CN211455647U

CN211455647U - Gallium nitride MISHEMT structure

Info

Publication number: CN211455647U
Application number: CN202020496854.4U
Authority: CN
Inventors: 刘春利
Original assignee: Shenzhen Jiahua Microelectronics Co ltd
Current assignee: Shenzhen Jiahua Microelectronics Co ltd
Priority date: 2020-04-07
Filing date: 2020-04-07
Publication date: 2020-09-08
Anticipated expiration: 2030-04-07

Abstract

The utility model provides a gallium nitride MISHEMT structure, which comprises a wafer, wherein the wafer is formed with source metal, drain metal and gate metal, a first insulating medium layer covers the source metal, the drain metal and the gate metal, the first insulating medium layer is respectively provided with an opening at the corresponding position of the source metal and the drain metal and is internally provided with first linking metal, a first source metal field plate and a first drain metal field plate cover the first linking metal, a second insulating medium layer covers the first source metal field plate, the first drain metal field plate and the exposed first insulating medium layer, the second insulating medium layer is respectively provided with an opening at the corresponding position of the source metal and the drain metal and is internally provided with second linking metal, the surface of the second linking metal is covered with a second source metal field plate and a second drain metal field plate, passivation layers are covered on the surfaces of the second source electrode metal field plate and the second drain electrode metal field plate, so that the pressure resistance of the device can be effectively improved.

Description

Gallium nitride MISHEMT structure

Technical Field

The utility model relates to the technical field of semiconductors, especially, relate to a gallium nitride MISHEMT structure.

Background

The GaN-based semiconductor has the excellent characteristics of large forbidden bandwidth, high breakdown electric field, high electron saturation migration speed, easy formation of heterostructure, strong spontaneous and piezoelectric polarization effect, strong radiation resistance, good chemical property stability and the like, thereby being suitable for preparing power electronic devices with high power, high speed and large voltage. However, the compressive strength of the existing GaN device is weak, and the compressive strength of the GaN device is generally improved by increasing the distance between the gate and the drain, which will increase the size of the GaN device, and the effect of simply adding a metal field plate on the gate to realize the compressive strength is very weak.

SUMMERY OF THE UTILITY MODEL

In view of the above, in order to solve one of the technical problems in the related art to a certain extent, it is necessary to provide a gallium nitride MISHEMT structure capable of effectively improving the device compressive performance.

The utility model provides a gallium nitride MISHEMT structure, which comprises a wafer, wherein the wafer is formed with source metal, drain metal and gate metal, a first insulating medium layer is covered above the source metal, the drain metal and the gate metal, the first insulating medium layer is respectively provided with an opening at the corresponding positions of the source metal and the drain metal and is formed with a first linking metal in the opening, a first source metal field plate and a first drain metal field plate are covered above the first linking metal, a second insulating medium layer is covered on the first source metal field plate, the first drain metal field plate and the exposed first insulating medium layer, a second insulating medium layer is respectively provided with an opening at the corresponding positions of the source metal and the drain metal and is formed with a second linking metal in the opening, the surface of the second linking metal is covered with a second source metal field plate and a second drain metal field plate, and passivation layers are covered on the surfaces of the second source electrode metal field plate and the second drain electrode metal field plate.

Further, the first source metal field plate extends to the drain electrode side and covers the gate metal; and/or

The second source metal field plate covers the first source metal field plate; and/or

The second drain metal field plate covers the first drain metal field plate.

Further, the wafer comprises a channel layer, a barrier layer located above the channel layer, a first passivation layer deposited on the barrier layer in real time, a constraint layer deposited on the first passivation layer in real time, and a second passivation layer deposited on the constraint layer in real time, the wafer forms a source groove, a drain groove and a gate groove, the source groove and the drain groove are etched from the second passivation layer to the barrier layer, source metal and drain metal are deposited in the source groove and the drain groove respectively, ohmic metal field plates are epitaxially formed on the tops of the source metal and the drain metal respectively, the gate groove comprises a gate field plate groove formed by etching part of the second passivation layer, and gate contact grooves are formed by continuously etching the remaining second passivation layer, all the constraint layer and part of the first passivation layer in the gate field plate groove, the width of the gate contact groove is smaller than that of the gate field plate groove, gate metal is formed in the gate contact groove and the gate field plate groove, the gate metal comprises a third step located above the gate field plate groove, and the third step extends towards the drain electrode direction.

Further, a separate gate metal is provided on the ohmic metal field plate of the source metal and/or the drain metal; wherein

The gate metal above the source metal extends to the drain electrode side and covers the ohmic metal field plate of the source metal; and/or

An ohmic metal field plate extending from the gate metal over the drain metal to the source side and covering the drain metal; and/or

The first source metal field plate covers the gate metal above the source metal; and/or;

the first drain metal field plate covers the gate metal over the drain metal.

Further, a layer of low-pressure plasma SiNx is deposited on all surfaces of the wafer.

Further, the source electrode metal and/or the drain electrode metal sequentially comprise a first Ti layer, an Al layer, a second Ti layer and a second TiN layer from bottom to top, the thickness of the first Ti layer is 1nm-200nm, the thickness of the Al layer is 100nm-500nm, the thickness of the second Ti layer is 1nm-200nm, and the thickness of the second TiN layer is 10nm-1000 nm.

Further, the gate metal sequentially comprises a third TiN layer, a first middle layer and a fourth TiN layer from bottom to top, the first middle layer is Al or Al-Cu or Al-Si-Cu, the thickness of the third TiN layer is 10nm-2000nm, the thickness of the first middle layer is 50nm-5000nm, and the thickness of the fourth TiN layer is 10nm-2000 nm.

Further, the first source electrode metal field plate and the first drain electrode metal field plate sequentially comprise a fifth TiN layer with the thickness of 10nm-2000nm, a second middle layer with the thickness of 50nm-5000nm and a sixth TiN layer with the thickness of 10nm-2000nm from bottom to top, and the second middle layer is Al, Al-Cu, Al-Si-Cu, W, Mo or Pt.

Further, the second source electrode metal field plate and the second drain electrode metal field plate sequentially comprise a seventh TiN layer, a third middle layer and an eighth TiN layer from bottom to top, and the third middle layer is Al or Al-Cu or Al-Si-Cu or W or Mo or Pt.

Further, the passivation layer includes a third passivation layer covering the second source metal field plate and the second drain metal field plate, and a fourth passivation layer covering the third passivation layer, and the third passivation layer and the fourth passivation layer are opened to form a source contact opening and a drain contact opening.

According to the above technical scheme, the utility model discloses a gallium nitride MISHEMT structure can effectively improve device compressive property, will combine specific embodiment to explain below the utility model discloses a concrete beneficial effect.

Drawings

Fig. 1 is a schematic view of a wafer structure according to a first embodiment.

Fig. 2 is a schematic view of a wafer structure according to a second embodiment.

Fig. 3 is a schematic structural diagram of the wafer of fig. 1 after opening the source trench and the drain trench.

Fig. 4 is a schematic view of the structure of fig. 3 after metal deposition.

Fig. 5 is a schematic structural diagram of the wafer of fig. 4 after the gate trench is opened.

FIG. 6 is a schematic diagram of the gate metal obtained by depositing the metal in FIG. 5.

Fig. 7 is a schematic structural diagram of the etched gate metal of fig. 6.

Fig. 8 is a schematic structural diagram of fig. 7 after a first insulating dielectric layer is deposited.

Fig. 9 is a schematic structural diagram of the first insulating dielectric layer of fig. 8 after being opened and a first link metal is formed.

Fig. 10 is a schematic structural diagram of fig. 9 after the first metal layer is deposited and etched.

Fig. 11 is a schematic structural view of fig. 10 after a second insulating dielectric layer is deposited.

Fig. 12 is a schematic structural diagram of the second insulating dielectric layer of fig. 11 after being opened and a second link metal is formed.

Fig. 13 is a schematic structural diagram of fig. 12 after the second metal layer is deposited and etched.

Fig. 14 is a schematic structural view of fig. 13 after a third passivation layer and a fourth passivation layer are sequentially deposited.

Fig. 15 is a schematic structural view of the third passivation layer and the fourth passivation layer after opening.

The following detailed description will further illustrate the invention in conjunction with the above-described figures.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention. It is to be understood that the drawings are provided solely for the purposes of reference and illustration and are not intended as a definition of the limits of the invention. The connection relationships shown in the drawings are for clarity of description only and do not limit the manner of connection.

It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It should also be noted that, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly and can include, for example, fixed connections, removable connections, or integral connections; either mechanically or electrically, and may be internal to both elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

It should be noted that in the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be configured in a specific orientation, and operate, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

The gallium nitride misfet is a (GaN metal insulator semiconductor high electronic mobility transistor), and the method of manufacturing the gallium nitride misfet according to the present invention will be described below with reference to specific embodiments.

In the first step, a GaN wafer is provided and cleaned, and the structure thereof is shown in fig. 1 or fig. 2.

In fig. 1, a GaN wafer may include a substrate 100, a channel layer 105 formed on the substrate 101, a barrier layer 106 over the channel layer 105, a first passivation layer 107 deposited (in-situ) on the barrier layer 106, a confinement layer 108 deposited (in-situ) over the first passivation layer 107, and a second passivation layer 109 over the confinement layer 108. The two-dimensional electron gas E1 is formed between the channel layer 105 and the barrier layer 106.

In other embodiments, as shown in fig. 2, the GaN wafer may include a substrate 100, and a nucleation layer 101, a transition layer 102, a super-junction lattice layer 103, a first two-dimensional electron gas confinement layer 104, a channel layer 105, a barrier layer 106, a first passivation layer 107 deposited (in-situ) on the barrier layer, a second two-dimensional electron gas confinement layer 108, and a second passivation layer 109 deposited (in-situ) on the second two-dimensional electron gas confinement layer 108, which are sequentially formed on the substrate 100. The two-dimensional electron gas E2 is formed between the channel layer 105 and the barrier layer 106.

The substrate 100 may be silicon (Si), silicon carbide (SiC), quartz (Diamond), Ga2O3, or other substrate 100.

The nucleation layer 101 has a thickness of 0.01um to 1um and may be made of AlN.

The thickness of transition layer 102 is 0.01um-5um, can adopt AlGaN, wherein, from last down or from down up, Al accounts for than can the ladder increase progressively, is equivalent to including a complete nucleation layer 101 that multilayer sub-nucleation layer 101 superposes the constitution promptly, from last down or from down up, sub-nucleation layer 101Al accounts for than the ladder and increases progressively.

Super junction lattice layer 103 has a thickness of 0.1um to 100um and may be made of al (ga) N/ga (al) N, where the AlN percentage in the al (ga) N layer may be 70% to 99% and the GaN percentage in the ga (al) N layer may be 70% to 99%.

The first two-dimensional electron gas confinement layer 104 is 0.5um-100 um. In this embodiment, the first two-dimensional electron gas confinement layer 104 is made of AlGaN, and the percentage of Al (Al content/algag total amount) may be 1% to 30%, where from bottom to top or from top to bottom, the Al content in the first two-dimensional electron gas confinement layer 104 increases in steps, that is, the Al content in the sublayer increases in steps, which is equivalent to a complete first two-dimensional electron gas confinement layer 104 formed by stacking a plurality of sublayers, and from top to bottom or from bottom to top, the Al content in the sublayer increases in steps, so that the forbidden bandwidth of the first two-dimensional electron gas confinement layer 104 can be increased, and the forbidden bandwidth is larger than that of the channel layer 105, so that the two-dimensional electron gas is more difficult to escape from the first two-dimensional electron gas confinement layer 104, and the two-dimensional electron gas is prevented from escaping from the lower layer.

The channel layer 105 has a thickness of 0.001um to 10um and may be made of GaN.

The thickness of the blocking layer 106 is 0.1nm-100nm, and the blocking layer can be made of AlGaN, the percentage of Al can be 1% -100%, and when the percentage of Al reaches 100%, the blocking layer is AlN. The presence of the barrier 106 helps to mitigate current collapse.

The first passivation layer 107 is a low-voltage plasma SiNx layer (LP SiNx), the thickness of the first passivation layer 107 can be 1nm-100nm, and the real-time deposited first passivation layer 107 can passivate the surface of AlGaN to prevent oxidation of Al. The thickness of the second two-dimensional electron gas confinement layer 108 is 1nm-100nm and is made of AlN.

The second passivation layer 109 can be a low-voltage plasma SiNx layer (LP SiNx), the thickness of the second passivation layer 109 can be 0.1um-20um, and the real-time deposited second passivation layer 109 can passivate the AlN surface to avoid Al oxidation.

The low-pressure plasma SiNx layer (LP SiNx) has high density (up to 3.2x 10)^-3kg/cm^-3) The dielectric constant of the first passivation layer 107 and the second passivation layer 109 is smaller than that of the plasma enhanced SiNx, tensile stress and compressive stress are superior to those of the plasma enhanced SiNx, and the forbidden band width reaches 5eV, so that gate leakage can be effectively prevented by the first passivation layer 107 and the second passivation layer 109, and two-dimensional electron gas can be prevented from escaping through the passivation layers to a certain extent.

The second two-dimensional electron gas confinement layer 108 serves as an upper escape barrier wall for the two-dimensional electron gas to prevent the two-dimensional electron gas from escaping from the upper layer. The first two-dimensional electron gas confinement layer 104 and the second two-dimensional electron gas confinement layer 108 serve as upper and lower barriers, so that the concentration of the two-dimensional electron gas and the dynamic resistance of the GaN device are kept from being increased due to the loss of the two-dimensional electron gas in use, and the dynamic on-resistance is reduced or eliminated.

The invention will be described with reference to a GaN wafer as shown in fig. 1.

The GaN wafer shown in fig. 1 was cleaned to remove surface impurities, particularly heavy metals harmful to the production line. The special cleaning process comprises the following steps: DHF (dilute HF wash): at 25 ℃, 1 min, SC1 wash: 55-85 ℃ for 20 min, SC2 cleaning: repeating for 2-5 times at 55-85 deg.C for 20 min.

And secondly, depositing a layer of low-pressure plasma SiNx on all the surfaces of the GaN wafer.

The low-pressure plasma SiNx is used as the outer protective layer 300, the outer protective layer 300 comprises a part located above the second passivation layer 109, the thickness of the outer protective layer 300 is 0.01-5 um, and the deposited LP SiNx can be deposited in a vertical oxidation furnace to cover the whole GaN wafer, so that cross contamination between the deposited LP SiNx and Si or other types of production lines in the later process can be prevented, and the function layer of the GaN wafer is prevented from being permeated with impurities to influence the performance of the GaN wafer.

Third, as shown in fig. 3-7, a trench is opened on the wafer and metal is deposited in the trench to obtain a source metal 110, a drain metal 111 and a gate metal 113.

First, a source region, a drain region and a gate region are defined, in fig. 3, the source region is located on the left side, the drain region is located on the right side, and the gate region is located in the middle.

Next, as shown in fig. 3, the second passivation layer 109, the confinement layer 108 and the first passivation layer 107 of the source region and the drain region are etched, which of course also includes etching the outer cap layer 300.

Etching is performed as far as the barrier layer 106, thereby obtaining a source trench 201 and a drain trench 202.

Then, as shown in fig. 4, metal is deposited in the source trench 201 and the drain trench 202 to obtain a source metal 110 and a drain metal 111.

It is possible that the source trench 201 and the drain trench 202 are filled in the metal blanket deposition process and pass over the surface of the second passivation layer 109 and cover the second passivation layer 109, and then the ohmic metal field plate 112 is epitaxially formed on top of the source metal 110 and the drain metal 111, respectively, by etching the excess ohmic metal portion on the second passivation layer 109 in real time or subsequently, which may be 0.5um epitaxially. In addition, the source metal 110 and the drain metal 111 may be deposited separately.

The ohmic metal field plate 112 can act as a field plate in direct contact with the source and drain electrodes, primarily reducing the electric field strength near the source and drain electrodes.

Specifically, a first Ti layer with a thickness of 1nm to 200nm is deposited in the source trench 201 and the drain trench 202, then an Al layer with a thickness of 100nm to 500nm is deposited, then a second Ti layer with a thickness of 1nm to 200nm is deposited, and finally a second TiN layer with a thickness of 10nm to 1000nm is deposited.

The source metal 110 and the drain metal 111 are subjected to Rapid Thermal Annealing (RTA). Rapid annealing with RTA can be performed in either N2 or H2. According to the temperature rising and falling curves, the annealing temperature can be set between 400 ℃ and 1250 ℃ and the time can be set between 30s and 300 s.

Then, as shown in fig. 5, a gate field plate trench 203 is formed by etching away a portion of the second passivation layer 109 in the gate region.

In particular, half or one third, in the illustration half, of the second passivation layer 109 may be etched.

As shown in fig. 5, before etching a portion of the second passivation layer 109 in the gate region to form the gate field plate trench 203, the ohmic metal layer covering the second passivation layer 109 for forming the source metal 110 and the drain metal 111 may be preserved in advance, so that it is necessary to etch away the ohmic metal layer on the second passivation layer 109 at a position for forming the gate field plate trench 203 and a portion of the second passivation layer 109 for forming the gate field plate trench 203.

Then, the remaining second passivation layer 109, the entire confinement layer 108, and a portion of the first passivation layer 107 are etched away in the gate field plate trench 203 to form a gate contact trench 204.

The gate contact trench 204 etch requires etching away the real-time deposited confinement layer 108, but leaving the real-time deposited portion of the first passivation 107 layer underneath as the gate dielectric.

The width of the gate contact groove 204 is smaller than that of the gate field plate groove 203, the gate contact groove 204 is preferably opened near the source, and the width is preferably half of the gate field plate groove 203, that is, the width of the gate field plate groove 203 is about 1 time of the gate contact groove 204. The width of the gate contact groove 204 may be 0.01um-10um and the width of the gate field plate groove 203 may be 0.1 um-5 um.

When the gate metal 113 is obtained by subsequent metal deposition, the metal layer of the gate contact groove 204 forms a first step of the gate metal 113, and the metal layer of the gate field plate groove 203 forms a second step of the gate metal 113, which is a part of the gate field plate.

Before metal deposition, metal back-sputtering is required, that is, inert gas ions are used for bombarding the surfaces of the source metal 110 and the drain metal 111 (ohmic metal layer), so that oxide deposition on the metal surface is removed, and the contact resistance is reduced.

Finally, as shown in fig. 6 and 7, metal is deposited to fill the gate contact trench 204 and the gate field plate trench 203 to form the gate metal 113.

Specifically, the gate metal 113 sequentially comprises a third TiN layer, a first intermediate layer and a fourth TiN layer from bottom to top, the first intermediate layer is Al or Al-Cu or Al-Si-Cu, the thickness of the third TiN layer is 10nm to 2000nm, the thickness of the first intermediate layer is 50nm to 5000nm, and the thickness of the fourth TiN layer is 10nm to 2000nm, and by adopting the structure and the thickness design, the appropriate resistance of the gate metal 113 can be obtained.

As shown in fig. 6, the gate metal 113 is deposited, and then the gate metal 113 in the gate region is etched and remained. As shown in fig. 8, the gate metal 113 of the gate region includes a first step 1131 located in the gate contact groove 204, a second step 1132 located in the gate field plate groove 203, and a third step 1133 located above the gate field plate groove 203. A third step 1133 is located above the gate field plate trench 203 and extends over the second passivation layer 109 towards the drain direction, the third step 1133 constituting part of the gate field plate. The width of the third step 1133 is greater than the width of the second step 1132, and is preferably about 2 times as large as the second step 1132. The second step 1132 and the third step 1133 can effectively reduce the electric field intensity of the gate preliminarily.

When the gate metal 113 is deposited, the gate metal 113 is deposited on the entire surface, the gate metal 113 is stacked on the ohmic metal layer, and then the unnecessary gate metal 113 is etched, the gate metal 113 of the third step 1133, the source and drain portions is remained, and the unnecessary ohmic metal layer is continuously etched, so as to obtain the source metal 110 and the ohmic metal field plate 112 extended from the drain metal 111. The gate metal 113 overlying the source metal 110 and the drain metal 111 has a field plate function, and preferably, the gate metal 113 above the source metal 110 extends to the drain side and covers the ohmic metal field plate 112 of the source metal 110, and/or the gate metal 113 above the drain metal 111 extends to the source side and covers the ohmic metal field plate 112 of the drain metal 111, so that the gate metal 113 above the source metal 110 and the drain metal 111 can shield the high-voltage electric field at the sharp corner of the underlying metal field plate (i.e., the ohmic metal field plate 112).

In a fourth step, as shown in fig. 8, a first insulating dielectric layer 114 is deposited on the surface.

The dielectric of the first insulating dielectric layer 114 can be TEOS (a kind of SiO2), SiNx, SiO2, AlN, sion x, or any oxide, nitride, or other insulating dielectric with high electric field resistance, and the thickness thereof can be designed, preferably between 0.1um and 10 um. The first insulating dielectric layer 114 covers the uncovered surface of the second passivation layer 109 and the gate metal 113.

Fifthly, as shown in fig. 9, the first insulating dielectric layer 114 is opened to open the source metal 110 and the drain metal 111, and a first link metal 115 is formed in the opening 1141.

The first link metal 115 is formed in two openings 1141 (an opening at the source location and an opening at the drain location), which partially or completely cover and contact the gate metal 113 of the source and drain. The shape of the opening 1141 may be circular or quadrilateral, etc., and the size is generally 1um-20 um.

Since the gate and the source/drain are covered by metal, the deposited dielectric is uneven, and a dielectric planarization process is required, and a cmp (chemical mechanical planarization) or etchback (post-etching) method may be used to remove the excess dielectric, so that the upper surface of the first insulating dielectric layer 114 is flat.

In the sixth step, as shown in fig. 10, a first metal layer 116 is deposited on the surface.

Before depositing the first metal layer 116, metal back sputtering is required, and inert gas ions are used for bombarding the surface of the first link metal 115, so that oxide deposition on the surface of the first link metal 115 is removed, and the contact resistance is reduced.

After the metal is back-sputtered, a fifth TiN layer with a thickness of 10nm-2000nm may be deposited first, then a second interlayer with a thickness of 50nm-5000nm may be deposited, and finally a sixth TiN layer with a thickness of 10nm-2000nm may be deposited, where the second interlayer is Al or Al-Cu or Al-Si-Cu or W or Mo or Pt.

Seventhly, the first metal layer 116 is etched to obtain a first source metal field plate 1161 linked to the source metal 110 and a first drain metal field plate 1162 linked to the drain metal 111.

In a cascode structure, the first metal layer 116 may be linked to a gate. In the etching process, photoresist is coated as required, and the unnecessary first metal layer 116 is etched away, so as to obtain a first source metal field plate 1161 and a first drain metal field plate 1162.

The third step 1133 connected to the first source metal field plate 1161 extends towards the gate to cover the gate metal 113, and the covered amplitude can be 0.5um-5 um. The width of the first source metal field plate 1161 is large, the high-voltage electric field at the sharp corner of the ohmic metal field plate 112 is shielded, the first source metal field plate 1161 interacts with the ohmic metal field plate 112 of the source metal 110, so that the electric field intensity at the source electrode is greatly reduced, and the first source metal field plate 1161 interacts with the second step 1132 and the third step 1133 of the gate metal 113 at the same time, so that the electric field intensity at the gate electrode is reduced, and the pressure resistance of the device is improved.

The first drain metal field plate 1162 extends towards the gate direction, the extension amplitude can be designed as required, preferably 0.1um to 10um, so that the width of the first drain metal field plate 1162 is greater than that of the ohmic metal field plate 112 of the drain metal 111 to cover the ohmic metal field plate 112 of the drain metal 111, the width of the first drain metal field plate 1162 is large, the high-voltage electric field at the sharp corner of the ohmic metal field plate 112 is shielded, and the first drain metal field plate 1162 interacts with the ohmic metal field plate 112 of the drain metal 111, so that the electric field intensity at the drain is greatly reduced.

If the gate metal 113 above the source metal 110 and the gate metal 113 above the drain metal 111 are remained, the first source metal field plate 1161 is preferably made to cover the gate metal 113 above the source metal 110, and the first drain metal field plate 1162 is made to cover the gate metal 113 above the drain metal 111, so that the high voltage electric field at the sharp corner of the lower metal field plate can be shielded by the first source metal field plate 1161.

In the eighth step, as shown in fig. 11, a second insulating dielectric layer 117 is deposited on the surface.

The dielectric of the second insulating dielectric layer 117 may be TEOS (a kind of SiO2), SiNx, SiO2, AlN, sion x, or any oxide, nitride, or other insulating dielectric with high electric field resistance, and the thickness thereof may be designed, preferably between 0.1um and 10 um. The second insulating dielectric layer 117 covers the first source metal field plate 1161, the first drain metal field plate 1162 and the etched and exposed first insulating dielectric layer 114.

In a ninth step, as shown in fig. 12, the second insulating dielectric layer 117 is opened to open the first source metal field plates 1161 and the first drain metal field plates 1162, respectively, and the second link metal 118 is formed in the opening 1171.

The position of the opening 1171 corresponds to the position of the source and the drain, and the size and the shape of the opening 1171 may be the same as those of the opening 1141 of the first insulating dielectric layer 114, and may be 1um to 20 um. Opening 1171 may also be continuous and may cover the entire first metal layer 116 left after etching.

The deposited dielectric is rugged, and needs to be planarized, and the excess dielectric can be removed by using cmp (chemical polishing) or etch back (post etch) method, so that the upper surface of the second insulating dielectric layer 117 is flat.

In the tenth step, as shown in fig. 13, a second metal layer 119 is deposited on the surface.

Before depositing the second metal layer 119, metal back-sputtering is required, and inert gas ions are used to bombard the surface of the second link metal 118, so as to remove the oxide deposition on the surface of the second link metal 118 and reduce the contact resistance.

After the metal is sputtered back, during the deposition of the second metal layer 119, a seventh TiN layer may be deposited, then a third intermediate layer may be deposited, and finally an eighth TiN layer may be deposited, where the third intermediate layer is Al, Al-Cu, Al-Si-Cu, W, Mo, or Pt, and the thickness of each layer is not limited herein.

The tenth step is to etch the second metal layer 119 to obtain a second source metal field plate 1191 linking the first source metal field plate 1161 and a second drain metal field plate 1192 linking the first drain metal field plate 1162.

In a cascode structure, the second metal layer 119 may be linked to a gate. In the etching process, photoresist is coated as required, and the unnecessary second metal layer 119 is etched away, so that a second source metal field plate 1191 and a second drain metal field plate 1192 are obtained. The second source metal field plate 1191 covers the first source metal field plate 1161, the cover width can be 0.5um to 5um, the second drain metal field plate 1192 covers the first drain metal field plate 1162, the cover width can be designed as required, and can be 0.1um to 20 um. The second source metal field plate 1191 can shield the high voltage electric field at the sharp corner of the first source metal field plate 1161, and the second drain metal field plate 1192 can shield the high voltage electric field at the sharp corner of the first drain metal field plate 1162.

The second source metal field plate 1191, the first source metal field plate 1161, the gate metal 113 above the source metal 110, and the ohmic metal field plate 112 of the source metal 110 together, through the multi-layer electric field shielding, greatly reduce the electric field strength at the source electrode, so that the electric field strength at the source electrode reaches a very low reliable value. The second drain metal field plate 1192, the first drain metal field plate 1162, the gate metal 113 above the drain metal 111, and the ohmic metal field plate 112 of the drain metal 111 together reduce the electric field strength at the drain by a large margin through multi-layer electric field shielding, so that the electric field strength at the drain reaches a very low reliable value, and thus, the compressive capacity of the GaN device is significantly improved.

In a twelfth step, shown in fig. 14-14, a passivation layer is deposited on the surface to cover the second source metal field plate 1191 and the second drain metal field plate 1192.

First, as shown in fig. 14, a third passivation layer 120 is deposited on the surface to cover the second source metal field plate 1191 and the second drain metal field plate 1192.

The third passivation layer 120 may be SiNx with a thickness of 0.5um to 10 um.

Next, a fourth passivation layer 121 is deposited on the surface covering the third passivation layer 120. The upper surface of the fourth passivation layer 121 is a flat surface.

The fourth passivation layer 121 may be imine (polyimide), and has a thickness of 0.5um to 20um after high temperature softening (curing), curing, and the like. The third passivation layer 120 and the fourth passivation layer 121 may improve the stress resistance and reliability of the device.

Finally, as shown in fig. 15, the third passivation layer 120 and the fourth passivation layer 121 are opened 205 to form a source contact opening and a drain contact opening.

The gallium nitride MISHEMT structure obtained by the above specific manufacturing method comprises a wafer, wherein a source metal 110, a drain metal 111 and a gate metal 113 are formed on the wafer, a first insulating dielectric layer 114 covers the source metal 110, the drain metal 111 and the gate metal 113, the first insulating dielectric layer 114 is provided with an opening at the corresponding position of the source metal 110 and the drain metal 111 and is provided with a first link metal 115 in the opening, a first source metal field plate 1161 and a first drain metal field plate 1162 cover the first link metal 115, a second insulating dielectric layer 117 covers the first source metal field plate 1161, the first drain metal field plate 1162 and the exposed first insulating dielectric layer 114, a second insulating dielectric layer 117 is provided with an opening at the corresponding position of the source metal 110 and the drain metal 111 and is provided with a second link metal 118 in the opening, the second link metal 118 is covered with a second source metal field plate 1191 and a second drain metal field plate 1192, and the second source metal field plate 1191 and the second drain metal field plate 1192 are covered with a passivation layer.

Throughout the description and claims of this application, the words "comprise/comprises" and the words "have/includes" and variations of these are used to specify the presence of stated features, values, steps or components but do not preclude the presence or addition of one or more other features, values, steps, components or groups thereof.

Some features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, certain features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination in different embodiments.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A gallium nitride MISHEMT structure is characterized in that the gallium nitride MISHEMT structure comprises a wafer, wherein a source electrode metal, a drain electrode metal and a gate metal are formed on the wafer, a first insulating medium layer covers the source electrode metal, the drain electrode metal and the gate metal, the first insulating medium layer is respectively provided with an opening at the corresponding position of the source electrode metal and the drain electrode metal and is internally provided with a first link metal, a first source electrode metal field plate and a first drain electrode metal field plate cover the first link metal, a second insulating medium layer covers the first source electrode metal field plate, the first drain electrode metal field plate and the exposed first insulating medium layer, a second insulating medium layer is respectively provided with an opening at the corresponding position of the source electrode metal and the drain electrode metal and is internally provided with a second link metal, and the surface of the second link metal is covered with a second source electrode metal field plate and a second drain electrode metal field plate, and passivation layers are covered on the surfaces of the second source electrode metal field plate and the second drain electrode metal field plate.

2. The gallium nitride MISHEMT structure of claim 1, wherein:

the first source electrode metal field plate extends towards the side of the drain electrode and covers the gate metal; and/or

The second drain metal field plate covers the first drain metal field plate.

3. The gallium nitride MISHEMT structure according to claim 1 or 2, wherein the wafer comprises a channel layer, a barrier layer over the channel layer, a first passivation layer deposited on the barrier layer in real time, a confinement layer deposited on the first passivation layer in real time, and a second passivation layer over the confinement layer, the wafer forms a source trench, a drain trench, and a gate trench, the source trench and the drain trench are etched from the second passivation layer down to the barrier layer, a source metal and a drain metal are deposited in the source trench and the drain trench, respectively, an ohmic metal field plate is epitaxially formed on top of the source metal and the drain metal, respectively, the gate trench comprises a gate field plate trench formed by etching a portion of the second passivation layer and a gate contact trench formed by continuously etching away the remaining second passivation layer, all of the confinement layer, and a portion of the first passivation layer in the gate field plate trench, the width of the gate contact groove is smaller than that of the gate field plate groove, gate metal is formed in the gate contact groove and the gate field plate groove, the gate metal comprises a third step located above the gate field plate groove, and the third step extends towards the drain electrode direction.

4. The gallium nitride MISHEMT structure of claim 3, wherein the ohmic metal field plate of the source metal and/or the drain metal has a separate gate metal thereon; wherein

the first drain metal field plate covers the gate metal over the drain metal.

5. Gallium nitride MISHEMT structure according to claim 1 or 2, characterized in that a layer of low-pressure plasma SiNx is deposited on all the surface of the wafer.

6. The gallium nitride MISHEMT structure according to claim 1 or 2, wherein the source metal and/or the drain metal comprises a first Ti layer having a thickness of 1nm to 200nm, an Al layer having a thickness of 100nm to 500nm, a second Ti layer having a thickness of 1nm to 200nm, and a second TiN layer having a thickness of 10nm to 1000nm in this order from bottom to top.

7. The gallium nitride MISHEMT structure according to claim 1 or 2, wherein the gate metal comprises, in order from bottom to top, a third TiN layer, a first interlayer and a fourth TiN layer, the first interlayer being Al or Al-Cu or Al-Si-Cu, the third TiN layer having a thickness of 10nm to 2000nm, the first interlayer having a thickness of 50nm to 5000nm, the fourth TiN layer having a thickness of 10nm to 2000 nm.

8. The gallium nitride MISHEMT structure according to claim 1 or 2, wherein the first source metal field plate and the first drain metal field plate comprise, in order from bottom to top, a fifth TiN layer with a thickness of 10nm to 2000nm, a second interlayer with a thickness of 50nm to 5000nm, a sixth TiN layer with a thickness of 10nm to 2000nm, and the second interlayer is Al or Al-Cu or Al-Si-Cu or W or Mo or Pt.

9. The gallium nitride MISHEMT structure of claim 1 or 2, wherein the second source metal field plate and the second drain metal field plate comprise a seventh TiN layer, a third interlayer, and an eighth TiN layer in sequence from bottom to top, and the third interlayer is Al or Al-Cu or Al-Si-Cu or W or Mo or Pt.

10. The gallium nitride MISHEMT structure of claim 1 or 2, wherein the passivation layer comprises a third passivation layer covering the second source metal field plate and the second drain metal field plate, a fourth passivation layer covering the third passivation layer, the third passivation layer and the fourth passivation layer being opened to form a source contact opening and a drain contact opening.