EP4634725A2

EP4634725A2 - Universal photolithography tool

Info

Publication number: EP4634725A2
Application number: EP23855756.5A
Authority: EP
Inventors: Thomas Smith; Hanspeter BLEULER
Original assignee: Semiconductor Technology Ltd
Current assignee: Semiconductor Technology Ltd
Priority date: 2022-12-13
Filing date: 2023-12-12
Publication date: 2025-10-22
Also published as: WO2024126995A3; GB202218776D0; CN120883142A; TW202439014A; WO2024126995A2

Abstract

A photolithography apparatus (50) has a controller (55) an exposure system (66,67) and a wafer loader system (94). The controller (55) is operable to configure and directly control the exposure system (66,67), the wafer loader system (94) and at least one of an inspection system (72) and a resist processing system (82). The exposure system can have an LED illumination source (66) configurable to emit G- line, H-line and/or i-line radiation and the controller (55) is operable to configure and directly control the LED illumination source (66) to select and cause the emission of G-line, H-line or i-line radiation.

Description

UNIVERSAL PHOTOLITHOGRAPHY TOOL

Technical Field

The present invention is generally in the field of semiconductor manufacturing. More particularly, the invention is in the field of semiconductor photolithography apparatus. The invention also relates to computer programs and computer program products for configuring and controlling photolithographic apparatuses.

Background Art

Photolithography in conventional semiconductor fabrication facilities (tabs) typically uses four separate systems: stepper tool for exposure, inspection tool, coater tool, and developer tool.

Such arrangements are not able to perform all the photolithography steps in one tool, process any wafer size, and expose with any wavelength.

Semiconductor manufacturers need to purchase multiple tools to implement a given process, and then purchase more equipment when their process changes.

Mercury arc lamps are used as illumination sources in conventional steppers, but difficult to configure, expensive to run and have relatively short working life.

Summary

A photolithography apparatus, substantially as shown in and/or described in connection with at least one of the figures, and as set forth more completely in the claims. According to a first aspect of the present invention, there is provided a photolithography apparatus comprising:

- a controller;

- an exposure system; and

- a wafer loader system, wherein the controller is operable to configure and directly control the exposure system, the wafer loader system and at least one of:

- an inspection system; and

- a resist processing system.

Preferably, the photolithography apparatus further comprises the inspection system.

Preferably, the photolithography apparatus further comprises the resist processing system.

Preferably, the exposure system comprises an LED illumination source configurable to emit G-line, H-line and/or i-line radiation and the controller is operable to configure and directly control the LED illumination source to select and cause the emission of G-line, H-line or i-line radiation.

Preferably, the wafer loader system comprises a pre-aligner and a carrier plate configured to receive wafers of a plurality of nominal diameters.

Preferably, the photolithography apparatus further comprises a machine vision system operable to function as a camera for an alignment system for the exposure system and as a camera for the inspection system.

Preferably, the resist processing system comprises a coater, an oven, and a developer and the processor is operable to configure and directly control the coater, oven, and developer.

Preferably, the wafer loader system comprises a wafer ID reader and the processor is operable to configure and directly control the exposure system based on readings from the wafer ID reader. According to a second aspect of the present invention, there is provided a computer program comprising computer readable instructions which, when run on suitable computer apparatus, cause the controller to configure and directly control the exposure system and the wafer loader system and at least one of the inspection system and the resist processing system, in accordance with the first aspect.

According to a third aspect of the present invention, there is provided a computer program product comprising the computer program of the second aspect.

Brief description of the Drawings

It would be desirable to have one tool that is configurable for any photolithography process.

Embodiments of the present invention will now be described, by way of example only, with reference to the drawings, in which:

Figure 1 illustrates, in schematic form, a prior art photolithography equipment line.

Figure 2, illustrates, in schematic form, a photolithography apparatus in accordance with an embodiment of the present invention.

Detailed Description of embodiments

The following description contains specific information pertaining to the implementation of the present invention. One skilled in the art will recognize that the present invention may be implemented in a manner different from that specifically discussed in the present application. Moreover, some of the specific details of the invention are not discussed in order not to obscure the invention.

The drawings in the present application and their accompanying detailed description are directed to merely exemplary embodiments of the invention. To maintain brevity, other embodiments of the present invention are not specifically described in the present application and are not specifically illustrated by the present drawings.

Embodiments of the present invention may provide a cluster tool that is modular and configurable to do the following multiple photolithographic processes in one piece of equipment:

• Coat wafers

• Align Targets on a wafer

• Expose wafer with GHI or i-line radiation

• Develop wafers

• Inspect the completed printed pattern

Such a tool may process a wafer of any standard size.

With reference to Figure 1 , a photolithography equipment line having four separate systems (tools) is illustrated. A stepper tool 10 comprises a stepper system 12 and a dedicated stepper controller 15 running its own discrete software. The stepper system has its own wafer-in indexer 13 and wafer-out indexer 14. The stepper system 12 has an exposure system that includes a mercury lamp illumination source 16 configured to emit G-line, H-line or i-line radiation G/H/i. It also has an alignment system 18 for aligning a pattern, formed by the radiation’s projection through a reticle, to patterns on the wafer being exposed.

An inspection tool 20 comprises an inspection system 22 and a dedicated inspection controller 25 running its own discrete software. The inspection system 22 has its own wafer-in indexer 23 and wafer-out indexer 24. The inspection system 22 has one or more inspection camera 26, for imaging features on a wafer, for example to measure critical dimensions (CD).

A coater tool 30 comprises a coater system 32 and a dedicated coater controller 35 running its own discrete software. The coater system 32 has its own wafer-in indexer 33 and wafer-out indexer 34. The coater system 32 has a coater 36 and an oven 37, used to coat resist on a wafer and bake or cure the resist. A developer tool 40 comprises a developer system 42 and a dedicated coater controller 45 running its own discrete software. The developer system has its own wafer-in indexer 43 and wafer-out indexer 44. The developer system 42 has a developer 48, used to develop the pattern that has been exposed in the resist.

With reference to Figure 2, a photolithography apparatus 50 has a controller 55, an exposure system 66,67 and a robotic wafer loader system 94. The controller 55 is operable to configure and directly control the exposure system 66,67, the wafer loader system 94 and at least one of: an inspection system 72 and a resist processing system 82. The controller 55 is operable to configure the systems for example by setting their operational parameters, or selecting specific operations of the respective systems. In other words the controller does not just initiate operation of each system at a high-level, with the control being performed by a separate controller for each respective system.

In this example the photolithography apparatus 50 includes the inspection system 72 and the resist processing system 82. However, these may be missing from the apparatus, and embodiments allows them to be easily added and controlled.

The exposure system comprises an LED (Light Emitting Dode) illumination source 66 configurable to emit G-line, H-line and/or i-line radiation and the controller 55 is operable to configure and directly control the LED illumination source 66 to select and cause the emission of G-line, H-line and/or i-line radiation, i-line radiation is approximately 355-nm, H-line is approximately 405nm, and G-line is approximately 435nm wavelength. A green alignment LED 57 is provided, having approximately 520nm wavelength.

The wafer loader system comprises a pre-aligner and a carrier plate configured to receive wafers of a plurality of nominal diameters (e.g. 150mm, 200mm or 300mm).

A machine vision system 92 is operable to function as a camera for an alignment system 68 for the exposure system 66,67 and as a camera for the inspection system 72. The MVS is a camera, having software, that is mounted on to the stepper and inspection systems, with optics to make it adaptable for both systems. The resist processing system 82 comprises a coater 86, an oven 87, and a developer 88 and the processor is operable to directly control the coater 86, oven 87, and developer 88.

The wafer loader system 94 comprises a wafer ID (identifer) reader 99 and the processor is operable to configure and directly control the exposure system based on readings from the wafer ID reader 99.

A computer program 58 is loaded into a computer in the controller 55 in this example. The computer program 58 has computer readable instructions which, when run on suitable computer apparatus such as embedded in the controller in this example, cause the controller 55 to configure and directly control the exposure system 66,67 and the wafer loader system 94 and at least one of the inspection system 72 and the resist processing system 82, as described above.

A computer program product 59 is shown, which stores the computer program 58.

The photolithography apparatus 50 described with reference to Figure 2 has just one modular non-application-specific controller 55 / software 58 and robotic wafer loader 94 to replace four distinct tools 10,20,30,40 shown in Figure 1 .

Furthermore, the photolithography apparatus 50 described with reference to Figure 2 has a LED illumination source 66 instead of mercury arc lamp illumination source 16 for exposing wafers on the respective stepper system. The LED illumination source 66 has three switchable wavelengths (G-line/H-line/i-line). G, H, i-line wavelengths or any combination may be selected for the illumination.

The controller 55 uses software that is written to be non-application-specific, so it can control different photolithographic systems. In this example it controls:

- a machine vision system (MVS) pattern recognition system 92 which is used for the stepper system 62 alignment and for the inspection system 72;

- the LED power supply 66 in the exposure system for the stepper;

- process equipment for the coater 86 and developer 88; and - the universal robotic wafer loader system 94 for handling wafers for the systems, as shown by the connecting lines in Figure 2.

Embodiments have the advantage that the complete photolithography equipment line can be easily integrated into one piece of equipment. Embodiments also have the advantage of using LED for exposure on a stepper that can switch from G-line or H- line to i-line.

There is an advantage in system/equipment savings. In a conventional photolithography fab described with reference to Figure 1 the systems will use:

1 . Control ler/software - four in total 15, 25, 35, 45

2. Wafer-in indexers for each system - four in total 13, 23, 33, 43

3. Wafer-out Indexers for each system - four in total 14, 24, 34, 44

4. Alignment system 18

5. Inspection Cameras 26

Embodiments use one of each of:

1 . Control ler/software to replace the four shown in Figure 1 , 15, 25, 35, 45

2. Robotic loader 94 to replace eight wafer indexers 13, 23, 33, 43, 14, 24, 34, 44

3. Machine Vision System 92 to replace one alignment system 18 and one camera system 26

There is an advantage in equipment floor space savings:

In a normal photolithography fab the four systems described with reference to Figure 1 will typically use the following floor space:

• Stepper tool 10: 1 .5m x 1 ,5m

• Inspection tool 20: 1 .5m x 1 ,5m

• Coater tool 30: 1 .0m x 3.0m

• Developer tool 40: 1 .0m x 3.0m

The total for the four systems described with reference to Figure 1 (with required small space between each tool) is approximately 15m². An embodiment described with reference to Figure 1 uses one photolithography apparatus with the floor space of:

• photolithography apparatus:! .3m x 2.3m = 3m²

This is approximately 5 times less area than the conventional systems.

Further advantages of LEDs compared to mercury lamps are reduced cost and energy use. Mercury arc lamps combined with reflectors have an efficiency of approx. 2.5% in the 400-450nm spectral range. In an example, the usable optical radiation is approximately 30w. The mercury lamp is operated at (500 or 1000W).

In embodiments, the LED source provides up to 30w of optical radiation.

LED service life is highly dependent on the use case. LEDs should be switched off whenever no exposure is performed. Generally, 3000 - 5000 hours of exposure time can be expected.

There follows an example of how one would calculate total operating hours until a LED module needs replacement:

Exposure time per shot: 0.2sec.

Shots per wafer: 20.

Processed wafers per hour: 50.

Duty Cycle: (0.5s * 20 * 25) / 3600s = 250/3600 = 0.069 = 7%.

Service life: 3000h / 7% ~ 42000h.

If duty cycle is less then:

40000/24 days = 1759 days = 4.7 years.

4000/7% = 57000h = 2375 = 6.5 years.

With 5000 hours it’s 71400h/24 = 2976 days = 8 years.

Cost of LED modules is €6000, or approximately €1000/year. A mercury lamp costing €600 needs changed 6 x year = €3600/year.

Actual power used by LED is 0.5% of the power of mercury lamp, giving a saving of approximately 4.2 Mega watts/year

A mercury lamp uses 94% more power/exposure than LED. A mercury lamp uses 92% more watt/hours than LED. Apart from the above cost and energy savings of using LED lamps. Another very important point is the removal of Mercury from the environment. Mercury is a dangerous material and needs to be handled as such. Removing this material helps wafer tabs be more environmentally healthy.

Advantages of LED illumination on the process side are:

The LED illumination allows the exposure system to be switched from a standard GHI tool, to an i-line tool, i-line allows printing down to 0.6pm which the conventional tools cannot do (as line width is limited to 1 .0pm with G H I-line) . Normally wafer tabs would need to buy another i-line specific tool to run these processes.

A comparison of LED versus mercury lamp operation is given below.

Mercury:

1 . The mercury lamp is always on.

2. For alignment, the exposure shutter is closed and the green filter shutter is opened (to align the wafer without exposing)..

3. To expose the exposure shutter is opened and the energy dose time clock Is started (to measure the intensity/time)

4. When the desired exposure energy is reached the green shutter opens and the exposure shutter closes.

LED:

1 . For alignment the green LED is switched ON.

2. For exposure G/H/i-line (or any combination) is switched ON (while the green light is switched OFF). In the latter case, it is an advantage that there is no measuring of dose time required as the LED is merely switched on for the required energy.

It is apparent to one of ordinary skill in the art that the innovative method of the present invention is, at least in some embodiments, implemented by a computer programmed with code to configure and directly control the systems as described above. Moreover, the code necessary to program such computer can of course be stored in and/or read from any computer-readable medium, such as a compact disk (CD), a digital video disk (DVD), a flash memory storage device, a hard disk, a random access memory (RAM), or a read only memory (ROM), as well as numerous other computer-readable media not specifically mentioned in this application.

From the above description of the invention it is manifest that various techniques can be used for implementing the concepts of the present invention without departing from its scope. Moreover, while the invention has been described with specific reference to certain embodiments, a person of ordinary skill in the art would appreciate that changes can be made in form and detail without departing from the spirit and the scope of the invention. Thus, the described embodiments are to be considered in all respects as illustrative and not restrictive. It should also be understood that the invention is not limited to the particular embodiments described herein but is capable of many rearrangements, modifications, and substitutions without departing from the scope of the invention.

Claims

1 . A photolithography apparatus comprising:

- a controller;

- an exposure system; and

- an inspection system; and

- a resist processing system.

2. The photolithography apparatus of claim 1 further comprising the inspection system.

3. The photolithography apparatus of claim 1 or claim 2 further comprising the resist processing system.

4. The photolithography apparatus of any preceding claim wherein the exposure system comprises an LED illumination source configurable to emit G-line, H-line and/or i-line radiation and the controller is operable to configure and directly control the LED illumination source to select and cause the emission of G-line, H-line or i- line radiation.

5. The photolithography apparatus of any preceding claim wherein the wafer loader system comprises a pre-aligner and a carrier plate configured to receive wafers of a plurality of nominal diameters.

6. The photolithography apparatus of any preceding claim further comprising a machine vision system operable to function as a camera for an alignment system for the exposure system and as a camera for the inspection system.

7. The photolithography apparatus of any preceding claim wherein the resist processing system comprises a coater, an oven, and a developer and the processor is operable to configure and directly control the coater, oven, and developer.

8. The photolithography apparatus of any preceding claim wherein the wafer loader system comprises a wafer ID reader and the processor is operable to configure and directly control the exposure system based on readings from the wafer ID reader.

9. A computer program comprising computer readable instructions which, when run on suitable computer apparatus, cause the controller to configure and directly control the exposure system and the wafer loader system and at least one of the inspection system and the resist processing system, in accordance with of any of claims 1 to 8.

10. A computer program product comprising the computer program of claim 9.