JPH0638455B2 - Laser trimming method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser trimming method for replacing a defective bit with a spare memory in a memory IC with a redundant memory.

[Conventional technology]

Conventionally, laser trimming for replacing a defective bit of a memory IC with redundancy with a spare memory is performed by the configuration shown in FIG. In FIG. 2, 1 is a tester, 2 is a prober, 3 is a laser trimmer, 8 is one chip of a memory IC, and 9 is a bonding pad for electrically connecting the chip 8 and the package.

In this apparatus, the tester 1 and the prober 2 determine whether each memory chip on the wafer is a good product or a defective product, or a good product (hereinafter referred to as a RE product) that replaces a spare memory. The position information of the upper chip and information about which defective element in the chip should be replaced with which spare memory are transmitted to the laser trimmer 3 (hereinafter referred to as a trimmer). At this time, as means for transmitting information, the tester 1 and the trimmer 3 may be directly connected, or may be transmitted by means such as a floppy disk. Then, the trimmer 3 detects the R on the wafer based on the information obtained by the means.
The laser is blown only on the E product to replace the defective element with the spare memory.

At this time, the trimmer 3 found the position of the RE product on the wafer by the following method. Next, the method will be described with reference to FIG.

FIG. 3 shows a method of detecting the position of the RE product using the coordinate system of the wafer, 4 is the wafer, 5 is the coordinate system for determining the position of the chip on the wafer, 6 is the orientation flat, and 7 is the RE product. Is. The trimmer 3 determines the orientation of the wafer 4 by the orientation flat 6 of the wafer,
Next, the edge in the X direction of the wafer 4 and the edge in the Y direction are detected,
The origin of the coordinate system 4 of the wafer 4 is determined. Next, tester 1
The RE product 7 is found according to the coordinate value of the RE product 7 from (1), ((a, b) information, and the laser is blown.

[Problems to be solved by the invention]

In the conventional method, the trimmer 3 often erroneously recognizes the origin of the coordinate system of the wafer, and often the laser should be blown to the RE product to another chip.

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and provides a laser trimming method by which a trimmer can surely recognize a chip to be blown and can perform laser trimming accurately. It is an object.

[Means for solving problems]

In the laser trimming method according to the present invention, the pad of the RE product is marked in the pretest process, and in the laser trimming process, it is determined whether or not the chip found is really the RE product by the presence or absence of the mark on the pad. It is a thing.

[Action]

In the present invention, the RE product pad is marked in the pretest process, and in the laser trimming process, whether or not the found chip is really the RE product is determined by the presence or absence of the mark on the pad. The RE product to be processed can be surely recognized, and the laser trimming can be performed accurately.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration for carrying out a laser trimming method according to an embodiment of the present invention. In the figure, 1, 2,
3, 8 and 9 are the same as the conventional example, 10 is a detection pad,
11 is a scratch mark.

Next, the laser trimming method of this embodiment will be described with reference to FIG.

A scratch mark 11 is attached to the detection pad 10 of the chip determined to be a RE product in the pretest process. The scratch mark 11 may be attached by a method used in a normal wafer test. Further, the method of transmitting the chip position information of the RE product and the information to be replaced to the laser trimming process, and the method of recognizing the coordinate system of the wafer by the trimmer (FIG. 3) are the same as the conventional method.

The trimmer 3 finds the RE product 7 based on the chip coordinate information by finding the coordinate system as shown in FIG.
It is determined whether or not there are scratch marks 11 on the detection pad. If there is a scratch mark 11, laser blow is performed as it is to replace the defective memory with a spare memory. If the scratch mark 11 cannot be detected, the process returns to the operation of detecting the coordinate system of the wafer again.

As described above, after confirming whether the chip position information of the RE product 7 obtained from the tester 1 is correct by detecting the scratch mark 11, the laser blow is performed so that the information from the tester 1 is correct. Or, it can be determined whether the trimmer 3 has correctly found the coordinate system. If the coordinate system is not correct, the coordinate system detection operation can be performed again to find the correct coordinate system, and laser trimming can be performed accurately.

Although the scratch mark is provided on the detection pad in the above-mentioned embodiment, this may of course be provided on a normal bonding pad. Further, ink may be used instead of the scratch mark.

The scratch marks may be attached to all chips other than RE products.

〔The invention's effect〕

As described above, according to the laser trimming method of the present invention, the pad of the RE product is marked in the pretest process, and whether the chip found in the laser trimming process is the RE product or not is determined by the presence or absence of the mark on the pad. The RE product to be laser blown can be surely recognized and the precision of laser trimming can be improved.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a laser trimming method according to an embodiment of the present invention, FIG. 2 is a diagram for explaining a conventional laser trimming method, and FIG. 3 is an RE product using a wafer coordinate system. FIG. 6 is a diagram for explaining a method of detecting the position of FIG. 1 ... Tester, 2 ... Prober, 3 ... Laser trimmer,
4 ... Wafer, 5 ... Coordinate system, 6 ... Orientation flat, 7 ... RE product, 8 ... Chip, 9 ... Bonding pad, 10 ... Detection pad, 11 ... Scratch mark. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (4)

[Claims] 1. In an off-line laser trimming method, a step of marking a pad of a chip to be laser trimmed when performing a pretest step for determining whether or not to perform laser trimming, and laser trimming The laser trimming method, wherein the step of performing the step (a) is performed by confirming that the positional information on the wafer of the chip obtained in the pretest step is correct by detecting the mark. 2. The laser trimming method according to claim 1, wherein the pad for marking is a bonding pad. 3. The laser trimming method according to claim 1, wherein the pad for marking is a dedicated detection pad for marking. 4. The laser trimming method according to claim 1, wherein the mark is a scratch mark.