JPS6026298B2 - bonding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bonding apparatus, and in particular, in the assembly of microelectronic devices such as semiconductor integrated circuits, a plurality of electrodes and external leads on a semiconductor integrated circuit element (hereinafter referred to as a chip) are bonded with gold. The present invention relates to bonding equipment that connects wires, aluminum wires, etc.

In the semiconductor integrated circuit industry, labor costs have recently skyrocketed, and operations that require manual labor have become important problems that must be solved.

In particular, labor saving in the so-called bonding process that connects chip electrodes and external leads has been attracting a lot of attention.

Wire bonding equipment (hereinafter referred to as bonder), which is still the mainstream in this bonding process, uses microcomputers, etc. to replace the traditional manual work by simply positioning the first starting point and then automatically performing the bonding process. It is common to use an image sensor made of a semiconductor element instead of the human eye to automatically detect the amount of deviation between the chip and the lead side, and that can be unmanned like the bonder mentioned above. It came to a boil. In the former case, these automatic bonders are equipped with a spotlight that indicates the position of the bonding tool, and the operator uses this to position the starting point each time, thereby detecting the amount of deviation from the specified position in the x, y, and 8 directions. ,
Based on this, calculations are made using a correction calculation formula, and the rest can be bonded correctly automatically.In the latter case, for example, the position of the chip is recognized each time by scanning an image sensor, and this is processed by the graphic processing unit. Usually, the bonding can be done automatically by performing arithmetic processing at the step. All of these devices generally include a correction calculation section capable of performing somewhat complex calculations inside or outside the device.

In the case of thermocompression bonding (hereinafter referred to as NTC) in these automatic bonders, automation has progressed without any accuracy problems in actual bonding because there is no rotation mechanism, but in ultrasonic bonding (hereinafter referred to as US bonding) Unlike NTC bonding, since a rotating element is involved, if the mechanical rotation center does not match the calculation center used in the correction calculation formula, as will be explained later, no matter how accurately the chip position deviation can be detected, the actual Since the pad to be bonded has a 100 to 120 mm corner and 4 mm, it does not fit well with the bonding tool, resulting in the problem of so-called bonding position shift on the pad. This is N.T.
This was a major factor in the delay in automation of the US bonder compared to the C bonder. In order to solve this problem, one of the objects of the present invention is to easily find out '0' during the mechanical rotation in order to make the mechanical rotation center coincide with the calculation center.

Another object of the present invention is to easily determine the mechanical rotation center and then
It is an object of the present invention to provide an automatic bonding device whose bonding accuracy is not much different from that of NTC by aligning its rotation center with the calculation center. According to the present invention, in a bonding apparatus that performs wire bonding to a semiconductor chip on a rotating body, there is provided a means for detecting the distance between the calculated position and the actual position of the chip, and a means for detecting the distance between the calculated position and the actual position of the chip, and A bonding apparatus is obtained which is characterized in that a center of rotation is calculated and an initial correction formula is further corrected based on this center of rotation.

In particular, according to the present invention, in a bonding device that includes a rotating element for connecting a semiconductor integrated circuit chip and an external lead, a bonding operation is performed on an arbitrary chip, and the amount of deviation between an actual bonding pad and a bonding tool is measured. An automatic bonding device for semiconductor integrated circuits is obtained, which is characterized in that it derives the mechanical center of rotation of the device with respect to the arithmetic reference by measuring it multiple times and having the arithmetic device perform back calculations based on the measurements. That is, in the case of a general automatic bonder as described above, the actual mechanical rotation center and the calculation center (the ideal center, and the mechanical rotation center does not deviate from each other) are shown.

(hereinafter referred to as the ideal center), if you position and start the tool as usual, the tool will be located at the location based on the output value from the conventional correction calculation formula based on the ideal center. Since the bonding pad of the semiconductor chip is moved by the actual mechanical center, the position of this pad and the position of the above-mentioned ring do not correspond. This discrepancy can be determined by using a manipulator, etc. (the ponder is generally equipped with a fine movement mechanism that can be manually moved in the X and Y directions) to determine the position of the tool. By manually moving the spot indicating the actual pad onto the actual pad, the amount of deviation can be measured. That is, the deviation between the ideal center and the actual mechanical center of rotation cannot be directly measured. Therefore, in the present invention, the deviation between the tool position and the pad position caused by this deviation is measured, the deviation of the rotation center is converted from this, and this deviation of the rotation center is calculated using the above correction calculation formula. In this method, a new correction calculation formula is created by introducing the correction calculation formula, and the tool is operated using this new correction calculation formula. In this way, the movement of the tool includes the deviation of the actual center of rotation, so that the position of the pad of the chip and the position of the tool can be matched. Note that this operation may be performed, for example, at the beginning of the day's work using a monitoring chip for the positional relationship between the pad and the tool at several locations, and the average of the results may be calculated to establish the correction calculation formula for that day. Next, the present invention will be explained in detail using the drawings.

Since US bonding is a typical bonder having a rotation mechanism, it will be explained below. Figure 1 shows a schematic side view of the US bonder, but the difference from the NTC bonder is that the NTC bonding tool can move freely (non-directionally) in front, back, left and right relative to the operator;
In the case of bonding, the tool can only move in the wire direction (back and forth) (currently it is mainstream to apply US in the front and back direction), so in order to thoroughly bond all the pads of the chip, it is necessary to move the pedestal on which the chip is placed. You have to rotate the other side. The head side to which the bonding tool 1 is attached in Fig. 1 has a drive motor that moves in the x-y directions like the NTC bonder.

On the other hand, the pedestal 2 on which the IC is mounted has a drive motor 3 in its lower part. Here, we will discuss the mechanical rotation center at issue and the ideal center used in correction calculations. In Fig. 1, the rotational center line 5 of the pedestal 2 and the ideal center line for determining the position of the tool, that is, the center line 4 used for calculation.
should match in an ideal case, and the central processing unit (CPU) calculates according to the calculation formula based on the common center line on both the tool 1 side and the pedestal 2 side, and one pulse of the calculation output signal Correct bonding is possible with an accuracy of 5 to 10 mm. This is based on an ideal center, so there is no bonding misalignment that would occur in the so-called pad. On the other hand, in reality, the mechanical center of rotation 5 on the pedestal 2 side is not clearly visible, and it is impossible to align the two center lines 4 and 5 just by mechanically setting it. close. Conventionally, calculations were made assuming that the center of the pedestal 2 was on the ideal center line 4, and the output was output to each motor on the tool side and the pedestal side, but in reality, the center of rotation 5 on the pedestal side was calculated. is shifted from the ideal center 4 mentioned above. Therefore, the tool moves according to the result calculated based on the ideal center line 4, i.e. the center of calculation, and is located at a predetermined location, but the pad is rotated by the actual center of rotation 5. There will be a difference in the positions of the two.
The larger the chip size, the more this deviation will increase. For example, in the case of a chip with 21 pads and 22 pins (5.77 x 4.26 side), the pad dimensions are 120 mounds, the lead width is 400 rms (sufficiently wide), and the pads near the maximum of 70 rms. If you consider the positioning error, other mechanical total errors, etc., it is clear that it cannot be used in practice.
Therefore, the present invention seeks to provide a method for easily bringing this mechanical rotation center as close to the calculation center as possible. In explaining the present invention, it is necessary to start with the correction calculation method used in this US bonder, so that will be explained below.

Figure 2 is an explanatory diagram for deriving correction calculations for correct bonding even if the chip mount is misaligned, and shows the situation when positioning is performed using the spot 6 etc. as reference while looking at the microscope 7 in Figure 1. It shows. Since this correction calculation is only a calculation, it is assumed that the pedestal 5 shown in FIG. 1 does not exist and that the center lines 4 and 5 are coincident. In Fig. 2, reference number 8 is the center of the actual chip when only the rotational direction is adjusted, 9 is the regular chip position without mounting misalignment, 1 river is the actual chip position,
11 shows the chip position when only the rotational direction is adjusted. Also, 12 is the regular n-th pad coordinate (xn
, enemy), 13 is the n-th pad coordinate of the chip 11 (Yanagi', Hada') when only the rotation is matched, and 14 is n in the normal case.
No. lead coordinates (xLn, yLn), 15 represents the n-th lead coordinate (kari n'"yLn') when only the rotation is combined, that is, when the chip comes to 11. And 16 and 17 represent the n-th lead coordinates (kari n'"yLn') when only the rotation is combined. (the amount of deviation from the normal position when only the rotation is combined) is yo.In this case, the following formula holds true for the pad side.The following formula holds true for the lead side.Mountain n'=A
・cos(8-a.

) However, since the tool only operates in one direction, that is, in the y direction, all the bonding positions on the pad and lead sides must be parallel to the y axis.

Therefore, the angle 8n (18 in FIG. 2) for doing so is as follows. 8n=nen-, empty earth rainbow …………
t3'yn'-yLn' Then, during actual bonding, the above an will be output to the motor 3 of the pedestal 2, and on the other hand, the value output to the X-Y motor on the tool 1 side will be Xn.
, Yn (pad side), XLn, and YLn (lead side), the general formula for the output value is as follows.

However, as n changes (depending on the position of the pad and lead), + and 1 also change.

The correction calculation formula has been determined as described above, and now we will explain how to find the mechanical center according to the present invention.

In Fig. 3, reference numeral 19 is initially assumed to be the center of mechanical rotation and calculation center, that is, the ideal center, and the starting point of 21 is aligned by regular positioning, and when the start point is started, the correction calculation is completed. As the output on the n-th pad side, (Xn, Yn) is obtained from the equation {4', and the tool moves to point 22. However, if the mechanical rotation center is actually at 20, that is, the difference between the rotation center 20 and the calculation center, that is, the ideal center 19, is shifted by 8 in the x and y directions. For example, the actual nth pad is at 23, whereas the tool is at 22, so the difference between pads 22 and 23 is
If no, Yno, for the nth pad, this difference x ratio,
Bonding will be performed with the position shifted by Yno.
Here, as mentioned above, the output value obtained with 19 as the center of calculation is m
~t5}, but if the actual center of calculation, that is, the ideal center, is assumed to be 20, '1l' in the previous equation can be replaced with the following equation. Therefore, using formulas m~■, we finally set the calculation center, that is, the ideal center 20, Xn・2o, Yn
・2.

is as shown in the following formula. Here, (Xn, Yn, Yo) is different from 4-, so we added 20, that is, '41', which is a coordinate system with center 19, and '7} is a coordinate system with center 20. be.

Therefore, in Fig. 3, the tool is at position 22, the actual pad is at position 23, and the spot indicating the position of the tool is illuminating 22, so move the tool from 22 to onto pad 23 using a manipulator. be able to. As mentioned above, this moving distance is the difference between 22 and 23, that is, X ~, Y
Since ~, the following relationship holds true. To match the coordinate system on the right, Q and 8 were added to the left side.

Also, the X ratio and Y~ can be easily determined by setting an electric micro or counter in advance as described above. Therefore'
7', ■Xn+Xn from the formula.

10Q Ni (blood + 80 tame) Xn- (knock 18 10 pine) xm
...■Yn+Yn.

10 B ni (blood + Q + reason) Xm + (skin 180 y.

)xn...[IQHowever, m=sina
Let n, n=coson. It is clear that this will hold true. Therefore, from ■×(n-1) and 00×m, Q=(n-1) {戊n+Xnji○n+xoh+blood+y
o) Mountain} (n-1 a 10 m 20 m {.

n10YnQ) Kishi Kiseiken Tokiwa - (Go m + Earth) n}
‐‐‐‐‐‐‐‐‐‐‐‐‐(11) Similarly, B is 8=enemy -1) {〇n+Yn.

)-〇n+xo) 川-(19)nri-1￥1m2m
{〆n+xn.

)−(xn+x.h+0n+y.)m}
…………(12) (n-1) 20m2
Then, Q and B can be found.

In the manner described above, the differences Q and B between the calculation center, that is, the ideal center, and the mechanical rotation center are determined, but this work is easy to perform with an actual bonder.

That is, it is possible to easily program m to equations (12) by designing software. If the bonder is equipped with, for example, a changeover switch for setting the center of rotation, the operator first turns on this switch before starting work for the day. Next, set any sample IC on the pedestal, position it as usual, and start. For example, if you set an arbitrary pad to stop at number 2, the actual tool and pad will naturally differ by some amount (X2.o, Y2.o), so
By aligning this with pad No. 2 using the manipulator and pressing the switch called centering calculation etc., rotational centering will be completed (Q, 8 has been calculated and stored in the bonder's memory). Become). Q, 8 is (11),
(12) When we start the actual work, [61
, {71 is calculated, and the actual point 23 of the pad, that is, (Xn.2o, Yn.base) is output, making it possible to perform correct bonding. In the above example, we stopped at pad No. 2 and issued Q and B, but it is possible to use any pad, so if necessary, this operation can be performed using several pads, that is, Q.・・・・・・・・・・・・Qn and 3.・・・・・・
・・・・・・・・・8n is calculated, and the arithmetic mean 3(Q, 10.., .., ..Qn) and 3(8, .., ..
．． ．． ．． ．． 、． ．． 8n) as Q and P, the operator's positioning errors are averaged out, which increases the accuracy of rotation centering.

With the above-described method, in the ponder adopting the present invention, it has been difficult to match (find) the mechanical rotation center and the calculation center, that is, the ideal center, but with simple operation, it can be done accurately in a short time. Now I can ask for it.

Therefore, it contributes to improved yield and workability of the US bonder, and has the advantage of lowering IC manufacturing costs. The above can be summarized as follows.

In the conventional arithmetic unit, only formulas [11th to 5th] were used.

That is, pad position 13 (formula '11) and lead position 15 (formula [21]) shown in FIG. 2 are rotated by 8n according to formula [3'] so that they are parallel to the y-axis direction. It was calculated that the pads and leads were located at the positions shown in Equation 4 and Equation No. 4. In other words, the calculation was performed assuming that the actual center of the pedestal was not shifted. In Figure 3, it was calculated that the pad at position 21 was moved to position 22. This position 22 is the position calculated by formula (2), and the position of the lead above it is the position calculated by formula (5). Therefore, the tool will be located at this calculated location. However, the actual mechanical center of the pedestal does not coincide with the ideal center, but is offset by Q,8 as shown in FIG. Therefore, the actual pad is not located at location 22. This center shift cannot be directly measured.

In the present invention, the actual pad position 23 and the calculated position 22 are first measured. As mentioned above, the tool is located at position 22, which is calculated assuming that the centers are ideally aligned, and the spot is placed directly below this tool, so position 23 and position 22 are Misalignment×
~, Y ratio can be easily measured. Next, this X ratio and Y~ are introduced into equations (11) and (12), and the center shift Q, 8 is calculated by the calculation unit of the present invention. Next, this Q,8 is expressed as '6',
Introducing this formula, the calculating section of the present invention calculates the actual position of the pad when the mechanical center of the rotary table is deviated.
If the bonder is moved based on this formula '7}, the tool will be located at (Xn.2o, Yn.2o). That is, the position of the tool coincides with the actual position of the pad when the mechanical center of the rotary table is shifted. Normally, the position of the mechanical center of rotation does not always change. Therefore, for example, by performing the above operations using a monitor wafer at the beginning of a day's work, tools can be reliably positioned on the pads and leads during that day's work.

[Brief explanation of the drawing]

Figure 1 is a schematic side view of a general US bonder, Figure 2 is a schematic diagram for explaining correction calculations, and Figure 3 is a diagram for determining the mechanical rotation center based on an embodiment of the present invention. An explanatory diagram of
1... (bonding) tool, 2... (IC) pedestal,
3... Rotating motor, 4... Calculation center, 5...
...Rotation center, 6...Spot, 7...Microscope, 8...Actual chip center, 9...
・Regular chip position, 10...actual chip position, 11...chip position with matching rotation direction,
12... Regular n pad, 13...
N pad with matching direction of rotation, 14... Regular n lead, 15... N lead with matching rotation direction, 16, 17... Displacement after rotation, 18 ...y
Angle to make it parallel to the axis, 19, 20...Calculation center and machine center, 21-23...Start pad and 19
, 20 is the center position of the pad. Multi-figure hair 2 figure 3

Claims (1)

[Claims] 1 A bonding tool that performs ultrasonic bonding,
It has a rotary table on which a semiconductor element is placed, and a correction calculation calculation unit, and the correction calculation calculation unit calculates the deviation value of the semiconductor element from the normal position of the bonding pad and the relative relationship of the lead with respect to the bonding pad. It has a function that calculates and rotates the bonding pad and lead so that they are positioned on a straight line in a predetermined direction, and positions the bonding tool at a predetermined location based on the calculation results. In a bonding apparatus that rotates the rotary table by a predetermined angle, the position of the bonding tool based on the calculation and the It has a detection means for detecting the amount of deviation from the actual position of the bonding pad, and the correction calculation calculation unit calculates the deviation value of the two centers by introducing the amount of deviation, and calculates the deviation value of the two centers. It has a function that calculates the actual bonding pad position of the semiconductor element to be placed on the rotary table by calculating including the deviation value, and based on this result, the bonding tool is placed in the same place as the actual bonding pad. A bonding device characterized by being able to be positioned at.