JP2890616B2 - Wiring forming method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a wiring, and more particularly, to a wiring using a laser CVD reaction which is one of semiconductor manufacturing processes using laser light. The present invention relates to a forming method and an apparatus therefor.

[Conventional technology]

Conventionally, a focused laser beam is applied to a substrate in a source gas atmosphere, and the focused laser beam is absorbed by the substrate surface to induce a thermal decomposition reaction and deposit a conductive substance. There is known a laser direct writing CVD method in which a substrate is relatively scanned with respect to a laser beam to draw wiring directly on the substrate.

For example, the Journal of Vacuum Science Technology in 1987
Technology), Vol. 5, page 843, reports a wiring drawing method and apparatus by WMGrossman et al. According to this document, a laser beam is condensed and radiated onto a substrate placed in a source gas atmosphere using an acousto-optic modulator so that the intensity of argon laser light can be modulated. It is shown that a metal line can be directly drawn by scanning by moving the stage. Further, in this document, in order to stably perform direct writing, the reflectance of the laser beam irradiation part on the substrate is monitored, and a difference signal from the reference value of the reflectance is calculated so that the reflectance falls within a certain range. A configuration in which the degree of modulation of the acoustooptic modulator is fed back is used. In this configuration, by utilizing the fact that the reflectance of the tungsten line to be drawn is higher than the reflectance of the substrate, when the reflectance is higher, the intensity of the irradiation light is weakened, and the fluctuation of the drawing characteristics due to the decrease in the deposition rate can be suppressed. There are advantages.

[Problems to be solved by the invention]

In the above-described conventional method and apparatus for forming a wiring, the reflectance of the light irradiating portion is used as a feedback signal for stabilizing the drawing characteristics. Is formed on the substrate and it is necessary to traverse or contact the wirings formed by direct drawing and these substrate wirings. To be included from other sources than
It is difficult to perform desired feedback and control, and there are drawbacks such as disconnection of wiring and variation in line width.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described conventional problems, and provides a wiring control method and a device which are free from disconnection and line width fluctuation and have excellent controllability. With the goal.

[Means for solving the problem]

The present invention provides a method for wiring a substrate by concentrating a deposition laser beam on a substrate in an atmosphere of a source gas containing a compound gas that deposits a conductive substance by a thermal decomposition reaction while scanning the substrate relative to the deposition laser beam. In the wiring forming method for drawing a pattern, the height of the deposit at the irradiation position of the deposition laser light and the substrate surface height at a nearby drawing scheduled point are detected by a laser focus detection method, and the height of the irradiation position of the deposition laser light is detected. And a feedback control of the irradiation intensity of the deposition laser light or the substrate scanning speed using the difference as an error signal so that the difference between the above and the previously obtained substrate surface height at the same position becomes constant. An apparatus for realizing the method includes a chamber having a window, a source gas supply unit for introducing a source gas for depositing a conductive substance by a thermal decomposition reaction into the chamber, An irradiation observation optical system capable of observing the substrate surface while condensing and irradiating a deposition laser beam from a laser light source onto a substrate disposed in a chamber exposed to a body atmosphere; and the deposition laser. In a wiring forming apparatus including a stage that relatively scans the substrate with respect to light, the height of the surface of the deposit at the position where the laser light for deposition from the laser light source on the substrate is focused, and the wiring drawing in the vicinity Height detection unit that measures the height of the substrate surface in the direction in real time, the intensity of the focal height signal at the condensing position of the deposition laser light, and the stage movement time difference between the nearby substrate position The deposition thickness at the deposition laser beam irradiation position is obtained from the difference in signal intensity from the focal height of the delayed position in the vicinity, and the emission intensity of the laser light source or the moving speed of the stage is adjusted so that this thickness is constant. Fee A wiring forming apparatus characterized by comprising a signal processing unit for back control.

[Action]

Using the temperature rise caused by the laser beam condensing irradiation to cause thermal decomposition of the source gas, when drawing wiring directly, it is necessary to draw wiring stably without being affected by changes in the thermal characteristics of the substrate. Detects a signal reflecting the temperature or thermal diffusion constant of the laser beam irradiating part or the resulting deposition amount with a good S / N ratio by some method, and based on this signal, the temperature rise falls within a predetermined range. It is necessary to perform feedback control of the irradiation intensity of the laser beam or the like so as to be contained.

The present invention is characterized in that while directly measuring the thickness of a direct drawing line of a laser beam irradiation part in real time, the measured value is used as a feedback control signal for stabilizing the direct drawing. As a method of indirectly measuring the surface height of a specific minute spot on a substrate, a method using a shallow depth of focus of a condensed laser beam is well known as one method of an automatic focus detection method. This measurement method is reported by Mitsui et al., For example, from page 136 of the February issue of the Journal of Precision Optics, 1987. According to this measurement method, a cylindrical lens is used for returning light from laser light condensed on a substrate. Applying the astigmatism detection method combining the four-segment diode, several μm
It describes that the height of the region on the spot can be measured with an accuracy of 2 nm. In the present invention, this surface height measuring method has been improved in order to accurately measure the thickness of the deposited direct drawing line. That is, the height of two points, ie, the irradiation position of the laser beam that causes the deposition and the planned drawing position on the substrate surface separated from the laser irradiation position in the wiring drawing direction is first measured in real time, and the height of the latter is measured. With respect to the signal of, the signals up to the time point delayed by the movement time of the two stages are stored, and the surface height when there is no deposit at the laser beam irradiation position at a certain point in advance is obtained in advance. It is characterized in that the thickness of the deposition is measured in real time by determining the difference from the surface height. Obtaining the thickness of the deposition from the difference between the heights of the two points is considered to be indispensable especially when wiring is directly drawn at an arbitrary position on a substrate having irregularities such as a laser direct drawing method. By measuring the exact height of the substrate surface immediately before drawing a direct drawing line, the occurrence of film thickness measurement errors caused by local irregularities on the substrate, gradual undulations, or the passage of time is minimized. Can be minimized. In this method, the reflectivity of the surface affects the intensity of the returned light, but the height detection uses the relative intensity ratio between the outputs of the four-segment diodes, so that the height measurement accuracy is hardly affected. Since the feedback signal can be detected, there is no problem that the feedback control becomes difficult due to a change in the reflectance of the base. Further, since the film thickness is directly monitored, the controllability of the film thickness of the directly drawn line is greatly improved. Also, since the line width changes following the change in the film thickness, there is an advantage that the controllability of the line width can be similarly improved.

FIG. 1 is a view for explaining the principle of measuring the thickness of a deposited film according to the present invention. FIG. 1A shows the positional relationship between the deposit on the substrate and the laser spot for measurement at time T = T ₀ ,
(B) is a diagram showing a positional relationship on the substrate at a time T = T ₀ + dt. The time width dt is the time required for the stage to move the distance between the laser spots A and B, and the measured height at T = T ₀ is defined as Z for each of the laser spots A and B.
_A (T), when expressed as Z _B (T), the thickness of the deposition at the time T = T ₀ + dt _{is, Z A (T 0 + dt} ) -Z B (T 0) and determining it is possible. By monitoring the height at two places, the substrate surface and the deposition surface, it is possible to accurately measure the thickness of the directly drawn line to be deposited, and use the difference between the signal and the reference value as an error signal. By feeding back to the laser beam intensity for CVD or the stage moving speed, the variation of the line width and thickness of the direct drawn line due to local fluctuation of thermal conductivity on the substrate, etc., and realize stable drawing Becomes possible.
The direction of the feedback is to increase the laser power or decrease the stage moving speed when the thickness becomes thinner than the reference value, and to decrease the laser power or decrease the stage moving speed when the thickness becomes larger than the reference value. Control in the up direction.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a configuration diagram of an embodiment of a wiring forming method and apparatus according to the present invention. The substrate 1 is placed in a CVD chamber 3 having a window 2, and a source gas supply unit 4 for supplying a source gas for CVD and an exhaust pump 5 are connected to the CVD chamber 3. Light emitted from a first laser light source 6 composed of an Ar laser serving also as a light source for laser CVD, deposition and height measurement is bent by a first multiplexing mirror 7, and is multiplexed by a second multiplexing mirror 8, λ / 4. After passing through the plate 12, it is focused by the objective lens 13,
The beam diameter 1 passes through the window 2 to the substrate 1 in the CVD chamber 3.
Irradiated as a focused spot of μm. On the other hand, the optical system including the irradiation lamp 10, the third multiplexing mirror 9, the second multiplexing mirror 8, the λ / 4 plate 12, the objective lens 13, and the TV 14
A microscope optical system for observing the surface shape of the substrate 1 is configured. The second laser light source 17 which forms a condensed spot with a beam diameter of 1 μm on the surface of the substrate 3 μm away from the condensing position of the light emitted from the first laser light source is a He-N beam having a wavelength of 633 nm.
e-laser, the output light of which is polarized splitter 16
And the light is slightly deflected by the XY deflector 15 so that the condensed spot is directed in the direction of movement of the stage 11. The first multiplex mirror 7, the second multiplex mirror 8, the λ / 4 plate 12, the objective lens
13. Through the window 2, the substrate 1 is irradiated. Of the laser light from the first laser light source 6 and the light from the second laser light 17, the light reflected by the substrate reverses the incident optical path and separates from the incident optical path by the polarization splitter 16. Enter the focus height detection unit. The focus height detecting unit is a multiplexing mirror for separating the light of the first laser light source 6 and the light of the second laser light source 17
18, a first cylindrical lens 19, a first quadrant diode 2
1, a second cylindrical lens 20 and a second cylindrical lens 22. The combination of a cylindrical lens and a four-division diode is such that the output is 0 if the laser beam on the substrate is at the focal position by the astigmatism method. Generates voltage. As the height detection sensitivity, about 300 mm was obtained with good reproducibility, and sufficient accuracy was obtained as a monitor for the thickness of direct drawing. In this configuration, the combination of the first cylindrical lens 19 and the first quadrant diode 21 is used for measuring the focal spot from the first laser light source, that is, the height of the tip of the deposition, and the focal height measurement is performed. The other side of the unit measures the height of the planned writing position on the substrate surface slightly away from the deposition. The signal processing unit 23 receives the output signal of the first quadrant diode 21 and the output signal of the second quadrant diode 22 and the operating state of the stage 11 as inputs, and obtains the thickness of the laser direct-writing portion in real time,
The difference from the reference value is calculated, and from the result, a signal for increasing or decreasing the output of the first laser light source 6 or a signal for increasing or decreasing the moving speed of the stage 11 is output. It has the function of increasing and decreasing the height of the objective lens so that it is constant with respect to the surface. The source gas used for the CVD was 1 Torr of W (CO) ₆ , and Ar gas at atmospheric pressure was used as a carrier gas.

Next, the operation sequence of this device will be described. Substrate 1
Is mounted on the CVD chamber 3, the residual gas in the CVD chamber is exhausted by the exhaust pump 5, and then the source gas flows from the source gas supply unit 4 to the CVD chamber 3. The stage 11 is moved to the start point of the position where the wiring of the substrate 1 is to be drawn, and the laser light is emitted from the first laser light source 6 to start drawing. Simultaneously with the start of the drawing, the focal height detection unit measures the deposition height at the focal position of the laser beam for CVD and the height of the substrate surface in the drawing direction slightly away therefrom. For the latter, the data is temporarily stored.
When the stage 11 moves and moves to the next measurement point, the height data of the substrate at this point is called, the difference from the height data of the deposition is obtained, the thickness of the deposition is obtained at that point, and the reference value and When the deposition pressure is lower than the reference value, the laser power is increased or the stage moving speed is decreased. Conversely, when the deposition pressure becomes thicker than the reference value, the laser power is reduced or the stage is moved. Feedback control is performed in the direction of increasing the speed. At the end of one cycle of the measurement of the focal height, the automatic focusing mechanism that raises and lowers the height of the objective lens 13 so that the focal point comes to the surface of the deposition is operated to collect the laser light on the substrate. Stabilize the light state.

As a result of stabilizing the direct drawing in this way, on a substrate simulating an LSI, a line with a deposition thickness of 3000 mm, a line width of 1.5 μm can be formed with high accuracy of ± 10% regardless of the presence or absence of the underlying wiring. The W wiring could be drawn stably without the wiring being interrupted at a step or the like.

This is, according to the present invention, compared to the conventional method of directly drawing the reflectance from the substrate as a feedback signal.
Provided is a wiring forming method and a wiring forming apparatus having excellent controllability, with little change in the line width and thickness of a directly drawn line even when the thermal conductivity is largely changed locally due to the presence of wiring on the base. Indicates that you can do it.

As described above, in one embodiment, a light source for laser CVD,
Although the case where the light source for detecting the focal position is partially used has been described, it is needless to say that a dedicated laser light source may be used for the detection of the focal height. In this case, the degree of freedom in selecting the wavelength of the light source is increased. If a light source with a short wavelength is selected, the depth of focus of the focal point becomes shallower, so that the height measurement accuracy can be further improved.

As the light source for CVD, a case where a CW light source is used has been described, but a pulse light source having a high repetition rate may be used. In this case, if the pulse width is set to be equal to or less than the thermal diffusion time of the substrate, the influence of the change in the thermal conductivity of the substrate is relatively reduced, and the thermal diffusion on the substrate surface is suppressed. There is an advantage that drawing becomes easy, and by applying the present invention, there is an advantage that a thin and thick wiring required as a realistic wiring can be drawn stably.

Since the signal processing unit, the objective lens position adjusting mechanism (automatic focusing mechanism), and the stage moving mechanism used in the present invention can be those used in compact disk devices, optical disk devices, and the like, detailed descriptions are omitted.

〔The invention's effect〕

As described above, according to the present invention, the thickness of the deposited laser beam irradiation part is directly monitored in real time and the feedback control is performed as compared with the conventional wiring drawing method and apparatus, so that the direct drawn wiring is printed on the substrate. It is possible to suppress the occurrence of disconnection and line width variation due to variations in reflectance and thermal characteristics due to the above location, and to provide a practical wiring forming method with excellent controllability and a device therefor. I can do it.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of the present invention, and is a diagram showing a relative relationship between a deposition position at two different times at the same substrate position and a focusing position of a beam for height measurement; FIG. 2 is a configuration diagram of one embodiment of the present invention. 1 ... substrate, 2 ... window, 3 ... CVD chamber, 4 ...
Source gas supply unit, 5 ... exhaust pump, 6 ... first
Laser light source, 7 first multiplex mirror, 8 second multiplex mirror, 9 third multiplex mirror, 10 illumination, 11
…… Stage, 12… λ / 4 plate, 13… Objective lens, 14…
… TV, 15 …… XY deflector, 16… Polarization splitter, 17…
... Second laser light source, 18... Demultiplexing mirror, 19... First cylindrical lens, 20... Second cylindrical lens, 21.
Split diode, 22... Second quadrant split diode, 23.
... Signal processing unit.

Claims (2)

(57) [Claims] A substrate is scanned relative to a deposition laser beam while concentrating the deposition laser beam on a substrate in a source gas atmosphere containing a compound gas for depositing a conductive substance by a thermal decomposition reaction. In the wiring forming method of drawing wiring, the height of the deposit at the irradiation position of the deposition laser light and the height of the substrate surface at the nearby drawing scheduled point are detected by a laser focus detection method, and the irradiation position of the deposition laser light is detected. Wiring characterized by performing feedback control on the irradiation intensity of the deposition laser light or the substrate scanning speed using this difference as an error signal so that the difference between the height and the substrate surface height at the same position previously obtained becomes constant. Forming method. 2. A chamber having a window, a source gas supply unit for introducing a source gas for depositing a conductive substance by a thermal decomposition reaction into the chamber, and a substrate disposed in a chamber exposed to a source gas atmosphere. An irradiation observation optical system capable of observing the substrate surface while condensing and irradiating deposition laser light from a laser light source, and a stage that scans the substrate relative to the deposition laser light. In the wiring forming apparatus, the height of the deposit surface at the condensing position of the deposition laser light from the laser light source on the substrate and the height of the substrate surface in the nearby wiring drawing direction are measured in real time. A focus height detection unit, a signal from the focus height at the focus position at the vicinity position obtained by delaying the intensity of the focus height signal at the focus position of the deposition laser light and the stage movement time difference from the substrate position at the vicinity position Strength A signal processing unit for obtaining a deposition thickness at a deposition laser light irradiation position from the difference and feedback-controlling the emission intensity of the laser light source or the moving speed of the stage so that the thickness becomes constant. Forming equipment.