JPH0796711B2 - Thin film forming method and etching method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thin film forming method and an etching method using ECR plasma with high frequency and magnetic field, and more particularly to magnetic field intensity distribution.

Conventional technology Plasma CVD and plasma dry etching are one of the important key technologies in thin film processes such as semiconductor processes, and currently, in order to lower the processing temperature of the substrate and reduce the damage of the substrate, the ion A lot of research is being conducted to reduce the incident energy. Regarding this field, basic techniques are described in, for example, “Electronic Materials”, editorial department, “Plasma Chemistry in the VLSI Age”, Industrial Research Committee, published in 1983, p.117-p.119. The frequency of the high frequency and the strength and distribution of the magnetic field play important roles in reducing the energy of the ions incident on the substrate and maintaining the plasma discharge.

If the frequency of the high frequency is increased or the strength of the magnetic field is set to the electron cyclotron resonance (ECR) condition determined by the high frequency, for example, in the case of 2.45 GHz microwave, it is easy to set the magnetic field strength to 0.0875T. Plasma discharge can be maintained. For example, microwave power reaches an electron temperature of about 10 to 20 eV with an input of about 200 W, and can be sufficiently activated even in a gas having a low ionization rate. It is also known that the incident energy of ions on the substrate can be lowered to about several tens of eV by giving an appropriate magnetic field distribution. The use of such plasma for CVD and etching has been studied.

Furthermore, activated ions and highly excited neutral particles (radicals) also return to neutral particles due to collision with the chamber wall of the vacuum chamber. Also, due to the collision of these activated particles with the vessel wall, impurities (carbon,
Oxygen and hydrogen, etc.) are mixed in. For example, 0.02m ³
When a CVD gas is introduced into a vacuum chamber with a volume of about 100 W and a microwave power of about 100 W is input, various gas species are analyzed by a mass spectrometer. A peak of impurities reaching to was observed.

For this reason, in order to suppress the mixing of impurities, as shown in Fig. 2, the microwave and magnetic field satisfying the ECR condition (f = 2.45G
At Hz, B ₀ = 0.0875T. ), A plasma forming chamber 4 for forming plasma and a film forming chamber 6 for forming a film on the substrate 2 by introducing the plasma are disclosed (Japanese Patent Application Laid-Open No. 57-133636). Gazette).

According to the film forming method as described above, a high quality film can be formed on the substrate 2 in the film forming chamber 6 without being directly exposed to ECR discharge and with less impurities mixed therein.

Problems to be Solved by the Invention However, the above-mentioned configuration has the following problems.

Since the generation of plasma and the subsequent film formation are performed from the direction perpendicular to the substrate surface, nonuniformity of the film thickness occurs within the substrate surface.

Further, because of the two-chamber structure of the plasma chamber and the film forming chamber, the deposition rate is slow and it is difficult to increase the area.

Further, since the plasma is transported to the film forming chamber, highly excited ions and radicals are neutralized by recombination and the like.

The present invention has been made in view of the above points and provides a thin film forming method and an etching method capable of forming a uniform film thickness on a substrate with a distribution of magnetic field strength, preventing impurities from entering, and efficiently. Is.

Means for Solving the Problems In order to solve the above problems, in the thin film forming method and etching method of the present invention, a magnetic field is applied substantially parallel to the substrate, and the magnetic field strength in the vicinity of the substrate is set to the microwave intensity. A plasma region is formed with a magnetic field strength that satisfies the electron cyclotron resonance (ECR) condition that is determined by the frequency, and the magnetic field intensity of the region that is distant in the outer peripheral direction of the substrate is less than the magnetic field intensity that satisfies the ECR condition for film formation in the plasma chamber. Introduce gas and ECR
The structure is such that it is excited or ionized under the conditions, the excited or ionized particles are deposited on the substrate, or the sample is etched.

With the above configuration, the thin film forming method and the etching method in the present invention apply a magnetic field almost parallel to the substrate, and the magnetic field strength in the substrate vicinity region is equal to or higher than the magnetic field strength satisfying the ECR condition. A uniform plasma region can be formed in the parallel direction. Therefore, a uniform film can be formed in the direction parallel to the substrate. Further, since the magnetic field strength of the region distant in the outer peripheral direction of the substrate is set to be less than the magnetic field intensity satisfying the ECR condition, ECR discharge does not occur in this region. Therefore, the inner surface of the plasma is not directly exposed to the ECR discharge. Further, since the plasma is collected in a region where the magnetic field strength is high, not only ions in the ECR discharge but also highly excited neutral particles (radicals) can be efficiently supplied. In particular, since the radicals cannot be controlled by the magnetic field, the structure of the present invention can supply the radicals onto the substrate and prevent damage to the vessel wall due to the radicals. Furthermore, the magnetic field strength is
Since the ECR conditions are satisfied, ions and radicals can be efficiently formed.

Examples Hereinafter, the present invention will be described together with examples. FIG. 1 (a) is a schematic view of a plasma apparatus for forming and etching a thin film according to the present invention, and FIG. 1 (b) shows magnetic field strength when a silicon nitride film is formed by a plasma CVD apparatus.

2.45GHz microwave is used, introduced into the plasma chamber 1,
The substrate 2 was placed in the plasma chamber 1, silane gas and nitrogen gas were introduced into the plasma chamber 1, and the total pressure was kept at 0.08 Pa. The microwave power was 100 to 500 W.

The magnetic field was applied substantially parallel to the substrate, and the magnetic field was applied by the pole piece 8 placed outside the plasma chamber 1. This pole piece 8
Is a metal (Fe, Fe, C) inserted between coils (not shown).
Alloys such as o) are used to make the magnetic field between metal plates uniform.

Here, as shown in FIG. 1 (b), the magnetic field strength distribution is near the substrate 2, and the magnetic field strength satisfying the ECR condition (the magnetic field strength is 0.0875T when the microwave frequency is 2.45 GHz) and is 0.1T or more.
The magnetic field strength near the chamber wall of the plasma chamber 1 was set to 0.05 T, which is less than the magnetic field strength. Also, the magnetic field strength from the substrate 2 to the plasma chamber wall decreases monotonically, and ECR
There is a region of magnetic field strength that satisfies the condition.

The substrate holder 3 can apply direct current or high frequency electrolysis, and is also provided with a cooling and heating mechanism. In this example, no electric field was applied, and neither substrate heating nor cooling was performed.

When the silicon nitride film was formed on the substrate 2 with the above-described structure, high-speed deposition of 10 to 30 A per second was possible, and this value was 5 times faster than the conventional device. In addition, the etching rate with buffer hydrofluoric acid (50% HF: 46% NH ₄ F = 15:85) is 2 A / min, which is smaller than that of conventional equipment by an order of magnitude. Means that.

Moreover, the wall of the plasma chamber was not exposed to ECR discharge during film formation, and the temperature did not rise.

Although the plasma apparatus is described as plasma CVD here, etching may be performed by using an etching gas as an introduction gas, and as a result of the experiment, the substrate could be etched without being directly exposed to ECR discharge. Although the pole piece is used as the means for applying the magnetic field, any means may be used as long as the strength distribution of the magnetic field can form the magnetic field distribution of the present invention. The microwave frequency and the introduction method thereof are not limited to those in the embodiment, and may be any as long as the ECR discharge can be generated.

EFFECTS OF THE INVENTION As is clear from the above description, the thin film forming method and the etching method of the present invention can form a thin film having a uniform film thickness by using the distribution of the magnetic field strength of the present invention, and can reduce the microwave power. It is possible to efficiently absorb the impurities and prevent impurities from being mixed. First, a magnetic field is applied almost parallel to the substrate, and the magnetic field strength near the substrate is measured by ECR.
Since the magnetic field strength is set to satisfy the condition, a uniform plasma region can be formed, and thus a film having a uniform film thickness can be formed. Further, since the magnetic field strength of the region distant in the outer peripheral direction of the substrate is set to be less than the magnetic field strength satisfying the ECR condition, the base wall of the plasma chamber is not directly exposed to the ECR discharge,
Mixing of impurities can be prevented. Furthermore, the magnetic field strength is
Since the ECR conditions are satisfied, ions and radicals can be efficiently formed.

[Brief description of drawings]

1 (a) and 1 (b) are schematic vertical sectional views of a plasma apparatus for forming a thin film according to an embodiment of the present invention, a magnetic field strength distribution diagram, and a second diagram.
The figure is a schematic vertical sectional view of a conventional plasma apparatus. 1 ... Plasma chamber, 2 ... Substrate, 3 ... Substrate holder,
4 ... Plasma chamber of conventional device, 5 ... Electromagnet, 6 ...
Film forming chamber, 7 ... Plasma window, 8 ... Pole piece.

Claims (2)

[Claims] 1. A step of applying a microwave and a magnetic field substantially parallel to the substrate in a plasma chamber having a substrate therein, and an electron cyclotron resonance condition for determining the magnetic field strength in the region near the substrate by the frequency of the microwave. A step of forming a plasma region at a magnetic field strength equal to or higher than a satisfying magnetic field strength, and a step of making the magnetic field strength of a region distant in the outer peripheral direction of the substrate in the plasma chamber less than the magnetic field strength satisfying the electron cyclotron resonance condition determined by the frequency of the microwave Introducing a film forming gas into the plasma chamber, exciting or ionizing the film forming gas in the plasma region, and depositing the excited or ionized particles on the substrate. 2. A step of applying a magnetic field substantially parallel to the microwave and the substrate in a plasma chamber having a sample therein, and an electron cyclotron resonance condition in which the magnetic field strength in the sample vicinity region is determined by the microwave frequency. A step of forming a plasma region with a magnetic field strength equal to or higher than the satisfying magnetic field strength, and a step of making the magnetic field strength of a region distant in the outer circumferential direction of the sample in the plasma chamber less than the magnetic field strength satisfying the electron cyclotron resonance condition determined by the frequency of the microwave And a step of introducing an etching gas into the plasma chamber to excite or ionize the etching gas in the plasma region, and perform etching with the excited or ionized particles.