DE102007009281B4 - Method for producing material precipitates and semiconductor material disc and semiconductor components - Google Patents

Abstract

A method for producing material precipitates, the method comprising: generating damages (V6, V17) in a semiconductor material (10, 100) by creating a damaged area (10b, 100b) by mechanical action, and then performing a heat treatment (T2, t2 T5 , t5) of the semiconductor material (10, 100) in an inert atmosphere to produce oxygen precipitates (P1, P11) having a concentration greater than 10 precipitates per cubic centimeter in the damaged region (10b, 100b, 10c, 100c).

Description

The embodiments of the invention relate to a method for the targeted production of material precipitations in semiconductor material and a semiconductor wafer with material precipitations.

Zones of material precipitates in a semiconductor material are generated to effectively remove heavy metals that may diffuse into the semiconductor material during the manufacturing process of the semiconductor device in that zone. In addition, a so-called "denuded zone", which is largely free of oxygen precipitation, to be provided in order to accommodate in this zone, the electrically active regions of the semiconductor device.

A known method of providing such a "denuded zone" is to diffuse oxygen atoms in a first high-temperature process and later carry out a high-temperature step, which leads to precipitates in the oxygen-rich regions of the semiconductor wafer and in the region of the semiconductor wafer in which oxygen atoms are significantly diffused out, to a "denuded zone" because there are not enough oxygen atoms in this latter zone to cause precipitate formation. The problem with this method, however, is that the vertical extent of the "denuded zone" is very limited, since the outdiffusion of oxygen is limited due to its relatively small diffusion constant. In addition, the stability of these oxygen precipitates is limited because the extent of these precipitates is relatively low. Only when this excretion has reached a certain extent, they have a very good stability in later high-temperature steps.

In the article by Falster, R., "Orthogonal defect solutions for silicon wafers: MDZ and micro-defect free crystal growth", Future Fab International Issue 12, (2002), a method is described in which vacancies in the depth of the semiconductor wafer are generated by a nitriding "Rapid Thermal Annealing (RTA)" step in conjunction with an additional Ausdiffusionsprozess and form in a subsequent special annealing process precipitates in the disc depth, as the additional voids require the formation of oxygen precipitates. This increased vacancy density also causes a larger expansion of the precipitates and an improved stability thereof, but also in this method, the expansion of the precipitates is limited, since the concentration of vacancies additionally generated by the RTA step is limited.

From the US 6,451,672 B1 For example, there is known a method of generating gettering sites in which rare gas ions are implanted at energies of about 20 KeV or more, with 50 to 300 KeV being indicated as practicable in the context of the prior art.

From the KR 10 20060061625 A For example, a method of removing defects is known in which oxygen ions are implanted into the front of a wafer at energies in the range of 10 to 20 KeV.

From the not pre-published DE 10 2006 002 903 A1 For example, a method of treating an oxygen-containing semiconductor wafer by irradiation with high-energy particles, namely, protons, rare gas ions, semiconductor ions, or doping particles is known.

From D.H. Weiner, "Oxygen Implantation for Internal Taming and Reducing Carrier Lifetime", Appl. Phys. Lett. 50 (15), 13 April 1987, page 986 to page 988, the implantation of oxygen ions at 200 keV into the front of a wafer is known. Thereafter, an epitaxial layer is grown on the front side of the wafer.

From the DE 39 34 140 A1 For example, there is known a method of forming getterable-center-inducing surface treatment in which a static pressure is applied to a semiconductor wafer. Then it is annealed for thirty minutes. "Dopant, defects and oxygen interaction in MeV implanted Czochralski silicon", A. La Ferla et al., Nuclear Instruments and Methods in Physics Research B 96 (1995), 232-235, discloses a study in which oxygen is implanted into a semiconductor wafer becomes. Thereafter, it is tempered for 30 minutes.

Nevertheless, there is a need for a simple method in which, in particular, the maximum concentration of the voids produced in this way can be set within a wide range, and in particular also for large values. In addition, a semiconductor material disc is to be specified, which has been produced in particular by such a method.

• – Erzeugen von Schädigungen in einem Halbleitermaterial unter Erzeugen eines geschädigten Bereichs durch mechanisches Einwirken oder durch Implantation und
• – anschließend Durchführen einer Wärmebehandlung des Halbleitermaterials unter Erzeugen von Materialausscheidungen in dem geschädigten Bereich.

A method is disclosed for producing material precipitates,
the method comprising:

• Generating damage in a semiconductor material to produce a damaged area by mechanical action or by implantation and
• - then performing a heat treatment of the semiconductor material to produce material precipitates in the damaged area.

During this heat treatment, the crystal defects or vacancies formed can also be distributed further into the depth of the semiconductor wafer. By means of these methods, very high vacancy concentrations are generated, resulting in relatively large and therefore very stable precipitates.

• – mit einem ersten Bereich, der ausscheidungsfrei ist oder ausscheidungsarm mit einer Konzentration kleiner als 10⁴ Materialausscheidungen je Kubikzentimeter, und
• – mit einem zweiten Bereich, der Materialausscheidungen enthält mit einer Konzentration größer als 10⁷ Ausscheidungen je Kubikzentimeter.

In addition, a semiconductor material disc, and semiconductor components or integrated circuits are indicated:

• - with a first range which is free of precipitation or low in precipitation with a concentration of less than 10 ⁴ material precipitations per cubic centimeter, and
• - With a second area containing material precipitates with a concentration greater than 10 ⁷ precipitates per cubic centimeter.

In the following, embodiments and embodiments will be explained. With regard to the embodiments, reference is made to the figures. Show:

1A and 1B the basic sequence of a method for producing material precipitates in a semiconductor material,

2 A cross-section through a semiconductor material with material precipitates,

3A to 3E a process variant, and

4A to 4E another process variant.

As far as "can" or "may" is mentioned in this application, both the possibility and the actual implementation of said measure in one embodiment are meant.

• – Erzeugen von Schädigungen in einem Halbleitermaterial unter Erzeugen eines geschädigten Bereichs durch mechanisches Einwirken oder durch Implantation, und
• – anschließend Durchführen einer Wärmebehandlung des Halbleitermaterials unter Erzeugen von Ausscheidungen in dem geschädigten Bereich.

Disclosed is a method for producing material precipitates, the method comprising the steps:

• Generating damage in a semiconductor material creating a damaged area by mechanical action or by implantation, and
• - then performing a heat treatment of the semiconductor material to produce precipitates in the damaged area.

The semiconductor material is, for example, monocrystalline before the damage, ie provided only with lattice defects that can not be avoided in the production. In particular, the material should, for example, include a high oxygen concentration that is in the range of oxygen solubility. In silicon, this solubility limit is approximately 8 × 10 ¹⁷ oxygen atoms per cm ^-3 . For example, semiconductor wafers are cut off from a semiconductor material. The semiconductor material slices have, for example, circular outlines, possibly with a marking of the crystal direction, z. B. a flat or a "flat". A typical thickness of the semiconductor material disc is, for example, 700 micrometers. The diameter is, for example, in the range of 15 centimeters to 30 centimeters, in future, over 30 centimeters.

The semiconductor material is, for example, a semiconductor material whose basic lattice contains only one type of atom, for example silicon atoms or germanium atoms. Alternatively, a compound semiconductor material is used whose basic lattice contains two or more than two types of atoms, for example gallium arsenide, indium phosphide or silicon carbide. On the other hand, the precipitates contain types of atoms that are not contained in the basic lattice. The precipitates arise from material that is dissolved or implanted in the semiconductor material, namely oxygen. The precipitates have an expansion and density that are sufficiently large to provide a gettering effect for heavy metals.

The heat treatment is carried out, for example, at a temperature greater than or equal to 800 ° C for at least 5 hours or at least 10 hours, the temperature is in particular less than 1100 ° C (degrees Celsius). The heat treatment is z. B. single stage, d. H. that, for example, a constant temperature is used during this time. Alternatively, the heat treatment is multi-stage and preferably two-stage. In particular, the heat treatment is shorter than 24 hours.

Mechanical damage or damage due to implantation can be better targeted than damage only by heat treatment. Thus, the center of the damage, for example, be arranged in the vicinity of only one main surface or flat surface of a semiconductor wafer. In addition, damages with a high concentration can be achieved with mechanical damage or with implantation. This has an effect on the concentration of the resulting precipitates, so that the concentration, the size and thus also the stability of the precipitates can be higher than with previously used methods.

The said steps can be carried out in particular prior to the production of semiconductor devices in the semiconductor material, namely z. For example, before a well implantation, for example. With dopant atoms of a doping type, which differs from the doping type of the dopant atoms of the semiconductor material. Alternatively, the wells are placed in undoped semiconductor material. In particular, the steps may be prior to a gate oxide production be carried out so that in the critical production of the gate oxide already has a high getter effects on the material precipitates.

Furthermore, vacancies and / or vacancy agglomerates z. B. in a non-damaged area of the semiconductor material, for example. Before the injury or after the injury. The area in which voids are removed may be at least 10 micrometers or at least 30 micrometers thick, measured, for example, from the one surface of a wafer. The vacancies are in particular unoccupied lattice sites.

For example. For example, the vacancies may be removed by thermal oxidation to produce semiconductor oxide, where at the boundary between the oxide layer and semiconductor, semiconductor atoms may be generated on interstitials, which then diffuse into the semiconductor material, e.g. In the wafer. Thus, a "complete" elimination is possible, ie the voids have, for example, only a concentration less than 10 ¹¹ spaces per cubic centimeter. The oxide production can be carried out in an oven or with an RTP process (Rapid Thermal Processing). For example. an RTP process is carried out with a heating time of less than two minutes.

Alternatively, the vacancies with RTP can preferably be reduced only in a certain area of the semiconductor wafer, e.g. B. at a tempering in oxygen, in particular using a previously applied on one side of the semiconductor wafer previously applied protective layer, for. B. silicon nitride layer.

The vacancies can be removed in regions on both planar sides of the semiconductor material or the semiconductor material disc. Alternatively, the vacancies may be removed only in an area on one side but not in an area on the flat side facing away from this side. For example. is that side with a protective layer, for. B. covered a silicon nitride layer on which no area is to arise with few vacancies. This also creates additional degrees of freedom for setting the excretion profile. Existing voids can be used, for example, in addition to the vacancies generated by the damage to produce excretions. Also, a higher vacancy concentration can be achieved, which can then lead to higher excretion concentration.

The mechanical damage can be caused by grinding or lapping or by other suitable mechanical processing methods. Thus, loops or lapping with resulting surface roughness greater than 0.5 microns or greater 2 microns are suitable, but in particular less than 10 microns. However, polishing, in particular with CMP (chemical mechanical polishing) methods and with a roughness of less than 1 micrometer, does not lead to the required degree of damage, for example.

The area damaged by the mechanical damage can be partially etched back, for example in the range from 0.5 micrometers to 10 micrometers, preferably in the range between 1 and 3 micrometers. As a result, impurities introduced by the mechanical action can be removed again from the semiconductor material.

The damage can alternatively or additionally be caused by ion implantation. A typical ion implantation dose may range from 10 ¹⁴ to 10 ¹⁶ ions per cubic centimeter. A typical ion implantation energy can range from 200 KeV (kilo-electron volts) to 10 MeV, preferably in the range between 2 MeV and 8 MeV.

An oxygen implantation is used since it additionally introduces oxygen into the semiconductor material, which further promotes precipitation formation. Thus, it is also possible to use semiconductor material which contains only comparatively little oxygen in the production, for example float zone material. For this purpose, it may also be advantageous to achieve a more homogeneous distribution of the implanted oxygen atoms both after implantation and after the subsequent temperature treatment by using a plurality of implantation energies.

In addition to the damage, it is not possible according to the invention to introduce a high phosphorus doping, for example by implantation or another method. High phosphorus concentrations further increase the getter effect.

The method can be performed by a disc manufacturer. Thereafter, the semiconductor material is transported to a manufacturer of circuits or components. Thus, the process can be carried out with high reproducibility and also similar for several component manufacturers, as it is advantageous for large-scale industrial processes that are to be standardized to a high degree.

The damaged area containing the desired oxygen precipitates may be removed after the fabrication of devices, particularly in the manufacture of power devices. These components can have a vertical current flow through the entire semiconductor material.

Alternatively, however, the damaged area may remain with a single device or an integrated circuit. The damaged area can, for example, contribute to the mechanical stability. The getter effect is maintained and can be beneficial to the life and reliability of the product.

Due to the high gettering effect, a higher input of heavy metals during production can be accepted, so that targeted "unclean" processes can be used.

In addition, a semiconductor material disc is concerned, in particular a semiconductor material disc produced by a method mentioned above. The semiconductor material disc contains a first layer region, which is precipitation-free or low-precipitation with a concentration of less than 10 ⁴ precipitates per cubic centimeter. In addition, the wafer contains a second region containing material precipitates having a concentration greater than 10 ⁷ precipitates per cubic centimeter. The detection limit for material precipitations is, for example, at a concentration of 5 × 10 ⁶ precipitates per cubic centimeter. The proof can be done, for example, via cross sections and defect etching.

Thus, the semiconductor material disc also has the technical effects mentioned above for the method. The outline of the disc is z. B. a circle, a rectangle or another shape. The first area has the function of a "denuded" zone because it contains very little or no vacancies or excretions. The first region is most commonly used for semiconductor devices, such as transistors (FET field effect transistors, BT bipolar transistors), diodes, capacitors, or other devices.

The concentration of the precipitates in the second region can be in particular in the range of 10 ⁷ to 10 ¹⁶ precipitations per cubic centimeter. The concentration of the precipitates may be constant in the second range or may change by less than three orders of magnitude.

The excretions may be or contain oxygen precipitates. Oxygen or semiconductor material oxygen compounds are not critical for most manufacturing processes, but allow a very good getter effect. It can not according to the invention but also other material precipitates are generated which are suitable for gettering of heavy metal ions or heavy metal atoms during the processing of the semiconductor material disc.

The semiconductor material disc may have a planar first side and a second side facing away from the first side, as is typical for wafers. Both sides can be parallel to each other. The terms "flat" or "parallel to one another" are to be interpreted within the scope of the manufacturing tolerances and the production-related deflections.

The first region or the second region can each form a layer region that occupies laterally the same area as the first side or at least 90 percent of this surface. The first area may be adjacent to the first page. Likewise, the second area may adjoin the second side.

The first region may have a layer thickness that is at least 1 micrometer. The second region may have a layer thickness which is at least one third of the layer thickness of the semiconductor material disc or at least 150 micrometers. The thicker the second area, the greater the getter effect. In the case of the layer thickness mentioned, the second region may contain, in addition to the desired oxygen precipitations, in particular damage, as is typical for mechanical damage, eg. B. microcracks or dislocations. This mechanical method makes it possible to produce more targeted damage than other methods or damage in higher concentration with comparable or less effort.

The second region may alternatively have a layer thickness which is less than one tenth of the layer thickness of the semiconductor material disc or less than 75 microns. In this case, the second region can in particular contain damage, as is typical for ion implantation.

The first area may be vacancy-free or vacancy-poor with a concentration of vacancies less than 10 ¹² or 10 ¹¹ spaces per cubic centimeter. Thus, the catalytic effect of the voids in the first region when generating the material precipitates is low, so that no or negligible few material precipitates arise in the first region.

The semiconductor material disc may contain a carbon concentration less than 5 × 10 ¹⁵ or 5 × 10 ¹⁶ atoms per cubic centimeter. Thus, not the carbon atoms but the vacancies are decisive for the formation of precipitates.

Furthermore, a semiconductor device or integrated circuit is concerned with a semiconductor substrate having a first layer region contains no precipitate or low in precipitation with a concentration of less than 10 ⁴ material precipitates per cubic centimeter. The semiconductor substrate also includes a second layer region containing precipitates having a concentration greater than 10 ⁷ material precipitates per cubic centimeter. Thus, the technical effects mentioned for the methods or for the semiconductor wafers also apply to the semiconductor component or to the integrated circuit. In particular, the layer thicknesses and concentration mentioned are present in the component or circuit.

Hereinafter, some embodiments of the invention will be illustrated with reference to figures, which are given by way of illustration only and are not intended to limit the scope of the invention.

1A and 1B show the basic sequence of an embodiment of a method according to the invention for producing material precipitates in a semiconductor material. As in 1A is shown, a semiconductor material disc 2 a damage process 4 subjected, for example, a mechanical grinding process or an ion implantation and in particular an oxygen implantation. For example, the semiconductor wafer is subjected to an oxidation step beforehand, which at least for the most part fills in voids present by injection of interstitial silicon atoms. Likewise, a two-sided diffusion of oxygen over a certain depth range can be carried out beforehand, in which case the layer thickness removed by the mechanical damage method (lapping or polishing) should be greater than or equal to the vertical extent of the region in which appreciable oxygen diffusion takes place , so that this area is eroded back.

As in 1B is shown, the semiconductor material disc 2 then exposed to a temperature process at a temperature T in the range of, for example. 800 ° C to 1000 ° C over a period in the range of 5 to 25 hours or from 10 to 20 hours, z. B. a temperature T of 900 ° C for a period of 10 hours.

Subsequently, electronic semiconductor devices are generated in the semiconductor device in a region which has not been damaged. In this case, a gettering for impurities in the damaged and - depending on the annealing - in an adjacent area occurs.

2 shows a cross section through a semiconductor material disc 5 with material precipitates visible as white dots. A distance of about four centimeters in the 2 illustrates a distance of about 300 microns in the semiconductor wafer 5 , It is an image taken with an optical microscope, whereby the material precipitates have been visualized by means of defect etching.

A layer thickness D0 is, for example, about 700 micrometers, wherein on the back side, for example, 25 micrometers have been ground off an original layer thickness D0 in order to produce damage which promotes the material precipitations. An upper layer area 7 , a middle layer area 8th and a lower layer area 9 each have a layer thickness of about 150 microns. In the upper layer area 7 There are hardly any excretions, being in the upper third 6 of the upper layer area 7 Nearly no precipitates are present, so this area is particularly suitable for the manufacture of integrated components. In the middle area 8th There are excretions in a low concentration. In the lower area 9 on the other hand, there are precipitates in a very high concentration, for example greater than 10 ⁸ precipitates per cubic centimeter.

3A to 3E show a first process variant, in which of a semiconductor wafer 10 is assumed, for example, has a layer thickness D1 of 700 microns. The exemplary embodiment is a monocrystalline silicon wafer 10 in which unavoidable voids are present during manufacture. In 3A For example, five spaces V1 to V5 are indicated by crosses. In reality, the concentration of vacancies - as already mentioned - is considerably higher. The blanks are also referred to as vacancies.

The semiconductor wafer 10 is etched on both sides and possibly polished on a top OS.

In a manufacturing stage according to 3B becomes the semiconductor wafer 10 oxidized on both sides with a layer 12a at the top OS and a layer 12b at the bottom US arises. The layers 12a and 12b exist in the embodiment of silicon oxide with a layer thickness of a few hundred nanometers, z. B. in the range of 100 to 1500 nanometers. When creating the layers 12a and 12b Interstitial silicon is generated which diffuses into the silicon wafer and the voids in the semiconductor wafer 10 fills, in particular the voids V1 to V5, so that these voids are no longer in the semiconductor wafer 10 available. For example, at a temperature T1 in the range between 950 ° C and 1180 ° C, it is oxidized for a time t in the range of 1 to 5 hours. Alternatively, other process temperatures and process times are used to create the layers 12a and 12b used.

Optionally, then the front side layer 12a followed by optionally an oxygen diffusion step and / or a polishing step on the wafer front side OS can be performed. Alternatively, oxidative RTP methods are performed to remove the vacancies.

As in 3C is shown, then a back damage generation is performed, ie at the bottom US. For example, approximately 25 microns are abraded, the layer thickness of the semiconductor wafer 10 is reduced to the layer thickness D1b of 675 microns. In a shift range 10b the semiconductor wafer 10 cause numerous damage, especially blanks, of which in 3C five empty spaces V6 to V10 are shown by way of example. An upper layer area 10a the semiconductor wafer 10 is not harmed. The layer area 10a in the exemplary embodiment, for example, has a layer thickness D3 of, for example, 600 micrometers.

Optionally, a short partial etch back of the damaged layer 10b z. B. carried out by wet chemical etching or plasma process to eliminate possibly present in the near-surface disc area contaminants.

After that, as in 3D is shown, a high-temperature step for the formation of oxygen precipitates, of which in 3D four excretions P1 to P4 are shown by way of example. The excretions are also referred to as precipitates or "precipitates". For example, a one-stage high-temperature process associated with the 1B process parameters, ie T1 equal to 900 ° C and t1 equal to 10 hours. Alternatively, for example, a two-step process is performed, for example, with a temperature T2a of 800 ° C for a time t2a of five hours and then with a temperature T2b of 1000 ° C for a time t2b of 15 hours.

The high-temperature step becomes a layer region 10c formed, containing precipitates of high concentration. Due to the diffusion of the voids becomes the layer area 10a thinned, with a layer area 10a1 arises, which contains no or only little space. A layer thickness D4 of the layer region 10a1 is smaller than the layer thickness D3, for example by at least 30 percent. In the exemplary embodiment, the layer thickness D4 is still 300 micrometers.

Optionally, a backside phosphorus diffusion is then not carried out according to the invention, which is subsequently protected against outdiffusion with an oxide layer. If necessary, a front side polish and / or a Vorderpitepitaxie.

As in 3E is shown, the layer 12a For example, be removed only at a component manufacturer. Subsequently, with known methods, components are produced on the upper side OS, for. B. field effect transistors Tr1, Tr2, etc. and / or bipolar transistors. A zone for a component BE1 preferably has a smaller depth than the layer region 10a1 , When manufactured in the semiconductor wafer 10 introduced parasitic impurities, such as. Heavy metal atoms, accumulate in the layer region 10c on the precipitates, see, for example, heavy metal atom S1 at the precipitate P4. Thus, the heavy metals are far removed from the components BE1 and can not damage them.

If required, after the production of the components BE1, optionally a slice thinning and / or backside damaging etching can take place as far as possible at the end of the production process. In the embodiment shown, the layer region remains 10c on the other hand, at the layer area 10a1 , so that when separating both layer areas 10a1 and 10c be severed, see, for example, separating cut 20 between two integrated circuits IC1 and IC2.

In another variant, instead of grinding, oxygen implantation is used to create the lesion.

Since a high dose of oxygen is thereby introduced, this variant can also be used to produce oxygen precipitates in oxygen-poor "float zones", in contrast to the previously described variant, which can be used with oxygen-rich material (such as Czochralski (CZ) material). Materials are used. This variant, which uses ion implantation injury, may also be combined with the variant using mechanical damage to further promote the formation of oxygen precipitates.

Also, the layer can 12a be removed earlier. The method according to 3A to 3E can also be used for the production of individual components, in particular of power components.

4A to 4E show a second process variant. It is made of a semiconductor wafer 100 assumed, for example, a silicon wafer. The semiconductor wafer 100 contains blanks due to production, of which six blanks V11 to V16 in 4A are shown as examples. Two spaces V12 and V15 are closer to the bottom US than the other spaces V11, V13, V14 and V16 shown. A layer thickness D5 of the semiconductor wafer 100 is, for example, 700 microns.

According to 4B Damage generation takes place on the rear of the disk US, for example, in the case of a semiconductor wafer that has been etched or polished on the front side 100 , For example. the semiconductor wafer is used to generate the damage 100 mechanically processed, z. B. ground to a layer thickness D5b of, for example, 650 microns. This is a damaged layer 100b in the semiconductor wafer 100 which contains, by way of example, additional vacancies V17 to V21 as well as the original blank location V12. The upper layer area 100a the semiconductor wafer 100 has been correspondingly thinned and has a layer thickness D6 of, for example, 575 micrometers.

Optionally, a brief partial etch back of the damaged layer occurs 100b to remove impurities. Furthermore, optionally, a deposition of a protective layer 110 on the back of the wafer US, for example, a silicon nitride layer with a layer thickness in the range of 50 to 500 nanometers. If necessary, an auxiliary layer may be previously formed on the underside US, for example, an oxide deposited at relatively low process temperatures, for cracking in the nitride layer 110 to avoid.

As in 4C is shown, then an oxidation is carried out for the injection of interstitial silicon atoms, wherein a layer 112 at the top OS is generated. The injection is preferably carried out down to the depth, which is given by the vertical extent of the electrically active zone, or slightly lower. In the exemplary embodiment, for example, only the vacancies V12 and V15 and V17 to V21 remain of the vacancies shown. With regard to the process parameters T4 and t4, reference is made to the description of 3B directed. Alternatively, RTP methods are performed to remove the vacancies.

As in 4D is shown, then a single-stage or multi-stage high temperature step is performed to form oxygen precipitates, z. B. with the process parameters temperature T5 and time t5 corresponding to T and t according to the description of 1B , Alternatively, for example, a two-stage process is performed, for. B. temperature T5a equal to 800 ° C and time t5 equal to 5 h and temperature T5b equal to 1000 ° C and time t5b equal to 15 h. In particular, not only the vacancies V17 to V21 serve as a catalyst but also the remaining vacancies V12 and V15. This results in comparatively many oxygen precipitations, of which in 4D by way of example, five precipitates P11 to P15 in a layer region 100c are shown. The layer area 100c arises from the layer area 100b and has a layer thickness of, for example, 300 micrometers. Thus, a layer thickness D7 is one in the high-temperature step from the layer region 100a resulting layer area 100a1 for example, still 275 microns.

Optionally, a backside phosphorus diffusion is then not carried out according to the invention, which is subsequently protected against outdiffusion with an optional oxide layer. If necessary, a front side polish and / or a Vorderpitepitaxie.

As in 4E is shown, the layer 112 For example, be removed only at a component manufacturer. Subsequently, with known methods, components are produced on the upper side OS, for. B. field effect transistors Tr3, Tr4, etc. and / or bipolar transistors. A zone for a component BE2 preferably has a smaller depth than the layer region 100a1 , Furthermore, at least one metallization layer is applied, for example. From at least 80 atomic percent aluminum or at least 80 atomic percent copper, z. B. Damaszene method. Furthermore, a passivation and the attachment of contact surfaces, eg. For bonding or for the flip-chip assembly. When manufactured in the semiconductor wafer 10 impurities introduced, such as, for example, heavy metal atoms, accumulate in the layer region 100c at the excretions, z. P11 to P15. Thus, the heavy metals are far removed from the components Tr3, Tr4, BE2 and can not damage them.

If necessary, after the manufacture of the components optionally a disc thinning and / or Rückseitendamageätzung done as far as possible at the end of the manufacturing process. In the embodiment shown, the layer region remains 100c on the other hand, at the layer area 100a1 , so that when separating both layer areas 100a1 and 100c be severed, see, for example, separating cut 120 between two integrated circuits IC3 and IC4.

In another variant, instead of grinding, oxygen implantation is used to create the lesion. Also, the layer can 112 be removed earlier. The method according to 4A to 4E can also be used for the production of individual components, in particular of power components.

In other words, for example, a method for the targeted local production of oxygen precipitates in CZ material (Czochalski) is given. Commercially available CZ material may be modified to suit the manufacture of power semiconductors or other semiconductor devices; that is, it may on the one hand contain a low-defect zone, which is sufficiently extended in depth, so that the electrically active zone or at least the largest part thereof to implement it and on the other hand on the back of the disc a stable getter zone, which largely avoids the incorporation of unwanted heavy metals in the electrically active zone during the implementation of the high-temperature steps.

It is proposed on the one side of the disk, z. B. a disc back, for example. CZ discs by a targeted damage to the semiconductor material, in particular the silicon material to produce a high vacancy density. The high vacancy density in turn leads to a relatively high density of, for example, oxygen precipitates in a subsequent special high-temperature step. The high-temperature step is carried out inertly in the temperature range between, for example, 800 ° C. and 1000 ° C. over a period of a few hours (in total, for example, in the range of 10 to 20 hours). The damage can be done in particular by mechanical methods, as they are anyway used for targeted thickness adjustment of the discs. For this come z. B. lapping or grinding processes in question.

After this backside treatment, the damaged surface may optionally be subjected to a relatively short etching step so as to restore potential surface contamination introduced by the ablation process by means of silicon ablation, which may range between, for example, 0.3 micrometer and 3 micrometers remove. Thus, the partial re-etching of the damaged zone differs from a complete removal of the damaged zone, as could be done, for example, by CMP (chemical mechanical polishing).

It is also conceivable to produce such a damage to the back of the disc by a damage implantation by implantation of oxygen in particular. In particular, the excretion formation is further promoted by the additionally offered oxygen. For this purpose, it may also be advantageous to achieve a more homogeneous distribution of the implanted oxygen atoms both after implantation and after the subsequent temperature treatment by using a plurality of implantation energies, wherein typically two or three different implantation energies are advantageous. The latter method can therefore also be used when using silicon material which has a low oxygen concentration, for example in the case of "float zone" material.

In order to ensure a defined starting state before carrying out the above-described process and to ensure a precipitate-free or at least low-precipitate zone, it is recommended to inject at the beginning at least in the later electrically active regions of the semiconductor wafer interstitial silicon atoms which are emitted from the Removal process to eliminate blanks in this area. For this purpose, preferably a wet or dry oxidation at a suitable temperature (depending on the thickness of the disk usually between 950 ° C and 1180 ° C) carried out over a few hours, z. In the range of 1 to 5 hours.

If required, it is not possible according to the invention to further enhance the targeted gettering effect by means of near-surface backside phosphorus diffusion, for example with a dopant concentration greater than 10 ¹⁸ phosphorus atoms per cubic centimeter. The phosphorus doping should be protected from outdiffusion by downstream oxide deposited on the back of the wafer with respect to subsequent manufacturing processes.

Thus, the production of a stable getter layer on the back of, for example, CZ silicon wafers is affected, for which purpose oxygen precipitates are generated in this area by a backside near surface damage to the back of the disk, an increased vacancy concentration is generated in this area and thus the elimination of oxygen is favored in a subsequent special annealing step, wherein before the damage of the disc backside a special oxidizing high-temperature step for eliminating the original vacancies ensures the reproducibility of the result.

The damage is preferably caused by mechanical processing methods, since this variant can be very cost-effectively integrated into the usual process flow. Alternatively, the damage can also be generated in particular by an implantation of oxygen atoms, with the advantage of high reproducibility, a very good homogeneity of the oxygen excretions and, above all, a favorable effect of the precipitates due to the additional supply of oxygen. If the implanted oxygen dose is high enough during implantation, the method can also be used for originally low-oxygen silicon base material, such. Magnetic CZ, float zone replacements or float zone material.

The process allows a good reproducibility as required for large-scale industrial processes, but so far was largely unachievable.

The vacancy concentrations mentioned relate in particular to single spots in a central region of the wafer in relation to the lateral extent.

LIST OF REFERENCE NUMBERS

2

Semiconductor wafer

3

damage process

5 to 9

layer region

10, 100

Semiconductor wafer

10a to 10c

layer region

12a, 12b

layer

20

separating cut

D0 to D7

layer thickness

OS

top

US

bottom

V1 to V21

void

T, T1 to T5

temperature

t, t1 to t5

process time

P1 to P15

excretion

S1

Heavy metal atom

IC1 to IC4

integrated circuit

Tr1 to Tr4

transistor

BE1, BE2

module

100a to 100c

layer region

110

protective layer

112

layer

120

separating cut

Claims (41)

A method for producing material precipitates, the method comprising: generating damages (V6, V17) in a semiconductor material ( 10 . 100 ) creating a damaged area ( 10b . 100b ) by mechanical action, and then performing a heat treatment (T2, t2 T5, t5) of the semiconductor material ( 10 . 100 ) in an inert atmosphere to produce oxygen precipitates (P1, P11) having a concentration greater than 10 precipitates per cubic centimeter in the damaged area (P1, P11) 10b . 100b . 10c . 100c ). A method for producing material precipitates, the method comprising: generating damages (V6, V17) in a semiconductor material ( 10 . 100 ) creating a damaged area ( 10b . 100b ) by ion implantation, wherein oxygen ions are implanted, and then performing a heat treatment (T2, t2 T5, t5) of the semiconductor material ( 10 . 100 ) producing material precipitates (P1, P11) in the damaged area ( 10b . 100b . 10c . 100c ), wherein the heat treatment carried out after the damage is carried out at a temperature greater than or equal to 800 ° C for at least 10 hours, or wherein the heat treatment carried out after the damage at at least two different temperatures in the range between 800 ° C and 1050 ° C. be carried out in total for at least 10 hours. Method according to one of the preceding claims, characterized in that the semiconductor material is produced by the Czochralski method. Method according to one of the preceding claims, characterized in that before or after the generation of the damage existing voids in the entire semiconductor body are eliminated. Method according to one of claims 1 to 4, characterized by removing voids (V1, V11) before producing the damage in an area not damaged after the generation of the damage ( 10a . 100a ) of the semiconductor material ( 10 . 100 ). A method according to claim 4 or 5, characterized in that the removal of the vacancies takes place by oxidizing processes. A method according to claim 6, characterized in that the oxidizing processes include wet oxidations. A method according to claim 6, characterized in that the oxidizing processes involve dry oxidations. A method according to claim 6, characterized in that the oxidizing processes are carried out at temperatures between 950 ° C and 1150 ° C. A method according to claim 9, characterized in that the oxidizing processes are carried out over a period of one to five hours. A method according to claim 6, characterized in that the oxidizing processes are carried out by means of a rapid thermal annealing process. A method according to claim 11, characterized in that the oxidizing processes are carried out at temperatures between 1000 ° C and 1300 ° C. A method according to claim 12, characterized in that the oxidizing processes are carried out over a period of five to 60 seconds. Method according to one of claims 5 to 13, characterized in that on the later to Damaged wafer side is deposited before performing the oxidation process, a nitride layer. Method according to one of the preceding claims as far as dependent on claim 1, characterized in that the damage is caused by grinding or lapping. A method according to claim 15, characterized in that at least one layer thickness of the semiconductor body of 5 microns is removed in this damage. Method according to one of the preceding claims as far as dependent on claim 1, characterized in that the damaged surface is etched back in the range between 0.3 and 3 microns. Method according to one of the preceding claims as far as dependent on claim 2, characterized in that the ion implantation energy is in the range between 200 KeV and 10 MeV. Method according to one of the preceding claims as far as dependent on claim 2, characterized in that the implantation dose is in the range between 5 × 10 ¹³ to 10 ¹⁶ oxygen atoms per cm ² . Method according to one of the preceding claims as far as dependent on claim 2, characterized in that the implantation dose is in the range between 10 ¹⁴ to 2 × 10 ¹⁵ oxygen atoms per cm ² . Method according to one of the preceding claims, as far as not dependent on claim 3, characterized in that the semiconductor material is produced by the float zone method. Method according to one of the preceding claims as far as dependent on claim 2, characterized in that only one implantation energy is used. Method according to one of the preceding claims as far as dependent on claim 2, characterized in that a plurality of implantation energies are used. A method according to claim 23, characterized in that two or three implantation energies are used. Method according to one of the preceding claims, characterized in that the damaged area ( 10c . 100c ) remains in the finished processed semiconductor material. Method according to one of the preceding claims, as far as not dependent on claim 25, characterized in that the damaged area ( 10c . 100c ) was removed in the finished processed semiconductor material. Method according to one of the preceding claims as far as dependent on claim 1, characterized in that the heat treatment carried out after the damage at a temperature greater than or equal to 800 ° C for at least 5 hours or at least 10 hours is performed, or that carried out after the damage heat treatment at least two different temperatures, which are in the range between 800 ° C and 1050 ° C, carried out in total for at least 10 hours. Method according to one of the preceding claims, characterized in that the steps before the production of semiconductor devices (BE1) in the semiconductor material ( 10 . 100 ) and / or that the damaged area ( 10b . 100b . 10c . 100c ) is not removed or partially etched back prior to fabrication of the semiconductor devices (BE1). Method according to one of the preceding claims as far as not dependent on claim 3, characterized in that the semiconductor material is produced by the float zone method, the magnetic Czochralski method or from a float zone replacement material method. Semiconductor material disc ( 2 . 10 . 100 ), with a first area ( 10a1 . 100a1 ) which is free of precipitates or low in precipitates with a concentration of less than 10 ⁴ material precipitations per cubic centimeter, with a second area ( 10c . 100c ) containing precipitates (P1, P11) having a concentration greater than 10 ⁷ material precipitates per cubic centimeter, the material precipitates being oxygen precipitates, characterized in that the second region contains damages typical of mechanical damage. Semiconductor material disc ( 2 . 10 . 100 ) according to claim 30, characterized in that the material precipitates are suitable for the gettering of heavy metal ions during the processing of the semiconductor material disc. Semiconductor material disc ( 2 . 10 . 100 ) according to one of claims 30 or 31, characterized characterized in that the first area ( 10a1 . 100a1 ) has a layer thickness (D7) which is at least 1 μm. Semiconductor material disc ( 2 . 10 . 100 ) according to one of claims 30 to 32, characterized in that the first region ( 10a1 . 100a1 ) has a layer thickness (D7) which is at least 10 μm. Semiconductor material disc ( 2 . 10 . 100 ) according to one of claims 30 to 32, characterized in that the first region ( 10a1 . 100a1 ) has a layer thickness (D7) which is at least 50 μm. Semiconductor material disc ( 2 . 10 . 100 ) according to one of claims 30 to 32, characterized in that the second region ( 10c . 100c ) has a layer thickness which is at least one third of the layer thickness (D1b, D5b) of the semiconductor material disc ( 2 . 10 . 100 ) or at least 150 microns. The semiconductor material disc according to claim 35, wherein the semiconductor material disc ( 2 . 10 . 100 ) is preferably made of material made according to the Czochralski process. Semiconductor material disc ( 2 . 10 . 100 ) according to one of claims 30 to 32, characterized in that the second region ( 10c . 100c ) has a layer thickness which is less than one tenth of the layer thickness (D1b, D5b) of the semiconductor material disc ( 2 . 10 . 100 ) or less than 75 microns, wherein the semiconductor material disc ( 2 . 10 . 100 ) is preferably made of material prepared according to float zone techniques, Czochralski magnetic or float zone replacement processes. Semiconductor material disc ( 2 . 10 . 100 ) according to one of claims 30 to 32, characterized in that the first region is vacancy-free or vacancy-poor with a concentration of vacancies smaller than 10 ¹² or 10 ¹¹ vacancies per cubic centimeter. Semiconductor material disc ( 2 . 10 . 100 ) according to one of claims 30 to 32, characterized in that the semiconductor material disc ( 2 . 10 . 100 ) contains a carbon concentration less than 5 x 10 ¹⁵ or 5 x 10 ¹⁶ atoms per cubic centimeter. Semiconductor device (BE1) or integrated circuit (IC1) with a semiconductor substrate ( 2 . 10 . 100 ) with a first layer region ( 10a1 . 100a1 ) which is free of precipitates or low in precipitates with a concentration of less than 10 ⁴ material precipitations per cubic centimeter, with a second area ( 10c . 100c ) containing precipitates (P1, P11) having a concentration greater than 10 ⁷ material precipitates per cubic centimeter, the material precipitates being oxygen precipitates, characterized in that the second region contains damages typical of mechanical damage. Semiconductor device (BE1) or integrated circuit (IC1) with a semiconductor substrate ( 2 . 10 . 100 ) with a first layer region ( 10a1 . 100a1 ) which is free of precipitates or low in precipitates with a concentration of less than 10 ⁴ material precipitations per cubic centimeter, with a second area ( 10c . 100c ) containing material precipitates (P1, P11) having a concentration in the range of 10 ¹¹ to 10 ¹⁶ per cubic centimeter, the material precipitates being oxygen precipitates, the second region ( 10c . 100c ) on a back side of the semiconductor substrate ( 2 . 10 . 100 ), wherein at least one semiconductor device is disposed on a front side of the semiconductor substrate.

Images