RU2531381C1 - High-power semiconductor resistor and method of making said resistor - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: group of inventions relates to the design and technology of producing semiconductor devices. A resistive element provides content of platinum atoms, selected as an impurity which creates deep trapping levels in a silicon band gap, with concentration ranging from 2.5·10¹³ cm^-3 for silicon with p-type conductivity with initial resistivity ρ_p0=150 ohm·cm to 9·10¹⁴ cm^-3 for silicon with p-type conductivity with ρ_p0=0.4 ohm·cm, and the disclosed method of making a high-power semiconductor resistor includes diffusion of platinum atoms at temperature ranging from 870°C for silicon with p-type conductivity with initial resistivity ρ_p0=150 ohm·cm to 1190°C for silicon with p-type conductivity with ρ_p0=0.4 ohm·cm.

EFFECT: providing high temperature stability of resistance, increasing the maximum allowable temperature of the resistor (to +260°C) and the operating pulsed voltage 2-2,5 times (to 5000 V).

2 cl, 2 dwg, 3 tbl

Description

The proposed group of inventions relates to the design and manufacturing technology of semiconductor devices and can be used in the manufacture of high-power high-voltage high-temperature silicon resistors and tablet shunts having high temperature resistance in a wide range of operating temperatures.

The most effective is their use in powerful conversion technology in a single cooling system with key tablet-type semiconductor devices (powerful thyristors, IGBT, IGCT, etc.).

A powerful semiconductor resistor is known (RU 2206146 C1, H01L 29/36, published June 10, 2003, item 1) [1], consisting of a resistive element made in the form of a disk of n-type monocrystalline silicon containing electrical conductivity, containing platinum atoms with a concentration of 1.1 · 10 ¹⁴ cm ^-3 for silicon with an initial specific resistance ρ ₀ of 150 Ohm · cm, up to 1.1 · 10 ¹⁷ cm ^-3 for silicon with a ρ ₀ of 0.8 Ohm ·cm.

The ratio of the introduced concentration of platinum atoms (N _Pt ), proposed in solution [1], depending on the initial specific resistivity of silicon (ρ ₀ ) in order to reduce the temperature dependence of the resistance is valid for resistors made exclusively of n-type silicon of electrical conductivity.

Also known is a powerful semiconductor resistor (GB 2025147 V, class N1K, IPC: H01C 7/06, published September 22, 1992) [2], selected as a prototype and containing a resistive element that is made of p-type single crystal silicon of electrical conductivity containing impurity atoms, creating deep levels of capture in the band gap of silicon.

In a specific example of execution [2], the design of a resistive element made of p-type silicon of electrical conductivity with an initial specific resistance ρ _p0 equal to 5 Ω · cm is given. In order to reduce the temperature dependence of the resistance of TCS from 215% to 20% in the temperature range 25-200 ° C, the diffusion of gold atoms was carried out, while neither the diffusion temperature of gold atoms nor the amount of introduced gold were specified, the knowledge of which is necessary to achieve the specified in [2 ] result.

A known method of manufacturing a powerful semiconductor resistor based on monocrystalline silicon n-type electrical conductivity (RU 2206146 C1, H01L 29/36, published June 10, 2003, p. 2 f-ly) [1], including the creation of a silicon resistive element diffusion contact regions, conducting diffusion of platinum atoms at a temperature of from 910 ° C for silicon with an initial specific resistance ρ ₀ equal to 150 Ω · cm, up to 1300 ° C for silicon with ρ ₀ equal to 0.8 Ω · cm.

The diffusion modes of platinum atoms indicated in [1, Section 2] to minimize the TCS resistor, strictly related to the initial value of the resistivity, are suitable only for n-type silicon with electrical conductivity.

The closest is a method of manufacturing a powerful semiconductor resistor (GB 2025147 V, class N1K, IPC: H01C 7/06, published 09/22/82) [2], including the creation in a silicon resistive element of a p-type electrical conductivity of diffusion contact regions p- such as electrical conductivity, conducting diffusion of impurity atoms, creating deep levels of capture in the silicon forbidden zone before creating metal contacts. As shown in the example of the implementation of the technical solution [2], gold was used as an impurity that creates deep levels of capture in the band gap of silicon p-type electrical conductivity. It was indicated that the initial specific resistivity of p-type silicon of electrical conductivity ρ _p0 was 5 Ohm · cm, the diffusion of gold atoms was carried out at a temperature from the interval (800 ÷ 1000) ° C for two hours. In the indicated range of diffusion temperature, the concentration of gold atoms varies several times, as a result of which it is impossible to predict the degree of compensation of the temperature dependence of resistance (TCS).

As our studies show, in the manufacture of silicon resistors to obtain TCS ≤ ± 10%, the temperature and diffusion time of “deep” impurities are strictly related to the value of the initial silicon resistivity of both n- and p-type conductivity.

Recently, in the development of powerful silicon resistors, great interest has been shown in p-type silicon of electrical conductivity. First of all, this is due to the possibility of increasing the pulse operating voltage (Urab) of resistors made of p-type silicon of electrical conductivity, because the critical electric field in p-Si (E _cr = 7.5 · 10 ³ V / cm) is about 3 times greater than in n-Si (E _cr = 2.5 · 10 ³ V / cm) (Fistul V .I. Introduction to Semiconductor Physics. Moscow, Higher School, 1975) [3], a U _slave = E _cr · d: where d is the thickness of the resistive element.

The main objective of the proposed group of technical solutions is to create a powerful semiconductor resistor based on silicon p-type electrical conductivity containing impurities that create deep levels in the silicon forbidden zone, and a method for its manufacture, which, while maintaining high temperature stability of the resistance (i.e. worse than ± 10%) to increase the maximum allowable temperature of the resistor (up to + 260 ° C) and the working impulse voltage by 2 ÷ 2.5 times (up to 5000 V) without significant material costs.

The technical result of the proposed group of inventions is:

- by reducing the temperature dependence of resistance from 100 ÷ 200% to ± 10% (while TCS tends to 0) in high-power silicon resistors made on p-type silicon of electrical conductivity and containing impurities that create deep levels of capture in the band gap of silicon, increase Efficiency and reliability of the devices using the proposed powerful silicon resistors (power supplies, converters, snubbers, etc.);

- by increasing the maximum allowable temperature to + 260 ° C, it is possible to increase the real power of the resistor (by 10 ÷ 15%) without changing the dimensions and price, which increases the margin for overheating and, as a result, their reliability and service life;

- the possibility of increasing the pulse voltage of a discrete resistor allows to reduce the number of resistors in high-voltage assemblies, which reduces the overall dimensions and the price of power equipment;

- while maintaining the magnitude of the pulse voltage, it is possible to reduce the thickness of the silicon wafer and, as a consequence, reduce the cost of manufacturing devices by 20 ÷ 30%.

To achieve the task and the technical result indicated above, in a powerful semiconductor resistor containing a resistive element, which is made in the form of a p-type single-crystal silicon disk with p-type contact regions on both sides and contains impurity atoms that create deep capture levels in the silicon forbidden zone, platinum atoms with a concentration of 2.5 · 10 ¹³ cm ^{-3 were} selected as impurity atoms creating deep trapping levels in the silicon forbidden zone for silicon p-type electrical conductivity with an initial specific resistance ρ _p0 = 150 Ohm · cm to 9 · 10 ¹⁴ cm ^-3 for silicon p-type electrical conductivity with ρ _p0 = 0.4 Ohm · cm.

To achieve the task and technical result in a method for manufacturing a powerful semiconductor resistor, which includes creating p-type electrical conductivity in a silicon resistive element on both sides of the p-type electrical contact regions, conducting diffusion of impurity atoms, creating deep trapping levels in the band gap of silicon, diffusion carried out by platinum atoms at a temperature of from 870 ° C for p-type silicon with an initial specific resistance ρ _p0 = 150 Ohm · cm to 1190 ° C for p-type silicon electrical conductivity with the initial specific resistance ρ _p0 = 0.4 Ohm · cm.

The achieved technical effect when using the above distinguishing features is explained by the fact that the growing temperature dependence of the resistivity of silicon is ρ _p0 = 1 / p _o · q · µ _p (where p ₀ is the concentration of mobile holes in the valence band of the initial silicon; q is the electron charge; μ _p - hole mobility) is determined by the temperature dependence of the incident hole mobility μ _p ≈T ^-2,2 range of operating temperatures of the resistor, which is proposed to compensate for the increasing of the temperature dependence of the hole concentration p _o ≈T ^+2,2 (TCS strives I to 0) liberated with increasing temperature of the trapping centers introduced by diffusion of platinum atoms. In this case, the values of the concentration of trapping centers (N _Pt ), the depths of their occurrence in the band gap of silicon (Et) and the cross section of hole capture (σ _p ) with the initial concentration of moving holes (p ₀ = 1 / ρ _po ) in the valence band and temperature dependence of hole mobility in the initial p-type silicon of electrical conductivity. The ratios of the required platinum concentration (N _pt ) determined by the diffusion temperature (T _D ) depending on the initial resistivity (ρ _po ) were experimentally found. Thus, to reduce the temperature dependence of the resistance of powerful silicon resistors, simply introducing atoms of "deep" impurities is not sufficient.

The content of platinum atoms with a concentration in the range from 2.5 · 10 ¹³ cm ^-3 for silicon p-type electrical conductivity with an initial specific resistance ρ _p0 = 150 Ohm · cm to 9 · 10 ¹⁴ cm ^-3 for silicon p-type electrical conductivity with ρ _p0 = 0.4 Ohm · cm in the resistive element and conducting for this diffusion of platinum atoms at a temperature in the range from 870 ° C for silicon p-type conductivity with the initial specific resistance ρ _p0 = 150 Ohm · cm to 1190 ° C for silicon p -type conductivity with ρ _p0 = 0,4 ohm · cm in the method of manufacturing a power semiconductor resistor Parts Required and sufficient to reduce the TCS to ± 10% over a wide range of operating temperatures.

Known technical solutions with such a combination of features were not found in the patent and scientific literature, which allows us to conclude that the proposed group of technical solutions meets the criterion of "novelty."

The claimed technical solutions are characterized by a combination of features exhibiting new qualities, which allows us to conclude that the proposed technical solutions meet the criterion of "inventive step".

Figure 1 shows the design of the resistive element of the inventive powerful semiconductor resistor.

Figure 2 shows, for comparison, the experimental dependences of the required diffusion temperature of platinum atoms in resistive elements made of n-type silicon of electrical conductivity (curve 1) by the known method [1, item 2], and in resistive elements of silicon p-type electrical conductivity (curve 2) according to the proposed method from the value of the initial specific resistivity of silicon ρ ₀ to ensure TCS≤ ± 10%.

The basis of a powerful semiconductor resistor is the resistive element shown in FIG. 1, which has: a substrate in the form of a p-type single-crystal silicon disk 1 of conductivity; p-type diffusion contact regions 2 on both sides of the substrate 1; aluminum contacts 3 sprayed onto p-type contact areas 2; chamfers 4 to eliminate the influence of edge effects on both sides of the substrate in the form of a disk 1; organosilicon compound (KLT) 5, which protects bevels 4.

Platinum atoms are introduced by diffusion before deposition of Al contacts 3. The resistive element is placed in a tablet case (not shown in FIG. 1).

The linearity of the current-voltage characteristic of the resistor is achieved using diffusion near-contact regions of p ⁺ type 2 formed by diffusion of boron atoms under aluminum contacts 3.

During operation, the resistive element can heat in the temperature range from room temperature + 25 ° C to the maximum allowable (T _rm ). A resistive element not doped with platinum atoms has a TCS≥100%, which can lead to a violation of the thermal regimes of the circuit. TCS is improved by introducing platinum atoms, which create deep capture levels in the band gap of silicon, which compensate for the decreasing temperature characteristic of charge carrier mobility (µp ~ 1 / T) by the increasing temperature dependence of the concentration of charge carriers released from the donor level of platinum. The required value of the concentration of platinum (N _Pt ) to ensure TCS ≤ ± 10% is strictly related to the initial value of the specific resistance of silicon p-type conductivity (ρ _p0 ).

A comparative analysis of the dependences shown in Fig. 2 shows that the achievement of TCS ≤ ± 10% in samples made of p-type silicon of electrical conductivity occurs at lower diffusion temperatures of platinum atoms. In addition, the use of platinum diffusion in the manufacture of resistive elements based on silicon p-type electrical conductivity allowed us to expand the range of applicability of the initial resistivity to lower values ρ _p0 = 0.4 Ohm · cm and, as a result, increase the maximum allowable temperature of the resistors to +260 ° C without a significant increase in manufacturing costs.

The boundaries of the proposed interval of the initial specific resistivity of silicon p-type electrical conductivity ρ _p0 = 0.4 ÷ 150 Ohm · cm are justified as follows.

The choice of the upper limit ρ _p0 = 150 Ohm · cm is due to the fact that exceeding ρ _p0 = 150 Ohm · cm leads to a decrease in the maximum allowable temperature of the resistor T _rm ≤125 ° C, which is a violation of the technical specifications for the resistor.

The choice of the lower limit of the initial specific resistance equal to 0.4 Ohm · cm is associated with the limiting solubility of platinum atoms of 9 · 10 ¹⁴ cm ^-3 at a temperature of 1190 ° C in p-type silicon of electrical conductivity. Those. when using p-type silicon of electrical conductivity with ρ _p0 = 0.3 Ohm · cm to ensure TCS ≤ ± 10%, the diffusion temperature of platinum atoms was increased to 1200 ° C, however, the platinum concentration did not increase, and TCS exceeded the allowable limit.

The choice of the ranges of concentrations of platinum atoms and diffusion temperatures (870-1190 ° C) depending on the initial specific resistance (ρ _p0 ) is justified in a specific example of execution with the data presented in table 1.

Concrete example

In the manufacture of experimental samples of resistive elements, which are silicon disks 1 with a diameter of 32 mm, a thickness of 2.5 mm, of single-crystal silicon p-type electrical conductivity of the KDB brand with different resistivities ρ _p0 = 0.3 Ohm · cm, 0.4 Ohm · cm ; 0.8 ohm cm; 4.0 ohm cm; 20 ohm cm; 60 ohm cm; 150 ohm cm; 160 Ohm · cm, the proposed method was used.

Production was carried out according to the following scheme:

- cutting silicon ingots into wafers with a thickness of 2.6 mm;

- cutting discs 1 with a diameter of 32 mm;

- grinding with M28 micropowder on both sides of 50 microns to a thickness of 2.5 mm;

- creation of the contact areas of the 2 p ⁺ -type of electrical conductivity by two-stage boron diffusion, including a boron flare at a temperature of 1150 ° C for 1.5 hours, removal of borosilicate glass and boron distillation at a temperature of 1200 ° C for 25 hours;

- control of diffusion parameters (the depth of the p ⁺ type conductivity layers is about 20 μm and the surface boron concentration is ~ 10 ¹⁹ cm ^-3 );

- conducting diffusion of platinum atoms (an alcohol solution of platinum-hydrochloric acid, which is applied from 2 sides of silicon disks 1, is used as a source) in an atmosphere of air for 2 ÷ 3 hours at temperatures: a) for silicon with ρ _p0 = 0, 3 Ohm · cm T _d = 1200 ° C; b) for silicon with ρ _p0 = 0.4 Ohm · cm T _d = 1190 ° C; c) for silicon with ρ _p0 = 0.8 Ohm · cm T _d = 1180 ° C, 1185 ° C and 1190 ° C; d) for silicon with ρ _p0 = 4.0 Ohm · cm T _d = 1140 ° C, 1150 ° C and 1130 ° C; d) for silicon with ρ _p0 = 20 Ohm · cm T _d = 1060 ° C, 1070 ° C and 1050 ° C; f) for silicon with ρ _p0 = 60 Ohm · cm T _d = 970 ° C; g) for silicon with ρ _p0 = 150 Ohm · cm T _d = 870 ° C; h) for silicon with ρ _p0 = 160 Ohm · cm T _d = 860 ° C;

- creation of ohmic contacts 3 by spraying aluminum (metallization diameter 30 mm) according to standard technology;

- chamfering 4 from the side surface of the disks 1 to the boundary of the Al-contact 3;

- etching of the chamfers 4 and protection with a silicon-organic compound (KLT) 5, followed by drying at 180 ° C for 10 hours;

- measurement of the main parameters and characteristics: nominal resistance, TCS and current-voltage characteristics;

- assembly of elements in tablet housings of the type KZhTD4-32 (not shown in figure 1). The above relations between the values of the initial specific resistance (ρ _p0 ) and the required diffusion temperature of platinum atoms (T _d ) are taken from more numerous experimental studies sufficient to build the dependences of T _d on ρ _p0 (Figure 2, curve 2).

Table 1 and figure 2 shows the results of experimental studies. The number of elements made of p-type silicon of electrical conductivity with different initial specific resistivity ρ _p0 under various diffusion regimes of platinum atoms was 8-10 pcs.

Table 1 No. ρ _p0 , Ohm · cm N _Pt , cm ^-3 T _d , ° C R _nom , Ohm TCS,% T _rm , ° C one 160 2 · 10 ¹³ 860 11.2 ± 6.0 120 ÷ 125 2 150 2.510 ¹³ 870 10.5 ± 8.0 125 3 60 6 · 10 ¹³ 970 4.2 ± 6.0 160 four twenty 2 · 10 ¹⁴ 1060 1.4 ± 10.0 180 5 4.0 4 · 10 ¹⁴ 1140 0.28 -8.0 200 6 0.8 8 · 10 ¹⁴ 1185 0.056 -8.0 240 7 0.4 9 · 10 ¹⁴ 1190 0,028 -10.0 260 8 0.3 9 · 10 ¹⁴ 1195 0,021 -12.0 265

where ρ _p0 is the initial specific resistivity of silicon p-type conductivity;

N _Pt is the concentration of platinum atoms required to minimize TCS;

R _nom - nominal resistance of the resistor;

TCS - temperature characteristic of the resistor;

T _rm is the maximum allowable temperature of the resistor;

T _d - the diffusion temperature of platinum atoms, providing the desired concentration of platinum.

Table 2 shows the effect of deviations from the recommended diffusion temperatures of platinum atoms and the corresponding concentrations of platinum atoms indicated in Table 1, using silicon p-type conductivity as an example with an initial specific resistance ρ _p0 of 0.8; 4.0; 20.0 (Ohm · cm).

table 2 T _d , ° C N _Pt , cm ^-3 R, Ω TXC% T _rm , ° C ρ _po = 0.8 Ohm · cm 1190 9 · 10 ¹⁴ 0.06 -12 240 1185 8 · 10 ¹⁴ 0.056 -8 240 1180 7 · 10 ¹⁴ 0.05 -eleven 240 ρ _po = 4.0 Ohm · cm 1150 4,510 ¹⁴ 0.3 -13 200 1140 4 · 10 ¹⁴ 0.28 -8 200 1130 3.610 ¹⁴ 0.24 -10 200 ρ _po = 20 Ohm · cm 1070 2.210 ¹⁴ 1.45 -12 180 1060 2 · 10 ¹⁴ 1.4 ± 12 180 1050 1.810 ¹⁴ 1.36 +12 180

As follows from a comparative analysis of the results shown in Table 2, a slight deviation of the diffusion mode of platinum leads to a significant deterioration in TXC and a decrease in the yield of devices with the required TXC. Similar conclusions apply to samples with other ρ _po values.

To compare the proposed manufacturing method with the known prototype [2] is not possible due to the fact that the prototype temperature range of diffusion of gold atoms (in the present method suggests diffusion of platinum atoms) 800-1000 ° C is not consistent with the initial specific resistance of p-type silicon electrical conductivity. For example, if gold is diffused into a silicon-based resistive element with an initial specific resistance of 5 Ohm · cm at a temperature of 850 ° C (from the indicated interval) for two hours, then the TXC of such a resistor will be more than 120%, which does not correspond to the given technical effect with a value of 20% in [2], ie this result cannot be compared.

The advantages of the proposed design of a powerful semiconductor resistor and method of its manufacture, are presented in table 3, include:

- the possibility of increasing the pulse operating voltage due to the use of silicon p-type electrical conductivity, for which the diffusion temperature of platinum atoms is determined, providing the required TXC;

- the possibility of increasing the maximum permissible temperature of the resistor to + 260 ° C and, as a result, increasing the nominal power while maintaining the temperature stability of the resistance and relatively low cost.

Table 3 Resistor RK133 By analogy [1] (ρ _p0 = 0.8 Ohm · cm) The proposed solution (ρ _p0 = 0.4 Ohm · cm) U _rm , V 2500 5000 T _rm , ° C 240 260 P _nom , Tue 3100 3500 R _nom , Ohm 0.056 0,028

Claims (2)

1. A powerful semiconductor resistor containing a resistive element, which is made in the form of a disk of single-crystal silicon p-type electrical conductivity with the contact areas of the p ⁺ type conductivity on both sides and contains impurity atoms that create deep levels of capture in the band gap of silicon, characterized in in that the impurity atoms that create deep trapping levels in the band gap of silicon, platinum atoms are selected having a concentration of 2.5 × 10 ¹³ cm ^-3 for the p-type silicon with an initial specific conductivity with resistance ρ _p0 = 150 ohm-cm to 9 x 10 ¹⁴ cm ^-3 for the p-type silicon with electrical conductivity ρ _p0 = 0.4 ohm-cm. 2. A method of manufacturing a powerful semiconductor resistor, including the creation in a silicon resistive element of p-type electrical conductivity on both sides of the contact areas of the p ⁺ type of electrical conductivity, the diffusion of impurity atoms creating deep levels of capture in the band gap of silicon, characterized in that the diffusion is carried out by atoms platinum at a temperature of 870 ° C for a silicon p-type conductivity with the initial resistivity ρ _p0 = 150 Ohm · cm to 1190 ° C for silicon p-type conductivity with a specific starting with rotivleniem ρ _p0 = 0.4 ohm-cm.

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