N-surface GaN radio frequency device based on multi-threshold coupling technology and preparation method thereof

Abstract

The invention relates to an N-face GaN radio frequency device based on a multi-threshold coupling technology and a preparation method thereof, the device comprises a substrate layer, a buffer layer, a barrier layer, a channel layer and a multi-threshold coupling gate structure which are sequentially arranged from bottom to top, and the material of the channel layer is N-face GaN; two-dimensional electron gas is formed at the interface of the channel layer and the barrier layer; the multi-threshold coupling gate structure is used for applying threshold voltage gradually changing in the gate width direction to the two-dimensional electron gas. The threshold voltage gradually changing along the gate width direction is applied to the two-dimensional electron gas through the multi-threshold coupling gate structure, so that the device can be gradually started along the gate width direction along with the gradual increase of the gate voltage from negative to positive, and the transconductance flatness of the device is improved. The gate length of the device provided by the embodiment is not limited by transconductance flatness, the working frequency can be improved by greatly shortening the gate length, the device has higher working frequency and better linearity, and the future 6G terahertz frequency band communication requirement is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and in particular relates to an N-face GaN radio frequency device based on a multi-threshold coupling technology and a preparation method thereof. Background Art

[0002] At present, 5G technology has achieved large-scale commercialization. In view of its insufficient development potential, people have put forward new requirements for the sixth generation of mobile communications (6G). 6G technology will enter the higher frequency terahertz band, and achieve a leapfrog improvement in peak rate, mobility and spectrum efficiency. It will integrate satellite communications into 6G mobile communications and fully meet the needs of the new generation of information and communication services.

[0003] With the development of 6G technology, the application demand for data transmission rate and spectrum efficiency in modern wireless systems continues to grow, and the linearity of power amplifiers has become an indispensable measurement indicator. This requires the key components of 6G power amplifiers (GaN-based RF devices) to take into account both high frequency and high linearity.

[0004] At present, the research on GaN-based RF devices is mainly focused on Ga-face GaN. In the process of continuously reducing the gate length to increase the operating frequency of Ga-face devices, its transconductance flatness will deteriorate and the device linearity will deteriorate. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides an N-face GaN radio frequency device based on multi-threshold coupling technology and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] The first aspect of the present invention provides an N-face GaN radio frequency device based on a multi-threshold coupling technology, comprising: a substrate layer, a buffer layer, a barrier layer, a channel layer, and a multi-threshold coupling gate structure arranged in sequence from bottom to top, wherein:

[0007] The material of the channel layer is N-face GaN;

[0008] A two-dimensional electron gas is formed at the interface between the channel layer and the barrier layer;

[0009] The multi-threshold coupled gate structure is used to apply a threshold voltage that gradually changes along a gate width direction to the two-dimensional electron gas.

[0010] In one possible implementation, it further includes: a source, a drain and an isolation structure;

[0011] The source electrode is located on the upper surface of the channel layer and is located on one side of the multi-threshold coupling gate structure along the gate length direction;

[0012] The drain electrode is located on the upper surface of the channel layer and is located on the other side of the multi-threshold coupling gate structure along the gate length direction;

[0013] The isolation structure is located on one side of the source electrode along the gate length direction and on the other side of the drain electrode along the gate length direction, and extends from the upper surface of the channel layer to the inside of the buffer layer.

[0014] In an achievable manner, the multi-threshold coupled gate structure includes: a first gate and a plurality of first gate grooves spaced apart and distributed along the gate width direction, wherein:

[0015] Along the gate width direction, the lengths of the plurality of first gate grooves increase in sequence, and the interval between every two adjacent first gate grooves decreases gradually;

[0016] Each of the first gate grooves extends from the upper surface of the channel layer to the interior of the barrier layer;

[0017] The first gate is filled in the plurality of first gate grooves and covers spaces between the plurality of first gate grooves.

[0018] In one achievable manner, along the gate width direction, the length of the first gate gradually increases.

[0019] In an achievable manner, the multi-threshold coupled gate structure includes: a plurality of gate metals and a plurality of second gate grooves distributed at equal intervals along the gate width direction, wherein:

[0020] Each of the second gate grooves extends from the upper surface of the channel layer to the interior of the barrier layer, and a boss is formed between every two adjacent second gate grooves;

[0021] Each of the plurality of gate metals wraps around one of the bosses, and every two adjacent gate metals are in contact with each other;

[0022] Along the gate width direction, the work function of each gate metal in the plurality of gate metals gradually increases.

[0023] In an achievable manner, the plurality of gate metals include: a first gate metal, a second gate metal and a third gate metal sequentially arranged along the gate width direction;

[0024] The first gate metal comprises: Ti / Au stacked metal;

[0025] The second gate metal comprises: Cr / Au stacked metal or W / Cr stacked metal;

[0026] The third gate metal includes: Ni / Au stacked metal.

[0027] In an achievable manner, the multi-threshold coupled gate structure includes: a second gate and a plurality of gate dielectrics, wherein:

[0028] The plurality of gate dielectrics are distributed on the upper surface of the channel layer along the gate width direction, and every two adjacent gate dielectrics are in contact with each other;

[0029] Along the gate width direction, the dielectric constant of each gate dielectric in the plurality of gate dielectrics gradually increases;

[0030] The second gate covers the upper surfaces of the plurality of gate dielectrics.

[0031] In an achievable manner, the plurality of gate dielectrics include: a first gate dielectric, a second gate dielectric, and a third gate dielectric sequentially arranged along the gate width direction;

[0032] The material of the first gate dielectric includes: SiO 2 ;

[0033] The material of the second gate dielectric includes: Al 2 O 3 or HfSiO 4 ;

[0034] The material of the third gate dielectric includes: HfO 2 、ZrO 2 、 2 O 5 and La 2 O 3 One of them.

[0035] In one achievable manner, the material of the substrate layer includes: sapphire or SiC;

[0036] The material of the buffer layer includes: GaN;

[0037] The material of the barrier layer includes one or more of AlGaN, AlN and InAlN.

[0038] The second aspect of the present invention provides a method for preparing an N-face GaN radio frequency device based on a multi-threshold coupling technology, which is used for the N-face GaN radio frequency device based on a multi-threshold coupling technology provided by the first aspect of the present invention, comprising the following steps:

[0039] S1: growing a buffer layer, a barrier layer and a channel layer in sequence from bottom to top on the upper surface of the substrate layer; the material of the channel layer is N-face GaN; and a two-dimensional electron gas is formed at the interface between the channel layer and the barrier layer;

[0040] S2: preparing a multi-threshold coupled gate structure on the upper surface of the channel layer; the multi-threshold coupled gate structure is used to apply a threshold voltage that gradually changes along a gate width direction to the two-dimensional electron gas.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The N-face GaN radio frequency device based on multi-threshold coupling technology provided by the present invention applies a threshold voltage that gradually changes along the gate width direction to the two-dimensional electron gas through a multi-threshold coupling gate structure, so that the device can be gradually turned on along the gate width direction as the gate voltage gradually increases from negative to positive, thereby improving the transconductance flatness of the device. The gate length of the device provided in this embodiment is not restricted by the transconductance flatness, and the operating frequency can be increased by significantly shortening the gate length. It has a higher operating frequency and better linearity, meeting the future 6G terahertz frequency band communication requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic structural diagram of an N-face GaN radio frequency device based on a multi-threshold coupling technology provided by an embodiment of the present invention;

[0044] Figure 2a to Figure 2c is a structural schematic diagram of a multi-threshold coupled gate structure provided by an embodiment of the present invention;

[0045] Figure 3a to Figure 3b is a schematic structural diagram of a first gate trench provided by an embodiment of the present invention;

[0046] Figure 4a to Figure 4c is a structural schematic diagram of another multi-threshold coupled gate structure provided by an embodiment of the present invention;

[0047] Figure 5a to Figure 5b is a schematic structural diagram of a second gate trench provided by an embodiment of the present invention;

[0048] Figure 6a to Figure 6c It is a structural schematic diagram of another multi-threshold coupled gate structure provided by an embodiment of the present invention.

[0049] Reference numerals:

[0050] 1: substrate layer; 2: buffer layer; 3: barrier layer; 4: channel layer; 5: source; 6: drain; 7: isolation structure; 8: multi-threshold coupled gate structure; 811: first gate groove; 8111: first gradient sub-gate groove; 8112: second gradient sub-gate groove; 8113: third gradient sub-gate groove; 8114: fourth gradient sub-gate groove; 812: first gate electrode; 821: second gate groove; 8211: first equidistant sub-gate groove; 8212: second equidistant sub-gate groove; 8213: third equidistant sub-gate groove; 8214: fourth equidistant sub-gate groove; 822: gate metal; 8221: first gate metal; 8222: second gate metal; 8223: third gate metal; 831: gate dielectric; 8311: first gate dielectric; 8312: second gate dielectric; 8313: third gate dielectric; 832: second gate electrode. DETAILED DESCRIPTION

[0051] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0052] Embodiment 1

[0053] See also Figure 1 , Figure 1 It is a schematic diagram of the structure of an N-face GaN radio frequency device based on multi-threshold coupling technology provided in an embodiment of the present invention.

[0054] The N-face GaN radio frequency device based on multi-threshold coupling technology provided in this embodiment includes: a substrate layer 1, a buffer layer 2, a barrier layer 3, a channel layer 4, a source 5, a drain 6, an isolation structure 7 and a multi-threshold coupling gate structure 8. Among them, the substrate layer 1, the buffer layer 2, the barrier layer 3, the channel layer 4, and the multi-threshold coupling gate structure 8 are arranged in sequence from bottom to top. The source 5 is located on the upper surface of the channel layer 4, and is located on one side of the multi-threshold coupling gate structure 8 along the gate length direction. The drain 6 is located on the upper surface of the channel layer 4, and is located on the other side of the multi-threshold coupling gate structure 8 along the gate length direction. The isolation structure 7 is located on one side of the source 5 along the gate length direction and on the other side of the drain 6 along the gate length direction, and extends from the upper surface of the channel layer 4 to the inside of the buffer layer 2. The material of the channel layer 4 is N-face GaN. A two-dimensional electron gas (2DEG) is formed at the interface between the channel layer 4 and the barrier layer 3. The multi-threshold coupling gate structure 8 is used to apply a threshold voltage that gradually changes along the gate width direction to the two-dimensional electron gas.

[0055] In this embodiment, the multi-threshold coupled gate structure 8 is used to apply a threshold voltage that gradually increases or decreases along the gate width direction to the two-dimensional electron gas. The material of the substrate layer 1 includes: sapphire or SiC. The material of the buffer layer 2 includes: N-face GaN. The material of the barrier layer 3 includes: one or more of AlGaN, AlN and InAlN. Furthermore, the buffer layer 2 is Fe- or C-doped GaN. The channel layer 4 is an unintentionally doped N-face GaN. The gate width direction is the direction perpendicular to the line between the source 5 and the drain 6 in the horizontal plane, and the gate length direction is the direction of the line between the source 5 and the drain 6. The multi-threshold coupled gate structure 8 is located in the middle of the channel layer 4, and the source 5 and the drain 6 are respectively located on the left and right sides of the multi-threshold coupled gate structure 8, and there is a gap between the source 5 and the drain 6 and the multi-threshold coupled gate structure 8. The materials of the source 5 and the drain 6 both include Ti / Al / Ni / Au (20 / 100 / 10 / 50nm) stacked ohmic metal.

[0056] Specifically, the barrier layer 3 and the channel layer 4 form an N-face GaN-based heterojunction, the two-dimensional electron gas is located at the interface between the channel layer 4 and the barrier layer 3, and the N-face GaN HEMT device has a natural back barrier, which can enhance the suppression of the short channel effect. Moreover, by adjusting the thickness of the channel layer 4, the distance between the multi-threshold coupling gate structure 8 and the 2DEG channel can be adjusted. Without affecting the barrier, the distance between the multi-threshold coupling gate structure 8 and the two-dimensional electron gas channel is reduced by reducing the thickness of the channel layer 4, thereby enhancing the control ability of the multi-threshold coupling gate structure 8 and suppressing the short channel effect. In addition, since the multi-threshold coupling gate structure 8 applies a threshold voltage that gradually changes along the gate width direction to the two-dimensional electron gas, when a gate voltage is applied to the device, as the gate voltage gradually increases from negative to positive, the device is gradually turned on in the direction where the threshold voltage increases, thereby improving the transconductance flatness of the device. The gate length of the device provided in this embodiment is not restricted by the transconductance flatness, and the operating frequency can be increased by significantly shortening the gate length. The device provided in this embodiment has a higher operating frequency and better linearity, meeting the future 6G terahertz frequency band communication requirements.

[0057] This embodiment also provides a method for preparing an N-face GaN radio frequency device based on a multi-threshold coupling technology, which is used to prepare the N-face GaN radio frequency device based on a multi-threshold coupling technology provided in this embodiment. The preparation method comprises the following steps:

[0058] S1: growing a buffer layer 2, a barrier layer 3 and a channel layer 4 in order from bottom to top on the upper surface of the substrate layer 1. The material of the channel layer 4 is N-face GaN, and a two-dimensional electron gas is formed at the interface between the channel layer 4 and the barrier layer 3.

[0059] Specifically, a miscut sapphire or C-SiC material is obtained as the substrate layer 1, and a buffer layer 2, a barrier layer 3 and a channel layer 4 are grown on the substrate layer 1 by metal organic chemical vapor deposition (MOCVD). The barrier layer 3 and the channel layer 4 form a heterojunction.

[0060] In this embodiment, the steps between step S1 and step S2 further include:

[0061] The gate region, source region and drain region are defined on the upper surface of the channel layer 4, wherein the gate region is located in the middle of the upper surface of the channel layer 4, the source region and the drain region are respectively located on the upper surface of the channel layer 4 on both sides of the gate region, and the source region and the drain region are spaced apart from the gate region. The source metal and the drain metal are respectively prepared at both ends of the upper surface of the channel layer 4 by electron beam evaporation equipment, and rapid thermal annealing is performed in a nitrogen atmosphere at a temperature of 800 to 900°C for 20 to 40 seconds. After the annealing, the source 5 and the drain 6 are obtained. By ion implantation equipment, N ions are implanted on the side of the source region and the drain region away from the gate region, and the ion implantation depth is greater than the sum of the thickness of the buffer layer 2, the barrier layer 3 and the channel layer 4, forming an isolation structure 7 to isolate the active area of ​​the device.

[0062] S2: preparing a multi-threshold coupling gate structure 8 on the upper surface of the channel layer 4; the multi-threshold coupling gate structure 8 is used to apply a threshold voltage that gradually changes along the gate width direction to the two-dimensional electron gas.

[0063] Specifically, a multi-threshold coupled gate structure 8 is prepared in the gate region. The threshold coupled gate structure 8 is used to apply a threshold voltage that gradually changes along the gate width direction to the two-dimensional electron gas, so that when the gate voltage is applied to the device, as the gate voltage gradually increases from negative to positive, the device is gradually turned on along the gate width direction, thereby improving the transconductance flatness of the device.

[0064] The N-face GaN RF device based on the multi-threshold coupling technology provided in this embodiment applies a threshold voltage that gradually changes along the gate width direction to the two-dimensional electron gas through the multi-threshold coupling gate structure 8, so that the device can be gradually turned on in the direction where the threshold voltage increases as the gate voltage gradually increases from negative to positive, thereby improving the transconductance flatness of the device. The gate length of the device provided in this embodiment is not restricted by the transconductance flatness, and the operating frequency can be increased by significantly shortening the gate length. It has a higher operating frequency and better linearity, meeting the future 6G terahertz frequency band communication requirements.

[0065] Embodiment 2

[0066] On the basis of Example 1, this embodiment provides an N-face GaN RF device based on multi-threshold coupling technology, including: a substrate layer 1, a buffer layer 2, a barrier layer 3, a channel layer 4, a source 5, a drain 6, an isolation structure 7 and a multi-threshold coupling gate structure 8, the relative position relationship of which is the same as that of Example 1 and will not be repeated here.

[0067] See also Figure 2a to Figure 2c and Figure 3a to Figure 3b ,in, Figure 2a is a front view of a multi-threshold coupled gate structure provided by an embodiment of the present invention, Figure 2b is a top view of a multi-threshold coupled gate structure provided by an embodiment of the present invention, Figure 2c A multi-threshold coupled gate structure provided by an embodiment of the present invention is Figure 2b The cross-section of the A-A' plane, Figure 3a is a top view of a first gate groove provided by an embodiment of the present invention, Figure 3b The first gate groove edge provided by the embodiment of the present invention Figure 3a BB' plane cross-sectional view. In this embodiment, the multi-threshold coupling gate structure 8 includes: a first gate 812 and a plurality of first gate grooves 811 spaced apart along the gate width direction. Among them, along the gate width direction, the lengths of the plurality of first gate grooves 811 increase successively, and the interval between each two adjacent first gate grooves 811 gradually decreases, and the length of the first gate 812 gradually increases. Each first gate groove 811 extends from the upper surface of the channel layer 4 to the interior of the barrier layer 3. The first gate 812 is filled in the plurality of first gate grooves 811 and covers the intervals between the plurality of first gate grooves 811.

[0068] For further information, see Figure 3a to Figure 3b The plurality of first gate grooves 811 include: a first gradient sub-gate groove 8111, a second gradient sub-gate groove 8112, a third gradient sub-gate groove 8113, and a fourth gradient sub-gate groove 8114, which are sequentially distributed along the gate width direction. The width and depth of the first gradient sub-gate groove 8111, the second gradient sub-gate groove 8112, the third gradient sub-gate groove 8113, and the fourth gradient sub-gate groove 8114 are the same, and the interval between the first gradient sub-gate groove 8111 and the second gradient sub-gate groove 8112 is d 11 The interval between the second gradient sub-gate groove 8112 and the third gradient sub-gate groove 8113 is d 12 The interval between the third gradient sub-gate groove 8113 and the fourth gradient sub-gate groove 8114 is d 13 , d 13 Less than d 12 Less than d 11 , and the lengths of the first gradient sub-gate groove 8111, the second gradient sub-gate groove 8112, the third gradient sub-gate groove 8113, and the fourth gradient sub-gate groove 8114 increase in sequence. Figure 3a As shown, the top-view shapes of the first gradient sub-gate groove 8111, the second gradient sub-gate groove 8112, the third gradient sub-gate groove 8113, and the fourth gradient sub-gate groove 8114 are all isosceles trapezoids. Figure 2a and 2bAs shown, the first gate 812 is a T-shaped gate, and the first gate 812 extends to the surface of the channel layer 4 along the gate length direction. The top view shape of the first gate 812 is an isosceles trapezoid. Along the gate width direction, the length of the first gate 812 increases synchronously with the first gate grooves 811. In this embodiment, the length is in the gate length direction, the width is in the gate width direction, and the depth is in the up and down direction. Specifically, the interval between every two adjacent gate grooves is the channel. Since d 13 Less than d 12 Less than d 11 Therefore, the channel of the device provided in this embodiment gradually narrows along the gate width direction.

[0069] This embodiment provides a method for preparing an N-face GaN radio frequency device based on a multi-threshold coupling technology, comprising:

[0070] Step 1: A buffer layer 2, a barrier layer 3 and a channel layer 4 are grown sequentially from bottom to top on the upper surface of the substrate layer 1. The material of the channel layer 4 is N-face GaN, and a two-dimensional electron gas is formed at the interface between the channel layer 4 and the barrier layer 3.

[0071] Step 2: Define the gate region, source region and drain region on the upper surface of the channel layer 4, wherein the gate region is located in the middle of the upper surface of the channel layer 4, the source region and the drain region are respectively located on the upper surface of the channel layer 4 on both sides of the gate region, and the source region and the drain region are spaced apart from the gate region. Use electron beam evaporation equipment to prepare source metal and drain metal at both ends of the upper surface of the channel layer 4, and perform rapid thermal annealing in a nitrogen atmosphere at a temperature of 800 to 900°C for 20 to 40 seconds. After the annealing, the source 5 and the drain 6 are obtained. Use ion implantation equipment to implant N ions on the side of the source region and the drain region away from the gate region. The ion implantation depth is greater than the sum of the thickness of the buffer layer 2, the barrier layer 3 and the channel layer 4 to form an isolation structure 7 to isolate the device active area.

[0072] Step three: preparing a multi-threshold coupled gate structure 8 on the upper surface of the channel layer 4 .

[0073] Specifically, electron beam lithography is used to define a nanochannel array pattern whose length gradually decreases along the gate width direction, and a Cl-based etching device is used to etch an arrayed groove structure, and the etching depth is located below the heterojunction interface formed by the barrier layer 3 and the channel layer 4, forming a first gradient sub-gate groove 8111, a second gradient sub-gate groove 8112, a third gradient sub-gate groove 8113, and a fourth gradient sub-gate groove 8114. Using an electron beam evaporation device, Cr / Au (25 / 500nm) laminated metal is evaporated in the gate region, and the first gate 812 is formed after peeling.

[0074] Specifically, the two-dimensional electron gas is more easily depleted where the channel is narrow. In this embodiment, a gradually narrowing channel is formed by gradually reducing the interval between every two adjacent first gate grooves 811 along the gate width direction, and the lengths of several first gate grooves 811 are successively increased along the gate width direction, so that the length of the first gate 812 along the gate width direction is gradually increased, thereby forming different threshold voltages. When the gate voltage gradually increases from negative to positive, the device is gradually turned on along the gate width direction (the direction in which the channel gradually narrows), thereby improving the transconductance flatness of the device.

[0075] Embodiment 3

[0076] On the basis of Example 1, this embodiment provides an N-face GaN RF device based on multi-threshold coupling technology, including: a substrate layer 1, a buffer layer 2, a barrier layer 3, a channel layer 4, a source 5, a drain 6, an isolation structure 7 and a multi-threshold coupling gate structure 8, the relative position relationship of which is the same as that of Example 1 and will not be repeated here.

[0077] See also Figure 4a to Figure 4c and Figure 5a to Figure 5b ,in, Figure 4a is a front view of a multi-threshold coupled gate structure provided by an embodiment of the present invention, Figure 4b is a top view of a multi-threshold coupled gate structure provided by an embodiment of the present invention, Figure 4c A multi-threshold coupled gate structure provided by an embodiment of the present invention is Figure 4b The cross-sectional view of the C-C' plane, Figure 5a is a top view of a second gate groove provided by an embodiment of the present invention, Figure 5b The second gate groove edge provided by the embodiment of the present invention Figure 5a sectional view of the D-D' plane. In the present embodiment, the multi-threshold coupled gate structure 8 comprises: a plurality of gate metals 822 and a plurality of second gate grooves 821 equally spaced along the gate width direction. Each second gate groove 821 extends from the upper surface of the channel layer 4 to the interior of the barrier layer 3, and a boss is formed between every two adjacent second gate grooves 821. Each gate metal 822 of the plurality of gate metals 822 wraps a boss, and every two adjacent gate metals 822 contact each other. Along the gate width direction, the work function of each gate metal 822 of the plurality of gate metals 822 gradually increases.

[0078] Combination Figure 4b , Figure 4c , Figure 5a and Figure 5bIn this embodiment, the plurality of second gate grooves 821 include: a first equidistant sub-gate groove 8211, a second equidistant sub-gate groove 8212, a third equidistant sub-gate groove 8213 and a fourth equidistant sub-gate groove 8214 which are equally spaced along the gate width direction. The plurality of gate metals 822 include: a first gate metal 8221, a second gate metal 8222 and a third gate metal 8223 which are sequentially arranged along the gate width direction. The first equidistant sub-gate groove 8211 and the fourth equidistant sub-gate groove 8214 are respectively arranged at two ends of the channel layer 4 along the gate width direction, the second equidistant sub-gate groove 8212 and the third equidistant sub-gate groove 8213 have the same width, and the widths of the first equidistant sub-gate groove 8211 and the fourth equidistant sub-gate groove 8214 are both half of the width of the third equidistant sub-gate groove 8213. The depth and length of the first equidistant sub-gate groove 8211, the second equidistant sub-gate groove 8212, the third equidistant sub-gate groove 8213 and the fourth equidistant sub-gate groove 8214 are equal, and a first convex platform is formed between the first equidistant sub-gate groove 8211 and the second equidistant sub-gate groove 8212, a second convex platform is formed between the second equidistant sub-gate groove 8212 and the third equidistant sub-gate groove 8213, and a fourth convex platform is formed between the third equidistant sub-gate groove 8213 and the fourth equidistant sub-gate groove 8214. The first equidistant sub-gate groove 8211, the second equidistant sub-gate groove 8212, the third equidistant sub-gate groove 8213 and the fourth equidistant sub-gate groove 8214 are equally spaced, that is, the width d of the first convex platform 21 , the width of the second boss d 22 , the width of the third boss d 23 The first gate metal 8221, the second gate metal 8222 and the third gate metal 8223 respectively wrap the first boss, the second boss and the third boss, and the width of each gate metal is the same. The first gate metal 8221 is used as an example for explanation. The first gate metal 8221 wraps the first boss, that is, the first gate metal 8221 surrounds both sides of the first boss and covers the top of the first boss. It should be understood that a part of the first gate metal 8221 is in the first equidistant sub-gate groove 8211, a part is in the second equidistant sub-gate groove 8212, and a part is on the top of the first boss. In addition, the widths of the parts of the first gate metal 8221 on both sides of the first boss are equal. Only the first gate metal 8221 is filled in the first equidistant sub-gate groove 8211, and only the third gate metal 8223 is filled in the fourth equidistant sub-gate groove 8214. The side of the second equidistant sub-gate groove 8212 close to the first equidistant sub-gate groove 8211 is the first gate metal 8221, and the side of the second equidistant sub-gate groove 8212 close to the third equidistant sub-gate groove 8213 is the second gate metal 8222. The side of the third equidistant sub-gate groove 8213 close to the second equidistant sub-gate groove 8212 is the second gate metal 8222, and the side of the third equidistant sub-gate groove 8213 close to the fourth equidistant sub-gate groove 8214 is the third gate metal 8223.

[0079] In this embodiment, the first gate metal 8221 includes: Ti / Au laminated metal. The second gate metal 8222 includes: Cr / Au laminated metal or W / Cr laminated metal. The third gate metal 8223 includes: Ni / Au laminated metal. Taking the first gate metal 8221 as a Ti / Au laminated metal as an example, the portion of the first gate metal 8221 close to the first boss is Ti metal, and the portion away from the first boss is Au metal.

[0080] like Figure 2a and 2b As shown, the first gate metal 8221, the second gate metal 8222 and the third gate metal 8223 form a complete gate, and the first gate metal 8221, the second gate metal 8222 and the third gate metal 8223 are all T-shaped gates, and the first gate metal 8221, the second gate metal 8222 and the third gate metal 8223 have the same shape and structure, and are all rectangular when viewed from above.

[0081] This embodiment provides a method for preparing an N-face GaN radio frequency device based on a multi-threshold coupling technology, comprising:

[0082] Step 1: A buffer layer 2, a barrier layer 3 and a channel layer 4 are grown sequentially from bottom to top on the upper surface of the substrate layer 1. The material of the channel layer 4 is N-face GaN, and a two-dimensional electron gas is formed at the interface between the channel layer 4 and the barrier layer 3.

[0083] Step 2: Define the gate region, source region and drain region on the upper surface of the channel layer 4, wherein the gate region is located in the middle of the upper surface of the channel layer 4, the source region and the drain region are respectively located on the upper surface of the channel layer 4 on both sides of the gate region, and the source region and the drain region are spaced apart from the gate region. Use electron beam evaporation equipment to prepare source metal and drain metal at both ends of the upper surface of the channel layer 4, and perform rapid thermal annealing in a nitrogen atmosphere at a temperature of 800 to 900°C for 20 to 40 seconds. After the annealing, the source 5 and the drain 6 are obtained. Use ion implantation equipment to implant N ions on the side of the source region and the drain region away from the gate region. The ion implantation depth is greater than the sum of the thickness of the buffer layer 2, the barrier layer 3 and the channel layer 4 to form an isolation structure 7 to isolate the device active area.

[0084] Step three: preparing a multi-threshold coupled gate structure 8 on the upper surface of the channel layer 4 .

[0085] Specifically, electron beam lithography is used to define a nanochannel array pattern whose length gradually decreases along the gate width direction, and a Cl-based etching device is used to etch an arrayed groove structure, and the etching depth is located below the heterojunction interface formed by the barrier layer 3 and the channel layer 4, forming a first equidistant sub-gate groove 8211, a second equidistant sub-gate groove 8212, a third equidistant sub-gate groove 8213 and a fourth equidistant sub-gate groove 8214. Using an electron beam evaporation device, Ti / Au (30 / 600nm), Cr / Au (25 / 500nm) and Ni / Au (30 / 300nm) are sequentially evaporated in the gate region along the gate width direction, and the first gate metal 8221, the second gate metal 8222 and the third gate metal 8223 are obtained after stripping.

[0086] Specifically, the larger the work function of the gate metal, the more positive the threshold voltage. In this embodiment, along the gate width direction, the work function of each gate metal 822 in the plurality of gate metals 822 gradually increases, and the threshold voltage gradually shifts positively. When the gate voltage gradually increases from negative to positive, the device gradually turns on along the gate width direction (the direction in which the work function increases), thereby improving the transconductance flatness of the device.

[0087] Embodiment 4

[0088] On the basis of Example 1, this embodiment provides an N-face GaN RF device based on multi-threshold coupling technology, including: a substrate layer 1, a buffer layer 2, a barrier layer 3, a channel layer 4, a source 5, a drain 6, an isolation structure 7 and a multi-threshold coupling gate structure 8, the relative position relationship of which is the same as that of Example 1 and will not be repeated here.

[0089] See also Figure 6a to Figure 6c ,in, Figure 6a is a front view of a multi-threshold coupled gate structure provided by an embodiment of the present invention, Figure 6b is a top view of a multi-threshold coupled gate structure provided by an embodiment of the present invention, Figure 6c A multi-threshold coupled gate structure provided by an embodiment of the present invention is Figure 6b 8 is a cross-sectional view of the E-E' plane. In this embodiment, the multi-threshold coupled gate structure 8 includes: a second gate 832 and a plurality of gate dielectrics 831. Among them, the plurality of gate dielectrics 831 are distributed on the upper surface of the channel layer 4 along the gate width direction, and every two adjacent gate dielectrics 831 are in contact with each other. Along the gate width direction, the dielectric constant of each gate dielectric 831 in the plurality of gate dielectrics 831 gradually increases. The second gate 832 covers the upper surface of the plurality of gate dielectrics 831.

[0090] In this embodiment, the plurality of gate dielectrics 831 include: a first gate dielectric 8311, a second gate dielectric 8312, and a third gate dielectric 8313 arranged in sequence along the gate width direction. The material of the first gate dielectric 8311 includes: SiO 2The material of the second gate dielectric 8312 includes: Al 2 O 3 or HfSiO 4 The material of the third gate dielectric 8313 includes: HfO 2 、ZrO 2 、 2 O 5 and La 2 O 3 The second gate 832 covers the upper surfaces of the first gate dielectric 8311, the second gate dielectric 8312 and the third gate dielectric 8313. The material of the second gate 832 is Cr / Au laminated metal with a thickness of 25 / 500 nm.

[0091] This embodiment provides a method for preparing an N-face GaN radio frequency device based on a multi-threshold coupling technology, comprising:

[0092] Step 1: A buffer layer 2, a barrier layer 3 and a channel layer 4 are grown sequentially from bottom to top on the upper surface of the substrate layer 1. The material of the channel layer 4 is N-face GaN, and a two-dimensional electron gas is formed at the interface between the channel layer 4 and the barrier layer 3.

[0093] Step 2: Define the gate region, source region and drain region on the upper surface of the channel layer 4, wherein the gate region is located in the middle of the upper surface of the channel layer 4, the source region and the drain region are respectively located on the upper surface of the channel layer 4 on both sides of the gate region, and the source region and the drain region are spaced apart from the gate region. Use electron beam evaporation equipment to prepare source metal and drain metal at both ends of the upper surface of the channel layer 4, and perform rapid thermal annealing in a nitrogen atmosphere at a temperature of 800 to 900°C for 20 to 40 seconds. After the annealing, the source 5 and the drain 6 are obtained. Use ion implantation equipment to implant N ions on the side of the source region and the drain region away from the gate region. The ion implantation depth is greater than the sum of the thickness of the buffer layer 2, the barrier layer 3 and the channel layer 4 to form an isolation structure 7 to isolate the device active area.

[0094] Step three: preparing a multi-threshold coupled gate structure 8 on the upper surface of the channel layer 4 .

[0095] Specifically, a selective epitaxial growth technique is then used to grow the first gate dielectric 8311, the second gate dielectric 8312, and the third gate dielectric 8313 in the gate region along the gate width direction. Cr / Au stacked metal is evaporated on the upper surfaces of the first gate dielectric 8311, the second gate dielectric 8312, and the third gate dielectric 8313 using an electron beam evaporation device to obtain the second gate 832.

[0096] Specifically, the larger the dielectric constant of the gate dielectric is, the more positive the threshold voltage is. Therefore, in this embodiment, a plurality of gate dielectrics with increasing dielectric constants are sequentially arranged along the gate width direction, and the threshold voltage will gradually shift positively. When the gate voltage gradually increases from negative to positive, the device is gradually turned on along the gate width direction (the direction of increasing dielectric constant), thereby improving the transconductance flatness of the device.

[0097] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. N-face GaN RF device based on multi-threshold coupling technology, characterized in that: include: The substrate layer, buffer layer, barrier layer, channel layer, and multi-threshold coupled gate structure are arranged in sequence from bottom to top, wherein: The material of the channel layer is N-face GaN; A two-dimensional electron gas is formed at the interface between the channel layer and the barrier layer; The multi-threshold coupled gate structure is used to apply a threshold voltage that gradually changes along a gate width direction to the two-dimensional electron gas.

2. The N-face GaN radio frequency device based on multi-threshold coupling technology according to claim 1, characterized in that: Also includes: Source, drain and isolation structures; The source electrode is located on the upper surface of the channel layer and is located on one side of the multi-threshold coupling gate structure along the gate length direction; The drain electrode is located on the upper surface of the channel layer and is located on the other side of the multi-threshold coupling gate structure along the gate length direction; The isolation structure is located on one side of the source electrode along the gate length direction and on the other side of the drain electrode along the gate length direction, and extends from the upper surface of the channel layer to the inside of the buffer layer.

3. The N-face GaN radio frequency device based on multi-threshold coupling technology according to claim 1, characterized in that: The multi-threshold coupled gate structure comprises: a first gate and a plurality of first gate grooves spaced apart and distributed along the gate width direction, wherein: Along the gate width direction, the lengths of the plurality of first gate grooves increase in sequence, and the interval between every two adjacent first gate grooves decreases gradually; Each of the first gate grooves extends from the upper surface of the channel layer to the interior of the barrier layer; The first gate is filled in the plurality of first gate grooves and covers spaces between the plurality of first gate grooves.

4. The N-face GaN radio frequency device based on multi-threshold coupling technology according to claim 3, characterized in that: Along the gate width direction, the length of the first gate gradually increases.

5. The N-face GaN radio frequency device based on multi-threshold coupling technology according to claim 1, characterized in that: The multi-threshold coupled gate structure comprises: a plurality of gate metals and a plurality of second gate grooves distributed at equal intervals along the gate width direction, wherein: Each of the second gate grooves extends from the upper surface of the channel layer to the interior of the barrier layer, and a boss is formed between every two adjacent second gate grooves; Each of the plurality of gate metals wraps around one of the bosses, and every two adjacent gate metals are in contact with each other; Along the gate width direction, the work function of each gate metal in the plurality of gate metals gradually increases.

6. The N-face GaN radio frequency device based on multi-threshold coupling technology according to claim 5, characterized in that: The plurality of gate metals include: a first gate metal, a second gate metal and a third gate metal sequentially arranged along the gate width direction; The first gate metal comprises: Ti / Au stacked metal; The second gate metal comprises: Cr / Au stacked metal or W / Cr stacked metal; The third gate metal includes: Ni / Au stacked metal.

7. The N-face GaN radio frequency device based on multi-threshold coupling technology according to claim 1, characterized in that: The multi-threshold coupled gate structure includes: a second gate and a plurality of gate dielectrics, wherein: The plurality of gate dielectrics are distributed on the upper surface of the channel layer along the gate width direction, and every two adjacent gate dielectrics are in contact with each other; Along the gate width direction, the dielectric constant of each gate dielectric in the plurality of gate dielectrics gradually increases; The second gate covers the upper surfaces of the plurality of gate dielectrics.

8. The N-face GaN radio frequency device based on multi-threshold coupling technology according to claim 7, characterized in that: The plurality of gate dielectrics include: a first gate dielectric, a second gate dielectric and a third gate dielectric sequentially arranged along the gate width direction; The material of the first gate dielectric includes: SiO2; The material of the second gate dielectric includes: Al2O3 or HfSiO4; The material of the third gate dielectric includes: one of HfO2, ZrO2, Ta2O5 and La2O3.

9. The N-face GaN radio frequency device based on multi-threshold coupling technology according to claim 1, characterized in that: The material of the substrate layer includes: sapphire or SiC; The material of the buffer layer includes: GaN; The material of the barrier layer includes one or more of AlGaN, AlN and InAlN.

10. A method for preparing an N-face GaN radio frequency device based on multi-threshold coupling technology, characterized in that: The method for preparing the N-face GaN radio frequency device based on the multi-threshold coupling technology according to any one of claims 1 to 9 comprises the following steps: S1: growing a buffer layer, a barrier layer and a channel layer in sequence from bottom to top on the upper surface of the substrate layer; the material of the channel layer is N-face GaN; and a two-dimensional electron gas is formed at the interface between the channel layer and the barrier layer; S2: preparing a multi-threshold coupled gate structure on the upper surface of the channel layer; the multi-threshold coupled gate structure is used to apply a threshold voltage that gradually changes along a gate width direction to the two-dimensional electron gas.

Images