WO2020024668A1 - 一种磁隧道结刻蚀方法 - Google Patents

一种磁隧道结刻蚀方法 Download PDF

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WO2020024668A1
WO2020024668A1 PCT/CN2019/087843 CN2019087843W WO2020024668A1 WO 2020024668 A1 WO2020024668 A1 WO 2020024668A1 CN 2019087843 W CN2019087843 W CN 2019087843W WO 2020024668 A1 WO2020024668 A1 WO 2020024668A1
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Prior art keywords
etching
chamber
tunnel junction
magnetic tunnel
sample
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PCT/CN2019/087843
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English (en)
French (fr)
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许开东
车东晨
胡冬冬
陈璐
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江苏鲁汶仪器有限公司
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Priority to US17/265,227 priority Critical patent/US11963455B2/en
Publication of WO2020024668A1 publication Critical patent/WO2020024668A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/67005—Apparatus not specifically provided for elsewhere
    • H01L21/67011—Apparatus for manufacture or treatment
    • H01L21/67155—Apparatus for manufacturing or treating in a plurality of work-stations
    • H01L21/67161—Apparatus for manufacturing or treating in a plurality of work-stations characterized by the layout of the process chambers
    • H01L21/67167—Apparatus for manufacturing or treating in a plurality of work-stations characterized by the layout of the process chambers surrounding a central transfer chamber
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H10N50/01—Manufacture or treatment

Definitions

  • the invention relates to the field of magnetic random access memory, in particular to a magnetic tunnel junction etching method.
  • MRAM magnetic random access memory
  • SRAM static random access memory
  • DRAM dynamic random access memory
  • Flash Flash memory
  • the magnetic tunnel junction is the core structure of a magnetic random access memory.
  • the structure consists of a fixed layer, a non-magnetic isolation layer, and a free layer.
  • the fixed layer is thick and has strong magnetism, and the magnetic moment is not easy to reverse, while the free layer is thin and has weak magnetism, and the magnetic moment is easy to reverse.
  • the free layer is a magnetic film that stores information. It uses a soft ferromagnetic material and has a relatively low coercive force, a high magnetic permeability, and a high sensitivity to low magnetic fields.
  • the isolation layer is a non-magnetic thin film with a thickness of only 0.5 to 2 nm, such as MgO or Al 2 O 3 .
  • the fixed layer is a thin film having a fixed direction of a magnetic field in an MRAM cell. The choice of material should have a strong exchange bias effect with the antiferromagnetic layer, so that the magnetic moment of the pinned layer can be effectively pinned in a fixed direction. Regarding such materials, CoFe, CoFeB, etc. are more suitable.
  • the main method of patterning the magnetic tunnel junction still needs to be etched, because the materials of the magnetic tunnel junction are materials that are difficult to be dry-etched, such as Fe, Co, Mg, etc., and it is difficult to form volatile products, and the corrosive gas cannot be used (Cl 2 etc.), otherwise it will affect the performance of the magnetic tunnel junction, so more complicated etching methods are needed to achieve it.
  • the etching process is very difficult and challenging.
  • ion beam etching uses an inert gas, basically no chemically etched components are introduced into the reaction chamber, so that the sidewall of the magnetic tunnel junction is not attacked by chemical reactions. Under the condition that the side walls are clean, ion beam etching can obtain a more perfect side wall of the magnetic tunnel junction-clean and free of chemical damage. However, ion beam etching has its imperfections. On the one hand, a principle that ion beam etching can achieve is to use a high physical bombardment force.
  • the maximum angle that can reach the bottom of the magnetic tunnel junction during ion beam etching is 27 degrees.
  • This aspect ratio makes the angle commonly used for ion beam etching not reach the bottom of the magnetic tunnel junction, thereby failing to meet the need for magnetic tunnel junction device separation, making patterning fail.
  • the ion beam etching time is relatively long, and the yield of each device is limited.
  • the present invention discloses a magnetic tunnel junction etching method.
  • the etching device used includes a sample loading chamber, a vacuum transition chamber, a reactive ion plasma etching chamber, an ion beam etching chamber,
  • the coating chamber and the vacuum transfer chamber are characterized in that the wafer is processed in a reactive ion plasma etching chamber, an ion beam etching chamber, and a coating chamber according to a specific sequence and conditions without interrupting the vacuum.
  • Processing and processing include the following steps: a sample preparation step to form a structure to be etched including a magnetic tunnel junction on a semiconductor substrate; a sample loading step, loading the sample into a sample loading chamber, and passing the sample through a vacuum
  • the transition chamber enters the vacuum transmission chamber;
  • the reactive ion etching step causes the sample to enter the reactive ion plasma etching chamber, and uses the reactive ion plasma to etch the sample to the bottom electrode layer, and then returns the sample To the vacuum transmission chamber;
  • the ion beam cleaning step allows the sample to enter the ion beam etching chamber, and removes metal residues using the ion beam And the surface treatment of the sample, so that the sidewall metal contamination and the sidewall damage layer formed in the reactive ion etching step are completely removed, and at the same time, the device above the bottom electrode and the dielectric layer between the bottom electrodes of different devices are completely removed.
  • the protection step allows the sample to enter the coating chamber, and protects the upper surface and periphery of the etched sample from being coated, and then returns the sample to the The vacuum transfer chamber; and a sample removal step, removing the sample from the vacuum transfer chamber, passing through the vacuum transition chamber, and returning the sample to the sample loading chamber.
  • the etching and processing sequence is:
  • the etching and processing sequence is: using a reactive ion plasma etching chamber to completely etch the magnetic tunnel junction of the hard mask that has been opened in advance to expose the dielectric layer between the bottom electrode or the bottom electrode, and then etching the cavity with an ion beam
  • the chamber cleans the magnetic tunnel junction and its bottom, and then coats the magnetic tunnel junction with a coating chamber, and then returns the wafer to the atmospheric environment.
  • the angle of the ion beam etching is 10 degrees to 80 degrees, wherein the angle is an angle of the ion beam with respect to a normal surface of the sample stage.
  • a sidewall of the magnetic tunnel junction having a thickness of 0.1 nm to 10.0 nm is removed.
  • the gas used includes inert gas, nitrogen, oxygen, fluorine-based gas, NH 3 , amino gas, CO, CO 2 , Alcohols, and combinations thereof
  • the reactive ion etching step may be a single step or multiple steps.
  • the gas, power, gas flow, and pressure used in different steps may be the same or different.
  • a gas used in the ion beam cleaning step includes an inert gas, nitrogen, oxygen, and a combination thereof, and the ion beam cleaning step may be a single-step cleaning or Multi-step cleaning.
  • the gas used in different steps, the angle of the sample stage relative to the ion beam, the energy and density of the ion beam can be the same or different.
  • the plated film is a dielectric material that separates adjacent magnetic tunnel junction devices.
  • the material of the coating medium is a group IV oxide, a group nitride, a group 4 oxynitride, a transition metal oxide, a transition metal nitride, or a transition metal oxynitride.
  • a group IV oxide a group IV oxide, a group nitride, a group 4 oxynitride, a transition metal oxide, a transition metal nitride, or a transition metal oxynitride.
  • the thickness of the plating film is 1 nm to 500 nm.
  • the side wall metal formed in the reactive ion etching step is contaminated to a nanometer level.
  • the thickness of the sidewall damage layer formed in the reactive ion etching step is nanometer-scale.
  • the etching method is applicable to the etching of the magnetic tunnel junction with the fixed layer above the isolation layer or the fixed layer below the isolation layer.
  • the etching method is suitable for etching a magnetic tunnel junction with a single-layer or multi-layer isolation layer.
  • the magnetic tunnel junction etching method of the present invention is applicable to the etching of magnetic tunnel junctions, transition metals and their oxides.
  • the invention can overcome the bottleneck of high-density small device production, meanwhile, it can greatly improve the yield and reliability of the device, and the manufacturing method is simple and fast, thereby improving the production efficiency.
  • FIG. 2 is a functional block diagram of an etching device used in the magnetic tunnel junction etching method of the present invention.
  • FIG. 3 is a flowchart of a magnetic tunnel junction etching method.
  • FIG. 4 is a schematic structural diagram of a device to be etched including a magnetic tunnel junction.
  • FIG. 5 is a schematic structural diagram of a magnetic tunnel junction with a fixed layer above an isolation layer.
  • FIG. 6 is a schematic diagram of a device structure formed after a reactive ion etching step is performed.
  • FIG. 7 is a schematic structural view of a device formed after the ion beam cleaning step.
  • FIG. 8 is a schematic diagram of a device structure formed after a protection step.
  • orientations or positional relationships indicated by the terms “up”, “down”, “straight”, and “inclined” are based on the orientations or positional relationships shown in the drawings, and are In order to facilitate the description of the present invention and simplify the description, it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present invention.
  • first and second are used for descriptive purposes only and should not be interpreted as indicating or implying relative importance.
  • FIG. 2 is a functional block diagram of an etching device used in the magnetic tunnel junction etching method of the present invention.
  • the etching device includes a reactive ion plasma etching chamber 10, an ion beam etching (IBE) chamber 11, a coating chamber 12, a vacuum transfer chamber 13, a vacuum transition chamber 14, and a sample loading chamber. Cavity 15
  • the vacuum transition chamber 14 is connected to the sample loading chamber 15 and the vacuum transfer chamber 13 in a communicable manner, respectively.
  • the reactive ion plasma etching chamber 10, the ion beam etching chamber 11, and the coating chamber 12 are respectively connected to the vacuum transmission chamber 13 in a communicable manner.
  • each of the above-mentioned chambers may be plural.
  • the reactive ion plasma etching chamber 10 may be a reactive ion plasma etching chamber such as an inductively coupled plasma (ICP) chamber, a capacitively coupled plasma (CCP) chamber, and a spiral wave plasma chamber.
  • the ion beam etching (IBE) chamber 11 may be an ion beam etching, a neutral particle beam etching chamber, or the like.
  • the coating chamber 12 may be a physical vapor deposition (PVD) coating chamber, or a pulsed chemical vapor deposition (Pulsed CVD) coating chamber, a plasma enhanced chemical vapor deposition (PECVD) coating chamber, or an inductively coupled plasma enhanced chemistry.
  • Chemical vapor deposition (CVD) coating chambers such as vapor deposition (ICP-PECVD) coating chambers, atomic layer (ALD) coating chambers.
  • the etching device also includes a sample transfer system for achieving the transfer of samples in each chamber, a control system for controlling each chamber and the sample transfer system, etc., and a vacuum degree required for achieving each chamber.
  • Functional unit included in conventional etching equipment such as vacuum extraction system and cooling system.
  • FIG. 3 is a flowchart of a magnetic tunnel junction etching method. As shown in FIG. 3, the magnetic tunnel junction etching method of the present invention is implemented by the following steps.
  • a structure to be etched including a magnetic tunnel junction is formed on a semiconductor substrate.
  • a structure diagram of a device to be etched including a magnetic tunnel junction is shown in FIG. 4.
  • the structure to be etched includes a bottom electrode metal layer 100, a magnetic tunnel junction (including a fixed layer 101, an isolation layer 102, and a free layer 103), a cap layer 104, and a hard mask layer 105.
  • the composition of the magnetic tunnel junction may also be that the free layer is below the isolation layer, and the fixed layer is above the isolation layer, as shown in FIG. 5.
  • the isolation layer may be two or more layers, and so on.
  • the magnetic tunnel junction etching method of the present invention is applicable to all these different structures.
  • the sample is loaded into the sample loading chamber 15 and the sample is passed through the vacuum transition chamber 14 and into the vacuum transfer chamber 13.
  • the sample is entered into the reactive ion plasma etching chamber 10, the sample is etched by using the reactive ion plasma, and then the sample is returned to the vacuum transfer chamber 13.
  • the gas used in the reactive ion plasma etching chamber may be an inert gas, nitrogen, oxygen, fluorine-based gas, NH 3 , amino gas, CO, CO 2 , alcohol, and other organic gases that can be used for etching.
  • the etching reaches the bottom electrode, the etching is stopped. The etching process should achieve the separation of the device and the steepness required by the device.
  • FIG. 6 is a schematic diagram of a device structure formed after a reactive ion etching step is performed.
  • FIG. 6 schematically shows the metal contamination 106 and the damage layer 107 on the side wall of the magnetic tunnel junction formed during the plasma etching process.
  • the reactive ion etching step may be a single step or multiple steps. In the multi-step process, the gas, power, gas flow, and pressure used in different steps may be the same or different.
  • the sample is entered into the ion beam etching chamber 11, and the metal residue is removed and the sample surface treatment is performed by using the ion beam, so that the sidewall formed in the reactive ion etching step is performed. Metal contamination and sidewall damage layers are completely removed. At the same time, metal residues above the device bottom electrode and above the dielectric layer between different device bottom electrodes are completely removed to achieve complete electrical isolation of the device and avoid short circuits between the device and the device.
  • the sample is then returned to the vacuum transfer chamber 13.
  • the gas used in the ion beam etching chamber may be an inert gas, nitrogen, oxygen, or the like.
  • the ion beam cleaning step may be a single-step cleaning or a multi-step cleaning.
  • the gas used in different steps, the angle, energy and density of the ion beam may be the same or different.
  • the angle used for ion beam etching is preferably 10 degrees to 80 degrees (taken perpendicular to the wafer surface as a reference, and 0 degrees perpendicular).
  • the side wall of the magnetic tunnel junction of 0.1 nm to 10.0 nm is removed.
  • the thin film 108 is a dielectric material that separates adjacent magnetic tunnel junction devices.
  • the dielectric thin film material can be a Group IV oxide, a Group nitride, a Group IV oxynitride, a transition metal oxide, a transition nitride, a transition oxynitride, an alkaline earth metal oxide, an alkaline earth nitride, an alkaline earth nitrogen oxide, etc. Dielectric material for separation of adjacent magnetic tunnel junction devices.
  • the thickness of the plating film may be 1 nm or more and 500 nm or less.
  • the in-situ coating protection in the coating chamber can prevent the device from being damaged by being exposed to the atmospheric environment in the subsequent processes, and at the same time achieve complete insulation between the device and the device.
  • the sample is returned from the vacuum transfer chamber 13 through the vacuum transition chamber 14 to the sample loading chamber 15.
  • the magnetic tunnel junction etching method of the present invention has the following advantages: fast and complete patterning of the device by means of a reactive ion etching chamber that has been verified by mass production. Under the premise of not destroying the vacuum, the ion tunnel etching chamber is used to surface-treat the magnetic tunnel junction to eliminate the adverse effects caused by the reactive ion etching machine itself, including device metal contamination and sidewall damage. .
  • the mask layer has usually been consumed a lot.
  • the aspect ratio of the overall device is greatly reduced, which enables the subsequent cleaning process of the ion beam etching chamber to The relatively large inclined angle thoroughly cleans and cleans the entire device sidewall.
  • This method can overcome the bottleneck of small devices (20nm and below) with high density (1: 1 equal pitch). Due to metal contamination and removal of sidewall damage, the yield and reliability of the device can be greatly improved.
  • the manufacturing method is simple and fast, and the sample only needs to enter each type of chamber once to complete the process in sequence.
  • the etching time is shortened by 1/3 to 1/2 compared with the case where the ion beam is used to etch the chamber, thereby improving the productivity.

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Abstract

一种磁隧道结刻蚀方法，所使用的刻蚀装置包括样品装载腔室、真空过渡腔室、反应离子等离子体刻蚀腔室、离子束刻蚀腔室、镀膜腔室、以及真空传输腔室。本方法在反应离子等离子体刻蚀腔内完成磁隧道结的刻蚀，在离子束刻蚀腔室内进行离子束清洗，并在镀膜腔室内进行镀膜保护，上述各腔室间的传递均在真空状态下进行。本发明能够克服高密度的小器件生产的瓶颈，同时大幅提高器件的良率、可靠性以及生产效率。

Description

一种磁隧道结刻蚀方法 技术领域
本发明涉及磁性随机存储器领域，具体涉及一种磁隧道结刻蚀方法。
背景技术
随着半导体器件特征尺寸的进一步等比例缩小，传统的闪存技术将达到尺寸的极限。为进一步提高器件的性能，研发人员开始对新结构、新材料、新工艺进行积极的探索。近年来，各种新型非易失性存储器得到了迅速发展。其中，磁性随机存储器(MRAM)凭借其拥有静态随机存储器(SRAM)的高速读取写入能力，动态随机存储器(DRAM)的高集成度，功耗远远的低于动态随机存储器，并且相对于快闪存储器(Flash)随着使用时间的增加性能不会发生退化等优势，受到业界越来越多的关注，被认为是极有可能替代静态随机存取存储器、动态随机存取存储器、闪存，而成为下一代“通用”存储器的强有力候选者之一。产业界及科研机构致力于优化电路设计、工艺方法及集成方案以获得能够成功商业化的磁性随机存储器器件。
磁隧道结(MTJ)是磁性随机存储器的核心结构，该结构由固定层、非磁性隔离层和自由层组成。其中，固定层较厚，磁性较强，磁矩不容易反转，而自由层较薄，磁性较弱，磁矩容易反转。根据自由层和固定层之间磁矩平行和反平行的变化，输出“0”或“1”的状态。自由层是存储信息的磁性薄膜，使用软铁磁材料，具有比较低的矫顽力，较高的磁导率以及对低磁场的高敏感性。常见的材料如CoFe、NiFe、NiFeCo、CoFeB(使用较多)等。隔离层是厚度仅有0.5～2nm的非磁性薄膜，如MgO或Al 2O 3等。固定层是MRAM单元中磁场具有固定方向的薄膜。材料的选择应当与反铁磁层具有较强的交换偏置作用，从而使被钉扎层的磁矩能够被有效地钉扎在固定的方向上。关于这类材料，比较合适的有CoFe，CoFeB等。
磁隧道结图形化的主要方法还是需要通过刻蚀的方法，因为如上所述磁隧道结的材料是难于干法刻蚀的材料Fe，Co，Mg等，难以形成挥发产物， 且不能采用腐蚀气体(Cl 2等)，否则会影响磁隧道结的性能，所以需要用到比较复杂的刻蚀方法才能实现，刻蚀工艺非常具有难度和挑战。
传统的大尺寸磁隧道结刻蚀都是通过离子束刻蚀完成的。由于离子束刻蚀采用惰性气体，基本上没有引入化学刻蚀的成分进入反应腔室，从而使得磁隧道结的侧壁不受化学反应的侵蚀。在保证侧壁干净的情况下，离子束刻蚀可以获得比较完美的磁隧道结侧壁——干净并且没有受到化学破坏。但是，离子束刻蚀也有其不完美的一面。一方面，离子束刻蚀能够实现的一个原理是采用较高的物理轰击力，而过大的物理轰击力会导致磁隧道结侧壁尤其是隔离层以及附近的核心层的原子层排序受到干扰，从而破坏磁隧道结的磁性特征。另一方面，离子束刻蚀都采用一定的角度实现刻蚀，这个为离子束刻蚀带来了局限性。随着磁隧道结器件尺寸做的越来越小，磁隧道结本身膜层的厚度以及掩膜的厚度不能无止境的被压缩，进入30纳米以及以下的磁隧道结器件的高宽比一般都是在2:1以上。如图1所示，当高宽比为2:1时，磁隧道结的关键尺寸(CD)为线距的一半时，离子束刻蚀时可以达到磁隧道结底部的最大角度为27度。磁隧道结尺寸越小时，这个高宽比越高。这个高宽比使得离子束刻蚀常用的角度不能达到磁隧道结的底部，从而达不到磁隧道结器件分离的需求，使得图形化失败。再者，离子束刻蚀的时间相对较长，每台设备的产率有限。
发明内容
为解决上述问题，本发明公开一种磁隧道结刻蚀方法，所使用的刻蚀装置包括样品装载腔室、真空过渡腔室、反应离子等离子体刻蚀腔室、离子束刻蚀腔室、镀膜腔室以及真空传输腔室，其特征在于，在不中断真空的情况下，在反应离子等离子体刻蚀腔室、离子束刻蚀腔室、镀膜腔室依照特定序列及条件对晶圆进行加工、处理，包括以下步骤：样品准备步骤，在半导体衬底上形成包含磁隧道结的待刻蚀结构；样品装载步骤，将所述样品装载到样品装载腔室，并使所述样品通过真空过渡腔室，进入真空传输腔室；反应离子刻蚀步骤，使样品进入到反应离子等离子体刻蚀腔室，利用反应离子等离子体对样品进行刻蚀至底电极层，之后使所述样品返回到真空传输腔室；离子束清洗步骤，使所述样品进入到离子束刻蚀腔室，利用离子束进行金属残留 物去除以及样品表面处理，使所述反应离子刻蚀步骤中所形成的侧壁金属沾污以及侧壁损伤层完全去除，同时，完全去除器件底电极上方、以及不同器件底电极之间介质层上方的金属残留，之后使所述样品返回到真空传输腔室；保护步骤，使所述样品进入到镀膜腔室，在完成刻蚀的样品上表面和周边进行镀膜保护，之后使所述样品返回到所述真空传输腔室；以及样品取出步骤，将所述样品从所述真空传输腔室，通过所述真空过渡腔室，返回到样品装载腔室。
本发明的磁隧道结刻蚀方法中，所述刻蚀及处理序列为：
所述刻蚀及处理序列为：用反应离子等离子刻蚀腔室将硬掩膜已经预先打开的磁隧道结完整刻蚀到底电极或者底电极之间的介质层裸露，之后用离子束刻蚀腔室对磁隧道结及其底部进行清洗，之后用镀膜腔室对磁隧道结进行镀膜保护，然后使晶圆返回大气环境。
本发明的磁隧道结刻蚀方法中，优选为，所述离子束刻蚀的角度为10度到80度，其中，所述角度为离子束相对于样品台的法向面的角度。
本发明的磁隧道结刻蚀方法中，优选为，在所述离子束清洗步骤中，去除厚度为0.1nm～10.0nm的磁隧道结的侧壁。
本发明的磁隧道结刻蚀方法中，优选为，在所述反应离子刻蚀步骤中，所使用的气体包括惰性气体、氮气、氧气、氟基气体、NH 3、氨基气体、CO、CO 2、醇类及其组合，所述反应离子刻蚀步骤可以是单步或者多步，在多步的过程中，不同步骤所使用的气体、功率、气流、压力可以相同或者不同。
本发明的磁隧道结刻蚀方法中，优选为，在所述离子束清洗步骤中，所使用的气体包括惰性气体、氮气、氧气及其组合，所述离子束清洗步骤可以是单步清洗或多步清洗，在多步清洗的过程中，不同步骤所使用的气体、样品台相对于离子束的角度、离子束的能量以及密度可以相同或者不同。
本发明的磁隧道结刻蚀方法中，优选为，在所述保护步骤中，所镀薄膜为使相邻磁隧道结器件分离的介质材料。
本发明的磁隧道结刻蚀方法中，优选为，所述镀膜介质材料为四族氧化物、四族氮化物、四族氮氧化物、过渡金属氧化物、过渡金属氮化物、过渡金属氮氧化物、碱土金属氧化物、碱土金属氮化物、碱土金属氮氧化物、或其组合。
本发明的磁隧道结刻蚀方法中，优选为，在所述保护步骤中，镀膜的厚度为1nm～500nm。
本发明的磁隧道结刻蚀方法中，优选为，所述反应离子刻蚀步骤中所形成的所述侧壁金属沾污为纳米级。
本发明的磁隧道结刻蚀方法中，优选为，所述反应离子刻蚀步骤中所形成的所述侧壁损伤层厚度为纳米级。
本发明的磁隧道结刻蚀方法中，优选为，所述刻蚀方法适用于固定层在隔离层上方、或者固定层在隔离层下方的磁隧道结的刻蚀。
本发明的磁隧道结刻蚀方法中，优选为，所述刻蚀方法适用于隔离层为单层或者多层的磁隧道结的刻蚀。
本发明的磁性隧道结刻蚀方法，适用于磁性隧道结、过渡金属及其氧化物的刻蚀。本发明能够克服高密度的小器件生产的瓶颈，同时能够大幅提高器件的良率、可靠性，制造方法简单、快捷，由此提高了生产效率。
附图说明
图1是假设磁隧道结的分布都是CD＝1/2线距，采用离子束刻蚀磁隧道结时最大可使用的角度与磁隧道结高宽比的关系图。
图2是本发明的磁隧道结刻蚀方法所使用刻蚀装置的功能框图。
图3是磁隧道结刻蚀方法的流程图。
图4是包含磁隧道结的待刻蚀器件结构示意图。
图5是固定层在隔离层上方的磁隧道结的结构示意图。
图6是进行反应离子刻蚀步骤后所形成的器件结构示意图。
图7是进行离子束清洗步骤后所形成的器件结构示意图。
图8是进行保护步骤后所形成的器件结构示意图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，应当理解，此处所描述的具体实施例仅用以解释本发明，并不用于限定本发明。所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基 于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其它实施例，都属于本发明保护的范围。
在本发明的描述中，需要说明的是，术语“上”、“下”、“陡直”、“倾斜”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本发明和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本发明的限制。此外，术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性。
此外，在下文中描述了本发明的许多特定的细节，例如器件的结构、材料、尺寸、处理工艺和技术，以便更清楚地理解本发明。但正如本领域的技术人员能够理解的那样，可以不按照这些特定的细节来实现本发明。除非在下文中特别指出，器件中的各个部分可以由本领域的技术人员公知的材料构成，或者可以采用将来开发的具有类似功能的材料。
以下，结合附图，针对本发明的磁隧道结刻蚀方法所使用的装置进行说明。图2是本发明的磁隧道结刻蚀方法所使用的刻蚀装置的功能框图。如图2所示，刻蚀装置包括反应离子等离子体刻蚀腔室10、离子束刻蚀(IBE)腔室11、镀膜腔室12、真空传输腔室13、真空过渡腔室14和样品装载腔室15。其中，真空过渡腔室14分别与样品装载腔室15和真空传输腔室13以可联通的方式相连接。反应离子等离子体刻蚀腔室10、离子束刻蚀腔室11、镀膜腔室12分别与真空传输腔室13以可联通的方式相连接。此外，上述各腔室也可以为多个。
反应离子等离子体刻蚀腔室10可以是电感耦合等离子体(ICP)腔室、电容耦式等离子体(CCP)腔室、螺旋波等离子体腔室等反应离子等离子体刻蚀腔室。离子束刻蚀(IBE)腔室11可以是离子束刻蚀、中性粒子束刻蚀腔体等。镀膜腔室12可以是物理气相沉积(PVD)镀膜腔室，也可以是脉冲化学气相沉积(Pulsed CVD)镀膜腔室、等离子体增强化学气相沉积(PECVD)镀膜腔室、电感耦合等离子体增强化学气相沉积(ICP-PECVD)镀膜腔室、原子层(ALD)镀膜腔室等化学气相沉积(CVD)镀膜腔室。
此外，刻蚀装置还包括用于实现样品在各腔室的传递的样品传输系统、用于对各腔室及样品传输系统等进行控制的控制系统、用于实现各腔室所需的真空度的真空抽气系统、以及冷却系统等常规刻蚀装置所包含的功能单元。 这些装置结构均可以由本领域技术人员利用现有技术加以实现。
图3是磁隧道结刻蚀方法的流程图。如图3所示，本发明的磁隧道结刻蚀方法通过以下步骤实现。
首先，在样品准备步骤S1中，在半导体衬底上形成包含磁隧道结的待刻蚀结构。在图4中示出了包含磁隧道结的待刻蚀器件结构示意图。如图4所示，待刻蚀结构包括底电极金属层100、磁隧道结(包括固定层101、隔离层102和自由层103)、帽层104以及硬掩膜层105。需要说明的是，该结构仅示例，在实际的器件应用中，磁隧道结的组成还可以是自由层在隔离层的下方，而固定层在隔离层的上方，如图5所示。另外，隔离层还可以是两层或者两层以上，等等。本发明的磁性隧道结刻蚀方法适用于所有这些不同的结构。
接下来，在样品装载步骤S2中，将样品装载到样品装载腔室15，并使样品通过真空过渡腔室14，进入真空传输腔室13。
接下来，在反应离子刻蚀步骤S3中，使样品进入到反应离子等离子体刻蚀腔室10，利用反应离子等离子体对样品进行刻蚀，之后使样品返回到真空传输腔室13。在反应离子等离子体刻蚀腔室里所使用的气体可以为惰性气体、氮气、氧气、氟基气体、NH 3、氨基气体、CO、CO 2、醇类等可以用于刻蚀的有机气体。当刻蚀达到底电极时，停止刻蚀。刻蚀过程要实现器件的分离以及器件所需的陡直度。刻蚀形成的器件侧壁以没有金属沾污为目标，但是纳米级的金属沾污，或者极微量的如小于1nm的金属沾污是难以完全避免的。同时，刻蚀过程中可能会形成磁隧道结侧壁的纳米级的损伤层，也有可能没有完全清除掉器件底电极上方、以及不同器件底电极之间介质层上方的金属残留。图6是进行反应离子刻蚀步骤后所形成的器件结构示意图。图6中示意性地示出了在等离子体刻蚀过程中形成的金属沾污106以及磁隧道结侧壁的损伤层107。反应离子刻蚀步骤可以是单步或者多步，在多步的过程中，不同步骤所使用的气体、功率、气流、压力可以相同或者不同。
接下来，在离子束清洗步骤S4中，使所述样品进入到离子束刻蚀腔室11，利用离子束进行金属残留物去除以及样品表面处理，使上述反应离子刻蚀步骤中形成的侧壁金属沾污以及侧壁损伤层完全去除，同时，完全去除器件底电极上方、不同器件底电极之间的介质层上方的金属残留，实现器件的完全 电学隔离，避免器件与器件之间的短路。之后使样品返回到真空传输腔室13。离子束刻蚀腔室里使用的气体可以为惰性气体、氮气、氧气等。离子束清洗步骤可以是单步清洗或多步清洗，在多步清洗的过程中，不同步骤所使用的气体、离子束的角度、能量以及密度可以相同或者不同。离子束刻蚀使用的角度优选为10度到80度(以垂直于晶圆表面为参照，垂直为0度)。优选为，将0.1nm～10.0nm的磁隧道结的侧壁去除。在器件经过上述的两腔室的刻蚀步骤后，器件的侧壁干净并且实现了完全分离。在图7中示出了进行离子束清洗步骤后所形成的器件结构示意图。
接下来，在保护步骤S5中，使样品进入到镀膜腔室12，在完成刻蚀的样品上表面和周边进行镀膜保护，之后使样品返回到真空传输腔室13。在图8中示出了进行保护步骤后的器件结构示意图。其中，所镀薄膜108是使相邻磁隧道结器件分离的介质材料。介质薄膜材料可以是四族氧化物、四族氮化物、四族氮氧化物、过渡金属氧化物、过渡氮化物、过渡氮氧化物、碱土金属氧化物、碱土氮化物、碱土氮氧化物等可以实现相邻磁隧道结器件分离的介质材料。镀膜的厚度可以是1nm以上，500nm以下。通过在镀膜腔室的原位镀膜保护能够防止器件在后续的工艺中因裸露在大气环境中而被破坏，同时实现器件与器件间的完全绝缘隔离。
最后，在样品取出步骤S6中，将样品从真空传输腔室13，通过真空过渡腔室14，返回到样品装载腔室15。
相比较于传统的刻蚀而言，本发明的磁隧道结刻蚀方法具有如下优点：依靠经过大规模生产验证的反应离子刻蚀腔室对器件进行快速、完整的图形化。在不破坏真空的前提下，依靠离子束刻蚀腔室对磁隧道结进行表面处理，消除反应离子刻蚀机本身刻蚀过程中带来的不利影响，包括器件金属沾污及侧壁损伤等。
在反应离子刻蚀完成图形化后，掩膜层通常已经消耗很多，这时总体器件(包括掩膜层)的高宽比大幅下降，这使得后续的离子束刻蚀腔室的清洗工艺能够以相对较大倾斜的角度对整体的器件侧壁进行彻底的清洗及表面处理。此方法可以克服高密度(1：1等间距)的小器件(20nm及以下)生产的瓶颈。由于金属沾污以及侧壁损伤的去除，可以大幅提高器件的良率以及可靠性。制造方法简单、快捷，样品只需要进入每种腔室一次，即能够顺序完 成工艺加工。刻蚀时间比只用离子束刻蚀腔室的情况下缩短1/3到1/2，由此提高了产率。
以上，针对本发明的磁隧道结刻蚀方法的具体实施方式进行了详细说明，但是本发明不限定于此。各步骤的具体实施方式根据情况可以不同。此外，基于部分步骤的顺序可以调换，部分步骤可以省略等。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到的变化或替换，都应涵盖在本发明的保护范围之内。

Claims (13)

  1. 一种磁隧道结刻蚀方法，所使用的刻蚀装置包括样品装载腔室、真空过渡腔室、反应离子等离子体刻蚀腔室、离子束刻蚀腔室、镀膜腔室以及真空传输腔室，其特征在于，在不中断真空的情况下，在反应离子等离子体刻蚀腔室、离子束刻蚀腔室、镀膜腔室依照特定序列及条件对晶圆进行加工、处理，包括以下步骤：
    样品准备步骤，在半导体衬底上形成包含磁隧道结的待刻蚀结构；
    样品装载步骤，将所述样品装载到样品装载腔室，并使所述样品通过真空过渡腔室，进入真空传输腔室；
    反应离子刻蚀步骤，使样品进入到反应离子等离子体刻蚀腔室，利用反应离子等离子体对样品进行刻蚀至底电极，之后使所述样品返回到真空传输腔室；
    离子束清洗步骤，使所述样品进入到离子束刻蚀腔室，利用离子束进行金属残留物去除以及样品表面处理，使所述反应离子刻蚀步骤中所形成的侧壁金属沾污以及侧壁损伤层完全去除，同时，完全去除器件底电极上方、以及不同器件底电极之间介质层上方的金属残留，之后使所述样品返回到真空传输腔室；
    保护步骤，使所述样品进入到镀膜腔室，在完成刻蚀的样品上表面和周边进行镀膜保护，之后使所述样品返回到真空传输腔室；以及
    样品取出步骤，将所述样品从真空传输腔室，通过真空过渡腔室，返回到样品装载腔室。
  2. 根据权利要求1所述的磁隧道结刻蚀方法，其特征在于
    所述刻蚀及处理序列为：用反应离子等离子刻蚀腔室将硬掩膜已经预先打开的磁隧道结完整刻蚀到底电极或者底电极之间的介质层，之后用离子束刻蚀腔室对磁隧道结及其底部进行清洗，之后用镀膜腔室对磁隧道结进行镀膜保护，然后使晶圆返回大气环境。
  3. 根据权利要求1所述的磁隧道结刻蚀方法，其特征在于，
    所述离子束刻蚀的角度为10度到80度，其中所述角度为离子束相对于样品台的法向面的角度。
  4. 根据权利要求1所述的磁隧道结刻蚀方法，其特征在于，
    在所述离子束清洗步骤中，去除厚度为0.1nm～10.0nm的磁隧道结的侧壁。
  5. 根据权利要求1所述的磁隧道结刻蚀方法，其特征在于，
    在所述反应离子刻蚀步骤中，所使用的气体包括惰性气体、氮气、氧气、氟基气体、NH 3、氨基气体、CO、CO 2、醇类及其组合，所述反应离子刻蚀步骤可以是单步或者多步，在多步的过程中，不同步骤所使用的气体、功率、气流、压力可以相同或者不同。
  6. 根据权利要求1所述的磁隧道结刻蚀方法，其特征在于，
    在所述离子束清洗步骤中，所使用的气体包括惰性气体、氮气、氧气及其组合，所述离子束清洗步骤可以是单步清洗或多步清洗，在多步清洗的过程中，不同步骤所使用的气体、样品台相对于离子束的角度、离子束的能量以及密度可以相同或者不同。
  7. 根据权利要求1所述的磁隧道结刻蚀方法，其特征在于，
    在所述保护步骤中，所镀薄膜为使相邻磁隧道结器件分离的介质材料。
  8. 根据权利要求7所述的磁隧道结刻蚀方法，其特征在于，
    所述镀膜介质材料为四族氧化物、四族氮化物、四族氮氧化物、过渡金属氧化物、过渡金属氮化物、过渡金属氮氧化物、碱土金属氧化物、碱土金属氮化物、碱土金属氮氧化物、或其组合。
  9. 根据权利要求7所述的磁隧道结刻蚀方法，其特征在于，
    在所述保护步骤中，镀膜的厚度为1nm～500nm。
  10. 根据权利要求1所述的磁隧道结刻蚀方法，其特征在于，
    所述反应离子刻蚀步骤中所形成的所述侧壁金属沾污为纳米级。
  11. 根据权利要求1所述的磁隧道结刻蚀方法，其特征在于，
    所述反应离子刻蚀步骤中所形成的所述侧壁损伤层厚度为纳米级。
  12. 根据权利要求1所述的磁隧道结刻蚀方法，其特征在于，
    所述刻蚀方法适用于固定层在隔离层上方、或者固定层在隔离层下方的磁隧道结的刻蚀。
  13. 根据权利要求1所述的磁隧道结刻蚀方法，其特征在于，
    所述刻蚀方法适用于隔离层为单层或者多层的磁隧道结的刻蚀。
PCT/CN2019/087843 2018-08-03 2019-05-21 一种磁隧道结刻蚀方法 WO2020024668A1 (zh)

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