JPH0526329B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a pattern on a substrate by causing a photoplasma reaction such as photoplasma etching or photoplasma oxidation on the substrate according to a predetermined pattern. In particular, the present invention relates to a method in which a portion damaged by a photoplasma reaction can be annealed at the same time as forming such a pattern, or using the same equipment system.

In plasma etching that has been reported in the past, a resist pattern is formed in advance to serve as a protective mask, and pattern etching is performed by performing a plasma reaction on the entire surface.

Plasma oxidation, which grows oxide films on the surfaces of semiconductors and metals in a reduced-pressure oxygen discharge (oxygen plasma), is a low-temperature, high-speed process. Depending on the discharge state and whether a voltage is applied to the sample, it is broadly classified into non-anodic plasma oxidation, oxidation in high-density plasma, plasma anodic oxidation, etc. In either case, selective pattern oxidation is not possible unless a protective mask is added onto the substrate, and in addition, known methods that utilize a photoplasma reaction under light-mediated conditions, rather than a simple photoplasma treatment, In this method, no consideration has been given to the annealing of parts damaged as a result of such photoplasma reactions, or at least there has been only recognition that annealing is performed using a completely separate system of equipment.

The present invention has been developed in view of the above circumstances, and it is possible to cause a photoplasma reaction in a closed plasma reaction chamber in accordance with a predetermined pattern with respect to a substrate housed in the reaction chamber. A light beam that already has predetermined pattern information is irradiated from the outside, so that the photoplasma reaction of the part that follows the predetermined pattern is achieved with high precision, without the need for a mask that is brought into close contact with or in close proximity to the substrate. The purpose of the present invention is to disclose a method that enables the annealing of the substrate portion damaged by such a photoplasma reaction at the same time or by using the same equipment system.

Therefore, the apparatus of the present invention that has achieved the above object can be effectively used for patterning plasma etching, controlling the etching depth, simultaneous annealing of the etched surface, etc., and is effective in plasma oxidation. It becomes possible to pattern the oxide layer, control its depth, and improve film quality by annealing the oxidized pattern portion during or after oxidation.

In order to demonstrate the effectiveness of the present invention, each example will be described in detail below.

FIG. 1 shows one array of equipment used in the practice of the invention, which provides pattern information to a plurality of light beams;
A change in the substance that occurs when light and plasma act on the substrate material in the substrate area in the reaction chamber by projecting a laser or light beam pattern onto the substrate in a plasma gas atmosphere through a projection optical system. This is a device that can form a patterned state.

In FIG. 1, 1A, 1B, and 1C are light sources each having a certain wavelength range.

As the light sources 1A and 1B, for example, a large diameter ArF excimer laser (λ≈2000 Å) or an Ar laser (λ=4880 Å) is used.

As the light source 1C, a large diameter ruby laser (λ = 6900 Å) or a large diameter ruby laser is used as a light source for local heating.
Nd-YAG laser (λ=6300Å, or λ=
1.06μ) is used. Since the light sources 1A and 1B do not use lasers, they may be light sources in a short wavelength range. The selection criteria should be determined by the degree to which the plasma and light interact with the substrate and cause material changes.

Factors to be considered include activation of ion species in the plasma by optical excitation, local heating of the substrate by laser light, local laser annealing effect of the substrate, and their synergistic effect.

Next, 2A, 2B, and 2C are diffusers that remove the coherency of the laser light source.

When using a diffuser consisting of a bundle of optical fibers, the irradiation density can be made uniform by adjusting the position of each fiber.

Collimator optical systems 3A, 3B, and 3C are placed after the differential users 2A, 2B, and 2C. 3A, 3B,
After 3C, high-speed shutters 20A, 20B, and 20C are placed to open and close the light from the respective light sources. In some cases, neutral density filters 19A, 19B, and 19C are placed in front of the shutter for the purpose of adjusting the amount of light from the light source.

After the shutter, slits 5A, 5B, and 5C are arranged to define the irradiation area of the light sources 1A, 1B, and 1C, and after the slit 5A, a mask 6A unique to the light source 1A is arranged. Similarly, slit 5
After B and 5C, masks 6B and 6C are also given as unique items to the corresponding light sources 1B and 1C.
put For masks 6A, 6B, and 6C, if the amount of light is weak, a normal mask structure may be used, and they are placed on a quartz plate.
A mask pattern may be formed by photo-etching after depositing Cr or a high melting point metal film. However, if the light source is a high-output laser, there is a risk that the metal film will be destroyed, so in that case, a pattern made of a dielectric multilayer film that does not absorb laser light may be used. Direction changing mirrors 4A and 4B are placed next to the mask.

The mirrors 4A and 4B have dielectric multilayer films on the upper and lower sides. For example, a 4A mirror is 1 from the top.
By transmitting the light from the C light source and at the same time reflecting the light from the side of the 1A light source at right angles, this results in a 1A
Mixes the light from the light source and the 1B light source. The light beam exiting from 4B enters a reflective projection optical system consisting of a mirror system.

The catoptric projection optical system 30 has no chromatic aberration and can improve resolution even if the wavelength is shortened. Also, compared to refractive optical systems, it has the advantage of being able to achieve a deeper depth of focus. Therefore, even if the wavelengths of the light sources 1A to 1C are different from each other, the accuracy of pattern transfer is maintained well. A catoptric projection optical system has only an arcuate portion with good imaging performance, and in order to perform surface transfer, it is necessary to simultaneously move the mask and the wafer with respect to the optical system.

The illustrated optical system uses a trapezoidal mirror 8 and a pair of concave mirrors 9 and convex mirrors 10 to transfer a mask image onto a substrate at the same magnification. The substrate 13 is located inside the reaction chamber 11 whose internal structure is designed to prevent it from being attacked by plasma or the like. A part of the reaction chamber 11 has a window 12 made of quartz glass through which the pattern is projected. There is a wafer support stand 14 below the wafer substrate 13, and the wafer support stand 14 is held by an alignment mechanism 15.

It is preferable that this positioning mechanism 15 is capable of rotation in the θ direction. Such a positioning mechanism 15
This enables alignment of the wafer and mask. These are further placed on a moving table 16, which is controlled by an existing high-precision mask and wafer simultaneous constant-velocity moving mechanism or a step-by-step moving mechanism 17. If this reaction chamber is to be made into a high vacuum in advance, it is evacuated using the valve 27. In order to prevent distortion of the quartz window 12, it is effective to exhaust the outside as well. Different types of gases can be introduced into this reaction chamber from valve 18 through valves 21 and 22, respectively, depending on the case.

On the other hand, plasma can be introduced through the transport pipe 23. In front of the transport tube, a 2.45 GHz microwave generated by magnetron oscillation is introduced into a waveguide 24a, and a quartz tube reaction section 25 is inserted into a part of the waveguide. Impedance matching is performed at the end of the waveguide by a matching box 24b. CF ⁴ +O ₂ gas is introduced into the quartz tube through the introduction pipe 26 at about 0.1 Torr. When introduced at this level of pressure, the generated plasma hardly spreads even when the electric power increases and becomes stable, and the matching condition does not collapse even when the gas flow rate changes.

If the plasma transport pipe section 23 is coated with Teflon, the active species generated in the discharge section will not be much attenuated even in the reaction chamber approximately 1 m away, and will be transferred to the reaction chamber 1.
1 will be introduced. Such a plasma etch method using microwave excitation at 2.45 GHz has been previously reported. According to this method, various thin films such as polycrystalline silicon, Si ₃ N ₄ , SiO ₂ , Nb, W, Mo, and photoresist can be etched.

The conditions are CF ₄ pressure = about 0.12Torr and Pr =
Etching is possible when PO ₂ /P _CF4 is about 0 to 4. The advantage of this plasma etching method is that no discharge electrode is required in the reaction chamber 11. Therefore, there are no inclusions between the window 12 and the wafer, and a pattern can be projected from the optical system. These projected light patterns project light shading by laser light with an accuracy of 1 micron based on the same principle as that of a projection exposure apparatus. Moreover, this light can be used by excimer lasers (λ≒2000Å), large-diameter ruby lasers (λ=6900Å), Nd-
Projection can be performed by mixing a YAG laser (λ=1.06μ), etc. The plasma in the reaction chamber interacts with these lights to cause material changes in the wafer.

As mentioned earlier, CF ₄ + O ₂ gas can etch various substances, but if the device of the present invention is used, the reaction will occur in the area where the light hits due to the plasma photochemical reaction or the heating effect of the substrate. Promoted and deeply etched. It is also expected that the plasma formation conditions, such as plasma gas pressure, are set to such a level that almost no reaction occurs when the laser pattern is not irradiated, and that when the laser pattern is irradiated, the reaction is accelerated and etching occurs only there. ing. In other words, by finding such conditions, resistless pattern formation etching can be achieved. Moreover, since the uneven surface of the etched wafer is annealed by the laser beam, damage can be reduced. Finally, the characteristics of the pattern etching according to the present invention are shown in FIG. 2 as follows. If the amount of light is expressed by the length of the arrow, in Figure 2 A, part A and part B
Different amounts of light a and b are applied to masks 6A and 6, respectively.
Projected by B. 6000Å~ for light source 1C
Since a laser with a long wavelength of about 1 μm is used for local heating, it is assumed that this laser is applied commonly to the patterns of the masks 6A and 6B. Therefore part A
In this case, the etching reaction proceeds in large quantities and can reach the substrate. On the other hand, since the amount of light b in part B is small, the part B ends halfway. It is a significant advantage of the method of the present invention that etching at different depths can be performed in the same elementary step without using a protective mask such as a resist.

FIG. 2B shows an example of plasma oxidation or nitridation using plasma-activated oxygen or nitrogen using O ₂ or N ₂ as the introduced gas.

In the above, a one-to-one equal-magnification transfer method has been described for the reflective optical system. A feature of this case is that chromatic aberration can be reduced even if the wavelengths are different.

The pattern projection apparatus of the present invention shown in FIG. 1 has three light sources 1A, 1B, and 1C, which is a high-performance configuration in that it can perform complex adjustment functions.

However, it is also important to simplify the configuration of the laser pattern projection optical system and reduce the manufacturing cost of the device, for example, it is possible to use only one light source and one optical path.

If 1A and 1B are short wavelength light sources such as excimer lasers, and 1C is long wavelength light sources such as ruby lasers or Nd:YAG lasers, it is also possible to reduce the light sources as follows.

(1) Use only one light source: 1A, 1B, or 1C.

In the case of only an excimer laser, there is an annealing effect due to local heating only in a shallow region from the substrate surface.
Pattern formation can be added to the promotion of plasma etch due to the interaction between laser light in the Deep UV region and reactive plasma. In addition, in the case of using only a long wavelength laser, a pattern forming effect can be added to the annealing effect of local heating reaching a deep region from the surface and changes in the material due to interaction with plasma.

(2) In the case of two light sources such as (1A, 1C) and (1A, 1B) These are intermediate cases between (1) above and the case in Figure 1, and their effects can be easily understood from the above examples. It can be analogized to

On the other hand, when a refractive optical system (lens system) is used, chromatic aberration increases if the wavelengths of the light sources 1A and 1B are different, as shown in FIG. 3, for example. Therefore, it is desirable that the wavelengths of both light sources are in the same region. In the case of transfer using the lens system 28 as shown in FIG. 3, a reduced pattern can be transferred in the same manner as the principle of a reduction projection exposure apparatus. Therefore, in this case, the masks 6A and 6B do not need to be interlocked with the wafer 13, and the entire wafer area can be covered by step-and-repeat movement of the moving stage 16 using the moving mechanism 17B.

In this case as well, it is possible to simplify the optical system to one light source and one optical path. If a single optical path system is used, the second
When etching holes of different depths are simultaneously formed as shown in Figure a, different light intensities are irradiated to parts of the substrate with different materials depending on the location (for example, Si parts and SiO ₂ parts). becomes difficult.

In the reaction chamber in which the plasma reaction of the above-mentioned embodiments occurs, no microwave electrode or DC bias electrode is required for plasma generation. This is because long-lived radicals were generated in the plasma by 2.45GHz microwave excitation.

In plasma excitation by high frequency such as 13.56Mz,
Electrodes for plasma generation are usually incorporated within the reaction chamber. In this case as well, it is not difficult to attach a quartz window to a part of the outer wall of the reaction chamber at ground potential and perform laser pattern projection if design conditions are selected appropriately.

As described above, by utilizing the present invention, patterning such as plasma etching and plasma oxidation can all be performed using resistless low temperature processes.

Furthermore, in the case of plasma etching and reactive ion etching (RIE), high frequency electrolysis is usually applied to the substrate side.

On the other hand, plasma deposition, amorphous Si:
In the case of H deposition, etc., the substrate is at ground potential, and an electrode for a high frequency electric field is installed on a floating electrode installed in the space within the reaction chamber.

Therefore, the reaction mechanism and equipment configuration are different between RIE and plasma deposition.

However, in any case, it is possible to place a quartz plate window with a part of the outer wall of the reaction chamber at ground potential, and pattern projection using the light beam of the present invention is possible.

Therefore, the method of the present invention is also applicable to plasma deposition under appropriately selected design conditions.

In any case, the present invention is capable of causing changes in multiple materials on a substrate at the same time by means of independently selectable light beam(s), and as a result of plasma-mediated effects of such light beam(s). Damage to the changed parts caused by changes in various substances as a result of plasma reactions can be annealed at the same time or in the same system, so various electronic devices,
It can contribute to improving the efficiency and performance of integrated circuits and the like.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a first example of an apparatus used for implementing the method of the present invention, FIG. 2 is an explanatory diagram of a pattern formed by the present invention, and FIG. FIG. 2 is a schematic configuration diagram of two examples. In the figure, 1A, 1B, 1C are light sources, 6A, 6B,
6C is a mask, 11 is a reaction chamber, 12 is a window, 13 is a sample or substrate, 23 is a plasma transport tube, 24a is a waveguide, 25 is a reaction section, 28 is a lens system, and 30 is a projection optical system.

Claims (1)

[Claims] 1. By inserting a mask in the optical path of a single light beam having a desired wavelength band, pattern information possessed by the mask is directly given to the light beam; The light beam having the above projection optical system can be projected onto the substrate through the projection optical system; and the substrate is housed in a reaction chamber containing plasma, and the projection of the light beam from the projection optical system onto the substrate wherein the light beam is caused to follow the pattern by a photoplasma reaction in the presence of the plasma in the reaction chamber; 1. A pattern forming method using plasma, characterized in that the beam is a beam that selectively causes a photoplasma reaction in a portion of a substrate that has a pattern, and at the same time is a light beam that has a light intensity that can anneal a portion that follows the pattern. 2. By inserting a mask in the optical path of each of a plurality of light beams each having a desired wavelength band, pattern information held by each mask is directly given to each light beam; After the plurality of light beams having information are mixed into one optical path; the mixed plurality of light beams can be projected onto a substrate via a projection optical system; and the substrate is provided with plasma. The plurality of mixed light beams are projected from the projection optical system onto the substrate through a window provided in the reaction chamber and transparent to all of the plurality of light beams. while at least one of the plurality of light beams is
The other light beam has an intensity sufficient to anneal a portion of the substrate according to the given pattern information, and another light beam is applied to the substrate according to the pattern by a photoplasma reaction in the presence of the plasma in the reaction chamber. A pattern forming method using plasma, characterized in that the light beam selectively causes a photoplasma reaction in a substrate portion.