JP2924298B2 - Wafer type code identification system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer type code identification system, and more particularly to identification of a type code in lot integration of a master slice type.

[0002]

2. Description of the Related Art With the customization of semiconductor devices, production methods have been changed to small-quantity multi-products. A master slice type such as a gate array is a typical example, and a large number of types are derived from one master, and the production amount of each type is small. In a semiconductor device manufacturing process, dozens to tens of batch processes are often performed, and when the number of wafers constituting a lot as a manufacturing unit is reduced, production efficiency is extremely reduced. Therefore, several different kinds of lots of the same master are integrated,
Lot consolidation is considered as one large lot.

[0003] However, in a manufacturing process in which the integrated large lot has different manufacturing conditions depending on the product type, it is necessary to select again for each product type. The exposure step in the photolithography step is an example, and a photomask having a different pattern for each type is used.

Conventionally, as a technique for recognizing the type of each type of wafer to be manufactured, the following identification process has been performed before the exposure process. As shown in FIG. 6A, a method of reading the product code formed on the semiconductor chip 4a by using an optical microscope 15a and selecting by a human, as shown in FIG. A method in which a product code 15b marked using a laser marking device or the like is read by a CCD camera, processed and identified by a computer, and automatically selected.

[0005]

The conventional wafer type code identification system itself is a single step and is performed before the exposure step. Therefore, in the exposure step, a small number of lots of the same kind are simply collected. As the number of varieties in small lots increases, the number of varieties included in the integrated lot increases,
As the number of pieces of one type decreases, the exposure process involves working on a very large number of small lots, and there is a problem that workability is extremely deteriorated.

[0006]

SUMMARY OF THE INVENTION A wafer type identification system according to the present invention is provided with a stepper type exposure apparatus for applying a type code identification mark formed on a semiconductor wafer in accordance with a digital bit signal to a dimension of an alignment mark. Are read using the alignment mechanism described above, and sorted by product code.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of an alignment mechanism of a stepper type exposure apparatus used in the present invention. The He-Ne laser beam 2 that has passed through the reduction projection lens 1 is
The upper semiconductor wafer 4 is irradiated. When the wafer stage 3 is moved and the alignment mark 5 is scanned with the He-Ne laser light 2, the intensity of the diffracted light 6 generated by the alignment mark 5 changes. The change is converted into an electric signal by the detector 7, and the signal processing unit 8 performs an arithmetic operation to estimate the position of the alignment mark.

FIG. 2 is a diagram for explaining the operation in detail.
(A) shows the relationship between the shape of the alignment mark and the spot of the laser beam, and (b) shows the intensity of the electric signal converted by the detector 7. The alignment mark 5 is usually formed by vertically arranging squares of about 4 × 4 micro squares. The He-Ne laser beam 9 scans over the mark array in the direction of the arrow. The electric signal converted by the detector 7 changes as shown in FIG. This signal is calculated by the signal processing unit 8 to estimate the position of the alignment mark.

FIGS. 3A and 3B are a schematic plan view of a wafer and a waveform diagram of an identification signal according to an embodiment of the present invention, respectively. Two types of mark rows 5 and 5 having a long and short width in the laser scanning direction of the same pattern as the alignment mark 5
A product code identification mark 8 combining a is provided. These two types of mark row marks correspond to digital signals of "0" and "1", and represent the type code in binary. If eight marks are arranged, it is equivalent to eight bits, which is sufficient as a product code. He- is displayed on the type code identification mark 8.
When scanning is performed with the Ne laser light 11, the detector output signal 10a detected by the detector 7 becomes as shown in FIG. If the electric signal 13 is cut at a certain slice level 14, the product code binarized by the length of the cut signal can be restored.

FIGS. 4 (a) and 4 (b) are a flow chart and a flow chart of a wafer for explaining a kind code identification process using the wafer of FIG. (A) First, as shown by the solid line in FIG. 4B, the wafer is transferred from the loader 12 to the wafer stage 3, and (B) wafer alignment is performed. (C) Next, if this processing is the first time, (D) FIG.
As shown in (1), the type code is identified, and (E) it is determined whether the code is the same as the photomask set in advance. (F) If it is the same code, it is exposed and (G) is conveyed to the unloader 13 to complete the process. (H) If it is not the same coder, the product code is stored and returned to the (I) loader 12.

After this process has been performed on all the wafers of the loader 12, the photomask is converted into another type code and the process is repeated from the beginning, but the type code is stored for each wafer. Therefore, in (C), 2
If it is determined to be the first time or later, the type code identification in (D) becomes unnecessary.

As shown in FIG. 5, the present invention is made more efficient by placing a pattern of several different types of cords I, B, C and D on one photomask 14. The type code is identified, and the pattern other than one corresponding mask is blocked by the light shielding plate. As a result, exposure can be performed for some product codes without replacing the photomask 14, so that the processing that has been repeated in FIG. 4 can be reduced to a fraction.

[0013]

As described above, the present invention utilizes the alignment mechanism of the stepper type exposure apparatus to identify the type code as a part of the exposure step by the exposure apparatus, so that the same code can be obtained before the exposure step. This eliminates the need to divide into product codes, and can prevent the workability in the exposure process of a multiproduct integrated lot, which has conventionally been a problem, from deteriorating.

[Brief description of the drawings]

FIG. 1 is a schematic view of an alignment mechanism of a stepper type exposure apparatus for explaining the embodiment of FIG. 3 of the present invention.

FIGS. 2 (a) and 2 (b) are a schematic plan view of a wafer and a waveform diagram of an identification signal for explaining an operation using the alignment mechanism of FIG. 1, respectively.

FIGS. 3A and 3B are a schematic plan view and a waveform diagram of an identification signal of a wafer according to an embodiment of the present invention, respectively.

4 (a) and 4 (b) are a flow chart and a flow chart for explaining a kind code identification process using the wafer of FIG. 3, respectively.

FIG. 5 is a schematic plan view of a photomask used in the present invention.

FIGS. 6A and 6B are schematic plan views of two examples of a conventional wafer type code, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reduction projection lens 2 He-Ne laser beam 3 Wafer stage 4, 4a, 4b Semiconductor wafer 5, 5a Alignment mark 6 Diffracted light 7 Detector 8 Type code identification mark 9 Laser beam spot 10, 10a Detector output signal 11 Slice level 12 Loader 13 Unloader 14 Photomask 15a, 15b Product code

Claims (1)

(57) [Claims] 1. A type code identification mark formed on a semiconductor wafer with the size of an alignment mark corresponding to a digital bit signal is read using an alignment mechanism of a stepper type exposure apparatus, and sorted according to the type code. A kind code identification system for wafers, characterized in that: