A simple theory of the Johnsen-Rahbek effect

Atkinson, R. W.

doi:10.1088/0022-3727/2/3/303

Cited by 25 publications

(15 citation statements)

References 7 publications

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“…1 manifests a strongly nonlinear variation of the interface resistance R I with respect to the voltage V eff . Such nonlinearity is one of the evidences of Johnsen-Rahbek effect [8] and is attributed to field emission of electrons [9,10] under intense electric field as reported previously [7]. A relatively uniform current passing through the bulk layer is squeezed into numerous uneven contact points of the interface layer surface, which in turn leaves the surface charge Q 0 around contact points.…”

Section: Doi: 101585/pfr3028mentioning

confidence: 71%

Temporal Analysis of Electrostatic Chuck Characteristics in Inductively Coupled Plasma

Shim

Sugai

2008

Plasma and Fusion Research

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Johnsen-Rahbek electrostatic chuck (ESC) for holding a silicon wafer in semiconductor processing is investigated in inductively coupled plasma (ICP). Bi-layer model of the ESC consisting of a thick bulk layer and a thin interface layer is proposed. The resistance of each layer is obtained by measuring the ESC voltage-current (V-I) characteristic with and without the wafer in ICP, along with the voltage effectively applied to the interface layer. Surface charges stored in the interface layer capacitance are found by the time-integration of current in a turn-on phase of a ramped voltage. On the other hand, the chuck holding force is in situ obtained in a turn-off phase of slowly ramped voltage, from the critical conditions of helium gas pressurization for wafer de-chuck. The electrostatic force predicted on a basis of equivalent circuit in the bi-layer model coincides with the mechanical force obtained in the wafer de-touch experiments. In plasma-assisted processing of semiconductors, electrostatic chuck (ESC) has been widely used for holding a silicon wafer on stage in vacuum. Two types of ESC are used; Coulomb type [1-3] using insulating spacer layer (volume resistivity ρ > 10 14 Ω-cm), and Johnsen-Rahbek type [4, 5] using semiconductive spacer layer (ρ = 10 10 -10 12 Ω-cm) between the plates (i.e., chuck electrode and wafer). The electrostatic holding force stems from the opposite polarity surface charges appearing on the wafer and the chuck electrode at high applied voltages. In the J-R type, very strong holding force is achieved at lower chuck voltages than in the Coulomb type, owing to the high electric fields between the narrow gaps distributed over the spacer layer with surface irregularities. However, the J-R type is complex and sensitive to various interface parameters such as electrical conductivities, surface roughness on sub-microscopic scale, and large-scale flatness of two plates. And the ESC often leads to troubles such as poor process repeatability caused by residual charges, film damages induced by the chuck current, and wafer crack during lift by pins for wafer replacement.To avoid such troubles, a deeper understanding of the J-R type ESC is required, particularly in practical plasma conditions. In a previous paper [6], we reported remarkable effects of RF-induced self-bias voltage on the ESC voltage-current (V-I) characteristics which was observed in low-density capacitively-coupled plasma (CCP). In this paper, we present temporal analysis of J-R type ESC characteristics in high-density inductively-coupled plasma (ICP). author's e-mail: sugai-h@isc.chubu.ac.jpThe time-integration of chuck current during a voltage turn-on phase gives surface charges at the interface while the turn-off phase variation of pressurized helium flow behind a wafer enables evaluation of the electrostatic holding force. Bi-layer equivalent circuit model is proposed to explain the behavior of the J-R type ESC.The experiment was performed in an ICP device [7] where plasma is produced in a cylindrical stainless steel chamb...

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Section: Doi: 101585/pfr3028mentioning

confidence: 71%

Temporal Analysis of Electrostatic Chuck Characteristics in Inductively Coupled Plasma

Shim

Sugai

2008

Plasma and Fusion Research

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“…In such applications, the electrical conductivity of the ceramics must be welloptimized, in addition to a high thermal conductivity, as the working mechanism depends on the electrical properties under a high electric field [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Effects of carbothermal reduction on the thermal and electrical conductivities of aluminum nitride ceramics

Kim

Chae

et al. 2010

Ceramics International

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“…Assuming d = 1 µm, the electric field E = δV/d was calculated (see Table 1), which increased to 300 MV/m or higher at V > 0.4 kV. An intense electric field such as 500 MV/m is known to induce the field emission of electrons [7,8]. The chuck current nonlinearly increased above 0.5 kV, as seen in Fig.…”

Section: Doi: 101585/pfr2044mentioning

confidence: 99%

Plasma Effects on Electrostatic Chuck Characteristics on Capacitive RF Discharge

Shim¹,

Yamauchi

Sugai

2007

Plasma and Fusion Research

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Johnsen-Rahbek electrostatic chuck (ESC) is installed on the cathode side of a capacitive RF discharge, and the ESC voltage-current (V-I) characteristic is measured under various conditions. First, the reference V-I curve is obtained for a grounded aluminum (Al) wafer without discharge. The observed nonlinear characteristic is attributed to the field emission of electrons at irregular contacting surfaces. When the discharge is turned on with an electrically floating wafer, the V-I curve shifts from the reference curve toward the negative direction along the chuck voltage axis. The amount of shifted chuck voltage coincides with the self-bias DC voltage induced on the wafer. This plasma effect on the V-I characteristics can be explained well in terms of the effective chuck voltage, taking into account the self-bias. On the other hand, the replacement of the Al wafer with a silicon (Si) wafer leads to a considerable reduction in the chuck current. When a thin Al foil is inserted between the Si wafer and the aluminum nitride (AlN) spacer layer, the chuck current recovers upto the reference value, suggesting that the Johnsen-Rahbek effect is extremely sensitive to the electrical and mechanical properties of the contacting interface. Electrostatic chuck (ESC) is widely used for holding silicon wafers and controlling their temperature during the plasma-assisted processing of semiconductors. There are two holding configurations of ESC: the Coulomb type [1-3], using an insulating spacer layer (volume resistivity ρ > 10 14 Ω-cm), and the Johnsen-Rahbek (J-R) type [4,5], using a semiconductive spacer layer (ρ = 10 10 -10 12 Ω-cm) between plates (i.e., chuck electrode and wafer). The electrostatic holding force in the Coulomb type stems is generated due to the opposite polarity surface charges that appear on the wafer and chuck electrode at high applied voltages. A new experiment using thin plastic films and insulating sealant has been reported on the bipolar configuration of Coulomb-type ESC [6].In the J-R type, a very strong holding force is achieved even at low chuck voltages due to the high electric fields between the narrow gaps distributed over the spacer layer with surface irregularities. In comparison to the Coulomb type, the J-R type is very sensitive to the following physical conditions of the contacting surface: electrical conductivities, residual charges, surface roughness on submicroscopic scales, and large-scale flatness of two plates. Many questions arise on how such conditions influence clamping and declamping behaviors in actual ESC systems. Examples of ESC-related limitations include poor author's e-mail: sugai-h@isc.chubu.ac.jp process repeatability caused by residual charges, film damage induced by the chuck current, and wafer cracking when raised by lift pins.To solve these problems, a deeper understanding of the ESC-holding mechanism is required, particularly in practical plasma conditions. In this paper, we present a basic study on J-R ESC installed in a parallel-plate discharge, i.e., capacitive coup...

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A simple theory of the Johnsen-Rahbek effect

Cited by 25 publications

References 7 publications

Temporal Analysis of Electrostatic Chuck Characteristics in Inductively Coupled Plasma

Temporal Analysis of Electrostatic Chuck Characteristics in Inductively Coupled Plasma

Effects of carbothermal reduction on the thermal and electrical conductivities of aluminum nitride ceramics

Plasma Effects on Electrostatic Chuck Characteristics on Capacitive RF Discharge

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