WO2018142179A1

WO2018142179A1 - Apparatus for applying a deposition onto a substrate by a deposition process and method for carrying out a deposition process by use of such an apparatus

Info

Publication number: WO2018142179A1
Application number: PCT/IB2017/000931
Authority: WO
Inventors: Daniel Brors
Original assignee: C4E Technology Gmbh
Priority date: 2017-02-02
Filing date: 2017-07-31
Publication date: 2018-08-09

Abstract

The invention relates to an apparatus (1) for applying a deposition onto a substrate (2) by a deposition process, wherein the apparatus (1) comprises a first vacuum chamber (3) which can be evacuated by means of a first evacuation pump (4). To improve the deposition process the invention is characterized in that a second vacuum chamber (5) for receiving the substrate (2) is arranged within the first vacuum chamber (3). Furthermore, the invention relates to a method for carrying out a deposition process for applying a deposition onto a substrate by use of such an apparatus.

Description

Apparatus for Applying a Deposition onto a Substrate by a Deposition Process and Method for Carrying out a Deposition Process by Use of such an Apparatus

The invention relates to an apparatus for applying a deposition onto a substrate by a deposition process, wherein the apparatus comprises a first vacuum chamber which can be evacuated by means of a first evacuation pump. Furthermore, the invention relates to a method for carrying out a deposition process for applying a deposition onto a substrate by use of such an apparatus.

Various vacuum deposition processes such as PVD, CVD, PECVD and MB are well known in the art as well as respective apparatuses in which the deposition process can be carried out.

At such deposition processes two problems exist with the typical plasma deposition system. One problem is the formation of a secondary plasma formed in the evacuated chamber resulting in deposition on the walls of the chamber. In addition, the intensity of this secondary deposition can vary depending on the deposition on the walls of the vacuum chamber. This variation in the secondary plasma causes a variation in the primary plasma in the area where the deposition of a substrate takes place resulting detrimentally in variations in the deposition rates on the substrate. Another issue with the pre-known deposition apparatuses is a potential atmospheric contamination in the vacuum area. Any vacuum leak in the vacuum chamber can cause contamination in the deposited film on the substrate.

It is an object of the present invention to propose an apparatus as well as a method for using the same by which the above mentioned problems can be eliminated or at least decreased.

The solution of this object according to the invention is characterized in that the apparatus has a second vacuum chamber for receiving the substrate which is arranged within the first vacuum chamber.

The second vacuum chamber is preferably evacuated by means of a second evacuation pump.

The second vacuum chamber is preferably sealed against the first vacuum chamber so that different pressures can be maintained in the vacuum chambers during the deposition process.

A preferred embodiment provides that the second vacuum chamber is arranged concentrically within the first vacuum chamber (with respect to a longitudinal axis of the apparatus).

The second vacuum chamber can be electrically isolated against the first vacuum chamber; alternatively the second vacuum chamber can be electrically connected with the first vacuum chamber. The first evacuation pump is preferably a rotary vane pump, while the second evacuation pump is preferably a scroll pump. Means are preferably provided for feeding a process gas into the second vacuum chamber.

The method for carrying out a deposition process for applying a deposition onto a substrate by use of an apparatus as described above is characterized according to the invention in that before the deposition the first vacuum chamber is evacuated to a first pressure and the second vacuum chamber is evacuated to a second pressure, wherein the ratio between the first pressure and the second pressure is between 1 :5 to 1 :50. Preferably, the ratio between the first pressure and the second pressure is between 1 : 10 to 1 :30.

The deposition process is typically a PVD process (physical vapor deposition process), a CVD process (chemical vapor deposition process) or a PECVD process (plasma-enhanced chemical vapor deposition process). A preferred embodiment of the method proposes that the first pressure in the first vacuum chamber is below 30 mTorr, preferably below 20 mTorr (1 bar = 750,062 Torr).

At the other hand the second pressure in the second vacuum chamber is preferably between 50 to 600 mTorr, specifically preferred between 50 to 400 mTorr.

Thus, the present invention provides a system with two vacuum chambers which allow for a vacuum pressure differential preferably up to 20 times between the inner vacuum chamber and the outer vacuum chamber. Such an arrangement virtually eliminates possible atmospheric contamination and allows for greater process control particularly with respect to hollow cathode deposition in the inner chamber.

In the prior art various vacuum deposition processes such as PVD, CVD, PECVD and MB have typically utilized a single vacuum chamber. A single vacuum chamber is simple in construction and typically adequate for most deposition processes, however there are certain advantages in using two (concentric) vacuum systems according to the invention whereby an inner vacuum chamber is surrounded by an external vacuum chamber, wherein the vacuum pressure in the outer chamber is typically 20 times lower than the inner vacuum chamber. Such an arrangement effectually eliminates potential contamination from any leaks in the outer vacuum chamber. In addition, it has been found that a two chamber vacuum system eliminates extraneous plasma formation outside of the inner vacuum chamber, specifically when using PECVD depositions.

The proposed system comprises two vacuum chambers, an inner chamber and a surrounding outer vacuum chamber. The inner vacuum chamber is used for the deposition processes, while the outer vacuum chamber, which is preferably 20 times lower in pressure the than the inner chamber, prevents any atmospheric contamination from entering the inner chamber resulting in improved quality of deposited films in the inner chamber.

The inner and outer vacuum chambers are typically evacuated with independent vacuum pumps to eliminate any cross contamination due to back streaming from one vacuum chamber to the other vacuum chamber. The proposed vacuum system also allows for different types of vacuum pumps for the two chambers, for example the outer vacuum chamber could be pumped with a rotary vane pump and the inner vacuum chamber could be pumped with a scroll pump. If a one vacuum chamber deposition system was utilized according to the prior art, using a rotary vane pump could cause contamination due to back streaming, while if a scroll pump were utilized to eliminate back streaming, the scroll pump would not have sufficient pumping capacity to effectively evacuate the entire vacuum chamber. Utilizing the proposed two vacuum chambers with separate (different) vacuum pumps allows for optimization of the deposition system. In addition, since the outer vacuum chamber is preferably 20 times lower in pressure, there is no extraneous plasma formation outside of the inner vacuum chamber, such as at the electrical feedthroughs or the exterior of the inner chamber.

Thus, the main aspects of the present invention are as follows:

The proposed apparatus has as an outer vacuum chamber enclosing an inner vacuum chamber. The outer and inner vacuum chambers are preferably attached to separate vacuum pumps.

Preferably, the outer vacuum chamber pressure is a minimum of 20 times lower than the vacuum pressure of the inner vacuum chamber. More specifically, the outer chamber vacuum is typically and preferably less than 20 mTorr during CVD processing.

Beneficially, a vacuum less than 30 mTorr will not support a plasma, therefore there is no plasma present in the outer chamber. Dark space shields are not necessary in the outer chamber since the pressure is less than 30 mTorr.

The inner chamber can be electrically connected to the outer chamber or electrically isolated from the outer chamber. The inner chamber electrically connected to the outer chamber allows the inner chamber to be operated as a conventional CVD system. The inner chamber electrically isolated from the outer chamber allows the inner chamber to operate as a hollow cathode system. Hollow cathode operation of the inner chamber allows for high CVD deposition rates. Hollow cathode operation allows for CVD deposition rates in excess of 10 microns per minute at 200 mTorr pressure.

In the drawings embodiments according to the state of the art and according to the invention are shown.

Fig. 1 shows schematically an apparatus for applying a deposition onto a substrate by a PECVD vacuum deposition process according to the state of the art, Fig. 2 shows schematically an apparatus for applying a deposition onto a substrate by a PECVD vacuum deposition process according to a first embodiment of the invention, shows schematically an apparatus for applying a deposition onto a substrate by a deposition process according to a second embodiment of the invention, wherein a hollow cathode is employed, and shows schematically an apparatus for applying a deposition onto a substrate by a deposition process according to a third embodiment of the invention, wherein the system is configured for conventional PECVD.

In Fig. 1 a typical PECVD deposition system is shown according to the state of the art.

Fig. 1 shows a vacuum chamber 3 enclosing space 101 which is evacuated through a gate valve 114 to a vacuum pump 4. Gate valve 114 is attached to the chamber 3 with appropriate O-Ring seals, not shown, and vacuum pump 4 is attached to gate valve 114 with appropriate O-ring seals, not shown. A substrate 2 was placed in the vacuum chamber 101 and electrically attached to negative electrical lead 109. The electrical lead 109 passes through an electrical feed through 108 which electrically isolates the lead 108 from chamber 3 and provides a vacuum seal for lead 109 and chamber 3. After the substrate 2 is placed in the vacuum chamber 3 through an appropriate vacuum tight door, not shown, the gate valve 114 is opened and the chamber space 101 is evacuated to an appropriate vacuum, typically less than 10 mTorr.

Once the appropriate vacuum is reached in vacuum chamber 3, process gases 116 are allowed to enter the gas distribution chamber 104 through tube 7 (means for feeding process gas into the vacuum chamber). The gases 116 flow into the vacuum space 101 through openings 105 in the gas distribution chamber 104. The process gases 116 flow through area 112 and into the vacuum chamber 3 and flow out at 115 through gate valve 1 14 and into vacuum pump 4. The gas flow 116 is controlled, typically with mass flow controllers (not shown), such that the pressure in chamber 3 reaches an appropriate level for the required deposition process, typically 50 to 300 mTorr. When the proper pressure is reached in chamber 3, power supply 1 10 is turned on. Power supply 110 can be a DC supply or an RF supply. Fig. 1 shows a DC supply attached to the substrate 2 and gas distribution chamber 104. The negative lead 109 is attached to the substrate 2 through feed through 108 and the positive lead is typically attached to ground 1 17 and chamber 3 which is electrically connected to the gas distribution chamber 104 through gas tube 7.

Another configuration, not shown, electrically isolates the gas distribution chamber 104 from the chamber 3 and the electrical lead 11 1 is attached to the gas distribution chamber.

Power supply 110 is turned on and a plasma 1 12 forms between the substrate 2 and the gas distribution chamber 104 resulting in a deposition onto the surface of the substrate 2.

A dark space shield 107 is placed below the substrate 2 and around the lead 109. Such an arrangement prevents a plasma from forming on the sides and bottom surface of the substrate 2 and the electrical lead 109; however, such an arrangement does not entirely confine the plasma to the area 112 between the gas distribution chamber 104 and the top surface of the substrate 2. A secondary plasma is formed in the space 101 between the substrate 2 and the chamber walls of chamber 2. This secondary plasma is less intense than the plasma in area 112, however this secondary plasma causes a deposition on the walls of chamber 3 which much be routinely removed causing down time of the system. Attaching lead 11 1 to the gas distribution chamber 104 and electrically isolating the gas distribution chamber 104 from the chamber reduces the secondary plasma in space 101, but does not entirely eliminate the secondary plasma and deposition on the walls of chamber 3. The only way to prevent the formation of a secondary plasma is to reduce the pressure in area in the space 101 below 30 mTorr.

Coming now to the present invention reference is made to figures 2 to 4.

The invention eliminates the formation of secondary plasma and virtually eliminates any possible atmospheric contamination caused by vacuum leaks in the vacuum chamber.

Fig. 2 shows an embodiment according to the present invention. The depicted apparatus 1 uses a first, outer vacuum chamber 3 surrounding area 201 which includes a second, inner vacuum chamber 5. The outer vacuum chamber 3 is connected to a gate valve 219 which is connected to a first evacuation pump 4 which evacuates the first, outer chamber 3 through gate valve 219 attached to vacuum pump 4. O-Ring seals are present but not depicted. The second, inner vacuum chamber 5 has a chamber wall 209 connected to a gas injection chamber 203 which process gases 206 enter though gas tube 7 (means for feeding process gas into the second vacuum chamber) and holes 224. The chamber wall 209 is also connected to the chamber wall of the first vacuum chamber 3 which in turn is connected to gate valve 211 which is connected to a second evacuation pump 6. In Fig. 2 the substrate 2 as well as the power supply are not depicted, but also present.

The process gases 206 flow through the process or deposition chamber 226 and the exhaust gases 212 exit through gate valve 211. Such an arrangement allows the deposition chamber 226 to operate at a pressure p2 approximately 20 times higher than the pressure pi in the first, outer vacuum chamber 3. There are no O-Ring seals used between components comprising the deposition chamber 226, such as the surface between the gas injection chamber and the chamber wall 209, etc. There is a slight leakage between the components in deposition chamber 226 and the area 201, however it has been found a pressure differential of 20: 1 between the second, inner chamber 5 and the first, outer chamber 3 is easily obtained without the use of O-Rings or ultra flat surfaces between mating parts.

Fig. 3 shows another embodiment of the present invention. Here the apparatus 1 is configured as a hollow cathode system. The second, inner vacuum chamber 5 serves as hollow cathode and is electrically isolated from the first vacuum chamber 3 by insulator 222 and electrically isolated from the gas injection chamber 203 by insulator 207. An upper filament 208 is placed at the top of second vacuum chamber 5. Filament 208 is electrically attached to electrical lead 213 which is attached to the positive terminal of power supply 216. The lead 213 passes through the chamber wall 202 through an electrical feed through 204. A filament 223 is placed at the lower end of the second vacuum chamber (process chamber) 5. The filament 223 is also attached to power supply 216 through electrical lead 215 which passes through electrical feed through 214. Electrical lead 217 is attached to the wall of the second vacuum chamber 5. Electrical lead 217 passes through the wall of the first vacuum chamber 3 through electrical feed through 221 which is connected to the negative terminal of the power supply 216. In Fig. 3 the substrate 2 is not depicted, but also present.

Process gases 206 are injected into the gas injection chamber 203 through gas tube 7 (means for feeding process gas into the second vacuum chamber). The gases flow into the second vacuum chamber 5 through holes 224 and exhaust gases 212 flow through gate valve 21 1 attached to the second evacuation pump 6.

There is a slight leakage of process gases between the components comprising the deposition chamber 226. Standard machined parts yields pressure differentials of 20: 1 to 30:1 in the second, inner chamber 5 for a pressure range from 50 to 600 mTorr with a preferred pressure range of 50 to 400 mTorr for the pressure p2. With a pressure differential of 20: 1 and a pressure p2 in the second, inner vacuum chamber 5 below 400 mTorr, the first, outer vacuum chamber 3 has a pressure pi which never exceeds 20 mTorr. It has been found that a pressure of more than 30 mTorr is necessary to form a plasma; therefore beneficially there is never a secondary plasma formation in the first, outer vacuum chamber 3.

It has been found that there is no deposition on the chamber walls 202 after 1000 deposition cycles of DLC with an average of 10 microns per deposition cycle. In addition, since the first vacuum chamber operates at a pressure pi less than 20 mTorr while the inner chamber operates at a pressure p2 of at least 50 mTorr, no atmospheric contamination can enter the inner chamber 5 with the deposition chamber 226. Also no dark space shields are necessary in the first, outer chamber 5. In Fig. 4 a further embodiment of the invention is shown. Here, the outer chamber wall 202 of the first vacuum chamber 3 encloses a vacuum space 201 and the second, inner vacuum chamber 5 with in deposition chamber 226 enclosed by a chamber wall 209. A substrate 2 is placed in the second vacuum chamber 5 and is attached to the negative electrical lead 217 which is electrically isolated from the inner chamber wall 209 and is attached to the negative lead of power supply 216. A dark space shield 230 is placed around lead 217 as lead 217 is in the high pressure region of the deposition chamber 226 with the pressure p2.

The positive lead 215 is attached to the first vacuum chamber 3. There are no electrical insulators between the chamber wall 202 and the inner chamber wall 209 and there is no electrical insulator between the gas injection chamber 203. The inner chamber wall 209 is essentially attached to the positive lead 215.

Process gases are injected into the deposition chamber 226 through holes 224 in the gas injection chamber 203. When the deposition chamber 226 reaches the appropriate pressure, power supply 216 is turned on resulting in plasma to form between the inner chamber wall 209 and the substrate 2 resulting in CVD deposition on the substrate 2. There is no secondary plasma in area 201 and there is no chance for atmospheric contamination of the deposited film on the substrate 2. A significant further advantage of the described apparatus and method is a reduced pump down time between deposition cycles. Since there is a pressure differential of 20: 1 between the second, inner vacuum chamber 5 (with the pressure p2) and the first, outer vacuum chamber 3 (with the pressure pi), it has been found that there is no need to evacuate the outer chamber 3 to less than 20 mTorr before starting a deposition cycle.

In a pre-known deposition system as shown in Fig. 1 the vacuum chamber 101 is typically evacuated to less than 10 E-6 Torr before starting a deposition cycle to prevent atmospheric contamination of the deposited film. Evacuation of the chamber 101 to less than 10 E-6 Torr typically takes 20 to 30 minutes.

It has been found that there is no atmospheric contamination of the deposited film as long as the outer vacuum chamber is evacuated to less than 20 mTorr before starting the deposition cycle.

The outer vacuum chamber can typically be evacuated to less than 20 mTorr in 5 minutes or less resulting in greater machine though put.

Reference Numerals;

1 Apparatus

2 Substrate

3 First vacuum chamber

4 First evacuation pump (rotary vane pump)

5 Second vacuum chamber

6 Second evacuation pump (scroll pump)

7 Means for feeding process gas into the second vacuum chamber

101 Enclosed space

104 Gas distribution chamber

105 Opening

107 Dark space shield

108 Electrical feed through

109 Negative electrical lead

1 10 Power supply

1 11 Electrical lead

1 12 Area of plasma

1 14 Gate valve

115 Flow of gas

1 16 Process gas

117 Ground

201 Surrounding area / vacuum space

202 Chamber wall

203 Gas injection chamber 204 Electrical feed through

206 Process gas

207 Insulator

208 Filament

209 Chamber wall

211 Gate valve

212 Exhaust gas

213 Electrical lead

214 Electrical feed through

215 Electrical lead

216 Power supply

217 Electrical lead

219 Gate valve

221 Electrical feed through

222 Insulator

223 Filament

224 Hole

226 Deposition chamber

230 Dark space shield pressures in the first vacuum chamber pressures in the second vacuum chamber

Claims

Patent Claims:

1. Apparatus (1) for applying a deposition onto a substrate (2) by a deposition process, wherein the apparatus (1) comprises a first vacuum chamber (3) which can be evacuated by means of a first evacuation pump (4), characterized in that a second vacuum chamber (5) for receiving the substrate (2) is arranged within the first vacuum chamber (3).

2. Apparatus according to claim 1, characterized in that the second vacuum chamber (5) can be evacuated by means of a second evacuation pump (6).

3. Apparatus according to claim 1 or 2, characterized in that the second vacuum chamber (5) is sealed against the first vacuum chamber (3) so that different pressures (pi , p2) can be maintained in the vacuum chambers (3, 5) during the deposition process.

4. Apparatus according to one of claims 1 to 3, characterized in that the second vacuum chamber (5) is arranged concentrically within the first vacuum chamber (3).

5. Apparatus according to one of claims 1 to 4, characterized in that the second vacuum chamber (5) is electrically isolated against the first vacuum chamber (3).

6. Apparatus according to one of claims 1 to 4, characterized in that the second vacuum chamber (5) is electrically connected with the first vacuum chamber (3).

7. Apparatus according to one of claims 1 to 6, characterized in that the first evacuation pump (4) is a rotary vane pump.

8. Apparatus according to one of claims 1 to 7, characterized in that the second evacuation pump (6) is a scroll pump.

9. Apparatus according to one of claims 1 to 8, characterized in that means (7) are provided for feeding a process gas into the second vacuum chamber (5).

10. Method for carrying out a deposition process for applying a deposition onto a substrate (2) by use of an apparatus (1) according to one of claims 1 to 9, characterized in that before the deposition the first vacuum chamber (3) is evacuated to a first pressure (pi) and the second vacuum chamber (5) is evacuated to a second pressure (p2), wherein the ratio (pl/p2) between the first pressure (pi) and the second pressure (p2) is between 1 :5 to 1 :50.

1 1. Method according to claim 10, characterized in that the ratio (pl/p2) between the first pressure (pi) and the second pressure (p2) is between 1 :10 to 1 :30.

12. Method according to claim 10 or 1 1 , characterized in that the deposition process is a PVD process (physical vapor deposition process), a CVD process (chemical vapor deposition process) or a PECVD process (plasma-enhanced chemical vapor deposition process).

13. Method according to one of claims 10 to 12, characterized in that the first pressure (pi) in the first vacuum chamber (3) is below 30 mTorr, preferably below 20 mTorr.

14. Method according to one of claims 10 to 13, characterized in that the second pressure (p2) in the second vacuum chamber (5) is between 50 to 600 mTorr, preferably between 50 to 400 mTorr.