NL8000302A - STIMULATING SEMICONDUCTORS WITH BORIUM. - Google Patents

Description

4 η \ l '1 1

Stimulating semiconductors with boron.

The invention relates to diffusively connected semiconductor devices and more particularly to a new method for diffusing boron into semiconductors of silicon and germanium. More particularly, the invention relates to an accurate and easily controllable method of diffusing a boron-containing layer into at least a portion of the surface of a semiconductor of silicon or germanium to form a semiconductor compound therein.

Semiconductors have been known in the industry for years, the term semiconductor element being believed to refer generally to silicon, germanium and silicon-germanium alloys. The term "semiconductor" in the following description refers to silicon, germanium and silicon-germanium alloy semiconductor devices.

Such elements may be circular, right angled or triangular or have any other suitable geometric shape, although they are usually in the form of a wafer or disc for most applications.

Such silicon semiconductors have an active impurity incorporated therein during manufacture or later by diffusion, which impurity affects the electrical rectifying properties of the semiconductor to distinguish other impurities which cannot have a clear effect on these properties. Active impurities are usually classified as giving impurities or receiving impurities. The giving impurities include phosphorus, arsenic and antimony, the receiving impurities comprising 2 impurities boron, gallium, aluminum and indium. In other instances, the silicon semiconductors are substantially free from such contaminants, which semiconductors are then called "true" semiconductors.

As to the semiconductor nomenclature, it has been stated that a region of semiconductor material, which has an excess of emitting impurities and provides an excess of free electrons, exhibits an N-type conductivity. In contrast, a P conductivity is exhibited by a region containing an excess of receiving contaminants, resulting in a lack of electrons or an excess of "holes". In other words, an N-guide is characterized by an electron guide, a P-guide is characterized by a hole guide. "Genuine" (sometimes called I-type) silicon semiconductors contain neither giving nor receiving impurities.

When a solid semiconductor solid sample has an N region adjacent to a P region, the boundary therebetween is referred to as a PN or NP junction, where the semiconductor material sample is referred to as a semiconductor device with a PN junction. . When an area with a P conductivity is adjacent to an area with a larger P-. . 1+.

conductivity, the compound is called a P-P compound.

f

When an area with an N conductivity is adjacent to an area • »·

25 with greater N conductivity, the compound becomes an N-N

called connection. Semiconductor compounds of the P-I type and N-I type also exist. The invention includes diffusion stimulation with boron to form P (including P) regions in the described semiconductor device types.

30 Semiconductors find applications in and are suitable for rectifiers, transistors, photodiodes, solar batteries, semiconductor controlled rectifiers and other devices. In addition to the general electronic applications, the P-N junction semiconductor is often used as a radiation detector or a charged particle detector.

Various developments have taken place for 8000302

V

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3 effecting stimulation of the semiconductor material by adding stimulating impurities during melt-drawing of the silicon crystal or by applying alloying and diffusing methods to a growing crystal. Generally, the diffusion of the stimulant into the silicon material is accomplished by heating a predetermined amount of the particular stimulant material together with the silicon so that the atoms of the stimulator material from all sides in the semiconductor body will penetrate 10. A known method comprises stimulating silicon with phosphorus.

Methods that include depositing a stimulant on a limited surface area of the semiconductor body are described in U.S. Patent 3,287,187. This known method requires depositing an oxide of the semiconductor material by vapor deposition, followed by diffusing the stimulant into the semiconductor surface region by heating the semiconductor body.

Semiconductor devices, which contain a diffused PN compound, are made by heating N-silicon semiconductors in the presence of a decomposable gaseous boron composition, as described in U.S. Patent Nos. 3,5 ^ 2,609) 2,801 + .1 + Q5 and 3.52, 776. Boron is believed to form a glassy film over the surface of the semiconductor, with a boron species diffusing into the silicon with continued heating. According to the prior art, a boron composition can also be deposited on the surface of the silicon semiconductor at a low temperature and then heated to a temperature at which diffusion will take place.

Other methods of diffusing boron deposition include depositing vaporous from a molten boron oxide, as disclosed in U.S. Pat. Nos. 3,021,221, 2,791 + .8½ and 3,393,355.

More recently, the use of oxidized boron * 35 nitride platelets as a boron source in the treatment of silicon semiconductors has been suggested in the article "Boron Nitride as a 8000302 if diffusion Source for Silicon" by If.Goldsmith et al in the RCA Review of June 1967 at page 31 ^. The dissertation entitled "The Use of 93% Boron nitride Hot Pressed Wafers as a Boron Diffused Source for Silicon Solid State Diffusion" submitted by David B. Rupprecht to the Department of Electrical Engineering of the Graduate School of the University of Pennsylvania in June 1972 relates to a similar method. Also of interest is the article entitled "Oxidized Boron Nitride Wafers as an In-Situ Boron Dopant Source for Silicon Diffusion" by D. Rupprecht 10 and J. Stack in the September 1973 issue of the Journal of Electrochem. Soc., Solid State Science and Technology. In this boron nitride process, the boron nitride is oxidized in an oxidizing atmosphere before being used as a diffusion source. This provides a BgO 1 layer on the boron nitride surface, which layer later decomposes and provides boron for diffusion. This method is limited in that the thickness of the BgO2 aaS determines the amount of boron available for diffusion, where if an insufficient amount is present, the solid solution limit is not reached and the uniformity is controlled. diffusion is very difficult. Thus, when applying this known method, precise control of the boron nitride oxidation is very critical.

All known methods suffer from complicated process measures, which increase the costs of semiconductor production.

A first object of the invention includes a method for uniformly diffusing boron into a silicon semiconductor surface.

A further object of the invention relates to the provision of a new solid boron source which is used for diffusing into the semiconductor surfacer.

Yet a further object of the invention relates to providing a method using a ceramic glass body containing BgO4 as the stimulant source for the controlled application of BgO4 vapors to a surface of a silicon semiconductor element.

8000302 4 5

Yet another object of the invention relates to providing a solid source capable of releasing BgO vapors which can be used repeatedly to control and evenly stimulate a semiconductor surface.

A further object is to provide a second embodiment and an improved version of the invention, using a particular family of BgO-containing ceramic glass sources for the stimulant, which sources are thermally stable and rigid at stimulation temperatures greater than about 1050 ° C. The preferred range of ceramic glass sources for the stimulant is rigid at temperatures between 1100 and 1200 ° C, even in the form of thin plates. Furthermore, the starting glass compositions, which are thermally crystallized to form these improved ceramic glass sources for the stimulant, can be easily melted, being resistant to uncontrolled devitrification. This makes it possible to incorporate up to 60 moles # in the ceramic glass sources for the stimulant, retaining the stiffness and dimensional stability during the high-temperature stimulation. This feature is of particular importance because the degree to which BgO vapors are generated by the ceramic glass source for the stimulant during stimulation generally increases as the concentration in the stimulant source 25 increases. Unfortunately, the thermal stability and stiffness of ceramic glass materials in thin sections usually decreases with increasing BgO 2 concentration. Thus, a particular and desirable combination of a high concentration of BgO4 in the ceramic glass source for the stimulant is provided, as well as thermal stability and rigidity at temperatures above 1050 ° C, even when the stimulant source is in the form of a thin picture.

A difficulty in applying a high concentration of BgO 2 is that at high temperature stimulation (eg above 1050 ° C), it occurs to such an extent that a much heavier deposit of boron is deposited on the semiconductor. 8000302 6 then can dissolve and diffuse therein.

When the semiconductor to be stimulated is silicon, a deposit of an undesired composition, which is considered to be a boron silicide, is formed by the reaction of the excess boron with silicon. This undesirable composition is visible as a dark brown or bluish yellow stain depending on the thickness. The color and strength of the stain are believed to be a function of the amount of undesirable composition present due to interference patterns. The bluish-yellow spots indicate the thicker build-up of the unwanted deposit. This deposit is electrically insulating in nature and must be removed from the semiconductor to be stimulated. The borosilicidal composition cannot be easily removed by washing with hydrofluoric acid, and is usually "loosened" for removal by an oxidic reaction in an oxygen-containing atmosphere. The deposition of this borosilicidal composition is usually stronger when new sources of boron stimulant are used.

A further object is to provide a third embodiment and a further improved version of the invention, using a particular and desirable combination of concentration of BaO, B, ^, AlgO,, and SiOg for the ceramic glass source the stimulant in order to provide a controlled degree of stimulation at high temperatures (for example, more than 1050 ° C), which reduces the tendency to form the unwanted insulating deposit, as well as the thermal stability and stiffness at such temperatures in excess of 1050 ° C, even when the stimulant source is in the form of a thin plate.

The invention will now be described in more detail with reference to the accompanying drawing, in which: Fig. 1 shows a cross section of the semiconductor body which has been treated with the method according to the invention; Fig. 2 is a spatial view of a solid ceramic glass containing BgO ^ 35, stimulant wafer, and Fig. 3 is a view of a refractory container, wherein 8000302 •% 7 includes a number of solid wafers of B2 ° 3 containing ceramic glass, and a number of silicon wafers are arranged to perform the method.

The invention overcomes the difficulties of the known methods by using a rigid, dimensionally stable, substantially alkali metal oxide-free ceramic glass body made from alkaline earth metal compositions. The first embodiment includes a ceramic glass body containing at least about 10 moles as a stimulant source for the vapor phase transport 10 to the semiconductor. A second embodiment comprises an alkali metal oxide free, alkaline earth alumina borosilicate ceramic glass source for the vapor phase transport from the semiconductor. In a third embodiment, an alkali metal oxide is used the free, barium aluminum borosilicate ceramic glass source.

According to the invention, the BgO4-containing ceramic glass source for the stimulant is kept in vapor phase compound, (with or without the presence of a carrier gas) with a semiconductor at a temperature and for a time sufficient to convert BgO2 from the source of the stimulant to the surface of the semiconductor. The semiconductor thus stimulated is then heated, with or without the further presence of the ceramic glass source for the stimulant, for a time sufficient to allow the diffusion of boron into the semiconductor and to the desired depth.

A practically important embodiment of the invention is a silicon semiconductor, which is provided therein with a boron-containing layer, which defines a P region. The other side of the silicon chip or wafer retains its N nature, so that the product provided by the invention is a P-N compound semiconductor device.

The description speaks of the "darap phase transport of BgO 2", because it is not entirely clear which boron-containing substance is evaporated from the ceramic glass source. Therefore, this term encompasses any boron-containing substance, which is 8000302 * 8 responsible for the transport operation. Diffusion is also referred to as "boron diffusion" in the semiconductor, because it is not entirely clear which boron-containing substance is actually diffused. This term therefore includes any boron-containing substance responsible for the diffusion stimulating action.

Boron is deposited from the vapor phase on the surface of the semiconductor and diffuses to a controlled depth in the silicon wafer. The concentration and depth of the compound 10 is proportional to the time and temperature of the stimulation and diffusion.

The composition of the containing ceramic glass source for the stimulant is critical in that the source must contain enough to provide a vapor phase rich in 22 ^ 3 the usual stimulation temperatures between 700 ° C and 1200 ° C. It has been found that the ceramic glass source must contain at least 10 mole percent BgO 4 to provide sufficient BgO vapors, the lower mole percent BgO 4 requiring the higher temperatures. The ceramic glass source for the stimulant must be rigid and dimensionally stable at the stimulating temperatures, so that deformation is not a problem when the source has a flat shape. In planar stimulation by diffusion, a planar surface of a solid source of the stimulant and a planar surface of the semiconductor to be stimulated are spaced parallel to each other during the diffusion heat treatment. Since the concentration of BgO 2 on the surface of the semiconductor is a function of the distance between the flat surfaces, the dimensional stability of the source with the stimulant is very important for achieving evenness in the surface boron distribution. of the silicon semiconductor.

The ceramic stimulant glass sources, which are particularly suitable for the practice of the invention, are made of certain magnesium oxide alumina borosilicate glasses which are substantially free of alkali dioxide.

8000302 9

By substantially alkali-free is meant that the glasses do not contain enough alkali oxides (e.g. KgQ, NagO and LigO) to give a vapor phase containing these oxides at the stimulation temperatures. It has been found that the presence of such alkali oxides in the vapor phase gives undesired conductive properties to the obtained semiconductor. In the conventional practice of the present process, the combined alkali oxides are less than about 0.5 mole percent, and preferably less than 0.1 mole percent, of the ceramic glass source composition. The alkali oxides are preferably completely absent, although this is not always possible because the starting materials often contain alkali oxides as impurities.

The term "ceramic glass body" has been used in accordance with its usual meaning, and refers to a semi-crystalline ceramic body, which consists of at least one crystalline phase, which is randomly dispersed in a residual glassy phase or matrix. Such a crystalline phase is formed by the on-site thermal crystallization of a starting glass composition.

The heat stimulation for forming ceramic glass from a starting glass usually comprises a nucleating step at substantially the temperature of the slow cooling point (viscosity 10 Pa.s) of the starting glass, a developing step at a temperature below the softening point of the fibers of the starting glass. starting glass (preferably at a viscosity between 10 and 10 Pa.s), and a crystallization step (at a temperature of preferably from 83 to 167 ° C above the fiber softening point of the starting glass (i.e. a viscosity of 10 ^ * ^ Pa.s). _

Although the crystallization process itself is not an object of the invention, the following description is given for completeness. The starting glass to be crystallized is heated to a temperature corresponding to a viscosity of about 12 Pa / s, and held at this temperature for a sufficient time to allow the formation of submicroscopic crystals dispersed throughout an entire glassy matrix. The time required for this nucleation period is variable in composition composition 8000302, and is usually between 15 minutes and 2b hours.

The glassy matrix containing the core crystals is then heated to a temperature corresponding to a viscosity of approximately 10 Pa.s. This thermal state is maintained long enough to allow partial crystallization to form a rigid crystalline structure. The submicroscopic cores dispersed in the glassy matrix as a result of the core-forming step act as growth centers for the rigid framework formed during this second or development step of the heating cycle. The development step is variable depending on the composition and usually lasts from 15 minutes to four hours. The purpose of the development step is to provide a rigid, skeletal crystal framework for supporting the remaining matrix when the temperature is raised to full crystallization. The ceramic glass body is then formed by heating to a temperature of 83-16 ° C above the temperature, which corresponds to the viscosity of 10 ^ Pa Pa of the starting glass. This temperature is maintained until the desired degree of crystallinity is obtained. The final crystallization step of the heat stimulation cycle usually lasts from 15 minutes to four hours, and according to some aspects of the invention takes place at the highest imaginable temperature at which the ceramic glass is not yet flowing. This heat stimulation promotes the stability of the finished ceramic glass in dimensions at a high temperature. This heat stimulation temperature is close to the solid solution temperature.

It has been found in practice that all three steps of the heating stimulation can be performed by continuously increasing the temperature through areas of nucleation, development and crystallization. In many compositions of the invention, it has been found that a true development step is not necessary because the time required to heat the article from the core forming temperature to the crystallization temperature is sufficient. Further details for forming ceramic 8000302

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11 glass bodies are described in U.S. Patent 3,117,881.

According to the first embodiment of the invention, the ceramic glass source for the stimulant is made from a magnesium oxide alumina borosilicate starting glass, such as a (MgO, Al ^^). BgOg.SiOg glass, which is substantially free of alkali metal oxides, and consists essentially of the following ingredients, expressed in moles.

Wide range Preferred range 10 Ingredient Mol. # Mol · #

Si02 2-50 5-30 A1203 15-36 20-30 b2o3 10-50 25-50

MgO 15-36 20-36 15 Usually, the sum of the alkali metal oxides is less than about 0.5 mole #, and preferably less than 0.1 mole # in the foregoing compositions.

In addition to the foregoing oxides, the term "consisting essentially of" includes minor amounts (eg, up to about 10 moles #) of oxides other than alkali oxides, such as vitreous oxides, modifying oxides, nucleating oxides (eg TiO2 and / or ZrOg ) and refine auxiliaries, when such ingredients are desired to obtain certain chemical or physical properties.

An essential feature is that the alumina borosilicate, ceramic glass source for the stimulant contains at least 10 moles # B2Q3, which may be present in the glassy phase, the crystalline phase or in a combination thereof.

Examples I-XVII below illustrate the first embodiment of the invention.

According to a second embodiment of the invention, the ceramic glass source for the stimulant is made of an alkaline earth alumina borosilicate starting glass, which is substantially free of alkali metal oxides, and consists essentially of the following components, expressed in mole percent.

8000302 12

Wide range

Component Mol- #

SiOg 15- ^ 0 ai2o3 15-30 5 B203 '20-60 RO 5-25 where 1 *> A1203> 1 · 5

RO

where RO is: 10

MgO 0-15

CaO 0-10

SrO 0-10

BaO 0-10 15 La2 ° 3 0-5 lib205 0-5

Ta205 0-5

Usually, the sum of the alkali metal oxides is less than about 0.5 mole #, and preferably less than 0.1 mole #, in the foregoing compositions.

In a preferred application of this second embodiment of the invention within the previous range, the composition mainly consists of:

Preferred range 25 Component Mol. #

Si02 18-M) A1203 15-30 B90- 30-60 * 1 5-15 3Q where 1 *> A1203> 2 R0

Here, the MgO component of R0 is at least about -__ 4% of the total composition.

It will become apparent from Examples XVIII-LVII that the combination of MgO with CaO, SrO and / or BaO improves the resistance to accidental devitrification in the starting glass. It contributes the presence of LagO2, Nb2, and Ta2 O2 to the melting and molding of starting glass compositions which have a high content (e.g., more than about 50 moles #) of BgO2, which are resistant to accidental devitrification. .

In addition to the foregoing oxides, the term "consisting essentially of" includes minor amounts (ie, up to about 10 moles #) of oxides other than alkali oxides, such as glass-forming oxides, modifying oxides, core-forming oxides (eg, TiO4 and / or ZrOg ) and refine auxiliaries, when such components are not detrimental to the stimulation of the semiconductor, and are desired to achieve certain chemical or physical properties.

The ratio of is important in terms of

RO

The moldability of the glass and the high temperature stability in the obtained ceramic glass source for the stimulant. When this ratio is less than about 1.5, the glass ceramic well plates may have a tendency to deform at stimulating temperatures in the vicinity of 1100 to 1200 ° C. When the ratio is greater than about U, it becomes difficult to melt and form the starting glass.

In the practice of the third embodiment of the invention, the ceramic glass source for the stimulant is made of a barium alumino borosilicate starting glass, which is substantially free of alkali metal oxides, and consists essentially of the following components, expressed in mole percent.

Wide range

Component Mol. #

SiOg 1 + 0 / itot 60 30 A1203 10 to 30 B2Q3 20 to 1 + 0

BaO T to 15

Alkaline earth metals 3 to 20 oxides, such as BaO, MgO, CaO, 35 SrO and mixtures thereof 8000302 14 where k> - * 3. ,> 1.5 - Alkaline earth oxides "

Usually, the sum of the alkali metal oxides is less than about 0.5 mole #, and preferably less than 0.1 mole # in the foregoing compositions.

When using this third embodiment of the invention, which is preferred for a long life, as well as the efficiency and controlled stimulation with boron 10 and the structure stiffness at high temperatures within the previous range of compositions, mainly consists of:

Preferred range

Component Mol. #

SiO2 hO <to 55 15 AJ ^ O ^ 10 to 30

Β ,, Ο ^ 20 to UO

BaO 3 to 15

Alkaline earth oxides

20 in which A1 Q

4 \ -> 2 - alkaline earth oxides -

As will be apparent from Examples LVIII - LXIII, the combination of BaO with MgO and the other alkaline earth oxides extends the range of glass formation, with longer life, structural stiffness and controlled rate of boron stimulation at high temperatures are provided.

In addition to the foregoing oxides, the term "consisting essentially of" also includes minor amounts (ie, up to about 10 moles #) of oxides other than alkali oxides, such as glass-forming oxides, modifying oxides, nucleating oxides (e.g. TiO2 and / or ZrOg) and refining aids, when such ingredients are not detrimental to semiconductor treatment, and desired to obtain certain chemical and physical properties.

The Al2 ° 3 ratio is important for alkaline earth oxides in terms of glass availability and high temperature stability in the resulting ceramic glass source for the stimulant. When this ratio is less than about 1.5, the ceramic glass slides may have a tendency to deform at the stimulation temperatures, on the order of 1100 to 1200 ° C. When this ratio is greater than about 1+, it becomes difficult to melt and form the starting glass.

According to the invention, a suitable N silicon substrate 10 is made by any known method of obtaining monocrystalline silicon bodies. For example, an IQ single crystal casting can be made from high purity silicon. The casting is then cut into cross cuts, the cuts being cubed to provide silicon wafers of the desired dimensions. The surface of the underlayer can be pretreated by cleaning and polishing it appropriately. However, the polished and cleaned semiconductor silicon materials can be purchased commercially. The polishing and cleaning of the surface can be accomplished by mechanical means, such as grinding or the like, or by chemical means, such as etching, which is well known and not part of the invention.

The N silicon wafer may furthermore be part of a complicated semiconductor device, and already be provided with one or more β-ions which may be arranged therein according to any desired geometric pattern. The only important feature is that at least a portion of the free surface of the silicon wafer has an N-conductivity. The term N silicon, as used herein, encompasses complicated semiconductor devices having alternating regions of P and N conductivity.

For conventionally grown crystals, the surface can be chemically polished with a suitable etchant, for example, a concentrated solution of three parts of hydrofluoric acid, three parts of acetic acid and five parts of nitric acid by volume.

The surface can also be pretreated by grinding or etching with a hot solution of water containing about 8000302 1% 10% sodium hydroxide at ambient temperature and up to about 90 ° C. These cleaning and etching operations remove contamination from the surface and smooth the surface with a high degree of smoothness. These preparatory operations are well known in the art.

The formation of P-N compounds according to the invention has been found to take place to a desired extent on N silicon with a resistance of approximately 10 ohm centimeters. It will, of course, be understood that the precise dimensions and nature of the wafer are not critical. For example, a commonly used wafer can be 2.5, 5 or 7.5 cm in diameter or even more.

The thickness can be between 0.13 and 0.51 mm, although this can be variable. Conventional plates are 0.20 to 0.25 mm thick.

The resistance of suitable N silicon starting materials is also between 0.0001 and 100 ohm centimeters.

As shown in Fig. 1, an oxide layer 11 has grown on the surface of the wafer 10 according to the invention. The wafer is heated in the vapors of BgO 2 so that a film or coating is formed over at least a portion of the wafer surface. A masking or protective coating can be used to develop a random pattern, as is known in the art. The coating or film 11 has a glassy nature and contains boron in some form.

The temperature of this stimulation is such that simultaneously some boron from the film deposit 11 diffuses into the wafer 10, thereby forming a thin boron diffusion surface layer or region 12 at the coating 11. The region 12 is a barrier or boundary, which is formed in the interface between the boron diffusion surface layer 11 and the N conductive silicon 10. The bonding depth may be variable but is generally up to 10 microns in thickness. The minimum thickness can be variable, and is usually about 0.1 yam.

It is in or on or under this glassy layer 11 that the electrically insulating deposit of the borosilicidal composition forms. The third embodiment of the invention reduces the tendency to form this insulating composition and facilitates the removal of the reduced amount that may have formed.

Fig. 2 shows a disc or wafer of the BgO2-containing ceramic glass source for the stimulant, which wafer acts as the source for the Bo0 thank for contact with the silicon wafers.

When placed in a suitable oven used for the invention, and subjected to suitable temperatures, the ceramic glass stimulant glass releases Bg0 vapors, which then pass through the high temperature range of the oven. flows in the direction after contact with the silicon wafers disposed at the stimulant wafer. When using the first embodiment of the invention, the temperature is between 700 and 1200 ° C, but more in particular between 850 and 1100 ° C. In the second and third embodiments, the temperature should be between 700 and 1250 ° C, and more particularly between 1050 and 1200 ° C. Generally, the method includes diffusing boron into a semiconductor silicon element by placing at least one semiconductor silicon element in an oven, placing a solid stimulating wafer, disk or the like body in the vicinity of, but not in physical contact with the silicon element, and then subjecting the silicon element and the ceramic glass source to an elevated temperature within the described ranges. At these temperatures, the stimulant releases B 2 O 2 vapors which then pass through the oven and contact at least a portion of the surface of the silicon element.

This treatment is carried out long enough to allow the diffusion of boron into at least a portion of the surface of the silicon element to form a diffused region therein. After the vapors react with the hot silicon surface, elemental boron diffuses into the silicon wafer upon further heating. This boron diffusion step 35 can be performed in the absence of the ceramic glass stimulant glass, if desired.

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As a further aspect of this embodiment of the invention, stimulation is further controlled and enhanced using a free flowing inert carrier gas such as argon or nitrogen. The term "inert gas" as used in this specification 5 means that the carrier gas does not participate in the chemical reaction between the vapors and the hot silicon surface.

This is shown in Figure 3, in which the carrier gas enters from the left and flows over the wafer, where it is released and comes into contact with the free surfaces 10 of the silicon wafer 10. By placing two silicon wafers against each other, the other side receives of each of the silicon plates there is no boron by the stimulation, which side therefore retains its original nature as an N silicon. After the stimulation operation, the diffusion depth can be further increased to diffuse the compound deeper by simple heat stimulation in an inert atmosphere. This can be done in a separate oven, if desired. The method has been described with reference to silicon semiconductors because they are so important.

However, the same method can also be used for germanium semiconductors, although slightly lower temperatures are used to stimulate germanium due to its 937 ° C melting point.

In the pretreatment of ceramic glass stimulants, suitable compositions containing the appropriate starting materials can be melted to form a homogeneous glass. For example, the compositions described above can be melted to form a homogeneous glass at 1500 to 1650 ° C in a refractory vessel. Generally, this melting requires from about 15 minutes to several hours to achieve homogeneity. It may be desirable to additionally add Β ,, Ο ^ to the melt to make up for evaporative losses. It is desirable to keep the melting time as short as possible in order to reduce the evaporation losses. The starting material must also be as pure as possible so as to minimize the presence of impurities.

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The stimulant resource can be made in a number of ways. The starting glass may be melted from organically derived metal materials to minimize the content of undesirable components as described in US Pat. No. 3,6 ^ 0,093, or it may be melted from conventional high purity glazing ingredients.

Desirably, the glass or ceramic glass is free from contaminants having high vapor pressures at 900 to 1200 ° C. It will be clear that the presence of IQ impurities can adversely affect the electrical performance of the stimulating silicon semiconductor. Contaminants that should definitely be excluded or kept to an absolute minimum include the alkali oxides (i.e. Li ^ Q, Na20, KgO, CagO or RbgO) and other metal oxides with a high vapor pressure, such as 15 PbO, CuO and SnO ,,.

After the glass compositions are melted and formed into a homogeneously melted mass, the glass can be poured into any desired shape. This is preferably accomplished by casting the glass into preheated graphite molds of the shape of circular cylinders of diameter approximating the diameter of the finished diffusion disc. The glass is then allowed to cool, the glass being cold when removed, the molding or cylinder thereof and examined for defects, and then cut into platelets, which are usually between 0.6 and 25 mm in thickness. The glass slides are then in a mold to be transformed into a ceramic glass source. The glass molding or core cut obtained by core drilling can also be heat treated to form the ceramic glass, which is then cut into platelets.

Thanks to the very precise control made possible by the invention, a number of silicon elements can be treated by properly placing a number of ceramic glass plates with stimulant in the manner shown in Figure 3. In the practice of the invention, stimulation is accomplished by placing the ceramic glass plates with stimulant close to and parallel to, but 8000302 not in contact with the silicon plates to be stimulated. For best results, it has been determined that the distance should generally be about 3.2 mm. In a molten silica or other multi-slot refractory vessel, 100 or more silicon-5 wafers can be stimulated to an even level by alternately placing a ceramic glass wafer and a pair of wafers together, aligning the silicon wafers and the ceramic glass wafers are essentially parallel. This arrangement is shown in Fig. 3 · 10. The duration and temperature of the stimulation are chosen to give the correct P-N connection depth and plate resistance for the desired shape. This is illustrated in the following examples.

The spacings between the platelets in the vessel and the selection of the surrounding inert carrier gas and the flow rate are based on the requirement that silicon wafers turned in the direction of the gas flow receive equivalent stimulation with respect to the silicon wafers. turned in the other direction.

The various embodiments of the invention will now be further described in the following examples, all percentages being in mole percentages and the temperatures in ° C. Examples I-XVII relate to the first embodiment, Examples XVIII-LVII to the second embodiment, and Examples LVIII-LXIII to the third embodiment.

Example I Part A

A stirred reaction vessel is charged with 1132 g of ethyl silicate, 750 ml of ethanol, 60 ml of water and 6 ml of 1 K nitric acid. The mixture is stirred briefly and then can stand for several hours until the ethyl silicate is hydrolyzed.

A solution of 95 g aluminum sec-butoxide in 500 ml sec-butanol is slowly added with stirring to the hydrolyzed ethyl silicate. The reaction is somewhat exothermic, with the addition rate controlled to maintain the temperature of the reaction mixture below about 50 ° C.

8000302 21

When the addition of the aluminum sec-butoxide is complete, 100 ml of water is added with continuous stirring, followed by the addition of 2.09 g of trimethyl borate. The resulting mixture becomes quite gelatinous, and is diluted by adding 1 * 000 ml of water. After dilution, 368g of magnesium oxide is added in small amounts simultaneously with continuous stirring to obtain an even dispersion of the magnesium oxide throughout the solution. The reaction mixture is then stirred for an additional 20 minutes.

The reaction mixture is poured into shallow synthetic resin dishes, which are then placed in a forced air oven held at 60 ° C to evaporate the solvent from the dishes. After evaporation of the volatile solvents, a fine white powder is obtained.

The powder is dried at 150 ° C for about 20 to 2b hours. About 2500g of dry powder is obtained.

The powder is transferred to a platinum crucible. and melted at about 15l * 0 ° C for 5 hours with occasional hand stirring to form a clear, homogeneous glass having the following mole percent composition: 15 $ SiO2, 31 *, 7 $ B203 .25.2 $ MgO and 25.2 $ A1203.

Part B

The molten glass of Part A is poured into a preheated graphite mold in the form of a circular cylinder. The dimensions of the cylinder are 5.6 cm in diameter and 7.5 cm in length. The mold containing the glass is heated to 671 ° C.

Heating takes about 15 minutes to half an hour. The molds can then cool, after which the glass cylinder 30 is removed. The cylinders are then cut into plates with a thickness of 0.38 to 1.02 mm.

The plates are carefully stacked in a heat-stimulating oven, after which the temperature is raised to 8i * 5 ° C to initiate on-site thermal crystallization. The platelets are held at this temperature for k hours, after which the temperature is raised to 867 ° C, upon which the platelets are kept for 8000 hours for 1 hour. Finally, the temperature of the heat stimulation furnace is raised to 1100 ° C. The plates are kept at this lowest temperature for 1 hour, after which the oven is turned off and can cool to room temperature overnight.

The resulting non-porous ceramic glass slides are removed and dried to be used in stimulation diffusion.

Part C.

The plane diffusion stimulation is accomplished by placing a portion of the ceramic glass plates of the portion B at a distance of about 6 mm from a parallel to the silicon plates to be stimulated. The ceramic glass plates and the silicon plates are placed in fused, multi-slit silicon oxide shells by alternately applying a ceramic glass plate, two silicon plates together, a ceramic glass plate, etc. The entire assembly is shown in Figure 3.

The silicon wafers used in this example are originally of the II type, and have a resistance of about 9 ohm-cm.

The assembly is placed in a diffusion oven, after which argon gas is passed through it as an inert gas carrier,

O

as shown in Fig. 3, at a rate of 500 cm / minute, keeping the temperature at about 1050 ° C. These conditions are maintained for 1 hour.

At the end of this diffusion stimulation period, the silicon wafer is cooled to room temperature and cleaned with dilute hydrofluoric acid.

The surface of the stimulated silicon wafers has a P conductivity. The surface of the stimulated platelets is examined with a four-point conductivity probe, the measured surface resistance being about 13 ohms / cm. The P-N junction is estimated at a depth of about 3 to 1 µm from the surface of the silicon wafer.

The stimulator disc is not clearly collapsed or otherwise distorted at the end of the diffusion stimulation process. When treating an N germanium semiconductor according to the invention, slightly lower stimulation temperatures must be used, because the melting point of germanium is 937 ° C.

Several other diffusion stimulation studies are performed by the foregoing method, except that the time and temperature are changed as shown below. In any case, the stimulated silicon wafer exhibits a P conductivity.

10 Plate resistance of a P conductivity stimulated 2 _ silicon wafer (Ohm / cm) _

Temperature (° C) time (hours) l 1 2 k 15 1000 U8 k2 30 25 1025 32 17 12 16 10U0 26 20 1U 10 1050 18 13 10 8

Example II

20 -

Part A.

High purity inorganic starting materials containing reagent grade oxides and carbonates are mixed to give a 500g batch consisting of 15> 7 mol. # SiOg, 1 * 1.3 mol. # B ^, 21 .5 mol. # AlgOg and 21.5 mol. #

MgO. The material is placed in a platinum crucible, which is then placed in an oven kept at 150 ° C. The crucible is heated for about 6 hours with occasional stirring to form a melted, clear, homogeneous glass. The glass is removed from the oven and solidified in a heating oven, which is kept at 650 ° C for about half an hour.

Part B

The crucible is removed from the oven and cooled, after which cores of nominal diameters 5> 62 cm by 7.5 cm long are drilled out of the solidified glass. The cores are then cut into plates with the same dimensions as in Example 1, 8000302 »2k half that the temperature and time schedule is 852 ° C for one hour, and the final temperature and time is 1100 ° C for one hour, before the oven turns off and can cool to room temperature at the oven speed. The ceramic glass-5 plates obtained are non-porous and are dimensionally stable.

Part C.

Planar diffusion stimulation is performed with the plates of Part B as in Example I, except that the temperature is 950 ° C, and the argon flow rate and temperature are set as shown below. The data shows that the resistance decreases with increasing stimulation time. The change in resistance is due to the increased P stimulation. Plate resistance of P stimulated silicon wafers (ohm / cm).

O

Argon flow rate (cm / minute) time (hour) 15 2 1 2 k 100 181 * 90 39 23 3l * 0 93 75 69 1 * 0 500 53 1 * 0 32 28 20 61 * 0 71 1 * 1 * 35 33 2

The reason for the 18U ohm / cm reading at half an hour

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and an argon flow of 100 cm / minute is not clear, although it is believed that the conductivity changes just from N to P.

Another study is performed as before except that the argon flow rate is 550 cm / minute, and the spacing is 3.2 mm instead of 6.1 * mm. P stimulation is achieved in the stimulated silicon samples, the resistance of which is shown below as a function of time.

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Time (hours) Ohm / cm 30 l - 57 1 1 + 7 2 37 1 * 31 8000 302 25

Examples III - IX

Ceramic glass source stimulant are prepared from glasses of the composition, as shown in Table I. The process for melting and crystallizing the 5 glasses is described in Part A of Example II, except that the temperatures are maintained in the manner indicated in Table I. .

The crystallized ceramic glasses are removed from the crucible, preparing cross sections thereof to stimulate planar diffusion.

Diffusion stimulation is accomplished by placing the stimulant source in the bottom of a silicon oxide scale. An N silicon wafer with a resistance of about 5 ohm-cm is placed in one of the slots of the silicon oxide scale in a vertical position and at a distance of about 1.3 mm from the stimulant source.

The silica scale assembly is placed in a diffusion oven, then argon gas is passed through the oven at a rate of 500 cm / min, keeping the temperature at 1000 ° C. These conditions are maintained for one hour for each study.

At the end of the diffusion stimulation period, the silicon wafer is cooled to room temperature and observed. Interference patterns, which indicate the presence of a thin film, are noted on all silicon wafers shown in the following table. The surface of the silicon wafers is then cleaned with dilute hydrofluoric acid.

The surface conductivity of the silicon wafer is then checked, with all silicon wafers exhibiting a P conductivity.

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Examples X-XVII

The following examples further illustrate the principles of the invention and provide additional stimulation data, as well as a qualitative indication of the thermal stability of the ceramic glass fiber stimulant sources. Glass stimulant sources are made from glass mixtures of the compositions, as shown in the following Table II. The glass quality is also indicated in the table. The compositions, which are clear glassy, have been designated "good", with 10 other compositions appearing to be opal. The processes for melting and crystallizing the glass mixtures are described in Part A and Part B of Example II, except that the temperatures are maintained as indicated in Table II.

A random "sag test" is shown in the table below. In this study, glass bars of about 3.2 mm square and about 28.6 mm in length of the indicated glass are made and crystallized into a ceramic glass body with the indicated crystallization heat stimulation. After crystallization, each ceramic glass rod 20 is ground flat on both sides so that the final dimensions are 28.6mm x 3.2mm x 1.6mm. Each ceramic glass rod is then placed over a 22 mm wide platinum vessel (with 3.2 mm of the rod resting on the vessel, and maintained at temperatures between 1000 and 1250 ° C for half an hour). The distance by which the 1.6 mm thickness "sag" or deviates from the flat plane gives an arbitrary indication of the resistance to thermal deformation.

Although the amount of thermal deformation or sag, which is acceptable, changes with the thickness of the sample, the stimulation time and the stimulation temperature in any circumstance, a sag of more than about 0.3 mm in the described method corresponds approximately to the maximum allowable deformation of a very thin (for example, about 0.51 mm thick) 2.5 to 3.8 cm diameter stimulation pad in a stimulation assembly, as shown in Figure 3. For higher temperatures, thicker ceramic glass sources are applied.

Planar diffusion stimulation is accomplished like 8000302 23 in Part C of Example I, except that the diffusion stimulation period is half an hour at the temperatures indicated in the table. The results of this stimulation are also shown in the table.

The data in the table shows that the tendency to deformation increases with increasing temperatures, although good thermal stability is observed for very thin ceramic glass rods.

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Example XVIII

Part A.

Conventional high purity glass blend materials are melted in a platinum crucible at 15 ° C for 5 to 6 hours with manual stirring to give a clear, melted, homogeneous glass having the following composition.

Mol% Weight%

SiO2 15.7. 12.8 B203 U1.3 39.3 10 A1203 28.7 1 * 0.0

MgO 1-1 +, 3 8.0

The molten glass is removed from the oven and cooled to room temperature. The glass, which is still in the crucible, is transferred to a curing oven, which is kept at 650 ° C. The glass is cured at 650 ° C for half an hour, then removed and cooled to room temperature.

Part B

The crucible with the clear glass content is placed in a heat stimulation furnace, after which the temperature is raised to 690 ° C. The crucible is kept at this temperature for three hours. The temperature is then raised to 805 ° C, which temperature is held for one hour. Then the temperature is raised to 1100 ° C, which temperature is also maintained for 1 hour. The oven is then turned off and allowed to cool to room temperature before the crucible is removed. The obtained non-porous ceramic glass material has a milky white appearance. A core is obtained from this ceramic glass material with a 3.8 cm diameter hole saw, which is forged into thin plates with a diamond saw to thicknesses of 0.38 mm to 1.02 mm.

Part C.

Planar diffusion stimulation is performed by placing a portion of the ceramic glass plates of portion B at a distance of about 3.2 mm to 6.1 mm from and parallel to the silicon plates to be stimulated. The ceramic glass 8000302 31 platelets and the silicon platelets are placed in molten silicon oxide shells with a number of slots by alternately placing a ceramic glass platelet, etc.

The silicon wafers used in this example originally had an N conductivity and a resistance of about 9 ohm-cm.

The assembly is placed in a diffusion oven and argon gas is passed therethrough as an inert carrier gas, as shown in Figure 3, at a rate of 500 cm / minute, maintaining the stimulation period and temperature, as shown below.

At the end of this diffusion stimulus period, the silicon wafer is cooled to room temperature and cleaned with dilute hydrofluoric acid.

The surface of the silicon wafers to be stimulated shows a P conductivity. The surface of the stimulated platelets is examined with a four-point conductivity probe. The surface resistances in ohms per square of the obtained stimulated silicon sample are indicated below as a function of temperature. The conductivity of the stimulated silicon is of the P type.

3

Distance 3.2 - 6.4 mm - Flow rate: 500 cm / min.

Argon (Time (hours)) 2 ^ Temperature \ 1 2 1+ 950 ° C 71.0 61 + .7 56.0 5 ^ .5000 ° C 5 ^ .5 1 + 2.7 38.5 26.8 1078 ° C 16.7 11 +, 0 10.0 6.5

The stimulator disc was not clearly collapsed or otherwise deformed at the end of the diffusion stimulating process. In stimulating an N germanium semiconductor according to this embodiment of the invention, slightly lower temperatures are used because germanium melts at 937 ° C.

Several other diffusion stimulation studies are performed by the foregoing method, except that the time 8 0 0 C 3 0 2 32 and the temperature are changed as shown. In any case, the stimulated silicon wafer exhibits a P conductivity.

Plate resistance of P stimulated silicon wafer (- "VΠ) Temperature (° C) Time (hour) 5 l 1 2 k 1000 16 k2 30 25 1025 32 17 12 16 10l0 26 20 1U 10

10 1050 18 13 10 8 Examples XIX - XXXXVII

Ceramic glass slides as the source of the stimulant are made from glasses of the composition, as shown in the following Tables II and III. The process for melting and crystallizing the glasses are the same as those described in Example XVIII, except that the temperatures indicated in Tables III and IV are maintained and the molten glass is quenched by pouring of a plate thereof in a shallow metal tray at room temperature, instead of heating as in Part A of Example XVIII. Table III relates to compositions in which MgQ is the only R0 component, Table IV showing the different combinations of R0 components.

A random "sag test" is shown in the following tables. In this study, glass bars about 3.2 mm square and about 2.9 cm long are made of the indicated glass and crystallized into a ceramic glass body by the described crystallization heat stimulation. After crystallization, each ceramic glass rod 30 is ground flat on both sides so that the final dimensions are 2.9 cm x 3.2 x 1.6 mm. Each ceramic glass rod is then placed over a 22.2 mm wide platinum vessel (with 3.2 mm of the rod resting on the vessel), and held at a temperature between 1000 and 1250 ° C for half an hour. The distance by which the 1.6 mm thickness "sags" or deflects from the planar state gives an arbitrary indication of the resistance to thermal deformation. Although the amount of thermal deformation or sag that can be allowed varies depending on the thickness of the sample, the stimulation time and the stimulation temperature in any circumstance, a sag of more than about 0.3 mm occurs at the the foregoing method substantially corresponds to the maximum allowable deformation for a very thin (for example, about 0.51 mm thick) stimulation pad with a diameter of about 2.5 ^ ror 3.8 cm in diameter with a stimulation assembly, as shown in Figure 3 .

Thicker ceramic glass bodies with stimulant can be used for higher temperatures.

The data in the following tables indicate that the tendency for deformation increases with increasing temperatures, although good thermal stability has been observed for very thin ceramic glass rods at temperatures above 1050 ° C and even up to 1250 ° C.

* 8000332 3b

Table III

Example 19 .- 20 21 _-22 23 2b

Mol.%

Si02 15.7 36.0 2b, o 30.0 30.0 37.5 A1203 28.7 26.7 26.7 26.7 23.3 21.7 B203 i + 1.3 2b, 0 36.0 30.0 35.0 30.0

MgO 1, 3 13.3 13.3 13.3 11.7 10.8

Alg03 / Mg0 2 2 2 2 2 2

Glass appearance some clear clear clear clear opal crystals

Crystallization heat stimulation ° C for 16 hours 700 700 700 700 700 700 + ° C for 1 hour 1260 1260 1200 1200 1200 1260

Sagging research

Deflection in mm at ° C for half an hour 1000 0 0 0 0 0 0 1100 0 0 0 0 0 0 1200 0.3 0 0 0 0 0 1250 0.5 0.2 0 0.2 0.2 0.2

Plate resistance (11- / Π) after "P" stimulation at g hours bi.i ° C_ 1000 38 29 30 19 32 1100 8 7 7 5 7 1200 2 2 2 2 2 2 8000302

Table III (continued)

Example 25 26 27 28 29 30 35

Mol.%

Si02 35.0 22.5 30.0 25.0 20.0 23.0 A1203 20.0 21.7 20.0 23.3 26.7 25.7 B203 35.0 ^ 5.0 U0.0 U0 .0 U0.0 38.5

MgO 10.0 10.8 10.0 11.7 13.3 12.8

Al203 / Mg0 2 2 2 2 2 2

Glass appearance opal opal opal only some only crystal crystal numbers

Crystallization • heat stimulation ° C for 16 hours 700 700 700 700 700 700 + ° C for 1 hour 1260 1260 1260 1260 1260 1260

Sagging research

Deflection in mm at ° C for \ hour 1000 0 0 0 0 0 0 1100 0 0 0 0 0 0 1200 0 0.2 0.2 0 0 0.

1250 0.2 1.6 0.9 0.5 0 0.7

Plate resistance (-Π- / θ) after "P" stimulation at | hour at ° C_ 1000 27 29 28 29 28 26 iioo 578898 1200 2 2 2 2 2 2 3000 302

Table III (continued)

Example 31 32 33 3h 35 36

Mol./5

Si02 25.0 20.0 23.0 20.0 25.0 A1203 21.0 22.5 23.1 20.0 16.7 B203 1 * 0.0 ^ 2.5 33.5 50.0 50, 0

MgO 1M 15.0 15.1+ 10.0 8.3

Al203 / Mg0 1.5 1.5 1.5 2 2

Glass appearance clear clear clear opal single crystals

Crystallization heat stimulation ° C for 16 hours 700 700 700 700 700 + ° C for 1 hour 1260 1260 12Ö0 1260 1260

Sagging research

Deflection in mm at ° C for \ hour 1000 000 1100 000 0.2 0 1200 2.8> 3 2.6 0.5 0.6 1250 -> 3> 3

Plate spring resistance (XlJΠ) after "P" stimulation at § hour at ° C_ 1000 33 35 1100 9 9 9 9 10 1200 o 8000302

Table IV

Example 36 37 38 39 1 + 0 1 + 1 37

Mol.%

Si02 25.0 25.0 25.0 15.7 15.7 15.7 A1203 16.7 16.7 16.7 28.7 28.7 28.7 B203 50.0 50.0 50.0 1+ 1.3 1 + 1.3 1 + 1.3 EO 8.8 8.8 8.8 9.3 9.3 11.3

MgO 3.3 3.3 3.3 9.3 9.3 11.3

CaO 5.0

SrO 5.0

BaO 5.0 A1203 2 2 2 3.1 3.1 2.5 5.0 3.0

Nb205

Ta205 - 5.0

Glass appearance opal clear clear clear some clear crystals

Crystallization heat stimulation ° C for 16 hours 700 700 700 700 700 700 + ° C for 1 hour 1260 1260 1260 1200 1260 1260

Deflection in mm at ° C for 1 hour 1000 0 0 0 0 1100 0 0.8 0.9 0.5 1200 0.9 0.6 0.2> 3 2.1 2.1 1250 1+, 0 1+ , 0 2.0

Plate resistance (-Π- / O) after "P" stimulation at ü hour at ° C_ 1000 28 33 27 29 1 + 7 30 1100 382 8 1200 2 1+ 2 8000302

Table IV (continued)

Example 1 + 2 1 + 3 kb 1 + 5 1 + 6 1 + 7 38

Mol.%

SiO2 20.0 20.0 25.0 22.5 15.7 22.5

A1203 20.0 16.7 13.3 21.7 2hj 21J

B203 50.0 55.0 55.0 1 + 5.0 1 + 7.3 1 + 5.0 RO 10.0 8.3 6.7 8.8 12.3 10.8

MgO 5.0 3.3 8.8 7.3 5.8

CaO

SrO 5.0 5.0 6.7 5.0 5.0

BaO

Al203 / R0 2 2 2 2.5 2 2

La203 2.0 2.0

Nb205

TagO ^

Glass appearance some clear clear clear some clear crystal crystals

Crystallization heat stimulation ° C for 16 hours 700 700 700 700 700 700 + ° C for 1 hour 1260 1260 101 + 0 1260 1260 1260

Sagging research

Deflection in mm at ° C for g hours 1000 0 0 0.1 0 0 0 1100 0.1 0.0 0 0 0 1200 1.0 0.8 3.5 0.7 0.8 1250 1 +, 3 5 , 0 1 +, 0 3.5

Plate resistance (JTL / q) after "P" stimulation at \ hour at ° C_ 1000 32 33 30 30 31 32 1100 9 11 9 8 1200 8000 302

Table IV (continued)

Example 1 * 8 1 * 9 50 51 52 39 Μοί.ί

Si02 25.0 25.0 15.7 15.7 10.0 A1203 23.3 23.3 2KJ 2KJ 30.0 B203 1 * 0.0 ITO, 0 47.3 1 + 7.3 1 * 5.0 RO 9.7 11.7 12.3 7.3 10.0

MgO 9.7 6.7 7.3 7.3 10.0

CaO

SrO 5.0

BaO. 5.0 A1203 / R0 2.4 2 2 3.1 * 3

La203 2.0 5.0 "V5

Ta20? 5.0

Glass appearance clear clear some clear some crystal crystals

Crystallization heat stimulation ° C for 16 hours 700 700 700 700 700 + ° C for 1 hour 1260 1260 1260 1260 1260

Sagging research

Deflection in mm at ° C for \ hour 1000 0 0 0 0 0 1100 0 0 0 0 0.5 1200 1, 3 0.3 0.3 0.8 1 *, 6 1250 5.0 2.9 1 *, 5

Plate resistance (-A- / o) after "P" stimulation at 1 hour at ° C_ 1000 32 32 35 36 30 1100 9 8 9 9 1200 8000 302

Table IV (continued)

Example 53 5l + 55 56 57 l + o

Mol. #

SiO2 15.0 15.0 15.0 22.5 20.0 A1203 31.7 16.7 21J 21.7 20.0 B203. 37.5 60.0 52.5 1 + 5.0 50.0 RO 10.8 8.3 9.5 9.5 5.0

MgO 10.8 3.3 5.8 5.8 5.0

CaO

SrO 5.0

BaO

A1203 / R0 3 2.0 3.7 3.7 1+

Lsl2 ° 3 5.0

Nb2 ° 5 fa205 5.0 5.0 5.0

Glass appearance only single opal only single crystal crystals crystal crystals

Crystallization heat stimulation ° C for 16 hours 700 700 700 700 700 + ° C for 1 hour 1260 1260 1260 1260 1260

Sagging research

Deflection in mm at ° C for \ hour 1000 0 0 0 0 0 1100 0.5 o 0 0 o 1200 3.0 1.3 0.6 0.6 o 1250> 3> 3> 3> 3

Plate resistance (Si./O) after "P" stimulation at g hours at ° C_ 1000 28 36 37 31 3¾ 1100 10 10 99 1200 80 0 0 3 0 2, ύΐ

Example LVIII

Part A.

1 * 50g of high purity glass mixture materials are melted in a platinum crucible at 1260 ° C for about 5-6 hours in an electric oven under an air atmosphere and stir by hand from time to time to give a clear, melted, homogeneous glass with the following composition:

Ingredient Mol.%

SiO 2 b2.9 10 b2o3 29.6 ai2o3 19.0

Earth alkali oxides 8.5

BaO 5, ¾

MgO 3.1 15 A1203

Alkaline earth oxides 2.23

The molten glass is removed from the oven and poured into a steel mold (at room temperature), which has a cylindrical cavity with a depth of 6.3 cm and a diameter of 6.3 cm. When the glass looks solid and self-supporting, it is immediately transferred to a heat stimulation furnace at a temperature of 720 ° C and subjected to the following crystallization heat stimulation.

Part B

The Part A glass cylinder is held at 720 ° C for 16 hours. The temperature is then raised to 1200 ° C and maintained for an hour. The oven is then turned off and can cool to room temperature. The resulting non-porous ceramic glass cylinder has a milky-white opaque appearance.

The ceramic glass material is evenly ground to 3.8 cm in diameter using a sanding wheel, and sliced with a diamond saw to form a number of thin ceramic glass plates between 1.02 and 2.5 mm in thickness.

Part C.

The planar diffusion stimulation is accomplished by placing a portion of the 8000302 k2 ceramic glass slides part B at a distance of 3.2 to 6.0 mm parallel to the silicon wafers to be stimulated. the silicon wafers are disposed in a plurality of slotted molten silicon oxide trays by alternately placing a ceramic glass wafer, etc. The general assembly is shown in Fig. 3.

The silicon wafers used in this example are originally of the N type, and have a resistance of about 0.1 to 0.5 ohm-cm.

The assembly is placed in a diffusion oven, nitrogen gas being passed through it as an inert carrier gas, as shown in Fig. 3, at the rate of a standard liter / minute, the stimulation period being half an hour at a temperature of 1150 ° C .

At the end of this diffusion stimulation period, the silicon wafer is cooled to room temperature. The silicon wafer is then etched in dilute hydrofluoric acid to remove the glassy layer. The silicon wafer is examined, with only a just visible spot on the surface indicating that little boron silicide is present.

The surface of the stimulated silicon wafers has a P conductivity. The examination of the surface of the stimulated platelets is performed with a four-point conductivity probe. The surface resistance is approximately U ohm in the square. The light spot does not make it possible to measure the surface conductivity.

The stimulated plates (even these thin plates with a thickness of 1.02 mm) are not collapsed or otherwise physically deformed at the end of the diffusion stimulation process so as to make them unsuitable for further plane stimulation. When stimulating an N germanium semiconductor according to the invention, slightly lower temperatures are used, because germanium melts at 937 ° C.

The previous stimulations are repeated, except that for the last 5 to 10 minutes of the stimulation period, oxygen gas is substituted for the nitrogen gas at 8000302 at the same flow rate. Under these conditions, a light spot is still visible on the silicon after stimulation, which spot, however, is completely removed by hydrofluoric acid etching. The resulting surface resistance of the stimulated silicon is approximately ohms square.

Example LIX

Part A.

The following table demonstrates the extended life of the stimulant sources of the invention even after long periods of severe stimulating conditions of time and temperature. The term "stimulation time," as used herein, refers to the total period of time during which the particular stimulant resource has been used for effective stimulation. In many applications, the useful life of the stimulant source is not exceeded, even after 80 hours of stimulation.

In the following Table A, the temperature for the known stimulation time is the same as the temperature for the displayed stimulation study. The stimulation materials and methods are those shown in Example LVIII, with the time and emp r at hours shown below.

Table A

Stimulation Time in Temperature Plate Resistance (il / a) Hours (for this ° C after "P" Stimulation Test) Time (hours) 1A 1/2 1 2 1 * 5 875 238 ΓΠ ΓΪ5 86 61 * 925 107 78 56 ^ 3 30 820 975 52 39 32 2k 735 1025 31 21 16 12 6k 1075 A 10 7 61 * 1125 75 172 1150 b 3 35 132 1175 b 3 59 1200 3 2 8000302 't 1 * 1 *

At the end of the studies shown in Table A, the stimulant platelets are not sagged or otherwise physically deformed to make them unsuitable for further stimulation. The physical appearance of the stimulant wafer 5 is essentially the same as before any stimulation has taken place, the wafer still being effective for stimulation at the end of the studies, although the wafer has not been treated or somehow rejuvenated.

The silicon wafers stimulated with stimulants having a life of more than 150 to 200 hours further have no dark spot thereon, indicating that little or no boron silicide composition is present on the surface. In cases where a light spot does occur, it can be removed by the method of admitting oxygen gas to the stimulation furnace at the end of the stimulation period, followed by etching with hydrofluoric acid.

Part B

In order to further clarify the principles of the third embodiment of the invention, stimulation methods and materials, as used in part A of this example (except that the silicon being stimulated, originally has an N resistance of 1 * to 7 ohms -cm) applied. The time is half an hour, with the particular stimulant source stimulating a previous one! jd, as indicated, at the same temperature as the displayed test temperature. The stimulation is performed at at least two test temperatures of 975 ° C and 1025 ° C. The results are shown in the following table B.

* 8000302 1 + 5

Table B

Previous Stimulate Plate Spring Resistance (il / Ci) Plate Spring Resistance (ll / O) Time After P Stimulation At After P Stimulation At _975 ° C For J Hour_1025 ° C For \ Hour 0 39 21 25 37 18 50 36 21 75 36 21 100 21 125 39 20 150 37 22 175 200 1 + 0 22 225 39 21 250 21 275 21 300 39 21 325 350 375 39 21 1 + 00 1 + 25 1 + 1 22 1 + 50 1 + 75! +0 22 500 525 550 1 +0 23 575 600 625 fcl 23 725 37 21 825 39 8000 302 1 * 6

At the end of these study periods, none of the stimulant platelets (even the thin platelets of 1.02 mm thickness) have collapsed, the platelets retaining a flat shape suitable for additional planar stimulation.

The physical appearance of the stimulant platelets is essentially the same as for the stimulation, with the platelets still effective for stimulation at the end of these studies, although the stimulant platelets have not been stimulated or rejuvenated in any way.

The silicon wafers stimulated with the stimulants having a life of more than about 150 hours further have no dark spot thereon, indicating little or no boron silicide composition on the surface.

15 Examples LX - LXIII

In order to further clarify the principles of the third embodiment of the invention, various barium aluminosilicate ceramic glass sources for stimulant are made and tested for their value by the methods of Example LVIII. The results are shown in the following table V.

8000 302 47

Table V

Example 6θ 61 62 63

Mol. JI

Si02 46.8 55.0 55.0 48.0 ai2o3 20.6 11.0 17.0 13.0 B203 25.¾ 30.0 20.0 35.0

Alkaline earth oxides 7.3 4.0 8.0 4.0

BaO 5.5 3.0 5.0 3.0

MgO 1.7 1.0 3.0 1.0 Al2 O3 / alkaline earth oxides 2.85 2.75 2.13 3.25

Glass appearance clear clear clear clear

Crystallization heat stimulation ° C for (hours) 64 (720) 720 (16) 720 (16) 720 (16) + ° C for (hours) 1200 (1) 1200 (3) 1200 (3) 1200 (3)

Plate resistance (fl / n) after "P" stimulation at 1 hour at ° C_ 1000 1100 1150 4.3 3.9 4.0 3.9 1200

In each of Examples LVIII-LXIII, the state and appearance of the stimulant source after the stimulation is essentially the same as before the stimulation. There is no sag or other physical deformation, even for the thin plates 5 with a thickness of 1.02 mm, which would make the plates unsuitable for further flat stimulation.

The foregoing research results show that the compositions of the invention are easily formed by ceramic glass processes and are efficiently stimulated at temperatures up to 1200 ° C with structural capability and long life. From the foregoing data, it is also clear that the ranges of compositions have been extended and improved over other embodiments of the invention, as shown in Examples I-LVII. Examples LVII-LXIII demonstrate that glass melting, ceramic glass-forming and boron stimulating efficiency can be obtained with a relatively high content of SiO2 and relatively low levels of BgO2 to maintain a controlled rate of boron stimulating at high temperatures. to reduce the tendency to stain on the stimulated silicon due to the accumulation of an excess of boron, resulting in an insulating deposit of boron silicide. The BaO content (with or without other alkaline earth constituents, such as MgO) is believed to be responsible for this surprising and unexpected prolongation of the life and improvement of the composition range.

It will be understood that changes and improvements can be made without departing from the scope of the invention.

f 5 8000302

Claims (8)

A method of stimulating a semiconductor by holding vapor phase compound 1050 ° C at an elevated temperature with a semiconductor holding a solid boron-5-containing stimulant source for a time sufficient to form an area with P conductivity in the semiconductor, characterized in that the stimulant source is a ceramic glass body formed by the on-site thermal crystallization of a barium-alumino-borosilicate glass formed from a composition less than about 0.5 mol. alkali metal oxides, and in moles # mainly consists of 15-1 * 0 SiOg, 15-30 Al2 O3, 20-60 B2 O3, 0-5 La2 O, 0-5 HbgOj, 0-5 Ta2 and 5- Alkaline earth oxides, comprising in moles, # of 0-15 MgO, 0-10 CaO, 0-10 SrO and / or 0-10 BaO, the ratio of Al 2 3 to alkaline earth oxides being in the range of 1.5 until the ceramic glass body is rigid and dimensionally stable at temperatures exceeding 1050 ° C during the stimulation time, and the vapor phase body is held in communication with the semiconductor in a chamber heated to an elevated temperature. 2. Process according to claim 1, characterized in that the glass composition in mol # mainly consists of more than kO-55 SiOg, 10-30 Al2 O3, 20-U0 B203 and 5-15 alkaline earth oxides, where BaO is present in the amount of 3-15 mol. #, and the ratio of Al2 O3 to alkaline earth oxides is in the range of 2 to k. Ceramic glass body, obtained by the on-site thermal crystallization of a thermally crystallizable glass, formed from a barium-alumino-borosilicate glass composition, characterized in that the glass composition in moles # essentially consists of more than 10 and up to 60 SiO 2, 10-30 Al 2 O 3 »20-40 BgO 3-20 alkaline earth oxides selected from the group consisting of BaO, MgO, CaO, SrO and mixtures thereof, wherein BaO is present in the amount of 1-15 mol. and the ratio of Al 2 O 3 to alkaline earth oxides ranges from 1.5 to k. U. Body according to claim 3, characterized in that the composition in moles # mainly consists of more than 0 and up to 8000302. 55 SiOgj 10-30 AlgO 2, 20-1 + 0 Β, ΟΟ, and 5-15 alkaline earth oxides, the ratio of Al 2 to alkaline earth oxides being in the range of 2 to 1+. Body according to claim 3 or 1, characterized by a stimulant source for vapor phase transport of elevated temperatures, the body being a rigid thin disc and stable in size during stimulation at elevated temperatures. 6. Method substantially as described in description 10 and shown in the drawing. 7. Ceramic glass body substantially as described in the description and shown in the drawing. 8000302