JPH03241834A - Wiring formation method and device - Google Patents

Abstract

PURPOSE:To eliminate the generation of a disconnection and the generation of a fluctuation in a line width and to obtain a wiring formation method having a superior controllability by a method wherein the height of a deposition substance at the irradiation position of a laser beam for deposition use and the height of the surface of a substrate at a scheduled drawing spot in the vicinity of the irradiation position of the laser beam are detected by a laser focus detection method and the irradiation intensity or the substrate scanning rate of the laser beam is feedback-controlled in such a way that the difference between the heights is constant. CONSTITUTION:In a wiring formation method, wherein while a laser beam for deposition use is focused on a substrate, on which a conductive substance is deposited by a thermal decomposition reaction, in a compound gas-containing raw gas atmosphere, the substrate is scanned with the laser beam relatively to the laser beam and a wiring is drawn, the height of a deposited substance at an irradiation position A of the laser beam and the height of the substrate surface at a scheduled drawing spot B in the vicinity of the position A are detected by a laser focal point detection method and an irradiation intensity or a substrate scanning rate of the laser beam is feedback-controlled in such a way that a difference between the height of the deposition substance at the position A of the laser beam and the height of the substrate surface at the same position, where the height of the substrate surface is first found, is constant using the difference as an error signal. Thereby, the generation of a disconnection due to variation in the reflectivity and heat characteristics and the generation of variation in line width can be inhibited and the wiring formation method having a superior controllability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wiring forming method and an apparatus therefor, and more particularly, to a wiring forming method using a laser CVD reaction, which is one of the semiconductor manufacturing processes using laser light. The present invention relates to a forming method and an apparatus thereof.

[Conventional technology]

Conventionally, a substrate in a source gas atmosphere is irradiated with focused laser light, and the focused laser light is absorbed by the substrate surface, causing a local heat generation that induces a thermal decomposition reaction and deposits a conductive material. 2. Description of the Related Art A laser direct writing CVD method is known in which wiring is directly drawn on a substrate by scanning the substrate relative to a laser beam.

For example, ■ 987 Journal of Vacuum
Science and Technology (Journal of Va.
A wiring drawing method and apparatus are reported by W. M. Grossman et al. in Volume 5, page 843 of the journal Cuum 5 Science Technology. According to this document, a laser beam is focused and irradiated onto a substrate placed in a raw material gas atmosphere using an acousto-optic modulator that can modulate the intensity of the argon laser beam. It has been shown that it is possible to directly draw metal wires by scanning by moving the stage. Furthermore, in this document, in order to perform direct writing stably, the reflectance of the laser beam illumination part on the substrate is monitored, and the difference signal from the reference value of the reflectance is recorded acoustically to keep the reflectance within a certain range. A configuration is used in which feedback is provided to the modulation degree of the optical modulator. This configuration takes advantage of the fact that the reflectance of the tungsten wire to be drawn is greater than that of the substrate, and as the reflectance increases, the intensity of the irradiated light is weakened, making it possible to suppress fluctuations in the drawing characteristics due to a decrease in the deposition rate. There are advantages.

[Problem to be solved by the invention]

In the conventional wiring forming method and apparatus described above, since the reflectance of the lighting part is used as a feedback signal to stabilize the drawing characteristics, there are cases where the difference in reflectance between the substrate and the drawn wiring is small, or when the existing wiring is Under practically unavoidable drawing conditions, such as when it is necessary to cross or contact wiring formed on a substrate and formed by direct drawing, it is necessary to draw directly on the reflectance. Many contributions from sources other than the wiring are included, and as a result, it becomes difficult to perform desired feedback and control, resulting in drawbacks such as wiring breakage and line width fluctuations.

The present invention was made to solve the conventional problems as described above, and eliminates wire breakage and line width fluctuations.
It is an object of the present invention to provide a wiring forming method with excellent controllability and an apparatus therefor.

[Means to solve the problem]

The present invention focuses a deposition laser beam on a substrate in a source gas atmosphere containing a compound gas that deposits a conductive material by a thermal decomposition reaction, and scans the substrate relative to the deposition laser beam to conduct wiring. In the wiring formation method for drawing, the height of the deposit at the irradiation position of the deposition laser beam and the substrate surface height of the nearby drawing point are detected by a laser focus detection method,
In order to keep the difference between the height of the irradiation position of the deposition laser light and the previously determined substrate surface height at the same position constant, this difference is used as an error signal to feed back the irradiation intensity of the deposition laser light or the substrate scanning speed. This is a wiring formation method characterized by control, and the apparatus for realizing this method includes a chamber having a window and a source gas supply for introducing a source gas into the chamber to deposit a conductive material by a thermal decomposition reaction. an irradiation observation optical system capable of observing the substrate surface while focusing and irradiating a deposition laser beam from a laser light source onto the substrate disposed in a chamber exposed to the source gas atmosphere; In a wiring forming apparatus comprising a stage that scans the substrate relative to the deposition laser beam, the height of the deposit surface at the convergence position of the deposition laser beam from the laser light source on the substrate and the vicinity A focal height detection unit that measures the height of the substrate surface in the direction in which wiring is planned to be drawn in real time, and a focal height detection unit that measures the intensity of the focal height signal at the focal position of the deposition laser beam and the substrate position in the vicinity. Determine the deposition thickness at the deposition laser beam irradiation position from the difference in signal intensity from the focal point height at the nearby position delayed by the stage movement time difference,
The wiring forming apparatus is characterized by comprising a signal processing unit that performs feedback control of the emission intensity of the laser light source or the moving speed of the stage so that the thickness is constant.

[Effect]

How to stably draw wiring without being affected by changes in the thermal characteristics of the substrate when the temperature rise caused by focused laser beam irradiation is used to thermally decompose the raw material gas and damage the wiring. , a signal reflecting the temperature or thermal diffusion constant of the laser beam irradiated part or the resulting amount of deposition is detected by some method with a good S/N ratio, and based on this signal, the temperature rise is kept within a predetermined range. Therefore, it is necessary to perform feedback control of the irradiation intensity of the laser beam, etc.

The present invention is characterized in that the thickness of the loss line of the laser beam irradiation section is directly measured in real time, and the measured value is used as a feedback control signal for stabilizing the loss. As a method for non-contactly measuring the surface height of a specific minute spot on a substrate, a method that utilizes the shallow depth of focus of a focused laser beam is well known as an automatic focus detection method. Regarding this measurement method, for example, in 1987
There is a report by Mitsui et al. in Page 136 of the February issue of the Journal of Precision Optics, and according to this measurement method, the return light from the laser beam focused on the substrate is detected using an astigmatic method that combines a cylindrical lens and a 4-part diode. It is described that by applying an aberration detection method, the height of a spot on a spot of several μm on a substrate can be measured with an accuracy of 2 nm. In the present invention, this surface height measurement method is applied to Improved to accurately measure line thickness. That is, first, the heights of two points, the irradiation position of the laser beam that causes deposition and the planned drawing position on the substrate surface that is distant from the laser beam irradiation position in the wiring drawing direction, are measured in real time, and the height of the latter is measured in real time. Regarding the signal, the signal up to the point in time delayed by the movement time of the stage at these two points is memorized, the surface height at the laser beam irradiation position at a certain point when there is no deposit is determined in advance, and the height of the surface when there is no deposit is determined. The feature is that the thickness of the deposit is measured in real time by determining the difference from the surface height.

Determining the deposition thickness from the difference in height between two points is considered essential, especially when wiring is lost at an arbitrary position on an uneven substrate as in the case of direct laser writing. By measuring the exact height of the substrate surface immediately before drawing the loss line, it is possible to avoid film thickness measurement errors caused by local irregularities, gentle undulations, or the passage of time on the substrate. It can be kept to a minimum. In this method, although the reflectance of the surface affects the intensity of the returned light, it is difficult to detect the height.
Since the relative intensity ratio between the outputs of the four-division diode is used, the feedback signal can be detected with almost no effect on the height measurement accuracy, so there is no problem of difficulty in feedback control due to changes in the reflectance of the base. Furthermore, since the film thickness is directly monitored, the controllability of the film thickness of the lost wire is greatly improved. In addition, the line width also changes according to the change in film thickness, so
There is also the advantage that controllability regarding line width can be similarly improved.

FIG. 1 is a diagram illustrating the principle of measuring the thickness of a deposited film according to the present invention. FIG. 1<a) shows the positional relationship between the deposit on the substrate and the measurement laser spot at time T=To,
(b) is a diagram showing the positional relationship on the substrate at time T=To 10 dt. The 0 time width dt is the time required for the stage to move the distance between laser spots A and B, and T-
If the heights measured at 70 o'clock are expressed as ZA (T) and ZB (T) for laser spots A and B, respectively, then the deposition thickness at time T''To +dt is 2^(
It can be calculated as To +at)-Za (To). By monitoring the height at two locations, the substrate surface and the deposition surface, it is possible to accurately measure the thickness of the deposited loss wire, and the difference between this signal and the reference value is used as an error signal. By feeding back to the CVD laser light intensity or stage movement speed, it suppresses variations in the line width and thickness of the damaged line due to local fluctuations in thermal conductivity on the substrate, achieving stable drawing. It becomes possible to do so.

The direction of the feedback is to increase the laser power or slow down the stage movement speed if the thickness becomes thinner than the reference value, and to decrease the laser power or slow down the stage movement speed if the thickness becomes larger than the reference value. control in the upward direction.

〔Example〕

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

FIG. 2 is a block diagram of an embodiment of the wiring forming method and apparatus of the present invention. 6 The substrate 1 is placed in a CVD chamber 3 having a window 2, and a raw material gas supply unit supplies raw material gas for CVD. 4 and exhaust pump 5 are CVD chamber 3
It is connected to the.

The emitted light from a first laser light source 6 consisting of a laser CVD and an Ar laser that also serves as a light source for deposition and height measurement is bent by a first acoustic mirror 7, and then reflected by a second multiplexing mirror 8, λ
/4 plate 1 sheet metal 2, focused by objective lens 13, window 2
The beam diameter is 1 μm to the substrate 1 in the CVD chamber 3.
It is irradiated as a condensed spot of m. On the other hand, an illumination lamp 10, a third multiplexing mirror 9, a second multiplexing mirror 8
, an optical system consisting of one λ/4 plate, one sheet metal lens 13, and a TV 14 constitutes a microscope optical system for observing the surface shape of the substrate 1. In addition, the second laser light source 17 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 emitted light from the first laser light source.
It consists of a 33 nm He-Ne laser, and its emitted light is
It is bent by the polarization splitter 16, and the XY deflector 15
The light beam is slightly deflected so that the focused spot faces in the moving direction of the stage 11, and passes through the first multiplexing mirror 7, the second multiplexing mirror 8, one λ/4 plate, two sheet metal lenses 13, and the window 2. The substrate 1 is irradiated. Among 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 retraces the incident optical path and passes through the polarization splitter 16.
It separates from the incident optical path and enters the focal height detection unit.

The focal height detection unit includes a combining mirror 18 that separates the light from the first laser light source 6 and the second laser light source 17, and a first
, a cylindrical lens 19, a first four-division diode 21, a second
It consists of a cylindrical lens 20 and a second cylindrical lens 22. The combination of a cylindrical lens and a 4-split diode uses the astigmatism method to reduce the output to 0 if the laser beam on the substrate is at the focal position.
When it deviates from one focal position, it generates positive and negative output voltages depending on the direction and size of the deviation.As for the detection sensitivity of 6 heights, about 300A can be obtained with good reproducibility, and it can be used as a monitor for the thickness of damage. Sufficient accuracy was obtained.

In this configuration, a combination of one first cylindrical lens and a first four-part diode 21 is used to measure the height of the focused spot from the first laser light source, that is, the tip of the deposit, and is used to measure the focal height. The other unit measures the height of the intended writing position on the substrate surface slightly away from the deposition. The signal processing unit 23 uses the output signals of the first 4-division diode 21 and the second 4-division diode 22 and the operating state of the stage 11 as input, and calculates the thickness of the deposit in the laser-damaged portion in real time. The difference from the reference value is calculated, and based on the result, a signal to increase or decrease the output of the first laser light source 6 or a signal to increase or decrease the moving speed of the stage 11 is output, and the height of the objective lens is It has the function of increasing or decreasing the height of the objective lens so that it remains constant with respect to the surface. The raw material gas used for CVD was I Tor
r W(Co) 6 and atmospheric pressure Ar gas was used as the carrier gas.

Next, the sequence of operation of this device will be explained.

Mount the substrate 1 in the CVD chamber 3, exhaust the residual gas in the CD chamber with the exhaust pump 5, and then flow the source gas from the source gas supply unit 4 to the CVD chamber 3.The position where you want to draw the wiring on the substrate 1. The stage 11 is moved to the starting point, and a laser beam is emitted from the first laser light source 6 to start drawing. As soon as you start drawing,
The focal height detection unit measures the height of the deposition at the focal point of the CVD laser beam and the height of the substrate surface in the writing direction slightly away from the focal point. During the latter period, data is stored for -1 times. When the stage 11 moves to the next measurement point, the height data of the substrate at this point is called up, the difference with the deposition height data is determined, the thickness of the deposition at that point is determined, and the reference value is calculated. If the deposition pressure is lower than the reference value, increase the laser power or decrease the stage movement speed; conversely, if the deposition pressure becomes thicker than the reference value, decrease the laser power or decrease the stage movement speed. Feedback control is performed in the direction of increasing the moving speed, and an automatic focusing mechanism is provided that raises and lowers the height of the objective lens 13 so that the focal point is on the surface of the deposit when one cycle of focal height measurement is completed. The laser beam is operated to stabilize the convergence state of the laser beam on the substrate.

In this way, as a result of stabilizing the loss, the deposition thickness was 3000A and the line width was 1.5μ on a substrate simulating an LSI.
W.m wires with a high accuracy of ±10% regardless of the presence or absence of underlying wiring, without the wiring being interrupted at steps etc.
I was able to draw the wiring.

This means that, compared to the conventional method of using the reflectance from the substrate as a feedback signal, according to the present invention, even if there is wiring underneath and the thermal conductivity varies greatly locally, This shows that it is possible to provide a wiring forming method and a wiring forming apparatus with excellent controllability, with almost no change in the line width or thickness of straight and horizontal lines.

In one embodiment described above, a light source for laser CVD,
Although we have discussed the case where a part of the light source is also used for focal position detection, it goes without saying that a dedicated laser light source may also be used for focal height detection. Since the degree of freedom is increased, if a light source with a short wavelength is selected, the depth of focus of the converging point becomes shallower, and the accuracy of height measurement can be further improved.

Furthermore, although the case where a CW light source is used as the light source for CVD has been described, a high repetition rate pulsed light source may also be used. In this case, if the pulse width is set to less than the thermal diffusion time of the substrate, it will be relatively less susceptible to changes in the thermal conductivity of the substrate, and heat diffusion on the substrate surface will be suppressed, so thin wires can be used. There is an advantage that the drawing of the wiring becomes easy, and by applying the present invention, there is an advantage that thin and thick wiring required as a realistic wiring can be stably drawn.

Note that the signal processing unit, objective lens position adjustment mechanism (automatic focus mechanism), and stage movement mechanism used in the present invention can be those used in compact disk devices, optical disk devices, etc., and therefore detailed explanations are omitted.

〔Effect of the invention〕

As described above, according to the present invention, compared to the conventional wiring drawing method and apparatus, the thickness of the deposited laser beam part is directly monitored in real time and feedback control is performed, so that the damaged wiring can be removed from the board. It is possible to suppress the occurrence of wire breakage and fluctuations in line width due to changes in reflectance and thermal characteristics depending on the location of the wire, and it is possible to provide a practical wiring formation method and device with excellent controllability. .

... Raw material gas supply unit, 5... Exhaust pump, 6
... first laser light source, 7... first multiplexing mirror,
8... Second multiplexing mirror, 9... Third multiplexing mirror, 10... Lighting, 11... Stage, 12...^
/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... First 4-division diode, 22... 2nd 4-division diode, 23... Signal processing unit.

Claims (1)

[Claims] 1. While focusing the deposition laser light on the substrate in a raw material gas atmosphere containing a compound gas on which a conductive substance is deposited by a thermal decomposition reaction, the substrate is placed relative to the deposition laser light. In a wiring formation method that draws wiring by scanning, the height of the deposit at the irradiation position of the deposition laser beam and the substrate surface height of the nearby drawing point are detected using a laser focus detection method. The feature is that the irradiation intensity of the deposition laser beam or the substrate scanning speed is feedback-controlled using this difference as an error signal so that the difference between the height of the irradiation position and the previously determined substrate surface height at the same position is constant. Wiring formation method. 2. A chamber having a window, a source gas supply unit that introduces a source gas into the chamber for depositing a conductive material through a pyrolysis reaction, and a source gas supply unit that introduces a source gas into the chamber that is exposed to the source gas atmosphere from a laser light source. Wiring formation consisting of an irradiation observation optical system that can observe the surface of the substrate while focusing and irradiating the deposition laser beam, and a stage that scans the substrate relative to the deposition laser beam. In the device, the height of the deposit surface at the focal point of the deposition laser beam from the laser light source on the substrate and the height of the substrate surface in the direction in which nearby wiring is planned to be drawn are measured in real time. Difference between the intensity of the focal height signal of the detection unit and the focal position of the deposition laser beam, and the signal strength from the focal height of the neighboring position delayed by the stage movement time difference between the detection unit and the neighboring substrate position. Wiring formation characterized by comprising: a signal processing unit that determines the deposition thickness at the deposition laser beam irradiation position from the above and feedback-controls the emission intensity of the laser light source or the moving speed of the stage so that the thickness is constant. Device.