A method for determining AlGaN etching rate
By depositing a dielectric layer on the AlGaN layer, adjusting the etching conditions and calculating the etching rate, the problem of large wafer consumption during the AlGaN etching process is solved, and the cost saving and rapid research and development process effect is achieved.
Patent Information
- Application Number
- CN202411933346.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-02-21
- Estimated Expiration
- 2044-12-26
AI Technical Summary
During the AlGaN etching process, it is difficult for the prior art to effectively adjust the etching rate and time, resulting in large wafer consumption and high cost.
By depositing a dielectric layer on the AlGaN layer, performing etching and thickness measurements, adjusting the etching conditions, and calculating the etching rate of the dielectric layer and the AlGaN layer until the requirements are met.
This method can save wafer consumption during the AlGaN etching process, significantly reduce costs, and quickly develop AlGaN etching process.
Smart Images
Figure CN119361426B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of semiconductor technology, and in particular relates to a method for determining an AlGaN etching rate. Background Art
[0002] Reducing the ohmic contact can increase the knee voltage of GaN devices and improve the gain of RF devices. In gallium nitride devices, the ohmic contact resistance can generally be reduced by etching the AlGaN layer in the ohmic region. During the etching of AlGaN, the AlGaN layer cannot be completely etched, otherwise it will affect the two-dimensional electron gas. Generally, a few nanometers of AlGaN barrier layer need to be retained.
[0003] In addition, in order to realize GaN enhancement-mode devices, AlGaN etching is often performed on the gate. After AlGaN etching, it is also necessary to retain a few nm of AlGaN barrier layer to realize enhancement-mode devices.
[0004] Incomplete etching of the thickness of the AlGaN layer in either the ohmic region or the gate region requires adjustment of the etching rate and etching time, which consumes a large amount of wafers and time. Summary of the invention
[0005] The purpose of the present invention is to provide a method for determining an AlGaN etching rate, which can save wafer consumption in an AlGaN etching process and greatly save costs.
[0006] One aspect of the present invention provides a method for determining an AlGaN etching rate, comprising:
[0007] Step S1, depositing a dielectric layer on the AlGaN layer;
[0008] Step S2, etching the dielectric layer under predetermined etching conditions;
[0009] Step S3, measuring the thickness of the dielectric layer after etching;
[0010] Step S4, judging whether the thickness of the dielectric layer reaches a predetermined thickness according to the measurement result, if it is lower than the predetermined thickness, completely removing the dielectric layer and returning to step S1 to re-deposit the dielectric layer, if it is higher than the predetermined thickness, returning to step S2 to continue etching the dielectric layer until the thickness of the dielectric layer reaches the predetermined thickness;
[0011] Step S5, obtaining a dielectric layer etching rate V1 under the etching conditions according to the thickness of the dielectric layer before etching, the thickness of the dielectric layer after etching, and the etching time;
[0012] Step S6, opening a hole in the dielectric layer to form an opening area to expose the AlGaN layer to be etched;
[0013] Step S7, measuring the step height of the opening area as a first step height A;
[0014] Step S8, using the dielectric layer as a hard mask, using the same etching gas as in step S2, and etching the AlGaN layer for a time t that is less than the time required to completely etch away the hard mask;
[0015] Step S9, measuring the step height of the opening area after etching the AlGaN layer as the second step height B, and calculating the etching rate V2=(B-A+t×V1) / t of the AlGaN layer;
[0016] Step S10, determining whether the calculated AlGaN etching rate meets the requirement, if not, returning to step S1 until the requirement is met.
[0017] Preferably, in step S1, the material of the dielectric layer is SiN or SiO2, and the thickness is 150-180 nm.
[0018] Preferably, in step S2 and step S8, Cl-based gas is used as etching gas.
[0019] Preferably, in step S4, the predetermined thickness is 50-80 nm.
[0020] Preferably, in step S6, photolithography is performed by coating photoresist to expose the dielectric layer to be etched, and the dielectric layer is opened by etching with F-based gas to expose the AlGaN layer to be etched, and then the photoresist is removed.
[0021] Preferably, in step S8, the time required to completely etch away the hard mask is calculated based on the dielectric layer etching rate obtained in step S5 and the dielectric layer thickness at this time.
[0022] According to the method for determining the AlGaN etching rate of the above aspect of the present invention, wafer consumption in the AlGaN etching process can be reduced, thereby greatly saving costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work:
[0024] Figure 1 is a flow chart of a method for determining an AlGaN etching rate according to an embodiment of the present invention;
[0025] Figure 2is a schematic diagram of depositing a dielectric layer on an AlGaN layer according to an embodiment of the present invention;
[0026] Figure 3 is a schematic diagram of opening a hole in a dielectric layer according to an embodiment of the present invention;
[0027] Figure 4 is a schematic diagram of measuring the height of a first step according to an embodiment of the present invention;
[0028] Figure 5 FIG. 4 is a schematic diagram of measuring the height of the second step according to an embodiment of the present invention. DETAILED DESCRIPTION
[0029] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. 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.
[0030] An embodiment of the present invention provides a method for determining an AlGaN etching rate, such as Figure 1 As shown, the method for determining the AlGaN etching rate according to the embodiment of the present invention includes steps S1 to S10.
[0031] In step S1, Figure 2 As shown, a dielectric layer 102 is deposited on the entire surface of the AlGaN layer 101 of the wafer.
[0032] Before depositing the dielectric layer 102, it is necessary to ensure that there is no residual dielectric on the wafer surface. If there is residual dielectric, it needs to be removed by wet or dry process. The material of the dielectric layer 102 can be SiN, SiO2, etc., and the thickness is generally selected to be 150-180nm.
[0033] In step S2, the entire dielectric layer 102 is etched under predetermined etching conditions.
[0034] In this step, an etching condition is selected, and the etching gas under this etching condition is consistent with the etching gas for subsequent etching of AlGaN, for example, a Cl-based gas, to dry-etch the dielectric layer 102. The etching conditions here mainly include chamber pressure, etching gas flow rate and power size.
[0035] In step S3 , the thickness of the dielectric layer 102 is measured on the etched wafer.
[0036] After etching, the wafer needs to measure the thickness of the entire dielectric layer 102 again, and an ellipsometer can be used to perform the thickness measurement.
[0037] In step S4, it is determined whether the thickness of the dielectric layer reaches a predetermined thickness. If it is lower than the predetermined thickness, the dielectric layer 102 is completely removed and the process returns to step S1 to redeposit the dielectric layer. If it is higher than the predetermined thickness, the process returns to step S2 to continue etching the dielectric layer until the dielectric layer reaches the predetermined thickness.
[0038] In this step, it is determined whether the thickness of the dielectric layer reaches the predetermined requirement based on the measurement results after etching. The predetermined required thickness is, for example, 50 to 80 nm. If it is lower than this thickness value, the dielectric layer on the surface of the wafer is completely removed and the dielectric layer is re-deposited after returning to step S1. If it is higher than the predetermined thickness, it returns to step S2 to etch to the predetermined thickness value.
[0039] In step S5, the etching rate of the dielectric layer under the etching condition is calculated.
[0040] At this time, the thickness of the dielectric layer 102 reaches the predetermined requirement, for example, 50 to 80 nm. According to the thickness after etching and the thickness before etching, the dielectric layer etching rate under this etching condition is obtained, which is recorded as V1. Etching rate V1 = (thickness before etching - thickness after etching) / etching time.
[0041] In step S6, a hole is opened in the dielectric layer to form an opening area to expose the AlGaN layer to be etched.
[0042] In this step, if Figure 3 As shown, photoresist 103 is applied and photolithography is performed to expose the dielectric layer 102 to be etched, and a hole is formed in the dielectric layer 102. The dielectric layer 102 can be etched using F-based gas to expose the AlGaN layer 101 to be etched, and then the photoresist 103 is removed.
[0043] In step S7, the step height of the opening area is measured and recorded as the first step height A. Figure 4 shown.
[0044] In step S8, the dielectric layer 102 is used as a hard mask, and the same Cl-based gas as in step S2 is used to etch the AlGaN layer 101 for an etching time t that is shorter than the time required to completely etch away the hard mask, without completely etching away the hard mask.
[0045] With the dielectric layer 102 as a hard mask and the same Cl-based gas as in step S2, the time required to completely etch away the dielectric layer is calculated based on the dielectric layer etching rate V1 obtained in step S5 and the dielectric layer thickness at this time, and an etching time that is less than the complete etching time is determined, which is recorded as t. This etching time is as short as possible to ensure that the AlGaN layer 101 is etched without completely etching away the hard mask.
[0046] In step S9, if Figure 5As shown, after etching the AlGaN layer 101, the step height of the opening area is measured and recorded as the second step height B. According to the dielectric layer etching rate V1, the first step height A, the second step height B, and the etching time t, the etching rate V2 of the AlGaN layer 101 is obtained = (B-A+t×V1) / t.
[0047] In step S10, it is determined whether the AlGaN etching rate meets the requirement. If not, the process returns to step S1 until the requirement is met.
[0048] The method for determining the AlGaN etching rate of the above-mentioned embodiment of the present invention can verify the AlGaN etching process parameters several times on a wafer, which can save wafer consumption in the AlGaN etching process and quickly develop the AlGaN etching process. It can avoid consuming a large amount of wafers and time in the actual process development process, saving process development time and process development costs.
[0049] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.
Claims
1. A method for determining an AlGaN etching rate, characterized in that: include: Step S1, depositing a dielectric layer on the AlGaN layer; Step S2, etching the dielectric layer under predetermined etching conditions; Step S3, measuring the thickness of the dielectric layer after etching; Step S4, judging whether the thickness of the dielectric layer reaches a predetermined thickness according to the measurement result, if it is lower than the predetermined thickness, completely removing the dielectric layer and returning to step S1 to re-deposit the dielectric layer, if it is higher than the predetermined thickness, returning to step S2 to continue etching the dielectric layer until the thickness of the dielectric layer reaches the predetermined thickness; Step S5, obtaining a dielectric layer etching rate V1 under the etching conditions according to the thickness of the dielectric layer before etching, the thickness of the dielectric layer after etching, and the etching time; Step S6, opening a hole in the dielectric layer to form an opening area to expose the AlGaN layer to be etched; Step S7, measuring the step height of the opening area as a first step height A; Step S8, using the dielectric layer as a hard mask, using the same etching gas as in step S2, and etching the AlGaN layer for a time t that is less than the time required to completely etch away the hard mask; Step S9, measuring the step height of the opening area after etching the AlGaN layer as the second step height B, and calculating the etching rate V2=(B-A+t×V1) / t of the AlGaN layer; Step S10, determining whether the calculated AlGaN etching rate meets the requirement, if not, returning to step S1 until the requirement is met.
2. The method according to claim 1, characterized in that In step S1, the material of the dielectric layer is SiN or SiO2, and the thickness is 150-180 nm.
3. The method according to claim 1 or 2, characterized in that In step S2 and step S8, Cl-based gas is used as etching gas.
4. The method according to claim 1 or 2, characterized in that: In step S4, the predetermined thickness is 50 to 80 nm.
5. The method according to claim 1 or 2, characterized in that: In step S6, photolithography is performed by coating photoresist to expose the dielectric layer to be etched, and the dielectric layer is opened by etching with F-based gas to expose the AlGaN layer to be etched, and then the photoresist is removed.
6. The method according to claim 1 or 2, characterized in that: In step S8, the time required to completely etch away the hard mask is calculated based on the dielectric layer etching rate obtained in step S5 and the dielectric layer thickness at this time.
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