JP2750430B2 - Plasma control method - Google Patents

Description

The present invention relates to a CVD (Chemical Vapor Deposi) utilizing a plasma generated by electron cyclotron resonance (ECR) excitation using microwaves.
and a plasma control method in the process. [Prior art] A method of generating plasma by electron cyclotron resonance excitation using microwaves can generate plasma with high activity at low gas pressure, a wide selection of ion energy is possible, and a large ion current is required. However, it has advantages such as excellent directivity and uniformity of ion flow, and its research and development have been promoted as being indispensable for the manufacture of highly integrated semiconductor elements and the like. By the way, when various elements are formed three-dimensionally on the substrate surface, conductive wires such as Al wires connecting the elements are formed by laminating an insulating film between them. The surface is higher by the thickness of the conductive wire from the surface. Therefore, if an insulating film is formed on the insulating film so as to have a uniform thickness, a similar step is formed on the surface of the insulating film. For this reason, other conductors to be formed on the insulating film must be formed so as to exceed the step, which often leads to disconnection at the step, which is a major problem in product yield. As a countermeasure, an insulating film is formed by lamination so that its surface becomes flat. As a method of flattening, a method has been proposed in which etching using Ar or the like is performed simultaneously and in parallel during the process of forming an insulating film (Jpn.Vac.Sci.Te).
chad B4 (4) 818 (1986)). However, in this method, in order to avoid damage to the lower layer film due to etching, first, the amount of Ar gas serving as an etching gas is set to zero, and SiO serving as an insulating film is formed, and the insulating film has a certain thickness. After lamination is formed, a technique for increasing the etching ability by adding Ar gas to the source gas and flattening the surface of the insulating film by utilizing the difference in sputtering efficiency with respect to the step portion has been proposed and implemented. [Problems to be Solved by the Invention] However, when the composition of the gas is changed by adding Ar for increasing the etching ability to the raw material gas, the consistency of the microwave for excitation also changes according to the gas amount. Therefore, it is necessary to readjust the consistency each time, and there is a problem that the operation is extremely troublesome. The present invention has been made in view of such circumstances, and the purpose thereof is to allow the etching ability to be performed in parallel with film formation to be freely changed without changing the amount and type of etching gas. It is to provide a plasma control method. [Means for Solving the Problems] In the plasma control method according to the present invention, a source gas and an etching gas are introduced into a vacuum chamber, and plasma generated by electron cyclotron resonance excitation is electrostatically adsorbed on a sample. Then, the electrode for applying a bias voltage is guided to the upper surface of the sample on the sample table in which the electrode is embedded, and in the process of forming a film on the sample, the high-frequency power for applying the bias voltage to the electrode is zero, or The method is characterized by including a step of forming a film with a small setting, and a step of performing the film formation after setting the high frequency power higher than that in the step after the step. [Effect] The method of the present invention makes it possible to efficiently form a flat film without damaging the base film by preventing the electrode itself from being damaged by etching, and changing the etching ability by adjusting the high-frequency power. Can be done. EXAMPLES Hereinafter, the present invention will be specifically described with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of the method of the present invention, in which 1 is a plasma generation chamber, 2 is a waveguide, 3 is a reaction chamber as a sample chamber for forming a film on the sample S, and 4 is an exciting coil. Is shown. The plasma generation chamber 1 has a hollow cylindrical shape and is formed so as to form a cavity resonator for microwaves. The plasma generation chamber 1 has a microwave inlet 1c closed by a quartz plate 1b at the center of one side wall in the axial direction. In the center of the other side wall in the axial direction, a plasma extraction window 1d is provided at a position facing the microwave introduction port 1c.
It has. One end of a waveguide 2 is connected to the microwave introduction port 1c, and a reaction chamber 3 is disposed facing the plasma extraction window 1d. An exciting coil 4 is provided concentrically over one end of the waveguide 2 thus formed. The other end of the waveguide 2 is connected to a high-frequency oscillator (not shown) so that microwaves generated by the high-frequency oscillator are introduced into the plasma generation chamber 1 through the microwave inlet 1c. The exciting coil 4 is connected to a DC power supply (not shown), and forms a magnetic field so that plasma can be generated by introducing microwaves into the plasma generating chamber 1 by passing a DC current. A divergent magnetic field having a lower magnetic flux density is formed so that the plasma generated in the plasma generation chamber 1 is introduced into the reaction chamber 3. The reaction chamber 3 is formed in a hollow rectangular parallelepiped shape, and an exhaust port 3a connected to an exhaust device (not shown) is opened on a side wall facing the plasma extraction window 1d. A sample table 5 is disposed so as to face the sample table 5, and a sample S is detachably mounted on the upper surface of the sample table 5 so as to face the plasma extraction window 1 d by means such as electrostatic suction. An electrode 5a for electrostatically adsorbing the sample S and applying a bias is buried in the sample table 5, and an RF (radio high frequency) power source as a high frequency power source is interposed in the electrode 5a with a matching device 6 interposed therebetween. 7 is connected. In addition, 1g and 3g indicate a gas supply system, and 1h and 1i indicate a cooling water supply system and a drainage system, respectively. According to the method of the present invention, after the inside of the plasma generation chamber 1 and the reaction chamber 3 is set to a required degree of vacuum, the raw material gas is introduced into the plasma generation chamber 1 and the reaction chamber 3 through the gas supply system 1 g. For example, N2, O2 and Ar as an etching gas are supplied, and a source gas such as Si is supplied through a gas supply system 3g.
H is supplied to pass a DC current to the exciting coil 4, and a microwave is introduced into the plasma generation chamber 1 through the waveguide 2 and the microwave inlet 1 c. The introduced microwave is applied to the plasma generation chamber 1 which functions as a plasma cavity resonator.
In the resonance state, the raw material gas is decomposed and excited by resonance,
Generate plasma. The generated plasma is introduced into the reaction chamber 3 by a divergent magnetic field formed by the exciting coil 4, decomposes SiH gas and the like supplied from the gas supply system 3 g, and a self-bias voltage is induced by the RF power supply 7. The sample S is guided to the surface of the sample S, where the film is formed. In this film formation process, initially, one step of setting the RF power (W) for applying a self-bias voltage induced to the sample stage 5 and the sample S to zero or 3 W / cm ² or less, and following this step, The RF power (W) is divided into another step in which the RF power is set to be higher than the RF power in the above step. In the first step, the force for inducing the etching gas in the Ar + state to the surface of the sample S because the self-bias is zero or small is weak, and the etching ability is set to zero or extremely weak, thereby damaging the underlying film by the etching gas. Film formation can be performed without any problem. When the film is formed to a predetermined thickness, the RF power is set to a value exceeding 3 W / cm ² by another process to increase the inducing force against Ar +, and the film is formed while increasing the etching ability. In general, the sputtering efficiency depends on the angle between a substance and sputtered particles incident on the material. The sputter efficiency on a plane perpendicular to the incident direction of the sputtered particles is small, and the sputtering efficiency increases when the surface has a certain angle. Therefore, in other words, the sputtering efficiency on a flat surface, which is perpendicular to the incidence of the sputtered particles, is low, and the sputtering efficiency on a surface having a certain angle, such as a side wall surface portion, is high. The film speed relatively decreases, and as a result, the surface can be flattened. FIG. 2 is a graph showing the relationship between the applied power and the peeling of the film. The horizontal axis represents the applied power (W), and the vertical axis represents the peeling probability (%). As is clear from this graph, the two are in a substantially proportional relationship, and the etching (sputtering efficiency) can be adjusted in a wide range by adjusting the applied power. By the way, by setting the applied power to 3 W / cm ² , in other words, to 100 or less, the peeling probability (%), which is a sputtering effect, can be reduced to 30% or less. [Effects] As described above, in the method of the present invention, the electrode is in the sample stage and is not etched, and the high-frequency power applied to the electrode is initially set to zero or small, and the film is formed.
Next, the etching power is adjusted by increasing the high-frequency power applied to the electrode and adjusting the bias voltage,
This provides an excellent effect that a film having a flat surface can be efficiently obtained without causing electrical or physical damage to the underlying film.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view showing an embodiment of the method of the present invention, and FIG. 2 is a graph showing the relationship between applied power applied to a sample S and a peeling probability (%). DESCRIPTION OF SYMBOLS 1 ... Plasma generation chamber, 2 ... Waveguide 3 ... Reaction chamber, 4 ... Exciting coil, 5 ... Sample table 6 ... Matching device, 7 ... RF power supply, S ... Sample

Claims (1)

(57) [Claims] Introduce raw material gas and etching gas into the vacuum chamber,
In the process of conducting plasma generated by electron cyclotron resonance excitation, the sample is electrostatically adsorbed, and guided to the upper surface of the sample on a sample table on which electrodes for applying a bias voltage are embedded, and the sample is formed into a film. Forming a film by setting the high-frequency power for applying a bias voltage to the electrode to zero or small, and forming the film after setting the high-frequency power to be higher than that in the step. Performing a plasma control method.