KR20010091491A - Automatic parallel array type flip chip bonder - Google Patents

Abstract

PURPOSE: A flip chip bonder of an automatic particle alignment type is provided to adhere two semiconductor chips to each other by maintaining automatically parallelism of surfaces of the semiconductor chips. CONSTITUTION: An upper chip holder(4) is fixed to an upper supporter(2). A lower chip holder(5) is fixed to a lower supporter(7). An upper chip and a lower chip are adsorbed to the upper chip holder(4) and the lower chip holder(5), respectively. The upper supporter(2) is fixed to a frame(3) by a fixing device such as a clamp. A passing hole is formed in a center portion of the upper supporter(2). A perspective window is inserted into an upper portion of the upper chip holder(4). An airtight space is formed between the upper chip holder(4) and the perspective window. The airtight space is connected with the first vacuum hose(14) and the first vacuum valve(16). The upper chip is fixed to the upper chip holder(4) by a vacuum pump connected with the first vacuum hose(14). The lower supporter(7) includes a pressure chamber and a metal grating layer. An inner vacuum hose(6) is connected with a lower side hole of the lower chip holder(5). The inner vacuum hose(6) is connected with a lower vacuum absorption hole through the second vacuum hose(15) and the second vacuum valve(17). The lower supporter(7) is fixed on a location controller including three-axis linear mobile stage(9,10,11) and a rotary stage(8). The location controller is operated accurately by an external computer(20), a joystick(19), and a monitor(21).

Description

Automatic Parallel Array Flip Chip Bonder {AUTOMATIC PARALLEL ARRAY TYPE FLIP CHIP BONDER}

The present invention relates to an apparatus for arranging and joining surfaces of two semiconductor chips while maintaining precise parallelism. The present invention is useful for joining the surfaces of two articles to any other kind of article, but is particularly useful for aligning and joining the semiconductor IC chips while maintaining parallelism.

In the fabrication of integrated circuit devices, it is important to electrically connect the circuits patterned on the two chips to each other by precisely aligning and bonding the two chips. In general, in the bonding of two chips, an upper chip is called an upper chip, and an underlying chip is called a lower chip. In order to bond the upper chip and the lower chip to each other, a small lead, indium, or conductive epoxy is formed on the circuit of either chip or both chips. When the protrusions are formed only on one chip, only the conductive metal plate is formed in the pattern and bonded to the protrusions formed on the other chip. When protrusions are formed on both chips, the protrusions are bonded to each other. Therefore, it is important to precisely align the projections and projections formed on the chips or the projections and the metal plate for the bonding of the two chips. After the correct alignment between the top chip and the bottom chip is made, the two chips are usually joined by heat, pressure or ultrasonic vibrations.

Meanwhile, in order to bond the upper chip and the lower chip, the two chips are aligned as close as possible. To align the upper chip and the lower chip in the art, if the upper chip is transparent to visible light, the alignment is performed using a general optical microscope, but otherwise, another method is used for the alignment. For example, an infrared microscope may be used when the upper chip transmits infrared light instead of visible light. It also uses a device to align a small photodetector that can see the top and bottom chips simultaneously between two chips. At this time, the alignment is based on the projection formed on the upper chip and the lower chip or based on the cross-shaped pattern.

However, in order to successfully bond the upper chip and the lower chip in the art, there is a task that requires the bonding surface of the upper chip and the lower chip to be parallel in addition to the above-described alignment operation.

If the surface of the upper chip and the lower chip are not parallel, the distance between the projections varies from location to location, so that the small distance projections will join first, and even if the pressure is increased to further reduce the distance between the chips, the projections will not be joined. The problem arises. In addition, even if a large distance between chips is later bonded, in this case, the first bonded protrusion may be too depressed to damage the pressure-sensitive IC circuit. In this sense, keeping the upper chip and the lower chip parallel to each other is essential in the present technology.

Several methods have been used to maintain parallelism between the upper and lower chips. For example, a small photo detector is used to project a cross pattern onto the upper and lower chips, and then measure and adjust the parallelism by looking at the relative positions of the reflected images.

However, this method has a problem that it is very difficult to observe the cross pattern when the surface of the chip is uneven or the reflectivity is bad. In this case, the flat side of the chip is intentionally made, and the reflected cross pattern is used to adjust the parallelism. However, this is also an indirect method is likely to cause errors.

It is therefore an object of the present invention to solve the above problems and to provide an apparatus for aligning and bonding while automatically maintaining parallelism between chips when bonding semiconductor chips together.

To this end, an aspect of the present invention provides an upper chip holder for holding a semiconductor chip in a downward state, an upper vacuum suction means for holding the semiconductor chip by vacuum suction to the upper chip holder, and holding another semiconductor chip in an upward state. And a lower chip holder disposed to face the semiconductor chip held in the upper chip holder, lower vacuum suction means for holding the other semiconductor chip by vacuum suction to the lower chip holder, and a lower support holder for holding the lower chip holder. In the flip chip bonder of the automatic parallel arrangement method for bonding the semiconductor chip and the other semiconductor chip in parallel with each other, the lower support is a pressure chamber of the upper opening and the upper opening of the pressure chamber The other semiconductor chip is placed in an open state, and the other semiconductor chip is in an upward state. Chakdoen and the lower chip holder is fixed be provided a flip-chip bonder for automatic parallel array structure, including the thin membrane and for hermetically closing the pressure chamber, air injection means for injecting air in the pressure chamber.

1 is a schematic diagram of a flip chip bonder according to the present invention;

Figure 2 is an enlarged view of the upper and lower chip supports in the flip chip bonder of Figure 1;

Figure 3 is a chart of the results of testing the change in the height of the bonding projections in accordance with the bonding pressure.

<Explanation of symbols for the main parts of the drawings>

1: microscope / CCD camera

2: upper support

3: frame

4: upper chip holder

5: lower chip holder

6: internal vacuum hose

7: lower supporter

8: θrotating stage

9: x-shift stage

10: y-move stage

11: z-move stage

12: pressure gauge

13: pressure regulating valve

14: first vacuum hose

15: second vacuum hose

16: first vacuum valve

17: second vacuum valve

18: optical stage

19: joy stick

20: computer

21: monitor

22: pressure hose

23: upper chip

24: lower chip

25: metal diaphragm

26: pressure chamber

27: air inlet

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

The present invention is an apparatus for aligning and bonding while automatically maintaining parallelism between chips when bonding semiconductor chips.

1 and 2 illustrate a flip chip bonder according to the present invention.

As shown in FIG. 1, the flip chip bonder is fixed to the upper support 2, the upper chip holder 4 fixed to the upper support 2, the lower support 7, and the lower support 7. And a lower chip holder 5. The upper chip 23 and the lower chip 24 are respectively fixed to the upper chip holder 4 and the lower chip holder 5 by vacuum suction so as to face each other as shown in FIG.

Hereinafter, the upper supporter 2 and the lower supporter 7 will be described in detail with reference to FIGS. 1 and 2.

The upper support 2 is fixed to the frame 3 by fixing means (not shown) such as a clamp. In the center of the upper support 2 is formed a hole penetrating the upper and lower surfaces of the upper support (2). The upper chip holder 4 is fixed to the lower side of the hole formed in the upper support 2, and the viewing window 29 is fitted to the upper side thereof to form a closed space between the upper chip holder 4 and the viewing window 29. do. The upper chip holder 4 and the see-through window 29 may be made of a material transparent to visible light, preferably made of a sapphire disc transparent to infrared light. Therefore, when a visible light or an infrared microscope (or CCD camera) 1 is used when aligning the upper and lower chips, they can be aligned while observing protrusions or alignment patterns of the upper and lower chips.

The enclosed space formed in the hole of the upper support 2 by the upper chip holder 4 and the see-through window 29 is connected to the first vacuum hose 14 and the first through the through path 30 formed inside the support 2. It is in communication with the vacuum valve 16. In addition, the upper chip holder 4 is formed with a vacuum suction hole penetrating the upper and lower surfaces thereof, so that the upper chip 23 is applied to the vacuum suction applied by a vacuum pump (not shown) connected to the first vacuum hose 14. By the upper chip holder 4.

The lower support 7 comprises a pressure chamber 26 with an open top and a sheet metal diaphragm 25 for covering the open top of the pressure chamber 26. The pressure chamber 26 may preferably be cylindrical in shape. The air inlet 27 is formed in the wall surface of the pressure chamber 26. In addition, the center of the thin metal diaphragm 25 is open, and the lower chip holder 5 is fitted into the open center to be mounted on the lower support 7.

The lower chip holder 5 fixed to the lower support 7 is preferably a small cylindrical shape, and penetrates the upper and lower surfaces at the center thereof. An inner vacuum hose 6 is connected to the lower side hole of the lower chip holder 5, and the inner vacuum hose 6 is connected to the lower vacuum inlet 28 formed in the pressure chamber, which is the second vacuum hose 15. And a second vacuum valve 17 to a vacuum pump (not shown). Therefore, when fixing the lower chip 24 to the lower chip holder 5, the lower chip 24 is placed in the upper side hole of the lower chip holder 5, the vacuum pump for fixing the lower chip 24 It is fixed by vacuum suction by operating (not shown).

The entire lower support 7 is precisely machined and assembled so that air does not leak out. That is, in the present invention, when the lower chip holder 5 on which the lower chip 24 is mounted covers the pressure chamber 26 in a state where the lower chip holder 5 is mounted on the thin metal diaphragm 25, the pressure chamber 26 should be closed tightly. do. Accordingly, when compressed air is introduced into the pressure chamber 26 through the air inlet 27, the metal diaphragm 25 becomes convex upward by this pressure, and the lower chip holder 5 also rises up accordingly. The force to lift the holder up is controlled by the air pressure.

The lower support 7 is preferably fixed on a position controller of three axis linear movement stages 9, 10, 11, more preferably a three axis linear movement stage 9, 10, 11 and one rotating stage. (8) is fixed on the set of position controllers. That is, the three-axis linear moving stages 9, 10, and 11 may move in three axial directions, respectively, in the x-axis direction, the y-axis direction, and the z-axis direction, and all of them are connected to the external computer 20 by connecting a DC motor. The joystick 19 and the monitor 21 attached thereto can be precisely adjusted within 1 μm. In addition, a DC motor is also connected to the θ angular rotation stage 8 in which the rotation angle is adjusted in a direction parallel to the horizontal, so that the angle can be precisely adjusted with the computer 20 and the joystick 19. The lower support 7 and the position controller are located on the optical stage 18 as shown in FIG.

The upper chip 23 and the lower chip 24 are formed with a projection pattern made of fine lead, indium, or epoxy made by a method such as thermal deposition and etching. Therefore, if two facing semiconductors are pressed against each other in the state where the protrusions on the upper chip and the lower chip abut each other, the two semiconductor chips are joined by the bonding of these protrusions.

Hereinafter, a process of aligning and bonding the upper chip 23 and the lower chip 24 by using the flip chip bonder of the present invention will be described.

First, the upper chip 23 and the lower chip 24 are respectively sucked and fixed in vacuum. The upper support 2 is placed on the frame 3, and the upper support 2 is adjusted to the upper chip 23 and the lower chip 24 at about the same position, and then fixed to the frame 3 with a clamp. The lower support 7 is raised upward (z direction) to access the upper and lower chips 23 and 24 within a few tens of micrometers. At this time, in adjusting the position of the upper chip and the lower chip, it is preferable to use a position adjuster. These are aligned while observing the projections or alignment patterns of the upper and lower chips with a visible or infrared microscope (1). Then raise the lower support (7) a little more so that the projections slightly touch. Then, the pressure regulating valve 13 is opened to apply pressure to the lower support 7 through the pressure hose 22 and the air inlet 27. At this time, the pressure applied to the inside of the lower support 7 is measured by the pressure gauge 12 as shown in FIG. The lower chip 24 fixed to the lower chip holder 5 is joined by the upper chip 23 by being forced upward by air pressure. After bonding, the vacuum applied to the lower chip holder 5 is cut off and air is supplied, and then the pressure inside the lower support 7 is switched to normal pressure to complete the bonding operation.

Hereinafter, a description will be given of the principle that these chips automatically maintain parallel positions when joining the upper chip 23 and the lower chip 24.

First, assume that the top and bottom chips are not parallel at first. In this case, the projections where the distance between the two chips is small will touch first and will be resisted from being pushed up further. On the other hand, the projections of the places where the distance between the chips is not yet reached, so that the projections are not raised so much that the projections are lifted up and this part is raised and the projections are touched. After this, all the protrusions come into contact with each other and the pressure of the lower support 7 increases, so that all the protrusions receive the same force and the joint is made.

As described above, it is because of the thin metal diaphragm 25 that the upper and lower chips are bonded while maintaining parallelism. That is, when pressure is applied from the outside, a uniform pressure is applied to all parts of the metal diaphragm 25, and thus a uniform force is applied to the holder 5 and the lower chip 24 placed thereon. The upper and lower chips remain parallel.

(Example)

The inventors of the present application fabricated a flip chip bonder according to the basic concept shown in FIG. 2 using a metal plate made of a thin copper plate having a thickness of 0.2 mm as a metal plate, and then performed a bonding test between chips. The chips were all silicon wafers, on top of which were two-dimensional array elements with a total of 16,384 indium protrusions, 128 rows horizontally and 128 rows vertically. The size of the indium protrusions was 15 μm in both width and length, and the height was 6 μm. The interval between the protrusions was 40 μm. The chips were secured to the flip chip bonder of the present invention and aligned in the manner described in the detailed description of the invention and then contacted with very little force and the final bonding was done by applying air pressure. At this time, the bonding was performed while changing the pressure to 0.05 atm, 0.4 atm, 0.8 atm, 1.2 atm, and 1.7 atm.

After bonding, the spacing between the chips was measured at various locations. As shown in the upper part of Fig. 3, the measurement was performed by selecting one row (position A in the upper part of Fig. 3) and another row (B from the top of Fig. 3) positioned about 6 mm apart from the row. Experiments were conducted by selecting five locations at each line about 1.4 mm from either location (1A, 1B). Thus, 1A to 5A are positions positioned in one line of the indium protrusions, and 1B to 5B are protrusion positions located about 6 mm away from 1A to 5A.

In Fig. 3, the relationship between the spacing of the protrusions on the chip and the chip holder pressure is shown. When the pressure is small at 0.05 atm, the chip spacing in row A and row B is very different, and therefore, the projections in row A may not be in contact even when the projections in row B are in contact. However, it can be seen that as the pressure is increased above 0.8 atm, the bonding starts and the chip spacing in the A and B rows decreases to less than 9 μm, which is almost the same, and the two chips are automatically equilibrated during assembly.

The above results show that the self balancing flip chip bonder according to the present invention works well.

Bonding semiconductor chips using the apparatus of the present invention can achieve the effect of aligning and bonding while automatically maintaining parallelism between the chips.

In the present invention, the term "upper" or "lower" is only used to explain the present invention more easily, and should not be taken as limiting the present invention. That is, components such as the upper support, the lower support, etc. of the present invention are not fixed to the position as described in the detailed description of the present invention, and the position may be changed or may be positioned to face the side.

Thus, while the invention has been described with reference to the structures described herein, it is not limited to the details described above, and the scope of the invention includes modifications or changes that fall within the scope of the claims and the following claims for improvement. Should be taken into account.

Claims (6)

An upper chip holder for holding the semiconductor chip in a downward state, an upper vacuum suction means for holding the semiconductor chip by vacuum suction to the upper chip holder, an upper support for holding the upper chip holder, and another semiconductor chip in an upward state A lower chip holder arranged to hold and face a semiconductor chip held in the upper chip holder, lower vacuum suction means for vacuum-sucking the other semiconductor chip onto the lower chip holder, and for holding the lower chip holder. In the flip-chip bonder of the automatic parallel arrangement method comprising a lower support, for bonding the semiconductor chip and another semiconductor chip in parallel with each other, The lower support is, A pressure chamber with an open top, A thin diaphragm which is disposed to cover the upper opening of the pressure chamber, the center of which is open, and in which the lower chip holder, in which the other semiconductor chip is attached in an upward state, is fixed to hermetically close the pressure chamber; And an air injection means for injecting air into the pressure chamber. The flip chip bonder according to claim 1, wherein the upper vacuum suction means includes a vacuum suction hole penetrating the upper and lower surfaces of the upper chip holder. The viewing window of claim 1, wherein a space is formed in an upper portion of the upper chip holder, and the viewing window allows the upper chip holder to be viewed from above the upper support to observe the alignment of the semiconductor chip with the other semiconductor chip. Flip chip bonder characterized in that the arrangement. The vacuum suction hole of claim 1, wherein the lower vacuum suction means includes a vacuum suction hole penetrating the upper and lower surfaces of the lower chip holder, a tube connected to the vacuum suction hole and provided in the pressure chamber, and a vacuum suction hole penetrating the lower supporter. Flip chip bonder comprising a. The flip chip bonder according to any one of claims 1 to 4, further comprising a three-axis linear movement stage for linearly moving the lower support. 6. The flip chip bonder of claim 5 further comprising a rotating stage for pivoting the lower support.