HK1230787A - Method for mounting semiconductors provided with bumps on substrate locations of a substrate - Google Patents

Description

Method for mounting a semiconductor provided with bumps on a substrate positioning of a substrate

Technical Field

The present invention relates to a method for mounting a semiconductor chip provided with bumps as a flip chip on a substrate orientation (location) of a substrate.

Disclosure of Invention

The invention is based on the object of developing a method for mounting a semiconductor chip as a flip chip on a substrate, which method allows on the one hand a very high placement accuracy and on the other hand the highest possible throughput.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and together with the detailed description, serve to explain the principles and implementations of the invention. The figures are schematic and not drawn to scale. In the drawings:

figure 1 schematically shows a side view of an apparatus for mounting a bumped semiconductor chip as a flip chip,

FIG. 2 shows the camera support in a top view, an

Figure 3 shows a pixel coordinate system and a machine coordinate system.

Detailed Description

Fig. 1 schematically shows a side view of a device for mounting a semiconductor chip 2 provided with bumps 1 as a flip chip 3, which device is set up for carrying out the method according to the invention. The apparatus comprises a wafer stage 4 for providing semiconductor chips 2, a flip-chip apparatus 5 with a pick-up head 6, a first transport system 7 with a transport head 8, a second transport system 9 with a bonding head 10, a transport system (not shown) for supplying and providing substrates 11 on a support 12, a device 13 for wetting the semiconductor chips with flux, a first camera 14 and a second camera 15. The device 13 comprises: a camera support 16; a plate 17, the plate 17 having a cavity 18, the matrix of the cavity 18 being transparent; and a flux container 19 opened downward. The position (position) of the bonding head 10 is described by machine coordinates. The apparatus is controlled by a control device not shown.

The first transport system 7 is set up to move the transport head 8 in at least two spatial directions. The second transport system 9 is set up to move the bonding head 10 in three spatial directions.

In another apparatus, which is also suitable for carrying out the method according to the invention, there is no wafer stage 4 and flip-chip apparatus 5 with pick-up head 6, but instead a feed device (also called a feeder) directly supplies the semiconductor chips 2 as flip-chips 3. In this apparatus, the element shown with reference numeral 4 in fig. 1 represents a feeding device.

The camera support 16 is arranged in a fixed manner on the device and comprises a base 20 and at least two side walls 21, the first camera 14 being fastened to the base 20. The plate 17 is detachably mounted on the camera support 16. Fig. 2 shows the camera support 16 in a top view. The camera support 16 comprises a first optical marker 22 and optionally also at least one further optical marker 23. The camera support 16 is formed in a mechanically rigid manner as follows: the first camera 14 and the optical marker 22 and optionally the optical marker 23 are in a rigid geometric relationship with respect to each other such that the position and orientation of the pixel coordinate system assigned to the image of the first camera 14 is in a fixed relationship (i.e. provided that it is not changeable in this case) with respect to the position of the optical marker 22 and optionally the optical marker 23.

Preferably, the optical marks 22 and optionally the optical marks 23 are arranged in a direction extending perpendicular to the surface of the support 12 for the substrate 11, at a height substantially equal to the substrate positioning height. This provides the following advantages: when the second camera 15 records an image of the optical mark 22 and the optional optical mark 23 or an image of a substrate positioning or an image of a substrate mark of a recording substrate, the bonding head 10 is located at substantially the same height. This means that it is not necessary to raise the bonding head 10 to a different height in order to bring the object to be photographed to the focus plane of the second camera 15.

The pixel coordinates of the flip chip 3 are determined from the image of the flip chip 3 recorded by the first camera 14 and the pixel coordinates of the flip chip 3 are converted into the machine coordinates of the bonding head 10 by means of the first geometry data. The first geometric data includes the position of the first optical marker 22 and a vector a having a fixed value (u, v) indicating the direction and distance of the first optical marker 22 relative to a reference point of the pixel coordinate system of the first camera 14. The first geometry data further comprises a fixed angle Ψ describing a twist between the pixel coordinate system of the first camera 14 and the machine coordinate system of the bond head 10. If more than one optical marker is present, the first geometric data includes the position of each additional optical marker and an associated vector having a fixed value indicating the direction and distance of the additional optical marker relative to a reference point of the pixel coordinate system of the first camera 14.

Fig. 3 schematically shows a machine coordinate system MS in combination with head 10, a pixel coordinate system PS of first camera 14, first optical marker 22, vector a, and angle Ψ. The values (u, v) of the vector a are numbers in the machine coordinate system MS.

As will be explained in more detail below, in the method according to the invention the flip chip 3 is placed in the cavity 18 with the bumps 1 of the flip chip 3 immersed in the fluxing agent, the image is recorded with the first camera 14, and after the wetting cycle has expired, the flip chip 3 is removed from the cavity 18 and mounted on the substrate 11. During this stage the cavity 18 is in a fixed position above the first camera 14 and the field of view of the first camera 14 is directed to the base of the cavity 18 so that its image shows the bottom side of the flip chip 3 with the bumps 1.

In the first embodiment, the flux container 19 is arranged in a fixed manner. In this case, the device 13 comprises a drive for the reciprocating movement of the plate 17. The plate 17 moves to the following extent: the cavity 18 is filled with flux, the cavity 18 being located below the flux container 19 or on the opposite side of the flux container 19, and then the plate 17 is moved back again so that the cavity 18 is located at the aforementioned position above the first camera 14.

In the second embodiment, the plate 17 is arranged in a fixed manner, with the cavity 18 located above the first camera 14. In this case, the device 13 includes a drive for moving the flux container 19 from one side of the cavity 18 to the opposite side of the cavity 18. The flux container 19 is slid over the plate 17 and the cavity 18 is filled with flux.

The second camera 15 is fastened to the bonding head 10. The optical axis of the camera 15 extends parallel to the clamping axis of the bonding head 10. The second camera 15 is mechanically fastened to the bonding head 10 in the following manner: the orientation of the pixel coordinate system assigned to the image of the second camera 15 is in a fixed geometrical relationship to the clamping axis of the bonding head 10. The pixel coordinates of the substrate positioning determined by means of the at least one image of the substrate positioning or the marks on the substrate recorded by the second camera 14 are converted into machine coordinates of the bond head 10 by means of the second geometry data.

The second geometry data includes a vector B having a value (x, y) indicating the direction and distance of the fiducial of the pixel coordinate system of the second camera 15 relative to the fiducial of the machine coordinate system of the bond head 10. The second geometric data further includes an angleThe angle describes the twist of the two coordinate systems.

The first and second geometry data further include a scaling factor that enables the values in the pixel coordinate system of the respective camera to be converted to values in the machine coordinate system of the bond head 10. The first and second geometric data are determined in a calibration phase, wherein the calibration phase is performed before the installation phase. To increase the long-term stability of the device and method, the calibration phase may be performed at different points in time.

The described embodiments of the device enable to carry out the method according to the invention for mounting a semiconductor chip as a flip chip on a substrate. The method according to the invention comprises the aforementioned calibration phase and mounting phase of an aspect in which the first and second geometrical data are determined, the following steps being performed for each semiconductor chip in the mounting phase:

or: providing the semiconductor chip 2 at a predetermined position with a wafer stage 4;

removing the supplied semiconductor chip 2 with the pick-up head 6 of the flip device 5, and twisting the semiconductor chip 2 by 180 ° to supply the semiconductor chip 2 as a flip chip 3;

or: providing the semiconductor chip 2 as a flip chip with a feeding device;

receiving the flip chip 3 from the pick-up head 6 or the feeding device with the delivery head 8;

filling the cavity 18 with flux, the cavity 18 being arranged in the plate 17 and being formed by a transparent substrate, wherein the plate 17 is arranged in a fixed manner or is moved after filling the cavity 18, such that the cavity 18 is located above the first camera 14 in both cases;

placing the flip-chip 3 in the cavity 18 with the bumps 1 facing the matrix of the cavity 18;

recording an image of the flip chip 3 with the first camera 14 and determining the actual position of the flip chip 3 with respect to the machine coordinate system of the bonding head 10 based on the image and the first geometric data;

removing the flip-chip 3 from the cavity 18 by means of the bond head 10;

the actual position of the substrate location with respect to the machine coordinate system of the bond head 10 is determined by,

or by:

the bonding head 10 is moved to a position above the substrate positioning, which is in the field of view of the second camera 15,

at least one image is recorded by means of a second camera 15, and

calculating an actual position of the substrate positioning based on the substrate positioning of the at least one image and the second geometric data;

or by:

calculating an actual position of the substrate positioning by means of actual positions of at least two substrate marks, wherein the actual position of each of the at least two substrate marks is determined separately after supplying a new substrate 11 to the support 12 by:

the bonding head 10 is moved to a position above the substrate 11, in which the substrate mark is in the field of view of the second camera 15,

recording an image with the second camera 15, and

determining the actual position of the substrate mark by means of the image and the second geometric data; and is

Calculating a position to which the bonding head 10 will reach based on the determined actual position of the flip chip 3 and the determined actual position of the substrate positioning; and is

The bonding head 10 is moved to the calculated position and the flip chip 3 is placed on the substrate positioning.

Assembling the apparatus with the delivery head 8 and the bonding head 10, wherein the delivery head 8 receives the flip chip 3 from the pick-up head 6 or the feeding device and places said chip in the cavity 18, the bonding head 10 removes the flip chip 3 from the cavity 18 and places said chip on the substrate 11, allows to increase the throughput of the apparatus, since the delivery head 8 and the bonding head 10 can operate substantially simultaneously, i.e. in parallel. Control means are established to control the movement of the transport head 8 and the bonding head 10 so that the two heads move at least partially simultaneously without colliding with each other. With regard to the highest possible throughput of the apparatus, the control means are in particular programmed to control the sequence of the various steps of the method so that, once the bonding head 10 has removed the next flip-chip 3 to be mounted from the cavity 18, the transport head 8 places the next subsequent flip-chip 3 into the cavity 18 as quickly as possible, based on the duration of the various process steps.

Fig. 1 shows the apparatus at a point in time at which the pick-up head 6 of the flip-chip apparatus 5 has taken the semiconductor chip 2 from the wafer stage 4, the flip chip 3 has been placed in the cavity 18, and the bonding head 10 carries the flip chip 3 wetted with the flux to the substrate 11.

The image of the flip chip 3 recorded by the first camera 14 can be used to check, in addition to determining the actual position of the flip chip 3, whether all bumps 1 are present and/or correctly wetted. In addition to this, the first camera 14 can record an image after the other flip-chip 3, the image processing software can evaluate the image and check whether all bumps 1 have been correctly wetted, and upon this occurrence can issue a message that the bonding head 10 should immediately remove the flip-chip 3 from the cavity 18 and place it on the substrate positioning.

If the angle of view of the second camera 15 is relatively small such that the entire substrate positioning is not suitable for an image, it is advantageous to move the bonding head 10 to a different position and record an image at each position that contains a portion of the substrate positioning. The position and orientation of the substrate location is then determined based on these images.

In a first production mode, a position of a substrate positioning of the flip chip to be positioned is determined based on at least one image of the substrate positioning. In a second production mode, the position of the new substrate is determined once after it has been supplied on the basis of the substrate marking and the respective target position of the flip chip is then calculated with the aid of the geometrical material data. Such an application is "wafer level packaging" (WLB), where the substrate is a wafer with plastic cast thereon. The wafer does not contain any position marks where the individual substrates are positioned, but contains substrate marks attached near the edge of the wafer.

In order to exclude positioning errors of the flip-chip 3 on the substrate positioning caused by temperature changes, the position of the first optical mark 22 is determined in a calibration phase and updated at one or more predetermined points in time by:

moving the bond head 10 to a position in which the first optical marker 22 is in the field of view of the second camera 15;

recording the image with the second camera 15;

determining the position of the first optical marker 22 based on the image and the second geometric data; and is

The determined position is stored as the new position of the first optical mark 22.

When the cavity 18 of the plate 17 is in a position above the first camera 14, if the optical markers are covered by the plate 17, the method further comprises moving the plate 17 to a position in which the optical markers 22, 23 are exposed before the positions of the optical markers 22, 23 are updated.

Thus, the present invention makes use of the following findings: the one or more optical markers attached to the camera support 16, on which the first camera 14 is fixed, are sufficient to reduce the effect of variations between the pixel coordinate system of the first camera 14, the pixel coordinate system of the second camera 15 and the machine coordinate system of the bond head 10 on positioning the flip chip 3 on the substrate to a level that meets current requirements.

If one or more further optical markers are present, for example optical marker 23, the position of the further optical marker is determined in a similar manner in the calibration phase and updated at the aforementioned point in time.

Advantageously, two pick-and-place systems are provided, each of which comprises a flip-chip device 5 with a pick-up head 6, a first transport system 7 with a transport head 8, a second transport system 9 with a bonding head 10, means 13 for wetting the flip-chips with flux, and a first camera 14 and a second camera 15, which collect the semiconductor chips 2 from the wafer stage 4 in an alternating manner and mount the semiconductor chips 2 as flip-chips 3 on a substrate 11 provided on a support 12 in an alternating manner.

The method according to the invention offers the following advantages:

the same positioning of placing the flip chip in the cavity as the positioning of removing the flip chip from the cavity ensures that the flux distribution in the cavity does not change as the cavity moves from the first to the second positioning and that the flip chip does not shift in the cavity, which may have a negative effect on wetting the bumps of the flip chip or may lead to a reduction in the throughput of the device.

The duration of immersion of the bumps of the flip chip in the flux can be adjusted independently of the other processing steps. This is important for obtaining an optimal wetting of the bumps of the flip chip on the one hand and for obtaining the highest possible throughput on the other hand.

The assembly with the delivery head and the coupling head and the simultaneous parallel operation of the delivery head and the coupling head increase the throughput of the apparatus.

While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein. Accordingly, the invention is not to be restricted except in the spirit of the appended claims and their equivalents.

Claims (4)

1. Method for mounting semiconductor chips (2) provided with bumps (1) on a substrate positioning of a substrate (11), wherein first and second geometrical data are determined in a calibration phase and the following steps are performed for each semiconductor chip (2) in a mounting phase:

or: providing the semiconductor chip (2) at a predetermined position with a wafer stage (4);

removing the semiconductor chip (2) provided with a pick-up head (6) of a flip-chip device (5) and twisting the semiconductor chip (2) by 180 ° to provide the semiconductor chip (2) as a flip-chip (3);

or: -providing said semiconductor chip (2) as a flip chip (3) with a feeding device;

-receiving the flip chip (3) from the pick-up head (6) or the feeding device with a transport head (8);

filling a cavity (18) with flux, the cavity (18) being arranged in a plate (17) and being formed by a transparent substrate, wherein the plate (17) is arranged in a stationary manner or is moved after filling the cavity (18) such that the cavity (18) is in both cases located above a first camera (14), the first camera (14) being arranged in a stationary manner;

-placing the flip-chip (3) in the cavity (18), with the substrate of the bump (1) facing the cavity (18) placed;

-recording an image of the flip chip (3) with the first camera (14) and determining the actual position of the flip chip (3) with respect to the machine coordinate system of the bonding head (10) based on the image and the first geometrical data;

removing the flip chip (3) from the cavity (18) with the bond head (10);

determining the actual position of the substrate positioning with respect to the machine coordinate system of the bonding head (10) by means of a second camera (15) fastened to the bonding head (10) in such a way that

Or by:

moving the bonding head (10) to a position above the substrate positioning in which the substrate positioning is in the field of view of the second camera (15),

recording at least one image with said second camera (15), and

calculating an actual position of the substrate position based on the position of the substrate position in the at least one image and the second geometric data;

or by:

calculating an actual position of the substrate positioning by means of actual positions of at least two substrate marks, wherein the actual position of each of the at least two substrate marks is determined after supplying a new substrate (11) to the support (12) by:

moving the bonding head (10) to a position above the substrate in which the substrate mark is in the field of view of the second camera (15),

recording an image with said second camera (15), and

determining the actual position of the substrate marker by means of the image and the second geometric data; and is

Calculating a position to be reached by the bonding head (10) based on the determined actual position of the flip chip (3) and the determined actual position of the substrate positioning; and is

Moving the bonding head (10) to the calculated position and placing the flip chip (3) on the substrate positioning, wherein

The transport head (8) and the bonding head (10) are moved at least partially simultaneously.

2. The method according to claim 1, wherein the first geometrical data comprise a position of a first optical marker (22) and a first fixed vector indicating a direction of the first optical marker (22) to and a distance from a reference point of a pixel coordinate system of the first camera (14), and wherein the position of the first optical marker (22) is updated at least at one predetermined point in time by:

-moving the bonding head (10) to a position where the first optical marker (22) is in the field of view of the second camera (15);

recording an image with the second camera (15);

determining a position of the first optical marker (22) based on the image and the second geometric data; and is

Storing the determined position as a new position of the first optical mark (22).

3. The method according to claim 2, wherein the first geometrical data comprises a position of at least one further optical marker (23) and a further fixed vector indicating a direction of the further optical marker to the reference point of the pixel coordinate system of the first camera (14) and a distance from the reference point of the pixel coordinate system of the first camera (14), and wherein the position of the further optical marker (23) is updated by:

-moving the bonding head (10) to a position where the further optical marker (23) is in the field of view of the second camera (15);

recording an image with the second camera (15);

determining the position of the further optical marker (23) based on the image and the second geometric data; and is

Storing the determined position as a new position of the further optical marker (23).

4. A method according to claim 2 or 3, wherein the optical marker is covered by the plate (17) when the cavity (18) of the plate (17) is in a position above the first camera (14), the method further comprising moving the plate (17) to a position where the optical marker (22, 23) is exposed before the position of the optical marker (22, 23) is updated.