Modular pattern photolithography device

Abstract

The invention relates to a photolithography device (D1) for transferring at least one pattern onto a substrate (1) comprising: a radiation source (2) for emitting a beam at a predetermined wavelength (λ); a support (3) for holding the substrate fixed relative to the radiation source (2); a display screen (4) disposed between the radiation source (2) and the support (3) and configured to display the at least one pattern; the radiation source (2) being disposed so as to illuminate a first face of the substrate (1) through the display screen (4) to transfer the at least one pattern onto said first face of the substrate (1). Said display screen (4) comprising a pixel matrix, the pixel matrix comprising at least one pixel (41, 42, 43) having an opacity at said wavelength that can be adjusted to obtain one of at least the following opacity states: an opaque state (E2) or a transparent state (E1). Figure for the abridged version: Fig. 1

Description

Title of the invention: Photolithography device with modular patterns

[0001] The invention relates to the field of devices whose function is the control of light in transmission, and more particularly, photolithography devices used in the microelectronics industry. Furthermore, the invention is capable of addressing issues of cyber security and data archiving.

[0002] Photolithography is a process for manufacturing microsystems and semiconductors that involves transferring a pattern (commonly called a physical drawing or "integrated circuit layout" in English) of an electronic circuit onto a substrate using light. It is widely used in the electronics industry for the production of microprocessors, memories, integrated circuits, MEMS and / or NEMS type sensors and other electronic or microfluidic devices.

[0003] Initially, a layer of photosensitive resin is deposited on the surface of the substrate. The resin is exposed to light through a mask (or reticle) which contains the pattern of a level of layers of an electronic circuit to be produced. The light reacts with the resin in the exposed areas, thus creating a pattern of the electronic circuit on the surface of the substrate. Once exposed, the substrate is immersed in a bath of chemical development solution, which dissolves the unexposed resin and reveals the pattern of the electronic circuit. Alternatively, it is possible to choose a resin which reacts inversely with light: The resin is solidified when it is not exposed to light and conversely, the resin is dissolved when it is exposed to light.

[0004] The pattern is then transferred to the substrate using an etching or material deposition process.

[0005] Photolithography is a precision technological process that allows the creation of electronic circuit patterns with resolutions down to a few nanometers. It is essential for the manufacture of advanced electronic devices comprising billions of transistors on a single chip. Photolithography is also used in other industries, such as the manufacture of microsystems, the production of masks for printing and etching printed circuits, as well as in the production of optical devices and sensors.

[0006] In the fields of microelectronics and nanotechnologies, integrated circuits and nanometric devices are made by stacking several layers. The stacks are made by several successive iterations of the photolithography, layer deposition and etching operations. Concerning the pho tolithography, each iteration corresponds to a specific pattern and thus each iteration requires its own lithography mask. Each pattern, and thus each mask, corresponds to a physical drawing of the circuit at a certain height level and / or a certain material to be deposited. The number of iterations can exceed hundreds. This implies the need to manufacture several lithography masks to manufacture a single component. In addition, this implies the need to change the lithography mask for each iteration, which considerably increases the complexity of the process.

[0007] In this sense, several problems have been clearly identified with the photolithography devices known in the state of the art. Indeed, the reticle masks used are designed in hard, and the manufacturing of each layer level requires a dedicated mask; which causes an increase in the complexity of the process and an increase in the costs of the process due to the need to manufacture several masks.

[0008] We will begin by introducing the solutions known to those skilled in the art for producing photolithography reticle masks. A first known solution concerns masks (or reticles) produced by chrome tracks and patterns deposited on a quartz support. For photolithography carried out by an ultraviolet (UV) light beam, quartz is transparent to UV electromagnetic waves and the chrome tracks and patterns are opaque. The disadvantage of this solution consists of the need to use a dedicated mask for each layer level of the device to be manufactured. This results in manufacturing complexity, high manufacturing costs and, more particularly, the fact that the chrome patterns manufactured for a mask are non-modifiable.

[0009] To overcome the limitations of existing solutions, the invention proposes a photolithography device comprising a display screen arranged between the radiation source and the target substrate. The display screen acting as a filter comprises modular pixels making it possible to display a black (opaque), white (transparent) or shades of gray (intermediate) state. The modular display screen makes it possible to produce a single, unitary reticle per layer level, offering a versatile solution that can be adapted to each level of the thin-layer stack. The photolithography device according to the invention makes it possible to obtain a solution with unlimited and instant versatility allowing varied and efficient use. It becomes simpler to change the projected patterns for each lithography iteration. This saves time and costs in the manufacturing process.

[0010] The device according to the invention also offers the possibility of unique encoding of chips, such as QR codes.

[0011] In addition, this approach allows for the reduction of the number of masks required by avoiding the use of quartz and chrome, which helps to minimize waste and the associated recycling processes.

[0012] The unitary reticle screen also has advantages for carrying out grayscale lithography, whether in terms of absorption or pattern densification. Finally, it should be emphasized that the photolithography device according to the invention is fully compatible and complies with the standards of established microelectronic manufacturing processes.

[0013] The subject of the invention is a photolithography device for transferring at least one pattern onto a substrate comprising: - a radiation source for emitting a beam at a predetermined wavelength; - a support for holding the substrate fixed relative to the radiation source; - a display screen arranged between the radiation source and the support and configured to display the at least one pattern; The radiation source being arranged so as to illuminate a first face of the substrate through the display screen to transfer the at least one pattern onto said first face of the substrate.

[0014] Said display screen comprising a matrix of pixels, the matrix of pixels comprising at least one pixel having an opacity at said wavelength which can be modulated so as to obtain one of at least the following opacity states: an opaque state or a transparent state.

[0015] According to a particular aspect of the invention, said pixel is furthermore adjustable so as to obtain at least one intermediate state between the opaque state and the transparent state.

[0016] According to a particular aspect of the invention, the display screen is produced on a plate transparent to said wavelength.

[0017] According to a particular aspect of the invention, the width and / or the length of the pixel is between 0.1 pm and 10 pm.

[0018] According to a particular aspect of the invention, the wavelength is in the ultraviolet range.

[0019] According to a particular aspect of the invention, the display screen is a liquid crystal screen.

[0020] According to a particular aspect of the invention, the pixel is a liquid crystal component comprising an electrolyte comprising chromium or nickel.

[0021] According to a particular aspect of the invention, the display screen is an electronic ink screen.

[0022] According to a particular aspect of the invention, the photolithography device further comprises control means for controlling the opacity at said length predetermined waveform of said pixel from a digital code representing the at least one pattern.

[0023] According to a particular aspect of the invention, the photolithography device further comprises at least one lens arranged between the display screen and the support to focus the beam passing through the display screen onto an area of ​​the substrate.

[0024] Other characteristics and advantages of the present invention will appear better on reading the description which follows in relation to the following appended drawings.

[0025] [Fig-1] [Fig.l] illustrates a photolithography device according to a first mode of realization of the invention.

[0026] [Fig.2] [Fig.2] represents a view from below of the display screen playing the role pixelated filter of the photolithography device according to the invention.

[0027] [Fig.3a] [Fig.3a] represents a sectional view of a first example of structure obtained following lithography by the photolithography device according to the invention.

[0028] [Fig.3b] [Fig.3b] represents a sectional view of a second example of structure obtained following lithography by the photolithography device according to the invention.

[0029] [Fig.4] [Fig.4] illustrates a photolithography device according to a second mode of realization of the invention.

[0030] [Fig.5] [Fig.5] illustrates a photolithography device according to a third mode of carrying out the invention.

[0031] [Fig.l] illustrates a photolithography device DI according to a first embodiment of the invention. The photolithography device DI is configured to transfer a physical pattern onto a target substrate 1. The physical pattern corresponds, for example, to the physical mask (layout in English) of a metal level of an integrated circuit produced by a stack of thin layers. The photolithography device DI comprises a radiation source 2 for emitting a beam at a predetermined wavelength X; a support 3 for holding the target substrate 1; a display screen 4 and control means 5 for programming the display of the display screen 4 according to the physical pattern to be transferred.

[0032] The target substrate 1 is fixed on the support 2. A layer of photosensitive resin is spread on the upper surface of the target substrate 1. The display screen 4 is arranged between the radiation source 2 and the support 3. The display screen 4 is configured by the control means 5 to display the physical design to be transferred by the lithography operation. The display screen 4 comprises a matrix of pixels 41, 42 mounted on a plate 40 transparent to the wavelength X. The pixel matrix comprises a plurality of pixels having an opacity that can be modulated at said wavelength X. For each pixel 41, 43 of said plurality, the opacity is configured from among at least the states following opacity: an opaque state E2 at wavelength X or a transparent state El at wavelength X. Thus, it is possible to configure the display screen 4 to display the physical design associated with each lithography iteration of the manufacturing process, without the need to change the reticle. The pixel matrix of the display screen 4 can be produced entirely or partially by pixels having an opacity that can be modulated with respect to the emitted radiation.

[0033] The radiation source 2 emits a light beam towards the upper surface of the substrate 1 through the display screen 4. The pixels configured in the opaque state E2 block the emitted radiation, and conversely, the pixels configured in the transparent state E1 allow the emitted radiation to pass through. The exposed areas of the resin RES change nature. This defines patterns like the reticle produced by the display screen 4.

[0034] The control means 5 are connected to the display screen 4 via a wireless connection to ensure perfect integration into standard equipment. For each modulatable pixel of the display screen 4, the control means 5 emit a control signal d1, wireless (radio for example), to electrically program the opacity of said pixel. For example, the control means are implemented by a computer connected to the display screen 4. The computer reproduces a predetermined physical design by modulating the opacity of the pixels of the screen 4 from a digital code or a database representing the physical implementation of a predetermined layer level of the integrated circuit.

[0035] As an illustrative example, the lithography device D1 is a UV lithography device (for the ultraviolet range). Thus, the radiation source 2 is designed to emit radiation having a wavelength X in the ultraviolet range. The transparent plate 40 is made of a material transparent to UV waves, for example quartz or sapphire.

[0036] According to a particular aspect of the invention, each modulatable pixel 41, 42 is produced by a liquid crystal component LCD (acronym for Liquid Crystal Device) comprising an electrolyte confined between two electrodes. The electrolyte comprises a material absorbing the wavelength X, for example chromium or nickel. When a potential difference is applied between the two electrodes of a pixel, this causes a change in orientation of the molecules as well as a variation in the polarization plane, which results in a modification of the transparency to UV radiation.

[0037] Alternatively, the modulatable pixels 41, 42 of the display screen 4 are produced by reflective components of the electronic ink screen type. In this embodiment, the modulatable pixels 41, 42 of the display screen 4 are micro-capsules containing positively and negatively charged particles dispersed in a liquid. When an electrical voltage is applied, the particles move towards the corresponding electrode (positive or negative), which changes the distribution of the particles and causes a localized change in transparency. One of the main advantages of electrophoretic display is its ability to maintain the displayed image without consuming energy, because the particles remain in place once the voltage is applied.

[0038] Generally, the adjustable pixels of the display screen 4 have a width and / or a length of between 0.1 pm and 10 pm, preferably greater than or equal to 0.1 pm and less than or equal to 0.7 pm so as to allow the manufacture of micro and nanostructures. These dimensions can be achieved with LCD liquid crystal components and reflective electronic ink components. This makes it possible to be compatible with the methods for manufacturing micro and nanostructures, and more particularly for the manufacture of microelectronic circuits.

[0039] The use of a screen 4 with adjustable opacity in the lithography device DI according to the invention makes it possible to change the physical design reproduced during the operation without the need to physically replace the mask acting as a reticle. The modification of design or writing of a GDSII can therefore be integrated into a production line much more quickly, without going through the costly manufacture of a reticle. Each iteration / adaptation of correction or improvement of the design is carried out much more easily. Therefore, the physical change of the mask is no longer necessary and therefore no human intervention is required. This has the advantage of automation and simplification of the process and reduction of costs relating to the manufacture of several chrome masks (one per physical design).

[0040] In addition, the versatility of the screen 4 with adjustable opacity makes it possible to individually encrypt each of the electronic chips produced on the same substrate or semiconductor wafer. Indeed, it is common in microelectronic manufacturing processes to manufacture a plurality of electronic chips on the same substrate. In certain cases, the chips correspond to a repetition of the same integrated circuit. During a lithography operation, it is then possible to generate an identifier for each chip in the form of a unique marker thanks to the versatility of the screen 4 with adjustable opacity acting as a reticle.

[0041] [Fig.2] represents a view from below of the display screen 4 of the photolithography device according to the invention.

[0042] The display screen 4 comprises a matrix of pixels having an opacity that can be modulated at the lithography wavelength X. Several patterns (or geometric shapes) F1 to F4 are displayed by modulating the opacity of the pixels of the matrix encoded by the control means 5. The pixels are configurable according to an opaque state E2 at the wavelength X (called the black state) or a transparent state E1 at the wavelength X (called the white state) and advantageously according to a plurality of intermediate states E3 and E4 called gray states. For example, the pattern Fl comprises a first vertical line of five pixels 42 opaque at the wavelength / .. The pattern Fl further comprises a second vertical line of five pixels 44 at a first intermediate state E4 corresponding to an opacity lower than that of the opaque state E2. The pattern Fl further comprises a third vertical line of five pixels 43 at a second intermediate state E3 corresponding to an opacity lower than that of the first intermediate state E4. Finally, the pattern Fl comprises a fourth vertical line of five pixels 41 completely transparent at the wavelength X. The possibility of gradually controlling the opacity of the pixels in the matrix via the intermediate states (also called shades of gray) makes it possible to carry out “grayscale” type lithography operations. This makes it possible to control the thickness of the structures obtained by chemical modification (crosslinking) of the resist during lithography. [Fig.3a] represents a sectional view of a first example of a structure obtained following lithography by the photolithography device DI according to the invention. The sectional view corresponds to the structure obtained along the axis BB crossing the pattern F1 illustrated in [Fig.2]. As an illustrative and non-limiting example, we will consider the case where the resin is crosslinked when it is not exposed to light. Along the axis BB, the structure 11 obtained by solidification of the resin following lithography via the screen of [Fig.2] comprises: a first part 11a having a first thickness za, a second part 11b having a second thickness zb and a third part 11c having a third thickness zb such that za>zb>zc.The first part 11a is obtained by exposure through the opaque pixel 42 of the first vertical line of the pattern FL The second part 11b is obtained by exposure through the pixel 44 in the first intermediate state E4 of the second vertical line of the pattern FL The third part 11c is obtained by exposure through the pixel 43 in the second intermediate state E3 of the third vertical line of the pattern FL In addition, the structure 12 corresponds along the cutting axis BB to the structure obtained by exposure through the opaque pixel 45 illustrated in [Fig.2]. As a result, the lithography device according to the invention makes it possible to easily produce structures with variable thickness by a single lithography operation thanks to the shades of gray of the pixels of the modular display screen 4.

[0043] Advantageously, each pixel has a plurality of intermediate states between the opaque state E2 and the transparent state EL. Increasing the number of intermediate states makes it possible to display a continuum of shades of gray on the display screen 4. This makes it possible to manufacture structures having a gradual variation in thickness z as illustrated in [Fig. 3b]. [Fig. 3b] represents a sectional view of a second example of structure 11' having a gradual variation in thickness z by means of lithography through a display screen 4 with pixels having a plurality of intermediate states.

[0044] [Fig.4] illustrates a DI photolithography device according to a second embodiment of the invention.

[0045] In this embodiment, the photolithography device DI further comprises at least one lens 6 arranged between the display screen 4 and the support 3. The at least one lens 6 is intended to focus the beam passing through the display screen 4 onto a predetermined area 11 of the substrate 1. The distance separating the display screen 4 and the lens 6 is equal to the focal distance of said lens. The lens 6 then makes it possible to adapt the projection of the image of the display screen 4 onto a reduced area 11 of the upper surface of the substrate 1. This makes it possible to produce a plurality of electronic chips on the same substrate.

[0046] [Fig. 5] illustrates a photolithography device DI according to a third embodiment of the invention. In this embodiment, the display screen 4 further comprises a film 7 transparent to the wavelength X. The film 7 is fixed to the display screen 4 opposite the pixel matrix at a non-zero separation distance d. The separation distance d is between 1 mm and 2 cm. The film serves to protect the pixel matrix from contamination of the particle or dust type which can distort the image projected during lithography. Indeed, when a particle P is placed on the film P, the non-zero distance d means that the particle P is not located at the focal plane of the lens 6. As a result, the image P' of the particle P is not projected onto the upper surface of the substrate 1.This provides the advantage of a reliable lithography operation independent of potential contamination from the DI lithography device environment.

Claims

Claims

1. Photolithography device (Dl) for transferring at least one pattern onto a substrate (1) comprising: - a radiation source (2) for emitting a beam at a predetermined wavelength (X); - a support (3) for holding the substrate (1) fixed relative to the radiation source (2); - a display screen (4) arranged between the radiation source (2) and the support (3) and configured to display the at least one pattern; the radiation source (2) being arranged so as to illuminate a first face of the substrate (1) through the display screen (4) to transfer the at least one pattern onto said first face of the substrate (1).said display screen (4) comprising a matrix of pixels (41, 42, 43), the matrix of pixels (41, 42, 43) comprising at least one pixel (41, 42, 43) having an opacity at said wavelength (X) which can be modulated so as to obtain one of at least the following opacity states: an opaque state (E2) or a transparent state (El).

2. Photolithography device (Dl) according to claim 1 wherein said pixel (41) is furthermore modulable so as to obtain at least one intermediate state (E3, E4) between the opaque state (E2) and the transparent state (El).

3. Photolithography device (Dl) according to any one of claims 1 or 2 in which the display screen (4) is produced on a plate transparent to said wavelength (X).

4. Photolithography device (Dl) according to any one of claims 1 to 3 wherein the width and / or the length of the pixel is between 0.1 pm and 100 pm.

5. Photolithography device (Dl) according to any one of claims 1 to 4 wherein the wavelength (X) is in the ultraviolet range.

6. Photolithography device (Dl) according to any one of claims 1 to 5 wherein the display screen (4) is a liquid crystal screen.

7. A photolithography device (Dl) according to claim 6 in wherein the pixel (41, 42, 43) is a liquid crystal component comprising an electrolyte comprising chromium or nickel.

8. Photolithography device (Dl) according to any one of claims 1 to 5 wherein the display screen (4) is an electronic ink screen.

9. Photolithography device (Dl) according to any one of claims 1 to 8 further comprising control means (5) for controlling the opacity at said predetermined wavelength (X) of said pixel (41) from a digital code representing the at least one pattern.

10. Photolithography device (Dl) according to any one of claims 1 to 9 further comprising at least one lens (6) arranged between the display screen (4) and the support (3) for focusing the beam passing through the display screen (4) onto an area (11) of the substrate (1).

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