Etching method for contact holes with different depths
By adjusting the lateral cross-sectional area of the trench on field plates and metal layers at different depths and adjusting the etching rate, the problem of increasing contact resistance caused by over-etching in the prior art is solved, and a more accurate etching effect is achieved.
Patent Information
- Application Number
- CN202510060519.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-15
- Publication Date
- 2025-05-02
AI Technical Summary
In the prior art, when etching the field plate and the metal layer, contact holes of the same width are used, resulting in a small process window of metal layers at different depths, prone to over-etching, and increasing the contact resistance of metal interconnections.
By performing trench etching on field plates and metal layers at different depths, the lateral cross-sectional area of the trench is adjusted so that the trench lateral cross-sectional area of the field plate is smaller than the trench lateral cross-sectional area of the metal layer, thereby adjusting the etching rate and avoiding over-etching.
Over-etching is effectively avoided, ensuring that contact hole etching stops on metal layers or field plates of different heights, reducing the contact resistance of metal interconnections.
Smart Images
Figure CN119922940A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductor preparation, and in particular to an etching method for contact holes of different depths. Background Art
[0002] Since GaN HEMT power devices are usually lateral structures, field plates with different step heights need to be introduced to adjust the electric field. Contact hole etching needs to etch field plates and metal layers at different depths to complete metal interconnection. In the prior art, contact holes of the same width are used when etching field plates and metal layers. However, since the heights of various field plates and metal layers are different, the process window for completely stopping at metal layers at different depths is very small, resulting in a certain degree of over-etching when etching contact holes with low dielectric thickness, which will cause the contact resistance of metal interconnection to increase. Summary of the invention
[0003] In order to overcome the defects in the prior art, an embodiment of the present invention provides a method for etching contact holes of different depths, which is used to solve one or more of the above problems.
[0004] The embodiment of the present application discloses: a method for etching contact holes of different depths, comprising the following steps: providing a GaN layer; depositing an AlGaN layer on the surface of the GaN layer along the longitudinal direction; providing a metal layer that penetrates the GaN layer and the AlGaN layer along the longitudinal direction; depositing a dielectric layer on the surface of the AlGaN layer along the longitudinal direction, the dielectric layer covering the metal layer; depositing a field plate in the dielectric layer along the transverse direction, the longitudinal height of the field plate being greater than the longitudinal height of the metal layer; and performing groove etching on the field plate and the metal layer, wherein the transverse cross-sectional area of the groove of the field plate is smaller than the transverse cross-sectional area of the groove of the metal layer.
[0005] Furthermore, in the step of "trench etching the field plate and the metal layer, wherein the lateral cross-sectional area of the groove of the field plate is smaller than the lateral cross-sectional area of the groove of the metal layer", the following step is also included: the groove is etched longitudinally from the upper end of the dielectric layer.
[0006] Further, in the step of “providing a metal layer that penetrates the GaN layer and the AlGaN layer in the longitudinal direction”, the metal layer includes a source metal and a drain metal that are isolated from each other.
[0007] Furthermore, in the step of "depositing a dielectric layer on the surface of the AlGaN layer along the longitudinal direction, wherein the dielectric layer covers the metal layer", the following steps are included: depositing a first dielectric layer on the surface of the AlGaN layer along the longitudinal direction; depositing a second dielectric layer on the surface of the first dielectric layer along the longitudinal direction, wherein the second dielectric layer covers the metal layer.
[0008] Furthermore, in the step of "depositing a field plate in the dielectric layer along the transverse direction, wherein the longitudinal height of the field plate is greater than the longitudinal height of the metal layer", a first field plate, a second field plate and a third field plate having different longitudinal heights are sequentially arranged along the transverse direction, wherein the longitudinal heights of the first field plate, the second field plate and the third field plate are all greater than the longitudinal height of the metal layer.
[0009] Furthermore, the first field plate is connected to the second field plate, and the third field plate is isolated from the second field plate and the first field plate.
[0010] Furthermore, the first field plate, the second field plate and the third field plate are all located in the second dielectric layer, the lower end of the first field plate abuts against the first dielectric layer, and the second field plate and the third field plate are isolated from the first dielectric layer.
[0011] Further, the source metal and the drain metal are located at two ends of the first field plate, the second field plate and the third field plate in the lateral direction, and the source metal and the drain metal have the same vertical height.
[0012] Further, in the step of "trench etching the field plate and the metal layer, wherein the lateral cross-sectional area of the groove of the field plate is smaller than the lateral cross-sectional area of the groove of the metal layer", the following steps are included: etching the source metal, the drain metal, the second field plate and the third field plate, the source metal and the drain metal correspond to the first groove and the second groove respectively, the second field plate corresponds to the third groove, and the third field plate corresponds to the fourth groove, wherein the lateral cross-sectional area of the first groove is the same as the lateral cross-sectional area of the second groove, the lateral cross-sectional area of the third groove is larger than the lateral cross-sectional areas of the first groove and the second groove, and the lateral cross-sectional area of the fourth groove is larger than the lateral cross-sectional area of the third groove.
[0013] The beneficial effects of the present invention are as follows:
[0014] By adjusting the groove size at different etching depths, the etching rate can be adjusted so that the contact hole etching stops at metal layers or field plates at different heights, avoiding the problem of increased contact resistance of metal interconnects due to over-etching.
[0015] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are specifically cited below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0017] Figure 1 is a schematic flow chart of an etching method for contact holes of different depths in an embodiment of the present invention;
[0018] Figure 2 It is a structural schematic diagram of a product obtained by an etching method for contact holes of different depths in an embodiment of the present invention;
[0019] The figure marks of the above drawings are: 1. GaN layer; 2. AlGaN layer; 3. Source metal; 4. Drain metal; 5. First field plate; 6. Second field plate; 7. Third field plate; 8. First trench; 9. Second trench; 10. Third trench; 11. Fourth trench; 12. First dielectric layer; 13. Second dielectric layer. DETAILED DESCRIPTION
[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0021] like Figure 1 to Figure 2 As shown, a method for etching contact holes of different depths in this embodiment is characterized by comprising the following steps:
[0022] A GaN layer 1 is provided, and an AlGaN layer 2 and a dielectric layer may be sequentially stacked on the GaN layer 1 in this embodiment.
[0023] An AlGaN layer 2 is deposited on the surface of the GaN layer 1 along the vertical direction, so that the AlGaN layer 2 is disposed on the GaN layer 1 .
[0024] A metal layer is provided which penetrates the GaN layer 1 and the AlGaN layer 2 in the longitudinal direction.
[0025] A dielectric layer is deposited on the surface of the AlGaN layer 2 along the vertical direction, and the dielectric layer covers the metal layer, so that the metal layer is located inside the dielectric layer.
[0026] A field plate is deposited in the dielectric layer in the transverse direction, and the longitudinal height of the field plate is greater than the longitudinal height of the metal layer, that is, the field plate is closer to the end of the dielectric layer away from the AlGaN layer 2 than the metal layer.
[0027] Grooves are etched on the field plate and the metal layer to form contact holes for the field plate and the metal layer, wherein the lateral cross-sectional area of the groove of the field plate is smaller than the lateral cross-sectional area of the groove of the metal layer. According to the micro-load effect of the groove, the etching rates of grooves with different opening sizes are different. Generally, the etching rate of grooves with larger openings is faster, and the etching rate of grooves with smaller opening sizes is slower. The specific reason is that it is difficult for etching plasma gas to pass through smaller grooves, and etching by-products are also difficult to diffuse out. Therefore, by setting the lateral cross-sectional area of the groove of the field plate to be smaller than the lateral cross-sectional area of the groove of the metal layer, the opening size of the groove of the field plate is smaller than the opening size of the groove of the metal layer, thereby avoiding excessive etching of the contact hole in the field plate.
[0028] Specifically, in the step of “trench etching the field plate and the metal layer, wherein the lateral cross-sectional area of the trench of the field plate is smaller than the lateral cross-sectional area of the trench of the metal layer”, the following steps are also included:
[0029] The groove is etched vertically from the upper end of the dielectric layer. Figure 2 In the embodiment, the field plate and the grooves of the metal layer are etched from top to bottom, so that the etched holes can be isolated from each other.
[0030] Specifically, in the step of “arranging a metal layer that penetrates the GaN layer 1 and the AlGaN layer 2 in the longitudinal direction”, the metal layer includes a source metal 3 and a drain metal 4 that are isolated from each other.
[0031] Specifically, in the step of “depositing a dielectric layer on the surface of the AlGaN layer 2 along the longitudinal direction, wherein the dielectric layer covers the metal layer”, the following steps are included:
[0032] A first dielectric layer 12 is deposited on the surface of the AlGaN layer 2 along the vertical direction, so that the first dielectric layer 12 covers the AlGaN layer 2 .
[0033] A second dielectric layer 13 is deposited on the surface of the first dielectric layer 12 along the longitudinal direction, and the second dielectric layer 13 covers the metal layer.
[0034] Specifically, in the step of "depositing a field plate in the dielectric layer in the transverse direction, wherein the longitudinal height of the field plate is greater than the longitudinal height of the metal layer", a first field plate 5, a second field plate 6 and a third field plate 7 having different longitudinal heights are sequentially arranged in the transverse direction. Preferably, the heights of the first field plate 5, the second field plate 6 and the third field plate 7 are successively increased. The longitudinal heights of the first field plate 5, the second field plate 6 and the third field plate 7 are all greater than the longitudinal height of the metal layer.
[0035] Specifically, the first field plate 5 is connected to the second field plate 6, and the third field plate 7 is isolated from both the second field plate 6 and the first field plate 5. Therefore, when trench etching is performed, only the second field plate 6 and the third field plate 7 need to be etched.
[0036] Specifically, the first field plate 5, the second field plate 6 and the third field plate 7 are all located in the second dielectric layer 13, the lower end of the first field plate 5 is in contact with the first dielectric layer 12, and the second field plate 6 and the third field plate 7 are both isolated from the first dielectric layer 12. Thus, the first field plate 5 is connected to the first dielectric layer 12, the second field plate 6 is in contact with the first dielectric layer 12 by being connected to the first field plate 5, and the third field plate 7 is isolated from the first dielectric layer 12.
[0037] Specifically, the source metal 3 and the drain metal 4 are located at the two ends of the first field plate 5, the second field plate 6 and the third field plate 7 in the horizontal direction, and the source metal 3 and the drain metal 4 have the same vertical height, so that when the source metal 3 and the drain metal 4 are grooved, the opening size and etching depth of the contact hole are the same.
[0038] In this embodiment, the source metal 3, the drain metal 4, the second field plate 6 and the third field plate 7 are etched, the source metal 3 and the drain metal 4 correspond to the first groove 8 and the second groove 9 respectively, the second field plate 6 corresponds to the third groove 10, and the third field plate 7 corresponds to the fourth groove 11, wherein the lateral cross-sectional area of the first groove 8 is the same as the lateral cross-sectional area of the second groove 9, the lateral cross-sectional area of the third groove 10 is larger than the lateral cross-sectional areas of the first groove 8 and the second groove 9, and the lateral cross-sectional area of the fourth groove 11 is larger than the lateral cross-sectional area of the third groove 10. According to the micro-load effect of the groove, the etching rates of grooves with different opening sizes are different. Generally, the etching rate of the groove with a larger opening is faster, and the etching rate of the groove with a smaller opening size is slower. The specific reason is that it is difficult for the etching plasma gas to pass through the groove with a smaller size, and the by-products of the etching are also difficult to diffuse out, so that the depths of the first groove 8 and the second groove 9 after etching are the same and greater than the depths of the third groove 10 and the fourth groove 11, and the depth of the third groove 10 is greater than the depth of the fourth groove 11. Therefore, the etching rate of each groove can be changed by adjusting the transverse cross-sectional area of the groove, that is, the opening size, so that different grooves stop at metal layers or field plates at different heights after etching, thereby avoiding excessive etching and causing the contact resistance of the metal interconnect to increase.
[0039] By using the above method, by adjusting the groove size at different etching depths, the etching rate can be adjusted so that the contact hole etching stops at metal layers or field plates at different heights, thereby avoiding the problem of excessive etching causing the contact resistance of the metal interconnect to increase.
[0040] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.
Claims
1. A method for etching contact holes of different depths, characterized in that: The following steps are involved: providing a GaN layer; Depositing an AlGaN layer on the surface of the GaN layer along the vertical direction; Disposing a metal layer that penetrates the GaN layer and the AlGaN layer in the longitudinal direction; Depositing a dielectric layer on the surface of the AlGaN layer along the vertical direction, wherein the dielectric layer covers the metal layer; Depositing a field plate in the dielectric layer in a lateral direction, wherein a longitudinal height of the field plate is greater than a longitudinal height of the metal layer; The field plate and the metal layer are subjected to trench etching, wherein a transverse cross-sectional area of the trench of the field plate is smaller than a transverse cross-sectional area of the trench of the metal layer.
2. The etching method for contact holes of different depths according to claim 1, characterized in that: In the step of "trench etching the field plate and the metal layer, wherein the lateral cross-sectional area of the trench of the field plate is smaller than the lateral cross-sectional area of the trench of the metal layer", the following steps are also included: The groove is etched vertically from the upper end of the dielectric layer.
3. The etching method for contact holes of different depths according to claim 1, characterized in that: In the step of “providing a metal layer that penetrates the GaN layer and the AlGaN layer in the longitudinal direction”, the metal layer includes a source metal and a drain metal that are isolated from each other.
4. The etching method for contact holes of different depths according to claim 3, characterized in that: In the step of "depositing a dielectric layer on the surface of the AlGaN layer along the longitudinal direction, wherein the dielectric layer covers the metal layer", the following steps are included: Depositing a first dielectric layer on the surface of the AlGaN layer along the vertical direction; A second dielectric layer is deposited on the surface of the first dielectric layer along the vertical direction, and the second dielectric layer covers the metal layer.
5. The etching method for contact holes of different depths according to claim 4, characterized in that: In the step of "depositing a field plate in the dielectric layer along the transverse direction, wherein the longitudinal height of the field plate is greater than the longitudinal height of the metal layer", a first field plate, a second field plate and a third field plate having different longitudinal heights are sequentially arranged along the transverse direction, wherein the longitudinal heights of the first field plate, the second field plate and the third field plate are all greater than the longitudinal height of the metal layer.
6. The etching method for contact holes of different depths according to claim 5, characterized in that: The first field plate is connected to the second field plate, and the third field plate is isolated from both the second field plate and the first field plate.
7. The etching method for contact holes of different depths according to claim 6, characterized in that: The first field plate, the second field plate and the third field plate are all located in the second dielectric layer, the lower end of the first field plate abuts against the first dielectric layer, and the second field plate and the third field plate are isolated from the first dielectric layer.
8. The etching method for contact holes of different depths according to claim 6, characterized in that: The source metal and the drain metal are located at two ends of the first field plate, the second field plate and the third field plate in the lateral direction, and the source metal and the drain metal have the same vertical height.
9. The etching method for contact holes of different depths according to claim 8, characterized in that: In the step of "trench etching the field plate and the metal layer, wherein the lateral cross-sectional area of the trench of the field plate is smaller than the lateral cross-sectional area of the trench of the metal layer", the following steps are included: The source metal, the drain metal, the second field plate and the third field plate are etched, the source metal and the drain metal correspond to the first groove and the second groove respectively, the second field plate corresponds to the third groove, and the third field plate corresponds to the fourth groove, wherein the lateral cross-sectional area of the first groove is the same as the lateral cross-sectional area of the second groove, the lateral cross-sectional area of the third groove is larger than the lateral cross-sectional areas of the first groove and the second groove, and the lateral cross-sectional area of the fourth groove is larger than the lateral cross-sectional area of the third groove.