Abstract:
An endpoint detecting device used during a semiconductor manufacturing process to manufacture semiconductor devices. The endpoint detecting device is constructed such that a filter has a polyhedral shape or a semi-spherical shape.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field  
         [0002]     The present invention generally relates to a process endpoint detecting device adapted for use within a semiconductor manufacturing system. More particularly, the present invention generally relates to an endpoint detecting device capable of accurately detecting an etch endpoint during a dry plasma etch process.  
         [0003]     A claim of priority is made to Korean Patent Application No. 2004-56177, filed on Jul. 20, 2004, the disclosure of which is hereby incorporated by reference in its entirety.  
         [0004]     2. Discussion of Related Art  
         [0005]     With rapid technology developments in the telecommunication field together with the increasing popularity of information media such as computers, semiconductor devices have undergone great technical change. High operating speed, large storage capability, improved functionality, and a high degree of integration are required in contemporary semiconductor devices. With a trend toward higher integration and increased storage capacity, the respective size of unit devices forming contemporary memory devices have been reduced. The technology to form multi-layer structures in a limited surface area is essential to the fabrication of memory devices.  
         [0006]     Generally, this technology is characterized by a thin film which is deposited on a wafer surface and subsequently patterned to form various circuits. Corresponding manufacturing processes generally comprise a plurality of unit processes related to deposition and etching. Conventional photolithography is an exemplary process. In photolithography, a photoresist is applied to a semiconductor substrate using a deposition process. The photoresist is then exposed, and a process film is patterned on the semiconductor substrate. Then, a chemical mechanical polishing (CMP) process is used to remove step differences on the surface of an interlayer dielectric layer.  
         [0007]     In order to form a material film pattern having various functions on a semiconductor substrate, an etch process, either chemical or mechanical, is typically used to remove unwanted portions of the semiconductor substrate.  
         [0008]     A precise processing technology is required to increase aspect ratios in relation to increased step differences between respective unit regions of a memory cell. Typically, a dry etch process has been widely used because it does not require particularly good photoresist wettability, and requires a relatively small amount of etchant. Conventional dry etch processes include processes using plasma, sputtering, or ion beam. In contrast, a wet etch process has been less widely used because of poor wettability, and because etchants tend to infiltrate between a photoresist layer and an underlying material film degrading pattern accuracy  
         [0009]     Accordingly, a plasma dry etch process is used in the manufacture of semiconductor devices such as a DRAM (dynamic random access memory). In a plasma etch process, a reaction gas is introduced into a reaction chamber and high frequency or microwave energy is applied to form a plasma state. A material film on a wafer is patterned by free electrons and ions generated by the interaction between the reaction gas and the plasma. However, as stated above, increasing aspect ratios for adjacent pattern components cause an uneven deposition thickness of a material film between unit regions. These uneven deposition thickness which are formed during previous processing steps negatively impact the etch process such that it can not be ideally conducted on the entire surface of the wafer. Thus, an etch process duration (“etching process”) must be accurately determined in order to completely etch a desired material film. If the etching time is too long, layers beneath the target film, in addition to the target film, as well as other non-targeted areas are often etched. Furthermore, if an etchant with a lower selectivity is used to increase the etching rate, other problems may occur.  
         [0010]     In order to overcome such problems, the conventional plasma etch process commonly uses a method of detecting a specific point during the process, and upon detecting this point the etching conditions are changed. The method generally selects conditions having a fast etching rate prior to detecting the specific point, and thereafter selects conditions having a slower etching rate and a high selectivity for the film beneath the target film. The specific point generally relates to a point during the plasma etch when the film beneath the target film is just exposed, and is commonly called an endpoint. The etch step that just exposes (i.e., reaches the endpoint) the portion film beneath the target film is referred to as a “main etch step”, and the remaining etch step after reaching the specific point is known as an “over etch step”. In this two (2) step etch process, it is very important to accurately detect the endpoint. Although there are various endpoint detection methods, a method of monitoring emissions generated by the plasma using a monochrometor to identify an inherent wavelength related to a specific material is generally used.  
         [0011]     Specifically, a conventional endpoint detecting device detects an endpoint by detecting one or more wavelengths emitted when a material film, such as an oxide or polysilicon layer, reacts with plasma. One example of an endpoint detecting procedure comprises: first, when polysilicon is etched with chlorine (Cl 2 ) plasma, silicon chloride is produced as a byproduct. When the polysilicon etch is completed (i.e., begins to expose an underlying silicon dioxide film) this silicon chloride byproduct is no longer produced. Silicon chloride emits an inherent emission having a wavelength of 282.3 nm in plasma. Thus, the 282.3 nm wavelength is selectively detected among various wavelengths using an optical filter or a monochrometor, and the intensity of the detected wavelength is expressed as a function of time. A resulting detection profile can be obtained having a distinct infection point related to a certain time at which the detected wavelength intensity abruptly decreases. This infected point identifies the endpoint.  
         [0012]     In an endpoint detecting device, the optical filter is a key component. That is, accurately determining the intensity of the desired wavelength from the spectrum of wavelength apparent in the plasma allows accurate monitoring of the endpoint.  
         [0013]     A conventional an endpoint detecting device is generally disclosed in U.S. Pat. No. 5,980,676, for example.  
         [0014]      FIG. 1  is a block diagram illustrating major functional sections of a conventional endpoint detecting device.  
         [0015]     Referring to  FIG. 1 , the endpoint detecting device includes a filtering unit  10  to directly read plasma wavelength emitted from a process chamber (not shown), a sensor  12  to detect the plasma wavelength read by filtering unit  10 , an amplifier  14  to amplify the resulting signal from sensor  12 , an A/D converter  16  to convert the amplified resulting signal from amplifier  14  into a digital signal, and an I/O unit  18  to control the etching process being monitored. An EOP signal output from I/O unit  18  is transmitted to a control unit (not shown), which corresponding determines the endpoint. The endpoint detecting device is generally disposed on an outer wall of the process chamber.  
         [0016]      FIG. 2  illustrates the structure of filtering unit  10  of  FIG. 1 .  
         [0017]     Referring to  FIG. 2 , a structurally planar filtering unit  10  receives wavelengths emitted from a process chamber. Due to the flat planar structure, filtering unit  10  can only receive perpendicularly incident wavelengths from amongst the multidirectional wavelengths emitted from within the process chamber via an incidence surface  11  provided at one side of filtering unit  10 . That is, the solid arrow lines shown in  FIG. 2  indicate plasma wavelengths perpendicularly incident to incidence surface  11 , whereas dotted arrow lines indicate plasma wavelengths non-perpendicularly incident to incidence surface  11 .  
         [0018]     During a plasma dry etch process, plasma wavelengths are emitted in directions ranging from 0 to 180 degrees; however, the conventional filtering unit  10  can only effectively receive plasma wavelengths perpendicularly incident to incidence surface  11 .  
         [0019]     The plasma wavelengths emitted perpendicularly to incidence surface  11  are wavelengths generally emitted from a center area of a wafer being processed. Conventionally, an etch process is controlled such that an etch endpoint is detected using plasma wavelengths emitted from the center area of the wafer. However, the process control methodology relying on the endpoint detection is operated as if the entire area of the wafer is being accurately monitored. That is, the etch process is controlled on the assumption that the endpoint detected for only the center area of the wafer is correctly applicable to the entire wafer. Accordingly, the center area of the wafer achieves an excellent etch profile, whereas other areas such as an edge region, whose corresponding wavelengths are not accurately received through filtering unit  10 , are either overetched or underetched.  
         [0020]      FIG. 3  is a schematic view illustrating endpoint detecting ranges for a filtering unit having a structure like the one shown in  FIG. 2 .  
         [0021]     Referring to  FIG. 3 , reference numeral  20  indicates a process chamber, and reference numeral  22  indicates a radius inside of process chamber  20 . A filtering unit  10  is installed on an outer wall of process chamber  20 .  
         [0022]     Reference “A” indicates an area where plasma wavelengths are emitted in process chamber  20  that can be received by filtering unit  10 . Reference “B” indicates areas where plasma wavelengths are emitted that cannot be effectively received by filtering unit  10 .  
         [0023]     Accordingly, there is a need to provide a solution to the problem of accurately receiving and using plasma wavelengths corresponding to area “B”.  
         [0024]     Therefore an endpoint detecting device having an improved filter structure capable of effectively receiving plasma wavelengths emitted from a wide area of a wafer is required.  
       SUMMARY OF THE INVENTION  
       [0025]     Therefore, the present invention is directed to provide an endpoint detecting device having an improved filter structure capable of reading a wide range of plasma wavelength emitted within a process chamber.  
         [0026]     An embodiment of the present invention provides an endpoint detecting device to detect an endpoint during an etching process having a filter having at least two incidence surfaces adapted to receive plasma wavelengths, a sensor to detect the received plasma wavelengths and generate a corresponding signal, an analog/digital (A/D) converter to convert the corresponding signal to a digital signal, and a controller responsive to the digital signal and adapted to determine the endpoint.  
         [0027]     Another embodiment of the present invention provides an endpoint detecting device to detect an endpoint during an etching process having a filter having a curved incidence surface adapted to receive plasma wavelengths, a sensor to receive the plasma wavelengths and generate corresponding signal, an analog/digital (A/D) converter to convert the corresponding signal to a digital signal, and a controller responsive to the digital signal and adapted to determine the etching endpoint. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]     The above and other aspects of the present invention will become more apparent to those of ordinary skill in the art upon consideration of the description of the preferred embodiments that follows with reference to the attached drawings in which:  
         [0029]      FIG. 1  is a block diagram illustrating functional sections of a conventional endpoint detecting device;  
         [0030]      FIG. 2  illustrates a structure of a filtering unit of the prior art;  
         [0031]      FIG. 3  is a schematic view illustrating a detecting range of the filtering unit of  FIG. 2 ;  
         [0032]      FIG. 4  is a view illustrating a filter structure for an endpoint detecting device according to a first preferred embodiment of the present invention;  
         [0033]      FIG. 5  is a view illustrating a filter structure for an endpoint detecting device according to a second preferred embodiment of the present invention; and  
         [0034]      FIG. 6  is a schematic view illustrating a detecting range according to the embodiments of the present invention of  FIGS. 4 and 5 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]     The present invention will now be described more fully with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown. The present invention may, however, be embodied in different forms and should not be construed as limited to only the embodiments set forth herein. Rather, these embodiments are provided as teaching examples of the present invention. Like numbers in the drawings refer to like elements.  
         [0036]      FIG. 4  is a view illustrating a filtering unit for an endpoint detecting device according to one embodiment of the present invention.  
         [0037]     Referring to  FIG. 4 , a filter  100  has a polyhedron structure rather than the flat planar structure of the prior art. Filter  100  has at least two incidence surfaces  101  and  102 . More specifically, filter  100  illustrated in  FIG. 4  has a triangular prism shape. However, filter  100  may have various other polyhedron shapes such as a triangular pyramid, a quadrangular pyramid (pyramid structure), and a pentagonal pyramid.  
         [0038]     In the present invention, the triangular prism shaped filter  100  illustrated in  FIG. 4  is capable of receiving and reading plasma wavelengths emitted from a greater area on a wafer. That is, the effective receiving range for emitted plasma wavelengths extends from the center to an edge region of the wafer for both incidence surfaces  101  and  102 . Incidence surfaces  101  and  102  abut each other at a certain angle selected to accurately detect an endpoint in view of the etching process across the entire wafer.  
         [0039]     Filter  100  may have a curved shape such as sphere, semi-sphere, and sinewave.  FIG. 5  illustrates a semi-spherical filter structure according to another embodiment of the present invention.  
         [0040]     Referring to  FIG. 5 , filter  200  has a semi-spherical shape with a spherical incidence surface  201 . Semi-spherical filter  200  is capable of reading plasma wavelengths emitted from multiple directions within the process chamber. That is, since filter  200  has incidence surface  201  ranging from 0 to 180 degrees, it can receive the plasma wavelengths emitted from 0 to 180 degrees.  
         [0041]      FIG. 6  is a schematic view illustrating an emitted plasma wavelength detection range according to the embodiments of the present invention.  
         [0042]     Referring to  FIG. 6 , reference numeral  20  indicates a process chamber, and reference numeral  104  indicates a radius inside process chamber  20 . A filter  100 / 200  for an endpoint detecting device according to the present invention is installed at an outer wall of process chamber  20 .  
         [0043]     Reference “C” indicates an area from which plasma wavelengths may be received through filter  100 / 200 . In comparison with the prior art, the present invention is capable of receiving plasma wavelength from a wider area within process chamber  20 .  
         [0044]     The present invention has been described using preferred embodiments. However, it is to be understood that the scope of the invention is not limited to only the disclosed embodiments. On the contrary, the scope of the invention is intended to include various modifications and alternative arrangements within the capabilities of persons skilled in the art using presently known or future technologies and equivalents. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.