JPS6233082A - Laser trimming device - Google Patents

Abstract

PURPOSE:To increase a trimming accuracy and to automate the measurement by reducing the effect of a noise, etc. as far as possible by deciding the deciding signal obtd. by comparing with the prescribed reference plural times on each pulse simultaneously with the control pulse of a laser beam. CONSTITUTION:A laser beam is scanned by setting a probe on a resistance body. A pulse signal V4 is outputted from a laser beam control pulse generating circuit 6 on reaching to a trimming start point. In this case the laser beam becomes ON by transmitting a pulse signal V13 from a terminal 17 in case of the initial value of the resistance body being smaller than the trimming set value. The laser beam becomes OFF by generating a negative pulse signal V11 in case of the measured resistance value becoming bigger than the trimming set value. Thereafter the decision of the quality of the trimming is performed and the migration is performed to the following trimming. The increase in the trimming accuracy is thus made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser trimming device, and more particularly to a laser trimming device that adjusts the resistance value of a film resistor in a hybrid integrated circuit by turning on and off a laser beam.

Correct】UL■ Generally, the laser trimming procedure is performed as follows.

First, a laser beam is positioned near the resistor to be trimmed, and a probe and a measurement system range corresponding to the set resistance value are set. Next, if trimming is possible, that is, if the resistance value to be measured is smaller than the set resistance value, the laser beam is turned on and scanning is performed. At this time, the resistance values of the resistance to be measured and the set resistance are compared for each pulse in synchronization with the pulses of the laser beam, and if the former is larger, the laser beam is turned off. When the laser light is turned off,
Immediately after trimming, a pass/fail judgment is made and the process moves on to trimming the next resistor.

In the above procedure, sampling for comparing the resistance value to be measured and the set resistance value is normally performed only once, and if the result of sampling is that the resistance value to be measured is large, the laser beam is turned off. Therefore, when comparing the resistance value to be measured and the set resistance value, if the resistance value to be measured changes due to the influence of noise or the like, there is a sufficient possibility that false detection will occur, and in this case, trimming accuracy will deteriorate.

OBJECTS OF THE INVENTION An object of the present invention is to provide a laser trimming device that can minimize the influence of noise and improve trimming accuracy.

According to the present invention, there is provided a laser trimming device for adjusting the resistance value of a resistor to a predetermined value, comprising: a control pulse generation circuit for generating a control pulse for controlling on/off of a laser beam for trimming; means for detecting a resistance value and generating a detection signal of a level corresponding thereto; comparison means for comparing the level of this detection signal with a predetermined reference level; means for generating at least three sampling signals; the sampling signals sample the comparison results of the comparison means, and a comparison result indicating that the resistance value has reached a predetermined value is obtained by a majority of the sampling values; and determining means for outputting a determination signal when the determination signal is generated, and the control pulse is cut off in response to generation of the determination signal.

1 Yutaka 3 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram of an embodiment of a laser trimming control circuit of the present invention.

This circuit consists of a comparison circuit 3 between a voltage (2) proportional to the resistance value of the resistor and a voltage (3) proportional to the trimming setting resistance value, a laser light control pulse generation circuit 6, a frequency dividing circuit 7, and a comparison circuit 3.
A digital filter circuit 15 for the output voltage V5 of
It is composed of a laser beam on/off control circuit 18.

First, when a probe is set on the resistor to be trimmed, a constant current is applied. The resulting voltage V1 across the resistor is inputted from the terminal 1, converted into an output voltage 2 by the gain-switchable amplifier 2, and inputted to one input terminal of the comparator circuit 3. cpu <data processing bag@
)5, when the trimming setting resistance value is specified, D/
A (digital/analog) converter 4 outputs a voltage 3 proportional to the set resistance value, and this is input to the other input terminal of the comparison circuit 3. The level of the output voltage v5 of the comparator circuit 3 is equal to the input voltage V2. Changes to high or low depending on the magnitude of V3. In other words, before trimming, V
2<V3, and the level of the output voltage V5 is 0-, but the resistance value increases due to trimming, and when ■2≧■3, the level of the voltage ■5 becomes high. The output voltage of the comparison circuit 3 is input to the digital filter circuit 15.

In addition, the output voltage of the gate circuit 8 which uses the output voltage V4 of the frequency-variable laser light control pulse generation circuit 6 and the output voltage 6 obtained by inputting the same signal to the 1/10 frequency dividing circuit 7 is output voltage by two people. 7 and the aforementioned output voltage v6 are also input to the digital filter circuit 15.

In the digital filter circuit 15, the output voltage V5 of the comparator circuit 3 is, for example, a sampling signal of five pulses.
As a result, if the voltage signal 5 is detected to be high in three or more of the five samplings, the pulse signal V11 is output. Pulse shaping circuit 1 using pulse signal V1.1 and voltage signal v6
The output voltage v9 of 0 means that the laser beam on/off control circuit 18
is input.

Next, the digital filter circuit 15 and the laser light on/off control circuit 18 will be explained with reference to FIGS. 2 and 3, which show timing charts of the respective signals written in FIG. 1. Incidentally, FIG. 3 shows a partially enlarged time axis of the time chart of FIG. 2.

When a resistor is irradiated with pulsed laser light, the resistance value increases almost stepwise for each pulse of laser light irradiation. This situation is shown by signal V2 in FIG. Comparison (sampling) of the resistance values is performed after laser light irradiation using five pulse signals (7) synchronized with the laser light control pulse signal V6. Note that the voltage signal V7 is pulse-shaped by a pulse shaping circuit 9 into a voltage signal V8.

When the voltage signal V5 is at a low level, the output VIO of the gate circuit 11 is at a high level. The counter circuit 12 is counted down by the pulse signal V10. Immediately before sampling, the counter circuit 12 is preset to count 3 by the laser light control pulse signal 9, and when 3 or more pulses out of 5 pulses of the sampling pulse signal V7 are input to the counter circuit 12 by the gate circuit 11, a negative pulse is generated. Signal ■11 is output. The situation is shown in FIG. Note that the voltage signal V5 in FIG. 3 shows level fluctuations.

Also, at the start of laser trimming, that is, voltage signal V5
When is at low level, the output V of the flip-flop circuit 13
12 is in a high level state, but the voltage signal v5
becomes high level and the digital filter circuit outputs the pulse signal V11, the output V12 of the flip-flop circuit 13 is set to the low level state. This situation is shown in FIGS. 2 and 3. Note that the flip-flop circuit 13 is reset by a reset signal 16 before starting trimming.

On the other hand, a voltage signal V generated by ANDing the laser light control pulse signal V9 and the voltage signal V12 from the gate circuit 14
13 is output from the terminal 17 as an output signal of the laser beam on/off control circuit 18, and functions to turn on the laser beam only when the pulse signal V13 from this terminal 17 is generated. That is, when the output voltage V12 of the flip-flop circuit 13 is high, the laser light is turned on and the output V1
When 2 goes low, the laser light is turned off. The situation is shown in FIG.

An example of the laser trimming control circuit of the present invention having the above configuration will be described in detail below.

This article refers to laser trimming of film resistors in hybrid integrated circuits.

First, set the parameters of the measurement system, and then proceed to the first step! Set the probe on the eye resistor. Next, the laser beam is scanned,
When the trimming start point is reached, the laser light control pulse generation circuit 6 outputs a pulse signal V4. At this time, if the initial value of the resistor is smaller than the trimming setting value, that is, if V2 is 3, the output V5 is O-. Therefore, output v11 and output V12 remain high,
A pulse signal V13 is output from the terminal 17, and the laser beam is turned on.

When the laser beam is scanned and the resistance value to be measured is larger than the trimming setting value, that is, V2≧■3 and ■2≧■3 is detected in 3 or more pulses of the 5-pulse sampling signal v7, a negative pulse is detected. Signal V11 is generated and the flip
The output voltage V12 of the flop circuit 13 becomes low, and therefore the output V13 remains at a constant high level, and the laser beam is turned off. After the laser beam is turned off, the trimming is judged to be good or bad, and the next resistor is trimmed. The above procedure is repeated for the number of resistances.

As explained above, according to the present invention, sampling for comparing the measured resistance value and the set resistance value is performed multiple times, thereby minimizing the influence of noise etc. during comparison. It is possible to improve trimming accuracy. Further, since the laser beam is turned on and off by hardware, computer processing can be performed during this time, and the efficiency of software use can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, and FIGS. 2 and 3 are diagrams showing the timing of each signal shown in FIG. 1. Explanation of symbols of main parts 3... Comparison circuit 6... Pulse generation circuit 7... Frequency division circuit 12... Counter

Claims (1)

[Claims] A laser trimming device that adjusts the resistance value of a resistor to a predetermined value, the device comprising: a control pulse generation circuit that generates a control pulse to control on/off of a laser beam for trimming; and a control pulse generation circuit that detects the resistance value and responds accordingly. means for generating a detection signal of a certain level, comparison means for comparing the level of the detection signal with a predetermined reference level, and generating at least three sampling signals for each cycle of the control pulse in synchronization with the control pulse. means for sampling the comparison results of the comparison means using the sampling signal and outputting a determination signal when a comparison result indicating that the resistance value has reached a predetermined value is obtained by a majority of the sampling values or more; A laser trimming device comprising means for cutting off the control pulse in response to generation of the determination signal.