DD237081A3 - DIFFUSION PROCESS FOR THE MANUFACTURE OF P-LEADING AREAS IN III-V SEMICONDUCTORS - Google Patents

Abstract

The invention relates to a method for diffusing elements of the second group, FII, preferably zinc, into MIIIXV semiconductors and their n-type mixed compounds, especially in GaAs1xPx (0x1) in order to produce pn transitions. The process is of particular importance for the fabrication of GaAs1xPx (0.35x1) semiconductor light emitting devices. The aim of the invention is to greatly reduce the surface erosions which frequently occur in such diffusion doping, which are caused by unfavorable dopant sources and which unfavorably influence the further processing of the disks and the efficiency of the components, by means of an optimized diffusion process. In the process according to the invention, in the diffusion chamber, in addition to the semiconductor wafers, there is a three (four) component source, wherein the components FII, MIII, XV are in separate containers and the amounts of these elements are in a certain relation to each other, which for the system Ga - P - Zn at 650C is: EGa0.18 (EZn3.16 EP). The method is suitable for GaAs1xPx (0x1) in the temperature range from about 550C to 950C.

Description

,,, resp. A _f II (mIII, xV, _Y V,: Weights or atomic weights of the elements F "(M '", X ^V , Y ^V ); a, b, c, d: At% -seats F ", M ¹ ", X ^v , Y ^v in the liquidus) and the ratio E _F M / E _X V in the range 3A _F ! L / 2 A _x V ... (3A _F ! L / 2 A _X V) ( (2a + 3b) / 2c).

2. The method according to item!, Characterized in that the elements F ", M ¹ ", X ^v (Y ^v ) in a quartz glass container or in separate, juxtaposed quartz glass containers or the elements F ", X ^v (Y ^v ) in one and the element M ¹ "are arranged in a second, adjacent quartz glass container.

3. The method according to item 1, characterized in that the element M ¹ "is applied over a large area on a suitable silica glass carrier.

4. The method according to item 1, characterized in that diffused from a F ", X ^v source whose EpII, ExV values of the condition

satisfy (ς density of the III-V semiconductor in g / cm ³ , G total area of all semiconductor wafers in cm ² ).

5. The method according to item 1 to 4, characterized in that is used as the F "-Dandand zinc.

6. The method according to item 1 to 3 and 5, characterized in that as the Ill-V compound GaAs ₁ -XP _x (0.35 <χ <1) is used, the source is As-free and the Ga weigh-in the relationship

E _Ga == (2,16b / (2a-3c)) (E _Zn -3,16Ep).

7. The method according to item 1 to 6, characterized in that is diffused at temperatures of 550 ° C to 950 ° C and annealing times of 15min to 50h.

Field of application of the invention

The invention relates to a method for diffusing elements of the second group of the Periodic Table, preferably of zinc into III-V compounds and corresponding η-type mixed crystals, especially in n-GaAs ^ Px (O <χ <1), for the purpose of production of planar pn junctions of appropriate depth with minimal surface damage. The process is of particular importance for the fabrication of light emitting semiconductor devices of GaAs ₁ P _x (0.35 <χ <1).

Characteristic of the known technical solutions

In order to generate a pn junction in η-conducting III-V compounds or mixed compounds by means of diffusion, zinc is usually diffused from a source - usually via the gas phase - into the semiconductor material. For the production of particularly efficient GaAs | semiconductor light-emitting semiconductor devices. _x P _x (0.6 <χ <1), it has proved to be advantageous to diffuse the zinc at the lowest possible temperatures, for example at 650 ° C, wherein for the function of the semiconductor device, taking into account all necessary for the preparation of removal steps and to achieve e ^{: the} maximum intensity of the light requires a depth of the diffused pn junction of 5 to 10μηη. For such low temperature diffusion scannings, PTLindquist, TL Larsen, J. Electron. Mat. 4, 567 (1975) elemental zinc known as a source of diffusion. The unavoidably occurring damage (erosion) of the surface of the semiconductor material due to physical-chemical reasons by formation of a multi-component liquid phase (liquidus) on the semiconductor surface and / or by evaporation of the volatile X ^v component prove to be disadvantageous for further processing steps, such as photolithography and contacting in the manufacture of the semiconductor light-emitting device, and often lead to warping of semiconductor wafers.

One method for reducing the surface erosion caused by the elemental zinc source is to embed the semiconductor body with powder of such semiconductor material (US Pat. No. 3,660,178). The disadvantage of this method is the contamination of the semiconductor wafers by the difficult to produce in high purity powder.

In addition, Ga-rich zinc / gallium sources are known (DE-AS 1289035), but also lead to erosion and also are usually of no interest at low diffusion temperatures because of the low zinc vapor pressure and the associated long annealing times.

It is also known to use different mixtures of zinc and phosphorus as source material for higher temperatures (T> 800 ^° C.) (K. Gillessen et al., IEEE Trans. Electron Dev. ED24,944 [1977]; AF Widmer, R. Fehlmann Solid State Electronics 14, 423 [1971]; B. Tuck, PRJay, J. Phys. D. 10, 2089 [1977]). They often lead to nonplanar pn-transitions and surface damage.

ZnAs ₂ , ZnP ₂ , Zn ₃ As ₂ and Zn ₃ P ₂ sources, which were preferably used for higher diffusion temperatures (JC Marinace, J. Electrochem., Soc., 110, 1153 [1963], US Patent 3653989; -AS 1261831) - although they can deliver low-erosion surfaces due to their location in the phase diagram - prove to be unfavorable in the production because of the long diffusion times. For example, one would have to diffuse with a ZnP ₂ source at 650 ⁰ C over 100 h in order in a GaP 6μ, ιη

reach deep pn junction. Also known is a Zn ₃ P ₂ source with additional getter metals (FR-PS 7439679), but.

the mentioned disadvantages are not eliminated.

For the ternary Zn-Ga-P ternary sources operating in the liquid-phase-free section of the ternary phase diagram (S.F. Nygren,

GL Pearson, J. Electrochem. Soc. 116,648 [1969], US Pat. Nos. 3,485,685 and 3,753,808) for GaP and GaASv _x P _x (0 <χ <0.6), the further difficulty involved is the time-consuming preparation of these sources. The long diffusion times remain.

Object of the invention

The aim of the invention is a diffusion method for zinc and other elements of the second group of the Periodic Table (F ") in M ^m X ^v semiconductors or M ^m X ^v mixed compounds, in which the surface erosion is greatly reduced and the further processing of the semiconductor wafers undisturbed It should enable the production of efficient components, in particular optoelectronic semiconductor components with high constancy of the parameters and with a low rejection factor.

Explanation of the essence of the invention

The invention has for its object to make the diffusion process for zinc in GaAs ₁ -XP _x (O <χ <1), in particular for low temperatures so that with minimal time erosion semiconductor surfaces are obtained, with contamination of the semiconductor are excluded by the diffusion source , According to the invention the object is achieved by a method in which in the diffusion chamber next to the semiconductor wafers with high purity elemental zinc, gallium, phosphorus and optionally arsenic, the amounts of these elements of the condition (3) and satisfy in that area of the phase diagram in which the liquidus, zinc compound and III-V compound are coexistent. It is advantageous to apply the gallium over a large area, as this ensures the rapid adjustment of the liquidus composition.

It is assumed that the erosion of the GaAsi., (P _x disks in the one- and two-component zinc sources of the known technical solutions to the decomposition of the near-surface disc areas by the liquidus (Zn, Zn + P) which can only be formed there. As a measure of the damage to the surface, a mean erosion depth AX _R (in / im) after the., Source (or) by the P (As)) discharge for liquidus formation next to the semiconductor (Zn-Ga source) relationship

(mn - mass of the elicited Ill-V compound in g (see equation [2]), p-density of the III-V semiconductor in g / cm ³ , G - total semiconductor surface in cm ² ).

Defines rflächenerosion: Xv _x Y _x semiconductor material, taking into account the surface inhomogeneities are always present the degree of Ob "dissolved amount of M '(Cd Be etc. Zn)" to determine the exact during Diffusionstemperung with the dopants F! are the equations relevant to the reactions of liquidus formation in the phase diagram region with coexistent liquidus and N ₃ "X ₂ ^V (Y ₂ ^V )

TiU ₁ (in g),

the P ^ ^{I: E} X _O ^Y formation

--Ρ

III Y and the M X decomposition

taking into account the mass balance

«Μ <m». "TT ¹ " TT "TP T""T" T ¹ TT

IQj + IG-p = 23-p + j & -j- \ J-X + Ujpfl-L-LX + JljyV

to consider (T = Ε _χ Υ + (^ _n JS - (f j'f ifij

⁸ (

o. B. d. A. χ = 1). A, b, c: temperature-dependent At% fractions known from the specialist literature of F ", M '", X ^v in the liquidus, A: atomic weight, E: initial weight, (3A _F H / 2 A _x V) < (Epll / ExV) <(3A _F H / 2A _x V) (2a + 3b) / 3c as an approximate condition for being in the phase diagram of the present invention. This leads to the following relationship for m _R (in g):

( 2b / AmII

- \ 2a + 3b-3c ~ 3d / i

\ F _{o Λ} o _Oa \ /.3A-H ₁ ο IIA

I. / 2a-3C-3Q ). _E J ₁₁ ^j _tt Ie Y -

Aj ₁ II

2A _M IIli I 3b

(d At% -value of Y ^v in the liquidus), from which by m _R = O the condition

results. - '-

With (o.b. d. A.) usually given EfII, E _x V (E _y V) loading of the ampoule follows thus as regulation for the E _M III-Einwaage:

E.JII = f1'Ar -KU - UtV-EJ -

(3a)

For the Zn-Ga-P system results in the temperature range around 650 ^C C.

E _Ga «0,18 (E _Zn - 3,16Ep). (3b)

The method is suitable for GaAsi. _x P _x | 0 <x <1] based on the phase diagram parameters in the temperature range of about 550 to 95O ⁰ C.

From equation (2), however, it is generally recognized that erosion increases with increasing temperature, ie falling a fraction in the liquidus. In addition, the pure F "sources results (ie: Emhi = E _X V _(Y V) = 0). Lead to maxi painter erosion In cases where the semiconductor wafers may have a low surface roughness AX _R, is simplified Ampoule charging according to (3) or (3a) in such a way that the M "'weight can go to zero, provided that the F" -X ^v weigh-in ensures an operating point in the mentioned section of the phase diagram , 1 μηπ using an Epli ExV source from (1) and (2) the condition

In the selection of initial weights, the following should be noted: In systems of the Zn-Ga-P type, the dopant vapor pressure in the GaP-liquidus-ZnsPa partial triangle of the phase diagram is determined by the liquidus. It is desirable to have such Zn weighings which, given a vial volume V _{A, have} the maximum zinc pressure _p max , a, _D (o)

₍ p (o). ^r Zn - ^ JTb ' ^Vzn

Saturation vapor pressure of the pure zinc) can be achieved in approximately, because otherwise unnecessarily large annealing times are required for a certain pn-depth.

embodiment

The invention will be explained below with reference to an embodiment.

In LEC-GaP disks with a grown GaP: N epitaxial layer, for the purpose of producing green light-emitting diodes, a pn junction at a depth of 5 to 6 μm is to be produced using the per se known method of zinc ampule diffusion. The aim is to achieve the highest possible light intensity values of the diodes, smooth, erosion-free surfaces and - in subsequent process steps - good-adhering ohmic contacts.

For this purpose, a large number of cleaned slices according to formula (1) is placed in a cleaned quartz glass ampoule. The zinc source is an arrangement of two juxtaposed, a few mm quartz glass cups; in the first cup are zinc and phosphorus, in the second is gallium. These cups are placed in proximity to the semiconductor wafers. The ampoule has a volume of = 300 cm ³ and after pumping (10 " ³ Pa) and Zustshmelzen for a period of t = 15 hours at the uniform temperature of 650 ° C in a tube furnace chosen: 18mg Zn, 4mg P and according to formula (3 b) just under 1 mg Ga. In the ampoule then acts a zinc vapor pressure of about 1 900Pa, which at the selected temperature, time conditions planar pn transitions at = 5.1 μ.ιη has the result, the Zn or p-maximum concentrations are = 3 · 10 ¹⁸ crrT ³ ).

The cooling of the ampoule is relatively slow. By means of a charging device, an extension speed of ~ 4 cm / min is selected, the Zn or Zn ₃ P ₂ precipitates form on the front ampoule wall and the GaP disks remain clean. The EDAX analysis of the (Zn + P) cup revealed Zn ₃ P ₂ which, as indicated by short anneals, forms immediately after retraction of the ampoule.

The microscopic inspection of the panes and the determination of the mass of the panes before and after tempering result in erosion-free surfaces. In the subsequent AuBe contact the p-side good ohmic contacts are formed, the measurement of the light intensity of the diodes gave the same high values, which are achieved for example with the known 65O ⁰ C ampoule diffusion with pure Zn source, the latter source, however caused stronger surface erosion of the discs.

Corresponding experiments with a (Zn + Ga + P) source were also carried out on GaAs _a i ₅ P ₀ , 85 material, which forms the basis for yellow-lighted electroluminescent diodes.

Claims (1)

Invention claim: 1. A method for producing p-type regions in M '"X ^v -Halbleitern in which elements of the second group of the Periodic Table (F") in compounds of the type M "' X ^v and M '" X ^V Y ^V by Annealing the semiconductor bodies with a locally separate F-dopant source in a sealed container, characterized in that a three- or four-component source of elementary F ", M"', X ^v (Y ^v ) is used, which is at the same temperature as the semiconductor bodies, the following relation being maintained in the case of the ampoules: