JPH054813B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a wire bonding method for semiconductor devices, and particularly to a wire bonding method of so-called wedge bonding, which has directionality in wire bonding.

(Prior Art) Conventionally, the bonding method described above has been proposed, for example, in Japanese Patent Publication No. 61-20134.

To explain this based on FIG. 4, by rotating the semiconductor pellet 1 which is a sample and the package member 3,
The wire 5 is bonded by reciprocating the wedge tool between the bonding pad 2 and the bonding lead 4 of the package member 3. In this case, the straight line in the loop direction connecting the bonding pad 2 and the bonding lead 4 and the direction of movement of the wedge tool are need to match. Therefore, it is possible to perform bonding by rotating the sample so that the loop direction straight line, which includes the positional deviation of the semiconductor pellet 1 and the positional deviation of the package member 3, coincides with the advancing direction of the wedge tool, that is, the amplitude direction of the US transducer. It's tight. The angle θ _N between this straight line in the loop direction and the advancing direction of the wedge tool is determined by the amount of deviation from the standard coordinates (pre-memorized coordinates) of Δx and Δy by recognizing the two positions of the semiconductor pellet using a pattern recognition device. The amount of deviation in each direction of X, Y, and θ is calculated, and the position of each bonding pad 2 and bonding lead 4 is calculated based on the calculated amount of deviation, and the X-Y coordinate axis in the bonding loop direction is calculated. It is determined by the slope from .

Next, by rotating the sample by the angle _θN , the direction of the loop in which bonding is to be performed is adjusted in the direction of movement of the wedge tool (Y of the X-Y coordinates).
At the same time, the amount of movement in the X-Y direction due to the rotation is calculated, and the wedge tool is moved over the rotated bonding pad 2 to perform bonding.

Then, sequentially, rotation and XY movement → bonding to bonding pad 2 → XY movement → bonding to bonding lead 4 → rotation and XY movement → bonding to the next bonding pad 2,
In this way, bonding was performed one after another.

In this case, due to the accuracy of the bonding position, the pitch B of the bonding pad 2 is generally 150 μm,
Its width C is required to be about 100 μm, and if bonding pads 2 are arranged on the four sides of semiconductor pellet 1 in a 200-pin gate array, the size A of semiconductor pellet 1 is A = 1/4 x 200 (pin) x 0.15. The size was approximately (mm) = 7.5 (mm).

(Problems to be Solved by the Invention) Recently, as the number of pins in semiconductor products has increased, the need for high-density bonding has increased, and unless the pitch of bonding pads is reduced, the size of semiconductor pellets will become larger than necessary. Costs increase.
Furthermore, even when attempting to reduce the cost by reducing the size of the semiconductor pellet, there are similar limitations depending on the size of the area around the bonding pad.

Therefore, a major obstacle to reducing the bonding pad pitch and bonding pad size is the accuracy of the bonding position. The bonded portion protrudes from the pad or bonding lead, resulting in poor bonding and short wiring.

However, in the above conventional example, the causes of positional deviation are the same factors as in general bonding equipment, such as pattern recognition errors and the accuracy of the There are factors specific to the equipment, and errors increase as the sample size increases. Furthermore,
Since the X-Y coordinates after rotation had to be calculated, there was a problem in that calculation errors were added.

In view of the above-mentioned problems, the present invention improves the accuracy of bonding positions in wedge bonding, increases bonding density, provides finer semiconductor devices, reduces the area of semiconductor pellets and semiconductor devices, and, in particular, improves the accuracy of bonding positions in wedge bonding. The aim is to reduce the cost of LSIs and gate arrays.

[Structure of the invention]

(Means and effects for solving the problem) In order to improve the accuracy of the bonding position described above, the present invention rotates the sample so that the loop direction is in the direction of the wedge tool, in order to eliminate the error factor in the rotation direction, which is a major obstacle. After almost matching, positional deviation is detected and bonding is performed, and the bonding pad and bonding lead are arranged so that the loop directions are parallel to each other.
It is also possible to detect rotation and positional deviation after rotation for each group.

In addition, by aligning the loop direction parallel to one side of the semiconductor pellet, the size of the bonding pad can be further reduced in the width direction of the wire, and the shape of the bonding pad can be changed from a square to a shape in the width direction of the wire. The bonding pad can be made into a reduced rectangular shape, and the pitch of the bonding pad can be easily reduced.

(Example) FIGS. 1 to 3 show an example of the present invention,
A bonding pad 2 is formed around the semiconductor pellet 1, and a bonding lead 4 is formed on the package member 3, and the bonding pad 2 and the bonding lead 4 are connected to a bonding wire 5.
and is sealed by a package sealing member 6.

The bonded portion of the wire 5 is crushed in the vertical direction by the ultrasonic waves, and this crushed shape is about 2:1 in the length direction and width direction of the wire 5, and the wire 5 uses 26Φμm. Sometimes 80μm vs. 40μm
100μm vs. 60μm, which is suitable for this shape.
The bonding pad 2 has a rectangular size (width C=60 μm). In addition, the pitch B of the bonding pad 2 is 80 μm, so that the size A of the semiconductor pellet 1 when the bonding pads 2 on the four sides of the semiconductor pellet 1 are lined up in a 200-pin gate array is A = 1/4. ×200 (pin) × 0.08 (mm) = 4 (mm). The reason why the size can be reduced compared to the conventional one is because of the high positional accuracy as described below.

That is, the semiconductor pellet 1 and the package member 3
The positional deviation and its detection correction will be explained based on FIG. 1, which is a schematic plan view.

Normally, the position L' of the package member 3 deviates from the center _xy of the memorized bonding position coordinates _l1 to _l4 , and the center _L has an inclination of _θL in the θ direction. Furthermore, the position P' of the semiconductor pellet 1 is the center of the bonding position coordinates p ₁ to _{p 4} which are also memorized.
A deviation occurs from _xy , and the center _p has an inclination of θ _p in the θ direction.

The center O _xy of rotating the samples 1 and 5 at both positions P' and L' is the bonding coordinate p ₁ to _{p 4} , l ₁
Coordinate correction M is performed in advance so that it approximately coincides with the center of ~ _l4 . In this embodiment, even if there is a small error in this correction, the bonding position will not shift, but the distance between the center of the camera (not shown) for pattern recognition and the center of the wedge tool is
As is the case with the prior art, it is necessary to match the bonding position accurately and store it in memory, as this may cause a shift in the bonding position.

Then, pattern recognition is performed at two positions, position P' of semiconductor pellet 1 and position L' of package member 3, and bonding position p ₁ ' of bonding pad 2 and position L' of bonding pad 2 are determined from the amount of deviation at the four positions. Calculate the positional deviations Δx _p , Δy _p and Δx _L , Δy _L in the XY direction of bonding position l ₁ ' of bonding lead 4,
The angle θ ₃ formed by the line segment (loop direction) connecting p ₃ ′ and l ₃ ′ with the reference coordinate axis XY is determined.

Next, the positions P' and L' of both samples are rotated by the above angle θ ₃ , and when rotated by θ ₃ , the target position is again calculated from the memorized position coordinates for pattern recognition. The camera is moved in the X-Y direction, and pattern recognition is performed at two locations on the target after the θ ₃ rotation described above. Adding the amount of positional deviation after θ ₃ rotations to the distance between the camera center and wedge tool center, move the wedge tool to 1 of bonding pad 2.
to the bonding position P ₁ ′, and then sequentially press p ₁ ′ and
Wire bonding is performed between l ₁ ′, p ₂ ′ and l ₂ ′...p ₄ ′ and l ₄ ′, but the θ rotation is fixed during that time.

In the illustrated θ ₃ and θ ₄ , the line segments p ₃ ′ to p ₄ ′ and l ₃ ′ to _{l 4} ′ are equal,
As can be seen from the difference between p ₃ ′ to _{l 3} ′ and p ₄ ′ to _{l 4} ′, they do not match, but the accuracy of semiconductor pellet bonding to the package member by the automatic die bonding equipment is at a certain level, and the die bonding error (θ _p +θ _L ) is well within about ±2°, and the error between θ ₃ and θ ₄ is an extremely small angle. Therefore, in this embodiment, where the area of the bonding lead 4 has a certain margin, there is no actual harm in bonding in the direction of the wedge tool, ignoring the deviation of the lead coordinates.

Note that in this embodiment, the bonding lead 4 is
However, if there is not enough space for the bonding lead, the wire may be stretched in a loop direction that is different from the direction of the wedge tool without ignoring the deviation of the lead coordinates, but since the angle is small, there is no real harm.

In this example, samples 1 and 3 are divided into four groups, which are rotated by 90 degrees, and pattern recognition and bonding within the group are performed after each rotation. Since the loop directions are also parallel, the four groups are combined into two groups, and one half of the group is bonded from the bonding pad to the bonding lead, and the other half is bonded from the bonding lead to the bonding pad. ,
It is also possible to cut the time for pattern recognition and sample rotation in half. In this case, productivity can be improved and the rotation range of the sample can be improved.
A small rotation of 90° + α is sufficient, which is advantageous when the sample is equipped with a heater for heating the sample.

The number of pattern recognitions may be increased or decreased depending on mechanical positioning accuracy, manufacturing accuracy on the package member side, etc. For example, pattern recognition may be performed only on the semiconductor pellet side, or pattern recognition may be performed at two locations each on the semiconductor pellet side or at one location each on the pellet side. It's good as well.

Further, in this embodiment, the connection is made by wire bonding, but the present invention can also be applied to connection between a bonding pad and a bonding lead using a ribbon, or a connection between a bonding pad and a bonding pad using a tape.

〔Effect of the invention〕

Since the present invention has the above-mentioned configuration, it is possible to eliminate the problems caused by rotation of the sample, such as backlash of the rotation mechanism, errors in rotational position detection, errors in correcting the coordinate center by determining the center of rotation, errors in electrical positioning,
It is possible to achieve bonding with high positional accuracy by eliminating various errors such as calculation errors in determining the rotated position of coordinates, and this effect is particularly noticeable for large samples (semiconductor devices) with a large rotation radius. appear.

In this way, by improving the positional accuracy, it is possible to reduce the size of the periphery of the bonding pad of a semiconductor product, and it is also possible to reduce costs by reducing the size of the semiconductor pellet and to make the package smaller.

Note that the reduction in the width direction of the bonding pad caused by connecting it parallel to one side of the semiconductor pellet is an advantage that nail head bonding (ball bonding) does not have, and is an advantage of wedge bonding. If the wires were rotated for each wire as shown in the figure, this advantage could not be taken advantage of due to a decrease in accuracy, but the present invention has the effect that it is possible to make full use of this advantage.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention,
FIG. 1 is a plan view schematically showing the state of correction of positional deviation between the semiconductor pellet and the package member, and FIG.
The figure is a plan view showing the semiconductor device after bonding.
FIG. 3 is a sectional view, and FIG. 4 is a view corresponding to FIG. 2, showing a conventional example. DESCRIPTION OF SYMBOLS 1... Semiconductor pellet, 2... Bonding pad, 3... Package member, 4... Bonding lead, 5... Wire.

Claims (1)

[Claims] 1. In a wire bonding method in which a package member and a semiconductor pellet are rotated, the connection position between the package member and the semiconductor pellet is aligned in the direction of a bonding tool, and bonding is performed using a wire, the direction of the loop to be bonded and the reference coordinate axis are determined. The package member and the semiconductor pellet are rotated by θ based on this first information, and then the position of at least the semiconductor pellet in the X, Y, and θ directions is detected again, and the
A wire bonding method characterized by correcting positional information in the direction to obtain second information, and bonding the wire by moving a bonding tool from a first bonding position to a second bonding position based on the second information. . 2. Divide the bonding leads of the package member and the bonding pads of the semiconductor pellet into groups in which the wire connection directions are parallel or approximately parallel, perform a correction rotation in the θ direction for each group, and then 2. The wire bonding method according to claim 1, further comprising detecting a position of the wire and bonding each group based on this position information.