JP2007073420A - Plasma measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure plasma characteristics precisely by providing a reference electrode resistant to metal contamination in a chamber. <P>SOLUTION: A plasma measuring apparatus comprises: a chamber 100 made of a conductive material and having an insulated inner wall; a probe 101 to be inserted into plasma in the chamber 100; a DC power supply 104 for supplying a voltage to the probe 101; an ammeter 103 for measuring a probe current flowing into the plasma detected by the probe 101; and a reference electrode 105 provided in the chamber 100 for obtaining a reference electric potential for measuring the probe current. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma measuring apparatus for measuring plasma characteristics.

  Conventionally, processing by a dry etching apparatus using plasma has been frequently used in the manufacture of semiconductor devices. In the process of dry etching using plasma, it is effective to monitor the plasma state in order to determine the conditions of the plasma processing and to grasp the state of the dry etching apparatus and efficiently perform parts replacement etc. .

  As a method for measuring plasma characteristics, a technique called Langmuir probe method is known, in which a probe is loaded in plasma and its DC voltage-current characteristics are measured to measure plasma density, electron temperature, etc. (For example, see Patent Document 1 below.)

JP 2001-237097 A

  However, in the dry etching apparatus used in the above-described semiconductor manufacturing process, if there is metal contamination, a defective product is generated. Therefore, the inner wall of the container (apparatus) is made of alumite so that metal contamination does not occur. Insulated. Thus, since the inner wall of the container in contact with the plasma is insulated, the inner wall of the container does not function as a reference electrode. Under this condition, the resistance of the return path of the probe current becomes high, so that the current on the positive bias side stays at a low value, and accurate measurement cannot be performed as an example.

  An object of the present invention is to provide a plasma measuring apparatus capable of accurately measuring plasma characteristics without metal contamination in order to eliminate the above-described problems caused by the prior art.

  In order to solve the above-described problems and achieve the object, a plasma measuring apparatus according to the invention of claim 1 is made of a conductive material and has an inner wall insulated, and is inserted into the plasma in the chamber. A probe for supplying a voltage to the probe, a current measuring unit for measuring a probe current flowing in from the plasma detected by the probe, and a reference potential for measuring the probe current. And a reference electrode installed in the chamber.

  According to a second aspect of the present invention, in the plasma measuring apparatus according to the first aspect, the chamber is provided with a probe flange made of a conductive material that leads the probe out of the chamber. The probe flange is connected to the reference electrode and is grounded outside the chamber.

  According to a third aspect of the present invention, there is provided the plasma measuring apparatus according to the first or second aspect, wherein the reference electrode is formed in a ring shape and is a circular substrate to be processed which is installed on the bottom surface of the chamber. It is characterized by being installed concentrically on the outer periphery.

  According to a fourth aspect of the present invention, in the plasma measurement apparatus according to any one of the first to third aspects, at least a portion of the reference electrode that is directed in the descending direction of ions in the plasma is covered. As described above, an insulating member is provided.

  According to a fifth aspect of the present invention, there is provided the plasma measuring apparatus according to the fourth aspect, wherein the insulating member is provided so as to expose an inner peripheral side wall surface of the reference electrode.

  According to the invention described in any one of claims 1 to 3 described above, the influence of the return path resistance of the probe current can be prevented. Therefore, it is possible to accurately measure plasma characteristics. Moreover, according to the invention of Claim 4 or 5, metal contamination of the reference electrode can be prevented.

  According to the plasma measuring apparatus of the present invention, there is an effect that the plasma characteristics can be accurately measured without metal contamination.

  Exemplary embodiments of a plasma measuring apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

(Embodiment)
FIG. 1 is an explanatory diagram illustrating an outline of a plasma measuring apparatus according to an embodiment. In FIG. 1, a cylindrical probe 101 is loaded in the plasma to be measured. The shape of the probe 101 is not limited to a cylinder but may be a flat plate, a sphere, or the like. Further, tungsten, platinum, or the like can be used as the material of the probe 101.

  An electric wire 102 is connected to the other end of the probe 101. The probe 101 is grounded via an ammeter 103 that measures the probe current flowing through the probe and a DC power source 104 that applies a voltage to the probe 101. Further, the periphery of the electric wire 102 is insulated by an insulating film formed by anodizing.

  In the chamber 100, a ring is formed by forming a 3 mm diameter SUS wire to be a reference electrode 105 into a ring shape. In the present embodiment, the SUS wire is formed in a ring shape, but the object as the reference electrode 105 can be achieved even if the SUS wire is not in the ring shape. In the present embodiment, the reason why the SUS wire is formed in a ring shape is that the inventors thought that the reference electrode 105 in the ring shape can be grounded in a balanced manner in the chamber 100. is there. The reference electrode 105 is installed to obtain a reference potential when measuring the probe current.

  The reference electrode 105 is installed around the substrate to be processed 106. In addition, the reference electrode 105 is installed on the outer periphery of the focus ring 107 installed on the outer periphery of the substrate to be processed 106 in order to prevent a short circuit with a lower electrode (not shown). The reference electrode 105 is preferably installed at a position as far as possible from the substrate 106 to be processed. For measurement of Ar plasma, which will be described later, the measurement was performed with the reference electrode 105 placed about 10 mm inside the inner wall 108 of the chamber 100.

  The chamber 100 is made of a conductive material, and the inner wall 108 of the chamber 100 is provided with an insulating coating such as anodized. Furthermore, the chamber 100 is hermetically sealed in order to maintain a vacuum. For this reason, the reference electrode 105 is connected to a probe mounting flange 109 (hereinafter referred to as “probe flange”) whose conductive material is exposed by an electric wire 110, and the probe flange 109 is grounded. 105 grounding is realized. Here, the probe flange 109 is grounded outside the chamber 100. The probe flange 109 has a cylindrical shape with one opening, and is connected to the chamber 100 so that the opening and the opening formed in the chamber 100 face each other. The other end of the probe flange 109 is passed through the electric wire 102, but is sealed so that the inside of the chamber 100 is kept in a vacuum. Further, it is desirable that the inner surface of the probe flange 109 other than the connection portion with the electric wire 110 and the surface of the electric wire 110 other than the connection portion with the probe flange 109 are anodized.

  In addition, an insulating member 111 is provided above the reference electrode 105. The insulating member 111 is provided so that ions accelerated toward the bottom surface of the chamber 100 do not directly contact the reference electrode 105, so that metal contamination does not occur. An example of the insulating member 111 will be described later. With the above configuration, the plasma characteristics can be measured without being contaminated with metal in the chamber 100 and without being affected by the return path resistance of the probe current.

  Next, the insulating member 111 will be described. FIG. 2 is an explanatory view showing an example of the insulating member 111. In FIG. 2, a substrate to be processed 106 is placed at the approximate center of the bottom of the chamber 100. A substrate electrode (lower electrode) (not shown) is disposed under the substrate 106 to be processed, and the reference electrode 105 is disposed away from the substrate 106 so as not to short-circuit with the substrate electrode.

  The reference electrode 105 is covered with an insulating tubular insulating member 111. The insulating member 111 is formed in a substantially annular shape so as to cover the entire reference electrode 105. In FIG. 2, the insulating member 111 is provided so as to cover the reference electrode 105, but the insulating member 111 is provided so as to cover at least a portion of the reference electrode that faces the direction in which ions in the plasma descend. It only has to be. For example, the insulating member 111 has a notch 111a formed on the inner peripheral side surface so that the inner peripheral side wall surface of the reference electrode 105 is exposed. In FIG. 2, the cross section 201 of the insulating member 111 is substantially circular, but the shape of the cross section 201 is not limited to a circle.

(Processing procedure of plasma measuring device)
Next, a procedure for measuring plasma characteristics with the plasma measuring apparatus of the present invention and performing dry etching will be described. FIG. 3 is a flowchart showing a processing procedure from measuring plasma characteristics with the plasma measuring apparatus according to the present invention until dry etching is performed. In the flowchart of FIG. 3, first, the substrate to be processed 106 is installed (step S301), and the reference electrode 105 is installed around the substrate to be processed 106 (step S302).

  Next, the insulating member 111 is installed (step S303), and the inside of the chamber 100 is evacuated (step S304). Then, plasma is generated inside the chamber 100 (step S305), and plasma characteristics are measured (step S306). Next, plasma conditions are set (step S307), and the substrate to be processed 106 is dry-etched (step S308).

  FIG. 4 is a graph showing the results of measuring Ar plasma with a plasma measuring device. In the graph of FIG. 4, the vertical axis indicates current [A], and the horizontal axis indicates voltage [V]. In addition, a solid line 401 in the graph indicates the result of measurement with the reference electrode 105 installed, and a dotted line 402 indicates the result of measurement without the reference electrode 105 installed.

  The plasma was measured under the conditions of Ar: 100 sccm, Ws (source power): 200 W, Wb (bias power): 0 W, P: 25 mTorr. As shown in the graph, the result of measurement with the reference electrode 105 installed (solid line 401 in the figure) is a current on the positive bias side as compared to the result of measurement without the reference electrode 105 installed (dotted line 402 in the figure). The value of is increased by an order of magnitude, and accurate plasma measurement is possible.

  Further, the plasma measuring apparatus of the present invention can be applied to, for example, a capacitively coupled plasma (CCP) apparatus, an inductively coupled plasma (ICP) apparatus, an electron cyclotron resonance plasma (ECRP) apparatus, and the like.

  As described above, according to the plasma measuring apparatus, metal contamination can be prevented. Further, the influence of the return path resistance of the probe current can be prevented. Therefore, it is possible to accurately measure plasma characteristics.

  As described above, the plasma measuring apparatus according to the present invention is useful for measuring plasma characteristics, and is particularly suitable for a dry etching apparatus using plasma.

It is explanatory drawing which shows the outline of the plasma measuring device concerning embodiment. It is explanatory drawing shown about the example of an insulating member. It is a flowchart shown about the process sequence after measuring a plasma characteristic with the plasma measuring apparatus of this invention and performing dry etching. It is a graph which shows the result of having measured Ar plasma with the plasma measuring device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Chamber 101 Probe 102 Electric wire 103 Ammeter 104 DC power supply 105 Reference electrode 106 Substrate 107 Focus ring 108 Inner wall 109 Probe flange 110 Electric wire 111 Insulating member 111a Notch

Claims (5)

A chamber made of a conductive material and having an inner wall insulated;
A probe inserted into the plasma in the chamber;
Voltage supply means for supplying a voltage to the probe;
Current measuring means for measuring a probe current flowing from the plasma detected by the probe;
In order to obtain a reference potential for measuring the probe current, a reference electrode installed in the chamber;
A plasma measuring apparatus comprising: The chamber is provided with a probe flange made of a conductive material that leads the probe out of the chamber,
The plasma measuring apparatus according to claim 1, wherein the probe flange is connected to the reference electrode and is grounded outside the chamber.   3. The plasma measuring apparatus according to claim 1, wherein the reference electrode is formed in a ring shape and is concentrically disposed on an outer peripheral portion of a circular substrate to be processed disposed on a bottom surface of the chamber. .   The plasma measurement apparatus according to any one of claims 1 to 3, wherein an insulating member is provided so as to cover at least a portion of the reference electrode facing a direction in which ions in the plasma descend. The plasma measuring apparatus according to claim 4, wherein the insulating member is provided so as to expose an inner peripheral side wall surface of the reference electrode.

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