TW400582B - Processing method of V-groove airbridge gate with etch-stop layer - Google Patents

Abstract

A novel gate structure called V-groove Airbridge Gate is proposed here, as well as the processing method to fabricate it. The gate is formed by anisotropic wet etching of undoped semiconductor (e.g. GaAs, Si) layer grown on top of device active layer(s), followed by standard metal evaporation and lift-off process. Owing to the outward slope of the sidewalls of the V-groove, effective gate length that is substantially smaller than the minimum feature size of available lithographic technology can always be obtained. The vertical location of the bottom of the gate metal is controlled by introducing a layer of etch-stop material between the uppermost undoped layer and device active layer(s). Gate strip and gate pad are connected by an airbridge-like gate feeder, which is fabricated by a surface micromachining technique that etches away the semiconductor materials beneath the gate feeder. This kind of novel gate structure can shorten the effective gate length without the penalty of increased gate resistance, and can achieve smaller parasitic gate capacitances. It has been applied to the fabrication of InGaP/GaAs/InGaAs hetrojunction doped-channel FET's, and relatively good results have also been achieved compared with traditional gate structure. The introduction of the etch-stop layer leads to high yield and uniformity, which is important to the industrial mass-production applications.

Description

V. Description of the invention (1 10 Α7 Β7 Industrial use field extinction · Ministry of Standards% Staff Consumption System 20 Mai invention is a novel gate structure of a V-shaped valley bridge and its manufacturing method. Background description For transistors, the size of the gate length is closely related to the characteristics of the transistor itself. Generally speaking, the smaller the gate length, the better its high-frequency characteristics and noise performance. Currently commercialized integrated circuits' In the meantime, the length of the pole is mostly below 0.5 micrometers, in order to know the speed. In this way, the gate is defined by the so-called electron-beam lithography. It is similar to the general optical contact micro In comparison, although electron beam lithography has the ability to define sub-micron patterns, it also has the disadvantages of high cost and time-consuming process. In addition, as the gate length is reduced, the stray metal of the gate is reduced. The resistance is also increased in the same proportion. This increase in the gate resistance will also increase the time constant of the transistor, and also offset the benefits to some extent due to the shortened gate length. 4 This paper size applies to China National Standard (CNS) Α4 specifications ( 210 × 297 mm) (Read the precautions on the back before filling in this page}

A7 10 15 Printed by the Central Bureau of Standards, Ministry of Economic Affairs, Consumer Co-operation, Printed 20 Invention Description (Therefore, how to achieve the goal of reducing the gate length and reducing the gate resistance at the same time is the key to the use of high-frequency-low noise. The T-shaped or mushroom-shaped gate of the stomach, because it has a wide cross-section & shape, can shorten the gate length and reduce the gate resistance at the same time. This kind of idle pole process technology pays attention to the actual manufacture of the electric crystal contact. The result proves that the τ-shaped yoke or mushroom-shaped gate with wide upper and lower narrow can indeed achieve better frequency and noise performance than the traditional planar gate. But in filling some manufacturing methods, in addition to applying the aforementioned electron beam lithography technology, it is also necessary to cooperate with the so-called multilayer photoresist system. Due to the complexity of the process, the low yield and process uniformity 'plus the electronics Beam lithography is expensive and time-consuming, and the application of this gate in mass production always has its limitations. The problem to be solved by the present invention is to develop a simpler process method to As a gate structure with the same advantages as a Ϊ-shaped gate or a mushroom gate, to achieve a high yield and high process (谙 first read the notes on the back and then fill out this page) 0 m · nn H9 In -ΜΨ 5: Paper Scale I-I.

5. Description of the invention: Color uniformity. Sexual 5 poles are ordered by the new ^ ^-the name is "V Caikong Bridge." The material solution and solution 1 ”involve single-layer photoresist and traditional optical contact lithography technology, which not only significantly reduces costs” type policy ηΓΪ. Can has turned this structure wire into the submicro H) #Dream of the scaled steel bridging / fragmentation of the steel gallium heterojunction channel, and has made good results in the production of the electric switch. For the field-effect transistor of the prior art, according to Fuku · Fukui's IEEE Trans. Electron Devices, Ε-26-26 (Ό), pp. 1032-1037, 'If the gate length can be shortened and the gate can be reduced at the same time, Resistors can operate in a higher frequency range and have a lower noise index. The so-called T-shaped gate or mushroom-shaped gate has a cross-sectional shape with a wide width and a narrow width, so that the gate length can be shortened and the sweet resistance of the gate can be reduced at the same time. Europe, the United States, and Japan have developed many process technologies for manufacturing such gates since 1980, and P.C. Chao et al. Reported in 2%, 7 years, EEE, watts, Tech, digest, pages 410-413. It is applied to the actual manufacture of transistors. The results prove that the upper width is 6i. Please read the notice on the back first.—IT) -10 ^ .--- 1—Printed by the Consumer Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs

One swallow IIII n I- I-I ml.-11 I— I-I This paper size is applicable to China National Standard (CNS) A4 specification (210X297 mm) 5. Description of the invention (4 narrow T-shaped gates) Or the mushroom-shaped interpole can indeed achieve better frequency and noise performance than the traditional planar gate. However, in these process methods, 'expensive and time-consuming electron beam lithography technology is required, and it must be matched with a multilayer photoresist system. , And its yield and process uniformity are not very satisfactory. 10 The gate structure in the present invention is called " v-shaped valley-air bridge gate " because it is through S. iida et al. 丄 9 · ^ 工 幻 ectr〇c / je2H. Vol. lls No. 5 No. 768_771 15 p. 20 or D. Shaw, et al. In the same year Vol. 4 No. 874 The non-isotropic. Reported on page -880, the valley wet-side technology is used to reduce the equivalent gate length. In simple terms, the first step is to grow an undoped semiconductor layer (such as arsenide) on the active layer of the device. Gallium, silicon), a v-shaped valley is etched by anisotropic wet etching technology; then gold is evaporated The stripe method is used to define the shape of the gate. Due to the slope of the V-shaped valley, the minimum line cold that can be achieved by the lithography technique at the bottom of the valley is much smaller than the equivalent gate length. By a layer of side stop material located between the active layer of the element and the undoped semiconductor layer, we can control the vertical position of the bottom of the gate metal so that it is exactly on the neodymium stop layer. As for the " empty bridge " The word refers to the use of an empty bridge-shaped gate feeder between the metal strip and the gate metal plate. This paper applies to this paper.) A4— (7 Employees ’Cooperative Cooperative Printing Bag of the Central Standard Bureau of the Ministry of Economic Affairs. T1 * 7 ........ £ > / V. Description of the invention (5) —-*-To be connected 'This closed-pole feeder is a surface micro-machining technology, and the conductor is located below the gate electrode. The material falls off to form a shape similar to an empty bridge. Such an empty bridge structure has a small stray capacitance value of f, 5 according to κ · Y · Hur et al. Yu Yanian's bribe & EleCtr0, z > ewces, i.e. 40 (10), page i736_i739 study can further improve the height of the transistor Response; In addition, γ_ L ~ et al., 1991 as the left foot off the coffee f Device

Lett 'EDL 12 (7), pages 360-362 reported that the air bridge structure also increased the breakdown voltage of the transistor and increased its output power. OBJECTS OF THE INVENTION The present invention discloses a Xinlai structure 15 named "V-shaped valley_bridge difficult" and its manufacturing method. This type of gate has the same advantages as a τ-shaped gate or a free-pole, that is, it has a narrow cross-section shape with a wide width and a narrow width, which can simultaneously achieve the dual purpose of reducing the length of the gate and reducing the resistance of the gate. The advantage of τ-shaped gate or clear-shaped gate is that its process method is only transferred to the traditional optical contact lithography and uses only a single layer of photoresist, which greatly reduces the τ-shaped _ complex The 'process method' thus improves the process uniformity compared to the process uniformity. V makes this gate structure suitable for the industry's mass production applications. This paper size applies to Chinese national standards (CNS > A4 size (210X297 mm) -------- ο— (Please read the precautions on the back before filling out this page). Order AV. 5 Central Standards of the Ministry of Economy Bureau of the Consumer Cooperative printed A7 B7, invention description ⑫) The diagram illustrates the first ~ circle, epitaxial structure ... Undoed GaA5 is the layer to be formed; · Undoped InGaP insulator / etch stop layer 'y · GaAs channel 6 " .. Indium Gallium Arsenide (11 ^ 3) channel is not replaced with doped gallium buffer layer (Undoped GaAs buffer) 100 .... Insulator GaAs substrate (S * I. GaAs) Second picture, V-shaped valley gate process method (a) Spin-coat first resistance (b) Exposure Λ shadows a micron The gate length (c) is engraved with the sulfur solution to slop the {111} gallium (Ga) slope (Φ down, especially the rest of the time, it automatically stops at the scaled indium gallium (e) vapor-deposited metal I ..... Photoresist (Photoresist) 2 '... (1〇〇) Undoped GaN (10Q Undope4 GaAs) 3 ", · InGaP stop layer 4 " .. · GaAs / InGaAs channel (GaAs / InGaAs channel) 8 ". · 兰Gate metal 9…. {111} Gallium (Ga) bevel 3rd figure, gate feeder method of forming an empty bridge shape II… 'Photoresist mask 12 Open window ^ (window opening) 13 ... the fourth circle of the gate feed line ^ area, the traditional gate structure (a) top view (b) side view 2. "詧 f (drain) 15." "source (SOUrce) 〒 ·, Board (substrate) 18 ... · channel 2. "· gate strip metal gate (gate strip) 2〇. &Quot;

Ji ^ ate feeder) 21 .... gate pad (t d)

Fifth figure, empty bridge gate structure P (a) top view (b) side view sixth figure, production V-shaped valley gate structure cross section: surface view (a) the effective gate length is about 0 · 6 micron v-type valley gate (b) ▽ -type valley gate with a gate length of almost zero. Main 9 This paper size applies Chinese National Standard (CNS) A4 specification (210 X 297 mm) (Please read the notes on the back before filling out this page} ， 可 10 15 V. Description of the invention (7) Detailed description of the invention: The present invention is a novel gate structure 5 of a V-shaped valley bridge gate and a method for manufacturing the same. The method includes the following steps: (a) providing a semiconductor substrate; (b) growing on the semiconductor substrate with a worm crystal Or ion implantation to form one or more element channel layers; 棘 above the component pass, the spine-nucleus-private stop layer; ⑹ above the butterfly stop layer, grow-a layer of undoped semiconductor ； On the undoped semiconductor layer, define the ㈣ electrode pattern, and use the side of the chemical agent to select the non-doped conductor layer exposed with miscellaneous surface, make anisotropic rice carving to side out-V-shaped valley, and make The bottom secret stop layer is exposed at the bottom of the V-shaped valley; (f) Placing _ material in the V-shaped valley to form a pole; ⑻ Remove the material under the __ into the structure of the empty bridge pole. The semiconductor substrate is the third one on which other semiconductors can be grown. For Group 5 compound semiconductors, the most suitable semiconductor substrate can be selected from Kunhua. The above-mentioned channel layer is a semiconductor with high electron mobility, and the most suitable channel layer can be selected from gallium or gallium indium gallium. This unmixed semiconductor (Please read the precautions on the back before filling in this page) Printed by the Consumers' Cooperative of the Central Bureau of Standards of the Ministry of Economic Affairs 20 10 1 „--- ο ------ fIT ------ 艺 --- 7I --- i -111-am This paper size applies to Chinese national standards (cns mm) _ Printed by the Consumer Cooperatives of the Central Bureau of Standards of the Ministry of Economic Affairs 5. Creative Instructions (8 = 1_ Degree of Semiconductors' Most Suitable Undoped) The semi-secreted GaN can be used for the semiconductor layer. The side stop layer can be used as an alternative to the undoped conductor layer, such as indium gallium phosphide. The pattern formed on the gate is included in the substrate. The surface is coated with a sensing material layer, and the photosensitive material phase is exposed and developed to form a patterned photosensitive material layer; wherein the photosensitive material layer of the pattern can expose the insect crystal layer on the substrate. The part of the surface is exposed. The photosensitive material layer is a photoresist layer Mask and ultraviolet light for exposure, and use chemical fines such as sulfuric acid-hydrogen peroxide-aqueous solution, solutions with different etching rates for the undoped rotor and _stop layer; the chemical agent can It can be extended to the side. The empty bridge structure is _ any solution that has different etching rates for fine metals and underlying materials. The etching solution is selected from hydrochloric acid-scale acid solution and sulfuric acid-peroxide gas. 5 10 15 In the following examples, a scaled indium gallium / gallium arsenide / indium gallium arsenide heterojunction interface with 20 doped field effect transistors is used as an example to describe the application of the ν-type valley-air bridge gate structure. Process method and results obtained in transistor production. The structure of the heteromorphic worm crystal layer of this transistor is shown in the first figure. The top layer is a layer of undoped gallium arsenide with a thickness of about 1 micron. The v-shaped valley is here — 11 (Please read the precautions on the back before filling this page)-Yiding. Standard (CNS) A4 specification (21GX297 mm) V. Description of the invention (9 layer tilt = next anisotropy with non-isotropic hard-engraving technique _ unmixed layer thickness of 1QQ angstrom__ 依 昭 Η The person to work in Yu Nianshan wectr〇c_ • .., Vol. 5, Vol. 10, No. 3383-3386, reported that the method has a rhyme selection rate of 10, so it can be used as a side stop when v-shaped valleys = simultaneously It also plays the role of an insulating layer in a channel-doped field-effect transistor: the next 'both are 3x, cnn3 n-type layers of GaAs and Ti-GaAs, which are Used as the channel layer of the device. Below it is a 5 Angstrom undoped gallium buffer layer and a gallium halide substrate (100). 15 Member of the Central Standards Bureau of the Ministry of Economic Affairs X. Consumer Cooperative printed V of this transistor The manufacturing method of the valley gate is shown in the second figure. After the 6-shaped elements are completed on the wet side, and annealed to the source—the recorded New Metal Village sister loses the point, Twist-layer photoresist on difficult area 'Please refer to the second figure (a). Secondly, with the traditional optical pickup micro-surgery, the length of the interpole is defined on the wire along the direction of (Q1T) is about 1 The pattern of the micron gate metal strip is shown in the second figure ii). Next, use an anisotropic post-etching solution (such as a sulfuric acid-hydrogen peroxide-water 20 etching solution system) 'to etch in the area defined by the gate. Since the lattice bonding of gallium arsenide is a zinc flash structure, the {111} gallium (Ga) slope will appear in the anisotropic etching solution, as shown in the second figure (c). These 12 paper standards are applicable to China National Standard (CNS) A4 (21〇297297); printed by the Consumer Cooperatives of the Central Standards Bureau of the Ministry of Economic Affairs, and invented;! (〇) '~~-一 ~~ --- The anisotropic etching process will stop automatically when going down to the scaled indium gallium epitaxial stop layer, and a v M valley structure is formed as shown in the second figure (d). Finally, “metals such as titanium / Kan / Gold or Chromium / Gold etc. are vapor-deposited by vacuum evaporation” and then the legal metal gate area is braked off, as shown in the second figure 第二. In the second picture, the equivalent gate length of a, v-shaped valley gate (that is, the length of the contact portion between the gate metal and the indium gallium phosphide insulating layer) can be seen scrupulously. The length defined on the resistance is much smaller. If we choose the thickness of the top undoped aluminized gallium layer and the right side solution, we can even reach V-shaped valley gates with almost zero gate length. In addition to shortening the gate length, the V-shaped valley gate structure has the following advantages: (1) v-shaped valley etching can help achieve nearly 100% gate metal stripping yield; (2) v-shaped valley cut This makes the Boren inch increase the thickness of the gate metal and further reduce the resistance between the 15 poles; (3) V-shaped gates have the same width and narrow cross-section as the τ-shaped or mushroom-shaped gates. Suitable for the realization of self-aligned gate ('self-aligned gate)' can reduce the source and non-electrode resistance. 20 As for the method of forming the gate feeder of the empty bridge, please refer to the third figure. First, we rolled a layer of photoresistor on the completed V-shaped valley gate, and then opened a window with photofist contact lithography technology in the gate feeder area. 13 ----- ^-X --- 0- -, --- 1 order ------ (Please read the notes on the back before filling this page) This paper size applies to China National Standard (CNS) A4 (210X297 mm) Employees of the Central Standards Bureau of the Ministry of Economic Affairs Printed by the Consumer Cooperative V. Description of the invention h) ~ ~-------Table 2 'Surface micromachining technology with sulfuric acid-double recording-water and hydrochloric acid monoacetic acid solution, Qing _ under the pole feeder The semi-conductor layers are made of 'hydrochloric acid solution which is made of kneaded copper, and sulfur = oxygen water-water Na volume solution is used for gallium and bell chemical. The fourth figure shows the top view of the traditional gate structure (fourth figure (a)) and side view (fourth figure _, and the fifth _ bridge gate structure top view (fifth figure ⑻) and side view (Fifth figure (b)); From the two figures, we can see the difference between the two. 10- The sectional view of the completed v-shaped gate structure is shown in Figure 6. In Figure 6, you can It is clear that by using the method of the present invention to make an equivalent gate, a v-shaped valley gate with an M of about 0.6 micrometers has been successfully fabricated in a V-shaped valley without doped gallium bellows. The bottom of the metal is just in contact with the stop layer on the gallium side of the phosphor. The v-shaped valley gate is made by the optical contact lithography process technology with a line width of 1.2 micron. And in the sixth figure ( In b), 'we use the lithography technology with a line width of $ micron> In the thick undoped and fragmented gallium layer, a' type 7 'where the bottom length (ie, equivalent interpole length) is almost zero can be manufactured. Valley gate. In addition, it is worth to pay 20% because, because there are more V-type valley engraving process steps before metal evaporation, the gate metal can be plated more than ordinary planar gate. Thicker, the gate resistance can be further reduced. As clearly shown in Figure 6 (b), 14 paper standards are applicable to Chinese national standards (CNS> 8-4 specifications (210 > < 297)):- ------ ΓΙ --- Q ------- Order ---- 1—ΜΨ (Please read the precautions on the back before filling out this page) A7 Printed by the Consumer Cooperative of the Central Standards Bureau of the Ministry of Economic Affairs V. Description of the invention (12 丨-* ~ --- ~ S— Even if the intermetallic metal is thicker than _μm, metal stripping can still be successfully completed. 5 The above experimental results show that the v-shaped valley-air bridge gate is a An effective method to achieve sub-micron gate transistors. Compared with existing methods, it has lower cost and higher yield and process uniformity, which has great potential for mass production in the industry. Although the present invention has been The preferred example is disclosed above, but it is not intended to limit the present invention. Any person skilled in the art can make some changes and retouches without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention is The definitions of the scope of patent applications attached later shall prevail. 5 11 ο 2 15 Zhang appropriate scale (CNS) KA ^ M- (210x297 - ^^ 7 (please read the Notes on the back of the smell and then fill the page)

Claims (1)

Please smell t * first S f I order The Ministry of Economic Affairs of the People's Republic of China and the Central Government Bureau 5 Consumer Cooperation 衽 A8 B8 C8 D8, A patent scope-9. The manufacturing method described in item 8 of the scope of the application, where the etching stop layer is indium gallium phosphide. 10. The manufacturing method as described in item i of the scope of patent application, wherein the formation of the gate pattern includes coating a photosensitive substance layer on the substrate surface to expose and develop the photosensitive substance layer to form a patterned photosensitive substance. Floor. 11. The manufacturing method according to item 10 of the patent application park, wherein the pattern of the patterned phosphorescent material layer is formed such that a part of the surface of the base "yuan 1 epitaxial layer is exposed. F / soil Please respect I · 2. The manufacturing method as described in item 10 of the scope of patent application, and the current state of the salty light material layer is left in the middle layer so that the epitaxial surface of the substrate is not exposed. 9 person 13 · 如In the manufacturing method described in the first paragraph of the patent application, in the base i, only the exposed part of the surface of the earth's winter epitaxial layer is exposed in the step ^ (I4. As described in the tenth patent application park The manufacturing method described above, the layer is-photoresist layer borrowed-photomask and ultraviolet "3 · 5. The manufacturing method described in item i of the spectrum content patent range is any doped semiconductor and the rest is different Solution at the remaining rate. Layer 16. The manufacturer's chemical agent described in the scope of the patent application can etch a v-shaped ytterbium on the undoped semiconductor. The manufacturing method described in the fifth scope of the patent scope. Xunzhongxi Chemical Music Agent is a sulfuric acid-hydrogen peroxide aqueous solution. 8 · As the winter manufacturing method described in item [] in the application for patent revolving, the structure is formed by using the solution of the gate metal and the etching rate of the same space. The material is not as good as the patent application park. The manufacturer's remaining solution described in item 1S is salt brewing ~ phosphoric acid solution and sulfuric acid __ peroxide gas rη --- Q! (谙 Please read the notes on the back before filling this page), 1T