JP3140648B2 - Semiconductor sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor sensor using a piezoresistor such as a semiconductor pressure sensor and a semiconductor acceleration sensor, and more particularly, to a piezoresistor, a thin film resistor and a peripheral circuit IC integrated on the same chip. It relates to a so-called integrated semiconductor sensor.

[0002] Semiconductor sensors using piezoresistors are
Used as a semiconductor pressure sensor or a semiconductor acceleration sensor to measure the intake pressure of an automobile engine, the suction pressure of a home vacuum cleaner, or the acceleration in the traveling direction or lateral direction applied to a running car Have been.

[0003]

2. Description of the Related Art In this semiconductor sensor, a piezoresistor is formed on the surface of a silicon single crystal wafer in the same manner as in the manufacture of ICs, and this is used as a strain gauge. That is, a diaphragm portion or the like is provided by shaving the back surface of a silicon single crystal wafer having a piezoresistor formed on the front surface by anisotropic etching or the like, so that the thinned portion is deformed by pressure or acceleration, As the resistance of the piezoresistor changes due to the deformation, an electric signal corresponding to pressure or acceleration is obtained.

Recently, in response to a demand for miniaturization of this type of semiconductor sensor, an integrated semiconductor sensor in which a peripheral circuit IC including an amplifier for amplifying an output in addition to a piezoresistor is integrated on the same chip has been developed. ing. In the integrated semiconductor sensor, the resistance value in the circuit is adjusted for each element in order to adjust the variation in the characteristics of each element, improve the temperature characteristics, and align the amplified output for each element. Need to be done every time. Therefore, in addition to the piezoresistor and the peripheral circuit IC, a metal thin film resistor such as a Cr / Si alloy for characteristic adjustment is integrated on the same chip, and the resistance value of the metal thin film resistor is adjusted by a laser trimming method. Generally, adjustment is made for each element. This makes it possible to obtain a miniaturized semiconductor sensor having uniform characteristics with only one semiconductor chip without requiring an external peripheral circuit.

Conventionally, the metal thin film resistor is formed in a pattern as shown in FIG. That is, in FIG. 4, the metal thin film resistor 18 is formed between the wiring line 16 and the wiring line 17 in a rectangular pattern. Rough adjustment trimming section 41 of this rectangular metal thin film resistor 18
By performing a large number of laser trimmings alternately from both sides (so-called serpentine cut),
The resistance value is roughly adjusted, and the fine adjustment trimming section 42 performs a so-called double cut to adjust the amount of laser trimming in the two cut grooves to finely adjust the resistance value.

[0006]

However, the conventional laser trimming for resistance adjustment using a combination of serpentine cut and double cut has many problems. First, it is often necessary to increase the amount of trimming of the resistor pattern. However, the cut surface obtained by laser trimming is an unstable portion in terms of characteristics. Problems such as becoming stable occur. That is, in an actual semiconductor sensor, pressure sensitivity characteristics and temperature characteristics vary greatly in the piezoresistor portion (thinned portion), and in some cases, the resistance value is increased by four times to adjust the gain and temperature characteristics of the amplifier. It is unavoidable that it is necessary to change the resistance pattern to a certain degree, and it is inevitable that the trimming amount of the resistance pattern must be increased. Also, a large amount of cut by laser trimming means that trimming takes a long time, and the work is laborious.

[0007] In view of the above, the present invention requires only a small amount of laser trimming of a metal thin film resistor pattern, and as a result, it is possible to improve the accuracy of the resistance value, and to facilitate the trimming operation and shorten the operation time. It is intended to provide a semiconductor sensor.

[0008]

According to the first aspect of the present invention, there is provided a semiconductor chip, a piezoresistor formed on the chip, and the same piezoresistor as the piezoresistor. In a piezo-type semiconductor sensor comprising a thin-film resistor formed between wiring lines on a semiconductor chip, a plurality of the thin-film resistor patterns are electrically connected in parallel with the wiring line. It is characterized by including a meandering ladder pattern for resistance coarse adjustment trimming having a narrow width portion and a rectangular pattern for resistance fine adjustment trimming continuous with the meandering ladder pattern.

[0009]

The thin-film resistor pattern formed on the same semiconductor chip as the piezoresistor is formed by a meandering ladder pattern having a plurality of narrow portions and a rectangular pattern for successively fine-tuning the resistance. Because of this, it is possible to digitally adjust the resistance value by cutting some of the multiple narrow parts of the meandering ladder pattern by laser trimming or the like. The fine adjustment of the resistance value can be performed by finely adjusting the cutting amount by analog. As described above, since the coarse adjustment and the fine adjustment can be easily performed, the accuracy of the resistance value can be improved. As a result, it is possible to easily and quickly perform high-precision adjustment work to suppress variations in the characteristics of a piezo-type integrated semiconductor sensor in which peripheral circuits are integrated with a piezoresistor on a single semiconductor chip. Becomes In particular, in the case of a piezo-type semiconductor sensor, pressure sensitivity characteristics and temperature characteristics at the piezoresistor portion vary widely,
In some cases, it is inevitable that it is necessary to change the resistance value to about four times in order to adjust the gain and temperature characteristics of the amplifier, and it is inevitable that the amount of trimming of the resistance pattern must be increased. Rough adjustment of resistance The ability to digitally adjust the resistance value by cutting some of the multiple narrow parts of the meandering ladder pattern for trimming means that the amount of trimming can be reduced so that trimming does not take much time. This means that work can be reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In one embodiment of the present invention, as shown in FIG. 1, the metal thin film resistor 15 is formed between the wiring lines 16 and 17 so as to have a meandering ladder pattern. This meandering ladder pattern constitutes a coarse adjustment trimming section 31, and is connected to the pattern of the wiring line 16 by a plurality of narrow width sections 33. The fine adjustment trimming section 32 has a simple rectangular pattern as in the related art. This metal thin film resistor 15 is, for example, Cr /
It is formed of a Si alloy or the like.

In this embodiment, the semiconductor sensor is configured as a semiconductor pressure sensor for detecting pressure, and is configured as shown in FIG. In FIG. 2, the sensor chip 10 is mounted on a substrate 22 via a glass pedestal 21. The sensor chip 10 has a diaphragm 13 that is deformed in response to pressure. Substrate 22
Are provided with lead pins 23, and are connected to the sensor chip 10 by gold wires 24.

Further, a pressure guiding pipe 25 is provided on the substrate 22.
Has been fixed. A through-hole communicating with the hollow portion of the pressure guiding pipe 25 is provided in the substrate 22, and a through-hole communicating with the through-hole is provided in the pedestal 21.
Pressure is guided to the diaphragm 13 of the sensor chip 10 by the pressure guiding pipe 25 and these through holes. When the diaphragm 13 is deformed by the pressure thus introduced, an electrical signal corresponding to the pressure is output from the lead pin 23.

The sensor chip 10 will be described in more detail with reference to FIG. p-type silicon wafer 1
First, various regions are formed by selectively diffusing various impurities using a normal semiconductor manufacturing technique. The piezoresistor 12 is formed as one of such regions. A thin portion (diaphragm portion) 13 is formed by partially shaving the back surface of the portion where the piezoresistor 12 is formed by anisotropic etching or the like.

In this embodiment, a circuit such as an amplifier is formed as a bipolar IC portion adjacent to a pressure-sensitive portion including a piezoresistor 12, and a metal thin film resistor 15 made of, for example, a Cr / Si alloy is formed on a surface adjacent to the pressure-sensitive portion. Are formed by a pattern of aluminum or the like.
7 are formed. The pattern of the metal thin film resistor 15 and the wiring lines 16 and 17 is as shown in FIG.

After being assembled as individual semiconductor pressure sensors as shown in FIG. 2, the metal thin film resistor 15 is cut by a laser trimming method in accordance with the variation in the characteristics of the individual semiconductor pressure sensors. In this case, the laser trimming for the coarse adjustment is performed by cutting the narrow width portion 33 of FIG. 1 as indicated by an arrow. Some of the plurality of narrow portions 33 are cut. In this case, the resistance value increases as the number of cut narrow portions 33 increases. Since each narrow portion 33 is either cut or left, the change in resistance value is stepwise and can be said to be digital. Since the narrow portion 33 is cut by laser trimming, the cut amount is small.

After the coarse adjustment laser trimming is completed, the fine adjustment trimming section 32 performs laser trimming for fine adjustment. In this case, double cutting is performed as indicated by an arrow as in the conventional case. The cutting amount (length of the cut groove) is continuously fine-tuned in an analog manner.
Thus, fine adjustment of the resistance value is performed.

In this embodiment, as described above, in addition to the fine adjustment trimming section 32 which can perform analog adjustment,
Since the metal thin film resistor 15 is provided with the rough adjustment trimming portion 31 of the meandering ladder pattern having the plurality of narrow width portions 33, the amount of cutting by laser trimming is small and the rough adjustment can be performed, and the adjustment work by laser trimming becomes easy. ,
The time required for the entire adjustment work can be reduced. Furthermore, since the number of cut surfaces after laser trimming is small, the initial drift of the resistance value can be reduced, and the accuracy of the resistance value can be improved.

The above is a description of one embodiment, and the pattern of the metal thin film resistor 15 and the setting of the cut surface by laser trimming can be variously changed. Although the semiconductor pressure sensor has been described above, it goes without saying that other semiconductor sensors such as a semiconductor acceleration sensor can be similarly applied.

[0019]

As described above, according to the semiconductor sensor of the present invention, the thin-film resistor is arbitrarily cut to adjust its resistance value in order to eliminate variations in characteristics of the semiconductor sensor. In this case, it is possible to improve the accuracy of the resistance value by reducing the cut surface which becomes an unstable factor, to stabilize the resistance value, and to facilitate the adjustment work,
In addition, the time for the adjustment operation can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a view showing a pattern of a metal thin film resistor of a semiconductor sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the whole of the embodiment.

FIG. 3 is a sectional view of a sensor chip portion in the embodiment.

FIG. 4 is a view showing a pattern of a metal thin film resistor of a conventional semiconductor sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Sensor chip 11 Silicon wafer 12 Piezoresistor 13 Diaphragm part 14 Bipolar IC part 15 Metal thin film resistance (this invention) 16, 17 Wiring line 18 Metal thin film resistance (conventional) 21 Pedestal 22 Substrate 23 Lead pin 24 Gold wire 25 Pressure guiding pipe 31, 41 Coarse adjustment trimming part 32, 42 Fine adjustment trimming part 33 Narrow width part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-34471 (JP, A) JP-A-1-251601 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 9/04 101 G01P 15/12

Claims (1)

(57) [Claims] 1. A piezo semiconductor sensor comprising: a semiconductor chip; a piezoresistor formed on the chip; and a thin film resistor formed between wiring lines on the same semiconductor chip as the piezoresistor. The thin-film resistor pattern is continuous with the meandering ladder pattern for resistance coarse adjustment trimming including a plurality of narrow portions in a relationship electrically connected in parallel with the wiring line. A piezoelectric semiconductor sensor comprising a rectangular pattern for trimming resistance fine adjustment.