An integrated circuit structure includes a substrate having a front side and a back side, the back side being an opposite side of the substrate from the front side. A first power rail extends in a first direction, is embedded in the front side of the substrate, and provides a first supply voltage. A second power rail provides a second supply voltage different from the first supply voltage, extends in the first direction, is embedded in the front side of the substrate, and is separated from the first power rail in a second direction different from the first direction. A first device is positioned between the first power rail and the second power rail and located on the front side of the substrate. A first via structure extends to the back side of the substrate and is electrically coupled to the second power rail.

Provided is a mask blank for a phase shift mask having an etching stopper film, which satisfies the characteristics: higher durability to dry etching with fluorine-based gas that is used during the shift pattern formation as compared to that of a transparent substrate; high resistance to chemical cleaning; and high transmittance of exposure light.

The mask blank includes a light shielding film on a main surface of a transparent substrate, having a structure where an etching stopper film, a phase shift film, and a light shielding film are laminated in this order on the transparent substrate; wherein the phase shift film includes a material containing silicon and oxygen; and the etching stopper film includes a material containing silicon, aluminum, and oxygen.

An extreme ultraviolet lithography (EUVL) method includes providing at least two phase-shifting mask areas having a same pattern. A resist layer is formed over a substrate. An optimum exposure dose of the resist layer is determined, and a latent image is formed on a same area of the resist layer by a multiple exposure process. The multiple exposure process includes a plurality of exposure processes and each of the plurality of exposure processes uses a different phase-shifting mask area from the at least two phase-shifting mask areas having a same pattern.

A write assist circuit includes: a memory-adapted latch and memory-adapted third and fourth NMOS transistors. The latch includes: a memory-adapted first PMOS transistor and a memory-adapted first NMOS transistor connected in series between a power-supply voltage and a first node, the first node being selectively connectable to a ground voltage; and a memory-adapted second PMOS transistor and a memory-adapted second NMOS transistor connected in series between the power-supply voltage and the second node, the second node being selectively connectable to the ground voltage. The third NMOS transistor is connected in series between the first node and the ground voltage; and the fourth NMOS transistor connected in series between the second node and the ground voltage. A gate electrode of each of the third and fourth transistors is connected to a latch-enable signal-line thereby for controlling the memory-adapted latch.

A photoresist film is patterned into an array of island shapes with improved critical dimension uniformity and no phase edges by using two alternating phase shifting masks (AltPSMs) and one post expose bake (PEB). The photoresist layer is exposed with a first AltPSM having a line/space (L/S) pattern where light through alternating clear regions on each side of an opaque line is 180 phase shifted. Thereafter, there is a second exposure with a second AltPSM having a L/S pattern where opaque lines are aligned orthogonal to the lengthwise dimension of opaque lines in the first exposure, and with alternating 0 and 180 clear regions. Then, a PEB and subsequent development process are used to form an array of island shapes. The double exposure method enables smaller island shapes than conventional photolithography and uses relatively simple AltPSM designs that are easier to implement in production than other optical enhancement techniques.

A photoresist film is patterned into an array of island shapes with improved critical dimension uniformity and no phase edges by using two alternating phase shifting masks (AltPSMs) and one post expose bake (PEB). The photoresist layer is exposed with a first AltPSM having a line/space (L/S) pattern where light through alternating clear regions on each side of an opaque line is 180 phase shifted. Thereafter, there is a second exposure with a second AltPSM having a L/S pattern where opaque lines are aligned orthogonal to the lengthwise dimension of opaque lines in the first exposure, and with alternating 0 and 180 clear regions. Then, a PEB and subsequent development process are used to form an array of island shapes. The double exposure method enables smaller island shapes than conventional photolithography and uses relatively simple AltPSM designs that are easier to implement in production than other optical enhancement techniques.

The present invention provides a halftone mask comprising an assist pattern and a manufacturing method of the halftone mask, which uses an ArF excimer laser as an exposing source, is used for a projection exposure by an off axis illumination, does not resolve the as pattern while keeping the focal depth magnification effect as the assist pattern, and may form a transferred image having high contrast of a main pattern. A photomask is a photomask comprising the main pattern which is transferred to a transfer-target surface by the projection exposure and the assist pattern which is formed nearby the main pattern and not transferred, characterized in that the main pattern and the assist pattern are each constituted from a semi-transparent film made of the same material, a retardation of 180 is generated between the light transmitting through the main pattern and the light transmitting through a transparent region of a transparent substrate, and a predetermined retardation within the scope of 70 to 115 is generated between the light transmitting through the assist pattern and the light transmitting through the transparent region of the transparent substrate.

The present invention provides a halftone mask comprising an assist pattern and a manufacturing method of the halftone mask, which uses an ArF excimer laser as an exposing source, is used for a projection exposure by an off axis illumination, does not resolve the as pattern while keeping the focal depth magnification effect as the assist pattern, and may form a transferred image having high contrast of a main pattern. A photomask is a photomask comprising the main pattern which is transferred to a transfer-target surface by the projection exposure and the assist pattern which is formed nearby the main pattern and not transferred, characterized in that the main pattern and the assist pattern are each constituted from a semi-transparent film made of the same material, a retardation of 180 is generated between the light transmitting through the main pattern and the light transmitting through a transparent region of a transparent substrate, and a predetermined retardation within the scope of 70 to 115 is generated between the light transmitting through the assist pattern and the light transmitting through the transparent region of the transparent substrate.

A mask blank includes: a light transmitting substrate; a first layer disposed on the light transmitting substrate, and including a chromium compound that contains chromium and at least one element selected from oxygen, nitrogen, and carbon; and a second layer disposed on the first layer as an outermost layer from among the first and second layers, and including a silicon compound that contains silicon and at least one element selected from oxygen, nitrogen, and carbon, an alloy of a transition metal and silicon, or a transition metal and silicon compound that contains a transition metal, silicon, and at least one element selected from oxygen, nitrogen, and carbon. The thickness of the first layer is 45 nm or less, and the thickness of the second layer is 5 nm or greater. An optical density of a stack composed of the first layer and the second layer is 3 or greater.

A mask blank for a phase shift mask having a phase shift film on a transparent substrate. The phase shift film generates a phase difference of 150 degrees or more and 200 degrees or less and transmits exposure light of an ArF excimer laser at a transmittance of 10% or more. The film has a low transmitting layer and a high transmitting layer, stacked alternately to form a total of six or more layers from a side of the transparent substrate. The low transmitting layer is made of a material containing silicon and nitrogen and having a nitrogen content of 50 atom % or more. The high transmitting layer is made of a material containing silicon and oxygen and having an oxygen content of 50 atom % or more. The low transmitting layer has a thickness greater than that of the high transmitting layer, which has a thickness of 4 nm or less.