REAL TIME REGISTRATION IN LITHOGRAPHY SYSTEM

Abstract

A device for measuring reference points in real time during lithographic printing includes a light source providing an exposure beam; a light modulator modulating the exposure beam according to an exposure pattern; a measurement system configured to measure a position of a number of alignment marks previously arranged on a substrate; and an exposure optical system comprising a control unit. The exposure optical system delivers the modulated exposure beam as an image provided by the light modulator onto the substrate. The exposure system control unit is configured to calculate the orientation of the substrate based on the position of the alignment marks and control the delivering of the modulated exposure beam relative to the calculated orientation of the substrate.

Claims

1. A device for measuring reference points in real time during lithographic printing, comprising a light source providing an exposure beam; a light modulator modulating the exposure beam according to an exposure pattern; a measurement system configured to measure a position of a number of alignment marks previously arranged on a substrate; and an exposure optical system comprising a control unit, the exposure optical system delivering the modulated exposure beam as an image provided by the light modulator onto the substrate; wherein the exposure system control unit is configured to: calculate the orientation of the substrate based on the position of the alignment marks, and control the delivering of the modulated exposure beam relative to the calculated orientation of the substrate.

2. The device according to claim 1, wherein the XY position and rotation matrix for each alignment mark is calculated simultaneously to the exposure, and wherein the calculated position/rotation is used in the exposure system to control the positioning of the subsequent exposed images.

3. The device according to claim 2, wherein the exposure pattern is provided in stripes, and as each stripe is exposed, the position of alignment marks in the same stripe and/or the next stripe to be printed is measured.

4. The device according to claim 1, wherein the measurement system comprises a camera.

5. The device according to claim 4, wherein the camera system is arranged to use direct high data rate transfer directly from camera chip into a FPGA or processor for fast analysis and data transfer to a pattern calculation module in the exposure optical system control unit.

6. The device according to claim 1, wherein electrical connection pads on a die are used as alignment marks.

7. The device according to claim 1, wherein body or parts of the body of a die is used as alignment marks.

8. The device according to claim 1, where the measurement system and the exposure optical system have at least partially concurrent optical paths.

9. The device according to claim 4, wherein the camera's image area of interest is positioned close to and mechanically connected to the exposure optical system.

10. The device according to claim 4, wherein the measurement system defines the camera area(s) of interest to optimize fast camera data transfer.

11. The device according to claim 4, wherein the measurement system defines a special camera area of interest for autofocus laser light reflection detection similar to a line sensor, and utilizes the defined special camera area of interest for fast camera data transfer for autofocus calculation and autofocus regulation.

12. The device according to claim 1, wherein the light source comprises multiple light sources, with at least one wavelength.

13. The device according to claim 12, wherein the exposure optical system comprises a projection lens and the light sources are positioned and optically coupled through the projection lens.

14. The device according to claim 12, wherein the exposure optical system comprises a projection lens and the light sources are positioned in the bottom part of the exposure optical system, surrounding the projection lens.

15. A method measuring reference points in real time during lithographic printing comprising: modulating an exposure beam according to an exposure pattern; measuring a position of a number of alignment marks previously arranged on a substrate; delivering the modulated exposure beam as an image provided by the light modulator onto the substrate; calculating the orientation of the substrate based on the position of the alignment marks; and controlling the delivering of the modulated exposure beam relative to the calculated orientation of the substrate.

16. The method according to claim 15, further comprising: calculating the XY position and rotation matrix for each alignment mark simultaneously to the exposure, and using the calculated position/rotation in the exposure system to control the positioning of the subsequent exposed images.

17. The device according to claim 2, further comprising providing the exposure pattern in stripes, and as each stripe is exposed, measure the position of alignment marks in the same stripe and/or the next stripe to be printed.

18. The method according to claim 15, using direct high data rate transfer directly from the measurement to the calculation FPGA or processor for fast analysis and data transfer.

Description

[0034] The invention will now be described in more detail, and by reference to the accompanying figures.

[0035] FIG. 1 shows an example of an exposure system for direct imaging lithography.

[0036] FIG. 1a illustrates schematically various examples of applications of direct imaging lithography.

[0037] FIG. 1b-1c illustrate examples of components with high requirements for pattern accuracy.

[0038] FIG. 2a-2b illustrate examples of embedded dies.

[0039] FIG. 3-5 illustrate a typical process of advance packaging with embedded dies.

[0040] FIG. 6a-6b shows examples of wafer and panel comprising embedded dies.

[0041] FIG. 7-13 illustrate examples of configurations of the optical elements for exposure and camera capture of a device for direct imaging lithography.

[0042] FIG. 14a-14d shows details of different embodiments of optical elements for exposure and camera capture of a device for direct imaging lithography.

[0043] FIGS. 15a and 15b shows details of different embodiments of optical elements for exposure and camera capture of a device for direct imaging lithography.

[0044] FIG. 1 shows an example of an exposure system which comprises a light source 302 providing an exposure beam 306, a light modulator 301, 302 modulating the exposure beam 306 according to an exposure pattern, and an exposure optical system 303, 304, 308 delivering the modulated exposure beam as an image 311 provided by the light modulator onto a substrate 307. A measurement system 303, 304, 305, 308, 309 is incorporated in the exposure apparatus and is configured to measure a position of an alignment (fiducial) mark previously patterned on the substrate. The exposure optical system and the measurement system have at least partially concurrent optical paths in this embodiment.

[0045] In the following description, the term “photo head” will sometimes be used as a collective term comprising the optical elements of the exposure system.

[0046] The exposure system may further comprise a control unit (not shown) which is configured to calculate the orientation of the substrate based on the position of the alignment marks and control the delivery of the modulated exposure beam relative to the calculated orientation of the substrate. We will illustrate this in more detail below.

[0047] FIG. 1a illustrates various applications where there is need for smaller feature sizes in the patterning due to the constantly increasing demand for smaller devices. Due to this, there is a need for higher accuracy in the measurement of the alignment marks without increasing the time consumption of the process to any substantial extent.

[0048] FIG. 1b-1c illustrate examples of components with such high requirements for pattern accuracy. Typically, an embedded die with connection pads will have small pads/electrical connection points in the size range of 25-100 micrometer or less.

[0049] In order to optimize the space available for fine line patterning, it is desirable to optimize the usable space between pads on the dies ea. “the channel” Optimization of the available space requires high position accuracy in the application of the dies and pads onto the substrate. And further, for cost reasons, the number of redistribution layers (RDL) can be reduced if the “channel” is optimized.

[0050] Typical applications are a Fan Out Panel level packaging process FOPLP or Fan Out Wafer level packaging process FOWLP.

[0051] Examples of such application processes can be seen in FIGS. 2a-5.

[0052] In FIGS. 2b and 3 the first steps are illustrated. An established temporary base layer 20, such as a wafer is provided with an adhesive tape 21 or layer on top. Dies 22 are positioned and arranged onto the adhesive layer/tape 21 with connection pads towards the adhesive tape. Each die can for example be positioned with a “pick and place”-machine and this process will give some position and rotation error due to the accuracy limitations of such pick and place equipment where high speed and throughput are required.

[0053] Such dies are typically 1-10 mm square, and on a 300 mm round wafer or a 600 mm×600 mm panel you will be able to mount hundreds and thousands of such dies. FIG. 6 shows two examples of wafers with dies mounted onto them. FIG. 6a shows an example of Fan Out Wafer Level Packaging (FOWLP), while FIG. 6b shows an example of Fan Out Panel Level Packaging (FOPLP).

[0054] The dies are now over-molded with a compound 23, and in such molding process the dies might slightly move or rotate. Then the base layer and the adhesive tape/material 20, 21 are removed in a special process. The result is a compound layer 24 with the dies and the die pads/electrical connection points visible from one side.

[0055] To be able to optimize the pattern to be printed onto compound layer with dies, a registration/measurement of the dies' position and rotation is required. Such optimizing is typically required in a Fanout process, where the pads/electrical connection points are to be redistributed to a wider area so that it is possible to connect them to a solderable system with larger and wider distributed connection pads. Other cases can include to Fan out the connection points to the larger interconnecting systems (such as a substrate, PCB or RDL) such that the dies connection points are routed and connected to the other electrical components on the same substrate. In this way it is avoided the packaging process of such die, —embedded die.

[0056] For example, a registration/measurement accuracy of 1 um or better is required. In such systems one or more points on each die are measured to be able to measure and calculate position error and rotation, hence the number of measurements needed can get up to the 1.000-100.000 number range. Such an amount of measurements with high accuracy will challenge the throughout, as this is very time consuming with the presently used equipment, for example registration systems in DI machines and/or measuring machines.

[0057] A DI machine based on a system with light modulator (for example DLP, LCOS etc) will typically print the pattern in stripes, where each projector/photo head will print one or several stripes. There may also be arranged multiple photo heads to increase capacity/throughput of the machine. FIGS. 7-13 illustrates use of multiple photo heads and multiple registration cameras with different position configuration.

[0058] A DI machine, like Schmol's MDI TT Ultra using Visitech's LLS 2500 Photo Head or other machine with specifications that enables printing 2 μm line/space, will typically print 10-30 stripes per photo head depending on the configuration. Hence the photo head mechanical system will scan over the area to be printed several times.

[0059] By applying registration camera(s) to the projector mechanical system, and capture/register alignment marks/reference marks in real time, this can be applied to the real time pattern warping system in the photo head along with position/rotation calculations and data feed. The photo head can then print the calculated resulting pattern on the fly. FIG. 14a illustrates this process.

[0060] In the examples of FIG. 14a, 14d, the imaging optics and camera's optics are incorporated or arranged close to each other. The camera is here used as line sensor.

[0061] As each stripe is exposed, the system will measure the position of alignment marks in the same stripe and/or the next stripe to be printed. Simultaneously, ie. in real time, the XY position and rotation matrix for each alignment mark is calculated. The calculated position/rotation is then used by the exposure system to control the positioning of the subsequent exposed images.

[0062] The relative distance and scroll speed of the substrate, which is known by the system, can be used to determine image capture, position calculation, data transfer and image warping time window.

[0063] Further by analyzing given pattern and fiducial data, the camera area of interest can be determined with one or more areas of the camera image. This will reduce the number of camera pixels to capture, compared to the whole camera image, to be transferred and analyzed, such that the camera data transfer and the following calculation can be optimized for speed of data transfer to the calculation module.

[0064] Typically the camera measures the alignment marks in front of the projected pattern as illustrated in FIGS. 14a, 14d or on the next stripe to be printed (N+1, N+2 etc) as illustrated in the example of FIGS. 15a and 15b. The choice of embodiment may depend on the time needed to do the capture, calculations and coordinate data transfer and the positioning and warping while printing.

[0065] By applying a system as described herein, the problem with high time consumption of the high volume of high accuracy measurements in fine line lithography application can be drastically reduced.