JPH027520A - Dry-etching equipment - Google Patents

Abstract

PURPOSE:To perform precision etching while the temperature of a wafer is controlled by using a radio frequency voltage with a relatively low frequency by a method wherein a DC voltage is applied to one of a pair of planar electrodes through a low-pass filter and the radio frequency voltage with a frequency less than 1MHz is applied to a pair of the planar electrodes through capacitors. CONSTITUTION:A radio frequency voltage with a frequency less than 1MHz applied to a pair of planar electrodes 25 from an RF source 6 through capacitors 26 is further applied to a wafer 3 and a support table 11 whose temperature is controlled by water cooling or the like from a pair of the planar electrodes 25 through the insulating layer 20 of an electrostatic chuck. With this method, the impedance between the planar electrode and a plasma through an insulating layer 9 closer to the wafer is smaller than the impedance through the other route. Therefore, the plasma is generated above the wafer 3 with satisfactory balance, the distribution of etching is improved, an abnormal discharge in a gap 24 can be avoided and excel 3 ent etching can be performed. Further, as the electrostatic chuck having a pair of the planar electrodes whose applied radio frequency voltage is prevented from flowing into a DC source 22 by low-pass filters 21 is employed, the sttraction force is not degraded and a stable cooling effect can be obtained.

Description

[Detailed Description of the Invention] [Overview] Regarding dry etching equipment used in the manufacture of semiconductor devices, a high frequency wave having a frequency of less than 1 MHz, which is one of the relatively low frequencies, is applied to generate ion energy. The purpose is to make the control easier, and at the same time, with the electrostatic chuck, there is no thermal contact between the wafer and the dry etching system, so as to always obtain a good surface cooling effect. , etching workpiece 3, insulating layer 2
In an etching apparatus VC, etching is performed in plasma by applying a high frequency voltage using an electrostatic adsorption mechanism 200 having at least a pair of planar electrodes 25 embedded in an insulating l620. A DC voltage is applied between the pair of plane electrodes 250, and a high frequency voltage is applied to the pair of plane electrodes in a superimposed manner so as to be etched. 1 ; Constructed to be weak at less than 5ilXz.

[Industrial application field]

The present invention relates to drying and etching equipment used for manufacturing semiconductor devices.

In recent years, with the mass production and miniaturization of semiconductor devices, high-speed and high-precision dry and etching techniques are in demand. For this reason, plasma and etching equipment are required to etch fine patterns of semiconductor elements.

[Conventional technology]

Dry, etching technology, plasma etching.

Silicon (Si)-silicon dioxide (S) is
i01), Si compounds such as silicon nitride (Si, N4), as well as aluminum (AI), tungsten (W
), molybdenum (Mo), titanium (Ti), and other metals, and polymers such as resist.

And these include reactive ion, etching (
RIE) I child microtono resonance, etching (ECR
), ff; 70-etching, ion beam, etching, etc. %f! Iik's story is lol. Among these, t
The RIE-? RF
Bias ECR, etching (also known as RF bias m4
Microwave, etching) etc. are semiconductors! ! The production of tan has been widely used for a long time.

s3 diagram rx, R of an example of conventional dry etching equipment
This is a schematic diagram of an IE device. First, wafer 3
is installed on the RF* pole 2, and after once exhausting the inside of the retainer chamber 1 through the exhaust port 8, the gas for plasma generation is supplied from the gas introduction lower part. , into the chamber/bar, and adjust the gas flow to a pumping speed of 1 to obtain a predetermined pressure. Next, RFt pole 2 is
・High frequency (13, 56
MHz, etc.) to generate plasma in the chamber 1. The plasma exposes the surface of the wafer 3 and causes it to react, thereby etching the wafer 3.

In FIG. 3, the wafer is mounted and etched against gravity to prevent aI@ from adhering to the surface. In order to selectively etch only the target areas, a resist is applied to the surface of the sea urchin as an etching mask, as is well known. , during etching, the wafer 3 is exposed to heat of chemical reaction with plasma, ions or t-rays, etc.! A It is heated by the incident energy. In this case, if a resist is used as a mask, the resist on the surface of the wafer 3 will burn at about 130° C., so the wafer 3 will need to be cooled.

Furthermore, since the etching process is easily affected by temperature, precise control of 1 ul/Jl of the wafer is extremely important in forming fine patterns.

For that purpose, use +'ff, wafer 3 and water cooling to place it on! Between the RFt pole 2 and the 1M degree RFt pole,
There are certain A's that improve heat transfer 4t, including Ueno 3,
It is necessary to bring it into close contact with the RFt pole 2. For this reason, conventionally,
An electrostatic suction device 4111 (hereinafter referred to as electrostatic chuck) is installed on the RF electrode to bring the wafer into close contact with the electrostatic chuck, increase the contact area, establish thermal contact, and effectively control the temperature of the wafer. things are being done.

Compared to the mechanical clamp method, which mechanically holds the urchin/S, this method using an electrostatic chuck does not have anything that comes into contact with the front side of a wafer, so there is less dust generation and wafer contamination during the etching process. There are advantages.

FIG. 4 is a diagram showing an example of such a conventional electrostatic chuck. This figure shows that the third RFit pole 2 is
44747, the electrostatic chuck part is shown enlarged. This electrostatic chuck consists of a pair of flat electrodes 251 embedded in the insulating layer 20, and a DC voltage is applied to the flat electrodes 25 from the direct fL power source 22 through the low-pass filter 21A. By doing this, Ueno 13 that can be placed at a floating potential
The wafer is attracted to the electrostatic chuck 200 by the Kuhn force acting between the and the pairs of flat Llo electrodes. This electrostatic chuck 200 can always attract the Ueno 13' IC static chuck 200 even when etching is not performed, as long as a DC voltage is applied.

Further, the glare force of the electrostatic chuck hardly depends on the presence or absence of high frequency applied to the RF electrode 2 and the number of cycles thereof.

Further, as shown in FIG. 5, as another electrostatic chuck, an electrostatic chuck such as Japanese Patent Publication No. 56-53853 has been available. This is because the electrode 102 that applies the DC voltage is different from the electrostatic chuck described above, and has only one single pole.
The RF% source 106 and the DC power source 122 are connected to the same electrode 102.
is the one that is connected. This electrostatic chuck is
Unlike the electrostatic chuck shown in FIG. 4 mentioned earlier, the chuck is generated by the self-bias voltage of the wafer 103, which is generated when a high-frequency voltage is applied.
When kt pressure is not applied, that is, when etching is not performed,
I want it to work as an electrostatic chuck.

Using the two types of electrostatic chucks mentioned above to cool the wafer,
Conventional dry etching equipment such as RIE that uses a high frequency of 13.56 MHz to excite plasma.
When used in No. 1, fine processing of aluminum and polysilicon is possible.

However, in recent years, copper (Cu) has been attracting attention as a wiring material to replace aluminum. Aluminum-copper (Al
-Cu) alloy was difficult to etch.

[Problem to be solved by the invention]

It is said that in order to etch Cu or AI-Cu f, it is necessary to improve sputtering performance.

For this reason, when using Al-Cu alloy or Cuf, one way to control the ion energy is to lower the frequency of the applied high frequency in order to reduce the scorching property. , R.F.
Applying it to electrodes is being considered. Hereinafter, in this specification, 1M
High frequencies below Hz will be explained.

In the conventional apparatus using the static chuck shown in FIGS. 4 and 5, simply applying a high frequency of less than I MHz to the RFt pole does not provide a sufficient cooling effect, or etching the RFt pole. There were problems such as unevenness.

First, when using a single-pole electrostatic charger as shown in Fig. 5, the RFt pole 102 used for plasma generation is
However, when applying a high frequency of less than 1 MHz, there was a problem as described above. As is well known, the self-bias voltage of the wafer depends on the frequency of the applied high frequency.
．． If the 56 MHz isoperiodic α number is high, it is sufficient to attract the wafer to the electrostatic chuck. However, if there is a high frequency of 1 fl with a low frequency of less than 1 MHz, the voltage decreases to a self-bias voltage, so that the electrostatic chuck cannot obtain a sufficient adsorption force. Therefore, a contact area between the wafer 103 and the electrostatic chuck cannot be obtained, and a sufficient cooling effect cannot be obtained.

In addition, when a high frequency of less than 1 MHz is applied to the RF'ilLm102, the adsorption force of the electrostatic chuck decreases, and in extreme cases, the Ueno・103 and the dielectric film 205 (the fourth factor, the insulating layer 20) A gap 124 is created between the two (corresponding ones). Of the impedances, contactance is inversely proportional to the distance between the electrode 102 and the opposing electrode 104 and the frequency.
04 (as shown) is larger than the impedance Z2 (as shown) between the electrode 102 and the counter electrode 104. As a result, the electrode 10
VC1RF power is concentrated in the peripheral area of 2, and plasma 1
11 (shown) is generated unevenly. Note that plasma 111 is only partially shown to avoid cluttering the diagram.
If you understand, 1-< is a large drawing.

, the etching rate depends on the plasma density.C1 In this way, when the plasma is generated regardless of VC, etching occurs quickly at the periphery of the wafer 103, while at the center of the wafer 103, etching is slow. , the electrostatic chuck at the 7th part is damaged because the etching is no longer done and abnormal radiation areas are concentrated in the peripheral area of the wafer 103. Furthermore, in this electrostatic chuck, simply applying the output of the DC power supply 122 to the electrode 102 without applying a high frequency does not transmit the charge to the wafer 103, so no Coulomb force is generated and the chuck is not attracted. I can't get power. In other words, the adsorption force of the electrostatic chuck is only lost during plasma generation, which causes inconveniences such as poor workability.Secondly, when using the silent ζ chunk shown in factor A4, R
When a single frequency of less than 1 MHz was applied to the F electrode 2, the following problem occurred.

In this electrostatic chuck, in order to prevent the electrostatic chuck itself from being etched, the size of the wafer is smaller than that of the wafer placed on it.
In order to protect the + side, a 'tJ1 pole cover 23 is provided. In order to ensure close contact between the electrostatic chuck 200 and the wafer 3, a slight gap 24 is provided between the wafer and the electrode cover 23.

When the frequency applied to the RF electric camellia is a low frequency such as 1 MHz, the electrode cover 23. Ueno 13 and ltF electric coffin 2
The impedance gap between the plasma (not shown) and the plasma (not shown) through the gap 24 is smaller than other paths. Then, the RF power is
This will affect the gap 24 between the electrode 2 and the wafer 3, and the power applied to the wafer 3 will become very small. As a result,
Plasma is strongly generated only at the periphery of the 9eva 3, and etching is faster at the periphery, while the central part is hardly etched, and abnormal discharge concentrates in the gap 24, so that the electrostatic chuck in that area is The insulating layer will be damaged.

In the case of this electrostatic chuck, the adsorption force does not depend on the frequency of the applied high frequency wave, so there is no change in the adsorption force. Therefore, in the apparatus using the electrostatic chuck shown in FIG. 4, it is necessary to generate stable and uniform plasma even when the applied high frequency is less than 1 MHz.

The present invention was created to eliminate the drawbacks of the conventional dry etching equipment, and it reduces the frequency of the high frequency applied to the RF electrode to less than I MHz, making it easier to control the ion energy, and at the same time The object of the present invention is to provide a dry etching apparatus that makes thermal contact with a wafer using an electrostatic chaff and constantly obtains a sufficient cooling effect.

[Means to solve the problem]

FIG. 1 is an illustration explaining the principle of the present invention. Electrostatic charger 20
0's absolute #! A DC voltage 22 is applied to at least one of the pair of flat electrodes 25 embedded in the lattice 20 through the Cubase filter 21 .

Furthermore, this same planar electrode 25 is connected to a relatively low frequency high frequency signal, for example, I, through a capacitor 26.
All high frequencies below MHz are applied.

[Effect]

In the present invention, as shown in FIG.
An electric current is applied from a pair of flat electrodes 25 in 00 to the support table 11 and wafer 3 whose temperature is adjusted by water cooling or the like via the insulating layer 20 of the electrostatic chuck.

By doing so, the impedance between the insulating layer 9 on the side closer to the wafer and the plasma on the wafer is smaller than that by other routes, such as a route from the side of the electrodeposition through the gap 24. Therefore, plasma is generated in a well-balanced manner on the wafer 3, and as a result, the etching distribution is improved and abnormal discharge does not occur in the gap 24.
! 1. Good etching can be performed as in the case of using a high frequency of 1 MHz or higher. In addition, since an electrostatic charger having a pair of planar electrodes is used, even if the high frequency applied to the RF electrode is low, less than 1 MHz, the adsorption power will not decrease, and a stable cooling effect can be achieved. can get.

[Example 1] The present invention will be described in detail according to the first aspect.

The RIE apparatus shown in FIG. 3 has the electrode shown in FIG. i1 of the present invention,
Etching was performed using a dry etching device.

In one embodiment of the present invention, a tO loose chuck having the structure shown in FIG. 1 was used. The insulating layer 20 of the electrostatic chuck 200 is made of resin such as silicone resin or polyimide, or ceramic such as alumina.

When this insulating layer 20 is exposed to plasma, it is etched and consumed quickly, and the gas generated at that time does not adversely affect the etching process. Make the wafer 3 smaller than 9. Cover the wafer 3 with a 200f electric shock to prevent exposure to plasma. At this time, an electrode cover 23'ft is installed below the wafer 3 which protrudes like a canopy.

This electrode cover 23 is made of quartz, alumina, etc., so as not to have an adverse effect on the etching process. The thickness of the insulating layer 20 is 200 μms on the side 9 closer to the wafer 3.
The distance 10 far from the wafer 3 is approximately 300 μm, and plasma is generated on the wafer 3 in a well-balanced manner. That is, since the pair of planar electrodes 25 are embedded in the insulating layer 20, the electrodes that apply high frequency to the wafer are closer together in the conventional example shown in FIG. 4, so that RF power can be efficiently applied to the wafer. Conveyed. Further, the polarity of the DC power source 22 is irrelevant to the function of the electrostatic chuck, and it is sufficient to apply a DC voltage to the pair of planar electrodes 25. Note that the low-pass filter 21 is provided to prevent the applied high frequency from flowing to the DC 11L source.6 In Fig. 1, the means for cooling the electrostatic chuck is omitted to avoid complicating the cause. To cool the electrostatic chuck, a coolant such as water is flowed into the support stand 11 that holds the electrostatic chuck, and the electrostatic chuck is cooled through the support stand. In order to improve heat conduction between the wafer and the electrostatic chuck, helium (
There is a gas conduction cooling method that uses a gas such as He 2 ).

Using the electrostatic chuck as described above, S
i oxide film with a thickness of 1 am (D Al -Cu (Cu
4%) alloy was etched.

First, after adsorbing the wafer 3 to the electrostatic chuck 200,
The inside of the chamber is evacuated from the exhaust port 8, and a gas for plasma generation is introduced into the chamber 1 from the gas introduction lower part to a predetermined pressure. Next, through matching box 5, R
From the F power supply 6, through a capacitor 26 of several thousand pF,
Etching was performed by applying a high frequency of 400 KHz to generate plasma in the chamber 1. As a mask, it irradiates with ultraviolet rays and performs a so-called deep UV cure.
200'O base/1 line fc positive resist 0FPR80
0 (manufactured by Tokyo Ohka) and a resist baked at 110°C) OFPR8800 (manufactured by Tokyo Ohka).The etching conditions were as follows: The gas was a mixed gas of silicon tetrachloride and chlorine (Si
C14+CI,), gas pressure is 0.05 Torr,
Etching was performed for 3 minutes at a 4-frequency input of 500 W (0,1 freezing) and a wafer temperature of 100°C. Result is,
, there are no unetched areas (residues), and the etching variation within the convex surface of the 5-inch wafer is:
Good etching of 15% was achieved.

Due to the cooling effect via the electrostatic charger 200, the resist was not thermally damaged and no undercut occurred.

On the other hand, when using the conventional electrostatic chuck shown in FIG. 4 under the same conditions, plasma was generated only at the periphery of the wafer 3, and the periphery of the wafer 3 was etched, but the central part No etching was performed 〇 [Example 2] As shown in FIG. 2, a triode type etching apparatus, which is a modification of the RIE shown in FIG. 3, is an apparatus to which the present invention is applied! Etching of the Si) wrench was performed using the following.

The triode type etching apparatus applies a high frequency of less than I MHz, such as 100 KHz, to a pair of planar electrodes 25 on the side of the wafer 3 through a capacitor 26 of several thousand pF.
Further, this device is different from the RIE device described above in that a high frequency of 1 MHz or more, such as 13.56 MHz, is applied to the counter electrode 4. This generates a 13.56MHz tephrasma and accelerates ions at 100KHz, thereby independently controlling the generation of radicals and ion energy.
To perform etching with higher precision and efficiency,
Chill with the desired etching equipment.

In this device, Si sulfide I with a thickness of 1/I 111
I5! was used as a mask, and a diameter of 1μ was placed on a 6-inch Si wafer.
m.

Holes with a depth of 7 μm were etched. , the etching conditions were as follows: promotrifluorometa y was used as the etching gas.
The flow rate of (CBrFs) is 2.5 sccm s. The frequency of the RF power source 6-b applied to the planar electrode 25 on the wafer side is 100 KHz, its high frequency input is 180 W, and the frequency of the RFlu source 6-a on the opposite electrode is 13. .56MHz.

Its high frequency input is so ow and the pressure is 0.5 Tor
It's r.

Note that the cooling method is the same as in Example 1.

When the same electrostatic chuck as in Example 1 was used, the etch rate was 1.2 μm/min, the selectivity to the S+ oxide film was 10, and it was possible to etch dead stone. Due to the cooling effect of the electrostatic chuck 200 having a pair of planar electrodes 25, the temperature of Ueno-3 was cooled to 50°C to 60°0, resulting in good etching. However, when this electrostatic chuck 200 is not used, the temperature of the wafer 3 rises to 200° C. to 300° C., and so-called bowing, which is an arcuate undercut, occurs.

Furthermore, under the same conditions, when the conventional No. 4 electrostatic chuck is used, abnormal discharge occurs in the gap 24 between the wafer 3 and the electrode cover 23, the insulating film of the electrostatic chuck 200 is destroyed, and the normal electrostatic chuck is , no etching was performed.

In the above two examples, the frequency of the high frequency applied to the pair of planar electrodes is not limited to that used in the examples, and it goes without saying that it can be changed to obtain the desired ion energy. .

Further, even if the frequency of the high frequency is changed, the effects of the present invention remain the same.

Although the present invention has been described above using examples, various modifications such as the wafer temperature control mechanism can be made without departing from the spirit of the present invention, but these are not excluded from the present invention by the examples. , [Effects] As described above, according to the present invention, in a dry etching apparatus, plasma generation is performed using a relatively low frequency high frequency wave with good controllability of ion energy, for example, I
It has the effect of being able to use a high-speed waveform of less than MHz and controlling the wafer temperature at the same time, resulting in no residue and good distribution of a'&! The production of highly integrated semiconductor devices that can be etched and have high-density patterns will greatly contribute.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of the present invention, FIG. 2 is an explanatory diagram of an embodiment of the present invention, and FIG. 3 is a schematic diagram of an etching apparatus. 4 and 5 are partially enlarged views of a conventional electrostatic chuck. 1 and 101...Chamber 2 and 102...RF electrode. 3 and 103...Wafers 4 and 104...Counter electrodes 5 and 105...Matching box (g1 combiner)
6 and 106...RFIK source. 7・・・・・・・・・・・・・・・Gas inlet 8...
......Exhaust port 9...Insulation 1-10 on the side closer to the wafer...Insulating layer 11 on the side farther from the wafer...・Support stand 20...Insulating layers 21 and 121...Low pass filters 22 and 12
2...DC power supply 23... Electrode cover 24 and 1
24... Gap 25... Pair of flat electrodes 26
・・・・Capacitor electrostatic chuck・・・Dielectric film・・・Plasma agent Patent attorney Teiji Igata Unexploded vPItr + Principle of male concave RIE process・General view of notching device Kaya j map, book, A color day 8 one blow 77tZflσ) 8LE January figure Tsutomu 2 figure conventional pa 11 chuck t+ -4f'I s u :suko nine %4 figure

Claims (1)

[Claims] 1. An etching workpiece (3) is adsorbed using an electrostatic adsorption mechanism (200) having at least a pair of planar electrodes (25) embedded in an insulating layer (20), In an etching apparatus that performs etching in plasma by applying a high frequency voltage, a DC voltage is applied between the pair of planar electrodes (25), and a high frequency voltage is applied to the pair of planar electrodes in a superimposed manner. It is characterized by etching with
Dry etching equipment. 2. The dry etching apparatus according to claim 1, wherein the high frequency applied to the planar electrode (25) has a frequency of less than 1 MHz.