CN114334728A

CN114334728A - Semiconductor process cavity

Info

Publication number: CN114334728A
Application number: CN202111614005.XA
Authority: CN
Inventors: 谭华强; 申思; 黄明策
Original assignee: Piotech Inc
Current assignee: Piotech Inc
Priority date: 2021-12-27
Filing date: 2021-12-27
Publication date: 2022-04-12

Abstract

The invention discloses a semiconductor process chamber, which comprises an electric thermocouple. The electric thermocouple has a pipe sleeve which is wrapped with an inner core wire and has a downstream end and an upstream end, the downstream end is used as a temperature sensing part and is inserted into a part applied by radio frequency, and the upstream end is electrically connected to a cavity. The method is characterized in that: the cavity is grounded, so that the flowing current caused by the radio frequency on the surface of the pipe sleeve can flow to the ground through the cavity, and the radio frequency is shielded in the cavity.

Description

Semiconductor process cavity

Technical Field

The present invention relates to semiconductor devices, and more particularly to a semiconductor process chamber including an electric thermocouple.

Background

In semiconductor manufacturing, plasma vapor deposition (PECVD) is a process for depositing a thin film or etching a thin film. In a semiconductor process chamber for performing PECVD processes, the showerhead assembly and the wafer support plate are used as upper and lower electrodes, respectively, wherein the showerhead assembly is electrically connected to the rf source and the support plate is grounded as a common configuration, although the opposite configuration is also possible. In a multi-station batch process, the temperature of the shower assembly needs to be balanced to achieve a consistent deposited film. However, it is difficult to maintain station to station consistency in practice because the chamber temperature at each station may disrupt the temperature balance within the chamber due to differences in the temperature of each incoming wafer, resulting in slight differences in the station to station showerhead assembly temperatures. Thus, precise control of the temperature of each showerhead assembly contributes to wafer process uniformity.

U.S. patent application publication No. US2019256977a1 discloses an electric thermocouple for monitoring the temperature of a shower assembly, and the electric thermocouple is connected with a radio frequency filter (RF filter). The RF filter isolates the radio frequency signal from the electric thermocouple signal by means of circuit filtering, so as to avoid unreliable temperature sensing caused by mutual interference of the radio frequency signal and the electric thermocouple signal. The RF filter may consist of a high frequency filter (e.g., 13.56MHz) and a low frequency filter (e.g., 400 kHz).

Although the actual reaction temperature of the thermocouple can be accurately monitored by using the circuit approach, it is still difficult to ensure the uniformity of the electronic components in the circuit for multiple stations processing wafers in the same process. Therefore, there is a need to develop a simplified approach to the thermocouple that is easier to maintain than the circuit.

Disclosure of Invention

The present invention is directed to a semiconductor process chamber for shielding RF signals within the chamber.

The semiconductor process cavity provided by the invention comprises: an electric thermocouple having a sleeve which is wrapped with an inner core wire and has a downstream end and an upstream end, the downstream end serving as a temperature sensing portion and being inserted into a member to which radio frequency is applied, the upstream end being electrically connected to a cavity, characterized in that: the cavity is grounded, so that the flowing current caused by the radio frequency on the surface of the pipe sleeve can flow to the ground through the cavity, and the radio frequency is shielded in the cavity.

The semiconductor process cavity provided by the invention has the beneficial effects that: the upstream end of the electric thermocouple is connected with the cavity, the pipe sleeve and the cavity are conductive, the cavity is grounded, and flowing current caused by radio frequency signals can be sequentially transmitted to the ground end from the surface of the pipe sleeve and the cavity, so that the radio frequency signals are shielded in the closed cavity and cannot interfere with the inner core wire.

Optionally, the cavity is a closed metal cover.

Optionally, the thermocouple comprises a first insulating sleeve covering the downstream end and a second insulating sleeve partially covering the first insulating sleeve, and a portion of the first insulating sleeve is exposed.

Optionally, the first insulating sleeve and the second insulating sleeve are made of ceramic.

Optionally, the thermocouple is inserted into the member at a depth that is less than twice the diameter of the sleeve, and the signal processing unit is configured to execute a compensation algorithm to obtain accurate temperature data.

Optionally, the thermocouple is inserted into the component to a depth greater than twice the diameter of the shroud, and the shroud is electrically coupled to a pair of resistors to reduce the rf energy of the rf loop.

Optionally, the semiconductor process chamber further comprises a chamber top, and the component is a spray assembly fixed to the chamber top, wherein the thermocouple is partially inserted into the spray assembly to sense the temperature of the spray assembly, and a pressing assembly is provided on the chamber top and configured to connect the thermocouple and provide a pressing force along the insertion direction of the thermocouple, so that the downstream end of the thermocouple is in close contact with the temperature measuring point in the spray assembly.

Optionally, the pressing assembly includes a clamping seat fixed above the top of the cavity, a jacket located below the top of the cavity, and a spring located between the clamping seat and the jacket, the clamping seat and the jacket respectively clamp the pipe sleeves of the thermocouple, and the spring provides the pressing force to the jacket to force the downstream end of the thermocouple to tightly contact the temperature measuring part in the spraying assembly.

Optionally, the holder has a chuck and a shielding ring, the chuck clamps the pipe sleeve of the thermocouple, and the shielding ring is connected to the periphery of the holder, so that the holder is fixed to the upper surface of the top of the cavity through the shielding ring without contacting the holder with the top of the cavity.

Optionally, the jacket has an inner sleeve and an outer sleeve, the inner sleeve covers the pipe sleeve of the thermocouple, and the outer sleeve is tightly matched and jointed with the inner sleeve to clamp the pipe sleeve.

Drawings

FIG. 1 illustrates an exemplary thermocouple (a component inserted into a cavity) having the capability of shielding RF signals.

FIG. 2 is a schematic cross-sectional view of a spray assembly inserted into an electric thermocouple capable of shielding RF signals according to the present invention.

FIG. 3 is a cross-sectional view of an embodiment of an electric thermocouple arrangement according to the present invention.

FIG. 4 is an enlarged partial cross-sectional view of the chuck.

Fig. 5 is a perspective view of the chuck.

Detailed Description

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which specific exemplary embodiments are shown by way of illustration. The claimed subject matter may, however, be embodied in many different forms and should not be construed as limited to any example embodiments set forth herein; the exemplary embodiments are merely illustrative. As such, this invention is intended to provide a reasonably broad scope of coverage to the claimed subject matter as claimed or as covered thereby.

The use of the phrase "in one embodiment" in this specification does not necessarily refer to the same embodiment, and the use of "in other embodiment(s)" in this specification does not necessarily refer to different embodiments. It is intended that, for example, claimed subject matter include all or a portion of the exemplary embodiments in combination.

FIG. 1 shows an electric thermocouple 1 with RF signal shielding capability according to the present invention, which has a tube sleeve 11 and a core wire 12. The sleeve 11 is selected from a metal material having good thermal conductivity, such as stainless steel, and has a downstream end 13 and an upstream end 14. The downstream end 13 mainly serves as a temperature measuring portion, and the upstream end 14 is connected to a signal processing unit (not shown) for receiving and processing signals of the core wire.

Fig. 1 also shows a part 2 and a chamber 3. The chamber 3 depicted in the figures may actually be a structure in a semiconductor process chamber, and particularly refers to a structure in a plasma process chamber. In particular, the cavity 3 may be understood as a closed metal cover. The metal of the cavity structure is influenced by the rf signal to generate a current, i.e. a skin effect (skin effect), on the surface of the structure, as shown by the arrow direction. Component 2 refers to the target to which the rf signal is primarily applied, such as the upper electrode or the lower electrode, which are well known in the plasma processing art, and which may be the showerhead assembly and the wafer support plate, respectively. The component 2 is also typically a metal material, such as a metal plate of some sort in a shower assembly. The component 2 may be electrically connected to a radio frequency source via a cable, so that the surface of the component 2 also generates a flowing current, as indicated by the arrows in the figure.

The downstream end 13 of the thermocouple 1 according to the invention is inserted into the part 2 at a depth D via a first insulating sleeve 15. The first insulating sleeve 15 has an outer side and an inner side, the downstream portion 13 of the sleeve 11 contacts the inner side of the first insulating sleeve 15, and the outer side of the first insulating sleeve 15 contacts the member 2, whereby the first insulating sleeve 15 isolates the sleeve 11 from the member 2. In other embodiments, the first insulating sheath 15 can be modified or even omitted according to the part 2 in which the thermocouple 1 is inserted.

The upstream end 14 of the thermocouple 1 is connected to the cavity 3. Since the pipe sleeve 11 and the cavity 3 are conductive, the cavity 3 is grounded, and the flowing current caused by the radio frequency signal is transmitted to the ground end from the surface of the pipe sleeve 11 and the cavity 3 in sequence, so that the radio frequency signal is shielded in the closed metal cover without interfering with the temperature measuring core wire 12.

In one specific configuration, if the insertion depth D is less than twice the diameter D of the sleeve 11 (i.e., 2D), the signal processing unit is caused to execute a compensation algorithm to obtain accurate temperature data. This is because the insertion depth is too shallow, which easily causes inaccurate measurement result, and a compensation mechanism is required for calculation.

In another specific configuration, if the insertion depth D is greater than twice the diameter D of the shroud 11, a high resistance resistor (e.g., 10M ohm) is electrically coupled to the shroud 11 to prevent excessive rf current from flowing along the shroud 11. This is because when the insertion depth is large, parasitic capacitance is generated correspondingly, so that the surface current indicated by the arrow in fig. 1 is large and the current flowing into the discharge plasma region is small, and the high resistance value resistor needs to be further connected to compensate. As shown, the configuration is such that a pair of resistors 31 are electrically connected between the chamber 3 and the sleeve 11, so that the current indicated by the arrows in the figure is reduced, but the invention is not limited thereto.

Furthermore, in other embodiments, if the component 2 is grounded and the process requires a low frequency rf voltage (within 10V), the first insulating sleeve 15 and the resistor 31 may be omitted.

FIG. 2 is a schematic cross-sectional view of an electric thermocouple 1' of the present invention inserted into a shower assembly. The shower assembly is primarily constructed of metal components including a shower plate 21 proximate the chamber processing region, a plate 22 stacked on the shower plate 21, and a lid 23 pushed over the plate 22, although the invention is not so limited. Thermocouple 1' is inserted into the shower assembly at a depth, specifically through cover 23 and extends to plate 22, but does not contact shower plate 21, as the invention is not limited thereto. The length of the first insulating sheath 15 as shown in fig. 1 should be at least sufficient to isolate the downstream end of the thermocouple 1' from the plate 22 and/or the cover 23, thereby avoiding interference of rf signals.

FIG. 3 is a cross-sectional view of an embodiment of an electric thermocouple arrangement according to the present invention. Similar to fig. 1, a pipe sleeve 11 and a first insulating sleeve 15 are provided. The main difference between fig. 3 and fig. 1 is that it further comprises a second insulating sleeve 16 and a pressing member 4. As shown, the inner side portion of the second insulating sleeve 16 contacts the outer side of the first insulating sleeve 15, such that the second insulating sleeve 16 partially covers the first insulating sleeve 15 and the end of the first insulating sleeve 15 is exposed to contact the plate 22. The second insulating sleeve 16 has a length such that the second insulating sleeve 16 covers part of the downstream end of the pipe sleeve 11 in addition to the open end of the first insulating sleeve 15, and air is present between the second insulating sleeve 16 and the pipe sleeve 11. Part of the outer side of the second insulating sleeve 16 contacts the cover 23, so that the pipe sleeve 11 is isolated from the cover 23.

The first insulating sleeve 15 and the second insulating sleeve 16 are selected from materials having high thermal conductivity but no electrical conductivity, such as alumina (ceramic), but the present invention is not limited thereto. Therefore, the electric thermocouple can shield radio frequency signals and obtain data at the temperature measurement position of the component without additionally connecting an RF filter.

In addition, the upstream end of the pipe sleeve 11 is coupled to the chamber top 3' via the pressing assembly 4. The cavity top 3 'is a part of the structure of the cavity top, and the cavity top 3' is a layer above the spray assembly as shown in the figure, but the invention is not limited thereto. The hold-down assembly 4 is primarily configured to hold the shroud 11 in place and provide a hold-down force forcing the downstream end of the shroud 11 into positive contact with the first insulating sleeve 15 and the first insulating sleeve 15 into positive contact with the plate 22.

The pressing assembly 4 includes a holder 41, a collet 42 and a spring 43. The holder 41 is located above the top 3' of the chamber and has a passage for the pipe sleeve 11 to pass through. The bottom of the holder 41 is connected to the upper surface of the chamber top 3 'via a shielding ring 411, so that the holder 41 is not in contact with the chamber top 3'. This arrangement prevents rf signals from coupling to the sleeve 11 through the holder 41, since there is still a possibility of rf current in the top portion 3' of the chamber. Referring also to fig. 4 and 5, the top of the holder 41 is provided with a collet (412) which cooperates with the holder 41 to hold the socket 11, thereby fixing the socket 11 against easy vertical movement.

The jacket 42 is located below the top 3' of the chamber and above the second insulating sleeve 16. The jacket 42 is formed of an inner sleeve covering the outer side of the pipe sleeve 11 and an outer sleeve tightly fitted to the outer side of the inner sleeve so that the jacket 42 is fixed to the pipe sleeve 11.

Both ends of the spring 43 contact the bottom of the holder 41 and the top of the collet 42, respectively, and apply an elastic force to both sides. Specifically, the spring 43 contacts the holder 41 through the opening of the chamber top 3 ', and therefore the spring 43 does not contact the chamber top 3'. Since the holder 41 is fixed to the cavity top 3' via the shield ring 411, the elastic force forces the pipe sleeve 11 to move downward, thereby bringing the downstream end of the pipe sleeve 11 into close contact with the first insulating sleeve 15, and the first insulating sleeve 15 and the second insulating sleeve 16.

The electric thermocouple can be widely applied to a plasma process cavity, can measure the temperature of a part with a radio frequency signal, avoids the additional setting cost of an RF filter, and ensures the close contact of the electric thermocouple and a temperature measuring position by a pressing component. The RF signal-carrying component includes, but is not limited to, RF signal components of 27MHz, 13.56MHz, and 400 kHz.

Claims

1. A semiconductor process chamber, comprising: an electric thermocouple having a sleeve which is wrapped with an inner core wire and has a downstream end and an upstream end, the downstream end serving as a temperature sensing portion and being inserted into a member to which radio frequency is applied, the upstream end being electrically connected to a cavity, characterized in that: the cavity is grounded, so that the flowing current caused by the radio frequency on the surface of the pipe sleeve can flow to the ground through the cavity, and the radio frequency is shielded in the cavity.

2. The semiconductor process chamber of claim 1, wherein the chamber is a closed metal lid.

3. The semiconductor process chamber of claim 1, wherein the thermocouple comprises a first insulating sheath surrounding the downstream end and a second insulating sheath partially surrounding the first insulating sheath and exposing a portion of the first insulating sheath.

4. The semiconductor process chamber of claim 3, wherein the first insulating sleeve and the second insulating sleeve are made of ceramic.

5. The semiconductor process chamber of claim 1, wherein the thermocouple is inserted into the component to a depth that is less than twice a diameter of the sleeve, and the signal processing unit is configured to perform a compensation algorithm to obtain accurate temperature data.

6. The semiconductor process chamber of claim 1, wherein the thermocouple is inserted into the component to a depth greater than twice a diameter of the collar, and the collar is electrically coupled to a pair of resistors to reduce rf energy passing through the collar to a return path to ground.

7. The semiconductor process chamber of claim 1, further comprising a chamber top, the component being a showerhead assembly secured to the chamber top, wherein the thermocouple is partially inserted into the showerhead assembly to sense a temperature of the showerhead assembly, the chamber top being provided with a hold down assembly configured to engage the thermocouple and provide a hold down force along the direction of insertion of the thermocouple to bring the downstream end of the thermocouple into intimate contact with the temperature sensing point in the showerhead assembly.

8. The semiconductor process chamber of claim 7, wherein the clamping assembly comprises a clamping base fixed above the top of the chamber, a clamping sleeve located below the top of the chamber, and a spring located between the clamping base and the clamping sleeve, wherein the clamping base and the clamping sleeve respectively clamp the pipe sleeves of the thermocouple, and the spring provides the clamping force to the clamping sleeve to force the downstream end of the thermocouple to be in close contact with the temperature measurement site in the spray assembly.

9. The semiconductor process chamber of claim 8, wherein the chuck has a collet that grips the sleeve of the thermocouple and a shield ring that is attached to the periphery of the chuck such that the chuck is secured to the top surface of the top of the chamber via the shield ring without the chuck contacting the top of the chamber.

10. The semiconductor process chamber of claim 8, wherein the jacket has an inner sleeve and an outer sleeve, the inner sleeve covering the pipe sleeve of the thermocouple, the outer sleeve and the inner sleeve being in tight fit engagement to clamp the pipe sleeve.