DE2018517B2 - EXPERIENCE TO MANUFACTURE A SEMICONDUCTOR COMPONENT - Google Patents

Description

The invention relates to a method for producing a semiconductor component with excellent stability electrical properties, the component is provided with a passivation film, which has an excellent Provides moisture protection.

Since the electrical parameters of semiconductor components are different because of the activity of their pn junctions Under atmospheric influences, LO may not change reversibly, the transitions must counteract such atmospheric influences, such as moisture, by applying a suitable passivation film to be isolated. There are numerous methods and processes for producing such passivation films has been developed.

In the case of a typical silica passivation film. which is generally caused by thermal surface oxidation of the silicon semiconductor component is formed, the gradient of the concentration distribution tends to be at the pn junctions to prevent undesired diffusion of impurities to change, as a result of which the electrical properties of the component deteriorate or change in an impermissible manner will.

In order to avoid the undesirable thermal influences during thermal oxidation zn% various types of passive education films have already been used. In one of these known methods the half! 'ter platelets? for easier formation of Silicon dioxide on the planar surface with a Dan'r> f brought into contact. the hydrogen fluoride and contains nitric acid. In this case, however, it is difficult to make the passivation film thick enough do; rather, a significant number of tiny holes remain in the film.

In another method, the Siliziumdioxidnlm on aer surface of the wafer is formed in that silicon is deposited as silicon dioxide, obtained by decomposition of a volatile organic Siliziumverb '' _-: is produced dung. Since monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ), both volatile organic silicon ^{compounds, can be decomposed at temperatures below approximately 700 °} C., the passivation film can be formed at relatively lower temperatures. However, the silicon dioxide film formed by the chemical decomposition of the silicon compound does not constitute a usable passivation film because of its poor resistance to moisture, in particular because a very high leakage current occurs at the transition surfaces of the component.

It is aL.h known on semiconductor surfaces composite moisture resistant passivation layers applied by a silicon dioxide layer, a further layer is formed from a mixture of Phosphoroxyd and silicon oxide or lead oxide by thermal decomposition of an organic silicon compound, and it and eir ^p th <"mix-treatment carried out (German Offenlesunssschr ft I 923 035 and French patent specification 1 427 365).

According to a similar process (German Auslegeschrift 1 237 400), the passivation layer is produced in that the semiconductor surface is a vaporous mixture of SiO and / or B ₂ O ₃ and. or a lead oxide and simultaneously exposed to rapidly intermittent light or UV exposure, forming a vitreous, water-impermeable coating.

As is well known, however, P ₂ O _{5 is} a very powerful drying agent and is therefore used for dehydrating or drying chemical substances. B ₂ O ₅ also has a certain water absorption capacity.

It can thus be seen that P ₂ O ₅ and B ₂ O ₃ are unsuitable for the production of a passivation film because of their solubility in water.

Even if PbO shows poor solubility in water, Pb ions migrate out of the film, the PbO contains in the passivation film, which causes excessive leakage currents to occur on the surface of semiconductors.

Since PbO. P _ä O ₅ , B ₂ O _{3 are used} in combination with the SiO ₂ -FiIm, this can be made vitreous by a suitable heat treatment. However, such moisture-proof passivation films do not yet provide a satisfactory result, since they increase the leakage currents on the surface of the semiconductor wafer which is in contact with the SiO ₂ film.

It is therefore the object of the invention to provide a new method specify for the production of a semiconductor component, with the help of which a passivation film with very good moisture-proof wedge can. The electrical properties of the passivation film should be achieved through a suitable heat treatment can be significantly improved. In particular, the composite passivation film should not be Form leakage currents.

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The method for manufacturing a semiconductor structure does not produce a uniform film because the glow elements with a moisture-resistant, co-discharge between the electrodes with a passivation film in such a way that a small upper partial pressure is unstable.
In this description it is said that the semiconductor wafers having a pn junction are films of silicon dioxide and tantalum pentoxide with the vapor of a volatile organic silicon; However, it is noted that the chemical compound is brought into contact, not necessarily temperatures> mter about 700 ⁰ C under deposition of stoichiometric formula SiO ₂ or Ta ₂ O ₅ entvon silica of favor in the composition of these films on a free surface .

According to the invention, it has been found through numerous experiments that the formation of the film on the surface of the half-dioxide film by spraying tantalum in a conductor component, necessarily an increase in the oxygen atmosphere, a tantalum pentoxide film is formed on the silicon thus formed the surface charge density. If and then increased the wafer to heat treatment at the silicon dioxide film and the charge density, about 200 to 400 ⁰ C in a non-reducing at- 15 this tendency is subjected in the practically usable sphere. Films the least. As the increase in the density of

The silicon dioxide film is preferably placed in a surface charge that causes leakage currents.

Thickness of about 0.4 to 1 μm and the tantalum pentoxide ring is. is preferably on the silicon dioxide film

film applied in a thickness of at least 0.2; xm. formed on the platelet surface. Although this film

The method according to the invention is made possible by the 20 has a low surface charge density

Drawings and the following embodiments have a major disadvantage in that they have poor strength

explained in more detail. against moisture. At the invented

F i g. 1 is a diagram showing the relationship between the component and therefore the film with the

see the breakdown voltage of a tantalum pentoxide film of the invention, which has an excellent

custom-made semiconductor component and the 25 has resistance to moisture.

Represents the temperatures of the heat treatment; Nevertheless, it has been shown that the stability of the

F i g. Figure 2 is a diagram of the top components that can be formed with a silicon dioxide and

surface charge densities of the passivation, which is composed of various passivation tantalum pentoxide films,

construction element provided with vation films: and film are provided with regard to the passivation-inherent

F i g. 3 illustrates a diagram that the upper shafts are deficient. Most important is the surface charge densities of having different pass-area charge density considerably, reducing the leakage films provided components in dependent current increases and the breakdown voltage of the building of treatment temperatures shows. elements is reduced.

The volatile organic silicon to be used These disadvantages can be eliminated or reduced

Compound must have a decomposition temperature below 35 if after the formation of the compound

have about 700 ^° C. If it is above 700 ^c C, film a heat treatment, about 2C0 to 400 = C in

so it can be that electrical parameters of the building - non-reducing atmosphere are made,

elements due to thermal influences during the In this way, the surface charge density

Formation of the silicon dioxide film inadmissibly changed can be made so small that the leakage current at

will. 40 Sufficiently reduce the blocking operation of the component

The silicon dioxide is released from a steam. The reasons for the effects of the heat deposit, the silicon compound and an inert action are not known in detail, but contain carrier gas. In the case of monosilane - a platelet - it is assumed that the ^{oxygen vacancies remaining in the silicon dioxide film of about 300 to 400 0} C, a vapor, are filled with oxygen flow rates of 5 liters per minute and 45, thereby eliminating lattice defects or reducing an oxygen flow rate of 0.15 liters and applying the surface charge density per minute * with the film increasing at a rate. Because of the heat treatment at a ratio speed of about 0.5 to 1 μπι per minute moderately low temperatures, there is no growth, driving that the electrical properties of the construction

In the formation of the tantalum pentoxide film, there are elements during the formation of the film and the

preferably worked as follows: A tantalum rod deteriorate heat treatment. This is a very

becomes as a cathode and an important advantage with the silicon dioxide film.

The semiconductor wafer provided is switched as the anode. Suitable film thicknesses are determined experimentally. To remove residual gases and moisture from the. A thickness of the vacuum vessel is to be removed for the silicon dioxide film; this is ^{expedient to about 10 ~ 5} 55 about 0.4 to 1 μm. If the thickness is less than 10 ~ ^e mm Hg evacuated. Then a dust than 0.4 μm, so oleiben in the film tiny holes and anhydrous oxygen-argon gas mixture in the remaining, and the contact between the platelet upper vessel, passed to a suitable oxygen partial surface and the tantalum pentoxide film causes a pressure to be generated. When a voltage was applied, the surface charge density increased. On the other hand, if the film thickness between the cathode and anode of the 60 is greater than 1 μΐη, tantalum atoms occur in the tantalum rod connected to the BiI cathode on the formation of the film of the heat treatment and in the anode plate, so that a tantalum operation of the on the silicon Component is formed as a result of the different pentoxide film. The coefficient of thermal expansion of platelets and oxygen partial pressure preferred for this purpose is about 5 × 10 ~ ^: 1 until the film shows cracks in the film. As long as you still have 5 · 10 ~ ^a Torr. If the partial pressure is less than 5 × 65, a film without holes can be produced, the thinnest ΙΟ " ³ Torr, so it may be the most suitable because of the oxygen film, since the surface charge deficiency does not form a complete insulating film the strength of the other part of the Parlialdruck higher than 5 x 10 ^-2 Torr, the silicon dioxide film is, the smaller the smaller.

The heat treatment takes place in a non-reducing atmosphere, e.g. from oxygen, oxygen-nitrogen, an inert gas or a mixture of an inert gas and nitrogen. An oxygen-containing Atmosphere works best as the oxygen contributes to lattice defects or oxygen vacancies to reduce or eliminate in the film. A reducing agent containing, for example, hydrogen On the other hand, atmosphere cannot be used because hydrogen increases the oxygen vacancies in the film. The pressure for the atmosphere used in the heat treatment is not limited.

Experiments have shown that by forming a phosphate glass layer under the tantalum pentoxide film, a semiconductor device can be produced which has very small surface charge density and leakage current properties. The phosphate glass layer can be formed in that phosphorus pentoxide is deposited on the silicon dioxide film from an atmosphere containing vapor of a phosphorus _{compound, such as phosphine (PH 3} ) or phosphorus oxychloride (POCI ₃ ), or by adding a mixture of phosphorus pentoxide and Silica is deposited from an atmosphere containing the volatile organic silicon compound and the phosphorus compound.

Because the phosphorus pentoxide acts as an oxidizing agent to oxidize the oxygen vacancies in the silicon dioxide real! the film is about moisture stable. Since the phosphate glass has a high water absorption capacity, the phosphate glass layer must the tantalum pentoxide film can be formed in order to protect the component against moisture.

Example I.

Regarding the effects of the thickness of the silicon dioxide film, the following results were obtained from Tests received for tiny or pinholes.

Table 1

Test no. Thickness (μηι) Gaps in the film
(%) 1 0.2 90 2 0.3 40 3 0.4 16 4th 0.6 15th 5 ι, ο 15th 6th 0.6 to 0.7 10

In this experiment, the leak points were determined by currents flowing between on the silicon dioxide film and metal films formed on the chip were applied; gives the percentage of leaks is the ratio of those points at which current flowed to the total number of test points. From the In the results shown in Table 1, it is found that the number of pinholes in the film is sufficiently small if the film thickness is greater than 0.4 μίτι. To get a sufficiently small number of needle To achieve holes, the strength must be made greater than 0.4 μm.

The result obtained in Verb.idung with the test no. 6, in which the silicon dioxide film was formed by thermal oxidation of the wafer at a Temperatui above 1100 ⁰ C is shown for comparison with the film formed by chemical deposition of orgasmic African silicon compound silica .

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Example II

The results of heat crack tests on silicon dioxide films produced by chemical deposition; organic silicon compound were formed, are shown in Table 2.

Tabel

Tl T / ^ L * Λ / 1 1 1 ^ \ \ To To at 300 ° C Heat treatment at 400C at 600 ^° C at 800'C at 1000 ⁰ C L * ICKC vI-t-ITl / Film formation Photo etching 0 0 0 0 0 0.65 to 0.80 0 0 0 0 0 0 0 0.80 to 0.95 0 0 0 0 OX X 1.0 to 1.2 0 0 - - - - 1.2 to 1.5 0 X - - - > 1.5 X -

In Table 2, the occurrence of a crack in the film is represented by X. From the results from Table 2, it can be seen that the thickness of the silicon dioxide film in view of the heat treatment to improve the properties of the film must be less than about 1 μm. In particular is a Thickness of less than 0.95 μm is preferred.

Example III

Pinhole tests were carried out on the tantalum pentoxide film. In this experiment, the number of pinholes per unit area was calculated by converting the total number of pinholes in the film. The results are shown in Table 3 σρ-ΎΡλ crt

Table 3 Number of needle
holes per cm * Thickness (μπι) 300 ο, ι 140 0.2 100 0.3 96 0.4 95 0.5

Generally, the number of pinholes per unit area (cm ² ) is required to be small as about 150 from the standpoint of practical use. From Table 3 it can be seen that

18th

Example V Table 4

Forward leak rehearse current (μΑ) at 500 V. 4.0 without heat treatment 6.5 after 2 hours of heat treatment treatment at 35O ⁰ C in nitrogen the atmosphere 9.1 after 2 hours of heat treatment treatment at 350 ° C in oxygen the atmosphere 5.0

in addition, the thickness of the tantalum antoxide film is greater than must be about 0.2 μιιι. Since when spraying the growth rate of the tantalum pentoxide film only 0.1 to 0.3 μm per hour, a practical thickness may be around 0.2 to 0.7 (im.

Example IV

Regarding the effects of the heat treatment, an experiment was carried out on a thyristor of the f'lanar type executed, the an N-Kmittcrschicht with a thickness of 15 | im, a P base layer with a thickness of 20 | xm, an N-base layer with a thickness of 80 to 100 (im and a resistance of 2O £ 2cm, a P-Emiilcrschicht with a thickness of 40 to 50 | xm as well as had a composite passivation film composed of a silicon dioxide film of 0.8 to 0.9; xm thickness and a tantalum antoxide film. The samples were kept at 300 bis for 1 to 5 hours 600 C heat treated.

in Fig. 1 shows the curve Λ the reverse breakdown voltages and the curve B the forward breakdown voltages of said thyristor. Although according to the results from FIG. If a heat treatment above 300 ° C helps to improve the breakdown voltage, it would probably be unfavorable to heat the thyristor at temperatures above about 400 ° C. In a further experiment, it has been shown that no effect is to be expected from a heat treatment carried out below about 200 ° C., since the liner-desired substances such as water, for example, enclosed in the film are only insufficiently removed. The heat treatment should therefore be carried out ^{between around 200 and 400 G C.}

It should also be said that the effect of the heat treatment by removing the residual stress comes about in the film, for example, by the glow effect of the treatment.

Another test was carried out on diodes with a breakdown voltage of 1500VoIt, to determine the effects of heat treatment. The diodes used in this experiment had partly no passivation film, partly they were with the composite passivation film provided. The results of this experiment are shown in Table 4.

Since diodes without a film can change their electrical parameters during long periods of operation, the is Passivation film required, although the diodes without film have the lowest leakage current properties.

According to the results in Table 4, the heat treatment in an oxygen atmosphere is most suitable to reduce leakage currents. However, a nitrogen atmosphere can also be used, since the Leakage current is even less than 10 μΑ.

Example Vf

In Fig. 2 shows the relationship between the types of films and the surface charge density N /.-/ ». In this experiment, the thickness of the silicon dioxide film formed by chemical deposition of silane (SiH ₁ ) as an organic silicon compound was 0.8 to 0.9 μm, while the thickness of the tantalum oxide film (Ta ₂ O ₅ ) was changed. . Sample Nos. 1, 2 and 3 had thicknesses thereby μΐη of 0.2, 0.3 and 0.45 μηι on the heat treatment after the 13ϊI plication of Ta _ä O, -. Film by reactive sputtering was for 5 hours at 300 C carried out in an oxygen atmosphere. In the comparison sample no. 4 according to FIG. 2 is a component that only had a silicon dioxide film 0.8 to 0.9 μm thick.

From Fig. 2, it can be seen that the surface charge density by using the composite passivation film and appropriate heat treatment can be reduced.

In the case of one formed by thermal oxidation In the silicon dioxide film, the surface charge density is considerably larger than that of the present invention Process produced component, despite the superposition of the tantalum pentoxide film on the silicon dioxide film.

Experiment VII

Although the electrical properties of devices with a base resistance of less than about 10 f2cm, which contributes to the breakdown voltage of the device, can only be improved by heat treatment, devices with a base resistance of more than about 10Dem require a preheating treatment in conjunction with the silicon dioxide film is very beneficial for improving properties. The preheating is carried out at relatively high temperatures of about 700 to 900 ³ C for a short period of 1 to 30 minutes before the tantalum pentoxide film is formed.

While the influence of the surface charge density on the leakage current is not as noticeable in devices with a small base resistance, in devices with a relatively high base resistance the silicon dioxide should be heat-treated in such a way that the oxygen voids in the film are removed or reduced. This preheating treatment is carried out at about 700 to 900 ⁰ C over a short period of for example 3 to 5 minutes, pn junction to the undesirable influence of the impurity gradient at the well as to prevent the occurrence of cracks in the film.

As y'ch showed from the experiment, the preheat should in an atmosphere of an inert gas such as argon or helium. In particular a nitrogen atmosphere does not bring any advantages in terms of improving the electrical Properties of the component. On the other hand, an oxygen atmosphere is unsuitable because the silicon oxidized under the silicon dioxide film.

After the preheating treatment, the tantalum pentoxide film becomes reactive by the above

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Spray formed on the silicon dioxide film. The thus obtained composite passivation film is the heat treatment at 200 to 400 ° C unterwo ^r fen.

F i g. 3 shows a relationship between the types of the passivation film and the surface charge density N.pfl, where the values of component with a Silicon dioxide film formed by chemical deposition from a vapor of the organic silicon compound has been formed, are represented by ○, while ○ the results of components with the according to the invention represents produced passivation film. This was obtained as follows:

Depositing the silicon ^; oxide film by chemical precipitation on the: n platelets; 5 minutes

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long preheating of the plate in the case of the in F i g. 3 indicated temperatures in argon atmosphere; Forming the tantalum pentoxide film by reactive spraying on the silicon dioxide film; Heat treatment of the platelet at 300 ^° C. in an oxygen atmosphere.

The thickness of the silicon dioxide and tantalum pentoxide films are 0.8 to 0.9 μm and 0.3 μm, respectively.

From Fig. 3 it can be seen that the preheating

Treatment to reduce surface load

o tion density of the component contributes, so that the Can increase the breakdown voltage of the device.

The inventive method is suitable for. B. for the production of diodes, or transistors Thyristors.

1 sheet of drawings

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Claims (4)

Patent claims: 1. A method for producing a semiconductor component with a moisture-resistant, composite passivation film which has a low surface charge density, in which a semiconductor plate having at least one pn junction is brought into contact with the vapor of a volatile organic silicon compound which is at temperatures below approximately 700 ⁰ C decomposes with the deposition of silicon dioxide on a free surface of the platelet, characterized in that a Taittal pentoxide film is formed on the silicon dioxide film thus formed by spraying tantalum in an oxygen atmosphere, and then the platelet e ^; rer heat treatment at about 200 to 400 ^r C in a non-reducing atmosphere. 2. The method according to claim 1, characterized in that the silicon dioxide film in a Thickness of about 0.4 to 1 μπα and the tantalum pentoxide film in a thickness of at least 0.2 µm. 3. The method according to claim 1 or 2. characterized characterized in that prior to the formation of the tantalum pentoxide film, a phosphor glass layer of a Mixture of silicon dioxide and phosphorus pentoxide is applied. 4. The method according to claim 1, characterized in that that the silicon dioxide film or the Phosphonilas layer prior to the formation of the tantalum pentoxide film subjected to a heat treatment at a temperature of about 700 to 900 C. 35