JPS6057226B2 - How to align semiconductor elements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for positioning a semiconductor element, and particularly to a method for positioning a semiconductor element when a protective film is coated on the semiconductor element.

2. Description of the Related Art In the manufacturing process of semiconductor devices, such as memory devices, a protective film is deposited on the surface of a wafer and this protective film is patterned for each chip in order to maintain the quality and characteristics of the semiconductor device.

Although such a protective film has the advantage of extending the life of the chip, a new problem has arisen in the relationship between the outer edge of the protective film and the recognition pattern for measurement when performing measurements on wafers. [Prior Art] The above-mentioned wafer measurement will be briefly explained with reference to a measuring apparatus shown in a schematic plan view in FIG.

This measurement apparatus consists of a wafer chamber 1, a laser measurement chamber 2, a probe card measurement chamber 3, and a control panel 4. The wafer 11 to be measured (FIG. 2) is mounted on the rotor 5
The sheets are taken out one by one and carried by a belt 6 onto a chuck 7 located in a laser measurement chamber, and when the measurement described later is completed, they are stored in a rotor 5' at the lower side as seen in the figure. When the wafer 11 is positioned on the chuck 7 with its facets 12 correctly aligned as shown by solid lines 12 in FIG.
As shown in the figure, there is no problem if they are arranged in alignment with the X-axis direction of the running line in the left-right direction, but there is inevitably a slight misalignment of the fins as shown in an exaggerated manner by the dotted line 12' in the figure.

This positional shift is expressed as an angle θ, and such alignment is generally referred to as θ alignment. When the angle .theta. slips, the chuck 7 rotates in the direction shown by the arrow in FIG. 2 so that the facet 12' is at the position of the facet 12 shown by the solid line. As such, the chuck 7 is rotatable as shown by the curved arrow in FIG. A capacitive sensor (not shown) is used to measure the θ deviation, and a circle 13 is shown in Fig. 2.
Scanning the periphery of the wafer and measuring the thickness and area (size) of the wafer as shown in FIG. When the position is correct from the beginning or after θ alignment, the platform 10 on which the chuck 7 is mounted moves along the X-axis to the left when viewed on the rail 8 in the X-axis direction as shown in FIG. It will stop at the correct position.

For the sake of simplicity, the chuck 7 in the laser measurement chamber 2 is shown in FIG. 1 without the stand 10, and the state in which the wafer 11 is mounted on the chuck 7 is shown in cross section in FIG. The above operations and the operations described below are performed according to instructions from the control panel 4. When the table 10 stops at the position shown in FIG. 1, the chuck moves upward as shown by the arrow in FIG. , 15 and measurements are taken. By the way, the probe card 14 is attached to a machine (not shown), and the needle 15 should originally contact the pads of each chip of the wafer 11 which have been θ-aligned in a correct alignment relationship, but the reproducibility of the attachment of the probe card 14 is poor. Because of this, the needle 15 often does not align correctly with the pad. In this case, since the machine to which the probe card 14 is attached is fixed, the table 10 is moved in the X and Y directions shown in FIG. 1, and mechanical and electrical correction (initial settings). Such initial settings are made for the chip at the center of the wafer 11 and the four chips located at the periphery of the wafer. After making such corrections in the x and y directions, the correction values are stored in memory, and the wafers from the second wafer. When measuring, it is fed back. Returning to the first wafer 11, after the initial settings described above, all chips on the wafer 11 are
4. Make the necessary measurements using the needle 15. Therefore, 1
0 is Y direction rail 9 and X direction! The chuck 7 moves for each chip in the Y direction and the X direction along the direction rail 8.
makes a vertical movement (movement in the Z direction) shown by the arrow in FIG.
Thus, when measuring wafers in the manufacture of semiconductor devices, θ alignment of the wafer and correction in the X, Y, and Z directions have important significance. To explain the θ alignment in a little more detail with reference to FIG. separated by 21.

A semiconductor substrate, such as a silicon substrate, is exposed at the scribe line 21, and the wafer is cut along the scribe line to provide individual chips 20. In order to adjust θ, in the laser room 2,
After the measurement by the capacitive sensor, a fifth step is performed to determine whether the facet line 12 is correctly positioned.
For example, the spot diameter as shown exaggeratedly in Figure a is 15 [
A laser beam of [μm] is applied to the chip and the reflection is observed.

Figure b is a cross-sectional view taken along line B-B in figure a. When the laser beam spot 16 hits the leftmost position in figure a, for example, aluminum wiring or an insulating film is present there, so the laser beam is emitted. As shown in the left part of part b, the light is diffusely reflected and does not return to the laser light measuring instrument. This state is defined as high (H). For example 5 to the right of spot 16
If the tip is moved by [μm], the H state will be obtained as long as it is in contact with tip a. However, when the spot 16 hits the scribe line 21, the semiconductor substrate is exposed there, and since the surface of this substrate has a mirror finish, the laser beam is reflected as shown in E and returns to the laser beam measuring instrument. come. This state is called low L. To summarize the above, when the laser beam is moved from a certain position on the chip 20 in the It is confirmed that it is correct. When L appears, the laser spot 16 is moved in the Y direction to see if the L state continues. Thus, the scribe line 21 functions as a recognition pattern when measuring a wafer. Suppose that the facet line 12 is tilted.

At that time, the boundary line between the chip 20 and the scribe line 21 is at the position shown by the dotted line in FIG.
It is tilted at a certain angle θ'' with respect to the axis. When looking at the laser spot 16 at this time, the spot 16'' shown in c in the figure shows the L state. As mentioned above, if the spot is moved in the Y direction and it comes to the 16" position, the H state will occur.The 16" position should be on the scribe line 21 if the facet line 12 is not tilted. However, this is because the facet line falls on the chip 20 due to the slope of the facet line.

In this way, the angle θ'' is calculated from the distances between spots 16 and 16'', and between 16'' and 16'', and the chuck 7 is
to achieve correct positioning of the facet line 12. [Problems to be Solved by the Invention] By the way, when a protective film is deposited on a chip, the above-mentioned measurement problem occurs.

A plan view of one of the chips 20 with a protective coating 22 applied thereto is shown in FIG. to do. In FIG. 6, where the spot 16 is located, that is, where the protective film is applied almost flat, the laser beam is diffusely reflected, resulting in the above-mentioned state H. However, when the spot 16'' came to the outer edge of the protective film and was hit by the laser beam there, an apparent total reflection of the laser beam occurred, causing the state L. In other words, it was experienced that the scribe line 21 Regardless of whether or not the laser beam is hitting the scribe line, the result is as if the laser beam was hitting the scribe line.When spot 16'' is moved in the Y direction along the outer edge of the protective film, the L The condition will appear. In other words, at this time, the laser beam misreads the scribe line 21 and the outer edge of the protective film 22. In this case, first, the θ alignment, which should originally be based on the scribe line, was done on the outer edge of the protective film 22.

On the other hand, in a normal chip, the margin (indicated by m in FIG. 6) between the outer edge of the protective film 22 and one side of the scribe line 21 is 200 to 300 [μm]. This means that in laser light measurement, there is a corresponding distance deviation in the X direction. At this time, if the above-mentioned mechanical and electrical corrections in the If a wafer is fed with a misalignment (direction), this misalignment will not be corrected by the memorized correction value, and the needle 15 of the probe head 14 will come into contact with a portion of the chip other than the pad, causing the measurement to be impossible. Therefore, even if the chip is good, it will be determined to be defective. It is an object of the present invention to solve such problems experienced in the prior art.
[Means for solving the problem] The above problem can be solved by optically scanning a wafer on which a surface protection film is formed on each semiconductor element region, and detecting the reflected light from the scribe line. An alignment method that recognizes the alignment of a scribe line and performs alignment using the scribe line as a reference pattern, and distinguishes between light reflected from the scribe line and light reflected from the outer edge of the surface protective film. When the wafer is scanned in a first direction and reflected light is detected, the surface protection film is scanned from that point to the first direction.
When the uneven portion is detected by scanning a predetermined distance in a second direction perpendicular to the direction of This is achieved by distinguishing between light reflected from the scribe line and light reflected from the outer edge of the surface protective film.

[Effect]

FIG. 7 shows a chip similar to the chip of FIG. 6 in plan view, and parts that are the same as those of FIG. 6 are designated using the same reference numerals.

The chip 20 is formed with pads 23 whose shape and number are determined depending on each case, and some of them are selectively shown in the figure. A protective film 22 of organic material is deposited and patterned on the chip 20 to protect the elements of the chip 20.
The protective film 22 may be made of silicon oxide. In the illustrated embodiment, the protective film 22 covers almost the entire surface of the chip 20 and has four patterns 24, 24'', 24'', 24''.
``'' is formed. Because such a pattern is provided, when the laser beam reads the scribe line 21 for alignment, it is possible to prevent the scribe line 21 and the outer edge 22 of the protective film from being misidentified. It is.
[Embodiment] In the example shown in FIG. 7, the number of chips 20 is 5 [?
] The corner pattern was formed near the center of the outer edge 22 with a size of 0.1 to 0.5 [Tnln]×2 [in order].

In FIG. 7, spot 16 is in the H state, spot 1
6'' produces an L condition.

Here, if the spot moves in the Y direction, spot 16''''''
also produces the state L. However, the spot is pattern 24
When the laser beam enters 16'' and reaches 16'', an H state is generated, indicating that the laser beam is not on the scribe line 21. The position and size of the pattern 24 are determined by considering the relative scanning distance of the laser beam and the size of the chip.

The accuracy of alignment increases as the scanning distance of the laser beam increases, but the measurement takes too much time. Current technology generally scans a distance equal to the length of one side of the chip, so patterns 24, 24'', 24'', 2C
``'' is selected so that no matter where on the chip the laser beam starts scanning, the laser beam always remains within the path of the laser beam while scanning a distance of half the length of one side of the chip. Furthermore, if the laser beam travels only a distance of 1/4 of the length of one side of the chip, the position from which the laser beam starts traveling is not fixed as described above.
It may be necessary to provide multiple patterns on the outer edge of the protective film. The pattern 24... is made so that the outer edge 22 of the protective film is not a straight and clean pattern, and the scribe line,
This is because it is formed to avoid misidentification with
It may be concave toward the center of the chip, that is, the protective film may not be formed toward the center of the chip.

〔Effect of the invention〕

According to the present invention, by forming the unevenness on the outer edge of the surface protective film as described above, it is possible to distinguish between the scribe line, which is the reference pattern for alignment, and thereby prevent erroneous alignment. disappears.

Note that since such a pattern can be formed by ordinary photolithography techniques, no special technique or process is required to carry out the present invention. However, it is important to take care that the outwardly projecting or inwardly recessed portions of the pattern on the outer edge of the protective film do not peel off during handling of the wafer. As explained above, the pattern of the outer edge of the protective film of the present invention improves the accuracy of wafer alignment,
It has the effect of preventing a good product from being judged as a defective product in the unlikely event that it occurs, increases the reliability of manufactured semiconductor devices, and improves manufacturing yield.
It is effective when applied to OSI bipolar elements and the like.

[Brief explanation of drawings]

Figure 1 is a schematic plan view of the wafer measuring device, Figure 2 is a diagram of the wafer placed on the chuck, Figure 3 is a cross-sectional view of a part of the chuck in Figure 2, and Figure 4 is the same as in Figure 1. A cross-sectional view of a probe card used in the device, FIG. 5 is a diagram explaining measurement using a laser beam spot, FIG. 6 is a plan view showing a protective film according to the prior art, and FIG. 7 is a diagram showing a probe card provided with an outer edge pattern according to the present invention. FIG. 3 is a plan view of a protective film. 16... Laser light spot, 20... Chip, 2
1...Scribe line, 22...Outer edge of protective film, 2
4... Pattern.

Claims (1)

[Claims] 1 Optically scan a wafer on which a surface protection film is formed on each semiconductor element region, detect the reflected light from the scribe line to recognize the position of the scribe line, and use the scribe line as a reference pattern. The method includes forming irregularities on the outer edge of the surface protective film to distinguish between reflected light from the scribe line and reflected light from the outer edge of the surface protective film, and When the wafer is scanned in a first direction and reflected light is detected, scanning is performed for a predetermined distance from that point in a second direction perpendicular to the first direction, and the uneven portion is detected. In some cases, the reflected light from the scribe line and the reflected light from the outer edge of the surface guarantee film are distinguished by recognizing that the reflected light is the light reflected from the outer edge of the surface protection film. A method for aligning semiconductor elements, characterized in that: