JPS6235636A - Bit remedy method - Google Patents

Abstract

PURPOSE:To protect accuracy in detecting a target pattern for the remedy of defective bits from reduction by a method wherein the target pattern is exposed and a positioning laser beam is projected directly upon the exposed target pattern. CONSTITUTION:A laser beam applied to the region of a target pattern 10 attacks a passivation film 13 coating the target pattern 10 and burns it down. The target pattern 10 is exposed after the removal of the passivation film 13, which allows the laser beam to reach the target pattern 10. The laser beam is reflected by the target pattern 10, goes through a beam positioner 5, and enters a receptor 7 via a reflecting mirror 6. A portion of the laser beam reaching the edge of the target pattern 10 experiences random reflection, which reduces the luminous energy entering the receptor 7. The luminous energy reduced by random reflection is compared with the luminous energy of the other portion of the laser beam, which allows accurate optical detection to be accomplished of the target pattern 10.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to bit relief technology, particularly alignment technology in bit relief, and is effective when used to relieve defective bits in a wafer, for example, in the manufacture of semiconductor devices. related to technology.

[Background technology]

In the manufacturing of semiconductor devices, it is possible to repair defective bits in order to improve the yield of wafers.As a method for relieving defective bits, a redundant circuit is created on the wafer in advance, and this redundant circuit and defective bit are There is a method of substantially relieving defective bits by irradiating a laser to a switching part consisting of a fuse or a resistor, etc.
Conceivable.

In this method of repairing defective vias, it is necessary to position the wafer with respect to the laser irradiation position in order to irradiate the desired switching section with the laser, and for this positioning, a target pattern is formed on the wafer. It is conceivable to irradiate the area with a laser and detect its position.

However, in positioning in such a defective bit relief method, a bashing film or the like is coated on the laser 7) pattern on the wafer, so the signal-to-noise ratio decreases due to interference of laser light, and the target pattern is damaged. The inventor has revealed that there is a problem in that the detection accuracy decreases.

[Purpose of the invention]

An object of the present invention is to provide a bit relief technique □ that can prevent a decrease in target pattern detection accuracy.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, by exposing the target pattern for relieving defective bits, the alignment laser is directly irradiated onto the target pattern, thereby avoiding the adverse effects of light interference.

(Embodiment) FIG. 1 is a schematic diagram showing a bit relief device as an embodiment of the present invention, and FIG. 2 is a plan view of the periphery of a chip in a wafer state for explaining its operation.

In this embodiment, the bit relief device is equipped with an XY table 1 for holding a wafer in a mounted state, and this table 1 is configured to be movable in the XY directions by a drive device and a controller (not shown). has been done. XY
A laser device 2 for irradiating a laser beam is provided at a position different from the table 1, and an optical system 3 is interposed between the XY table 1 and the laser device 2. The optical system 3 is equipped with a lens system 4, a beam positioner 5 including a half mirror 1, an objective lens drive stage, etc., and a reflecting mirror 6. The lens system 4 is configured to be able to change and adjust the aperture diameter of the laser beam. ing. The beam positioner 5 is configured to reflect the laser beam in the direction of the XY table 1, scan it in a predetermined direction, and transmit the reflected light from the direction of the XY table 1 in the direction of the reflection mirror 6. There is. Reflection mirror 6
A light receiver 7 is disposed at an optically rear position, and the light receiver 7 is connected to the controller of the XY table 1.

As shown in FIG. 2, a large number of bits 9 are formed on a plurality of chips 8a formed vertically and horizontally on a wafer 8, and a target used for optical positioning during bit relief. A plurality of patterns 10 are created on the scribe line 8b. A redundant bit 11 for relieving defective bits is formed in the chip 8a, and a redundant bit 1 is formed between the redundant bit 11 and the normal bit 9.
Switching circuit 12 for switching between bit 1 and regular bit 9
is interposed. A switching link 12a is connected to a switching circuit consisting of a fuse, a resistor, and the like. The switching circuit 12 in this embodiment is configured to perform switching by being irradiated with a laser beam. Note that 12c in the figure indicates a readout circuit.

Next, the action will be explained.

The wafer 8 in which a defective bit has been found by a wafer prober or the like is placed on a realignment station run in a bit relief device, and prealigned by mechanical positioning using the orientation plane of the wafer 8.

Next, it is placed on a chuck on an XY table, and roughly aligned in the X1Y and θ directions by detecting scribe lines and the like. Thereafter, the center of the first relief chip is placed directly under the objective lens using the XY table (wafer alignment).

Next, by operating the beam positioner 5, the irradiation position of the laser beam is adjusted to the target pattern 10 of the chip.
is moved to the position of At this time, since the coordinate position of the target pattern 10 on the chip 8a is known in advance, by moving the beam positioner 5 in a predetermined amount and direction, the target pattern 10 and the laser beam irradiation position substantially match.

Subsequently, a laser is emitted from the laser device 2, and the region of the target pattern 10 on the wafer 8 is irradiated with the laser beam via the lens system 4 and the beam positioner 5. At this time, the lens system 4 narrows down the diameter of the laser beam to a relatively large diameter to ensure that the entire area of the target pattern 10 is irradiated with the laser beam.

Here, the upper layer of the wafer 8, including the Kugett pattern 10, is generally covered with a passivation film 13.

Therefore, the laser beam irradiated onto the region of the target pattern 10 irradiates the passivation film 13 deposited on the target pattern 10 and burns it out.

In this way, Passivation II! 13 is removed, the laser beam will directly irradiate the Kugett pattern 10. When the target pattern 10 is to be directly irradiated, the lens system 4 focuses the laser beam to a small diameter, and the beam positioner 5 vibrates to direct the laser beam to the target pattern 1o.
is scanned regularly in a predetermined direction.

The laser beam irradiated onto the target pattern 10 is reflected and transmitted through the beam positioner 5.1. Furthermore, the light is received by a light receiver 7 via a reflecting mirror 6. At this time, since the laser beam irradiated to the edge of the target pattern 10 is diffusely reflected, the amount of light received by the light receiver 7 decreases.
The target pattern 10 is detected by comparison with other parts.

In this way, when the position of the target pattern 10 is precisely detected by the optical method, h) the position coordinates of the target pattern 10 and the switching circuit 12 at the knob 8a are known in advance, so the switching link 12
The position coordinates of a and the switching circuit 12 are determined relatively.

By the way, when trying to detect the position of the Kugett pattern 10 by irradiating the target pattern 10 with the passivation film 13 still attached with the laser beam, the laser beam is subject to optical interference due to the passivation film 13. , it becomes difficult to distinguish between the edge signal of the target pattern 10 and the noise, and the position of the target pattern 10 cannot be accurately determined.

However, as described above, if the passivation film 13 is removed and the laser beam is directly irradiated onto the target pattern 1O, the negative effects of light interference of the laser beam are suppressed, resulting in a good S/N ratio. , the position of the target pattern 10 can be detected precisely.

When the positional force q of the target pattern 10 is detected, highly accurate alignment is ensured, so the chimp 8a
The positional relationship between the beam positioner 5 and the beam positioner 5 can be accurately recognized. As a result, the coordinate position of the switching section I2.12a corresponding to the bit 9 to be repaired is determined, and this switching section 12.12a is moved by operating the XY table 1 to the laser beam irradiation position.

Next, a laser is emitted from the laser device 2, and the switching section 12.12a is irradiated with the laser beam via the lens system 4 and the beam positioner 5.

By this irradiation, the defective bit is switched to the corresponding redundant bit 11, and the defective bit is substantially relieved.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, the exposure of the target pattern is not limited to performing bit relief, but after creating the target pattern, it is possible to perform a masking process to prevent the creation of an upper layer film such as a passivation film in the subsequent lithography process. The target pattern may be exposed in advance during bit relief by using a photo-etching technique.

〔effect〕

(1) By exposing the target pattern, it is possible to avoid the adverse effects of light interference during optical position detection of the target pattern, so that the target pattern can be detected optically with precision.

(2) By precisely detecting the target pattern, the switching part for switching between defective focus and redundant circuit can be precisely aligned with the laser irradiation position, so defective bits can be repaired accurately and quickly. At the same time, by increasing the density of wafer bits and redundant circuits, it is possible to promote higher integration in semiconductor devices.

(3) By removing the film on the target pattern during bit relief, the film removal work and the target pattern detection work can be performed continuously.
Workability can be improved.

(4) By removing the coating on the target pattern by laser irradiation, the target pattern can be easily exposed, so that it is possible to suppress a decrease in productivity due to coating removal.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a focus relief device according to an embodiment of the present invention, and FIG. 2 is a plan view of a wafer for explaining its operation. 1...XY table, 2...1 rappel, 3
...Optical system, 4... Lens system, 5... Beam positioner, 6... Reflection mirror, 7... Light receiver, 8...
・Wafer, 8a... Chip 7, 9... Memory bit, 10... Target pattern, II... Redundant circuit, 12... Switching circuit, 12a... Switching link, 13
... Panoshyhesion membrane. Figure 1 Figure 2

Claims (1)

[Claims] 1. A bit relief method characterized in that the position of the target pattern on the wafer is recognized while the target pattern is exposed. 2. The bit relief method according to claim 1, wherein the target pattern is exposed by being irradiated with a laser to burn away the coating during bit relief. 3. The bit relief method according to claim 1, wherein the target pattern is exposed by being masked in a lithography process when creating the target pattern.