JP3138694U - Mask etch plasma reactor with cathode lift pin assembly - Google Patents

Abstract

A lift pin for a plasma reactor for etching a workpiece is provided.
A lift pin is a longitudinal body having a circular cross section including a round first end and a round second end, a notch region formed in the second end, and a plasma chamber. A notch area used to be removably coupled to a lift plate disposed on the body, the body has a first diameter area, and the notch area is separated by a shoulder and has a smaller diameter Including at least two diameter regions.
[Selection] Figure 27A

Description

Invention background

  Manufacturing a photolithography mask used for processing ultra-large scale integration (ULSI) semiconductor wafers requires higher etching uniformity than semiconductor wafer processing. A single mask pattern typically occupies an area of 4 inches square on a quartz mask. The image of the mask pattern is focused to the area of a single die (1 inch square) on the wafer and steps are formed across the wafer to form a single image on each die. Prior to etching the mask pattern into the quartz mask, the mask pattern is written into the photoresist by a scanning electron beam. This makes the mask cost very expensive in a time consuming process. The mask etching process is not uniform across the mask surface. Furthermore, the e-beam written photoresist pattern itself is not uniform, and a 45 nm feature size on the wafer will show as much as 2-3 nm variation in critical dimensions (eg, line width) across the entire mask. (This variation is, for example, a 3σ difference in all measured line widths.) Such non-uniformities in photoresist critical dimensions are typically different for different mask sources or customers. In order to meet current requirements, in the mask etching process this variation must not be increased above 1 nm, so the variation of the etching mask pattern cannot exceed 3-4 nm. These stringent requirements arise from the use of diffraction effects on the quartz mask pattern to obtain a clear image on the wafer. With current technology, it is difficult to meet such requirements. This is even more difficult for future technologies that will include a 22 nm wafer feature size. This problem is exacerbated by the phenomenon of etching bias, and the line width (critical dimension) in the etching pattern on the quartz mask decreases due to the consumption of the photoresist pattern during mask etching. These problems are inherent in the mask etch process. This is because the etch selectivity of common mask materials (quartz, chrome, molybdenum silicide) to photoresist is typically less than 1 because the mask photoresist pattern is etched during the mask etching process.

  Some mask patterns require periodic openings to be etched into the quartz mask at a precisely defined depth. This is important to achieve very fine phase alignment of the interfering light beam during exposure of the wafer through the mask. For example, in one type of phase shift mask, each line is defined by a chrome line, a thin crystal line is exposed on each side of the chrome line, and one side of the crystal line is etched to a precise depth, A 180 degree phase shift is imparted to light passing through an unetched crystal line on the other side of the line. In order to precisely control the etching depth in the quartz, the etching process must be periodically interrupted and closely monitored to measure the etching depth in the quartz. For each such inspection, the mask is removed from the mask etch reactor chamber, the photoresist is removed, the etch depth is measured, and the remaining etch process time is estimated and the target based on the elapsed etch process time. It is necessary to reach depth, deposit a new photoresist, e-beam write the mask pattern on the resist, reintroduce the mask into the mask etch chamber and restart the etching process. The estimation of the remaining etching time to reach the desired depth is presumed to be unreliable because the etching rate is assumed to remain stable and uniform. Problems with such complicated procedures include low productivity, high cost, and increased possibility of contamination of the photoresist pattern or introduction of defects. However, because of the requirement for precisely controlled etch depth, there appears to be no way to avoid such problems.

  Narrow tolerance in critical dimension variations requires a very uniform distribution of etch rate across the mask surface. There are two critical dimensions in masks that require precise etching depth in the quartz material. One is the line width and the other is the etching depth. Uniformity for both types of critical dimensions requires a uniform etch rate distribution across the mask. The nonuniformity in the etching rate distribution can be reduced to some extent by using a power supply device that can change the radial distribution of plasma ion density, such as an induction power supply device consisting of inner and outer coil antennas covering the wafer. Can do. However, such an approach can only deal with non-uniformities that are symmetric, i.e., a high center or low center etch rate distribution. In fact, the non-uniformity of the etch rate distribution can be asymmetric, for example, one corner of the mask has a high etch rate. A more fundamental limitation is that the mask etch process tends to have a very low distribution of etch rate centers. Adjustable features such as inductive power applicators with inner and outer coils cannot convert the etch rate distribution out of the low center area.

  Another problem with non-uniform etch rate distribution is that the etch rate distribution tends to be very different in different reactors of the same design and is always larger in the same reactor when replacing major parts or consumable components, such as replacing the cathode. That is different. The etch rate distribution appears to be very sensitive to small variations in the features of the replaced part, and unpredictable changes occur when consumables are replaced.

Another problem is replacing the lift pins in the reactor when the lift pins are damaged or otherwise unsuitable for use. Conventional lift pins cannot be easily replaced without the use of depth gauges and / or fasteners. This proves that access and removal are difficult due to reactor limitations.
Accordingly, there is a need for lift pins that can be easily removed or replaced without significant disassembly of the reactor.

Outline of device

  A removable lift pin for a plasma reactor for etching a workpiece is described. In one embodiment, the lift pin is a longitudinal body having a circular cross-section including a round first end and a round second end, and a notch region formed in the second end, the plasma A notch region adapted to be removably coupled to a lift plate disposed in the chamber, wherein the body has a first diameter region, and the notch region is separated by a shoulder. At least two diameter regions having a diameter smaller than one diameter region.

  In other embodiments, the lift pin includes a longitudinal shaft having a circular cross-section, a first end, and a second end, the second end having a second diameter section and a third end. A diameter section, wherein the second diameter section and the third diameter section are separated by a shoulder section having a smaller diameter than the first diameter section and having a diameter substantially equal to the first diameter section. ing.

Detailed description of the device

One cause of non-uniform etch rate distribution in a cathode mask etch process with improved RF uniformity is the RF electrical non-uniformity at the support pedestal or cathode holding the mask in the plasma reactor where the mask etch process is performed. It was found that there was sex. RF bias power is applied to the pedestal to control the plasma ion energy at the mask surface. On the other hand, the RF power source is applied to the overhead coil antenna to generate, for example, plasma ions. The RF bias power controls the electric field at the mask surface that affects the ion energy. Since the ion energy on the mask surface affects the etching rate, the distribution of the etching rate on the entire mask surface becomes non-uniform due to the RF electric non-uniformity on the pedestal. It has been found that there are several causes for RF non-uniformity in the pedestal. One is a titanium screw for fixing the aluminum pedestal (cathode) and the aluminum equipment plate together. The screw creates a node of the electric field pattern over the entire pedestal surface (and thus the entire mask surface). This is because the electrical characteristics are different from those of the aluminum cathode. The other is a non-uniform distribution of conductivity between the cathode and the equipment plate. Electrical conduction between the equipment plate and the cathode is mainly limited to the periphery of the plate and the cathode. Cathode curvature during plasma treatment induced by vacuum pressure can be at least partially due to this. This ambient conduction can be non-uniform due to a number of factors such as uneven fastening of titanium screws and / or surface finish variations around either the plate or the pedestal. These problems were solved by introducing several features that improve the RF electrical uniformity across the pedestal. First, the RF field inhomogeneity or discontinuity caused by the presence of a titanium screw on the aluminum cathode is addressed by providing a continuous titanium ring. This ring extends around the upper surface of the cathode, including all titanium screw heads. Variations in conductivity due to surface differences or uneven fastening of the titanium screws provide a highly conductive nickel plate on the opposing peripheral surfaces of the equipment plate and cathode, and between them around the equipment plate and cathode. Is addressed by introducing an RF gasket that is compressed between the two.

  Referring to FIG. 1, a plasma reactor for etching a pattern with a mask includes a vacuum chamber 10 surrounded by a sidewall 12 and an overlying ceiling 14 and is evacuated by a vacuum pump 15 that controls the chamber pressure. A mask support base 16 inside the chamber 10 supports the mask 18. As described later in this specification, the mask generally comprises a quartz substrate, and may further include an additional mask thin film layer on the upper surface of the quartz substrate, such as chromium silicide or molybdenum. In addition, a pattern defining layer is present, which may be a photoresist or hard mask formed from a chrome layer. In other types of masks, the quartz substrate has no overlying layer other than the photoresist pattern.

  Plasma power is applied through each RF impedance matching circuit 28, 30 by placing the inner and outer coil antennas 20, 22 driven by each RF power generator 24, 26 on top. Although the sidewall 12 may be aluminum or other metal coupled to ground, the ceiling 14 is typically an insulating material that allows inductive coupling of RF power from the coil antennas 20, 22 to the chamber 10. Process gas is introduced from the gas panel 36 through the gas manifold 34 and from the evenly spaced injection nozzles 32 at the top of the sidewall 12. The gas panel 36 may comprise a different gas supply 38 coupled to an output valve or mass flow controller 42 coupled to the manifold 34 through each valve or mass flow controller 40.

  The mask support pedestal 16 comprises a metal (eg, aluminum) cathode 44 supported by a metal (eg, aluminum) equipment plate 46. The cathode 44 has an internal coolant or heated fluid flow path (not shown) that is supplied and discharged by a supply and drainage port (not shown) on the equipment plate 46. RF bias power is applied to the equipment plate by the RF bias generator 48 through the RF impedance matching circuit 50. RF bias power is conducted to the upper surface of the cathode 44 across the interface between the equipment plate 46 and the cathode 44. The cathode 44 has a central plateau 44a on which a square quartz mask or substrate 18 is supported. The size of the plateau is usually matched to the size of the mask 18, but the plateau 44a is somewhat small so that a small portion or edge 18a around the mask extends a short distance beyond the plateau 44a. This will be described later. The pedestal ring 52 that surrounds the plateau 44a is divided into a cover ring 52a that forms approximately 2/5 of the ring 52 and a capture ring 52b that forms the remaining 3/5 of the ring 52 (shown in FIG. 2B or FIG. 7). In wedge or pie section). The capture ring 52b has a shelf 54 on which the edge 18a of the mask 18 rests. Three lift pins 56 (only one of which is visible in FIG. 1) lift the capture ring 52b and lift the mask 18 at the edge 18a whenever it is desired to remove the mask 18 from the support pedestal 16. The pedestal ring 52 consists of material layers 53, 55 of different electrical properties selected to match the RF impedance provided by the combination of the quartz mask 18 and the aluminum plateau 44a at the frequency of the bias generator 48. (Both the cover ring 52a and the capture ring 52b are composed of different layers 53, 55.) Furthermore, the upper surface of the capture ring 52 is flush with the upper surface of the mask 18 and extends over the edge of the mask 18 in a wide uniform manner. The surface promotes a uniform electric field and sheath voltage across the entire surface of the mask 18 during plasma processing. Generally, these conditions are satisfied when the lower ring layer 55 is quartz and the upper ring layer 53 is a ceramic such as alumina. The process controller 60 controls the gas panel 36, the RF generators 24, 26, 48 and the wafer handling device 61. The wafer handling apparatus may include a lift servo 62 coupled to lift pins 56, a robot blade arm 63, and a slit valve 64 on the side wall 12 of the chamber 10.

  A series of uniformly spaced titanium screws 70 secure the cathode 44 and equipment plate 46 together around their perimeter. Due to the electrical difference between the aluminum cathode / equipment plates 44, 46 and the titanium screw 70, the screw 70 provides separate non-uniformities in the RF field on the top surface of the cathode 44. Variations in the opposing surfaces of the cathode 44 and the equipment plate 46 create non-uniformities along the periphery of the conductivity between the cathode 44 and the equipment plate 46. Corresponding inhomogeneities are imparted to the RF electric field. Because the cathode 44 tends to lift at its center during plasma processing (due to chamber vacuum), the main electrical contact between the cathode 44 and the equipment plate 46 is along its periphery. In order to reduce the sensitivity of electrical conduction between the cathode 44 and the equipment plate 46 which leads to variations in tightness in various titanium screws 70 and (b) variations in surface properties, an annular thin film 72 of a highly conductive material such as nickel is used. , Deposited around the lower surface 44b of the cathode 44. Meanwhile, a matching ring-shaped thin film 74 of nickel (for example) is deposited around the upper surface 46 a of the equipment plate 46. The nickel films 72, 72 are aligned with each other, and the two annular nickel thin films 72, 74 constitute opposing contact surfaces of the pedestal 44 and the equipment plate 46 and are very electrically conductive therebetween. To be evenly distributed. A further improvement in uniform electrical conductivity is achieved by providing an annular groove 76 along the periphery of the lower surface of the cathode 44 and placing a conductive RF gasket 80 in the groove 76. Optionally, a similar annular groove 78 aligned with the groove 76 may be provided on the top surface of the equipment plate 46. Because the cathode 44 and equipment plate 46 are pressed together and the screw 70 is tightened, the RF gasket 80 may be of any suitable conventional type, such as a compressed thin metal helix. In order to reduce or eliminate point non-uniformities in the electric field distribution that tend to occur at the head of the titanium screw 70, a continuous titanium ring 82 is placed in the annular groove 84 around the upper surface of the cathode 44.

  FIG. 2A shows the mask support pedestal 16 and the lift assembly 90 below it. The lift assembly 90 includes a lift spider 92 driven by a pneumatic actuator or lift servo 94 and three lift pins 56 mounted on the lift spider 92. The lift pin 56 is guided by a lift bellows 96 that includes a rolling bearing 98 for very smooth and substantially frictionless movement (to reduce contamination caused by wear). FIG. 2B shows the cathode 44 with the capture ring 52b and the mask 18 in the raised position. When the mask is raised, the robot blade can come into contact with the mask 18 by the void formed by the separation of the cover ring 52a and the capture ring 52b.

  The problem of very low center etch rate distribution across the entire surface of mask 18 is solved by changing the distribution of the electrical properties (eg, electrical permittivity) of cathode plateau 44a. This is accomplished in one embodiment by providing a central insert 102 and a surrounding outer insert 104 on the top surface of the plateau 44a. The two inserts form a continuous flat surface with the pedestal ring 52 and are made of electrically different materials. For example, in order to reduce the tendency for the etch rate distribution to be very low at the center, the center insert 102 is made of a conductive material (eg, aluminum) and the outer insert 104 is made of an insulating material (eg, a ceramic such as alumina). To do. By making the center insert 102 conductive in this manner, the impedance path for the RF current is much lower and boosts the ion energy and etch rate at the center of the mask 18. On the other hand, the insulating outer insert 104 exhibits a high impedance, which reduces the etch rate around the mask 18. This combination improves the etching rate distribution and makes it more uniform. With this feature, the etching rate distribution can be finely adjusted by adjusting the relative RF power levels applied to the inner and outer coil antennas 20,22. Changes in the radial distribution of plasma ion density necessary to achieve a uniform etch rate distribution are reduced to a very small amount, within the capability of RF power distribution between the inner and outer coils 20, 22, and uniform. Etch rate distribution is achieved. FIG. 3 is a plan view of the inner insert 102 and the outer insert 104. In an alternative embodiment, the inserts 102, 104 may be insulators having different dielectric constants (electrical dielectric constants). 4 and 5 show the details of this concept. The four concentric rings 102, 104, 106, 108 with gradually different electrical characteristics are used to make the etching rate distribution more uniform. 6 and 7 show a modified embodiment in which real-time adjustment of the distribution of the RF electrical characteristics of the cathode 44 is performed. The plunger 110 adjusts the axial position of the movable aluminum plate 112 in the hollow cylinder 114 inside the cathode 44. The aluminum plate 112 is in electrical contact with the remainder of the aluminum plateau 44a. An insulator (eg, ceramic) top film 116 can cover the top of the cathode 44. Pushing the aluminum plate 112 near the top of the cylinder 14 reduces the electrical impedance through the central region of the cathode 44 and increases the etch rate at the center of the mask 18. Conversely, when the aluminum plate 112 is moved downward from the cylinder 114 away from the mask 18, the etching rate at the center of the mask decreases. An actuator 118 that controls the axial movement of the plunger 110 can be managed by the process controller 60 (FIG. 1) to adjust the etch rate distribution to maximize uniformity or compensate for non-uniformity. .

Etch rate monitoring and endpoint detection from the back side of the mask The high manufacturing cost of periodically interrupting the etching process to measure the etching depth or critical dimension of the mask, through the cathode 44 and of the mask or substrate 18 Reduce or eliminate by using optical sensing through the backside. Performing such periodic measurements has required interruption of the etching process due to poor etch selectivity to the photoresist. Usually, the mask material is etched later than the photoresist. This problem is generally addressed by depositing a thick layer of photoresist on the mask, but high rate etching of the resist causes the photoresist surface to be randomly non-uniform or rough. This roughness affects the light passing through the photoresist and introduces noise in the optical measurement of critical dimensions or etch depth. Therefore, the photoresist is temporarily removed for each period measurement to ensure noise-free optical measurement. Prior to restarting the interrupted mask etch process, it is necessary to re-deposit the photoresist and redraw the reticle pattern on the photoresist.

  The mask etch plasma reactor shown in FIG. 8 eliminates these problems and allows continuous measurement of critical dimensions or measurement of etch depth during the entire etching process. Meanwhile, the mask or substrate 18 remains in place on the mask support pedestal 16 using the backside optical measurement device provided within the cathode 44. The back side measuring device utilizes the optically transparent nature of the mask substrate 18 which is generally quartz. The thin film deposited thereon (such as chromium silicide or molybdenum) may be opaque, but the formation of the patterned openings that define the reticle pattern of the mask 18 can be optically sensed. The change in light intensity reflected by or transmitted through such a layer is measured behind the mask through the cathode 44. This measurement may be used to perform etch process endpoint detection. When etching quartz material, optical depth measured on the back side of the mask through the cathode 44 may be sensed to perform etch depth measurements in real time during the etching process. One advantage is that the image or optical signal sensed from the back side of the mask is not affected by photoresist noise, or at least affected compared to trying to perform such a measurement from the top surface of the mask 18 (the photoresist side). There is very little.

  For these purposes, the reactor of FIG. 8 has a recess 120 in the upper surface of the cathode 44, in which a lens 122 is housed, with the optical axis facing the back side of the mask or substrate 18. ing. A pair of optical fibers 124 and 126 having a small diameter with respect to the lens 122 have end portions 124a and 126a in the vicinity of or in contact with the lens 122, and both are arranged next to each other along the optical axis of the lens 122. . Each of the optical fibers 124 and 126 shown in FIG. 8 may actually be a small bundle of optical fibers. The optical fiber 124 has a second end 124 b coupled to the light source 128. The light source emits light at a wavelength at which the mask 18 is transparent, typically a visible wavelength for a quartz mask. For interference depth measurement, the wavelength spectrum of the light source 128 is selected to promote local coherence of the reticle pattern of the mask 18. For periodic features (or periodic feature sizes less than 1 micron) in an etched mask structure of about 45 nm, this requirement is met when the light source 128 emits a visible light spectrum. The optical fiber 126 has a second end 126 b coupled to the optical receiver 130. In the case of simple end point detection, the optical receiver 130 may simply detect the light intensity. In the case of a critical dimension (eg, line width) measurement, the optical receiver 130 may sense an image of an etched line in the field of view of the lens 122. From this, the line width is determined. In the case of etching depth measurement, the optical receiver 130 may detect an interference pattern or interference fringe. From this, the etch depth is determined (ie inferred from the interference or diffraction pattern or calculated from the interference fringe count). In other embodiments, the optical receiver 130 may include a spectrometer for performing multi-wavelength interference measurements. From this, the etch depth is inferred or calculated. For such determination, the process controller 60 includes an optical signal processor 132 that can process the optical signal from the optical receiver. Such optical signal processing performs each process end point detection from ambient light intensity changes, measures critical dimensions from a two-dimensional image sensed by the optical receiver 130, calculates the etch depth by counting interference fringes, The etch depth is determined from the wavelength interference spectrum (in this case, the optical receiver 130 comprises a spectrometer) (depending on the particular implementation). Alternatively, using such a spectrometer, the end point of the etching process may be detected using light emitted by plasma from the backside of the wafer by light emission analysis and transmitted through the transparent mask 18. In this case, the light source 128 is not used.

  The process controller 60 responds to the process end point detection information (or etching depth measurement information) from the optical signal processor 132 in response to various configurations of the plasma reactor including the RF generators 24, 26, and 48 and the wafer handling device 61. Control elements. Generally, the process controller 60 stops the etching process and removes the mask 18 from the pedestal 16 when the etching process end point is reached.

  FIG. 9 is a graph showing ambient reflected light intensity sensed from the top (photoresist coating) side of the mask as a function of time during the chrome etching process (the chrome thin film on the quartz mask surface is etched according to the mask reticle pattern). ) The large fluctuation shown in the graph of FIG. 9 represents noise induced by the roughness of the upper surface of the photoresist layer. A broken line represents a step function signal hidden in noise. The step function is consistent with the end point of the chrome etching process. FIG. 10 is a graph of the same measurements taken from the backside of the wafer through the cathode 44 of the reactor of FIG. The optical receiver 130 senses the reflected light level. The photoresist induced noise is greatly reduced and the endpoint definition step function is clearly visible in the optical data. The end of the step function indicates the transition point where the reflected light intensity drops when the etching process reaches the bottom of the chromium thin film. At this point, the reflective surface area of chrome suddenly decreases.

  FIGS. 11 and 12 are graphs of light intensity over time (or equally spaced), as sensed by the optical receiver 130 in FIG. The periodic peak of light intensity corresponds to an interference fringe, the spacing of which is the depth of the etch or the thickness between different surfaces of the periodically spaced periodic features etched in the transparent quartz mask substrate 18. Determine the difference. FIG. 11 shows the intensity sensed through the photoresist from the top of the mask with severe photoresist induced noise components that impair interference fringe detection. FIG. 12 shows the intensity sensed through the back of the mask by the optical receiver 130 of FIG. There is little photoresist induced noise.

  FIG. 13 is a graph showing the light intensity as a function of wavelength when the optical receiver 130 is a spectrometer and the light source 128 generates a spectrum of wavelengths. The behavior of the intensity spectrum in the graph of FIG. 13 is unique when interference effects occur between light reflected from different depth surfaces in sub-micron features periodically spaced by the transparent mask 18. At low wavelengths, the peaks are fairly periodic and are evenly spaced. A significant optical effect is interference. At high wavelengths, the local coherence between the periodic features of the mask 18 is not strong and the effects of diffraction become increasingly greater with increasing wavelength. As a result, the intensity behavior at high wavelengths becomes more complicated rather than very uniform as shown in FIG. The peak spacing in FIG. 13 is a function of the etching depth, especially at low wavelengths, and is inferred from the spacing between peaks.

  FIG. 14 shows an embodiment of the reactor of FIG. The optical receiver 130 is an ambient light intensity detector and the optical signal processor 132 is programmed to look for a large curve (step function) in the total reflected light intensity corresponding to the endpoint detection graph of FIG. The light source 128 of the present embodiment can be any suitable light source. Alternatively, the light source 128 can be omitted and the light sensor 130 simply responds to light from the plasma transmitted through the transparent mask or substrate 18.

  FIG. 15 is an interference fringe detector in which the optical receiver 130 is sufficiently focused by the lens 122 to determine the interference fringes, and the optical signal processor 132 is programmed to count the interference fringes. The etch depth in the transparent quartz mask 18 is calculated (eg, from intensity versus time data of the type shown in FIG. 12). This calculation gives an almost instantaneous etch depth. This is compared by logic 200 with a user-defined target depth stored in memory 202. The logic 200 detects consistency between the stored value and the measured depth value using conventional numerical matching or minimal routines. Due to the matching, the logic 200 flags an etching end point in the process controller 60.

  FIG. 16 shows an embodiment of the reactor of FIG. 8 using the interferometry technique of FIG. 13 to measure or determine the etch depth in the transparent quartz mask or substrate 18. In this case, the light source 128 emits multiple wavelengths or spectra in the visible range (for periodic mask feature sizes of about a few hundred nanometers or less). The optical receiver 130 is a spectrometer. A signal conditioner and analog to digital converter 220 converts the spectral information collected by the spectrometer 130 (corresponding to the graph of FIG. 13) into digital data that can be processed by the optical signal processor 132. One mode in which end point detection can be performed is to calculate the etching depth from the interval between periodic peaks in the low wavelength range of the data shown in FIG. 13, as described above. Comparison logic 200 may compare the instantaneous measured etch depth with a user-defined target depth stored in memory 202 to determine if the etch process endpoint has been reached. In other modes, the comparison logic 200 converts the digitally represented wavelength spectrum (corresponding to the graph of FIG. 13) representing the instantaneous output of the spectrometer 130 into a known spectrum corresponding to the desired etch depth. It is strong enough to compare with. This known spectrum may be stored in the memory 202. An etch process end-point flag is sent to the process controller 60 by a match or approximate match between the measured spectrum and the stored spectrum detected by the comparison logic 200.

  FIG. 17 shows an embodiment of the reactor of FIG. 8, wherein the optical receiver 130 is an emission spectrometer that can distinguish emission lines from the optical radiation emitted by the plasma in the chamber, and emission analysis (OES). Is implemented. The processor 132 is an OES processor programmed to track (or detect disappearance) the intensity of a selected optical line corresponding to a chemical species indicative of the material of the layer being etched. Upon a predetermined transition (eg, the disappearance of the chrome wavelength line in the OES spectrum during the chrome etch process), the processor 132 sends an etch process endpoint detection flag to the process controller 60.

  FIG. 18 shows an embodiment constructed by having a pair of lenses 230, 232 in recesses 231, 233 spaced apart on the surface of the cathode 44. The lenses 230 and 232 are collected to determine an interference fringe, and the collected light is transmitted by each optical fiber 234 and 236 that faces or contacts each lens 230 and 232. The optical fibers 234, 236 are coupled to an interference detector 238 (which can be either a fringe detector or a spectrometer). Detector 238 has an output coupled to process controller 60. The lenses 230 and 232 receive light from the light source 240 through the optical fibers 242 and 244. This light is reflected back from the upper surface of the mask 18 to the lenses 230 and 232 and transmitted to the detector 238 through the optical fibers 234 and 236. Further, the embodiment of FIG. 18 has a third recess 249 on the cathode surface that houses a third lens 250 that is coupled through an optical fiber 252 to the input of an OES spectrometer 254. The OES processor 256 processes the output of the OES spectrometer 254 to perform end point detection and communicate the result to the process controller 60. The cathode 44 of the embodiment of FIG. 18 is shown in FIG. Three recesses 231, 233, 249 that house each lens 230, 232, 250 are shown. FIG. 20 shows corresponding holes 260, 261, 262 for receiving in an equipment plate 46 optic (not shown) that supports the lenses 230, 232, 250. FIG. 21 is a cross-sectional view showing coupling of an optical fiber to a lens inside the pedestal 16.

  Although the reactors of FIGS. 16, 17 and 18 have been described as using spectrometers 130 (FIGS. 16 and 17) and 254 (FIG. 18), one or more spectrometers 130 or 254 are tuned to a predetermined wavelength. The optical wavelength filter may be replaced. Each of these optical wavelength filters may be combined with a photomultiplier tube to improve the signal amplitude.

Backside Endpoint Detection Mask Etching Process FIGS. 22A and 22B illustrate a process for etching a reticle pattern in the mask quartz material. In FIG. 22A, the quartz mask substrate 210 is covered with a photoresist layer 212 having a periodic structure of spaced lines 214 and openings 216 defined in the photoresist layer 212. In the reactor of FIG. 15 or 16, a CHF 3 + CF 4 + Ar crystal etching process gas is introduced into the chamber 10, power is applied by the RF generators 24, 26 and 48, and the crystal material is an opening 216 formed in the photoresist layer 212. Etched in. The crystal etch depth is continuously measured by the interference between the light 218 reflected from the etched upper surface of the quartz substrate 210 and the light 219 reflected from the unetched upper surface. The etching process is stopped as soon as the desired etching depth is reached (FIG. 22A). Next, the photoresist is removed to form a desired mask (FIG. 22B).

  FIGS. 23A-23E show a photoresist layer with an underlying quartz mask substrate 210, molybdenum silicide layer 260 (containing silicon molybdenum oxynitride), a chromium layer 262, a chromium oxide antireflective coating 264, and an opening 268. A process for etching a three-layer mask structure of 266 is shown (FIG. 23A). In the step of FIG. 23B, the chromium layer 262 and the anti-reflective coating 264 are etched in a plasma reactor chamber with simple reflectance endpoint detection (chamber in FIG. 14) or OES endpoint detection (chamber in FIG. Etched using process. The photoresist layer 266 is removed (FIG. 23C). The molybdenum silicide layer 260 is etched as shown in FIG. 23D using a process gas which is an etching solution of molybdenum silicide such as CF 6 + Cl 2 and using the chromium layer 262 as a hard mask. This step is performed in a plasma reactor with an endpoint detector, such as by the simple ambient reflectivity, or by OES endpoint detection, such as the chamber of FIG. In FIG. 23E, the chromium layer 262 and the chromium oxide anti-reflective coating 264 are removed using a chromium etching process such as CH 3 + CF 4 + Ar. This step can be performed using the reactor of FIG. 14 or 17 with a simple endpoint detector without etching depth measurement. This leaves a quartz mask substrate with a layer overlying the molybdenum silicide defining the reticle pattern.

  24A-24E illustrate a process for manufacturing a binary mask made of periodic chrome lines at the exposed quartz transparent quartz mask side-face periodic intervals. The exposed quartz spacing is alternately etched to a depth where the transmitted light is phase shifted by a desired angle (eg, 180 degrees). FIG. 24A shows an initial structure consisting of a quartz mask substrate 300, a chromium layer 302, a chromium oxide antireflective coating 304 and a photoresist layer 306. In the step of FIG. 24B, the chromium and chromium oxide layers 302, 304 are etched in a process gas of Cl2 + O2 + CF4 in a reactor chamber such as the chamber of FIG. In the step of FIG. 24C, the photoresist layer 306 is removed, and then the exposed portion of the quartz mask substrate 300 is etched in a CHF 3 + CF 4 + Ar quartz etching process gas, as shown in FIG. 24D. The crystal etching step of FIG. 24D is performed in a reactor chamber that can sense or monitor the etching depth of the crystal mask substrate 300, such as the chamber of FIG. 15 or 16. During the etching process, the instantaneous etching depth is continuously monitored and as soon as the target etching depth is reached with the mask 300, the etching process is stopped. The final result is shown in FIG. 24E.

Continuous Monitoring of Etch Rate Distribution over the Mask Surface FIGS. 25 and 26 show an embodiment of the wafer support pedestal 16 of FIG. On the top surface of the cathode 44 is provided a matrix of backside etch depth sensing elements (lenses and optical fibers). An instantaneous image or sample of the etch rate distribution or etch depth distribution is continuously provided over the entire surface of the mask or substrate during the etching process without interrupting the etching process or otherwise interfering with the mask substrate. The aluminum plateau 44 a has a matrix of openings 320 on its upper surface, and each opening holds a lens 322 facing the back side of the mask substrate 300. A light source 324 provides light through an output optical fiber 326 coupled to each lens 322. Lens 322 provides sufficient light collection to determine interference fringes. An interference detector 328, which can be either a sensor that facilitates fringe counting or a spectrometer, is coupled to an input optical fiber 330 that is coupled to each lens 232. A switch or multiplexer 332 continuously enters light from each input optical fiber 330 into the detector 328. There are three modes in which the apparatus of FIGS. 25 and 26 operates. In the first mode, the etching depth in the field of view of one of the lenses 322 is calculated from the spacing between the interference fringes. In the second mode, the detector 328 is a spectrometer and the etch depth in the field of view of one of the lenses 322 is calculated from the low wavelength peak spacing of the multi-wavelength interference spectrum (corresponding to FIG. 13). In the third mode, the multi-wavelength interference spectrum is detected instantaneously and compared with a library of spectra 340 with known corresponding etch depths. The etching rate distribution is calculated from the etching depth and elapsed time. This distribution records the etch non-uniformity of the process and is provided to the process controller 132. The controller 132 can reduce non-uniformities in the etch rate distribution in response by adjusting the tunable features of the reactor.

  The embodiment of FIGS. 25 and 26 is shown as having a 3 × 3 matrix of etch depth sensors or lenses 322 on the top surface of the plateau 44a, but using any number of rows and columns of such sensors. The matrix may be an nxm matrix. Here, m and n are suitable integers.

  In one embodiment, the process controller 132 may be programmed to estimate whether the etch rate distribution is high center or low center (from etch rate distribution information provided by the spectrometer or sensor 130). In response to this information, the process controller 60 can reduce non-uniformities by adjusting certain adjustable features of the reactor. For example, the process controller 60 may change the RF power distribution between the inner and outer coils 20,22. Alternatively or in addition, the process controller 60 may change the height of the movable aluminum plate 112 in the reactor of FIGS. Feedback from an array or matrix of etch depth sensing elements in plateau 44a allows process controller 60 to improve etch rate distribution uniformity through continuous trial and error of reactor tunable elements.

FIG. 27A is a side view of one embodiment of the lift pin 56. The lift pin 56 includes a body 2705 having a first end 2710 and a second end 2715. The body 2705 may be made of a material that is compatible with the process, such as stainless steel, aluminum, ceramics, among others. In one embodiment, the body 2705 is formed from an aluminum oxide (Al ₂ O ₃ ) material. In one embodiment, the body 2705 includes a shaft having a circular cross section and includes at least one outer diameter, such as a first diameter region 2725, and one or more, such as a second diameter region 2730A and a third diameter region 2830B. And a smaller outer diameter region. The second diameter region 2730A and the third diameter region 2730B may be separated by a shoulder 2735, which may have an outer diameter that is substantially equal to the first diameter region 2725. In one embodiment, the second end 2715 has a notch region 2708 defined by an interface between the first diameter region 2725 and at least one of the second diameter region 2730A and the third diameter region 2730B. Have. In certain embodiments, the notch region 2708 has an interface between a first diameter region 2725 and second and third diameter regions 2730A, 2730B separated by a shoulder 2735.

  The notch region 2708 facilitates coupling with the lift assembly 90 and / or lift bellows 96 of FIG. 2A. The notch area 2708 also facilitates replacement by functioning as an indicator or gauge to determine when to place the lift pin 56 in the lift assembly 90. Other lift pins with a single diameter require monitoring and / or ambient gauge mechanisms, thereby accurately positioning and positioning the lift pins during replacement. Furthermore, other lift pins require a perimeter fastening device to facilitate the coupling of the lift assembly 90. Thus, in certain applications, the notch area 2708 provides a stop instruction when the lift pin 56 is replaced. For example, a tactile sense when the lift pin 56 is coupled to the lift assembly 90. In other embodiments, the notch region 2708 provides an additional function for fastening the lift pin 56 to the lift assembly 90 and / or lift bellows 96.

  FIG. 27B is an exploded side view of a portion of the second end 2715 taken from FIG. 27A. As described above, the shoulder 2735 may have an outer diameter that is substantially equal to the first diameter region 2725, and the second and third diameter regions 2730A, 2730B are more than the first diameter 2725 and the shoulder 2735. Slightly small. In one embodiment, the second and third diameter regions 2730A, 2730B are substantially equal, while in other embodiments, the second and third diameter regions 2730A, 2730B are slightly different from each other. Second end 2715 also includes a rounded end that is defined by two radii, such as first radius 2740A and second radius 2740B. In one embodiment, the second radius 2740B is approximately four times larger than the first radius 2740A. In certain embodiments, both the first end 2710 and the second end 2715 have two radii, such as a first radius 2740A and a second radius 2740B.

  While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, the scope of which is a utility model registration request. It is determined based on the range.

  BRIEF DESCRIPTION OF THE DRAWINGS The invention briefly summarized above will be more particularly described with reference to the embodiments illustrated in the accompanying drawings, so that the features listed above can be understood in detail. However, it should be noted that the accompanying drawings illustrate only typical embodiments of the present invention and are not considered to limit the scope thereof, and the present invention recognizes other equally effective embodiments. It is.

It is a figure which shows the plasma reactor for implementing a mask etching process. It is a figure which shows the low part of the reactor of FIG. FIG. 2 shows the mask support pedestal of the reactor of FIG. 1 in the raised position. It is a top view of the cathode of the reactor of FIG. ~ It is the top view and side view of one deformation | transformation embodiment of a cathode. ~ It is the top view and side view of other deformation | transformation embodiment of a cathode. It is a simplified diagram of a plasma reactor having a back side end point detection device. ~ It is a graph of the optical end point detection signal obtained from the front side and the back side of the mask. ~ It is a graph of the interference fringe optical signal obtained from the front side and the back side of the mask. FIG. 9 is a graph of a multi-wavelength interference spectrum signal obtained in one embodiment of the reactor of FIG. FIG. 11 illustrates one embodiment of the reactor of FIG. 8 with backside end point detection based on the overall reflected light intensity corresponding to FIG. FIG. 13 illustrates one embodiment of the reactor of FIG. 8 with backside endpoint detection based on interference fringe counting corresponding to FIG. FIG. 9 illustrates one embodiment of the reactor of FIG. 8 with backside endpoint detection based on multi-wavelength interferometry. FIG. 9 illustrates one embodiment of the reactor of FIG. 8 with backside endpoint detection based on luminescence analysis (OES). It is a figure which shows the Example of the back side end point detection based on both OES and interference. ~ FIG. 19 is an isometric view of the cathode and equipment plate of the embodiment of FIG. FIG. 20 is a cross-sectional view of the cathode of FIG. 19. ~ It is a figure which shows a series of processes in the quartz mask etching process using back side end point detection. ~ FIG. 6 shows a series of steps in a chromium-molysilicide-quartz mask etching process using backside endpoint detection. ~ FIG. 6 shows a series of steps in a chrome-quartz mask etching process using backside endpoint detection. ~ It is the side view and top view of embodiment whose real-time etching rate distribution is continuously measured from a mask back side. It is a side view of one embodiment of a lift pin. FIG. 27B is an exploded side view of a portion of the second end of the lift pin taken from FIG. 27A.

  To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The components and features of one embodiment are not specifically listed, but are believed to be advantageously incorporated into other embodiments. It should be noted, however, that the attached drawings are only illustrative of exemplary embodiments of the present invention and are not considered to limit the scope thereof, and that the present invention includes other similarly valid embodiments. It is.

Claims (17)

  A lift pin for a plasma chamber comprising a longitudinal body having a circular cross section, the body having a round first end, a round second end, and a notch region formed in the second end. The notch region is used to be removably coupled to a lift plate disposed in the plasma chamber, the body has a first diameter region, and the notch region is separated by a shoulder. A lift pin for a plasma chamber comprising at least two diameter regions having a diameter smaller than one diameter region.   The lift pin of claim 1, wherein the round first end and the round second end include two radii.   The round first end and the round second end have a first radius and a second radius, and the second radius is about four times greater than the first radius. The lift pin according to 1.   The lift pin of claim 1, wherein a diameter of the shoulder is substantially equal to the first diameter region, and the at least two diameter regions have a diameter smaller than the diameter of the shoulder.   The lift pin of claim 1, wherein the body comprises a ceramic material.   The lift pin of claim 1, wherein the body comprises an aluminum material. The lift pin of claim 1, wherein the body comprises an aluminum oxide (Al ₂ O ₃ ) material.   The lift pin according to claim 1, wherein the at least two diameter regions have a second diameter region and a third diameter region, and each region has a different length.   The lift pin of claim 1, wherein the at least two diameter regions each have a length and a diameter, the diameters are substantially equal and the lengths are different.   A longitudinal shaft having a circular cross-section, a first end, and a second end, the second end including a second diameter section and a third diameter section; A lift pin for a plasma chamber, wherein the second diameter section and the third diameter section have a smaller diameter than the first diameter section and are separated by a shoulder section having a diameter substantially equal to the first diameter section .   The lift pin of claim 10, wherein the second diameter section and the third diameter section define a notch region.   The lift pin of claim 10, wherein the shaft comprises an aluminum material. The lift pin of claim 10, wherein the shaft comprises an aluminum oxide (Al ₂ O ₃ ) material.   The lift pin according to claim 10, wherein each of the first end and the second end is round.   The lift pin of claim 14, wherein each of the first end and the second end has two radii.   The round first end and the round second end have a first radius and a second radius, and the second radius is about four times greater than the first radius. 14. The lift pin according to 14.   11. The lift pin of claim 10, wherein the second diameter section and the third diameter section each have a length and a diameter, the diameters are substantially equal and the lengths are different.

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