JPS6035805B2 - thin film resistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to trimming of thin film resistors and aims to improve trimming accuracy and workability.

The weighted resistor of the DA converter, which is a component of a high-precision AD converter, requires a relative accuracy of ±; when the number of conversion bits is n and the linearity is B. For this reason, a thin film resistor made of Ni--Cr or the like is usually used as the weight resistor, and trimming is performed by a laser to obtain the necessary accuracy. For this trimming, coarse adjustment trimming shown in FIG. 1 and fine adjustment trimming shown in FIG. 2 are used. In FIGS. 1 and 2, A shows the state before trimming, and the mouth shows the state after trimming, and current flow lines are schematically drawn. The numbers in Figures 1 and 2 correspond to 11, 1, respectively.
2, 21 and 22 indicate electrode parts at both ends made of a low resistance material such as aluminum, 13 and 23 indicate thin film resistors, and 14
and 24 are trimming lands by the thin film resistors 13 and 23, 15 and 25 are streamlines, and 16 and 26 are trimming parts by the laser. In FIG. 1, the trimming is performed so as to intersect with the streamline 15, so the rate of change in resistance is large, and the resistance value is determined by the current path. Therefore, it is called coarse adjustment trimming. In FIG. 2, the trimming is done parallel to the streamline 25. Therefore, the rate of change in resistance is small, and this is called fine adjustment trimming. In FIG. 2, the distribution of streamlines at the trimming land is not uniform, and it is difficult to determine the resistance at that portion. To obtain accurate streamlines, we must solve Laplace's equation, but this does not necessarily match reality. Therefore, it is not only difficult to perform trimming parallel to the streamlines in order to reduce the rate of change in resistance, but also does not improve workability. Not only that, but even the initial resistance value of the trimming land cannot be determined accurately. The reason why it is impossible to accurately know the initial resistance value of the trimming land and the rate of change in resistance after trimming is due to the non-uniformity of the current distribution flowing there. The present invention has been made in view of the above points, and will be described below with reference to FIG. 3 showing one embodiment thereof. As shown in FIG. 3, when forming the electrode parts 31 and 32 of the thin film resistor 33, the conductor parts 36 and 37 are trimmed by the thin film resistor 33 so as to cross the direction of the current flowing between the electrode parts 31 and 32. - Formed on the land 34 by Aoi-gi or the like.

Of course, the conductor parts 36 and 37 are not connected to an external circuit. 35 is a current flow line.

With such a configuration, the potentials of the conductor portions 36 and 37 can be made equal to each other.

Therefore, the current distribution from the electrode part 31 to the conductor part 36, from the conductor parts 36 to 37, and from the conductor part 37 to the electrode part 32 becomes uniform within each range, and
Resistance values ranging from 1 to 32 can be easily calculated. FIG. 4 shows another embodiment of the present invention, in which a trimming land 34 is provided between the conductor section 38 and the electrode section 32 to make the current distribution between the conductor section 38 and the electrode section 32 uniform. This is what I did.

If we take advantage of the advantage of making the current distribution uniform as described above, we can trim the entire width as shown in Figure 5.
If a width Δ is cut from the land, the resistance change rate of the trimming land at that time will be {1/(1-Δ/mountain)−1}.

Therefore, if the moving distance of the laser beam per step and the resistance accuracy are given, the shape of the trimming land is uniquely determined. In the above trimming example, the resistor is separated as shown in Fig. 5, but in Figs.
For finer trimming, as shown in the figure,
It is also possible to cut halfway, or to cut only the thin film resistor part parallel to the current flow line without cutting the electrode part.

Furthermore, the widths of the opposing conductor portions and the opposing widths of the conductor portion and the electrode portion may vary. The present invention is configured as described above, and the initial resistance value of the trimming land can be easily calculated compared to the conventional example, and the present invention is superior in terms of trimming accuracy and workability.

[Brief explanation of the drawing]

Figure 1A and Figure 2A and Figure 2A and Figure 2A and 2B are top views of a conventional thin film resistor before and after trimming, respectively, and Figure 3 is a top view of an embodiment of the thin film resistor according to the present invention. , FIG. 4 is a top view showing another embodiment of the present invention, and FIG. 5 is a top view showing another embodiment of the present invention.
6 and 7 are top views of the thin film resistor of the present invention after trimming, respectively. 31, 32... Electrode section, 33... Thin film resistor, 36, 37, 38... Conductor section. Figure 1 Figure 4 Figure 2 Figure 3 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A first thin film resistor with a uniform current distribution and a second thin film resistor with a uniform current distribution and trimmed, and both ends on the first and second thin film resistors. A thin film resistor, characterized in that the conductor portion is provided to make current distribution uniform, and the inside of the second thin film resistor has a width larger than that of the first thin film resistor.