JPH057118B2 - - Google Patents

Description

TECHNICAL FIELD 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.

Prior Art 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 range of the measurement system 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 beam is turned off, a pass/fail determination is made immediately after trimming, and the next resistor is trimmed.

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 good chance 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.

Structure of the Invention According to the present invention, there is provided a laser trimming device for adjusting the resistance value of a resistor to a predetermined value, which includes 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.

Embodiment 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 uses a voltage V2 proportional to the resistance value of the resistor.
and a voltage V3 proportional to the trimming setting resistance value, a comparison circuit 3, a laser light control pulse generation circuit 6, a frequency dividing circuit 7, a digital filter circuit 15 for the output voltage V5 of the comparison circuit 3, and a laser light on/off control circuit 18. It consists of

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 input from terminal 1,
Output voltage V2 due to gain-switchable amplifier 2
and is input to one input terminal of the comparator circuit 3. When the trimming setting resistance value is specified by the CPU (data processing unit) 5, the D/A (digital/analog) converter 4 outputs a voltage V3 proportional to the setting resistance value, and this is applied to the other input terminal of the comparison circuit 3. is input. The level of the output voltage V5 of the comparator circuit 3 changes between high and low depending on the magnitude of the input voltages V2 and V3. In other words, before trimming, V2<V3 and the level of output voltage V5 is low, but trimming increases the resistance value,
When V2≧V3, the level of voltage V5 becomes high. The output voltage of the comparison circuit 3 is input to the digital filter circuit 15.

In addition, the output voltage V4 of the frequency variable laser light control pulse generation circuit 6 and the same signal are applied to a 1/10 frequency dividing circuit 7.
The output voltage V7 of the gate circuit 8 whose two inputs are the output voltage V6 obtained by inputting the output voltage V7 and the output voltage mentioned above.
V6 is also input to the digital filter circuit 15.

In the digital filter circuit 15, the output voltage V5 of the comparator circuit 3 is sampled by the sampling signal V7 of five pulses, and if the voltage signal V5 is detected as high in three or more of the five samplings, the pulse is output. A signal V11 is output. The pulse signal V11 and the output voltage V9 of the pulse shaping circuit 10 which receives the voltage signal V6 are input to the laser light on/off control circuit 18.

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

When the voltage signal V5 is at a low level, the output V10 of the gate circuit 11 is at a high level. The counter circuit 12 is counted down by the signal V10. Immediately before sampling, the counter circuit 1 is activated by the laser light control pulse signal V9.
2 is preset to count 3, and when three or more pulses out of five pulses of the sampling pulse signal V7 are input to the counter circuit 12 by the gate circuit 11, a negative pulse signal 11 is output. The situation is shown in FIG. Note that the voltage signal V5 in FIG. 3 shows level fluctuations.

Furthermore, when laser trimming is started, that is, when the voltage signal V5 is at a low level, the output V12 of the flip-flop circuit 13 is at a high level. is output, the output V12 of the flip-flop circuit 13
is set to a 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 V13 generated by ANDing the laser light control pulse signal V9 and the voltage signal V12 from the gate circuit 14 is output from the terminal 17 as an output signal of the laser light on/off control circuit 18. It functions to turn on the laser beam only when the pulse signal V13 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
The laser light is turned off when V12 goes low. 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.
Here we will refer to laser trimming of film resistors in hybrid integrated circuits.

First, the parameters of the measurement system are set, and a probe is set on the first resistor. Next, the laser beam is scanned, and when the trimming start point is reached, the laser beam 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<V3, output V5 is low. Therefore the output
V11 and output V12 remain high, terminal 1
A pulse signal V13 is output from 7, and the laser beam is turned on.

The laser beam is scanned and the resistance value to be measured is greater than the trimming setting value, that is, V2≧V3 and 3 or more pulses of the 5-pulse sampling signal V7.
If V2≧V3 is detected, negative pulse signal V1
1 is generated, the output voltage V12 of the flip-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, a judgment is made as to whether the trimming is successful or not, and the next step is to trim the resistor. The above procedure is repeated for the number of resistances.

Effects of the Invention 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. Furthermore, 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 FIG.
3 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 dividing circuit, 12 ... Counter, 16 ... Flip-flop, 15 ... Digital filter circuit, 18 ... Laser on/off control circuit.

Claims (1)

[Claims] 1 A laser trimming device that adjusts the resistance value of a resistor to a predetermined value, which includes a control pulse generation circuit that generates a control pulse that controls on/off of a laser beam for trimming, and a control pulse generation circuit that detects the resistance value and applies it to the control pulse. means for generating a detection signal of a corresponding 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 period of the pulse in synchronization with the control pulse. means for sampling the comparison result 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; 1. A laser trimming apparatus, comprising: a determination means, and is configured to cut off the control pulse in response to generation of the determination signal.