Etching method of magnetic materials in MEMS

Abstract

The present invention discloses an etching method for magnetic materials in MEMS, comprising: step 1, sequentially forming a magnetic material layer and an etching barrier layer on an underlying structure; step 2, performing a first dry etching to remove the etching barrier layer in an etching area, wherein the etching gas uses a Cl-based gas, and the etching byproducts include a polymer containing Cl; step 3, performing a first removal of the deposited polymer using an IBE etching process; step 4, performing a second removal of the remaining polymer using a wet cleaning process and achieving complete removal of the polymer; step 5, performing a second dry etching to remove the magnetic material layer in the etching area. The present invention can eliminate etching abnormalities of the magnetic material layer and improve the uniformity of the magnetism of the magnetic material layer and the product yield.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a semiconductor integrated circuit, in particular to a method for etching a magnetic material in a MEMS. Background Art

[0002] Micro-electromechanical systems (MEMS) products are micro-integrated systems that use integrated circuit technology and micro-machining technology to manufacture micro-structures, micro-processors, control processing circuits, and even interface circuits, communication circuits, power circuits, etc. on one or more chips. It is the integration of microcircuits and micro-machines on a chip according to functional requirements.

[0003] Different from traditional semiconductor processes, MEMS products use magnetic materials such as nickel-iron alloy layers (NiFe), and TaN is used as the NiFe etching barrier layer. The etching process produces a lot of TaN-based polymers (Polymer). The baseline particle detection background is very poor, and online particle monitoring cannot be tested. It will also cause subsequent NiFe etching abnormalities (block etch), resulting in low product yield.

[0004] like Figures 1A to 1D FIG. 1 is a schematic diagram of the device structure in each step of the etching method of magnetic materials in the existing MEMS; the etching method of magnetic materials in the existing MEMS includes the following steps:

[0005] Step 1: Figure 1A As shown, a magnetic material layer 102 and an etching stop layer 103 are sequentially formed on the underlying structure.

[0006] Figure 1A Typically, the underlying structure includes a semiconductor substrate such as a silicon substrate (not shown) and a first insulating layer such as an oxide layer (not shown) formed on the surface of the semiconductor substrate.

[0007] Before forming the magnetic material layer 102, the step of forming a second dielectric barrier layer 101 on the surface of the first insulating layer is also included. The magnetic material layer 102 is formed on the surface of the second dielectric barrier layer 101. The second dielectric barrier layer 101 is used to protect the first insulating layer and prevent the magnetic material layer 102 from reacting with the first insulating layer.

[0008] After forming the etching stop layer 103, the method further includes forming a hard mask layer 104 on the surface of the etching stop layer 103.

[0009] Typically, the magnetic material layer 102 is made of an iron-nickel alloy layer, and the etching stop layer 103 is made of TaN. Figure 1AIn the embodiment, the magnetic material layer 102 is also represented by NIFE. The etching stop layer 103 is also represented by TaN.

[0010] The material of the hard mask layer 104 includes silicon nitride. The hard mask layer 104 is also represented by SiN.

[0011] The material of the second dielectric barrier layer 101 includes silicon nitride.

[0012] Step 2: Figure 1B As shown, a photolithography process is used to define an etching area, and then a first dry etching is performed. The etching gas for the first dry etching is a Cl-based gas. The first dry etching removes the hard mask layer 104 and the etching barrier layer 103 in the etching area in sequence. The etching by-products of the first dry etching include polymers containing Cl, and the polymers will be deposited on the surface of the exposed magnetic material layer 102 in the etching area and on the surface outside the etching area.

[0013] Step 3: Figure 1C As shown, a wet cleaning process is used to remove the polymer.

[0014] The liquid used in the wet cleaning process is usually SST-A2, which is a mixture of polar solvent (CH3)2SO, ammonium fluoride, hydrofluoric acid and water. It is not easy to control when the polymer is removed by a wet cleaning process. If the wet cleaning process is short, it is not easy to completely remove the polymer; and when the polymer is not completely removed, it will hinder the subsequent etching of NiFe. If the wet cleaning process is too long, since the polymer contains Cl, Cl is easy to react with the cleaning solution of the wet cleaning process to form acid, and the acid formed is easy to corrode NiFe, resulting in NiFe loss, and finally the magnetic uniformity of NiFe will deteriorate, which will also affect the yield.

[0015] Step 4: Figure 1D As shown, a second dry etching is performed to remove the magnetic material layer 102 in the etching area. Summary of the invention

[0016] The technical problem to be solved by the present invention is to provide a method for etching magnetic materials in MEMS, which can eliminate etching abnormalities of a magnetic material layer and improve the magnetic uniformity and product yield of the magnetic material layer.

[0017] In order to solve the above technical problems, the etching method of magnetic material in MEMS provided by the present invention comprises the following steps:

[0018] Step 1: forming a magnetic material layer and an etching stop layer in sequence on the underlying structure.

[0019] Step 2: Select an etching area and perform a first dry etching, wherein the etching gas for the first dry etching is a Cl-based gas. The first dry etching removes the etching barrier layer in the etching area. The etching byproducts of the first dry etching include a polymer containing Cl, which will be deposited on the surface of the exposed magnetic material layer in the etching area and the surface outside the etching area.

[0020] Step three: using an ion beam etching (IBE) process to remove the deposited polymer for the first time.

[0021] Step 4: Use a wet cleaning process to remove the remaining polymer for a second time and completely remove the polymer; through the first removal, the amount of the polymer removed for the second time is reduced, thereby preventing the acid formed when the wet cleaning process etches the polymer from causing damage to the magnetic material layer.

[0022] Step 5: Perform a second dry etching to remove the magnetic material layer in the etching area.

[0023] A further improvement is that in step one, the underlying structure includes a semiconductor substrate and a first insulating layer formed on a surface of the semiconductor substrate.

[0024] A further improvement is that in step one, before forming the magnetic material layer, it also includes the step of forming a second dielectric barrier layer on the surface of the first insulating layer, the magnetic material layer is formed on the surface of the second dielectric barrier layer, and the second dielectric barrier layer is used to protect the first insulating layer.

[0025] A further improvement is that after forming the etch stop layer, it also includes a step of forming a hard mask layer on the surface of the etch stop layer. In step two, the first dry etching etches the hard mask layer first, and then etches the etch stop layer.

[0026] A further improvement is that the material of the magnetic material layer includes an iron-nickel alloy layer.

[0027] A further improvement is that the thickness of the magnetic material layer is 100 angstroms to 300 angstroms.

[0028] A further improvement is that the material of the etch stop layer includes TaN.

[0029] A further improvement is that the thickness of the etching stop layer is 600 angstroms to 1200 angstroms.

[0030] A further improvement is that the material of the hard mask layer includes silicon nitride.

[0031] A further improvement is that the material of the second dielectric barrier layer includes silicon nitride.

[0032] A further improvement is that the semiconductor substrate comprises a silicon substrate.

[0033] A further improvement is that the material of the first insulating layer includes an oxide layer.

[0034] A further improvement is that, in step one, the magnetic material layer is formed by a PVD process.

[0035] A further improvement is that, in step one, the etching stop layer is formed by a PVD process.

[0036] A further improvement is that after the etch stop layer and the magnetic material layer are formed, a process of annealing the etch stop layer and the magnetic material layer is also included.

[0037] After completing the first dry etching of the etching barrier layer of the magnetic material layer, the present invention adopts a method combining an IBT etching process with a wet cleaning process to remove the polymer containing Cl deposited in the first dry etching. In this way, it can ensure that the polymer is completely removed, and the acid formed by the reaction with the polymer during the wet cleaning process can be prevented from corroding the magnetic material layer. Since the polymer is completely removed, the magnetic material layer can be well etched, and abnormal etching of the magnetic material layer can be prevented; at the same time, since the magnetic material layer will not be corroded during the wet cleaning process, the magnetic uniformity of the magnetic material layer can be improved, and finally the product yield can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0039] Figure 1A-Figure 1D It is a schematic diagram of the device structure in each step of the etching method of magnetic materials in the existing MEMS;

[0040] Figure 2 is a flow chart of a method for etching a magnetic material in a MEMS according to an embodiment of the present invention;

[0041] Figure 3A-3E It is a schematic diagram of the device structure in each step of the etching method of the magnetic material in the MEMS according to the embodiment of the present invention. DETAILED DESCRIPTION

[0042] like Figure 2 As shown in FIG. 1 , it is a flow chart of a method for etching a magnetic material in a MEMS according to an embodiment of the present invention; FIG. 3A to FIG. 3E, which is a schematic diagram of the device structure in each step of the method for etching a magnetic material in a MEMS according to an embodiment of the present invention; the method for etching a magnetic material in a MEMS according to an embodiment of the present invention comprises the following steps:

[0043] Step 1: Figure 3A As shown, a magnetic material layer 202 and an etching stop layer 203 are sequentially formed on the underlying structure.

[0044] In the embodiment of the present invention, the underlying structure includes a semiconductor substrate (not shown) and a first insulating layer (not shown) formed on the surface of the semiconductor substrate.

[0045] In some embodiments, the semiconductor substrate includes a silicon substrate.

[0046] The material of the first insulating layer includes an oxide layer.

[0047] Before forming the magnetic material layer 202, the step of forming a second dielectric barrier layer 201 on the surface of the first insulating layer is also included. The magnetic material layer 202 is formed on the surface of the second dielectric barrier layer 201. The second dielectric barrier layer 201 is used to protect the first insulating layer and prevent the magnetic material layer 202 from reacting with the first insulating layer.

[0048] After forming the etching stop layer 203, the method further includes forming a hard mask layer 204 on the surface of the etching stop layer 203.

[0049] The material of the magnetic material layer 202 includes an iron-nickel alloy layer. In some preferred embodiments, the thickness of the magnetic material layer 202 is 100 angstroms to 300 angstroms.

[0050] The material of the etch stop layer 203 includes TaN. In some preferred embodiments, the thickness of the etch stop layer 203 is 600 angstroms to 1200 angstroms.

[0051] The material of the hard mask layer 204 includes silicon nitride.

[0052] The material of the second dielectric barrier layer 201 includes silicon nitride.

[0053] The magnetic material layer 202 is formed by a PVD process.

[0054] The etching stop layer 203 is formed by a PVD process.

[0055] After the etch stop layer 203 and the magnetic material layer 202 are formed, a process of annealing the etch stop layer 203 and the magnetic material layer 202 is further included.

[0056] Step 2: Figure 3B As shown, an etching area is selected and a first dry etching is performed. The etching gas of the first dry etching adopts Cl-based gas. The first dry etching removes the etching barrier layer 203 in the etching area. The etching by-products of the first dry etching include polymers containing Cl, which will be deposited on the surface of the exposed magnetic material layer 202 in the etching area and the surface outside the etching area.

[0057] In the embodiment of the present invention, the first dry etching is performed to firstly etch the hard mask layer 204 and then to etch the etching stop layer 203 .

[0058] The etched area is defined by using a photolithography process.

[0059] Step 3: Figure 3C As shown, the deposited polymer is first removed by an IBE etching process.

[0060] The IBE etching process can remove most of the polymer in the first removal. The IBT etching process is a physical etching process and will not corrode the magnetic material layer 202 .

[0061] Step 4: Figure 3D As shown, a wet cleaning process is used to remove the remaining polymer for a second time and completely remove the polymer; through the first removal, the amount of the polymer removed for the second time is reduced, thereby preventing the acid formed when the wet cleaning process etches the polymer from causing damage to the magnetic material layer 202.

[0062] In the embodiment of the present invention, the liquid used in the wet cleaning process is SST-A2, which is a mixture of polar solvent (CH3)2SO, ammonium fluoride, hydrofluoric acid and water. The wet cleaning process will not cause morphological etching.

[0063] Step 5: Figure 3E As shown, a second dry etching is performed to remove the magnetic material layer 202 in the etching area.

[0064] After completing the first dry etching of the etching barrier layer 203 of the magnetic material layer 202, the embodiment of the present invention adopts a method combining the IBT etching process and the wet cleaning process to remove the polymer containing Cl deposited in the first dry etching. In this way, it can ensure that the polymer is completely removed, and the acid formed by the reaction with the polymer during the wet cleaning process can be prevented from corroding the magnetic material layer 202. Since the polymer is completely removed, the magnetic material layer 202 can be well etched to prevent abnormal etching of the magnetic material layer 202. At the same time, since the magnetic material layer 202 will not be corroded during the wet cleaning process, the magnetic uniformity of the magnetic material layer 202 can be improved, and finally the product yield can be improved.

[0065] The present invention has been described in detail above through specific embodiments, but these do not constitute limitations of the present invention. Without departing from the principle of the present invention, those skilled in the art may also make many variations and improvements, which should also be considered as the protection scope of the present invention.

Claims

1. A method for etching magnetic materials in MEMS, characterized in that: The steps include: Step 1: forming a magnetic material layer and an etching stop layer on the underlying structure in sequence; The material of the magnetic material layer includes an iron-nickel alloy layer; The material of the etching stop layer includes TaN; step 2, selecting an etching area and performing a first dry etching, wherein the etching gas of the first dry etching adopts a Cl-based gas, and the first dry etching removes the etching stop layer in the etching area, and the etching byproducts of the first dry etching include a polymer containing Cl, and the polymer will be deposited on the surface of the magnetic material layer exposed in the etching area and the surface outside the etching area; Step 3, using an IBE etching process to remove the deposited polymer for the first time; Step 4: using a wet cleaning process to remove the remaining polymer for a second time and completely remove the polymer; through the first removal, the amount of the polymer removed for the second time is reduced, thereby preventing the acid formed when the wet cleaning process etches the polymer from causing loss to the magnetic material layer; Step 5: Perform a second dry etching to remove the magnetic material layer in the etching area.

2. The method for etching magnetic materials in MEMS according to claim 1, characterized in that: In step 1, the underlying structure includes a semiconductor substrate and a first insulating layer formed on a surface of the semiconductor substrate.

3. The method for etching magnetic materials in MEMS according to claim 2, characterized in that: In step one, before forming the magnetic material layer, it also includes the step of forming a second dielectric barrier layer on the surface of the first insulating layer, the magnetic material layer is formed on the surface of the second dielectric barrier layer, and the second dielectric barrier layer is used to protect the first insulating layer.

4. The method for etching magnetic material in MEMS according to claim 3, characterized in that: After forming the etch stop layer, the method further includes forming a hard mask layer on the surface of the etch stop layer. In step 2, the first dry etching etches the hard mask layer first, and then etches the etch stop layer.

5. The method for etching magnetic material in MEMS according to claim 4, characterized in that: The thickness of the magnetic material layer is 100 angstroms to 300 angstroms.

6. The method for etching magnetic material in MEMS according to claim 5, characterized in that: The thickness of the etching stop layer is 600 angstroms to 1200 angstroms.

7. The method for etching magnetic material in MEMS according to claim 4, characterized in that: The material of the hard mask layer includes silicon nitride.

8. The method for etching magnetic material in MEMS as claimed in claim 3, characterized in that: The material of the second dielectric barrier layer includes silicon nitride.

9. The method for etching magnetic material in MEMS according to claim 2, characterized in that: The semiconductor substrate includes a silicon substrate.

10. The method for etching magnetic material in MEMS according to claim 9, characterized in that: The material of the first insulating layer includes an oxide layer.

11. The method for etching magnetic material in MEMS according to claim 1, characterized in that: In step one, the magnetic material layer is formed by a PVD process.

12. The method for etching magnetic material in MEMS according to claim 11, characterized in that: In step one, the etching stop layer is formed by a PVD process.

13. The method for etching magnetic material in MEMS according to claim 12, characterized in that: After the etch stop layer and the magnetic material layer are formed, the method further includes a process of annealing the etch stop layer and the magnetic material layer.

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