DD157486A1 - METHOD FOR ADJUSTING THE BREAKTHROUGH VOLTAGE IN PN TRANSITION DIODES - Google Patents

Abstract

The method of adjusting the breakdown voltage in pn junction diodes refers to zener and avalanche breakdown diodes and aims at tightly tolerated breakdown of the breakdown from the low to high voltage range and avoids variations in conductivity and diffusion conductivities. According to the invention, after enrichment of donors and acceptors in adjacent regions (8 and 12) and simultaneous amorphization in the Si body (6), an impinging from the wafer backside, through the residual volume up to the heightening absorbent areas (8 and 12) and laser radiation (14) converted there into thermal energy is used in order to install the dopants on conductance-determining grid locations without redistribution of the implanted doping profile in the area (12). The photon energy of the laser (14) is selected to be smaller than the band gap of the semiconductor body (6). The transparency for laser radiation is increased by cooling.

Description

TITLE OF THE INVENTION

Method for setting the breakdown voltage in pn junction diodes

Field of application of the invention

The invention relates to a method for the breakdown voltage setting in pn "transition diodes Betrie in the application", and case of operation in the opening "ben be" There are diodes based on the Zener "effektese in which the charge carriers tunnel through very narrow barriers and oioden based the Lavtfineneffektes * where the charge carriers through. Impact ionization j, especially under conditions of optical injection.

Characteristic of the known technical solutions

A generally customary production method for Si zener diodes with a precisely defined Zener chip and one of disturbing external influences

free Durcjibruch is "described OS 1858 817" in DE whose Dötier-ungs "determined concentration which Durchbruehsspannung mainly to a ni @ derohn lush base body, vsird a thin ₉ formed epitaxially © ;, higher-impedance layer of the same representative species formed _& Using d ® Pia «Rarfnaskierungste Ghoik a pn *» passage through the epitaxial layer diffuses down to the lower-order basic body _s Unwanted surface effects are somewhat limited in their effectiveness ©

The influence of the edge contour of the pn junction and the presence of local microplasma nucleation is not completely suppressed. Furthermore , doping variations in crystal growth lead to undesirable scattering of the resulting breakdown voltage ₀

In the method described in DE-AS 2 _e 207 _o 854, antimony in concentrations above 10 at / cm 2 diffuses over the length of the diffusion time or over the height d ®r Diffusionstemp »© temperature is specified later © Durchbruchsepannung · Finally, a pn Öbergang formed by boron diffusion is now best in" men di © inherent in the diffusion process sehvüankun · »» gen doping concentration, the Zuverläesigkaits · = · disorders d © r technology "

Under the name EPX "ZH3ioden introduced z © ner * - are diode> from L'onde El @ ctrique 1971 Issue 4 S _6323" · "328 and DE" OS 2 _e 133 _e 648 _e known you have a selective The transition of conductivity and conductivity through epitaxy © The over - cut © voltage range is, however, difficult due to di ©

the doping is limited to 6.2 to 9 V,

A © precise Dotierstoffkontrolle for steep doping · »material gradient for producing a Zensrdicde with a temperature coefficient of 5" IO% / degrees C is by depositing a boron-doped polykristial "" linen Si "layer on a single crystal substrate with nn ^ -Leitfähigkeitsstufe manufactured * During dor epitaxial layers of polycrystalline boron diffuses slowly into the einkristallinan base area and "164 _e 436 but a pn junction with high breakdown voltage ^ low Flußspan" reproduces the US ^ PS 4 nungöabfall "

From DE "OS 2" 807 _e 747 is a diode ^ known by OBF in direct contact with the pn ^ Obargangszons

The conduction of the confinement is set to a fixed value in a range defining the breakdown voltage. However, if the inclusion occurs, the confinement of the confinement is set to a fixed value in a range defining the breakdown voltage enriched with a very high dopant concentration _, then, during the thermal activation of the dopants in the confinement and during the formation of the inversion zone over the confinement, an undesired and partly un controllable redistribution of the dopants takes place.

In DE-OS 2,951 _e 733 describes a process by which a individual adjustment d © r breakdown voltage of Siliziüfii- "Zen © rdioden and AEVA" lanche diodes to individual diodes vorgenomns © fj is "to

The change in the pn ^ transitional catratrio in a deeper region remote from the surface is indicated by laser or electron flashes localized redistribution of dopants into the oppositely conducting, less doped region with continuous monitoring of the change in breakdown voltage.

nomine η * This method of fabrication improves the noise performance of the diodes * but reduces the power dissipated «. In addition, the re-solidification of a liquid / solid interface or the change of the crystalline state from the see can occur at the points of contact of the lasers and electron beams "crystalline to highly crystalline order of the formation of non fortset2baren into the support Git *» ormordnungen tert and result in cracks> Z ^ illii> gen or Versötzungen in the lattice structure, "especially ^ hen the Rekristaliisationsfront of 6 r surface into the Tie" ferestaurationsbedörftiger layers progresses _β Activation of buried layers is hardly possible without interference or error-free «,

All methods also the disadvantage 8RR liable that the Märsgsl at the crystal breeding bz 's · layer preparations and DiffusionenV ^ ie fluctuations in Schra ©;!? "Tierungen><zone conditions _for internal stresses at very high Thurs *, ring-like accumulations and Aforeicherungen o® r dopants the parameters of the diodes adversely affect "Hoh Hoh © Fertigungsteniperaturen and Tole 'tolerances of the technological characteristics of the electrically ac- tive areas force * to a relocation of the pn ** about" ganges deeper into the semiconductor body »

Object of the invention

It is an object d @ r invention to develop © in method of adjusting the breakdown voltage in semiconductor diodes with the vormieden reduces the disadvantages of the known methods ,, ..

For the zener or avalanche diodes produced according to the invention, the following beneficial effects result:

- more targeted manufacturing and enCy tolerated compliance with certain Zener voltage classes.

- Overcurrent coverage and extension of the breakdown voltage range in the low-voltage and high-voltage range with uniform technology

- Improvement of the breakdown of the breakdown and the high current carrying capacity

- Avoiding the difficulties due to the variations in resistances in Si source material and the surface concentration in diffused pft oil junctions

- Group processing and activation of buried layers with increased impurity concentration

Maintaining the stoichiometric equilibrium in mixed compounds during annealing despite the presence of volatile components or foreign atoms

The invention is based on the object to avoid the incorporation of the dopants on the conductivity-determining lattice sites and thereby the formation of multiple recrystallization fronts in the reorganization of the amorphized areas *

According to the invention, this object is achieved in that, in addition to the introduction of additional dopants for the development of a first Leitart in a first region with direct proximity to a second area enriched with dopants for the development of a second Leitart, means for increasing the Then at least the same energy as the entire semiconductor body is supplied by heat, laser or a non-coherent radiation to these areas. _Β Due to the considerably higher absorption, the energy input to a conversion into grid phonons is used The energy supply is preferably maintained only for the duration of Ein¬ = 'storage of the dopants supplied to the conductivity determining' grid locations During the power supply, a heat dissipation from the semiconductor body is made so that the temperature in the semiconductor body is at most as high as in the additional doped areas »

The generation of the regions with increased radiation absorption can take place in various ways;

Thus, it is possible to increase the absorption by implantation of dopant ions, of ions of the semiconductor atoms or by implantation of both ion species.

However, it is also possible to deposit doped amorphous semiconductor material or precipitate polycrystalline doped semiconductor material by means of a low-pressure chemical vapor deposition, for which purpose the semiconductor material or a semiconductor material having a smaller band gap can be used. For certain diode structures, it is advantageous to use Semiconductor material to make a pit or trench etching »

A further development of the invention provides that a heat, laser or non-coherent radiation whose photon energy is kept smaller than the energy gap of the residual volume of the solid is inserted into the semiconductor volume via non-absorbing or not excessively reflective areas of the surface Radiation is conducted through the semiconductor volume to the area of increased absorption, where it is absorbed and converted into thermal energy. " With the conversion of the radiation into heat and the incorporation of the dopants on the conductivity-determining lattice sites of the irradiation process is completed

Ee is advantageous to carry out the heat dissipation and the conversion of the radiation into thermal energy on the same surface side »In this context, but also without application of heat dissipation, the insertion of the laser radiation is appropriate from the back of the disc,

According to the invention, the transparency of the residual volume of the semiconductor for the laser radiation is increased by cooling the semiconductor.

In the method according to the invention, it has been assumed that monocrystalline, polycrystalline but also amorphous semiconductors have a pronounced energy band structure or a more or less sharp energy gap between the ground and excitation states due to the close and long order of the atoms.

Therefore, such semiconductors also have a significant wavelength dependence of the absorption of light or radiation. (Figure ".1) β In the usual use of the Auftreffetelie of radiation for the Erwörmung selected areas on the surface of semiconductors v ^ urde the lattice absorption of light or Radiation exploited This generally means that the photon energy of the laser radiation is greater than the band gap in the semiconductor.

It has been found that it is not possible to heat the point of impingement of the radiation but any region in the depth of the semiconductor body or even on the opposite side of the semiconductor body, the radiation being at a photon energy lower than the bandgap of the semiconductor body Semiconductor is "a prerequisite that the absorption communities in the areas to be heated change significantly *

The invention will be explained in more detail below with reference to exemplary embodiments. The accompanying drawing shows in FIG

Fig * Is Comparisons of the absorption coefficients of sputtered Ge _β Si j GaAs and GaP layers with EK silicon

Fig _e 2? Manufacturing stages of a zener diode structure with (a - f) dielectrically passivated central breakdown region

Fig. 3j Zener diode structure · with buried breakdown region V *

FIG. 4: GaAs zener diode with embedded breakdown region. FIG

Fig. 5: Dose dependence of the breakdown voltage of boron-implanted pn-junctions from the arsenic implantation

FIG. 1 shows the wavelength dependence of the absorption of light or radiation in various semiconductor materials which have a more or less sharp backbone between the ground and excited states.

The significant change in the absorption properties in the areas heated by a radiation of defined photon energy is evident from the absorption curve of the monocrystalline silicon 1 over that of sputtered or amorphised silicon rods 2, which is shifted far into the long wavelength range also for amorphous germanium 3, GaAs 4 _t GaP 5 and other «,

1 «Example. ,

In explaining the fabrication of an adjustable breakdown voltage diode structure using a central dielectrically passivated breakdown region, reference is made to FIG.

The zener diode has a homogeneous, η-type, single-crystal Si body 6 with a (lll) -oriented surface polished on one side. On the polished surface, a 7000 R thick frame mask 7 of SiO _{2 is} formed, which forms the central part and masking the outer edge of the substrate surface. Through the opening of the frame mask 7, boron ions having an energy of 180 W: and a dose of 5 × 10 × cm at room temperature may be used. implanted in the 7-degree tilted Si body 6. After activation

~ 10 -

of the boron at HOO ⁰ C, a p-type ring 8 is formed, which separated a central area 9 with the n-conductivity of the monocrystalline Si body 6 from an outer area of equal conductivity. The p-type ring 8 has a surface area of 2.5. 10 cm _t

-5 P the central area 9 of 2 _f 5 »10 cm"

The p-type ring 8 is then vaporized with a metal layer 10 '' which initially served as a mask for the implantation in the central region 9 the mask from the metal layer 10 terminates at the edges of the first frame mask 7 _e Now wilrd in the central region 9 under the 300 A ⁵ thick insulating layer 11 made of SiO ₂ an implantation of arsenic ions At an energy of 180 YM a range of 110 nm is achieved in the silicon body 7. The mask made of the metal layer 10 holds the essential part of the arsenic over the p-conductive ring 8 ab »Since the mask from the metal layer 10 remains as an adhesive mask on the p-type ring 8 and is subsequently galvanically reinforced, gold was used

The dose of arsenic implantation will vary with the dose of the targeted breakdown voltage of the zener diodes or avalanche diodes selected with a dose of

Ί3 15 -4-2 10 to 10 As / cm becomes - as shown in Figure 5 - a breakthrough voltage range of 4.5 _OPO 12 V overrun ©

The passivation of the Z-diodes is done by covering the arsenic implanted island region 12 with a protective layer 13 of SiO.sub.2. It is formed by anodic oxidation

With the next step of the procedure, the monocrystalline Si body 6, from the previously untreated backside, with a laser radiation 14 of the energy width from 1 _# O to 1ί, '2βΐ? shot "The radiant energy absorbed in a narrow space in the As-iraplantierten island area 12 (R» 110 nr, AR 37 ntn) leads to a location of "very limited warming." In this case, the metal layer 10 of gold is alloyed in the p-conducting ring and refracts Island area 12 the conductivity is greatly increased by d & n incorporation of Areen on lattice sites increased the adjacent ring 8 adjacent η-conductive island area 12 now has a conductivity profile> that absolutely matches the implanted profile »

The elimination of the migration of the Arsenatbme after implantation during the thermal activation by laser radiation leads to an extremely sharp localization of the breakdown of the diodes. This is advantageous both for the compliance of given breakdown voltage tolerances and for the realization of low Zener resistances. "The achievement of Zener voltages in the range of and below S volts is considerably facilitated

The completion of the diodes is carried out by galvanic reinforcement of the contacts in the form of a hill 15 and the application of a contact layer 16 on the back of the Si "body 6"

2 _e example

The preparation and the structural design of a Zener "diode structure with a buried breakdown region vi'ird reference to FIG 3 illustrates"

On a monocrystalline body 17 with a polished surface, an insulating layer of SiO _{2 is} formed. Using an opening in the insulating layer 18, a pit-like depression 19 is etched into the body 17 by arsenic implantation an "increased n" routing © nd © r region 20 formed © Thereafter © carried ine evaporation of the pit 19 with an amorphous boron-doped silicon "layer 21" DIQ vapor deposition vuird as longitudinally continuous "set ^ to about 2 to deep pit-like Then, a silicon body 17 with the additionally doped regions 20 and 21 in a vacuum vessel to a temperature below room temperature is formed Then, the side of the rock of the monocrystalline silicon body 17 of the radiation 22 of a Nd:. yAG ^ laser with a wavelength of l ' _e 06 .um and an irradiation of

2 *

ca © 1 o / cm "" pulses exposed The significantly reduced absorption of the laser bonds in the cooled Siliziunn and high absorption in the additionally doped Baröichen and 21 lead to a low loss and efficient conversion of the radiation into thermal energy _E with the beginning of the restoration of the additional doped Be "rich © place of the single-crystal underlay © of silicon body 17 AusV 20 and 21, an epitaxial re" building the araorphisierten or amorphous secluded areas equipped training disturbing dislocations or disturbances a®r lattice structure vsie them in the off "healing of multilayer superimposed arranged acceptor-donor areas arise ¹ , if the frontal annealing in the Grundgitterabsorptionsbareich is made-- is avoided one comes thereby into the advantage ^ considerably thicker amorphisierte area © than 1 absorption length of the radiation by field irradiation bsar «

to be able to work ©, #

79

3 »_Beisgiel

Similarly vile integrated Si circuits is the installation of Zener diodes for GaAs integrated circuits or MOS or MS-FET Systerne as a generic overload protection of great interest "The advantages are at such hedged AB ICs in the relatively long for the breakthrough operated diodes

A B -ICs in the relatively faster response time of the

The GaAs zener diode structure with an embedded breakdown region shown in FIG. 4 can be manufactured in the following stages:

A monocrystalline _t-side polished GaAs body 23 is on the polished surface side with an insulating layer 24 made of Si ₃ N ₄ covering in the Si ₀ N ₄ -Scnicht 24 is etched a to the GaAs surface through opening 25th This is followed by an implantation with solenions. "As already described, the dose value is used to specify the breakdown voltage of the pn junction. The n-doped region 26 is covered with an etching mask 27 only in the central part, and in the part of the GaAs body 23 not covered by the etching mask 27 or the SigN 2 layer 24, the GaAs is etched to a trench-like depth of 5 μm , in the middle of the ring trench 28 is now the η-doped region 26th

By dusting the ring trench 28 is then filled with zinc-doped amorphous GaAs 29 so that in this case the n-doped region 26 is surrounded from above and from the side with GaAs material. Upon irradiation with a laser 30 of the wavelength of 1.06 μm, cooling can be dispensed with because the absorption of the polished GaAs body 23 is very low and the absorption

«14 ~

in the additionally doped regions 26 and 29 that of silicon is comparably high in regions 20 and 21. "

Claims (1)

invention claim 1 * A method for adjusting the breakdown voltage in pn-junction diodes by additional doping and dopant activation based on beam processes, characterized in that in addition to the introduction of additional dopants for the development of a first Leitart in a first region (9) with direct proximity to a second Area (8, 21, 29), which is enriched with dopants for the development of a second Leitart, an increase in the radiation absorption at least in the first region (12, 20, 26} is performed, then the two adjacent regions (8, 12) at least the same energy as the entire semiconductor body (6, 17, 23) by heat, "laser or a non-coherent radiation (14, 22, 30) is supplied, which is maintained for the duration of the incorporation of the dopants on the conductivity determining lattice sites , And made during the power supply, a heat dissipation from the semiconductor body in such a way is that the temperature in the semiconductor body (6, 17, 23) is at most as high as in the additional doped regions (8, 12, 20, 28) * 2o method according to item 1, characterized in that the absorption is increased by implantation of dopant ions, ions of the semiconductor atoms or noble gas ions or »an ion mixture of dopant ions and one of the other two ion species«, 3β Method according to item 1, characterized in that the absorption is increased by precipitation of doped amorphous or polycrystalline semiconductor material by means of low-pressure / low-temperature CVD deposition, sputtering or vapor deposition. « 4 _e method according to item 1 to 3, characterized in that the absorption region of the same or a semiconductor material is formed with a smaller energy gap in comparison to the semiconductor body * 5 _f method according to item 1 to 4, characterized dsdurchy that the formation of Absorptlonsbereiche performed after a pit «or trench etching of the semiconductor surface β ", The method of item 1 to 5 _f wherein _{that the supply of energy as heat, laser" · or niehtkohä "pension radiation occurs, the photon energy is smaller than the energy gap of the residual volume of the Halbleiterkör · = pers, the radiation over non-absorbent and not reflected reflecting surfaces of the surface in the semiconductor body faded "passed through the volume of the semiconductor body up to the area of increased absorption _t there absorbed, converted into thermal energy and the incorporation of the dopants on conductivity-determining lattice sites the irradiation or exposure is terminated _e 7 _e method according to item 1 to 6 ', characterized in that the heat dissipation and the conversion of the radiation into thermal energy on the same surface side is made © 22847 8th,. Method according to item 1 to 7, characterized in that the radiation is faded in from the rear side of the pane. 9 ", method according to item 1 to 8, characterized in that _t that the semiconductor body is Abkünlt. For this .... 3.3 drawings