RU2507634C1 - Semiconductor device and method of its manufacturing - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: semiconductor device comprises a thinned substrate of single-crystal silicon of p-type conductivity, oriented according to the plane (111), with a buffer layer from AlN on it, above which there is a heat conducting substrate in the form of a deposited layer of polycrystalline diamond with thickness equal to at least 0.1 mm, on the other side of the substrate there is an epitaxial structure of the semiconducting device on the basis of wide-zone III-nitrides, a source from AlGaN, a gate, a drain from AlGaN, ohmic contacts to the source and drain, a solder in the form of a layer including AuSn, a copper pedestal and a flange. At the same time between the source, gate and drain there is a layer of an insulating polycrystalline diamond.

EFFECT: higher reliability of a semiconducting device and increased service life, makes it possible to simplify manufacturing of a device with high value of heat release from an active part.

3 cl, 7 dwg

Description

The group of inventions relates to the field of semiconductor technology, for example, microwave power transistors based on GaN, heterojunction field effect transistors (HEMT), bipolar transistors (BJT), heterobipolar transistors (HBT), pin diodes, Schottky barrier diodes and many others, as well as methods their manufacture.

The creation of optoelectronic and microelectronic devices based on semiconductor compounds of group A ³ with nitrogen (nitrides A ³ ) is very important in view of the significant expansion of the functionality of these devices. In particular, it became possible to manufacture microwave field-effect transistors, the power of which is several times greater than the power of such transistors made on the basis of traditional materials (arsenide A ³ ). At the same time, nitride-based transistors have unique thermal stability and can operate continuously at a temperature of 300-500 ° C, which was completely unavailable on traditional devices.

However, a significant difficulty in the industrial implementation of such a technical solution is the tendency of nitride transistors to degradation, i.e. to a quick change (deterioration) of the characteristics of the device over time. This degradation is observed during operation of the device and, moreover, a deterioration in the characteristics of transistor semiconductor structures in the absence of an electric current is recorded. It has been shown that the mobility and concentration of electrons in a nitride heterostructure randomly change over time, and over several months these changes reach tens of percent (S. Elhamri et al. Study of deleterious aging effects in GaN / AlGaN heterostructures. Journal of Applied Physics, vol. 93 2, pp. 1079-1082, January 15, 2003).

In conditions appropriate to the workers, i.e. with the current flowing under the action of the applied voltage, nitride transistors change their characteristics in a few hours, which is unacceptable for real use.

Known field-effect transistor based on gallium and aluminum nitrides, the structure of which consistently includes: a substrate, a GaN layer, a barrier layer made of two sublayers: Al _0.2 Ga _0.8 N, GaN on it; the second version of the barrier layer is Al _0.3 Ga _0.7 N, doped with Si, unalloyed Al _0.3 Ga _0.7 N on it. The contacts are made on the structure: drain, source and gate with corresponding gaps between them; Further, a dielectric coating of MgO, Sс ₂ О ₃ or SiN _{x was made} . Between the contacts, the dielectric coating is located on the barrier layer and serves to protect the exposed surfaces of the barrier layer from external influences, see B. Luo et al. The role of cleaning conditions and epitaxial layer structure on reliability of Sс ₂ О ₃ and MgO passivation on AlGaN / GaN HEMTS, Solid-State Electronics, 46, pp. 2185-2190, 2002.

The disadvantage of this technical solution is that the degradation level obtained due to the protective layers remains quite high.

Currently, devices based on a heterojunction epitaxial structure (HES) of the AlGaN / GaN type are widely used.

HES layers are deposited by epitaxial methods, such as the method of chemical vapor deposition of organometallic compounds (MOCVD), the method of molecular beam epitaxy (MBE), the method of hydride vapor epitaxy (HVPE), and others. Unlike traditional semiconductor materials, wide-gap III-nitrides have a hexagonal type of crystal lattice and are obtained in the form of thin heteroepitaxial structures on substrates having a hexagonal type of lattice. For this purpose, as a rule, substrates of sapphire (Al ₂ O ₃ ), silicon carbide (SiC), bulk aluminum nitride (AlN) or gallium nitride (GaN), pseudovolume GaN, silicon substrates with a plane orientation (111) are used (Si (111)), as well as GaN (or AlN) preforms on the substrate, one of which can be used (Compound Semiconductor. October 2004, 27-31).

The disadvantages of this method is the lack of production of reliable semiconductor devices due to the low thermal conductivity of the substrate and overheating of the working area of the semiconductor device.

In another known solution, a thin (from 0.5 to 30 μm) layer of diamond is grown on a substrate suitable for growing polycrystalline diamond, for example, from silicon, on the growth surface of which a layer suitable for epitaxial growth and the first layer of a complex semiconductor are formed. This layer may be single crystal and may be selected from the group consisting of Si, GaAs, SiC, and Al ₂ O ₃ .

There may be an additional second layer, a complex semiconductor, including: Al _x Ga _y In _z As _m P _n N _o Sb _k , in which x, y, z, m, n, o and k each has a value greater than or equal to zero and less or equal to unity and x + y + z = 1 and m + n + o + k = 1, in which the second layer of a complex semiconductor has a composition different from the first layer of a complex semiconductor.

There may be an additional buffer layer selected, for example, from the group consisting of HfN and AlN, and located between the base layer and the first layer of a complex semiconductor.

There may be an intermediate layer selected from the group consisting of polysilicon, silicon oxides, silicon nitride, silicon carbide, carbon, III-V semiconductors or a combination of them, and located between the diamond layer and the base layer.

The first layer of a complex semiconductor contains Al _x Ga _y In _z As _m P _n N _o Sb _k , in which x, y, z, m, n, o and k each have a value greater than or equal to "0" and less than or equal to unity and x + y + z = 1 and m + n + o + k = 1. The first layer of a complex semiconductor may contain GaN.

The known structure contains in order: a silicon substrate, a heat-conducting diamond layer, a single-crystal silicon layer and an epitaxial GaN layer, or a silicon substrate, a heat-conducting diamond layer, a polysilicon layer, a single-crystal silicon layer and an epitaxial GaN layer, and the buffer layer is selected from the group consisting of HfN and AlN.

The known structure has a bending parameter of up to 25 μm concave shape and up to 300 μm convex shape on the front side of GaN (US patent document No. 2006/0113545 Al, Jun. 1, 2006).

The main disadvantages of the analogue include:

- a thin layer of diamond (0.5-30 microns) limits the heat removal from semiconductor structures and requires laborious processing (grinding and polishing). This is due to the fact that a semiconductor structure is formed on the growth surface of a polycrystalline diamond, the roughness of which reaches 10% of the layer thickness, which does not allow to form a structure. With an increase in the thickness of the diamond layer to the structural thickness, for example, to 0.15 mm, the height of the microroughness will reach 15 microns, which significantly increases the complexity and duration of processing;

- the finished structure has a significant bend due to insufficient thickness of the diamond.

The closest analogue to the claimed method is the technical solution described in the patent of the Russian Federation No. 2368031, 09/20/2009. A known method of manufacturing a semiconductor device includes growing on a base substrate polycrystalline diamond, epitaxial auxiliary layers and the epitaxial structure of a semiconductor device based on wide-band III-nitrides. At the same time, auxiliary epitaxial layers are formed on the surface of the base substrate, one of which is basic for growing the epitaxial structure of a semiconductor device based on wide-band III-nitrides. Polycrystalline diamond is grown on auxiliary epitaxial layers, and after growing diamond, the base substrate is removed together with auxiliary epitaxial layers to the base layer, on which the epitaxial structure of a semiconductor device based on wide-band III-nitrides is grown.

The disadvantages of this method is the lack of production of reliable semiconductor devices, due to the low value of the heat sink from the active part of the semiconductor device.

The objective of this group of inventions is to eliminate the above disadvantages.

The overall technical result is achieved in increasing the reliability of a semiconductor device and increasing its service life, as well as in simplifying the method and the possibility of manufacturing devices with it with a high heat sink from their active part.

The technical result is ensured by the fact that the semiconductor device includes a thinned substrate of p-type single crystal silicon, oriented along the (111) plane, with an AlN buffer layer made on it, on top of which a heat-conducting substrate is made in the form of a deposited layer of polycrystalline diamond with a thickness equal to less than 0.1 mm, on the other side of the substrate, the epitaxial structure of a semiconductor device based on wide-band III-nitrides is made, source from AlGaN, gate, drain from AlGaN, ohmic contacts to the source and drain, a solder layer comprising AuSn, copper pedestal and the flange. In this case, a layer of insulating polycrystalline diamond is made between the source, gate and drain.

According to a particular embodiment, the epitaxial structure includes an undoped layer of a GaN solid solution, an undoped layer of an AlGaN solid solution, an undoped layer of an n-type AlGaN solid solution and an AlGaN solid solution layer.

The technical result is also ensured by the fact that the method of manufacturing a semiconductor device includes depositing an AuSn solder layer on a flange, onto which a copper pedestal is sealed, applying an AuSn sublayer, which secures the crystal of a semiconductor device to a copper pedestal, and deposition of an AlN buffer layer on a substrate surface onto the surface of which grow a heat-conducting layer of polycrystalline diamond, thinning the substrate. Then, on the thinned substrate, the epitaxial structure of III-nitrides is grown. Then a source, gate, drain are formed, ohmic contacts to the source and drain are provided, an insulating layer of polycrystalline diamond is applied between the source, gate and drain, on top of the transistor crystal.

The group of inventions is illustrated by the following illustrations:

figures 1-4 illustrate the manufacturing sequence of the device;

5 illustrates a semiconductor device;

Fig.6 displays the experimentally measured time dependence of the heating temperature of the active region of the microwave transistor;

Fig.7 displays the current-voltage characteristics of the semiconductor device.

The semiconductor device includes the following structural elements:

1 - flange;

2 - a layer of solder from AuSn;

3 - copper pedestal;

4 - sublayer of AuSn;

5 - substrate;

6 - buffer layer of AlN;

7 - heat-conducting substrate;

8 - undoped GaN layer;

9 - undoped layer of AlGaN solid solution;

10 - unalloyed layer of AlGaN solid solution;

11 - layer of AlGaN solid solution;

12 - source;

13 - shutter;

14 - stock;

15 - ohmic contacts;

16 - an insulating layer of polycrystalline diamond.

The proposed device is as follows.

Figures 1-5 illustrate the sequence of manufacturing a multilayer epitaxial structure of a semiconductor device according to both options. On the MD-40 1 brand flange with a thickness of 1600 μm, a 25 μm thick AuSn 2 solder layer is applied, onto which a copper pedestal 3 with a thickness of ~ 150 μm is sealed. A ~ 25 μm thick sublayer of AuSn 4 is applied over the copper layer, which subsequently serves as the basis for strengthening the transistor crystal to the copper pedestal 3. As substrate 5, for example, p-type single crystal silicon oriented along the (111) plane is used. A buffer layer of AlN 6 is deposited on the surface of the substrate 5. On the surface of the base substrate 5 with a layer 6, a thermally conductive CVD layer of polycrystalline diamond 7 with a thickness of ≥0.1 mm is grown. The diamond layer is grown in a microwave discharge on a UP-SA-100 installation (microwave power 5 kW, frequency 2.45 GHz) using the reaction mixture CH4 (10%) / H2 (88.5%) / O2 (1.5%). The deposition conditions were as follows: a hydrogen flow rate of 0.53 l / min, a pressure in the chamber of 95 torr, a microwave power input of 4.6 kW into the chamber, and a substrate temperature of 940 ° C. Even in the presence of tensile and compression stresses at the diamond-AlN interface, arising due to the difference in the thermal expansion of AlN and diamond after the deposition of diamond onto the AlN epitaxial layer upon cooling from the synthesis temperature to room temperature, a satisfactory adhesion of polycrystalline diamond to AlN. After growing polycrystalline diamond 7, the substrate 5 is drowned by well-known wet-etching methods to a thickness of 10 μm. Next, on the substrate 5, a heteroepitaxial structure of III-nitrides is successively grown, consisting, for example, of an unalloyed layer of a solid solution of GaN 8, an unalloyed layer of a solid solution of AlGaN space 9, an unalloyed layer of a solid solution of AlGaN n-type conductivity 10, a layer of an AlGaN solid solution (roof) 11. Then form the source 12, the gate 13, the drain 14. Provide the presence of ohmic contacts 15 to the source 12 and the drain 16. On top of the transistor crystal between the source, the gate and the drain, an insulating layer of polycrystalline diamond 16 is applied.

The advantage of the claimed technical solution is that all layers in the structures are obtained using well-known epitaxial methods and special processing technologies and / or methods for attaching layers, for example, such as “Smart” technology, are not required. The semiconductor structure appears to be formed practically on the surface of the substrate of large structural thickness from high-conductivity polycrystalline diamond. Eliminates the need for a time-consuming operation of polishing the surface of the diamond to a state suitable for the technology of thermal bonding layers in the further manufacture of devices.

The advantage of the claimed technical solution is that all layers in the structures are obtained using well-known epitaxial methods and special processing technologies and / or methods for attaching layers, for example, such as “Smart” technology, are not required. The semiconductor structure appears to be formed practically on the surface of the substrate of large structural thickness from high-conductivity polycrystalline diamond. In addition, the presence of a layer of insulating polycrystalline diamond between the source, gate and drain provides additional heat removal from the active region of the device, while the thermal resistance of the transistor structure decreases by 1.5 times.

7. The experimentally measured time dependences of the heating temperature of the active region of the microwave transistor are given.

The use of a layer of insulating polycrystalline diamond on the surface between the source, gate and drain of the microwave GaN transistor increases the breakdown voltage of the transistor by 30%.

Figure 7 shows the current-voltage characteristics of the microwave GaN transistor:

a) without a layer of insulating polycrystalline diamond on the surface of the crystal of a microwave transistor, between the source, gate and drain; b) with a layer of insulating polycrystalline diamond on the transistor's crystal surface, between the source, gate, and drain.

Claims (3)

1. A semiconductor device comprising a thinned substrate of p-type single crystal silicon, oriented along the (111) plane, with an AlN buffer layer made on it, over which a heat-conducting substrate is made in the form of a deposited layer of polycrystalline diamond with a thickness of at least 0 , 1 mm, the epitaxial structure of a semiconductor device based on wide-band III nitrides, a source from AlGaN, a gate, a drain from AlGaN, ohmic contacts to the source and drain, solder in the form of oya comprising AuSn, copper pedestal and the flange, wherein between the source, drain and gate insulating layer is made of polycrystalline diamond. 2. The device according to claim 1, characterized in that the epitaxial structure includes an unalloyed layer of a solid solution of GaN, an unalloyed layer of a solid solution of AlGaN, an unalloyed layer of an AlGaN solid solution of n-type conductivity and a layer of an AlGaN solid solution. 3. A method of manufacturing a semiconductor device, comprising applying an AuSn solder layer onto a flange, onto which a copper pedestal is soldered, applying an AuSn sublayer, which secures the crystal of a semiconductor device to a copper pedestal, depositing an AlN buffer layer on the surface of the substrate, on the surface of which a heat-conducting material is grown layer of polycrystalline diamond, thinning of the substrate, then on the thinned substrate the epitaxial structure of III-nitrides is grown, then the source, gate, drain are formed, provide of sul contacts to the source and drain of the transistor on top of the crystal, between the source, gate and drain is applied to the insulating layer of polycrystalline diamond.

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