Patent ID: 12198893

BEST MODE

Mode for Invention

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical idea of the present invention is not limited to the exemplary embodiments described herein and may be embodied in other forms. Further, the embodiments are provided to enable contents disclosed herein to be thorough and complete and provided to enable those skilled in the art to fully understand the idea of the present invention.

In the specification, when one component is mentioned as being on another component, it signifies that the one component may be disposed directly on another component or a third component may be interposed therebetween. In addition, in the drawings, shapes and sizes may be exaggerated to effectively describe the technical content of the present invention.

In addition, although terms such as first, second and third are used herein to describe various components in various embodiments of the present specification, the components will not be limited by the terms. The above terms are used merely to distinguish one component from another. Accordingly, a first component referred to in one embodiment may be referred to as a second component in another embodiment. Each embodiment described and illustrated herein may also include a complementary embodiment. In addition, the term “and/or” is used herein to include at least one of the components listed before and after the term.

The singular expression herein includes a plural expression unless the context clearly specifies otherwise. In addition, it will be understood that the term such as “include” or “have” herein is intended to designate the presence of feature, number, step, component, or a combination thereof recited in the specification, and does not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. In addition, the term “connection” is used herein to include both indirectly connecting a plurality of components and directly connecting the components.

In addition, in the following description of the embodiments of the present invention, the detailed description of known functions and configurations incorporated herein will be omitted when it possibly makes the subject matter of the present invention unclear unnecessarily.

FIG.1is a conceptual diagram for explaining a plasma process monitoring apparatus using terahertz waves according to one embodiment of the present invention;FIG.2is a view for explaining types of terahertz waves applied to the plasma process monitoring apparatus using terahertz waves according to the embodiment of the present invention;FIG.3is a block diagram showing the plasma process monitoring apparatus using terahertz waves according to the embodiment of the present invention;FIG.4is a schematic diagram for explaining a first monitoring module of the plasma process monitoring apparatus using terahertz waves according to the embodiment of the present invention;FIGS.5and6are reference diagrams for explaining an optical system provided in the first monitoring module of the plasma process monitoring apparatus using terahertz waves according to the embodiment of the present invention;FIG.7is a schematic diagram for explaining a transmission mode of a second monitoring module in the plasma process monitoring apparatus using terahertz waves according to the embodiment of the present invention; andFIG.8is a schematic diagram for explaining a reflection mode of the second monitoring module in the plasma process monitoring apparatus using terahertz waves according to the embodiment of the present invention.

As shown inFIG.1, a plasma process monitoring apparatus100(inFIG.3) according to one embodiment of the present invention refers to an apparatus capable of using terahertz waves (THz waves) to simultaneously monitor plasma formed inside a plasma chamber10into which a wafer is inserted during a plasma process, and the wafer having a film formed on a surface thereof through the plasma process, for example, a plasma etching process and a plasma deposition process.

In order to monitor the plasma formed inside the plasma chamber10using terahertz waves, a first transmission window11and a second transmission window12may be provided on one side and an opposite side of the plasma chamber10in a circumferential direction to face each other.

In addition, a third transmission window13may be provided on an upper side of the plasma chamber10in order to monitor the wafer having the film formed on the surface thereof through the plasma process using terahertz waves. The monitoring of the wafer may be performed through one measuring mode of a transmission mode and a reflection mode, and this will be described below in more detail.

The first transmission window11, the second transmission window12, and the third transmission window13may be formed of a material for allowing terahertz waves to pass therethrough. For example, the first transmission window11, the second transmission window12, and the third transmission window13may be formed of one selected from the candidate material group including Si, HRFZ-SI, PTFE, PTFE, TPX and quartz (SiO2) which have high transmittance to the terahertz waves.

Meanwhile, as shown inFIG.2, according to one embodiment of the present invention, the terahertz waves may be provided in a pulsed type. A femtosecond laser functioning as a pump light for generating pulse type terahertz waves may be irradiated to a first emitter111(inFIG.4) described later, thereby generating pulse type terahertz waves from the first emitter111.

The above pulse type terahertz waves are able to be detected at once because the pulse type terahertz waves contain numerous frequencies. On the other hand, since continuous wave type (CW type) terahertz waves in contrast thereto use only one frequency, changing the frequency may take time and accordingly it is disadvantageous for scanning. Therefore, according to the present invention, the plasma and the wafer are simultaneously monitored using pulse type terahertz waves.

Referring toFIG.3, the plasma process monitoring apparatus100according to the embodiment of the present invention may be formed to include a first monitoring module110and a second monitoring module120.

Referring further toFIG.4, the first monitoring module110may be disposed outside the plasma chamber10into which the wafer is inserted. The first monitoring module110may be disposed outside the plasma chamber10in a direction parallel to a width direction of the wafer.

The first monitoring module110may use terahertz waves to monitor plasma formed inside the plasma chamber10during a plasma process for forming a film on the wafer.

According to one embodiment of the present invention, the first monitoring module110may include a first emitter111, a first detector112, and a first calculation unit113.

The first emitter111may be disposed outside the plasma chamber10in the circumferential direction. The first emitter111may be disposed to face the first transmission window11provided on the one side of the plasma chamber10in the circumferential direction.

The first emitter111may generate pulse type terahertz waves in the direction of the first transmission window11.

Like the first emitter111, the first detector112may be disposed outside the plasma chamber10in the circumferential direction. The first detector112may be disposed to face the second transmission window12provided on the opposite side of the plasma chamber10in the circumferential direction.

The first detector112may detect pulse type terahertz waves generated from the first emitter111and passing through the plasma formed inside the plasma chamber10.

In other words, the pulse type terahertz waves generated from the first emitter111may sequentially pass through the first transmission window11, the plasma formed inside the plasma chamber10, and the second transmission window12, and then be detected by the first detector112.

The calculation unit113may analyze a state of the plasma based on a signal detected by the first detector112. For example, The calculation unit113may calculate changes in phase (time) and intensity (amplitude) of the terahertz waves subject to a plasma environment through a peak position of the pulse type terahertz waves detected by the first detector112. Thus, according to one embodiment of the present invention, the state of the plasma may be monitored by calculating the changes in phase and intensity of the terahertz waves subject to the plasma environment through the first calculation unit113.

Meanwhile, according to one embodiment of the present invention, the first monitoring module110may further include a first optical system114and a second optical system115in order to maximize sensitivity of the terahertz waves generated from the first emitter111, sequentially passing through the first transmission window11, the plasma formed inside the plasma chamber10, and the second transmission window12, and detected by the first detector112.

The first optical system114and the second optical system115may be disposed outside the plasma chamber10. In addition, the first optical system114and the second optical system115may be disposed on a propagation path of the pulse type terahertz waves generated from the first emitter111disposed on the one side in the circumferential direction of the plasma chamber10.

According to one embodiment of the present invention, the first optical system114may be provided between the first emitter111and the first transmission window11formed on the one side of the plasma chamber10in the circumferential direction. In addition, the second optical system115may be provided between the first detector112and the second transmission window12formed on the opposite side of the plasma chamber10in the circumferential direction.

The first emitter111and the first optical system114, and the second optical system115and the first detector112may be aligned in one direction with the plasma formed inside the plasma chamber10interposed therebetween.

The terahertz waves generated from the first emitter111may be irradiated to the plasma through the first optical system114and then guided to the first detector112by the second optical system115.

According to one embodiment of the present invention, the first optical system114and the second optical system115may be provided in the form of a lens.

Referring toFIG.5, the first optical system114and the second optical system115may be provided in the form of, for example, a convex lens. The first transmission window11and the second transmission window12may function as a flat lens.

In addition, referring toFIG.6, the first optical system114and the second optical system115may be provided in the form of, for example, an F-THETA lens. Likewise, the first transmission window11and the second transmission window12may function as a plane lens.

However, in addition thereto, the first optical system114and the second optical system115may be formed of any one or a combination of an aspherical lens, a telecentric lens, a meniscus lens, and an axicon lens.

The first monitoring module120may be disposed outside the plasma chamber10to face the wafer. The second monitoring module120may be disposed in a thickness direction of the wafer.

The first monitoring module120may use terahertz waves to monitor the wafer having a film formed on a surface thereof through a plasma process.

According to one embodiment of the present invention, the first monitoring module120may monitor the wafer through one measuring mode of a transmission mode and a reflection mode.

Referring toFIG.7, the second monitoring module120may include a second emitter121, a second detector122and a second calculation unit123so as to monitor the wafer in the transmission mode.

The second emitter121may be disposed above the plasma chamber10. The second emitter121may be disposed to face the third transmission window13provided at the top of the plasma chamber10.

The second emitter121may generate pulse type terahertz waves in a direction of the third transmission window13.

The second detector122may be disposed below the wafer. The second detector122may be disposed below the plasma chamber10. The second detector122may be aligned with the second emitter121in the thickness direction of the wafer.

The second detector122may detect the pulse type terahertz waves generated from the second emitter121and then passing through the wafer.

In other words, the pulse type terahertz waves generated from the second emitter121may sequentially pass through the third transmission window13, the plasma formed inside the plasma chamber10, the wafer seated on a bottom of the plasma chamber10and the bottom of the chamber10, and then be detected by the second detector122.

The second calculation unit123may analyze a state of the wafer based on a signal detected by the second detector122. The second calculation unit123may monitor a state of the wafer during the plasma process, for example, a deposition thickness of SiN formed as a film on the wafer, through changes in phase, intensity, refractive index, and extinction coefficient of the terahertz waves detected by the second detector122.

The first monitoring module120may monitor a single pixel, as a target, among pixels partitioned on the wafer through the second emitter121and the second detector122, and may simultaneously monitor multiple pixels. The simultaneous monitoring of multiple pixels may be performed by scanning the multiple pixels with the second emitter121and the second detector122which monitor a single pixel as a target.

According to one embodiment of the present invention, the first monitoring module120may further include a third optical system124and a fourth optical system125in order to maximize sensitivity of the terahertz waves generated from the second emitter121, sequentially passing through the third transmission window13, the plasma formed inside the plasma chamber10, the wafer seated on the bottom of the plasma chamber10and the bottom of the plasma chamber10, and then detected by the second detector122.

The third optical system124and the fourth optical system125may be disposed outside the plasma chamber10. In addition, the third optical system124and the fourth optical system125may be disposed on a propagation path of the pulse type terahertz waves generated from the second emitter121disposed above the plasma chamber10.

According to one embodiment of the present invention, the third optical system124may be provided between the second emitter121and the third transmission window13formed on the upper side of the plasma chamber10. In addition, the fourth optical system125may be provided between the wafer and the second detector122, more specifically, between the bottom of the plasma chamber10and the second detector122.

The second emitter121and the third optical system124, and the fourth optical system125and the second detector122may be aligned in one direction, that is, in the thickness direction of the wafer with the wafer seated inside the plasma chamber10interposed therebetween.

The terahertz waves generated from the second emitter121may be irradiated to the wafer through the third optical system124, pass through the wafer, and then be guided to the second detector122by the fourth optical system125.

According to one embodiment of the present invention, the third optical system124and the fourth optical system125may be provided in the form of lenses, like the first optical system114and the second optical system115.

The third optical system124and the fourth optical system125may be formed of any one or a combination of, for example, a convex lens, an F-THETA lens, a flat lens, an aspherical lens, a telecentric lens, a meniscus lens, and an axicon lens.

Meanwhile, referring toFIG.8, the second monitoring module120may further include a third detector126, a third calculation unit127, and a fifth optical system128. Through this, the second monitoring module120may switch the transmission mode into the reflection mode to monitor the wafer through the reflection mode.

The third detector126may be placed above the plasma chamber10. The third detector126may be disposed at one side of the second emitter121. The third detector126may be arranged to face a path different from the propagation path of the pulse type terahertz waves generated from the second emitter121.

The third detector126may detect pulse type terahertz waves generated from the second emitter121, irradiated to the wafer, and then reflected from the wafer.

The third calculation unit127may analyze a state of the wafer based on a signal detected by the third detector126. For example, the third calculation unit127may predict a deposition thickness of SiN through a relationship between the refractive index of the terahertz waves and the thickness of the SiN film formed on the wafer, and a relationship between the extinction coefficient of the terahertz waves and the thickness of the SiN film.

The fifth optical system128may be provided between the third optical system124and the third detector126. Accordingly, the pulse type terahertz waves generated from the second emitter121may be irradiated to the wafer through the third optical system124, reflected from the wafer, focused by the third optical system124, and irradiated toward the fifth optical system128. The terahertz waves irradiated toward the fifth optical system128may be guided to the third detector126by the fifth optical system128.

Hereinafter, a plasma process monitoring apparatus using terahertz waves according to another embodiment of the present invention will be described with reference toFIGS.9to12.

FIG.9is a block diagram showing a plasma process monitoring apparatus using terahertz waves according to another embodiment of the present invention;FIG.10is a schematic diagram for explaining a first monitoring module of the plasma process monitoring apparatus using terahertz waves according to another embodiment of the present invention;FIG.11is a schematic diagram for explaining a transmission mode of a second monitoring module in the plasma process monitoring apparatus using terahertz waves according to another embodiment of the present invention; andFIG.12is a schematic diagram for explaining a reflection mode of the second monitoring module in the plasma process monitoring apparatus using terahertz waves according to another embodiment of the present invention.

Referring toFIG.9, the plasma process monitoring apparatus200according to another embodiment of the present invention may be formed to include a first monitoring module210and a second monitoring module220.

Compared to the one embodiment of the present invention, another embodiment of the present invention differs only in that the emitter and detector are moved instead of omitting the optical system. Thus, the remaining identical components will be assigned the same reference numerals, and detailed descriptions thereof will be omitted.

As shown inFIG.10, according to another embodiment of the present invention, the first monitoring module210may include a first emitter211, a first detector212, and a first calculation unit213.

The first emitter211may be disposed outside the plasma chamber10in the circumferential direction. The first emitter211may be disposed to face the first transmission window11provided on one side of the plasma chamber10in the circumferential direction. The first emitter211may generate pulse type terahertz waves in the direction of the first transmission window11.

According to another embodiment of the present invention, the first emitter211may be provided to be movable in the width direction of the first transmission window11. Accordingly, the first emitter211may generate terahertz waves while moving in the width direction of the first transmission window11.

Like the first emitter211, the first detector212may be disposed outside the plasma chamber10in the circumferential direction. The first detector212may be disposed to face the second transmission window120provided on the opposite side of the plasma chamber10in the circumferential direction. The first detector212may be aligned with the first emitter211in one direction with the plasma formed inside the plasma chamber10interposed therebetween.

According to another embodiment of the present invention, the first detector212may be linked to the movement of the first emitter211. Accordingly, the first detector212may be movable in the width direction of the second transmission window12. The first detector212may detect terahertz waves while moving in the width direction of the second transmission window12in conjunction with the movement of the first emitter211.

The pulse type terahertz waves generated from the first emitter111may sequentially pass through the first transmission window11, the plasma formed inside the plasma chamber10, and the second transmission window12, and then be detected by the first detector112.

The first calculation unit213may analyze a state of plasma based on a signal detected by the first detector212. Since the first calculation unit213according to another embodiment of the present invention has the same function and operation as the first calculation unit113(inFIG.4) according to the one embodiment of the present invention, detailed description thereof will be omitted.

The second monitoring module220may be disposed outside the plasma chamber10in the thickness direction of the wafer. The second monitoring module220may use terahertz waves to monitor the wafer having a film formed on a surface thereof through a plasma process. According to another embodiment of the present invention, the second monitoring module220may monitor the wafer through one measuring mode of a transmission mode and a reflection mode.

Referring toFIG.11, the second monitoring module220may include a second emitter221, a second detector222, and a second calculation unit223. Through this, the second monitoring module220may monitor the wafer through the transmission mode. The second emitter221may be disposed above the plasma chamber10. The second emitter221may be disposed to face the third transmission window13provided at the top of the plasma chamber10.

According to another embodiment of the present invention, the second emitter221may be provided to be movable in the width direction of the third transmission window13. Accordingly, the second emitter221may generate pulse type terahertz waves in the direction of the third transmission window13while moving in the width direction of the third transmission window13.

The second detector222may be disposed below the wafer. The second detector222may be disposed below the plasma chamber10. The second detector222may be aligned with the second emitter221in the thickness direction of the wafer.

According to another embodiment of the present invention, the second detector222may be linked to the movement of the second emitter221. Accordingly, the second detector222may be movable in the width direction of the wafer. The second detector222may detect terahertz waves transmitting the wafer while moving in the width direction of the wafer in conjunction with the movement of the first emitter221.

In other words, the pulse type terahertz waves generated from the second emitter221may sequentially pass through the third transmission window13, the plasma formed inside the plasma chamber10, the wafer seated on the bottom of the plasma chamber10and the bottom of the chamber10, and then be detected by the second detector222.

The second calculation unit223may analyze a state of the wafer based on a signal detected by the second detector222. Since the second calculation unit223according to another embodiment of the present invention has the same function and operation as the second calculation unit123(inFIG.7) according to the one embodiment of the present invention, detailed description thereof will be omitted.

Meanwhile, referring toFIG.12, the second monitoring module220may further include a third detector226, a third calculation unit227, and a sixth optical system229. Through this, the second monitoring module220may switch the transmission mode into the reflection mode to monitor the wafer through the reflection mode.

The third detector226may be disposed above the plasma chamber10. The third detector226may be disposed at one side of the second emitter221. The third detector226may be arranged to face a path different from the propagation path of the pulse type terahertz waves generated from the second emitter221.

The third detector226may detect pulse type terahertz waves generated from the second emitter221, irradiated to the wafer, and then reflected from the wafer.

The third calculation unit227may analyze a state of the wafer based on a signal detected by the third detector226. Since the third calculation unit227according to another embodiment of the present invention has the same function and operation as the third calculation unit127(inFIG.8) according to the one embodiment of the present invention, detailed descriptions thereof will be omitted.

The sixth optical system229may be provided between the wafer and the third detector226. According to another embodiment of the present invention, the sixth optical system229may be linked to the movement of the second emitter221. Accordingly, the sixth optical system229may be movable in the width direction of the wafer.

According to another embodiment of the present invention, the second emitter221may generate pulse type terahertz waves while moving in the width direction of the third transmission window13, and the sixth optical system229may guide the pulse type terahertz waves reflected from the wafer to the third detector226in conjunction with the movement of the second emitter221.

Meanwhile,FIGS.13to15show the results of monitoring wafers having different SiN deposition thicknesses through the transmission mode of the present invention.FIG.13is a graph showing waveforms of pulse type terahertz waves for each wafer;FIG.14is a graph showing changes in refractive index of the pulse type terahertz waves for each wafer; andFIG.15is a graph showing changes in extinction coefficient of the pulse type terahertz waves for each wafer.

As shown in the above graphs, it can be confirmed that the refractive index of the terahertz waves tends to decrease and the extinction coefficient of the terahertz waves tends to increase as the thickness of SiN deposited on the wafer increases. In other words, it can be analyzed that the deposition thickness of SiN increases when the refractive index of the terahertz waves is monitored as decreasing and the extinction coefficient is monitored as increasing.

FIGS.16and17are graphs for predicting the SiN thickness through the reflection mode of the present invention.FIG.16is a graph obtained by curve fitting the relationship between the refractive index of terahertz waves and the thickness of SiN; and

FIG.17is a graph obtained by curve fitting the relationship between the extinction coefficient of terahertz waves and the thickness of SiN.

As shown in the above graphs, the thickness of SiN deposited on a silicon wafer may be predicted by calculating estimation data based on actual measured data.

FIGS.18to20are graphs separately showing a refractive index and an extinction coefficient of terahertz waves, and a relationship between the refractive index and the extinction coefficient according to materials (nitride, photo resist, thermal oxide) deposited on the silicon wafer.

As shown in the above graphs, since terahertz waves have different optical properties depending on the type of material deposited on the silicon wafer, the refractive index and extinction coefficient range are different for each material. Accordingly, it is confirmed that the type of material deposited on the silicon wafer can be predicted through terahertz waves.

Meanwhile,FIG.21is a graph showing waveforms of terahertz waves collected through a transmission mode of a pulse type terahertz equipment. Changes in phase (time) and intensity (amplitude) subject to the plasma environment may be calculated through peak positions of the waveforms collected through the pulse type terahertz equipment. Accordingly, the state of plasma may be monitored using terahertz waves.

In addition,FIGS.22to24are graphs showing terahertz waves, intensity changes, and phase changes for each plasma process condition using the transmission mode of the present invention.

As shown in the above graphs, it can be seen that the plasma has the higher intensity as the output and mass flow rate of an RF generator for generating plasma are higher, thereby gradually decreasing the intensity and phase of terahertz waves passing therethrough. Plasma process conditions may be distinguished by analyzing the changes in intensity and phase of terahertz waves.

Hereinafter, a plasma process monitoring method using terahertz waves according to one embodiment of the present invention will be described with reference toFIG.25. The reference numerals of each component refer toFIGS.1to8.

FIG.25is a flowchart showing a plasma process monitoring method using terahertz waves according to one embodiment of the present invention.

Referring toFIG.25, the plasma process monitoring method using terahertz waves according to the one embodiment of the present invention may include step S110and step S120. The plasma process monitoring method using terahertz waves according to the one embodiment of the present invention may be performed through the plasma process monitoring apparatus100using the terahertz waves according to the one embodiment of the present invention.

Step S110

Step S110refers to a step of using the terahertz waves to monitor plasma formed inside the plasma chamber10during the plasma process for forming a film on a wafer inserted into the plasma chamber10.

In step S110, first, pulse type terahertz waves may be generated in an inner direction of the plasma chamber10through the first emitter111.

Thereafter, in step S110, the pulse type terahertz waves passing through plasma formed inside the plasma chamber10during the plasma process such as an etching or deposition process may be detected through the first detector112.

Thereafter, in step S110, a state of the plasma may be analyzed, through the first calculation unit113, based on the signal detected by the first detector112.

In step S110, in order to maximize sensitivity of the pulse type terahertz waves generated from the first emitter111, passing through the plasma, and then detected by the first detector112, the first optical system114may be disposed between the first emitter111and the first transmission window11, and the second optical system115may be disposed between the second transmission window12and the first detector112.

The first optical system114and the second optical system115may be provided in the form of lenses, and for example, may be provided as any one or a combination of a convex lens, a flat lens, an F-THETA lens, an aspherical lens, a telecentric lens, a meniscus lens, and an axicon lens.

Step S120

Step S120refers to a step of using pulse type terahertz waves to monitor the wafer having the film formed on the surface thereof through the plasma process. According to one embodiment of the present invention, step S110of monitoring the plasma and the step S120of monitoring the wafer may be performed simultaneously.

In step S120, a state of the wafer may be analyzed based on the signal detected from the pulse type terahertz waves passing through the wafer.

To this end, in step S120, first, pulse type terahertz waves may be generated toward the wafer through the second emitter121provided above the wafer.

Thereafter, in step S120, the pulse type terahertz waves generated from the second emitter121and passing through the wafer may be detected through the second detector122. Thereafter, in step S120, the state of the wafer may be analyzed, through the second calculation unit123, based on the signal detected by the second detector122.

In step S120, in order to maximize sensitivity of the pulse type terahertz waves generated from the second emitter121, passing through the wafer, and then detected by the second detector122, the third optical system124may be disposed between the second emitter121and the wafer, and the fourth optical system124may be disposed between the wafer and the second detector122.

The third optical system124and the fourth optical system124may be disposed outside the plasma chamber10.

Meanwhile, in step S120, the state of the wafer may be analyzed based on the signal detected by the pulse type terahertz waves reflected from the wafer.

To this end, in step S120, the pulse type terahertz waves may be generated toward the wafer through the second emitter121provided above the wafer.

Thereafter, in step S120, the pulse type terahertz waves generated from the second emitter121, irradiated to the wafer, and then reflected from the wafer may be detected through the third detector126provided at one side of the second emitter121.

Thereafter, in step S120, the state of the wafer may be analyzed, through the third calculation unit127, based on the signal detected by the third detector126.

In step S120, the fifth optical system128may be disposed between the third optical system124and the third detector126in order to guide the pulse type terahertz waves reflected from the wafer and focused by the third optical system124to the third detector126.

Although the present invention has been described in detail with reference to the preferred embodiments, the present invention is not limited to the specific embodiments and shall be interpreted by the following claims. In addition, it will be apparent that a person having ordinary skill in the art may carry out various deformations and modifications for the embodiments described as above within the scope without departing from the present invention.