RU2086043C1 - Power semiconductor resistor and method for its manufacturing - Google Patents

Abstract

FIELD: semiconductor instruments. SUBSTANCE: device is designed as n-type monocrystal silicon with radiation flaws which concentration is in range from 3•10¹² per cubic centimeter for silicon which specific resistance ρ_o= 700 to 3•10¹³ per cubic centimeter for silicon which specific resistance ρ_o= 150. Flaws in silicon are generated by means of electron beam which power is 2-5 MeV and density is in range from 2,5•10¹⁴ per square centimeter for silicon with ρ_o= 700 to 2,5•10¹⁵ per square centimeter for silicon with ρ_o= 150. After radiation temperature-stabilization firing is performed. EFFECT: increased functional capabilities. 2 cl, 4 tbl, 2 dwg

Description

 The invention relates to the design and manufacturing technology of semiconductor devices and can be used in the production of powerful silicon tablet-type resistors having high temperature resistance resistance. The most effective is their use in powerful conversion technology in a single cooling system with key tablet-type semiconductor devices (powerful diodes, thyristors, etc.).

 Powerful non-wire resistors with metal oxide resistive elements are known [1] However, such resistors have a low ratio of rated power to volume and, as a result, the use of such resistors worsens the overall dimensions of converting devices.

Also known is a semiconductor resistor [2] consisting of a resistive element made in the form of a disk of monocrystalline silicon p-type conductivity with a specific resistance (ρ _o ) of 150 700 Ohm • see

 However, the resistance of such a resistor is very unstable in the operating temperature range, while there is a wide range of applications of silicon resistors in power systems of electrical equipment, powerful converting equipment, etc. where a fairly high stability of resistance is required.

 A known method of manufacturing a powerful semiconductor resistor [3] comprising creating in the silicon resistive element diffusion contact areas and sputtering of metal contacts.

 In this method, the creation of diffusion near-contact regions provides a linear current-voltage characteristic of the resistor, but does not compensate for the strong change in its resistance from temperature.

 There is another method of manufacturing a powerful semiconductor resistor [4], which includes the creation of diffusion contact areas in a silicon resistive element, the introduction of defects that create deep energy levels in the silicon forbidden zone, and the deposition of metal contacts.

Defects are introduced through diffusion into the resistive element of a deep impurity of gold, platinum, etc. This solution allows you to compensate for the temperature characteristic of resistance (TXC) only up to ± 25% in the temperature range from +25 ^o C to +125 ^o C.

где R_ном номинальное сопротивление, измеренное при 25^oC, Ом;
R сопротивление, измеренное при максимальной температуре +125^oC, Ом.The temperature characteristic of resistance is defined as

where R _{nom is the} nominal resistance measured at 25 ^o C, Ohm;
R resistance, measured at a maximum temperature of +125 ^o C, Ohm.

 The purpose of the invention is to increase the thermal stability of the resistance of a powerful semiconductor resistor in the operating temperature range and manufacturability of the method.

To do this, in a known powerful semiconductor resistor consisting of a resistive element made in the form of a disk of single-crystal silicon and p-type conductivity with a specific resistance (ρ _o ) of 150 700 Ohm • cm, the resistive element contains radiation defects with a concentration of 3 • 10 ¹² cm ^-3 for silicon with ρ _o 700 Ohm • cm to 3 • 10 ¹³ cm ^-3 for silicon with ρ _o 150 Ohm • see

In the known method for manufacturing a powerful semiconductor resistor, including creating in the silicon resistive element diffusive contact areas, introducing defects that create deep energy levels in the silicon forbidden zone, and sputtering metal contacts, defects are introduced after the metal contacts are sputtered by irradiating the resistive element with accelerated electrons with energy 2 -5 MeV, dose from 2.5 • 10 ¹⁴ cm ^-2 for silicon with ρ _o 700 Ohm • cm to 2.5 • 10 ¹⁵ cm ^-2 for silicon with ρ _o 150 Ohm • cm followed by thermal stabilization annealing.

Distinctive features of the proposed technical solutions:
1. The resistive element contains radiation defects with a concentration lying in the range from 3 • 10 ^o C cm ^-3 for silicon p-type conductivity with ρ _o 700 Ohm • cm to 3 • 10 ^o C cm ^-3 for silicon with ρ _o 150 Ohm • cm;
2. These defects are introduced by irradiating the resistive element with accelerated electrons with an energy of 2-5 MEV, a dose lying in the range from 2.5 • 10 ¹⁴ cm ^-2 for p-type silicon of electrical conductivity with ρ _o 700 Ohm • cm to 2.5 • 10 ¹⁵ cm ^-2 for silicon with ρ _o 150 Ohm • cm;
3. Defects are introduced after the operation of sputtering contacts, ie the sequence of operations has been changed;
4. After electron irradiation, thermostabilizing annealing is performed.

 Known technical solutions with such a combination of features are not found in the scientific and technical literature.

The main positive effects of the proposed technical solutions are:
improving the thermal stability of a semiconductor resistor to a TXC value of not more than ± 10% in the operating temperature range from +25 ^o C to +125 ^o C while increasing the nominal resistance R _nom ;
high adaptability of the method.

Improving the thermal stability of a semiconductor resistor while increasing R _{nom is} achieved by introducing radiation defects with the concentration indicated above into the resistor element.

,
где n концентрация носителей заряда (НЗ) в кремнии после облучения ускоренными электронами, см^-3;
n₀ концентрация НЗ в кремнии до облучения, см^-3;
Φ(см^-2) доза облучения;
K_i скорость введения дефекта i-го типа, см^-1;
g_i спиновый фактор вырождения дефекта, отн.ед.As a result of irradiation with accelerated electrons, several types of radiation defects are formed in the silicon crystal lattice, creating a spectrum of deep energy levels (GI) in the band gap of silicon [5]
The GU spectrum affects the concentration of the main charge carriers (electrons in p-silicon) in accordance with the formula:

,
where n is the concentration of charge carriers (NS) in silicon after irradiation with accelerated electrons, cm ^-3 ;
n _{0 the} concentration of NS in silicon before irradiation, cm ^-3 ;
Φ (cm ^-2 ) radiation dose;
K _{i the} rate of introduction of the defect of the i-th type, cm ^-1 ;
g _i spin factor of degeneracy of the def, rel.

E _{i is the} energy level of the defect of the i-th type, eV;
F position of the Fermi level, eV;
k Boltzmann constant, eV / K;
T absolute temperature, K.

где

суммарная концентрация неотожженных радиационных дефектов (р. д.) (далее по тексту концентрация радиационных дефектов), см^-3.When conducting thermally stabilizing annealing after electron irradiation, formula (2) takes the form

Where

total concentration of unannealed radiation defects (s.d.) (hereinafter referred to as the concentration of radiation defects), cm ^-3 .

The mobility of charge carriers (nc) varies with temperature according to the law
μ = AT- ^α , (4)
where μ is the N.C. mobility cm ² / V • s;
A, α are constant coefficients;
T absolute temperature, K.

где ρ удельное сопротивление кремния после облучения и отжига, Ом;
q=1,6•10^-19 [Кл] заряд электрона;
m подвижность н.з. см²/В•;
n концентрация н.з. см^-3.The specific resistance of silicon after irradiation and annealing is

where ρ is the resistivity of silicon after irradiation and annealing, Ohm;
q = 1.6 • 10 ^-19 [C] electron charge;
m N.C. mobility cm ² / V •;
n concentration n.a. cm ^-3 .

в формуле (3). Для кремния п-типа электропроводности с ρ_o 150 Ом•см оптимальная суммарная концентрация р. д. после облучения и термостабилизирующего отжига равна ≈ 3•10¹³ см^-3, а для кремния с ρ_o 700 Ом•см

Этим концентрациям соответствуют дозы облучения: Φ 2,5•10¹⁵ см^-2 для кремния с r_o 150 Ом•см и Φ 2,5•10¹⁴ см^-2 для кремния с r_o 700 ом•см. Причем при выходе за границы указанных доз электронного облучения изменяется концентрация р.д. (после отжига) и существенно ухудшается ТХС, что подтверждено экспериментально (табл. 1 3). Высокая технологичность предлагаемого способа изготовления мощного полупроводникового резистора достигается благодаря следующим преимуществам радиационной технологии:
равномерности введения дефектов по площади единичного резистора элемента и большой партии элементов, что существенно снижает разброс параметров резисторов (например, в сравнении с диффузией примесных глубоких центров);
возможности прецизионной подгонки режимов электронного облучения и последующего термостабилизирующего отжига в зависимости от исходных и требуемых значений сопротивления резистора, что позволяет значительно повысить процент выхода годных образцов.The nature of the stabilization of the temperature dependence of the specific resistance of silicon from which the resistive element is made is determined by the total concentration of radiation defects

in the formula (3). For silicon p-type conductivity with ρ _o 150 Ohm • cm, the optimal total concentration of p. after irradiation and thermostabilizing annealing is ≈ 3 • 10 ¹³ cm ^-3 , and for silicon with ρ _o 700 Ohm • cm

The radiation doses correspond to these concentrations: Φ 2.5 • 10 ¹⁵ cm ^-2 for silicon with r _o 150 Ohm • cm and Φ 2.5 • 10 ¹⁴ cm ^-2 for silicon with r _o 700 ohm • cm. Moreover, when going beyond the boundaries of the indicated doses of electron irradiation, the concentration of the s.d. (after annealing) and TCS deteriorates significantly, which is confirmed experimentally (tab. 1 3). High manufacturability of the proposed method for manufacturing a powerful semiconductor resistor is achieved due to the following advantages of radiation technology:
uniformity of introduction of defects over the area of a single element resistor and a large batch of elements, which significantly reduces the spread of resistor parameters (for example, in comparison with the diffusion of deep impurity centers);
the possibility of precision fitting of the electron irradiation regimes and subsequent thermostabilizing annealing depending on the initial and required values of the resistor resistance, which can significantly increase the percentage of suitable samples.

 The electron energy limits of 2-5 MeV are limited by a decrease in the manufacturability of the manufacturing method (reproducibility, deterioration, etc.).

The need for the irradiation of the resistive element after the deposition of metal contacts is due to the fact that the creation of metal contacts is accompanied by high-temperature treatment (for example, Al is burned at T ≈ 500 ^o C), which leads to uncontrolled annealing of radiation defects.

 To increase the temperature stability of the resistance after irradiation of the resistive element with accelerated electrons, thermostabilizing annealing is required.

 Thus, each of the signs is necessary, and together they are sufficient to achieve the goal.

In FIG. 1 shows the design of the resistive element of the inventive powerful semiconductor resistor; in FIG. 2 comparative temperature dependence of the resistance (at ρ _o 400 Ohm • cm and other equal conditions): a proposed semiconductor resistor; b a resistor made by a known design adopted as a prototype; in a resistor made by known technology adopted as a prototype.

The semiconductor resistor consists of a resistive element (Fig. 1), made of p-type single-crystal silicon in the form of a disk, which includes P ⁺ type 1 diffusion contact regions with metal (Al) contacts 2 deposited on them. To remove edge effects the disk has a chamfer 3, protected by an organosilicon compound (CLT) 4. Radiation defects were introduced by electron irradiation (e ^- ). The resistive element is placed in a tablet case (not shown).

The semiconductor resistor works as part of electrical circuits of both alternating and direct current as a constant type resistor. During operation during natural or liquid cooling, the resistive element heats up in the range from +25 to +125 ^o C. When heated, the resistance of the resistor changes within insignificant limits (TCS no more than ± 10% of the nominal value; Fig. 2, curve a). This allows you to save the parameters of the electrical circuit in the operating temperature range. The current-voltage characteristic of the resistor is linear in both directions due to highly doped contact areas and metal contacts on both sides.

An example of a specific implementation. The proposed method was used in the manufacture of resistive elements from ingots of neutron-doped p-silicon grade KOF 56-400. The following sequence of operations was used:
cutting a silicon ingot into wafers 2.01 mm thick and cutting from them disks with a diameter of 24 mm;
grinding discs with micropowder M28 to a thickness of 2 mm;
creation of contact p ⁺ regions by two-stage diffusion, including;
a) a phosphorus pen at a temperature of 1150 ^o C for 1.5 hours;
b) removal of phosphorosilicate glass;
C) the distillation of phosphorus at a temperature of 1200 ^o C for 25 hours;
d) control of diffusion parameters: diffusion depth (about 20 μm) and surface phosphorus concentration (N _sn ≈ 10 ²⁰ cm ^-3 );
the creation of ohmic contacts by sputtering aluminum (metallization diameter 21 mm), followed by annealing at a temperature of about 500 ^o C;
chamfering from the side surface of the disks to the boundary of the Al-contact (Fig. 1);
control of nominal resistance R _nom ;
irradiation of disks by accelerated electrons with an energy of 3 MeV, dose φ 6 • 10 ¹⁴ ; 9 • 10 ¹⁴ ; 1.2 • 10 ¹⁵ (cm ^-2 ) on the linear accelerator "Electronics ELU-6" at a temperature of T 25 ^o C,
control R _nom ;
annealing of resistive elements at a temperature of 200 ^o C for 1 h. The temperature is selected from the temperature range of thermostabilized annealing of radiation defects 180-230 ^o C. The annealing time (1 h) is determined by the completion of structural adjustment of defects;
bevel etching and protection with an organosilicon compound (KLT) followed by drying at a temperature of T 180 ^o C;
control of the main parameters: linearity of the current-voltage characteristic, nominal resistance and temperature characteristic of resistance;
assembly of elements in standard tablet cases.

2,0•10¹⁵; 2,5•10¹⁵; 3,0•10¹⁵ (см^-2) и из кремния с r_o 700 Ом•см соответственно облученные: Φ 2,0•10¹⁴; 2,5•10¹⁴; 3,0•10₁₄ (см^-2).Similarly, resistive elements were made of p-type silicon with r _o 150 Ohm • cm, irradiated doses

2.0 • 10 ¹⁵ ; 2.5 • 10 ¹⁵ ; 3.0 • 10 ¹⁵ (cm ^-2 ) and from silicon with r _o 700 Ohm • cm respectively irradiated: Φ 2.0 • 10 ¹⁴ ; 2.5 • 10 ¹⁴ ; 3.0 • 10 ₁₄ (cm ^-2 ).

The measurement results of the main parameters (R _nom and TCS) of the proposed semiconductor resistors and resistors made by a known design and by a known method are shown in table. 1-3, and the dependence of the resistance R on temperature T in figure 2.

Comparative analysis of the parameters given in table. 1-3 and figure 2, shows that the best combination of TCS and R _{nom is} achieved by irradiation with doses: F 2.5 • 10 ¹⁵ cm ^-2 for silicon with r _o 150 ohm • cm; Φ 9 • 10 ¹⁴ cm ^-2 for r _o 400 Ohm • cm; Φ 2.5 • 10 ¹⁴ cm ^-2 for r _o 700 Ohm • cm, i.e. TCS is much lower and does not exceed 10% and R _{nom is} higher than that of the above prototypes.

The advantages of the proposed design and method of manufacturing a semiconductor resistor include:
high temperature stability of resistance (TCS no more than ± 10% in the operating temperature range);
high ratio of rated power to resistor volume, as can be seen from the table. 4. In columns 2-4, the main parameters of the proposed resistors are given, in columns 5 and 6 are known (volume resistor TVO-60 and metal oxide MOU-200);
thanks to the tablet design of the proposed resistor, its use in a single cooling system with powerful key tablet devices allows to reduce the overall dimensions of powerful converting units;
high manufacturability of the manufacturing method;
increase in the percentage of suitable devices up to 97%
reducing the cost of manufacturing devices through the use of cheaper silicon with lower resistivity while maintaining the nominal values of the main parameters and stable TCS.

Claims (1)

1. Powerful semiconductor resistor, consisting of a resistive element made in the form of a disk of monocrystalline silicon n-type electrical conductivity with a specific resistance ρ _o = 150-700 Ohm • cm, characterized in that the resistive element contains radiation defects with a concentration of 3 • 10 ^{1 2} cm ^{- 3} for silicon with ρ _o = 700 Ohm • cm to 3 • 10 ¹³ cm ^-3 for silicon with ρ _o = 150 Ohm • cm.
2. A method of manufacturing a powerful semiconductor resistor, including the creation in the silicon resistive element of diffusive contact areas, the introduction of defects that create deep energy levels in the forbidden zone of silicon and the deposition of metal contacts, characterized in that the defects are introduced after the deposition of metal contacts by irradiation of the resistive element with accelerated electrons with an energy of 2 5 MeV, a dose of 2.5 • 10 ^{1 4} cm ^{- 2} for silicon ρ _o = 700 Ohm • cm to 2.5 • 10 ^{1 5} cm ^{- 2} for silicon with ρ _o = 150 Ohm • cm followed by t thermally stabilizing annealing.

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