JP6573252B2 - Substrate temperature adjustment mechanism for plasma processing equipment - Google Patents

Description

  The present invention relates to a plasma processing apparatus for etching or depositing a surface of a semiconductor substrate such as a silicon wafer, and more particularly to a substrate temperature adjusting mechanism for adjusting the temperature of the semiconductor substrate during processing.

  When a semiconductor substrate is plasma-treated, the temperature of the semiconductor substrate rises with the treatment, and proper processing cannot be performed or the semiconductor substrate may be damaged. Therefore, the semiconductor substrate must be cooled during the processing. Don't be. Usually, the semiconductor substrate is cooled by flowing a heat transfer medium between the lower surface of the semiconductor substrate and the upper surface of the lower electrode on which the semiconductor substrate is mounted, and cooling the heat transfer medium with a cooling mechanism. As this heat transfer medium, generally, helium (He) gas having high thermal conductivity and high fluidity is used.

  During the plasma treatment, a high-frequency voltage for generating plasma is applied to the lower electrode on which the semiconductor substrate is placed, and a high bias DC voltage is generated depending on the plasma treatment. On the other hand, a cooling mechanism that supplies a heat transfer medium between the lower electrode and the semiconductor substrate and cools it must be kept at ground potential because it must first ensure safety during work. I must. Then, the same high voltage as that applied (and generated) to the lower electrode is applied to the heat transfer medium flowing between the two, and the heat transfer medium has a sufficiently high electric resistance such as helium gas. In the absence of media, a discharge may occur through it. When such a discharge occurs, sufficient power for plasma generation is not supplied to the lower electrode, and the cooling medium supply mechanism may be damaged by the discharge.

  In order to prevent such discharge, in Patent Document 1, a plurality of flow path members (separating materials) provided with a large number of small-diameter holes are provided in the flow path of the heat transfer medium. In addition, by disposing a plurality of flow path members in which the positions of the holes are changed in series, it is further difficult to cause discharge. Similarly, Patent Document 2 discloses a separation material provided with a spiral passage, a separation material using a porous material, a separation material using a porous material, and the like. Patent Document 3 discloses a technique in which a ridge projecting vertically from a side wall is provided in a flow path of a heat transfer medium. Patent Document 4 discloses a technique of reducing the diameter of the flow path to a predetermined value or more. Patent Document 5 discloses a technique in which a separating material called a top having random air bubbles is arranged in a flow path.

JP 06-244119 A Japanese Patent Laid-Open No. 11-031680 JP2008-117849 JP 2008-117850 A JP2009-218607

The above-mentioned conventional techniques are designed to prevent the ionized heat transfer medium from easily moving between two points to which a high voltage is applied by reducing the size of the flow path or arranging a separating material in the flow path. It is composed of
However, such a configuration simultaneously has a problem that sufficient heat transfer (cooling) cannot be performed because the flow resistance of the heat transfer medium is generated even when no discharge occurs.

  The problem to be solved by the present invention is to provide a substrate temperature adjusting mechanism for a plasma processing apparatus capable of preventing a discharge in a heat transfer medium as much as possible while ensuring a sufficient heat transfer effect.

The substrate temperature adjusting mechanism for a plasma processing apparatus according to the present invention, which has been made to solve the above problems,
A part of the substrate mounting table having a heat transfer medium holding space disposed in the plasma processing chamber and a heat transfer medium source for supplying the heat transfer medium to the heat transfer medium holding space, partly in a reverse direction. A heat transfer medium flow path having a flow path is provided.

  In the substrate temperature adjusting mechanism for a plasma processing apparatus according to the present invention, a flow path in the reverse direction is provided in a part of the heat transfer medium flow path provided between the heat transfer medium holding space of the substrate mounting table and the heat transfer medium source. Have. That is, when the heat transfer medium is supplied from the heat transfer medium source to the heat transfer medium holding space of the substrate mounting table, the heat transfer medium as a whole is directed from the heat transfer medium source to the heat transfer medium holding space (substrate mounting table). However, it flows in the direction of the heat transfer medium source from the heat transfer medium holding space (substrate mounting table) in a part of the flow paths (reverse flow paths). In the substrate temperature adjusting mechanism for a plasma processing apparatus according to the present invention, it is not always necessary to reduce the diameter of these flow paths, so that resistance to the flow of the heat transfer medium hardly occurs. On the other hand, even if a discharge occurs normally in the heat transfer medium between the heat transfer medium source at the ground potential and the substrate mounting table to which a high voltage for plasma processing is applied, the electric charge due to the discharge is in the reverse flow path. In this case, it is necessary to flow against a reverse potential difference, and thus it is difficult to continue the discharge.

  In the substrate temperature adjustment mechanism for a plasma processing apparatus according to the present invention, since a part of the heat transfer medium flow path between the heat transfer medium holding space of the substrate mounting table and the heat transfer medium source has a reverse flow path, Even if a discharge occurs in the heat transfer medium between the heat transfer medium source and the substrate mounting table, it is difficult to continue the discharge because the discharge charge must flow against the reverse potential difference in the reverse flow path. Become. On the other hand, since it is not always necessary to reduce the diameter of the flow path, there is almost no resistance to the flow of the heat transfer medium.

1 is an overall configuration diagram of an inductively coupled reactive ion plasma processing apparatus using a substrate temperature adjusting mechanism according to the present invention. Sectional drawing of an example of the reverse path part of the board | substrate temperature adjustment mechanism which concerns on this invention. The perspective view (a) of another example of the reverse path part of the board | substrate temperature adjustment mechanism based on this invention, and the top view, front view, and side view (b) of the half member which comprise the said reverse path part. 1 is an overall configuration diagram of a capacitively coupled plasma processing apparatus using a substrate temperature adjusting mechanism according to the present invention.

  A plasma processing apparatus provided with a substrate temperature adjusting mechanism according to the present invention will be described. FIG. 1 is a schematic configuration diagram of the plasma processing apparatus according to the present embodiment. As is clear from this figure, the plasma processing apparatus 10 has an inductively coupled type in which a high-frequency coil 13 for plasma excitation is provided above a processing chamber 11. Reactive ion plasma processing equipment (ICP-RIE).

  More specifically, a dielectric window 14 is provided on the upper portion of the casing 12 surrounding the processing chamber 11, and the high-frequency coil 13 is provided immediately above the dielectric window 14. In the lower part of the processing chamber 11, a planar lower electrode 16 on which the substrate 15 to be processed is placed is disposed. The upper end of the high-frequency coil 13 is connected to one terminal of the upper high-frequency power source 18 via the matching unit 17, and the lower end is grounded and connected to the other terminal of the upper high-frequency power source 18. The lower electrode 16 is connected to a lower high-frequency power source 21 via a blocking capacitor 19 and a matching unit 20.

  A cooling water channel 22 for cooling the lower electrode 16 is provided in the lower electrode 16 formed of a metal such as aluminum. An electrostatic chuck 23 for fixing the substrate to be processed 15 is provided above the lower electrode 16, and a groove for flowing a heat transfer medium for cooling the substrate to be processed 15 is passed through the electrostatic chuck 23. A heat transfer medium holding space 24 is provided. A heat transfer medium is fed into the heat transfer medium holding space 24 from a heat transfer medium source provided outside the housing 12 through a metal heat transfer medium flow path 25 by a pump (both not shown). . Generally, helium gas having high thermal conductivity and high fluidity is used as the heat transfer medium. These and a substrate temperature control unit (not shown) constitute a substrate temperature adjusting mechanism, and control is performed so that the temperature of the substrate 15 to be processed is maintained within an appropriate range during the plasma processing.

  The housing 12 is also provided with a gas introduction port 26 for introducing plasma gas into the housing 12 and an exhaust port 27 for exhausting the inside of the processing chamber 11.

  For example, when the substrate to be processed 15 is etched by the plasma processing apparatus 10, it is performed as follows. The load lock 28 is opened, the substrate 15 to be processed is placed on the lower electrode 16, and the substrate 15 to be processed is fixed to the lower electrode 16 by the electrostatic chuck 23. After sealing the load lock 28, the inside of the processing chamber 11 is evacuated by a vacuum pump (not shown) connected to the exhaust port 27. When a sufficient degree of vacuum is reached, plasma gas is introduced into the processing chamber 11 from the gas inlet 26. Supply. Then, high frequency power is supplied to the high frequency coil 13 and a bias high frequency voltage is applied to the lower electrode 16. As a result, plasma is generated on the upper portion of the substrate to be processed 15, and the surface of the substrate to be processed 15 is etched by the reactive ions generated thereby.

  Here, the high frequency voltage is applied to the lower electrode 16 as described above, while the housing 12 is grounded. Therefore, the lower electrode 16 and the housing 12 are insulated by the insulating plate 29. Further, since the heat transfer medium source provided outside the housing 12 is also electrically at the ground potential, the insulating plate 29 is also interposed between the lower electrode 16 and the heat transfer medium source. Since it must be continuously supplied from the heat transfer medium source to the heat transfer medium holding space 24 of the lower electrode 16, a high voltage is applied to the heat transfer medium at both locations.

  For example, when a bias high frequency (RF) power of about 1 kW is supplied, an RF voltage of about 3000 V (Vpp) is generated between the lower electrode 16 and the ground, depending on the area of the lower electrode 16 and the pressure of the plasma gas. If it is a high vacuum of 100 Pa or less or a low vacuum of 10000 Pa or more to about atmospheric pressure, it is difficult for electric discharge to occur. However, when the heat transfer medium is helium, it is in the lowest pressure range necessary for cooling the substrate 15 to be treated with helium. At a pressure of about 1000 Pa to 5000 Pa, discharge is likely to occur due to Paschen's law. For this reason, the discharge is easily started when a separating material such as a ceramic of about several centimeters is provided in the middle of the heat transfer medium flow path 25 as in the prior art.

  Therefore, in the substrate temperature adjusting mechanism of the plasma processing apparatus 10 of the present embodiment, the reverse path portion 30 is provided in the heat transfer medium flow path 25. One configuration example of the reverse path unit 30 is shown in FIG. The reverse passage portion 30 shown in FIG. 2 is provided with a concentric cylindrical flow path nested in a cylindrical main body 31 from the center to the outer side. In FIG. 2, the medium (helium gas) flows from the bottom to the top, the next flow path 33 conversely flows from the top to the bottom, and the central flow path 32 again flows from the bottom to the top. Of course, all of these directions can be reversed by reversing the reverse path portion 30. Such a reverse path portion 30 can be formed by combining two upper and lower members 35 and 36 and a core member 37. The core member 37 is fixed to the upper member 35 or the lower member 36 by a thin stem 38 or the like at an appropriate location.

  With this configuration, while the heat transfer medium (helium gas) is supplied from the heat transfer medium source to the heat transfer medium holding space 24 via the heat transfer medium flow path 25, the reverse path portion 30. The three flow paths 32, 33, and 34 (for example, the flow path 33 in FIG. 2) flow in the opposite direction. If the voltage applied to the heat transfer medium as a whole of the heat transfer medium flow path 25 is a forward voltage, the heat transfer medium receives a reverse voltage in the flow path (flow path 33 in FIG. 2). Even if a discharge occurs, the charged particles must move in the direction of the reverse voltage in that portion, and the propagation of the discharge is prevented. For this reason, in the substrate temperature adjusting mechanism of the present embodiment, it is possible to prevent only the discharge through the heat transfer medium (helium gas) without substantially disturbing the flow of the heat transfer medium (helium gas).

  Another configuration example of the reverse path unit 30 is shown in FIG. The reverse path portion 40 has a linear flow path (called a “two-folded linear flow path”) that forms a Z shape by folding twice in the main body 41. Thereby, in the intermediate flow path 43, the heat transfer medium flows in the direction opposite to the flow paths 42 and 44 before and behind the intermediate flow path 43, and thus the same effect as described above can be obtained. Such a reverse path part 40 can be manufactured by joining the half member 45 as shown in FIG.3 (b), Therefore It can be manufactured at low cost.

  In the above embodiment, the inductively coupled reactive ion plasma processing apparatus (ICP-RIE) has been described. However, the substrate temperature adjusting mechanism according to the present invention is not limited to the inductively coupled plasma processing apparatus or capacitively coupled plasma. The processing apparatus (FIG. 4) can be used similarly. In the capacitively coupled plasma processing apparatus of FIG. 4, the lower electrode or the like on which the substrate to be processed is placed can be configured in substantially the same manner as the inductively coupled reactive ion plasma processing apparatus (ICP-RIE) of the above embodiment, Only the upper electrode 50 is different.

DESCRIPTION OF SYMBOLS 10 ... Plasma processing apparatus 11 ... Processing chamber 12 ... Case 13 ... High frequency coil 14 ... Dielectric window 15 ... Substrate 16 ... Lower electrode 17, 20 ... Matching device 18 ... Upper high frequency power supply 19 ... Blocking capacitor 21 ... Lower high frequency Power supply 22 ... Cooling water path 23 ... Electrostatic chuck 24 ... Heat transfer medium holding space 25 ... Heat transfer medium flow path 26 ... Gas introduction port 27 ... Exhaust port 28 ... Load lock 29 ... Insulating plate 30 ... Reverse path part 31 ... Main body 32 , 33, 34 ... flow path 35 ... upper member 36 ... lower member 37 ... core member 38 ... stem 40 ... reverse path 41 ... main body 42, 43, 44 ... flow path 45 ... half member 50 ... upper electrode

Claims (4)

A portion of the substrate transfer table, which is disposed in the plasma processing chamber and has a heat transfer medium holding space, and a heat transfer medium source that supplies the heat transfer medium to the heat transfer medium holding space, partially includes the heat transfer medium. A substrate temperature adjusting mechanism for a plasma processing apparatus, comprising a heat transfer medium flow path having a flow path in a direction opposite to a direction from a heat medium source to the substrate mounting table .   The substrate temperature adjustment mechanism for a plasma processing apparatus according to claim 1, wherein the heat transfer medium flow path includes a triple nested cylindrical flow path.   The substrate temperature adjusting mechanism for a plasma processing apparatus according to claim 1, wherein the heat transfer medium flow path includes a two-folded linear flow path. a) a substrate mounting table disposed in the plasma processing chamber and having a heat transfer medium holding space;
b) a heat transfer medium source for supplying a heat transfer medium to the heat transfer medium holding space;
c) A heat transfer medium provided between the heat transfer medium holding space and the heat transfer medium source and having a flow path in a direction opposite to the direction from the heat transfer medium source to the substrate mounting table. A plasma processing apparatus comprising: a flow path.

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