DE2560267C2 - Use of a glass ceramic body as a dopant source for the vapor phase doping with B 2 O 3 - Google Patents

Description

5-25 alkaline earth metal oxides with 0-15 MgO, 0-10 CaO, 0-10 SrO and 0-10 BaO, the mol% ratio Al ₁ O ₁ : alkaline earth metal oxides between 1.5 and 4, as a dopant source for the Vapor phase doping with B ₂ Oj.

2. Use according to claim 1, characterized in that the glass has the following composition MoI- * has:

Μ 18-40SlO ₂

15-3OAI ₁ Oj 30-60 B ₁ O,

5-15 alkaline earth metal oxides including 3-15 MgO and that the Moi -% - Ratio AI ₁ O ₁ : alkaline earth metal oxides between 2 and 4.

3. Use according to one of the preceding claims, characterized in that the GlaskerarrUkkörper has the shape of a thin disc.

The invention describes the use of a glass ceramic body which is produced by thermal In sltu-Kristalllsatlon a thermally crystallizable glass which contains less than 0.5 mol% alkali metal oxide and which has the following composition in mol%: 15-40 SIO ₂ , 15-30 Al ₁ O ,, 20-60 B ₁ Oj, 0-5 La ₂ Oj, 0-5 Nb ₁ O ₅ , 0-5 Ta ₂ O ₅ , 5-25 alkaline earth metal oxides with 0-15 MgO, 0- 10 CaO, 0-10 SrO and 0-15 BaO, the mol% ratio of Al ₂ Oj: alkaline earth metal oxide being between 1.5 and 4, as a dopant source for the vapor phase doping with B ₂ Oj.

Glass ceramic bodies based on alkaline earth aluminum boron silicate are known (DE-AS 15 96 848).

DE-OS 25 45 628 describes B ₂ O, - «n-containing dopant sources in the form of thin disks, which do not undergo any significant deformation at doping temperatures in the range of 1000 ° C.

The invention is based on the object of providing a dopant source of the specified type which is characterized by a particularly high thermal resistance at temperatures above approximately 1050.degree and which can be produced from starting glasses, which can be melted quickly and are resistant to uncontrollable devitrification.

According to the invention, this object is achieved by the use of a glass ceramic body as defined in claim 1 reproduced type solved.

The most important feature of the invention is that it _{enables the inclusion of B 2} Oj on the order of 60 mol% in the glass-ceramic dopant source while maintaining strength and dimensional stability during high temperature doping. This feature is of such great importance because the rate at which the BjOj vapors are generated by the glass-ceramic dopant source usually increases during doping as the concentration, e.g. B. of B ₂ O in the dopant source increases. Unfortunately, the thermal resistance and strength of the glass-ceramic material decreases in thin parts with increasing B ₂ O, concentration. By means of the present invention, a combination of a high concentration of B ₁ Oj In Dotlerstoffquelle of glass ceramic with thermal resistance and strength at temperatures of 1050 ° C is reached, namely when the Dotlerstoffquelle is in the form of thin slices.

Further developments of the subject matter of the invention emerge from the subclaims. The invention is described in detail below with reference to the drawing. It shows

Flg. 1 shows a section through a semiconductor body; Flg. 2 is a perspective view of a solid glass ceramic dopant source containing B ₂ O ₁ ; and

Flg. 3 shows a longitudinal section through a fire-resistant container in which a number of solid _{glass ceramic disks containing B 2} O 1 and a number of glass ceramic disks are arranged.

The invention overcomes the previous difficulties by using a solid, dimensionally stable, essentially alkali metal oxide-free dopant source made of alkaline earth aluminum luminescent cat glass ceramic for transporting the B ₂ O in a gaseous state to the semiconductor. The B ₂ Oj-containing dopant source made of ceramic is kept in vapor form (in the presence or absence of a carrier gas) with a semiconductor at a temperature above a space sufficient to transfer the B ₂ Oj from the dopant source to the surface of the semiconductor transport. The semiconductor treated in this way is then heated, with or

without further presence of the glass-ceramic doping material, over a period of time which is sufficient to allow the boron to diffuse into the semiconductor to the desired depth.

An economically significant embodiment is an n-lelting silicon half-elder, in which a boron-containing layer is produced which forms a p-type zone. The back of the chip or the silicon disk retains its n-lelifahlgkelt, so that the manufactured object is a semiconductor with s p-n junction 1st.

In the following, the term "transport of the B ₂ Oj in the gaseous state" is used because there is no clear understanding of the boron-containing species that evaporate from the glass ceramic dispenser. Accordingly, this term includes any boron-containing species responsible for the transport effect. Similarly, the diffusion process is described by the term "boron diffusion" in semiconductors because of the lack of a clear understanding of the boron-containing species that actually occur. Accordingly, this term includes any boron-containing species responsible for the diffusion doping effect.

The boron precipitates from the gaseous phase on the surface of the semiconductor and diffuses over a specified depth in the semiconductor material. The concentration and the depth of the transition are proportional to the time and temperature of the doping and diffusion process. '5

The glass-ceramic dopant material must be strong and dimensionally stable at the doping temperatures so that no deformation problems occur when the dopant source lies in a flat position. In the case of planar diffusion doping, a planar surface of a solid Dotlermatertal donor and a planar surface of the semiconductor to be doped lie parallel to one another during the diffusion heat treatment. Since the concentration of B ₃ O ₃ on the surface of the semiconductor is a function of the distance between the planar surfaces, dimensional stability of the dopant dispenser is of utmost importance in order to achieve uniformity in the boron distribution on the surface of the silicon semiconductor.

The glass ceramic panes are made from certain alkaline earth metal lumborsilcat glasses that are im are essentially free of alkali metal oxides.

In particular, certain magnestum aluminum borosilicate glasses are used for the production. "Essentially alkali-free" means that the glasses only _{contain so much alkali metal oxides (e.g. K 2} O, Na ₂ O and Ll ₂ O) that no vapor phase is formed which contains such oxides at the doping temperatures . It has been found that the presence of such alkali metal oxides in the vapor phase induces undesirable properties in the electrical conductivity of the resulting semiconductors. The proportion of the alkali metal oxides is normally less than 0.5 mol% and preferably less than 0.1 mol% of the glass-ceramic doping material quenching. It is preferred that no alkali metal oxides are included at all, although this is not always possible since the raw material often contains alkali metal oxides as impurities.

The term »glass ceramic« is used in accordance with its usual meaning and refers to a semicrystalline ceramic composed of at least one crystalline phase randomly remaining in a glass-like phase dlsperglert is composed. Such a crystalline phase is created by the in situ resulting thermal crystallization of an original glass mixture formed.

The heat treatment process for producing the glass-ceramic from a glass usually includes a crystal formation at about the upper cooling temperature (viscosity 10 "d Pas.s) of the original glass, a development stage at a temperature below the fiber softening point of the original glass (preferably at a viscosity in the Area from 10 * to 10 ¹² d Pas s) and a crystallization <to tlon stage (at a temperature preferably between 65 ° to 150 ° C above the fiber softening point of the original glass (ie viscosity of 10 ⁷ · ⁶⁵ d Pas s) .

Although the principle of operation itself is not the subject of the present invention, the following description is given in the interest of completeness of the disclosure. The original glass to be crystallized is heated to a temperature corresponding to a viscosity of 10 "d Pas s and held at that temperature long enough to allow the formation of submicroscopic crystals, dlsperglert In a vitreous matrix. This is known as crystal formation. The time required for the crystal formation cycle depends on the composition and is usually between ₄ and 24 hours.

The vitreous material which contains the crystal skeleton is then heated to a temperature which ^{corresponds to a viscosity of approximately 10 1} U Pas-s. This thermal state is maintained for a period long enough to allow partial crystallization to form a solid crystalline structure. The submicroscopic seeds that are dispersed in the vitreous matrix as the result of the crystal formation phase act as growth centers for the solid framework that forms during this second or developmental phase of the heating cycle. This developmental phase is composition dependent and is typically to 4 hours During this development phase, a solid skeletal structure should be created to support the remaining material when the temperature is increased for complete crystallization.

The glass ceramic body is then formed by heating to a temperature of 65-15O ⁰ C above the temperature which ^{corresponds to a viscosity of 10 7} · ⁶⁵ d Pas · s of the original glass. This temperature is maintained until the desired degree of crystallization is reached. The final crystal phase in the heat treatment cycle is typically ¹ to 4 hours at the highest possible temperature that the glass-ceramic does not yet liquefy. This heat treatment promotes the dimensional stability of the finished glass ceramic against high temperatures. The heat treatment temperature is close to the setpoint temperature.

In practice it has been found that all three stages of the heating process are accomplished can by changing the temperature continuously through the areas of Krlstalllsatlonskelmblldung, development and crystallization is increased. Many glass mixtures have been found to have a "formal" design

The processing stage is not necessary, as the time required to heat the product from the crystal formation temperature to the crystallization temperature is sufficient.

The glass-ceramic panes are made from an alkaline-earth aluminum-lumborsil-cat base glass, which is Is essentially free of alkali metal oxides and has the following composition in mol%.

Component proportion

Mol%

SiO ₂ 15-40

Al ₂ O ₃ 15-30

B ₂ O ₃ 20-50

_{! 5} La ₂ O ₃ 0-5

Nb ₂ Os 0-5

Ta ₂ O ₅ 0-5

RO 5 - 25,

> 1.5 and

- HO

RO:

WgO 0-15

25 CaO 0-10

SrO 0-10

BaO 0-10

is.

The total amount of the alkali metal oxides is less than 0.5 mol%, preferably less than 0.1 mol%. In a preferred embodiment, the glass ceramic panes contain:

Component proportion

MoI-K.

40 SiO ₂ 18-40

Ai ₂ O ₃ 15-30

B ₂ Oj 30-60

RO 5 - 15,

⁴⁵ where 4> ^^ > 2

and the MgO content of RO is at least 3% of the total composition

As can be seen from the following examples, improves AnteÜskomblnaUon ^v on MgO. CaO, SrO and / or BaO the resistance of the original glass to uncontrolled devitrification. The presence of La ₂ Oj, Nb ₂ Os and Ta ₂ O ₅ promotes the melting and production of glass compositions which have a high proportion (ie greater than about 50 mol%) of B ₂ O ₃ and are resistant to uncontrolled devitrification.

In addition to the above oxides, small amounts (ie up to about 10 mol%) of oxides other than alkali metal oxides can be present, such as e.g. B. glass-forming oxides, modifying oxides, nucleating oxides (z. B. TlO ₂ and / or ZrO) and refining agents, if such additives are not harmful to the half-aging and necessary to achieve certain chemical or physical properties.

The ratio - = ^ ρ is for the glass capacity and the high temperature resistance of the doping material-

Al Ci

Glass ceramic dispensers are important. If the ratio is less than about 1.5, the Glass ceramic panes have a tendency to deform at doping temperatures in the vicinity of 1100 ° C 1200 ° C. When the ratio is larger than about 4, there will be melting and deformation the starting glass more difficult.

As can be seen from the drawing, a suitable n-leltendes Slllzlumsubstrat 10 with the help of a the known techniques prepared in order to obtain a monocrystalline Slllzlumkörper. For example, a monocrystalline ingot can be formed from highly pure oil. The ingot is in transverse direction Sticks are cut, and the cubes are; to deliver. The surface of the substrate can be prepared by suitable cleaning and bollarding. However, the polished and cleaned half-parents-sllllummaterlal can also be obtained in stores. That Bollards or cleaning of the surface can be done by mechanical means, such as sanding or the like or can be completed by chemical means such as etching.

Furthermore, the n-type silicon wafer can form part of a complex semiconductor and already one or have several p-n junctions in any geometric arrangement. The only important characteristic is that at least a part of the existing surface of the Silllumschelbe has n-line. Accordingly the term n-type silicon, as it is often used, also includes complex semiconductors which have alternating p- and n-letter zones

In the case of conventionally grown crystals, the surface can be chemically polished with a suitable Etchant, e.g. B. a solution of three volumes of hydrogen fluoride, three volumes of acetic acid and five Voiumenteiien nitric acid. On the other hand, the surface can be hot by sanding or etching with a Solution of water containing about 10% sodium hydroxide at room temperature or up to about 90 ° C will. These cleaning and etching workers are used to remove contaminants from the surface and provide a uniform surface of particular smoothness. Such preparatory work is known.

It has been found that the formation of a p-n junction to the desired extent with an n-leltenden Slllziumelement expires with a sheet resistance of approximately 10 ohms. It is easy to see that the the exact size and nature of the slices is not critical. The disks normally used can for example a diameter of 2.5; 5 or 7, ii cm. The thickness can be between 0.125 mm and 0.5 mm although this can also be changed. Typical disks are between 0.2 mm and 0.25 mm thick. Likewise, the sheet resistance of suitable n-type silicone starting materials lies between about 0.001 and about 100 ohms.

As in Flg. 1, an oxide layer 11 has formed on the surface of the disk 10. A mask or protective layer can be used to create any pattern, such as is used in the art known 1st. The layer or film 11 is vitreous in nature and contains boron in any one Shape.

The temperature of the doping process is such that at the same time some boron from the layer 11 into the Disc 10 diffused and there a thin boron-containing surface layer 12 adjacent to the layer 11 forms. The layer 12 represents a barrier or boundary layer, which in the area between the boron penetrated Surface layer 11 and the n-type silicon 10 is formed. The depth of the transition zone can vary, but is usually up to about 10 μm. The minimum thickness can vary and is approximately 0.1 μη :.

2 shows a plate or disk of the B2U'3-containing dopant source made of glass ceramic, which serves as a supplier for the B ₂ O ₃ vapors for contact with the silencer.

When the glass ceramic panel 14 is placed in a suitable oven and when it is exposed to temperatures between 700-1250 ° C., especially between 1050-1200 ° C., it releases B ₂ Oj vapors which then come into contact through the high temperature zone of the oven with the silicon wafers, which are attached in the vicinity of the doping material wafer, flow. Viewed as a whole, the process for diffusing boron into a semiconductor silicon element consists in introducing at least one semiconductor silicon element into a furnace; Likewise, a glass ceramic plate in the furnace is placed in the vicinity, but not in direct contact with the silicon element. The cover element and the glass ceramic pane are then exposed to an increased temperature in the range of 700-1250 ° C. described above. At these temperatures, the doping material releases B ₂ Oj vapors, which then flow through the furnace and come into contact with at least part of the surface of the substrate. This process is sustained for a period long enough to allow diffusion of the boron in at least a portion of the surface of the silicon element to form a dilation zone therein. After the B ₂ Oj vapors have reacted with the hot silicon surface, the elementary boron diffuses into the silicon chip with continued heating. This boron diffusion solution can, if desired, be in the absence of the vitreous. Dotlermaterlalschelbe be carried out.

The doping process can be further controlled and improved by using a free-flowing inert carrier gas such as argon or nitrogen. The term "inert gas" is intended to mean that the gas In does not undergo any chemical reaction with the B ₂ O ₃ vapors and the hot silicon surface.

This is shown in FIG. 3. In which the carrier enters from the left and flows over the disk 14, where the B ₂ Os is released and touches the available surfaces of this Slllzlumschelbe 10. Because two silicon wafers are grounded back-to-back, the back of each chip does not come into contact with the boron and thus retains its origins; its property as n-cell silicon. After the doping process, the diffusion depth can be increased further by allowing the transition to indentate deeper by means of a simple heat treatment in an inert atmosphere. This can be done if desired. To be made in a separate oven. The above process has been described as applied to silicon semiconductors because of its great economic importance. However, the same process can also be used for germanium semiconductors, although somewhat lower temperatures have to be used when doping germanium because of its melting point of 937 ° C.

When preparing the glass-ceramic doping material, suitable starting materials that contain the Contain appropriate compositions, are melted to form a homogeneous glass mass.

j "For example, compositions described above can be used at 1500 ⁰ C to 165O ⁰ C in a heat-resistant

Crucibles are melted to obtain a homogeneous glass. Usually this melting process takes about 15 minutes to several hours to achieve homogeneity. It may be desirable _{to add additional B 2} Oj to the melt to make up for the losses due to evaporation. It is desirable to keep the melt tent as short as possible in order to keep the losses due to evaporation low. The starting material should also be as pure as possible in order to keep the presence of impurities as low as possible.

The glass ceramic panes can be manufactured in different ways. The original glass can Organometallic derivatives are melted to reduce the content of undesired components ίο to be kept as low as possible, as is disclosed in US Pat. No. 3,640,093, or it can be made from the usual high-purity glass-forming components are melted.

The presence of impurities can adversely affect the electrical properties of the doped silicon semiconductor. Impurities that must be particularly avoided or kept to an absolute minimum are alkali metal oxides, ie Ll ₂ O, Na ₂ O, K ₂ O, Cs ₂ O or Rb ₂ O, and other metal oxides with high vapor pressure such as PbO, CuO and SnO ₂ .

After the glass compositions have melted and form a homogeneous molten mass, the glasses can be brought into any desired shape. Usually this takes place by the Glass is placed in preheated graphite molds, which have the shape of a right circular cylinder with a diameter approximately corresponding to that of the final disks. The glass can then be subjected to the cooling process and, after cooling, the glass bars or cylinders are removed Cracks looked through and then sliced, their thickness usually between 0.625 mm and 2.5 mm. The glass panes can then be converted into glass ceramic.

Another possibility is to subject the glass bars or a part drilled from the core to a heat treatment to form the glass ceramic; this glass ceramic is then cut into slices. Because of the very good regulation possibilities, a larger amount of silicon elements can be obtained by a suitable arrangement of a larger amount of glass ceramic panes in a container, as in Flg. 3 shown be treated.

The doping is carried out. By placing the glass ceramic panes close to and parallel to the Slllzlum panes. which are to be doped can be arranged without touching them. The distance at which Best results are) 0 obtained nlsse is about 3 mm. In a slotted quartz container or another fire-resistant crucible, vessel or the like, 100 or more slices or slices of the same strength can be spiked. By alternately arranging a glass ceramic panel and a pair of panels back-to-back with fronts seldom placed opposite one another, the glass-ceramic panels and the glass-ceramic panels being essentially parallel to one another. The arrangement can according to Flg. 3 take place.

The time and temperature of the doping conditions are selected to provide the appropriate p-n junction temperature and obtain the appropriate sheet resistance for the desired task. This will be done in the following Examples shown.

The spacing of the chips in the container, the selection of the surrounding inert carrier gas and the flow rate are selected so that the slurry which is in the direction of the flow of the surrounding gas show the same amount of doping as those directed against the flow.

In the following examples, all percentages are given in mol% and all temperatures are given in "C, if not marked otherwise.

example 1

Tell A

Conventional high-purity starting materials were melted in a platinum crucible at 154O ⁰ C for 5 or 6 hours with manual stirring to obtain a clear, molten, homogeneous glass of the following composition:

Moi-% wt

SiO ₂ 15.7 12.8

B ₂ O ₃ 41.3 39.3

AJ ₂ O ₃ 26.7 40.0

MgO 14.3 8.0

W The molten glass was removed from the furnace and cooled to room temperature. The glass, still in the crucible, was placed in a cooling furnace maintained at 650 ° C. The glass was cooled at 650 ° C. for Ά hour and then removed and cooled to room temperature.

Part B

Crystal stadium treatment The crucible with the clear glass contents was placed in a heat treatment oven and the temperature raised

690 ° C increased. The crucible was exposed to the temperature of 690 ° C. for 3 hours. Then the temperature increased to 805 ° C, and the crucible exposed to this temperature for 1 hour. Then you increased the Temperature to 1100 ° C, the crucible was exposed to this temperature for 1 hour. Finally it was the oven turned off and allowed to cool to room temperature before removing the crucible. The thus obtained, non-porous glass-ceramic material had a generally white appearance. From the glass ceramic material a core 3.75 cm in diameter was predicted with a hole saw and In cut thin slices, the thickness of which was between 0.4 mm and 1 mm.

PartC

Flat diffusion doping

The doping was carried out. By removing some of the glass ceramic panels from Tell B about 0.3 mm to 0.6 mm away from the slides to be doped so that they are parallel opposite faces. The glass ceramic disks and glass panes were placed in slotted quartz glass bowls at is alternating position of a glass ceramic disc, silicon disc, etc. arranged. This arrangement is shown in Flg. 3 shown.

The sill plates used in this example were originally n-lelted and possessed a sheet resistance of approximately 9 ohms.

The assembly was placed in a diffusion furnace and argon was passed at a flow rate of 500 cm / ml. passed as an inert carrier gas, as in Flg. 3 is shown during the doping time and temperature was set as shown below.

At the end of this diffusion doping period, the slides were cooled to room temperature and cleaned with dilute hydrofluoric acid.

The surface of the doped silicon wafers had p-Leltfählgkelt. Surface tests of the spiked discs were made with a four-point Leltfählgkeltssonde. The surface resistances in ohms of the so doped silicon samples obtained are given below as a function of temperature. The endowed Silicon is p-lelting.

Sheet resistance [Ω] of p-doped silicon wafers

Distance 0.3 mm to 0.7 mm
Flow velocity 500 cmVmin. argon

Temperature time (hours)

> h 1 2 4

950 ⁰ C 71.8 64.7 55.0 54.5 1000 ⁰ C 54.5 42.7 38.5 26.8 1078 ° C 16.7 14.6 13.0 6.5

The doping material disks had not visibly collapsed at the end of the diffusion doping process or otherwise deformed. If an η-conducting germanium semiconductor is to be doped, slightly lower ones are used Temperatures appropriate because of the germanium melting point of 937 ° C.

A few more diffusion doping tests according to the method given above were carried out, wherein the parameters tent and temperature have been changed as indicated below. In any case, the endowed rejected Silicon wafer p-Leitfählgkelt on.

Sheet resistance of p-doped silicon wafers [Q]

Examples 2 to 40

Glass ceramic panes were made from glasses with the compositions given in Tables I and II below manufactured. The melting and crystallization process was carried out as described in Example 1, only the temperatures were kept at a value as indicated in Tables I and II, and that molten glass was quenched. By placing it as a plate in a flat metal bowl at room temperature

Temperature Time ("hours) 1 2 4th ⁰ C 42 30th 25th 1000 48 17th 12th 16 1025 32 20th 14th 10 1040 26th 13th 10 8th 1050 18th

was introduced, instead of cooling it as in Part A of Example 1. Table I describes mixtures, in where MgO is the long "RO" component, and Table II describes various compositions of "RO" components. The results of a "bending test" are also listed in the tables below. In this test Glass rods about 0.3 mm high or wide and about 2.8 cm long were made from the indicated glass and made into a glass-ceramic body with the aid of the specified crystallization heat treatment convicted. After crystallization, each glass ceramic rod was ground flat on both sides so that the final dimensions were 2.8 cm by 0.3 cm by 0.15 cm. Each glass ceramic rod was then over one Platinum crucible 2.2 cm wide (with a length of 0.3 cm, the rod rests on the crucible) and one

Exposed to temperature range between 1000 and 1250 ° C for ¹ A hour. The amount by which the 0.15 cm thick rod "bends" or by which it deviates from the planar shape gives an arbitrary value for the resistance to thermal deformation. Since the tolerable size of the thermal deformation or deflection is different depending on the sample thickness, doping time and doping temperature, a deflection of more than about 0.3 mm in the above-mentioned test procedure corresponds approximately to the maximum

Is allowed deformation for a very thin (about 0.5 mm) wafer to be doped of about 2.5 to 3.75 cm Diameter in a doping arrangement as shown in Fig. 3 shown 1st. Thicker glass ceramic dopler material forms can be used for higher temperatures.

The values given in the tables below show that the tendency to deformation increases with the temperature of the wash, although a good thermal resistance for very thin glass ceramic panes at temperatures above 1050 ° C and even at higher temperatures of 1250 ° C:

25th

30th

35

40

45

50

55

60

65

Tabel

Example no. 2 15.7 at ⁰ C door '/ 2 hours 0 3 36.0 4th 24.0 S. 30.0 6th 30.0 7th 37.5 8th 35.0 9 22.5 10 30.0 11th 25.0 12th 20.0 13th 23.0 700 14th 25.0 clear 15th 20.0 16 23.0 17th 20.0 18th 25.0 Mol% 28.7 1000 0 26.7 26.7 26.7 23.3 21.7 20.0 21.7 20.0 23.3 26.7 25.7 1260 21.0 22.5 23.1 20.0 16.7 SiO ₂ 41.3 1100 0.3 24.0 36.0 30.0 35.0 30.0 35.0 45.0 40.0 40.0 40.0 38.5 40.0 42.5 38.5 50.0 50.0 Al ₂ O ₃ 14.3 1200 0.5 13.3 13.3 13.3 11.7 10.8 10.0 10.8 10.0 11.7 13.3 12.8 14.0 15.0 15.4 10.0 8.3 B ₂ O ₃ 2 1250 2 2 2 2 2 2 2 2 2 2 2 1.5 700 1.5 1.5 2 2 MgO some clear clear clear clear milk milk milk milk some some some 0 1260 clear clear milk some Al ₂ Oj / MgO Crystals Glass Glass Glass Glass Crystals Crystals crystals 0 Glass Crystals Glass texture 0 0.7 Crystallization 700 700 700 700 700 700 700 700 700 700 700 0 700 700 700 700 heat treatment 1260 1260 1200 1200 1200 1260 1260 1260 1260 1260 1260 0 1260 1260 1260 1260 ⁰ C for 16 hours 2.8 ⁰ C for 1 hour _ Bending test Deviation in mm 0 0 0 0 0 0 0 0 0 0 0 0 - - 0 0 0 0 0 0 0 0 0 0 0 0 0.2 0 0 0 0 0 0 0 0.2 0.2 0 0 > 3 2.6 0.5 0.6 0.2 0 0.2 0.2 0.2 0.2 1.6 0.9 0.5 0 _ _ > 3 > 3

Sheet resistance
(Ω) after p-doping
at ⁰ C for V ₂ hours

1000 38

1100 8

1200 2

29 30th 19th 32 27 29 28 29 28 26th 7th 7th ς 7th 5 7th 8th 8th 9 8th 2 2 2 2 2 2 2 2 2 2

33
9

35 10

Table II

Example no. 19th 25.0 20th 25.0 21 25.0 22nd 15.7 23 15.7 24 15.7 25th 20.0 26th 20.0 27 25.0 28 22.5 29 15.7 Mol% 16.7 16.7 16.7 28.7 28.7 28.7 20.0 16.7 13.3 21.7 24.7 SiO ₂ 50.0 50.0 50.0 41.3 4U 41.3 50.0 55.0 55.0 45.0 47.3 Al ₂ O ₃ 8.8 8.8 8.8 9.3 9.3 11.3 10.0 8.3 6.7 8.8 12.3 B ₂ O ₃ 3.3 3.3 3.3 9.3 9.3 11.3 5.0 3.3 - 8.8 7.3 RO 5.0 - - - - - - - - - - MgO - 5.0 - - - - 5.0 5.0 6.7 - 5.0 CaO - - 5.0 - - - - - - - - SrO 2 2 2 3.1 3.1 2.5 2 2 2 2.5 2 BaO - - - 5.0 - - - 2.0 - 2.0 - A1 ₂ O ₃ / RO - - - - - - - - - - - La ₂ O ₃ - - - - 5.0 - - - - - - Nb ₂ O ₅ milk clear clear clear some clear some clear clear clear some Ta ₂ O ₅ Glass Crystals Crystals Crystals Procuring glass Ness Crystallization 700 700 700 700 700 700 700 700 700 700 700 heat treatment ⁰ C for 16 1260 1260 1260 1260 1260 1260 1260 1260 1260 1260 1260 hours ⁰ C for 1 hour deviation in mm at ⁰ C - - 0 0 0 0 0 0 0.1 0 0 for two and a half hour - - 0 0.8 0.9 0.5 0.1 0.0 - 0 0 1000 0.9 0.6 0.2 > 3 2.1 2.1 1.0 0.8 - 3.5 0.7 1100 4.0 4.0 2.0 - - - 4.3 5.0 - - 4.0 1200 1250 Sheet resistance (Ω) after p-doping at ⁰ C 28 33 27 29 47 30th 32 33 30th 30th 31 for two and a half hour 3 8th 2 - 8th - - 9 _ 11th 9 1000 2 4th 2 _ _ 1100 1200

% 10

(Continuation)

Example no.

30th

31

32

33

34

36

37

39

Mol% SiO ₂ Al ₂ O ₃ B ₂ O ₃ RO MgO

CaO SrO BaO

AI2O3 / RO La ₂ O ₃ Nb ₂ O ₅ Ta ₂ O ₅

Gas quality

22.5 25, υ 25.0 15.7 15.7 10.0 15.0 15.0 15.0 22.5 20.0 21.7 23.3 23.3 24.7 24.7 30.0 31.7 16.7 21.7 ■ Λ, Ί 20.0 45.0 40.0 40.0 47.3 47.3 45.0 37.5 60.0 52.5 45.0 50.0 10.8 9.7 11.7 12.3 7.3 10.0 10.8 8.3 9.5 9.5 5.0 5.8 9.7 6.7 7.3 7.3 10.0 10.8 3.3 5.8 5.8 5.0 5.0 _ 5.0 _ _ _ _ 5.0 _ _ _ - - - 5.0 - - - - - - - 2 2.4 2 2 3.4 3 3 2.0 3.7 3.7 4th _ 2.0 _ 5.0 5.0 _ _ _ _

clear clear clear

5.0 - - - 5.0 5.0 5.0

some clear some some some milk some some kri kri kri glas kri crystals stalls stalls stalls stalls

Crystallization heat treatment

⁰ C for 16 700 700 700 700 700 700 700 700 700 700 700

hours

+
⁰ C for! Hour 1260 1260 1260 1260 1260 1260 1260 1260 1260 1260 1260

Bending test 0 0 0 0 0 0 deviation
in mm at ⁰ C
for ¹ Z; hour 0 0 0 0 0.0 0.5 1000 0.8 1.3 0.3 0.3 0.8 4.6 1100 0.5 5.0 2.9 - 4.5 - 1200 1250 32 32 32 35 36 30th Sheet resistance
(Ω) after
p-doping
at ⁰ C
for ^l h Hour 8th 9 8th 9 9 - 1000 _ _ _ _ _ _ 1100 1200

0 0 0 0 0

0.5 0 0 0 0

3.0 1.3 0.6 0.6 0

0> 3> 3> 3> 3

28

36
10

37
10

31 9

1 sheet of drawings

Claims (1)

Patent claims: 1. Use of a glass ceramic body, which by thermal In sltu-KristaUisatlon a thermally crystallizable glass is produced, which contains less than 0.5 mol% alkali metal oxide and which the after- ^{5 has the} following composition in mol%: 15-40 SlO ₂ 15-30 Al ₁ O, 20-60B ₁ Oj ¹⁰ 0-5 U ₁ O, 0-5 Nb ₁ O ₅ 0-5 Ta ₁ O ₃