`
`[19]
`
`[11] Patent Number:
`
`6,063,710
`
`Kadomura et al.
`
`[45] Date of Patent:
`
`May 16, 2000
`
`US0060637 10A
`
`[S4]
`
`[4’OR
`
`5,681,730
`5.711.351
`_<,9on.1n5
`
`.......................... 437’22X
`I0/‘I997 Mihuru el al.
`.
`.
`I50/643.1
`131998 Blalock et al.
`5,1999 Toshima ..........
`156/345
`
`[75]
`
`Inventors: Shlngo Kudomuru; Tomohlde Jozakl;
`-
`-
`~
`,
`§:"f:"k° H'm"°’ an °t K""ag““a'
`P‘
`[73] Assigncc: Sony Corporation, Tokyo, Japan
`
`
`
`fi““’l‘J'("“'“ "1 “'-
`rat
`net‘
`.............
`.
`3..
`1111999 Kadonntm cl nl
`5,981,913
`6.004,882 1211999 Kim et al.
`......... ..
`6.008.133 1211999 Kitniiliashi et al.
`
`I
`'
`. 21914441
`438/706
`.................... .. 210437
`
`FOREIGN PATENT DOCUMENTS
`
`[21] Appl. No.: 08/804,412
`
`4302l4lA 1011992
`
`Japan .
`
`at on
`
`I, ma
`
`8-(H779!
`
`[ r]l
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`27 lqqémilgjtgl pi:
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`[JP]
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`H1995
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`30
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`apan ...................................,
`0
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`Japan .................................... 84145868
`Mar. 4. I996
`________________________ __ H01]; 21/302
`[51]
`|m_ (j|_7
`................. .. 438/715; 4331733
`[52] U.s. Cl.
`[58]
`Field of Search ................................... .. 4381695, 696,
`438/714, 715, 733, 738
`
`[56]
`
`References Clted
`
`4,971,653
`5320.932
`5,584,071
`5,005,000
`
`U-S- PATENT DOCUMENTS
`1111991) Powell etal. .. ........
`611994 Tsubonc ctal.
`12,-‘I996 Kominu
`211997 Muller et -.11.
`
`. . . .. . .. 210159
`.. 4371223
`21o,~'s9
`........................... .. z1o.:'t>7
`
`Primar__v E.\'mniner-—Randy Gulakowski
`Assistant Examitter—Anita Alanko
`
`Attorney, Agent, or Firm—1Iil1 & Simpson
`
`ABSTRACT
`[57]
`Amethod of dry etching treatment capable of attaining both
`high selectivity and line fabrication at a high accuracy
`simultaneously is provided. in which an etching treatment
`comprising a plurality ofstcps are applied to a specimen W
`in one identical processing, apparatus, and the temperature of
`the specimen is changed between etching of one step and
`etching of another step succeeding thereto, among the plu-
`rality of the steps, thereby applying etching at temperatures
`dilferent between the one step and the step succeeding
`"1°"=‘0—
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`16 Claims, 4 Drawing Sheets
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`34
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`34
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`rtiilzirliarzlpz 33
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`32
`‘ 3!
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`
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`Page 1 of 12
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`Samsun Exhibit 1006
`g
`Samsung Electronics Co., Ltd. v. Daniel L. Flamm
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`U.S. Patent
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`May 16,2000
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`Sheet 1 of4
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`6,063,710
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`FIG.
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`U.S. Patent
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`May 16, 2000
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`Sheet 3 of 4
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`6,063,710
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`F|G.3A
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`Page 4 of 12
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`1
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`METHOD AND APPARATUS FOR DRY
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`ETCHING VVITH TEMPERATURE CONTROL
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`BACKGROUND OF THE INVENTION
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`1. Field of the Invention
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`The present invention concerns a dry etching method used
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`mainly for the production of semiconductor devices and,
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`more in particular, it relates to a method and an apparatus for
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`dry etching providing compatibility for anisotropic fabrica-
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`tion and high selectivity.
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`2. Description of the Related Art
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`In recent years, a demand for fi11e fabrication in super LSI
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`has become severer and it is indispensable, for example, in
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`etching treatment, a processing method of providing com-
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`patibility for fine fabrication at high accuracy with mini-
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`mized dimensional conversion tolerance and high selectivity
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`to underlying material.
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`However, in a case of plasma etching materials other than
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`oxide films, an anisotropic shape has been ensured as is
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`well-known by the presence of a so-called side wall protec-
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`tion film. The side wall protection film is formed by the
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`deposition, on the side wall of a pattern of various deposits
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`including organic polymers which are formed when reaction
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`products formed during plasma etching are dissociated again
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`in the plasmas and they serve to protect the side wall of the
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`pattern and prevent the side wall from being etched.
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`By the way, since the side wall protection film is formed
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`by the deposits from the reaction products, when a pattern
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`formed by etching is convex and if the width of the pattern
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`is fine,
`the thickness of the side wall protection wall is
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`relatively increased excessively, making the width of the
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`entire pattern larger than a desired width. In the same
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`manner, when a pattern formed by etching is of a concave
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`recess and if the width is narrow, the thickness of the side
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`wall protection film is relatively increased excessively, mak-
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`ing the entire pattern width narrower than a desired width.
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`Accordingly, as vario11s kinds of patterns have been made
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`finer and the with of the pattern is made finer (narrowed) as
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`described above, the dimensional accuracy of the obtained
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`pattern is lowered when if it
`is intended to ensure the
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`anisotropy of etching by utilizing the side wall protection
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`film.
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`In order to overcome such a disadvantages, it has recently ,
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`been attempted and attracted attention to apply etching While
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`conducting exhaustion at high speed thereby ensuring a
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`dimensional accuracy.
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`In the high speec exhaustion process, a pump of a higher
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`exhaustion speed than that of existent etching apparatus is _
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`attached, and conductance of the etching gas is improved to,
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`whereby the residence time of an etching gas during etching
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`is shortened and Lissociation of the reaction products in
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`plasmas is suppressed during etching. According to the high
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`speed exhaustion process, since the amount of deposits by
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`redissociation of tie reaction products can be decreased
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`significantly, the absolute value for the dimensional conver-
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`sion tolerance and variation thereof can be suppressed
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`extremely elfectively.
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`However, in the iigh speed exhaustion process described
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`above, since the reaction products are exhausted rapidly, a
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`supply source for no side wall protection film is decreased
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`and the side wall protection film of a satisfactory thickness
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`is not formed,
`the anisotropic shape can not be ensured
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`enough, so that it results in an additional problem that the
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`configurational accuracy of the pattern obtained upon apply-
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`ing overetching is worsened.
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`2
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`That is, if a bias applied to a substrate is lowered in order
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`to ensure the selectivity relative to the underlying material,
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`since the side wall protection film is thin and, accordingly,
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`weak, occurrence of side etch or notching is inevitable. On
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`the other hand, if the applied bias is increased in order to
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`ensure the shape, selectivity relative to the underlying mate-
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`rial is deteriorated.
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`As a technique capable of overcoming the problem that
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`the selectivity and the shape are in a trade—off relation and
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`capable of attaining both the selectivity and the anisotropic
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`shape simultaneously, a so-called low temperature etching
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`technique of cooling the wafer to a temperature lower than
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`0° C. during etching has been proposed.
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`The low temperature etching technique has been
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`disclosed,
`for example, as an invention made by K.
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`Tsiljimoto in Proceedings of Symposium of Dry Process
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`(Oct. 24-25, 1988, Tokyo), p.p. 42—49.
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`In this technique, radical reaction is suppressed by low-
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`ering the specimen temperature, so that anisotropy can be
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`ensured even under a low substrate bias.
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`However, even the low temperature etching technique has
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`the following disadvantages.
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`At first, fabrication is difficult to a material such as W
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`polyside in which vapor pressures of reaction products are
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`di ‘erent. This is because the vapor pressure of reaction
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`products such as WCl,_ and WO,_Cly formed upon etching of
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`WSix is low, etching for WSix can not be applied if the
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`temperature of the specimen is lowered to such a tempera-
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`ture as convenient for etching the polysilicon.
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`Secondly, deltaT (difference between a temperature set for
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`a specimen stage and a wafer temperature) is increased upon
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`etching. That is, although temperature lowering is effective
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`for ensuring the selectivity relative to the underlying Si, for
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`example, in the fabrication of contact holes, since tempera-
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`ture lowering results a contact hole of a tapered shape due
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`to deposition of an excessive polymer, so that setting for the
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`low temperature condition is dilficult as described above
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`and, in addition, incident energy has to be increased inevi-
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`tably in order to disconnect Si—O bonds in the fabrication
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`of contact holes, which results in the increase of deltaT.
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`Accordingly, because of the disadvantage described
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`above, even the low temperature etching can be applied
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`actually only at a halfway temperature. In order to overcome
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`such a disadvantage, it may be considered to vary the setting
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`temperature for a specimen comprising, for example, a
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`wafer between etchings for materials having different vapor
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`pressures of reaction products or between just etching and
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`overetching. However, the temperature can not be changed
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`within a short time in an existent cooling system by a chiller
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`using a liquid such as fluorinate as a coolant and,
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`accordingly, existent low temperature etching can not be
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`practiced at a temperature to provide a sufficient effect
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`to the low temperature etching technique as
`inherent
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`described above.
`
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`SUMMARY OF THE INVENTION
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`It is an object of the present invention to provide a dry
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`etching method capable of attaining both high selectivity
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`and fine fabrication at high accuracy simultaneously, as well
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`as an apparatus for manufacturing a semiconductor device
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`capable of actually putting the low temperature etching
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`technique into practical use.
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`In accordance with a dry etching method as a first aspect
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`of the present invention, the foregoing object can be attained
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`by applying an etching treatment comprising a plurality of
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`Page 6 of 12
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`6,063,710
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`3
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`steps to a specimen within an identical processing apparatus,
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`wherein the temperature of the specimen is changed between
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`etching in one step and etching in the succeeding step,
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`thereby applying etching at temperature di erent between
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`the one step and the succeeding step.
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`That is, according to the dry etching method, since the
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`specimen temperature is changed between the etching in one
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`step and etching in the succeeding step, if a main etching as
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`the one step is applied at a normal
`temperature, and
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`overetching as the succeeding step is conducted at a low
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`temperature for instance, since radical reaction can be sup-
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`pressed during overetching by temperature lowering even if
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`the thickness of the formed side wall protection film is thin,
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`it can endure resultant excessive radical attack.
`so that
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`Accordingly, due to the radical reaction suppressing e ect
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`by the temperature lowering, even if the bias applied to the
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`specimen is lowered, formation of undercut or notching can
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`be prevented.
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`llurther, since each of the etching treatments is conducted
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`within an identical processing apparatus, the time for the
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`change of the specimen temperature between the steps can
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`be shortened.
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`Further,
`the foregoing object can be attained in a dry
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`etching method in accordance with the second aspect of the
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`present invention by applying an etching treatment compris-
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`ing plurality of steps repeatedly to a plurality of specimens
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`respectively in a dry etching method, wherein the method
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`changing the temperature of a specimen stage supporting the
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`specimen between etching in the initial step and etching in
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`the final step of the steps described above, applying etching
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`at dilferent temperatures between the initial step and the final
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`step, and changing the temperature of the specimen stage to
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`a setting temperature for the specimen in the etching at the
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`initial step after the completion of the etching at the final
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`step and before putting of a next specimen into the process-
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`ing apparatus.
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`According to the dry etching method, since the etching
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`treatment is conducted at temperatures different between the
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`etching at the first step and etching at the final step, the same
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`effect as in the first feature of the present invention can be
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`obtained and, since the temperature of the specimen stage is
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`changed to the setting temperature for the specimen in the
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`etching at the initial step after the completion of the etching ,
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`at the final step and before putting the next specimen in the
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`identical processing apparatus, the time from the completion
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`of etching for a specimen to the start of etching for the next
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`specimen can be shortened.
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`Further, the foregoing object can be solved by an appa-
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`ratus for producing a semiconductor device in accordance
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`with third aspect of the present invention, having a vacuum
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`chamber in which a specimen stage equipped with a cooling
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`means is disposed at the inside and a plasma generation
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`means disposed in the vacuum chamber for generating
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`plasmas for processing a semiconductor substrate by gen-
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`erating plasmas while controlling the temperature of a
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`semiconductor substrate placed on the specimen stage by
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`cooling the specimen stage by the cooling means, wherein
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`the cooling means uses a liquefied gas or a gas as a coolant,
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`a flow channel of the coolant is formed by disposing in
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`parallel a plurality of pipelines of different diameters at a
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`position before flowing to the specimen stage, and the
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`specimen stage is cooled by flowing the coolant through the
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`pipelines to the specimen stage, and the cooling means has
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`a control means disposed for controlling the flow rate of the
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`coolant to each of the plurality of pipelines.
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`4
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`In the apparatus for producing the semiconductor device,
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`since the temperature of the semiconductor substrate on the
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`specimen stage is controlled (cooled) by using a coolant
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`comprising a liquefied gas or a gas, more rapid cooling is
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`possible as compared with an existent cooling method using
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`a liquid as the coolant. That is, while it is basically desirable
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`to supply a great amount of coolants at a temperature as low
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`as possible for rapid temperature lowering, if the liquid is
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`used for the coolant as usual, it is diflicult to supply a great
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`amount of the coolant since the viscosity thereof is increased
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`at a low temperature failing to attain sufficient heat
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`exchange. On the other hand, in the present invention, since
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`a liquefied gas or gas is used as the coolant as described
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`above in the present invention, supply of a great amount of
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`the coolant is not inhibited by the increase of the viscosity,
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`so that the coolant can be supplied in a su icient amount to
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`enable rapid cooling to a desired temperature.
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`to the
`Further, since the flow channel of the coolant
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`specimen stage is formed by arranging in parallel a plurality
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`of pipelines of different diameters and the flow rate of the
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`coolant to each of the pipelines is controlled by the control
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`means, a desired flow rate can be controlled reliably and
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`briefly, for example, by selecting a pipeline for flowing the
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`coolant
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`accordingly, the flow can be controlled at a higher accuracy
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`thereby enabling finer temperature control compared with a
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`case of forming the flow channel by one pipeline and
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`controlling the degree of cooling by adjusting the flow rate
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`of the coolant flowing through the pipeline.
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`In the dry etching method as defined in the first feature of
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`the present
`invention, since the specimen temperature is
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`changed between etching in one step and etching in a
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`succeeding step, when the main etching is conducted as one
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`step at a normal temperature, while overetching is conducted
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`as the succeeding step at a low temperature for instance,
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`since radical reaction can be suppressed in the overetching
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`even if the thickness of the formed side wall protection film
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`is thin the radical reaction can be suppressed as described
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`above by the temperature lowering, it can withstand exces-
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`sive radical attack resulted. Accordingly, due to the effect of
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`suppressing the radical
`reaction by the temperature
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`lowering, even if the bias applied to the specimen is lowered,
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`formation of undercut or notching can be prevented. Thus,
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`it is possible to attain both the high selectivity and ensurance
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`of anisotropic shape, that is, fine fabrication at high accuracy
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`simultaneously.
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`l"urther, since each of the etching treatments is conducted
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`in the identical processing apparatus, the time for the chang-
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`ing the specimen temperature between the steps can be
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`shortened. Accordingly, if the change of the specimen tem-
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`perature is conducted about within a time required for a
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`series of operations, for example, interruption of electric
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`discharge or alternation of etching gases between the steps,
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`dry etching treatment comprising a plurality of steps can be
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`applied without deteriorating the throughput.
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`In the second feature of the method of dry etching
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`according to the aresent invention, since etching treatment is
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`conducted at di erent temperatures between the etching of
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`the initial step and the etching of the final step, the same
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`effect as that in the first feature can be obtained. Further,
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`when the etching of the final step has been completed, since
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`the temperature for the specimen stage is changed previ-
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`ously to a setting temperature for the specimen in the etching
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`of the initial step, before putting the next specimen in the
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`identical processing apparatus, the time from the completion
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`of etching for one specimen to the time starting the etching
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`for the next specimen can be shortened, by which the
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`productivity can be improved.
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`Page 7 of 12
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`6,063,710
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`5
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`Further, in the apparatus for producing the semiconductor
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`device according to the present invention, since the coolant
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`comprising a liquefied gas or a gas which can be supplied in
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`a great amount easily is used as the coolant, by which the
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`semiconductor substrate specimen) on the specimen stage is
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`cooled,
`the semiconductor substrate can be cooled more
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`rapidly compared with the existent cooling method using the
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`liquid as the coolant and, accordingly, the semiconductor
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`substrate can be controlled to a desired temperature in a
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`short period of time.
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`Furthermore, since the temperature for the semiconductor
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`substrate can be controlled in a short period of time, it is
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`possible to attain both the high selectivity a11d ensurance of
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`the anisotropic shape, that is, fine fabrication at high accu-
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`racy simultaneously by applying two step etching treatment,
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`that is, main etching at a normal temperature and overetch-
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`ing at a low temperature also, for example, to W polycide
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`having different vapor pressures for reaction products. In
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`addition, since the temperature of the semiconductor sub-
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`strate can be changed rapidly in a short period of time
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`between the steps, the temperature can be changed about
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`within a time required for a series of operations such as
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`interruption of electric discharge or alteration of etching
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`gases between the steps and, accordingly,
`the dry etching
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`treatment comprising a plurality of steps can be conducted
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`rapidly without lowering the throughput.
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`Further, since the flow channel for the coolant to the
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`specimen stage is formed by arranging in parallel a plurality
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`of control pipelines of different diameters and adjusting the
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`flow rate of the coolant to each of the pipelines by a control
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`means, if the control degree of the control means is control,
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`for example, by disposing a feed back control means or data
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`base control means, the flow rate of the coolant supplied to
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`the specimen stage can be controlled reliably and instanta-
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`neously to a desired amount a11d, accordingly, the flow rate
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`can be controlled at a higher accuracy compared with a case
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`of forming the flow channel with one pipeline and control-
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`ling the cooling degree by adjusting the flow rate of the
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`coolant flowing through the pipeline, by which finer tem-
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`perature control is possible to enable higher accuracy for the
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`etching fabrication.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIGS. 1A—1C are cross sectional side elevational views
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`for a main portion for explaining a first embodiment of a dry /
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`etching method according to the present invention in the
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`order of processing;
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`FIGS. 2A—2C are cross sectional side elevational views
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`for a main portion for explaining a second embodiment of
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`the dry etching method according to the present invention in I
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`the order of processing;
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`FIGS. 3A—3C are cross sectional side elevational views
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`for a main portion for explaining a third embodiment of the
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`dry etching method according to the present invention in the
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`order of processing;
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`FIG. 4 is a schematic constitutional view illustrating one
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`embodiment of applying the apparatus for producing the
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`semiconductor device according to the present invention to
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`a plasma etching apparatus; and
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`FIG. 5 is a schematic constitutional view for a cooling
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`control section and a periphery thereof.
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`DETAILED DESCRIPTION OF THE
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`PREFERRED EMBODIMENTS
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`A dry etching method according to the present invention
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`will be explained more in details.
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`6
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`At first, a first embodiment of the dry etching method
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`according to the present invention will be explained with
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`reference to FIGS. 1A—1C.
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`This method is an example of applying the method
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`according to the present invention to a method of fabricating
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`a W polycide by a two step etching treatment. That is, as
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`shown in FIG. 1A in this embodiment, a W polycide
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`comprising a polysilicon layer 32 and a WSix layer 33 is
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`formed on a SiO2 film 31 on a silicon substrate 30, on Wl1icl1
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`a photo-resist pattern 34 is further formed to prepare a
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`specimen VV. The W polycide of the specimen is fabricated
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`by etching into a pattern shape corresponding to the photo-
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`resist pattern 34,
`in which main etching is applied at a
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`normal
`temperature as the first step and overetching is
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`applied at a low temperature as the succeeding second step.
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`At first, main etching of the first step is applied at a normal
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`temperature (20° C.) under the following conditions to
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`remove the WSiX layer 33 and the polysilicon layer 32 by
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`etching to a state of partially leaving the polysilicon layer 32
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`as shown in FIG. 1B.
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`First Step (Main Etching)
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`Etching gas: C1202 50/10 SCCM
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`Pressure: 5 mTorr
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`Source power-1 (RF antenna 4): 2500W (13.56 Hz)
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`Source power-2 (RF antenna 3,3): 2500W (13.56 Hz)
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`RF bias: 100W
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`Specimen temperature: 20° C.
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`For the control of the specimen temperature in this
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`embodiment, a heater (not illustrated) of an electrostatic
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`chuck provided to a stage 12 to be described later and
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`cooling by a chiller 17 are applied in combination, and the
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`specimen temperature is controlled finely by the cooling
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`_ control of a control device 23.
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`Then, for applying overetching of the second step suc-
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`ceeding to the first step, electric discharge in the etching
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`device is once disconnected, and gases remaining in a
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`di usion chamber 2 are exhausted. Then, an etching gas
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`used in the second step to be described later (a gas identical
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`with that in the first step is used in this embodiment) is
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`in roduced into the diffusion chamber, and the gas is stabi-
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`liLed and the inside of the dilfusion chamber 2 is controlled
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`to a constant pressure. Further, d11ring a series of such
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`operations,
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`is, directly after the completion of the
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`etching of the first step, an electronic control valve 22 for a
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`by-pass pipeline 21 in the cooling system by the chiller 17
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`is Wholly closed, and an electronic control valve 20 for the
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`coolant pipeline 15 is opened wholly, and the gas coolant at
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`—140° C. from the chiller 17 is supplied to the stage 12 to
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`rapidly cool the specimen W
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`Then, the temperature of the specimen W reached —30°
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`C, which is an etching temperature to be described later
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`within a short period of time of about 30 see by such rapid
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`cooling. In this case, since the series of operations described
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`that,
`is a series of operations of interrupting
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`discharge, exhausting remaining gases in the diffusion
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`chamber 2 and, further, introducing and stabilizing a fresh
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`etching gas take a time equal with or more than the time
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`required for rapid cooling, the time required for the rapid
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`cooling does not constitute a factor of delaying the time
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`required for the etching treatment of the specimen W
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`Successively, discharging is applied again to conduct
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`overetching of the second step at a low temperature (—30°
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`(1.) under the following conditions, and a portion of a
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`polysflicon layer remaining being disposed on the SiO2 film
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`32 is removed by etching as shown in FIG. 1C.
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`Page 8 of 12
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`6,063,710
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`7
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`Second Step (Overetching)
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`Etching gas: C1202 50/10 SCCM
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`Pressure: 5 mTorr
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`Source power-l (RF antenna 4): 2500W (13.56 Hz)
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`Source power—2 (RF antenna 3): 2500W 13.56 Hz)
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`RF bias: 20W
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`Specimen temperature: —30° C.
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`When the overetching is thus applied, since the etching is
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`a treatment under the low temperature, radical reactions can
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`be suppressed by the temperature lowering even if the
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`formed side wall protection film is thin and, accordingly, it
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`is possible to withstand excessive radical attack and sup-
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`press the occurrence of undercut or notching even if the bias
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`applied to the specimen is lowered from 100W iii the first
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`step to 20W. Accordingly, sufficient anisotropic shape can be
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`ensured as shown in FIG. 1C while keeping selectivity to
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`higher than 100 with no effect on the shape even under 100%
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`overetching.
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`In the dry etching method described above, it is possible
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`to attain both the high selectivity and ensurance for the
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`anisotropic shape, that is,