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  Plasma processing apparatusUSPTO Application #: 20060016559Title: Plasma processing apparatus Abstract: The object of the invention is to provide a plasma processing apparatus having enhanced plasma processing uniformity. The plasma processing apparatus comprises a processing chamber 1, means 13 and 14 for supplying processing gas into the processing chamber, evacuation means 25 and 26 for decompressing the processing chamber 1, an electrode 4 on which an object 2 to be processed such as a wafer is placed, and an electromagnetic radiation power supply 5A, wherein at least two kinds of processing gases having different composition ratios of O2 or N2 are introduced into the processing chamber through different gas inlets so as to control the in-plane uniformity of the critical dimension while maintaining the in-plane uniformity of the process depth. (end of abstract) Agent: Antonelli, Terry, Stout & Kraus, LLP - Arlington, VA, US Inventors: Hiroyuki Kobayashi, Kenji Maeda, Kenetsu Yokogawa, Masaru Izawa, Tadamitsu Kanekiyo USPTO Applicaton #: 20060016559 - Class: 156345340 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060016559. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The present application is based on and claims priority of Japanese patent application No. 2004-217118 filed on Jul. 26, 2004, the entire contents of which are hereby incorporated by reference. FIELD OF THE INVENTION [0002] The present invention relates to a plasma processing apparatus used in the fabrication of semiconductors. DESCRIPTION OF THE RELATED ART [0003] Heretofore, plasma etching utilizing weakly-ionized plasma is adopted widely in the process of fabricating a semiconductor device such as a DRAM or a microprocessor. Now, FIG. 10 is referred to in explaining the mechanism of etching, taking the etching of an SiOC film as an example. A mixed gas containing CHF.sub.3, CF.sub.4 and N.sub.2 is used as the processing gas, for example. Radicals such as CF and CF.sub.2 dissociated from CHF.sub.3 and CF.sub.4 in the plasma are deposited on the SiOC 51 and resist 52, forming a deposition film 53. Then, the ions generated in the plasma are accelerated by bias power to be incident on the object to be processed, by which energy is applied to the interface between the SiOC 51 and the deposition film 53, causing reaction of the SiOC 51 and the deposition film 53 and progressing etching. [0004] The finishing contour formed after etching depends not only on the energy and variation of ions being incident on the object to be processed but also on the thickness and composition of the deposition film. For example, according to conditions where the deposition film becomes excessively thick or conditions where considerable amount of components such as C that inhibit etching are contained in the deposition film, the etching rate is deteriorated or the etching is stopped before it is completed. This is because the ions being incident on the object to be processed cannot easily reach the interface between the deposition film and SiOC. Moreover, if the deposition film deposited on the side walls of the holes or trenches becomes excessively thick, the etching of the side walls of the holes and trenches may be suppressed excessively, causing the processed bottom portion of the holes and trenches to have a narrowed tapered shape. Oppositely, if the deposition film is too thin, the lack of deposition film to be reacted with SiOC deteriorates the etching rate. According to the example illustrated in FIG. 10, the thickness and composition of the deposition film depends mainly on the balance of deposition of radicals such as CF and CF.sub.2 radicals dissociated from CHF.sub.3 and CF.sub.4, the deposition of reaction products generated by the etching and being incident on the object again, the removal of the deposition film by the N radicals dissociated from N.sub.2, and the consumption of the deposition film along with the progression of etching. [0005] The mechanism of etching has been described by taking as an example the etching of SiOC film using CHF.sub.3, CF.sub.4 and N.sub.2, but in etching SiO.sub.2 or SiOF films, for example, a process gas containing Ar, CF-based gas such as C.sub.4F.sub.6 or C.sub.5F.sub.8 and O.sub.2 is used. In this case, radicals such as CF and CF.sub.2 dissociated from C.sub.4F.sub.6 or C.sub.5F.sub.8 contribute to the generation of the deposition film, and O radicals dissociated from O.sub.2 function to remove the deposition film. [0006] Next, the general outline of a plasma processing apparatus is described with reference to the example illustrated in FIG. 11. The present apparatus is a parallel plate plasma etching apparatus, having equipped in a processing chamber 1 a substantially disk-like antenna 3 for electromagnetic radiation and an electrode 4 on which an object 2 to be processed is placed, which are disposed in parallel and facing each other. An electromagnetic radiation power supply 5A for generating plasma is connected to the antenna 3 via a matching network 6A. [0007] Below the antenna 3 is disposed a shower plate 11. Processing gases are supplied from gas cylinders 20, which are adjusted to predetermined flow rates via gas flow controllers 13, and introduced through gas holes provided to the shower plate 11 to the processing chamber 1. Moreover, in order to control the radical distribution within the plasma, it is possible to introduce processing gases having different compositions or flow rates through the inner area and the outer area of the shower plate 11. An RF power supply 5C is connected to the electrode 4 via a matching network 6C, by which the ions being incident on the object 2 is accelerated to etch the object. [0008] There has already been proposed a parallel plate electrode-type RIE apparatus in which a stage electrode and a gas supply electrode are disposed in confronting relationship in the etching chamber to realize uniform etching of a large-diameter wafer, wherein the gas supply surface of the gas supply electrode is divided into three areas, a first gas supply area, a second gas supply area and a third gas supply area, and the gas supply to each gas supply area is controlled independently through a first gas flow rate control system, a second gas flow rate control system and a third gas flow rate control system, respectively. Thereby, the flow rate of etching gas and the flow ratio of gases having different ionization potential to be supplied via the first, second and third gas supply areas are optimized (refer for example to patent document 1). [0009] Moreover, the present applicant has filed a patent application disclosing a plasma etching apparatus comprising a processing chamber for performing plasma etching to an object to be processed, a first gas supply source for supplying processing gas, a second gas supply source disposed independently from the first processing gas, a first gas inlet for introducing the processing gas into the processing chamber, a second gas inlet disposed independently from the first gas inlet, a flow controller for controlling the flow rate of the processing gas, and a gas flow divider for dividing the process gas into plural flows, wherein the second gas is supplied between the gas flow divider and at least one of the first or second gas inlets so as to supply the processing gas via two systems (refer for example to patent document 2). [Patent document 1] [0010] Japanese Patent Application Laid-Open No. 2002-184764 [Patent document 2] [0011] Japanese Patent Application No. 2003-206042 [0012] In order to perform uniform etching across the plane of an object such as a wafer, the in-plane distribution of ions being incident on the surface of the object (plasma distribution) and the thickness and composition of the deposition film being deposited on the object must be uniform across the plane of the object. The conventional plasma processing apparatus mentioned earlier is equipped with a means for controlling the plasma distribution and radical distribution in order to carry out uniform plasma processing across the plane of the object. However, the process dimension regarded important in the fabrication of semiconductor devices include the process depth and the critical dimension (CD), and according to the prior art plasma processing apparatus, the in-plane uniformity of the process depth and the in-plane uniformity of the critical dimension could not be controlled independently. Here, critical dimension (CD) refers for example to the width of a trench, a width of a line or a diameter of a hole in the micropattern formed on the object being processed. Therefore, the in-plane uniformity of the critical dimension may be deteriorated by enhancing the in-plane uniformity of process depth, so it is necessary to seek the process conditions that fulfill both the in-plane uniformity of process depth and in-plane uniformity of critical dimension through trial and error, by adjusting little by little the flow rate and composition of the process gases supplied through the inner area and outer area of the shower plate, the bias power and the discharge power. [0013] Compared to the process depth, the critical dimension depends greatly on the thickness and composition of the deposition film, so it is preferable that the in-plane distribution of the critical dimension be uniformized without changing the uniformity of process depth by appropriately controlling the thickness and composition of the deposition film. Since the method for controlling the composition and flow rate of gases being introduced through the inner gas holes and the outer gas holes of the shower plate allows a large degree of freedom of radical distribution control, the method is promising as a way for appropriately controlling the thickness and composition of the deposition film. SUMMARY OF THE INVENTION [0014] In consideration of the above-mentioned problems, the present invention aims at providing a plasma processing apparatus that optimizes the gas supply system thereof to enable the process depth uniformity and the critical dimension uniformity of the object to be controlled independently, or in other words, to enable the critical dimension to be controlled without changing the process depth uniformity. [0015] The present invention provides a plasma processing apparatus comprising a processing chamber, a means for supplying processing gas to the processing chamber, an evacuation means for decompressing the processing chamber, an electrode on which an object to be processed is placed, and an electromagnetic radiation power supply, wherein at least two kinds of processing gases having different flow ratio or O.sub.2 or N.sub.2 composition ratio are introduced from different gas inlets to thereby uniformize the critical dimension across the plane of the object while maintaining a uniform process depth across the plane of the object. [0016] Furthermore, according to the present invention, process gases other than O.sub.2 and N.sub.2 are divided into plural flows as first processing gas, and O.sub.2 and N.sub.2 are added as second gas to the first gas having been divided, so that processing gases having different O.sub.2 or N.sub.2 composition or different flow rate can be introduced through different gas inlets into the processing chamber. At this time, regardless of the amount of O.sub.2 or N.sub.2 to be added to the first gas having been divided into plural flows, a gas distributor for dividing the first gas into plural flows is used to divide the first processing gas into predetermined flow ratios. [0017] Moreover, the present invention is equipped with a gas distributor for dividing O.sub.2 or N.sub.2 into predetermined flow ratios in order to add the O.sub.2 or N.sub.2 of predetermined flow ratios to the divided first gas. [0018] Further, the present invention characterizes in disposing gas flow meters between the first gas outlet provided in the processing chamber and the gas distributor and between the second gas outlet provided in the processing chamber and the gas distributor, so as to monitor whether the gas distributors are operating normally. [0019] Even further, the present invention characterizes in connecting gas lines for evacuating processing gases without passing through the processing chamber between the first gas outlet provided in the processing chamber and the gas distributor and between the second gas outlet provided in the processing chamber and the gas distributor, so as to check whether the gas distributors are operating normally. Continue reading... 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