JPH07114287B2 - Semiconductor resistance element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor resistance element used for a semiconductor strain gauge, a pressure sensor, an acceleration sensor, and the like.

(Prior Art) A conventional semiconductor resistance element is formed by forming a p-type or n-type diffusion layer on a silicon substrate by a thermal diffusion method.

(Problems to be Solved by the Invention) In the above-described conventional semiconductor resistance element using the thermal diffusion method, the impurity distribution is represented by a function represented by a complementary error function, and the piezoresistance coefficient of the diffusion layer is the impurity concentration distribution. In other words, it changes depending on the conductivity distribution. Therefore, the measured values of the piezoresistive coefficient and the gauge factor of the diffusion layer are given by the average value π of the conductivity distribution σ (X) of the diffusion layer and can be expressed by the following equation.

= 1 + γ + πE≈E (2) where X is the distance from the surface to the diffusion layer, X _o is the depth of the diffusion layer, π (X) is the piezoresistance coefficient in the diffusion layer, and s is the stress.
γ is the Poisson's ratio and E is the Young's modulus.

Equation (1) becomes non-linear due to π (X) {1-π (X) s}. Therefore, there is a disadvantage that the gauge factor of the semiconductor resistance element in which the diffusion layer is formed by thermal diffusivity decreases with the increase of the piezoresistance coefficient and also decreases with the increase of the stress. Further, the piezoresistive coefficient has a non-linearity with respect to temperature change, and there is a disadvantage that use at a high gauge factor is restricted.

(Means for Solving the Problem) The present invention was created by an experiment of excimer laser doping, and the invention according to claim 1 is a semiconductor resistance element, in which the concentration gradient is steep and the depth is less than 1000Å. 3. The invention according to claim 2, wherein a shallow diffusion layer is provided on a silicon substrate, a pn junction is formed by the diffusion layer, and a change in external force applied to the silicon substrate is detected as a change in resistance value of the diffusion layer. Is a semiconductor resistance element according to claim 1, wherein ohmic contact diffusion layers are provided at both ends of the diffusion layer, an insulating film for preventing current leakage is formed on the surface of the silicon substrate, and the insulating film is opened. An electrode is formed on the ohmic contact diffusion layer,
A third aspect of the present invention is the semiconductor resistance element according to any one of the first and second aspects, wherein a plurality of the diffusion layers are provided on one side or both sides of the same silicon substrate, and all or a bridge circuit is provided. It is characterized in that a part is formed.

(Operation) Obtaining a change in the external force applied to the silicon substrate by diffusing impurities in the silicon substrate, forming a pn junction in the diffusion layer, and detecting a change in the resistance value of the diffusion layer when an external force is applied. You can

If the diffusion layer is formed by the excimer laser doping method in which the rise of the pulse wave front is steep, the concentration gradient becomes steeper as compared with the thermal diffusion method of the solid line b in FIG. 1 as shown by the solid line a in FIG. Since the depth can be formed as shallow as less than 1000Å, that is, the so-called box-like impurity profile, the diffusion layer is not affected by the stress change in the depth direction, and the nonlinearity of the piezoresistive coefficient can be reduced. It is possible to use it with a high gauge rate exceeding.

Further, by providing ohmic contact diffusion layers at both ends of the diffusion layer, forming an insulating film on the surface of the silicon substrate, opening a window of the insulating film, and forming an electrode on the diffusion layer, current leakage is eliminated. , Improve the performance of the device.

Furthermore, since a plurality of diffusion layers are provided on one surface or both surfaces of the same silicon substrate to form the bridge circuit in whole or in part, temperature correction can be performed, so that the change in the piezoresistive coefficient with respect to temperature change can be made linear. It can be used with a high gauge rate.

(Example) Next, the Example of this invention is described based on drawing.

FIG. 2 shows a first embodiment of the semiconductor resistance element of the present invention, and its manufacturing process will be described below.

First, the n-type silicon substrate 1 (1a) is set to diborane gas (B ₂ H ₆ ).
The substrate 1 is irradiated with an XeCl excimer laser (wavelength 308 nm) consisting of a pulse having a steep wave front of 3 nanoseconds to melt the substrate 1 instantaneously and decompose the dibola gas adsorbed on the substrate 1 to decompose the substrate. 1 is doped with boron (B). At this time, a shallow p-type diffusion layer 2 (2b) of about several hundred Å is formed in which the impurity concentration profile is box-like by controlling the number of laser pulses and the energy density.

Then, a P ⁺ diffusion layer 3 (3b) is formed on both ends of the diffusion layer 2 of the substrate 1 by the same XeCl excimer laser doping,
Next, an insulating film 4 for preventing current leakage is formed on the entire surface of the substrate 1 which is XeCl excimer laser doped.

Finally, a hole 5 is formed in a portion of the insulating film 4 located above the ohmic contact diffusion layer 3 and an electrode 6 made of gold is formed by vacuum evaporation. In this way, the semiconductor resistance element 7 including the ohmic electrode 6 is obtained.

In this case, when an external force (stress) acts on the diffusion layer 2, the specific resistance ρ or the resistance value R of the diffusion layer 2 changes, and the change in the external force is detected in the form of stress s or strain ε according to the following equation. it can.

The semiconductor resistance element obtained by the above-described manufacturing process has a strain-resistance characteristic of linearity of 0.25% or less of full scale up to a stress of at least 800 kgf / cm ² .

Figure 3 shows the energy density of the excimer laser at 0.5 J / cm ²
Is an example of the result of measuring the gauge factor by changing the concentration of diborane gas, in other words, controlling the impurity concentration and changing the value of the specific resistance of the diffusion layer 2. According to this, the gauge factor increases as the resistivity increases, in other words, as the impurity concentration decreases, and becomes a solid line a, which is higher than the value of the dotted line b obtained by the thermal diffusion method. I understand.

FIG. 4 shows a second embodiment of the semiconductor resistance element of the present invention. In this case, a single p-type silicon substrate 1 (1b) is provided with an n-type diffusion layer 2 (2a) on one side. In the semiconductor resistance element 7 of FIG. 1, the n-type diffusion layer 2a having a shallow impurity concentration profile formed by excimer laser doping in the p-type silicon substrate 1b is in ohmic contact with the pair of electrodes 6 and 6. ⁺ Ohmic contact diffusion layers 3a and 3b and an insulating film 4 for preventing current leakage are provided.

In this case as well, as in the case of the first embodiment, a higher gauge factor than the thermal diffusion method can be obtained.

FIG. 5 shows a third embodiment of the semiconductor resistance element of the present invention, in which p is formed on one surface of the same n-type silicon substrate 1a.
A p-type semiconductor resistance element 7b in which two resistance bodies each including a diffusion layer 2b are provided to form a half of a bridge circuit of the resistance bodies. By using two sets of the p-type semiconductor resistance elements 7b, A bridge circuit is formed by the resistors.

If a p-type silicon substrate 1b is used, an n-type semiconductor resistance element
You can make 7a.

FIG. 6 shows a fourth embodiment of the semiconductor resistance element of the present invention, in which p is formed on one surface of the same n-type silicon substrate 1a.
This is a p-type semiconductor resistance element 7 in which four resistors made up of the diffusion layers 2b are provided to form the entire bridge circuit of the resistors.

If a p-type silicon substrate 1b is used, an n-type semiconductor resistance element
You can make 7a.

FIG. 7 shows a fifth embodiment of the semiconductor resistance element of the present invention, which is a resistor composed of a p-type or n-type diffusion layer 2 on both sides of the same n-type or p-type silicon substrate 1, respectively. It is a p-type or n-type semiconductor resistance element 7 in which two bodies are provided to form a bridge circuit by the resistors.

Also in the third to fifth embodiments, as in the first and second embodiments, the ohmic contact diffusion layer 3 which makes ohmic contact with the electrode 6 and the insulating film which prevents current leakage. 4 is provided to obtain a higher gauge factor than the thermal diffusion method. However, according to the third to fifth embodiments, since the bridge circuit is formed by the resistors, The temperature of the body can be corrected, the piezoresistive coefficient can be made linear with respect to the temperature change, and the strain-resistance characteristic having better linearity than that of the first and second embodiments can be obtained. .

By providing the insulating groove 8 to form the mesa structure as in the embodiment of FIGS. 8 and 9 or the embodiment of FIGS. 10 to 12, the current leakage can be prevented more reliably. it can.

(Effects of the Invention) As described above, the semiconductor resistance element of the present invention has a higher gauge factor than that of the conventional one in which a diffusion layer serving as a resistor is formed by a thermal diffusion method, and strain with good linearity is obtained. A semiconductor resistance element having resistance characteristics can be obtained, and if this semiconductor resistance element is used, the change in external force can be detected as a change in resistance with high sensitivity and linearity. The application of this semiconductor resistance element can be expected to produce highly sensitive semiconductor strain gauges, pressure sensors, acceleration sensors, and the like, and the effect of the present invention is great even for industrial applications.

Further, when the semiconductor resistance element according to claim 2 is used, current leakage is prevented, and the element performance is improved.

Further, according to the semiconductor resistance element of claim 3, the piezo resistance coefficient can be made linear with respect to the temperature change by correcting the temperature of the resistor formed of the diffusion layer, and the stability is further improved at a high gauge factor. Expected to be used.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a difference in impurity concentration distribution between excimer laser doping and thermal diffusion, FIG. 2 is a cut side view showing a first embodiment of a semiconductor resistance element of the present invention, and FIG.
Resistivity-gauge characteristics when boron is diffused into a silicon substrate in the 1> direction by excimer laser doping, FIG. 4 is a cut side view showing a second embodiment of the semiconductor resistance element of the present invention, and FIG. FIG. 6 is a plan view showing a third embodiment of the semiconductor resistance element of the present invention excluding the insulating film, and FIG. 6 is a plan view showing the fourth embodiment of the semiconductor resistance element of the present invention excluding the insulation film. 7 is a cut side view showing a fifth embodiment of the semiconductor resistance element of the present invention, FIG. 8 is a cut side view showing a sixth embodiment of the semiconductor resistance element of the present invention, and FIG. 9 is a plan view thereof.
FIG. 10 is a cut side view showing a seventh embodiment of the semiconductor resistance element of the present invention, FIG. 11 is its plan view, and FIG. 12 is XII of FIG.
It is a -XII sectional view. 1 ... Silicon substrate 1a ... n type silicon substrate 1b ... p type silicon substrate 2 ... diffusion layer 2a ... n type diffusion layer 2b ... p type diffusion layer 3 ... ohmic contact diffusion layer 3a ... n ⁺ ohmic contact diffusion layer 3b ... p ⁺ Ohmic contact diffusion layer 4 ... Insulating film 5 ... Hole 6 ... Electrode 7 ... Semiconductor resistance element 7a ... N-type semiconductor resistance element 7b ... P-type semiconductor resistance element 8 ... Insulation groove

Claims (3)

[Claims] 1. A shallow diffusion layer having a steep concentration gradient and a depth of less than 1000Å is provided on a silicon substrate, a pn junction is formed by the diffusion layer, and a change in external force applied to the silicon substrate is measured by a resistance value of the diffusion layer. Semiconductor resistance element that detects changes in 2. An ohmic contact diffusion layer is provided on both ends of the diffusion layer, an insulating film for preventing current leakage is formed on the surface of the silicon substrate, and the insulating film is opened to form a window on the ohmic contact diffusion layer. The semiconductor resistance element according to claim 1, wherein an electrode is formed. 3. The silicon substrate according to claim 1, wherein a plurality of the diffusion layers are provided on one surface or both surfaces of the same silicon substrate to form all or part of a bridge circuit. Semiconductor resistance element.