

Furthermore, the connecting element and the replacement connecting element can be designed as screws.

In particular, the receptacle can comprise at least one upper area for receiving the connecting element and a lower area for receiving the replacement connecting element. The upper and lower area of the receptacle can have a thread of the same size be trained. In this case, the thread can advantageously be produced in one process step.

Alternatively, the upper area of the receptacle can be designed with a larger thread than the lower area of the receptacle.

In particular, the upper area of the receptacle can be removed without restricting the function of the lower area of the receptacle. For this purpose, for example, the connecting means can be drilled out of the receptacle. When the connecting means is bored out of the receptacle, a thread arranged in the lower area is not damaged. By flushing the bore and the thread, contamination of the thread with chips can also be avoided, so that the function of the lower area of the receptacle is guaranteed.

When drilling out the connecting means, for example, isopropanol can be used as a lubricant. Isopropanol lubricates the drilling tool sufficiently and can also be used to flush the hole and the thread at the same time. By flushing, the chips and particles produced during drilling are flushed out and can, for example, be extracted directly. The advantage of isopropanol is that it evaporates with almost no residue, which means that the components do not need to be cleaned after they have been bored out, without compromising the requirements for working in a clean room or for vacuum suitability.

With the method described above, a complex process of dismantling, reworking, cleaning and reassembling vacuum-compatible assemblies in a clean room can advantageously be avoided.

• 1 den prinzipiellen Aufbau einer EUV-Projektionsbelichtungsanlage, in welcher die Erfindung verwirklicht sein kann,
• 2a, b eine schematische Darstellung einer ersten Ausführungsform der Erfindung,
• 3 eine schematische Darstellung einer weiteren Ausführungsform der Erfindung, und
• 4 ein Flussdiagramm zu einem erfindungsgemäßen Verfahren.

In the following, exemplary embodiments and variants of the invention are explained in more detail with reference to the drawings. Show it

• 1 the basic structure of an EUV projection exposure system in which the invention can be implemented,
• 2a, b a schematic representation of a first embodiment of the invention,
• 3 a schematic representation of a further embodiment of the invention, and
• 4th a flowchart for a method according to the invention.

1 shows an example of the basic structure of an EUV projection exposure system 1 for microlithography in which the invention can find application. A lighting system of the projection exposure system 1 points next to a light source 3 an illumination optics 4th for illuminating an object field 5 in one object level 6th on. One by the light source 3 generated EUV radiation 14th as useful optical radiation is by means of an in the light source 3 Integrated collector aligned in such a way that it is in the area of an intermediate focus plane 15th passes through an intermediate focus before moving onto a field facet mirror 2 meets. According to the field facet mirror 2 becomes the EUV radiation 14th from a pupil facet mirror 16 reflected. With the help of the pupil facet mirror 16 and an optical assembly 17th with mirrors 18th , 19th and 20th become field facets of the field facet mirror 2 in the object field 5 pictured.

One is illuminated in the object field 5 arranged reticle 7th , that of a reticle holder shown schematically 8th is held. A projection optics shown only schematically 9 serves to map the object field 5 in an image field 10 in an image plane 11 . A structure is imaged on the reticle 7th onto a light-sensitive layer in the area of the image field 10 in the image plane 11 arranged wafers 12 , that of a wafer holder also shown in detail 13 is held. The light source 3 can emit useful radiation in particular in a wavelength range between 5 nm and 120 nm.

The invention can also be used in a DUV system which is not shown. A DUV system is basically like the EUV system described above 1 constructed, whereby mirrors and lenses can be used as optical elements in a DUV system and the light source of a DUV system emits useful radiation in a wavelength range from 100 nm to 300 nm.

2a shows a connection 30th that is a first component 31 and a second component 32 includes which by a screw 38 , which serves as a connecting element in this embodiment, are connected. In the second component 32 is a threaded hole 34 formed, which serves as a receptacle in which the screw 38 is screwed in. Here lies the head 39 the screw 38 on top of the first component 31 , in which a through hole 33 for the body 40 the screw 38 is trained on. The threaded hole 34 includes a threaded upper portion 35 in which the screw 38 is recorded. The threaded hole 34 further comprises a lower area 37 , which also has a thread 35 includes and at a first joining of the connection with the screw 38 does not come into contact. The threads 35 in the upper and lower area of the threaded hole 34 are as a continuous thread 35 educated. The size of the thread can vary, especially in projection optics 9 and lighting systems the projection exposure system 1 small threads, such as an M4 thread and smaller are often used.

2 B shows the same connection 30th as in 2a with a first 31 and a second component 32 that with a screw 38 connected, being the body 40 the screw 38 in the thread 35 the threaded hole 34 has eaten, so the body 40 the screw 38 in the thread 35 the threaded hole 34 is blocked so that the screw is 38 can no longer be solved non-destructively. The head 39 the screw 38 does not lie on top of the first component 31 which makes the connection 30th has no function and needs to be reworked or replaced.

3 again shows the same connection 30th as in 2a and 2 B , with the upper range 36 the threaded hole 34 along with the seized screw 38 was drilled out so that instead of the top area 36 of the thread 35 now a countersunk hole 44 in the second component 32 is trained. The replacement connector is also available as a screw 41 and includes the same thread size, such as M4, but a longer body 43 than the one before to connect the two components 31 , 32 used screw 38 . The body 43 the screw 41 is designed so that this is in the lower area 37 the threaded hole 34 by drilling out the upper area 36 was not damaged with the second component 32 connected is. On the first component 31 with the through hole 33 there were no changes compared to the representation in 2a and 2 B performed. The lower area 37 the recording 34 can also have a smaller thread 35 ' than the upper range 36 include, whereby also the replacement connecting element 41 has a smaller thread, which with the lower area 37 the recording 34 corresponds.

Through the formation of the thread 35 with an upper area 36 and a lower area 37 is it possible to reduce the expense of repairing a connection 30th between two components 31 , 32 beneficial to minimize. In the case of a connection 30th in the clean room, such as in the assembly of projection exposure systems 1 for semiconductor lithography, the drilling can advantageously be carried out in a clean room. By avoiding lubricants that are not approved for the clean room when drilling, all requirements for the vacuum suitability of the connection can be met.

4th describes one possible method of repairing a connection 30th in a projection exposure system 1 for semiconductor lithography between a first 31 and a second component 32 with a connector 38 , being in one of the two components 31 , 32 a recording 34 for the fastener 38 is designed and the method is suitable for use in a clean room.

In the first process step 50 becomes a defect in the connection 30th detected.

In a second process step 51 becomes the connector 38 away.

In a third process step 52 becomes a replacement connector 41 Are defined.

In a fourth process step 53 becomes the replacement connector 41 with the recording 34 connected.

List of reference symbols

1

Projection exposure system

2

Facet mirror

3

Light source

4th

Lighting optics

5

Object field

6th

Object level

7th

Reticle

8th

Reticle holder

9

Projection optics

10

Field of view

11

Image plane

12

Wafer

13

Wafer holder

14th

EUV radiation

15th

Interfield focus plane

16

Pupil facet mirror

17th

module

18th

mirror

19th

mirror

20th

mirror

30th

connection

31

first component

32

second component

33

Through hole

34

Threaded hole

35, 35 '

thread

36

upper thread area

37

lower area thread

38

screw

39

head

40

body

41

Replacement screw

42

head

43

body

44

Counterbore

50

First procedural step

51

Second process step

52

Third procedural step

53

Fourth process step

Claims (7)

Method for repairing a connection (30) between a first (31) and a second component (32) with a connection element (38) in a projection exposure system (1) for semiconductor lithography, wherein in one of the two components (31), (32) a receptacle (34) is formed for the connecting element (38), comprising the following method steps: a) detection of a defect in the connection (30), b) removing the connecting element (38), c) definition of a replacement connecting element (41), d) connecting the replacement connecting element (41) to the receptacle (34), the method being suitable for use in a clean room, the receptacle (34) having at least one upper area (36) for receiving the connecting element (38) and a lower area (37) for receiving the replacement connecting element (41), and wherein the upper region (36) of the receptacle (34) is designed with a larger thread (35) than the lower region (37) of the receptacle (34). Procedure according to Claim 1 , characterized in that the method is suitable for vacuum. Method according to one of the Claims 1 or 2 , characterized in that the connection (30) is designed as a screw connection and the receptacle (34) is designed as a threaded hole. Method according to one of the preceding claims, characterized in that the connecting element (38) and the replacement connecting element (41) are designed as screws (38), (41). Method according to one of the Claims 1 to 4th , characterized in that the upper region (36) of the receptacle (34) can be removed without restricting the function of the lower region (37) of the receptacle (34). Method according to one of the Claims 1 to 5 , characterized in that the connecting means (38) is drilled out of the receptacle (34). Procedure according to Claim 6 , characterized in that isopropanol is used as a lubricant when drilling out the connecting means (38).

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