JPS61113775A - Treatment of surface - Google Patents

Abstract

PURPOSE:To prevent damage, contamination and a temp. rise by using beams of molecules having excited molecular vibration units. CONSTITUTION:A means 1 of generating excited molecular beams is composed of a gas introducing valve 6, a furnace 7, a heating means 8 and a plate having pores 9, and excited molecules are spouted into a vacuum chamber 5 from the pores 9 as excited molecular beams. The excited molecular beams pass through a collimator 2 and reach the surface of a sample 3 on a sample stand 4 at a uniform rate in a uniform direction, treating the surface of the sample 3.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a dry process (dry processing method) for treating the surface of a solid, and is particularly suitable for the production of semiconductor devices with no damage, no contamination, high selectivity, and low temperature. The present invention relates to a surface treatment method that can realize the process.

[Background of the invention]

Traditional dry processes, especially in semiconductor device manufacturing, have used ion beams or plasma (
Edited by Takuo Kanno; “Semiconductor Plasma Process Technology,” Sangyo Tosho, 1980). However, in this method, ions, two molecules of atoms, electrons, etc. with high kinetic energy (approximately 100 eV or more) are deposited on the surface of the device or sample that is the object to be processed, or on solid surfaces near the device, such as the walls of the vacuum chamber or the surface of the sample stage. incident on the device, inevitably causing damage and contamination on the device surface.

Furthermore, the element temperature also increased due to the incidence of such high-energy particles. As semiconductor device manufacturing decreases (below 1 μm), this kind of damage will occur.

Contamination and device temperature rise become serious problems.

Moreover, such damage, contamination, and temperature rise are fatal to three-dimensionally structured semiconductor devices, which are expected to be realized in the near future, and conventional dry processes cannot be used.

[Purpose of the invention]

An object of the present invention is to provide a surface treatment method that does not cause damage, contamination, or temperature rise.

[Summary of the invention]

Dry processes have been actively used in the field of surface treatment, particularly in the field of semiconductor device manufacturing, for about 10 years. Here, the dry process is a term used in contrast to the previous wet process (method using an aqueous solution), and refers to a method in which the sample surface is treated in a vacuum (including light) or in a gas phase. However, in conventional dry processes, gas-phase plasma or ion beams are used, and the interlocking energy of electrons, ions, and ion beams incident on the sample surface is distributed in the range of several eV to 10' eV (first ), however, the DisplacaI+ of atoms in the crystal
+ent Energy (energy required to shift atoms from their normal crystal lattice positions) Ed is approximately 10 eV
It is. For example, in Si crystal Ed=12.9 eV
(G, Carter and J, S
.

ColCo11i, “Ion Bombardme
nt of 5olids”.

Heineman Educational Book
s Ltd, , London.

196B, p. 214), for this reason, in the conventional dry process, damage was inevitably formed on the sample surface. Furthermore, the sample temperature also increased due to the incidence of such high-energy particles, reaching 300° C. or higher in some cases. Such an increase in sample temperature may result in the formation of other crystal defects (damages) on the sample surface or extremely limit the scope of process application. In addition, when such high-energy particles were incident on the surface near the sample, they physically and chemically sputtered the surface material, which re-attached to the sample surface and caused surface contamination. Such damage, contamination, and temperature rise are fatal in surface treatment technology, especially in semiconductor device manufacturing technology.

The essential things that must be done in a dry process are to remove substances from the sample surface using physical and chemical reactions on the sample surface or in the gas phase (etching), and to deposit substances on the sample surface (deposition, epitaxy). ), modifying the sample surface substance (oxidation.

nitriding, etc.). At this time, chemical reactions rather than physical reactions play a leading role. This is chemistry exhibition 1
・This is because it is possible to achieve a more varied reaction.

Now, as shown in Figure 1, the energy related to chemical reactions (chemical bond energy) is distributed between 0.1 and 1 oeV, and the energy that generates crystal defects is approximately 10eV.
It is V. therefore.

The optimal energy used to carry out the dry process is in the range of 0.1 to 10 eV.

This allows dry processes to be carried out without damage, contamination, or temperature increases. As shown in FIG.
In order to supply energy of 1 eV to 10 eV, it is appropriate to use the vibrational level of molecules or the electronic level of atoms/molecules. However, the lifetime of the electronic level is generally short (approximately 10-s to 10-7 sec), and it is difficult to supply the necessary amount of atoms and molecules excited at the electronic level to the sample surface. On the other hand, the lifetime of a molecular vibrational level is on the order of 10-"see, and its energy is
It is rarely lost unless it collides with molecules or surfaces. Therefore, it is optimal to use single molecule vibrational level energy to perform the dry process. Hereinafter, a molecule in which at least a molecular vibrational level is excited (a rotational level and an electronic level may be excited simultaneously) will be referred to as an excited molecule.

In order to supply excited molecules to the sample surface, Fig. 2(a)
There is a method using an excited molecular population with an isotropic velocity distribution as shown in Figure 2(b), and a method using an excited molecular population with an anisotropic velocity distribution as shown in Figure 2(b). There is a method using an excited molecular beam (referred to as an excited molecular beam). In general, dry processes often require anisotropic processing (for example, anisotropic etching) on the sample surface, so it is advisable to use an excited molecular beam. Furthermore, the use of an excited molecular beam improves process controllability.

Based on the above idea, the present invention is characterized by a surface treatment method using an excited molecular beam excited by molecular vibration.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIG. Examples are:
Excited molecule beam generation means 1. Collimator 2, sample 3. Sample stage 4. It is composed of a vacuum chamber 5. The excited molecular beam generating means 1 includes a gas introduction valve 6, a furnace 7. Heating means8.
It is composed of pores 9. The excited molecule beam generating means of this embodiment will be referred to as a heating furnace method. Gas molecules (hereinafter referred to as M) introduced into the furnace 7 by the gas introduction valve 6 are heated to a required temperature by the heating means 8, and the molecular vibration level is excited, and some of them become excited molecules (hereinafter referred to as M''). As the heating means, electric resistance heating, heating with an infrared lamp, RF heating, etc. can be used.The excited molecules are ejected into the vacuum chamber 5 from one or more pores 9. The excited molecular beam becomes an excited molecular beam.By passing through the collimator 2, the excited molecular beam becomes more uniform in its velocity direction.6 The collimator is formed of countless pores penetrating in the beam passing direction.Collimator The excited molecular beam that has passed through reaches the surface of the sample 3 and performs surface treatment.The sample 3 is held by a sample stage 4.The collimator 2 is equipped with a cooling means, and the sample stage 4 is equipped with heating and cooling means. is also possible.

In some cases, it is also possible to perform surface treatment without a collimator.

In this case, the excited molecular weight (flux) reaching the sample surface is
increases, but the directionality of the molecular beam becomes slightly worse. In addition, when processing a large-area sample (or when processing multiple samples), place the sample stage 4 and sample 3 in a plane (in the x-y plane) that has a certain angle to the beam. By driving, it becomes possible to perform processing with good uniformity.

For example, when etching the surface of a Si (silicon) sample, it is effective to use SF as the introduced gas molecules. The etching mechanism in this case will be explained below.

The 5Fl1 molecules introduced into the furnace are heated and their molecular vibrational levels are excited.For example, according to calculations, if the gas pressure in the furnace is set to I Torr and heated to 800°C, the SF
, 95% of the molecules are E, 1. ≧3E, 3...(1)4
Yo, 7□5. . , fi aww, eee1. 9.1
This is the excitation energy of the vibrational level of the ear molecule.

SF molecules have six types of fundamental molecular vibration modes, and the excitation energy of the molecular vibration level, Evtb, is written as. Here, nl is a natural number (0, 1, 2°3,
), and E9. is the fundamental energy of the first fundamental molecular vibration mode. E9. The specific value of E
,,*0.09 eV, 0.08eV in E-2,
E, 0.11e V in 3, E,, happiness 0.07e V,
E,, medium 0.06 eV.

E vi 10, 04 e V. E,, is SFG
is the fundamental energy of the third mode of the six types of fundamental molecular vibration modes that E v3-=0.
11 e V, 6 and E, 8. ≧3E, SF excited to 1.

The molecule will be denoted as SFg'' (v, > 3). Also, SFg with E, , > O will be generally denoted as SF-. SF, the molecule is heated to the required temperature in a furnace. In order to achieve thermal equilibrium (SF, the molecular vibrational temperature of the molecules and the furnace temperature), it is effective to set the furnace internal volume to 0.1 cc or more.

SF5 is S by spouting out from the pore 9 into the vacuum.
F, "form a beam. In order not to lose molecular vibrational excitation energy due to adiabatic expansion during ejection, the diameter of the pore (the minimum length of the opening if it is not circular) should be approximately 1ff.
It is effective to make it less than a.

In collimator 2, part of the SF♂ beam collides with the inner wall, and part passes through the collimator without colliding. The SF♂ molecules that collide with the inner wall lose molecular vibrational excitation energy, so the velocity distribution of the SF♂ beam after passing through the collimator becomes more uniform in one direction.

The SF2 molecules that have reached the Si sample surface combine with the Si atoms on one surface 28F♂ (g) + S 1 (s) → SiF, (g) + 2 SF, (g) ... (
The reaction 3) is carried out to etch the Si surface. Here, (g) and (s) mean that the molecules are present in the gas phase or on the sample surface, respectively. The reaction probability of SF, ″(v3)3) in the above reaction is about 0.2 (T, J, Chuang, J, Chsm, Phys,
74 *1453 (1981), p. 1459)
.

FIG. 4 shows the relationship between the Si etching speed and the SFG gas flow rate when Si etching is performed using the apparatus of this embodiment. Etching rates are shown for a 4 inch diameter Si wafer. The experimental conditions were a furnace temperature of 800°C;
As can be seen from FIG. 6, where the gas pressure in the furnace is ITorr, there is a proportional relationship between the etching speed and the gas flow rate. Etching speed obtained when gas flow rate is 1008CCIII 57
．． 3 nm/min is a value that satisfies practical requirements.

The apparatus of this example allows S
Anisotropic etching (vertical etching) of i is realized.

The mechanism is as follows (see FIG. 5): SF, which has passed through the collimator 2, is incident perpendicularly onto the surface of the sample 3 and etches the portion not covered by the mask 10.

When the etching progresses, there is a possibility that the SF2 reflected from the bottom surface 11 of the pattern may etch the side surface 12 of the pattern.

However, SFt reflected from the bottom surface 11 does not lose its molecular vibrational energy and is in the ground state of 5Fa (hereinafter referred to as SF1).
(J, Misewich, C, N, Plum.

G, Blyholdsr and P, L, 1lous
ton, J. Chem, Phys.

78, 4245 (1983)).

SF, @ is chemically stable and does not etch Si. Therefore, it can be seen that the etching of the side surface 12 does not actually progress. As a result, anisotropic etching (vertical etching) is realized.

When etching Si using the apparatus of this embodiment, the energy of the incident molecules is 3E, , = 0.
It is on the order of 33eV. This energy is d
isplacement energy (12, 9a
V), so there is no damage to the Si surface, and substances near the sample are not physically sputtered, so there is no contamination of the Si surface. The small amount of energy possessed means that the temperature rise on the sample surface is small. For this reason, traditional drives. Yani (puss, yaioppi)
Compared to G+7)) using G4, it is possible to process at a lower temperature (almost close to room temperature).

In this example, only Si etching was described, but
Other substances containing Si atoms as a constituent (polycrystalline, silicon, silicon oxide (SiO2), silicon nitride (S
It can be similarly applied to etching of silicide (Si-W, 51-Mo, etc.)).

In this embodiment, a heating furnace method is used to form molecules M8 subjected to molecular vibrational excitation. This method is suitable for producing a large amount of M8 with a simple device configuration.

Another embodiment of the invention is shown in FIG.

This example shows a method of obtaining an excited molecule beam using an infrared laser instead of the heating furnace of the previous example.

The device includes a gas introduction valve 6 cells 13, a nozzle 14, a spout 15. It is composed of an infrared laser generating means 16, a lens 17, a laser introduction window 18, and a vacuum chamber 5. Molecules M are introduced from the gas introduction valve 6, temporarily stored in the cell 13, and then guided to the nozzle 14. The infrared laser generated from the infrared laser generating means 16 is transmitted through the lens 17. The light passes through the laser introduction window 18 and is focused in the middle of the nozzle 14 . The molecular vibration level of a part of the molecules M in the nozzle is excited by the laser, and the excited molecules M'' are ejected into the vacuum chamber 5 through the ejection port 15 and become an excited molecule beam. For example, SF, excited molecules of gas (
SF,") To obtain a beam, use SF as the above M, and use an infrared laser that emits continuous light with a wavelength of 10.6 μm, an output of 5 to IOW, and a laser beam cross section of about 20. In order to efficiently introduce the laser beam into the nozzle, Zn5e is suitable as the material for the laser introduction window 18.

Furthermore, in order to generate efficiency <SF, it is preferable to set the gas pressure inside the cell 13 to about 200 Torr.

Moreover, if the nozzle 14 is made of metal (for example, 80) and the inner wall is processed into a mirror-like finish, the introduced laser light will be multiple reflected (scattered) within the nozzle 14 and will efficiently excite <S Fr. Become. By using the method of this example, an excited molecule MX having a high excited level (large E, . . . ) can be easily obtained. On the other hand, the disadvantage is that the apparatus is larger and more expensive than the previous embodiment.

Another embodiment of the invention is shown in FIG.

This example shows a method of performing crystal epitaxy at low temperatures. Although epitaxy of Si (silicon) will be described below, similar methods can be applied to epitaxy of other crystals. The apparatus includes an excited molecule beam generating means 1, a Si beam generating means 19, a sample 3. It consists of a sample stage 4 and a vacuum chamber 5. As the excited molecule of the excited molecule beam generating means 1, a molecule that etches Si at an appropriate speed, such as SF♂, is used. In addition, sample stage 4
is equipped with suitable heating means.

Si atoms or S flying from the Si beam generating means 19
The i molecules (Si, ) adhere to the surface of sample 3 and grow crystals. FIG. 8 schematically shows the growth process of Si crystal. The crystal side indicates the part where the correct Si crystal has already been formed, and the outermost layer indicates the part where the Si crystal has been formed. As shown in Fig. 8, SiA adheres to the correct crystal position (regular position), and some of the SiA
It attaches to the incorrect crystal position (incorrect position) as shown in 1. If the adhesion process continues in this state, the crystal will grow not as a single crystal but as a polycrystal. The method of this embodiment uses an excited molecule (SFg'') beam to remove (etch) only Si atoms (Si'') at incorrect positions.

This makes it possible to grow a single crystal using only Si atoms (Si') in the correct position. The fact that selective etching is possible depending on the deposition position is explained as follows. That is, the bonding energy between the Si atom at the wrong position and Si on the crystal side is smaller than the bonding energy between the Si atom at the correct position and Si on the crystal side.

Therefore, by appropriately selecting the molecular vibrational energy (E-ah) of the excited molecule SF, it becomes possible to selectively etch only Si'.

In conventional Si epitaxy (e.g., molecular beam epitaxy (MBE)), the sample is exposed to high temperature.
Single crystal growth was achieved by heating to 1 (600 to 800° C.) and moving the Si atoms in the wrong positions to the right positions by thermal movement. However, in this method, the processing temperature was too high and the range of application was extremely limited. If the method of this example is used, it becomes possible to grow single crystals at low temperatures (100" to 200°C), and the range of application will be widened. Especially in the future
This example describes epitaxy (single crystal growth), which is extremely effective for next-element elemental processes.
By appropriately selecting the size of E vlk , it is possible to grow a polycrystalline film with an appropriate grain size. In this case, a deposition technique is used.

Another embodiment of the invention is shown in FIG.

This example shows a method of surface modification using an excited molecular beam. A similar method can be applied to (for example, nitriding).The apparatus is composed of an excited molecular beam generating means 1, a sample 3, a sample stage 4, and a vacuum chamber 5.The sample stage is equipped with an appropriate heating means. Assume that 0 is emitted from the excited molecular beam generating means 1 to the surface of the sample (Si).
The □8 molecules oxidize the surface by the reaction of Si+O-→Sin. The features of this embodiment include o2 plasma and
Compared to the conventional method using a positive ion beam, there are extremely few defects at the interface between the SiO□ film and Si, and within the SiO film. Further, other impurities are not mixed into the SiO□ film.

Additionally, the process temperature can be lower than in conventional methods.

〔Effect of the invention〕

According to the present invention, surface chemical reactions can proceed with the minimum necessary energy. As a result, damage-free, non-contaminating, and low-temperature surface treatment can be achieved.

Such processing technology is used in the field of semiconductor device manufacturing.
It is particularly effective for three-dimensional element structures that are expected to be realized in the near future.

[Brief explanation of drawings]

Fig. 1 is a diagram showing approximate values of various energies, Fig. 2 is a diagram showing the situation of isotropic velocity distribution and anisotropic velocity distribution, and Fig. 3 is a diagram showing an embodiment of the present invention, especially in the case of etching. FIG. 4 is a diagram showing the relationship between Si etching speed and SFG gas flow rate in the embodiment of FIG. 3, FIG. 5 is a diagram showing the vertical etching situation in the embodiment of FIG. 3, and FIG. 7 shows another embodiment of the present invention, particularly in the case of using a laser, FIG. 7 shows another embodiment of the present invention, particularly in the case of Si epitaxy, and FIG. 8 shows the embodiment of FIG. 7. FIG. 9 is a diagram showing the situation of Si epitaxy in still another embodiment of the present invention, particularly in the case of oxidation. DESCRIPTION OF SYMBOLS 1... Excited molecule beam generation means, 2... Collimator, 3... Sample, 4... Sample stage, 5... Vacuum chamber, 6
... Gas introduction valve, 7... Furnace, 8... Heating means, 9... Pore, 10... Mask, 11... Pattern bottom surface, 12... Pattern side surface, 13...・Cell, 1
4... Nozzle, 15... Spout port, 16... Infrared laser generating means, 17... Lens, 18... Laser introduction window, 19... Si beam first port

Claims (1)

[Claims] 1. A surface treatment method characterized by using a beam composed of molecules whose molecular vibration levels are excited. 2. The surface treatment method according to claim 1, wherein the molecule is SF_6. 3. The surface treatment method according to claim 1 or 2, characterized in that the molecules are heated using a heating furnace to generate an excitation beam for the SF_6 molecules.