CN115565843A - A Plasma Chamber for Improving Radial Uniformity of Plasma - Google Patents

Abstract

The invention discloses a plasma chamber for improving the radial uniformity of plasma, which comprises a vacuum chamber with a coil arranged above and a gas reaction chamber arranged below, wherein the upper chamber and the lower chamber are separated by a middle medium window; an electrostatic chuck is arranged in the gas reaction chamber and used for fixing the wafer; the substrate of the gas reaction chamber is connected with a lower radio frequency bias assembly and is used for forming a bias electric field on the surface of the wafer; the dielectric window is of a ladder-shaped structure with a concave center and a convex periphery, and the ladder is positioned right above the edge of the maximum wafer which can be etched and is used for increasing the number of plasmas at the edge of the wafer and reducing the difference of the number of plasmas from the center to the edge of the wafer; the coil comprises an inner coil and an outer coil, the inner coil is positioned at the concave position of the mass window, and the outer coil is positioned at the convex position of the mass window; the vertical distance of the coil relative to the dielectric window is adjustable, and the coil is used for changing the depth of the radio frequency power coupling plasma at the gas reaction position, so that the uniformity of the plasma in the reaction cavity is improved.

Description

Translated fromChinese

一种提高等离子体径向均匀性的等离子体腔室A Plasma Chamber for Improving Radial Uniformity of Plasma

技术领域technical field

本发明属于半导体制造领域，涉及一种应用于半导体表面改性及表面处理的感性耦合等离子体反应室。The invention belongs to the field of semiconductor manufacturing and relates to an inductively coupled plasma reaction chamber applied to semiconductor surface modification and surface treatment.

背景技术Background technique

随着硅基集成电路技术遵循摩尔定律向更小尺度发展,在晶圆边缘的晶体管数目越来越多。因此,对晶圆边缘刻蚀工艺的优化也越来越重要。在传统的感性耦合等离子源产生的等离子体在反应腔室内的分布特征，通常是沿着腔室径向，靠近腔室中间位置分布较多且均匀，靠近腔室边缘等离子体数目逐渐减小。由于待刻蚀的晶圆位于腔室的底部，其直径也达到腔室内径向等离子体均匀性发生变化的临界位置。这会导致沿圆径向不同位置处的参与刻蚀反应的等离子体通量不同，造成刻蚀速率不一，无法满足半导体生产工艺的要求，产生次品。As silicon-based integrated circuit technology follows Moore's law and develops to smaller scales, the number of transistors at the edge of the wafer is increasing. Therefore, the optimization of the wafer edge etching process is becoming more and more important. The distribution characteristics of the plasma generated by the traditional inductively coupled plasma source in the reaction chamber are usually distributed more and uniformly along the radial direction of the chamber, near the middle of the chamber, and the number of plasma gradually decreases near the edge of the chamber. Since the wafer to be etched is located at the bottom of the chamber, its diameter also reaches the critical position where radial plasma uniformity in the chamber changes. This will lead to different plasma fluxes participating in the etching reaction at different positions along the radial direction, resulting in different etching rates, which cannot meet the requirements of the semiconductor production process and produce defective products.

发明内容Contents of the invention

本发明的目的在于提供一种提高感性耦合等离子体径向均匀性的等离子体腔室，以可以提高气体反应腔室内径向边缘区域的等离子体数量，从而提高等离子体的径向均匀性。The object of the present invention is to provide a plasma chamber that improves the radial uniformity of the inductively coupled plasma, so as to increase the amount of plasma in the radial edge region of the gas reaction chamber, thereby improving the radial uniformity of the plasma.

实现本发明目的的技术解决方案为：The technical solution that realizes the object of the present invention is:

一种提高等离子体径向均匀性的等离子体腔室，包括上方放置线圈的真空腔室以及下方的气体反应腔室，上下两腔室由中间介质窗隔开；A plasma chamber for improving the radial uniformity of plasma, comprising a vacuum chamber with coils placed above and a gas reaction chamber below, the upper and lower chambers are separated by an intermediate dielectric window;

所述气体反应腔室内设有静电卡盘，用于固定晶圆；The gas reaction chamber is provided with an electrostatic chuck for fixing the wafer;

所述气体反应腔室的基底连接下射频偏压组件，用以在晶圆表面形成偏压电场；The base of the gas reaction chamber is connected with a lower RF bias component to form a bias electric field on the surface of the wafer;

所述介质窗采用中心下凹，一周凸起的阶梯型结构，阶梯位于所能刻蚀的最大晶圆的边缘的正上方，用于提升晶圆边缘等离子体数，减少从晶圆中心到边缘的等离子体数目的差异；The dielectric window adopts a stepped structure with a concave center and a raised circumference. The step is located directly above the edge of the largest wafer that can be etched, which is used to increase the number of plasmas at the edge of the wafer and reduce the number of plasmas from the center to the edge of the wafer. The difference in the number of plasmas;

线圈包括内线圈和外线圈，内线圈位于质窗下凹位置，外线圈位于质窗上凸位置；The coil includes an inner coil and an outer coil, the inner coil is located at the concave position of the mass window, and the outer coil is located at the convex position of the mass window;

线圈相对介质窗的垂直距离可调，用于改变气体反应处射频功率耦合等离子体的深度，从而改善反应腔室内等离子体的均匀性。The vertical distance of the coil relative to the dielectric window is adjustable, which is used to change the depth of the RF power coupling plasma at the gas reaction place, thereby improving the uniformity of the plasma in the reaction chamber.

本发明与现有技术相比，其显著优点是：Compared with the prior art, the present invention has the remarkable advantages of:

本发明相较传统感性耦合等离子体腔室，将平面形介质窗替换成阶梯形介质窗，可显著增加气体反应腔室内径向边缘区域处的等离子体数量，提高了气体反应腔室内等离子体径向均匀性；将同一平面固定的线圈改进成高度可调整的内外线圈，可进一步达到提高对气体反应腔室内等离子体径向均匀性的调控能力。Compared with the traditional inductively coupled plasma chamber, the present invention replaces the planar dielectric window with a stepped dielectric window, which can significantly increase the amount of plasma in the radial edge region of the gas reaction chamber, and improve the radial direction of the plasma in the gas reaction chamber. Uniformity: improving the fixed coils on the same plane into height-adjustable inner and outer coils can further improve the ability to control the radial uniformity of the plasma in the gas reaction chamber.

附图说明Description of drawings

图1为本发明一种改善径向刻蚀均匀性的感性耦合等离子体反应腔室的主视局部剖视结构图。FIG. 1 is a front view partial cross-sectional structure diagram of an inductively coupled plasma reaction chamber for improving radial etching uniformity according to the present invention.

具体实施方式detailed description

下面结合附图及具体实施例对本发明做进一步的介绍。The present invention will be further introduced below in conjunction with the accompanying drawings and specific embodiments.

结合图1，本实施例提供了一种提高感性耦合等离子体径向均匀性的等离子体腔室，整个腔体为圆柱形，其中包括：上方放置线圈的真空腔室1以及下方的气体反应腔室16；上下两腔室由中间的阶梯形石英介质窗17隔开；位于石英介质窗17上侧平面放置多个可以调整高度的内外感性耦合射频线圈7a&7b。其中，内线圈7a共四匝，位于阶梯形石英介质窗17下凹位置，外线圈7b共两匝，位于阶梯形石英介质窗17上凸位置；内线圈7a连接低于射频电源3和与第一射频电源3相对应的第一阻抗匹配器4；外线圈7b连接第二射频电源5和与第二射频电源5相对应的第二阻抗匹配器6；位于所述气体反应腔室16的侧壁中部开有Langmuir探针通道8，用以放置Langmuir探针9，在不进行探针测量时处于封闭状态。用于盛放晶圆的基底14位于所述气体反应腔室16底部。所述基底14的上设有用以固定晶圆的圆环静电卡盘10，基底14连接下射频偏压组件，下射频偏压组件包括下射频偏压电源及下匹配器；基底14的底部连接用以控制等离子体鞘层的外部射频偏压电源12以及对应射频偏压电源12的阻抗匹配器13，用以在晶圆表面形成偏压电场；圆柱气体导管2位于整个腔体的中心，贯穿上方真空腔1和阶梯形石英介质窗17，内部与气体反应腔相通，外部与充有反应气体的气泵相连。所述基底两侧为气体反应腔室的气体出口15，接通分子泵和离子泵。1, this embodiment provides a plasma chamber that improves the radial uniformity of inductively coupled plasma. The entire chamber is cylindrical, including: a vacuum chamber 1 with coils placed above and a gas reaction chamber below. 16. The upper and lower chambers are separated by a stepped quartzdielectric window 17 in the middle; on the upper side of the quartzdielectric window 17, a plurality of internal and external inductively coupledradio frequency coils 7a & 7b that can be adjusted in height are placed on the plane. Among them, theinner coil 7a has a total of four turns, located at the concave position of the stepped quartzdielectric window 17, and theouter coil 7b has two turns, located at the raised position of the stepped quartzdielectric window 17; theinner coil 7a is connected lower than the radio frequency power supply 3 and connected to the first A first impedance matcher 4 corresponding to the radio frequency power supply 3; theouter coil 7b is connected to the second radio frequency power supply 5 and the second impedance matcher 6 corresponding to the second radio frequency power supply 5; located on the side of thegas reaction chamber 16 There is a Langmuir probe channel 8 in the middle of the wall for placing the Langmuir probe 9, which is in a closed state when the probe is not being measured. Abase 14 for containing wafers is located at the bottom of thegas reaction chamber 16 . Thebase 14 is provided with an annularelectrostatic chuck 10 for fixing the wafer, thebase 14 is connected to the lower RF bias assembly, and the lower RF bias assembly includes the lower RF bias power supply and the lower matching device; the bottom of thebase 14 is connected to An external radio frequencybias power supply 12 for controlling the plasma sheath and an impedance matcher 13 corresponding to the radio frequencybias power supply 12 are used to form a bias electric field on the surface of the wafer; the cylindrical gas conduit 2 is located in the center of the entire chamber, Through the upper vacuum chamber 1 and the stepped quartzdielectric window 17, the inside communicates with the gas reaction chamber, and the outside connects with the gas pump filled with reaction gas. Both sides of the substrate aregas outlets 15 of the gas reaction chamber, which are connected to molecular pumps and ion pumps.

本发明利用反应腔室上方的阶梯形石英介质窗17阻碍处于阶梯形状位置左右两端电子的输运，使得该阶梯位置处(阶梯位置处正对晶圆外轮廓处，如图中虚线)的热电子浓度升高。热电子将会与反应腔室内的中性气体产生较多碰撞电离进而在该处而产生足够多的等离子体。由于该阶梯形状位于所能刻蚀的最大晶圆11的边缘的正上方(虚线所标示)。所以，这种设计可以有效提升晶圆边缘等离子体数，减少从晶圆中心到边缘的等离子体数目的差异。从而满足晶圆径向刻蚀均匀性的工艺要求。The present invention utilizes the step-shaped quartzdielectric window 17 above the reaction chamber to hinder the transport of electrons at the left and right ends of the step-shaped position, so that the electrons at the step position (the step position is directly opposite to the outer contour of the wafer, as shown in the dotted line in the figure) The concentration of hot electrons increases. The hot electrons will generate more impact ionization with the neutral gas in the reaction chamber to generate enough plasma there. Since the stepped shape is located directly above the edge of thelargest wafer 11 that can be etched (indicated by a dotted line). Therefore, this design can effectively increase the number of plasmas at the edge of the wafer and reduce the difference in the number of plasmas from the center of the wafer to the edge. In this way, the technological requirement of radial etching uniformity of the wafer is met.

可以调整高度的内外感性耦合射频线圈7a&7b位于阶梯形石英介质窗17上侧。其中，内线圈7a共四匝等间距排布于阶梯形石英介质窗下凹位置，外线圈(图一7b)共两匝位于阶梯形石英介质窗上凸位置。一般情况下，二者的高度处于同一水平面。调整感应耦合线圈与阶梯形石英介质窗17的垂直距离，可改变气体反应处射频功率耦合等离子体的深度，从而改善所述反应腔室内等离子体的均匀性。例如，利用Langmuir探针9探测到沿气体反应腔室内的径向某个区域的等离子体密度相较主体区域低很多时，可将与该区域离得最近的感应耦合线圈与阶梯形石英介质窗的垂直距离适当的调小，可增大该区域的感应电磁场强度，使电子在该区域受电磁场的加速增强，产生较多的电离碰撞，最终使得该区域的等离子体密度提高。The height-adjustable internal and external inductive couplingradio frequency coils 7a & 7b are located on the upper side of the stepped quartzdielectric window 17 . Among them, a total of four turns of theinner coil 7a are arranged at equal intervals at the concave position of the stepped quartz dielectric window, and a total of two turns of the outer coil (Fig. 1 7b) are located at the convex position of the stepped quartz dielectric window. In general, the heights of the two are at the same level. Adjusting the vertical distance between the inductive coupling coil and the stepped quartzdielectric window 17 can change the depth of the RF power coupled plasma at the gas reaction place, thereby improving the uniformity of the plasma in the reaction chamber. For example, when the Langmuir probe 9 is used to detect that the plasma density in a certain area along the radial direction in the gas reaction chamber is much lower than that in the main body area, the inductive coupling coil closest to the area can be connected with the stepped quartz dielectric window Appropriately reducing the vertical distance can increase the intensity of the induced electromagnetic field in this area, so that electrons are accelerated by the electromagnetic field in this area, resulting in more ionization collisions, and finally increasing the plasma density in this area.

可改变位于阶梯形石英介质窗17上平面的内外感性耦合射频线圈7a&7b各自所加的电流和频率，来调整气体反应腔室16内的感应电磁场强度和空间分布，从而对电子在该电磁场的作用下发生电离碰撞的数量产生影响。通过上述机制，可调节反应腔室气体电离的径向均匀性，使气体反应腔室内产生的等离子体在晶圆11的刻蚀过程中沿径向保持均匀分布。The current and frequency applied by the inner and outer inductively coupledradio frequency coils 7a & 7b on the upper plane of the stepped quartzdielectric window 17 can be changed to adjust the induced electromagnetic field intensity and spatial distribution in thegas reaction chamber 16, thereby controlling the effect of electrons in the electromagnetic field. impact on the number of ionizing collisions that occur next. Through the above mechanism, the radial uniformity of gas ionization in the reaction chamber can be adjusted, so that the plasma generated in the gas reaction chamber can be uniformly distributed in the radial direction during the etching process of thewafer 11 .

当待加工的晶圆尺寸较小时，通过等离子体探针测得晶圆上方等离子体在径向分布较为均匀(在设定阈值范围内)。此时，排布于阶梯形石英介质窗的下凹平面的感应线圈在腔室工作时处于通电状态；排布于阶梯形石英介质窗的上凸平面的感应线圈在腔室工作时处于断电状态。When the size of the wafer to be processed is small, the radial distribution of the plasma above the wafer is relatively uniform (within the set threshold range) as measured by the plasma probe. At this time, the induction coil arranged on the concave plane of the stepped quartz dielectric window is in a power-on state when the chamber is working; the induction coil arranged on the convex plane of the stepped quartz dielectric window is in a power-off state when the chamber is working state.

随着待加工的晶圆半径尺寸增大，当等离子体探针测出等离子体在晶圆上方径向分布不均匀(在设定阈值范围外)(等离子体在晶圆边缘的数量较晶圆中心区域的数量少很多)，此时让梯形介质窗的上凸平面的感应线圈从原先断电状态变为通电状态。给晶圆边缘部分气体施加适当的额外功率促使其电离，增加边缘等离子体的密度。可通过调整调节感应线圈与介质窗上表面的垂直距离以及各自所加的电流和频率，来调节反应腔室气体电离的径向均匀性，使所述气体反应腔室内产生的等离子体在晶圆刻蚀过程中保持径向分布均匀，以满足刻蚀的均匀性的必要条件。As the radius of the wafer to be processed increases, when the plasma probe detects that the radial distribution of the plasma above the wafer is uneven (outside the set threshold range) (the amount of plasma at the edge of the wafer is greater than that of the wafer The number of central regions is much less), at this time, the induction coil on the upper convex plane of the trapezoidal dielectric window is changed from the original power-off state to the power-on state. Appropriate extra power is applied to the gas at the edge of the wafer to promote its ionization and increase the density of the edge plasma. The radial uniformity of gas ionization in the reaction chamber can be adjusted by adjusting the vertical distance between the induction coil and the upper surface of the dielectric window and the respective applied current and frequency, so that the plasma generated in the gas reaction chamber During the etching process, the radial distribution is kept uniform, so as to meet the necessary conditions for the uniformity of etching.

Claims (6)

Translated fromChinese

1.一种提高等离子体径向均匀性的等离子体腔室，包括上方放置线圈的真空腔室以及下方的气体反应腔室，上下两腔室由中间介质窗隔开；1. A plasma chamber for improving the radial uniformity of plasma, comprising a vacuum chamber with coils placed above and a gas reaction chamber below, the upper and lower chambers are separated by an intermediate dielectric window;所述气体反应腔室内设有静电卡盘，用于固定晶圆；The gas reaction chamber is provided with an electrostatic chuck for fixing the wafer;其特征在于，It is characterized in that,所述气体反应腔室的基底连接下射频偏压组件，用以在晶圆表面形成偏压电场；The base of the gas reaction chamber is connected with a lower RF bias component to form a bias electric field on the surface of the wafer;所述介质窗采用中心下凹，一周凸起的阶梯型结构，阶梯位于所能刻蚀的最大晶圆的边缘的正上方，用于提升晶圆边缘等离子体数，减少从晶圆中心到边缘的等离子体数目的差异；The dielectric window adopts a stepped structure with a concave center and a raised circumference. The step is located directly above the edge of the largest wafer that can be etched, which is used to increase the number of plasmas at the edge of the wafer and reduce the number of plasmas from the center to the edge of the wafer. The difference in the number of plasmas;线圈包括内线圈和外线圈，内线圈位于质窗下凹位置，外线圈位于质窗上凸位置；The coil includes an inner coil and an outer coil, the inner coil is located at the concave position of the mass window, and the outer coil is located at the convex position of the mass window;线圈相对介质窗的垂直距离可调，用于改变气体反应处射频功率耦合等离子体的深度，从而改善反应腔室内等离子体的均匀性。The vertical distance of the coil relative to the dielectric window is adjustable, which is used to change the depth of the RF power coupling plasma at the gas reaction place, thereby improving the uniformity of the plasma in the reaction chamber.2.根据权利要求1所述的提高等离子体径向均匀性的等离子体腔室，其特征在于，于所述气体反应腔室的侧壁中部开有Langmuir探针通道，用以放置Langmuir探针，利用Langmuir探针9探测到沿气体反应腔室内的径向某个区域的等离子体密度相较主体区域低很多时，将与该区域离得最近的感应耦合线圈与介质窗的垂直距离调小，以增大该区域的感应电磁场强度，使电子在该区域受电磁场的加速增强，最终使得该区域的等离子体密度提高。2. the plasma chamber that improves plasma radial uniformity according to claim 1, is characterized in that, has Langmuir probe channel in the sidewall middle part of described gas reaction chamber, in order to place Langmuir probe, When the Langmuir probe 9 is used to detect that the plasma density in a certain area along the radial direction in the gas reaction chamber is much lower than that in the main body area, the vertical distance between the induction coupling coil closest to the area and the dielectric window is adjusted to be small, In order to increase the intensity of the induced electromagnetic field in this area, the electrons in this area are accelerated by the electromagnetic field, and finally the plasma density in this area is increased.3.根据权利要求1所述的提高等离子体径向均匀性的等离子体腔室，其特征在于，通过改变位于介质窗上的内、外线圈各自所加的电流和频率，来调整气体反应腔室内的感应电磁场强度和空间分布。3. The plasma chamber for improving the radial uniformity of plasma according to claim 1, characterized in that, by changing the current and frequency applied by the inner and outer coils on the dielectric window, the gas reaction chamber can be adjusted The induced electromagnetic field strength and spatial distribution.4.根据权利要求1所述的提高等离子体径向均匀性的等离子体腔室，其特征在于，所述介质窗采用石英介质。4 . The plasma chamber for improving plasma radial uniformity according to claim 1 , wherein the dielectric window adopts a quartz medium.5.根据权利要求1所述的提高等离子体径向均匀性的等离子体腔室，其特征在于，所述气体反应腔室两侧设有气体出口，用于接通分子泵和离子泵。5 . The plasma chamber for improving the radial uniformity of plasma according to claim 1 , wherein gas outlets are provided on both sides of the gas reaction chamber for connecting molecular pumps and ion pumps. 5 .6.根据权利要求1所述的提高等离子体径向均匀性的等离子体腔室，其特征在于，当待加工的晶圆尺寸较小时，等离子体探针测得晶圆上方等离子体在径向分布较为均匀，排布于介质窗的下凹平面的内线圈在腔室工作时处于通电状态；排布于质窗的上凸平面的外线圈在腔室工作时处于断电状态；6. The plasma chamber for improving plasma radial uniformity according to claim 1, wherein when the size of the wafer to be processed is small, the plasma probe measures the radial distribution of the plasma above the wafer Relatively uniform, the inner coil arranged on the concave plane of the dielectric window is in the energized state when the chamber is working; the outer coil arranged on the convex plane of the mass window is in the de-energized state when the chamber is working;随着待加工的晶圆半径尺寸增大，当等离子体探针测出等离子体在晶圆上方径向分布不均匀，介质窗的上凸平面的感应线圈从原先断电状态变为通电状态，并在晶圆边缘部分气体施加适当的额外功率促使其电离，增加边缘等离子体的密度。As the radius of the wafer to be processed increases, when the plasma probe detects that the radial distribution of the plasma above the wafer is uneven, the induction coil on the convex plane of the dielectric window changes from the original power-off state to the power-on state. Appropriate additional power is applied to the gas at the edge of the wafer to promote its ionization and increase the density of the edge plasma.

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