JPH0582967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a wiring forming method and apparatus that utilize laser light and are used in the manufacture of semiconductor integrated circuits and the like.

(Prior Art) In recent years, in semiconductor processes, research and development have been actively conducted on thin film forming methods using lasers, as they can lower process temperatures and shorten process steps through maskless processes. In particular, direct writing technology, in which metals and highly conductive semiconductors are directly deposited in linear form through CVD reactions, is being actively researched for application to LSI interconnect formation. This technology includes high-speed wiring correction that significantly shortens the development period from LSI design to prototyping, as well as customization.
It is expected that this technology can be applied to important process technologies for future LSI interconnect formation technology, such as the customization of interconnects that are essential for LSIs.

In this direct writing technique using a laser, a thermal decomposition reaction of a raw material gas is mainly used to deposit a conductive material by heating the substrate or the deposited material using focused laser light. In addition to this method, there is also a method of depositing a conductive material by a photochemical decomposition reaction using ultraviolet laser light, but with this method,
Only metals with poor chemical durability such as Cd and Zn have been able to deposit good conductive materials, making it difficult to apply this method to actual LSI processes. Therefore, the former method, which uses a thermal decomposition reaction, is exclusively used, and the thermal decomposition reaction due to the heat generated when the conductive material that has been deposited absorbs the laser beam is used to deposit the material in the scanning direction of the laser beam. Wiring was formed by stretching it. So far, conductive semiconductors such as poly-Si and low-resistance, high-melting-point metals such as W and Mo have been deposited. For example, on pages 33 to 38 of the Proceedings of the 30th Symposium on Semiconductor and Integrated Circuit Technology (July 1986), Uesugi et al. used an Ar laser as the light source and MO(CO) ₅ as the raw material gas. An example of direct drawing of low-resistance Mo wire has been reported. According to this paper, the resistivity between the A wirings on S _i O ₂ /Si is 40 μΩcm,
Wiring with A was possible using Mo wire with a contact resistance efficiency of 4.1×10 ₈ Ωcm ² . These values are good values comparable to those of ordinary sputtered films, indicating that the laser wiring process can be fully used in actual LSI processes.

(Problems to be Solved by the Invention) In conventional direct writing techniques including this paper, the laser beam irradiation pattern on the substrate uses a circular beam having a Gaussian intensity distribution. In this method, in order to obtain a narrow wiring width, the laser beam irradiation position must be shifted before the wiring width expands due to significant heat leakage to the substrate, that is, the scanning speed of the laser beam must be increased. is necessary. On the other hand, in order to form a thick film required for low-resistance wiring, it is desirable to reduce the scanning speed. Because of this trade-off, it has been difficult to draw thick wiring at high speed using conventional methods. For example, the wiring drawing speed obtained in the paper introduced earlier is slow at about 6 μm/s, and cannot be applied to higher-speed wiring methods required for applications such as custom wiring. In conventional methods, if the scanning speed is increased without changing the irradiation power, the film thickness becomes thinner and the wiring becomes disconnected. In addition, in order to eliminate this drawback, if the scanning speed is increased and the irradiation power is increased at the same time, problems such as damage to the central part of the wiring and expansion of the range in which the thermal decomposition temperature of the raw material gas is reached in the horizontal direction of the wiring, resulting in an increase in the line width. was occurring. Furthermore, it is conceivable to increase the amount of raw material supplied in order to increase the scanning speed, but in this case, problems such as deterioration of film quality and increase in specific resistance arise. For this reason, with conventional methods, it has been difficult to form wiring at high speed without deteriorating characteristics such as film quality, thickness, and line width of the wiring.

Furthermore, if the minimum movement distance of the stage used for scanning is close to the spot size of the laser beam, the area of the beam overlap region due to the movement of the stage will be small, and therefore, when drawing a step on the substrate, There were drawbacks such as the wiring being interrupted and the thickness of the wiring becoming thinner. This drawback can be overcome by using a stage with a minimum travel distance of sub-μm, which is much smaller than the spot size of the irradiated laser beam, but the stage is very expensive and the equipment environment must be Other problems arise, such as the need to pay special attention to

An object of the present invention is to provide a wiring forming method and apparatus that solves such conventional problems.

(Means for Solving the Problems) According to the first invention of the present application, a focused laser beam is applied onto a substrate placed in an atmosphere containing a compound gas that deposits a conductive substance by a thermal dissociation reaction. A wiring forming method in which wiring is drawn by irradiating and scanning the laser light relative to a substrate,
A method is obtained in which the pattern of the laser beam irradiated onto the substrate is elongated in the wiring drawing direction.

Next, according to the second invention of the present application, there is provided a laser light source, a CVD cell having a window, and an optical system for condensing and irradiating light emitted from the laser light source onto a substrate in the CVD cell through the window. a raw material gas supply system that supplies the CVD cell with a compound gas that deposits a conductive substance through a thermal dissociation reaction, a mechanism that holds the substrate within the CVD cell, and irradiation of the substrate with laser light. The wiring forming apparatus includes an X-Y stage that scans the position, the optical system includes a beam shape converter that makes the irradiation pattern on the substrate into an elongated shape, and the beam shape converter is arranged on the optical axis. There is obtained an apparatus characterized in that it is equipped with a rotation unit that rotates the irradiation pattern so that the long axis direction of the irradiation pattern coincides with the scanning direction.

Furthermore, according to a third invention of the present application, there is provided a CVD cell including a laser light source, a window, and an optical system for condensing and irradiating light emitted from the laser light source onto a substrate in the CVD cell through the window. a raw material gas supply system that supplies the CVD cell with a compound gas that deposits a conductive substance through a thermal dissociation reaction, a mechanism that holds the substrate within the CVD cell, and irradiation of the substrate with laser light. The wiring forming apparatus includes an X stage that scans the position, the optical system includes a beam shape converter that makes the irradiation pattern on the substrate elongated, and further controls the direction of the substrate to change the irradiation pattern. There is obtained an apparatus characterized in that it is equipped with a rotation stage that aligns the long axis direction with the scanning direction.

(Function) The feature of the first invention of the present application is that the beam pattern of the laser beam irradiated onto the substrate, which was conventionally circular, has been changed to an elongated shape with a long axis in the scanning direction of the laser beam. . By doing this, when the spread of the beam in the line width direction is almost the same, the duration of laser light irradiation at each laser light irradiation position becomes more elliptical than when using a circular beam at the same scanning speed. It can be made longer by the ratio of the length of the short axis to the long axis. As a result, when the irradiation light intensity is the same, when a long and narrow beam is used, the scanning speed is faster by this ratio than the scanning speed when using a circular beam. It is possible to achieve the same irradiation conditions as in the case of Therefore, according to this method, wiring can be formed at high speed without affecting the line width, film thickness, film quality, etc., compared to the case where a circular beam is used. Furthermore, even when drawing wiring onto a step on a substrate, the beam diameter in the scanning direction can be made sufficiently larger than the minimum step of the stage without changing the horizontal spot size of the wiring. The overlapping of the irradiating beams is sufficient, which solves problems such as wiring being interrupted at stepped portions and thinning. The second and third inventions of the present application provide apparatuses suitable for carrying out the first invention of the present application.

(Example) The present invention will be described in more detail below with reference to the drawings.

FIG. 1 is a configuration diagram of a wiring forming apparatus which is an embodiment of the second invention of the present application. Examples of the first and second inventions of the present application will be described with reference to this figure. This example is on top of a poly-Si interconnect layer on SiLSI.
This is an example in which wiring was corrected by drawing Mo lines directly on the SiN insulating layer. The emitted light from a laser light source 1 composed of an Ar laser is a circular Gaussian beam, which is converted into an elongated elliptical Gaussian beam by a beam shape converter 2, reflected by a mirror 4, and then reflected by an objective lens 7. The light is focused through the window 8 and irradiated onto the substrate 9 inside the CVD cell 5. The beam shape converter 2 has a beam expander configuration consisting of two cylindrical lenses, and is designed so that the beam diameter in the vertical direction is expanded five times and the beam diameter in the horizontal direction remains unchanged. ing. The substrate 9 is the SiLSI chip mentioned above.
The CVD raw material Mo(CO) ₆ is supplied from the gas supply system 6 to Ar
It is diluted with gas and guided to the CVD cell 5. Mo
The partial pressure of (CO) ₆ is 1 Torr and the total pressure is 1 atmosphere, and the exhaust gas after the reaction is made harmless in the exhaust gas treatment unit 10. The X-Y stage 11 controls the drawing position of the Mo line to be drawn and the scanning direction and speed of the wiring. Furthermore, a rotation unit 3 attached to the beam shape converter 2 controls the rotation angle around the optical axis of the beam shape converter 2 so that the long axis of the focused elliptical beam is aligned with the scanning direction of the X-Y stage. .

The operation of this device will be explained below. A substrate 9 is prepared in advance with via holes made in the SiN film on poly-Si at the locations where wiring is desired, and is held at a predetermined position within the CVD cell. Next, move the X-Y stage,
The laser beam irradiation position is aligned with the position of one of the via holes on the substrate 9, and the direction in which the wiring is drawn and the position of the end point are set on the XY stage. At this time, the rotation unit 3 aligns the long axis of the elliptical irradiation pattern with the scanning direction of the stage. Then, raw material gas is supplied from the gas supply system 6. After these preparations are completed, laser light is emitted from the laser light source 1, and at the same time the XY stage is scanned at a predetermined speed. In this way, Mo lines are drawn between predetermined poly-Si.

Next, the results obtained will be explained in comparison with the case using a circular beam. The spot size of the circular beam was 2 μmφ, and the spot size of the elliptical beam was 10 μm on the long axis side and 2 μm on the short axis side. The minimum step movement distance of the X-Y stage is 1 μm.

When using a circular beam, a good wiring is obtained when the scanning speed is 6 μm/s, the irradiation light intensity is 500 mW, the wiring width is 5 μm, the thickness is 0.5 μm, and the resistivity is
It was 30μΩcm. If the scanning speed was made higher than this without changing the irradiation intensity, the thickness of the wiring would decrease, causing problems such as disconnection of the wiring at stepped portions on the substrate. Furthermore, when the scanning speed was increased to 10 μm/s and the irradiation power was increased to 700 mw, the line width of the film decreased.
The line width spread to 7 μm, resulting in large variations in line width and causing problems such as dents appearing to be damage in some places in the wiring. In other words, using a circular beam, the drawing speed for obtaining good wiring was about 6 μm/s.

On the other hand, when using an elliptical beam, the scanning speed is
At around 30 μm/s, the thickness and line width are the same as in the circular case.
It was possible to form wiring with good resistivity. At this time, the irradiation light power was 2W, starting from 1.5W.
Good wiring could be formed even when the irradiation power was changed up to 2.5W. Furthermore, the frequency of wire breakage at step portions was significantly reduced compared to when a circular beam was used, and breakage no longer occurred even with large step differences of about 1.5 μm.

In the embodiment described above, a beam expander is used as the configuration of the beam shape converter 2, but as a simpler configuration, the beam shape can be made into an ellipse by using only one cylindrical lens. I can do it. However, in that case,
Adjustment of the optical system becomes somewhat complicated because the beam spread angle changes with the shape. Another possible configuration of the beam shape converter 2 is a configuration in which a beam splitter converts the incident light into a plurality of parallel beams arranged in a line. In this case, the beam shape on the substrate is changed to a small spot. It has a long and narrow shape with the lines lined up in a row. Furthermore, in the above embodiment, a case was described in which Mo(CO) ₆ was used as the raw material gas, but the present invention
It goes without saying that the present invention can be applied to all other methods and devices for forming wiring by direct writing that utilize thermal decomposition reactions.

FIG. 2 is a diagram showing an embodiment of the third invention of the present application. The difference from FIG. 1 is that the beam shape converter 2 does not have a rotation unit 3, and the stage for scanning the substrate is an X stage 12 and a rotation stage 1.
It consists of 3. With this device,
This embodiment differs from the embodiment shown in FIG. 1 in that the operation of aligning the long axes of the irradiated elongated beams in the scanning direction is performed by a rotary stage 13. According to this configuration, there is no movable part in the laser beam irradiation optical system, and it is possible to suppress the occurrence of misalignment of the wiring location due to optical axis deviation or the like. In addition, the rotary stage 13 has the function of aligning the long axis direction of the elongated beam with the scanning direction and the function of aligning the scanning direction with the direction of the required wiring on the substrate 9, so the configuration of the device is simple and the device is inexpensive. There are advantages that can be achieved.

(Effects of the Invention) As described above, according to the present invention, the wiring drawing speed can be significantly improved compared to the conventional wiring forming method and apparatus using a circular beam, and the wiring forming process can be performed at the stepped portion on the substrate. It is possible to provide an excellent wiring forming method and device that is less likely to cause disconnection.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the second invention of the present application, and FIG. 2 is a diagram showing an embodiment of the third invention of the present application. 1... Laser light source, 2... Beam shape converter,
3...Rotating unit, 4...Mirror, 5...
CVD cell, 6... gas supply system, 7... lens,
8...Window, 9...Substrate, 10...Exhaust gas treatment unit, 11...X-Y stage, 12...X stage, 13...Rotation stage.

Claims (1)

[Claims] 1. A substrate placed in an atmosphere containing a compound gas that deposits a conductive material by a thermal dissociation reaction is irradiated with a focused laser beam, and the laser beam is directed relative to the substrate. 1. A wiring forming method for drawing wiring by scanning, wherein the pattern of the laser beam irradiated onto the substrate is elongated in the wiring drawing direction. 2. A CVD cell equipped with a laser light source, a window, an optical system that focuses and irradiates the light emitted from the laser light source onto a substrate in the CVD cell through the window, and a conductive material that is formed by a thermal dissociation reaction. Contains compound gas that deposits
Raw material gas supply system that supplies to the CVD cell and the CVD
In a wiring forming apparatus that includes a mechanism for holding the substrate in a cell and an X-Y stage for scanning a laser beam irradiation position with respect to the substrate, the optical system is configured to form an irradiation pattern on the substrate into an elongated shape. 1. A wiring forming apparatus comprising: a beam shape converter that rotates the beam shape converter with respect to an optical axis; and a rotation unit that rotates the beam shape converter with respect to an optical axis to align the long axis direction of the irradiation pattern with the scanning direction. 3. A CVD cell equipped with a laser light source, a window, an optical system that focuses and irradiates the light emitted from the laser light source onto a substrate in the CVD cell through the window, and a conductive material formed by a thermal dissociation reaction. Contains compound gas that deposits
Raw material gas supply system that supplies to the CVD cell and the CVD
In a wiring forming apparatus that includes a mechanism for holding the substrate in a cell and an X stage that scans the irradiation position of the laser beam with respect to the substrate, the optical system is provided with a beam that makes the irradiation pattern on the substrate into an elongated shape. A wiring forming apparatus comprising a shape converter and a rotation stage that controls the orientation of the substrate to align the long axis direction of the irradiation pattern with the scanning direction.