JPH08204129A - Semiconductor device - Google Patents

Abstract

PURPOSE: To minimize the damage in a laser trimming step by a method wherein the wiring layer for laser trimming step is provided on an insulating layer on conductivity well opposite to that of a silicon substrate. CONSTITUTION: The trimming step is performed by cutting off wiring layers 14 for a laser trimming step so that the damage to a silicon substrate 11 can be suppressed during the laser trimming step in a P type well 12. Besides, the damage caused in the P type well 12 can be prevented from expanding outward. Since the P type well 12 is provided beneasth a silicon oxide layer 13, the damage can be minimized during the laser trimming step. Accordingly, the wiring layers 14 are preliminarily formed for laser trimming so that said layers 14 may be cut off if necessary. Thus, the semiconductor device can be realized without deteriorating the characteristics and the reliability of the IC.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device having a wiring layer for laser trimming.

[0002]

2. Description of the Related Art Conventionally, in an IC provided with a wiring layer for laser trimming, an insulating layer is provided on a silicon substrate, and a wiring layer for laser trimming is provided on this insulating layer.

[0003]

Generally, when the laser trimming wiring layer is cut by a laser, the influence extends to the silicon substrate, so that the silicon substrate is damaged. Conventionally, no measures have been taken on the silicon substrate under the laser trimming wiring layer, so damage received during laser trimming gradually spreads around the silicon substrate, which adversely affects the characteristics and reliability of the IC. There was a problem.

An object of the present invention is to provide a semiconductor device capable of reducing the effect of damage received during laser trimming.

[0005]

A semiconductor device according to the present invention comprises a well of a conductivity type opposite to that of a silicon substrate,
It has an insulating layer formed on the well and a laser trimming wiring layer formed on the insulating layer.

[0006]

EXAMPLE FIG. 1 is a diagram showing an example. A silicon oxide layer 13 having a LOCOS structure is formed in a predetermined region on the N-type silicon substrate 11, and a P-type well 12 is formed under the silicon oxide layer 13. The P-type well 12 is formed in a CMOS well manufacturing process, and the well depth and the impurity concentration are the same as those used in a normal CMOS IC. A laser trimming wiring layer 14 (metal wiring) is formed on the P-type well 12. It should be noted that MOS transistors, various wirings, and the like are formed in a region (not shown).

The trimming is performed by the wiring layer 1 for laser trimming.
This is done by cutting 4 with a laser, but damage to the silicon substrate 11 during laser trimming can be suppressed within the P-type well 12. Also, P-type well 1
It is possible to prevent the damage generated inside 2 from spreading outside the P-type well 12.

As described above, since the P-type well 12 is provided under the silicon oxide layer 13 in this embodiment, it is possible to reduce the influence of damage received during laser trimming. Therefore, the wiring layer 1 for laser trimming is previously prepared.
4 can be formed and the laser trimming wiring layer 14 can be cut as needed without any deterioration in the characteristics or reliability of the IC.

Although the N-type silicon substrate and the P-type well are used in the above embodiment, the P-type silicon substrate and the N-type well may be used in reverse.

[0010]

According to the invention of the present application, since the well is provided under the insulating layer, it is possible to reduce the influence of damage received during laser trimming, and prevent deterioration of IC characteristics and reliability. It becomes possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the invention according to the present application.

[Explanation of symbols]

 11 ... Silicon substrate 12 ... P-type well 13 ... Silicon oxide layer (insulating layer) 14 ... Laser trimming wiring layer

Claims (1)

[Claims] 1. A semiconductor device having a well of a conductivity type opposite to that of a silicon substrate, an insulating layer formed on the well, and a laser trimming wiring layer formed on the insulating layer.