JP2012028482A - Silicon electrode plate for plasma etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon electrode plate for plasma etching which eliminates surface asperities due to plasma etching enabling a uniform etching.SOLUTION: The silicon electrode plate for plasma etching comprises a single crystal silicon to which B and Fe are added as dopants and a heat treatment with temperature of 500 to 800°C is applied. In this silicon electrode plate for plasma etching, an electric characteristic of the single crystal silicon is uniformed in a plane and surface asperities are highly eliminated when the surface is damaged during the plasma etching.

Description

  The present invention relates to a silicon electrode plate for plasma etching that improves the in-plane uniformity of plasma etching.

  In general, in a plasma etching apparatus for etching a silicon wafer used in a process of manufacturing a semiconductor integrated circuit, as shown in FIG. 2, a silicon electrode plate 2 and a pedestal 3 are provided in a vacuum container 1 at intervals. The silicon wafer 4 is placed on the gantry 3, and the etching gas 7 is flown toward the silicon wafer 4 through the through-holes 5 provided in the silicon electrode plate 2, and the electrode plate 2 is connected to the electrode plate 2 by the high frequency power source 6. A high frequency voltage is applied between the gantry 3 and a plasma 10 is generated in the space between the silicon electrode plate 2 and the gantry 3 by the application of the high frequency voltage. A physical reaction by the plasma 10 and a chemical reaction by the silicon-etching gas 7 are generated. Thus, it is known that the apparatus etches the surface of the silicon wafer 4 (see Patent Document 1).

  Although an electrode plate made of carbon has been used as the silicon electrode plate 2, in recent years, a silicon electrode plate mainly made of single crystal silicon, polycrystalline silicon or columnar crystal silicon has been used.

JP 2003-51491 A

The following problems remain in the conventional technology.
In the conventional silicon electrode plate, the surface is gradually consumed by the plasma generated between the object to be etched at the time of plasma etching, and irregularities are generated, which may cause abnormal discharge. When abnormal discharge occurs, there is a disadvantage that the uniformity of etching deteriorates.
Such unevenness of the surface due to plasma etching is considered to be caused by nonuniform plasma density between the object to be etched because the specific resistance value varies in a plane. Therefore, in order to suppress the unevenness of the surface, it is necessary to suppress the in-plane variation of the specific resistance value. However, since there is an in-plane difference in the dopant content, it is difficult to suppress the in-plane variation of the specific resistance value. It was. In particular, at a high specific resistance value, the in-plane difference of the dopant content greatly affects, so it is difficult to suppress the in-plane variation of the specific resistance value. As described above, conventionally, since it is difficult to uniformly maintain the plasma density with the object to be etched, there is a problem that it is difficult to make the etching rate within the wafer surface, which is the object to be etched, uniform.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a silicon electrode plate for plasma etching that can suppress surface unevenness caused by plasma etching and enables uniform etching.

  The inventors of the present invention have studied to obtain a silicon electrode plate having good in-plane uniformity of specific resistance and improved in-plane uniformity of etching rate during plasma etching. As a result, it was found that plasma etching can be performed with almost no irregularities on the surface by heat-treating silicon doped with Fe at a specific temperature.

  Therefore, the present invention has been obtained from the above findings, and the following configuration has been adopted in order to solve the above problems. That is, the silicon electrode plate for plasma etching of the present invention is characterized in that it is composed of single crystal silicon that is heat treated at 500 to 800 ° C. with B (boron) and Fe added as dopants.

  In this silicon electrode plate for plasma etching, B and Fe are added as dopants and are composed of single crystal silicon that is heat-treated at 500 to 800 ° C., so that the electrical characteristics of the single crystal silicon are made uniform in the plane, When the surface is consumed in plasma etching, unevenness can be extremely reduced. This is because Fe-B pairs formed by the combination of doped Fe and B are dissociated by heat treatment, and Fe as a donor having a large diffusion coefficient is distributed unevenly in the plane. Thus, it is considered that the carrier is compensated to uniform the in-plane specific resistance value. Since the in-plane uniformity of the specific resistance value is improved in this way, the plasma density with the object to be etched is made uniform, the surface wear state is also made uniform, and irregularities are hardly generated. Etching can be suppressed and etching can be made uniform.

  The reason for setting the temperature range of the heat treatment to 500 to 800 ° C. is that if it is less than 500 ° C., the existing oxygen atoms become donors and change from the target specific resistance value, and the in-plane distribution of the specific resistance value is This is because when the temperature exceeds 800 ° C., a gettering phenomenon of Fe atoms occurs, and the effect of adding Fe disappears.

The present invention has the following effects.
That is, according to the silicon electrode plate for plasma etching according to the present invention, it is composed of single crystal silicon that is heat-treated at 500 to 800 ° C. with B and Fe added as dopants. The surface unevenness caused by the plasma etching can be extremely reduced by being uniformed in the plane. Therefore, by adopting the silicon electrode plate for plasma etching of the present invention in a plasma etching apparatus, abnormal discharge can be suppressed and plasma etching with high in-plane uniformity can be achieved.

In the Example and comparative example of the silicon electrode plate for plasma etching which concern on this invention, it is an enlarged photograph which shows the surface state after plasma etching. It is sectional explanatory drawing of the conventional plasma etching apparatus.

  Hereinafter, an embodiment of a silicon electrode plate for plasma etching according to the present invention will be described together with a manufacturing method thereof.

First, a method for manufacturing the silicon electrode plate for plasma etching according to the present embodiment will be specifically described below.
For example, a single crystal silicon ingot having a diameter of 300 mm is prepared, and the ingot is cut into a thickness of 4 mm using a diamond band saw to produce a disk-shaped single crystal silicon substrate. In the single crystal silicon ingot, B (boron) is added at a dopant concentration of 2 × 10 ¹⁴ cm ^{−3 to} 3 × 10 ¹⁴ cm ⁻³ , and Fe is 2 × 10 ¹³ cm ^{−3 to} 3 × 10. ^The crystal was grown by adding a dopant concentration of ¹³ cm ⁻³ . Note that the dopant concentrations of B and Fe are adjusted so as to be p-type as a whole.

Next, this single crystal silicon substrate is subjected to heat treatment at 500 to 800 ° C. for 1 to 2 hours in an air atmosphere, and then rapidly cooled.
Further, the upper and lower surfaces of the single crystal silicon substrate are surface ground, the warp is removed and the thickness is adjusted, and then the attachment hole and the through hole are processed. For example, through pores having an inner diameter of 0.5 mm are formed with an inter-hole pitch of 8 mm. Thereafter, surface grinding is further performed to obtain a predetermined thickness of the product.

  In this embodiment, the dopant Fe is added in advance during crystal growth to obtain a single crystal silicon ingot. However, only B is cut from the single crystal silicon ingot added during crystal growth and processed into the above-described silicon substrate. The Fe-containing paint containing Fe may be applied to the surface, and the heat treatment may be performed to diffuse the Fe in the Fe-containing paint into the silicon substrate and add it to the crystal. In this case, as the Fe-containing paint, a component that evaporates without being diffused into the silicon substrate during the heat treatment is adopted as a component other than Fe, for example, a mixed paint of C (carbon) and Fe is adopted. .

  Since the silicon electrode plate for plasma etching according to the present embodiment manufactured in this way is composed of single crystal silicon in which B and Fe are added as dopants and heat-treated at 500 to 800 ° C., the electrical characteristics of the single crystal silicon Can be made uniform in the surface, and unevenness can be extremely reduced when the surface is consumed in plasma etching. Therefore, the surface wear state during plasma etching is made uniform and unevenness is hardly generated, so that the occurrence of abnormal discharge can be suppressed and the etching can be made uniform.

  Next, an example of the silicon electrode plate actually produced based on the above-described embodiment was set in a plasma etching apparatus, and plasma etching was performed under the following conditions. Note that a silicon wafer was used as an object to be etched. Further, as a comparative example, plasma etching was similarly performed by adopting a silicon electrode plate to which Fe was not added and only B was added.

<Etching conditions>
Chamber pressure: 13Pa
Etching gas composition: 90 sccm CHF ₃ +4 sccm O ₂ +150 sccm He
High frequency power: 2kW
Frequency: 20kHz

FIG. 2 shows an enlarged photograph of the surface of both the silicon electrode plates of this example and the comparative example observed after this plasma etching.
As can be seen from these enlarged photographs, in the comparative example in which no Fe was added, a number of holes were formed on the surface by plasma etching and many irregularities were formed, whereas in this example in which Fe was added, The surface has few holes, and a flat surface is maintained after etching.

  The technical scope of the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 2 ... Electrode plate, 3 ... Mount, 4 ... Silicon wafer, 5 ... Through-hole, 6 ... High frequency power supply, 7 ... Plasma etching gas, 10 ... Plasma

Claims (1)

  A silicon electrode plate for plasma etching, characterized in that it is composed of single crystal silicon in which B and Fe are added as dopants and heat-treated at 500 to 800 ° C.