JP3397917B2 - Plasma etching method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching method, and more particularly, to a reduction in an etching rate around a wafer and a reduction in resist dust due to low-temperature plasma etching. The present invention relates to a plasma etching method in which generation is suppressed. 2. Description of the Related Art Generally, in plasma etching, an etching gas is introduced into a reaction chamber, a gas plasma is generated by applying a high-frequency electric field, and a wafer is generated by halogen atoms (radicals) or positive ions generated by gas dissociation. Etch the surface. By the way, in the recent plasma etching apparatus, since the conventional batch type has been changed to the single-wafer type, particularly in the case of an oxide film (SiO 2 film) etch, a high AC power of about 1000 W is required to secure an etching rate. Needs power. [0003] For this reason, the resist film serving as an etching mask is deteriorated by burning, resulting in a change in the shape of the resist, resulting in a problem that the processed shape is deteriorated and the removal of the resist film becomes difficult. Therefore, set the wafer to 0
By performing plasma etching while cooling from about -10 ° C. to about −10 ° C., resist burning was prevented, and deterioration in processing accuracy and the like was prevented. FIG. 5 is a sectional view for explaining a conventional plasma etching method. This is an example using a parallel plate type etching apparatus. A wafer to be etched (2) is placed on a lower electrode (1), the lower electrode (1) is grounded, and an upper electrode (3) facing the lower electrode (1). ), The etching gas introduced between the two electrodes is turned into a plasma state by supplying high-frequency power to the wafer to be etched (2).
Is etched. At this time, in order to cool the wafer to be etched (2), a tube is inserted into the lower electrode (1) to circulate a coolant. Further, by flowing He gas into the gap between the lower electrode (1) and the wafer to be etched (2), the heat conduction efficiency between the two is increased, and the temperature distribution of the wafer to be etched (2) is made uniform. I have. Further, in order to increase the thermal contact between the lower electrode (1) and the wafer to be etched (2), a ring-shaped clamp (4) is provided around the wafer to be etched (2), and the wafer to be etched ( The mechanical load was applied to 2). The above technology is described, for example, on page 226 of "Latest Version Super LSI Process Data Handbook" (published by Science Forum). However, in the above-mentioned conventional example, as shown in FIG. 6, the wafer to be etched (2) is clamped from the upper surface thereof, so that the clamp (4) is attached to the wafer to be etched. A good integrated circuit chip cannot be obtained at all from the portion in contact with (2), and the etching rate decreases and charge-up tends to occur in the portion of the wafer (2) to be etched near the clamp (4). was there. Further, there is another problem that the clamp (4) damages the resist and becomes a source of dust. According to the present invention, in order to solve the above-mentioned problems, a wafer to be etched is placed on a cooled lower electrode, and He gas is filled in a gap between the lower electrode and the wafer to be etched. When performing plasma etching while flowing, the wafer to be etched was clamped from the side to apply a mechanical load to the wafer to be etched. According to the present invention, the wafer to be etched is clamped from the side rather than from the upper surface as in the prior art, so that the wafer to be etched is plasma-etched with the entire surface exposed. Is performed. This makes it possible to solve problems such as a reduction in etching rate and generation of resist dust. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plasma etching method according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view illustrating a plasma etching method according to an embodiment of the present invention. This is an example using a parallel plate type etching apparatus. A wafer to be etched (12) is placed on a lower electrode (11), the lower electrode (11) is grounded, and an upper electrode (13) facing the lower electrode (11) is grounded. ) Is supplied with high-frequency power to convert the etching gas introduced between the two electrodes into a plasma state, and to form a wafer (1)
Etch the surface of 2). In the case of silicon oxide film etching, a high frequency of about 1000 W is applied using a mixed gas of Ar, CHF3 and CF4, or a single gas such as C2F6 and C2F8. At this time, the wafer to be etched (12) is cooled to prevent resist burning. In this apparatus, a tube is inserted into the lower electrode (11) to circulate the refrigerant. I have. Further, by flowing He gas into the gap between the lower electrode (11) and the wafer to be etched (12), the heat conduction efficiency between the two is increased, and the temperature distribution of the wafer to be etched (12) is made uniform. Is also the same as before. The present embodiment is characterized in that the wafer to be etched (12) is clamped (14) from the side and the wafer to be etched (1
By applying a mechanical load to 2), the thermal contact property is enhanced. FIG. 2 is an enlarged cross-sectional view of a dashed line portion of FIG. 1, and the clamp (14A) clamps the etched wafer (12) from obliquely above the side surface,
Wafer to be etched (12) via lower electrode (11)
Is applied with a weight of about 3 kg / cm2. FIG. 3 is an enlarged cross-sectional view of the dashed line portion of FIG. 1, but this clamp (14B) clamps the wafer (12) to be etched almost from the side. FIG. 4 is a top view of the clamps (14A, 14B). In order to equalize the load applied to the wafer (12) to be etched, the two divided ring pieces are pressed from the left and right. Clamping. The ring piece may be further divided into four or more pieces. Thus, according to the above embodiment, the wafer to be etched (1
Since 2) is clamped not from the upper surface but from the side surface, the wafer to be etched (12) is subjected to plasma etching with the entire surface exposed. Therefore, it is possible to solve problems such as a reduction in etching rate and generation of resist dust, which are caused by conventional low-temperature plasma etching. As described above, according to the present invention,
In performing plasma etching with a wafer to be etched placed on the cooled lower electrode, the wafer to be etched is clamped from the side instead of being clamped from the upper surface as in the related art, so that the entire surface of the wafer to be etched is exposed. The plasma etching is performed in a state where the substrate is in a closed state. This makes it possible to solve problems such as a reduction in etching rate and generation of resist dust.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view illustrating a plasma etching method according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view of a dashed line portion in FIG. FIG. 3 is an enlarged sectional view of a dashed line portion in FIG. 1; FIG. 4 is a top view illustrating a clamp. FIG. 5 is a cross-sectional view illustrating a plasma etching method according to a conventional example. FIG. 6 is an enlarged sectional view of a dashed line portion in FIG. 5;

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/3065 C23F 4/00 H01L 21/68

Claims (1)

(57) Claims 1. When a wafer to be etched is placed on a cooled lower electrode and the plasma etching is performed while flowing He gas into a gap between the lower electrode and the wafer to be etched, The wafer to be etched is divided into multiple parts from the side
A plasma etching method , wherein a mechanical load is applied to the wafer to be etched by a clamp .