JP7012602B2 - Local dry etching equipment - Google Patents

Description

The present invention relates to a local dry etching apparatus. The processing method called local dry etching processing is a technology for flattening or making the thickness distribution uniform by locally etching the convex parts of the work surface such as silicon wafers and semiconductor wafers with active seed gas. Is.

FIG. 1 is an explanatory diagram for explaining the principle of a work flattening method by local dry etching using plasma. Reference numeral 100 is a plasma generation unit forming a part of the discharge tube, and the active species gas G in the plasma generated by the plasma generation unit 100 is injected from the nozzle 101 onto the surface of the work W. The work W is placed and fixed on the work table 120, and the work table 120 is scanned at a speed and pitch controlled in the horizontal direction with respect to the nozzle 101.

Before processing, the work W has a different thickness depending on the location and has fine irregularities. Prior to the local dry etching process, the thickness of each subdivided region is measured for each work W. This measurement provides thickness data at the location of each region, i.e., position-thickness data.

In the local dry etching process, the amount of material removed for each region corresponds to the time that the region is exposed to the active species gas G. Therefore, the relative speed at which the nozzle passes with respect to the work (hereinafter referred to as the nozzle speed) is low on the relatively thick portion Wa, and moves at a relatively high speed on the relatively thin portion. The speed is determined.

FIG. 2 is a graph showing the distribution of the amount (depth) of the work material removed per unit time by the injected active seed gas, that is, the etching rate. This curve called the etching rate profile is a curve very close to the Gaussian distribution. As shown in FIG. 2, the etching rate E has a maximum value Emax on the center line of the nozzle 101, and decreases as the distance from the center increases in the radius r direction.

Since the material removal capacity shows a distribution according to the distance from the nozzle center in this way, the material removal amount required for one region cannot be determined only by the nozzle speed of one region. That is, even if the necessary material removal is performed in one region, when etching is performed on the adjacent region or further the adjacent region, the material removal corresponding to the etching rate profile is also performed on the first region. Is done.

In this way, one region is affected by etching on all other regions, so that the surface heights of each region are equal to each other as a result of superimposing these effects on all regions. Nozzle velocity is calculated.

Japanese Unexamined Patent Publication No. 10-147893 Japanese Unexamined Patent Publication No. 2000-208487 Japanese Unexamined Patent Publication No. 2002-198200 Japanese Unexamined Patent Publication No. 2000-174001

A desired flat surface or thickness should be obtained by performing local dry etching at the nozzle speed calculated based on the above position-thickness (or unevenness) data and the etching rate profile. However, when the wafer surface is actually processed and the processed wafer surface is measured, an error that cannot be explained as a mere error occurs.

That is, the pressure of the plasma generating part affects the etching rate, and when viewed in detail, this etching rate is not only the pressure of the plasma generating part but also the cumulative use of the time that the discharge tube has been used. It is also affected by the time and the elapsed start time of the local dry etching apparatus, eg, starting the apparatus for the start of work for the day.

In other words, basically, the etching rate can be calculated by detecting the pressure of the plasma generating part, but in order to make finer adjustments, in addition to the measured value of the pressure of this plasma generating part, the cumulative usage time and the elapsed start time should be calculated. It means that it can be corrected by using. Furthermore, it is the electromagnetic waves emitted to the plasma generating part that generate the plasma, and the magnitude of the output of the electromagnetic wave oscillator is reflected in the etching rate. Therefore, the pressure, the cumulative usage time, and the start of the plasma generating part are reflected. If the correspondence between the elapsed time and the etching rate (here referred to as the etching rate function) is acquired in advance, the corrected etching rate can be calculated from these measured values, and the output of the electromagnetic wave oscillator is output according to this calculation result. We have come to the finding that the etching rate can be kept constant by controlling it.

According to the present invention, in the local dry etching apparatus, the local dry etching process is performed by correcting the etching rate to be kept constant based on the pressure of the plasma generating portion, the cumulative usage time, and the elapsed start time. As a result, it is an object to make the processing error extremely small.

The above problem is solved by the following means. That is, the first invention is a vacuum chamber, a nozzle opening in the vacuum chamber, a discharge tube connected to the nozzle, a work table arranged in the vacuum chamber for mounting a work, and the work. A table drive device for driving a table, a table drive control device for controlling the table drive device, a raw material gas supply device for supplying a raw material gas to the discharge tube, a plasma generating unit formed in the discharge tube, and an electromagnetic wave. An oscillator , an electromagnetic wave transmission means for irradiating the plasma generating portion with the electromagnetic wave oscillated by the electromagnetic wave oscillator, and a vicinity of the plasma generating portion of the discharge tube in order to detect the pressure of the plasma generating portion. A pressure gauge provided on the upstream side of the plasma, which is a function obtained in advance and is based on the etching rate function representing the correspondence between the pressure of the plasma generating portion and the etching rate, from the measured value of the pressure gauge. The etching rate calculator for calculating the etching rate and the electromagnetic wave output control device for controlling the output of the electromagnetic wave oscillator so that the etching rate becomes constant based on the calculated value of the etching rate calculator are provided. It is a local dry etching apparatus characterized by this.

The second invention is the local dry etching apparatus of the first invention, wherein the etching rate function is a function corrected by the cumulative usage time of the discharge tube. Is.

The third invention is the local dry etching apparatus of the first or second invention, wherein the etching rate function is a function further corrected by the start elapsed time from the start of the local dry etching apparatus. It is a local dry etching apparatus characterized by.

According to the present invention, an etching rate function indicating the correspondence between the pressure of the plasma generating portion, the cumulative usage time of the discharge tube, the starting elapsed time of the local dry etching apparatus, and the etching rate is acquired in advance, and these Since the etching rate is calculated from the measured value and the output of the electromagnetic wave oscillator is controlled according to the calculation result, the etching rate can be kept constant, more precise flattening can be performed, or a uniform thickness can be obtained. It is possible to obtain a distribution.

It is explanatory drawing for demonstrating the principle of the wafer flattening method by local dry etching using plasma. It is a graph which shows the distribution of the etching rate of the injected active species gas. It is explanatory drawing which shows one Example of the local dry etching apparatus of this invention.

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

FIG. 3 is an explanatory diagram showing an example of the local dry etching apparatus of the present invention. The local dry etching apparatus includes a plasma generator 1, a discharge tube 2, a nozzle 20, a raw material gas supply device 3, a vacuum chamber 4, and a table drive device 5.

The plasma generator 1 is a device for converting a raw material gas sent into a discharge tube 2 made of, for example, alumina or the like into plasma to generate an active species gas G containing a neutral radical, and is an electromagnetic wave oscillator 10 and an electromagnetic wave. It is provided with a waveguide 11 which is a transmission means. The electromagnetic wave oscillator 10 can oscillate an electromagnetic wave M (for example, a microwave) having a predetermined frequency.

The waveguide 11 which is an electromagnetic wave transmission means is for transmitting the electromagnetic wave M oscillated from the electromagnetic wave oscillator 10, and is externally attached to the discharge tube 2. A reflector 12 (short plunger) 12 that reflects the electromagnetic wave M to form a standing wave is attached to the opposite end of the waveguide 11 to which the electromagnetic wave oscillator is connected. Further, in the middle of the waveguide 11, a stub tuner 13 for adjusting the phase of the electromagnetic wave M and an isolator 14 for bending the reflected electromagnetic wave M toward the electromagnetic wave oscillator 10 in the 90 ° direction are attached.

The discharge pipe 2 is a cylindrical body having a nozzle 20 formed at one end thereof, and a supply pipe 30 of the raw material gas supply device 3 is connected to the other end portion. The raw material gas supply device 3 is a device for supplying the raw material gas into the discharge pipe 2, and has a cylinder 31 of the raw material gas (SF6 (sulfur hexafluoride) gas, etc.), and the cylinder 31 has a valve 32 and a flow rate. It is connected to the supply pipe 30 via the controller 33. Sulfur hexafluoride gas as a raw material gas is an example, and CF4, NF3, and the like can also be selected. Further, although it may be a single gas, another gas may be simultaneously supplied to the supply pipe 30 to be a mixed gas.

When the raw material gas is supplied from the raw material gas supply device 3 to the discharge tube 2 and the electromagnetic wave M is oscillated by the electromagnetic wave oscillator 10, the gas is converted into plasma in the discharge tube 2. The active species gas G generated by plasma formation is injected from the nozzle 20.

The work W is arranged on the work table 40 in the vacuum chamber 4, and is attracted to the work table 40 by electrostatic force. A vacuum pump 41 is attached to the vacuum chamber 4, and the inside of the vacuum chamber 4 is evacuated (reduced) by the vacuum pump 41.

Further, a hole 42 is formed in the central portion of the upper surface of the vacuum chamber 4, and the nozzle 20 of the discharge tube 2 is inserted into the vacuum chamber 4 through the hole 42. A duct 43 is provided around the nozzle 20 inserted into the hole 42. Another vacuum pump 44 is connected to the duct 43, and the reaction-generated gas during etching is discharged to the outside of the vacuum chamber 4 through the duct 43.

The duct 43 is provided so as to surround the nozzle 20. When the exhaust gas passes through the duct 43, the gas in the vacuum chamber is concentrated, so that the etching profile of the active species gas ejected can be adjusted by this exhaust gas flow rate. A flow rate adjusting device 46 for adjusting the exhaust flow rate is provided between the vacuum pump 44 and the vacuum chamber 4.

The table drive device 5 is arranged in the vacuum chamber 4 and supports it from below the work table 40. The table drive device 5 integrally moves the work table 40 and the Y drive motor 51 described later by the X drive motor 50 in the left-right direction of FIG. 3, and the Y drive motor 51 moves the work table 40 to the X drive motor 50. Is moved in a direction horizontally orthogonal to the driving direction (the front and back directions of the paper in FIG. 3). That is, the table drive device 5 can move the nozzle 20 and the work W relatively in the XY directions.

When the valve 32 of the raw material gas supply device 3 is opened, the raw material gas in the cylinder 31 flows out to the supply pipe 30 and is supplied to the discharge pipe 2. The flow rate of the raw material gas is adjusted by the opening degree of the valve 32.

The electromagnetic wave oscillator 10 is driven in parallel with the supply work of the raw material gas. The raw material gas in the discharge tube 2 is turned into plasma by the electromagnetic wave M. The active species gas G is generated by plasma conversion of the gas. The active seed gas G is guided by the nozzle 20 of the discharge tube 2 and is ejected from the opening 20a of the nozzle 20 toward the surface of the work W.

In parallel with the injection of the active seed gas, the table drive device 5 is controlled by the table drive control device 47, and the work table 40 moves in the XY directions at a pre-calculated speed along a predetermined trajectory.

The injected active seed gas chemically reacts with the material on the surface of the work. Since the product produced by this chemical reaction is gaseous, the product can be easily removed (flushed) from the field. As a result, the material is removed from the surface of the work W.

Since the amount removed is substantially proportional to the time the material surface is exposed to the active seed gas, the amount removed is controlled by controlling the relative movement speed between the work W and the nozzle 20. This relative moving speed is determined based on the data of the unevenness of the work W measured in advance, that is, the position-thickness data.

The electromagnetic wave output control unit 6 includes a pressure gauge 61, an etching rate calculator 62, an etching rate function device 63, a cumulative usage time timer 64, a start elapsed time timer 65, and an electromagnetic wave output control device 66.

The pressure gauge 61 is provided in the vicinity of the plasma generating portion 21 forming a part of the discharge tube 2 and on the upstream side thereof. This makes it possible to accurately measure the pressure inside the discharge tube 2 while preventing the pressure gauge 61 from being damaged by the active seed gas G plasmalized in the plasma generating section 21 of the discharge tube 2. The etching rate calculator 62 is a predetermined etching rate function stored in the etching rate function device 63, and determines the correspondence between the pressure in the discharge tube 2 detected by the pressure gauge 61 and the etching rate. The etching rate is calculated from the measured value of the pressure gauge 61 based on the represented etching rate function.

Further, at this time, the etching rate calculated above can be corrected according to the cumulative usage time and the elapsed start time. Here, the cumulative usage time is the time measured by the cumulative usage time timer 64, and is the cumulative usage time from the start of use of the discharge tube 2 to the present. The cumulative usage time is an index indicating the deterioration state of the discharge tube 2 (for example, the amount of deposits inside the discharge tube 2).

Further, the start elapsed time is the time measured by the start elapsed time timer 65, which is the time elapsed from the start of this local dry etching apparatus to the present. The elapsed start time is an index indicating the degree of temperature rise of the plasma generating unit 21, that is, the degree of warming up.

The electromagnetic wave output control device 66 is based on the calculated value of the etching rate calculator 62 or the calculated value corrected by the cumulative usage time and the elapsed start time, so that the etching rate becomes constant. Controls the output of 10. As a result, the etching rate is stabilized, and the error caused by the change in the etching rate as described above can be reduced.

An example of the processing operation in the local dry etching apparatus of the present invention is shown below. First, the carry-in / carry-out door 45 of the vacuum chamber 4 under vacuum is opened, the work W is carried into the vacuum chamber 4 by a robot (not shown), placed on the work table 40, and sucked and gripped. When the work W is adsorbed on the work table 40, the carry-in / carry-out door 45 is closed, the valve 32 is opened, and the raw material gas in the cylinder 31 is sent to the discharge pipe 2.

The electromagnetic wave oscillator 10 is operated to turn the raw material gas in the discharge tube 2 into plasma to generate the active seed gas G and eject it from the nozzle opening 20a. Next, the X drive motor 50 and the Y drive motor 51 are driven to move the work table 40 from the retracted position so that the work W is below the opening 20a, and the nozzle speed calculated in advance (for each region). Scan with).

During this local dry etching process, the pressure in the discharge tube 2 is measured by a pressure gauge 61 provided in the vicinity of the plasma generating portion 21 in the discharge tube 2. Using the measured value and the etching rate function stored in the etching rate function device 63 in advance, the pressure threshold in the discharge tube 2 so as to obtain a desired etching rate is calculated in advance by the etching rate calculator 62. I will do it. The threshold value is compared with the measured value of the pressure in the discharge tube 2, and if the measured value exceeds the threshold value, the pressure in the discharge tube 2 is set to the threshold value by the electromagnetic wave output control device 66 before processing the next workpiece. The output of the electromagnetic wave oscillator 10 is controlled by using the etching rate function obtained in advance so as to be within the range of. This makes it possible to process the work W at a desired etching rate.

Further, the cumulative usage time (time from the start of discharge) from the start of use of the discharge tube 2 to the present may be used when controlling the output of the electromagnetic wave oscillator 10 described above. In this case, the cumulative usage time timer 64 measures the cumulative usage time from the start of use of the single discharge tube 2 to the present, and the relationship between the cumulative usage time and the deterioration state of the discharge tube 2 (function). ) Is obtained in advance by the etching rate calculator 62. By correcting the function with respect to the etching rate function stored in the etching rate function device 63 in advance, it is possible to reduce the amount of deviation from the desired etching rate as much as possible.

Further, the elapsed time of continuous operation from the start of the local dry etching apparatus to the present may be used when controlling the output of the electromagnetic wave oscillator 10 described above. In this case, the start elapsed time timer 65 measures the elapsed time from the start of the local dry etching apparatus to the present, and the start elapsed time and the temperature rise state of the discharge tube 2, particularly the plasma generation unit 21. The relationship (function) with the temperature rise state is obtained in advance by the etching rate calculator 62. By correcting the function with respect to the etching rate function stored in the etching rate function device 63 in advance, it is possible to reduce the amount of deviation from the desired etching rate as much as possible.

Further, it may be used when controlling the output of the above-mentioned electromagnetic wave oscillator 10 from the amount of work W taken after the local dry etching process. In this case, the thickness or shape of the work W before and after machining is measured by a work measuring instrument (not shown), and the work allowance amount due to machining is calculated. Since the electromagnetic wave output is proportional to the calculated allowance amount, if the threshold value of the set allowance amount is exceeded, the output of the electromagnetic wave oscillator 10 is controlled by the electromagnetic wave output control device 66 before processing the next workpiece. May be good. This makes it possible to reduce the amount of deviation from the desired etching rate as much as possible.

After the flattening is completed, the work table 40 is moved to the retracted position, and when the loading / unloading door 45 is opened, a robot (not shown) takes out the finished work W and puts the unprocessed work W into a vacuum chamber according to the procedure described above. Bring it into 4.

Although the control of the output of the electromagnetic wave oscillator 10 described above is reflected in the next local dry etching process in which the local dry etching process is performed, it may be performed at any time during the same local dry etching process.

In addition, the main reason why the elapsed start time affects the etching rate is that the parts that come into contact with the active species gas G, such as the plasma generating part 21 and its vicinity, are not warmed up at the time of starting, and the temperature rises after a while after starting. Since it is considered that the steady state will be reached soon, it is possible to exclude the elapsed start time from consideration if the warm-up operation is performed for a certain period of time.

Further, the influence of the cumulative usage time is that the inside of the plasma generating portion 21 of the discharge tube 2 reacts with the generated active seed gas G as the use continues, and the inside (inner wall) of the plasma generating portion 21 of the discharge tube 2 deteriorates. Is believed to occur because of. Since this effect progresses at a very slow rate, it is not always necessary to have it performed frequently and automatically, and it is possible to correct it manually.

Further, when the local dry etching apparatus is on standby, the temperature of the portion where the active seed gas G contacts, such as the plasma generating portion 21 and its vicinity, may not reach the desired etching rate. It is also possible to replace the elapsed time of the temperature change during standby by the local dry etching apparatus with time, and simply control the output of the electromagnetic wave oscillator 10 by the elapsed time to obtain a desired etching rate.

As described above, according to the local dry etching apparatus of the present invention, local dry etching is corrected so as to maintain a constant etching rate based on the pressure of the plasma generating part, the cumulative usage time, and the elapsed start time. Processing can be performed, and processing errors can be extremely reduced.

1 Plasma generator 10 Electromagnetic wave oscillator 100 Plasma generator 101 Nozzle 11 Electromagnetic wave transmission means (waveguide)
12 Reflector (short plunger)
120 Worktable 13 Stub tuner 14 Isolator 2 Discharge tube 20 Nozzle 20a Opening 21 Plasma generator 3 Raw material gas supply device 30 Supply pipe 31 Bomb 32 Valve 33 Flow controller 4 Vacuum chamber 40 Worktable 401 Wafer support surface 402 Heater 41 Vacuum pump 42 Holes 43 Ducts 44 Vacuum pumps 45 Carry-in / carry-out doors 46 Flow control device 47 Table drive control device 5 Table drive device 50 X drive motor 51 Y drive motor 6 Electromagnetic wave output control unit 61 Pressure gauge 62 Etching rate calculator 63 Etching rate function 64 Cumulative usage time timer 65 Start elapsed time timer 66 Electromagnetic wave output control device

Claims (3)

Vacuum chamber,
Nozzle that opens in the vacuum chamber,
Discharge tube connected to the above nozzle,
A work table placed in the vacuum chamber and on which the work is placed,
A table drive that drives the work table,
A table drive control device that controls the table drive device,
Raw material gas supply device for supplying raw material gas to the discharge pipe,
The plasma generating part formed in the discharge tube,
Electromagnetic wave oscillator ,
An electromagnetic wave transmission means for irradiating the plasma generating portion with an electromagnetic wave oscillated by the electromagnetic wave oscillator,
A pressure gauge provided in the vicinity of the plasma generating portion of the discharge tube and on the upstream side thereof in order to detect the pressure of the plasma generating portion.
An etching rate calculator that calculates the etching rate from the measured values of the pressure gauge based on the etching rate function, which is a function obtained in advance and represents the correspondence between the pressure of the plasma generating portion and the etching rate, and the etching rate calculator. ,
A local dry etching apparatus including an electromagnetic wave output control device that controls the output of the electromagnetic wave oscillator so that the etching rate becomes constant based on the calculated value of the etching rate calculator. In the local dry etching apparatus according to claim 1,
The etching rate function is a local dry etching apparatus further characterized by being a function corrected by the cumulative usage time of the discharge tube. In the local dry etching apparatus according to claim 1 or 2.
The local dry etching apparatus is characterized in that the etching rate function is a function corrected by a start elapsed time from the start of the local dry etching apparatus.

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