JPH0550841B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a resistance measuring device used in a laser trimmer device etc. that trims a resistor with a laser beam, and in particular, a resistance measuring device that measures a resistance value until a target value is reached. The present invention relates to a resistance measuring device used in a method of trimming by irradiating a laser beam.

[Overview of conventional technology and its problems]

A conventional resistance measuring device used when trimming a resistor as described above, which will be explained later using a diagram, has a reference circuit that emits a reference voltage corresponding to the trimming target value, and a resistance measuring device that measures the resistance of the resistor to be processed. Measuring instruments are widely used, which consist of means for detecting a voltage proportional to the resistance value of It has fulfilled its role satisfactorily at the scale of production. However, regarding laser trimmer equipment,
Recently, the demand for film-type resistors has increased rapidly, and processing speeds of, for example, several tens of seconds per second are now required. It has become difficult to maintain the processing accuracy of the equipment at the required value. This is because laser processing has the problem of so-called drift, where the resistance value changes during processing, and with conventional processing speeds, there was a margin to measure the changed resistance value after it approached a steady state, so this was not a particular problem. However, if the machining speed is increased as described above, measurements must be taken before the steady state is reached, resulting in larger drifts and poorer machining accuracy.

If the amount of drift is constant, a correction method can be used to take into account the amount and finish trimming earlier, but the amount of drift is not constant and depends on the shape of the resistor, the shape of the cut, and especially the depth of the cut. Therefore, no suitable correction method has been known so far, and it has been difficult to achieve both machining accuracy and throughput.

[Purpose of the invention]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a resistance measuring device that can obtain good processing accuracy even when trimming is performed at high speed in a laser trimmer device or the like.

[Structure of the invention]

The present invention focuses on the fact that even when the drift amount of the resistance value during processing is large, the time constant itself remains almost constant.

According to the present invention, there is provided a reference circuit that generates a reference voltage corresponding to a trimming target value, and a detection voltage generating means that generates a voltage proportional to the resistance value of the resistor obtained from both ends of the processed low antibody as a detection voltage. ,
a comparison circuit that compares the value of the voltage based on the generated detection voltage with the reference voltage, and issues an instruction signal instructing the end of trimming when the value of the voltage based on the detection voltage reaches the value of the reference voltage; In a resistance measuring device that is used in a method of trimming by continuously irradiating a laser until a target value is reached while measuring the resistance value, the amount of change over time of the detection voltage generated by the detection voltage generation means is determined, a correction voltage generating means that outputs a correction voltage proportional to the amount of change over time; and a correction voltage generating means that adds the output correction voltage to the detection voltage to obtain a convergence voltage, and converts the obtained convergence voltage into a voltage based on the detection voltage. A resistance measuring device is obtained, which is characterized in that it further includes an adder circuit that outputs .

Next, a detailed description will be given with reference to the drawings.

[Specific Example of Conventional Device] FIG. 4 is a block diagram showing the functional configuration of a conventional standard resistance measuring device, which is shown to clarify the features of the present invention. Since a constant current is supplied to the resistor 1 to be processed from a constant current source 2, a potential difference is generated between both ends thereof, which is determined by the product of the resistance value and the current value at that time. This potential difference is detected, and this detected voltage is compared with a reference voltage corresponding to a trimming target value produced by a reference circuit 3 in a comparator circuit 4. Based on the results, if trimming is completed when the resistance value reaches or slightly exceeds the target value, the target resistance value can be obtained. However, with this configuration, as explained above, when trimming is performed at high speed, the influence of drift becomes large, and there is a problem that sufficient processing accuracy cannot be obtained.

[Example of the present invention]

FIG. 1 is a diagram showing the configuration of a first embodiment of the present invention, which consists of a resistor to be processed 1 and a constant current source 2, and a fourth part detects a potential difference proportional to the resistance value of the resistor. It is the same as the case of the conventional device shown in the figure, but
To explain more specifically for later explanation, this part is a detection voltage generation unit that detects a voltage E(t) proportional to the resistance R(t) at each point in time of the resistor 1 and sends it out as a detection voltage. Department. The reference circuit 3 that generates the reference voltage E _R and the comparison circuit 4 are also exactly the same as in the case of FIG.

A newly added component in the present invention consists of a resistor R and a capacitor C, and detects the amount of time change in the voltage E(t), that is, the differential coefficient E'(t) obtained by differentiating E(t) with respect to t. A time change amount detection circuit (differentiation circuit) 5 and an amplifier circuit 6 that amplifies this differentiated value by a predetermined value.
and adder 7. Next, these operations will be explained together with the basic idea of the present invention.

The resistance value R(t) of the resistor 1 corresponding to the detected voltage E(t), which is the input signal of the differentiating circuit 5, is approximately equal to the time t.
The function of is expressed as the following equation (1).

R(t)=R ₀ (1-e ^-t/ 〓) ...(1) Here, R ₀ is the temperature that temporarily decreased or increased due to trimming, but returned to the original temperature over time. The focusing resistance value at that time, τ, represents the time constant of the speed at which the temperature returns. Therefore, the differential coefficient R'(t) of the resistance value corresponding to the output signal E'(t) of the differentiating circuit 5 can be obtained by differentiating equation (1), and R'(t)=R ₀ /τe ^-t/ 〓 ...(2) By eliminating time t from equations (1) and (2), the following equation (3) is obtained.

R ₀ = R(t) + R′(t)・τ ……(3) Also, if we express this equation (3) in terms of voltage, the focusing resistance value
When the voltage corresponding to R ₀ is E ₀ , E ₀ =E(t)+E′(t)τ (4).

As can be seen from equations (3) and (4), the time constant is constant, so the detection signal E(t) indicating the resistance value R(t) at a certain measurement point has the differential coefficient of the resistance change. By adding the time-varying voltage E′(t) representing R′(t) multiplied by the time constant τ, the focused voltage corresponding to the final resistance value R ₀ can be obtained.
This shows that E ₀ can be obtained. As mentioned at the beginning, the time change detection circuit (differentiation circuit) 5 calculates this time change voltage, and the amplifier 6 multiplies the detected voltage E(t) by τ, which can also be called a correction voltage. The adder 7 adds E′(t)τ, and the output of this adder becomes the focused voltage E ₀ . And in comparator 4, the focused voltage E ₀
and the reference voltage E _R , and when the former value reaches the latter value, an instruction signal that instructs the end of trimming.
S′ outputs.

Therefore, according to the configuration of the embodiment shown in FIG. 1, even immediately after machining, it is possible to predict and correct the amount of drift that will occur thereafter, and it is possible to obtain good machining accuracy even when trimming at high speed. I can do it.

Note that the value of the time constant τ varies greatly depending on the material of the resistor to be processed, and actually varies from milliseconds to about 0.1 seconds, and the sign is opposite between semiconductors and metals.

FIG. 2 is a block diagram showing the configuration of the time variation detection circuit 5 used in the second embodiment of the present invention.
The rest is the same as the first embodiment. In FIG. 2, an input signal E(t) is sampled and held in a first sample and hold circuit 11 using a periodic timing signal from a timing generator 12. On the other hand, the second sample hold circuit 13
receives a timing signal that operates immediately before the sampling operation of the first sample-and-hold circuit 11, and samples and holds the output signal of the first sample-and-hold circuit. Then, when the arithmetic circuit 14 takes the difference signal between the output signals of the two sample and hold circuits 11 and 13, except for a part of the period during sampling, the value is the amount of change in the input signal during the time determined from the sampling period. Voltage E′(t)
In other words, since it shows the resistance value change R'(t), this configuration also allows the differential coefficient of the resistance value change to be found and corrected in the same way as in the first embodiment, and even when trimming is performed at high speed. , good machining accuracy can be obtained.

FIG. 3 is a block diagram showing the configuration of the third embodiment, in which the output signal E'(t) of the time variation detection circuit 15 is amplified by τ times by an amplifier 16 whose amplification degree can be varied, and then the amplified correction is performed. Adding voltage E′(t)・τ circuit 7
is added to the detected voltage E(t) to make the focusing voltage E ₀ . In this configuration, the amplification factor of the amplifier 16 can be controlled by an external control signal _EV , so the material of the resistor to be trimmed is different.
Even if the drift time constant changes, the velocity can be appropriately corrected.

〔Effect of the invention〕

As detailed above, according to the resistance measuring instrument according to the present invention, it is possible to detect the amount of time change in a signal proportional to the resistance value, calculate the drift amount that occurs after measurement from this signal, and correct the drift amount in advance. Therefore, even when trimming is performed at high speed, the influence of drift can be removed and good processing accuracy can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a resistance measuring device according to the first embodiment of the present invention, and FIG. 2 shows the configuration of a time rate of change detection circuit used in the resistance measuring device according to the second embodiment of the present invention. 3 is a block diagram showing the configuration of a third embodiment of the present invention, and FIG. 4 is a block diagram showing the configuration of a conventional standard resistance measuring instrument. Symbol explanation: 1 is the resistance to be processed, 2 is the constant current source,
3 is a reference circuit, 4 is a comparison circuit, 5 is a time change detection circuit (differentiator circuit), 6 is an amplifier, 7 is an adder,
11 and 13 are sample and hold circuits. 14 represents an arithmetic circuit, and 16 represents a variable amplifier.

Claims (1)

[Scope of Claims] 1. A reference circuit that generates a reference voltage corresponding to the trimming target value, and a detection voltage generating means that generates, as a detection voltage, a voltage obtained from both ends of the resistor to be processed that is proportional to the resistance value of the resistor. and a comparison circuit that compares the value of the voltage based on the generated detection voltage with the reference voltage, and issues an instruction signal to instruct the end of trimming when the value of the voltage based on the detection voltage reaches the value of the reference voltage. In a resistance measuring device that is used in a method of trimming by continuously irradiating a laser until a target value is reached while measuring the resistance value, the amount of change over time of the detection voltage generated by the detection voltage generation means a correction voltage generating means for outputting a correction voltage proportional to the amount of change over time, a correction voltage generating means for adding the output correction voltage to the detection voltage to obtain a convergence voltage, and adding the obtained convergence voltage to the detection voltage. 1. A resistance measuring device characterized by comprising an additional circuit that outputs a base voltage. 2. The mechanism for determining the amount of time change in the detected voltage in the correction voltage generating means includes a plurality of sample and hold circuits connected in series and a calculation circuit for the plurality of output signals of these sample and hold circuits. A resistance measuring device according to claim 1. 3. Claim 1 or 3, characterized in that the mechanism for obtaining the correction voltage from the amount of time change in the detected voltage in the correction voltage generating means has a variable amplification function capable of controlling the amplification factor from the outside. 2.Resistance measuring device.