阅读说明：本技术 一种抑制短沟道效应的p-GaN HEMT器件 (P-GaN HEMT device for inhibiting short channel effect ) 是由 郑崇芝 信亚杰 段力冬 王方洲 孙瑞泽 张波 于 2021-08-20 设计创作，主要内容包括：本发明属于半导体器件及集成电路技术领域,具体的说是涉及一种抑制短沟道效应的p-GaN HEMT器件。与常规的p-GN HEMT器件不同的是,本发明的位于AlGaN势垒层上方的p-GaN层不仅包括厚度较大的、使器件实现增强型器件功能的p-GaN层,还包括厚度较小的经过凹槽刻蚀的p-GaN。当器件漏极的电压较高时,凹槽刻蚀的p-GaN层下方的2DEG耗尽,能够承受漏极电压,从而使厚度较大的p-GaN层一侧的电位钳位,从而降低短沟道效应。本发明的器件能降低处在高漏偏压时阈值电压的减小量,同时能够提升击穿电压。另外,本发明工艺与传统p-GaN HEMT器件制备工艺完全兼容。(The invention belongs to the technical field of semiconductor devices and integrated circuits, and particularly relates to a p-GaN HEMT device for inhibiting a short channel effect. Different from the conventional p-GN HEMT device, the p-GaN layer positioned above the AlGaN barrier layer not only comprises a p-GaN layer with larger thickness and enabling the device to realize the function of an enhancement device, but also comprises p-GaN with smaller thickness and subjected to groove etching. When the voltage of the drain electrode of the device is high, the 2DEG below the p-GaN layer etched by the groove is exhausted and can bear the voltage of the drain electrode, so that the potential on one side of the p-GaN layer with the larger thickness is clamped, and the short channel effect is reduced. The device can reduce the reduction of threshold voltage when in high leakage bias voltage, and can improve breakdown voltage at the same time. In addition, the process of the invention is completely compatible with the preparation process of the traditional p-GaN HEMT device.)

1. A p-GaN HEMT device for inhibiting short channel effect comprises a substrate layer (1), a buffer layer (2), a GaN channel layer (3), an Al (in) GaN layer barrier layer (4), a p-GaN layer (5) and a passivation layer (7) which are sequentially stacked from the lower layer to the upper layer; the GaN layer (3) and the Al (in) GaN layer (4) form a heterojunction; one end of the upper layer of the Al (in) GaN layer (4) is provided with a first metal electrode (10), the other end is provided with a second metal electrode (9), and ohmic contact is formed between the first metal electrode (10) and the second metal electrode (9) and the Al (in) GaN layer (4); the p-GaN layer (5) is of a raised structure with a raised middle part, one side of the two sides of the raised structure in the middle part of the p-GaN layer (5) close to the first metal electrode (10) is defined as a source side p-GaN layer (12), and one side close to the second metal electrode (9) is defined as a drain side p-GaN layer (11); the upper surface of the p-GaN layer (5) is covered with a third metal electrode (6), and Schottky contact or ohmic contact is formed between the third metal electrode (6) and the p-GaN layer (5); the third metal electrode (6) is used as a grid electrode of the device; a passivation layer (7) covers the upper surfaces of the Al (in) GaN layer barrier layer (4) and the third metal electrode (6); the first metal electrode (10) extends to be close to the second metal electrode (9) along the upper surface of the passivation layer (7), and the first metal electrode (10) is used as a source electrode of the device; the second metal electrode (9) extends along the upper surface of the passivation layer (7) to one side close to the first metal electrode (10), an isolation layer (8) is arranged between the first metal electrode (10) and the second metal electrode (9), and the second metal electrode (9) is used as a drain electrode of the device.

2. The p-GaN HEMT device for suppressing the short channel effect according to claim 1, wherein the length of said drain side p-GaN layer (11) is 0 μm or more.

3. The p-GaN HEMT device for suppressing the short channel effect according to claim 1, wherein the substrate (1) is made of one of Si, SiC and sapphire.

4. The p-GaN HEMT device for inhibiting the short channel effect according to claim 1, wherein the buffer layer (2) is made of a material containing one or more of GaN, AlGaN and AlN.

5. The p-GaN HEMT device for suppressing the short channel effect according to claim 1, wherein the passivation layer (7) is made of one of nitride, aluminum oxide and AlN.

6. The p-GaN HEMT device for suppressing the short channel effect as claimed in claim 1, wherein the material used for the isolation layer (8) is an oxide or a nitride.

Technical Field

The invention belongs to the technical field of semiconductor devices and integrated circuits, and particularly relates to a p-GaN HEMT device for inhibiting a short channel effect.

Background

Gallium nitride (GaN) is a representative third generation wide bandgap semiconductor material and has received much attention from researchers in various countries. The GaN material has the characteristics of large forbidden bandwidth, high saturated electron drift velocity, small dielectric constant, good chemical stability and the like, so that compared with a Si-based device, the GaN-based HEMT device has the excellent performances of lower on-resistance, smaller parasitic capacitance, higher breakdown voltage and the like, and can meet the application requirements of a next generation system on higher power, smaller volume and higher frequency of a semiconductor device.

However, the conventional AlGaN/GaN-based heterojunction device is a depletion device because a natural two-dimensional electron gas conduction channel is formed due to the spontaneous polarization and piezoelectric polarization effects. However, since depletion mode devices increase the complexity and reliability of the driver circuit design in applications, enhanced GaN devices are needed to meet the application requirements. Of the several commonly used enhancement technologies, p-GaN enhancement devices have been commercialized. The p-GaN HEMT device is realized by extending a p-type GaN layer on a grid region, the p-GaN and the AlGaN/GaN heterojunction form a PiN-like structure, and an electric field built in the diode-like structure can eliminate the action of an electric field generated by spontaneous polarization and piezoelectric polarization in the AlGaN/GaN heterojunction, so that two-dimensional electron gas below the grid can be exhausted, and the device has normally-off characteristics. Because the specific Metal/p-GaN/AlGaN grid structure of the p-GaN HEMTs limits the grid working voltage range, the working voltage range of the grid of the current common p-GaN HEMTs is about-4 to 6V. Meanwhile, in the device design, in order to reduce the on-resistance of the device during operation, the length of the gate of the device is reduced to reduce the on-resistance. However, when the gate channel length of the device is small, a short channel effect, i.e., a drain induced barrier lowering effect (DIBL), occurs, resulting in a decrease in threshold voltage, and breakdown voltage.

According to the previous research result, when the p-GaN HEMT device is under high leakage bias voltage, the threshold voltage is reduced by about 0.3V relative to the low leakage bias voltage, and the phenomenon that the device is easily triggered by mistake during use is caused. Therefore, a p-GaN HEMT device capable of suppressing the short channel effect is urgently needed to improve the reliability and stability of the p-GaN HEMT device in practical use.

Disclosure of Invention

The invention aims to solve the problems of low threshold voltage and breakdown voltage of the traditional short-channel p-GaN HEMT device and provides a device for inhibiting the short-channel effect. The p-GaN HEMT device has the advantages of no influence on normal operation of the device, more stable threshold voltage, higher breakdown voltage and complete compatibility with the traditional preparation process.

The technical scheme of the invention is as follows:

a p-GaN HEMT device for inhibiting short channel effect comprises a substrate layer 1, a buffer layer 2, a GaN channel layer 3, an Al (in) GaN layer barrier layer 4, a p-GaN layer 5 and a passivation layer 7 which are sequentially stacked from the lower layer to the upper layer; the GaN layer 3 and the al (in) GaN layer 4 form a heterojunction; one end of the upper layer of the Al (in) GaN layer 4 is provided with a first metal electrode 10, the other end is provided with a second metal electrode 9, and ohmic contact is formed between the first metal electrode 10 and the second metal electrode 9 and the Al (in) GaN layer 4; the p-GaN layer 5 is of a raised structure with a raised middle part (formed by partial groove etching), one side of two sides of the raised structure in the middle part of the p-GaN layer 5, which is close to the first metal electrode 10, is defined as a source side p-GaN layer 12, and one side close to the second metal electrode 9 is defined as a drain side p-GaN layer 11; the upper surface of the p-GaN layer 5 is covered with a third metal electrode 6, and Schottky contact or ohmic contact is formed between the third metal electrode 6 and the p-GaN layer 5; the third metal electrode 6 is used as a grid electrode of the device; a passivation layer 7 covers the upper surfaces of the Al (in) GaN layer barrier layer 4 and the third metal electrode 6; the first metal electrode 10 extends to be close to the second metal electrode 9 along the upper surface of the passivation layer 7, and the first metal electrode 10 is used as a source electrode of the device; the second metal electrode 9 extends along the upper surface of the passivation layer 7 to a side close to the first metal electrode 10, there is a separation layer 8 between the first metal electrode 10 and the second metal electrode 9, and the second metal electrode 9 serves as a drain electrode of the device.

Further, the length of the drain side p-GaN layer 11 is 0 μm or more.

Further, the substrate 1 is made of one of Si, SiC, and sapphire.

Furthermore, the buffer layer 2 is made of one or more materials selected from GaN, AlGaN, and AlN.

Further, the passivation layer 7 is made of one of nitride, aluminum oxide and AlN.

Further, the material used for the isolation layer 8 is oxide or nitride.

The invention has the beneficial effects that: the p-GaN layer positioned above the AlGaN barrier layer not only comprises a p-GaN layer with larger thickness and enabling the device to realize the function of an enhancement device, but also comprises p-GaN with smaller thickness and etched through the groove. When the voltage of the drain electrode of the device is high, the 2DEG below the p-GaN layer etched by the groove is exhausted and can bear the voltage of the drain electrode, so that the potential on one side of the p-GaN layer with the larger thickness is clamped, and the short channel effect is reduced. The device can reduce the reduction of threshold voltage when the leakage bias voltage is high, and can improve the breakdown voltage. In addition, the process of the invention is completely compatible with the preparation process of the traditional p-GaN HEMT device.

Drawings

FIG. 1(a) is a schematic diagram of the structure of a conventional p-GaN HEMT device; (b) the invention provides a structural schematic diagram of a p-GaN HEMT device for inhibiting short channel effect.

FIG. 2(a) is an equivalent model of the device of the present invention, and (b) is a potential V of the device of the present invention_CThe condition of the drain-source voltage changes.

FIG. 3(d) shows different thicknesses T of the present invention_p2The threshold voltage of the p-GaN layer device etched by the groove is changed along with the change of the drain voltage, and (e) the breakdown voltage and the DIBL parameter are changed along with the change of the thickness.

FIG. 4 shows the present invention with different lengths G_rThe threshold voltage of the groove-etched p-GaN layer device changes along with the change of the drain voltage, (b) the breakdown voltage and the DIBL parameter change along with the length G_rChange and change of the situation.

FIG. 5 shows a cross-sectional view of a trench with different trenches according to the present inventionLength L_gThe threshold voltage of the p-GaN layer device changes along with the change of the drain voltage, and (b) the breakdown voltage and the DIBL parameter change along with the channel length L_gChange and change of the situation.

Fig. 6(a) transfer characteristic curves of the conventional p-GaN HEMT device and the device of the present invention, (b) the case where the threshold voltages of the conventional p-GaN HEMT device and the device of the present invention change with the drain voltage, (c) transfer characteristic curve of the conventional p-GaN HEMT device with a change in the exponential range, and (d) transfer characteristic curve of the p-GaN HEMT device of the present invention with a change in the exponential range.

FIG. 7 is a comparison of the static I-V characteristics of the present invention with a conventional p-GaN HEMT device; (a) outputting a characteristic curve; (b) breakdown characteristic curve; (c) the variation of the conduction band energy level in the x-direction at the channel.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the p-GaN layer on the AlGaN barrier layer according to the present invention includes not only the p-GaN layer 5 having a large thickness, which enables the device to perform an enhancement device function, but also the groove-etched p-GaN layers 11 and 12 having a small thickness, as compared to the conventional p-GaN HEMT device. When the voltage of the drain electrode of the device is high, the 2DEG below the p-GaN layer etched by the groove is exhausted and can bear the voltage of the drain electrode, so that the potential on one side of the p-GaN layer with the large thickness is clamped, and the short channel effect is reduced.

The working principle of the p-GaN HEMT device for inhibiting the short channel effect is as follows:

the device equivalent model of the present invention is shown in FIG. 2(a), and comprises a high threshold voltage device HEMT1 and a low threshold voltage HEMT 2. The drain of HEMT1 and the threshold of HEMT2 are tied together (the potential at this junction is defined as V_C) The gate of HEMT1 and the gate of HEMT2 are connected together. Threshold voltage V due to HEMT1 device_TH1Greater than the threshold voltage V of the HEMT device 2_TH2When the gate voltage reaches the threshold voltage of the HEMT1, the HEMT1 device has turned on. The threshold voltage of the device is primarily dependent on the threshold voltage of the HEMT1 device, i.e., V_TH≈V_TH1。

When 0 is present<V_C<V_GS-V_TH2(i.e. V)_GS-V_C>V_TH2) When so, the HEMT2 is turned on. At this time, V_CWith V_DSIs increased.

When V is_C>V_GS-V_TH2When the HEMT2 is in the OFF state, i.e., the two-dimensional electron gas channel under the p-GaN layer 11 with smaller thickness is exhausted, the drain voltage V can be borne_DS. Thus, V_CWith V_DSIs increased while remaining unchanged, as shown in fig. 2 (b).

As shown in fig. 3, the threshold voltage and breakdown voltage of the p-GaN layers 11 and 12 of different thicknesses were simulated. It can be seen that the threshold voltage increases slightly with increasing thickness, while the breakdown voltage remains substantially unchanged. To show the capability of inhibiting short channel effect under high leakage voltage, DIBL parameter is defined, and the parameter isThe larger the value of the DIBL parameter, the weaker the ability to suppress short channel effects (i.e., DIBL). As can be seen from fig. 2, as the thickness of the p-GaN layer increases, the DIBL value increases, indicating that the ability to suppress short channel effects becomes weaker.

As shown in fig. 4, the threshold voltage and breakdown voltage of p-GaN layers 11 of different lengths were simulated. It can be seen that as the length increases, the breakdown voltage increases first and then decreases, and the ability to suppress short channel effects becomes increasingly stronger.

As shown in fig. 5, the threshold voltage and breakdown voltage of the p-GaN layer 5 for different channel lengths were simulated. It can be seen that as the channel length increases, the breakdown voltage gradually increases, and the ability to suppress short channel effects also gradually becomes stronger.

As shown in fig. 6, the transfer characteristic curves and threshold voltages of the device of the present invention were simulated in comparison with those of the conventional p-GaN HEMT device. It can be seen that the threshold voltage of the conventional p-GaN HEMT device is greatly reduced along with the increase of the drain voltage, and the threshold voltage of the device is relatively stable, which shows that the device can effectively inhibit the short channel effect.

Finally, the I-V characteristics of the device of the present invention were compared to a conventional device, as shown in FIG. 7. It can be seen that, for the output characteristics, the device of the invention is completely consistent with the traditional p-GaN HEMT device; for the breakdown characteristic, the breakdown voltage of the invention can be improved by 87%. FIG. 7(c) shows the variation of the conduction band energy level in the x-direction at the channel at different drain voltages, and it can be seen that V is at a high drain voltage_CThe potential can be clamped, thereby indicating that short channel effects can be suppressed.