EP2324690A1

EP2324690A1 - Pick/place head assembly

Info

Publication number: EP2324690A1
Application number: EP09788295A
Authority: EP
Inventors: Raymond Jacobus Wilhelmus Knaapen; Sander Christiaan Broers
Original assignee: Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
Current assignee: Nederlandse Organisatie voor Toegepast Natuurwetenschappelijk Onderzoek TNO
Priority date: 2008-09-01
Filing date: 2009-09-01
Publication date: 2011-05-25
Also published as: WO2010024679A1

Abstract

A pick/place head assembly comprising: a mounting head for connection to a transport robot; a plurality of pick/place elements, each pick/place element being mounted to the mounting head via a corresponding adjustment unit operable to adjust the position of the corresponding pick/place head within a plane, each pick/place element being actuatable to perform a pick or place motion along an axis that is perpendicular to the plane; wherein each adjustment unit is controllable by a control signal such that the position of the corresponding pick/place element can be individually adjusted for precision alignment.

Description

Pick/Place Head Assembly

The present invention relates to a pick/place head assembly intended for use in a pick-and-place machine. The present invention has particular, but not exclusive, application to the field of manufacturing three dimensional integrated circuits (3D ICs).

It is well known that pick-and-place machines are used to place a broad range of electronic components onto substrates, such as printed circuit boards or lead frames. It is also known that, in the interests of boosting throughput, to equip a pick-and-place machine with a pick/place head assembly having multiple pick/place elements such that a number of pick or place operations can be performed in parallel, an example of which is shown in US5575376.

Conventionally, the pitch between pick/place elements is set a priori and the placement alignment is carried out on the basis of one of the pick/place elements. Such an approach results in the other pick/place elements being placed with sufficient precision for applications requiring lower accuracy. However, in manufacturing 3D ICs of the die-to-wafer and die-to-die varieties in which through silicon vias (TSVs) are used to provide electrical interconnection between the dies in a stack, it is necessary to achieve high alignment accuracy. For this reason, hitherto, dies have generally been picked up one-by-one and placed one-by-one.

It is an object of the present invention to extend the parallelism achieved in applications requiring lower alignment accuracy to applications requiring higher alignment accuracy. With this in mind, according to a first aspect of the invention, the present invention may provide a pick/place head assembly comprising:

a mounting head for connection to a transport robot;

a plurality of pick/place elements, each pick/place element being mounted to the mounting head via a corresponding adjustment unit operable to adjust the position of the corresponding pick/place head within a plane, each pick/place element being actuatable to perform a pick or place motion along an axis that is perpendicular to said plane;

wherein each adjustment unit is controllable by a control signal such that the position of the corresponding pick/place element can be individually adjusted for precision alignment.

By making the position of each pick/place element individually adjustable under the control of a control signal, each pick/place element may be precisely aligned in an independent manner, thereby permitting parallelism and accuracy to be achieved.

According to a second aspect, the present invention may provide a method of stacking dies in the manufacture of three dimensional integrated circuits using a pick-and-place machine comprising a pick/place head assembly having a mounting head to which a plurality of pick/place elements are mounted, comprising:

with the pick/place elements carrying dies for stacking, moving the pick/place head assembly into a stationary position over a target substrate;

for each individual pick/place element, adjusting its position relative to the mounting head so as to achieve precision alignment with a destination stack on the target substrate; and

placing the die onto the destination stack.

Further aspects and preferred features of the invention are described in the following description and defined in the appended claims.

Exemplary embodiments of the invention are hereinafter described with reference to the accompanying drawings, in which:

Figure 1 shows a schematic view of a pick/place head assembly located at a pick position performing individual nozzle adjustment prior to the pick operation;

Figure 2 shows the head assembly during the pick operation;

Figure 3 shows the head assembly moved to a place position;

Figure 4 shows the head assembly performing individual nozzle adjustment prior to stacking;

Figure 5 shows the head assembly performing the stacking operation;

Figure 6 shows the head assembly being moved away after the stacking operation;

Figure 7 shows the construction of the head assembly according to a first embodiment of the invention in more schematic detail; and

Figure 8 shows the construction of the head assembly according to a second embodiment of the invention in more schematic detail. Figure 1 shows a pick/place head assembly 10 of a pick-and-place machine generally designated 1. The pick-and-place machine 1 comprises a controller 50 (depicted in Figures 7 and 8) which co-ordinates the overall operation of the machine 1, including the head assembly 10.

The pick/place head assembly 10 comprises a mounting or bond head 15 which is connected to a transport robot 12 by means of a connection part 13. An array of discrete adjustment units 20a-e are mounted to the underside of the mounting head 15 such that they occupy the same horizontal plane and are equally spaced from one another. To each adjustment unit 20a-e, a corresponding pick/place element 30a-e is mounted in a manner which allows its position on the adjustment unit to be adjusted in a horizontal plane within the bounds defined by the respective adjustment unit. The X- direction component of the positional adjustment within the horizontal plane is signified by the double-headed arrows X. The Y- direction component (into the plane of the paper) has not been labeled for diagrammatic simplicity. Each pick/place element 30a-e comprises a vacuum nozzle 31a-e which is mounted on an actuator 32a-e. The actuation of the actuator 32a-e performs a pick or place motion moving the nozzle 31a-e vertically between a retracted position and an extended position along a vertical axis indicated by the arrows Z.

Figure 7 shows in more schematic detail the construction of the head assembly in accordance with a first embodiment of the invention All the adjustment units 20a-e and the pick/place elements 30a-e are identical and as an example the leftmost element and unit are now described. For simplicity, the following description is limited to the positional adjustment of the pick/place element 30a in the X- direction. However, corresponding means (not shown) are used to achieve positional adjustment in the Y-direction. The adjustment unit 20a comprises a motor 21a, fixedly suspended from the underside of the mounting head 15, having an elongate, horizontally-oriented spindle 22a at its output shaft.

The pick/place element 30a comprises a base portion 33a having a threaded through-hole into which the spindle 22a is threaded. On activation of the motor 21a, the rotation of the spindle 22a causes the horizontal displacement of the pick/place element 30a along the spindle 22a. The adjustment unit 20a also comprises bearings 23a located between the base portion 33a and the underside of the mounting head 15.

The pick/place element 30a further comprises an encoder scale 34a formed on the uppermost surface of the base portion 33a. The encoder scale 34a operates in conjunction with an encoder 24a located on the underside of the mounting head 15. The encoder 24a provides a signal 25a indicative of the position of the pick/place element 30a along the spindle 22a. The encoder 24a may be an absolute position encoder or an incremental encoder. In other embodiments, the positions of the encoder 24a and the encoder scale 34 may be interchanged. The position of the pick/place element 30a is controlled by a control loop 41a which compares a target position signal 40a with the signal 25a to provide a positional error signal to a loop controller 42a that produces a control signal 43a for the motor 21a.

Associated with the pick/place element 30a is also a camera means 26a operable to ascertain, by visual inspection, the position of a die or die stack located below the pick/place element 30a. Based on the visual inspection, the camera means 26a calculates how the pick/place element 30a needs to be moved to achieve precision alignment, and translates that into a target position signal 40a suitable for the control loop 41a in order to achieve the requisite position adjustment. In this manner, the pick/place element 30a can be precision aligned with a die or die stack beneath it. The camera means 26 also provides a target position signal for Y-direction positional adjustment.

In other embodiments, the functionality of the loop controller 42a may be performed off the head assembly 10, for example, in the controller 50. Similarly, the camera means 26a may only capture image data, and the additional data processing functionality ascribed to it above may be performed off the head assembly 10, for example, in the controller 50.

The operation of the pick/place head assembly 10 is now described.

Figure 1 shows the head assembly 10 maneuvered into stationary pick position over a source wafer generally designated 45 which has been diced into dies.

Once in the pick position, each of the pick/place elements 30a- e are individually precision aligned to a corresponding die 45a-e by the mechanism described above. It will be noted that, in the example shown, in becoming so aligned, each of the pick/place elements 30a-e adopts a different relative position with respect to its own adjustment unit in order to achieve a suitable positioning of the nozzles 31a-e. Referring to Figure 2, the pick/place elements 30a-e are actuated to perform a pick operation. The pick/place elements 30a-e can be picked up sequentially or in parallel. Referring to Figure 3, the head assembly 10 is then moved by the transport robot 12 into a stationary place position over a target wafer generally designated 48. It will be noted that as shown the pick/place elements 30a-e are still positioned in the manner dictated for pick up. Referring to Figure 4, the pick/place elements 30a-e are adjusted a priori to the known nominal spacing requirements of the stacks on the target wafer 48. In other embodiments, this adjustment can take place on the way to the place position. Then, the pick/place elements 30a-e are individually precision aligned by the mechanism described above to a corresponding destination stack of dies 48a-e. Thereafter, placement as shown in Figure 5 takes place sequentially or in parallel. Finally, the head assembly 10 starts its return as shown in Figure 6 to the pick position.

A second embodiment of the head assembly 10 shown in Figure 8 differs from the first embodiment in that each adjustment unit 20a-e, instead of the motor and spindle arrangement, comprises an actuator 25a-e for adjusting the position of the corresponding pick/place element 30a-e. Similarly, only X- direction displacement is illustrated. Similar means are used to achieve displacement in the Y-direction. Each actuator 25a-e is identical and as an example the leftmost actuator 25a is now described. The actuator 25a comprises a stator part 26a, fixed to the mounting heading 15, and the pick/place element 30a comprises a translator part 27a of the actuator 25a projecting from its base portion 33a that extends along the axis X. The actuator parts 26a, 27a are arranged such that, upon actuation of the actuator 25a by a drive coil (not illustrated), the pick/place element 30a is displaced along the axis X. In other respects, notably the control of the adjustment units 20a-e, the second embodiment is the same as the first embodiment.

The illustrated preferred embodiments of the invention provide a pick/place head assembly 10 having multiple pick/place elements 30a-e which are precisely alignable in an individual and independent manner. As a result, the embodiments are able to operate with a high throughput and to high accuracy. The independent and free positional adjustability of the pick/place elements 30a-30e make the embodiments very flexible in use. For example, without change in hardware, they can handle a change in pitch of the source dies, a difference between the pitch of the source die and the inter-stack spacing on the target wafer, and irregular inter- stack spacing on the target wafer.

In other embodiments (not shown), the pick/place head assembly 10, the source wafer 45, and the target wafer 48 may be arranged in an orientation different to that shown. In other embodiments, the adjustment units 20a-e may also adjust the Z- direction offset position of the pick/place elements 30a-e.

Claims

1. A pick/place head assembly comprising:

a mounting head for connection to a transport robot;

a plurality of pick/place elements, each pick/place element being mounted to the mounting head via a corresponding adjustment unit operable to adjust the position of the corresponding pick/place head within a plane, each pick/place element being actuatable to perform a pick or place motion along an axis that is perpendicular to the plane;

2. An assembly as in claim 1, wherein a said adjustment unit comprises a motor, fixed to the mounting head, having a spindle at its output shaft that extends along a first axis within said plane, to which a said corresponding pick/place element is mounted for displacement along the spindle on activation of the motor.

3. An assembly as in claim 1, wherein a said adjustment unit comprises a stator part of an actuator, fixed to the mounting heading, and the corresponding pick/place element comprises a translator part of the actuator, the said adjustment unit being arranged such that upon actuation of the actuator the pick/place element is displaced along a first axis within said plane.

4. An assembly as in claims 2 or 3, wherein a said adjustment unit comprises a means for determining the position of the corresponding pick/place element along the first axis.

5. An assembly as in any preceding claim, further comprising, associated with each adjustment unit, a camera unit for capturing image data of a die to be picked or a destination stack of dies.

6. A pick-and-place machine comprising a pick/place head assembly as in claims 4 or 5, further comprising a control means, the control means including, for each adjustment unit, a positional control loop, responsive to a position signal from said determining means, to control the position of the corresponding pick/place element.

7. A pick-and-place machine comprising a pick/place head assembly as in claim 6, wherein the control means is further operable, for each adjustment unit individually, based on the image data from the associated camera unit, to set a target position for the positional control loop so as to achieve precision alignment of the corresponding pick/place element.

8. A method of stacking dies in the manufacture of three dimensional integrated circuits using a pick-and-place machine comprising a pick/place head assembly having a mounting head to which a plurality of pick/place elements are mounted, comprising:

for each individual pick/place element,

adjusting its position relative to the mounting head so as to achieve precision alignment with a destination stack on the target substrate; and

placing the die onto the destination stack.

9. A method as in claim 8, further comprising moving the pick/place head assembly into a stationary position over a source substrate; for each individual pick/place element, adjusting its position relative to the mounting head so as to achieve precision alignment with a die to be picked on the source substrate; and picking the die from the source substrate.